Process for refining sulfur by using coking desulfurization waste liquid and desulfurization foam

Abstract

The invention relates to a process for refining sulfur by using coking desulfurization waste liquid and desulfurization foam, which comprises the following steps: filtering the sulfur foam, separating to obtain liquid crude sulfur and desulfurization liquid, concentrating the desulfurization liquid, burning together with the liquid crude sulfur to obtain SO2, dedusting, feeding into a reduction furnace, and carrying out catalytic reaction under bauxite and low-temperature conditions to reduce into elemental sulfur; tail gas enters an alkaline washing tower for purification treatment and then is discharged. Compared with the prior art, liquid sulfur and high-concentration sulfur-containing salt are adopted for feeding, moisture in furnace gas is reduced, and the problem that a catalyst is corroded by condensed acid is completely eradicated; a step-by-step catalytic reduction and conversion process is adopted, and oxygen with the highest oxidation activity in furnace gas is removed firstly, so that conditions during conversion reaction are mild and controllable; coal gas is heated through reaction heat to reach the ignition temperature, and energy is saved; exothermic reaction is carried out in the incinerator, the reduction furnace and the conversion furnace, and waste heat resources can be extracted in a multi-stage mode; the whole reaction adopts a closed system, tail gas is discharged after being purified, environmental pollution is reduced, and energy conservation and environmental protection are facilitated.

Description

Technical Field

[0001] The present invention relates to a post-treatment technology in the coking desulfurization industry, and specifically relates to a process for refining sulfur using coking desulfurization waste liquid and desulfurization foam. Background Art

[0002] At present, pre-positioned wet ammonia desulfurization is commonly used in coking desulfurization, which will produce by-products such as sulfur foam and sulfur-containing by-products salts. The composition of coke oven gas is complex. In the pre-positioned ammonia desulfurization, a large amount of dust and organic oils will enter the sulfur foam, resulting in the quality of the by-product sulfur products not meeting the national solid sulfur product quality standards. Most enterprises continue to produce sulfuric acid after obtaining the crude sulfur products. At present, for the refinement of this kind of crude sulfur, the sulfur sublimation process is adopted, and the sulfur content of the refined sulfur produced is still difficult to exceed the national product qualification standard of 99.5%. At the same time, the other sulfur-containing by-products salts cannot be used to produce sulfur, and an additional salt extraction process needs to be added. Summary of the Invention

[0003] Aiming at the deficiencies in the prior art, the present invention provides a process for refining sulfur using coking desulfurization waste liquid and desulfurization foam.

[0004] To achieve the above object, the present invention provides the following technical solutions: A process for refining sulfur using coking desulfurization waste liquid and desulfurization foam, comprising the following steps: S1. Pretreatment stage After the sulfur foam sent from the ammonia desulfurization unit is filtered, it is pumped into a multi-stage separator through a transfer pump for separation. Sulfur flows out from the bottom of the tower to obtain liquid crude sulfur. After impurity removal, it is transported to an incinerator; the desulfurization liquid is concentrated, and the concentrated liquid is pumped to the incinerator by a pump; S2. Incineration stage The liquid crude sulfur and the concentrated liquid are atomized by compressed air through atomizing nozzles respectively and then enter the incinerator. They are burned with air assistance at a temperature of 1050 - 1180 °C to convert the sulfur elements in the liquid crude sulfur and the concentrated liquid into SO 2 ; S3. Reduction and conversion stage The SO 2 obtained by incineration in step S2 is cooled by a waste heat boiler, and then dust is removed by a high-temperature electrostatic precipitator. The SO 2 after dust removal is sent into a reduction furnace. Using the reduction of hydrogen and methane, under the condition of a mild catalyst of bauxite at a low temperature, the oxygen in the furnace gas is removed. At the same time, part of it is reduced to generate a mixture containing sulfur dioxide, hydrogen sulfide, etc. Then, using a high-efficiency catalyst of alumina under an oxygen-free condition, it is catalytically converted into elemental sulfur; S4. Sulfur collection stage The recovered elemental sulfur is cooled and then trapped in a sulfur trap to obtain solid sulfur. After being heated to form liquid sulfur, it enters the reflux tank and is regularly sent to a sulfur slicing machine to produce finished sulfur. S5. Tail gas absorption stage The tail gas is discharged after being purified in an alkali scrubbing tower.

