Sulfuric Acid Manufacture (eBook)

William G. Davenport, Matt King, Matthew J. King, Michael Moats (Autoren)

eBook Download: PDF

2005 | 1. Auflage
425 Seiten
Elsevier Science (Verlag)
978-0-08-048123-4 (ISBN)

Infos

More sulfuric acid is produced every year than any other chemical. It has a wide range of uses including phosphate fertilizer production, explosives, glue, wood preservatives, and lead-acid batteries. It is also a particularily corrosive and dangerous acid, with extreme environmental and health hazards if not manufactured, used, and regulated properly.

Sulfuric Acid Manufacture: Analysis, Control and Optimization keeps the important topics of safety and regulation at the forefront as it overviews and analyzes the process of sulfuric acid manufacture.

The first nine chapters focus on the chemical plant processes involved in industrial acidmaking, with considerable data input from the authors' industrial colleagues. The last 15 chapters are dedicated to the mathematical analysis of acidmaking.

Both Authors bring years of hands-on knowledge and experience to the work, making it an exceptional reference for anyone involved in sulfuric acid research and/or manufacture.

* Only book to examine the processes of sulfuric acid manufacture from an industrial plant standpoint as well as mathematical.

* Draws on the industrial connections of the authors, through their years of hands-on experience in sulfuric acid manufacture.

* A considerable amount of industrial plant data is presented to support the text.

