# LESSONS LEARNED FROM SCR EXPERIENCE OF

**COAL FIRED UNITS IN JAPAN, EUROPE AND USA;**

**ARE THESE ENOUGH?**

**Dr. Anupam**  **Sanyal International Environmental & Energy Consultants, Inc.** 

**Naperville, Illinois 60563**

**And**
**William Ellison**
**Ellison Consultants Monrovia, Maryland 21770** 
**Presented at the 2002 Conference on Selective Catalytic Reduction**  **And Non-Catalytic Reduction for NOx**  **Control Pittsburgh, Pennsylvania, May 15-16, 2002**  **Sponsored by U.S. Department of Energy, National Energy Technology Laboratory** 

# Outline

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## Introduction

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## The Japanese & European Experience

– 

## Coal

– 

## Boiler Design

– 

## Performance – NOx Removal, NH 3 

## Slip, APH, Catalyst

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## The US Experience

– 

## Applicability of This Experience to the Advanced US SCR Needs W.R.T.

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## Coal

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## NOx Removal Efficiency

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## Opacity Compliance

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## What Else is Required?

– 

## Coal/Ash Characterization

– 

## Catalyst Development

– 

## Chemicals as Remedial/Preventive Measure

– 

## Arsenic Poisoning/SO 3 

## Plume Mitigation/Prevention

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## Conclusions and Recommendation

# Introduction **Development of SCR in Japan, Europe & USA**

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# ~23,100 MW Total Japanese Utility Capacity Comprising 61 Plants

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# ~55,000 MW Total European Utility Capacity

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# ~Until end 90’s, 2,211 MW of US Capacity. By 2004, this is Expected to Increase to over100,000 MW ≡ Over 33% of the Total Coal Fired Capacity of the USA

# Pioneers of Japan, Europe & USA for SCR

**Installations on Coal Fired Commercial Units**

**Sequence of Milestones**

**1 st**  

### Arsenic poisoning in Stanton #2 of OUC **2000 1**  **st** 

### PRB Application Feb 2000 to **AECI’s 600 MW New Madrid #2** 

**E NOx 93%, NH 3**  

### Slip 3ppmvdc

**1 st**  

### largest cyclone unit (700 MW) firing high sulfur bit coal to TVA’s **Paradise #2 Spring 2000; ENOx**  **90% NH 3**  

### Slip 2 **ppmvdc 1995**  **1 st**  

### New **US P.C. Fired PG&E’s 265 MW Carney’s Point Cogen**  **Plant &**

**1 st**  

### Retrofit **Merrimack Unit 2 (1 st**  

### US Gas Unit is LADWP Haynes) **1990 Arsenic Poisoning reported in German pilot plants. 1**  **st** 

### coal fired German

**Dry Bottom Commercial Unit is**  **Neckerwerk’s Altbach/Deizisau**  **420 MW Unit 5 & 1**  **st** 

### coal fired German slag tap 175 MW unit of **Knepper C**  **1985 Fed.**  **Rebuplic of Germany’s ordinances for 111**  **ppm (0.12 lb/**  **Mbtu )** 

**(200 mg/Nm 3**  

### ) from large boiler installations **1980 Japanese – Pilot plants firing oil, gas & refinery gas. 1**  **st** 

### coal fired Japanese

**demo. on 1⁄2 x 175 MW of Chogoku**  **Electric’s Shimoneski**  **Unit followed by Hokkaido Electric’s Tomato -**  **Atsuma (1/4 x 250 MW ) &**  **EPDC’s Takehara**  **250 MW Unit 1 Low Dust Demo. 1975** 

# Performance of Earlier Japanese SCR Plants **on Coal Fired Utility Boilers**

**1983 2**  **60 160**  **400 2,600**  **Plate 175**  **1 Sendai**  **Tohuku Electric**  **80 40**  **200 2,800**  **7.4 Honeycomb**  **500 1**  **Shin- Onada**  **Chuguku 1984**  **1 70**  **60 200**  **4,000 7**  **Honeycomb 265**  **1,2 Yokosuka**  **Tokyo 1983**  **1 70**  **90 330** 

