CN112930320B - Method for producing sulfur - Google Patents

Method for producing sulfur Download PDF

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Publication number
CN112930320B
CN112930320B CN201980070586.XA CN201980070586A CN112930320B CN 112930320 B CN112930320 B CN 112930320B CN 201980070586 A CN201980070586 A CN 201980070586A CN 112930320 B CN112930320 B CN 112930320B
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claus
gas
reaction
sulfuric acid
reactor
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CN112930320A (en
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M·特莱夫森
L·P·布罗霍尔特
P·A·索伦森
M·利克
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Topsoe AS
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Haldor Topsoe AS
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/02—Preparation of sulfur; Purification
    • C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
    • C01B17/0404—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8603—Removing sulfur compounds
    • B01D53/8612—Hydrogen sulfide
    • B01D53/8615—Mixtures of hydrogen sulfide and sulfur oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/869—Multiple step processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8693—After-treatment of removed components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
    • B01J20/28042—Shaped bodies; Monolithic structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3202—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
    • B01J20/3204—Inorganic carriers, supports or substrates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
    • B01J20/3234—Inorganic material layers
    • B01J20/3236—Inorganic material layers containing metal, other than zeolites, e.g. oxides, hydroxides, sulphides or salts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/02—Preparation of sulfur; Purification
    • C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
    • C01B17/0404—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process
    • C01B17/0426—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process characterised by the catalytic conversion
    • C01B17/0434—Catalyst compositions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/50—Inorganic acids
    • B01D2251/506—Sulfuric acid
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Abstract

The invention relates to a process device: comprising a Claus reaction furnace, a Claus waste heat boiler and SO 3 A decomposition section and a claus conversion section, wherein the claus reaction furnace has an inlet and an outlet, the claus waste heat boiler has a gas inlet, a gas outlet and optionally an elemental sulfur outlet, SO 3 The decomposition section has a gas inlet and a gas outlet, the claus conversion section has a gas inlet, a gas outlet, and an elemental sulfur outlet, and wherein the inlet of the claus reaction furnace is configured to receive a feed gas, sulfuric acid, fuel, oxidant, and optionally a sulfuric acid atomization medium, and the outlet of the claus reaction furnace is configured to be in fluid communication with the inlet of a claus waste heat boiler, wherein the outlet of the claus waste heat boiler is configured to be in fluid communication with the SO 3 The inlet of the decomposing field is in fluid communication with SO 3 The outlet of the decomposition section is in fluid communication with the inlet of the claus conversion section. The process has the associated benefit that it avoids undesirable poisoning of the claus catalyst (sulfation) and contamination of the elemental sulphur product with sulfuric acid in the claus conversion stage.

Description

Method for producing sulfur
The invention relates to a method for converting H in a Claus process plant 2 Method for converting S into elemental sulphur, wherein H is added in the hot stage of a Claus process plant 2 SO 4 。
H 2 S is a common by-product in many processes, including hydrodesulfurization of refinery product streams, viscose production, and natural gas desulfurization. Due to H 2 S is extremely toxic, odorous and environmentally unfriendly, and is ideal in the case of H 2 S is converted before being discharged to the atmosphere.
In addition to producing the well-known high concentration of H during refining 2 In addition to the S gas, it is also generally possible to produce a so-called sour water stripping gas which comprises approximately equimolar amounts of H 2 S、H 2 O and NH 3 。
Especially in refineries, for H elimination 2 The process of choice for S has been the claus process, which is well known and optimized over the last eighty years. The claus process is carried out by sub-stoichiometrically combusting H in a claus reactor 2 S generates SO 2 To provide a claus reformer feed gas. Subsequent claus process will leave H 2 S and SO formed 2 Converted to elemental sulfur, which can be condensed and withdrawn.
