Method for treating scaling substances of mechanical steam recompression device

Abstract

The invention relates to the technical field of preparation of phosphate flame retardant products, in particular to a method for treating scaling substances of a mechanical vapor recompression device, which comprises the following steps: S1) performing heat exchange on a cleaning solution in a first forced circulation heat exchanger and a second forced circulation heat exchanger of an MVR (mechanical vapor recompression) device, and circulating the cleaning solution in the MVR device; the cleaning solution comprises water, an alcohol substance and a component a; the component a comprises an alkaline substance or an alkaline solution; s2) collecting a scaling substance dissolving solution in the MVR device, standing, and separating an organic phase from a water phase; s3) mixing the organic phase with water, stirring, cleaning, dehydrating, measuring the mass content of the organic phase TCPP, and recovering; mixing the water phase obtained in the step S2) with the water phase after the organic phase is cleaned, and rectifying; and S4) evaporating and concentrating the rectified water phase, and centrifuging the concentrated solution to obtain salt and centrifugal mother liquor. According to the invention, scaling substances of the MVR device can be effectively dissolved, and TCPP products in the scaling substances can be effectively recovered.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of phosphate flame retardant products, and in particular to a method for treating scaling substances in a mechanical steam recompression device. Background Art

[0002] Tris(2-chloropropyl) phosphate (TCPP) is an additive low molecular weight halogen phosphorus flame retardant with the advantages of low volatility, hydrolysis resistance and strong weather resistance. It is widely used in flame retardant materials such as polyvinyl chloride, soft and hard polyurethane, epoxy resin, phenolic resin, etc. TCPP products are also used as plasticizers.

[0003] The domestic TCPP production process is basically mature, and the production process of manufacturers generally includes esterification, alkali washing, water washing, dehydration and other processes. Among them, the alkali washing, water washing and dehydration processes will produce a certain amount of wastewater, and about 1% of TCPP products will enter the wastewater during alkali washing and water washing.

[0004] TCPP production wastewater is often treated by evaporation and concentration using a mechanical vapor recompression (MVR) device. The MVR device is generally composed of evaporators, separators, compressors, circulating pumps, control cabinets and other components. In the process of treating TCPP production wastewater, the heat exchanger inside the evaporator has a significant decrease in heat exchange efficiency due to scaling problems. It needs to be regularly dismantled for manual mechanical cleaning of scaling materials. Scaling materials need to be outsourced as hazardous wastes. In addition, the shutdown of the MVR device during the cleaning period will lead to wastewater accumulation and abnormal adjustments to the production schedule, which seriously hinders the normal delivery of TCPP products.

[0005] At present, the TCPP product industry has saturated production capacity and fierce market competition. How to solve the scaling problem of TCPP wastewater MVR device to improve production line efficiency, recover TCPP in wastewater, reduce production costs, and reduce the generation of hazardous waste plays an important role in maintaining the competitive advantage of TCPP products.

[0006] Patent application document CN109912644B discloses a post-processing purification process for crude TCPP production. This process allows crude TCPP esterification products to stand and settle at 100-110°C for more than 12 hours, so that most of the catalyst sinks to the bottom and is recycled. Only the upper TCPP is washed and post-processed, and the waste water after washing is subjected to reduced pressure distillation to obtain distilled water and solid waste salt. Although this method recycles the catalyst at the bottom of TCPP, reducing the amount of catalyst used and the amount of wastewater generated, it is impossible to accurately control the amount of catalyst used in the subsequent esterification reaction. Too much catalyst will make the esterification reaction violent and the hydrolysis resistance of the product will decrease, affecting product performance. Too little catalyst will lead to a series of problems such as a reduced esterification reaction rate and incomplete reaction. At the same time, the crude esterification product needs to stand for more than 12 hours. Too long a standing time will lead to a decrease in production line utilization and an increase in product acid value.

[0007] Patent application document CN110550796B discloses a method for reducing the amount of waste liquid containing phosphate esters, in which the organic phase of the waste liquid is added to an excess of acid for acid hydrolysis reaction multiple times to reduce the generation of oil phase solid waste; however, this method does not take economic benefits into consideration, does not effectively recycle the phosphate esters in the wastewater, and the use of a large amount of acid during the operation will increase production costs.

