A device for catalytic thermal cracking of residual oil and resource utilization of waste alkali liquid from coal to olefins

Abstract

The invention discloses a waste alkali liquor resource utilization device for catalytic thermal cracking of residual oil and coal-to-olefins, comprising a waste alkali liquor deoiling section, an oxidation section, an organic matter removal section, a causticizing section, an evaporation and concentration section, a miscellaneous salt removal section, a sodium thiosulfate recovery section and a liquid caustic soda modulation recovery section, wherein the waste alkali liquor of a DCC device and an MTO device is subjected to oil-water separation in the waste alkali liquor deoiling section, the contained sodium sulfide is converted into sodium thiosulfate in the oxidation section, the organic matter is removed by adsorption of activated carbon in the organic matter removal section, the contained sodium carbonate is converted into calcium carbonate and sodium hydroxide by adding quicklime in the causticizing section, the water and residual sodium sulfide, sodium carbonate, sodium chloride and sodium sulfate are further removed in the evaporation and concentration section and the miscellaneous salt removal section, the sodium thiosulfate is separated in the sodium thiosulfate recovery section and the liquid caustic soda modulation recovery section, and the concentration of sodium hydroxide is adjusted. The invention realizes the efficient and low-cost resource utilization of mixed salts in the waste alkali liquor.

Description

Technical Field

[0001] The invention relates to the recycling of waste alkali liquor in large-scale coal chemical and petrochemical enterprises, and in particular to the resource utilization of waste alkali liquor mixed salt from catalytic thermal cracking of residual oil and coal-to-olefins. Background Art

[0002] Large-scale coal, oil and gas resource comprehensive utilization projects will produce a large amount of waste alkali liquid during the alkali washing of acid gas. The devices that produce acid gas are mainly residual oil catalytic cracking (DCC) devices and methanol to olefins (MTO) devices. Taking the DCC device as an example, the mixed salt content in the waste alkali liquid discharged is about 10%. The inorganic salt components in the mixed salt are mainly sodium carbonate, sodium sulfide, sodium chloride, sodium thiosulfate and a small amount of sodium sulfate, and also contain a small amount of sodium hydroxide. At present, the treatment of this type of waste alkali liquid (wastewater containing dispersed oil and mixed salt) is generally to remove oil, oxidize, remove organic matter, evaporate and concentrate, and then send the evaporated mother liquor to the downstream reclaimed water plant after mixing treatment at the sewage treatment station, so as to recover all the water in the waste alkali liquid and achieve "zero sewage discharge". However, with the improvement of the pollution prevention and control standards for mixed salts in industrial waste disposal, it has become more difficult to utilize mixed salts as resources through blending treatment. It is urgently necessary to propose a set of mixed salt recovery and utilization equipment with step-by-step and quality-based treatment according to the components and salt characteristics of waste alkali liquor from catalytic thermal cracking of residual oil and coal-to-olefins, so as to reduce the amount of evaporation mother liquor generated and realize the separation of mixed salts and water in the evaporation mother liquor, and ultimately achieve the recovery of all wastewater while improving the resource utilization of mixed salts.

[0003] Chinese patent CN107445329A discloses a method for treating waste alkali liquor of liquid hydrocarbons, which processes waste alkali liquor of MTO to degasify by oil washing, remove floating oil by standing in a storage tank, remove organic matter by gas stripping, remove carbonate by adding a precipitant, and complete liquid alkali regeneration by adding sodium hydroxide, thereby achieving zero discharge and recycling of waste alkali liquor. However, the problems are as follows: ① For the process mainly treating waste alkali liquor discharged from a DCC device, the physical properties of sodium thiosulfate in the waste alkali liquor result in the generation of a large amount of extremely high salt content and viscous mother liquor during steam heating, thereby failing to achieve effective removal and resource utilization of sulfide and sodium thiosulfate; ② Only carbonate removal is achieved, which aggravates the formation of hazardous waste and makes it difficult to achieve resource utilization of carbonate; ③ A small amount of inorganic salts will be continuously concentrated during the recycling process, and the produced water cannot be continuously recycled for a long period of time. Summary of the invention

