阅读说明：本技术 亚磷酸三甲酯母液资源化利用的方法及其装置 (Method and device for recycling trimethyl phosphite mother liquor ) 是由 孙亚峰 王建清 沈书群 于 2020-07-19 设计创作，主要内容包括：本发明公开了一种亚磷酸三甲酯母液资源化利用的方法,包含下列工艺：将亚磷酸三甲酯母液送进入精馏塔A,塔顶温度为65-70℃,塔釜温度100-111℃,水分蒸发出来用于配制碱液,少量的亚磷酸三甲酯基本保留在精馏残液中。精馏残液进入到MVR蒸发结晶装置中进行提浓,蒸发后得到盐；蒸发残液送去焚烧炉得到焦磷酸钠。采用的装置中,具有依次连接的反应釜、水洗釜、分层塔,在分层塔中流出的三甲酯废水出口之后,还依次连接有精馏塔A、MVR设备、盐精制槽。本发明使亚磷酸三甲酯的废水基本能够到达零排放,废水中有用的甲醇、氯化钠、有机磷、水分都能得到回收利用。(The invention discloses a method for recycling trimethyl phosphite mother liquor, which comprises the following processes: and (3) feeding the trimethyl phosphite mother liquor into a rectifying tower A, wherein the tower top temperature is 65-70 ℃, the tower bottom temperature is 100-111 ℃, water is evaporated out for preparing alkali liquor, and a small amount of trimethyl phosphite is basically reserved in the rectification residual liquor. The rectification residual liquid enters an MVR evaporation crystallization device for concentration, and salt is obtained after evaporation; and sending the evaporation residual liquid to an incinerator to obtain sodium pyrophosphate. The device comprises a reaction kettle, a water washing kettle and a layering tower which are connected in sequence, and a rectifying tower A, MVR device and a salt refining tank are connected in sequence after a trimethyl ester wastewater outlet flowing out of the layering tower. The invention can basically realize zero discharge of the wastewater of trimethyl phosphite, and useful methanol, sodium chloride, organic phosphorus and water in the wastewater can be recycled.)

1. A method for recycling trimethyl phosphite mother liquor comprises the steps of taking methanol and phosphorus trichloride as raw materials, taking triethylamine or organic base as an acid-binding agent, taking diethyl ether, benzene, acetone or carbon tetrachloride as a solvent, reacting, and then washing with water for layering to obtain trimethyl phosphite mother liquor and fine filtrate; drying the fine filtrate and then rectifying to obtain the trimethyl phosphite; the method is characterized in that:

the treatment of the trimethyl phosphite mother liquor comprises the following steps:

1) sending trimethyl phosphite mother liquor into a rectifying tower A, and fractionating and separating methanol and water in the rectifying tower A;

2) the rectification residual liquid enters an MVR evaporation crystallization device for concentration, the crystallization product obtained after evaporation is mainly crude salt, and the evaporation residual liquid contains trimethyl phosphite and phosphorous acid;

3) refining the crude salt to obtain refined salt;

4) and sending the evaporation residual liquid to an incinerator for incineration treatment.

2. The method for recycling trimethyl phosphite mother liquor as claimed in claim 1, wherein: the temperature of the top of the rectifying tower A is controlled to be 65-70 ℃, and the temperature of the bottom of the rectifying tower A is controlled to be 100-111 ℃.

3. The method for recycling trimethyl phosphite mother liquor as claimed in claim 1, wherein: and (3) the water vapor generated by the distillation in the two steps 1) and 2) is used for preparing alkali liquor, the alkali liquor is fed into a washing kettle after the synthesis reaction, and the hydrochloric acid generated in the synthesis reaction is subjected to a neutralization reaction to generate sodium chloride.

4. The method for recycling trimethyl phosphite mother liquor as claimed in claim 1, wherein: the highest burning temperature in the burning furnace is 900-950 ℃.

5. A device adopting the trimethyl phosphite mother liquor resource utilization method of claim 1, which is characterized in that: the adopted device comprises a reaction kettle, a water washing kettle, a layering tower, a drying tower and a rectifying tower which are connected in sequence; further, a rectifying column A, MVR facility and a salt refining tank were connected in this order after the outlet of the trimethyl ester wastewater from the fractionating column.

