CN113292191A - Residual oil catalytic pyrolysis and coal-to-olefin waste alkali liquor resource utilization device - Google Patents
Residual oil catalytic pyrolysis and coal-to-olefin waste alkali liquor resource utilization device Download PDFInfo
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Abstract
本发明公开了一种渣油催化热裂解及煤制烯烃废碱液资源化利用装置，包括废碱液除油工段、氧化工段、有机物脱除工段、苛化工段、蒸发浓缩工段、杂盐脱除工段、硫代硫酸钠回收工段及液碱调制回收工段，将DCC装置及MTO装置废碱液于废碱液除油工段进行油水分离，于氧化工段将所含硫化钠转化为硫代硫酸钠，于有机物脱除工段通过活性炭的吸附去除有机物，于苛化工段通过加入生石灰将所含碳酸钠转化为碳酸钙和氢氧化钠，于蒸发浓缩工段和杂盐脱除工段进一步去除水分和残留的硫化钠、碳酸钠及氯化钠、硫酸钠，于硫代硫酸钠回收工段、液碱调制回收工段分离硫代硫酸钠、调节氢氧化钠浓度。本发明实现了对废碱液中混盐的高效、低成本资源化利用。
The invention discloses a residual oil catalytic thermal cracking and coal-to-olefin waste alkali liquid resource utilization device, comprising a waste alkali liquid removal section, an oxidation section, an organic matter removal section, a causticization section, an evaporation concentration section, and a miscellaneous salt removal section. In the removal section, the sodium thiosulfate recovery section and the liquid alkali preparation and recovery section, the waste lye of the DCC device and the MTO device is separated from oil and water in the waste lye oil removal section, and the sodium sulfide contained in the oxidation section is converted into sodium thiosulfate. , in the organic matter removal section, the organic matter is removed by the adsorption of activated carbon, in the causticization section, the sodium carbonate is converted into calcium carbonate and sodium hydroxide by adding quicklime, and the evaporation concentration section and the miscellaneous salt removal section are further removed. Sodium sulfide, sodium carbonate, sodium chloride and sodium sulfate are separated in the sodium thiosulfate recovery section and the liquid alkali preparation and recovery section, and the concentration of sodium hydroxide is adjusted. The invention realizes the efficient and low-cost resource utilization of the mixed salt in the waste alkali liquor.
Description
Technical Field
The invention relates to the recycling of waste alkali liquor of large-scale coal chemical and petrochemical enterprises, in particular to the catalytic thermal cracking of residual oil and the resource utilization of waste alkali liquor mixed salt of coal-to-olefin.
Background
A large-scale coal oil gas resource comprehensive utilization project can generate a large amount of waste alkali liquor in the process of washing acid gas with alkali, wherein devices for generating the acid gas mainly comprise a residual oil catalytic pyrolysis (DCC) device and a methanol-to-olefin (MTO) device, the DCC device is taken as an example, the content of mixed salt in the discharged waste alkali liquor is about 10 percent, and inorganic salt components in the mixed salt mainly comprise 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 such waste alkali liquor (wastewater containing dispersed oil and mixed salt) generally comprises oil removal, oxidation, organic matter removal, evaporation concentration, blending treatment of evaporation mother liquor in a sewage treatment station and then sending the evaporation mother liquor into a downstream regeneration water plant, so that all water in the waste alkali liquor is recovered, and 'zero sewage discharge' is realized. However, with the improvement of the standard for preventing and controlling mixed salt pollution in industrial waste disposal, the resource utilization of mixed salt through mixing treatment becomes difficult, and it is urgently needed to provide a set of mixed salt recycling device for step-by-step and quality-by-quality treatment according to the components and the salinity characteristics of residual oil catalytic thermal cracking and coal-to-olefin waste lye, so as to reduce the generation amount of evaporation mother liquor, realize the separation of mixed salt and water in the evaporation mother liquor, and finally realize the improvement of the resource utilization degree of mixed salt while realizing the complete recovery of wastewater.
Chinese patent CN107445329A discloses a method for treating liquid hydrocarbon waste alkali liquor, which comprises the steps of carrying out oil washing and degassing on MTO waste alkali liquor, standing a storage tank to remove floating oil, carrying out air stripping on organic matters, adding a precipitator to remove carbonate and adding sodium hydroxide to complete liquid alkali regeneration, thereby achieving zero discharge and recycling of the waste alkali liquor. But has problems in that: firstly, for a process mainly using waste alkali liquor discharged by a DCC device as a treatment object, a large amount of viscous mother liquor with extremely high salt content is generated in a steam heating process due to the physical properties of sodium thiosulfate in the waste alkali liquor, so that effective removal and resource utilization of sulfide and sodium thiosulfate cannot be realized; secondly, only the removal of carbonate is realized, the formation of dangerous waste is aggravated, and the resource utilization of the carbonate is difficult to realize; and thirdly, a small amount of inorganic salt is continuously concentrated in the recycling process, and the produced water cannot be continuously recycled for a long period.
