Coking sulfur paste and dedusting ash resourceful treatment process

Abstract

The invention discloses a coking sulfur paste and fly ash resourceful treatment process, and belongs to the technical field of coking. The process comprises the following steps: carrying out solid-liquid separation on sulfur foam led out from a desulfurization unit, returning a liquid phase to a desulfurization system, mixing a solid phase with fly ash in a kneading machine, and then feeding into a drying tower; feeding gas generated by drying into a washing tower for acid washing, then filtering, feeding part of washing liquid into an ammonium sulfate working section, and feeding dried solid into a fluidized bed furnace for incineration; high-temperature gas generated from the fluidized bed furnace is fed into a waste heat boiler, generated saturated steam enters a low-pressure steam pipe network after pressure reduction, SO2-containing process gas in the waste heat boiler is sequentially washed and purified, the purified gas is fed into a second drying tower, the dried gas is fed into an SO2 conversion tower and an absorption tower to prepare sulfuric acid, and waste gas is discharged after being treated by a washing tower and reaching the standard. The method has the advantages that the cost is reduced, and resources are saved; sulfur and nitrogen in the sulfur paste are respectively recovered, so that the economic benefit is improved while the pollution is reduced.

Description

Technical Field

[0001] The invention relates to a resource processing process for coking sulfur paste and dust removal ash, and in particular to an integrated processing process for desulfurized paste produced in a coke oven gas wet desulfurization process and dust removal ash produced in a coke oven coking production process, belonging to the field of coking technology. Background Art

[0002] At present, the treatment of coke oven gas widely adopts the wet desulfurization process with HPF and PDS as catalysts. A large amount of low-grade sulfur will be produced during the desulfurization process, with an annual output of about 800,000 tons nationwide. Among them, coking sulfur paste is the main form of existence. In addition to sulfur, it also contains desulfurization by-products such as NH4SCN, (NH4)2S2O3, desulfurization catalysts, and impurities such as tar-like organic matter. It has become a difficult-to-use and highly polluting industrial solid waste. At present, in the field of coking sulfur paste treatment, a mature treatment solution that is both economical and efficient has not yet been developed. The disposal of coking sulfur paste has become a technical problem faced by coking enterprises, which has had an extremely severe restrictive effect on the advancement of coking, fertilizer and other industries in terms of sustainability and environmental protection.

[0003] The dust ash is obtained by removing dust from various tail gases through dust collectors during the production process of the coking plant. It contains a variety of components, such as coke dust, metal oxides, and a small amount of incompletely reacted sulfur-containing compounds. The amount is large and it is difficult to achieve high-value utilization. Because its particles are relatively fine, if it is not handled in time, long-term storage will not only occupy a large area of ​​the site, but also cause great pollution to the plant and nearby living places. In order to make more rational use of resources, realizing the closed-loop circulation and high-value utilization of dust ash in the coking plant has become a difficult problem that the coking plant urgently needs to solve.

[0004] In order to solve the above problems, the present invention provides a resource processing process for coking sulfur paste and dust removal ash. Summary of the invention

[0005] The present invention aims to provide a process for recycling coking sulfur paste and dust removal ash to obtain sulfuric acid products, and effectively solves the problems of large investment, complex process, high energy consumption in process treatment, etc. in the prior art.

[0006] Coking sulfur paste is a waste produced during the desulfurization process of coke oven gas, but the sulfur content is as high as 40%-60%. If it can be burned to produce acid, the sulfur resources can be rationally utilized, and the sulfuric acid produced can be used as a raw material for the production of ammonium sulfate. However, the water content in the sulfur paste is high, and burning alone cannot effectively maintain the furnace temperature, and it also brings certain difficulties to the transportation process into the furnace. With the widespread use of dry coke quenching in the industry, a large amount of coke powder generated by enterprises needs to be processed urgently. The coke powder has low water content and high carbon content. Mixing it with sulfur paste can effectively solve the problem of insufficient heat and difficult transportation of sulfur paste during the incineration process.