[0008] The article "Experimental Study on Resource Utilization of Wastewater from the Production of Phosphate Flame Retardants" in Volume 35, Issue 7 of "Modern Chemical Industry" in July 2015 adopted the "coupled energy-saving distillation-solid separation-extraction" integrated process, and used distillation to recover propylene oxide, sodium chloride, titanium dioxide catalyst and TCPP products from TCPP wastewater. The distillation of wastewater consumes a large amount of steam; and the use of organic solvents as extractants to extract trace TCPP in the wastewater not only easily causes secondary pollution to the water body, but also increases the difficulty of the water treatment link and the cost of wastewater treatment. In addition, the extracted organic phase needs to be distilled and recovered again. The operation process is cumbersome and difficult to apply to the actual production process. Summary of the invention

[0009] In view of this, the technical problem to be solved by the present invention is to provide a method for treating scaling materials in a mechanical steam recompression device, which can effectively dissolve the scaling materials in the MVR device for treating tris(2-chloropropyl) phosphate (TCPP) wastewater and effectively recover the TCPP product therein.

[0010] The present invention provides a method for treating scaling materials in a mechanical steam recompression device, comprising the following steps:

[0011] S1) transporting the cleaning liquid to the forced circulation evaporator of the mechanical vapor recompression device, and under the action of the forced circulation pump, the cleaning liquid exchanges heat in the first forced circulation heat exchanger and the second forced circulation heat exchanger, and continuously circulates in the mechanical vapor recompression device;

[0012] The cleaning liquid comprises water, an alcohol substance and component a; the component a comprises an alkaline substance or an alkaline solution;

[0013] S2) collecting the scale solution in the mechanical steam recompression device, allowing it to stand, and separating the organic phase and the aqueous phase;

[0014] S3) mixing the organic phase with water, stirring and washing, dehydrating, determining the mass content of tris(2-chloropropyl) phosphate in the organic phase, and recovering the organic phase;

[0015] The aqueous phase obtained in step S2) is mixed with the aqueous phase after washing the organic phase, and distilled;

[0016] S4) evaporating and concentrating the water phase after the rectification, and centrifuging the concentrate to obtain salt and centrifugal mother liquor.

[0017] Preferably, in step S1), the component a comprises one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, ammonia water and liquid caustic soda.

[0018] Preferably, in step S1), the alcohol substance includes one or more of methanol, ethanol, propanol, ethylene glycol, glycerol, benzyl alcohol and cyclohexanol.

[0019] Preferably, in step S1), in the cleaning solution, the mass content of component a is 10% to 50%, and the mass content of alcohol substances is 1% to 30%.

[0020] Preferably, in step S1), the temperature of the cleaning liquid after heat exchange is 30-100°C.

[0021] Preferably, in step S1), during the heat exchange of the cleaning liquid, the vacuum degree in the first forced circulation heat exchanger is above -0.080 MPa.

[0022] Preferably, in step S2), the pH value of the scale dissolving solution is > 13;

[0023] The standing temperature is 60-90° C. and the standing time is 0.5-3 h.

[0024] Preferably, in step S3), the water accounts for 10% to 20% of the mass of the organic phase;

[0025] The stirring and cleaning temperature is 60-90°C;

[0026] Finally, the pH value of the aqueous phase after stirring and washing is 6-7.

[0027] Preferably, in step S3), the mass content of tris(2-chloropropyl) phosphate in the organic phase after stirring and washing is determined by gas chromatography;

[0028] In the organic phase, the mass content of TCPP is greater than 98.0%, and the mass content of alcohol substances is less than 1%.

[0029] Preferably, in step S3), after distillation, the mass content of alcohol in the obtained organic phase is greater than 99.0%.