Disclosure of Invention
The invention aims to provide a device for catalytic thermal cracking of residual oil and resource utilization of waste alkali liquor of coal-to-olefin.
In order to achieve the purpose, the invention adopts the following technical scheme:
a waste alkali liquid resource utilization device comprises a waste alkali liquid deoiling section, an oxidation section, an organic matter removing section, a causticization section, an evaporation concentration section, a mixed salt removing section and a sodium thiosulfate recovery section which are sequentially connected, wherein the waste alkali liquid deoiling section comprises an oil removing tank, the oxidation section comprises an oxidation reactor for converting sodium sulfide in the residual waste alkali liquid after the oil removing tank into sodium thiosulfate under the action of a catalyst, the organic matter removing section comprises an adsorption medium and a filtering medium for respectively removing the organic matter and purifying the water quality of the waste alkali liquid after the conversion of the oxidation reactor, the causticization section comprises a causticization reactor for converting sodium carbonate in the residual waste alkali liquid after the conversion of the adsorption medium and the filtering medium into calcium carbonate and sodium hydroxide, the evaporation concentration section comprises an evaporator for concentrating sodium hydroxide solution which is separated from the causticization reactor and contains sodium thiosulfate and inorganic salt impurities, the mixed salt removing section comprises a primary salting-out reactor for separating corresponding inorganic salt impurities in the discharge of the evaporator and a primary solvent recovery unit for recycling the organic solvent (organic solvent A) added in the primary salting-out reactor through rectification, and the sodium thiosulfate recovery section comprises a secondary salting-out reactor for separating sodium thiosulfate from the residual solution of the primary solvent recovery unit and a secondary solvent recovery unit for recycling the organic solvent (organic solvent B) added in the secondary salting-out reactor through rectification.
Preferably, the waste alkali liquid oil removal section further comprises an adjusting tank, an adjusting tank outlet lift pump, an oil storage tank and a sump oil pump, wherein the oil storage tank and the adjusting tank are respectively connected with the oil removal tank, the sump oil pump is connected with the oil storage tank, and the adjusting tank outlet lift pump is respectively connected with the adjusting tank and the oxidation section; the waste alkali liquid enters the oil removal tank and then is subjected to oil-water separation in the oil removal tank, the separated dirty oil automatically flows into the oil storage tank and is collected and then is output by the dirty oil pump (for example, the dirty oil can be sent into a DCC device for recycling), and the deoiled waste alkali liquid automatically flows into the regulating tank and is sent into an oxidation section by the lifting pump.
Preferably, the oxidation section further comprises a catalyst adding 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 with a steam pipe network arranged outside the oxidation reactor, the aeration unit is connected with a fan arranged outside the oxidation reactor, and the oxidation reactor is respectively connected with the organic matter removing section, the outlet lift pump of the regulating tank and the catalyst adding unit; the oxidation section is used for oxidizing sodium sulfide in the waste alkali liquor pumped to the oxidation reactor through the outlet of the adjusting tank into sodium thiosulfate, wherein the steam heating unit is used for providing the temperature required by the reaction, and the aeration unit is used for providing the oxygen required by the reaction.
Preferably, the organic matter removal section specifically comprises a powdered activated carbon adsorption tank and a water production filter, the powdered activated carbon adsorption tank is respectively connected with an inlet of the water production filter and the oxidation reactor, and an outlet of the water production filter is connected with the causticization section.
Preferably, the outlet side of the water production filter is provided with a return line connected with the inlet of the water production filter.
Preferably, the causticizing section further comprises a calcium oxide adding unit, a clear liquid filtering unit and a calcium carbonate drying unit, the causticizing reactor is respectively connected with the calcium oxide adding unit, a clear liquid filtering unit inlet lift pump, a calcium carbonate drying unit inlet lift pump and the water production filter, and the clear liquid filtering unit outlet is connected with the evaporation and concentration section.
Preferably, the evaporation concentration section further comprises a secondary steam cooling unit and a material lift pump, wherein a steam pipeline of an evaporator (for example, a triple-effect evaporator) is respectively connected with the steam pipe network and the secondary steam cooling unit, a material pipeline of the evaporator is respectively connected with the clear liquid filtering unit and an inlet of the material lift pump, and an outlet of the material lift pump is connected with the miscellaneous salt removal section.