It has now been found that the addition of sulfuric acid to a claus reactor provides an opportunity for optimization of the size and operating costs of the claus process equipment. H 2 SO 4 Is O 2 Is added to the concentrated source and temperature regulator. Both of these characteristics are valuable for the compatibilization of the claus process. It has also been determined that such H 2 SO 4 The addition of (2) may damage the catalyst of the claus process by sulfation, thus requiring the use of SO before catalyzing the claus process 3 Protective agent
In WO 2012/152919 A1, a sulfuric acid process for treating claus tail gas is proposed, wherein H in claus tail gas is described 2 S-direction H 2 SO 4 Is transformed by the above method. The method comprises the following steps:
1. sub-stoichiometric oxidation in a claus reactor
2. Claus conversion
3. Oxidizing the reduced sulfur species (H) in the Claus tail gas in an oxygen-enriched atmosphere at 400-700 DEG C 2 S)
4.SO 2 To SO 3 Is of the catalytic oxidation of (a)
5.H 2 SO 4 Is condensed by (a)
It has been recognized that H 2 SO 4 The product is not always satisfactory and, as mentioned above, it is recommended to recycle sulfuric acid to the claus reaction furnace or H 2 Upstream of the S oxidation step. However, the recycling of sulfuric acid is considered only one abatement of sulfuric acid, and recycling H has not been evaluated yet 2 SO 4 The effect on the sulfuric acid process or the claus process, i.e. H is not recognized 2 SO 4 Recycling requires reduced O introduction to the Claus reactor 2 Nor have the beneficial effects of the claus process and sulfuric acid process been recognized. Nor the effect on the chemicals in the claus plant. Finally, the document does not consider H 2 SO 4 To SO 2 Is not fully converted by the claus process, therefore, SO is not present 3 Is the core hypothesis of this document and does not take into account the removal of SO 3 Is not limited to the above-described embodiments.
The sulfuric acid does not have to be recovered from a downstream sulfuric acid plant as a claus tail gas treatment plant, but may be from other sources. Addition of H to a Claus process plant 2 SO 4 The benefits of (a) can be demonstrated using H 2 SO 4 Because of H as described in patent application PCT/EP2017/080721 2 SO 4 Can be used as effective O 2 The carrier can also be used as a temperature regulator. The addition of sulfuric acid increases the capacity of the claus process plant by up to 50% without affecting the process gas flow in the claus process plant.
In Danish patent application PA 2018 00057, the introduction of liquid H is described 2 SO 4 Stream addition to claus process equipmentDifferent ways of thermal stage (also called claus reactor). It is important to ensure that the injection does not significantly disturb the flame in the reactor furnace while still being close to the hot flame to evaporate rapidly and then mix with the gas phase to carry out the desired claus reaction.
And will H 2 SO 4 The prior art relating to the thermal stage of the feed to the claus process plant assumes complete evaporation and quantitative conversion of sulfuric acid to SO 2 . However, the present disclosure relates to the following recognition: h 2 SO 4 To SO 2 May not be complete.
In a broad sense, the present invention relates to a process for producing a substantially SO-free stream from a feed gas and sulfuric acid 3 A claus reformer feed gas comprising 30vol%, 40vol% or 50vol% to 99vol% or 100vol% of H 2 S, comprising the following steps:
a. providing a claus reaction furnace feed stream comprising the feed gas, an amount of sulfuric acid, an amount of molecular oxygen, and optionally an amount of fuel, wherein the amount of molecular oxygen is sub-stoichiometric,
b. the claus reactor feed stream is directed to a claus reactor operating at a high temperature (e.g., above 900 ℃) to provide a claus reactor off-gas,
c. cooling the Claus reaction furnace off-gas and optionally extracting elemental sulphur from the gas,
d. directing cooled claus reactor off-gas with SO 3 The protectant material contacts, absorbs and/or converts SO 3 To provide a substantially SO-free composition 3 Is fed to the claus reformer,
e. directing the substantially SO-free 3 Is contacted with a material that is catalytically active in the claus reaction,
f. optionally extracting elemental sulphur by cooling the effluent from the material having catalytic activity in the claus reaction,
characterized in that the SO 3 The protectant material is different from the material having catalytic activity in the claus reaction, whereinIf the droplets of sulfuric acid are not completely vaporized and reduced in the gas phase, then the reaction is carried out in SO 3 Removal of active SO 3 The protective agent material ensures long-term operation of the catalyst active in the claus reaction, SO that long-term operation of the claus process plant can be maintained even if the material active in the claus reaction is inactive or only temporarily active in SO3 conversion or absorption.