[0004] The object of the present invention is to provide a device for resource utilization of waste alkali liquor from catalytic thermal cracking of residual oil and coal-to-olefins.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A waste alkali liquor resource utilization device, the device comprises a waste alkali liquor deoiling section, an oxidation section, an organic matter removal section, a causticizing section, an evaporation concentration section, a miscellaneous salt removal section and a sodium thiosulfate recovery section which are connected in sequence, the waste alkali liquor deoiling section comprises an oil removal tank, the oxidation section comprises an oxidation reactor for converting sodium sulfide in the waste alkali liquor remaining after passing through the oil removal tank into sodium thiosulfate under the action of a catalyst, the organic matter removal section comprises an adsorption medium and a filter medium for respectively removing organic matter and purifying water quality of the waste alkali liquor after the conversion in the oxidation reactor, the causticizing section comprises a filter medium for converting sodium carbonate in the waste alkali liquor remaining after passing through the adsorption medium and the filter medium into calcium carbonate and hydrogen The invention relates to a causticizing reactor for sodium oxide, wherein the evaporation and concentration section comprises an evaporator for concentrating a sodium hydroxide solution containing sodium thiosulfate and inorganic salt impurities separated from the causticizing reactor, the impurity salt removal section comprises a primary salting-out reactor for separating corresponding inorganic salt impurities in the evaporator discharge and a primary solvent recovery unit for recycling the organic solvent (organic solvent A) added to the primary salting-out reactor by distillation, and the sodium thiosulfate recovery section comprises a secondary salting-out reactor for separating sodium thiosulfate from the solution remaining in the primary solvent recovery unit and a secondary solvent recovery unit for recycling the organic solvent (organic solvent B) added to the secondary salting-out reactor by distillation.

[0007] Preferably, the waste alkali liquid oil removal section also includes a regulating tank, a regulating tank outlet lifting pump, an oil storage tank and a dirty oil pump. The oil storage tank and the regulating tank are respectively connected to the oil removal tank, the dirty oil pump is connected to the oil storage tank, and the regulating tank outlet lifting pump is respectively connected to the regulating tank and the oxidation section; after the waste alkali liquid enters the oil removal tank, oil and water are separated in the oil removal tank, the separated dirty oil flows by gravity into the oil storage tank for collection and is then transported out through the dirty oil pump (for example, it can be sent to a DCC device for refining), and the waste alkali liquid after oil removal flows by gravity into the regulating tank and is sent to the oxidation section through the lifting pump.

[0008] Preferably, the oxidation section further includes a catalyst dosing unit, a steam heating unit and an aeration unit, the steam heating unit and the aeration unit are arranged in the oxidation reactor, the steam heating unit is connected to the steam pipe network arranged outside the oxidation reactor, the aeration unit is connected to the fan arranged outside the oxidation reactor, and the oxidation reactor is respectively connected to the organic matter removal section, the above-mentioned regulating tank outlet lifting pump, and the catalyst dosing unit; the function of the oxidation section is to oxidize the sodium sulfide in the waste alkali liquid sent to the oxidation reactor by the above-mentioned regulating tank outlet lifting pump into sodium thiosulfate, wherein the function of the steam heating unit is to provide the temperature required for the reaction, and the function of the aeration unit is to provide the oxygen required for the reaction.

[0009] Preferably, the organic matter removal section specifically includes a powdered activated carbon adsorption tank and a water production filter, the powdered activated carbon adsorption tank is respectively connected to the water production filter inlet and the above-mentioned oxidation reactor, and the water production filter outlet is connected to the causticizing section.

[0010] Preferably, a reflux pipeline connected to the inlet of the water production filter is provided on the outlet side of the water production filter.

[0011] Preferably, the causticizing section further comprises a calcium oxide dosing unit, a clear liquid filtration unit and a calcium carbonate drying unit, the causticizing reactor is respectively connected to the calcium oxide dosing unit, the clear liquid filtration unit inlet lift pump, the calcium carbonate drying unit inlet lift pump and the above-mentioned water production filter, and the clear liquid filtration unit outlet is connected to the evaporation concentration section.

[0012] Preferably, the evaporation and concentration section also includes a secondary steam cooling unit and a material lifting pump, the steam pipeline of the evaporator (for example, a triple-effect evaporator) is respectively connected to the above-mentioned steam network and the secondary steam cooling unit, the material pipeline of the evaporator is respectively connected to the above-mentioned clear liquid filtration unit and the inlet of the material lifting pump, and the outlet of the material lifting pump is connected to the impurity salt removal section.

[0013] Preferably, the impure salt removal section also includes an impure salt drying unit, a first-level recovery lift pump and a first-level external delivery lift pump, the first-level salt precipitation reactor is respectively connected to the impure salt drying unit, the first-level solvent recovery unit, and the above-mentioned material lift pump, the first-level recovery lift pump is respectively connected to the first-level salt precipitation reactor and the first-level solvent recovery unit, the first-level external delivery lift pump is respectively connected to the first-level solvent recovery unit and the sodium thiosulfate recovery section, and the above-mentioned steam pipeline network is respectively connected to the first-level solvent recovery unit and the impure salt drying unit.