Preferably, the mixed salt removing section further comprises a mixed salt drying unit, a primary recovery lift pump and a primary outward-conveying lift pump, the primary salt separating reactor is respectively connected with the mixed salt drying unit, the primary solvent recovery unit and the material lift pump, the primary recovery lift pump is respectively connected with the primary salt separating reactor and the primary solvent recovery unit, the primary outward-conveying lift pump is respectively connected with the primary solvent recovery unit and the sodium thiosulfate recovery section, and the steam pipe network is respectively connected with the primary solvent recovery unit and the mixed salt drying unit.
Preferably, the sodium thiosulfate recovery section further comprises a sodium thiosulfate drying and packaging unit, a secondary recovery lift pump and a secondary delivery lift pump, the secondary salt precipitation reactor is respectively connected with the sodium thiosulfate drying and packaging unit, the secondary solvent recovery unit and the primary delivery lift pump, the secondary recovery lift pump is respectively connected with the secondary salt precipitation reactor and the secondary solvent recovery unit, the secondary delivery lift pump is respectively connected with the secondary solvent recovery unit and the liquid alkali modulation recovery section, and the steam pipe network is respectively connected with the secondary solvent recovery unit and the sodium thiosulfate drying and packaging unit.
Preferably, the device also comprises a liquid caustic soda modulation recovery section for adjusting the concentration of sodium hydroxide in the solution remaining in the secondary solvent recovery unit.
Preferably, the liquid caustic soda preparing and recovering section specifically includes a liquid caustic soda concentration unit and/or a liquid caustic soda concentration blending unit, and both the liquid caustic soda concentration unit and the liquid caustic soda concentration blending unit are connected to the second-stage outward-feeding lift pump.
A method for treating residual oil catalytic thermal cracking and coal-to-olefin waste lye by utilizing the device comprises the following steps:
1) oil removal
Conveying the waste alkali liquor discharged after the DCC device and/or the MTO device washes acidic gas with alkali to an oil removal tank, and automatically flowing the waste alkali liquor to an adjusting tank after oil-water separation is realized in the oil removal tank;
2) oxidation by oxygen
The deoiled waste alkali liquor enters an oxidation reactor from a self-regulating tank and is subjected to oxidation reaction under the action of steam heating, compressed air aeration and a catalyst, so that sodium sulfide in the waste alkali liquor is converted into sodium thiosulfate;
3) removal of organic matter
Sequentially feeding the waste alkali liquid treated in the step 2) into a powder activated carbon adsorption tank and a water production filter, removing organic matters from the waste alkali liquid through activated carbon adsorption, and filtering to remove activated carbon powder;
4) causticizing and concentrating
The waste alkali liquid treated in the step 3) enters a causticization reactor and reacts with added calcium oxide, calcium carbonate precipitate generated by the reaction is dried to be used as a product, and supernatant liquid is filtered and then enters a triple-effect evaporator for further removing water (namely, concentration);
5) salt removal
Concentrated solution (discharged material) output by the triple-effect evaporator enters a first-stage salting-out reactor, and salting-out is carried out by using an added organic solvent A, so as to remove miscellaneous salts (the miscellaneous salts mainly comprise residual sodium sulfide in an oxidation section, residual sodium carbonate in a causticization section and a small amount of sodium chloride and sodium sulfate);
6) recovery of sodium thiosulfate
And (3) the concentrated solution output by the triple-effect evaporator enters a secondary salting-out reactor after removing miscellaneous salts and recovering the solvent, and is salted out by using the added organic solvent B, so that the separation of sodium thiosulfate and sodium hydroxide is realized, and the separated sodium thiosulfate is dried to be used as a product.
Preferably, the method for treating residual oil catalytic thermal cracking and coal-to-olefin waste lye by using the device further comprises the following steps:
7) and (3) liquid caustic soda preparation, namely, separating the sodium thiosulfate, then recovering the solvent, and then performing sodium hydroxide concentration preparation or concentration to obtain a liquid caustic soda product.
Preferably, the organic solvent A and the organic solvent B are selected from alcohol solvents such as methanol and ethanol; in the first-stage salting-out reactor, the volume ratio of the concentrated solution 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 concentrated solution output by a triple-effect evaporator for removing miscellaneous salts and recovering the solvent to the organic solvent B is 1: 2-3.
Preferably, the organic solvent (organic solvent A) added in the first-stage salting-out reactor is methanol, and the organic solvent (organic solvent B) added in the second-stage salting-out reactor is ethanol; the adding proportion of the organic solvent of the first-stage salting-out reactor is higher than that of the organic solvent of the second-stage salting-out reactor.