[0030] The invention provides a method for treating scaling substances in a mechanical steam recompression device, comprising the following steps: S1) transporting a cleaning liquid to a forced circulation evaporator of the mechanical steam recompression device, and under the action of a forced circulation pump, the cleaning liquid exchanges heat in a first forced circulation heat exchanger and a second forced circulation heat exchanger, and continuously circulates in the mechanical steam recompression device; the cleaning liquid comprises water, an alcohol substance and a component a; the component a comprises an alkaline substance or an alkaline solution; S2) collecting a scale solution in the mechanical steam recompression device, and separating an organic phase from an aqueous phase after standing; S3) mixing the organic phase with water, stirring and cleaning, and after dehydration, determining the mass content of tris(2-chloropropyl) phosphate in the organic phase, and then recovering the mixture; mixing the aqueous phase obtained in step S2) with the aqueous phase after cleaning the organic phase, and performing rectification; S4) evaporating and concentrating the aqueous phase after rectification, and centrifuging the concentrated liquid to obtain salt and a centrifugal mother liquor. The treatment method provided by the invention can effectively dissolve the scaling substances of the MVR device for treating tris(2-chloropropyl) phosphate (TCPP) wastewater, and effectively recover the TCPP product therein. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A process flow chart of treating fouling materials in a mechanical steam recompression device according to an embodiment of the present invention;

[0032] Figure 2 This is the TCPP gas phase spectrum of normal production in the workshop;

[0033] Figure 3 This is the TCPP gas phase spectrum obtained in Example 12;

[0034] Figure 4 This is the TCPP gas phase spectrum obtained in Example 13. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In the process of treating TCPP production wastewater, the heat exchange efficiency of the internal heat exchanger of the evaporator is greatly reduced due to scaling. The applicant has found through research that the scaling substance is the complex substance obtained by the formation of hydrogen bonds between aluminum hydroxide in the wastewater and the TCPP product in the wastewater during the evaporation of the wastewater; the structural formula is shown in formula (1).

[0037]

[0038] The increased viscosity of the complexing substance causes it to adhere to the surface of the heat exchanger of the MVR device, and aluminum hydroxide has a large specific surface area and a certain positive charge, which enables aluminum hydroxide to physically adsorb organic matter and flocculate negatively charged impurities, such as silt and colloid particles.

[0039] In order to solve the scaling problem of the MVR device for treating TCPP production wastewater, the present invention provides a method for treating scaling substances in a mechanical steam recompression device, comprising the following steps:

[0040] S1) transporting the cleaning liquid to the forced circulation evaporator of the mechanical vapor recompression device, and under the action of the forced circulation pump, the cleaning liquid exchanges heat in the first forced circulation heat exchanger and the second forced circulation heat exchanger, and continuously circulates in the mechanical vapor recompression device;

[0041] The cleaning liquid comprises water, an alcohol substance and component a; the component a comprises an alkaline substance or an alkaline solution;

[0042] S2) collecting the scale solution in the mechanical steam recompression device, allowing it to stand, and separating the organic phase and the aqueous phase;

[0043] S3) mixing the organic phase with water, stirring and washing, dehydrating, measuring the mass content of tris(2-chloropropyl) phosphate (TCPP) in the organic phase, and recovering the organic phase;

[0044] The aqueous phase obtained in step S2) is mixed with the aqueous phase after washing the organic phase, and distilled;

[0045] S4) evaporating and concentrating the water phase after the rectification, and centrifuging the concentrate to obtain salt and centrifugal mother liquor.

[0046] Figure 1 A process flow chart of treating fouling materials in a mechanical steam recompression device provided in accordance with an embodiment of the present invention.

[0047] The mechanical vapor recompression device comprises:

[0048] Forced circulation evaporator;

[0049] A first forced circulation heat exchanger connected to the circulating liquid outlet of the forced circulation evaporator;

[0050] A second forced circulation heat exchanger connected to the liquid outlet of the first forced circulation heat exchanger; the liquid outlet of the second forced circulation heat exchanger is connected to the circulating liquid inlet of the forced circulation evaporator;

[0051] The first forced circulation heat exchanger, the second forced circulation heat exchanger and the forced circulation evaporator form a circulation loop through a forced circulation pump;

[0052] a gas-liquid separator connected to the steam outlet of the forced circulation evaporator;

[0053] A mechanical steam compressor is connected to the gas phase outlet of the gas-liquid separator; the gas phase outlet of the mechanical steam compressor is connected to the shell side of the first forced circulation heat exchanger and the shell side of the second forced circulation heat exchanger.

