Low-energy-consumption purification process for chloromethane in organic silicon production
By adopting a low-energy chloromethane purification process in the production of silicones, distillation and rectification are used to utilize the phase change enthalpy of gaseous chloromethane for distillation, the problems of low chloromethane purity and high energy consumption are solved, and the chloromethane purification effect with high purity and low energy consumption is achieved.
Patent Information
- Application Number
- CN202510355596.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2025-06-27
AI Technical Summary
In the silicone production process, chloromethane is not purified due to impurity contamination, and the existing distillation purification process has high energy consumption, resulting in an increase in production costs.
A low-energy consumption chloromethane purification process is adopted, and the phase change enthalpy of the gaseous chloromethane after pressure is lifted is distilled and rectified to achieve high energy-saving purification of chloromethane. This process includes the use of a chloromethane de-height column reboiler and a distillation column, which uses the phase change enthalpy of hot chloromethane for heating, and makes full use of the phase change enthalpy of high-temperature and high-pressure chloromethane.
High energy-saving purification of chloromethane has been achieved, with a purity of more than 99.99%, and a significant reduction in energy consumption. The energy consumption per ton of chloromethane only requires about 0.05 tons of steam.
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Figure CN120208753A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of organosilicon production, and particularly relates to a purification process for methyl chloride in organosilicon production with low energy consumption. Background Art
[0002] In the process of organosilicon production, methyl chloride is used to synthesize methylchlorosilane with silicon powder. Hydrogen chloride and methanol generated during the hydrolysis process of methylchlorosilane in each process continue to synthesize methyl chloride for use in the synthesis of methylchlorosilane. However, in the actual production process, due to the complex reaction between methyl chloride and silicon powder and the large number of by-products, impurities generated by side reactions are carried in the hydrogen chloride reproduced during the subsequent production process, resulting in impurities (mainly 2,2,3-trimethylbutane and 2,4-dimethylpentane) carried in the synthesized methyl chloride. Methyl chloride contains about 100 ppm of impurities (mainly chloroethane) due to other miscellaneous alkanes carried in methanol.
[0003] In the conventional organosilicon production process, the synthesized methyl chloride gas contains about 500 ppm of impurities (chloroethane, 2,2,3-trimethylbutane, 2,4-dimethylpentane, etc.) after alkali washing and sulfuric acid drying treatment. This part of the gas is compressed to 0.8 MPag by a compressor and then condensed into liquid methyl chloride, and then transported to the methylchlorosilane synthesis device to react with silicon powder. The purity of the methyl chloride produced in the actual methyl chloride production process is about 99.95%. The carried impurities are all stable organic substances and cannot be directly removed. If this part of methyl chloride is rectified, higher-purity methyl chloride can be obtained, but the rectification energy consumption is relatively high. About 1.2 t of steam is consumed for rectifying and purifying each ton of methyl chloride, resulting in a significant increase in production costs.
[0004] In view of this, the present invention proposes a new purification process for methyl chloride in organosilicon production, and this purification process has low energy consumption. Summary of the Invention
[0005] The object of the present invention is to provide a purification process for methyl chloride in organosilicon production with low energy consumption, and utilize the phase change enthalpy of the pressurized gaseous methyl chloride to achieve highly energy-saving purification of methyl chloride.
[0006] In order to achieve the above object, the technical solution adopted is as follows:
[0007] A purification process for methyl chloride in organosilicon production with low energy consumption, comprising the following steps:
[0008] (1) The methyl chloride gas is pressurized to 0.9 - 1.1 MPag by a compressor to obtain methyl chloride gas 1;
[0009] (2) The methyl chloride gas 1 is transported to the reboiler of the methyl chloride stripping tower and cooled to a liquid state to obtain methyl chloride liquid 1;
[0010] (3) The methyl chloride liquid 1 enters from the top of the methyl chloride stripping tower. After being depressurized to 0.68 - 0.76 MPag, it is heat-exchanged with the methyl chloride gas 1 described above, thereby performing stripping and purification treatment;
[0011] The methyl chloride gas 1 after heat exchange becomes a liquid phase and is transported to the reboiler of the methyl chloride stripping tower, which is the chlorosilane liquid 1;
[0012] The methyl chloride gas extracted from the top of the methyl chloride stripping tower is transported to the condenser at the top of the methyl chloride stripping tower and cooled into a liquid state to obtain methyl chloride liquid 2;
[0013] (4) The bottom liquid of the methyl chloride stripping tower enters from the top of the methyl chloride rectification tower. After being depressurized to 0.4 - 0.54 MPag, rectification is carried out. The methyl chloride gas extracted from the top is transported to the condenser at the top of the methyl chloride rectification tower and cooled into a liquid state to obtain methyl chloride liquid 3.
