Search

CN-121974520-A - Method for treating waste alkali liquor of coal-to-olefin device

CN121974520ACN 121974520 ACN121974520 ACN 121974520ACN-121974520-A

Abstract

The invention discloses a method for treating waste alkali liquid of a coal-to-olefin device. The method comprises the following steps of (1) removing butter in waste lye, removing butter by a butter remover, (2) treating the butter-removed waste lye, removing salt in the waste lye by reduced pressure low temperature evaporation treatment after the pH value of the butter-removed waste lye is regulated, and delivering evaporated condensate to a sewage treatment field for treatment and recycling, (3) carrying out harmless treatment on the butter and recycling accompanying sand, mixing the butter and the accompanying sand in proportion, carrying out incineration treatment, removing the butter, and simultaneously recycling the accompanying sand. The method can effectively remove butter in the waste alkali liquor of the coal-to-olefin device, solves the problem of butter blockage in the waste alkali liquor treatment process, effectively removes salt in the waste alkali liquor, reduces COD of effluent, and realizes the recycling of waste alkali liquor and sewage of the coal-to-olefin device.

Inventors

  • YU YUANBO
  • WANG FEIHU
  • JING YONGCHAO
  • YAN WEIHUA
  • GUO XINING
  • WANG HAITAO
  • LIN SHENHAI
  • GAO BO

Assignees

  • 西安德兴环保科技有限公司

Dates

Publication Date
20260505
Application Date
20260212

Claims (10)