[0014] Preferably, the sodium thiosulfate recovery section also includes a sodium thiosulfate drying and packaging unit, a secondary recovery lift pump and a secondary external delivery lift pump, the secondary salt precipitation reactor is respectively connected to the sodium thiosulfate drying and packaging unit, the secondary solvent recovery unit, and the above-mentioned primary external delivery lift pump, the secondary recovery lift pump is respectively connected to the secondary salt precipitation reactor and the secondary solvent recovery unit, the secondary external delivery lift pump is respectively connected to the secondary solvent recovery unit and the liquid alkali modulation recovery section, and the above-mentioned steam pipeline network is respectively connected to the secondary solvent recovery unit and the sodium thiosulfate drying and packaging unit.

[0015] Preferably, the device further comprises a liquid caustic soda modulation recovery section for adjusting the concentration of sodium hydroxide in the remaining solution of the secondary solvent recovery unit.

[0016] Preferably, the liquid alkali conditioning and recovery section specifically includes a liquid alkali concentration unit and / or a liquid alkali concentration adjustment unit, and the liquid alkali concentration unit and the liquid alkali concentration adjustment unit are both connected to the above-mentioned secondary external delivery lift pump.

[0017] A method for treating waste alkali liquor from catalytic thermal cracking of residual oil and coal-to-olefins using the above device comprises the following steps:

[0018] 1) Degreasing

[0019] The waste alkali liquid discharged from the DCC unit and / or MTO unit after alkali washing of the acid gas is sent to the deoiling tank, where the waste alkali liquid is separated from oil and water and then flows to the regulating tank by gravity;

[0020] 2) Oxidation

[0021] The waste alkali liquid after oil removal enters the oxidation reactor from the regulating tank and undergoes oxidation reaction under steam heating, compressed air aeration and the action of a catalyst, so that the sodium sulfide in the waste alkali liquid is converted into sodium thiosulfate;

[0022] 3) Removal of organic matter

[0023] The waste alkali liquid treated in step 2) enters the powdered activated carbon adsorption tank and the water production filter in sequence, so that the waste alkali liquid is adsorbed by the activated carbon to remove organic matter and then filtered to remove the activated carbon powder;

[0024] 4) Causticization and concentration

[0025] The waste alkali liquid treated in step 3) enters the causticizing reactor and reacts with the added calcium oxide. The calcium carbonate precipitate generated by the reaction is dried as a product. The supernatant is filtered and then enters a triple-effect evaporator to further remove moisture (i.e., concentrate).

[0026] 5) Removal of impurities

[0027] The concentrated liquid (discharge) outputted from the triple-effect evaporator enters the primary salting-out reactor and is salted out by using the added organic solvent A, thereby removing the impurities (the impurities are mainly the residual sodium sulfide in the oxidation section, the residual sodium carbonate in the causticizing section, and a small amount of sodium chloride and sodium sulfate);

[0028] 6) Recovery of sodium thiosulfate

[0029] The concentrated liquid output from the triple-effect evaporator enters the secondary salting-out reactor after removing impurities and recovering the solvent, and is salted out by the added organic solvent B, thereby achieving the separation of sodium thiosulfate and sodium hydroxide, and the separated sodium thiosulfate is dried as a product.

[0030] Preferably, the method for treating waste alkali liquor from catalytic thermal cracking of residual oil and coal-to-olefins using the above-mentioned device further comprises the following steps:

[0031] 7) Liquid caustic soda preparation, i.e., separating sodium thiosulfate and recovering the solvent, and then adjusting the concentration of sodium hydroxide or concentrating it to obtain a liquid caustic soda product.

[0032] Preferably, the organic solvent A and the organic solvent B are selected from alcohol solvents such as methanol and ethanol; in the primary salting-out reactor, the volume ratio of the concentrated liquid output by the triple-effect evaporator to the organic solvent A is 1:3-4; in the secondary salting-out reactor, the volume ratio of the concentrated liquid output by the triple-effect evaporator after removing impurities and recovering the solvent to the organic solvent B is 1:2-3.

[0033] Preferably, the organic solvent (organic solvent A) added to the primary salting-out reactor is methanol, and the organic solvent (organic solvent B) added to the secondary salting-out reactor is ethanol; the organic solvent addition ratio of the primary salting-out reactor is higher than that of the secondary salting-out reactor.