In another embodiment, the SO 3 The protective agent is SO 3 Absorbents, e.g. alumina or titania, where SO 3 With the associated benefits that such an absorbent is inexpensive and that alumina and titania have moderate catalytic action, allowing for the absorption of SO 3 Some degree of conversion occurs.
In a further embodiment, wherein said SO 3 The protective agent material is prepared by reacting H with 2 S reaction reduction of SO 3 Catalytically active material, thereby providing a material substantially free of SO 3 Is a claus reformer feed gas with the associated benefits of SO 3 The lifetime of the protectant material is not limited by the absorption capacity.
In another embodiment, the SO 3 The arrangement of the protectant material downstream of the claus reactor and upstream of the claus reformer has the associated benefit of SO 3 The protectant material is far away and thus is not affected by the flame in the claus reactor.
In another embodiment, the SO 3 The protective agent material is arranged as a top layer on top of the catalytically active material in the claus reaction, with the associated benefit of avoiding the use of SO 3 Cost of the separate reactor for the protectant.
In another embodiment, in the reduction of SO 3 Comprises one or more elements selected from V, mn, fe, co, cu, zn, ni, mo, W, sb, ti and Bi, and a carrier comprising one or more elements selected from Al, ti, si, zr and Mg, with the associated benefit thatIs to SO 3 Conversion to SO 2 Or sulfur.
In another embodiment, the support comprises diatomaceous earth and/or cordierite, with the associated benefit that such materials are stable and have high surface areas.
In another embodiment, in the reduction of SO 3 The active material in (a) is in the form of particles or monoliths, with the associated benefit that the particles are cost-effective to produce, while monoliths benefit from low pressure drop.
In another embodiment, the claus reactor is operated at a temperature between 900 ℃ and 1500 ℃ with the associated benefit that the temperature range is suitable for the use of H 2 SO 4 Decomposition into H 2 O and SO 3 Further to SO 3 Decomposition into SO 2 Will H 2 S is partially oxidized and the impurities are decomposed.
In another embodiment, in the reduction of SO 3 The catalytically active material in (a) is operated at a temperature between 130 ℃ and 1500 ℃ with the associated benefit that the temperature is suitably within the temperature interval of the catalytic claus reaction and the non-catalytic claus reaction furnace.
In a further embodiment, in the reduction of SO 3 The catalytically active material in (a) operates at a temperature between 250 ℃ and 500 ℃ with the associated benefit of being able to react from SO without the need for high resistance materials at this temperature range 3 Rapid conversion to SO 2 And/or sulfur.
In another embodiment, in the reduction of SO 3 The catalytically active material in (a) is operated at a temperature between 300 ℃ and 400 ℃, with the associated benefit that, in this temperature range, no foreign material (exotic material) is required, in the range from SO 3 Rapid conversion to SO 2 Or sulfur.
In another embodiment, the sulfuric acid stream is produced in a wet sulfuric acid plant that processes off-gas from a claus plant with the associated benefits that such a process is thermally efficient and is capable of greatly reducing sulfur compound emissions.
The term sulfuric acid in liquid phase means H 2 SO 4 And H 2 Mixtures of O, because of H 2 SO 4 Is hygroscopic and will absorb water from the gas phase. In principle, any concentration of H can be used 2 SO 4 But requires a very high concentration, as this would reduce the energy required for evaporation and minimize dilution of the claus reactor off-gas with the associated water. For practical purposes only consider sulfuric acid to be>90％w/wH 2 SO 4 Most relevant.
