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

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temperature produces hard fused nodules called clinker which are further ground to a desired fineness. Five types of portland cement are recognized in the United States which contain varying amounts of the basic clinker compounds given in Table 3-1. 2 Different types of cements are produced by starting with appropriate kiln feed composition, blending the clinker with the desired amount of calcium sulfate, and grinding the product mixture to appropriate fineness. Manufacture of cements of all of the various types involves the same basic high temperature fusion and clinkering process responsible for the NO emissions x from cement kilns. 3.2 TYPES OF CEMENT PRODUCED The five basic types of portland cement recognized and 2 produced in the United States are described below. In addition, different varieties are prepared by using various blending formulations. 3 Type I. Regular portland cements are the usual products for general concrete construction, most commonly known as gray cement because of its color. White cement typically contains less ferric oxide and is used for special applications. There are other types of regular cements such as oil-well cement, quick- setting cement, and others for special uses. TABLE 3-1. BASIC CLINKER COMPOUNDS 2 Formula Name 2CaO"SiO Dicalcium silicate 2 3CaO"SiO Tricalcium silicate 2 3CaO"Al O Tricalcium aluminate 2 3 4CaO"Al O "Fe O Tetracalcium aluminoferrite 2 3 2 3 MgO Magnesium oxide in free state or combined in di- or tricalcium silicate lattice. 3-2
Type II. Moderate-heat-of-hardening and sulfate resisting portland cements are for use where moderate heat of hydration is required or for general concrete construction exposed to moderate sulfate action. Type III. High-early-strength cements are made from raw materials with a lime to silica ratio higher than that of Type I cement and are ground finer than Type I cements. They contain a higher proportion of tricalcium silicate (3CaO"SiO ) than regular 2 portland cements. Type IV. Low-heat portland cements contain a lower percentage of tricalcium silicate (3CaO"SiO ) and tricalcium 2 aluminate (3CaO"Al O ) than type I, thus lowering the heat 2 3 evolution. Consequently, the percentage of dicalcium silicate is increased substantially and the percentage of tetracalcium aluminoferrite (4CaO"Al O "Fe O ) may be increased or may stay the 2 3 2 3 same. Type V. Sulfate-resisting portland cements are those which, by their composition or processing, resist sulfates better than the other four types. The use of air-entraining agents increases the resistance of the hardened concrete to scaling from alternate freezing and thawing. By adding these materials to the first three types of cements, IA, IIA, and IIIA varieties of cements are produced. Additional varieties of cements are produced for special applications by blending different ingredients: masonry cement, expansive cement, oil-well cement, etc. Masonry cements are commonly finely ground mixtures of portland cement, limestone, and air-entraining agents. Granulated blast furnace slags and natural or artificial pozzolans are mixed and interground with portland cement to prepare still other varieties such as blended types IP, IS, S, I(PM), and I(SM). 3 3.3 INDUSTRY CHARACTERIZATION 3.3.1 Description of the Cement Industry About 80.8 million tons of gray portland cement were produced in a total of 213 cement kilns at 109 plants in the 3-3
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: CHAPTER 3 INDUSTRY DESCRIPTION 3.1
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 50 and 51: temperatures are on the order of 16
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 74 and 75: TABLE 4-3. (con.) Capacity Heat in
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TABLE 4-3. (con.) Capacity Heat in
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in estimating uncontrolled and cont
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13. Letter from Sheridan, S.E., to
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44. Chemecology Corporation Source.
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73. Letter and attachments from Smi
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NO control approaches applicable to
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5.1.2.2 Kiln Fuel Changing the prim
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oxygen content of the primary air m
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tend to recirculate hot combustion
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e about 15 to 38 percent depending
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combustion system shown in Figure 5
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5-14
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Figure 5-3. Schematic of hazardous
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5-18
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higher than typical cement kiln flu
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window is in the middle of a kiln.
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Figure 5-4. Application of the sele
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in Section 5.1.2 is usually difficu
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5.4 REFERENCES 1. Helmuth, R.A., F.
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25. Letter from Wax, J., Institute
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TABLE 6-1. CEMENT KILN MODEL PLANTS
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6-4
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6-6
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The total capital cost is the sum o
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TABLE 6-3. ANNUALIZED COST ELEMENTS
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6-12
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6.1.3.7 Administrative Charges. The
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At this time only three installatio
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6-18
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The annualized costs for low NOx bu
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No additional costs for utilities o
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20 percent PEC cost for contingenci
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TABLE 6-7. ANNUALIZED COSTS FOR RET
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6-28
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PEC for model plant 300,000 ' Heat
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TABLE 6-9. ANNUALIZED COSTS FOR MID
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6-34
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TABLE 6-10. CAPITAL COSTS FOR A URE
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TABLE 6-11. ANNUAL OPERATING COSTS
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6-40
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TABLE 6-12. CAPITAL COSTS FOR AN AM
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TABLE 6-13. ANNUAL OPERATING COSTS
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6-46
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costs range from $9.9 million for t
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The estimated annualized costs for
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6.3 COST EFFECTIVENESS OF NOx CONTR
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emoved. Cost effectiveness were det
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TABLE 6-17. COST EFFECTIVENESS OF R
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6-58
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TABLE 6-18. COST EFFECTIVENESS OF M
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TABLE 6-19. COST EFFECTIVENESS OF U
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6.3.4 Selective Catalytic Reduction
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6-66
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TABLE 6-21. COST EFFECTIVENESS OF S
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6-70
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11. Letter and attachments from Nov
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Tables 7-1 7-2
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TABLE 7-2. REDUCTION IN NO x EMISSI
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model plants described in Section 6
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temperature and excess air may be u
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NOxemissions will form. The heater
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equirement for the flue gas reheati
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