[0034] The beneficial effects of the present invention are embodied in:

[0035] The present invention adopts an oil removal section, an oxidation section, an organic matter removal section, and an evaporation concentration section, and adds a causticizing section, a miscellaneous salt removal section, and a sodium thiosulfate recovery section. The miscellaneous salt removal section and the sodium thiosulfate recovery section realize the graded and cyclic addition of solvents by introducing a solvent recovery unit, thereby establishing a salting-out separation system for inorganic salt impurities and sodium thiosulfate, and can effectively purify and transform waste alkali liquor from catalytic thermal cracking of residual oil and coal-to-olefins. While recovering all wastewater, the mixed salt in the waste alkali liquor is utilized as a resource, and the discharge of solid mixed salts is significantly reduced, which meets the development requirements of emission reduction and efficiency improvement.

[0036] Furthermore, by setting a reflux pipeline on the outlet side of the produced water filter, the content of suspended matter in the produced water is reduced, thereby preventing suspended matter such as powdered activated carbon from entering the subsequent processing section, ensuring that the purity of the corresponding product meets the standard requirements.

[0037] Furthermore, by utilizing the solubility characteristics of inorganic salts and the salting-out effect of organic solvent A and optimizing the addition ratio of organic solvent A, the impure salts that cannot be recycled can be removed, thereby reducing the solvent replenishment and loss.

[0038] Furthermore, by utilizing the solubility characteristics of sodium thiosulfate and sodium hydroxide and the salting-out effect of the organic solvent B and optimizing the addition ratio of the organic solvent B, the separation of sodium thiosulfate and liquid sodium hydroxide is achieved, thereby reducing the solvent replenishment and loss.

[0039] Furthermore, by optimizing the types of solvents added to the primary salting-out reactor and the secondary salting-out reactor, that is, determining that the organic solvent added to the primary salting-out reactor is methanol and the organic solvent added to the secondary salting-out reactor is ethanol, combined with the optimization of the addition ratio, it is possible to avoid improper use of the organic solvent in the primary salting-out reactor, resulting in a low removal rate of impure salts, affecting the purity of sodium thiosulfate and sodium hydroxide, increasing the loss of organic solvents and causing unnecessary energy consumption. At the same time, it is also possible to avoid improper use of the organic solvent in the secondary salting-out reactor, resulting in a decrease in the purity of the sodium thiosulfate and sodium hydroxide products, difficulty in meeting the standard requirements, and increased resource utilization costs.

[0040] Furthermore, the solution remaining after separating sodium thiosulfate and recovering the solvent can be directly evaporated and concentrated (entering the liquid alkali preparation and recovery section) or mixed with solid sodium hydroxide (caustic soda flakes) to prepare a liquid alkali product and use it as a cleaning liquid or other purposes, thereby achieving complete harmless treatment of the waste alkali liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic structural diagram of a waste alkali solution mixed salt resource utilization device in an embodiment of the present invention;

[0042] In the figure: 1 is an oil removal tank, 2 is an oil storage tank, 3 is a dirty oil pump, 4 is a regulating tank, 5 is a regulating tank outlet lifting pump, 6 is a desulfurization reactor, 7 is a steam heating unit, 8 is a catalyst dosing unit, 9 is an aeration unit, 10 is a powdered activated carbon adsorption tank, 11 is a water production filter, 12 is a calcium oxide dosing unit, 13 is a causticizing reactor, 14 is a clear liquid filtration unit, 15 is a calcium carbonate drying unit, 16 is a triple-effect evaporator, 17 is a secondary steam cooling unit, 18 is a primary salting-out reactor, 19 is a primary solvent recovery unit, 20 is a miscellaneous salt drying unit, 21 is a secondary salting-out reactor, 22 is a secondary solvent recovery unit, 23 is a sodium thiosulfate drying and packaging unit, 24 is a liquid alkali concentration unit, and 25 is a liquid alkali concentration adjustment unit. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The embodiments are only used to explain the present invention, but not to limit the scope of protection of the present invention.