  1. 1. The method for treating the waste alkali liquid of the coal-to-olefin device is characterized by comprising the following steps of: (1) Butter removal from spent lye Conveying waste lye of a coal-to-olefin device to a butter remover, layering the waste lye and butter by utilizing the density difference of the butter and the waste lye, wherein the upper part of the butter remover is butter, and the lower part of the butter remover is butter waste lye, the separated butter automatically flows to a butter bag for collection, and the butter waste lye is conveyed to a buffer tank; (2) Butter-removing waste lye treatment Sending a part of the butter-removed waste alkali liquid obtained after the treatment in the step (1) to a reduced pressure evaporation concentrator, concentrating at the temperature of 30-50 ℃ and the pressure of-98 to-90 kPa, and storing the concentrated liquid in a concentrated liquid storage tank; the other part of the waste alkali liquor except butter is added with acid substances to adjust the pH value to 9.5-10.5, and then the waste alkali liquor is sent to a decompression evaporation crystallizer, decompression evaporation concentration treatment is carried out under the conditions that the temperature is 30-50 ℃ and the pressure is minus 98 to minus 90kPa, after the concentrated mother liquor is treated by a mother liquor drier, the generated salt and the crystal salt generated by evaporation crystallization are subjected to external commission treatment, and the generated evaporation condensate is sent to a sewage treatment field for treatment and then is recycled; (3) Butter innocent treatment and companion sand regeneration cyclic utilization The butter in the butter oil and the regenerated companion sand are sent to a sand oil mixing feeder, and the companion sand and the butter are mixed by impeller stirring, wherein the weight ratio of the companion sand to the butter is 5:1-12:1; The sand-oil mixed feeder sends the mixed and adhered sand and butter mixed material into the pyrolysis incinerator, the pyrolysis is carried out at the temperature of 650-800 ℃, the butter adhered on the surface of the sand is oxidized and decomposed at high temperature, the pyrolyzed sand and ash are subjected to indirect heat exchange and cooling by using circulating cooling water in a jacket layer through a water-cooling screw conveyor, the cooled regenerated sand and ash are sent to the ash remover, the sand after ash removal is sent to the sand-oil mixed feeder for recycling, the ash and the crystalline salt in the step (2) are subjected to external commission treatment, the flue gas generated by the incineration pyrolysis is burnt in a secondary combustion chamber after passing through a high-temperature bag filter to intercept tiny particle sodium salt and ash generated in the pyrolysis process, and then the flue gas is sequentially subjected to cooling tower and spray tower treatment after heat energy is recovered by a waste heat boiler, and is discharged up to the standard.
  2. 2. The method of claim 1, wherein the waste lye of the coal-to-olefin apparatus in the step (1) is waste lye of 1-2wt% of sodium hydroxide (NaOH), 1.5-4wt% of sodium carbonate (Na 2 CO 3 ), 2500-600mg/L of butter, 8000-20000 mg/L of Chemical Oxygen Demand (COD), 40000-80000 mg/L of TDS and 13-14 of pH.
  3. 3. The method according to claim 1, wherein in the step (1), the effective liquid level of the butter remover is not less than 5m, the surface hydraulic load is 0.03-0.1 m 3 /（m 2 h, and the butter package is integrated on the side wall of the butter remover and shares a butter port with the butter remover, so that long-distance transmission of butter is avoided; preferably, the hydraulic load on the surface of the butter remover is 0.05-0.06 m 3 /（m 2 & h); The butter remover comprises a waste lye inlet, a butter removing waste lye outlet, a butter outlet, an emptying port, an online densimeter instrument port, a public engineering port, a temperature instrument port, a flange liquid level meter lower port, a flange liquid level meter upper port, a pressure instrument port, a breathing valve port, a nitrogen seal, an emergency discharge port, a waste gas outlet, an upper inspection manhole, a lower inspection manhole, an oil-water collector, a water distribution ring pipe, a water collecting ring pipe, a water inlet communicating pipe, a water outlet communicating pipe, a siphon breaking pipe, a sight glass a, a sight glass b, a sight glass c, a sight glass d, a drainage liquid level regulator and a butter bag, wherein the structure of the oil-water collector in the butter remover comprises a liquid inlet, a water distribution ring pipe interface, a water collecting ring pipe interface, a liquid outlet, an inner cavity and an annular interlayer cavity, and the structure of the drainage liquid level regulator comprises a water inlet, an adjustable sleeve, a sleeve water inlet, a water outlet and a siphon breaking interface, and the structure of the butter bag comprises a sight glass manhole, a temperature instrument port, a drain Huang Youkou, a liquid level instrument port and a liquid inlet Huang Youkou; The diameter of the butter remover is D; the oil-water collector is positioned in the center of the butter remover; the vertical height of the water distribution ring pipe from the bottom of the butter remover is H1, H1 is 2.5-3 m, water distribution holes with upward openings are uniformly distributed on the water distribution ring pipe, the water distribution ring pipe is communicated with a water distribution ring pipe interface of the oil-water collector through three communicating pipes which form 120 degrees with each other, the water distribution ring pipe interface is communicated with a liquid inlet of the butter remover through an annular interlayer cavity, and the liquid inlet of the butter remover is communicated with a waste alkali liquid inlet through a water inlet communicating pipe; the water collecting ring pipe is positioned at the lower part of the butter remover, the vertical height from the bottom of the butter remover is H2, H2 is 0.4-0.8 m, water receiving holes with downward openings are uniformly distributed on the water collecting ring pipe, the water collecting ring pipe is communicated with a water collecting ring pipe interface of an oil-water collector through three communicating pipes which are 120 degrees each other, the water collecting ring pipe interface is communicated with a liquid outlet of the butter remover through an inner cavity, the liquid outlet of the butter remover is