### E LECTRIC 

### P OWER 

### 2007 Conference and Exhibition EP-07 Session 12E

1 of 18 

## R ESULTS OF 

## FGD U PGRADE 

## P ROJECTS ON 

## L OW 

## -R ANK 

## C OALS Paul Farber, Bill Siegfriedt, Steve Katzberger Sargent & Lundy, L.L.C.

Don Caverly Joseph G. Eutizi Tommy J. Slater Tucson Electric Power San Migue l Electric Cooperative AEP/SWEPCO



## A BSTRACT This paper describes the approach es used to successfully implem ent flue gas desulfurization (FGD) upgrade projects at three power generating stations. Specifically, the FGD projects consisted of:

• Upgrades of the wet scrubber at American Electric Power/Southwestern Electric Power Company’s (AEP/SWEPCO) Pirkey Unit 1.

• Upgrades of the wet scrubber at San Miguel Electric Cooperative, Inc.’s (SMEC) San Miguel Unit 1.

• Increase of dry scrubber capacity at Tucson Electric Power’s (TEP) Springerville Units 1 and 2. Impetus for these upgrades was the following, either singly or in combination:

• Tightening of emission regulations

• Increase in SO 2 emission allowance prices

• Degradation of coal quality over time.

• Need to reduce emissions to allow expansion

• Desire for improved reliability The design alternatives and the challenges encount ered on each of these projects, as well as their results, are presented below.E LECTRIC P OWER 2007 RESULTS OF FGD U PGRADE P ROJECTS ON L OW -R ANK C OALS Conference and Exhibition EP-07 Session 12E

Page 13 of 18 Performance Results In August 2006, San Miguel Unit 1 was re-tested. The results showed that although the sulfur in the lignite was 20% higher than during the baseline testing, the average SO 2 removal (module inlet to outlet) improved from 92% to 96%. The mass of SO 2 removed increased by 24%. At the same time, limestone consumption decreased by 8%, as a result of the stoichiometric ratio improving by 26%. Overall, Stage I was successful. However, in 2012 the San Miguel FGD system will have to achieve 97% removal to stay within its allotment of SO 2 emission allowances. During the September 2006 outage, an inspection of the FGD system revealed a new phenomenon - extensive pluggage of the lower tray in each absorber had occurred. The accumulation was a crystalline growth on the bottom of the tray. S&L developed a computer flow model of the FGD module and verified the flue gas maldistribution at the plate. Planned Upgrades SMEC is planning further upgrades during the scheduled 2007 and 2008 spring outages. These are:

• Add flow straighteners to achieve uniform flow at the absorber trays.

• Balance flue gas flow, module to module.

• Blank off the bypass.

• Institute monitoring and control of inhibited oxidation.

• Upgrade instrumentation, to improve control (pH, SO 2 , module Δ P, recycle flow). 

## S PRINGERVILLE 

## G ENERATING 

## S TATION TEP’s Springerville Unit 1 commenced operation in 1985, with Unit 2 following in 1990 (on the right in Figure 9). These are replicate units, each with gross capacity of 425 MW and firing a New Mexico (Lee Ranch) sub-bituminous coal (ana lysis summarized in Table 1). Both units are equipped with Combustion Engineering (now Alst om Power) tangentially fired boilers and with Joy Manufacturing-Niro (now B&W) spray dryers with reverse air fabric filters (dry FGD system). The planned construction of the new Springerville Units 3 and 4 units (approximately equivalent in size to Units 1 and 2) required an o ffset in the emissions by reducing the NO Xand SO 2 emissions from Units 1 and 2. The original and revised emissions limits are noted in Table 3. Table 3. Springerville Units 1 and 2 Emission Rates Parameter Prior to Unit 3 Oper ation Post-Unit 3 Operation SO 2 , lb/mmBtu 0.60 0.24 NO X , lb/mmBtu 0.45 0.20E LECTRIC P OWER 2007 RESULTS OF FGD U PGRADE P ROJECTS ON L OW -R ANK C OALS Conference and Exhibition EP-07 Session 12E