The invention has the beneficial effects that:
the invention adds a causticization working section, a mixed salt removal working section and a sodium thiosulfate recovery working section on the basis of adopting an oil removal working section, an oxidation working section, an organic matter removal working section and an evaporation concentration working section, wherein the mixed salt removal working section and the sodium thiosulfate recovery working section realize the graded cyclic addition of a solvent by introducing a solvent recovery unit, thereby establishing a salting-out separation system aiming at inorganic salt impurities and sodium thiosulfate, effectively purifying and converting residual oil catalytic thermal cracking and coal-to-olefin waste alkali liquor, realizing the resource utilization of mixed salt in the waste alkali liquor while recovering all waste water, obviously reducing the discharge amount of solid mixed salt, and meeting the development requirements of emission reduction and efficiency improvement.
Furthermore, the outlet side of the water production filter is provided with a return pipeline, so that the content of suspended matters in the produced water is reduced, the situation that the suspended matters such as powdered activated carbon enter a subsequent treatment working section is avoided, and the purity of corresponding products meets the standard requirement is ensured.
Furthermore, by utilizing the solubility characteristic of inorganic salt and the salting-out effect of the organic solvent A and optimizing the adding proportion of the organic solvent A, the miscellaneous salt which cannot be recycled is removed, and the supply amount and the loss of the solvent are reduced.
Furthermore, the separation of the sodium thiosulfate and the liquid sodium hydroxide is realized by utilizing the solubility characteristics of the sodium thiosulfate and the sodium hydroxide and the salting-out effect of the organic solvent B and optimizing the adding proportion of the organic solvent B, so that the supply amount and the loss of the solvent are reduced.
Further, by optimizing the types of the added solvents of the first-stage salting-out reactor and the second-stage salting-out reactor, namely determining that the organic solvent added in the first-stage salting-out reactor is methanol, the organic solvent added in the second-stage salting-out reactor is ethanol, and combining the optimization of the adding proportion, the problems that when the organic solvent in the first-stage salting-out reactor is not used properly, the removal rate of mixed salt is low, the purity of sodium thiosulfate and sodium hydroxide is influenced, the loss of the organic solvent is increased, unnecessary energy consumption is caused are avoided, and meanwhile, when the organic solvent in the second-stage salting-out reactor is not used properly, the purity of the sodium thiosulfate and sodium hydroxide products is reduced, the standard requirements are difficult to meet, and the resource utilization cost is increased are avoided.
Further, the solution left after separating the sodium thiosulfate and recovering the solvent can be directly evaporated and concentrated (entering a liquid caustic soda preparation and recovery section) or mixed with solid sodium hydroxide (flake caustic soda) to prepare a liquid caustic soda product which is used as a cleaning solution or other purposes, so that the complete harmless treatment of the waste lye is realized.
Drawings
FIG. 1 is a schematic structural diagram of a waste lye mixed salt resource utilization device in an embodiment of the present invention;
in the figure: the system comprises a degreasing tank 1, an oil storage tank 2, a sump oil pump 3, an adjusting tank 4, a lift pump 5, a desulfurization reactor 6, a steam heating unit 7, a catalyst feeding unit 8, an aeration unit 9, a powdered activated carbon adsorption tank 10, a water production filter 11, a calcium oxide feeding unit 12, a causticization reactor 13, a filtering unit 14, a calcium carbonate drying unit 15, a three-effect evaporator 16, a secondary steam cooling unit 17, a primary salting-out reactor 18, a primary solvent recovery unit 19, a miscellaneous salt drying unit 20, a secondary salting-out reactor 21, a secondary solvent recovery unit 22, a sodium thiosulfate drying and packaging unit 23, a liquid alkali concentration unit 24 and a liquid alkali concentration allocation unit 25.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. The examples are given solely for the purpose of illustration and are not intended to limit the scope of the invention.
