A trichloroethylene rectification separation device and method

Abstract

This invention relates to the field of trichloroethylene technology and discloses a trichloroethylene distillation separation apparatus and method, including a desorption tower bottom tank. The output end of the desorption tower bottom tank is connected to a low-boiling tower, and the output end of the low-boiling tower is connected to a low-boiling tower reflux tank and a trichloroethylene tower, wherein the output end of the low-boiling tower reflux tank is connected to the input end of the low-boiling tower, and the output end of the trichloroethylene tower is connected to a TCE tower reflux tank and a TCE intermediate tank. In this invention, a trichloroethylene distillation separation method is implemented by designing a TCE stirred tank and adding silver ammonia solution and color-changing silica gel inside the stirred tank to remove acidic impurities contained in trichloroethylene during the distillation process. This achieves secondary purification of trichloroethylene after the distillation process, reducing the likelihood of decomposition and instability of trichloroethylene during actual use, which can corrode the surface of cleaned devices and cleaning equipment, directly damaging the performance of the devices and the cleaning equipment.

Description

Technical Field

[0001] This invention relates to the field of trichloroethylene technology, specifically to a trichloroethylene distillation and separation apparatus and method. Background Technology

[0002] Trichloroethylene (TCE) is an important chemical raw material. It is a solvent with extremely strong dissolving power and is used in industry for metal cleaning (thorough degreasing) and fiber degreasing and cleaning of electronic components. As a raw material intermediate, trichloroethylene can be used to produce tetrachloroethylene, chloroacetic acid, dichloroacetyl chloride, octachlorodipropyl ether, HCFC-123, HCFC-124, HFC-125, HFC-134a, etc. It is also used as an extractant, solvent and low-temperature heat transfer oil medium.

[0003] In recent years, with the rapid development of the electronics and metal processing industries, the demand for trichloroethylene has been continuously increasing due to its excellent performance as a cleaning agent, with annual imports exceeding 40,000 tons, 90% of which is used as a cleaning agent. Furthermore, a significant factor driving the continuous growth in trichloroethylene demand is its role as a crucial raw material for the green refrigerant HFC-134a. In the United States and Europe, HFC-134a has become the best alternative to ODS (Optical Dissolved Substances). In recent years, my country has established industry standards and regulations for the application of HFC-134a in automotive air conditioning, refrigerators, and foaming agents. Therefore, the demand for trichloroethylene will inevitably undergo a qualitative change with the development of HFC-134a production technology and its wider market penetration in my country. In short, trichloroethylene, whether used as an organic solvent or an intermediate product, has a promising market prospect in my country and is a chlorine product that is in short supply and urgently needs development.

[0004] Currently, trichloroethylene technology is fully mature, and the improvement and maturation of new technologies provide strong support for the construction of trichloroethylene plants. However, some crude trichloroethylene, such as superior grade and chemically pure trichloroethylene, contains a certain amount of water, free chlorine, and silver ammonia reducing agents, which accelerate its decomposition, producing hydrogen chloride, which is acidic. In actual use, it is prone to decomposition and instability, which in turn corrodes the surface of the cleaned devices and the cleaning equipment, directly damaging the performance of the devices and the cleaning equipment. As for the methods of producing trichloroethylene, although there are many methods, any manufacturing method has the above-mentioned problems. That is, crude trichloroethylene contains various by-products with different degrees of chlorination, which affects the cleaning use of trichloroethylene in the electronics industry. At the same time, during the production process, a liquid containing trichloroethylene is generated at the bottom of the desorption tower. If it is discharged directly, it will pollute the external environment.

