A resource processing process for coking sulfur paste and dust removal ash

Abstract

The present invention discloses a resource processing process for coking sulfur paste and dust removal ash, belonging to the field of coking technology. The process comprises: separating the sulfur foam drawn out from the desulfurization unit into solid and liquid, returning the liquid phase to the desulfurization system, mixing the solid phase with the dust removal ash in a kneader and then sending it to a drying tower; sending the gas generated by drying into a washing tower for acid washing, and then filtering, and part of the washing liquid will be sent to the ammonium sulfate section, and the solid after drying will be sent to a boiling furnace for incineration; the high-temperature gas generated from the boiling furnace is sent to a waste heat boiler, and the saturated steam generated is depressurized and enters a low-pressure steam network, and the SO2-containing process gas in the waste heat boiler is washed and purified in turn, and the purified gas is sent to a second drying tower, and the dried gas is sent to 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 meeting the standards. The present invention has the advantages of reducing costs and saving resources; the sulfur and nitrogen in the sulfur paste are recovered separately, reducing pollution while improving economic benefits.

Description

Technical Field

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

[0002] Currently, wet desulfurization processes using HPF and PDS as catalysts are widely used in the treatment of coke oven gas. This desulfurization process produces a large amount of low-grade sulfur, with an annual national output of approximately 800,000 tons. Coking sulfur paste is the primary form of this sulfur. Because it contains, in addition to sulfur, desulfurization byproducts such as NH4SCN and (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. Currently, a mature, economical, and efficient treatment solution for coking sulfur paste has not yet been developed. The disposal of coking sulfur paste has become a technical challenge facing coking enterprises, severely restricting the sustainability and environmental protection efforts of industries such as coking and fertilizer.

[0003] During the coking plant's production process, dust ash is removed from various exhaust gases through dust collectors. It contains a variety of components, such as coke dust, metal oxides, and a small amount of incompletely reacted sulfur compounds. This large amount of dust is difficult to utilize at high value. Due to its fine particles, if not promptly processed and stored for a long time, it will not only occupy a large area of ​​land but also cause significant pollution to the plant and nearby residential areas. To more rationally utilize resources, achieving closed-loop circulation and high-value utilization of dust ash within the coking plant has become a pressing challenge for coking plants.

[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 resource-based treatment of coking sulfur paste and dust removal ash to produce sulfuric acid products, effectively solving the problems of large investment, complex process, and high energy consumption in the prior art.

[0006] Coking sulfur paste is a waste product generated during the desulfurization process of coke oven gas. However, its sulfur content is as high as 40%-60%. Incineration to produce acid can effectively utilize sulfur resources, and the resulting sulfuric acid can be used as a raw material for the ammonium sulfate production process. However, the high water content in sulfur paste makes it difficult to maintain furnace temperature when incinerated alone, and also creates certain difficulties in transporting the paste into the furnace. With the widespread use of dry coke quenching (CDQ) within the industry, companies are generating large quantities of coke fines that urgently need to be processed. Coke fines have a low water content and a high carbon content. Mixing them with sulfur paste can effectively solve the problems of insufficient heat and difficult transport of sulfur paste during incineration.

[0007] The present invention provides a resource processing process for coking sulfur paste and dust removal ash, which includes 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 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, and regularly feeding a portion of the washing liquid into the 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 meeting the standards.

[0008] The above-mentioned process for resource utilization of coking sulfur paste and dust removal ash specifically includes the following steps:

[0009] (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 ratio of 30%-50% and the dust removal ash with a mass ratio of 50%-70% are sent to the kneader. During the stirring process, the stirring speed is maintained at 80-100 r / min and the stirring time is 40-60 min.

[0010] (2) The mixture stirred by the kneader is sent to the drying tower for drying;

[0011] (3) The gas generated in the drying tower is introduced into the scrubbing tower for acid washing to remove residual ammonia and other impurities in the gas. After acid washing, 10-15% of the generated scrubbing liquid is pressurized by a pump and sent to the ammonium sulfate section. At the same time, 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% to 10%.

[0012] (4) The solids dried in the drying tower are sent to the boiling furnace for incineration;

[0013] (5) The high-temperature SO2 gas from the boiling furnace enters the waste heat boiler, generating 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;

[0014] (6) The SO2-containing process gas with a temperature of 300-350°C from the waste heat boiler passes through the humidification tower, cooling tower, scrubbing tower and electrostatic demister in sequence 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 ;

[0015] (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 model. The main chemical reactions in the conversion process are as follows:

[0016]

[0017] The converted gas undergoes heat exchange with the dried furnace gas through a heat exchanger, where its temperature is reduced to 160-180°C before being fed into an absorption tower. The absorption process utilizes two absorption towers, one for each of the two conversion stages within the conversion section. The tail gas absorbed by the first absorption tower is heated in a heat exchanger and then returned to the conversion tower for secondary conversion. The secondary conversion tail gas undergoes heat exchange and absorption in the second absorption tower before entering the subsequent process. During the absorption process, 98% concentrated sulfuric acid absorbs the SO₃ in the converted gas. The water in the concentrated sulfuric acid reacts with the SO₃ to form a sulfuric acid product. The sulfuric acid product is pumped out via an acid absorption pump, cooled in a product acid cooler, and then fed into a product acid storage tank. The product acid pump then regularly delivers the product acid to the ammonium sulfate unit for use.