[0014] Furthermore, in the step (1), the temperature of the methyl chloride gas 1 is 100 - 150 °C;
[0015] In the step (2), the pressure of the methyl chloride liquid 1 is 0.9 - 1.2 MPag, and the temperature is 45 - 50 °C.
[0016] Still further, in the step (1), the pressure of the methyl chloride gas 1 is 0.9 MPag, and the temperature is 125 °C;
[0017] In the step (2), the pressure of the methyl chloride liquid 1 is 0.9 MPag.
[0018] Furthermore, in the step (3), the temperature of the stripping treatment is 33 - 40 °C, and the pressure is 0.68 - 0.76 MPag.
[0019] Still further, in the step (3), it is depressurized to 0.75 MPag, the temperature of the stripping treatment is 38 °C, and the pressure is 0.75 MPag.
[0020] Furthermore, in the step (3), the non-condensable gas in the condenser at the top of the methyl chloride stripping tower is sent out for tail gas treatment.
[0021] Furthermore, in the step (3), after the bottom liquid of the methyl chloride stripping tower enters the reboiler of the methyl chloride stripping tower and becomes a gas phase, it is then transported back to the methyl chloride stripping tower.
[0022] Furthermore, in the step (4), the temperature of the rectification treatment is 40 - 80 °C, and the pressure is 0.4 - 0.54 MPag.
[0023] Furthermore, in the step (4), the temperature for rectification treatment is 60°C and the pressure is 0.5 MPag.
[0024] Furthermore, in the step (4), the bottom liquid of the methyl chloride rectification column enters the reboiler of the methyl chloride rectification column, turns into gas phase, and then is transported back to the methyl chloride rectification column.
[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0026] 1. The technical solution of the present invention uses a single-stage stripping method + residue rectification method to directly produce methyl chloride with a purity exceeding 99.99%.
[0027] 2. In the technical solution of the present invention, the high-energy-consuming methyl chloride stripping column uses the phase change enthalpy of hot methyl chloride for heating, fully utilizing the phase change enthalpy of high-temperature and high-pressure methyl chloride. The methyl chloride rectification column uses traditional rectification technology, but the amount of methyl chloride after stripping only accounts for about 3% of the raw material methyl chloride, achieving the separation of more than 99% of the impurities in methyl chloride with extremely low energy consumption (about 0.05 tons of steam per ton of methyl chloride). BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 is a flow chart of the present invention;
[0029] In the drawings, equipment E-0501 is the reboiler of the methyl chloride stripping column, equipment E-0502 is the reboiler of the methyl chloride rectification column, equipment E-0503 is the top condenser of the methyl chloride stripping column, equipment E-0504 is the top condenser of the methyl chloride rectification column, equipment K-0501 is the methyl chloride compressor, equipment C-0501 is the methyl chloride stripping column, equipment C-0502 is the methyl chloride rectification column, equipment V-0501 is the reflux drum of the methyl chloride rectification column, and equipment P-0501 is the reflux pump of the methyl chloride rectification column.
[0030] Material A is raw material methyl chloride, material B is finished product methyl chloride, material C1 is the vent gas from the methyl chloride stripping column, material C2 is the vent gas from the methyl chloride rectification column, and material D is miscellaneous alkanes. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0031] In order to further elaborate on a purification process for methyl chloride in the production of low-energy-consuming silicone, and to achieve the intended invention purpose, the following, in combination with preferred embodiments, details the specific implementation manner, structure, characteristics, and effects of a purification process for methyl chloride in the production of low-energy-consuming silicone proposed according to the present invention. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.
[0032] The following will further introduce in detail a purification process of methyl chloride in the production of organosilicon with low energy consumption according to specific embodiments of the present invention:
[0033] During the actual production process of methyl chloride, the impurities carried are all stable organic substances and cannot be directly removed. If this part of methyl chloride is rectified, methyl chloride with a relatively high purity can be obtained, but the rectification energy consumption is relatively high, resulting in an increase in production costs. In view of this situation, the present invention has been improved. The specific embodiment of the present invention is as follows:
[0034] Example 1.