**- 7.5**  **Honeycomb 250**  **2 Saijo**  **Shikoku 1983**  **1 65**  **130 380**  **4,000 7**  **Honeycomb 156**  **1 Saijo**  **Shikoku 1984**  **2 65**  **120 350**  **2,200 6**  **Plate 156**  **2 Mizushima**  **Chuguku 1981**  **2 65**  **140 400**  **4,000 7**  **Honeycomb 156**  **3 Shin-Ube**  **Chuguku 1980**  **1 57**  **180 420**  **3,000 10**  **Honeycomb 175**  **1 Shimonoseki**  **Chugoku 1983**  **2 81**  **48 250**  **2,370 10**  **Plate 700**  **3 Takehara**  **EPDC 1981**  **4 81**  **67 350**  **2,000**

**- Tube**  **250 x 1⁄2**  **2 Takehara**  **EPDC 1981**  **4 81**  **67 350**  **2,300 10**  **Plate 250**  **x 1⁄2 1**  **Takehara EPDC**  **Up Year**  **NH 3**  **( ppm**  **) Slip**  **DeNOx (%)**  **NOx (**  **ppm )** 
**In Out SV**  **{h -1**  **} Pitch**  **(mm) Catalyst**  **Type Boiler** 
**No. MW Plant Site**  **Plant Owner** 

# Typical European Units

**Providing NOx**  **Reduction >85% (High Performance SCR)** 

**Excess catalyst volume 220**  **1250 1785**  **83 Franken**  **Relatively large reactor, with excess of catalyst, APH corrosion/SO**  **3 350**  **1528 2308**  **83 Kiel**  **Catalyst volume is not excessive, but tower design boiler and small reactor**  **promote good gas distribution and mixing**  **170 2364**  **3152 85**  **Bremen Excess of catalyst, small reactor size**  **100 943**  **1257 85**  **Tiefstack Reactor size is one of the largest for**  **high performance SCR Catalyst Management**  **293**

**- -**  **85 Staudinger**  **3 Extremely small reactor size**  **63**

**- -**  **84 Staudinger**  **1⁄2 Same as**  **Kneper 140 + 40**  **1839 2449**  **85 Walheim**  **Combined high initial NOx**  **, small reactor size, and relatively low space**  **velocity provide ideal conditions for maximum**  **NOx removal**  **175 1412**  **Not defined 90**  **Knepper C**  **Comment Reactor** 
**Size (MW)**  **Final Space Velocity (h** 

**-1 )**  **Initial Space**  **Valocity (h**  **-1 )**  **NOx**
**% Unit** 

# Japanese & European Coal

**Quality Indigenous and Imported** 

# Analyses of Typical Japanese Coals

**38 33.7**  **14,490 48.4**  **3.4 8.2**  **Horonai 36**  **33.7 14,510**  **55.8 12.9**  **16.8 Hahoro**  **54 33.9**  **14,590 46.4**  **2.6 30.8**  **Akama 53**  **34.3 14,740**  **44.9 2.4**  **21.6 Yubetsu**  **47 33.3**  **14,330 45.9**  **3.6 15.1**  **Bihai 49**  **31.9 13,710**  **49.7 1.6**  **38.0 Sunagawa**  **Hokkaido 72**  **34.7 14,900**  **9.5 2.2**  **31.7 Sanyo**  **Yamaguchi 38**  **32.6 14,040**  **47.6 4.4**  **29.7 Takamatsu**  **Shikoku 51**  **34.2 14,690**  **46.9 3.6**  **23.3 Shinkokusko**  **47 34.4**  **14,800 51.7**  **2.2 15.4**  **Meiji-Saga 43**  **31.2 13,400**  **45.8 2.2**  **51.3 Yamano**  **46 33.6**  **14,440 46.2**  **2.4 23.8**  **Onoura 37**  **30.6 13,160**  **53.6 6.1**  **39.1 Kokura**  **49 34.2**  **14,700 40.0**  **3.0 24.5**  **Hiyoski 44**  **33.5 14,410**  **48.3 2.2**  **22.1 Iizuka**  **45 31.81**  **13,660 51.2**  **3.9 35.4**  **Tagawa Kyushu**  **Hardgrove**
**Grind. Moisture and Ash-Free** 
**HHV % VM Btu/lb MJ/kg**  **As Received**
**% Ash % H 2**  **O Mining District**  **or Seam Area** 0.9% 0.6% 0.6% 0.3% 0.9% Sulfur (%) 3.78 1.83 15.00 3.33 10.78 Total Ca/S 9.78 6.02 22.00 10.00 16.18 Total Alkali/S 8.80% 3.61% 13.20% 3.00% 14.56% Total Alkali Error SO3 P Ti K Na Mg CA Fe Al Si Ash Chemistry N H C Sulfur Heating Value Moisture FC VM Ash **Analysis**

