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# E RNEST 

# O RLANDO 

# L AWRENCE


# B ERKELEY 

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# Energy Efficiency Improvement Opportunities for the Cement Industry

Ernst Worrell, Christina Galitsky and Lynn Price

Environmental Energy Technologies Division

January 2008

This work was supported by the Climate Pr otection Partnerships Division of the U.S. Environmental Protection Agency as part of its ENERGY STAR program through the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231. Revision of this report fo r use in China was undertaken with funding provided by the U.S. EPA’s Office of International Af fairs, the Energy Foundation’s China Sustainable Energy Program and Dow Ch emical Company.Disclaimer

This document was prepared as an account of work sponsored by the United States Government.

While this document is believed to contain co rrect information, neither the United States Government nor any agency thereof, nor The Regent s of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infri nge privately owned rights. Reference herein to any specific commercial product, process, or servi ce by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or The Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof, or The Regents of the University of California.

Ernest Orlando Lawrence Berkeley National Labor atory is an equal opportunity employer.

### Energy Efficiency Improveme nt Opportunities for the Cement Industry

Ernst Worrell, Christina Galitsky and Lynn Price

Environmental Energy Technologies Division Lawrence Berkeley National Laboratory

ABSTRACT

This report provides information on the energy savings, costs, and carbon dioxide emissions reductions associated with implem entation of a number of technologies and measures applicable to the cement industry. The technologies and measures include both state-of-the-art measures that are currently in use in cement enterprises worldwide as well as advanced measures that are either only in limited use or are near commercialization.

This report focuses mainly on retrofit measures using commercially available technologies, but many of th ese technologies are applicable for new plants as well. Where possible, for each technology or measur e, costs and energy savings per tonne of cement produced are estimated and then carbon dioxide emissions reductions are calculated based on the fuels used at the pro cess step to which the technology or measure is applied. The analysis of cement kiln en ergy-efficiency opportuni ties is divided into technologies and measures that are applicable to the different stages of production and various kiln types used in China: raw materials (and fuel ) preparation; clinker making (applicable to all kilns, rotary kilns only, vert ical shaft kilns only); and finish grinding; as well as plant wide measures and product a nd feedstock changes that will reduce energy consumption for clinker making. Table 1 lists al l measures in this re port by process to which they apply, including plant wide meas ures and product or feedstock changes. Tables 2 through 8 provide the following in formation for each technology: fuel and electricity savings per tonne of cement; annua l operating and capital costs per tonne of cement or estimated payback period; and, carbon dioxide emissions reductions for each measure applied to the production of cement.

This information was originally collected for a report on the U.S. cement industry (Worrell and Galitsky, 2004) and a report on opportunities for China’s cement kilns (Price and Galitsky, in press). The informat ion provided in this report is based on publicly-available reports, journal articles, and case studies from applications of technologies around the world.

### Table of Contents

Introduction ................................................................................................................1 Energy Efficiency Improvement Opportunities ........................................................1
Raw Materials Preparation.............................................................................................. 2 Fuel Preparation .............................................................................................................. 4 Clinker Making - All Kilns ............................................................................................. 5 Clinker Making – Rotary Kilns ....................................................................................... 8 Clinker Making – Vertical Shaft Kilns ......................................................................... 17 Finish Grinding ............................................................................................................. 18

Plant Wide Measures .................................................................................................... 21 Plant Wide Lighting ...................................................................................................... 25 Product and Feedstock Change ..................................................................................... 26 

### Acknowledgements ..................................................................................................31

References ................................................................................................................32

Tables

Table 1. Energy Efficiency Measures and Technologies for the Cement Industry. ....................... 1 Table 2. Energy Efficiency Measures for Raw Materials Preparation in Cement Plants. .............. 2 Table 3. Energy-Efficiency Opportuniti es Applicable to All Kiln Types. ..................................... 5 Table 4. Energy-Efficiency Opportuniti es Applicable to Rotary Kilns........................................ 10 Table 5. Energy-Efficiency Opportunities Applicable to Vertical Shaft Kilns. ........................... 17 Table 6. Energy Efficiency Measures for Fi nal Grinding of Products in Cement Plants ............. 19 Table 7. Energy Efficiency Measures for Plant Wide Measures in Cement Plants ...................... 21 Table 8. Product and Feedstock Changes to Improve the Energy Efficiency of Clinker

Production. ..................................................................................................................... 27 Table 9. Prices and Transportation Modes for Different Additives Used in China ...................... 28

### Introduction

This report provides information on the en ergy savings, costs, and carbon dioxide emissions reductions associated with implem entation of a number of technologies and measures applicable to the cement industry. The technologies and measures include both state-of-the-art measures that are currently in use in cement enterprises worldwide as well as advanced measures that are either only in limited use or are ne ar commercialization. Mainly the focus is on retrofit measures us ing commercially available technologies, but many of these technologies are applicable fo r new plants as well. Where possible, for each technology or measure, costs and energy savings per tonne of cement produced are

estimated and then carbon dioxide emissions reductions are calculated based on the fuels used at the process step to which the technology or measure is applied. The analysis of cement kiln energy-efficiency opportunities is divided into technol ogies and measures that are applicable to the different stages of production and various kiln types used in China: raw materials (and fuel) preparation; clinker making (appl icable to all kilns, rotary kilns only, vertical shaft kilns only); and finish gr inding; as well as pl ant wide measures and product and feedstock changes that wi ll reduce energy consumption for clinker making.



### Energy Efficiency Improvement Opportunities

Table 1. Energy Efficiency Measures and Technologies for the Cement Industry.

Raw Materials Preparation All Kilns Efficient transport systems (dry process) Improved refractories Raw meal blending systems (dry process) Kiln shell heat loss reduction Process control vertical mill (dry process) High-efficiency roller mills (dry process) Energy management & process control Adjustable speed drive for kiln fan High-efficiency classifiers (dry process) Slurry blending and homogenization (wet process) Vertical Shaft Kilns Conversion to closed circuit wash mill (wet process) Convert to new suspension preheater/precalciner kiln Fuel Preparation Kiln combustion sy stem improvements Roller mills for fuel preparation Roller press for coal grinding Rotary Kilns Finish Grinding Preheater kiln upgrade to precalciner kiln Energy management and process control Long dry kiln upgrade to preheater/precalciner kiln High-pressure roller press Older dry kiln upgrade to multi-stage preheater kiln High efficiency classifiers Convert to reciprocating grate cooler Improved grinding media (ball mills) Kiln combustion system improvements

General Measures Indirect Firing Preventative maintenance (insulation, compressed air

system, maintenance) Optimize heat recovery/upgrade clinker cooler Seal replacement High efficiency motors Efficient fans with variable speed drives Low temperature heat recovery for power (capital costs given in $/kW) Optimization of compressed air systems High temperature heat recovery for power Efficient lighting Low pressure drop cyclones

Efficient kiln drives Product & Feedstock Changes

Blended cements

Use of waste derived fuels

Limestone cement

Low alkali cement Use of steel slag in kiln

1Table 1 shows the energy efficiency measures included in this report by process step as well as general measures. Efficiency measures are described below in more detail in the applicable section, by process step.

Raw Materials Preparation Table 2 shows fuel and electricity savings , estimated payback period and carbon dioxide (CO 2 ) savings for each measure related to ra w materials preparation (including the preparation of fuels). A description for each measure is given below.

Table 2. Energy Efficiency Measures for Raw Materials Preparation in Cement Plants. More information can be found in the description of the measures below.

Energy Efficiency Measure (for raw materials production) Fuel Savings (GJ/t) Electricity Savings (kWh/t) Estimated Payback Period (years) (1) CO 2 Savings (kgC/t)
Efficient Transport System

- 3.4 > 10 (1) 0.78 Raw Meal Blending

- 1.7-4.3 NA (1) 0.4-1.0

Process Control Vertical Mill

- 1.4-1.7 1 0.3-0.4 High-Efficiency Roller Mill

- 10.2-11.9 > 10 (1) 2.3-2.7 High-Efficiency Classi fiers

- 4.8-6.3 > 10 (1) 1.1-1.4 Slurry Blending and Homogeni zing 0.5-0.9 < 3 0.1-0.2

Wash Mills with Closed Circuit Classifier

- 8.5-11.9 > 10 (1) 2.0-2.7 Roller Mills for Fuel Preparation

- 0.7-1.1 NA (1) 0.2-0.3

Notes: All data is given per tonne of cement

(1) Payback periods are calculated on the basis of energy savi ngs alone. In reality this investment may be driven by other considerations than energy efficiency (e.g. productivity , product quality), and will happen as part of the normal business cycle or expansion project. Under these conditions the measure will have a lo wer payback period depending on plant-specific conditions.

NA = not available

Efficient Transport Systems (Dry Process). Transport systems are required to convey powdered materials such as kiln feed, kiln dust, and finish ed cement throughout the plant. These materials are usually transported by m eans of either pneumatic or mechanical conveyors. Mechanical conveyors use less po wer than pneumatic systems. Based on Holderbank, (1993) the average energy savi ngs are estimated to be 2.0 kWh/t raw material with a switch to mechanical conveyo r systems. Installation costs for the system are estimated to be $3/t raw material produc tion based on the Hold erbank study (1993). Conversion to mechanical conveyors is cost -effective when replacement of conveyor systems is needed to increase reliability and reduce downtime.

Raw Meal Blending (Homogenizi ng) Systems (Dry Process). To produce a good quality product and to maintain optimal and efficient combustion conditions in the kiln, it is crucial that the raw meal is completely homogenized. Quality control starts in the quarry and continues to the blending silo. On-line an alyzers for raw mix control are an integral part of the quality control system (Fujimoto, 1993; Holderbank, 1993).

Most plants use compressed air to agitate th e powdered meal in so-called air-fluidized homogenizing silos (using 1.1-1.5 kWh/t raw meal). Older dry process plants use mechanical systems, which simultaneously with draw material from 6- 8 different silos at variable rates (Fujimoto, 1993), using 2.2-2.6 kWh/t raw meal. Modern plants use gravity-type homogenizing silos (or conti nuous blending and stor age silos) reducing

2power consumption. In these s ilos, material funnels down on e of many discharge points,

where it is mixed in an inverted cone. Gravit y-type silos may not give the same blending efficiency as air-fluidized systems. Although most older plants us e mechanical or airfluidized bed systems, more and more new plants seem to have gravity-type silos, because of the significant reduction in power consumption (Holderbank, 1993). Silo retrofit options are cost-effective when the si lo can be partitioned with air slides and divided into compartments which are sequentia lly agitated, as opposed to the construction of a whole new silo system (Gerbec, 1999). The energy savings are estimated to be 1.0- 2.5 kWh/t raw meal (Fujimoto, 1993; Holder bank, 1993; Alsop & Post, 1995, Cembureau, 1997b; Gerbec, 1999). Costs for the silo retrofit are estimated to be $3.7/t raw material (assuming $550K per silo and an average cap acity of 150,000 tonnes annual capacity).

Raw Meal Process Control (Dry process - Vertical Mill). The main difficulty with existing vertical roller mills are vibration trips. Operation at high throughput makes

manual vibration control difficult. When the ra w mill trips, it cannot be started up for one hour, until the motor windings cool. A model predictive multivariable controller maximizes total feed while maintaining a target residue and enforcing a safe range for trip-level vibration. The first application eliminated avoidabl e vibration trips (which were 12 per month prior to the contro l project). The cited increase in throughput was 6% with a corresponding reduction in specific energy consumption of 6% (Martin and McGarel, 2001b), or 0.8 – 1.0 kWh/tonne of raw ma terial (based on Cembureau, 1997b).

Use of Roller Mills (Dry Process). Traditional ball mills used for grinding certain raw materials (mainly hard limestone) can be replaced by high-efficiency roller mills, by ball mills combined with high-pressure roller presse s, or by horizontal roller mills. The use of these advanced mills saves energy wit hout compromising produc t quality. Energy savings of 6-7 kWh/t raw materials (C embureau, 1997b) are assumed through the

installation of a vertical or horizontal roller mill. An additional advantage of the inline

vertical roller mills is that they can combine raw material drying with the grinding process by using large quantities of low grade wa ste heat from the kilns or clinker coolers (Venkateswaran and Lowitt, 1988). Various roller mill process designs are marketed.

In 1998, Arizona Portland cement (Rillito, Arizona, U.S.) installed a roller mill for raw material grinding increasing throughput, fl exibility, raw meal fineness and reducing electricity consumption (De Hayes, 1999). In vestments are estimated to be $5.5/t raw material (Holderbank, 1993).

High-efficiency Classifiers/Separators. A recent development in efficient grinding technologies is the use of high-efficiency classi fiers or separators. Cl assifiers separate the finely ground particles from the coarse particles. The large particles are then recycled back to the mill. High efficiency classifiers ca n be used in both the raw materials mill and in the finish grinding mill.

