Chloromethane cooling recovery system and chloromethane cooling recovery method

Abstract

The invention belongs to the field of chemical production, and particularly relates to a chloromethane cooling recovery system and a chloromethane cooling recovery method. The chloromethane cooling recovery system provided by the invention comprises a first condenser, a second condenser, a third condenser and a recovered chloromethane storage tank, a shell pass inlet of the second condenser is connected with a tube pass outlet of the third condenser, and a tube pass inlet of the third condenser is used for introducing liquid chloromethane. Chloromethane is cooled and recovered by using a liquid chloromethane vaporization heat absorption principle, so that the economical efficiency is good; in addition, due to the fact that the to-be-cooled object and the refrigerant are both methyl chloride, even if mutual leakage occurs in the heat exchange process, the quality of recycled methyl chloride cannot be affected, and raw material losses cannot be caused.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical production, and particularly relates to a methyl chloride cooling and recovery system and a methyl chloride cooling and recovery method. BACKGROUND

[0002] Direct synthesis of methyl chlorosilane is to use chloromethane and silicon powder as raw materials, and to generate target product through high-temperature reaction under the action of copper catalyst. In actual production, direct synthesis of methyl chlorosilane is mainly carried out in a fluidized bed reactor, and the reaction product is mainly dimethyldichlorosilane. Many by-products are produced in the reaction, including monomethyl, trimethyl, hydrogen-containing, silicon tetrachloride, high-boiling and low-boiling, and some non-condensable gases such as chlorine and hydrogen chloride are also produced in the reaction.

[0003] In the process of synthesizing methyl chlorosilane in the fluidized bed reactor, unreacted chloromethane and non-condensable gas are separated out together. In order to make the chloromethane re-enter the bed reaction, the current methyl chlorosilane manufacturers basically use frozen brine or ethylene glycol to cool and recover the chloromethane, and the non-condensable gas is vented to the tail gas disposal. However, the cost of using frozen brine or ethylene glycol to cool and recover the chloromethane is high, and the economy is poor. At the same time, using frozen brine or ethylene glycol as refrigerant, the chloromethane may leak into the refrigerant, causing raw material loss. The frozen brine or ethylene glycol may also leak into the chloromethane, thereby causing poor quality of recovered chloromethane and affecting the reaction. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a methyl chloride cooling and recovery system and a methyl chloride cooling and recovery method. The present application uses the vaporization heat absorption principle of liquid chloromethane to cool and recover the chloromethane, which is economical. Moreover, since the to-be-cooled substance and the refrigerant are both chloromethane, even if mutual leakage occurs in the heat exchange process, it will not affect the quality of the recovered chloromethane and cause raw material loss.

[0005] The application provides a chloromethane cooling and recycling system, comprising a first condenser, a second condenser, a third condenser and a recycled chloromethane storage tank; the first condenser, the second condenser and the third condenser each comprise a shell side and a tube side; the cooling medium in the shell side of the first condenser is water, the tube side inlet of the first condenser is used for passing in chloromethane-containing gas to be cooled and recycled, the tube side liquid phase outlet of the first condenser is connected with the recycled chloromethane storage tank, and the tube side gas phase outlet of the first condenser is connected with the tube side inlet of the second condenser; the tube side liquid phase outlet of the second condenser is connected with the recycled chloromethane storage tank, the tube side gas phase outlet of the second condenser is used for discharging non-condensed gas, the shell side inlet of the second condenser is connected with the tube side outlet of the third condenser, and the shell side outlet of the second condenser is connected with the shell side inlet of the third condenser; the tube side inlet of the third condenser is used for passing in liquid chloromethane, and the shell side outlet of the third condenser is used for discharging gaseous chloromethane.

[0006] Preferably, a first regulating valve is arranged on the connecting pipeline between the shell side inlet of the second condenser and the tube side outlet of the third condenser.

[0007] Preferably, a second regulating valve is connected with the shell side outlet of the third condenser.

[0008] Preferably, a liquid level meter and a gas pressure gauge are arranged on the shell side of the second condenser.

[0009] Preferably, a flow meter is connected with the tube side inlet of the third condenser.