1.30% 1.30%

- 0.81% 0.71% 0.41% 2.00% 1.00% 6.00% 0.20% 8.34% 0.50% 0.40% 2.00% 0.50% 0.10% 1.60% 1.00% 1.50% 1.00% 0.80% 2.20% 1.50% 0.50% 1.00% 1 .185% 1.00% 0.90% 2.00% 0.40% 0.48% 2.20% 0.11% 1.70% 0.60% 2.53% 3.40% 1.10% 9.00% 1.00% 9.70% 7.00% 9.00% 4.00% 3.00% 11.60% 25.00% 24.00% 32.00% 21.00% 23.20% 51.00% 57.00% 43.00% 70.00% 38.90% Pct of Ash Pct of Ash Pct of Ash Pct of Ash Pct of Ash 1.1% 1.2% 1.6% 1.4% 1.9% 4.4% 5.0% 4.0% 4.0% 5.0% 55.7% 69.0% 65.0% 64.0% 69.0% 0.90% 0.60% 0.60% 0.30% 0.90% 9,926 11,755 11,240 10,854 12,858 7.50% 9.00% 8.00% 13.00% 4.90% 43.5% 48.0% 5 4.0% 54.0% 0% 28.0% 36.0% 24.0% 25.0% 37.7% 21.0% 7.0% 14.0% 8.0% 9.5% **Poland Columbia**  **Guasare S. Africa**  **Transvaal Australia**  **N.S. Wales Germany**  **Ruhr Valley Characteristics of Typical European Indigenous & Coals Imported by Europe & Japan** 

# Highlights of SCR Experience of

**Japan & Europe**

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## Coal – Mostly imported, med. Sulfur, low arsenic sub-bit.

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## Design Features **Remarks**
Inlet NOx lb/

Mbtu 0.50-1.25
deNOx E 50-90%

NH 3 

## Slip ppmvdc 1-10
SO 2 

## -SO 3 

## Conv . % <2%
SV hr -1 

## 1,257-4,000 Low/High Dust Both

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## Catalyst Pitch & Geometry Pitch 7-10 mm; pipe, honeycomb,plate, (graduated) fiberreinforced corrugated Composition V 2 

## O5 

## , TiO 2, 

## MoO 3 

## on S.S. or Ceramic Management By coupon testing, inspection, cleaning regularly, poisoning/blockage

# Highlights of SCR Experience of

**Japan & Europe (Cont’d.)**

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## SCR Process **Parameters** Gas Velocity Dist N 

## 15-20% SD
NH 3/ 

## NO Ratio SD 4-6% Physical & CFD Modeling Yes

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## Reactor Layout Various – e.g. For simple tower boilers “Elbow” to complicated layouts achieved by prior modeling of specific needs – e.g. wide load
range

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## Reagent Type & Application Anhydrous NH 3 

## (Mostly) AIG Designs – High Density Injectors & Low Density Injectors w/Mixing Devices

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## Reagent Monitoring From flyash ; shiftwise or weekly

# Highlights of SCR Experience of

**Japan & Europe (Cont’d.)**

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# Air Heater **European mostly Enamel Coated DP up to 8 in. w.g., Deposition** 

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# Flue Gas Handling **Typically 3-7 in. w.g. Equipment upgrade during FGD retrofit**  **mostly accommodated SCR requirement** 

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# I & C **Feed forward Signal for reagent**
**demand from boiler NOx**  **with a feedback signal based on outlet**  **NOx**