[0035] Combined with Figure 1 , the specific operation steps are as follows:
[0036] (1) The methyl chloride gas synthesized during the conventional organosilicon production process is obtained as material A after alkali washing and sulfuric acid drying.
[0037] (2) After pressurizing material A to 0.9 MPag using a methyl chloride compressor (equipment K - 0501), the methyl chloride gas is also heated to 125 °C to obtain methyl chloride gas 1.
[0038] (3) The methyl chloride gas 1 is transported to the reboiler of the high methyl chloride stripping tower (equipment E - 0501) to be cooled into a liquid state to obtain methyl chloride liquid 1. The pressure of methyl chloride liquid 1 is 0.9 MPag, and the temperature is 50 °C.
[0039] The first methyl chloride liquid 1 is obtained by cooling methyl chloride gas 1 through the reboiler of the high methyl chloride stripping tower (equipment E - 0501). And the subsequent methyl chloride liquid 1 is: methyl chloride gas 1 exchanges heat with the high methyl chloride stripping tower (equipment C - 0501) and becomes the liquid-phase methyl chloride.
[0040] (4) Methyl chloride liquid 1 enters from the top of the high methyl chloride stripping tower (equipment C - 0501), is depressurized to 0.75 MPag, and then undergoes stripping treatment. The temperature of the stripping treatment is 38 °C, and the pressure is 0.75 MPag.
[0041] After the pressure of methyl chloride liquid 1 is reduced, the temperature drops, generally to 33 - 38 °C (according to the pressure change) °C, and a small part vaporizes. After being heated to 38 °C during the stripping process, the liquid methyl chloride liquid 1 evaporates into a gas phase, and after gas-liquid mass transfer and heat transfer with the liquid methyl chloride entering from the top of the tower in the tower, methyl chloride gas at 38 °C, 0.75 MPag, and a purity of 99.995% is obtained at the top of the tower. After being cooled to 35 °C using circulating water through the condenser at the top of the high methyl chloride stripping tower (equipment E - 0503), liquid finished methyl chloride (material B) is obtained, and the liquid methyl chloride is transported to the product storage tank. The non-condensable gas (material C1) in the condenser at the top of the high methyl chloride stripping tower is sent to the tail gas treatment.
[0042] The bottom liquid of the high - tower of methyl chloride enters the reboiler of the high - tower of methyl chloride. Due to the reduction of its own pressure, after being heated by methyl chloride gas 1, it becomes a gas phase and enters the high - tower of methyl chloride and flows to the top of the tower. During the process, mass transfer occurs with the methyl chloride liquid supplied to the top of the tower, realizing the purification of methyl chloride. The residue in the tower bottom (the residue less than 3% remaining) enters the methyl chloride rectification tower for separation and purification.
[0043] After the high - tower separation, more than 97% of the methyl chloride in the feed amount of material A can be rectified, and the impurities in the produced methyl chloride are ≤ 50 ppm.
[0044] Among them, during the rectification process, the methyl chloride gas 1 after being heated and pressurized is used for heat exchange. After heat exchange, the methyl chloride gas 1 becomes a liquid phase and is transported to the reboiler of the high - tower of methyl chloride. At this time, the pressure is 0.9 MPag and the temperature is 38 - 45 °C, obtaining chlorosilane liquid 1.
[0045] Since the methyl chloride gas 1 is after being heated and pressurized, the heat released during the process of cooling and becoming liquid is greater than the heat released during the process of the decompressed methyl chloride liquid becoming gas. The present invention is conducive to using the large amount of heat released during the process of the heated and pressurized methyl chloride gas becoming liquid to meet the heat demand required for the rectification treatment of the high - tower of methyl chloride, thereby realizing the highly energy - saving purification of methyl chloride.
[0046] (5) 3% of the bottom liquid 1 of the high - tower of methyl chloride in the feed amount of material A enters from the top of the methyl chloride rectification tower (equipment C - 0502). After being depressurized to 0.5 MPag, rectification is carried out. The temperature for rectification treatment is 60 °C and the pressure is 0.5 MPag.