6. The apparatus of claim 5, wherein: a water vapor outlet is arranged above the rectifying tower A and connected with an alkali preparation tank, and a liquid outlet below the rectifying tower A is connected with MVR equipment; the upper part of the MVR equipment is respectively provided with an evaporation gas outlet, a crystal outlet and an evaporation residual liquid outlet; the evaporation gas outlet is connected to the alkali preparation tank, the crystal outlet is connected to the salt refining tank, and the evaporation residual liquid outlet is also connected to the incinerator.

7. The apparatus of claim 5, wherein: the salt refining tank has functional components of salt washing, dissolution, membrane separation and electrolysis connected in sequence.

Technical Field

The invention relates to a treatment technology of wastewater generated in trimethyl phosphite production.

Background

Trimethyl phosphite (hereinafter abbreviated as trimethyl phosphite) is a colorless transparent liquid, has an offensive odor, and is flammable. Melting point < -60 ℃, boiling point of 112 ℃, relative density (25/5 ℃) of 1.0520, refractive index of 1.4095, viscosity (25 ℃) of 0.58 mPas and flash point (open cup) of 38 ℃. Insoluble in hot water, and soluble in organic solvent such as ethanol, diethyl ether, benzene, acetone, and carbon tetrachloride. It is an important intermediate of agricultural chemicals, and can be used for preparing series of vinyl phosphate insecticides of phosphamidon, monocrotophos, dichlorvos, etc. and can also be used for preparing products of fire retardant, etc.

The production process includes the steps of enabling raw materials of phosphorus trichloride, methanol, an acid-binding agent of triethylamine and the like, enabling solvent benzene and the like to continuously enter a reaction kettle for reaction, enabling crude trimethyl ester generated by the reaction to enter a water washing kettle through overflow, mixing the crude trimethyl ester with diluted alkali, enabling triethylamine hydrochloride to be reduced into triethylamine and a byproduct of sodium chloride, and enabling water washing liquid after water washing to continuously enter a layering tower for layering.

And (3) allowing trimethyl ester and the solvent on the upper layer of the layering tower to enter a rectifying tower for trimethyl ester rectification.

The trimethyl ester salt-containing mother liquor at the lower layer of the layering tower reacts with calcium oxide to produce calcium phosphate or calcium phosphite to remove total phosphorus in a system, and then the wastewater is subjected to biochemical treatment.

The invention of application number 2012103461138 relates to a process for continuously producing trimethyl phosphite by an N, N-dimethylaniline method, belonging to the technical field of trimethyl phosphite preparation. Through the steps of synthesis, water washing, layering, drying, distillation, wastewater recovery and the like, the sewage treatment cost is low, the product quality and the production quantity of trimethyl phosphite are ensured, and the sewage is an ammonium chloride fertilizer with wide application after concentration and crystallization. The method can represent the traditional production process, has low resource recovery rate and large subsequent wastewater treatment capacity.

The prior process route is shown in figure 1 in the attached drawing of the specification.

The disadvantages of this conventional approach: the wastewater treatment capacity is large, a large amount of wastewater is required for diluting the high-salt wastewater into a biochemical treatment system, and the treatment cost of the produced calcium phosphate solid slag is high, so that a wastewater treatment process which has the advantages of reasonable process, small wastewater yield and cyclic utilization of the produced solid slag is urgently needed to be found.

Disclosure of Invention

The purpose of the invention is as follows:

the method and the device for recycling the trimethyl phosphite mother liquor with high salt content have the advantages of low mother liquor yield and capability of respectively recycling the byproducts of methanol, phosphorus and water.

The technical scheme is as follows:

the invention provides a method for recycling trimethyl phosphite mother liquor, which comprises the steps of reacting a reaction system which takes methanol and phosphorus trichloride as raw materials, triethylamine or organic base as an acid-binding agent and takes diethyl ether, benzene, acetone, carbon tetrachloride and the like as solvents, and then washing with water for layering to obtain trimethyl phosphite mother liquor and refined filtrate; and drying the fine filtrate and then rectifying to obtain the trimethyl phosphite.

The treatment of the trimethyl phosphite mother liquor comprises the following steps:

1) the trimethyl phosphite mother liquor is fed into a rectifying tower A and is lower than the boiling point (112 ℃) of trimethyl phosphite, and the rectifying tower A fractionates and separates methanol (the content of methanol component in distilled liquor is not lower than 55% -70%) and water, so that the methanol and the water are evaporated, and a small amount of trimethyl phosphite is basically remained in the rectification residual liquor. In addition, the mother liquor contains a small amount of phosphorous acid, the phosphorous acid is decomposed into phosphine and orthophosphoric acid at 180 ℃, the phosphorous acid is not decomposed at the distillation temperature and is remained in the rectification residual liquid. The water content is fractionated to prepare alkali liquor.

