CN117160205A - Sulfur recovery tail gas treatment method and device - Google Patents
Sulfur recovery tail gas treatment method and device Download PDFInfo
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- CN117160205A CN117160205A CN202210594909.9A CN202210594909A CN117160205A CN 117160205 A CN117160205 A CN 117160205A CN 202210594909 A CN202210594909 A CN 202210594909A CN 117160205 A CN117160205 A CN 117160205A
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- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 239000011593 sulfur Substances 0.000 title claims abstract description 102
- 229910052717 sulfur Inorganic materials 0.000 title claims abstract description 102
- 238000000034 method Methods 0.000 title claims abstract description 85
- 238000011084 recovery Methods 0.000 title claims abstract description 54
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 98
- 239000003546 flue gas Substances 0.000 claims abstract description 98
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims abstract description 94
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 81
- 229910052938 sodium sulfate Inorganic materials 0.000 claims abstract description 80
- 235000011152 sodium sulphate Nutrition 0.000 claims abstract description 80
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- 230000008569 process Effects 0.000 claims abstract description 57
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 52
- 230000003647 oxidation Effects 0.000 claims abstract description 51
- 238000010521 absorption reaction Methods 0.000 claims abstract description 49
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- 238000001704 evaporation Methods 0.000 claims abstract description 33
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 28
- 230000008020 evaporation Effects 0.000 claims abstract description 23
- 239000003345 natural gas Substances 0.000 claims abstract description 14
- 239000003518 caustics Substances 0.000 claims abstract description 5
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 claims description 78
- 238000002425 crystallisation Methods 0.000 claims description 47
- 230000008025 crystallization Effects 0.000 claims description 47
- 239000007788 liquid Substances 0.000 claims description 39
- 235000010265 sodium sulphite Nutrition 0.000 claims description 39
- 239000000047 product Substances 0.000 claims description 26
- 239000002562 thickening agent Substances 0.000 claims description 21
- 239000006228 supernatant Substances 0.000 claims description 19
- 239000012071 phase Substances 0.000 claims description 15
- 239000000428 dust Substances 0.000 claims description 14
- 239000007791 liquid phase Substances 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- 239000012452 mother liquor Substances 0.000 claims description 10
- 239000001301 oxygen Substances 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 10
- 238000010979 pH adjustment Methods 0.000 claims description 10
- 239000012530 fluid Substances 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 7
- 238000004064 recycling Methods 0.000 claims description 7
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- 238000000926 separation method Methods 0.000 claims description 7
- 238000009835 boiling Methods 0.000 claims description 6
- 238000005243 fluidization Methods 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 5
- 238000010405 reoxidation reaction Methods 0.000 claims description 5
- 235000011121 sodium hydroxide Nutrition 0.000 claims 6
- 238000000746 purification Methods 0.000 abstract description 11
- 230000009467 reduction Effects 0.000 abstract description 5
- 239000013078 crystal Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 93
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 15
- 239000003513 alkali Substances 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 10
- 238000005516 engineering process Methods 0.000 description 10
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- AKEJUJNQAAGONA-UHFFFAOYSA-N sulfur trioxide Chemical compound O=S(=O)=O AKEJUJNQAAGONA-UHFFFAOYSA-N 0.000 description 4
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 102100027330 Phosphoribosylaminoimidazole carboxylase Human genes 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
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- UPRXAOPZPSAYHF-UHFFFAOYSA-N lithium;cyclohexyl(propan-2-yl)azanide Chemical compound CC(C)N([Li])C1CCCCC1 UPRXAOPZPSAYHF-UHFFFAOYSA-N 0.000 description 1
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- Treating Waste Gases (AREA)
Abstract
The invention provides a sulfur recovery tail gas treatment method and a device suitable for the natural gas purification industry, wherein the method comprises the following steps: the tail gas treated by the sulfur recovery device is burnt by a positive pressure incinerator to form sulfur-containing flue gas; the sulfur-containing flue gas is desulfurized through caustic washing with sodium hydroxide to form sodium sulfate product solution; evaporating and crystallizing the sodium sulfate product solution to form qualified sodium sulfate salt and condensate water, and finishing sulfur recovery tail gas treatment. Adopts' positive-pressure incineration of tail gas + alkaline washing desulfurization of flue gas NaOH + evaporation of sodium sulfate solutionThe total process for treating the crystal combined sulfur recovery tail gas combines and optimizes the traditional process flow, conditions and devices, and can meet the requirements of different treatment gas volumes, different elemental sulfur and H 2 SO under S content condition 2 The standard emission is achieved, the quality of sodium sulfate products is guaranteed, the applicability of sulfur recovery tail gas treatment is improved, and the engineering investment and the operation cost of the method are lower than those of the common tail gas treatment processes by a reduction absorption method and an oxidation absorption method in the field of natural gas purification.
Description
Technical Field
The invention belongs to the technical field of desulfurization, and particularly relates to a sulfur recovery tail gas treatment method and device.
Background
Acid gas is a common industrial emission in industrial production, and in recent years, various countries in the world pay great attention to environmental protection while developing industry with the deterioration of global environment. The sulfur-containing process technology in industry is particularly important to environmental pollution, so the development and application of the sulfur recovery technology are important, and the tail gas treatment technology is converted from a single scientific technology into an important process technology which takes environmental protection benefit and economic benefit into consideration.
The existing sulfur recovery tail gas treatment technology in domestic natural gas factories and oil refineries is usually only adopted by the tail gas treatment technology adopting a reduction absorption method and an oxidation absorption method.