[0007] The present invention provides a process for resource processing of coking sulfur paste and dust removal ash, comprising the following steps: separating the sulfur foam drawn out from the desulfurization unit into solid and liquid, returning the liquid phase to the desulfurization system, and feeding the solid phase and the dust removal ash into a kneader in proportion for mixing; feeding the obtained mixed solid into a drying tower; feeding the gas generated by drying into a washing tower for acid washing, filtering after washing, regularly feeding a part of the washing liquid into an ammonium sulfate section, and feeding the dried solid into a boiling furnace for incineration; feeding the high-temperature gas generated from the boiling furnace into a waste heat boiler, and the generated saturated steam enters a low-pressure steam network after decompression, and the SO2-containing process gas in the waste heat boiler is washed and purified in turn, and the purified gas is fed into a second drying tower, and the dried gas is fed into an SO2 conversion tower and an absorption tower to produce sulfuric acid, and the waste gas is discharged after being treated in the washing tower and meets the standards.

[0008] The above-mentioned coking sulfur paste and dust ash resource processing process specifically includes the following steps: (1) The sulfur foam sent from the desulfurization unit is centrifuged in a centrifuge to obtain solid and liquid phases; the liquid phase is returned to the desulfurization system, and the solid phase is sulfur paste. 30%-50% by weight of sulfur paste and 50%-70% by weight of dust removal ash are sent to a kneader. During the stirring process, the stirring speed is maintained at 80-100r / min and the stirring time is 40-60min; (2) The mixture stirred by the kneader is sent to a drying tower for drying; (3) The gas generated in the drying tower is introduced into the washing tower for acid washing to remove residual ammonia and other impurities in the gas. After acid washing, 10-15% of the generated washing liquid is sent to the ammonium sulfate section after being filtered and pressurized by a pump, and new sulfuric acid solution is added to maintain the continuity of the washing process. During the washing process, the mass concentration of the sulfuric acid solution is 6%~10%; (4) Sending the solids dried in the drying tower to a boiling furnace for incineration; (5) The high-temperature SO2 gas from the boiling furnace enters the waste heat boiler to generate 2.5-3.0MPa saturated steam, which is then reduced to below 0.8MPa and enters the low-pressure steam network and returns to the drying tower; (6) The SO2-containing process gas with a temperature of 300-350°C from the waste heat boiler passes through a humidifying tower, a cooling tower, a cleaning tower and an electrostatic demister in turn to humidify, cool, purify and demister the process gas to remove excess water and harmful impurities such as dust, arsenic, selenium, fluorine and chlorine. The purified SO2-containing process gas enters the second drying tower; concentrated sulfuric acid with a mass concentration of 93% to 95% is used to dry and remove the water in the process gas, thereby ensuring the strict requirements of the dry contact acid catalyst in the conversion process on the water content of the gas; after drying, the water content of the process gas is controlled at <0.1g / Nm 3 ; (7) The gas discharged from the second drying tower is introduced into the SO2 conversion tower and absorption tower through a heat exchanger to convert and absorb SO2 to produce sulfuric acid. The conversion and acid production process can adopt a two-conversion and two-absorption process. In the SO2 conversion tower, the catalyst can be arranged in five layers, including a total of five catalyst beds, and the reaction conversion is carried out according to the III+II mode. The main chemical reactions in the conversion process are as follows:

[0009] The converted gas is heat exchanged with the dried furnace gas through a heat exchanger, and the temperature is reduced to 160-180℃ before being sent to the absorption tower. Two absorption towers are set up in the absorption process, corresponding to the two-stage conversion process of the conversion section. The tail gas absorbed by the first absorption tower is heated by the heat exchanger and returned to the conversion tower for secondary conversion. After the secondary conversion, the tail gas is heat exchanged and absorbed in the second absorption tower before entering the subsequent process. During the absorption process, 98% concentrated sulfuric acid is used to absorb SO3 in the conversion gas, and the water in the concentrated sulfuric acid reacts with SO3 to form sulfuric acid product. The sulfuric acid product is sent out by the acid absorption pump, cooled by the product acid cooler, and enters the product acid storage tank, and is regularly transported to the ammonium sulfate unit by the product acid pump for use.