Due to the consideration of SO 3 Is to hydration reaction of (C)Very fast, which can be regarded with confidence as chemical equilibrium, gas phase term H 2 SO 4 (sulfuric acid) and SO 3 (sulfuric anhydride) is commonly referred to as "SO 3 ”。SO 3 And H 2 SO 4 The distribution between the two depends on the temperature, pressure and H in the gas 2 O concentration, SO 3 At high temperature and low temperature H 2 Advantageous at O concentration, H 2 SO 4 At low temperature and high H 2 The O concentration is advantageous. Above 400 ℃ and almost no H 2 SO 4 Exists below 200 ℃ and has almost no SO 3 Both molecules are present in different amounts (if moisture) and in the range of 200-400 ℃.
The following is with H 2 SO 4 The chemical reactions involved will take place in the reaction furnace:
H 2 SO 4 (liquid phase) →H 2 SO 4 (gas phase) (1)
SO 3 (gas phase) →SO 2 (gas phase) +0.5O 2 (3)
SO 3 (gas phase) +H 2 S (gas phase) →SO 2 (gas phase) +S (gas phase) +H 2 O (gas phase) (4)
H 2 S (gas phase) +1.5O 2 →SO 2 (gas phase) +H 2 O (gas phase) (5)
SO 2 (gas phase) +2H 2 S (gas phase) →3S (gas phase) +2H 2 O (gas phase) (6)
"S" means S from 2 To S 8 Elemental sulfur in any form.
Reactions (5) and (6) are overall reactions of the claus process, in which the H in the feed gas 2 S and insufficient O 2 Burning to form H 2 S/SO 2 The ratio of combustion gases is about 2, which is the best ratio for the highest conversion to element S.
When H is introduced 2 SO 4 As can be seen from reactions (2) + (3), sulfuric acid is decomposed into SO 2 And O 2 Finally for every mole of added H 2 SO 4 ，O 2 The demand was reduced by 2 moles. With air as O 2 Source, 2 moles of O 2 With 8 moles of N 2 Bind, thus add H 2 SO 4 The amount of inert gas in the process gas is significantly reduced.
Reaction (1) describes the evaporation of liquid sulfuric acid after injection into the reaction furnace. Typically, the sulfuric acid stream is atomized into a "mist" of small droplets, the size distribution of which is determined by the atomization method. The droplets evaporate from the outer droplet surface, so the initial droplet size is critical to the time required for complete evaporation. The time to complete evaporation depends on the third power of the droplet diameter, i.e. doubling the droplet diameter increases the evaporation time by a factor of 8. The process gas temperature and gas/droplet mixing also have a significant impact on the evaporation time of the droplets.
To obtain minimum droplets, two-phase atomization is required, wherein an atomizing medium (typically compressed air, N 2 Or vapor) to "cut" the liquid stream into fine droplets.
Reaction (2) is a very rapid gas phase reaction, SO can be assumed with confidence 3 And H 2 SO 4 The chemical balance is between。
Reactions (3) and (4) describe the conversion of SO 3 Decomposition into SO 2 And O 2 Can then react with H by reactions (5) and (6) 2 S reaction or direct reaction with H 2 S reacts to form SO 2 And S, where SO 2 Can be reacted with H by reaction (6) 2 S reaction.
Reaction (3) is highly temperature dependent, and unless a catalyst is present, the reaction is only carried out at higher temperatures, i.e. > 800 ℃.
Reaction (4) also occurs at lower temperatures, but the reaction rate at temperatures below 400 ℃ may be too low to be relevant for industrial applications.
At the claus furnace temperature, reactions (2) to (6) are very rapid, typically reaching chemical equilibrium in less than 0.5 seconds. The residence time in the reactor is generally less than 1-2 seconds.
According to the chemical equilibrium calculation, under the condition of the Claus reaction furnace gas, no H exists in the process gas 2 SO 4 、SO 3 Nor does O exist 2 。
In the absence of H 2 SO 4 In the case of (1), H 2 S and O 2 The stoichiometric balance between is 2:1. however, in H 2 SO 4 In the presence of the desired O 2 Fewer. Thus, the sub-stoichiometric amount of molecular oxygen is defined as being less than H 2 A molar amount of half the molar amount of S.