# Summary of European & Japanese

**SCR Experience**

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# Coal sulfur mostly within 1.7%

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# Av. Max. 85% NOx removal

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# Significant number of tower boilers with a few SCR **operating problems**

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# Routine use of combustion controls

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# Graduated catalyst geometry

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# Inconsequential Am. Sulfate/bisulfate deposition – low **SO 3**  

# - <2 **ppm NH**  **3** 

# slip – enameled APH surfaces

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# Alkali injection – arsenic bonding and SO **3** 

# control

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# Catalyst channel blockage by unburned carbon and **coarse fly ash**

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# Ammonia slip monitoring

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# Catalyst performance monitoring & regeneration

# Evaluation of Transferability of

**Japanese & European Experience to U.S. SCR Application** 

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## Japanese & European experience mostly transferable to US with respect to deNOx effy ., NH 3 

## Slip, SO 2 

## /SO 3 

## Conv . E, SV, High/Low Dust, Catalyst Composition, Geometry & Management

– 

## Gas Velocity Distribution

– 

## NH 3 

## /NO Ratio SD

– 

## Air Heater Performance US Situation Differs With Respect To:

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## Reactor layout due to boiler design difference

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## Reagent – Aq . Ammonia & Urea

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## Higher deNOx effy . – advanced goal

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## Most importantly Coal Type & its concomitant issues – e.g. Arsenic Poisoning, Pore Blockage by PRB Coal Ash & SO 3 

## Plume

# Typical U.S. **SCR Experience**

## Typical U.S. Performance

**Serial # 1**  **2 3**  **4 5**  **6 7**  **8 9**  **10 11**  **12**

Unit New

Madrid #2 Gavin Somerset Paradise #1&2 Bowen

1 & 2 Bowen

3 & 4 Gorgas #10 Birchwood Roxboro #4 Hawthorn

#5 Brandon

Shores Logan

Size Mwe 640 2 x 1,300 675 700 756 950 780 250 2 x 735 500 1370 200

Utility AECI AEP AES TVA GA PWR GA PWR AL Pwr So Energy CP&L KCP&L Constellatio

n PG&E

Date Commissioned 2/7/00 5/01 7/99 Spring 2000 & 2001 5/01 5/03 5/02 11/96 7/01 5/01 5/01 9/94

Firing Mode Cyclone W all Wall Cyclone Corner Corner Corner Corner PC PC PC PC Coal Type 100%

PRB High Vol.

Bit. Bit./PRB Bit. Bit. AL Bit Bit. PRB Low S Bit.

Inlet NOx lb/ Mbtu 1.5 0.55 0.86-1.6 0.45 0.45 0.55 0.46 0.225

Outlet NOx lb/ Mbtu 0.105 0.05 0.07 0.07 0.08 0.1 0.097 0.099

DeNOx Eff. % 93 90 90 90 85 85 85 79 56 90 63 NH 3 Slip PPM 3 <0.2 3 2 2 2 2 5 2 2 2 (1 achieved initially) SO 2 lb/ Mbtu 0.4 4.75-6.5 2 2 3.0 % Sulfur .23 3.4 1.5-4..60 2-3 1 1 1.5 1.5 0.56 <1.0 SO 2 to SO 3 Conv. % 3.0 1.6 0.75 0.75 <1.0 <0.75

Catalyst Type Plate Plate Plate Plate Honeycomb Honeycomb Honeycomb Plate Plate Plate Plate Pitch mm 9.2 5.6 6.0 8.2 Reagent Ammonia Urea NH 3 anhy. NH 3 NH 3 anhy. NH 3 anhy. NH 3 anhy. NH 3 anhy. Ammonia Ammonia Am.Aq.