[0010] Preferably, an air outlet is arranged on the recycled chloromethane storage tank, and the air outlet is connected with the tube side inlet of the second condenser.

[0011] The application further provides a chloromethane cooling and recycling method.

[0012] The chloromethane-containing gas to be cooled and recycled enters the tube side of the first condenser, exchanges heat with water in the shell side of the first condenser to be cooled, the liquid phase formed in the cooling process flows out from the tube side liquid phase outlet of the first condenser and enters the recycled chloromethane storage tank, and the non-condensed gas not liquefied in the cooling process is discharged from the tube side gas phase outlet of the first condenser and enters the tube side inlet of the second condenser;

[0013] The liquid chloromethane enters the tube side of the third condenser, exchanges heat with gaseous chloromethane in the shell side of the third condenser to be cooled, and the liquid chloromethane cooled is discharged from the tube side outlet of the third condenser and enters the shell side inlet of the second condenser.

[0014] The non-condensed gas from the first condenser tube passes into the tube of the second condenser, and the liquid methyl chloride from the third condenser tube passes into the shell of the second condenser, and they exchange heat in the second condenser; in the process of heat exchange, the temperature of the non-condensed gas in the tube is reduced, and the formed liquid phase flows out from the liquid phase outlet of the tube of the second condenser and enters the recovered methyl chloride storage tank, and the non-liquefied non-condensed gas is discharged from the gas phase outlet of the tube of the second condenser; in the process of heat exchange, the temperature of the liquid methyl chloride in the shell is increased, and part of the liquid methyl chloride is vaporized, and the formed gaseous methyl chloride is discharged from the shell outlet of the second condenser and enters the shell of the third condenser as a cold source;

[0015] The gaseous methyl chloride, which is heated in the shell of the third condenser, is discharged from the shell outlet of the third condenser.

[0016] Preferably, the inlet pressure of the chlorine-containing gas is 0.8-0.9 MPa.

[0017] Preferably, the pressure of the tube of the second condenser is 0.8-0.9 MPa, and the pressure of the shell is 0.03-0.05 MPa.

[0018] Preferably, the liquid level of the shell of the second condenser is 40-50% of the height of the shell.

[0019] Compared with the prior art, the present application provides a methyl chloride cooling and recycling system and a methyl chloride cooling and recycling method. The methyl chloride cooling and recycling system provided by the present application comprises a first condenser, a second condenser, a third condenser and a recycled methyl chloride storage tank; the first condenser, the second condenser and the third condenser each comprise a shell side and a tube side; the cooling medium in the shell side of the first condenser is water, the tube side inlet of the first condenser is used for passing in the methyl chloride-containing gas to be cooled and recycled, the tube side liquid phase outlet of the first condenser is connected with the recycled methyl chloride storage tank, and the tube side gas phase outlet of the first condenser is connected with the tube side inlet of the second condenser; the tube side liquid phase outlet of the second condenser is connected with the recycled methyl chloride storage tank, the tube side gas phase outlet of the second condenser is used for discharging non-condensable gas, the shell side inlet of the second condenser is connected with the tube side outlet of the third condenser, and the shell side outlet of the second condenser is connected with the shell side inlet of the third condenser; the tube side inlet of the third condenser is used for passing in liquid methyl chloride, and the shell side outlet of the third condenser is used for discharging gaseous methyl chloride. The present application utilizes the principle of heat absorption of vaporization of liquid methyl chloride, uses liquid methyl chloride as refrigerant, and does not use refrigerated brine or ethylene glycol as refrigerant, so as to save energy. In addition, since the present application uses methyl chloride for heat exchange with methyl chloride, compared with the heat exchange of refrigerated brine and ethylene glycol, the risk of methyl chloride leakage into refrigerated brine or ethylene glycol when the condenser leaks can be eliminated. In addition, if a small amount of leakage occurs in the second heat exchanger or the third heat exchanger in the present application, the leaked methyl chloride can also be reused with gaseous methyl chloride back to the system for directly synthesizing methyl chlorosilane, and the loss caused by methyl chloride raw material leakage due to cooling with refrigerated brine or ethylene glycol can be eliminated. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of the provided drawings.