[0005] Therefore, to address the above problems, we propose a trichloroethylene distillation separation apparatus and method. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention, in a trichloroethylene distillation and separation device and method, designs a TCE stirred tank and adds silver ammonia solution and color-changing silica gel inside the stirred tank to remove acidic impurities contained in trichloroethylene during the distillation process. This achieves secondary purification of trichloroethylene after the distillation process, reducing the likelihood of decomposition and instability of trichloroethylene during actual use, which can corrode the surfaces of cleaned devices and the cleaning equipment, directly damaging the performance of the devices and undermining the advantages of the cleaning equipment. This invention solves the problem that while current trichloroethylene technology is fully mature, the improvement and maturity of this new technology provides a strong guarantee for the construction of trichloroethylene plants. However, some crude trichloroethylene, such as analytical grade and chemically pure trichloroethylene... Trichloroethylene contains a certain amount of water, free chlorine, and silver ammonia reducing agents, which accelerate its decomposition, producing hydrogen chloride, which is acidic. In actual use, it is prone to decomposition and instability, thus corroding the surface of the cleaned devices and the cleaning equipment, directly damaging the performance of the devices and the cleaning equipment. Although there are many methods for producing trichloroethylene, all of them have the above-mentioned problems. Crude trichloroethylene contains various byproducts with different degrees of chlorination, affecting its use in cleaning in the electronics industry. At the same time, during the production process, a liquid containing trichloroethylene is generated at the bottom of the desorption tower. If directly discharged, it will pollute the external environment.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a trichloroethylene distillation and separation apparatus, comprising a bottom tank of a stripping column, the output end of which is connected to a low-boiling column, the output end of which is connected to a low-boiling column reflux tank and a trichloroethylene column, wherein the output end of the low-boiling column reflux tank is connected to the input end of the low-boiling column, the output end of the trichloroethylene column is connected to a TCE column reflux tank and a TCE intermediate tank, wherein the output end of the TCE column reflux tank is connected to the input end of the trichloroethylene column, and the output end of the TCE intermediate tank is connected to a TCE product tank and a TCE stirring tank, wherein the output end of the TCE stirring tank is connected to the input end of the trichloroethylene column.

[0010] Preferably, the bottom liquid tank of the stripping tower is used to store the bottom liquid of the stripping tower after condensation by the stripping tower cooler. A low-boiling tower feed pump is installed between the low-boiling tower and the bottom liquid tank of the stripping tower, and a low-boiling tower reboiler and a low-boiling tower total condenser are installed on the low-boiling tower. The low-boiling tower is used to collect the low-boiling substances in the bottom liquid inside the bottom liquid tank of the stripping tower.

[0011] Preferably, a trichloroethylene tower feed pump is installed between the trichloroethylene tower and the low-boiling tower, and the trichloroethylene tower is equipped with a trichloroethylene tower reboiler, a trichloroethylene tower total condenser, a trichloroethylene tower tail cooler, a tail gas fan, and an activated carbon filter. The trichloroethylene tower tail cooler, tail gas fan, and activated carbon filter can discharge the waste gas that does not condense when condensed by the trichloroethylene tower total condenser.

[0012] Preferably, the TCE tower reflux tank is used to temporarily store the low-boiling tower bottom liquid condensed after the exhaust gas is discharged, and at the same time, a TCE tower reflux pump is installed between the TCE tower reflux tank and the trichloroethylene tower. The TCE tower reflux pump can reflux the internal low-boiling tower bottom liquid to the trichloroethylene tower to form trichloroethylene tower bottom liquid.

[0013] Preferably, a TCE cooler is installed between the TCE intermediate tank and the trichloroethylene tower. The TCE cooler can inject the trichloroethylene tower bottom liquid into the TCE intermediate tank. A TCE stirring tank reflux pump is installed between the TCE stirring tank and the trichloroethylene tower. The TCE stirring tank is used to remove impurities from the trichloroethylene tower bottom liquid and purify it.

[0014] Preferably, the TCE finished product tank is used to store trichloroethylene after distillation and purification for later sale.

[0015] This invention also proposes a method for distilling and separating trichloroethylene, comprising the following specific steps:

[0016] Step 1: The liquid in the bottom of the stripping column is injected into the bottom liquid tank of the stripping column, and then sent to the low-boiling column for low boiling. The low-boiling substance collected from the top of the low-boiling column is injected into the low-boiling column reflux tank, and then refluxed back into the low-boiling column through the low-boiling column reflux tank to obtain the bottom liquid of the low-boiling column.

[0017] Step 2: Inject the liquid from the bottom of the low-boiling tower into the trichloroethylene tower for heating. Control the outlet temperature at the top of the tower at 83-84℃. Then, it passes through the TCE tower total condenser and enters the TCE tower reflux tank. The non-condensable gas portion is discharged into the atmosphere.

[0018] Step 3: Inject the trichloroethylene from the reflux tank in Step 2 into the TCE intermediate tank. Then, purify the trichloroethylene inside the TCE intermediate tank by mechanically stirring the trichloroethylene and distilled water for 2 hours. The distilled water contains 2%-5% silver ammonia solution. Let it stand for 30 minutes to separate into layers, remove the upper layer of water, and repeat the above operation several times. Then test the "silver ammonia reducing agent" index until the silver ammonia reducing agent is clear and free of turbidity to be considered qualified.