Standard classifiers may have a low separation efficiency, whic h leads to the recycling of fine particles, and results in to extra power use in the grinding mill. Various concepts of high-efficiency classifiers ha ve been developed (Holderb ank, 1993; Süssegger, 1993). In

3high-efficiency classifiers, the material stay s longer in the separator, leading to sharper separation, thus reducing ove rgrinding. Electricity savings through implementing highefficiency classifiers are estimated to be 8% of the specific electricity use (Holderbank, 1993).

In 1990, Tilbury Cement (Delta, British Columb ia, Canada) modified a vertical roller mill with a high-efficiency classifier incr easing throughput and decreasing electricity use (Salzborn and Chin-Fatt, 1993). Case studi es have shown a reduction of 2.8-3.7 kWh/t raw material (Salzborn and Chin-Fatt, 1993; Süssegger, 1993). Replacing a conventional classifier by a high-efficiency classifier ha s led to 15% increases in the grinding mill capacity (Holderbank, 1993) and improved product quality due to a more uniform particle size (Salzbor n and Chin-Fatt, 1993), both in ra w meal and cement. The better

size distribution of the raw meal may lead to fuel savings in the kiln and improved clinker quality. Investment costs are estimated to be $2.2/annual t raw material production, according to Holderbank (1993).

Slurry Blending and Homogenizing (Wet Process). In the wet process, the slurry is blended and homogenized in a batch process. The mixing is done using compressed air and rotating stirrers. The use of compressed air may lead to relativel y high energy losses because of its poor efficiency. An efficien tly run mixing system may use 0.3 – 0.5 kWh/t raw material (Cembureau, 1997b). The main en ergy efficiency improvement measures for slurry blending systems are found in the co mpressed air system (see below under plantwide measures).

Wash Mills with Closed Circui t Classifier (Wet Process). In most wet process kilns,

tube mills are used in combina tion with closed or open circuit classifiers. An efficient tube mill system consumes about 13 kWh/t (Cembur eau, 1997b). Replacing the tube mill by a

wash mill would reduce electri city consumption to 5-7 kW h/t (Cembureau, 1997b) at comparable investment and operation costs as a tube mill system. When replacing a tube

mill a wash mill should be considered as an alternative, reducing electricity consumption for raw grinding by 5-7 kWh/t, or 40-60%.

Fuel Preparation Coal is the most widely used fuel in the cement industry. Fuels preparation is most often performed on-site. Fuels preparation may in clude crushing, grinding and drying of coal. Coal is shipped “wet” to prevent dust formation and fire during tr ansport. Passing hot gasses through the mill combines the grinding and drying. An impact mill would consume around 45-60 kWh/t and a tube mill around 25 – 26 kWh/t (total system requirements) (Cembureau, 1997b). Waste heat of the kiln system (e.g. the clinker cooler) is used to dry the coal if needed.

Other advantages of a roller mill are that it is able to handle larger sizes of coal (no precrushing needed) and coal types with a higher humidity, and can manage larger variations in throughput. However, tube mills are preferre d for more abrasive coal types. Coal roller mills are available for throughputs of 5.5 to 220 t/hour. Lehigh Portland Cement installed a vertical roller mill for coal grinding in 1999 at the Union Bridge, Maryland, U.S. plant.

4Blue Circle cement has ordered a vertical ro ller mill for the new kiln line V at the Roberta plant in Calera, Alabama, U.S. It has a capacity of 41.3 t/hr and was commissioned in early 2001. Co al grinding roller mills can be found in many countries around the world, e.g. Brazil, Canada, China, Denmark, Germany, Japan and Thailand. All major suppliers of cement technology offer roller mills for coal grinding.

Vertical roller mills have been developed for coal grinding, and are used by over 100 plants around the world (Cembureau, 1997b). Elect ricity consumption for a vertical roller mill is estimated to be 16-18 kWh/t coal (Cembureau, 1997b). The investment costs for a roller mill are typically higher than that of a tube mill or an impact mill, but the operation costs are also lower; roughly 20% compared to a tube mill and over 50% compared to an impact mill (Cembureau, 1997b), estimating savings at 7-10 kWh/t coal.

Roller Press for Coal Grinding. Roller presses, like thos e used for cement and raw material grinding, are generally more effici ent than conventional grinding mills. Roller presses can be used to grind raw materi als and coal interchangeably, although coalgrinding equipment needs special protection against explosions.

Clinker Making - All Kilns All kilns can implement improved refractories, kiln shell heat loss reduction measures, energy management and process control systems, and adjustable speed drives for the kiln fan. Although all kilns can benefit from kiln combustion system improvements, we have split this measure into two distinct measures for rotary and shaft kilns, in those respective sections, below. Distinctions between ener gy management and process control for each kiln type are explained in the measure desc ription in this sect ion. Table 3 provides information on the initial capital costs, the operations and maintenance (O&M) costs, the simple payback period, the specific fuel savings , the specific electric savings, the specific

CO 2 emissions reductions, and the lifetime a ssociated with each of these measures.

Table 3. Energy-Efficiency Opportunities Applicable to All Kiln Types.

Capital

Costs ($/t) O & M

Costs ($/t) Payback

Period (years) Fuel Savings (GJ/t) Electric Savings (kWh/t) CO 2 Savings (kgC/t) Lifetime (years)

Improved refractories NA NA 0.4-0.6 1

- 10.3-15.5 NA

Kiln shell heat loss reduction 0.25 1 0.1-0.63 2

- 2.8-10.3 20

Energy management & process

control 0.3-1.7 < 2 0.1-0.2 1.5-3.2 2.9-5.9 10

Adjustable speed drive for kiln fan 0.23 0 2-3

- 6.1 1.4 10 Note: Energy savings and costs are based on case study data from the U.S., except where noted. Costs in China will vary depending on technology and availabili ty. Where possible, we have included more data for China in the following text. All data are given per tonne of c linker. For U.S. data, the estimated savi ngs and payback periods are based on the average performance of the U.S. cement i ndustry (e.g. clinker to cement ratio).

1 Data taken from Chinese case studies

2 Data from Chinese case studies indicate savings of 0.46 to 0.63 GJ/t clinker, wh ile U.S. data show savings of 0.1 to

0.4 GJ/t clinker.

NA = not available

Improved Refractories. Refractories protect the steel kiln shell against heat, chemical

and mechanical stress. The choice of refract ory material depends on the combination of

5raw materials, fuels and operating conditi ons. Extended lifetime of the higher quality refractories will lead to longer operating periods and reduced lost production time between relining of the kiln, and, hence, offs et their higher costs (S chmidt, 1998; van Oss, 2002). It will also lead to a dditional energy savings due to the relative reduction in startup time. The energy savings are difficult to quantify, as they will strongly depend on the current lining choice and management.

In one vertical shaft kiln in South China, a new energy-efficient lin ing was applied. Fuel consumption was reduced from 930 to 950 kcal/kg clinker (3.9 to 4.0 GJ/t clinker) to 800 to 820 kcal/kg clinker (3.4 to 3.5 GJ/t cl inker), a savings of approximately 14% (ITIBMIC, 2004). The output also increased by about 1 tonne per hour. Another cement plant in North China utilizing vertical sh aft kilns employed energy efficient lining and found a reduction of fuel use from 900 to 920 kcal/kg clinker (3.8 GJ /t clinker) to about 800 kcal/kg clinker (3.4 GJ/t clinker) (ITIB MIC, 2004). The output of the kiln also increased per unit of raw materials input.

Refractories are made by foreign companies operating in China, particularly in the Liaoning Province, such as Refratechnik (G erman) and RHI (Austrian) (Cui, 2006). China also produces medium and smaller refractories but the energy efficiency is poorer than those made by the leading in ternational companies (Cui, 2006).

Kiln Shell Heat Loss Reduction. There can be considerable heat losses through the shell of a cement kiln, especially in the burning zone. The use of better insulating refractories (e.g. Lytherm) can reduce heat losses (Ve nkateswaran and Lowitt, 1988). Refractory

choice is the function of insu lating qualities of the brick and the ability to develop and maintain a coating. The coating helps to reduce heat losses and to protect the burning zone refractory bricks. Estimates suggest that the development of high-temperature insulating linings for the kiln refractori es can reduce fuel use by 0.12 to 0.4 GJ/t of clinker (Lowes and Bezant, 1990; COWIco nsult, 1993; Venkateswaran and Lowitt, 1988). Costs for insulation systems are es timated to be $0.25/annual tonne clinker capacity (Lesnikoff, 1999). Structural consider ations may limit the use of new insulation materials. The use of improved kiln-refractor ies may also lead to improved reliability of the kiln and reduced downtime, reducing pr oduction costs consid erably, and reducing energy needs during start-ups.

Changjiang Cement Factory in Zhejiang City, Jangsu Province applied energy saving kiln lining to its shaft kiln and found energy sa vings of 0.46 to 0.63 GJ /t clinker (ITIBMIC, 2004). In addition to these energy savings, they were able to increase production. Generally this technology is imported (Cui, 2006).

Energy Management and Pr ocess Control Systems. Heat from the kiln may be lost through non-optimal process c onditions or process manage ment. Automated computer control systems may help to optimize the combustion process and conditions. Improved process control will also help to improve the product quality and grindability, e.g. reactivity and hardness of the produced clinker, which may lead to more efficient clinker grinding. In cement plants across the worl d, different systems are used, marketed by

6different manufacturers. Most modern system s use so-called 'fuzzy logic' or expert control, or rule-based cont rol strategies. Expert contro l systems do not use a modeled process to control process conditions, but try to simulate the best human operator, using information from various stages in the process.

One such system, called ABB LINKman, wa s originally developed in the United Kingdom by Blue Circle Industries and SI RA (ETSU, 1988). The first system was installed at Blue Circle's Hope Works in 1985, which resulted in a fuel consumption reduction of nearly 8% (ETSU, 1988). The LI NKman system has successfully been used in rotary kilns (both wet and dry). After th eir first application in 1985, modern control systems now find wider application and can be found in many European plants. Other developers also market ‘fuzzy logic’ contro l systems, e.g., F.L. Smidth (Denmark) Krupp Polysius (Germany) and Mitsui Mining (Japan). Several companies in China also provide optimized information technology for energy ma nagement and process control, such as the

ABB or the Chinese software co mpany Yun Tian (Wang, 2006b).

All foreign produced control systems describe d above report typical energy savings of 3 to 8%, while improving productivity of the k iln. For example, Krupp Polysius reports typical savings of 2.5 – 5%, with similar in creased throughput and increased refractory life of 25 –100%. Ash Grove implemented a fuzzy control system at the Durkee Oregon plant in 1999.

An alternative to expert systems or fuzzy l ogic is model-predictive control using dynamic models of the processe s in the kiln. A model predictive control system was installed at a kiln in South Africa in 1999, reducing energy needs by 4%, while increasing productivity and clinker quality. The payback period of this project is estimated to be 8 months, even with typically very low coal prices in South Africa (Martin & McGarel, 2001a).

Additional process control systems include th e use of on-line anal yzers that permit operators to instantaneously determine the chemical compos ition of raw materials being processed, thereby allowing for immediate ch anges in the blend of raw materials. A uniform feed allows for steadier kiln opera tion, thereby saving ul timately on fuel requirements. Blue Circle’s St. Marys plant (C anada) installed an on- line analyzer in 1999 in its precalciner kiln, and achieved better pro cess management as well as fuel savings.

Energy savings from foreign produced proce ss control systems may vary between 2.5% and 10% (ETSU, 1988; Haspel and He nderson, 1993; Ruby, 1997), and the typical savings are estimated to be 2.5 to 5%. The economics of advanced process control systems are very good and payback periods can be as short as 3 months (ETSU, 1988). The system at Blue Circle's Hope Works (U.K.) needed an i nvestment of £203,000 (1987), equivalent to $0.3/a nnual tonne clinker (ETSU, 1988), including measuring instruments, computer hardware and traini ng. Holderbank (1993) notes an installation cost for on-line analyzers of $0.8 to 1.7/annual tonne clinker. A payback period of 2 years or less is typical for kiln control systems, while often much lower payback periods are achieved (ETSU, 1988; Martin and McGarel, 2001a).

7Process control of the clinker cooler can help to improve heat recovery, material throughput and improved control of free lime c ontent in the clinker, and to reduce NOx emissions (Martin et al., 2000). Installing a Process Perfecter ® (of Pavilion Technologies Inc.) has increased cooler throughput by 10%, reduced fr ee lime by 30% and reduced energy by 5%, while reducing NOx emissions by 20% (Martin et al., 1999; Martin et al., 2001). The installation costs equal $0.35/annual tonne of clinker, with an estimated payback period of 1 year (Martin et al., 2001).

