A methyl chloride cooling recovery system and a methyl chloride cooling recovery method

Abstract

The present application belongs to the field of chemical production, and particularly relates to a chloromethane cooling and recycling system and a chloromethane cooling and recycling method. The chloromethane cooling and recycling system comprises a first condenser, a second condenser, a third condenser and a chloromethane recycling tank. The shell side inlet of the second condenser is connected with the tube side outlet of the third condenser, and the tube side inlet of the third condenser is used for passing in liquid chloromethane. The present application uses the vaporization endothermic principle of liquid chloromethane to cool and recycle chloromethane, and is good in economy. Moreover, since the to-be-cooled substance and the refrigerant are both chloromethane, even if mutual leakage occurs in the heat exchange process, the quality of the recycled chloromethane will not be affected and the loss of raw materials will not be caused.

Description

Technical Field

[0001] This invention belongs to the field of chemical production, and particularly relates to a chloromethane cooling and recovery system and a chloromethane cooling and recovery method. Background Technology

[0002] The direct synthesis of methylchlorosilanes uses chloromethane and silicon powder as raw materials, and generates the target product through a high-temperature reaction in the presence of a copper catalyst. In actual production, the direct synthesis of methylchlorosilanes is mainly carried out in a fluidized bed reactor. The main reaction product is dimethyldichlorosilane, and many byproducts are generated during the reaction, including monomethyl, trimethyl, hydrogen-containing, silicon tetrachloride, high-boiling and low-boiling gases, etc. Some light non-condensable gases are also generated during the reaction, mainly chlorine and hydrogen chloride.

[0003] In the synthesis of methylchlorosilanes in a fluidized bed reactor, unreacted chloromethane and non-condensable gases are separated together. To allow the chloromethane to re-enter the reactor, methylchlorosilane manufacturers currently primarily use chilled brine or ethylene glycol to cool and recover the chloromethane, while the non-condensable gases are vented to the tail gas disposal system. However, using chilled brine or ethylene glycol for chloromethane recovery is costly and uneconomical. Furthermore, using chilled brine or ethylene glycol as a refrigerant may result in chloromethane leakage into the refrigerant, causing raw material loss. Chilled brine or ethylene glycol may also leak into the chloromethane, leading to poor quality recovered chloromethane and affecting the reaction. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a chloromethane cooling and recovery system and a chloromethane cooling and recovery method. The present invention utilizes the principle of heat absorption during vaporization of liquid chloromethane to cool and recover chloromethane, which is economical. Moreover, since both the material to be cooled and the refrigerant are chloromethane, even if mutual leakage occurs during the heat exchange process, it will not affect the quality of the recovered chloromethane or cause raw material loss.

[0005] This invention provides a chloromethane cooling and recovery system, comprising: a first condenser, a second condenser, a third condenser, and a chloromethane recovery storage tank; each of the first, second, and third condensers includes 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 to introduce chloromethane-containing gas to be cooled and recovered; the tube side liquid phase outlet of the first condenser is connected to the chloromethane recovery storage tank; the tube side gas phase outlet of the first condenser is connected to the tube side inlet of the second condenser; the tube side liquid phase outlet of the second condenser is connected to the chloromethane recovery storage tank; the tube side gas phase outlet of the second condenser is used to discharge non-condensable gas; the shell side inlet of the second condenser is connected to the tube side outlet of the third condenser; the shell side outlet of the second condenser is connected to the shell side inlet of the third condenser; the tube side inlet of the third condenser is used to introduce liquid chloromethane; and the shell side outlet of the third condenser is used to discharge gaseous chloromethane.

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

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

[0008] Preferably, the shell side of the second condenser is equipped with a level gauge and a pressure gauge.

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

[0010] Preferably, the recovered chloromethane storage tank is provided with a gas outlet, which is connected to the tube inlet of the second condenser.

[0011] This invention provides a method for cooling and recovering chloromethane, comprising the following steps:

[0012] The chloromethane gas to be cooled and recovered enters the tube side of the first condenser and exchanges heat with the water in the shell side of the first condenser. The liquid phase formed during the cooling process flows out from the liquid phase outlet of the tube side of the first condenser and enters the chloromethane recovery storage tank. The non-condensable gas that is not liquefied during the cooling process is discharged from the gas phase outlet of the tube side of the first condenser and enters the tube side inlet of the second condenser.

[0013] Liquid chloromethane enters the tube side of the third condenser and exchanges heat with the gaseous chloromethane in the shell side of the third condenser. The cooled liquid chloromethane flows out from the tube side outlet of the third condenser and enters the shell side inlet of the second condenser.