Page 14 of 18 Figure 9. Springerville Generating Station

The dry FGD system for each unit comprises thr ee spray dryer absorbers (SDA) with rotary atomizers and a reverse-air fabric filter. The Springerville Station receives high-calcium pebble lime via rail, and a pneumatic system transports the lime to a day bin located at each unit. Horizontal ball mill slakers convert the pebble lim e to lime slurry, which is combined with a slurry of recycled material from the fabric filter just prior to being fed to the rotary atomizer. When the units were constructed, the dry FGD sy stems were built with a partial bypass, the result of which is that 75% of the flue gas is treated in the spray dryers and the bypassed flue gas is recombined with the scrubbed stream before entering the fabric filter. TEP, with S&L as Owner’s Engineer, implemented the following modifications to reduce NO X and SO 2 emissions:

• Installation of low-NO Xburners and overfire air (NO X ).

• Installation of a fourth spray dryer and elimination of the flue gas bypass (SO 2 ). Based on an evaluation of proposals received, B& W was selected as the turnkey contractor for the FGD upgrade. To complete the upgrade, two infr astructure upgrades were necessary:

• Relocation of the cooling tower water blowdown tank for each unit (cooling tower blowdown is used to make up the recycle slurry for the dry FGD system).

• Installation of a new 10-ton/hour lime slaker to accommodate the increased lime usage.E LECTRIC P OWER 2007 RESULTS OF FGD U PGRADE P ROJECTS ON L OW -R ANK C OALS Conference and Exhibition EP-07 Session 12E

Page 15 of 18 Both upgrades were successfully completed and the gas path tie-ins coordinated with the scheduled unit outages. The new spray dryers were installed just outside the building housing the existing spray dryers (Figure 10 and Figure 11) with access to the new spray dryer penthouses at the existing SDA penthouse level. Figure 10. Springerville Unit 1 Spray Dryer

The performance testing of the upgraded Sp ringerville Unit 1 FGD system was done during April 29, 2005 through May 3, 2005, and consisted of tests at low-load (140 MW gross), medium-load (250 MW gross), and high-load (420 MW gross).E LECTRIC P OWER 2007 RESULTS OF FGD U PGRADE P ROJECTS ON L OW -R ANK C OALS Conference and Exhibition EP-07 Session 12E

Page 16 of 18 Figure 11. Springerville Unit 2 Spray Dryer Installation

For the low-load testing, the entire flue gas flow was directed through the new spray dryer chamber (Module D). Consequently, approximately 33% of the total design flue gas flow rate was channeled through 25% of the total spray dryer capacity. During the medium-load testing, approximately 65% of the total design flue gas flow rate was directed through 50% of the operating spray dryer modules. In the high-load testing, the entire flue gas flow was sent through all four spray dryer modules. The purpose of the high-load testing was not only to confirm that the SO 2 emission rate was in accordance with the contract between TEP and B& W, but also that the flue gas flows were properly balanced between modules. The full-load testing on May 2 also had the purpose of acquiring data on the lime slurry feed to the FGD system, pressure drop across the modules, and electrical power consumption by the new module to determine contract compliance with these values. The objective of the performance testing was to validate the guarantees provided by B&W in the contract with TEP. Flue gas flow and SO 2 measurements were performed by a third-party testing company, METCO, out of Dallas, Texas. These measurements were taken at the inlets of each module’s central gas disperser (CGD) and roof gas disperser (RGD). Si milar measurements were taken in the exit duct of each spray dryer module. Summaries of the Springerville Unit 1 test results are provided in Table 4 and Table 5. Flow measurements were taken in accordance with U.S. EPA Methods 1 and 2. SO 2 and oxygen measurements were taken in accordance with U.S. EPA Methods 1, 6c, and 3a, respectively. AllE LECTRIC P OWER 2007 RESULTS OF FGD U PGRADE P ROJECTS ON L OW -R ANK C OALS Conference and Exhibition EP-07 Session 12E

Page 17 of 18 concentrations determined by METCO were source- gas-sampled, with the moisture removed, and therefore measured on a dry basis. The design co al for the upgrade project had a calculated SO 2 emission of 2.6 lb SO 2 /mmBtu. The SO 2 emissions from the coal being fired at Springerville during the performance tests were lower than woul d have been measured if the design coal had been available. TEP expressed concern that if a coal with an SO 2 content equal to the design coal is fired in the boilers at the Springerville, there might be difficulty in achieving an emissions rate of 0.24 lb SO 2 /mmBtu. Consequently, TEP requested th at the testing demonstrate the capability of the system to achieve a minimum of 91% SO 2 removal (the removal required to meet the required emissions rate while firing the design coal) during the full-load tests. The results of the testing demonstrated that indeed the system was capable of achieving the desired 91% removal requested by TEP. Table 4. Springerville Unit 1 SO 2 Removal

