Stuart The Problems of Sulphur

Reviews in Coal Science
1. Auflage 2013
ISBN: 978-1-4831-6208-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 366 Seiten

The Problems of Sulphur discusses all aspects of the problems associated with sulfur in coal. The book is divided into three parts. Part 1 addresses the forms of sulfur in coal and evaluates processes directed at the chemical removal of sulphur. Part 2 expands on this to look at alternative means of removing sulfur both physically and biologically, sulfur removal during the combustion of coal and flue gas desulfurization processes. Part 3 looks at the role of sulphates in the atmosphere from the points of view of their formation, transport and deposition and of their effects on health, materials and the atmosphere. The book will be of value to engineers, environmentalists, and chemists.

Dr. Sam Stuart is a physiotherapist and a research Fellow within the Balance Disorders Laboratory, OHSU. His work focuses on vision, cognition and gait in neurological disorders, examining how technology-based interventions influence these factors. He has published extensively in world leading clinical and engineering journals focusing on a broad range of activities such as real-world data analytics, algorithm development for wearable technology and provided expert opinion on technology for concussion assessment for robust player management. He is currently a guest editor for special issues (sports medicine and transcranial direct current stimulation for motor rehabilitation) within Physiological Measurement and Journal of NeuroEngineering and Rehabilitation, respectively.

Autoren/Hrsg.

Stuart, Sam

Inhaltsverzeichnis

1;Front Cover;1
2;The Problems of Sulphur;4
3;Copyright Page;5
4;Preface;6
5;Table of Contents;8
6;Part 1 Chemical desulphurisation of coal;12
6.1;Chapter 1 Introduction;14
6.2;Chapter 2 Sulphur in coal;16
6.2.1;Pyritic sulphur;16
6.2.2;Organic sulphur;19
6.3;Chapter 3 Requirements for chemically cleaned coal;21
6.4;Chapter 4 Chemistry of coal cleaning;22
6.4.1;Reactions of pyritic sulphur;22
6.4.2;Reactions of organic sulphur;23
6.5;Chapter 5 Processes for the chemical cleaning of coal;25
6.5.1;Processes based on the oxidation of sulphur;25
6.5.2;Processes based on the displacement of sulphur;45
6.5.3;Other processes;49
6.6;Chapter 6 Evaluation of processes;52
6.7;Chapter 7 Current research on chemistry of desulphurisation reactions;54
6.7.1;Oxidation reactions;54
6.7.2;Displacement reactions;60
6.8;Chapter 8 Conclusions;62
7;Part 2 Control of sulphur oxides from coal combustion;70
7.1;Chapter 9 Introduction;72
7.2;Chapter 10 The occurrence of sulphur;73
7.3;Chapter 11 Physical desulphurisation of coal;76
7.3.1;Differences in relative densities;79
7.3.2;Separation using surface properties;80
7.3.3;Separation using magnetic properties;83
7.4;Chapter 12 Microbiological desulphurisation of coal;90
7.5;Chapter 13 Sulphur removal during combustion;93
7.5.1;Selection and utilisation of sorbent;94
7.5.2;Pretreatment of limestone;96
7.5.3;Operating parameters;99
7.5.4;Post-sulphation treatment;102
7.6;Chapter 14 Wet scrubbing flue gas desulphurisation processes;110
7.6.1;Non-regenerable processes;111
7.6.2;Regenerable processes;122
7.7;Chapter 15 Dry flue gas desulphurisation processes;128
7.7.1;Dry injection processes;129
7.7.2;Spray dryer processes;130
7.7.3;Dry adsorption;132
7.8;Chapter 16 Disposal of flue gas desulphurisation waste;136
7.8.1;Direct ponding;136
7.8.2;Landfill of untreated sludge;137
7.8.3;Treatment of sludge;137
7.9;Chapter 17 Conclusions;140
7.9.1;References;142
8;Part 3 Sulphates in the atmosphere;158
8.1;Chapter 18 Introduction;161
8.2;Chapter 19 The sulphur cycle;170
8.2.1;Atmosphere;174
8.2.2;Pedosphere;176
8.2.3;Hydrosphere;177
8.2.4;Lithosphere;177
8.2.5;Man-made component;177
8.2.6;Summary and comments;184
8.3;Chapter 20 Atmospheric chemistry of sulphur;186
8.3.1;Reduced sulphur compounds;187
8.3.2;Gas phase oxidation of SO2;187
8.3.3;Aqueous phase oxidation of SO2;191
8.3.4;Gas/particle interactions;195
8.3.5;Nucleation;196
8.3.6;Particle size;197
8.3.7;Summary and comments;199
8.4;Chapter 21 Sulphate formation in plumes;201
8.4.1;Plume dispersion;201
8.4.2;Coal-fired power plant plumes;203
8.4.3;Oil-fired power plant plumes;214
8.4.4;Smelter plumes;215
8.4.5;Urban plumes;216
8.4.6;Particle formation;216
8.4.7;Summary and comments;217
8.4.8;Chapter 22 Atmospheric aerosol concentration patterns;219
8.4.9;Summary and comments;226
8.5;Chapter 23 Transport;227
8.5.1;Mesoscale transport;227
8.5.2;Long-range transport;228
8.5.3;Summary and comments;236
8.6;Chapter 24 Deposition;237
8.6.1;Dry deposition;238
8.6.2;Occult deposition;239
8.6.3;Wet deposition processes;240
8.6.4;Precipitation chemistry;243
8.6.5;Summary and comments;266
8.7;Chapter 25 Long-range transport and deposition models;268
8.7.1;Statistical trajectory analyses;268
8.7.2;Theoretical models;273
8.7.3;Contribution of local sources;286
8.7.4;Summary and comments;288
8.8;Chapter 26 Human health;289
8.8.1;Particle deposition in the respiratory tract;290
8.8.2;Animal studies;292
8.8.3;Human clinical studies;294
8.8.4;Epidemiology;296
8.8.5;Non-respiratory health effects;302
8.8.6;Summary and contents;304
8.9;Chapter 27 Visibility;305
8.9.1;Summary and comments;311
8.10;Chapter 28 Climate;312
8.10.1;Summary and comments;313
8.11;Chapter 29 Materials;315
8.11.1;Summary and comments;317
8.12;Chapter 30 Conclusions;318
8.12.1;References;320
9;Index;350
10;Information for the coal industry;366