[0047] The reboiler of the methyl chloride rectification tower (equipment E - 0502) uses 0.5 MPag steam to heat the methyl chloride containing impurities to generate gas, which undergoes gas - liquid mass transfer (the principle of rectifying and separating components in the material, using a tower device where the gas flows from the tower bottom to the top, the liquid phase flows from the top to the bottom, the two phases fully contact in the tower internals, the heavier components in the gas phase tend to transfer to the liquid phase, and the lighter components in the liquid phase tend to transfer to the gas phase to achieve component separation) and heat transfer with the liquid methyl chloride (i.e., bottom liquid 1) entering the methyl chloride rectification tower (equipment C - 0502). At the top of the tower, methyl chloride gas at 60 °C, 0.5 MPag, and a purity of 99.995% is obtained. After being condensed to 20 °C by using - 10 °C chilled brine in the top condenser of the methyl chloride rectification tower (equipment E - 0504), high - purity liquid methyl chloride is obtained, and the non - condensable gas (material C2) in the system is vented to the tail gas treatment.
[0048] High-purity liquid methyl chloride enters the reflux drum of the methyl chloride rectification tower (equipment V-0501). Part of it is pumped by the reflux pump of the rectification tower (equipment P-0501) and transported to the methyl chloride product storage tank together with the high-purity methyl chloride (material B) drawn from the top of the de-tower. Part of it is refluxed to the methyl chloride rectification tower and the methyl chloride de-tower (to control the stability of the bottom liquid level).
[0049] The material drawn from the bottom of the methyl chloride rectification tower is other impurities in methyl chloride (mainly chloroethane, water, 2,2,3-trimethylbutane, 2,4-dimethylpentane). This part of the impurities (material D) is transported to the waste liquid treatment section. Part of the bottom liquid can also enter the reboiler of the methyl chloride rectification tower, turn into gas phase, and then be transported back to the methyl chloride rectification tower: the amount of liquid phase material entering the reboiler depends on the heat supplied by the reboiler. The higher the heat, the more vaporized material and the more material needs to be supplied. This part does not require additional control, and natural thermosiphon can achieve the cycle.
[0050] Example 2.
[0051] Combined Figure 1 , the specific operation steps are as follows:
[0052] (1) The methyl chloride gas synthesized in the conventional organosilicon production process is obtained as material A after alkali washing and sulfuric acid drying.
[0053] (2) After pressurizing material A to 1.0 MPag using the methyl chloride compressor (equipment K-0501), the methyl chloride gas is also heated to 140 °C to obtain methyl chloride gas 1.
[0054] (3) Transport methyl chloride gas 1 to the reboiler of the methyl chloride de-tower (equipment E-0501) to be cooled into liquid, obtaining methyl chloride liquid 1. The pressure of methyl chloride liquid 1 is 1.0 MPag and the temperature is 50 °C.
[0055] (4) Methyl chloride liquid 1 enters from the top of the methyl chloride de-tower (equipment C-0501), is depressurized to 0.68 MPag, and then undergoes stripping treatment. The temperature of the stripping treatment is 33 °C and the pressure is 0.68 MPag.
[0056] After methyl chloride liquid 1 is depressurized, its temperature drops according to the pressure change, and a small part vaporizes. During the stripping process, after heating to 33 °C, the liquid methyl chloride liquid 1 evaporates into gas phase. After gas-liquid mass transfer and heat transfer with the liquid methyl chloride entering the tower top in the tower, methyl chloride gas at 33 °C, 0.68 MPag, and purity of 99.995% is obtained at the tower top. After being cooled to 30 °C using circulating water by the condenser at the top of the methyl chloride de-tower (equipment E-0503), liquid finished methyl chloride (material B) is obtained. The liquid methyl chloride is transported to the product storage tank. The non-condensable gas (material C1) in the condenser at the top of the methyl chloride de-tower is sent out for tail gas treatment.
[0057] The bottom liquid of the high chlorine methane removal tower enters the reboiler of the high chlorine methane removal tower. Due to the reduction of its own pressure, it is heated by the chlorine methane gas 1 and becomes a gas phase, then enters the high chlorine methane removal tower and flows towards the top. During the process, mass transfer occurs with the chlorine methane liquid fed into the tower top, realizing the purification of chlorine methane. The remaining materials at the bottom of the tower (residual materials less than 3%) enter the chlorine methane rectification tower for separation and purification.
[0058] After the high removal, more than 97% of the chlorine methane in the feed amount of material A can be rectified, and the impurities in the produced chlorine methane are ≤50 ppm.