[0021] Figure 1 is a system flow diagram provided by the embodiment of the present application.

[0022] The figure mark explanation: 1 is a first condenser, 2 is a second condenser, 3 is a third condenser, 4 is a recycled methyl chloride storage tank, 5 is a first regulating valve, 6 is a second regulating valve, 7 is a liquid level meter, 8 is a gas pressure gauge, and 9 is a flow meter. DETAILED DESCRIPTION

[0023] Clearly, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts are within the protection scope of the present application.

[0024] The present application provides a methyl chloride cooling and recovery system, as shown in the figure, comprising: a first condenser 1, a second condenser 2, a third condenser 3 and a recovered methyl chloride storage tank 4; the first condenser 1, the second condenser 2 and the third condenser 3 each comprise a shell side and a tube side; the cooling medium in the shell side of the first condenser 1 is water, the tube side inlet of the first condenser 1 is used for passing in the chlorine-containing gas to be cooled and recovered, the liquid phase outlet of the tube side of the first condenser 1 is connected with the recovered methyl chloride storage tank 4, the gas phase outlet of the tube side of the first condenser 1 is connected with the tube side inlet of the second condenser 2; the liquid phase outlet of the tube side of the second condenser 2 is connected with the recovered methyl chloride storage tank 4, the gas phase outlet of the tube side of the second condenser 2 is used for discharging non-condensed gas, the shell side inlet of the second condenser 2 is connected with the tube side outlet of the third condenser 3, and the shell side outlet of the second condenser 2 is connected with the shell side inlet of the third condenser 3; the tube side inlet of the third condenser 3 is used for passing in the liquid methyl chloride, and the shell side outlet of the third condenser 3 is used for discharging gaseous methyl chloride. Figure 1

[0025] In the system provided by the present application, the connecting pipeline between the shell side inlet of the second condenser 2 and the tube side outlet of the third condenser 3 is preferably provided with a first regulating valve 5, and the present application can control the liquid level of the liquid methyl chloride in the shell side of the second condenser 2 through the first regulating valve 5.

[0026] In the system provided by the present application, the shell side of the second condenser 5 is preferably provided with a liquid level meter 7, which can monitor the shell side liquid level data of the second condenser 5 in real time and send the related data to the first regulating valve 5, and the first regulating valve 5 can control the liquid level of the liquid methyl chloride in the shell side of the second condenser 2 in real time based on the real-time data sent by the liquid level meter 7.

[0027] In the system provided by the present application, the shell side outlet of the third condenser 3 is preferably connected with a second regulating valve 6, and the present application can control the shell side gas pressure of the second condenser 2 and the third condenser 3 through the second regulating valve 6.

[0028] In the system provided by the present application, the shell side of the second condenser 5 is preferably provided with a gas pressure gauge 8, which can monitor the shell side gas pressure data of the second condenser 5 in real time and send the related data to the second regulating valve 6, and the second regulating valve 6 can control the shell side gas pressure of the second condenser 2 and the third condenser 3 in real time based on the real-time data sent by the gas pressure gauge 8. ​

[0029] In the system provided by the present application, the tube side inlet of the third condenser 3 is preferably connected with a flow meter 9, and the present application can measure the amount of liquid chloromethane by the flow meter 9.

[0030] In the system provided by the present application, the recovery chloromethane storage tank 4 is preferably provided with an outlet, which is connected with the tube side inlet of the second condenser 2, for sending the residual gas phase in the recovery chloromethane storage tank 4 into the tube side of the second condenser 2 for heat exchange and cooling.