[0010] (8) The tail gas absorbed by the second absorption tower enters the tail gas scrubber for cooling and purification. The purified tail gas meets the emission standards. The scrubbing liquid used in the purification process can be NaOH solution or Na2CO3 solution, or dilute ammonia solution.

[0011] Beneficial effects of the present invention: (1) Compared with the prior art, the present invention has the advantages of reducing costs and saving resources; (2) This process can efficiently process two industrial by-products, reduce their negative impact on the environment, and achieve the goal of turning waste into treasure; (3) This process recovers sulfur and nitrogen from sulfur paste separately, reducing pollution while improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1This is a process flow chart of preparing sulfuric acid from sulfur paste and dust removal ash of the present invention; In the figure: 1-centrifuge; 2-kneading machine; 3-drying tower; 4-washing tower; 5-filtering tower; 6-centrifugal pump; 7-boiling furnace; 8-waste heat boiler; 9-low-pressure steam pipe network; 10-humidifying tower; 11-cooling tower; 12-cleaning tower; 13-electric demister; 14-second drying tower; 15-III heat exchanger; 16-I heat exchanger; 17-SO2 conversion tower; 18-II heat exchanger; 19-first absorption tower; 20-V heat exchanger; 21-IV heat exchanger; 22-second absorption tower; 23-tail gas washing tower; 24-product acid storage tank; A-sulfur foam; B-dust removal ash; C-desulfurization system; D-ammonium sulfate section; E-SO2-containing process gas; F-low-pressure steam; J-NaOH solution; K-Na2CO3 solution. DETAILED DESCRIPTION

[0013] The present invention is further illustrated by the following examples, but is not limited to the following examples.

[0014] Embodiment 1: The sulfur paste used in this embodiment is obtained by solid-liquid separation of sulfur foam produced by coking gas in a coking plant, and the dust ash is the dust ash produced in the dry quenching process.

[0015] The present invention first provides a coking sulfur paste and dust ash resource processing device, comprising a centrifuge 1, a kneading machine 2, a drying tower 3, a boiling furnace 7, a waste heat boiler 8, a humidifying tower 10, a cooling tower 11, a cleaning tower 12, an electric precipitator 13, and a second drying tower 14 connected in sequence; the gas outlet of the drying tower 3 is connected to a washing tower 4, a filtering tower 5, and a centrifugal pump 6; the reduced pressure steam outlet of the waste heat boiler 8 is connected to a low-pressure steam pipe network 9; the second drying tower 14 is connected to a two-turn two-absorption device, the two-turn two-absorption device comprises an SO2 conversion tower 17, a first absorption tower 19, a second absorption tower 22 and a heat exchanger, the SO2 conversion tower 17 comprises a first section to a fifth section of catalyst beds arranged in sequence from top to bottom, each section of the catalyst bed is respectively connected to a heat exchanger to realize two-stage conversion and absorption of SO2 process gas; the liquid outlets of the first absorption tower 19 and the second absorption tower 22 are connected to a product acid storage tank 24; the gas outlet of the second absorption tower 22 is connected to a tail gas washing tower 23.