Inhalt

Front Cover 1
Title Page 4
Copyright Page 5
Table of Contents 8
Preface 6
Chapter 1 Overview 16
1.1 Catalytic Oxidation of SO2 to SO3 17
1.2 H2SO4 Production 19
1.3 Industrial Flowsheet 20
1.4 Sulfur Burning 20
1.5 Metallurgical Offgas 20
1.6 Spent Acid Regeneration 22
1.7 Sulfuric Acid Product 22
1.8 Recent Developments 23
1.9 Alternative Process 23
1.10 Summary 23
Suggested Reading 24
References 24
Chapter 2 Production and Consumption 26
2.1 Uses 28
2.2 Acid Plant Locations and Costs 30
2.3 Price 30
2.4 Summary 31
Suggested Reading 31
References 32
Chapter 3 Sulfur Burning 34
3.1 Objectives 34
3.2 Sulfur 35
3.3 Molten Sulfur Delivery 35
3.4 Sulfur Atomizers and Sulfur Burning Furnaces 37
3.5 Product Gas 41
3.6 Summary 43
References 44
Chapter 4 Metallurgical Offgas Cooling and Cleaning 46
4.1 Initial and Final SO2 Concentrations 46
4.2 Initial and Final Dust Concentrations 48
4.3 Offgas Cooling and Heat Recovery 49
4.4 Electrostatic Collection of Dust 50
4.5 Water Scrubbing 54
4.6 H2O(g) Removal from Scrubber Exit Gas 57
4.7 Summary 58
Suggested Reading 59
References 59
Chapter 5 Regeneration of Spent Sulfuric Acid 62
5.1 Spent Acid Compositions 64
5.2 Spent Acid Handling 64
5.3 Decomposition 65
5.4 Decomposition Furnace Product 67
5.5 Optimum Decomposition Furnace Operating Conditions 67
5.6 Preparation of Offgas for SO2 Oxidation and H2SO4 Making 69
5.7 Summary 71
Suggested Reading 71
References 71
Chapter 6 Dehydrating Air and Gases with Strong Sulfuric Acid 74
6.1 Objectives 76
6.2 Dehydration with Strong Sulfuric Acid 76
6.3 Residence Times 79
6.4 Recent Advances 79
6.5 Summary 84
Suggested Reading 84
References 84
Chapter 7 Catalytic Oxidation of SO2 to SO3 86
7.1 Objectives 86
7.2 Industrial SO2 Oxidation 87
7.3 Catalyst Necessity 89
7.4 SO2 Oxidation 'Heatup' Path 91
7.5 Industrial Multi Catalyst Bed SO2 Oxidation 92
7.6 Industrial Operation 95
7.7 Recent Advances 103
7.8 Summary 103
Suggested Reading 103
References 103
Chapter 8 SO2 Oxidation Catalyst and Catalyst Beds 104
8.1 Catalytic Reactions 105
8.2 Maximum and Minimum Catalyst Operating Temperatures 106
8.3 Composition and Manufacture 106
8.4 Choice of Size and Shape 108
8.5 Choice of Chemical Composition 108
8.6 Catalyst Bed Thickness and Diameter 109
8.7 Gas Residence Times 111
8.8 Catalyst Bed Maintenance 112
8.9 Summary 112
Suggested Reading 113
References 113
Chapter 9 Production of H2SO4(l) from SO3(g) 114
9.1 Objectives 115
9.2 Sulfuric Acid Rather than Water 115
9.3 Industrial H2SO4 Making 117
9.4 Choice of Input and Output Acid Compositions 119
9.5 Acid Temperatures 120
9.6 Gas Temperatures 120
9.7 Operation and Control 120
9.8 Double Contact H2SO4 Making 122
9.9 Intermediate vs. Final H2SO4 Making 124
9.10 Summary 131
Suggested Reading 131
References 131
Chapter 10 Oxidation of SO2 to SO3 - Equilibrium curves 134
10.1 Catalytic Oxidation 134
10.2 Equilibrium Equation 136
10.3 KE as a Function of Temperature 137
10.4 KE in Terms of % SO2 Oxidized 138
10.5 Equilibrium % SO2 Oxidized as a Function of Temperature 139
10.6 Discussion 141
10.7 Summary 142
Reference 142
Problems 142
Chapter 11 SO2 Oxidation Heatup Paths 144
11.1 Heatup Paths 144
11.2 Objectives 145
11.3 Preparing a Heatup Path - the First Point 145
11.4 Assumptions 146
11.5 A Specific Example 146
11.6 Calculation Strategy 147