[0031] The present application also provides a method for cooling and recovering chloromethane. Figure 1 The method for cooling and recovering chloromethane in the system shown above comprises the following processes:

[0032] The chloromethane-containing gas to be cooled and recovered enters the tube side of the first condenser 1, and exchanges heat with the water in the shell side of the first condenser 1 for cooling, and the liquid phase formed in the cooling process flows out from the liquid phase outlet of the tube side of the first condenser 1 and enters the recovery chloromethane storage tank 4, and the non-condensable gas not liquefied in the cooling process is discharged from the gas phase outlet of the tube side of the first condenser 1 and enters the tube side inlet of the second condenser 2;

[0033] The liquid chloromethane enters the tube side of the third condenser 3, and exchanges heat with the gaseous chloromethane in the shell side of the third condenser 3 for cooling, and the cooled liquid chloromethane flows out from the tube side outlet of the third condenser 3 and enters the shell side inlet of the second condenser 2;

[0034] The non-condensable gas from the tube side of the first condenser 1 enters the tube side of the second condenser 2, and the liquid chloromethane from the tube side of the third condenser 3 enters the shell side of the second condenser 2, and they exchange heat in the second condenser 2; in the heat exchange process, the temperature of the non-condensable gas in the tube side is reduced, the liquid phase formed flows out from the liquid phase outlet of the tube side of the second condenser 2 and enters the recovery chloromethane storage tank 4, and the non-condensable gas not liquefied is discharged from the gas phase outlet of the tube side of the second condenser 2; in the heat exchange process, the temperature of the liquid chloromethane in the shell side is increased, and part of it is vaporized, and the gaseous chloromethane formed is discharged from the shell side outlet of the second condenser 2 and enters the shell side of the third condenser 3 as a cooling source;

[0035] The gaseous chloromethane whose temperature is increased by heat exchange in the shell side of the third condenser 3 is discharged from the shell side outlet of the third condenser 3.

[0036] In the method provided by the present application, the inlet pressure of the chloromethane-containing gas is preferably 0.8-0.9 MPa, and more preferably 0.85 MPa.

[0037] In the method provided by the present application, the inlet temperature of the liquid chloromethane is preferably 15-30℃, and more preferably 25℃ (room temperature).

[0038] In the method provided by the present application, the tube side pressure of the second condenser 2 is preferably 0.8-0.9 MPa, more preferably 0.85 MPa; the shell side pressure of the second condenser 2 is preferably 0.03-0.05 MPa, more preferably 0.04 MPa; and the shell side liquid level of the second condenser 2 is preferably 40-50% of the shell side height, which is mainly to prevent the gas-liquid entrainment of chloromethane and facilitate heat exchange.

[0039] In the method provided by the present application, the shell side pressure of the third condenser 3 is preferably 0.03-0.05 MPa, more preferably 0.04 MPa.

[0040] The technical solution provided by the present application uses the vaporization heat absorption principle of liquid chloromethane to cool and recover chloromethane, which is good in economy; and since the to-be-cooled substance and the refrigerant are both chloromethane, even if there is mutual leakage in the heat exchange process, the quality of the recovered chloromethane will not be affected and the loss of raw materials will not be caused. More specifically, the present application has at least the following advantages:

[0041] 1) The present application uses the vaporization heat absorption principle of liquid fresh chloromethane, the used equipment is simple in structure and easy to manufacture, the deep cooling of the recovered chloromethane can be realized, the purpose of energy saving and consumption reduction is achieved, and good economy is realized.

[0042] 2) The present application uses chloromethane to exchange heat with chloromethane, which eliminates the use of chilled brine or ethylene glycol for heat exchange, eliminates the risk of chloromethane leakage, solves the problem of raw material loss caused by chloromethane leakage, and eliminates the risk of chilled brine or ethylene glycol leaking into chloromethane to affect the reaction, the process is simple, the overall operation energy consumption is low, and the reliability is high, and the device maintenance is low.

[0043] 3) The present application uses the first regulating valve to control the liquid level of the shell side liquid chloromethane of the second condenser, uses the second regulating valve to control the shell side gas pressure of the second condenser, and uses the flow meter to measure the amount of liquid chloromethane, which is simple in control principle and easy to realize, and the chloromethane can be recycled.

[0044] For a clearer understanding, the following examples are described in detail below.