[0016] use Figure 1The process flow shown is as follows: sulfur foam A is added into centrifuge 1, and the liquid phase obtained after centrifugal separation is directly sent to desulfurization system C; the solid phase (i.e. sulfur paste) enters kneading machine 2, is mixed and stirred with dust removal ash B, and the mixture enters drying tower 3 for drying, and the gas generated in the drying tower is sent to washing tower 4 (pickling) and filtering tower 5 (filtration), and the filtered washing liquid is sent to ammonium sulfate section D through centrifugal pump 6; the solid after drying in drying tower 3 is sent to boiling furnace 7 for incineration, and the high-temperature SO2 furnace gas in the boiling furnace is heated to generate high-pressure steam, which is sent to waste heat boiler 8, which is decompressed and sent to low-pressure steam network 9, and then the low-pressure steam F is sent to drying tower 3; the waste heat boiler contains The SO2 process gas E enters the humidifying tower 10, the cooling tower 11, the cleaning tower 12, the electrostatic precipitator 13, and the second drying tower 14 in sequence; the treated SO2 process gas enters the SO2 conversion tower 17 for the first conversion, and after the first conversion, it is heat exchanged in the heat exchanger, and the catalyst bed in the conversion tower undergoes a catalytic reaction before entering the first absorption tower 19; after heat exchange, it enters the SO2 conversion tower 17 for the second conversion, and after the second conversion, it is heat exchanged in the heat exchanger, and the catalyst bed in the conversion tower undergoes a catalytic reaction before entering the second absorption tower 22, and the excess concentrated sulfuric acid enters the product acid storage tank 24; the exhaust gas discharged from the second absorption tower 22 enters the exhaust gas washing tower 23 for washing and treatment, and is discharged after meeting the standards.

[0017] according to Figure 1 The specific implementation process of the process flow chart shown includes the following steps: In the first step, the sulfur foam drawn out from the regeneration tower is separated by a centrifuge. The liquid phase obtained after separation is directly sent to the desulfurization system. The solid phase (sulfur paste) and dust removal ash are sent to the kneader at a mass ratio of 1:1 for mixing. The stirring speed is maintained at 100r / min and the stirring time is 60min.

[0018] In the second step, the mixture stirred by the kneader is sent to a drying tower for drying.

[0019] In the third step, the gas generated in the drying tower is sent to the washing tower for acid washing to remove other gases such as ammonia contained in the gas during the drying process. After acid washing, it is filtered and 10% of the generated washing liquid is sent to the ammonium sulfate section through the centrifugal pump 6, and then new sulfuric acid solution is added. The mass concentration of sulfuric acid is maintained at 8% during the washing process.

[0020] The fourth step is to send the solids dried in the drying tower into the boiling furnace for incineration.

[0021] In the fifth step, the high-temperature SO2 gas in the boiling furnace is heated to produce 2.5MPa saturated steam, which is sent to the waste heat boiler 8, where it is depressurized to about 0.5MPa and enters the low-pressure steam network and returns to the drying tower.

[0022] In the sixth step, the SO2-containing process gas with a temperature of about 350°C from the waste heat boiler is cooled, purified, and demisted to remove excess moisture and dust, arsenic, selenium, fluorine, chlorine and other impurities that are harmful to the V2O5 catalyst for converting SO2. The purified SO2 process gas enters the second drying tower and is dried with 95% concentrated sulfuric acid. After drying, the water content of the process gas is 0.08g / Nm 3 .