The claus reactor is preferably operated at a temperature between 900 ℃ and 1500 ℃.
For relatively large droplets, reaction (1) will be the limiting step for the reaction to proceed to equilibrium, and the available 1-2 second residence time may be too short for the reaction to complete. This may occur if, for example, the nozzles for sulfuric acid atomization have worn out and/or the flow or pressure of the atomizing medium is outside the normal range. As a result, H 2 SO 4 /SO 3 The conversion leaving the claus reactor is incomplete and enters a heat exchanger (waste heat boiler) that cools the claus reactor gas to about 300-400 ℃. At this temperature, reaction (1)And (2) remain active, while the reaction rates of (3) to (6) are too low to be of practical significance.
In a usual claus process layout, the claus reactor off-gas at 300-400 ℃ is fed to a catalytic claus reactor in which a catalyst active for reaction (6) is installed. The catalysts are well known in the industry and are most often used as particles, the active material being TiO 2 Or Al 2 O 3 . It is also well known that such catalysts are susceptible to "sulfation", i.e. the sulfate "poisons" the active sites of the catalyst, and thus the catalyst loses catalytic activity, with the result that fewer products are produced, and H 2 S and SO 2 And the discharge amount of (c) increases. The sulfate can pass through SO 2 And O 2 The reaction between them forms SO on the surface of the catalyst 3 Or SO present in the process gas 3 Can be directly attached to the catalyst surface.
In another claus process configuration, the claus reactor off-gas at 300-400 ℃ is directed to a sulfur condenser where the process gas is cooled to 130-160 ℃ to condense elemental sulfur and withdraw product. The process gas is then reheated and directed to a catalytic claus reactor as described above. If SO is present in the waste gas from the Claus reactor 3 There is a risk of condensing sulfuric acid in the elemental sulfur product, producing off-grade products, and there is an increased risk of corrosion of the sulfur treatment equipment. The off-gas from the sulphur condenser also contains a part of the SO present in the off-gas of the Claus reactor 3 (in H) 2 SO 4 In the form of (c) a), such SO 3 Can poison downstream claus catalysts.
As mentioned above, it is very important that the waste gas from the Claus reactor does not contain a significant amount of SO 3 As it can have a detrimental effect on the downstream catalyst, equipment and operation of the claus process equipment.
In order to ensure safe and long-term operation of claus process plants, a new catalyst has been developed which is resistant to SO 3 And H is 2 The reaction of S is active to form SO 2 And S. The catalyst is also capable of inhibiting SO 3 Formation of O 2 (reaction 3) because of O 2 Escape and SO 3 Escape is also problematic. The catalyst is preferably installed at the outlet of the waste heat boiler connected to the claus reactor and at the inlet connected to the plant and/or possibly due to the presence of SO 3 Between the destroyed catalysts. The new catalyst may be installed in a separate reactor, which is necessary in a claus process layout in which cooled claus reactor furnace off-gas is fed to a sulfur condenser before the catalytic claus reactor, or the new catalyst may be installed as a top layer in an existing claus reactor, which may be achieved in a layout in which the process gas directly enters the catalytic claus reactor.
In another embodiment, the catalyst is installed at the outlet of the claus reactor using high temperature and high reaction rate.
The catalyst may be of any shape and size for the purpose of optimal layout of the claus process equipment. If it were installed as the top layer in a claus reactor, a particulate catalyst would be most desirable because claus catalysts are typically particulate.
If it is to pass through H 2 The S reaction mode is to reduce SO 3 (and H) 2 SO 4 ) If the catalytically active material is installed in a separate vessel, it is possible to install a particulate catalyst or a monolithic catalyst, depending on the available pressure drop on the process gas side, the space constraints of the reactor and which solution is most cost-effective.