[0054] In certain embodiments of the present invention, both the first forced circulation heat exchanger and the second forced circulation heat exchanger are plate heat exchangers.

[0055] Regarding step S1):

[0056] The cleaning liquid is transported to the forced circulation evaporator of the mechanical vapor recompression device. Under the action of the forced circulation pump, the cleaning liquid exchanges heat in the first forced circulation heat exchanger and the second forced circulation heat exchanger, and continuously circulates in the mechanical vapor recompression device.

[0057] Specifically, they include:

[0058] Under the action of the forced circulation pump, the cleaning liquid is transported from the forced circulation evaporator to the first forced circulation heat exchanger and the second forced circulation heat exchanger for heat exchange, and enters the forced circulation evaporator after being heated to the evaporation temperature. The steam generated by the forced circulation evaporator is condensed in the gas-liquid separator, and the obtained condensate returns to the forced circulation evaporator, and enters the first forced circulation heat exchanger and the second forced circulation heat exchanger again through the forced circulation pump, and circulates in sequence.

[0059] The cleaning liquid exchanges heat with the fresh steam in the shell side in the first forced circulation heat exchanger and the second forced circulation heat exchanger, and enters the forced circulation evaporator after being heated to the evaporation temperature.

[0060] The cleaning liquid is selected from water, alcohol substances and component a; and the component a is selected from alkaline substances or alkaline solutions.

[0061] In certain embodiments of the present invention, the component a is selected from one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, ammonia water and liquid caustic soda; preferably sodium hydroxide. The mass concentration of the ammonia water is 20% to 30%, such as 25%. The mass concentration of the liquid caustic soda is 30% to 40%, such as 32%. In the cleaning solution, the mass content of component a is 10% to 50%, preferably 10% to 30%, such as 30%.

[0062] In certain embodiments of the present invention, the alcohol substance is selected from one or more of methanol, ethanol, propanol, ethylene glycol, glycerol, benzyl alcohol and cyclohexanol, preferably ethylene glycol. The mass content of the alcohol substance in the cleaning liquid is 1% to 30%, preferably 2% to 10%, such as 10%.

[0063] In certain embodiments of the present invention, the cleaning liquid is pumped into the forced circulation evaporator of the MVR device by a feed pump.

[0064] The process of heat exchange between the cleaning liquid and the fresh steam in the first forced circulation heat exchanger and the second forced circulation heat exchanger of the mechanical vapor recompression (MVR) device is the process of heating the cleaning liquid. The temperature of the cleaning liquid after heat exchange (heating) is 30-100°C, preferably 70-80°C. During the heat exchange of the cleaning liquid, the vacuum degree in the first forced circulation heat exchanger is above -0.080Mpa, for example -0.080Mpa.

[0065] Regarding step S2):

[0066] The scale solution in the mechanical vapor recompression (MVR) device is collected and allowed to stand to separate the organic phase and the aqueous phase.

[0067] The standing can be carried out in a reactor with a through-view mirror.

[0068] In certain embodiments of the present invention, the pH value of the scale dissolving solution is greater than 13.

[0069] In certain embodiments of the present invention, the standing time is 0.5 to 3 hours, preferably 1 to 2 hours, such as 2 hours; the standing temperature (ie, the insulation phase separation temperature) is 60 to 90°C, preferably 70 to 80°C, such as 75°C.

[0070] Regarding step S3):

[0071] The organic phase is mixed with water, stirred and washed, and dehydrated. After the mass content of tris(2-chloropropyl) phosphate (TCPP) in the organic phase is measured, the organic phase is returned to the production workshop for recycling.

[0072] The stirring and washing makes the organic phase transparent without obvious particulate impurities. In certain embodiments of the present invention, the number of stirring and washing is preferably 2 times. The water accounts for 10% to 20% of the mass of the organic phase, such as 15%. The temperature of the stirring and washing is 60 to 90°C, preferably 70 to 80°C, such as 75°C, 70°C. In certain embodiments of the present invention, the pH value of the aqueous phase after the stirring and washing is finally 6 to 7.

