Chloromethane waste acid treatment device

Abstract

The utility model provides a chloromethane waste acid treatment device, which comprises a waste acid halogenation unit, a water washing unit and a methanol recovery unit, and is characterized in that a waste acid halogenation reactor and a methanol recovery tower are additionally arranged on the basis of the current chloromethane synthesis device adopting an excess hydrogen chloride method, and meanwhile, an MVR heat pump rectification technology is adopted at the methanol recovery tower. According to the utility model, excessive methanol is added into the waste acid halogenation reactor, so that the excessive added hydrogen chloride is prevented from being analyzed and deeply desorbed from the waste water, and the production energy consumption is reduced. And meanwhile, the technical problems that the reaction speed of a methanol excess method is relatively low, and a reaction kettle with a relatively large volume is needed to provide enough retention time are also solved. And meanwhile, an MVR heat pump rectification technology is adopted in the methanol recovery tower, and a large amount of low-grade waste heat carried by gaseous methanol is increased to high-grade heat for reuse by utilizing heat pump rectification, so that steam consumption is greatly reduced.

Description

Technical Field

[0001] This utility model relates to the chemical industry, and in particular to a chloromethane waste acid treatment device. Background Technology

[0002] Chloromethane Also known as methyl chloride, chloromethane has a wide range of applications in the chemical industry due to its unique chemical structure and properties, including its use as a solvent, catalyst, and methylating agent. Currently, the demand for chloromethane is increasing year by year, but its production process requires the use of toxic substances such as chlorine or hydrochloric acid, and is characterized by high energy consumption and high pollution. Therefore, its preparation process needs further optimization.

[0003] The synthesis methods for chloromethane are relatively mature. Currently, the methanol chlorination process is mainly used in actual industrial production, and its reaction formula is as follows:

[0004]

[0005] Furthermore, the methanol chlorination process commonly uses the excess hydrogen chloride method. This method involves adding excess hydrogen chloride during the synthesis of chloromethane to achieve approximately 99% methanol conversion in the reaction. The disadvantages of the excess hydrogen chloride method include complex separation and purification processes. The excess hydrogen chloride requires desorption and deep desorption from wastewater, increasing the complexity and energy consumption of the production process. Inadequate recovery and treatment of excess hydrogen chloride can lead to excessive emissions, necessitating additional investment in environmental protection facilities. Moreover, approximately 70% of the steam heat in the excess hydrogen chloride method is consumed in hydrochloric acid desorption and deep desorption, with the remaining steam heat consumed in heating reactants and catalyst post-treatment, thus highlighting its high energy consumption.

[0006] Another commonly used method is the methanol excess method, which involves adding excess methanol during the synthesis of chloromethane to achieve approximately 99% conversion of hydrogen chloride in the reaction. The methanol excess method generally does not use a catalyst, resulting in a slower reaction rate and requiring a larger reactor to provide sufficient residence time. Furthermore, in the methanol excess method, approximately 60% of the steam heat is consumed in the reboiler of the methanol recovery tower, and approximately 35% of the steam heat is consumed in the vaporization of methanol before it enters the reactor, resulting in a high steam consumption problem. Utility Model Content

[0007] To address the problems raised in the background art, this application provides a chloromethane waste acid treatment device. Based on the chloromethane synthesis unit using the excess hydrogen chloride method commonly used by domestic enterprises, this device significantly reduces steam consumption by adding a waste acid halogenation reactor and a methanol recovery tower employing MVR heat pump distillation technology. Therefore, this chloromethane waste acid treatment device is essentially a technical modification of the chloromethane unit using the excess hydrogen chloride method. With only minor modifications to the existing unit, it achieves substantial energy savings and consumption reduction.

[0008] This utility model provides a chloromethane waste acid treatment device, which is used to separate materials generated during the synthesis of chloromethane and is connected to the reaction unit for synthesizing chloromethane. The device includes:

[0009] Waste acid halogenation unit: includes waste acid halogenation reactor;

[0010] The outlet of the chloromethane reactor in the chloromethane synthesis reaction unit is connected to the first inlet of the waste acid halogenation reactor;

[0011] Water washing unit: includes water washing tower and double-effect heat exchanger;

[0012] The outlet of the waste acid halogenation reactor is connected to the first inlet of the double-effect heat exchanger; the bottom outlet of the water washing tower is connected to the second inlet of the double-effect heat exchanger and a second inlet located at the top of the water washing tower via pipes; the first outlet of the double-effect heat exchanger is connected to the bottom inlet of the water washing tower, and the double-effect heat exchanger is used to exchange heat between the product in the waste acid halogenation reactor and the material collected from the bottom of the water washing tower.

[0013] Methanol recovery unit: includes methanol recovery tower, double-effect reboiler, compression unit and condensation unit;

[0014] The second outlet of the double-effect heat exchanger is connected to the inlet located in the middle of the methanol recovery tower; the top outlet of the methanol recovery tower is connected to the inlet of the compression device via a pipe, the outlet of the compression device is connected to the first inlet of the double-effect reboiler via a pipe, the bottom outlet of the methanol recovery tower is connected to the second inlet of the double-effect reboiler; the second outlet of the double-effect reboiler is connected to the first inlet at the bottom of the methanol recovery tower, the first outlet of the double-effect reboiler is connected to the inlet of the condensing device; and the outlet of the condensing device is connected to the inlet at the top of the methanol recovery tower.