By combining with H 2 S reacts to reduce SO 3 (and H) 2 SO 4 ) Comprises one or more compounds selected from V, mn, fe, co, cu, zn, ni, mo, W, sb, ti and Bi supported on one or more compounds selected from Al, ti, si, zr, mg and cordierite, the support typically comprising diatomaceous earth. Although Al alone 2 O 3 And TiO 2 Is susceptible to sulfate poisoning, but these compounds are useful as SO 3 Conversion to SO 2 And a carrier of compounds active in the process of S, which compounds are not harmful to downstream claus catalysts. It is further believed that Al 2 O 3 And TiO 2 Can absorb SO by sulfation 3 And acts as a protective agent, such an active metal-free material may therefore act as a protective agent, but occasionally require replacement or reactivation.
By combining with H 2 S reacts to reduce SO 3 (and H) 2 SO 4 ) The catalytically active material is operated at a temperature of between 130 and 1500 ℃, for example between 250 and 500 ℃ or between 300 and 400 ℃.
Drawings
Figure 1 shows a claus reactor furnace wherein a first claus reactor is located upstream of a first sulphur condenser.
Figure 2 shows a claus reactor furnace wherein a first sulphur condenser is located upstream of the first claus reactor.
In fig. 1, the feed to the claus furnace (claus heat stage) is one or more acid gases, which include H 2 S (2), optionally a fuel gas (4), an oxygen source (6) (typically air, containing 21vol% O 2 The method comprises the steps of carrying out a first treatment on the surface of the Or oxygen-enriched air containing 21-100vol% of O 2 ) And a sulfuric acid stream (8). The sulfuric acid stream may optionally be concentrated sulfuric acid produced in a sulfuric acid plant installed as a tail gas treatment plant in a claus process plant. The sulfuric acid atomization method that produces minimal droplets is a two-phase atomization in which sulfuric acid liquid is "cut" into droplets using an atomization medium (10). The atomizing medium is typically compressed air or steam, but other media are also possible, such as fuel gas, oxygen-enriched air or process gas.
In the Claus reaction furnace chamber (12), a part of H 2 S is oxidized to SO 2 Then with H 2 S combines to form elemental sulfur. Sulfuric acid evaporates and reacts with H 2 S reacts to form SO 2 And elemental sulfur. The temperature in the reactor is typically above 900 ℃, and the average residence time is typically 1-2 seconds. The exhaust gas from the reaction chamber (14) is passed through a heat exchanger (16) where the process gas is cooled to 300-400 ℃. Heat exchangeThe generator is typically a waste heat boiler that generates high pressure steam. If elemental sulphur condenses in the heat exchanger, it is discharged through a liquid outlet (18).
The cooled claus reaction furnace off-gas (20) is then passed over one or more layers of catalyst (22), wherein any SO in the claus reaction furnace off-gas 3 By combining with H 2 S reaction to effectively convert into SO 2 And S, essentially free of SO 3 Is directed to a claus catalyst layer in a claus reactor (26). The (22) and (26) may be combined such that SO in (22) 3 The decomposition catalyst may act as the top layer in the claus reactor (26).
In the Claus reactor (26), by H 2 S and SO 2 The reaction between them forms more elemental sulphur and the claus reactor off-gas (28) is passed through a first sulphur condenser (30) where the process gas is cooled and a portion of the elemental sulphur is condensed and withdrawn as a liquid through outlet 32. The exhaust gas (34) is typically reheated and then passed through a claus reactor-sulphur condenser-reheater one or more times to ensure H is removed 2 S is converted to elemental sulfur sufficiently high.
In fig. 2, the claus reactor (12) and waste heat boiler (16) are similar in arrangement and operation to those described in fig. 1. The layout differs in that the cooled claus reactor off-gas (20) is condensed directly by a first sulphur condenser (30) and a portion of the elemental sulphur is withdrawn through line 32, and the condenser off-gas (34) is then reheated and passed through the first claus reactor. In this arrangement, a higher overall conversion of the first claus reactor may be achieved as the product is withdrawn, favoring the claus reaction equilibrium in the first claus reactor. For such an arrangement, it is necessary to install in a separate container (22) the two-way H 2 S reaction to reduce SO 3 (and H) 2 SO 4 ) To be substantially free of SO 3 Is fed to a first sulphur condenser (30) to avoid contamination of sulphur product by sulphuric acid and to avoid non-captured sulphuric acid being fed to a downstream first claus reactor.