[0073] In certain embodiments of the present invention, the mass content of tris(2-chloropropyl) phosphate (TCPP) in the organic phase after stirring and washing is determined by gas chromatography.

[0074] In certain embodiments of the present invention, the dehydration is performed using a rotary evaporator.

[0075] The mass content of TCPP in the recovered organic phase is required to be greater than 98.0%, and the mass content of alcohols is less than 1%, so that it can be returned to the TCPP workshop for recycling. Preferably, the mass content of alcohols in the recovered organic phase is less than 0.3%.

[0076] In the present invention, the aqueous phase obtained in step S2) is mixed with the aqueous phase after washing the organic phase and distilled.

[0077] The aqueous phase after washing the organic phase includes the aqueous phase after stirring and washing and the aqueous phase obtained by dehydration.

[0078] The alcohols in the cleaning solution can be recovered by distillation and recycled. In certain embodiments of the present invention, the distillation is preferably ultra-gravity distillation. After distillation, the mass content of alcohols in the obtained organic phase is greater than 99.0%, and the recovered alcohols can be reused in the preparation of the cleaning solution.

[0079] Regarding step S4):

[0080] The water phase after the rectification is evaporated and concentrated, and the concentrate is centrifuged to obtain salt and centrifugal mother liquor.

[0081] The centrifugation is performed in a centrifuge.

[0082] The salt can be sold as a by-product.

[0083] Beneficial effects:

[0084] 1) A process route is provided for effectively dissolving the scaling materials in the MVR device and effectively recovering the TCPP product therein.

[0085] 2) The treatment method provided by the present invention is green, economical, and highly operable. The alcohol solvent used can be recycled and reused, which reduces the output of hazardous wastes in the TCPP production process and reduces the cost of outsourcing hazardous waste disposal for enterprises.

[0086] 3) It takes about 3 days to manually disassemble the MVR device to clean the scaling and installation process. The treatment method provided by the present invention only takes 0.5 days to clean the device, or even less time, avoiding the problem of long-term production stoppage caused by manual mechanical cleaning of scaling materials in the MVR device, and greatly improving the wastewater treatment efficiency of the TCPP production line.

[0087] 4) The present invention can dissolve the scaling material of the MVR device and recover TCPP. The recovered TCPP has a purity of more than 98.0%. It can be returned to the process device for further processing and sold externally, thereby increasing the comprehensive yield of TCPP products by about 0.6% to 0.8%.

[0088] 5) The treatment method of the present invention can save the cost of manual mechanical cleaning of the MVR device once a month, thereby reducing production operation costs.

[0089] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0090] In order to further illustrate the present invention, a method for treating scaling materials in a mechanical steam recompression device provided by the present invention is described in detail below in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0091] Example 1

[0092] Small test: The dissolution test method of the scaling material in the mechanical steam recompression device includes the following steps:

[0093] 1) The components and contents of the multi-component cleaning solution prepared in different proportions are shown in Table 1.

[0094] 2) Weigh 50 g of scale scraped from the forced circulation heat exchanger of the MVR device.

[0095] 3) The scale is placed in a beaker filled with cleaning solution and heated to a specified temperature, and then kept warm. The temperature is shown in Table 1.

[0096] 4) Observe the dissolution state of the scale in the beaker and record the dissolution time, as shown in Table 1.

[0097] 5) The scale solution obtained in step 4) is transferred to a separatory funnel for phase separation.

[0098] 6) Weigh the separated organic phase, add clean water at 20% of the weight of the organic phase, stir and wash with water and separate the phases twice to wash out excess alcohol substances and salts.

[0099] 7) The organic phase after washing was dehydrated by a rotary evaporator and weighed, and the mass content of tris(2-chloropropyl) phosphate (TCPP) was determined by gas chromatography.

[0100] The components and contents of the cleaning solution, as well as the recovery rate and mass content of TCPP are shown in Table 1. The temperature in Table 1 refers to the temperature after heating in the above step 3).