[0005] Furthermore, in the step S1, the temperature in the multi-phase separator is set to 135 °C, the pressure is set to 0.3 mpa, and the specific gravity of the separated clear liquid is 1.1 kg / L. The concentration condition is negative pressure evaporation under the conditions of -80 kpa and 85 °C provided by the vacuum system. Thus, the goal of low water content in sulfur and concentrated salt materials is achieved, the water content in the furnace gas is lower than 1 g / m³, and low-temperature dew point corrosion of subsequent equipment is prevented.

[0006] Furthermore, in the step S2, the outlet temperature of the incinerator is set to 1050 °C to ensure the full decomposition of the salts in the desulfurization waste liquid. The oxygen content in the flue gas at the outlet of the incinerator is 0.2 - 2%. It is necessary to ensure both the full reaction of sulfur and salts and the safety of introducing coke oven gas into the reduction furnace.

[0007] It is completely decomposed at a high temperature of 1050 °C, and the problem of azeotropic oil that cannot be removed by the 450 °C sulfur sublimation method is completely solved. The product purity can reach the first-class product of solid sulfur. The reaction formula can be expressed as follows: Furthermore, in the step S3, the SO obtained by incineration 2 is cooled to 400 - 450 °C by a waste heat boiler, and then the dust content is reduced to 0.2 g / m³ by a high-temperature electrostatic precipitator, and the furnace gas temperature is reduced to 300 - 350 °C. This temperature can not only ensure no dew point corrosion of the equipment but also be far lower than the spontaneous ignition point of 650 °C of coke oven gas, ensuring the safety of the reduction furnace gas.

[0008] Furthermore, in the step S3, the reduction furnace is divided into upper and lower catalyst layers. After dust removal, the SO 2 enters the upper catalyst layer and the temperature rises to 600 - 700 °C, and the temperature rises to 650 °C to 800 °C after reaction in the lower layer. In the upper layer, mainly heat-exchanged high-temperature gas removes the oxygen in the furnace gas safely at a lower temperature state. In the lower layer, low-temperature gas is introduced to reduce the temperature of the furnace gas and make the reduction reaction occur in a safer area. The catalyst used is a mild catalyst, preferably bauxite, to effectively control the deoxygenation reaction.

[0009] Since there is still some reducing gas in the coke oven gas, in this application, with the reduction of 65% hydrogen and 25% methane gas in the furnace gas, sulfur dioxide generated by incineration is catalytically reacted under the catalysis of bauxite and at low temperature to be reduced to elemental sulfur. The oxygen in the furnace gas reacts first. In the case of excessive hydrogen, part of the sulfur will also be catalytically generated into hydrogen sulfide. The reaction formula is as follows: Further, in step S3, the furnace gas output from the reduction furnace passes through a waste heat boiler and a coke oven gas heat exchanger, and the temperature is reduced to 300°C, and then enters the reformer. Since the furnace gas still contains a certain proportion of hydrogen sulfide, organic sulfur and sulfur dioxide, an alumina-based high-efficiency catalyst is used in the converter to completely convert them into sulfur vapor. The reaction formula is as follows: The beneficial effects of the present invention are as follows: post-treatment is carried out on the by-products sulfur foam and sulfur-containing by-salts generated by coking desulfurization to realize resource recovery and utilization. Compared with the prior art, liquid sulfur and high-concentration sulfur-containing salts are used as feeds, reducing the moisture in the furnace gas and eliminating the problem of condensation acid corrosion of the catalyst, thus saving the traditional washing and condensation water removal process, and co-firing them to solve all sulfur-containing by-products generated by the pre-stage wet ammonia desulfurization in one stop, without the need for the traditional triple processes of molten sulfur + sublimation method sulfur refining + salt extraction; In the incineration stage, it is completely decomposed at a high temperature of 1050°C, completely removing the problem of azeotropic oil that cannot be removed by the sulfur sublimation method at 450°C, and the product purity can reach the first-class product of solid sulfur; In addition, the present application creatively adopts a step-by-step catalytic reduction and conversion process, using low-reaction-intensity aluminum ore as a catalyst to first remove the oxygen with the highest oxidation activity in the furnace gas, making the conversion reaction conditions mild and controllable; Using the reaction heat to heat the coal gas to reach the ignition temperature, saving energy; the incinerator, reduction furnace, and reformer are all exothermic reactions, and waste heat resources can also be extracted at multiple levels; Finally, the whole reaction adopts a closed system, and the tail gas is discharged after purification, reducing environmental pollution and being beneficial to energy conservation and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0011] Figure 1 It is a process flow diagram of a process for refining sulfur using coking desulfurization waste liquid and desulfurization foam in the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0013] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0014] Embodiment 1 This case provides a process flow as Figure 1 shown below. The specific process steps are as follows: 100 t / d of sulfur foam with a sulfur content of 5% is transported by the ammonia desulfurization unit. After passing through the sulfur foam concentration device, it becomes 50 t / d of sulfur foam concentrate with a sulfur content of 10%. The filtered clear liquid with a sulfur content ≤ 1.5 g / L, 50 t / d, returns to the desulfurization system through the clear liquid tank.