11.7 Input SO2, O2 and N2 Quantities 147
11.8 Sulfur, Oxygen and Nitrogen Molar Balances 148
11.9 Enthalpy Balance 150
11.10 Calculating Level L Quantities 153
11.11 Matrix Calculation 153
11.12 Preparing a Heatup Path 155
11.13 Feed Gas SO2 Strength Effect 156
11.14 Feed Gas Temperature Effect 158
11.15 Significance of Heatup Path Position and Slope 159
11.16 Summary 160
Problems 160
Chapter 12 Maximum SO2 Oxidation: Heatup Path-Equilibrium Curve Intercepts 162
12.1 Initial Specifications 162
12.2 % SO2 Oxidized-Temperature Points Near an Intercept 163
12.3 Discussion 164
12.4 Effect of Feed Gas Temperature on Intercept 165
12.5 Inadequate % SO2 Oxidized in 1st Catalyst Bed 166
12.6 Effect of Feed Gas SO2 Strength on Intercept 166
12.7 Minor Influence - Equilibrium Gas Pressure 167
12.8 Minor Influence - O2 Strength in Feed Gas 167
12.9 Minor Influence -CO2 in Feed Gas 168
12.10 Catalyst Degradation, SO2 Strength, Feed Gas Temperature 169
12.11 Maximum Feed Gas SO2 Strength 170
12.12 Exit Gas Composition = Intercept Gas Composition 170
12.13 Summary 171
Problems 172
Chapter 13 Cooling 1st Catalyst Bed Exit Gas 174
13.1 1st Catalyst Bed Summary 175
13.2 CooldownPath 176
13.3 Gas Composition Below Equilibrium Curve 178
13.4 Summary 178
Problem 178
Chapter 14 2nd Catalyst Bed Heatup Path 180
14.1 Objectives 180
14.2 % SO2 Oxidized Re-defined 180
14.3 2nd Catalyst Bed Heatup Path 181
14.4 A Specific Heatup Path Question 182
14.5 2nd Catalyst Bed Input Gas Quantities 183
14.6 S, O and N Molar Balances 184
14.7 Enthalpy Balance 185
14.8 Calculating 760 K (level L) Quantities 186
14.9 Matrix Calculation and Result 187
14.10 Preparing a Heatup Path 187
14.11 Discussion 189
14.12 Summary 189
Problem 189
Chapter 15 Maximum SO2 Oxidation in a 2nd Catalyst Bed 192
15.1 2nd Catalyst Bed Equilibrium Curve Equation 192
15.2 2nd Catalyst Bed Intercept Calculation 194
15.3 Two Bed Oxidation Efficiency 196
15.4 Summary 196
Problems 197
Chapter 16 3rd Catalyst Bed SO2 Oxidation 198
16.1 2-3 Cooldown Path 199
16.2 Heatup Path 199
16.3 Heatup Path-Equilibrium Curve Intercept 201
16.4 Graphical Representation 201
16.5 Summary 203
Problems 203
Chapter 17 SO3 and CO2 in Feed Gas 204
17.1 SO3 204
17.2 SO3 Effects 208
17.3 CO2 208
17.4 CO2 Effects 212
17.5 Summary 212
Problems 213
Chapter 18 3 Catalyst Bed Acid Plant 214
18.1 Calculation Specifications 214
18.2 Example Calculation 214
18.3 Calculation Results 215
18.4 3 Catalyst Bed Graphs 215
18.5 Minor Effect - SO3 in Feed Gas 217
18.6 Minor Effect - CO2 in Feed Gas 217
18.7 Minor Effect - Bed Pressure 219
18.8 Minor Effect - SO2 Strength in Feed Gas 220
18.9 Minor Effect - O2 Strength in Feed Gas 221
18.10 Summary of Minor Effects 222
18.11 Major Effect - Catalyst Bed Input Gas Temperatures 222
18.12 Discussion of Book's Assumptions 224
18.13 Summary 225
Reference 225
Chapter 19 After-H2SO4-Making SO2 Oxidation 226
19.1 Double Contact Advantage 228
19.2 Objectives 228
19.3 After-H2SO4-Making Calculations 228
19.4 Equilibrium Curve Calculation 229
19.5 Heatup Path Calculation 232
19.6 Heatup Path-Equilibrium Curve Intercept Calculation 232
19.7 Overall SO2 Oxidation Efficiency 236
19.8 Double/Single Contact Comparison 237
19.9 Summary 238
References 238
Problems 238
Chapter 20 Optimum Double Contact Acidmaking 244