The prior art has the following problems in practical application:
(1) reduction absorption method
a. The circulation amount of the tail gas absorption solution is large, and the solution system equipment is large;
b. the total energy consumption of the regenerated steam of the tail gas absorption solution is high;
c.SO 2 hydrogenationThe reduction requires high temperature, consumes fuel gas,
(2) oxidation absorption process
a. The normal process is to produce salt-containing wastewater, a special sewage treatment facility is needed to be newly built for treatment, the treated concentrated water is needed to be evaporated and dried to produce a certain amount of solid waste, a solid waste storage yard is also needed to be arranged, and the solid waste storage yard is delivered to a professional company for treatment;
b. the system is provided with an acidic medium, equipment has the problem of acid corrosion, and expensive special stainless steel materials are required to be selected, so that the maintenance cost is high;
c. an amine liquid on-line purification system is needed to be additionally arranged for removing heat-stable salt in normal production;
d. patent solvents are expensive in unit price and there is an uncontrollable risk of international trade if imported solvents are used.
The two types of process devices are complex, the investment, the operation cost and the energy consumption are quite high, and especially the application cost is high in the sulfur recovery tail gas treatment of a natural gas purification plant with small undercurrent content or medium-small scale, so that the sulfur recovery tail gas treatment process with mature process and low operation cost needs to be researched.
Disclosure of Invention
In view of the above problems, the present invention provides a method for treating sulfur recovery tail gas, the method comprising:
the tail gas treated by the sulfur recovery device is burnt by a positive pressure incinerator to form sulfur-containing flue gas;
the sulfur-containing flue gas is desulfurized through caustic washing with sodium hydroxide to form sodium sulfate product solution;
evaporating and crystallizing the sodium sulfate product solution to form dry sodium sulfate salt and condensed water, and finishing sulfur recovery tail gas treatment.
Further, the formation of sulfur-containing flue gas includes:
the tail gas treated by the sulfur recovery device sequentially passes through the positive pressure incinerator and the flue gas cooler to form sulfur-containing flue gas, the sulfur-containing flue gas is treated by the flue gas cooler to form saturated steam, wherein,
the front end temperature of the incinerator is set to be above 1000 ℃, the middle and tail temperatures of the incinerator are set to be 700-720 ℃, and the oxygen content in flue gas at the outlet of the incinerator is set to be 3%.
Further, the desulfurization of the sulfur-containing flue gas by caustic washing with sodium hydroxide to form a sodium sulfate solution comprises:
the sulfur-containing flue gas is sequentially processed by a washing tower, a desulfurization absorption tower and an oxidation tank to form a crude sodium sulfate solution, the crude sodium sulfate solution is decolored and filter-pressed to form a sodium sulfate solution, wherein,
washing the sulfur-containing flue gas by a washing tower, and controlling the temperature of the sulfur-containing flue gas to be reduced to 40-50 ℃;
and in the process of circularly washing the washing tower, the method also comprises the step of circularly conveying the crude sodium sulfate solution to the washing tower for PH adjustment.
Further, the desulfurization and oxidation of the sulfur-containing flue gas by the desulfurization absorption tower and the oxidation tank specifically comprises:
the sulfur-containing flue gas introduced from the bottom of the desulfurization absorption tower contacts with sodium hydroxide solution sprayed from the top to form sodium sulfite solution, wherein the concentration of the sodium hydroxide solution is less than 10wt%;
one part of sodium sulfite solution is pumped out by a tower bottom circulating desulfurization pump and flows into the top of the desulfurization absorption tower for recycling, and the other part of sodium sulfite solution is pumped out by the tower bottom circulating desulfurization pump and flows into an oxidation tank for oxidation treatment by PH adjustment and heating treatment;
the sodium sulfite solution treated by the oxidation tank is subjected to oxidation treatment to form a crude sodium sulfate solution.
Further, evaporating and crystallizing the sodium sulfate solution to form dry sodium sulfate salt and condensed water includes:
introducing the sodium sulfate solution into a crystallization separator to form a liquid phase and a gas phase;
the liquid phase enters a thickener through a discharge pump, wherein solids generated by the thickener enter a centrifugal machine for centrifugal separation, and sodium sulfate is obtained after boiling, fluidization and drying;
supernatant fluid from the thickener and centrifugalized liquid enter a mother liquor tank, supernatant fluid deposited by the mother liquor tank is introduced into a desulfurization absorption tower and an oxidation tank of the alkaline washing device for reoxidation treatment, and then enters the evaporation crystallization device again.
Further, the gas phase is processed by a secondary separator, a water bath dedusting gas washing tower and a vapor compressor in sequence to form pressure-increasing steam, and the pressure-increasing steam enters a forced circulation heat exchanger to heat sodium sulfate solution.
The invention also provides a sulfur recovery tail gas treatment device, which comprises: an incineration device, an alkaline washing device and an evaporation crystallization device,
the incineration device is used for incinerating the tail gas treated by the sulfur recovery device through the positive pressure incinerator to form sulfur-containing flue gas;
the alkaline washing device is used for performing alkaline washing desulfurization on the sulfur-containing flue gas by sodium hydroxide to form a sodium sulfate product solution;
and the evaporation crystallization device is used for evaporating and crystallizing the sodium sulfate product solution to form dry sodium sulfate salt and condensed water, and finishing sulfur recovery tail gas treatment.
Further, the incineration device comprises a positive pressure incinerator and a flue gas cooler,
the front end temperature of the incinerator is set to be above 1000 ℃, the middle and tail temperatures of the incinerator are set to be 700-720 ℃, and the oxygen content in flue gas at the outlet of the incinerator is set to be 3%.
The flue gas cooler is also used for forming saturated steam.
Furthermore, the incinerator is provided with two groups of air inlets and tail gas inlets, and the two groups of air inlets and the tail gas inlets are independently controlled and symmetrically arranged on two sides of the incinerator body.