[0015] Furthermore, the chloromethane waste acid treatment device also includes: a raw material supply unit; the raw materials supplied by the raw material supply unit to the chloromethane reactor in the chloromethane synthesis reaction unit include: gaseous hydrogen chloride, hydrochloric acid solution, and gaseous methanol; the raw material supply unit is connected to the second inlet of the waste acid halogenation reactor, and the raw materials supplied by the raw material supply unit to the waste acid halogenation reactor include: liquid methanol; the raw material supply unit is connected to the first inlet located at the top of the water washing tower, and the raw materials supplied by the raw material supply unit to the water washing tower include: water.

[0016] Furthermore, the raw materials in the chloromethane reactor include hydrogen chloride and gaseous methanol, the molar ratio of methanol to hydrogen chloride is (0.9-1):1, and the hydrogen chloride includes gaseous hydrogen chloride and hydrochloric acid solution; the raw materials in the waste acid halogenation reactor include liquid methanol and the product of the reaction in the chloromethane reactor; the feed molar ratio of total methanol to total hydrogen chloride in the two reactors is (1.05-1.1):1.

[0017] Furthermore, the chloromethane reactor may be equipped with a 75% zinc chloride acidic solution as a catalyst as needed; water is added to the first inlet at the top of the water washing tower to control the methanol content at the top outlet of the tower.

[0018] Furthermore, the concentration of hydrochloric acid solution in the waste acid halogenation reactor is 6 wt.% to 16 wt.%.

[0019] Furthermore, the reaction pressure of the chloromethane reactor and the waste acid halogenation reactor is 2-5 barg, and the reaction temperature is 125-150℃.

[0020] Furthermore, the temperature at the top of the water washing tower is 15-50℃, and the temperature at the bottom of the tower is 25-60℃.

[0021] The methanol recovery tower has a top temperature of 80-95℃ and a bottom temperature of 110-130℃.

[0022] Furthermore, the chloromethane waste acid treatment device also includes a preheating unit; the preheating unit includes a preheater, which is connected to the bottom outlet of the water washing tower and the second inlet of the double-effect heat exchanger via pipelines.

[0023] Furthermore, the bottom outlet of the methanol recovery tower is also connected to the preheater unit, which can use the heat from the material collected at the bottom of the methanol recovery tower to preheat the material collected at the bottom of the water washing tower.

[0024] Furthermore, the chloromethane waste acid treatment device also includes a cooling unit; the cooling unit includes a cooler, which is connected to the bottom outlet of the water washing tower and the second inlet at the top of the water washing tower via pipes.

[0025] Furthermore, the cooler is also connected to cooling water, which cools and washes the methanol and hydrogen chloride from the waste acid halogenation reactor in the water washing tower, thereby ensuring the quality of the chloromethane product extracted from the top of the water washing tower.

[0026] Furthermore, the methanol recovery unit also includes a methanol recovery tower reflux tank; the methanol recovery tower reflux tank is connected to the outlet of the condensation device and the inlet of the top of the methanol recovery tower via pipelines.

[0027] Furthermore, the chloromethane waste acid treatment device also includes a steam reboiler and a temperature sensor. The steam reboiler is located downstream of the outlet of the double-effect reboiler of the methanol recovery tower. The temperature sensor is located at the bottom of the methanol recovery tower to measure the temperature of the material at the bottom of the tower.

[0028] Furthermore, the chloromethane waste acid treatment device also includes: a DCS system, a regulating valve installed on the steam pipeline of the steam reboiler and connected to the DCS system, and a bypass pipeline installed between the compression device and the connecting pipeline from the double-effect reboiler to the condensation device, with a regulating valve installed on the bypass pipeline and connected to the DCS system.

[0029] Furthermore, the regulating valve is an automatic regulating valve.

[0030] This utility model has at least the following beneficial effects:

[0031] This utility model provides a chloromethane waste acid treatment device. The device is based on the current device for synthesizing chloromethane using the excess hydrogen chloride method, with the addition of a waste acid halogenation reactor and a methanol recovery tower. At the same time, MVR heat pump distillation technology is adopted at the methanol recovery tower.

[0032] This invention transforms the hydrogen chloride excess reaction into a methanol excess reaction by adding excess methanol to the waste acid halogenation reactor. This avoids the need for hydrochloric acid desorption and deep desorption from the wastewater after adding excess hydrogen chloride, which consumes a large amount of steam heat, thus reducing production energy consumption. Simultaneously, the hydrogen chloride excess method for chloromethane synthesis, which can use 75% zinc chloride as a catalyst, offers a faster reaction rate, thus solving the technical problem of the slow reaction rate and the need for a large-volume reactor to provide sufficient residence time in the methanol excess method. MVR heat pump distillation technology is used at the methanol recovery tower to elevate the large amount of low-grade waste heat carried by gaseous methanol to high-grade heat for reuse, thereby significantly reducing steam consumption and providing a systematic solution for the green and sustainable development of enterprises and society. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the technical solutions of this application.