[0044] See also Figure 1The present invention proposes a waste alkali mixed salt resource utilization device, which includes a series of waste alkali deoiling section, oxidation section, organic matter removal section, causticizing section, evaporation concentration section, impurity salt removal section, sodium thiosulfate recovery section and liquid alkali conditioning recovery section. The specific process flow of using the above sections to treat the waste alkali liquid (referred to as residual oil thermal cracking waste alkali liquid and coal-to-olefin waste alkali liquid) generated by the DCC unit and MTO unit in the plant area (the waste alkali liquid generated by the DCC unit in the plant area is much more than that generated by the MTO unit) during the alkali washing of acid gas is as follows:

[0045] 1) Waste alkali liquid deoiling section

[0046] The waste alkali liquid oil removal section comprises an oil removal tank 1, an oil storage tank 2, a waste oil pump 3 and an adjusting tank 4. The waste alkali liquid from thermal cracking of residual oil produced by the DCC device and the waste alkali liquid from coal-to-olefins produced by the MTO device are respectively pressurized and enter the oil removal tank 1 for mixing. Under the action of the oil removal tank 1, the mixed waste alkali liquid in the oil removal tank 1 is separated into oil and water. The separated waste oil (light oil) flows by gravity into the oil storage tank 2, and is then sent to the DCC device for refining through the waste oil pump 3. The remaining waste alkali liquid after the waste oil is separated flows by gravity into the homogenizing adjusting tank 4. The waste alkali liquid in the homogenizing adjusting tank 4 is stably sent to the oxidation reactor of the oxidation section by the adjusting tank outlet lifting pump 5 at the outlet of the homogenizing adjusting tank 4.

[0047] The above-mentioned oil removal tank 1 (ordinary vertical oil removal tank) mainly removes dispersed oil with a particle size of 10 to 100 μm. The dispersed oil can be floated and removed due to the density difference between oil and water. The vertical oil removal tank can reduce the dispersed oil concentration in the waste alkali liquid from 200 to 500 mg / L to 20 to 50 mg / L. The hydraulic retention time of the mixed waste alkali liquid in the waste alkali liquid oil removal section is about 50 hours.

[0048] 2) Oxidation section

[0049] The oxidation section includes an oxidation reactor, an aeration fan and a dosing system. The oxidation reactor specifically adopts a desulfurization reactor 6 divided into three stages. The sodium sulfide in the waste alkali solution from the homogenization adjustment tank 4 is converted into sodium thiosulfate through an oxidation reaction through the series operation of the three-stage desulfurization reactor 6. Steam heating units 7 and aeration units 9 are provided inside the first-stage, second-stage and third-stage desulfurization reactors. The reaction temperature in each stage of the desulfurization reactor 6 is automatically controlled by the steam heating unit 7 (generally 65-70°C), and the heat source is steam (pressure of 0.5-0.6 MPa, from the steam network in the plant area); due to the relatively low reaction temperature, the conversion of sodium sulfide to sodium thiosulfate needs to be carried out under the action of a catalyst (such as a molybdenum-based desulfurizer). The dosing system mainly includes a catalyst dosing unit 8, and its catalyst dosing position is the first-stage desulfurization reactor directly connected to the regulating tank outlet lift pump 5 at the outlet of the homogenization adjustment tank 4. The oxygen source in each level of desulfurization reactor 6 is compressed air, which is pressurized by an aeration fan and sent to the aeration unit 9. The aeration unit 9 uses a diffuse aerator (single aeration volume is about 0.45m3 / min). After the waste alkali liquid completes the reaction in the oxidation section (the reaction hydraulic time is about 90h), it is sent to the powdered activated carbon adsorption tank 10 of the organic matter removal section.

[0050] 3) Organic matter removal section

[0051] The organic matter removal section includes a powdered activated carbon adsorption tank 10 and a water production filter 11. The powdered activated carbon adsorption tank 10 adopts a powdered activated carbon adsorption process to remove organic matter. In order to eliminate the influence of dispersed powdered activated carbon on subsequent processes and product quality, a water production filter 11 is set at the water outlet of the powdered activated carbon adsorption tank 10. A reflux pipeline is provided on the outlet side of the water production filter 11, and the powdered activated carbon can be circulated and filtered until the turbidity at the outlet of the water production filter 11 reaches a set value (≤5NTU) and then is sent to the causticizing reactor 13 of the causticizing section.

[0052] 4) Caustic chemical section

[0053] The causticizing section includes a calcium oxide dosing unit 12, a causticizing reactor 13, a clear liquid filtration unit 14 (the causticizing section also introduces a water filter as a clear liquid filtration unit; the turbidity of the water outlet reaches a set value, i.e., ≤5 NTU) and a calcium carbonate drying unit 15. The working principle of the causticizing section is as follows: quicklime is fed into the causticizing reactor 13 by the calcium oxide dosing unit 12, and the quicklime is directly reacted with the water in the waste alkali liquid from the water filter 11 to generate calcium hydroxide, and the calcium hydroxide reacts with the sodium carbonate in the waste alkali liquid to generate calcium carbonate precipitate and a solution containing sodium hydroxide. After the waste alkali liquid finally enters the causticizing reactor 13, after completing the above reaction, the upper layer reaction material (mainly clear liquid) in the causticizing reactor 13 is pressurized and fed into the clear liquid filtration unit 14 for filtration, and the filtrate enters the triple-effect evaporator 16 of the evaporation and concentration section, and the lower layer reaction material (including precipitate) in the causticizing reactor 13 is pressurized and fed into a sedimentation tank for recovery, and the recovered precipitate is fed into the calcium carbonate drying unit 15 for drying, so as to obtain a calcium carbonate product.