[0101] Table 1 Components and contents of cleaning solution, as well as recovery rate and purity of TCPP

[0102]

[0103] As can be seen from Table 1, in the cleaning solution, the proportion of component a and ethanol cannot be too low, otherwise it will affect the dissolution time and solubility, and increasing the temperature is conducive to promoting dissolution. Considering the recovery rate, purity and economy of TCPP, the cleaning solution component distribution ratio of the experimental group 12 is adopted: sodium hydroxide 30wt%, water 60wt%, ethylene glycol 10wt%.

[0104] Example 2

[0105] A method for treating scaling materials in a mechanical steam recompression device comprises the following steps:

[0106] 1) Prepare 4 t of cleaning solution according to experimental group 12.

[0107] 2) The cleaning liquid is pumped into the forced circulation evaporator of the mechanical vapor recompression device by the feed pump; under the action of the forced circulation pump, the cleaning liquid is transported from the forced circulation evaporator to the first forced circulation heat exchanger and the second forced circulation heat exchanger for heat exchange, and after being heated to the evaporation temperature, it enters the forced circulation evaporator, and the steam generated by the forced circulation evaporator is condensed in the gas-liquid separator, and the obtained condensate returns to the forced circulation evaporator, and enters the first forced circulation heat exchanger and the second forced circulation heat exchanger again through the forced circulation pump, and circulates in sequence.

[0108] The temperature of the cleaning liquid after heat exchange (temperature increase) is 70° C. During the heat exchange of the cleaning liquid, the vacuum degree in the first forced circulation heat exchanger is -0.080 MPa.

[0109] Step 2) The cycle time is 4 hours, and the evaporation capacity increases from 1.8 cubic meters / hour to 4.1 cubic meters / hour. The evaporation capacity is greater than 3.5 cubic meters / hour, which is considered to be restored to normal evaporation capacity.

[0110] 3) Collect the scale solution in the mechanical vapor recompression (MVR) device and weigh 6.73t. Test the pH value of the upper aqueous phase of the scale solution. If the pH value is greater than 13, place it in a reactor with a through-view mirror at 70°C for 1 hour to separate the organic phase and the aqueous phase.

[0111] 4) mixing the organic phase with water (the water accounts for 20% of the mass of the organic phase), stirring and washing at 70° C., stirring and washing for 2 times, until the organic phase is transparent without obvious particulate impurities, and the pH value of the aqueous phase after stirring and washing is 6-7; using a rotary evaporator to remove water from the washed organic phase and weighing it, using gas chromatography to determine that the mass content of tris(2-chloropropyl) phosphate (TCPP) in the stirred and washed organic phase is 99.59%, and the mass content of ethylene glycol is less than 0.1%, and the organic phase is returned to the production workshop for recycling and dehydration treatment;

[0112] The TCPP substance in the organic phase after washing weighed 2.21t. It was calculated that the recovered TCPP accounted for 80.9% of the mass of the scale.

[0113] The aqueous phase obtained in step 3) is mixed with the aqueous phase after washing the organic phase, weighing 4.4 t, and subjected to ultra-gravity distillation; after distillation, the obtained ethylene glycol can be reused to prepare the cleaning liquid. The weight of ethylene glycol recovered by distillation is 0.37 t, the ethylene glycol recovery rate is 92.5%, and the purity of the recovered ethylene glycol is 99.2%.

[0114] 5) The water phase after the rectification is evaporated and concentrated, and the concentrated solution is centrifuged in a centrifuge to obtain salt and centrifuged mother liquor. The salt can be sold as a by-product.

[0115] Example 3

[0116] 1) In this example, 0.37 t of ethylene glycol recovered in Example 2 was added with 0.03 t of fresh ethylene glycol to prepare a cleaning solution in the same proportion as in Example 2 (the mass content of sodium hydroxide in the cleaning solution was 30% and the mass content of ethylene glycol was 10%).

[0117] 2) The cleaning liquid is pumped into the forced circulation evaporator of the mechanical vapor recompression device by the feed pump; under the action of the forced circulation pump, the cleaning liquid is transported from the forced circulation evaporator to the first forced circulation heat exchanger and the second forced circulation heat exchanger for heat exchange, and after being heated to the evaporation temperature, it enters the forced circulation evaporator, and the steam generated by the forced circulation evaporator is condensed in the gas-liquid separator, and the obtained condensate returns to the forced circulation evaporator, and enters the first forced circulation heat exchanger and the second forced circulation heat exchanger again through the forced circulation pump, and circulates in sequence.