[0045] Example 1

[0046] This example mainly uses the characteristics of chloromethane vaporization heat absorption, and the gas containing chloromethane separated from the device for synthesizing methyl chlorosilane by a direct method is cooled by water without deep cooling by chilled brine or ethylene glycol, but is cooled by using the vaporization heat absorption principle of liquid fresh chloromethane. In combination with the description of the flow chart shown in FIG. 1, the detailed flow process is described as follows. Figure 1

[0047] ​The gas containing chloromethane separated by the synthesis device enters the tube side of the first condenser 1 and exchanges heat with water in the shell side of the first condenser 1 to be cooled, and the liquid phase formed in the cooling process flows out from the liquid phase outlet of the tube side of the first condenser 1 and enters the recovered chloromethane storage tank 4, and the non-condensed gas not liquefied in the cooling process is discharged from the gas phase outlet of the tube side of the first condenser 1 and enters the tube side inlet of the second condenser 2;

[0048] The liquid fresh chloromethane enters the tube side of the third condenser 3 and exchanges heat with gaseous fresh chloromethane in the shell side of the third condenser 3 to be cooled, and the cooled liquid fresh chloromethane flows out from the tube side outlet of the third condenser 3 and enters the shell side inlet of the second condenser 2;

[0049] The non-condensed gas from the tube side of the first condenser 1 enters the tube side of the second condenser 2, and the liquid fresh chloromethane from the tube side of the third condenser 3 enters the shell side of the second condenser 2, and they exchange heat in the second condenser 2; in the heat exchange process, the temperature of the non-condensed gas in the tube side is reduced, and the liquid phase formed flows out from the liquid phase outlet of the tube side of the second condenser 2 and enters the recovered chloromethane storage tank 4, and the non-condensed gas not liquefied is discharged from the gas phase outlet of the tube side of the second condenser 2; in the heat exchange process, the temperature of the liquid fresh chloromethane in the shell side is increased, and part of it is vaporized, and the gaseous fresh chloromethane formed is discharged from the shell side outlet of the second condenser 2 and enters the shell side of the third condenser 3 as a cooling source;

[0050] The gaseous fresh chloromethane whose temperature is increased by heat exchange in the shell side of the third condenser 3 is discharged from the shell side outlet of the third condenser 3.

[0051] In this embodiment, the pressure of the gas containing chloromethane separated by the synthesis device entering the first condenser 1 is maintained at about 0.85 MPa.

[0052] In this embodiment, the liquid recovered chloromethane collected in the recovered chloromethane storage tank 4 is sent back to the device for synthesizing methyl chlorosilane by direct method to participate in the synthesis of methyl chlorosilane.

[0053] In this embodiment, the liquid fresh chloromethane is at room temperature (25°C) before entering the third condenser 3, and the liquid fresh chloromethane is metered by the flow meter 9.

[0054] In this embodiment, the gaseous chloromethane in the shell side of the third condenser 3 is about -15°C.

[0055] In this embodiment, the liquid level of chloromethane in the shell side of the second condenser 2 is monitored in real time by the liquid level meter 7, and the first regulating valve 5 is used to control the liquid level of chloromethane in the shell side of the second condenser 2 to be 40-50% (maintaining the liquid level in this range is mainly to prevent gas-liquid entrainment of chloromethane and to facilitate heat exchange).

[0056] In the present embodiment, the shell side pressure of the second condenser 2 is monitored in real time by the air pressure gauge 8, and the shell side pressure of the second condenser 2 is controlled by the second regulating valve 6 to be kept at about 0.04 MPa, at which the temperature of chloromethane is about -15°C, so that the shell side temperature of the second condenser 2 is kept at about -15°C.

[0057] In the present embodiment, the pressure in the tube side of the second condenser 2 is 0.85 MPa, at which the dew point temperature of chloromethane is 44°C, and since the shell side temperature of the second condenser 2 is kept at about -15°C, the chloromethane in the tube side of the second condenser 2 can be substantially all condensed into liquid and collected into the chloromethane recovery tank 4.

[0058] The chloromethane cooling and recovery system and the chloromethane cooling and recovery method disclosed in the embodiment 1 are applied to a methyl chlorosilane device with a capacity of 150,000 tons / year, and compared with the deep cooling by using frozen brine or ethylene glycol, the embodiment 1 can save energy of about 648,000 KJ per hour, which is equivalent to saving electricity of 180 degrees per hour.