communicated with an oil removing waste lye outlet through a water outlet communicating pipe, one end of the broken siphon is connected with a siphon breaking interface of the drain lye level regulator, the other end of the broken siphon is connected with a gas phase space in the butter remover, the balance between the butter removing waste lye level and the butter level is maintained, the butter outlet is the same with a yellow oil inlet of butter oil, the vertical distance between the lower edge of the butter outlet and the center of an adjustable sleeve water inlet in the drain level regulator is delta H, delta H can be adjusted between 0.05-0.20 m, the vertical distance between the lower edge of the butter outlet and the oil-water inlet is the oil layer thickness H=ρ x delta H/rho, rho is the density of the butter is 3 kg, the density of the density is the density of the butter is the density, the density of the butter is the density of the butter is the density, the density is the density of the butter is the density, and the density of the density is the density of the butter is the density, and the density is the density is the density and the density is the density and the and the and, the unit is kg/m 3 , the sight glass a-sight glass d is uniformly distributed on the side wall of the butter remover and at the height of the oil layer, the water inlet of the drainage liquid level regulator is connected with the butter removing waste lye outlet of the butter remover, the height of the adjustable sleeve is adjusted to control the oil layer thickness H, the butter bag is positioned on the side wall of the butter remover and is shared with the butter remover, the top of the butter remover is provided with a pressure instrument port, a breathing valve port, a nitrogen seal, an emergency discharge port, an exhaust gas outlet and an upper inspection manhole, the side wall is provided with a liquid level meter lower flange port, a liquid level meter upper flange port, a temperature instrument port, the sight glass a-sight glass d, a lower inspection manhole and an online densimeter port, and the bottom of the butter bag is provided with an evacuation port.
  4. 4. The method according to claim 1, wherein in the step (2), the method further comprises the steps of lifting the density of the waste lye according to the density condition of the waste lye in the butter remover, maintaining the density of the waste lye in the butter remover to be not less than 1100kg/m 3 , and lifting the density of the waste lye by refluxing the concentrated solution after the decompression evaporation and concentration of the waste lye of the butter or adding mixed salt or sodium sulfate salt generated by the evaporation and crystallization of an enterprise sewage treatment field into the butter remover; Preferably, the method for improving the density of the waste lye is that the concentrated solution is refluxed after the waste lye of butter is removed, the flow rate of the concentrated solution in the concentrated solution storage tank to the butter remover is controlled, and the density of the waste lye in the butter remover is maintained to be 1100-1150 kg/m 3 .
  5. 5. The method of claim 1, wherein in step (1), the inner wall of the butter pack and the inner wall of the transfer butter pipe are lined with an oleophobic material, which reduces butter adhesion, the lining material being Polytetrafluoroethylene (PTFE), silicone, fluorinated ethylene propylene copolymer (FEP) or perfluoroalkoxy resin (PFA); Preferably, the oleophobic material is lined with Polytetrafluoroethylene (PTFE).
  6. 6. The method according to claim 1, wherein in step (2), the acidic substance is sulfuric acid, hydrochloric acid or sodium bisulfate; preferably, the pH value of the waste lye is adjusted to 10, and the acidic substance used is sulfuric acid.
  7. 7. The method according to claim 1, wherein in step (2), the butter-removal spent lye evaporative concentration and crystallization treatment equipment is a multi-effect evaporative concentrator and crystallizer, or a MVR evaporative concentrator and crystallizer, or a vacuum low temperature heat pump evaporative concentrator and crystallizer; Preferably, the butter-removing waste alkali liquor evaporation concentration and crystallization treatment equipment is a vacuum low-temperature heat pump evaporation concentrator and a crystallizer.
  8. 8. The method according to claim 1, wherein in the step (3), the pyrolysis time of the incinerator is 1 to 2 hours, the pyrolysis temperature is 650 to 800 ℃, and preferably, the pyrolysis temperature of the incinerator is 680 to 750 ℃; The accompanying sand can be quartz sand, river sand, ceramic sand or metal sand, the grain size is 0.1-5 mm, the Mohs hardness is not lower than 5, the melting point is not lower than 900 ℃, the preferable accompanying sand grain size is 0.2-1.5 mm, the Mohs hardness is not lower than 6, the melting point is not lower than 1200 ℃, and the more preferable accompanying sand is quartz sand.
  9. 9. The method of claim 1, wherein in step (3), the water-cooled screw conveyor, ash remover and sand-oil hybrid feeder are an integrated device; Preferably, the integrated equipment has a structure with a plurality of integrated equipment, and comprises an auger end shaft, a bearing gland, a bracket, an oil seal gland, a seat cover, a copper sleeve, an auger shell end flange, a companion sand feed inlet, an auger shell, a blade, an auger shaft, a companion sand and butter mixture outlet, a rear end cover, an oil seal gland II, a cooling water jacket, a cooling water inlet, a cooling water outlet, a sieve plate auger shell, an ash outlet, an ash auger, a gas phase outlet, a gravity door, an inspection port and a butter inlet; The mesh aperture of the ash remover is smaller than the minimum particle size of the companion sand.
  10. 10. The method of claim 1, wherein in the step (3), a high-temperature bag type dust collector is arranged at the pyrolysis section and the secondary combustion chamber section of the incinerator to intercept tiny sodium salt particles and fly ash generated in the pyrolysis process, and flue gas from the secondary combustion chamber firstly passes through a waste heat boiler to recover heat energy, and then passes through a cooling tower and a spray tower to be treated, and then reaches the standard and is discharged at high altitude through a chimney; Preferably, the high-temperature bag type dust collector is a high-temperature metal fiber bag type dust collector, and the temperature resistance is not less than 750 ℃.