20.1 Total % SO2 Oxidized After All Catalyst Beds 245
20.2 Four Catalyst Beds 245
20.3 Improved Efficiency with 5 Catalyst Beds 246
20.4 Input Gas Temperature Effect 248
20.5 Best Bed for Cs Catalyst 248
20.6 Triple Contact Acid Plant 249
20.7 Summary 249
Chapter 21 Enthalpies and Enthalpy Transfers 250
21.1 Input and Output Gas Enthalpies 251
21.2 H2SO4 Making Input Gas Enthalpy 254
21.3 Heat Transfers 254
21.4 Heat Transfer Rate 256
21.5 Summary 256
Problems 257
Chapter 22 Control of Gas Temperature by Bypassing 258
22.1 Bypassing Principle 258
22.2 Objective 258
22.3 Gas to Economizer Heat Transfer 260
22.4 Heat Transfer Requirement for 480 K Economizer Output Gas 261
22.5 Changing Heat Transfer by Bypassing 261
22.6 460 K Economizer Output Gas 262
22.7 Bypassing for 460, 470 and 480 Economizer Output Gas 263
22.8 Bypassing for 470 K Economizer Output Gas While Input Gas Temperature is Varying 263
22.9 Industrial Bypassing 264
22.10 Summary 265
Problems 266
Chapter 23 H2SO4 Making 268
23.1 Objectives 269
23.2 Mass Balances 270
23.3 SO3 Input Mass 270
23.4 H2O(g) Input from Moist Acid Plant Input Gas 271
23.5 Water for Product Acid 272
23.6 Calculation of Mass Water In and Mass Acid Out 273
23.7 Interpretations 276
23.8 Summary 279
Problem 280
Chapter 24 Acid Temperature Control and Heat Recovery 286
24.1 Objectives 286
24.2 Calculation of Output Acid Temperature 286
24.3 Effect of Input Acid Temperature 291
24.4 Effect of Input Gas Temperature 292
24.5 Effect of Output Acid H2SO4 Concentration on Output Acid Temperature 293
24.6 Effect of Input Gas SO3 concentration on Output Acid Temperature 293
24.7 Acid Cooling 295
24.8 Target Acid Temperatures 296
24.9 Recovery of Acid Heat as Steam 296
24.10 Summary 299
References 299
Problems 300
Appendices 302
Appendix A: Sulfuric Acid Properties 302
Appendix B: Derivation of Equilibrium Equation (10.12) 308
Appendix C: Free Energy Equations for Equilibrium Curve Calculations 319
Appendix D: Preparation of Fig. 10.2 Equilibrium Curve 321
Appendix E: Proof that Volume% = Mole% (for Ideal Gases) 324
Appendix F: Effect of CO2 and Ar on Equilibrium Equations (None) 326
Appendix G: Enthalpy Equations for Heatup Path Calculations 331
Appendix H: Matrix Solving Using Tables 11.2 and 14.2 as Examples 336
Appendix I: Enthalpy Equation in Heatup Path Matrix Cells 337
Appendix J: Heatup Path-Equilibrium Curve Intercept Calculations 341
Appendix K: 2nd Catalyst Bed Heatup Path Calculations 348
Appendix L: Equilibrium Equation for Multi-Catalyst Bed SO2 Oxidation 351
Appendix M: 2nd Catalyst Bed Intercept Calculations 354
Appendix N: 3rd Catalyst Bed Heatup Path Worksheet 359
Appendix O: 3rd Catalyst Bed Intercept Worksheet 361
Appendix P: Effect of SO3 in Fig. 10.1 Feed Gas on Equilibrium Equations 363
Appendix Q: SO3-in-Feed-Gas Intercept Worksheet 371
Appendix R: CO2-and SO3-in-Feed-Gas Intercept Worksheet 373
Appendix S: 3-Catalyst-Bed 'Converter' Calculations 375
Appendix T: Worksheet for Calculating After-Intermediate-H2SO4-Making Heatup Path Equilibrium Curve Intercepts 382
Appendix U: After-H2SO4-Making SO2 Oxidation with SO3 and CO2 in Input Gas 385
Appendix V: Moist Air in H2SO4 Making Calculations 390
Appendix W: Calculation of H2SO4 Making Tower Mass Flows 393
Answers to Numerical Problems 398
Author Index 410
Index 412