[0018] (8) The tail gas after absorption in 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.

[0019] Beneficial effects of the present invention:

[0020] (1) Compared with the existing technology, the present invention has the advantages of reducing costs and saving resources;

[0021] (2) This process efficiently treats two industrial by-products, reduces their negative impact on the environment, and achieves the goal of turning waste into treasure;

[0022] (3) This process recovers sulfur and nitrogen from sulfur paste separately, reducing pollution while improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart for preparing sulfuric acid from sulfur paste and dust ash according to the present invention;

[0024] In the figure: 1-centrifuge; 2-kneader; 3-drying tower; 4-washing tower; 5-filter tower; 6-centrifugal pump; 7-boiling furnace; 8-waste heat boiler; 9-low-pressure steam network; 10-humidifying tower; 11-cooling tower; 12-washing tower; 13-electric demister; 14-second drying tower; 15-third heat exchanger; 16-first heat exchanger; 17-SO2 conversion tower; 18-second heat exchanger; 19-first absorption tower; 20-fifth heat exchanger; 21-fourth 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

[0025] The present invention is further illustrated below by way of examples, but is not limited to the following examples.

[0026] Example 1:

[0027] 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 during the dry quenching process.

[0028] The present invention first provides a resource processing device for coking sulfur paste and dust removal ash, comprising a centrifuge 1, a kneader 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 electrostatic precipitator 13, and a second drying tower 14 connected in sequence; the gas outlet of the drying tower 3 is connected to a cleaning 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, which includes an SO2 conversion tower 17, a first absorption tower 19, a second absorption tower 22, and a heat exchanger. The SO2 conversion tower 17 includes first to fifth catalyst beds arranged in sequence from top to bottom, and each catalyst bed is connected to a heat exchanger to achieve 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; and the gas outlet of the second absorption tower 22 is connected to an exhaust gas scrubber 23.

[0029] use Figure 1 The process flow shown is as follows: sulfur foam A is added to the centrifuge 1, and the liquid phase obtained after centrifugal separation is directly sent to the desulfurization system C; the solid phase (i.e. sulfur paste) enters the kneader 2, is mixed and stirred with the dust removal ash B, and the mixture enters the drying tower 3 for drying, and the gas generated in the drying tower is sent to the washing tower 4 (pickling) and the filter tower 5 (filtration), and the filtered washing liquid is sent to the ammonium sulfate section D through the centrifugal pump 6; the solid after drying in the drying tower 3 is sent to the boiling furnace 7 for incineration, and the high-temperature SO2 gas in the boiling furnace is heated to generate high-pressure steam, which is sent to the waste heat boiler 8, which is decompressed and sent to the low-pressure steam network 9, and then the low-pressure steam F is sent to the 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 a catalytic reaction occurs in the catalyst bed in the conversion tower, and then enters 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 a catalytic reaction occurs in the catalyst bed in the conversion tower, and then enters 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.

[0030] according to Figure 1 The specific implementation process of the process flow chart shown includes the following steps:

[0031] 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 in a mass ratio of 1:1 for mixing. The stirring speed is maintained at 100r / min and the stirring time is 60min.

[0032] In the second step, the mixture stirred by the kneader is sent to the drying tower for drying.

[0033] In the third step, the gas generated in the drying tower is sent to the washing tower for acid washing to remove ammonia and other gases contained in the gas during the drying process. After acid washing, it is filtered and 10% of the washing liquid generated 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.

[0034] The fourth step is to send the solids dried in the drying tower into the boiling furnace for incineration.

[0035] 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, decompressed to about 0.5MPa, enters the low-pressure steam network, and returns to the drying tower.

[0036] In the sixth step, the SO2-containing process gas from the waste heat boiler at a temperature of about 350°C is cooled, purified, and demisted to remove excess moisture, dust, arsenic, selenium, fluorine, chlorine and other impurities that are harmful to the V2O5 catalyst used to convert 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 .