[0019] Step 4: After the trichloroethylene has been purified once, a certain amount of color-changing silica gel (1 / 10 volume ratio) is added. The silica gel turns blue. Shake thoroughly for 2 hours to allow trace amounts of moisture to be adsorbed by the silica gel. Let it stand and filter, then remove the trichloroethylene and check whether it meets the standards. If it does, it is transferred back into the TCE tower for heating. The outlet temperature of the tower top is controlled at 83-84℃. After passing through the TCE tower condenser, the condensate enters the TCE tower reflux tank. The 99.99% trichloroethylene product in the TCE tower reflux tank, after passing through the TCE cooler and activated alumina filter to remove acid, enters the trichloroethylene metering tank. A stabilizer is added to the metering tank, and after mixing evenly, it is sent to the TCE intermediate tank and the TCE finished product tank.

[0020] Trichloroethylene can be further separated into tetrachloroethylene after distillation, specifically through the following steps:

[0021] Step 1: The trichloroethylene in the distillation separation step 3 of the vinyl chloride tower bottom liquid is injected into the TCE tower bottom liquid tank, and then pumped into the middle of the intermediate tower. After being heated in the intermediate tower, the product collected at the top of the tower is cooled by the intermediate tower total condenser and flows into the intermediate tower reflux tank. The non-condensable gas is cooled by the intermediate tower tail cooler and then discharged into the tail gas tower for venting. Part of the condensate flows by gravity to the desorption tower bottom liquid tank or the recovery top liquid tank according to the liquid level difference, and part of it is pumped back to the intermediate tower to form the intermediate tower bottom liquid.

[0022] Step 2: The intermediate tower bottom liquid produced in Step 1 is injected into the PCE tower for heating. After cooling, the product from the top of the tower flows into the PCE tower reflux tank. Non-condensable gases are discharged to the outside. Part of the condensate is returned to the intermediate tower, and part of it is cooled and enters the tetrachloroethylene storage tank.

[0023] (III) Beneficial Effects

[0024] Compared with the prior art, the present invention provides a trichloroethylene distillation and separation apparatus and method, which has the following beneficial effects:

[0025] 1. In a trichloroethylene distillation separation device and method, this invention designs a TCE stirred tank and adds silver ammonia solution and color-changing silica gel inside the stirred tank to remove acidic impurities contained in trichloroethylene during the distillation process. This achieves secondary purification of trichloroethylene after the distillation process, reducing the likelihood of decomposition and instability of trichloroethylene during actual use, which can corrode the surface of the cleaned devices and the cleaning equipment, directly damaging the performance of the devices and the cleaning equipment.

[0026] 2. The present invention designs an intermediate tower, an intermediate tower reflux tank, a PCE tower, a PCE tower reflux tank, and a tetrachloroethylene storage tank in a trichloroethylene distillation separation device and method. After trichloroethylene is separated from the bottom liquid of the stripping tower by distillation, tetrachloroethylene can be separated again from the trichloroethylene bottom liquid, thereby improving the utilization rate of bottom liquid distillation separation and reducing bottom liquid waste. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the trichloroethylene rectification and separation system of the present invention;

[0028] Figure 2 This is a schematic diagram of the tetrachloroethylene rectification and separation system of the present invention. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0030] Embodiment 1:

[0031] Please refer to Figure 1 , a trichloroethylene rectification and separation method, including the following specific steps:

[0032] Step 1: Cool the analytical column bottom liquid through a cooler and then enter the analytical column bottom liquid tank, and then send it to the low-boiling tower through the low-boiling tower feed pump. The steam is sent to the low-boiling tower reboiler after pressure regulation (0.3 MPa). The low-boiling substances extracted from the top of the tower are cooled by the low-boiling tower total condenser and then enter the low-boiling tower reflux tank. Most of them flow back into the low-boiling tower, and a part is discharged into the low-boiling substance tank for sale or enters the recycled top liquid tank;

[0033] Step 2: Feed the bottom liquid inside the low-boiling tower into the trichloroethylene tower through the TCE tower feed pump, heat it through the TCE tower reboiler, control the outlet temperature at the top of the tower at 83 - 84 °C, pass through the TCE tower total condenser, and the condensate enters the TCE tower reflux tank. The non-condensable gas is cooled by the TCE tower tail cooler and then pumped into the activated carbon filter by the tail gas fan for adsorption treatment and then discharged into the atmosphere;