[0015] The sulfur foam concentrate enters the sulfur foam tank and is pumped to the multi-phase separator. In the multi-phase separator under the pressure environment of 135 °C and 0.3 mpa, melting separation is fully carried out. 5 t of crude liquid sulfur formed enters the sulfur purification tower, about 200 kg of pulverized coal is discharged in the purification tower, and the remaining sulfur enters the incinerator.

[0016] The upper part of the separated clear liquid, 45 t / d, coming out of the multi-phase separator enters the transfer tower for further separation. Among them, about 30 t / d of the clear liquid returns to the desulfurization system after being cooled by the cooler, and about 15 t / d of the clear liquid enters the concentration system.

[0017] The clear liquid entering the concentration system undergoes vacuum evaporation in the concentration tower under the conditions of -80 kpa and about 85 °C. The ammonia gas passes through the vacuum system and after being condensed by the heat exchanger, 10 t / d of ammonia water is sent back to the desulfurization system, and 5 t / d of the concentrated liquid enters the incinerator.

[0018] The crude sulfur and the concentrated liquid are burned in the incinerator at a high temperature of 1050 °C. Online analyzers for sulfur dioxide and oxygen content are set after the high-temperature electrostatic precipitator. By controlling the air volume and material ratio, the sulfur dioxide in the furnace gas is controlled at 9 - 11% and the oxygen content at 0.2 - 2%. At this time, the flue gas volume is about 3750 m³ / h. After passing through the waste heat boiler, the temperature is reduced to 400 - 450 °C, and then through the high-temperature electrostatic precipitator, the dust content is reduced to 0.2 g / m³, and the furnace gas temperature is reduced to 300 - 350 °C. The steam pressure of the waste heat boiler is 3.8 Mpa, and through the temperature reduction and pressure reduction device, it is sent to the 0.5 mpa low-pressure steam pipe network.

[0019] The reduction furnace is divided into upper and lower catalyst layers, and the space velocity is designed to be 400 m³ / (h·m³). Thermometers are respectively installed in the upper, middle and lower parts of the reduction furnace, and an on-line analyzer for sulfur dioxide and hydrogen sulfide is installed at the tail of the reduction furnace. By controlling the consumption of coke oven gas entering the upper layer of the reduction furnace, the temperature in the middle of the reduction furnace is maintained at 600 - 700 °C; by controlling the consumption of coke oven gas entering the lower layer of the reduction furnace, the on-line monitoring of the furnace gas after the reaction is carried out: the sulfur dioxide content is 0.95 - 1.1%, and the hydrogen sulfide content is 1 - 1.4%. The temperature after the reaction rises to 650 °C to 800 °C. After the furnace gas recovers part of the heat in the waste heat boiler, the temperature drops to 400 - 450 °C, and after heat exchange with coke oven gas in the coke oven gas heat exchanger, the temperature drops to 300 °C.

[0020] The furnace gas enters the conversion furnace, and the space velocity is designed to be 200 m³ / (h·m³). Under the action of the alumina catalyst, the reducing gas in the furnace gas reacts completely with the residual sulfur dioxide to form elemental sulfur. At this time, the temperature of the furnace gas is ≥250 °C, and it enters the sulfur cooler to be cooled to 120 - 135 °C. At this time, the sulfur in the flue gas is in a liquid state, and then it passes through the sulfur trap and is cooled to below 60 °C. At this time, the sulfur is in a solid state and is trapped in the sulfur trap. The trapped solid sulfur is heated to form liquid sulfur and then enters the reflux tank, and is regularly sent to the sulfur slicing machine to produce finished sulfur. After testing, the sulfur content of the finished sulfur reaches more than 99.8%, which belongs to first-class industrial sulfur.