[0059] Among them, during the rectification process, the chlorine methane gas 1 after heating and pressurization is used for heat exchange. After heat exchange, the chlorine methane gas 1 becomes a liquid phase and is transported to the reboiler of the high chlorine methane removal tower. At this time, the pressure is 1.0 MPag and the temperature is 38 - 45°C, obtaining the chlorosilane liquid 1.
[0060] (5) The bottom liquid 1 of the high chlorine methane removal tower with 3% of the feed amount of material A enters from the top of the chlorine methane rectification tower (equipment C - 0502). After the pressure is reduced to 0.4 MPag, rectification is carried out. The temperature for rectification treatment is 40°C and the pressure is 0.4 MPag.
[0061] The reboiler of the chlorine methane rectification tower (equipment E - 0502) uses 0.5 MPag steam to heat the impure chlorine methane to generate gas, which undergoes gas - liquid mass transfer (the principle of rectifying and separating components in the material, using a tower device where the gas flows from the bottom of the tower to the top, the liquid phase flows from the top of the tower to the bottom, the two phases fully contact in the tower internals, the heavy components in the gas phase tend to transfer to the liquid phase, and the light components in the liquid phase tend to transfer to the gas phase to achieve component separation) and heat transfer with the liquid chlorine methane (i.e., the bottom liquid 1) entering the chlorine methane rectification tower (equipment C - 0502). At the top of the tower, chlorine methane gas at 40°C, 0.4 MPag, and with a purity of 99.995% is obtained. After being condensed to 20°C by using - 10°C chilled brine in the top condenser of the chlorine methane rectification tower (equipment E - 0504), high - purity liquid chlorine methane is obtained, and the non - condensable gas (material C2) in the system is vented to the tail gas treatment.
[0062] The high - purity liquid chlorine methane enters the reflux drum of the chlorine methane rectification tower (equipment V - 0501). Using the reflux pump of the rectification tower (equipment P - 0501), part of it is transported to the chlorine methane finished product storage tank together with the high - purity chlorine methane (material B) taken out from the top of the high removal tower, and part of it is refluxed to the chlorine methane rectification tower and the high chlorine methane removal tower (for controlling the stability of the bottom liquid level).
[0063] The material withdrawn from the bottom of the methyl chloride rectification column is other impurities in methyl chloride (mainly chloroethane, water, 2,2,3 - trimethylbutane, 2,4 - dimethylpentane). This part of the impurities (material D) is transported to the waste liquid treatment section. Part of the bottom liquid can also enter the reboiler of the methyl chloride rectification column, turn into gas phase, and then be transported to the methyl chloride rectification column: the amount of liquid phase material entering the reboiler depends on the heat supplied by the reboiler. The higher the heat, the more material needs to be vaporized and the more material needs to be supplied. This part does not require additional control, and natural thermosiphon can achieve the circulation.
[0064] Example 3.
[0065] Combined with Figure 1 , the specific operation steps are as follows:
[0066] (1) The methyl chloride gas synthesized in the conventional organosilicon production process is obtained as material A after alkali washing and sulfuric acid drying.
[0067] (2) After pressurizing material A to 1.1 MPag using a methyl chloride compressor (equipment K - 0501), the methyl chloride gas is also heated to 150 °C to obtain methyl chloride gas 1.
[0068] (3) Transport methyl chloride gas 1 to the reboiler of the methyl chloride de - high tower (equipment E - 0501) to be cooled into a liquid state to obtain methyl chloride liquid 1. The pressure of methyl chloride liquid 1 is 1.1 MPag and the temperature is 50 °C.
[0069] (4) Methyl chloride liquid 1 enters from the top of the methyl chloride de - high tower (equipment C - 0501), is depressurized to 0.76 MPag, and then undergoes stripping treatment. The temperature of the stripping treatment is 40 °C and the pressure is 0.76 MPag.
[0070] After methyl chloride liquid 1 is depressurized, its temperature drops according to the pressure change, and a small part vaporizes. During the stripping process, after being heated to 40 °C, the liquid methyl chloride liquid 1 evaporates into a gas phase. After gas - liquid mass transfer and heat transfer with the liquid methyl chloride entering from the top of the tower in the tower, methyl chloride gas at 40 °C, 0.76 MPag, and a purity of 99.995% is obtained at the top of the tower. After being cooled to 30 °C using circulating water by the condenser at the top of the methyl chloride de - high tower (equipment E - 0503), liquid finished methyl chloride (material B) is obtained. The liquid methyl chloride is transported to the product storage tank. The non - condensable gas (material C1) in the condenser at the top of the methyl chloride de - high tower is sent to the tail gas treatment.