[0054] Due to the introduction of the clear liquid filtering unit 14, the upper clear liquid of the causticizing reactor 13 is directly filtered after a short residence time (still containing solid particles), which can shorten the reaction residence time and thus reduce the area occupied by the sedimentation tank.

[0055] 5) Evaporation and concentration section

[0056] The evaporation and concentration section includes a triple-effect evaporator 16. The waste alkali liquid (filtrate) from the clear liquid filtration unit 14 enters the triple-effect evaporator 16 (which can be operated in series or in parallel) for concentration. The concentrated waste alkali liquid (discharge from the triple-effect evaporator 16) is pressurized again and sent to the salting-out reactor (i.e., the primary salting-out reactor 18) of the impurity salt removal section. The heating steam used by the triple-effect evaporator 16 comes from the steam network in the plant area (pressure is 0.5-0.6 MPa). The primary steam condensate is recovered and processed by the condensate refining system and can be used as desalted water for external transmission. The secondary steam evaporated from the material side enters the secondary steam cooling unit 17 for cooling (heat exchange with cooling feed water, and the heat is taken away by cooling return water) and is supplemented to the fresh production water system. The temperature of the secondary steam condensate after heat exchange is about 40°C.

[0057] In the evaporation and concentration section, the volume of the material after concentration is about 1 / 3 of that before concentration, which reduces the processing scale of subsequent sections.

[0058] 6) Salt removal section

[0059] The discharge of the triple-effect evaporator 16 enters the primary salting-out reactor 18. According to the difference in solubility of various inorganic salts contained in the discharge in the specific organic solvent A and the property that the organic solvent A and water are mutually soluble in any proportion, the discharge of the triple-effect evaporator 16 and the organic solvent A can be mixed in a ratio (volume ratio) of about 1:3 by adding the organic solvent A (specifically methanol) into the salting-out reactor, so as to achieve the precipitation of inorganic salt impurities (miscellaneous salts) such as sodium sulfate, sodium sulfide, sodium chloride in the waste alkali liquid and sodium carbonate remaining in the causticizing section, and then the precipitate in the primary salting-out reactor 18 is sent to the miscellaneous salt drying unit 20 for drying (the heat source comes from the steam network in the plant area, and the pressure is 0.5-0. 6 MPa), the remaining liquid in the primary salting-out reactor 18 (a mixture A consisting of an organic solvent A and a solution containing sodium thiosulfate and sodium hydroxide, wherein the sodium thiosulfate mainly comes from the oxidation section and the sodium hydroxide mainly comes from the causticizing section) is pressurized and sent to the primary solvent recovery unit 19, in which the organic solvent A is separated and purified by distillation (the heat source comes from the steam network in the plant area, and the pressure is 0.5-0.6 MPa) and then supplied to the primary salting-out reactor 18 for recycling, and the solution (mixed liquid) containing sodium thiosulfate and sodium hydroxide is pressurized and sent to the salting-out reactor of the sodium thiosulfate recovery section (i.e., the secondary salting-out reactor 21).

[0060] The core equipment of the above-mentioned primary salting-out reactor 18 is a crystallizer, which also includes a waste alkali liquid inlet, an organic solvent inlet, a miscellaneous salt discharge port and a mixture discharge port. The working principle of the crystallizer is as follows: the discharge of the triple-effect evaporator 16 entering through the waste alkali liquid inlet is mixed with the organic solvent A entering through the organic solvent inlet in a mixing zone with a stirring device, and then enters a three-phase separator (liquid phase, solid phase and critical phase) to complete the crystallization process, the liquid phase component enters the separation zone, the solid phase component enters the sedimentation zone, the solid phase in the sedimentation zone is finally discharged to the miscellaneous salt drying unit 20 through the miscellaneous salt discharge port, and the solution in the separation zone is finally discharged to the primary solvent recovery unit 19 through the mixture discharge port.

