Energy-saving method for producing trialkyl phosphite by linkage of liquid chlorine evaporation

Abstract

The present application relates to the technical field of chemical production process, and relates to an energy-saving method for producing trialkyl phosphite by linkage liquid chlorine evaporation, which comprises the following steps: liquid chlorine in a liquid chlorine storage tank is adjusted by a cut-off valve and an adjusting valve, and then sequentially enters a refrigerant evaporator to be preliminarily evaporated and then enters a hot water evaporator to be completely evaporated, and the gasified chlorine is sent to a chlorination section for use; the cold energy generated by the refrigerant evaporator is delivered to a trialkyl phosphite workshop and used for a caustic soda precooling process; the heated heat medium after heat exchange of the caustic soda precooling is returned to the refrigerant evaporator to provide heat for the preliminary evaporation of the liquid chlorine, thereby forming a linkage energy-saving system for recycling cold energy and heat energy. According to the present application, the low-temperature cold energy of the liquid chlorine is recovered by the refrigerant evaporator, and the waste heat after the precooling of the caustic soda is returned to be used for the preliminary evaporation of the liquid chlorine, so that the heat energy supply of the heat medium evaporator is significantly reduced, the steam consumption in the whole liquid chlorine evaporation process is reduced by one third, the steam energy consumption and production cost are effectively reduced, and the heat energy utilization rate is improved.

Description

Technical Field

[0001] This invention relates to the field of chemical production process technology, specifically to an energy-saving method for producing trialkyl phosphite through combined liquid chlorine evaporation. Background Technology

[0002] The earliest method for evaporating liquid chlorine was direct steam heating. However, due to safety concerns, this was changed to heating hot water with steam, and then using the hot water to vaporize the liquid chlorine. This process requires a large amount of steam for liquid chlorine evaporation.

[0003] The method of producing trimethyl phosphite or triethyl phosphite using phosphorus trichloride and alcohol as raw materials, and triethylamine or N,N,1-dimethylaniline as acid-binding agent requires the use of caustic soda for reduction reaction. The reaction is exothermic and requires low temperature. The caustic soda in the production process needs to be diluted with water to a certain concentration. The heat released by dilution consumes a large amount of cooling energy, which is provided by a refrigerant machine and requires a large amount of electrical energy. Summary of the Invention

[0004] The purpose of this invention is to provide an energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation, comprising: liquid chlorine in a liquid chlorine storage tank is regulated by a shut-off valve and a regulating valve, and then enters a refrigerant evaporator for preliminary evaporation, and then enters a hot water evaporator for complete evaporation; the vaporized chlorine gas is then sent to the chlorination section for use.

[0006] The cooling energy generated by the refrigerant evaporator is transported to the trialkyl phosphite workshop for use in the caustic soda precooling process.

[0007] After the caustic soda is pre-cooled and heat-exchanged, the heated medium is returned to the refrigerant evaporator to provide heat for the initial evaporation of liquid chlorine, forming a linkage energy-saving system that utilizes both cooling and heating.

[0008] Preferably, the refrigerant evaporator is a shell-and-tube heat exchanger, a coil heat exchanger, or a spiral plate heat exchanger, with a coil heat exchanger being the preferred option and a shell-and-tube evaporator being the second choice; the hot water evaporator can independently complete the evaporation of liquid chlorine when the refrigerant evaporator is not working.

[0009] Preferably, the refrigerant system is equipped with a refrigerant self-circulation pump and a refrigerant delivery pump; the self-circulation pump is used to enhance the heat exchange between the refrigerant and liquid chlorine, and the refrigerant delivery pump is used to deliver the low-temperature refrigerant to the caustic soda precooler.

[0010] Preferably, the refrigerant is sodium chloride brine, calcium chloride brine, or an aqueous solution of ethylene glycol.

[0011] Preferably, the caustic soda precooler uses a shell and tube heat exchanger, a coil heat exchanger, or a spiral plate heat exchanger, with a spiral plate heat exchanger being the preferred option.

[0012] Preferably, the trialkyl phosphite is trimethyl phosphite or triethyl phosphite, and the production process of the trialkyl phosphite includes synthesis, water washing, and may also include one or more of drying, distillation, and rectification.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] Liquid chlorine evaporation reduces steam consumption by one-third.

[0015] The evaporation capacity of 100t liquid chlorine can reduce the cooling capacity of trialkyl phosphite by 250,000 kcal / h. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the three-dimensional structure of the present invention.

[0017] In the diagram: 1. Liquid chlorine storage tank; 2. Shut-off valve; 3. Regulating valve; 4. Refrigerant evaporator; 5. Pump set; 501. Self-circulating pump; 502. Refrigerant transfer pump; 6. Hot water evaporator; 7. Hot water generator; 8. Dilute alkali storage tank; 9. Caustic soda precooler. Detailed Implementation

[0018] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0019] Please see Figure 1 As shown, an energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation is described. Liquid chlorine in liquid chlorine storage tank 1 is controlled to flow at a rate of 3 to 5 tons / hour via shut-off valve 2 and regulating valve 3, and then enters refrigerant evaporator 4 for low-temperature preliminary evaporation. Liquid chlorine indirectly exchanges heat with refrigerant in refrigerant evaporator 4, and by utilizing the low-temperature vaporization characteristics of liquid chlorine (boiling point -34℃, freezing point -101℃), the temperature of refrigerant is reduced to -8℃ to -5℃ and stably controlled at -5℃.