[0071] The bottom liquid of the methyl chloride de - high tower enters the reboiler of the methyl chloride de - high tower. Due to the reduction of its own pressure and being heated by methyl chloride gas 1, it turns into a gas phase and enters the methyl chloride de - high tower and flows towards the top. During the process, mass transfer occurs with the liquid methyl chloride supplied from the top of the tower to achieve the purification of methyl chloride. The remaining material at the bottom of the tower (residual material less than 3%) enters the methyl chloride rectification column for separation and purification.
[0072] After separation, more than 97% of the methyl chloride in the feed rate of material A can be rectified, and the impurities in the produced methyl chloride are ≤50 ppm.
[0073] Among them, in the rectification process, the methyl chloride gas 1 after heating and pressurization is used for heat exchange. After heat exchange, the methyl chloride gas 1 becomes a liquid phase and is transported to the reboiler of the methyl chloride stripping tower. At this time, the pressure is 1.1 MPag and the temperature is 38 - 45 °C, obtaining chlorosilane liquid 1.
[0074] (5) The bottom liquid 1 of the methyl chloride stripping tower, which is 3% of the feed rate of material A, enters from the top of the methyl chloride rectification tower (equipment C - 0502). After depressurizing to 0.54 MPag, rectification is carried out. The temperature for rectification treatment is 80 °C and the pressure is 0.54 MPag.
[0075] The reboiler of the methyl chloride rectification tower (equipment E - 0502) uses 0.5 MPag steam to heat the methyl chloride containing impurities to generate gas, which undergoes gas - liquid mass transfer (the principle of rectifying and separating components in the material, using a tower device where the gas flows from the bottom of the tower to the top, and the liquid phase flows from the top of the tower to the bottom. The two phases fully contact in the tower internals. The heavy components in the gas phase tend to transfer to the liquid phase, and the light components in the liquid phase tend to transfer to the gas phase to achieve component separation) and heat transfer with the liquid methyl chloride (i.e., bottom liquid 1) entering the methyl chloride rectification tower (equipment C - 0502). At the top of the tower, methyl chloride gas at 80 °C, 0.54 MPag, and a purity of 99.995% is obtained. After being condensed to 20 °C by using - 10 °C chilled brine in the condenser at the top of the methyl chloride rectification tower (equipment E - 0504), high - purity liquid methyl chloride is obtained, and the non - condensable gas (material C2) in the system is vented to the tail gas treatment.
[0076] The high - purity liquid methyl chloride enters the reflux drum of the methyl chloride rectification tower (equipment V - 0501). Using the reflux pump of the rectification tower (equipment P - 0501), part of it is transported to the methyl chloride product storage tank together with the high - purity methyl chloride (material B) drawn from the top of the stripping tower, and part of it is refluxed to the methyl chloride rectification tower and the methyl chloride stripping tower (for controlling the stability of the bottom liquid level).
[0077] The material drawn from the bottom of the methyl chloride rectification tower is other impurities in methyl chloride (mainly chloroethane, water, 2,2,3 - trimethylbutane, 2,4 - dimethylpentane). This part of the impurities (material D) is transported to the waste liquid treatment section. Also, part of the bottom liquid can enter the reboiler of the methyl chloride rectification tower to become a gas phase and then be transported back to the methyl chloride rectification tower: the amount of liquid phase material entering the reboiler depends on the heat supplied by the reboiler. The higher the heat, the more material needs to be vaporized and the more material needs to be supplied. This part does not require additional control and can achieve circulation through natural thermosiphon.
[0078] Combined with Examples 1-3, it can be seen that more than 97% of methyl chloride can be purified to methyl chloride with a purity of more than 99.995% without additional energy consumption in the front-stage stripping. The remaining less than 3% is purified by distillation using a distillation column. Under the conditions of 12 theoretical plates and a reflux ratio of 1, more than 99% of the impurities in this part of the methyl chloride liquid containing impurities can be separated by distillation. Impurities are obtained at the bottom of the column, and methyl chloride with a purity of more than 99.995% is obtained by condensation at the top of the column. In this operating condition, 1.6 tons of steam is consumed for each ton of methyl chloride distillation. The methyl chloride that needs to be distilled here only accounts for 3%, and the actual energy consumption is 0.048 tons.