Referring to fig. 1, the invention provides a waste alkali liquid mixed salt resource utilization device, which comprises a waste alkali liquid oil removal section, an oxidation section, an organic matter removal section, a causticization section, an evaporation concentration section, a mixed salt removal section, a sodium thiosulfate recovery section and a liquid alkali modulation recovery section which are connected in series. The specific process flow for treating the waste alkali liquids (respectively called residual oil thermal cracking waste alkali liquid and coal-to-olefin waste alkali liquid) generated in the acid gas alkaline washing process by using the DCC device and the MTO device in the plant (the waste alkali liquid generated by the DCC device in the plant is far more than that generated by the MTO device) by using each section is as follows:
1) waste alkali liquid oil removal section
The waste alkali liquid deoiling workshop section comprises an oil removal tank 1, an oil storage tank 2, a sump oil pump 3 and an adjusting tank 4, residual oil thermal cracking waste alkali liquid generated by a DCC device and coal-to-olefin waste alkali liquid generated by an MTO device are respectively pressurized and then enter the oil removal tank 1 to be mixed, under the action of the oil removal tank 1, oil-water separation is realized by the mixed waste alkali liquid in the oil removal tank 1, separated sump oil (light oil) automatically flows into the oil storage tank 2, then the separated sump oil (light oil) is sent into the DCC device through the sump oil pump 3 to be recycled, the residual waste alkali liquid after the sump oil is separated automatically flows into a homogeneous adjusting tank 4, and the waste alkali liquid in the homogeneous adjusting tank 4 is stably sent into an oxidation reactor of the oxidation workshop section by a lifting pump 5 at the outlet of the homogeneous adjusting tank 4.
The oil removing tank 1 (common vertical oil removing tank) mainly removes dispersed oil with the particle size of 10-100 mu m, the dispersed oil can float upwards through the density difference of oil and water, the concentration of the dispersed oil in the waste alkali liquor can be reduced from 200-500 mg/L to 20-50 mg/L through the vertical oil removing tank, and the water conservancy residence time of the mixed waste alkali liquor in the waste alkali liquor oil removing section is about 50 hours.
2) Oxidation section
The oxidation section comprises an oxidation reactor, an aeration fan and a dosing system, the oxidation reactor specifically adopts a desulfurization reactor 6 which is divided into three stages, and sodium sulfide in the waste alkali liquor from the homogenizing adjusting tank 4 is converted into sodium thiosulfate through oxidation reaction by the series operation of the three-stage desulfurization reactor 6. The steam heating unit 7 and the aeration unit 9 are arranged in the first-stage desulfurization reactor, the second-stage desulfurization reactor and the third-stage desulfurization reactor, the reaction temperature in each stage of desulfurization reactor 6 is automatically controlled (generally 65-70 ℃) through the steam heating unit 7, and a heat source adopts steam (with the pressure of 0.5-0.6 MPa and comes from a steam pipe network of a plant area); because the reaction temperature is relatively low, the conversion from sodium sulfide to sodium thiosulfate needs to be carried out under the action of a catalyst (such as a molybdenum-based desulfurizer), and the dosing system mainly comprises a catalyst dosing unit 8, wherein the catalyst dosing position of the dosing system is a first-stage desulfurization reactor directly connected with a lift pump 5 at the outlet of a homogenizing adjusting tank 4. The oxygen source in each desulfurization reactor 6 adopts compressed air, the compressed air is pressurized by an aeration fan and then is sent to an aeration unit 9, and the aeration unit 9 adopts a flow dispersing aerator (the single aeration rate is about 0.45 m)3In/min). The waste alkali liquor is sent into a powdered activated carbon adsorption tank 10 of an organic matter removal section after the reaction is finished in an oxidation section (the reaction hydraulic time is about 90 hours).
3) Organic matter removal section
The organic matter removal working section comprises a powdered activated carbon adsorption tank 10 and a water production filter 11, the powdered activated carbon adsorption tank 10 removes organic matters by a powdered activated carbon adsorption process, in order to eliminate the influence of dispersed powdered activated carbon on the subsequent process and the product quality, the water production filter 11 is arranged at the water outlet of the powdered activated carbon adsorption tank 10, a return pipeline is arranged at the outlet side of the water production filter 11, the powdered activated carbon can be subjected to circulating filtration, and the water is conveyed to a causticization reactor 13 of the causticization working section until the turbidity of the water outlet of the water production filter 11 reaches a set value (less than or equal to 5 NTU).
4) Causticization section
The causticizing section comprises a calcium oxide adding unit 12, a causticizing reactor 13, a filtering unit 14 (a water producing filter is also introduced into the causticizing section to be used as the filtering unit; the turbidity of a water outlet reaches a set value, namely less than or equal to 5NTU) and a calcium carbonate drying unit 15. The working principle of the causticization section is as follows: the quick lime is fed into a causticizing reactor 13 by a calcium oxide feeding unit 12, the quick lime is directly reacted with water in the waste alkali liquor from a water production filter 11 to generate calcium hydroxide, the calcium hydroxide is then reacted with sodium carbonate in the waste alkali liquor to generate calcium carbonate precipitate and solution containing sodium hydroxide, finally the waste alkali liquor fed into the causticizing reactor 13 completes the reaction, an upper layer reaction material (mainly clear liquid) in the causticizing reactor 13 is pressurized and then fed into a filtering unit 14 for filtering, a filtrate is fed into a triple-effect evaporator 16 of an evaporation and concentration section, a lower layer reaction material (containing precipitate) in the causticizing reactor 13 is pressurized and then fed into a precipitation tank for recycling, and the recycled precipitate is fed into a calcium carbonate drying unit 15 for drying to obtain a calcium carbonate product.