Combustion control in vertical kilns is more difficult than in rotary kilns where the flow of raw materials is controlled by a mechanical ly-rotating horizontally-oriented shaft at a slight angle instead of just gr avity (Liu et al., 1995). In these kilns, operating skills and hence, proper training is more important for energy effi ciency and product quality. If automatic controls are going to be successfully implemented, they must link all processes from mine management to raw materials input in to the kiln to kiln fuel input in order to realize stable production; none should be done manually (ITIBMIC, 2004). Control technologies also exist for c ontrolling the air intake. (For more information on kiln combustion system improvements and controls for VSKs, see “kil n combustion system improvements” in Energy Efficiency Opportu nities for Clinker Pr oduction – Vertical Shaft Kilns, below). Raw materials and fuel mix can be improved by a careful analysis of the chemical and physical ch aracteristics of each, and by automating the weighing process and the pellet production (water conten t and raw feed mixtures), the blending process, the kiln operation (optimizing air flow, temperature distribution, and the speed of feeding and discharging). Cui (2006) repor ts that most technologies for this measure are made by international companies such as Siemens and ABB; few if any are made by domestic companies.

Adjustable Speed Drive for Kiln Fan. Adjustable or variable speed drives (ASDs) for the kiln fan result in reduced power use and reduced maintenance costs. The use of ASDs for a kiln fan at the Hidalgo plant of Cruz Azul Cement in Mexico resulted in improved operation, reliability and a reduction in electricity consumption of almost 40% (Dolores and Moran, 2001) for the 1,000 horsepower moto rs. The replacement of the damper by an ASD was driven by control and maintenance problems at the plant. The energy savings may not be typical for all plants, as the system arrangement of the fans was different from typical kiln arrangements. Fo r example, Fujimoto, (1994) notes that Lafarge Canada’s Woodstock plant repl aced their kiln fans with ASDs and reduced electricity use by 5.5 kWh/t of cement (6.1 kWh/t clinker). The Zhonglida Group, operating ten cement enterprises (with both VSKs and new dry rotary kilns), installed variable speed drives in 40 large motors (over 55 kW) and over 40 of its smaller motors (< 55 KW) and found energy savings of over 30% (I TIBMIC, 2004). ASDs are currently being made in China, although many of the parts and instrumentation are still being imported from Germany and/or Japan (Cui, 2006).

Clinker Making – Rotary Kilns For rotary kilns, an existing preheater kiln may be converted to a multi-stage preheater/precalciner kiln by a dding a precalciner and an ex tra preheater, an existing long dry kiln can be upgraded to use a multi-stag e preheater/precalciner kiln, and older dry kilns can be upgraded to multi- stage preheater/precalciner kilns. Other energy-efficiency

8technologies and measures include kiln com bustion system improvements, reciprocating grate coolers, optimize heat recovery and upg rade the clinker cooler , seal replacement, low temperature waste heat recovery for po wer generation, high temperature waste heat recovery for power generation, low pressure dr op cyclones for suspen sion preheaters, and efficient kiln drives. Table 4 provides in formation on the initial capital costs, the operations and maintenance (O &M) costs, the simple payb ack period, the specific fuel savings, the specific electric savings, the speci fic carbon dioxide savings and the lifetime

associated with each of these measures.

Installation or Upgrading of a Preh eater to a Preheater/Precalciner Kiln. An existing preheater kiln may be converted to a multi-st age preheater/precalciner kiln by adding a precalciner and, when possible an extra preh eater. The addition of a precalciner will generally increase the capacity of the plant, while lowering the specific fuel consumption and reducing thermal NOx emissions (due to lower combustion temperatures in the precalciner). Using as many features of the ex isting plant and infrastructure as possible, special precalciners have been developed by various manufacturers to convert existing plants, e.g. Pyroclon®-RP by KHD in Germ any. Generally, the kiln, foundation and towers are used in the new plant, while cooler and preheaters are replaced. Cooler replacement may be necessary in order to increase the cooling capacity for larger production volumes. The conversion of a plant in Italy, using the existing rotary kiln, led to a capacity increas e of 80 to 100% (from 1100 tpd to 2000 to 2200 tpd), while reducing specific fuel consumption from 3.6 to 3.1-3.2 GJ /t clinker, resulting in savings of 11 to 14% (Sauli, 1993). Fuel savings will depend st rongly on the efficiency of the existing kiln and on the new process para meters (e.g. degree of precalcination, c ooler efficiency). The European Commission (2000) estimates a multi-stage preheater/pre calciner kiln uses approximately 3 GJ/t clinker.

Older precalciners can also be retrofitted for energy efficiency improvement and NOx emission reduction. Retrofitting the precalciner at the Lengerich plant of Dyckerhoff Zement (Germany) in 1998 reduced NOx emissions by almost 45% (Mathée, 1999).

Similar emission reductions have been found at kilns in Germany, Italy and Switzerland (Menzel, 1997). Ash Grove’s Durkee, Or egon original 1979 pl ant installed new preheaters and a precalcin er in 1998, expanding producti on from 1500 tonnes/day to 2500 tonnes/day (Hrizuk, 1999). The reconstruc tion reduced fuel consumption by 0.16 to 0.7 GJ/t clinker (Hrizuk, 1999), while reducin g NOx emissions. Capitol Cement (San Antonio, Texas) replaced an ol der in-line precalciner with a new downdraft precalciner to improve production capacity. This was part of a larger project replacing preheaters, installing SOx emission reduction equipment, as well as increasing ca pacity of a roller mill. The new plant was successfully commissi oned in 1999. Fuel consumption at Capitol

Cement was reduced to 3.4 GJ/t clinker (Frailey & Happ, 2001).

9Table 4. Energy-Efficien cy Opportunities Applicable to Rotary Kilns.

Capital

Costs ($/t) O & M

Costs ($/t) 1 Payback

Period (years) Fuel Savings (GJ/t) Electric Savings (kWh/t) 2 CO 2 savings (kgC/t) Lifetime (years)

Preheater kiln upgrade to precalciner kiln 9.4-28 -1.1 5 0.16-0.7 4.1-18.1 40

Long dry kiln upgrade to preheater/precalciner kiln 8.6-29 > 10 1.4

- 36 40

Older dry kiln upgrade to multi-stage preheater kiln 28-41 > 10 0.9

- 23 40

Convert to reciprocating grate cooler 0.4-5.5 0.11 1-2 0.27 -3.0 6.3 20

Kiln combustion system improvements 1.0 0 2 – 3 0.1-0.5

- 2.6-12.9 20

Indirect Firing 7.4 NA 0.015-0.022

- 0.39-0.57 NA

Optimize heat recovery/upgrade clinker

cooler 0.1-0.3 1-2 0.05-0.16 -2 0.8-3.7 20

Seal replacement NA ≤ 0.5 0.011

- 0.3 NA

Low temperature heat recovery for power (capital costs given in $/kW) 800-1250 ($/kW) 3 0.007 < 3

- 20-35 4.6-8.1 NA

High temperature heat recovery for

power 2.2-4.4 0.22-0.33 3

- 22 5.1 35

Low pressure drop cyclones 3 > 10

- 0.7-4.4 0.16-1.0 20

Efficient kiln drives +0-6% 4 NA

- 0.55-3.9 0.13-0.9 10 Note: Energy savings and costs below are based on case study data. Costs in China will vary depending on technology and availability. Where possible, we have included more data for China in the following text. All data are given per tonne of clinker. For U.S. data, the estimated savings and payback periods are based on the average performance of the U.S. cement industry (e.g. clinker to cement ratio).

1 Negative numbers represen t operation and maintenance savings

. 2 Negative numbers represent an increase in electricity due to the measure.

3 Domestic technology cost is 6000 to 10,000 RMB per investment, which is about 10 ,000 RMB less than foreign

technology (16,000 to 22,000 RMB per kW). We use estimat es from Chinese case studies to determine the numbers

in the tables above.

4 Initial costs given as the additional % required relative to standard U.S. technology (0 to 6%).

NA = data not available

According to Sauli (1993), average savings of new precalciners can be 0.4 GJ/t clinker. Sauli (1993) does not outline the investments made for the conversion project. Vleuten (1994) estimates the cost of adding a precal ciner and suspension preheaters to be $28 U.S./annual tonne clinker annual capacity (it is not clear what is included in this estimate). Jaccard and Willis (1996) estimat e a much lower cost of $9.4/t clinker capacity. The increased production capacity is likely to save considerably in operating costs, estimated to be $1.1/t clinker (J accard & Willis, 1996).The Hejiashan Cement Company, Ltd. in Jiangshan City, Zhejiang Pr ovince installed two new dry process kilns

in 2001 and 2003 at a cost of 105 million RMB for a 1000 tonne per day kiln and 156 million RMB for a 1500 tonne per day kiln, respectively (ITIBMIC, 2004). This equates to roughly 300 RMB/t clinker ($37 U.S./t). Power consumpti on is expected to be 85.87 kWh/t clinker and fuel consumption 2.5GJ/t clinker for the 1000 t onne per day kiln.

Cui (2006) reports that many precalciner ki lns have been constructed from 2001 and about 10 to 20% are imported while 80 to 90% are domestic technology. Cui states that domestic technology, made by a few leading ma nufacturers in China, costs roughly 1/3 to 1/5 the cost of imported technology but doe sn’t last as long. Most companies are

10adopting domestic technologies (Cui, 2006) . Domestic technology, however, is not

available for kiln sizes over 5000 tonne per day (Wang, 2006b).

Conversion of Long Dry Kilns to Preheater/Precalciner Kiln. A long dry kiln can be upgraded to the current state of the art multi-stage preheate r/precalciner kiln. Energy savings are estimated to be 1.4 GJ/t clinker for the conversion. These savings reflect the difference between the average dry kiln specif ic fuel consumption and that of a modern preheater, pre-calciner kiln based on a st udy of the Canadian cement industry and the retrofit of an Italian plan t (Holderbank, 1993; Sa uli, 1993). The Holderbank study gives a range of $23 to 29/t clinker for a pre-heater, pre-calciner kiln. J accard and Willis (1996) give a much lower value of $8.6/t clinker capacity.

Dry Process Upgrade to Mu lti-Stage Preheater Kiln. Older dry kilns may only preheat in the chain section of the long kiln, or may have single- or two-stage preheater vessels. Installing multi-stage suspension preheating (i.e . four- or five-stage ) may reduce the heat losses and thus increase efficiency. Modern cyclone or suspension preheaters also have a reduced pressure drop, leading to increased h eat recovery efficiency and reduced power use in fans (see low pressure drop cyclone s above). By installing new preheaters, the productivity of the kiln will increase, due to a higher degree of pre-calcination (up to 30 to 40%) as the feed enters th e kiln. Also, the kiln length may be shortened by 20 to 30% thereby reducing radiation losse s (van Oss, 1999). As the cap acity increases, the clinker cooler may have to be adapted to be able to cool the large amounts of clinker. The

conversion of older kilns is at tractive when the old kiln need s replacement and a new kiln would be too expensive, assuming that limestone reserves are adequate.

Energy savings depend strongly on the specifi c energy consumption of the dry process

kiln to be converted as well as the number of preheaters to be installed. For example,

cement kilns in the former German Democr atic Republic were rebuilt by Lafarge to replace four dry process k ilns originally constructed in 1973 and 1974. In 1993 and 1995, three kilns were equipped with four-stage suspension preheaters. The specific fuel consumption was reduced from 4.1 GJ/t clinker to 3.6 GJ/t clinker, wh ile the capacity of

the individual kilns was increased fr om 1650 to 2500 tpd (Duplouy and Trautwein, 1997). In the same project, the power consumption was reduced by 25%, due to the replacement of fans and the finish grinding mill. Energy savings are estimated to be 0.9

GJ/t clinker for the conversion which reflects the difference be tween the average dry kiln specific fuel consumption and that of a m odern preheater kiln, based on a study of the Canadian cement industry (Holderbank, 1993). The study estimates the specific costs at $39 to 41/annual tonne clinker capacity for co nversion to a multi-stage preheater kiln while Vleuten (1994) estimates a cost of $28/annual tonne clinker capacity for the installation of suspen sion pre-heaters.

Conversion to Reciproc ating Grate Cooler. Four main types of c oolers are used in the cooling of clinker: (1) shaft; (2) rotary; (3) planetary; and, (4) reciprocating grate coolers. There are no longer any rotary or shaft coolers in operation in North America; in China, there are few if any rotary or shaft coolers (Cui, 2006). However, some reciprocating grate coolers may still be in operation.