Textauszug

CHAPTER 1 Overview

Sulfuric acid is a dense clear liquid. It is used for making fertilizers, leaching metallic ores, refining petroleum and for manufacturing a myriad of chemicals and materials. Worldwide, about 180 million tonnes of sulfuric acid are consumed per year (Kitto, 2004).

The raw material for sulfuric acid is SO2 gas. It is obtained by:

(a) burning elemental sulfur with air

(b) smelting and roasting metal sulfide minerals

(c) decomposing contaminated (spent) sulfuric acid catalyst.

Elemental sulfur is far and away the largest source.

Table 1.1 describes three sulfuric acid plant feed gases. It shows that acid plant SO2 feed is always mixed with other gases.

Table 1.1. Compositions of acid plant feed gases entering SO2 oxidation ‘converters’, 2005. The gases may also contain small amounts of CO2 or SO3. The data are from the industrial tables in Chapter 3 through 9.

Sulfuric acid is made from these gases by:

(a) catalytically reacting their SO2 and O2 to form SO3(g)

(b) reacting (a)’s product SO3(g) with the H2O() in 98.5 mass% H2SO4, 1.5 mass% H2O sulfuric acid.

Industrially, both processes are carried out rapidly and continuously, Fig. 1.1.

Fig. 1.1. Schematic of sulfur burning sulfuric acid plant, courtesy Outokumpu OYJ www.outokumpu.com The main components are the catalytic SO2 + ½O2 ≡⃥ SO3 ‘converter’ (tall, back), twin H2SO4 making (‘absorption’) towers (middle distance) and large molten sulfur storage tank (front). The combustion air filter and air dehydration (‘drying’) tower are on the right. The sulfur burning furnace is hidden behind. Catalytic converters are typically 12 m diameter.

1.1 Catalytic Oxidation of SO2 to SO3

O2 does not oxidize SO2 to SO3 without a catalyst. All industrial SO2 oxidation is done by sending SO2 bearing gas down through ‘beds’ of catalyst, Fig. 1.2. The reaction is:

Fig. 1.2. Catalyst pieces in a catalytic SO2 oxidation ‘converter’. Converters are ˜15 m high and 12 m in diameter. They typically contain four, ½-1 m thick catalyst beds. SO2-bearing gas descends the bed at ˜3000 Nm3 per minute. Individual pieces of catalyst are shown in Fig. 8.1. They are ˜0.01 m in diameter and length.

     (1.1).

It is strongly exothermic . Its heat of reaction provides considerable energy for operating the acid plant.

1.1.1 Catalyst

At its operating temperature, 700-900 K, SO2 oxidation catalyst consists of a molten film of V, K, Na, (Cs) pyrosulfate salt on a solid porous SiO2 substrate. The molten film rapidly absorbs SO2(g) and O2(g) – and rapidly produces and desorbs SO3(g), Chapter 7 and 8.

1.1.2 Feed gas drying

Eqn. (1.1) indicates that catalytic oxidation feed gas is always dry#. This dryness avoids:

(a) accidental formation of H2SO4 by reaction of H2O(g) with the SO3(g) product of catalytic SO2 oxidation

(b) condensation of the H2SO4 in cool flues and heat exchangers

(c) corrosion.

The H2O(g) is removed by cooling/condensation (Chapter 4) and by dehydration with H2SO4(), Chapter 6.

1.2 H2SO4 Production

Catalytic oxidation’s SO3(g) product is made into H2SO4 by contacting catalytic oxidation’s exit gas with strong sulfuric acid, Fig. 1.3. The reaction is:

Fig. 1.3. Top of H2SO4-making (‘absorption’) tower, courtesy Monsanto Enviro-Chem Systems, Inc. www.enviro-chem.com The tower is packed with ceramic saddles. 98.5 mass% H2SO4, 1.5 mass% H2O sulfuric acid is distributed uniformly across this packed bed. Distributor headers and ‘downcomer’ pipes are shown. The acid flows through slots in the downcomers down across the bed (see buried downcomers below the right distributor). It descends around the saddles while SO3-rich gas ascends, giving excellent gas-liquid contact. The result is efficient H2SO4 production by Reaction (1.2). A tower is ˜7 m diameter. Its packed bed is ˜4 m deep. About 25 m3 of acid descends per minute while 3000 Nm3 of gas ascends per minute.

     (1.2)

Reaction (1.2) produces strengthened sulfuric acid because it consumes H2O() and makes H2SO4().

H2SO4() is not made by reacting SO3(g) with water. This is because Reaction (1.2) is so exothermic that the product of the SO3(g)+H2O() → H2SO4() reaction would be hot H2SO4 vapor – which is difficult and expensive to condense.