Because the filtering unit 14 is introduced, the supernatant liquid of the causticizing reactor 13 is directly filtered after being kept for a short time (still containing solid particles), so that the reaction retention time can be shortened, and the occupied area of a sedimentation tank is further reduced.
5) Evaporation concentration section
The evaporation concentration section comprises a triple-effect evaporator 16, waste alkali liquor (filtrate) from a filtering unit 14 enters the triple-effect evaporator 16 (which can be operated in series or in parallel) for concentration, and the concentrated waste alkali liquor (discharged from the triple-effect evaporator 16) is pressurized again and then sent into a salting-out reactor (namely a first-stage salting-out reactor 18) of a mixed salt removal section. Heating steam adopted by the triple-effect evaporator 16 comes from a steam pipe network (the pressure is 0.5-0.6 MPa) in a plant area, a primary steam condensate is recovered and then treated by a condensate refining system to be used as desalted water for outward transportation, secondary steam evaporated from a material side enters a secondary steam cooling unit 17 for cooling and then (exchanges heat with cooling feed water and takes heat away from cooling return water) is supplemented to a fresh production water system, and the temperature of the secondary steam condensate after heat exchange is about 40 ℃.
In the evaporation concentration section, the volume of the concentrated material is about 1/3 before concentration, and the treatment scale of the subsequent section is reduced.
6) Miscellaneous salt removal section
The discharged material of the triple-effect evaporator 16 enters a primary salting-out reactor 18, according to the solubility difference of various inorganic salts contained in the discharged material in a specific organic solvent A and the characteristic that the organic solvent A and water are mutually soluble in any proportion, the discharged material of the triple-effect evaporator 16 and the organic solvent A are mixed in a proportion (volume ratio) of about 1:3 by adding the organic solvent A (specifically methanol) into the salting-out reactor, so that inorganic salt impurities (mixed salt) such as sodium sulfate, sodium sulfide, sodium chloride and sodium carbonate remained in a causticization section in waste alkali liquor are separated out, the separated out material in the primary salting-out reactor 18 is sent into a mixed salt drying unit 20 for drying (a heat source is from a steam pipe network in a plant area and the pressure is 0.5-0.6 MPa), and the liquid remained in the primary salting-out reactor 18 (a mixture A consisting of the organic solvent A and a solution containing sodium thiosulfate and sodium hydroxide, wherein, the sodium thiosulfate mainly comes from an oxidation section, the sodium hydroxide mainly comes from a causticization section) is pressurized and then sent into a first-stage solvent recovery unit 19, in the first-stage solvent recovery unit 19, an organic solvent A is separated and purified by adopting a rectification mode (a heat source comes from a plant steam pipe network and the pressure is 0.5-0.6 MPa) and then is recycled by a first-stage salting-out reactor 18, and a solution (mixed solution) containing the sodium thiosulfate and the sodium hydroxide is pressurized and then sent into a salting-out reactor (namely a second-stage salting-out reactor 21) of the sodium thiosulfate recovery section.
The core equipment of the first-stage salting-out reactor 18 is a crystallizer, and further comprises a waste alkali liquor inlet, an organic solvent inlet, a mixed salt discharge port and a mixture discharge port, and the working principle of the crystallizer is as follows: the discharge of the triple-effect evaporator 16 entering through the waste alkali liquor inlet is mixed with the organic solvent A entering through the organic solvent inlet in a mixing zone with stirring equipment, and then enters a three-phase separator (liquid phase, solid phase and critical phase) to complete the crystallization process, the liquid phase component enters a separation zone, the solid phase component enters a settling zone, the solid phase in the settling zone is finally discharged to a mixed salt drying unit 20 through a mixed salt discharge port, and the solution in the separation zone is finally discharged to a primary solvent recovery unit 19 through a mixture discharge port.