Leseproben

Chapter 7

Current research on chemistry of desulphurisation reactions

Publisher Summary

This chapter focuses on the current research on chemistry of desulfurization reactions. Squires ., 1980, have determined the potential of oxidation techniques for the removal of organic sulphur from coal by subjecting model compounds to the oxydesulphurization conditions used in the Ames process. The model compounds used represent the major types of sulfur compounds commonly believed to be present in coal. They are all in the divalent or sulfide oxidation state that is consistent with the generally reduced state of coal. The chapter presents the results of the oxydesulfurization of the model compounds. The amount of starting material recovered is an indication of the degree of reaction that the compound underwent. To assess the possibility that coal may act catalytically in oxidation, reactions of four compounds were carried out in the presence of coal. Compounds of the thiophene type and all sulphides except benzylic sulphides are inert to oxidation under the Ames oxydesulphurization conditions. Oxidation of benzylic sulfides is believed to occur by oxidation of the C atom in the CH2 group and not by oxidation of the S atom. To eliminate the possibility that the benzylic sulfides are, in fact, oxidized to either the sulfide or sulfone, which may then be responsible for the observed products, both benzyl phenyl sulfoxide and benzyl phenyl sulfone were subjected to the reaction conditions. The sulfoxide was converted partially to the sulfone, which did not undergo further reaction. The fact that sulphone is not a product of the oxidation of benzylic sulphides is evidence that the oxidation of the S atom does not occur.

Oxidation reactions

Squires (1980) have determined the potential of oxidation techniques for the removal of organic sulphur from coal by subjecting model compounds to the oxydesulphurisation conditions used in the Ames process (Chang ., 1980). The model compounds used, which are shown in Figure 7.1, represent the major types of sulphur compounds commonly believed to be present in coal. They are all in the divalent or sulphide oxidation state which is consistent with the generally reduced state of coal.

Figure 7.1 Compounds used to model the reactions of organic sulphur in coal (after Squires ., 1980)

The results of the oxydesulphurisation of the model compounds are presented in Table 7.1. The amount of starting material recovered is an indication of the degree of reaction that the compound underwent. In order to assess the possibility that coal may act catalytically in the oxidation, reactions of four compounds were carried out in the presence of coal. These results are presented in Table 7.2. To take into account the decreased recovery expected due to adsorption of the model compounds onto coal, experiments using both oxygen and nitrogen were performed. The right hand column of Table 7.2 shows the yields of recovered starting material corrected for this adsorption.

Table 7.1

Effect of the Ames process on model organic sulphur compounds

Reaction conditions: 150°C, 1.38 MPa, 0.2 M Na2CO3, 3600s

(after Squires ., 1980)

Table 7.2

Effect of the Ames process on model organic sulphur compounds in the presence of coal

(after Squires ., 1980)

The results presented in Tables 7.1 and 7.2 show that compounds of the thiophene type and all sulphides except benzylic sulphides are inert to oxidation under the Ames oxydesulphurisation conditions. These compounds represent the principal functional groups believed to be in coal. Thiophenol is readily oxidised to the diphenyl disulphide which under more severe conditions is oxidised to benzene sulphonic acid.