Further, the alkaline washing device comprises a washing tower, a desulfurization absorption tower and an oxidation tank,
the washing tower is used for washing the sulfur-containing flue gas, introducing the sulfur-containing flue gas into the desulfurization absorption tower, and controlling the temperature of the sulfur-containing flue gas to be reduced to 40-50 ℃; the washing tower is also used for circularly conveying the crude sodium sulfate solution to the washing tower for PH adjustment in the process of circularly washing;
the desulfurization absorption tower is used for contacting sulfur-containing flue gas introduced from the bottom with sodium hydroxide solution sprayed from the top to form sodium sulfite solution, and the concentration of the sodium sulfite solution is less than 10wt%;
one part of sodium sulfite solution is pumped out by a tower bottom circulating desulfurization pump and flows into the top of the desulfurization absorption tower for recycling, and the other part of sodium sulfite solution is pumped out by the tower bottom circulating desulfurization pump and flows into an oxidation tank for oxidation treatment by PH adjustment and heating treatment;
the oxidation tank is used for carrying out oxidation treatment on the inflowing sodium sulfite solution to form a crude sodium sulfate solution.
Further, the evaporation crystallization device comprises a crystallization separator, a thickener and a mother liquid tank,
the crystallization separator is used for treating the introduced sodium sulfate solution to form a liquid phase and a gas phase, and the liquid phase enters the thickener through the discharge pump;
the thickener is used for centrifugally separating generated solids in a centrifugal machine, and obtaining sodium sulfate after boiling, fluidization and drying;
the thickener is also used for feeding the supernatant and the centrifugated liquid after centrifugal separation into the mother liquid tank;
and the mother liquor tank is used for introducing the deposited supernatant into a desulfurization absorption tower and an oxidation tank of the alkaline washing device for reoxidation treatment.
Further, the evaporative crystallization device also comprises a gas washing tower and a vapor compressor,
the gas washing tower is used for removing liquid drops and solid impurities in the gas phase through water bath dust removal;
and the vapor compressor is used for boosting the gas phase processed by the gas washing tower, and the boosted vapor enters the forced circulation heat exchanger to heat the sodium sulfate solution.
The invention also provides an application of the sulfur recovery tail gas treatment method in purifying natural gas.
The method and the device for treating the sulfur recovery tail gas adopt the combined total process of 'positive-pressure tail gas incineration, alkaline cleaning and desulfurization of flue gas NaOH and evaporative crystallization of sodium sulfate solution', optimize the traditional process flow, conditions and devices and can meet the H under the working conditions of different treatment gas amounts 2 S conversion efficiency, at the same timeCan also prevent the nitrogen oxides from exceeding the standard, ensure the quality of sodium sulfate products, and remove SO by adopting a double-tower alkaline washing process of a washing tower and a desulfurization absorption tower 2 Is suitable for purifying the acid gas quantity and H of a factory 2 The method has the characteristics of large S content variation range, adopts an evaporation crystallization process, utilizes clean electric energy, is suitable for the characteristic of high concentration of sodium sulfate solution, has lower operation cost by adopting the evaporation crystallization process, and increases the applicability of sulfur recovery tail gas treatment.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows a schematic view of an incinerator in an embodiment of the invention;
FIG. 2 is a schematic diagram showing the relationship between the concentration of sodium sulfite solution and the oxidation conversion in the example of the present invention;
FIG. 3 shows a schematic side view of an incinerator in an embodiment of the invention;
FIG. 4 shows a flow chart of a positive tail gas incineration process in an embodiment of the invention;
FIG. 5 shows a flue gas NaOH alkaline cleaning desulfurization process flow chart in an embodiment of the invention;
fig. 6 shows a flow chart of a sodium sulfate solution evaporative crystallization process in an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides a sulfur recovery tail gas treatment method, which comprises the following steps:
the tail gas treated by the sulfur recovery device is burnt by a positive pressure incinerator to form sulfur-containing flue gas;
the sulfur-containing flue gas is desulfurized through caustic washing with sodium hydroxide to form sodium sulfate product solution;
evaporating and crystallizing the sodium sulfate product solution to form dry sodium sulfate salt and condensed water, and finishing sulfur recovery tail gas treatment.
The invention aims to provide a novel method for treating sulfur recovery tail gas of a natural gas purification plant and a device for implementing the method so as to meet the requirements of the tail gas treatment of the current natural gas purification plant.
The method provided by the invention mainly comprises the following steps:
(1) Optimizing the process flow: the total process of tail gas positive pressure incineration, flue gas NaOH alkaline washing desulfurization and sodium sulfate solution evaporation crystallization is combined type sulfur recovery tail gas treatment;
(2) Optimizing the process conditions: determination of incinerator temperature in different areas, and guarantee of H 2 S conversion efficiency; oxygen amount control to prevent the exceeding of nitrogen oxides; the concentration of alkali liquor is regulated, so that the concentration of sodium sulfite solution is regulated, the oxidation effect is improved, and the quality of sodium sulfate products is ensured; according to the temperature of circulating water, the flue gas is cooled to 40-50 ℃ generally, but the temperature is too low, the circulating water is large, and the water vapor carried by the flue gas is large when the temperature is high, so that the water supplementing amount is large, the water vapor carried by alkaline washing flue gas can be discharged, and the water supplementing amount of desalted water of an alkaline washing device is further increased, and the flue gas cooling temperature is optimized to 42 ℃ in the embodiment of the invention;
(3) Optimizing process equipment: optimizing the setting of the acid gas inlet of the incinerator,meet H under the working conditions of different treatment gas volumes 2 S conversion efficiency requirements;
the function of positive pressure incineration of tail gas in the scheme (1) provided by the invention is to incinerate elemental sulfur and H 2 Conversion of S combustion to SO 2 Relative to negative pressure combustion, H 2 S conversion efficiency is higher.