7) Sodium thiosulfate recovery section
Adding an organic solvent B (specifically ethanol) into a secondary salting-out reactor 21 according to the dissolution characteristics of sodium thiosulfate and sodium hydroxide, mixing the solution from a primary solvent recovery unit 19 and the organic solvent B in a ratio (volume ratio) of about 1:2 to realize the precipitation (purification) of the sodium thiosulfate, sending the purified sodium thiosulfate into a sodium thiosulfate drying and packaging unit 23 for treatment (wherein the heat source in the drying process is from a plant steam pipe network and has a pressure of 0.5-0.6 MPa), taking the sodium thiosulfate as a product for outward transportation, pressurizing the residual liquid (a mixture B consisting of the organic solvent B and a solution containing the sodium hydroxide) in the secondary salting-out reactor 21, sending the pressurized liquid into a secondary solvent recovery unit 22, separating and purifying the organic solvent B in the secondary solvent recovery unit 22 in a rectification mode (the heat source is from the plant steam pipe network and has a pressure of 0.5-0.6 MPa), and recycling the organic solvent B in the secondary salting-out reactor 22, the solution containing sodium hydroxide is pressurized and then sent to a liquid caustic soda preparation and recovery section.
The core equipment of the second-stage salting-out reactor 21 is a crystallizer, and further comprises a mixed liquid inlet, an organic solvent inlet, a sodium thiosulfate discharge port and a mixture discharge port, and the working principle of the crystallizer is as follows: the solution containing sodium thiosulfate and sodium hydroxide entering through the mixed solution inlet and the organic solvent B entering through the organic solvent inlet are mixed in a mixing zone with stirring equipment, then enter a three-phase separator for crystallization (liquid phase, solid phase and critical phase), the liquid phase component enters a separation zone, the solid phase component enters a settling zone, the solid phase in the settling zone is finally discharged to a sodium thiosulfate drying and packaging unit 23 through a sodium thiosulfate discharge port, and the solution in the separation zone is finally discharged to a secondary solvent recovery unit 22 through a mixture discharge port.
8) Liquid caustic soda conditioning and recovering section
The concentration of sodium hydroxide in the solution from the secondary solvent recovery unit 22 is low, and the solution needs to be evaporated and concentrated or prepared by using caustic soda flakes and then is output as a product (caustic soda liquid), so that the caustic soda liquid preparation and recovery section comprises an independent caustic soda liquid concentration unit 24 and a caustic soda liquid concentration preparation unit 25.
Through detection, the calcium carbonate obtained by the process flow accords with the standard of limestone (HG/T2504-.
Because the work sections are operated in series, the downstream work section has strict requirements on the effluent quality of the upstream work section, and the work sections need to strictly control the operation process parameters and the water production indexes; meanwhile, the reliability requirement on a core treatment component (a filter element of a water production filter) of key equipment is also higher. Because the process flow is long, the process of each section needs to be strictly controlled. Particularly, the relevant process parameters of the first and second salting-out reactors 18 and 21 and the first and second solvent recovery units 19 and 22 are the results of small-scale optimization tests on the introduced operational process parameters of the salting-out reactors and the solvent recovery units at the initial stage of operation and adjustment and amplification, otherwise (for example, when the organic solvent in the first and second salting-out reactors is not used properly), the consumption of the organic solvent is increased, the product purity is reduced, and even the purification and separation cannot be performed, so that the resource utilization operation cost is influenced.
The process flow is suitable for residual oil catalytic thermal cracking and/or coal-to-olefin enterprises which have large production amount of waste alkali liquor and can not carry out blending treatment in sewage treatment plants. By calculating the generation amount of the mixed waste alkali liquor as 15 tons per hour, wherein the content of sodium carbonate is considered as 7 percent, and the content of sulfide is considered as 3 percent, about 7000 tons of calcium carbonate, about 2000 tons of sodium thiosulfate and 3650 tons of sodium hydroxide qualified products can be recovered by the waste alkali liquor mixed salt recycling device every year, about 13000 tons of mixed salt can be reduced, and about 85 percent of mixed salt in the waste alkali liquor can be recycled.
Claims (10)
1. A device for recycling waste alkali liquor is characterized in that: the device comprises a waste alkali liquid deoiling section, an oxidation section, an organic matter removing section, a causticization section, an evaporation concentration section, a mixed salt removing section and a sodium thiosulfate recovery section which are sequentially connected, wherein the waste alkali liquid deoiling section comprises an oil removing tank (1), the oxidation section comprises an oxidation reactor for converting sodium sulfide in the residual waste alkali liquid after passing through the oil removing tank (1) into sodium thiosulfate, the organic matter removing section comprises an adsorption medium and a filtering medium for respectively removing the organic matter and purifying the water quality of the waste alkali liquid after being converted by the oxidation reactor, the causticization section comprises a causticization reactor (13) for converting sodium carbonate in the residual waste alkali liquid after passing through the adsorption medium and the filtering medium into calcium carbonate and sodium hydroxide, and the evaporation concentration section comprises an evaporator for concentrating sodium hydroxide solution which is separated from the causticization reactor (13) and contains sodium thiosulfate and inorganic salt impurities, the mixed salt removing section comprises a primary salting-out reactor (18) for separating corresponding inorganic salt impurities in the discharge of the evaporator and a primary solvent recovery unit (19) for recycling the organic solvent added in the primary salting-out reactor (18) by rectification, and 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 in the secondary salting-out reactor (21) by rectification.