The small amount of H2O() and the massive amount of H2SO4()in Reaction (1.2)’s input acid avoids this problem. The small amount of H2O()limits the extent of the reaction. The large amount of H2SO4()warms only 25 K while it absorbs Eqn. (1.2)’s heat of reaction.

1.3 Industrial Flowsheet

Fig. 1.4 is a sulfuric acid manufacture flowsheet. It shows:

(a) (a) the three sources of SO2 for acid manufacture (metallurgical, sulfur burning and spent acid decomposition gas)

(b) (b) acid manufacture from SO2 by Reactions (1.1) and (1.2).

Fig. 1.4. Double contact sulfuric acid manufacture flowsheet. The three main SO2 sources are at the top. Sulfur burning is by far the biggest source. The acid product leaves from two H2SO4 making towers at the bottom. Barren tail gas leaves the final H2SO4 making tower, right arrow.

(b) is the same for all three sources of SO2. The next three sections describe (a)’s three SO2 sources.

1.4 Sulfur Burning

About 70% of sulfuric acid is made from elemental sulfur. All the sulfur is obtained as a byproduct from refining natural gas and petroleum.

The sulfur is made into SO2 acid plant feed by:

melting the sulfur

spraying it into a hot furnace

burning the droplets with dried air.

The reaction is:

     (1.3)

Very little SO3(g) forms at the 1400 K flame temperature of this reaction, Fig. 7.4. This explains Fig. 1.4’s two-step oxidation, i.e.:

(a) burning of sulfur to SO2

then:

(b) catalytic oxidation of SO2 to SO3, 700 K.

The product of sulfur burning is hot, dry SO2, O2, N2 gas. After cooling to ˜700 K, it is ready for catalytic SO2 oxidation and subsequent H2SO4-making.

1.5 Metallurgical Offgas

SO2 in smelting and roasting gas accounts for about 20% of sulfuric acid production. The SO2 is ready for sulfuric acid manufacture, but the gas is dusty. If left in the gas, the dust would plug the downstream catalyst layers and block gas flow. It must be removed before the gas goes to catalytic SO2 oxidation.

It is removed by combinations of:

(a) settling in waste heat boilers

(b) electrostatic precipitation

(c) scrubbing with water (which also removes impurity vapors).

After treatment, the gas contains ˜1 milligram of dust per Nm3 of gas. It is ready for drying, catalytic SO2 oxidation and H2SO4 making.

1.6 Spent Acid Regeneration

A major use of sulfuric acid is as catalyst for petroleum refining and polymer manufacture, Chapter 5. The acid becomes contaminated with water, hydrocarbons and other compounds during this use. It is regenerated by:

(a) spraying the acid into a hot (˜1300 K) furnace – where the acid decomposes to SO2, O2 and H2O(g)

(b) cleaning and drying the furnace offgas

(c) catalytically oxidizing the offgas’s SO2 to SO3

(d) making the resulting SO3(g) into new H2SO4() by contact with strong sulfuric acid, Fig. 1.4.

About 10% of sulfuric acid is made this way. Virtually all is re-used for petroleum refining and polymer manufacture.

1.7 Sulfuric Acid Product

Most industrial acid plants have three flows of sulfuric acid – one gas-dehydration flow and two H2SO4-making flows. These flows are connected through automatic control valves to:

(a) maintain proper flows and H2SO4...

Produkt-Details

• Erscheint lt. Verlag: 4.11.2005
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber
• Themenwelt: Naturwissenschaften ► Chemie ► Technische Chemie
• Themenwelt: Technik ► Bauwesen
• Themenwelt: Technik ► Maschinenbau
• Themenwelt: Technik ► Umwelttechnik / Biotechnologie
• ISBN-10: 0-08-048123-X / 008048123X
• ISBN-13: 978-0-08-048123-4 / 9780080481234