Ingenieure GmbH


# In Situ Catalyst RegenerationA Cost Saving Technology for SCR Operators

Dr. Herwig Maier EnBW Ingenieure GmbH Kriegbergstrasse 11, Stuttgart, Germany D-70174 Phone: +-49-711-128-29-49

Fax: +-49-711-128-20-21 E-mail: herwig.maier@enbw.com

Dr. Werner Goetz EnBW Ingenieure GmbH Kriegbergstrasse 11, Stuttgart, Germany D-70174 Phone: +-49-0711-128-2318

Fax: +-49-0711-128-2318 E-mail: werner.goetz@enbw.com



## Power-Gen International 2001 Las Vegas, Nevada

December 2001Ingenieure GmbH

#05
2 

### Introduction

SCR systems for efficient NOx reduction are now commonly accepted by U.S. utilities. Operating expenses for such units are mostly driv en by the cost of catalyst maintenance. The continued effect of plugging, ma sking and poisoning, particular ly in high dust applications, reduces the activity of catalyst below the design value. This loss of activity is detected either by an increase of ammonia in fly ash or flue gas. To compensate this decline in activity it has been a standard procedure to add a new layer of catalyst or to replace the most deactivated

one.

Regenerating the old catalyst instead of its re placement can significantly reduce the cost of operating SCR units by increasing the effective li fe of the catalyst. A unique technology for in-situ catalyst regeneration (w ithout removing catalyst from the SCR reactor) was developed and patented by EnBW, one of the largest utility companies in Germany. During the last six years regeneration efficiency has been successfu lly demonstrated by EnBW for different types of catalysts (honeycomb and plate) installe d at power plants burning various coals.

The technology is protected and in the U.S. known by the trade mark ReAct TM

.



### The ReAct TM 

### Technology

The in-situ regeneration has been develope d since 1994 by EnBW, a utility company which operates in total more than 11,000 MW of generating capacity. Over 2000 m 3 of catalysts from different suppliers are installed in mo re than 2000 MW bituminous coal fired power plants since 1986.

After two years of research and developmen t and eight years of following the standard procedure of replacing deactivated catalysts on their numerous SCRs, EnBW commercialized 1996 the catalyst regeneration technology.

A regeneration method had to fulfill following demands:

• Simple, economical and repeatable

• Performance within the SCR box with no removing of the modules

• Usage of a water-based regeneration solution

• Minor amounts of non-toxic addi tives which needs no special allowances

• Circulation of the regeneration solu tion to improve the efficiency and minimize the waste water amount

• Minimum effort of time and man power (ideally performance within short outages)

Facing these goals the technology was developed, refined and ex tensively tested in the lab and successfully implemented in EnBW power plan ts. In the meantime it has been proven as a reliable technology in several plants.Ingenieure GmbH

#05
3 The ReAct TM technology is protected by U.S. and Eur opean patents and commercially offered in the U.S. The regeneration process involves th e in-situ washing of th e catalyst with a safe and economic regeneration soluti on and is efficient in catalys t cleaning, dissolving masking materials and removing some poisonous species . The procedure involve s following steps:

• Received samples are analyzed (both surf ace and bulk material) by means of X-ray diffraction, electronic microscopy, atomic absorption spectroscopy and the like to determine the mechanisms of degradation.

• The residual activity is measured.

• The results are compared with the da ta base of our numerous experiences.

• The sample is regenerated with the pre-tuned parameters deducted from the analyses in our lab scale facility. During that procedur e process relevant parameters are measured online.

• After the lab scale regeneration, the activity of the regenerated catalyst and the residual suspension are analyzed to veri fy the regenera tion efficiency.

• The parameters for a full scal e application can be fixed.

• The full-scale regenera tion takes place with the regenera tion solution sprayed over the catalyst modules, collected at the bottom of the layer and circulated.

• The equipment is simple, section and adaptable to any type of SCR plant. A team of 5 to 7 people can regenerate over 35 cu bic feet of catalyst per hour.