Description

Method for treating waste alkali liquor of coal-to-olefin device Technical Field The invention relates to a method for treating waste alkali liquid of a coal-to-olefin device, and belongs to the technical field of environmental engineering. Background Olefins are increasingly demanded by the chemical industry as important petrochemical base stocks and core products. For traditional olefin products, produced mainly by light oil (naphtha, light diesel) cracking, too much depends on petroleum. The energy structure of China is rich in coal, oil and gas, and the shortage of petroleum resources becomes one of the main bottlenecks of the development of the olefin industry in China. The coal-to-olefin technology is adopted to replace the petroleum-to-olefin technology, so that the excessive dependence of China on petroleum resources can be reduced, and the method has important significance for promoting the industrial development of lean oil areas and uniformly and reasonably utilizing the Chinese resources. The olefin separation unit of the coal-to-olefin device adopts sodium hydroxide solution to wash, so that acid gas existing in reaction gas is removed, and a large amount of waste alkali liquid which is high in salt content, high in alkali content and high in COD content and is difficult to treat is generated in the alkaline washing process. In addition, diolefin and other unsaturated hydrocarbon matters in the waste alkali liquor induce free radical reaction under the condition of trace oxygen to generate cross-linked polymer, aldehyde or ketone induces aldol condensation reaction under the action of alkali to form high molecular polymer, and these viscous polymers are commonly called butter. The waste alkali liquor contains a large amount of inorganic salts such as sodium hydroxide, sodium carbonate and the like, and is strongly alkaline. The waste alkali liquor has poor fluidity of yellow oil, is easy to block a pipeline, has complex organic pollutant components and poor biodegradability, and cannot be received by a sewage treatment system. The method for treating the waste alkali liquid of the coal-to-olefin device commonly used at home and abroad mainly comprises an incineration method, wherein the waste alkali liquid is directly subjected to incineration treatment at about 1100 ℃. On the other hand, sodium hydroxide and sodium carbonate in the waste alkali liquor burn at high temperature to form molten ash slag, and the molten slag adheres to furnace walls and furnace tubes and is combined with fly ash in flue gas, and the molten slag is cooled and hardened at the parts of a waste heat recovery boiler, a quenching tower, a flue and the like with lower temperature to form hard coking and ash accumulation, so that the incinerator is blocked and frequently stopped and overhauled and cannot normally and stably run. In addition, the direct incineration has the problems of large investment of the incinerator, high operation cost and large hazardous waste production amount due to large volume of waste alkali liquid. In some coal-to-olefin enterprises, the waste alkali liquor and the coal are mixed and then sent to an industrial boiler for burning or the waste alkali liquor is used as coal grinding water. This is in fact a pollution transfer behaviour of hazardous waste. The coal-to-olefin industry in China is mainly distributed in northwest regions, and the productivity of more than 80% is distributed in four modern coal chemical industry demonstration regions (Ningxia Ningdong, inner Mongolia Erdos, shaanxi Ulmin and Xinjiang Guangdong) planned in China and provinces where the production is located. Coal resources in these areas provide adequate feed assurance for the coal-to-olefins industry, and thus coal-to-olefins enterprises tend to develop in these areas. However, these places belong to inland, due to drought and lack of water, the environmental protection department requires that enterprises cannot discharge sewage outwards, and the zero discharge treatment of sewage of the whole factory is realized. Therefore, the treatment problem of butter and salt in the waste alkali liquid of the coal-to-olefin is effectively solved, so that zero emission of the waste alkali liquid can be realized, and the problem which is urgent to be solved by enterprises is solved. In view of the problems of the waste alkali liquid treatment of the coal-to-olefin device, a method which can stably and continuously run and can effectively remove butter and salt in high-salt, high-alkali and high-COD waste alkali liquid difficult to treat is developed, and has important significance for enterprise production. Disclosure of Invention Aiming at the problems in the prior art, the invention aims to provide a method for treating waste alkali liquid of a coal-to-olefin device. The method utilizes the principle of a communicating vessel to carry out hydraulic full-automatic oil removal on waste alkali liquor containing butter under the pro