SCR/ deltaP ( Iwg) 8 2.8

Catalyst Life Hrs. 20,000 24,000 20,000 24,000

Catalyst m 3 897 314 477 Arsenic ppm <20 2 deltaP Catalyst ( Iwg) 1.3 2.0 New

General Remarks World’s

1 st SCR for 100% PRB Lime addition Continuous Low Dust Continuous Low Dust High Dust

# U.S. Coals

# Coal Quality Parameters Affecting SCR Performance

**Coal Parameter:**

**Sulfur:**

**Arsenic:**

**Calcium:**

**Sodium & Potassium:**

**Chlorine & Fluorine:**

**Unburnt Carbon:**

**Ash Burden** • **Impact**

• **SO 3**  **Formation in catalyst chamber by V-oxide**

• **Catalyst pluggage**  **by am. sulfate/bisulfate**

• **High ammonia usage**

• **Catalyst surface masking**

• **Airheater**

**corrosion & pluggage** 

• **Catalyst surface & pore blockage**

• **Catalyst poisoning by arsenic oxide.**

• **Reduction in available catalyst sites by fine lime particles from PRB coal** 

• **Blockage also by Na&K-sulfates**

• **Reduction in active catalyst site by formation of vanadium chloride/fluoride** 

• **Catalyst pore blockage by Am-chloride/fluoride**

• **Increased ammonia usage**

• **Blockage of initial catalyst layers**

• **Higher the ash burden, higher catalyst deactivation & air heater corrosion/blockage** **Table 1 Typical Mineral Ash Analysis**  **Of U.S. Bituminous Coals Constituent weight percent of ash** 

Origin Sample No. SiO 2 A1 2

0 2 Fe 2 O 3 TiO 2 CaO MgO Na 2 O K 2 O SO 3 Sample No. Comments

Kentucky Deane 2

3 59.6

68.5 26.7

20. 8 4.2

2.6 3.4

3.6 2.3

1.4 0.7

0.4 0.8

0.6 0.1

<0.1 1.8

1.7 2

3 High in silica

Illinois Carrier Mills Utah Horse Canyon 26

67 17.5

25.6 9.2

21.0 64.1

20.5 0.4

0.6 4.1

15.8 0.4

0.7 0.3

2.0 1.0

0.2 1.8

10.9 26

67 Low in silica, sample 26, exceptionally high

in iron; sample 67 moderately high in iron and calcium

Utah Horse Canyon 124 42.0 26.5 7.5 1.2 7.9 1.6 1.2 1.6 9.5 124 Moderately high in silica West Virginia, Bickmore 127 46.1 34.5 7.5 1.5 2.5 0.7 0.3 2.0 3.0 127

Pennsylvania, Ebensburg 142 19.4 10. 5 36.6 0.4 8.9 5.8 0.4 1.1 15.9 142 Low in silica, exceptionally high in iron

Oklahoma, Redstone 143 29.2 14.2 27.8 0.5 7.1 5.1 0.6 1.5 14.0 143

**Table 2 Typical Mineral Ash Analysis**  **O f**  **U.S. Sub**

**- Bituminous/Lignite**  **Constituent weight percent of as h** 

Origin Sam

ple No. SiO 2 A1 2 0 3 Fe 2 O 3 TiO 2 CaO MgO Na 2 O K 2 O SO 3 Sample No. Comments

North Dakota, Zap lignite 87

88 20.0 23.5 9.3

13.6 7.5

5.7 0.5

0.5 20.8

18.3 6.0

5.4 11.5

8.3 0.4

0.3 21.9

21.7 87

88 Exceptionally high in sodium, fairly high in

calcium, low in silica and alumina
Montana, Savage lignite 91

92 17.0 12.5 14.6

13.3 1.2

6.8 0.4

0.3 34.6

26.1 13.3

10.4 0.3

0.3 0.1

0.1 14.3 26.17 91

92 Low in sodium, exceptionally high in calcium,

low in silica and alumina

Wyoming, Gle nrock and Gilette sub

bituminous 99

100 39.8 9.8 19.4

12.9 3.9

6.7 0.9

1.0 15.0

33.4 2.4

7.9 0.2

1.6 1.1

0.2 16.2

21.7 99

100 Glenrock fuel

- ash sample moderately high in

calcium; Gilette sample exceptionally high in calcium and exceptionally low in silica and alumina Texas; Darco lignite 140