11The grate cooler is the modern variant and is used in almost a ll modern kilns. The advantages of the grate cooler are its larg e capacity (allowing large kiln capacities) and efficient heat recovery (the temperature of th e clinker leaving the cooler can be as low as 83°C, instead of 120 to 200°C, which is expected from planetary coolers (Vleuten, 1994). Tertiary heat recovery (needed for precalci ners) is impossible with planetary coolers (Cembureau, 1997b), limiting heat recovery e fficiency. Grate coolers recover more heat than do the other types of coolers. For large capacity plants, grate coolers are the preferred equipment. For plants producing less than 500 tonnes per day the grate cooler may be too expensive (COWIconsult et al., 1993). Replaceme nt of planetary cooler s by grate coolers is not uncommon (Alsop and Post, 1995).

Modern reciprocating coolers have a higher degree of heat recovery than older variants, increasing heat recovery efficiency to 65% or higher, while reduci ng fluctuations in recuperation efficiency (i.e. increasing producti vity of the kiln). In China, the Liulihe Cement Factory implemented a TCIDRI third ge neration grate cooler and achieved a heat recovery rate of over 72% on a 2500 tonne/d ay precalciner kiln (ITIBMIC, 2004). This aerated beam grate cooler also saves water by replacing the water spray cooling with air cooling (ITIBMIC, 2004). When compared to a planetary cool er, additional heat recovery is possible with grate coolers at an extra power consumptio n of approximately 3.0 kWh/t clinker (COWIconsult et al., 1993; Vleuten, 19 94). The savings are estimated to be up to 8% of the fuel consumption in the kiln (V leuten, 1994). Cooler co nversion is generally economically attractive only when installing a precalciner, which is necessary to produce the tertiary air (see above), or when expanding production capacity. The cost of a cooler conversion is estimated to be between $. 044 and $5.5/annual tonne clinker capacity, depending on the degree of reconstruction needed. Annual operation costs increase by $0.11/t clinker (Jaccard and Willis, 1996).

Kiln Combustion System Improvements. Fuel combustion systems in kilns can be

contributors to kiln inefficiencies with such problems as poorly adjusted firing, incomplete fuel burn-out with high CO formation, and combus tion with excess air (Venkateswaran and Lowitt, 1988). Improved combustion systems aim to optimize the shape of the flame, the mixing of combustion air and fuel and reducing the use of excess air. Various approaches have been developed. One techniqu e developed in the U.K. for flame control resulted in fuel savings of 2 to 10% depending on the kiln type (Venkateswaran and Lowitt, 1988). Lowes an d Bezant, (1990) discuss advancements from combustion technology that improve combustion through the use of better kiln control. They also note that fuel savings of up to 10% have been demonstrated for the use of flame design techniques to eliminate reducing conditions in the clinkering zone of the kiln in a Blue Circle plant (Lowes and Bezant, 1990).

For rotary kilns, the Gyro-Therm technology improves gas flame quality while reducing NOx emissions. Originally developed at the Univ ersity of Adelaide (Australia), the GyroTherm technology can be applied to gas burners or gas/coal dual fuel. The Gyro-Therm burner uses a patented "precessing jet" t echnology. The nozzle desi gn produces a gas jet leaving the burner in a gyroscopic-like prece ssing motion. This stirri ng action produces rapid large scale mixing in wh ich pockets of air are engulfe d within the fuel envelope without using high velocity gas or air jets. The combustion takes place in pockets within

12the fuel envelope under fuel rich conditions. This creates a highly luminous flame, ensuring good irradiative heat transfer. A demo nstration project at an Adelaide Brighton plant in Australia found average fuel savings between 5 and 10% as well as an increase in output of 10% (CADDET, 1997a). A second de monstration project at the Ash Grove plant in the U.S. (Durkee, Oregon) found fuel savings between 2.7% and 5.7% with increases in output between 5 and 9% (C ADDET, 1997a; Videgar, Rapson and Dhanjal, 1997). Costs for the technology va ry by installation. An averag e cost of $1/annual tonne clinker capacity is assumed based on repor ted costs in the demonstration projects.

Indirect Firing. Historically the most common firing system is the direct-fired system. Coal is dried, pulverized and cl assified in a continuous syst em, and fed directly to the kiln. This can lead to high levels of primary air (up to 40% of stoich iometric). These high levels of primary air limit the amount of s econdary air introduced to the kiln from the clinker cooler. Primary air percentages va ry widely, and non-optimized matching can cause severe operational problem s with regard to creating re ducing conditions on the kiln wall and clinker, refractory wear and reduced efficiency due to having to run at high

excess air levels to ensure effective bu rnout of the fuel within the kiln.

In more modern cement plants, indirect fire d systems are most commonly used. In these systems, neither primary air nor coal is fed di rectly to the kiln. All moisture from coal drying is vented to the atmosphere and the pul verized coal is transported to storage via cyclone or bag filters. Pulveri zed coal is then densely conve yed to the burner with a small amount of primary transport air (Smart and Je nkins, 2000). As the primary air supply is decoupled from the coal mill in multi-channel designs, lower primary air percentages are used, normally between 5 and 10%. The multi-channel arrangement also allows for a degree of flame optimization. This is an import ant feature if a range of fuels is fired. Input conditions to the multi-channel burner must be optimized to secondary air and kiln aerodynamics for optimum operation (Smart a nd Jenkins, 2000). The optimization of the

combustion conditions will lead to reduced NOx emissions, better operation with varying fuel mixtures, and reduced energy losses. This technology is standard for modern plants.

Excess air infiltration is estimated to result in heat losses equal to 75 MJ/t of clinker. Assuming a reduction of excess air between 20 % and 30%, indirect firing may lead to fuel savings of 15 to 22 MJ/t of clinker. The advantages of improved combustion conditions will lead to a longer lifetime of the kiln refractories and reduced NOx emissions. These co-benefits may result in la rger cost savings than the energy savings

alone.

The disadvantage of an indir ect firing system is the addi tional capital co st. In 1997, California Portland’s plant in Colton, Californi a implemented an indirect firing system for their plant, resulting in NOx emission re ductions of 30 to 50%, using a mix of fuels including tires. The investment costs of the indirect firing system were $5 million for an annual production capacity of 680,000 t onnes clinker, or $7.4/t clinker.

Optimize Heat Recovery/Upgrade Clinker Cooler. The clinker cooler drops the clinker temperature from 1200°C down to 100°C. The most common cooler designs are of the

13planetary (or satellite), trav eling and reciprocating grate type. All coolers heat the secondary air for the kiln combustion process and sometimes also tertiary air for the precalciner (Alsop and Post, 1995). Reciprocating grate cool ers are the modern variant and are suitable for large-scal e kilns (up to 10,000 tpd). Grat e coolers use electric fans and excess air. The highest temperature port ion of the remaining air can be used as tertiary air for the precalciner. Rotary coolers (used for approximately 5% of the world clinker capacity for plants up to 2200 to 5000 tpd) and plan etary coolers (u sed for 10% of the world capacity for plants up to 3300 to 4400 tpd) do not need combustion air fans and use little excess air, resulting in relatively lower heat losses (Buzzi and Sassone, 1993; Vleuten, 1994).

Grate coolers may recover between 1.3 and 1.6 GJ/t clinker sensible heat (Buzzi and Sassone, 1993). Improving heat rec overy efficiency in the cool er results in fuel savings, but may also influence product quality and emission levels. Heat recovery can be improved through reduction of excess air vol ume (Alsop and Post, 1995), control of clinker bed depth and new grates such as ri ng grates (Buzzi and Sa ssone, 1993; Lesnikoff, 1999). Control of cooling air distribution ove r the grate may result in lower clinker temperatures and high air temperatures. Additional heat recovery results in reduced energy use in the kiln and prec alciner, due to higher com bustion air temperatures. Birch, (1990) notes a savings of 0.05 to 0.08 GJ/t clinker through the improved operation of the grate cooler, while Holderbank, (1993) notes savings of 0.16 GJ/t cli nker for retrofitting a grate cooler. COWIconsult et al. (19 93) note savings of 0.08 GJ/t clinker but an increase in electricity use of 2.0 kWh/t clinker. The co sts of this measure ar e assumed to be half the costs of the replacement of the planetar y with a grate cooler , or $0.22/annual tonne clinker capacity.

A recent innovation in clinker coolers is the inst allation of a static gr ate section at the hot

end of the clinker cooler. This has result ed in improved heat recovery and reduced

maintenance of the cooler. Modification of the cooler would result in improved heat recovery rates of 2 to 5% over a conventiona l grate cooler. Investments are estimated to be $0.11 to $0.33/annual tonne clinker capacity (Young, 2002).

Seal Replacement. Seals are used at the kiln inlet and ou tlet to reduce false air penetration, as well as heat losses. Seals may start leaki ng, increasing the heat re quirement of the kiln. Most often pneumatic and lamella-type seals ar e used, although other designs are available (e.g. spring-type). Although seals can last up to 10,000 to 20,000 hour s, regular inspection may be needed to reduce leaks. Energy losse s resulting from leakin g seals may vary, but are generally relatively small. Philips Kiln Serv ices (2001) reports that upgrading the inlet pneumatic seals at a relatively modern plan t in India (Maihar Cement), reduced fuel consumption in the kiln by 0.4% (0.011 GJ /t clinker). The payback period for improved

maintenance of kiln seals is es timated to be 6 months or less (Canadian Lime Institute, 2001). This technology is produced and ava ilable domestically in China (Cui, 2006).

Low Temperature Heat Recove ry for Power Generation 1

. Despite government

1 The adoption of low temperature wast e heat recovery for electricity pr oduction in cement plants changes the temperature profile of the flue gas which may imp act the low-temperature, cat alytic dioxin formation

14policies to promote adoption of the technology (through the China Medium and Long Term Energy Conservation Plan , for example), using low temperature waste heat for power generation has not been widely adopt ed by Chinese cements plants (GEI, 2005) although 45 cement rotary kilns have alrea dy adopted this measure (Cui, 2006). Even many large-scale rotary kilns built after 2003 do not us e this technology. One plant has utilized this technology, received through donation from Japan (GEI, 2005). The Anhui Ningguo cement plant installed a power genera tion system on a 4000 tonne per day kiln cement production line and found electricity generated reached 39 kWh per tonne of clinker since operation be gan in 1998 (Anhui Ninggou, 2002) . Pan (2005) estimates a cost for imported (Japanese) technol ogy of 18,000 to 22,000 RMB ($2,250 to $2,750) per kW with an installation capacity ove r 6 MW. Chinese domestic technology was developed in 1996 and is currently availabl e from three Chinese companies: Tianjin Designing Institute of Cement Industr y, Zhongxin Heavy Machine Company, and

Huaxiao Resource Co. Ltd. All three companies have on-going demonstration programs in Chinese cement plants. In stallation cost of domestic technology and equipment is currently about 10,000 RMB ($1,250) per kW. The installation cost would be a bit lower if kilns and generation system are constructed simultaneously. At China United Cement Company, two 6000 kW systems were installed for RMB 101.8 million ($12.7 million 2006 U.S.), RMB 36 million ($4.5 million 2006 U.S.) of private capital and RMB 64 million of bank loans ($8 million 2006 U.S.), equaling about RMB 8500 per kW (CNBM, 2005). The electricity being generated is 79.8 kWh/t clinker. Beijing Cement Ltd. also

installed waste heat recovery equipment on its 2400 tpd and 3200 t pd kilns (BEIC, 2006). Total capacity is now 7.5 MW and the total investment was RMB 47.43 million ($6 million 2006 U.S.), equaling about 6,300 RMB per kW ($800 2006 U.S. per kW). Of this, 70% was provided by the Beijing Energy Investment Company.

In another demonstration project summarized by GEI (2005), the waste heat from two

clinker kilns of Taishan Cement Ltd is to be used. The capac ity of the two kilns is 5000 tonnes per day and 2500 tonnes per da y. Operation was to begin on 1 st Oct 2005; equipment has already been installed but is still under adjustment . Maximum capacity is designed at 13.2 MW and annual output of 95 GWh. Of this, 90.8 GWh would be supplied to cement production, accounting for mo re than 30% of the energy needs of cement production (Guo, 2004).

ITIBMIC (2004) estimates for a 2000 tonne per day (730,000 a nnual tonne) kiln capacity, about 20 kWh/t clinker of electricity could be generated for an investment of 20 to 30

million RMB.

reactions. Heat recovery from waste-to-energy boilers increases the residence time for the flue gas at the dioxin formation temperature window (700 -200 C) increases dioxin formation. Flue gas cooling temperature profile is one the important factors determining dioxin formation potential of a combustion facility. Some hazardous waste inci nerators use rapid flue gas quenching to reduce residence time of the flu gas passing through the formation window for controlling dioxin formation. On the other hand, it may be due to less boiler surface area in the optimum temperature window in quenched vs. non-quenched systems, rather than a gas residence time. The su rface area tends to accumulate reactive carbon and trace metals. More area likely means higher D/F concentrations. Research is n eeded to find out whether there is significant effect of waste heat recovery on dioxin emissions from cement kilns (Lee, 2006; Gullett, 2006).