[0034] Step 3: Part of the trichloroethylene in the reflux tank is pumped back to the TCE tower by the TCE tower reflux pump, and part of it enters the TCE intermediate tank after passing through the TCE cooler. Then, the trichloroethylene inside the TCE intermediate tank is purified once. The trichloroethylene and distilled water are mechanically stirred for 2 hours. The distilled water contains 2% - 5% silver ammonia solution. Let it stand for 30 minutes to separate layers, suck off the upper layer of water, and repeat the above operations several times. Then, check the "silver ammonia reduction product" index until the silver ammonia reduction product is clear and without turbidity, which is qualified

[0035] Step 4: After the trichloroethylene has been purified once, a certain amount of color-changing silica gel (1 / 10 volume ratio) is added. The silica gel turns blue. Shake thoroughly for 2 hours to allow trace amounts of moisture to be adsorbed by the silica gel. Let it stand and filter, then remove the trichloroethylene and check whether it meets the standards. If it does, it is transferred back into the TCE tower. It is heated by the TCE tower reboiler, and the outlet temperature of the tower top is controlled at 83-84℃. After passing through the TCE tower total condenser, the condensate enters the TCE tower reflux tank. The 99.99% trichloroethylene product in the TCE tower reflux tank, after passing through the TCE cooler and activated alumina filter to remove acid, enters the trichloroethylene metering tank. A stabilizer is added to the metering tank, and after mixing evenly, it is sent to the TCE intermediate tank and the TCE finished product tank.

[0036] Example 2:

[0037] Please see Figure 2 A method for distilling and separating tetrachloroethylene, comprising the following specific steps:

[0038] Step 1: After the liquid in the bottom of the stripping tower is cooled by the cooler, it enters the bottom liquid tank of the stripping tower. Then, it is sent into the low boiling tower by the low boiling tower feed pump. After the steam is pressure regulated (0.3MPa), it is sent into the reboiler of the low boiling tower. The low boiling material collected from the top of the tower is cooled by the total condenser of the low boiling tower and enters the reflux tank of the low boiling tower. Most of it is refluxed into the low boiling tower, and a part of the output enters the low boiling material tank for sale or enters the recovery top liquid tank.

[0039] Step 2: The liquid in the bottom of the low-boiling tower is fed into the trichloroethylene tower via the TCE tower feed pump. It is heated by the TCE tower reboiler and the temperature at the top outlet of the tower is controlled at 83-84℃. After passing through the TCE tower total condenser, the condensate enters the TCE tower reflux tank. The non-condensable gas is cooled by the TCE tower tail cooler and then drawn into the activated carbon filter by the tail gas fan. After adsorption treatment, it is discharged into the atmosphere.

[0040] Step 3: Trichloroethylene in the reflux tank is partially pumped back to the TCE tower by the TCE tower reflux pump. The TCE tower bottom liquid enters the TCE tower bottom liquid tank through the TCE bottom liquid cooler, and is then pumped into the middle of the intermediate tower by the intermediate tower feed pump. It is heated by the intermediate tower reboiler. The top product flows into the intermediate tower reflux tank after being cooled by the intermediate tower total condenser. The non-condensable gas is discharged into the tail gas tower after being cooled by the intermediate tower tail cooler. Part of the condensate flows by gravity to the intermediate tower top liquid tank according to the liquid level difference, and then returns to the stripping tower bottom liquid tank or the recovery top liquid tank. The rest is pumped back to the intermediate tower by the intermediate tower reflux pump to obtain the intermediate tower bottom liquid.

[0041] Step 4: The liquid in the intermediate tower is fed into the PCE tower via the PCE tower feed pump, heated by the tetrachloroethylene tower reboiler, and the product collected at the top of the tower is cooled by the PCE tower total condenser before flowing into the PCE tower reflux tank. The non-condensable gas is cooled by the PCE tower tail cooler before being discharged into the tail gas tower for venting. The condensate is 99.0% tetrachloroethylene product, and part of it is pumped back to the intermediate tower by the PCE tower reflux pump, while the other part is cooled by the PCE cooler before entering the tetrachloroethylene storage tank.