Example 1
In laboratory scale devices, H has been studied in a reaction chamber 2 S and SO 3 Non-catalytic reaction between the two, the reaction chamber is formed by 40cm long installed in a temperature control ovenGlass tube.
Supplying H from a gas cylinder 2 S, and use N 2 Diluted and then added to the reaction chamber. Second N 2 Saturated with water to allow H to be present in the process gas 2 O. Make the third small N 2 Flow through oleum solution to use SO 3 The stream is saturated.
Table 1A shows an initial experiment performed at an undefined residence time of about 1 second, with these three streams added and reacted at a controlled temperature interval of 300-400 ℃.
Analysis of the reaction chamber outlet for elemental sulphur, sulphuric acid (=so 3 With H in gas 2 O reaction) and SO 2 Is contained in the composition. The results shown in Table 1A indicate that SO 3 And H 2 Some gas phase reaction occurs between S but is relatively slow and not fast enough to ensure SO in industrial claus process equipment 3 Is completely decomposed.
TABLE 1
Reactor temperature [ DEGC] 300 400
Inlet SO 3 Concentration of [ ppmv ]] 690 180
Inlet H 2 S concentration [ ppmv] 3000 3000
SO 3 Outlet concentration [ ppmv] 237 64
SO 3 Reduction rate [%] 66 64
Table 1B shows additional experiments at controlled residence times where these three streams were added and allowed to react at a controlled temperature of 350 ℃ with a reaction chamber residence time of 0.4 to 1 second.
The results shown in Table 1B also demonstrate that SO 3 And H 2 Some gas phase reaction occurs between S but is relatively slow and not fast enough to ensure SO in industrial claus process equipment 3 Is completely decomposed. In contrast, by using a catalyst, this rapid and almost complete SO 3 Decomposition is possible.
Examination of the material showed that SO was removed by alumina 3 The reason for (a) may be due to sulfation of alumina rather than catalytic conversion. However, if a certain amount of alumina is used as a protector material, such sulfation may still be of commercial interest, since the subsequent claus catalyst is protected from SO 3 Resulting in its deactivation.
TABLE 1B
Example 2
Many chemical reactions take place in the claus furnace and calculations were made using very detailed kinetic models, including over 50 chemicals and over 1000 chemical base reactions, describing the temperature dependent rate constants of each reaction.
The model has been used to calculate the kinetics of the claus reactor and the chemical equilibrium of the claus reactor mixture, i.e. the model is used to predict whether the sulfuric acid feed will react with H in the reactor 2 S reacts completely.
The acid gas fed to the claus reactor was composed of 91.4vol% of H 2 S, 2.1vol% CO 2 3.3vol% of H 2 O, 1.4vol% CH 4 And 1.9vol% H 2 Composition, representing the concentrated acid gas from, for example, a refining process.
Sulfuric acid 93% w/w H 2 SO 4 Represents the sulfuric acid product from a wet sulfuric acid plant installed downstream of the claus process plant as a tail gas treatment plant. The sulfuric acid flow rate was 9.8% of the total sulfur fed to the claus reactor.
The reaction temperature was 1050℃and the pressure was 1.65 bar absolute.
Fig. 3 shows that the chemical reaction in the claus furnace is very fast and that the chemical equilibrium is reached in less than 0.5 seconds, i.e. the composition of the process gas is unchanged.
However, the kinetic model only includes the gas phase species and does not include the time required to evaporate the sulfuric acid droplets. If the evaporation of the droplets is less than 0.5 seconds, the process gas from the claus reactor (residence time of 1 second) will be substantially free of SO 3 And the operation of the claus process plant will not be problematic. However, if some droplets require more than 1-2 seconds to evaporate, the reactor off-gas cannot be considered SO free 3 Thus, the operation of a problem-free claus process plant cannot be guaranteed.