[0079] The purification of methyl chloride can be carried out by using a traditional distillation process and separating it with a distillation column. However, during the separation process, a large amount of steam is required to heat the bottom of the column to vaporize the bottom material, and gas-liquid mass transfer separation is carried out in the column. To achieve the purpose of energy conservation and consumption reduction, a heat pump distillation method can also be used. After the gas phase at the top of the column is pressurized by a compressor, the enthalpy value is used to supply heat to the bottom of the column. However, this method requires a high equipment investment, with an expected equipment investment of 500,000 yuan / (ton * hour), and the cost is relatively high.
[0080] The purification process of methyl chloride in the production of organosilicon with low energy consumption described in the embodiments of the present invention is a new process route for methyl chloride purification. A set of methyl chloride stripping and stripping tower is used to perform one-stage stripping of methyl chloride by using the self-heat of methyl chloride, and the remaining very small part of methyl chloride is separated by distillation between methyl chloride and the impurities in methyl chloride using a set of methyl chloride distillation and impurity removal tower. Only 0.005 tons of steam is consumed for each ton of methyl chloride processed in this process. The main energy source for distillation is the phase change enthalpy of pressurized gaseous methyl chloride, realizing highly energy-efficient purification of methyl chloride.
[0081] The above description is only the preferred embodiment of the embodiments of the present invention, and does not impose any form of limitation on the embodiments of the present invention. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the embodiments of the present invention still fall within the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A low-energy purification process for methyl chloride in organosilicon production, characterized in that: The following steps are involved: (1) The methyl chloride gas is pressurized to 0.9-1.1 MPag by a compressor to obtain methyl chloride gas 1; (2) transporting the methyl chloride gas 1 to a methyl chloride removal tower reboiler and cooling it into a liquid state to obtain methyl chloride liquid 1; (3) The methyl chloride liquid 1 enters from the top of the methyl chloride removal tower, and after being depressurized to 0.68-0.76 MPag, the methyl chloride gas 1 is used for heat exchange, thereby performing distillation and purification treatment; The methyl chloride gas 1 after heat exchange becomes liquid phase and is transported to the methyl chloride removal tower reboiler to become the chlorosilane liquid 1; The methyl chloride gas produced from the top of the methyl chloride removal tower is transported to the top condenser of the methyl chloride removal tower and cooled into a liquid state to obtain methyl chloride liquid 2; (4) The bottom liquid of the methyl chloride removal tower enters from the top of the methyl chloride distillation tower, is depressurized to 0.4-0.54 MPag, and then is distilled. The methyl chloride gas produced from the top of the tower is transported to the top condenser of the methyl chloride distillation tower and cooled into a liquid state to obtain methyl chloride liquid 3.
2. The purification process according to claim 1, characterized in that: In the step (1), the temperature of the methyl chloride gas 1 is 100-150° C.; In the step (2), the pressure of the methyl chloride liquid 1 is 0.9-1.2 MPag and the temperature is 38-50°C.
3. The purification process according to claim 2, characterized in that: In the step (1), the pressure of the methyl chloride gas 1 is 0.9 MPag and the temperature is 125° C.; In the step (2), the pressure of the methyl chloride liquid 1 is 0.9 MPag.
4. The purification process according to claim 1, characterized in that: In the step (3), the temperature of the distillation treatment is 33-40°C and the pressure is 0.68-0.76MPag.
5. The purification process according to claim 4, characterized in that: In the step (3), the pressure is reduced to 0.75 MPag, and the temperature of the distillation treatment is 38° C. and the pressure is 0.75 MPag.
6. The purification process according to claim 1, characterized in that: In the step (3), the non-condensable gas in the condenser at the top of the methyl chloride removal tower is sent to tail gas treatment.
7. The purification process according to claim 1, characterized in that: In the step (3), the bottom liquid of the methyl chloride removal tower enters the reboiler of the methyl chloride removal tower and becomes a gas phase, and then is transported to the methyl chloride removal tower.
8. The purification process according to claim 1, characterized in that: In the step (4), the temperature of the distillation treatment is 40-80°C and the pressure is 0.4-0.54MPag.
9. The purification process according to claim 8, characterized in that: In the step (4), the temperature of the distillation treatment is 60° C. and the pressure is 0.5 MPag.
10. The purification process according to claim 1, characterized in that: In the step (4), the bottom liquid of the chloromethane distillation tower enters the reboiler of the chloromethane distillation tower and changes into a gas phase, and then is transported to the chloromethane distillation tower.