[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A trichloroethylene distillation and separation apparatus, comprising a bottom tank of a stripping column, characterized in that: The bottom tank of the analytical column is connected to a low-boiling-point column. The output of the low-boiling-point column is connected to a low-boiling-point column reflux tank and a trichloroethylene column. The output of the low-boiling-point column reflux tank is connected to the input of the low-boiling-point column. The output of the trichloroethylene column is connected to a TCE column reflux tank and a TCE intermediate tank. The output of the TCE column reflux tank is connected to the input of the trichloroethylene column. The output of the TCE intermediate tank is connected to a TCE product tank and a TCE stirring tank. The output of the TCE stirring tank is connected to the input of the trichloroethylene column. The bottom tank of the analytical column stores the liquid condensed by the analytical column cooler. A low-boiling-point column feed pump is installed between the low-boiling-point column and the bottom tank of the analytical column. A low-boiling-point column reboiler and a low-boiling-point column total condenser are installed on the low-boiling-point column. The low-boiling-point column is used to collect the low-boiling-point substances from the bottom tank of the analytical column. A trichloroethylene column feed pump is installed between the trichloroethylene column and the low-boiling-point column. The trichloroethylene tower is equipped with a trichloroethylene tower reboiler, a trichloroethylene tower total condenser, a trichloroethylene tower tail cooler, a tail gas fan, and an activated carbon filter. The trichloroethylene tower tail cooler, tail gas fan, and activated carbon filter discharge the non-condensable waste gas condensed in the trichloroethylene tower total condenser. The TCE tower reflux tank is used to temporarily store the low-boiling tower bottom liquid condensed after the waste gas is discharged. A TCE tower reflux pump is installed between the TCE tower reflux tank and the trichloroethylene tower, which refluxes the internal low-boiling tower bottom liquid back to the trichloroethylene tower to form trichloroethylene tower bottom liquid. A TCE cooler is installed between the TCE intermediate tank and the trichloroethylene tower, which injects the trichloroethylene tower bottom liquid into the TCE intermediate tank. A TCE stirring tank reflux pump is installed between the TCE stirring tank and the trichloroethylene tower. The TCE stirring tank is used to remove impurities from the trichloroethylene tower bottom liquid for purification.

2. The trichloroethylene distillation and separation apparatus according to claim 1, characterized in that: The TCE finished product tank is used to store trichloroethylene after distillation and purification, for later sale.

3. The trichloroethylene distillation and separation apparatus according to claim 1 further includes an intermediate column, characterized in that: The input end of the intermediate tower is connected to the output end of the trichloroethylene tower. The output end of the intermediate tower is connected to an intermediate tower reflux tank and a PCE tower. The output end of the PCE tower is connected to a PCE tower reflux tank and a tetrachloroethylene storage tank.

4. A method for distilling and separating trichloroethylene, comprising the trichloroethylene distillation and separation apparatus according to any one of claims 1-3, characterized in that: The specific steps include the following: Step 1: The liquid in the bottom of the stripping column is injected into the bottom liquid tank of the stripping column, and then sent to the low-boiling column for low boiling. The low-boiling substance collected from the top of the low-boiling column is injected into the low-boiling column reflux tank, and then refluxed back into the low-boiling column through the low-boiling column reflux tank to obtain the bottom liquid of the low-boiling column. Step 2: Inject the liquid from the bottom of the low-boiling tower into the trichloroethylene tower for heating. Control the outlet temperature at the top of the tower at 83-84℃. Then, it passes through the TCE tower total condenser and enters the TCE tower reflux tank. The non-condensable gas portion is discharged into the atmosphere. Step 3: Inject the trichloroethylene from the reflux tank in Step 2 into the TCE intermediate tank. Then, purify the trichloroethylene inside the TCE intermediate tank by mechanically stirring the trichloroethylene and distilled water for 2 hours. The distilled water contains 2%-5% silver ammonia solution. Let it stand for 30 minutes to separate the layers, remove the upper layer of water, and repeat the above operation several times. Then test the "silver ammonia reduction product" index until the silver ammonia reduction product is clear and free of turbidity to be considered qualified. Step 4: After the trichloroethylene has been purified once, a certain amount of color-changing silica gel (1 / 10 volume ratio) is added. The silica gel turns blue. Shake thoroughly for 2 hours to allow trace amounts of moisture to be adsorbed by the silica gel. Let it stand and filter, then remove the trichloroethylene and check whether it meets the standards. If it does, it is transferred back into the TCE tower for heating. The outlet temperature of the tower top is controlled at 83-84℃. After passing through the TCE tower condenser, the condensate enters the TCE tower reflux tank. The 99.99% trichloroethylene product in the TCE tower reflux tank passes through the TCE cooler and activated alumina filter to remove acid before entering the trichloroethylene metering tank. A stabilizer is added to the metering tank, and after mixing evenly, it is sent to the TCE intermediate tank and the TCE finished product tank.

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