141 38.4 62.1 21.0

16.8 11.2

3.9 1.1

0.9 10.0

5.2 1.7

1.1 0.7

0.5 0.5

0.6 14.6

8.9 140

141 Sample 140 moderately high in calcium and iron;

sample141 exceptionally high in silica

## A Typical Example of **The Difference in the Form of Presence of**  **Alakaline & Alkaline Earth Components in**  **US bituminous & Sub-Bituminous Coal**

**85 15**  **66 34**  **Fe 2**  

## 0 **3** 

## 28 **72 0**  **100 T**  **i** 

## 0 **2** 

## 45 **55 9**  **91 Al**  **2** 

## 0 **3** 

## 0 **100 0**  **100 S**  **i** 

## 0 **2** 

## 69 **31 16**  **84 K**  **2** 

## 0 **100 0**  **44 56**  **Na 2**  

## O **94 6**  **54 46**  **MgO 97**  **3 30**  **70 CaO**  **55 46**  **20 80**  **Coal Ash Organically** 
**Associated Mineral** 

**Matter Organically** 
**Associated Mineral** 

**Matter % Total In** 
**Each Portion Wyoming Sub-Bituminous** 

**Illinois Bituminous**

# Main Features of U.S. Coals With Adverse

**Impact on SCR Technology**

**Bituminous**

• **Higher sulfur than the coals used in Europe & Japan**

• **Higher arsenic (comes with sulfur)**

• **Higher ash burden (compared to sub-bituminous)**

• **More slagging type coal** 

# Sub-Bituminous/Lignite

• **Higher calcium & Magnesium mostly coal bound as in PRB**

• **(These in European & Japanese cases are in form of minerals)**

• **Higher sodium & potassium**

• **These pose perhaps the greatest challenge to U.S. SCR installations**  

# Eastern/Western Blends

• **Still contains coal bound calcium, magnesium**

• **Little European & Japanese experience (blends are of imported coals low in sulfur, calcium & sodium)** 

# Mechanism of Catalyst Deactivation

**by PRB Fly Ash**

• **PRB coal contains high (up to 30% of ash) calcium & high (up to 10% of ash) magnesium** 

• **These are mostly (up to 80%) present in the coal matrix**

• **These are readily released in the furnace as fine particles of reflective calcium oxide & magnesium**  **oxides & silicates which combine with sulfur trioxide in the convective pass to form calcium (and magnesium)**  **sulfates which plug the catalyst pores.**

• **Sodium ( and potassium) of PRB coals form sticky sulfates and phosphates on the catalyst sites promoting**  **additional deposition of fly ash.**

# What Are Required?

**And What Should Be Done?**

# Use Chemicals to Improve Catalyst Pore Blockage **using PRB Coal, Reduce LOI and Catalyst Surface Masking Firing Bituminous Coal** 

• **Convert fine calcium oxides & magnesium oxides into compounds prior to contact with SO**  **3** 

# and thereby minimize **formation of Ca & Mg sulfates and reduce catalyst pore blockage** 

• **A chemical has been developed to control PRB’s**  **reflective ash generated slagging. This is considered to be able to**  **minimize Ca & Mg sulfate formation & thereby reduce catalyst pore blockage** 

• **Used over adecade**  **, a chemical is used by the U.S. utility industry firing bituminous coals to reduce LOI and improve**  **cycle efficiency by recovering superheat & reheat steam temperatures.** 

# Improved Understanding of Coal

**and Ash Quality**

**Laboratory Studies for Inorganic Coal Constituents & Ash Deposit evaluation**  **Physical Computer controlled scanning electron**  **microscopy & X-ray Diffraction** 

# Chemical
**Fractionation for modes of occurrence of calcium, magnesium, sodium & potassium in**  **coal**

# Arsenic Poisoning Mitigation

# Mean Arsenic content of U.S. Coals

**Source: U.S. Geological Survey**

**As PPM**

• 

# Appalachian Basin **22**
**n 2835**

• 

# Illinois Basin **10**
**n 298**

• 

# Powder River Basin **2.6**
**n 160**

• 

# Colorado Plateau **3.1**
**n 180**

• 

# Gulf Coast **Lignites 5.1** 
**n 135**

**n represents number of measurements**

# Physical & Chemical Deactivation Mechanisms

**Physical – Arsenic Oxide (As**  **2** 

## O **3** 

## ) Molecules Condense in Catalyst **Pores**

**Chemical – As 2**  

## O **3** 

## Reacts with V **2** 

## O **5** 

## to form **Non-Catalytic Arsenic**  **Vanadate Compounds**  **Mitigating**
**Measures: 1)**  **Molybdenum Oxide (MoO 3**  