• The process runs at ambient temperature a nd moderate pressure, so energy consumption and danger of corrosion is negligible.

• The final step is drying the catalyst after regeneration, wh ich does not take much longer than the normal start-up of the SCR reactor.

The waste water, approximately 1 m 3 /m 3 of catalyst reactivated, can be easily handled containing about 5% solids and be ing nothing else than the air he ater or boiler washing water. It can be treated in the waste water treatment plant downstream FGD, if there is one, or be used in the FGD as process water or be "burned" in the boiler via the start up fuel burners or be used for ash moistening. If none of these options is available, the waste water has to be treated externally.



### Results and ExperiencesIngenieure GmbH

#05
4 So far, 14 successful full scale appli cations with regeneration of over 1700 m 3 of catalyst and numerous lab scale tests even with catalysts from US power plants have proven ReAct TM as a powerful and reliable technology. Different types of catalyst s have been regenerated and ReAct TM was found to be equally efficient w ith plate type and honeycomb catalysts.

The effect of ReAct TM is more pronounced when the degradation of the catalyst is already substantial:

• Lower catalyst activity (k/k 0 << 100%) leaves more room for improvement

• Exponential nature of deactivation process yields more additional operating time per percent of increased activity.

Two parameters are most instrumental in eval uating the efficiency of regeneration process:

• Gain of lost activity , which is measured as a fraction of lost activity reversed by regeneration. Typically this parameter is in the 35 to 70 % range. Even heavily Arsenic poisoned catalysts from U.S. power plants ha ve been regenerated with incredible good success (27 to 36%) by modifying slig htly the technology without giving up the philosophy of a simple, in situ procedure.

• Te regeneration prolongs the additional operation time without replacing a catalyst layer and shifts necessary i nvestments significantly.

Both these parameters, gain of lost activity and additional operating time are highly site specific and can be predicted based on the lab sc ale tests of representa tive samples and using the historic trend of catalyst activity at the power plant.

The achievable improvement differs for various mechanisms of catalyst degradation and depends on such factors as furnace type, as h composition, flue gas parameters and SCR reactor operating practices.

The ReAct TM process has some limitations:

• Complete recovery of the initial activity (k/k 0 = 100%) is not achievable; however the recovery of lost activity is usually high enough to yield a signi ficant increase in operating time without catalysts replacement.

• If the catalyst is mechanically at the end of its lifetime, no regeneration procedure, whatsoever applied, can help.

Monitoring the catalyst activity before and after regeneration shows no change in the degradation pattern, it only brings the activit y to a new higher level which means, that the process is repeatable several times without ch anging the performance of the SCR plant.



### Economics and SavingsIngenieure GmbH

#05
5 Normally after an operating time of 3 to 5 year s exhausted catalysts have to be renewed and because the degradation occurs to all layers, th e replacement procedure will then be necessary approximately every three years.

Assuming a price for new catalyst of actually about $ 5,500/m3 escala ting moderately up to $7,000/m3 within nine years with a depreciation of 9 years and interest on capital of 8%, the table below shows the cost developmen t of a SCR plant within 11 years.

Year Replacement Costs/m3 Costs/Year m3 Cumulated Costs x 1st $ 5,500 $ 880 $ 880 x+1 - $ 0 $ 880 $ 1,760 x+2 - $ 0 $ 880 $ 2,640 x+3 2nd $ 6,000 $ 1,840 $ 4,480 x+4 - $ 0 $ 1,840 $ 6,320 x+5 - $ 0 $ 1,840 $ 8,160 x+6 3rd $ 6,500 $ 2,880 $ 11,040 x+7 - $ 0 $ 2,880 $ 13,920 x+8 - $ 0 $ 2,880 $ 16,800 x+9 1st $ 7,000 $ 3,120 $ 19,920 x+10 - $ 0 $ 3,120 $ 23,040 x+11 - $ 0 $ 3,120 $ 26,160

Using the ReAct TM technology our experience has proven th at within the considered period of 11 years maximum one replacement would be ne cessary. A regeneration every two years can overcome the catalyst degradation and will avoid investment cost s of about $20,000/m3. Focusing on a typical 180 m3 layer these savings will sum up to 3.6 million (!) dollars in total or more than $ 330,000 a year.