[0023] In the seventh step, the cold gas after drying in the second drying tower and defogged by the wire mesh defogger on the top of the drying tower is pressurized by the SO2 blower and enters the third heat exchanger 15 and the first heat exchanger 16 in turn for heating. After the temperature reaches 420°C, it enters the first section of the SO2 converter (which is divided into the first to fifth sections of the catalyst bed from top to bottom) for conversion. After the reaction, the furnace gas temperature rises to about 585°C and enters the first heat exchanger 16 to exchange heat with the cold gas from the SO2 blower for cooling. The cooled furnace gas enters the second section of the converter catalyst bed for catalytic reaction, then exits the converter and enters the second heat exchanger 18 for cooling, and then enters the third section of the converter catalyst bed for further reaction. The gas from the outlet of the third section of the converter enters the tube of the third heat exchanger, and after the temperature drops to 170°C, it enters the first absorption tower 19 to absorb SO3 in the gas, and after passing through the wire mesh demister at the top of the tower to remove the acid mist in the gas, it enters the fifth heat exchanger 20, the fourth heat exchanger 21, and the second heat exchanger 18 in turn. After the gas is heated, it enters the fourth section catalyst bed of the converter for the second conversion. The gas from the fourth section bed enters the fourth heat exchanger 21 and cools to 415°C, and then enters the fifth section catalyst bed of the converter for reaction. The outlet gas of the fifth section passes through the tube of the fifth heat exchanger for heat exchange and cooling with the cold furnace gas, and the temperature drops to about 165°C before entering the second absorption tower 22 to absorb a small amount of SO3 in the gas, and passes through the demister at the top of the tower to remove the acid mist. The absorption acid circulation tank is equipped with an automatic water feeder to add process water to adjust and control the concentration of the absorption acid (concentrated sulfuric acid) to 98%. The excess circulating acid is discharged from the outlet of the absorption acid cooler as a product, and after being measured by an electromagnetic flowmeter, it is sent to the underground acid tank and then sent to the product acid storage tank 24 of the main device by an acid pump for storage.

[0024] In the eighth step, the tail gas absorbed by the second absorption tower is passed into the tail gas washing tower 23, and after being washed by the NaOH spray liquid, the SO2 in the tail gas is ≤10mg / m 3 , this exhaust gas is discharged directly.

Claims

1. A process for recycling coking sulfur paste and dust removal ash, characterized in that The following steps are involved: The sulfur foam drawn out from the desulfurization unit is separated into solid and liquid, the liquid phase is returned to the desulfurization system, and the solid phase and dust removal ash are sent to the kneader in proportion for mixing; The obtained mixed solid is sent to the drying tower; the gas generated by drying is sent to the washing tower for acid washing, and after washing, it is filtered, and a part of the washing liquid is regularly sent to the ammonium sulfate section, and the dried solid is sent to the boiling furnace for incineration; the high-temperature gas generated from the boiling furnace is sent to the waste heat boiler, and the saturated steam generated is decompressed and enters the low-pressure steam network, the SO2-containing process gas in the waste heat boiler is washed and purified in turn, and the purified gas is sent to the second drying tower, and the dried gas is sent to the SO2 conversion tower and the absorption tower to produce sulfuric acid, and the waste gas is discharged after being treated in the washing tower and meeting the standards.

2. The process for recycling coking sulfur paste and dust ash according to claim 1, characterized in that The following steps are involved: (1) The sulfur foam sent from the desulfurization unit is centrifuged in a centrifuge to obtain solid and liquid phases; the liquid phase is returned to the desulfurization system, and the solid phase is sulfur paste. The sulfur paste with a mass proportion of 30%-50% and the dust removal ash with a mass proportion of 50%-70% are sent to a kneader for stirring and mixing; (2) The mixture stirred by the kneader is sent to a drying tower for drying; (3) The gas generated in the drying tower is introduced into the washing tower for acid washing to remove the impurities remaining in the gas. After acid washing, 10-15% of the washing liquid is filtered and pumped into the ammonium sulfate section after pressurization. At the same time, new sulfuric acid solution is added to maintain the continuity of the washing process. (4) Sending the solids dried in the drying tower to a boiling furnace for incineration; (5) The high-temperature SO2 gas from the boiling furnace enters the waste heat boiler, generates 2.5-3.0MPa saturated steam, which is then reduced to below 0.8MPa and enters the low-pressure steam network and returns to the drying tower; (6) The SO2-containing process gas with a temperature of 300-350°C from the waste heat boiler passes through a humidifying tower, a cooling tower, a cleaning tower and an electrostatic demister in sequence to humidify, cool, purify and demister the process gas to remove excess water and harmful impurities. The purified SO2-containing process gas enters the second drying tower; (7) The gas discharged from the second drying tower is introduced into the SO2 conversion tower and the absorption tower through a heat exchanger to convert and absorb SO2 to prepare sulfuric acid; the conversion and acid production process can adopt a two-conversion and two-absorption process; in the SO2 conversion tower, the catalyst can be arranged in five layers and the reaction conversion is carried out according to the III+II mode; the converted gas is heat exchanged with the dried furnace gas through a heat exchanger, and the temperature is reduced to 160-180°C before being sent to the absorption tower; (8) The exhaust gas absorbed by the second absorption tower enters the exhaust gas washing tower for cooling and purification. The purified exhaust gas meets the emission standards.