[0014] Non-condensable gas from the tube side of the first condenser enters the tube side of the second condenser, while 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. During this heat exchange, the temperature of the non-condensable gas in the tube side decreases, and the resulting liquid phase flows out from the liquid phase outlet of the second condenser's tube side and enters the chloromethane recovery tank. Unliquefied non-condensable gas is discharged from the gas phase outlet of the second condenser's tube side. During the heat exchange, the temperature of the liquid chloromethane in the shell side increases, and it partially vaporizes. The resulting gaseous chloromethane is discharged from the shell side outlet of the second condenser and serves as a cold source in the shell side of the third condenser.

[0015] The gaseous chloromethane that has undergone heat exchange and temperature rise in the shell side of the third condenser is discharged from the shell side outlet of the third condenser.

[0016] Preferably, the inlet pressure of the chloromethane gas is 0.8 to 0.9 MPa.

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

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

[0019] Compared with the prior art, the present invention provides a chloromethane cooling and recovery system and a chloromethane cooling and recovery method. The chloromethane cooling and recovery system provided by the present invention includes: a first condenser, a second condenser, a third condenser, and a chloromethane recovery storage tank; the first, second, and third condensers each include 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 to introduce the chloromethane-containing gas to be cooled and recovered; the tube side liquid phase outlet of the first condenser is connected to the chloromethane recovery storage tank; the tube side gas phase outlet of the first condenser is connected to the tube side inlet of the second condenser; the tube side liquid phase outlet of the second condenser is connected to the chloromethane recovery storage tank; the tube side gas phase outlet of the second condenser is used to discharge non-condensable gases; the shell side inlet of the second condenser is connected to the tube side outlet of the third condenser; the shell side outlet of the second condenser is connected to the shell side inlet of the third condenser; the tube side inlet of the third condenser is used to introduce liquid chloromethane; the shell side outlet of the third condenser is used to discharge gaseous chloromethane. This invention utilizes the principle of heat absorption during the vaporization of liquid chloromethane, employing liquid chloromethane as the refrigerant instead of chilled brine or ethylene glycol, thereby saving energy. Furthermore, because this invention uses chloromethane-to-chloromethane heat exchange, compared to heat exchange with chilled brine or ethylene glycol, the risk of chloromethane leaking into the chilled brine or ethylene glycol in the event of a condenser leak is eliminated. In addition, if a small leak occurs in the second or third heat exchanger, the leaked chloromethane can be subsequently returned to the system for the direct synthesis of methylchlorosilanes along with the gaseous chloromethane for reuse, eliminating the loss of chloromethane raw materials due to cooling with chilled brine or ethylene glycol. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the system flow provided in an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached diagram: 1 is the first condenser, 2 is the second condenser, 3 is the third condenser, 4 is the chloromethane recovery storage tank, 5 is the first regulating valve, 6 is the second regulating valve, 7 is the level gauge, 8 is the pressure gauge, and 9 is the flow meter. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a chloromethane cooling and recovery system, such as Figure 1 As shown, it includes: a first condenser 1, a second condenser 2, a third condenser 3, and a chloromethane recovery storage tank 4; the first condenser 1, the second condenser 2, and the third condenser 3 each include 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 to introduce the chloromethane-containing gas to be cooled and recovered; the tube side liquid phase outlet of the first condenser 1 is connected to the chloromethane recovery storage tank 4; the tube side gas phase outlet of the first condenser 1 is connected to the tube side inlet of the second condenser 2; the tube side liquid phase outlet of the second condenser 2 is connected to the chloromethane recovery storage tank 4; the tube side gas phase outlet of the second condenser 2 is used to discharge non-condensable gas; the shell side inlet of the second condenser 2 is connected to the tube side outlet of the third condenser 3; the shell side outlet of the second condenser 2 is connected to the shell side inlet of the third condenser 3; the tube side inlet of the third condenser 3 is used to introduce liquid chloromethane; the shell side outlet of the third condenser 3 is used to discharge gaseous chloromethane.

[0025] In the system provided by the present invention, a first regulating valve 5 is preferably provided on the connecting pipe between the shell-side inlet of the second condenser 2 and the tube-side outlet of the third condenser 3. The present invention can control the liquid level of liquid chloromethane in the shell side of the second condenser 2 through the first regulating valve 5.

[0026] In the system provided by the present invention, a level gauge 7 is preferably provided in the shell side of the second condenser 5. The level gauge 7 can monitor the shell side liquid level data of the second condenser 5 in real time and send the relevant data to the first regulating valve 5. The first regulating valve 5 can control the liquid level of liquid chloromethane in the shell side of the second condenser 2 in real time based on the real-time data sent by the level gauge 7.

[0027] In the system provided by the present invention, the shell-side outlet of the third condenser 3 is preferably connected to a second regulating valve 6, and the present invention 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 invention, the shell side of the second condenser 5 is preferably equipped with a pressure gauge 8. The pressure gauge 8 can monitor the shell side pressure data of the second condenser 5 in real time and send the relevant data to the second regulating valve 6. The second regulating valve 6 can control the shell side pressure of the second condenser 2 and the third condenser 3 in real time based on the real-time data sent by the pressure gauge 8.