The flue gas NaOH alkaline washing desulfurization function provided in the scheme (1) provided by the invention is used for removing SO in the flue gas 2 The smoke emission reaches the standard, and the process flow optimization is mainly embodied in the following three aspects:
(1) determining a scheme for producing sodium sulfate products, wherein although sodium sulfite has higher selling price, sulfurous acid belongs to dangerous chemicals, and a natural gas purification plant has no relevant sales qualification, so that the technical scheme for producing the sodium sulfate products is determined by combining the enterprise properties of the purification plant;
(2) adopting a washing tower and desulfurization absorption tower double-tower alkaline washing process to remove SO 2 Is suitable for purifying the acid gas quantity and H of a factory 2 The S content has a large variation range;
(3) and (3) canceling the process of adding concentrated sulfuric acid, and circularly conveying the sodium sulfate solution pool solution to a washing tower when the pH value of the solution is higher, so that the purpose of reducing the pH value is realized.
The evaporation crystallization function provided in the scheme (1) provided by the invention is used for washing Na generated by alkali in the sulfur recovery tail gas treatment device 2 SO 4 The solution is evaporated and crystallized to produce a dried sodium sulfate salt product and condensed water. The process flow optimization is mainly embodied in the following three aspects:
(1) the MVR (mechanical vapor recompression, MVR is a technology for reusing the energy of secondary steam generated by the MVR, so that the demand on external energy is reduced) is adopted for evaporative crystallization, and the MVR evaporative crystallization technology is adopted for responding to the national policy of reducing carbon emission, so that clean electric energy is utilized, and simultaneously, the operation cost is lower for adapting to the characteristic of high concentration of sodium sulfate solution;
(2) adding a supernatant fluid of a mother solution tank to return to a desulfurization absorption tower process of an alkaline washing device, wherein the supernatant fluid of the mother solution tank is mainly sodium sulfite with smaller particles, if the supernatant fluid is not discharged in actual operation, the sodium sulfite of a crystallization device is enriched, so that the problems of unqualified sodium sulfate products, small particle size and blockage of a pipeline are caused, and the supernatant fluid containing the sodium sulfite is returned to the desulfurization absorption tower to be oxidized into sodium sulfate and then enters an evaporation crystallization device;
(3) the dry dust removal is optimized to be water bath dust removal, in the operation process of the dry dust removal, the temperature of the high-temperature air sucked into the water vapor is reduced in the conveying process, water is separated out, then sodium sulfate solid is hardened when meeting water, and a pipeline is blocked, so that the dry dust removal is optimized to be water bath dust removal, the flushing water is selected as raw material liquid, and the liquid returns to the raw material water tank, so that the evaporation crystallization load is not increased.
The process condition optimization in the scheme (2) provided by the invention is that the temperature of the front end of the incinerator is controlled to be more than 1000 ℃, the temperature of the rear part in the hearth is controlled to be about 720 ℃, and the incineration temperature and the incineration process are determined according to the characteristics of tail gases of different natural gas purification plants (the tail gases contain elemental sulfur and hydrogen sulfide with different concentrations) in the embodiment of the invention, so that the H in the flue gas can be ensured 2 S is less than 10mg/m 3 But the temperature of the rear part in the furnace cannot be controlled to be more than 700 ℃. Fig. 1 shows a schematic view of an incinerator structure in an embodiment of the invention, in fig. 1, temperature intervals inside the incinerator are arranged in sections, and a front thermometer port, a middle thermometer port and a tail thermometer port are arranged in the incinerator.
The optimization of the process conditions in the scheme (2) provided by the invention is that the peroxy amount of the original design incinerator is about 6%, but in actual operation, nitrogen oxides are found to exceed the standard, and a large amount of sulfur trioxide is generated, so that the corrosion of a washing tower is serious. Gradually reducing the content to about 3% according to an on-site operation test, wherein P140 in the book of Petroleum industry Press of sulfur recovery technology and engineering relates to the content of the excess coefficient of air in the flue gas of an incinerator, and O in the flue gas after combustion 2 The content is controlled to be 2 percent, but according to the field operation of a natural gas purification plant, the tail gas entering the incinerator is considered to contain elemental sulfur and have higher concentration of H 2 S, the oxygen excess coefficient in the flue gas needs to be improved, but a large amount of sulfur trioxide is generated when the oxygen excess coefficient is too large, the corrosion of a downstream waste heat boiler and a washing tower is aggravated, and the fuel gas content is increasedThe oxygen content in the moderate flue gas is very important to control, the nitrogen oxides are qualified, and the corrosion condition of equipment is found to be improved greatly during overhaul.
The optimization of the process conditions in the scheme (2) provided by the invention is to adjust the alkali liquor concentration from 15% to less than 10% by weight, and a conclusion is drawn according to the laboratory test result, wherein the conclusion is shown in FIG. 2, FIG. 2 shows a schematic diagram of the relationship between the sodium sulfite solution concentration and the oxidation conversion rate in the embodiment of the invention, and in FIG. 2, the abscissa is Na 2 SO 3 Concentration of (2), ordinate is Na 2 SO 3 As is evident from the graph, the higher the concentration of the sodium sulfite solution is, the lower the oxidation conversion is, and the process needs the sodium sulfite conversion to reach more than 90 percent, so that the produced anhydrous sodium sulfate can meet the requirement that the sodium sulfate content in the class III first-class product industrial anhydrous sodium sulfate in industrial anhydrous sodium sulfate GB/T6009-2014 is not less than 95 percent (mass concentration).