## ) Added to Catalyst **Composition which form Arsenic Molybdate**  **– More**  **reactive than As- Vanadate**  **which slows down de-**  **activation of active V 2**  

## O **5** 

## sites

**2) Calcium Oxide (**  **CaO ) added in furnace form Ca**  **Arsenide [Ca**

**3** 

## (AsO

**4** 

## ) **2** 

## ] which reduces As **2** 

## O **3** 

## conc. in boiler

**Reliable method of measurement of coal arsenic by EPA 2051 or ASTM D6357 required &**  **NOT by ASTM D4606** 

# SO **3** 

# Plume Visibility **Prevention**

## TABLE 1

**(Ref.. Mineral Impurities in Coal Combustion** 

**– E.**  **Raask P. 404**  **Table 19.1 SO 3**  **concentration, dewpoint**  **temperature, and acid deposition in coal-fired boilers**



## <1 **<285 (<54)**  **<1 >10**  **<1 Low sulfur,**  **high calcium 1-2.5**  **285-295 (54-72)**  **1-5 5-10**  **1-2.5 Medium sulfur,** 
**Medium calcium 2.5-5**  **295-400 (72-261)**  **5-10 2-5**  **1-2.5 Medium sulfur,** 
**low calcium 5-10**  **400-410 (261-279)**  **10-25 2-5**  **>2.5 High sulfur,** 
**low calcium Maximum Acid**  **Deposition Rate (mg m**  **-2** 

## ) **Dewpoint Temperature**  **K (F) SO**  **3** 

## in
**Flue Gas (**  **ppm v/v)**  **CaO**
**In Ash (%)**  **Sulfur**
**In Coal (%)**  **Type of Coal**

# Development of Improved Prediction Method

**Required For SO 3**  

# Concentration **Across High Sulfur Flue Gas System (Current Methods Found**  **Inapplicable To Field Performance)**

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# Coal Sulfur, Ash Chemistry, Flue Gas SO 3 

# Conc. & Acid Dew Point Relationship need review and development

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# Mechanism of SO 3 

# Concentration Enhancement by ESP needs to be Ascertained

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# Multi-Point Application of Chemicals for SO 3 

# Mitigation Should be Considered

# • **Alternative Catalyst Development**

**Without Oxides of Vanadium, Titanium, Molybdenum & Tungsten** 

• **Catalyst regeneration**

• **Reliable on line ammonia slip monitoring**

# Conclusions

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# Over 100,000 MW of coal fired units in the USA might need SCR retrofit by 2004 in response to EPA’s SIP Call rule

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# Evolved from two generations of design in the 70’s & 80’s in Japan & Europe, SCR technology has made great strides W.R.T. NOx removal, NH 3 

# slip, catalyst, reactor design, process conditions, etc.

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# While this experience has been utilized by the US SCR industry, it is not adequately transferable to meet the challenges of US boiler designs and **especially** the unique US coal quality

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# High sulfur & high arsenic bituminous & high coal-bound calcium based PRB coal have not been experienced in Europe & Japan

# Conclusions (Cont’d.)

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# Elimination of SO 3 

# plume formation firing high sulfur bituminous coal in units with wet FGD needs:

ÿ 

# Development of improved SO 3 

# formation prediction methods

ÿ 

# Improved understanding of the role of process equipment/conditions

ÿ 

# Multiple control strategy

• 

# Use of additives to control catalyst deactivation by calcium oxide & arsenic needs immediate consideration since the deactivation mechanisms are understood & additives effectiveness are proven

• 

# Development of non-vanadium based catalyst formulations for high dust application needs promotion 

# These goals need to be achieved as **“Necessity is the Mother of Invention”**