NOx Emissions from Cement Mfg - US Environmental Protection ...

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temperatures are on the order of 1650 EC (3000 EF). Figure 4-1. Theoretical equilibrium concentrations of NO in gas from combustion sustained in air. 1 4-4
Fuel combustion in the kiln burning zone is the primary source of thermal NO formation in cement kilns due to x temperatures well above 1400 EC (2550 EF). In contrast, the fuel combustion temperature in a precalciner or in a kiln riser duct is well below 1200 EC (2200 EF), suppressing thermal NOx 4 formation. Mainly fuel and feed NO x may be formed in the secondary firing zone of preheater and precalciner kiln systems. Along with the combustion temperature, the gas-phase residence time and the available oxygen concentration in the high temperature kiln burning zone are important parameters. Longer residence times at the high temperatures will allow the NO to be formed in the equilibrium quantities. Greater amounts of oxygen in the combustion zone will of course lead to greater amounts of NO formation. Once formed, the decomposition of NO at lower temperatures, although thermodynamically favorable, is kinetically limited. Thus, strategies to reduce NO emissions x need to be based upon reducing formation of NO which may be x achieved by reducing combustion temperature, oxygen concentration in the high temperature combustion zone, and the gas residence time at high temperatures. 4.1.2 Fuel NO Formation x Fuel NO is formed by the conversion of nitrogen present in x the fuel used. A recent survey of the cement industry by Portland Cement Association (PCA) indicates that almost 76 percent of the energy requirement of the cement industry is 4-5
Page 1 and 2: EPA-453/R-94-004 ALTERNATIVE CONTRO
Page 3 and 4: ALTERNATIVE CONTROL TECHNOLOGY DOCU
Page 5 and 6: Chapter Page 4.1 MECHANISMS OF NO F
Page 7 and 8: TABLE OF CONTENTS (con.) Chapter Pa
Page 9 and 10: LIST OF TABLES Number Page 2-1 UNCO
Page 11 and 12: CHAPTER 1 INTRODUCTION Congress, in
Page 13 and 14: CHAPTER 2 SUMMARY This chapter pres
Page 15 and 16: 2.2 NO EMISSION CONTROL TECHNOLOGIE
Page 17 and 18: TABLE 2-2. ACHIEVABLE NO REDUCTIONS
Page 19 and 20: TABLE 2-4. CAPITAL AND ANNUAL COSTS
Page 21 and 22: TABLE 2-5. COST EFFECTIVENESS OF NO
Page 23 and 24: eductions ranged from 470 tons/year
Page 25 and 26: CHAPTER 3 INDUSTRY DESCRIPTION 3.1
Page 27 and 28: Type II. Moderate-heat-of-hardening
Page 29 and 30: 3 a TABLE 3-2. UNITED STATES CEMENT
Page 31 and 32: Figure 3-1. U.S. Portland cement pl
Page 33 and 34: Table 3-3. (con.) Rank Clinker 3 (1
Page 35 and 36: 5 cement processes: wet process and
Page 37 and 38: Figure 3-3. New technology in dry-p
Page 39 and 40: substantial levels of silica and al
Page 41 and 42: are achieved by clinker coolers of
Page 43 and 44: 126,000 to 963,000 tons/year with a
Page 45: such as crushing and grinding opera
Page 48 and 49: 4.1.1 Thermal NO Formation x Therma
Page 52 and 53: 4-6
Page 54 and 55: expected to produce more fuel NO th
Page 56 and 57: introduce a large proportion of com
Page 58 and 59: will also mean a somewhat lower sec
Page 60 and 61: ILC systems: In these systems, the
Page 62 and 63: which indicates an average and the
Page 64 and 65: 4-18
Page 66 and 67: Uncontrolled NO x emissions Plant c
Page 68 and 69: from 2 to 9 lb/ton of clinker, and
Page 70 and 71: Capacity Heat in NO x emissions Met
Page 72 and 73: TABLE 4-3. (con.) Capacity Heat in
Page 78 and 79: in estimating uncontrolled and cont
Page 80 and 81: 13. Letter from Sheridan, S.E., to
Page 82 and 83: 44. Chemecology Corporation Source.
Page 84 and 85: 73. Letter and attachments from Smi
Page 86 and 87: NO control approaches applicable to
Page 88 and 89: 5.1.2.2 Kiln Fuel Changing the prim
Page 90 and 91: oxygen content of the primary air m
Page 92 and 93: tend to recirculate hot combustion
Page 94 and 95: e about 15 to 38 percent depending
Page 96 and 97: combustion system shown in Figure 5
Page 98 and 99: 5-14
Page 100 and 101:
Figure 5-3. Schematic of hazardous
Page 102 and 103:
5-18
Page 104 and 105:
higher than typical cement kiln flu
Page 106 and 107:
window is in the middle of a kiln.
Page 108 and 109:
Figure 5-4. Application of the sele
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in Section 5.1.2 is usually difficu
Page 112 and 113:
5.4 REFERENCES 1. Helmuth, R.A., F.
Page 114 and 115:
25. Letter from Wax, J., Institute
Page 116 and 117:
TABLE 6-1. CEMENT KILN MODEL PLANTS
Page 118 and 119:
6-4
Page 120 and 121:
6-6
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The total capital cost is the sum o
Page 124 and 125:
TABLE 6-3. ANNUALIZED COST ELEMENTS
Page 126 and 127:
6-12
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6.1.3.7 Administrative Charges. The
Page 130 and 131:
At this time only three installatio
Page 132 and 133:
6-18
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The annualized costs for low NOx bu
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No additional costs for utilities o
Page 138 and 139:
20 percent PEC cost for contingenci
Page 140 and 141:
TABLE 6-7. ANNUALIZED COSTS FOR RET
Page 142 and 143:
6-28
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PEC for model plant 300,000 ' Heat
Page 146 and 147:
TABLE 6-9. ANNUALIZED COSTS FOR MID
Page 148 and 149:
6-34
Page 150 and 151:
TABLE 6-10. CAPITAL COSTS FOR A URE
Page 152 and 153:
TABLE 6-11. ANNUAL OPERATING COSTS
Page 154 and 155:
6-40
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TABLE 6-12. CAPITAL COSTS FOR AN AM
Page 158 and 159:
TABLE 6-13. ANNUAL OPERATING COSTS
Page 160 and 161:
6-46
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costs range from $9.9 million for t
Page 164 and 165:
The estimated annualized costs for
Page 166 and 167:
6.3 COST EFFECTIVENESS OF NOx CONTR
Page 168 and 169:
emoved. Cost effectiveness were det
Page 170 and 171:
TABLE 6-17. COST EFFECTIVENESS OF R
Page 172 and 173:
6-58
Page 174 and 175:
TABLE 6-18. COST EFFECTIVENESS OF M
Page 176 and 177:
TABLE 6-19. COST EFFECTIVENESS OF U
Page 178 and 179:
6.3.4 Selective Catalytic Reduction
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6-66
Page 182 and 183:
TABLE 6-21. COST EFFECTIVENESS OF S
Page 184 and 185:
6-70
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11. Letter and attachments from Nov
Page 188 and 189:
Tables 7-1 7-2
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TABLE 7-2. REDUCTION IN NO x EMISSI
Page 192 and 193:
model plants described in Section 6
Page 194 and 195:
temperature and excess air may be u
Page 196 and 197:
NOxemissions will form. The heater
Page 198:
equirement for the flue gas reheati
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