[0118] The temperature of the cleaning liquid after heat exchange (temperature increase) is 70° C. During the heat exchange of the cleaning liquid, the vacuum degree in the first forced circulation heat exchanger is -0.080 MPa.

[0119] Step 2) The cycle time is 4 hours, and the evaporation capacity increases from 1.9 cubic meters / hour to 4.2 cubic meters / hour. The evaporation capacity is greater than 3.5 cubic meters / hour, which is considered to be restored to normal evaporation capacity.

[0120] 3) Collect the scale solution in the mechanical vapor recompression (MVR) device and weigh 7.05t. Test the pH value of the upper aqueous phase of the scale solution. If the pH value is greater than 13, place it in a reactor with a through-view mirror at 70°C for 1 hour to separate the organic phase and the aqueous phase.

[0121] 4) mixing the organic phase with water (the water accounts for 20% of the mass of the organic phase), stirring and washing at 70° C., stirring and washing for 2 times, until the organic phase is transparent without obvious particulate impurities, and the pH value of the aqueous phase after stirring and washing is 6-7; using gas chromatography to determine the mass content of tris(2-chloropropyl) phosphate (TCPP) in the organic phase after stirring and washing is 99.61%, and the mass content of ethylene glycol is less than 0.1%, and the organic phase is returned to the production workshop for recycling and dehydration treatment;

[0122] The TCPP substance in the organic phase after washing weighed 2.53t. It was calculated that the recovered TCPP accounted for 82.9% of the mass of the scale.

[0123] The aqueous phase obtained in step 3) is mixed with the aqueous phase after washing the organic phase, weighing 4.6 t, and subjected to ultra-gravity distillation; after distillation, the obtained ethylene glycol can be reused to prepare the cleaning liquid. The weight of ethylene glycol recovered by distillation is 0.376 t, the ethylene glycol recovery rate is 94.0%, and the purity of the recovered ethylene glycol is 99.1%.

[0124] 5) The water phase after the rectification is evaporated and concentrated, and the concentrated solution is centrifuged in a centrifuge to obtain salt and centrifuged mother liquor. The salt can be sold as a by-product.

[0125] Comparing Example 2 with Example 3, Example 2 uses fresh ethylene glycol to prepare the cleaning liquid, while Example 3 uses recycled ethylene glycol to prepare the cleaning liquid. This shows that using recycled ethylene glycol to prepare the cleaning liquid can also achieve a good effect of cleaning the MVR device and thus recovering TCPP materials, and the solution is feasible.

[0126] Comparative Example 1

[0127] The indicators of TCPP produced normally in the workshop were compared with those of TCPP recovered in Examples 2 and 3. The results are shown in Table 2.

[0128] Normal production TCPP method in workshop:

[0129] A catalyst is added to phosphorus oxychloride, and then propylene oxide is added dropwise. After the reaction is completed, a crude TCPP product is obtained, and the product is obtained by removing low-boiling substances, alkali washing, water washing, and dehydration;

[0130] The molar ratio of the reaction raw material phosphorus oxychloride to the catalyst is 1:0.015; the catalyst is aluminum chloride; the reaction temperature range is 40-80°C, and the reaction is judged to be complete when the acid value is less than 2.0 mgKOH / g, and the addition of propylene oxide is stopped.

[0131] When removing low boiling substances, it is carried out under high temperature and vacuum conditions, the temperature is 150°C, the vacuum degree is -0.095Mpa, and the time is 20 minutes.

[0132] Regarding alkali washing, the mass ratio of crude TCPP, water and sodium hydroxide was 1:0.2:0.01, and the alkali washing temperature was 70°C.

[0133] Regarding water washing, the mass ratio of crude TCPP to water is 1:0.2, and the water washing temperature is 70°C.

[0134] The dehydration adopts the same temperature and vacuum conditions as the dehydration of low boiling points. After the dehydration is completed, the TCPP finished product is obtained.