[0020] The refrigerant evaporator 4 is equipped with a refrigerant self-circulation pump 501 to enhance the heat exchange efficiency between the refrigerant and liquid chlorine and improve the initial evaporation effect of liquid chlorine; at the same time, it is equipped with a refrigerant delivery pump 502 to quantitatively deliver the low-temperature refrigerant to the caustic soda precooler 9 in the trialkyl phosphite workshop.

[0021] The liquid chlorine / chlorine gas mixture that has undergone preliminary evaporation enters the hot water evaporator 6, where it is heated to 20℃~60℃ by the hot water generator 7 to achieve complete vaporization. The vaporized chlorine gas is then stably sent to the chlorination section for use.

[0022] The trimethyl phosphite workshop and the triethyl phosphite workshop store dilute alkali solutions with a concentration of 15%±5% in dilute alkali storage tanks 8, and each pumps them to the caustic soda precooler 9 through pump group 5 at a flow rate of 7200 kg / hour. The initial temperature of the dilute alkali solution is 35℃~40℃. After heat exchange with the refrigerant, the temperature drops to 8℃~12℃. The precooled dilute alkali solution then enters the reduction and water washing process of trialkyl phosphite production, reducing the heat load of the reaction system and reducing the cooling demand.

[0023] After absorbing the heat of caustic soda dilution in the caustic soda precooler 9, the refrigerant temperature rises and carries the waste heat back to the refrigerant evaporator 4, providing heat for the initial evaporation of liquid chlorine, reducing the steam consumption of the hot water evaporator 6, and forming a closed loop of cooling and heating.

[0024] The refrigerant evaporator 4 uses a coil heat exchanger, but a shell-and-tube heat exchanger or a spiral plate heat exchanger can also be selected; the caustic soda precooler 9 uses a spiral plate heat exchanger, but a shell-and-tube or coil heat exchanger can also be selected; the hot water evaporator 6 can independently complete the evaporation of liquid chlorine when the refrigerant evaporator 4 is not working; the refrigerant is selected from sodium chloride brine, calcium chloride brine, or ethylene glycol aqueous solution, with an applicable temperature range of -20℃ to 10℃, and does not solidify or corrode the equipment.

[0025] The system is equipped with temperature and pressure interlock protection: when the refrigerant temperature is below -10℃, the hot water flow rate of the heat transfer medium evaporator is automatically increased to ensure complete evaporation of liquid chlorine; the evaporator is equipped with an overpressure relief device and a liquid chlorine regulation or shut-off device to ensure safe operation.

[0026] Actual operation has verified that this process reduces the amount of steam used for liquid chlorine evaporation by one-third; for every 100 tons of liquid chlorine evaporation, the refrigeration load for trialkyl phosphite production can be reduced by 250,000 kcal / hour, achieving dual energy savings in both liquid chlorine evaporation and trialkyl phosphite production, with stable, safe and environmentally friendly operation.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation, characterized in that: After being regulated by the shut-off valve and the regulating valve, the liquid chlorine in the liquid chlorine storage tank enters the refrigerant evaporator for preliminary evaporation and then enters the hot water evaporator to complete the evaporation. The vaporized chlorine is then sent to the chlorination section for use. The cooling energy generated by the refrigerant evaporator is transported to the trialkyl phosphite workshop for use in the caustic soda precooling process. After the caustic soda is pre-cooled and heat-exchanged, the heated medium is returned to the refrigerant evaporator to provide heat for the initial evaporation of liquid chlorine, forming a linkage energy-saving system that utilizes both cooling and heating.

2. The energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation according to claim 1, characterized in that: The refrigerant evaporator is a shell-and-tube heat exchanger, a coil heat exchanger, or a spiral plate heat exchanger, preferably a coil heat exchanger, and secondarily a shell-and-tube evaporator; the hot water evaporator can independently complete the evaporation of liquid chlorine when the refrigerant evaporator is not working.

3. The energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation according to claim 2, characterized in that: The refrigerant system is equipped with a refrigerant self-circulation pump and a refrigerant delivery pump; the self-circulation pump is used to enhance the heat exchange between the refrigerant and liquid chlorine, and the refrigerant delivery pump is used to deliver the low-temperature refrigerant to the caustic soda precooler.

4. The energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation according to claim 3, characterized in that: The refrigerant is sodium chloride saline, calcium chloride saline, or ethylene glycol aqueous solution.

5. The energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation according to claim 4, characterized in that: The caustic soda precooler uses a shell and tube heat exchanger, a coil heat exchanger, or a spiral plate heat exchanger, with a spiral plate heat exchanger being preferred.

6. The energy-saving method for producing trialkyl phosphite by combined liquid chlorine evaporation according to claim 5, characterized in that: The trialkyl phosphite is trimethyl phosphite or triethyl phosphite. The production process of the trialkyl phosphite includes synthesis, water washing, and may also include one or more of drying, distillation, and rectification.

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