[0059] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A chloromethane cooling and recovery system characterized by, The application relates to a chloromethane recovery system. The first condenser, the second condenser, the third condenser and the chloromethane recovery tank; the first condenser, the second condenser and the third condenser each comprise a shell side and a tube side; The cooling medium in the shell side of the first condenser is water, the tube side inlet of the first condenser is used for feeding the chloromethane-containing gas to be cooled and recovered, the tube side liquid phase outlet of the first condenser is connected with the chloromethane recovery tank, the tube side gas phase outlet of the first condenser is connected with the tube side inlet of the second condenser, the tube side liquid phase outlet of the second condenser is connected with the chloromethane recovery tank, the tube side gas phase outlet of the second condenser is used for discharging non-condensed gas, the tube side outlet of the second condenser is connected with the tube side inlet of the third condenser, the shell side outlet of the second condenser is connected with the shell side inlet of the third condenser, the tube side inlet of the third condenser is used for feeding liquid chloromethane, and the shell side outlet of the third condenser is used for discharging gaseous chloromethane.

2. The chloromethane cooling and recovery system of claim 1, wherein, A first regulating valve is arranged on the connecting pipeline between the shell side inlet of the second condenser and the tube side outlet of the third condenser.

3. The chloromethane cooling and recovery system of claim 1, wherein, A second regulating valve is connected with the shell side outlet of the third condenser.

4. The chloromethane cooling and recovery system of claim 1, wherein, A liquid level meter and a gas pressure gauge are arranged on the shell side of the second condenser.

5. The chloromethane cooling and recovery system of claim 1, wherein, A flow meter is connected with the tube side inlet of the third condenser.

6. The chloromethane cooling and recovery system of claim 1, wherein, An air outlet is arranged on the chloromethane recovery tank, and the air outlet is connected with the tube side inlet of the second condenser.

7. A method for cooling and recovering chloromethane, characterized by, The application further relates to a chloromethane recovery method. The chloromethane-containing gas to be cooled and recovered enters the tube side of the first condenser, exchanges heat with water in the shell side of the first condenser, and is cooled; the liquid phase formed in the cooling process flows out from the tube side liquid phase outlet of the first condenser and enters the chloromethane recovery tank; the non-condensed gas which is not liquefied in the cooling process is discharged from the tube side gas phase outlet of the first condenser and enters the tube side inlet of the second condenser; Liquid chloromethane enters the tube side of the third condenser, exchanges heat with gaseous chloromethane in the shell side of the third condenser, and is cooled; the liquid chloromethane after being cooled flows out from the tube side outlet of the third condenser and enters the shell side inlet of the second condenser; The non-condensed gas from the tube side of the first condenser enters the tube side of the second condenser, and the liquid chloromethane from the tube side of the third condenser enters the shell side of the second condenser; the two exchange heat in the second condenser; in the heat exchange process, the temperature of the non-condensed gas in the tube side is reduced, the liquid phase formed flows out from the tube side liquid phase outlet of the second condenser and enters the chloromethane recovery tank, and the non-condensed gas which is not liquefied is discharged from the tube side gas phase outlet of the second condenser; in the heat exchange process, the temperature of the liquid chloromethane in the shell side is increased, part of the liquid chloromethane is vaporized, and the gaseous chloromethane formed is discharged from the shell side outlet of the second condenser and enters the shell side of the third condenser as a cooling source; The gaseous chloromethane which is cooled and heated in the shell side of the third condenser is discharged from the shell side outlet of the third condenser.

8. The chloromethane cooling and recovery method according to claim 7, characterized by, The inlet pressure of the chloromethane-containing gas is 0.8-0.9 MPa.

9. The chloromethane cooling and recovery method according to claim 7, characterized by, The pressure of the tube side of the second condenser is 0.8-0.9 MPa, and the pressure of the shell side of the second condenser is 0.03-0.05 MPa.

10. The chloromethane cooling and recovery process according to claim 7, wherein The liquid level height of the shell side of the second condenser is 40-50% of the height of the shell side.

Images