[0135] Table 2 Comparison of TCPP produced normally in the workshop and TCPP recovered in Examples 2 and 3

[0136]

[0137]

[0138] Figure 2 This is the TCPP gas phase spectrum of normal production in the workshop (Comparative Example 1); Figure 3 The TCPP gas phase spectrum obtained in Example 2; Figure 4 This is the TCPP gas phase spectrum obtained in Example 3.

[0139] from Figures 2 to 4 It can be seen that the purity of the TCPP obtained in Example 2 and Example 3 and the TCPP product normally produced in the workshop are 99.59%, 99.61% and 99.39% respectively, and the purity of the recovered TCPP is even higher than that of the normally produced TCPP product. At the same time, the other indicators of the recovered TCPP are basically consistent with those of the normally produced TCPP product in the workshop.

[0140] The polyurethane foam flame retardant performance test was conducted using TCPP normally produced in the workshop and TCPP obtained in Example 2 and Example 3. The formula data that reached the V2 grade fire protection standard are shown in Table 3.

[0141] Table 3 Formula data that meet V2 fire protection standards

[0142]

[0143] As can be seen from Table 3, the purity of TCPP obtained in Examples 2 and 3 is higher than that of the normally produced TCPP product. Therefore, the amount of the recovered TCPP product used to meet the V2 fire protection standard is slightly lower than that of the normally produced TCPP product in the workshop, which proves that the recovered TCPP product (the TCPP product obtained in the embodiment of the present invention) maintains good flame retardant properties.

[0144] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating scaling materials in a mechanical steam recompression device, comprising the following steps: S1) transporting the cleaning liquid to the forced circulation evaporator of the mechanical vapor recompression device, and under the action of the forced circulation pump, the cleaning liquid exchanges heat in the first forced circulation heat exchanger and the second forced circulation heat exchanger, and continuously circulates in the mechanical vapor recompression device; The cleaning liquid comprises water, an alcohol substance and component a; the component a comprises an alkaline substance or an alkaline solution; S2) collecting the scale solution in the mechanical steam recompression device, allowing it to stand, and separating the organic phase and the aqueous phase; S3) mixing the organic phase with water, stirring and washing, dehydrating, determining the mass content of tris(2-chloropropyl) phosphate in the organic phase, and recovering the organic phase; The aqueous phase obtained in step S2) is mixed with the aqueous phase after washing the organic phase, and distilled; S4) evaporating and concentrating the water phase after the rectification, and centrifuging the concentrate to obtain salt and centrifugal mother liquor.

2. The processing method according to claim 1, characterized in that: In step S1), the component a includes one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, ammonia water and liquid caustic soda.

3. The processing method according to claim 1, characterized in that: In step S1), the alcohol substance includes one or more of methanol, ethanol, propanol, ethylene glycol, glycerol, benzyl alcohol and cyclohexanol.

4. The processing method according to claim 1, characterized in that: In step S1), in the cleaning solution, the mass content of component a is 10% to 50%, and the mass content of alcohol substances is 1% to 30%.

5. The processing method according to claim 1, characterized in that: In step S1), the temperature of the cleaning liquid after heat exchange is 30-100°C.

6. The processing method according to claim 1, characterized in that: In step S1), during the heat exchange of the cleaning liquid, the vacuum degree in the first forced circulation heat exchanger is above -0.080Mpa.

7. The processing method according to claim 1, characterized in that: In step S2), the pH value of the scale dissolving solution is greater than 13; The standing temperature is 60-90° C. and the standing time is 0.5-3 h.

8. The processing method according to claim 1, characterized in that: In step S3), the water accounts for 10% to 20% of the mass of the organic phase; The stirring and cleaning temperature is 60-90°C; Finally, the pH value of the aqueous phase after stirring and washing is 6-7.

9. The processing method according to claim 1, characterized in that: In step S3), the mass content of tris(2-chloropropyl) phosphate in the organic phase after stirring and washing is determined by gas chromatography; In the organic phase, the mass content of TCPP is greater than 98.0%, and the mass content of alcohol substances is less than 1%.

10. The processing method according to claim 1, characterized in that: In step S3), after distillation, the mass content of alcohol in the obtained organic phase is greater than 99.0%.

Images