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

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

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

[0032] The chloromethane 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. The liquid phase formed during the cooling process flows out from the tube side liquid phase outlet of the first condenser 1 and enters the chloromethane recovery storage tank 4. The non-condensable gas that is not liquefied during the cooling process is discharged from the tube side gas phase outlet of the first condenser 1 and enters the tube side inlet of the second condenser 2.

[0033] 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. 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] Non-condensable gas from the tube side of the first condenser 1 enters the tube side of the second condenser 2, while liquid chloromethane from the tube side of the third condenser 3 enters the shell side of the second condenser 2. The two exchange heat in the second condenser 2. During the heat exchange, the temperature of the non-condensable gas in the tube side decreases, and the resulting liquid phase flows out from the liquid phase outlet of the tube side of the second condenser 2 and enters the chloromethane recovery storage tank 4. The unliquefied non-condensable gas is discharged from the gas phase outlet of the tube side of the second condenser 2. During the heat exchange, the temperature of the liquid chloromethane in the shell side increases, and it partially vaporizes. The resulting gaseous chloromethane is discharged from the shell side outlet of the second condenser 2 and enters the shell side of the third condenser 3 as a cold source.

[0035] The gaseous chloromethane that has undergone heat exchange and temperature rise 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 invention, the inlet pressure of the chloromethane gas is preferably 0.8 to 0.9 MPa, more preferably 0.85 MPa.

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

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

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

[0040] The technical solution provided by this invention utilizes the endothermic vaporization principle of liquid chloromethane to cool and recover chloromethane, which is economical. Furthermore, since both the material to be cooled and the refrigerant are chloromethane, even if mutual leakage occurs during the heat exchange process, it will not affect the quality of the recovered chloromethane or cause raw material loss. More specifically, this invention has at least the following advantages:

[0041] 1) This invention utilizes the principle of heat absorption during the vaporization of fresh liquid chloromethane. The equipment used is simple in structure and easy to manufacture, and can achieve deep cooling of chloromethane recovery, thereby achieving the purpose of energy saving and consumption reduction, and realizing good economic efficiency.

[0042] 2) This invention uses chloromethane to exchange heat with chloromethane, eliminating the risk of chloromethane leakage that occurs when using chilled brine or ethylene glycol for heat exchange. This solves the problem of raw material loss caused by chloromethane leakage and also eliminates the risk of chilled brine or ethylene glycol leaking into chloromethane and affecting the reaction. The process is very simple, the overall operating energy consumption is very low, the reliability is high, and the equipment requires very little maintenance.

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

[0044] For clarity, the following examples will be used to provide a detailed description.

[0045] Example 1

[0046] This embodiment primarily utilizes the endothermic vaporization property of chloromethane. The chloromethane-containing gas separated from the apparatus for the direct synthesis of methylchlorosilane is cooled by water, without the need for deep cooling with chilled brine or ethylene glycol, but rather by the endothermic vaporization principle of fresh liquid chloromethane. Combined with... Figure 1 As shown, the detailed process is described below:

[0047] The chloromethane-containing gas separated by the synthesis unit 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. The liquid phase formed during the cooling process flows out from the tube side liquid phase outlet of the first condenser 1 and enters the chloromethane recovery storage tank 4. The non-condensable gas that is not liquefied during the cooling process is discharged from the tube side gas phase outlet of the first condenser 1 and enters the tube side inlet of the second condenser 2.

[0048] Liquid fresh chloromethane enters the tube side of the third condenser 3 and exchanges heat with the gaseous fresh chloromethane in the shell side of the third condenser 3. 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] Non-condensable gas from the tube side of the first condenser 1 enters the tube side of the second condenser 2, while liquid fresh chloromethane from the tube side of the third condenser 3 enters the shell side of the second condenser 2. The two exchange heat in the second condenser 2. During the heat exchange, the temperature of the non-condensable gas in the tube side decreases, and the resulting liquid phase flows out from the liquid phase outlet of the tube side of the second condenser 2 and enters the chloromethane recovery storage tank 4. The unliquefied non-condensable gas is discharged from the gas phase outlet of the tube side of the second condenser 2. During the heat exchange, the temperature of the liquid fresh chloromethane in the shell side increases, and it partially vaporizes. The resulting gaseous fresh chloromethane is discharged from the shell side outlet of the second condenser 2 and enters the shell side of the third condenser 3 as a cold source.

[0050] The gaseous fresh chloromethane that has undergone heat exchange and heating 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 chloromethane-containing gas separated by the synthesis device entering the first condenser 1 is maintained at around 0.85 MPa.