15In May 2002, the Tianjin Cement Industry De sign and Research Inst itute in cooperation with the Shanghai Wanan Enterprise Cor poration began renovations on a 1350 tonne four-stage cyclone preheater kiln to genera te low-temperature waste heat electricity (ITIBMIC, 2004). They installed domestic low temperature waste heat recovery technology, and the facility now generates over 1.8 MW of electricity, operating 7000 hours per year. Including the 10% electricity re quired to operate the system, the facility generates an additional 11.34 GWh annually. W ith an electricity price of 0.50 RMB/kWh, the Tianjin Cement plant found savings of 11 to 14 RMB per tonne of clinker. The operating cost is about 0.06 RMB/kWh and the payback period about 3 years. Lowtemperature waste heat recovery has been impl emented at other plants, as well, including the 4000 tonne/day precalciner kiln at the Ningguo Cement Factory of the Conch Group and the Liuzhou Cement Factory (ITIBMIC, 2004).

ITIBMIC (2004) reports genera ting capacity of domestic te chnology to be approximately 24 to 32 kWh, while foreign technology will generate about 28 to 36 kWh. Cui (2006) most recently reported domestic technol ogy could produce 35kWh /t of clinker while Japanese technology now produces 45 kWh/t of clinker; German technology better but no data is available. Investment, however, is much less – about 6000 RMB for domestic technology and 16,000 RMB for foreign equipmen t. Running time and required labor are approximately the same.

High Temperature Heat Recov ery for Power Generation. Waste gas discharged from the kiln exit gases, the clinker cooler system, and the kiln pre-heater system all contain useful energy that can be conve rted into power. In the U.S., only in long-dry kilns is the temperature of the exhaust gas sufficiently high to cost-effectively recover the heat through power generation. 2 Cogeneration systems can either be direct gas turbines that utilize the waste heat (top cycl e), or the installation of a wa ste heat boiler system that runs a steam turbine system (bottom cycle). This measure focuses on the steam turbine system since these systems have been inst alled in many plants worldwide and have proven to be economic (Steinbliss, 1990; Jaccard and Willis, 1996; Neto, 1990). Heat recovery has limited application for plants with in-line raw mills, as the heat in the kiln exhaust is used for raw material drying. While electrical efficiencies are still relatively low (18%), based on several case studies power generation may vary between 11 and 25 kWh/t clinker (Scheuer & Sprung, 1990; St einbliss, 1990; Neto, 1990). Electricity savings of 22 kWh/t clinker are assumed. Jaccard and Willis (1996) estimate installation costs for such a system at $2.2 to 4.4/annual to nne clinker capacity with operating costs of $0.22 to 0.33/t clinker. In 1999, four U.S. cement plants cogenerated 486 million kWh (USGS, 2001). In China, most high temp wa ste heat is recycled to the preheated and precalciner.

Low Pressure Drop Cyclones for Suspension Preheaters. Cyclones are a basic component of plants with pre-heating system s. The installation of newer cyclones in a

2 Technically, organic rankine cycles or Kalina cycles (using a mixture of water and ammonia) can be used to recover low-temperature waste heat for power production, but this is currently not economically attractive, except for locations with high power costs. In China, however, low temperature heat is being recovered; see previous measure for details.

16plant with lower pressure losses will reduce the power consumption of the kiln exhaust gas fan system. Depending on th e efficiency of the fan, 0.66 to 0.77 kWh/t clinker can be saved for each 50 mm W.C. (water column) the pressure loss is reduced. For most older kilns this amounts to savings of 0.66 to 1.1 kWh/t clinker (Birc h, 1990). Fujimoto (1994) discussed a Lehigh Cement plant retrofit in which low-pressure drop cyclones were

installed in their Mason Cit y, Iowa plant and saved 4.4 kW h/t clinker (Fujimoto, 1994). Installation of the cyclones can be expensive, however, since it may often entail the rebuilding or the modification of the preheater tower, and the costs are very site specific. Also, new cyclone systems may increase ove rall dust loading and increase dust carryover from the preheater tower. However, if an inline raw mill follows it, the dust carryover problem becomes less of an issue. A cost of $3/annual tonne clinker is assumed for a low-pressure drop cyclone system. The best technology available in China is imported from the Austrian PMT Company (Cui, 2006).

Efficient Kiln Drives. A substantial amount of power is used to rotate the kiln. The highest efficiencies are achie ved using a single pinion drive with an air clutch and a synchronous motor (Regitz, 1996). The system would reduce power use for kiln drives by a few percent, or roughly 0.55 kWh/t clinker at slightly higher capita l costs (+6%). More recently, the use of alternate current (AC) moto rs is advocated to replace the traditionally used direct current (DC) drive. The AC mo tor system may result in slightly higher efficiencies (0.5 – 1% reducti on in electricity use of the kiln drive) and has lower investment costs (Holland, 2001). Using high-effi ciency motors to replace older motors or instead of re-winding old motors may reduce power costs by 2 to 8%.

Clinker Making – Vert ical Shaft Kilns For vertical shaft kilns, the main energy-e fficiency opportunity is to replace the VSK with new suspension preheater/precalciner kilns. In addition, combustion system improvements can be made for the kiln. Ta ble 5 provides information on the initial capital costs, the operations and maintenan ce (O&M) costs, the simple payback period, the specific fuel savings, the specific electric savings, the specific carbon dioxide savings

and the lifetime associated with each of these measures.

Replace vertical shaft kiln with new su spension preheater/precalciner kilns. The new suspension preheater (NSP) technique is being developed for 1000 t/day, 2000 t/day and 4000 t/day (GEI, 2005). NSP should be used fo r medium- or large- scale cement plants that are being either enlarged or rebuilt. For the small cement plants, earthen vertical kiln (and hollow rotary kiln with dry method) should be gradually abandoned. Further description of these kilns is made above.

According to Liu et al. (1995), some “key” Chinese plants 3 use 5.4 GJ/t clinker, while advanced precalciner kilns use about 3 GJ/t cl inker; a savings of 2.4 GJ/t clinker. The Liulihe Cement Factory installed a precalci ner kiln with a 5-st age preheater and a preburning furnace and found fuel consumption to be 3.011 GJ/t (ITIBMIC, 2004).

3 “Key” Chinese plants generally refer to large, cent rally administered state-owned enterprises (Sinton, 1996).

17Table 5. Energy-Efficien cy Opportunities Applicable to Vertical Shaft Kilns.

Capital Costs ($/t) O & M

Costs ($/t) Payback

Period (years) Fuel Savings (GJ/t) Electric Savings (kWh/t) CO 2 savings (kgC/t) Lifetime (years)

Convert to new suspension preheater/precalciner kiln 28-41 NA 5-7 1 2.4

- 62 40

Kiln combustion system improvements NA NA NA NA NA NA NA

Note: Energy savings and costs below are based on case study data. Costs in China will vary depending on technology and availability. Where possible, we have included more data for China in the following text. All data are given per tonne of clinker.

1 Payback period calculated using approx imate costs of bituminous coal for industrial boilers (bitu2) in China for the year 2005 (approximately $55/t coal). NA = data not available; efficiency data unavailable because case studies genera lly measure fuel savings for a package of measures; individual measures are rarely applied and hence, savings for th em are often not measured or calculated (Liu et al, 1995). For example, Liu et al. (1995) reports a package of measures for VSKs usually result in a 10-30% savings in fuel intensity and a payback period of 2 years.

By the end of 2004, China put into service 140 new suspen sion preheater/precalciner (NSP) and suspension preheater (SP) kilns; of those, 50 were new in 2004 (Cui, 2004). For more information on this technology, al so see measures in Energy Efficiency Opportunities for Clinker Production – Rotary Kilns Section, above.

Kiln Combustion System Improvements. Fuel combustion systems in kilns can be contributors to kiln inefficiencies, often resu lting in higher CO formation. Inefficiencies are caused by incomplete combustion of fuel, combustion with excess or inadequate air, uneven air distribution, and oversupply of coal (Venkateswaran and Lowitt, 1988; Liu et al., 1995). Inadequate blower capacity and leakage can result in insufficient air supply. Improvement of air distribution requires bett er quality raw material pellets and precise kiln operation. Sophisticated VSKs are m echanized with automatic feeding and discharging equipment, while older VSKs are still operated manually (Liu et al., 1995). Oversupply of coal often results from coal powder that has been overground, supplying high fuel density. At low temperatures a nd insufficient oxygen, overground coal reacts

with CO 2 and generates CO. More information on automation of the kiln, feed, and blending can be found in the measure “E nergy Management and Process Control Systems”, above.

In China, domestic technologies are being us ed for medium and small cement plants; for larger plants, many are using im ported technologies (Cui, 2006).

Finish Grinding Table 6 shows fuel and electricity savings, estimated payback period and carbon dioxide (CO 2 ) savings for each measure related to final grinding. A description for each measure is given below.

Process Control and Manage ment – Grinding Mills. Control systems for grinding operations are developed using the same approaches as for kilns (see above). The systems control the flow in the mill and classifiers, attaining a stable and high quality product. Several systems are marketed by a number of manufacturers. Expert systems have been commercially available since the early 1990 ’s. The Karlstadt plant of Schwenk KG

18(Germany) implemented an expert system in a finishing mill in 1992, increasing mill throughput and saving energy. The payback is estimated between 1.5 and 2 years in Germany (Albert, 1993). Magotteaux (Belgium) has marketed a control system for mills since 1998 and has sold six units to plan ts in Germany (Rohrdorfer Zement), Greece (Heracles General Cement), South Africa (PPC Group) and the United Kingdom (UK) (Rugby Group). Experience with a cement mill at the South Ferriby plant of the Rugby Group in the UK showed increased production (+3.3%) and power savings equal to 3%,

while the standard deviation in fineness went down as well (Van den Broeck, 1999). Krupp Polysius markets the PolExpert syst em and reports energy savings between 2.5 and 10% (typically 8%), with increased pr oduct quality (lower deviation) and production increases of 2.5 –10%, after installing control systems in finishing mills (Goebel, 2001).

Similar results have been achieved with mode l predictive control (using neural networks) for a cement ball mill at a South-African cement plant (Martin and McGarel, 2001a). Pavilion Technologies (US) has developed a ne w control system using neural networks. Pavilion Technologies reports a 4-6% throughput increase (and corresponding reduction in specific power consumption) for installing a model predictive control system in finish ball mill (Martin et al., 2001). Payback periods are typically between 6 and 8 months (Martin and McGarel, 2001a).

Table 6. Energy Efficiency Measures for Final Grinding of Products in Cement Plants. More information can be found in the description of the measures below.

Energy Efficiency Measure (for Finish Grinding) Fuel Savings (GJ/t) Electricity Savings (kWh/t) Estimated Payback Period (years) (1) CO 2 Savings (kgC/t)
Energy Management & Process Cont rol

- 3.8-4.2 < 1 to 2 0.9-1.0 High Pressure Roller Press

- 8-28 > 10 (1) 1.8-6.3 High-Efficiency Classifiers

- 1.9-6.0 > 10 (1) 0.4-1.4 Improved Grinding Media in Ball Mills

- 3-5 8 (1) 0.7-1.2

Notes: All data is given per tonne of cement

(1) Payback periods are calculated on the basis of energy savi ngs alone. In reality this investment may be driven by other considerations than energy efficiency (e.g. productivity , product quality), and will happen as part of the normal business cycle or expansion project. Under these conditions the measure will have a lo wer payback period depending on plant-specific conditions.

Advanced Grinding Concepts. The energy efficiency of ball mills for use in finish grinding is relatively low, consuming up to 30-42 kWh/t clinker depending on the fineness of the cement (Marchal, 1997; Cembureau, 1997b). Several new mill concepts exist that can significantly reduce power cons umption in the finish mill to 20-30 kWh/t clinker, including roller presses, roller mills, and roller presses used for pre-grinding in combination with ball mills (Alsop and Post, 1995; Cembureau, 1997b; Seebach et al.

, 1996). Roller mills employ a mix of compressi on and shearing, using 2-4 grinding rollers carried on hinged arms riding on a horizon tal grinding table (Cembureau, 1997b; Alsop and Post, 1995). In a high-pressure roller press, two rollers pressurize the material up to 3,500 bar (Buzzi, 1997), improving the grinding e fficiency dramatically (Seebach et al., 1996).