[0037] In the seventh step, the cold gas, after being dried in the second drying tower and defogged by the wire mesh demister at the top of the drying tower, is pressurized by the SO2 blower and subsequently enters heat exchanger III 15 and heat exchanger I 16. After heating to 420°C, it enters the first section of the SO2 converter (separated from top to bottom by the first to fifth catalyst beds) for conversion. After the reaction, the gas temperature rises to approximately 585°C before entering heat exchanger I 16 to exchange heat with the cold gas from the SO2 blower for cooling. The cooled gas then enters the second catalyst bed of the converter for catalytic reaction. After exiting the converter, it enters heat exchanger II 18 for cooling before entering the third catalyst bed of the converter for further reaction. The gas exiting the third stage of the converter enters the third heat exchanger tube, where its temperature drops to 170°C before entering the first absorption tower 19, where it absorbs SO₃. After passing through a wire mesh demister at the top of the tower to remove acid mist, it enters the fifth heat exchanger 20, the fourth heat exchanger 21, and the second heat exchanger 18, where it is heated and then enters the fourth stage catalyst bed of the converter for a second conversion. The gas exiting the fourth stage bed enters the fourth heat exchanger 21, where it is cooled to 415°C before entering the fifth stage catalyst bed of the converter for reaction. The gas exiting the fifth stage passes through the fifth heat exchanger tube, where it exchanges heat with cold furnace air and cools to approximately 165°C before entering the second absorption tower 22, where it absorbs a small amount of SO₃. The demister at the top of the tower removes acid mist. An automatic water feeder is installed in the absorption acid circulation tank to add process water and regulate and control the absorption acid (concentrated sulfuric acid) concentration at 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 flow meter, 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.

[0038] 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 with NaOH spray liquid, the SO2 content 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 portion of the washing liquid is regularly sent to the ammonium sulfate section. 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. The dried gas is sent to the SO2 conversion tower and the absorption tower to produce sulfuric acid. The waste gas is treated in the washing tower and discharged after meeting the standards; The process for recycling coking sulfur paste and dust removal ash comprises 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. The sulfur paste with a mass ratio of 30%-50% and the dust ash with a mass ratio of 50%-70% are sent to the kneader for stirring and mixing; (2) The mixture stirred by the kneader is sent to the drying tower for drying; (3) The gas generated in the drying tower is introduced into the scrubbing tower for acid washing to remove the residual impurities in the gas; after acid washing, it is filtered and 10-15% of the generated scrubbing liquid is pressurized by a pump and sent to the ammonium sulfate section, and new sulfuric acid solution is added at the same time to maintain the continuity of the scrubbing process; (4) The solids dried in the drying tower are sent to the boiling furnace for incineration; (5) The high-temperature SO2 gas from the boiling furnace enters the waste heat boiler, generating 2.5-3.0 MPa saturated steam, which is then reduced to below 0.8 MPa 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 the humidification tower, cooling tower, scrubbing tower and electrostatic demister in sequence, and the process gas is humidified, cooled, purified and demisted 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 absorption tower through a heat exchanger to convert and absorb SO2 to produce sulfuric acid; the conversion and acid production process adopts a two-conversion and two-absorption process; in the SO2 conversion tower, the catalyst is arranged in five layers and the reaction conversion is carried out according to the III+II model; 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; (8) The tail gas absorbed by the second absorption tower enters the tail gas washing tower for cooling and purification. The purified tail gas meets the emission standards.

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

3. The process for recycling coked sulfur paste and dust ash according to claim 1, characterized in that: In step (3), during the acid washing process, the mass concentration of the sulfuric acid solution is 6% to 10%.

4. The process for recycling coked sulfur paste and dust ash according to claim 1, 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 gas moisture content; after drying, the water content of the process gas is controlled at <0.1g / Nm 3 .

5. The process for recycling coked sulfur paste and dust ash according to claim 1, 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.

6. The process for recycling coked sulfur paste and dust ash according to claim 5, 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 the heat exchanger, and a catalytic reaction occurs in the catalyst bed in the conversion tower before entering the first absorption tower; after the heat exchange, it enters the SO2 conversion tower for the second conversion, and after the second conversion, it is heat exchanged in the 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.

7. The process for recycling coked sulfur paste and dust ash according to claim 1, characterized in that: The washing liquid used in the purification process of step (8) is NaOH solution, Na2CO3 solution or dilute ammonia solution.

8. A coking sulfur paste and dust ash resource processing device for implementing the coking sulfur paste and dust ash resource processing process according to any one of claims 1 to 7, characterized in that: It includes a centrifuge, a kneader, a drying tower, a boiling furnace, a waste heat boiler, a humidifying tower, a cooling tower, a cleaning tower, an electrostatic precipitator, and a second drying tower connected in sequence; the gas outlet of the drying tower is connected to the washing tower, the filter tower, and the centrifugal pump; the reduced pressure steam outlet of the waste heat boiler is connected to the low-pressure steam network; the second drying tower is connected to a two-turn two-absorption device, which includes an 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 arranged in sequence from top to bottom, and each catalyst bed is connected to a heat exchanger respectively, to achieve 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 the product acid storage tank; the gas outlet of the second absorption tower is connected to the tail gas washing tower.

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