Year Regen./ Replace. Costs/m3 Costs/m3 Cumulated

costs Savings/Year m3 Cumulated Savings/m3 x reg. 1st $ 0 $ 0 $ 0 $ 880 $ 880 x+1 $ 0 $ 0 $ 0 $ 880 $ 1,760 x+2 reg. 2nd $ 0 $ 0 $ 0 $ 880 $ 2,640 x+3 $ 0 $ 0 $ 0 $ 1,840 $ 4,480 x+4 reg. 3rd $ 0 $ 0 $ 0 $ 1,840 $ 6,320 x+5 $ 0 $ 0 $ 0 $ 1,840 $ 8,160 x+6 repl. 1st $ 6,500 $ 1,040 $ 1,040 $ 1,840 $ 10,000 x+7 $ 0 $ 1,040 $ 2,080 $ 1,8 40 $ 11,840 x+8 reg. 2nd $ 0 $ 1,040 $ 3,120 $ 1,840 $ 13,680 x+9 $ 0 $ 1,040 $ 4,160 $ 2,080 $ 15,760 x+10 reg. 3rd $ 0 $ 1,040 $ 5,200 $ 2,080 $ 17,840Ingenieure GmbH

#05
6

x+11 $ 0 $ 1,040 $ 6,240 $ 2,080 $ 19,920

For example in the EnBW Heilbronn power st ation Unit 7 (760 MW, bituminous coal fired with high dust S CR), where ReAct TM has been regularly implemen ted in 1996, the savings till the end of its technical life have been forecast ed to be million of dollars, which is a severe argument in the deregulated European energy market.

Of course the life expectancy of catalyst and th e time of necessary changes of layers depends on various parameters like

• Coal quality

• Mode of operation

• Boiler characteristics

• Ash composition

• Ash usage (pond, cement industry)

Therefore, the effectiveness of the ReAct TM regeneration has to be determined for each specific case.



### Recommendations

The optimal usage of ReAct TM and the planning of the most reasonable catalyst management strategy set forth:

• Sufficient space around the SCR duct to place the regeneration equipment (10x30 ft).

• Man holes (2-3 ft diameter) to bring in the spray grid, collecting trough, and of course staff.

• Sufficient space between catal yst layers (about 6 ft).

• Exact knowledge of soot blowers position and the steel construction to adopt the construction of the regenerati on equipment within the SCR duct.

• Information on activity (or even a sample) of the fresh catalyst.

• Regular activity measurements of installed catalyst samples to establish a degradation pattern.

• Frequent measurements of ammonia in th e fly ash as an indicator of current catalyst condition.

• Availability of representative sample s of catalyst for test regeneration.

The test regeneration results and the establishe d degradation curve can be used to make a prudent economic choice between regeneration and replacement.



### ConclusionIngenieure GmbH

#05
7 ReAct TM is an excellent, proven tool to affect significantly the operati onal costs of a SCR plant. In the power plant Heilbronn, where the technology has been developed and first applied, savings of several milli on dollars are a severe argument in the deregulated European energy market.



### ReAct TM 

### is

• Simple

- In-situ regeneration without removing the catalyst from the SCR box

- Minimal man-hours to accomplish re generation during short outages

- No special start up requirements

• Safe

- Regeneration procedure is de signed for each specific case

- No harm to catalyst or SCR box

- Chemicals are benign requi ring no special permits

• Proven

- Many successful full layer applications

- Repeatable process with no cha nge in the deactivation pattern

- Protected by U.S. and European patents

• Economical

- Catalyst disposal vol ume and cost reduced

- Significant reduction of cat alyst replacement cost

• Available - ReAct TM is commercially available in the U.S.