[0061] 7) Sodium thiosulfate recovery section

[0062] According to the solubility characteristics of sodium thiosulfate and sodium hydroxide, an organic solvent B (specifically ethanol) is added to the secondary salting-out reactor 21, so that the solution from the primary solvent recovery unit 19 is mixed with the organic solvent B in a ratio of about 1:2 (volume ratio), thereby realizing the precipitation of sodium thiosulfate (purification is completed), and the purified sodium thiosulfate is sent to the sodium thiosulfate drying and packaging unit 23 for treatment (wherein the heat source of the drying process comes from the steam network of the plant area, and the pressure is 0.5-0.6 MPa) and then shipped as a product. The remaining liquid in the secondary salting-out reactor 21 (a mixture B composed of the organic solvent B and the solution containing sodium hydroxide) is pressurized and sent to the secondary solvent recovery unit 22. In the secondary solvent recovery unit 22, the organic solvent B is separated and purified by distillation (the heat source comes from the steam network of the plant area, and the pressure is 0.5-0.6 MPa) and then circulated in the secondary salting-out reactor 22. The solution containing sodium hydroxide is pressurized and sent to the liquid alkali modulation recovery section.

[0063] The core equipment of the above-mentioned secondary salting-out reactor 21 is a crystallizer, which also includes a mixed liquid inlet, an organic solvent inlet, a sodium thiosulfate discharge port and a mixture discharge port. The working principle of the crystallizer is as follows: the solution containing sodium thiosulfate and sodium hydroxide entering through the mixed liquid inlet is mixed with the organic solvent B entering through the organic solvent inlet in a mixing zone with a stirring device, and then enters the three-phase separator for a crystallization process (liquid phase, solid phase and critical phase). The liquid phase component enters the separation zone, and the solid phase component enters the sedimentation zone. The solid phase in the sedimentation zone is finally discharged to the sodium thiosulfate drying and packaging unit 23 through the sodium thiosulfate discharge port, and the solution in the separation zone is finally discharged to the secondary solvent recovery unit 22 through the mixture discharge port.

[0064] 8) Liquid caustic soda conditioning and recovery section

[0065] The sodium hydroxide concentration in the solution from the secondary solvent recovery unit 22 is low, and needs to be evaporated and concentrated or modulated with caustic soda flakes before being transported as a product (liquid caustic soda). Therefore, the liquid caustic soda modulation and recovery section includes an independent liquid caustic soda concentration unit 24 and a liquid caustic soda concentration adjustment unit 25.

[0066] After testing, the calcium carbonate obtained through the above process meets the qualified product standard of limestone for chemical industry (HG / T 2504-1993), the sodium thiosulfate meets the second-class standard of industrial sodium thiosulfate (HG / T2328-2006), and the liquid alkali (i.e., solution sodium hydroxide) meets the qualified product standard of natural alkali caustic soda sodium hydroxide (HG / T 3825-2006). All of these qualified products can be sold, especially industrial sodium thiosulfate, which can obtain higher economic benefits.

Claims

1. A waste alkali liquid resource utilization device, characterized in that: The device comprises a waste alkali liquid deoiling section, an oxidation section, an organic matter removal section, a causticizing section, an evaporation and concentration section, a foreign salt removal section and a sodium thiosulfate recovery section which are connected in sequence. The waste alkali liquid deoiling section comprises an oil removal tank (1), the oxidation section comprises an oxidation reactor for converting sodium sulfide in the waste alkali liquid remaining after passing through the oil removal tank (1) into sodium thiosulfate, the organic matter removal section comprises an adsorption medium and a filter medium for respectively removing organic matter and purifying water quality of the waste alkali liquid after conversion in the oxidation reactor, the causticizing section comprises a causticizing reactor (13) for converting sodium carbonate in the waste alkali liquid remaining after passing through the adsorption medium and the filter medium into calcium carbonate and sodium hydroxide, the evaporation and concentration section comprises an oxidation reactor (14) for converting sodium carbonate in the waste alkali liquid remaining after passing through the adsorption medium and the filter medium into calcium carbonate and sodium hydroxide, the oxidation section comprises an oxidation reactor (15) for converting sodium sulfide in the waste alkali liquid remaining after passing through the oxidation reactor, and the causticizing section comprises an evaporation and concentration section. The section comprises an evaporator for concentrating the sodium hydroxide solution containing sodium thiosulfate and inorganic salt impurities separated from the causticizing reactor (13); the impurity salt removal section comprises a primary salting-out reactor (18) for separating the corresponding inorganic salt impurities in the evaporator discharge and a primary solvent recovery unit (19) for recycling the organic solvent added to the primary salting-out reactor (18) by distillation; the sodium thiosulfate recovery section comprises a secondary salting-out reactor (21) for separating sodium thiosulfate from the solution remaining in the primary solvent recovery unit (19) and a secondary solvent recovery unit (22) for recycling the organic solvent added to the secondary salting-out reactor (21) by distillation; The waste alkali liquid oil removal section further comprises a regulating tank (4), a regulating tank outlet lifting pump (5), an oil storage tank (2) and a dirty oil pump (3); the oil storage tank (2) and the regulating tank (4) are respectively connected to the oil removal tank (1); the dirty oil pump (3) is connected to the oil storage tank (2); and the regulating tank outlet lifting pump (5) is respectively connected to the regulating tank (4) and the oxidation section; The organic matter removal section specifically comprises a powdered activated carbon adsorption tank (10) and a water production filter (11); the powdered activated carbon adsorption tank (10) is connected to the water production filter inlet and the oxidation reactor respectively; and the water production filter outlet is connected to the causticizing section.