The optimization of the process conditions in the scheme (2) provided by the invention is to reduce the cooling temperature of the flue gas from the conventional 50 ℃ to 42 ℃, so that the water vapor carried by the flue gas emission is greatly reduced, the desalted water supplementing amount of the device is reduced, and the water is saved.
The optimization of the process equipment in the scheme (3) provided by the invention is that the air inlet and the tail gas inlet of the tail gas incinerator are symmetrically arranged to form two inlets, and in detail, as shown in fig. 3, fig. 3 shows a schematic side view structure of the incinerator in the embodiment of the invention, in fig. 3, the incinerator body is provided with two groups of air inlets and tail gas inlets, and the first air inlet and the first tail gas inlet are symmetrically arranged with the second air inlet and the second tail gas inlet. The tail gas forms a circulation in the incinerator, so that the combustion effect is improved, and meanwhile, when the gas quantity is low, a single inlet can be adopted, so that the operation flexibility is high.
The embodiment of the invention specifically describes a tail gas positive pressure incineration process, an alkaline washing desulfurization process and a sodium sulfate solution evaporation crystallization process:
the positive pressure incineration process of tail gas comprises the following steps:
FIG. 3 is a schematic side view of an incinerator according to an embodiment of the present invention, wherein FIG. 3 shows the temperature from a sulfur recovery deviceThe tail gas with the temperature of 125 ℃ and 10KPa enters a tail gas incinerator, and H in the tail gas is converted by means of the high temperature generated by the afterburning fuel gas 2 S, oxidation of elemental sulfur to SO 2 . The designed incineration temperature is about 760 ℃ and the residence time is 1.2 seconds, so that the pyrolysis and oxidization of the waste gas are ensured to generate CO 2 、H 2 O、SO 2 The small molecules are equal, and a large amount of N is also generated in the flue gas 2 And part of excess O 2 The method comprises the steps of carrying out a first treatment on the surface of the In order to recover most of heat in the high-temperature flue gas, the flue gas is cooled, conditions are provided for an alkaline washing system, a flue gas cooler is arranged behind the incinerator, the temperature of the flue gas can be reduced from 760 ℃ to about 260 ℃ through the flue gas cooler, an acid dew point is not formed, and then the flue gas enters an alkaline washing part flow; when the flue gas is cooled, saturated steam with the pressure of 1.5MPa is generated (the temperature of the saturated steam is about 201 ℃ and is higher than the acid dew point temperature of the flue gas by about 30 ℃, equipment corrosion caused by the acid dew point is prevented), the generated steam is used for heating low-temperature heat conduction oil of a purification plant, so that heat recovery is realized, condensate is returned to a flue gas cooler for recycling, and meanwhile, a steam air cooling self-circulation system (air cooler) is reserved, so that stable operation of the device is ensured.
In the embodiment of the invention, natural gas with the temperature of 20 ℃ and the pressure of 0.4MPa is selected as afterburning fuel gas to enter the incinerator for afterburning, and in the process of burning, the inside of the incinerator is blown by an incinerator blower, so that the burning process is more thorough, and in FIG. 4, FV represents a flow regulating valve and is arranged between the incinerator blower and the incinerator; TIC indicates temperature indication and adjustment, and is arranged at a natural gas conveying pipeline and an incinerator; TRCA represents temperature recording, adjusting and alarming, and is arranged at a natural gas conveying pipeline; PC represents pressure control, and is provided on the flue gas cooler.
Alkaline washing desulfurization process:
FIG. 5 shows a flue gas NaOH alkaline washing desulfurization process flow chart in an embodiment of the invention, in FIG. 5, high-temperature sulfur-containing flue gas (temperature 260 ℃ C., 5 kPa) from a tail gas incinerator enters from the lower part of a washing tower, and the flue gas is washed to remove smoke dust, and meanwhile, the flue gas is cooled to about 42 ℃ C.; and the sulfur-containing flue gas subjected to temperature reduction and dust removal in the washing tower flows out from the top of the tower and is removed to the desulfurization absorption tower. Washing hot water flows into the bottom of the washing tower, is pumped by a circulating washing pump, is cooled by a circulating washing water cooler and is sent into the washing tower from the upper part of the washing tower, and the residual wastewater condensed in the washing process is discharged out of the washing tower through a sewage discharge pipeline arranged at the bottom of the tower;
the sulfur-containing flue gas from the top of the washing tower enters from the lower part of the desulfurization absorption tower, and in the tower, the flue gas flows upwards to contact with NaOH solution sprayed from top to bottom on the surface of a filler, SO that SO in the sulfur-containing flue gas 2 Absorption and removal, namely removing liquid carried in the flue gas through a liquid remover arranged at the upper part of the desulfurization absorption tower, and then flowing out from the tower top to be directly emptied;
absorption of SO 2 The solution of (2) is rich solution, and the main component is sodium sulfite (Na 2 SO 3 ) Pumping out the mixed solution by using a bottom pump for desulfurization absorption tower, returning part of the mixed solution from the upper part of the desulfurization absorption tower to the desulfurization absorption tower for recycling, realizing solution circulation, and supplementing fresh alkali liquor into the circulating solution, thereby fully utilizing the test alkali liquor, ensuring gas-liquid ratio, ensuring gas-liquid full contact, and partially regulating the liquid level at the bottom of the tower and then delivering the mixed solution to an oxidation tank. At the same time, SO in the flue gas is purified at the top of the tower according to the liquid level at the bottom of the tower, the PH value 2 The concentration is changed, the fresh NaOH solution with set flow is supplemented, and the PH value of the absorption liquid at the tower bottom is maintained to be about 6.5.