Run SO 2 Inlet (lb/mmBtu) SO 2 Outlet (lb/mmBtu) Percent Removal Low-load 1.870 0.206 89 Medium-load 1.887 0.196 89.6 High-load, May 5, 2005 (Note 1) 2.086 0.113 94.6 High-load, May 3, 2005 (Note 1) 1.792 0.145 91.9
Note: 1. Based on inlet SO 2 measurements taken by METCO. Similar to the concentration measurements, the flowmeasurements at the inlets to the spray dryer modules were analyzed. It was determined that the distribution, calculated from the measured inlet flows to the modules, was balanced to with in approximately 5% of the average module gas flow. Consequently, based on the flow and emissions measurements , TEP and S&L concluded that the upgrade of the FGD system at Springerville Unit 1 had met all of its requirements. Table 5. Springerville Unit 1 Flow Distribution (Note 1)
Run Module A Module B Module C Module D Medium-load -- 45% -- 55%

High-load 24.3% 23.3% 26.3% 26.1%
Note: 1. Distribution percentages are based on total flowto the module at the time of the test. The performance testing of the upgraded Sp ringerville Unit 2 FGD system was done during June 9 through June 10, 2005, and consisted of test s at high-load (420 MW gross). Similar to the Unit 1 testing, the purpose of the high-load testing was not only to confirm that the SO 2 emission rate was in accordance with the contract between TEP and B&W, but also that the flue gas flows were properly balanced between modules. Due to operating problems on June 9, SDA Module A was isolated and the entire flue gas flow was directed through Modules B, C, and the new SDA Module D. On June 10, Module A was returned to service and a series of gas flow measurements performed to determine flue gasE LECTRIC P OWER 2007 RESULTS OF FGD U PGRADE P ROJECTS ON L OW -R ANK C OALS Conference and Exhibition EP-07 Session 12E

Page 18 of 18 distribution. Consequently, and with B&W’s c oncurrence, the official performance test for Unit 2, with regard to SO 2 removal and lime consumption, was performed on June 9. As indicated in Table 6, the system achieved emissions well below the 0.24 lb SO 2 /mmBtu permit value and nearly achieved the 91% removal effici ency attained by Unit 1 during its performance testing. Since, during the SO 2 removal tests, Springerville Unit 2 was operating at 100% MCR with all of the flue gas being sent through 75% of the modules, it was concluded that this demonstrated satisfactory operation of the upgrad ed FGD system. The testing on June 10 was used to determine the flue gas distribution with in the four Unit 2 SDA modules. Both in the three-module and four-module cases, the flow dist ribution was within 3.5% of the average gas flow through each module. Table 6. Springerville Unit 2 SO 2 Removal

Inlet Measurement SO 2 Inlet (lb/mmBtu) SO 2 Outlet (lb/mmBtu) Percent Removal
SO 2 inlet monitor 1.90 0.195 89.7 Coal analysis 2.105 0.195 90.7 Table 7. Springerville Unit 2 Flow Distribution (Note 1)
Run Module A Module B Module C Module D June 9, 2005 Offline 32% 32% 36% June 10, 2005 28.4% 23.9% 22.1% 25.6%
Note: 1. Distribution percentages are based on total flowto the module at the time of the test. 

## C ONCLUSIONS Many of the FGD systems installed in the 1980s were designed for SO 2 collection efficiencies of between 75% and 90% to meet the then current emission limits (typically 1.2 lb SO 2 /mmBtu). Upgrading these FGD systems to achieve 95% or more SO 2 removal presents an opportunity to generate SO 2 allowances for sale or to offset the emi ssions of new units. Upgrades to the existing equipment of that vintage, i.e., 20 years old, also is typically required to restore the original design function, improve operability and ma intainability and ensure unit availability. The three FGD upgrade projects described in th is paper posed unique requirements and challenges, and all were successfullyupgraded to meet the Owners’ needs.