3. The process for recycling coking sulfur paste and dust ash according to claim 2, characterized in that: In step (1), the stirring speed is maintained at 80-100 r / min and the stirring time is maintained at 40-60 min during the stirring process.

4. The process for recycling coking sulfur paste and dust ash according to claim 2, characterized in that: In step (3), during the acid washing process, the mass concentration of the sulfuric acid solution is 6% to 10%.

5. The process for recycling coking sulfur paste and dust ash according to claim 2, characterized in that: In step (6), concentrated sulfuric acid with a mass concentration of 93% to 95% is used to dry and remove the moisture in the process gas, thereby ensuring the strict requirements of the dry contact acid catalyst in the conversion process on the moisture content of the gas; after drying, the moisture content of the process gas is controlled to <0.1g / Nm 3 .

6. The process for recycling coking sulfur paste and dust ash according to claim 2, characterized in that: In step (7), two absorption towers are set up in the absorption process, corresponding to the two-stage conversion process of the conversion section; the tail gas absorbed by the first absorption tower is heated by the heat exchanger and then returned to the conversion tower for secondary conversion; the tail gas after the secondary conversion is subjected to heat exchange and absorbed in the second absorption tower before entering the subsequent process; during the absorption process, 98% concentrated sulfuric acid is used to absorb SO3 in the conversion gas, and the water in the concentrated sulfuric acid reacts with SO3 to form sulfuric acid product.

7. The process for recycling coking sulfur paste and dust ash according to claim 6, characterized in that: In step (7), the treated SO2 process gas enters the SO2 conversion tower for the first conversion, and after the first conversion, it is heat exchanged in a heat exchanger, and a catalytic reaction occurs in the catalyst bed in the conversion tower before entering the first absorption tower; after heat exchange, it enters the SO2 conversion tower for the second conversion, and after the second conversion, it is heat exchanged in a heat exchanger, and a catalytic reaction occurs in the catalyst bed in the conversion tower before entering the second absorption tower; the excess concentrated sulfuric acid enters the product acid storage tank.

8. The process for recycling coking sulfur paste and dust ash according to claim 2, characterized in that: The washing liquid used in the purification process of step (8) is NaOH solution, Na2CO3 solution or dilute ammonia solution.

9. A coking sulfur paste and dust ash resource processing device, used for implementing the coking sulfur paste and dust ash resource processing process according to any one of claims 1 to 8, characterized in that: It includes a centrifuge, a kneading machine, a drying tower, a boiling furnace, a waste heat boiler, a humidifying tower, a cooling tower, a cleaning tower, an electric demister, and a second drying tower which are connected in sequence; the gas outlet of the drying tower is connected to a washing tower, a filtering tower, and a centrifugal pump; the reduced pressure steam outlet of the waste heat boiler is connected to a low-pressure steam network; the second drying tower is connected to a two-turn two-absorption device, which includes a SO2 conversion tower, a first absorption tower, a second absorption tower, and a heat exchanger, the SO2 conversion tower includes first to fifth catalyst beds which are arranged in sequence from top to bottom, each catalyst bed is respectively connected to a heat exchanger to realize two-stage conversion and absorption of SO2 process gas; the liquid outlets of the first absorption tower and the second absorption tower are connected to a product acid storage tank; the gas outlet of the second absorption tower is connected to an exhaust gas washing tower.

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