Air swept vertical roller mills with integral classifiers are used for finish grinding, whereas a recent off-shoot technology which is not air swept is now being used as a pregrinding system in combination with a ball mill. A variation of the roller mill is the air

19swept ring roller mill, which has been shown to achieve an electricity consumption of 25 kWh/t with a Blaine of 3000 (Folsberg, 1997). A new mill concept is the Horomill, first demonstrated in Italy in 1993 (Buzzi, 1997). In the Horomill, a horizontal roller within a cylinder is driven. The centrifugal forces re sulting from the movement of the cylinder cause a uniformly distributed layer to be carri ed on the inside of the cylinder. The layer passes the roller (with a pre ssure of 700-1000 bar) (Marchal, 1997). The finished product is collected in a dust filter. The Horomill is a compact mill that can produce a finished product in one step and hence has relatively low capital costs. Grinding Portland cement

with a Blaine of 3200 cm 2 /g consumes approximately 23 kWh/t (Buzzi,1997) and even for pozzolanic cement with a Blaine of 4000, power use may be as low as 30 kWh/t (Buzzi,1997).

Today, high-pressure roller pres ses are most often used to expand the capacity of existing grinding mills, and are found especially in coun tries with high electricity costs or with poor power supply (Seebach et al, 1996). After the first demonstration of the Horomill in Italy, this concept is now al so applied in plants in Mexico (Buzzi, 1997), Germany, Czech Republic and Turkey (Duplouy and Tr autwein, 1997). New designs of the roller mills allow for longer operation times (> 20, 000 hours). The electricity savings of a new finish grinding mill when replacing a ball mill is estimated to be 28 kWh/t cement. The addition of a pre-grinding syst em to a ball mill will result in savings of 7- 24 kWh/t cement for (Cembureau, 1997b; Holland et al., 1997; Scheuer and Sprung, 1990) Capital cost estimates for installing a new roller press vary widely in the litera ture, ranging from low estimates like $2.5/annual tonne cement capac ity (Holderbank, 1993) or $3.6/annual tonne cement capacity (Kreisberg, 1993) to high estimates of $8/annual tonne cement capacity (COWIconsult et al. , 1993). The capital costs of roller press systems are lower than those for other systems (Kreisberg, 1993) or at l east comparable (Patzelt, 1993). Some new mill concepts may lead to a reduction in opera tion costs of as much as 30-40% (Sutoh et al

., 1992).

High Efficiency Classifiers. A recent development in efficient grinding technologies is the use of high-efficiency cla ssifiers or separators. Classifi ers separate the finely ground particles from the coarse particles. The large particles are then recycl ed back to the mill. Standard classifiers may have a low separation efficiency, whic h leads to the recycling of fine particles, resulting in extra power us e in the grinding mill. In high-efficiency classifiers, the material is more cleanly separated, thus reduc ing over-grinding. High efficiency classifiers or separators ha ve had the greatest impact on improved product quality and reducing elec tricity consumption.

A study of the use of high efficiency classi fiers in Great Britain found a reduction in electricity use of 7 kWh/t cement after the inst allation of the classifiers in their finishing mills and a 25% production increase (Parkes, 1990). Holderbank (1993) estimates a reduction of 8% of electricity use (6 kWh /t cement) while other studies estimate 1.9-2.5 kWh/t cement (Salborn and Chin-Fatt, 1993; Süssegger, 1993). Newer designs of highefficiency separators aim to improve the separation efficiency further and reduce the required volume of air (hence reducing power use), while optimizing the design. All major suppliers market new classifier designs, e.g. Polysius (SEPOL), F. L.

20Smidth/Fuller and Magotteaux (Sturtevant SD). The actual savings will vary by plant and cement type and fineness required. For example, the electricity savings from installing a new high-efficiency classifier at a cement plant in Origny -Rochefort (France) varied between 0 and 6 kWh/t (Van den Broeck, 1998 ), and investment co sts were $2/annual

tonne finished material ba sed on Holderbank (1993).

Improved Grinding Media. Improved wear resistant materials can be installed for grinding media, especially in ball mills. Grinding media are usually selected according to

the wear characteristics of the material. Increas es in the ball charge distribution and surface hardness of grinding media a nd wear resistant mill linings have shown a potential for reducing wear as well as energy cons umption (Venkateswaran and Lowitt, 1988). Improved balls and liners made of high chromi um steel is one such material but other materials are also possible. Other improvements include the use of improved liner designs, such as grooved classifying liners. These ha ve the potential to reduce grinding energy use by 5-10% in some mills, which is equivalent to estimated savings of 3-5 kWh/t cement (Venkateswaran and Lowitt, 1988).

Plant Wide Measures Table 7 shows fuel and electricity savings, estimated payback period and carbon dioxide (CO 2 ) savings for each plant wide measure. A description for each measure is given

below.

Table 7. Energy Efficiency Measures for Plant Wide Measures in Cement Plants. More information can be found in the de scription of the measures below.

Energy Efficiency Measure (Plant Wide Measures) Fuel Savings (GJ/t) Electricity Savings (kWh/t) Estimated Payback Period (years) CO 2 Savings (kgC/t)

Preventative Maintenance 0.05 0-6 < 1 1.3-2.6 High Efficiency Motors

- 0-6 < 1 0-1.3 Adjustable Speed Drives

- 6-8 2- 3 1-2 Optimization of Compressed Air Systems

- 0-6 < 3 0-1 Efficient Lighting

- 0-0.6 <3 0-0.1

Notes: All data is given per tonne of cement

Preventative Maintenance. Preventative maintenance incl udes training personnel to be attentive to energy consumption and efficien cy. Successful programs have been launched in a variety of industries (Caffal, 1995; Nelson, 1994). While many processes in cement production are primarily automated, there st ill are opportunities, requiring minimal training of employees, to increase energy sa vings. Also, preventative maintenance (e.g. for the kiln refractory) can also increase a plant’s utilization ratio, since it has less downtime over the long term. Birch (1990) men tions that the reducti on of false air input

into the kiln at th e kiln hood has the poten tial to save 0.05 GJ/t. Lang (1994) notes a reduction of up to 5 kWh for various preven tative maintenance and process control measures (typically around 3 kWh/t). Based on similar programs in other industries, annual and start up costs for implementing this training are estimated to be minimal and would be paid back in less than one year. Fo r preventative maintenance of compressed air systems, see below.

21High-Efficiency Motors and Drives. Motors and drives are used throughout the cement plant to move fans (preheater, cooler, alka li bypass), to rotate the kiln, to transport materials and, most importantly, for grinding. In a typical cement pl ant, 500-700 electric motors may be used, varying fr om a few kW to MW-size (Vle uten, 1994). Power use in the kiln (excluding grinding) is roughly estimate d to be 40-50 kWh/tonne clinker (Heijningen

et al ., 1992). Variable speed drives, improved control strategies and high-efficiency motors can help to reduce power use in cement kilns. If the replacement does not influence the process operation, motors may be replaced at any time. However, motors are often rewired rather than being replaced by new motors . Power savings may va ry considerably on a plant-by-plant basis, ranging from 3 to 8% (F ujimoto, 1994). Vleuten (1994) estimates the potential power savings at 8% of the power use. Based on an analysis of motors in the U.S. Department of Energy’s MotorMaster+ software , and a breakdown of mo tors in a 5,000 tpd cement plant given in Bösche (1993), it is assumed that high-efficiency motors replace existing motors in all pl ant fan systems with an average co st of $0.22/annual tonne cement capacity.

Adjustable or Variable Speed Drives. Drives are the largest power consumers in cement making. The energy efficiency of a drive system can be improved by reducing the energy losses or by increasing the efficiency of th e motor (see above). Decreasing throttling can reduce energy losses in the system and coup ling losses through the installation of adjustable speed drives (ASD). Most motors are fixed speed AC models. However, motor systems are often operated at pa rtial or variable load (Nadel et al ., 1992). Also, in cement plants large variations in load occur (Bös che, 1993). There are various technologies to control the motor (Worrell et al ., 1997). The systems are offe red by many suppliers and are

available worldwide. Worrell et al . (1997) provide an overview of savings achieved with ASD in a wide array of applications. The sa vings depend on the flow pattern and loads. The savings may vary between 7 and 60%. AS D equipment is used more and more in cement plants (Bösche, 1993; Fujimoto, 19 93), but the application may vary widely, depending on electricity costs. Within a plant, ASDs can mainly be applied for fans in the kiln, cooler, preheater, separator and mills, and for various drives . For example, Blue Circle’s Bowmanville plant (Canad a) installed a variable air in let fan, reducing electricity and fuel use in the kiln (because of reduced inlet air volume), sa ving C$75,000/year in energy costs (approximately $47 ,000 in U.S. dollars) (CIPEC , 2001). One case study for a modern cement plant estimated potential application for 44% of the installed motor power capacity in the plant (Bösche, 1993). ASDs fo r clinker cooler fans have a low payback, even when energy savings ar e the only reason for installin g ASDs (Holde rbank, 1993). Energy savings strongly depend on the applica tion and flow pattern of the system on which the ASD is installed. Although savings are significant (Holderbank, 1993), not many quantitative studies are available for the ce ment industry. One hypothetical case study estimates the savings at 70%, compared to a system with a throttle valve (or 37% compared with a regulated system) for the raw mill fan (Bösche, 1993) . In practice savings of 70% are unrealistic (Young, 2002). Fu jimoto, (1994) notes that La farge Canada’s Woodstock plant replaced their kiln ID fans with ASDs and reduced electricity use by 6 kWh/t. It is estimated that the potential savings are 15% for 44% of the insta lled power, or roughly equivalent to 8 kWh/t cement. The specific cost s depend strongly on th e size of the system. For systems over 300 kW the co sts are estimated to be 70 ECU/kW (75 US$/kW) or less

22and for the range of 30-300 kW at 1 15-130 ECU/kW (120-140 US$/kW) (Worrell et al

., 1997). Using these cost estimates, the specific costs for a modern cement plant, as studied by Bösche (1993), can be estimated to be rou ghly $0.9 to 1.0/annual tonne cement capacity. Other estimates vary between $0.4 and $3/a nnual tonne cement (H olland et al., 1997; Holderbank, 1993).

Compressed Air Systems. Compressed air systems are used in different parts of the plants, i.e. mixing of slurry (in wet process plants) and in the baghouse Pulse-Jet or

Plenum Pulse dust collector filters and other parts. Total energy consumption by compressed air systems is relatively small in cement plants, however, it can amount to a considerable expense if the systems run cont inuously and end-uses are offline. Still, energy efficiency improvement measures may be found in these systems. Compressed air is probably the most expensive form of ener gy available in a plant because of its poor efficiency. Typically overall efficiency is around 10% for compressed air (LBNL et al., 1998). Because of this inefficiency, if compre ssed air is used, it s hould be of minimum quantity for the shortest possible time, c onstantly monitored and weighed against

alternatives.

Maintenance of Comp ressed Air Systems. Inadequate maintenance can lower compression efficiency and increase air leakage or pressure variability, as well as lead to increased operating temperatures, poor moistu re control, and excessive contamination. Improved maintenance will reduc e these problems and save energy. Proper maintenance includes the following (L BNL et al., 1998):

• Keep the compressor and intercooli ng surfaces clean and foul-free. Blocked filters increase pressure drop. By inspecting and periodically cl eaning filters, the pressure drop may be kept lo w. Seek filters with ju st a 1 psig pressure drop over 10 years. The payback for filter cleaning is usually unde r 2 years (Ingersoll- Rand, 2001). Fixing improperly operating filters will also prevent contaminants from en tering into tools and causing them to wear out prematurely. Genera lly, when pressure drop exceeds 14 to 20

kN/m 2 , replace the particulate and lubricant removal elements, and inspect all systems at least annually. Also, consid er adding filters in parallel th at decrease air velocity, and, therefore, decrease air pressu re drop. A 2% reduction of a nnual energy consumption in compressed air systems is projected for mo re frequent filter ch anging (Radgen and Blaustein, 2001).

• Keep motors properly lubricated and cleaned . Poor motor cooling can increase motor temperature and winding resistance, shorteni ng motor life, in addition to increasing energy consumption. Compressor lubricant should be changed every 2 to 18 months

and checked to make sure it is at the proper level. In additio n to energy savings, this can help avoid corrosion and de gradation of the system.

• Inspect drain traps periodically to ensure they are not stuck in either the open or closed position and are clean. Some users leave automatic condensate traps partially open at

all times to allow for consta nt draining. This practice wastes substantial energy and should never be undertaken. Instead, install simple pressure driven valves. Malfunctioning traps should be cleaned and re paired instead of left open. Some auto drains, such as float switch or electronic drains do not waste air. Inspecting and maintaining drains typically has a payback of less than 2 years (Ingersoll-Rand, 2001).

23• Maintain the coolers on the compressor to ensure that the dryer gets the lowest possible inlet temperature (Ingersoll-Rand, 2001).

• Check belts for wear and adjust them. A good rule of th umb is to adjust them every 400 hours of operation.