In this case, the new development is performed by combining H 2 S reaction reduction of SO 3 (and H) 2 SO 4 ) The catalytically active material is essential for the long-term operation of the claus process plant.

Claims (16)

1. A process for producing sulfur from a feed gas and a sulfuric acid stream, the feed gas comprising from 30vol%, from 40vol% or from 50vol% to 99vol% or to 100vol% H 2 S, the method comprises the following steps:
a. providing a claus reaction furnace feed stream comprising the feed gas, an amount of sulfuric acid, an amount of molecular oxygen, and optionally an amount of fuel, wherein the amount of molecular oxygen is sub-stoichiometric,
b. directing the claus reactor feed stream to a claus reactor to provide a claus reactor off-gas,
c. cooling the claus reaction furnace off-gas to provide cooled claus reaction furnace off-gas and optionally extracting elemental sulfur from the gas,
d. directing cooled claus reactor off-gas with SO 3 The protectant material contacts, absorbs and/or converts SO 3 To provide a substantially SO-free composition 3 Is fed to the claus reformer,
e. directing the SO-free 3 Is contacted with a material that is catalytically active in the claus reaction,
f. optionally extracting elemental sulphur by cooling the effluent from the material having catalytic activity in the claus reaction,
characterized in that the SO 3 The protectant material is different from the material that is catalytically active in the claus reaction.
2. The method of claim 1, wherein the SO 3 The protectant material is SO 3 An absorbent, wherein SO 3 The content of (2) increases with time.
3. The method of claim 2, wherein the SO 3 The absorbent is alumina or titania.
4. The method of claim 1, wherein the SO 3 The protectant material is prepared by reacting H with 2 S reaction in reduction of SO 3 To provide a material substantially free of SO 3 Is fed to the claus reformer.
5. The method of any one of claims 1-4, wherein the SO 3 The protectant material is disposed downstream of the claus reactor and upstream of the claus reformer.
6. The method of any one of claims 1-4, wherein the SO 3 The protective agent material is arranged as a top layer on top of the catalytically active material in the claus reaction.
7. The method of claim 4, wherein the SO is reduced 3 Comprises one or more elements selected from V, mn, fe, co, cu, zn, ni, mo, W, sb, ti and Bi and a support comprising one or more elements selected from Al, ti, si, zr and Mg.
8. The method of claim 5, wherein the method comprises the step of reducing SO 3 Comprises one or more elements selected from V, mn, fe, co, cu, zn, ni, mo, W, sb, ti and Bi and a support comprising one or more elements selected from Al, ti, si, zr and Mg.
9. The method of claim 6, wherein the method comprises the step of reducing SO 3 Comprises one or more elements selected from V, mn, fe, co, cu, zn, ni, mo, W, sb, ti and Bi and a support comprising one or more elements selected from Al, ti, si, zr and Mg.
10. The method of any of claims 7-9, wherein the support comprises diatomaceous earth and/or cordierite.
11. The square according to any one of claims 1 to 4A process in which SO is reduced 3 The active material is in the form of pellets or monoliths.
12. The process according to any one of claims 1 to 4, wherein the claus reactor is operated at a temperature of 900-1500 ℃.
13. The method of any one of claims 1 to 4, wherein in reducing SO 3 The catalytically active material is operated at a temperature of 130 to 1500 ℃.
14. The method of any one of claims 1 to 4, wherein in reducing SO 3 The catalytically active material is operated at a temperature of 250 to 500 ℃.
15. The method of any one of claims 1 to 4, wherein in reducing SO 3 The catalytically active material is operated at a temperature of 300 to 400 ℃.
16. The process according to any one of claims 1 to 4, wherein the sulfuric acid stream is produced in a wet sulfuric acid plant that processes off-gas from a claus plant.
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