Mixing desulfurization waste liquid from a desulfurization absorption tower with fresh NaOH solution from a lean liquid pump in a pipeline, regulating the PH value to 8.0-8.5, heating to 65 ℃, and conducting alkaline environment to facilitate oxidation, high temperature to facilitate oxidation and Na 2 SO 3 Sequentially feeding the solution into an oxidation reactor, introducing air into the oxidation reactor, and introducing Na into the solution 2 SO 3 Oxidation to Na 2 SO 4 The oxidized desulfurization waste liquid is crude sodium sulfate solution, and automatically flows into an intermediate solution storage tank or a neutralization decoloration tank.
The sodium sulfate solution from the oxidation tank is either directly fed to the neutralization decolorization tank or fed to the sodium sulfate solution storage tank. Adding a small amount of de-ironing agent and decolorizing agent into the tank as required, continuing stirring for about 30 minutes, stopping stirring, and finishing the neutralizing, decolorizing and de-ironing work. Starting a pressurized filter pump, pumping out the solution in the neutralization and decoloration tank, sending the solution into a plate-and-frame filter press for filter pressing, removing solid impurities (including smoke dust, de-iron precipitate, decoloration adsorbent and the like) in the solution, taking the filtrate as sodium sulfate product solution, sending the solution into a product solution tank, and then sending the solution into a downstream evaporation crystallization device.
In the embodiment, the alkali liquor which is pulled in is mixed with the self-evaporating crystallization condensed water to form alkali liquor through an alkali unloading/distributing pump, the alkali liquor is stored in an alkali liquor storage tank, and is mixed with sodium sulfite through an alkali liquor supplementing pump, and in fig. 5, LIC represents liquid level indication and adjustment and is arranged at the bottoms of a washing tower and a desulfurization absorption tower; TIC indicates temperature indication, adjusts, is set up in the water cooler of washing, top pipeline of washing tower, oxygen tank feed heating tank; FIC represents flow indication and regulation, and is arranged at the position of partial desulfurization absorption tower circulation and sodium sulfite flowing through an oxidation tank; LICA represents liquid level indication, regulation and alarm, and is arranged on an alkali liquor storage tank; AIRC means composition analysis indication, record, adjustment, set up in oxidation tank entering the tank; PIC indicates pressure indication and regulation, FIR indicates flow indication and record, and the PIC indicates flow indication and record are arranged at the communication position of oxidizing air and an oxidizing tank; FIRQ indicates flow indication, recording, accumulation, set at the sodium sulfate product solution outlet system.
Evaporating and crystallizing sodium sulfate solution:
FIG. 6 shows a flow chart of a sodium sulfate solution evaporative crystallization process in an embodiment of the invention, in FIG. 6, na from an alkaline washing apparatus 2 SO 4 The solution with 15-18% of salt content enters a plate-and-frame filter press for filtering and separating, the separated filtrate automatically flows into a stock solution tank, the temperature is raised to 96 ℃ by a fresh steam preheater, the solution enters a crystallization separator and is divided into two paths of gas phase and liquid phase, in the figure, LC represents liquid level adjustment and is arranged at the stock solution tank.
Liquid phase: the raw liquid enters a crystallization separator and then a forced circulation pump is opened for forced circulation, specifically, raw materials enter the crystallization separator through a forced circulation heat exchanger under the action of the forced circulation pump, concentrated liquid (the temperature is 96 ℃, the salt content is 38 percent, and the water content is 62 percent) enters a thickener after passing through a discharge pump, solid products enter a centrifugal machine for centrifugal separation, sodium sulfate products (the temperature is 96 ℃, the salt content is 99.5 percent, and the water content is 0.5 percent) are obtained after boiling, fluidization and drying, supernatant liquid from the thickener and centrifugal liquid after centrifugal separation enter a mother liquid tank and then overflow to a cleaning tank, and medium-lower supernatant liquid in the mother liquid tank returns mother liquid to double-effect evaporation through the mother liquid pump for circulation through the forced circulation pump; when the solid coming out of the thickener is dried, the gas generated during drying is subjected to dust removal operation through a bag type dust collector, the bag type dust collector is connected with a blower, sodium sulfate salt products generated by the dryer enter a storage bin through a bucket elevator, and the storage bin is packaged by a further packaging machine.
The supernatant in the mother liquor tank is returned to the desulfurization tower of the alkaline washing device, the supernatant in the mother liquor tank is mainly sodium sulfite with smaller particles, if the sodium sulfite is not discharged in actual operation, the sodium sulfite of the crystallization device is enriched, so that the problems of unqualified sodium sulfate products, small particle size and blockage of pipelines are caused, and the supernatant containing the sodium sulfite is returned to the desulfurization tower and oxidized into sodium sulfate and then enters the evaporation crystallization device.
Gas phase: the steam is discharged from the crystallization separator and then enters a secondary separator and a water bath dedusting gas washing tower to remove substances such as liquid drops, solid impurities and the like in the steam, secondary steam (with the temperature of 90 ℃ and the pressure of-31 Pa) enters a steam compressor to be boosted to 74Pa (with the temperature of 102 ℃) and enters a forced circulation heat exchanger to heat sodium sulfate solution, and condensed water after steam condensation is conveyed to a storage tank to be used for preparing sodium hydroxide solution.
The embodiment of the invention also provides a sulfur recovery tail gas treatment device, which comprises: an incineration device, an alkaline washing device and an evaporation crystallization device,
the incineration device is used for incinerating the tail gas treated by the sulfur recovery device through the positive pressure incinerator to form sulfur-containing flue gas;
the alkaline washing device is used for performing alkaline washing desulfurization on the sulfur-containing flue gas by sodium hydroxide to form a sodium sulfate product solution;
and the evaporation crystallization device is used for evaporating and crystallizing the sodium sulfate product solution to form dry sodium sulfate salt and condensed water, and finishing sulfur recovery tail gas treatment.