• Replace air lubricant separators according to specifications or sooner. Rotary screw compressors generally start with their air l ubricant separators having a 14 to 20 kN/m 2
pressure drop at full load. Wh en this increases to 70 kN/m 2 , change the separator (LBNL at al., 1998).

• Check water cooling systems for water quality (pH and to tal dissolved solids), flow, and temperature. Clean and replace filters and heat exchangers per manufacturer’s specifications.

Reduce Leaks. Leaks can be a significant source of wa sted energy. A typical plant that has not been well maintained will likely have a leak rate equal to 20 to 50% of total compressed air production capacity (Ingerso ll Rand, 2001; Price a nd Ross, 1989). Leak

maintenance can reduce this number to less th an 10%. Overall, a 20% reduction of annual energy consumption in compre ssed air systems is projected for fixing leaks (Radgen and Blaustein, 2001). Estimations of leaks vary with the size of the hole in the pipes or equipment. In addition to in creased energy consumption, le aks can make air tools less efficient and adversely affect production, shorte n the life of equipment, lead to additional maintenance requirements and increase unscheduled downtime. In the worst case, leaks can add unnecessary compressor capacity.

The most common areas for leak s are couplings, hoses, tubes, fittings, pressure regulators, open condensate traps and shut-off valves, pipe joints, disconnects, and thread sealants. A simple way to detect leaks is to apply soapy water to suspect areas. The best way to detect

leaks is to use an ultrasonic acoustic detect or, which can recognize the high frequency hissing sounds associated with air leaks. Af ter identification, leaks should be tracked, repaired, and verified. Leak detection and co rrection programs should be ongoing efforts.

Reducing the Inlet Air Temperature. Reducing the inlet air temperature reduces energy used by the compressor. In many plants, it is po ssible to reduce inlet air temperature to the compressor by taking suction from outside th e building. Importing fresh air can have paybacks of 2 to 5 years (CADDET, 1 997b). As a rule of thumb, each 3 ° C will save 1% compressor energy use (CADDET , 1997b; Parekh, 2000).

Maximize Allowable Pressure Dew Point at Air Intake. Choose the dryer that has the maximum allowable pressure dew point, and be st efficiency. A rule of thumb is that desiccant dryers consume 7 to 14% of the total energy of the compressor, whereas refrigerated dryers consume 1 to 2% as mu ch energy as the comp ressor (Ingersoll Rand, 2001). Consider using a dryer with a floating dew point.

Compressor Controls. The objective of any control stra tegy is to shut off unneeded compressors or delay bringing on additional compressors until needed. All units that are on should be running at full-load, except for one . Positioning of the control loop is also important; reducing and controlling the system pressure downstream of the primary

24receiver can result in energy consumption of up to 10% or more (LBNL, et al., 1998). Energy savings for sophisticated controls ar e 12% annually (Radgen and Blaustein, 2001). Start/stop, load/unload, throttling, multi-step , variable speed and network controls are options for compressor controls and described below.

Start/stop (on/off) is the simple st control available and can be applied to reciprocating or rotary screw compressors. Fo r start/stop controls, the moto r driving the compressor is turned on or off in response to the discharge pressure of th e machine. They are used for applications with very low dut y cycles. Applications with frequent cy cling will cause the motor to overheat. Typical payback for st art/stop controls is 1 to 2 years.

Load/unload control, or constant speed contro l, allows the motor to run continuously but unloads the compressor when the discharge pres sure is adequate. In most cases, unloaded rotary screw compressors still consume 15 to 35% of full-lo ad power while delivering no useful work (LBNL et al., 1998). Hence, lo ad/unload controls can be inefficient.

Modulating or throttling controls allow the outp ut of a compressor to be varied to meet flow requirements by closing down the inle t valve and restrictin g inlet air to the compressor. Throttling controls are applied to centrifugal and rotary screw compressors. Changing the compressor control from on/zero/of f to a variable speed control can save up to 8% per year (CADDET, 1997b).

Sizing Pipe Di ameter Correctly. Inadequate pipe sizing can cause pressure losses, increase leaks and increase generating costs. Pipes must be sized correctly for optimal performance or resized to fi t the current compressor system . Increasing pipe diameter typically reduces annual energy consumpti on by 3% (Radgen and Blaustein, 2001).

Heat Recovery for Water Preheating. As much as 80 to 93% of the electrical energy used by an industrial air compressor is conv erted into heat. In many cases, a heat recovery unit can recover 50 to 90% of this available thermal energy for space heating, industrial process heating, water heating, makeup air heating, boiler makeup water preheating, industrial drying, i ndustrial cleaning processes, heat pumps, laundries or preheating aspirated air for oil burners (Parekh, 2000). It’s been estimated that approximately 50 MJ/hour of energy is available for each 0.05 m 3 /second of capacity (at full load) (LBNL et al., 1998). Paybacks are typi cally less than one year. Heat recovery for space heating is not as common with water-cooled compressors because an extra stage of heat exchange is re quired and the temperature of th e available heat is lower. However, with large water cooled compressors , recovery efficiencies of 50 to 60% are typical (LBNL et al., 1998). Implementing this measure saves up to 20% of the energy used in compressed air systems annually for space heating (Radgen and Blaustein, 2001).

Plant Wide Lighting Energy use for lighting in the cement industr y is very small. Still, energy efficiency opportunities may be found that can reduce energy use cost-effectively. Lighting is used either to provide overall ambi ent lighting throughout the manufa cturing, storage and office spaces or to provide low-bay and task lighting to specific areas. High-intensity discharge

25(HID) sources are used for th e former, including metal halide, high-pressure sodium and mercury vapor lamps. Fluorescent, compact fluorescent (CFL) and incandescent lights are typically used for task lighting in offices.

Lighting Controls. Lights can be shut off during non-working hours by automatic controls, such as occupancy sensors whic h turn off lights wh en a space becomes unoccupied. Manual controls can also be used in addition to automatic controls to save additional energy in smaller areas. Payback of lighting control systems is generally less than 2 years.

Replace T-12 Tubes by T-8 Tubes . In industry, typically T-12 tubes have been used. T-12

refers to the diameter in 1/8 inch increments (T-12 means 12/8 inch or 3.8 cm diameter tubes). The initial output for thes e lights is high, but energy co nsumption is also high. They also have extremely poor efficacy, lamp li fe, lumen depreciation, and color rendering index. Because of this, maintenance and energy costs are high. Replac ing T-12 lamps with T-8 lamps (smaller diameter) approximately doubles the efficacy of the former.

Replace Mercury Lights by Metal Halide or High Pressure Sodium Lights. Where color rendition is critical, metal halide lamps ca n replace mercury or fl uorescent lamps with an energy savings of 50%. Where color rendition is not cr itical, high pressure sodium lamps offer energy savings of 50 to 60% comp ared to mercury lamp s (Price and Ross, 1989).

Replace Metal Halide HI D with High-Intensity Fluorescent Lights. Traditional HID lighting can be replaced with high-intens ity fluorescent lighting. These new systems incorporate high-efficiency fluorescent lamps, electronic ballasts and high-efficacy fixtures that maximize output to the work plane. Advantages to the ne w system are many; they have lower energy consumption, lower lumen depreci ation over the lifetime of the lamp, better dimming options, faster start-up and restrike capability, be tter color rendition, higher pupil lumens ratings and less glare (Martin, et al., 2000). High-intensity fluorescent systems yield 50% electricity savings over standard meta l halide HID. Dimming controls that are impractical in the metal halide HIDs can also save significant ener gy. Retrofitted systems cost about $185 per fixture, including installati on costs (Martin, et al., 2000). In addition to energy savings and better lighting qualities, hi gh-intensity fluorescen ts can help improve productivity and have reduced maintenance costs.

Replace Magnetic Ballasts with Electronic Ballasts. A ballast is a mechanism that regulates the amount of electri city required to st art a lighting fixture and maintain a steady output of light. Electr onic ballasts save 12-25 percen t more power than their magnetic predecessors do (U.S. EPA, 2001).

Product and Feedstock Change Product and feedstock changes include the pr oduction of blended cements, use of wastederived fuels, production of limestone cement a nd low alkali cement, and the use of steel slag in the kiln. Table 8 provides informati on on the initial capital costs, the operations and maintenance (O&M) costs, the simple pa yback period, the specific fuel savings, the

26specific electric savings, the specific carbon di oxide savings and the lifetime associated

with each of these measures.

Blended Cements. The production of blended cements involves the intergrinding of clinker with one or more additives (fly as h, pozzolans, granulated blast furnace slag, silica fume, volcanic ash) in various propor tions. The use of blended cements is a particularly attractive efficiency option si nce the intergrinding of clinker with other additives not only allows for a reduction in the energy us ed (and carbon emissions) in clinker production, but also co rresponds to a reduction in carbon dioxide emissions in

calcination as well. Blended cement has been used for many decades around the world.

Table 8. Product and Feedstock Changes to Improve the Energy Efficiency of Clinker

Production.

Capital Costs ($/t) O & M

Costs ($/t) Payback

Period (years) Fuel Savings (GJ/t) Electric Savings (kWh/t) 1 CO 2 savings (kgC/t) Lifetime (years)

Blended cements 0.7 -0.06 < 1 0.9-3.4 2 -11 21-85 20

Use of waste-derived fuels 0.1-3.7 < 0 3 1 > 0.6

- 12 4 20

Limestone cement 5 minimal -5% < 1 0.3 2.8 8.4 NA

Low alkali cement (rotary

only) 0 0 Immediate 0.19-0.5 6 4.6-12.1 NA

Use of steel slag in kiln * < 2 0.19

- 4.9 NA Note: Energy savings and co sts below are based on case study data, except where noted. Costs in China will vary depending on technology and availability. Where possible, we have included more data for China in the following text. All data are given per tonne of clinker

. 1 Negative numbers represent an increase in electricity due to the measure.

2 Data from Chinese case studies indicate savings of 2.6 to 3.4 GJ/t clinker, whil e U.S. data shows savings of 0.9 GJ/t

clinker (or 1.4 GJ/t cement at a clinker to cement ratio of 0.65).

3 Reduces operating costs but amount is not known

4 In calculating specific CO 2 savings for this measure, we used an emission factor for solvents of 0.02 tC/GJ.

5 Savings for this measure are calculated based on data given on a per tonne of cement basis and a clinker to cement ratio of 0.85. O&M savings are given based on percent savings in the kiln operating costs.

6 Some electricity is saved but exact amounts are unknown. * Total investment costs are $400, 000 to $1,000,000 per installation.

NA = data not available

Blended cements are very common in Europe; blast furnace and pozzolanic cements account for about 12% of total cement pr oduction with Portla nd composite cement accounting for an additional 44% (Cemburea u, 1997b). Blended cements were introduced in the U.S. to reduce production costs for cem ent (especially energy costs), to expand capacity without extensive capital costs, to reduce emissions from th e kiln. In Europe, a common standard has been developed fo r 25 types of cement (using different compositions for different applications). It allows wider applications of additives. Many

other countries around the world use blended cement. In China, a range of materials are used in blended cements (see below), but cement plants mainly produce Portland cement (about 95% of total output) (Cui, 2004). Ble nded cements demonstrate a higher long-term strength, as well as improved resistance to acids and sulfates, while using waste materials for high-value applications. Short-term strengt h (measured after less than 7 days) may be lower, although cement containing less than 30% additives will generally have setting times comparable to concrete based on Portland cement.

27In the U.S., the consumption and production of blended cement is still limited. However, Portland ordinary cement and Portland slag cement are used widely in cement produced in China (ITIBMIC, 2005). In addition, due to technical advancement and market development allowing the production of differe nt kinds and grades of cement, some industrial byproducts like blast furnace slag, fly ash, coal gangue, limestone, zeolite, pozzolana as well as natural minerals are widely used in cement production. The average percentage of admixtures in Chinese cemen t products stands at 24% to 26% (ITIBMIC, 2005). Table 9 gives the prices and different methods of transportation for the various

additives used in China. Prices for different additives vary greatly. Prices change with location, output, market need, produce t ype and ways of handling. ITBIMIC (2005) estimates fuel savings of at least 10%, and a similar increase in production.

Table 9. Prices and Transportation Modes for Different Additives Used in China

Additive Blast

Furnace

Slag Fly ash Cinder Coal

gangue Limestone Gypsum Pebble Kiln

dust

Price (Yuan/t) 13 - 80 12 - 35 14 - 26 10 - 38 11 - 40 52 19 0

Method of transportation Train and

truck Truck and pipe Train and

truck Truck Truck

and belt Truck Truck Pipe

Adapted from ITIBMIC, 2005, Table 26. Pric es of additives vary according to lo cation, market need, product type and method of transportation.