2. The device for recycling waste alkali liquor as claimed in claim 1, wherein: waste lye deoiling workshop section still includes holding tank (4), holding tank export elevator pump (5), oil storage tank (2) and sump oil pump (3), and oil storage tank (2), holding tank (4) link to each other with except that oil tank (1) respectively, and sump oil pump (3) link to each other with oil storage tank (2), and holding tank export elevator pump (5) link to each other with holding tank (4), oxidation workshop section respectively.
3. The device for recycling waste alkali liquor as claimed in claim 2, wherein: the oxidation section further comprises a catalyst adding 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 with an external steam pipe network, the aeration unit (9) is connected with an external fan, and the oxidation reactor is respectively connected with the organic matter removing section, the adjusting tank outlet lifting pump (5) and the catalyst adding unit (8).
4. The device for recycling waste alkali liquor as claimed in claim 1, wherein: the organic matter removal working section specifically comprises a powdered activated carbon adsorption tank (10) and a water production filter (11), wherein the powdered activated carbon adsorption tank (10) is respectively connected with an inlet of the water production filter and an oxidation reactor, and an outlet of the water production filter is connected with the causticization working section.
5. The device for recycling waste alkali liquor as claimed in claim 4, wherein: and a return pipeline connected with the inlet of the water production filter is arranged on the outlet side of the water production filter (11).
6. The device for recycling waste alkali liquor as claimed in claim 4, wherein: the causticizing section also comprises a calcium oxide adding unit (12), a clear liquid filtering unit (14) and a calcium carbonate drying unit (15), the causticizing reactor (13) is respectively connected with the calcium oxide adding unit (12), the clear liquid filtering unit (14), the calcium carbonate drying unit (15) and the water production filter (11), and the clear liquid filtering unit (14) is connected with the evaporation and concentration section.
7. The device for recycling waste alkali liquor as claimed in claim 6, wherein: the evaporation concentration working section further comprises a secondary steam cooling unit (17) and a material lifting pump, a steam pipeline of the evaporator is respectively connected with the secondary steam cooling unit (17) and an external steam pipe network, a material pipeline of the evaporator is respectively connected with the clear liquid filtering unit (14) and the material lifting pump, and the material lifting pump is connected with the miscellaneous salt removal working section.
8. The device for recycling waste alkali liquor as claimed in claim 1, wherein: the device also comprises a liquid caustic soda modulation recovery section for adjusting the concentration of sodium hydroxide in the solution remaining in the secondary solvent recovery unit (22).
9. A method for treating residual oil catalytic thermal cracking and coal-to-olefin waste lye is characterized in that: the method comprises the following steps:
1) oil removal
Deoiling waste alkali liquor discharged after the DCC device and/or the MTO device washes acid gas with alkali through oil-water separation;
2) oxidation by oxygen
Carrying out oxidation reaction on the deoiled waste alkali liquor under the action of steam heating, compressed air aeration and a catalyst, so that sodium sulfide in the waste alkali liquor is converted into sodium thiosulfate;
3) removal of organic matter
Adsorbing organic matters in the waste alkali liquor treated in the step 2) by using activated carbon, and then filtering to remove the activated carbon;
4) causticizing and concentrating
Reacting the waste alkali liquor treated in the step 3) with calcium oxide, drying calcium carbonate precipitate generated by the reaction, filtering supernatant, and concentrating to obtain concentrated solution;
5) salt removal
Salting out the concentrated solution obtained in the step 4) by using an added alcohol organic solvent to remove miscellaneous salts, wherein the miscellaneous salts comprise sodium sulfide, sodium carbonate, sodium chloride and sodium sulfate;
6) recovery of sodium thiosulfate
After removing miscellaneous salts and recovering the solvent, salting out by using an added alcohol organic solvent to separate sodium thiosulfate and sodium hydroxide, and drying the separated sodium thiosulfate.
10. The method for treating catalytic thermal cracking of residual oil and waste lye of coal-to-olefins according to claim 9, wherein: further comprising the steps of:
7) separating sodium thiosulfate, recovering solvent, and adjusting the concentration of sodium hydroxide or concentrating.
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| CN113716809A (en) * | 2021-09-09 | 2021-11-30 | 南方创业（天津）科技发展有限公司 | Alkali residue wastewater treatment and alkali recovery method |
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