2. A waste alkali liquid resource utilization device according to claim 1, characterized in that: The oxidation section further comprises a catalyst dosing unit (8), a steam heating unit (7) and an aeration unit (9). The steam heating unit (7) and the aeration unit (9) are arranged in the oxidation reactor. The steam heating unit (7) is connected to an external steam network, and the aeration unit (9) is connected to an external fan. The oxidation reactor is respectively connected to the organic matter removal section, the regulating tank outlet lifting pump (5), and the catalyst dosing unit (8).

3. The waste alkali liquid resource utilization device according to claim 1, characterized in that: The outlet side of the water production filter (11) is provided with a return pipeline connected to the inlet of the water production filter.

4. The waste alkali liquid resource utilization device according to claim 1, characterized in that: The causticizing section further comprises a calcium oxide dosing unit (12), a clear liquid filtering unit (14) and a calcium carbonate drying unit (15); the causticizing reactor (13) is respectively connected to the calcium oxide dosing unit (12), the clear liquid filtering unit (14), the calcium carbonate drying unit (15) and the produced water filter (11); and the clear liquid filtering unit (14) is connected to the evaporation concentration section.

5. A waste alkali liquid resource utilization device according to claim 4, characterized in that: The evaporation and concentration section also includes a secondary steam cooling unit (17) and a material lifting pump. The steam pipeline of the evaporator is respectively connected to the secondary steam cooling unit (17) and an external steam network. The material pipeline of the evaporator is respectively connected to the clear liquid filtering unit (14) and the material lifting pump. The material lifting pump is connected to the impurity salt removal section.

6. The waste alkali liquid resource utilization device according to claim 1, characterized in that: The device also includes a liquid caustic soda modulation and recovery section for adjusting the concentration of sodium hydroxide in the remaining solution of the secondary solvent recovery unit (22).

7. A method for treating waste alkali liquor from catalytic thermal cracking of residual oil and coal-to-olefins, based on the waste alkali liquor resource utilization device according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) Degreasing Deoiling the waste alkali liquid discharged from the DCC unit and / or MTO unit after alkali washing of the acid gas by oil-water separation; 2) Oxidation The waste alkali liquid after oil removal is subjected to oxidation reaction under steam heating, compressed air aeration and catalyst action, so that the sodium sulfide in the waste alkali liquid is converted into sodium thiosulfate; 3) Removal of organic matter Adsorbing organic matter in the waste alkali solution treated in step 2) using activated carbon, and then filtering to remove the activated carbon; 4) Causticization and concentration The waste alkali solution treated in step 3) is reacted with calcium oxide, the calcium carbonate precipitate generated by the reaction is dried, and the supernatant is filtered and concentrated to obtain a concentrated solution; 5) Removal of impurities The concentrated solution obtained in step 4) is subjected to salting out by adding an alcohol organic solvent to remove impurities, wherein the impurities include sodium sulfide, sodium carbonate, sodium chloride and sodium sulfate; 6) Recovery of sodium thiosulfate After removing impurities and recovering the solvent, the concentrated solution is subjected to salting out by using an added alcohol organic solvent to separate sodium thiosulfate and sodium hydroxide, and the separated sodium thiosulfate is dried.

8. The method for treating waste alkali liquor from catalytic thermal cracking of residual oil and coal-to-olefins according to claim 7, characterized in that: The following steps are also included: 7) After separating the sodium thiosulfate and recovering the solvent, the concentration of sodium hydroxide is adjusted or concentrated.

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