Specifically, the incineration device comprises a positive pressure incinerator and a flue gas cooler,
the front end temperature of the incinerator is set to be above 1000 ℃, the middle and tail temperatures of the incinerator are set to be 700-720 ℃, and the oxygen content in flue gas at the outlet of the incinerator is set to be 3%.
The flue gas cooler is also used for forming saturated steam.
Specifically, the incinerator is provided with two groups of air inlets and tail gas inlets, and the two groups of air inlets and the tail gas inlets are independently controlled and symmetrically arranged on two sides of the incinerator body.
Specifically, the alkaline washing device comprises a washing tower, a desulfurization absorption tower and an oxidation tank,
the washing tower is used for washing the sulfur-containing flue gas, introducing the sulfur-containing flue gas into the desulfurization absorption tower, and controlling the temperature of the sulfur-containing flue gas to be reduced to 40-50 ℃; the washing tower is also used for circularly conveying the crude sodium sulfate solution to the washing tower for PH adjustment in the process of circularly washing;
the desulfurization absorption tower is used for contacting sulfur-containing flue gas introduced from the bottom with sodium hydroxide solution sprayed from the top to form sodium sulfite solution, and the concentration of the sodium sulfite solution is less than 10wt%;
one part of sodium sulfite solution is pumped out by a tower bottom circulating desulfurization pump and flows into the top of the desulfurization absorption tower for recycling, and the other part of sodium sulfite solution is pumped out by the tower bottom circulating desulfurization pump and flows into an oxidation tank for oxidation treatment by PH adjustment and heating treatment;
the oxidation tank is used for carrying out oxidation treatment on the inflowing sodium sulfite solution to form a crude sodium sulfate solution.
Specifically, the evaporation crystallization device comprises a crystallization separator, a thickener and a mother liquid tank,
the crystallization separator is used for treating the introduced sodium sulfate solution to form a liquid phase and a gas phase, and the liquid phase enters the thickener through the discharge pump;
the thickener is used for centrifugally separating generated solids in a centrifugal machine, and obtaining sodium sulfate after boiling, fluidization and drying;
the thickener is also used for feeding the supernatant and the centrifugated liquid after centrifugal separation into the mother liquid tank;
and the mother liquor tank is used for introducing the deposited supernatant into a desulfurization absorption tower and an oxidation tank of the alkaline washing device for reoxidation treatment.
Specifically, the evaporative crystallization device also comprises a gas washing tower and a vapor compressor,
the gas washing tower is used for removing liquid drops and solid impurities in the gas phase through water bath dust removal;
and the vapor compressor is used for boosting the gas phase processed by the gas washing tower, and the boosted vapor enters the forced circulation heat exchanger to heat the sodium sulfate solution.
The method and the device for treating the sulfur recovery tail gas adopt the combined total process of 'positive-pressure tail gas incineration, alkaline cleaning and desulfurization of flue gas NaOH and evaporative crystallization of sodium sulfate solution', optimize the traditional process flow, conditions and devices and can meet the H under the working conditions of different treatment gas amounts 2 S conversion efficiency, and can also prevent nitrogen oxides from exceeding standard and ensure the quality of sodium sulfate products, and SO is removed by adopting a double-tower alkaline washing process of a washing tower and a desulfurization absorption tower 2 Is suitable for purifying the acid gas quantity and H of a factory 2 The method has the characteristics of large S content variation range, adopts an evaporation crystallization process, utilizes clean electric energy, is suitable for the characteristic of high concentration of sodium sulfate solution, has lower operation cost by adopting the evaporation crystallization process, and increases the applicability of sulfur recovery tail gas treatment.
Although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (13)
1. A method for treating sulfur recovery tail gas, the method comprising:
the tail gas treated by the sulfur recovery device is burnt by a positive pressure incinerator to form sulfur-containing flue gas;
the sulfur-containing flue gas is desulfurized through caustic washing with sodium hydroxide to form sodium sulfate product solution;
evaporating and crystallizing the sodium sulfate product solution to form dry sodium sulfate salt and condensed water, and finishing sulfur recovery tail gas treatment.
2. The sulfur recovery tail gas treatment process of claim 1, wherein the forming of the sulfur-containing flue gas comprises:
the tail gas treated by the sulfur recovery device sequentially passes through the positive pressure incinerator and the flue gas cooler to form sulfur-containing flue gas, the sulfur-containing flue gas is treated by the flue gas cooler to form saturated steam, wherein,
the front end temperature of the incinerator is set to be above 1000 ℃, the middle and tail temperatures of the incinerator are set to be 700-720 ℃, and the oxygen content in flue gas at the outlet of the incinerator is set to be 3%.
3. The sulfur recovery tail gas treatment process of claim 1, wherein the desulfurization of the sulfur-containing flue gas by caustic soda wash to form a sodium sulfate solution comprises:
the sulfur-containing flue gas is sequentially processed by a washing tower, a desulfurization absorption tower and an oxidation tank to form a crude sodium sulfate solution, the crude sodium sulfate solution is decolored and filter-pressed to form a sodium sulfate solution, wherein,
washing the sulfur-containing flue gas by a washing tower, and controlling the temperature of the sulfur-containing flue gas to be reduced to 40-50 ℃;
and in the process of circularly washing the washing tower, the method also comprises the step of circularly conveying the crude sodium sulfate solution to the washing tower for PH adjustment.