For blended cement with, on average, a cli nker/cement ratio of 65% , the reduction in clinker production corresponds to a specific fuel savings of 1.42 GJ/t cement. There is an

increase in fuel use of 0.09 GJ/t cement for drying of the blas t furnace slags but a corresponding energy savings of 0.2 GJ/t cement for reducing the need to use energy to bypass kiln exit gases to remove alkali-rich dust. En ergy savings are esti mated to be 9 to 23 MJ/t cement per percent bypass (Alsop and Post, 1995). The bypass savings are due to the fact that blended cements offer an additional advantage in that the inter-ground materials also lower alkali-silica reactivity (A SR), thereby allowing a reduction in energy consumption needed to remove the high alka li content kiln dusts. In practice, bypass savings may be minimal to avoid plugging of the preheaters, requiring a minimum amount of bypass volume. This measure therefor e results in total fuel savings of 1.4 GJ/t blended cement (0.9 GJ/t clinker for 0.65 clinke r to cement ratio). However, energy consumption is expected to increase, due to the added electricity consumption associated with grinding blast furnace slag (as othe r materials are more or less fine enough).

The costs of applying additives in cement production may vary. Capital costs are limited to extra storage capacity for the additives. Ho wever, blast furnace slag may need to be dried before use in cement production. This can be done in the grinding mill, using exhaust from the kiln, or supplemental firing, either from a gas turbine used to generate power or a supplemental air heater. The operational cost savings will depend on the purchase (including transpor t) costs of the additives 4 , the increased electricity costs for (finer) grinding, the reduced fu el costs for clinker production and electricity costs for raw

4 To avoid disclosing proprietary data, the USGS does not report separate value of shipments data for “cement-quality” fly ash or granulated blast furnace slag, making it impossi ble to estimate an average cost

of the additives.

28material grinding and kiln drives, as well as the reduced handling and mining costs. These costs will vary by location, and would need to be assessed on the basis of individual plants. An increase in electricity consumption of 16.5 kWh/t cement (11 kWh/t clinker) (Buzzi, 1997) is esti mated while an investment cost of $0.72/t cement capacity ($0.5/t clinker), which reflects the cost of new delivery and storage capacity (bin and weigh-feeder) is assumed.

The Lianzhuo cement Factory in Guangdong Provin ce, China, replaced some of its high grade limestone with 33 to 34% calcium oxide (CaO), alon g with copper tailing high content iron sulfide from a nearby county (IT IBMIC, 2004). They found fuel savings of 2.6 to 3.4 GJ/t clinker, a coal savings of ove r 50%. The clinker production has increased from 2 tonne/day to 14 tonne/day, its stre ngth has improved and its quality is stable (ITIBMIC, 2004).

China produces 25 Mt of blast furnace slag per year and has a long history of using this type of waste (Cui, 2006). Where utilized, a bout 20 to 25% of clinker is replaced; the country’s highest slag ratio is 50% (Cui, 2006). In addition, blast furnace slag is added into concrete as well as clinker. Fly ash is also increasingly being used in China. China has 100 Mt of blast furnace slag an d 300 tonnes of fly ash (Cui, 2006).

Use of Waste-Derived Fuels. Waste fuels can be substituted for traditional commercial fuels in the kiln. For example, the U.S. ceme nt industry is increasi ngly using waste fuels.

In 1999 tires accounted for almost 5% of total fuel inputs in the industry in the U.S.,

while all wastes total about 17% of all fuel inputs. The trend toward s increased waste use will likely increase after successful tests with different wastes in Europe and North America are performed. New waste streams incl ude carpet and plastic wastes, filter cake, paint residue and (dewatered) sewage sludge (Hendriks et al., 1999). Cement kilns also use hazardous wastes. Since the early 1990’s ce ment kilns burn annually almost 1 Mt of hazardous waste (CKRC, 2002). The revenues from waste intake have helped to reduce the production costs of all wast e-burning cement kilns, and especially of wet process kilns. Waste-derived fuels may replace the use of commercial fuels, and may result in net energy savings and reduced CO 2 emissions, depending on the alternative use of the wastes (e.g. incineration with or without energy recovery). Currently, in China only three cement plants are burning waste fuels. Beijing Cement Plant has the capacity to dispose of 10 kt per year of 25 types of waste; the plant is burning solid waste from the chemical industry, some paints, solvents and waste sludge from water treatment (Cui, 2004; Wang, 2006a). Shanghai Jinshan Cement Plant dispos es of sludge dredged from the Huangpu River which runs through Shanghai (Cui, 2004). Hong Kong Cement Plant purchases waste from other provinces to utilize in its kilns (Wang, 2006a). Other plants are utilizing wastes but the amounts are very small (Wang, 2006a).

A cement kiln is an efficient way to r ecover energy from wast e. The carbon dioxide emission reduction depends on the carbon content of the waste-derived fuel, as well as the alternative use of the waste and efficiency of use (e.g. incinerati on with or without heat recovery). In Table 8, we used the carbon content of solvents to determine the CO 2 savings. The high temperatures and long residence times in th e kiln destroy virtually all

29organic compounds, while efficient dust fi lters may reduce some other potential emissions to safe levels (Hendr iks et al., 1999; Cembureau, 1997b).

In North America, many of the alternative fu els are focused on the use of tires or tirederived fuel. Since 1990 more than 30 cement plants have gained approval to use tirederived fuels, burning around 35 million tires per year (CKRC, 2002). The St. Lawrence Cement Factory in Joliette, Quebec complete d a project in 1994 where they installed an automated tire feed system to feed whole tires into the mid-section of the kiln, which replaced about 20% of the energy (CADDET, 1996) . This translates to energy savings of

0.6 GJ/t clinker. Costs for the installation of the Joliette system ran about $3.70/annual tonne clinker capacity. Costs fo r less complex systems where the tires are fed as input fuel are $0.11 to $1.1/annual tonne clinker. Othe r plants have experi ence injecting solid and fluid wastes, as well as ground plastic wastes. A ne t reduction in operating costs (CADDET, 1996; Gomes, 1990, Venkateswar an and Lowitt, 1988) is assumed.

Investment costs are estimated to be $1.1/annual tonne clinker for a storage facility for

the waste-derived fuels and retrof it of the burner (if needed).

Limestone Portland Cement. Similar to blended cement, ground limestone is interground with clinker to produce cement, reducing the needs for clinker-making and calcination. This reduces energy use in the kiln and clinke r grinding as well as CO 2 emissions from calcination and energy use. The addition of up to 5% limestone has shown to have no negative impacts on the performance of Portland cement, while optimized limestone cement would improve the workability slightly (Detwiler and Tennis, 1996). Adding 5% limestone would reduce fuel consumption by 5% (or on average 0.35 GJ/t clinker), power consump tion for grinding by 3.3 kWh/t cement, and

CO 2 emissions by almost 5%. Additional costs would be minimal, limited to material storage and distribution, while redu cing kiln operation costs by 5%.

Low-Alkali Cement. In North America, part of the pr oduction of the ceme nt industry are cements with a low alkali content (probabl y around 20 to 50% of the market), a much higher share than found in many other countries (Holderbank, 1993). In some areas in the U.S. as well as China, aggregate quality may be such that low-alkali cements are required by the cement company’s customers or by the cl imate in a particular region (e.g., alkali

cements are more suitable the south of China in areas of higher rainfall than in drought areas in the North). Reducing the alkali c ontent is achieved by venting (called the bypass) hot gases and particulates from the pl ant, loaded with alkali metals. The by-pass also avoids plugging in the pr eheaters. This becomes cemen t kiln dust (CKD). Disposal of CKD is regulated under the Resource C onservation and Recovery Act (RCRA). Many customers demand a lower alkali content, as it allows greater freedom in the choice of aggregates. The use of fly-ash or blast-furn ace slags as aggregates (or in the production of blended cement, see below) may reduce th e need for low-alkali cement. Low alkali cement production leads to higher energy consum ption. Savings of 8 to 21 MJ/t (2 to 5 Kcal/kg) per percent bypass are assumed (Als op and Post, 1995). The lower figure is for precalciner kilns, while the higher figure is for preheater kilns. Typically, the bypass

takes 10 to 70% of the kiln exhaust gases (Alsop and Post, 1995). Additionally, electricity is saved due to the increased cement production, as the CKD would otherwise

30end up as clinker and not cemen t, requiring further processi ng. For illustrative purposes, assume a 20% point reduction in bypass volum e, resulting in energy savings of 0.19 to

0.5 GJ/t clinker. There are no investments involved in this product change, although cement users (e.g. ready-mix producers) may need to change the type of aggregates used (which may result in costs). Hence, this m easure is most successfully implemented in coordination with ready-mix producers and ot her large cement users. Low alkali cement is produced using domestic tec hnology in China (Cui, 2006).

Use of Steel Slag in Kiln. Texas Industries (Midlothian, Texas) in 1994 developed a system to use electric arc furnace (EAF) slags of the steel industry as input in the kiln, reducing the use of limestone. The slag that contains tri calcium silicate (C 3 S) can more easily be converted to free lime than limestone. The slags replace limestone (approximately 1.6 times the weight in lim estone). EAFs produce between 0.055 and 0.21 tonnes of slag per tonne of steel (on aver age 0.12 tonnes/tonne) (U.S. DOE OIT, 1996).

The CemStar ® process allows replacing 10 to 15% of the clinker by EAF-slags, reducing energy needs for calcination. The advantage of the CemStar ® process is the lack of grinding the slags, but adding them to the k iln in 5 cm lumps. Depending on the location of injection it may also save heating energy. Calcination energy is estimated to be 1.9 GJ/t clinker (Worrell et al., 2001). Because the lime in the slag is already calcined, it also

reduces CO 2 emissions from calcination, while th e reduced combustion energy and lower flame temperatures lead to reduced NOx em issions (Battye et al ., 2000). For illustrative purposes alone, using a 10% injection of slags would reduce energy consumption by 0.19 GJ/t clinker, while reducing CO 2 emissions by roughly 11%. Energy savings can be higher in wet kilns due to the reduced evaporation needs. Reductions in NOx emissions vary by kiln type and may be between 9 a nd 60%, based on measurements at two kilns (Battye et al., 2000). Equipment costs are main ly for material handling and vary between $200,000 and $500,000 per installation. Total investments are approximately double the equipment costs. CemStar ® charges a royalty fee (Batty e et al., 2000). Costs savings

consist of increased income from additiona l clinker produced without increased operation and energy costs, as well as reduced iron ore purchases (as the slag provides part of the iron needs in the clinker). The iron content ne eds to be balanced with other iron sources such as tires and iron ore. In the U.S., the U.S. Environmental Protection Agency

awarded the CemStar ® process special recognition in 1999 as part of the ClimateWise

program.

China does not produce this technology domesti cally, and to date the measure has not been implemented in cement kilns in China (Cui, 2006).



### Acknowledgements

This work was supported by the Climate Prot ection Partnerships Di vision of the U.S. Environmental Protection Agency as part of its ENERGY STAR program through the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Revision of this report for use in China was undertaken with funding provided by the U.S. EPA’s Office of International Affairs, the Energy Foundation’s China Su stainable Energy Program and

31Dow Chemical Company. We would like to thank the U.S. EPA, the Energy Foundation and the Dow Chemical Corporation for their support in making this version of this report.

Many people have been very helpful in the data collection and review of earlier versions of this report. We especially would like to thank Alexander Goebel (Krupp Polysius, Germany), Steve McGarel, Tom Evans, Amy George and Greg Martin (Pavilion Technologies Inc., Texas) for providing data for the earlier study. We thank the following people for reviewing the draft of earlier re ports: John Chadbourne (Essroc), Greg Galvin (RMC Pacific), Gerald Young (Penta Engineerin g), Robert Miller (Met so Minerals), Joel Fleming (Lafarge North America), Greg Mi ller (CTL, IL), Hendrik van Oss (USGS), Robin Riester (FLS Automation), Dan Willi s (Trinity Consultants, TX), and Ray Worthington (BMH Americas Inc.). We tha nk Tom Carter (PCA) for helping to collect the helpful suggestions. We thank Ann Dough erty and Gregg Miller (Portland Cement Association, Skokie, IL), George Lesni koff (Hanson Cement, Cupertino, CA), and Michael Nisbet (JAN Consulta nts, Montreal, Canada) for reviewing earlier reports on which this report is based and providing t echnical information. We also thank Suzanne Giannini-Spohn (U.S. EPA) for her helpful gui dance during the research and writing of the sections on kiln energy use and efficienc y. We thank Prof. Wang Yanjia of Tsinghua University for the helpful review and inform ation that she has provided to us. We thank Professor Cui Yuansheng, Vice President of the Institute of Technica l Information for the Building Materials Industry of China, for m eeting with us and providing documents and data regarding China’s cement industry.

Any remaining errors in this report are th e responsibility of the authors. The views expressed in this report do not necessarily reflect those of the U.S. Environmental Protection Agency, the U.S. Department of Energy or the U.S. Government.



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