(7.1)

(7.2)

The oxidation of benzylic sulphides (benzyl methyl sulphide and benzyl phenyl sulphide) is believed to occur by the oxidation of the C atom in the CH2 group and not by oxidation of the S atom. To eliminate the possibility that the benzylic sulphides are, in fact, oxidised to either the sulphide or sulphone, which may then be responsible for the observed products, both benzyl phenyl sulphoxide and benzyl phenyl sulphone were subjected to the reaction conditions. The sulphoxide was converted partially to the sulphone which did not undergo further reaction. The fact that sulphone is not a product of the oxidation of benzylic sulphides (see Table 7.1) is evidence that the oxidation of the S atom does not occur. As further evidence that the oxidation takes place at the C atom, fluorene, which also contains a CH2 group, was found to be oxidised to fluorenone under similar reaction conditions.

(7.3)

Dibenzothiophene, did not react. The 55% yield of fluorenone is in good agreement with the yields obtained from the oxidation of the benzylic sulphides.

More recent work has involved subjecting sulphur-containing synthetic polymers and the pyridine extract of Iowa Lovilia coal to the Ames process conditions (Squires and Venier, 1981; Squires ., 1981). The results obtained with three modified polystyrenes, shown in Table 7.3, add support to the model compound studies (Squires ., 1981). Phenylthiomethyl and tolylthiomethyl polystyrenes are analogues of the model compound, benzyl phenyl sulphide. As expected, these polymers were reactive, but less so than the corresponding model compound. Polystyrene cross-linked by dibenzothiophene was unreactive, confirming the inertness of the dibenzothiophene moiety to oxydesulphurisation.

Table 7.3

Effect of the Ames process on sulphur-containing polystyrene polymers

Reaction conditions: 150°C; 1.38 MPa; 0.2 aqueous Na2CO3, 3600s

aP – polystyrene backbone; substituents are attached through the para position.
DBT – dibenzothiophene nucleus.

(after Squires ., 1981)

Perhaps the most complete evidence of the unreactive nature of some organic sulphur in coal to oxydesulphurisation has been obtained with a pyridine coal extract (Squires and Venier, 1981; Squires ., 1981). All the sulphur in an extract is organically bound and hence the total sulphur analysis, which is quite accurate, is also the organic sulphur determination. The results in Table 7.4 show that oxydesulphurisation apparently does not reduce the organic sulphur content of the extract. However, some of the carbon in the extract is oxidised as evidenced by the increases in S/C ratio, the oxygen content and O/C ratio.

Table 7.4

Effect of the Ames process on pyridine extract of Lovilia coala

a150°C, 0.2 M aqueous Na2CO3, 3600 s

b1.38 MPa N2 pressure

c1.38 MPa O2 pressure

dSamples contain a small amount of ash or NaCl. Element percents are expressed ash or NaCl free

(after Squires ., 1981)

Warzinski (1980) have studied the effect of the PETC oxydesulphurisation process on the following model sulphur compounds:

The reactions of the thiol and the sulphonic acid are similar to those reported by Squires (1980). Compound 4, a sulphonated polystyrene copolymer also reacted in a manner similar to that reported by Squires (1980) for organic compounds containing benzylic sulphides. Compound 5, polyphenyl sulphide, which contains no benzylic carbon was treated at 200°C with and without the presence of coal. In all cases the polymer was recovered (95%) unchanged.

The major disagreement between the work of Warzinski (1980) and Squires (1980) is in the reaction of benzothiophene. Squires (1980) report an 87% recovery of the compound after subjection to the Ames oxydesulphurisation conditions. Warzinski (1980) report 97% conversion of benzothiophene into 2-sulphobenzoic acid, benzoic acid, benzothiophene-1, 1-dioxide, and phenol, by the following proposed reaction:

It is unlikely that the differences in the process conditions (200°C, acidic solution, compared with 150°C and basic solution) would account for the disagreement. Oxidation of the S atom, as proposed by Warzinski (1980), is unlikely in view of the work at Ames, reported above.

Attar (1980) has summarised the relative reactivities of sulphur containing species in coal to oxidation and reduction (Table 7.5).

Table 7.5

Reactivity of sulphur-containing compounds in coal

(after Attar, 1980)

The stability of the thiophenic sulphur and sulphides under oxydesulphurisation conditions may be more simply explained in terms of bond strengths. A strong bond exists between a S atom and a C atom within an aromatic ring. Indeed, nowhere in the oxidation of the model compounds shown in Table 7.1 is such a bond broken. Thiophene converts to diphenyl disulphide which is oxidised by the...