[0021] The tail gas enters the caustic scrubber, and sodium hydroxide solution is used to wash the residual hydrogen sulfide and sulfur dioxide in the furnace gas. The solution in the caustic scrubber is regularly sent to the coking ammonia distillation system for treatment. After being washed by the caustic solution, the tail gas enters the tail gas fan and is discharged through the chimney. The operation of the tail gas fan ensures that the entire system from the incinerator to the conversion furnace is in a negative pressure state to prevent the release of hydrogen sulfide or sulfur dioxide gas into the air.

[0022] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated examples here.

Claims

1. A process for refining sulfur using coking desulfurization waste liquid and desulfurization foam, characterized in that: The steps include: S1. Preprocessing stage The sulfur foam sent from the ammonia desulfurization unit is filtered and then pumped into multiple separators for separation. The sulfur flows out from the bottom of the tower to obtain liquid crude sulfur, which is then transported to the incinerator after impurities are removed. The desulfurized liquid is concentrated, and the obtained concentrated liquid is pumped to the incinerator; S2. Incineration stage The liquid crude sulfur and concentrated liquid are respectively atomized by compressed air through an atomizing nozzle and then enter the incinerator, where they are incinerated with air-assisted combustion at a temperature of 1050-1180°C to convert the sulfur element in the liquid crude sulfur and concentrated liquid into SO2; S3, reduction and conversion stage The SO2 obtained by the incineration in step S2 is cooled by a waste heat boiler, and then dedusted by a high-temperature electrostatic precipitator. The dedusted SO2 is sent to a reduction furnace, and reduced to elemental sulfur by a catalytic reaction under a mild catalyst and low temperature conditions using the reducing effect of hydrogen and methane; S4, Sulfur Collection Stage After the elemental sulfur obtained by reduction is cooled, it is captured in the sulfur collector to obtain solid sulfur, which is then heated to form liquid sulfur and enters the reflux tank and is regularly sent to the sulfur slicer to produce finished sulfur. S5, tail suction stage The tail gas enters the alkali washing tower for purification and then is discharged.

2. The process for refining sulfur using coking desulfurization waste liquid and desulfurization foam according to claim 1, characterized in that: In step S1, the temperature in the multi-separator is set to 135°C, the pressure is set to 0.3 MPa, and the specific gravity of the separated clear liquid is 1.1 kg / L; the concentration condition is negative pressure evaporation under the condition of -80 kPa and 85°C provided by the vacuum system.

3. The process for refining sulfur using coking desulfurization waste liquid and desulfurization foam according to claim 1, characterized in that: In step S2, the outlet temperature of the incinerator is set to 1050°C.

4. The process for refining sulfur using coking desulfurization waste liquid and desulfurization foam according to claim 1, characterized in that: In step S3, the SO2 obtained by incineration is cooled to 400-450°C by a waste heat boiler, and then the dust content is reduced to 0.2 g / m³ by a high-temperature electrostatic precipitator, and the furnace gas temperature is reduced to 300-350°C.

5. The process for refining sulfur using coking desulfurization waste liquid and desulfurization foam according to claim 1, characterized in that: In step S3, the reduction furnace is divided into two layers of catalyst, the temperature of the dust-removed SO2 entering the upper catalyst layer rises to 600-700°C, and the temperature rises to 650°C to 800°C after the reaction in the lower layer.

6. The process for refining sulfur using coking desulfurization waste liquid and desulfurization foam according to claim 5, characterized in that: The catalyst is a bauxite-based mild catalyst.

7. The process for refining sulfur using coking desulfurization waste liquid and desulfurization foam according to claim 1, characterized in that: In step S3, the furnace gas output from the reduction furnace passes through the waste heat boiler and the coke oven gas heat exchanger to reduce the temperature to 300° C., and then enters the converter. Under the action of the alumina-based high-efficiency catalyst, the reducing gas in the furnace gas and the residual sulfur dioxide are completely reacted to generate elemental sulfur.

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