[0052] In this embodiment, the liquid recovered chloromethane collected in the chloromethane recovery tank 4 is fed back into the apparatus for the direct synthesis of methylchlorosilane to participate in the synthesis of methylchlorosilane.

[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 being transported is metered by the flow meter 9.

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

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

[0056] In this embodiment, the shell-side pressure of the second condenser 2 is monitored in real time using a pressure gauge 8, and the shell-side pressure of the second condenser 2 is controlled by the second regulating valve 6 to always be maintained at about 0.04 MPa. At this pressure, the temperature of chloromethane is about -15°C, so the shell-side temperature of the second condenser 2 is maintained at about -15°C.

[0057] In this embodiment, the pressure inside the tube side of the second condenser 2 is 0.85 MPa, and the dew point temperature of chloromethane at this pressure is 44°C. Since the shell side temperature of the second condenser 2 is maintained at around -15°C, almost all of the chloromethane inside the tube side of the second condenser 2 can be condensed into liquid and collected into the chloromethane recovery storage tank 4.

[0058] When the chloromethane cooling and recovery system and method disclosed in Example 1 are applied to a methylchlorosilane plant with a capacity of 150,000 tons / year, under the same production capacity, compared with the use of chilled brine or ethylene glycol cryogenics, Example 1 can achieve energy savings of approximately 648,000 KJ per hour, which is equivalent to saving 180 kWh of electricity per hour.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A chloromethane cooling and recovery system, characterized in that, include: The system comprises a first condenser, a second condenser, a third condenser, and a chloromethane recovery storage tank; the first condenser, the second condenser, and the third condenser each include 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 to introduce the chloromethane gas to be cooled and recovered. The tube-side liquid phase outlet of the first condenser is connected to the recovered chloromethane storage tank. The tube-side gas phase outlet of the first condenser is connected to the tube-side inlet of the second condenser. The tube-side liquid phase outlet of the second condenser is connected to the recovered chloromethane storage tank. The tube-side gas phase outlet of the second condenser is used to discharge non-condensable gas. The shell-side inlet of the second condenser is connected to the tube-side outlet of the third condenser. The shell-side outlet of the second condenser is connected to the shell-side inlet of the third condenser. The tube-side inlet of the third condenser is used to introduce liquid chloromethane, and the shell-side outlet of the third condenser is used to discharge gaseous chloromethane.

2. The chloromethane cooling and recovery system according to claim 1, characterized in that, A first regulating valve is installed on the connecting pipe 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 according to claim 1, characterized in that, The shell-side outlet of the third condenser is connected to a second regulating valve.

4. The chloromethane cooling and recovery system according to claim 1, characterized in that, The shell side of the second condenser is equipped with a level gauge and a pressure gauge.

5. The chloromethane cooling and recovery system according to claim 1, characterized in that, A flow meter is connected to the tube inlet of the third condenser.

6. The chloromethane cooling and recovery system according to claim 1, characterized in that, The recovered chloromethane storage tank is equipped with a gas outlet, which is connected to the tube inlet of the second condenser.

7. A method for cooling and recovering chloromethane, characterized in that, Includes the following processes: The chloromethane gas to be cooled and recovered enters the tube side of the first condenser and exchanges heat with the water in the shell side of the first condenser. The liquid phase formed during the cooling process flows out from the liquid phase outlet of the tube side of the first condenser and enters the chloromethane recovery storage tank. The non-condensable gas that is not liquefied during the cooling process is discharged from the gas phase outlet of the tube side of the first condenser and enters the tube side inlet of the second condenser. Liquid chloromethane enters the tube side of the third condenser and exchanges heat with the gaseous chloromethane in the shell side of the third condenser. The cooled liquid chloromethane flows out from the tube side outlet of the third condenser and enters the shell side inlet of the second condenser. Non-condensable gas from the tube side of the first condenser enters the tube side of the second condenser, while 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. During this heat exchange, the temperature of the non-condensable gas in the tube side decreases, and the resulting liquid phase flows out from the liquid phase outlet of the second condenser's tube side and enters the chloromethane recovery tank. Unliquefied non-condensable gas is discharged from the gas phase outlet of the second condenser's tube side. During the heat exchange, the temperature of the liquid chloromethane in the shell side increases, and it partially vaporizes. The resulting gaseous chloromethane is discharged from the shell side outlet of the second condenser and serves as a cold source in the shell side of the third condenser. The gaseous chloromethane that has undergone heat exchange and temperature rise in the shell side of the third condenser is discharged from the shell side outlet of the third condenser.

8. The method for cooling and recovering chloromethane according to claim 7, characterized in that, The inlet pressure of the chloromethane gas is 0.8–0.9 MPa.

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

10. The method for cooling and recovering chloromethane according to claim 7, characterized in that, The shell-side liquid level height of the second condenser is 40-50% of the shell-side height.

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