4. The method for treating sulfur recovery tail gas according to claim 3, wherein the desulfurization and oxidation of the sulfur-containing flue gas by the desulfurization absorption tower and the oxidation tank specifically comprises:
the sulfur-containing flue gas introduced from the bottom of the desulfurization absorption tower contacts with sodium hydroxide solution sprayed from the top to form sodium sulfite solution, wherein the concentration of the sodium hydroxide solution is less than 10wt%;
one part of sodium sulfite solution is pumped out by a tower bottom circulating desulfurization pump and flows into the top of the desulfurization absorption tower for recycling, and the other part of sodium sulfite solution is pumped out by the tower bottom circulating desulfurization pump and flows into an oxidation tank for oxidation treatment by PH adjustment and heating treatment;
the sodium sulfite solution treated by the oxidation tank is subjected to oxidation treatment to form a crude sodium sulfate solution.
5. A sulfur recovery tail gas treatment process according to claim 3, wherein subjecting the sodium sulfate solution to evaporative crystallization to form dried sodium sulfate salt and condensate comprises:
introducing the sodium sulfate solution into a crystallization separator to form a liquid phase and a gas phase;
the liquid phase enters a thickener through a discharge pump, wherein solids generated by the thickener enter a centrifugal machine for centrifugal separation, and sodium sulfate is obtained after boiling, fluidization and drying;
supernatant fluid from the thickener and centrifugalized liquid enter a mother liquor tank, supernatant fluid deposited by the mother liquor tank is introduced into a desulfurization absorption tower and an oxidation tank of the alkaline washing device for reoxidation treatment, and then enters the evaporation crystallization device again.
6. A sulfur recovery tail gas treatment process according to claim 5, wherein,
the gas phase is processed by a secondary separator, a water bath dedusting gas washing tower and a vapor compressor in sequence to form pressure-boosting steam, and the pressure-boosting steam enters a forced circulation heat exchanger to heat sodium sulfate solution.
7. A sulfur recovery tail gas treatment device, the device comprising: an incineration device, an alkaline washing device and an evaporation crystallization device,
the incineration device is used for incinerating the tail gas treated by the sulfur recovery device through the positive pressure incinerator to form sulfur-containing flue gas;
the alkaline washing device is used for performing alkaline washing desulfurization on the sulfur-containing flue gas by sodium hydroxide to form a sodium sulfate product solution;
and the evaporation crystallization device is used for evaporating and crystallizing the sodium sulfate product solution to form dry sodium sulfate salt and condensed water, and finishing sulfur recovery tail gas treatment.
8. The sulfur recovery tail gas treatment device according to claim 7, wherein the incineration device comprises a positive pressure incinerator and a flue gas cooler,
the temperature of the front end of the incinerator is set to be more than 1000 ℃, the temperatures of the middle part and the tail part of the incinerator are set to be 700-720 ℃, and the oxygen content in flue gas at the outlet of the incinerator is set to be 3%;
the flue gas cooler is also used for forming saturated steam.
9. The sulfur recovery tail gas treatment device according to claim 8, wherein the incinerator is provided with two sets of air inlets and tail gas inlets, and the two sets of air inlets and tail gas inlets are independently controlled and symmetrically arranged on two sides of the incinerator body.
10. The sulfur recovery tail gas treatment apparatus according to claim 7 or 8, wherein the alkaline washing apparatus comprises a washing tower, a desulfurization absorbing tower and an oxidation tank,
the washing tower is used for washing the sulfur-containing flue gas, introducing the sulfur-containing flue gas into the desulfurization absorption tower, and controlling the temperature of the sulfur-containing flue gas to be reduced to 40-50 ℃; the washing tower is also used for circularly conveying the crude sodium sulfate solution to the washing tower for PH adjustment in the process of circularly washing;
the desulfurization absorption tower is used for contacting sulfur-containing flue gas introduced from the bottom with sodium hydroxide solution sprayed from the top to form sodium sulfite solution, and the concentration of the sodium sulfite solution is less than 10wt%;
one part of sodium sulfite solution is pumped out by a tower bottom circulating desulfurization pump and flows into the top of the desulfurization absorption tower for recycling, and the other part of sodium sulfite solution is pumped out by the tower bottom circulating desulfurization pump and flows into an oxidation tank for oxidation treatment by PH adjustment and heating treatment;
the oxidation tank is used for carrying out oxidation treatment on the inflowing sodium sulfite solution to form a crude sodium sulfate solution.
11. The sulfur recovery tail gas treatment device according to claim 10, wherein the evaporative crystallization device comprises a crystallization separator, a thickener and a mother liquor tank,
the crystallization separator is used for treating the introduced sodium sulfate solution to form a liquid phase and a gas phase, and the liquid phase enters the thickener through the discharge pump;
the thickener is used for centrifugally separating generated solids in a centrifugal machine, and obtaining sodium sulfate after boiling, fluidization and drying;
the thickener is also used for feeding the supernatant and the centrifugated liquid after centrifugal separation into the mother liquid tank;
and the mother liquor tank is used for introducing the deposited supernatant into a desulfurization absorption tower and an oxidation tank of the alkaline washing device for reoxidation treatment.
12. The sulfur recovery tail gas treatment device of claim 11, wherein the evaporative crystallization device further comprises a scrubber and a vapor compressor,
the gas washing tower is used for removing liquid drops and solid impurities in the gas phase through water bath dust removal;
the vapor compressor is used for boosting the gas phase processed by the gas washing tower, and the boosted vapor enters the forced circulation heat exchanger to heat the sodium sulfate solution.
13. Use of a sulfur recovery tail gas treatment process according to any of claims 1-6 for purifying natural gas.
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