2) And (4) concentrating the rectification residual liquid in an MVR evaporation crystallization device, wherein the evaporation temperature is 100-111 ℃. The distilled liquid is basically water vapor, and then the prepared liquid caustic soda is removed; the crystal product obtained after water evaporation is mainly crude salt; the rest is evaporation residual liquid containing trimethyl phosphite and phosphorous acid.

3) The two streams of water generated in the two steps are used for preparing alkali, the wastewater treatment cost can be reduced, the prepared alkali liquor is sent into a washing kettle for washing after the synthesis reaction (synthesis kettle), the hydrochloric acid generated in the synthesis reaction is subjected to neutralization reaction to generate sodium chloride, impurities are not brought to subsequent processes, other adverse effects are avoided, and the processes after washing are physical processes in the process of the process.

4) And (3) sending the evaporation residual liquid to an incinerator for incineration treatment (the highest incineration temperature is 900-950 ℃, so that energy is wasted excessively, and sodium pyrophosphate cannot be formed excessively), thereby obtaining more than 90% of sodium pyrophosphate.

5) And (3) washing, dissolving and performing membrane separation on the crude salt, removing impurities, and then electrolyzing in an electrolytic cell to obtain refined salt for recycling.

The device adopted by the invention comprises a reaction kettle, a water washing kettle, a layering tower, a drying tower and a rectifying tower which are connected in sequence; further, a rectifying column A, MVR facility and a salt refining tank were connected in this order after the outlet of the trimethyl ester wastewater from the fractionating column.

A water vapor outlet is arranged above the rectifying tower A and connected with an alkali preparation tank, and a liquid outlet below the rectifying tower A is connected with MVR equipment. The upper part of the MVR equipment is respectively provided with an evaporation gas outlet, a crystal outlet and an evaporation residual liquid outlet; the evaporation gas outlet is connected to the alkali preparation tank, the crystal outlet is connected to the salt refining tank (with functional components of salt washing, dissolving, membrane separation, electrolysis, etc.), and the evaporation residual liquid outlet is also connected to the incinerator.

The water vapor generated by the distillation in the two steps 1) and 2) is used for preparing the alkali liquor. The prepared alkali liquor is sent into a washing kettle for washing after the synthesis reaction (synthesis kettle), the hydrochloric acid generated in the synthesis reaction is neutralized to generate sodium chloride, impurities are not brought to the subsequent processes, other adverse effects are avoided, and the processes after washing are physical processes in the process of the flow.

Has the advantages that:

the wastewater of trimethyl phosphite can basically reach zero discharge, useful methanol, sodium chloride and organic phosphorus in the wastewater can be recycled, and meanwhile, the distilled liquid mainly contains water and can also be recycled, so that water resources are saved, and the reaction system is not influenced when the water is used for alkali preparation and recycling. The temperature and other technological parameters of each part of the reaction can be accurately controlled, so that the purity of the recovered product is relatively guaranteed.

Drawings

FIG. 1 is a process flow diagram of a conventional apparatus in the background of the invention;

FIG. 2 is a schematic diagram of the device process of the present invention;

in the figure, 1-synthesis kettle; 2-washing the kettle; 3-a layering tower; 4-a rectifying tower; 5-rectifying column A; 6-MVR equipment; 7-an incinerator; 8-a salt refining tank; 9-alkali preparation tank.

Detailed Description

The device shown in FIG. 2 comprises a reaction kettle, a water washing kettle, a layering tower, a drying tower and a rectifying tower which are connected in sequence; further, a rectifying column A, MVR facility and a salt refining tank were connected in this order after the outlet of the trimethyl ester wastewater from the fractionating column.

A water vapor outlet is arranged above the rectifying tower A and connected with an alkali preparation tank, and a liquid outlet below the rectifying tower A is connected with MVR equipment. The upper part of the MVR equipment is respectively provided with an evaporation gas outlet, a crystal outlet and an evaporation residual liquid outlet; the evaporation gas outlet is connected to the alkali preparation tank, the crystal outlet is connected to the salt refining tank, and the evaporation residual liquid outlet is also connected to the incinerator.

And a water vapor outlet of the rectifying tower A and an evaporation gas outlet of the MVR equipment are connected into a whole and then communicated with the alkali distribution tank.