[0034] Figure 1 This is a schematic diagram of the structure of the chloromethane waste acid treatment device provided by this utility model.

[0035] Figure label:

[0036] Waste acid halogenation reactor 1, double-effect heat exchanger 2, water washing tower 3, methanol recovery tower 4, compression unit 5, condensation unit 6, tower top reflux tank 7, double-effect reboiler 8, preheater 9, cooler 10. Detailed Implementation

[0037] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0038] In the description of this utility model, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0039] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature, that is, include one or more of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. When a feature "includes or contains" one or more of the features it encompasses, unless otherwise specifically described, this indicates that other features are not excluded and may be further included.

[0040] Unless otherwise expressly specified and limited, the terms "connection," "installation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art should be able to understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0041] Unless otherwise specified, all terms (including technical and scientific terms) used in the description of this embodiment have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0042] Figure 1 This is a schematic structural diagram of a chloromethane waste acid treatment device according to an embodiment of the present invention.

[0043] like Figure 1 As shown, in a specific embodiment, this utility model provides a chloromethane waste acid treatment device. This device is used to separate materials generated during the synthesis of chloromethane and is connected to the reaction unit for chloromethane synthesis. The device includes: a waste acid halogenation unit, comprising a waste acid halogenation reactor 1; the outlet of the chloromethane reactor in the chloromethane synthesis reaction unit is connected to the first inlet of the waste acid halogenation reactor 1. It should be explained here that... Figure 1 The diagram illustrates a waste acid halogenation reactor 1. A chloromethane reactor is connected in series upstream of the waste acid halogenation reactor 1. The chloromethane reactor has a reactant outlet on its top and a reactant inlet (i.e., the first inlet) on its top. The reactant outlet of the chloromethane reactor is connected to the first inlet of the waste acid halogenation reactor 1. During the treatment of chloromethane waste acid, the products generated after the reaction in the chloromethane reactor enter the waste acid halogenation reactor 1 through the reactant outlet of the chloromethane reactor, where they react again with the raw materials in the waste acid halogenation reactor.

[0044] Specifically, the reaction formula for synthesizing chloromethane using the methanol chlorination method is as follows:

[0045]

[0046] The apparatus of this invention is used for the excess synthesis of chloromethane from methanol, and the following reaction occurs in the waste acid halogenation unit:

[0047] The waste acid halogenation reactor 1 in the waste acid halogenation unit is connected in series with the chloromethane reactor in the chloromethane synthesis reaction unit. The raw materials in the chloromethane reactor include gaseous hydrogen chloride, hydrochloric acid solution, and gaseous methanol. In the chloromethane reactor, methanol and hydrogen chloride (here, hydrogen chloride includes gaseous hydrogen chloride and hydrochloric acid solution) react at a molar ratio of (0.9-1):1. In this invention, a slight excess of hydrogen chloride is added to the chloromethane reactor during the reaction process to ensure that the gaseous methanol reacts completely within the chloromethane reactor, thereby reducing the generation of the byproduct dimethyl ether and increasing the yield of the product chloromethane. The product generated from the reaction then enters the waste acid halogenation reactor 1 through a pipeline. Simultaneously, approximately 10% of the amount of methanol added to the waste acid halogenation reactor 1 is added beforehand to carry out a methanol chlorination reaction in the waste acid halogenation reactor 1. After the reaction in the waste acid halogenation reactor 1, the hydrogen chloride content in the reaction system can be reduced from approximately 5% to approximately 1%. The feed molar ratio of total methanol to total hydrogen chloride in the two reactors is approximately (1.05-1.1):1. In this invention, a slight excess of methanol is used in the waste acid halogenation reactor 1 to ensure that the hydrogen chloride in the reactor reacts as completely as possible, thereby increasing the conversion rate of hydrogen chloride, reducing the workload of discharging waste acid, reducing solid waste emissions, and achieving green production.

[0048] In one specific embodiment, the chloromethane waste acid treatment device further includes: a raw material supply unit; the raw materials supplied by the raw material supply unit to the chloromethane reactor in the chloromethane synthesis reaction unit include: gaseous hydrogen chloride, hydrochloric acid solution, and gaseous methanol; the raw material supply unit is connected to the second inlet of the waste acid halogenation reactor 1, and the raw materials supplied by the raw material supply unit to the waste acid halogenation reactor 1 include: liquid methanol; the raw material supply unit is connected to the first inlet located at the top of the water washing tower 3, and the raw materials supplied by the raw material supply unit to the water washing tower 3 include: water. Further, the chloromethane reactor may, as needed, add 75% zinc chloride acidic solution as a catalyst; adding water to the first inlet at the top of the water washing tower 3 is to control the methanol content at the top outlet of the tower.

[0049] In one specific embodiment, the raw materials in the chloromethane reactor include hydrogen chloride and gaseous methanol, the molar ratio of methanol to hydrogen chloride is (0.9-1):1, and the hydrogen chloride includes gaseous hydrogen chloride and hydrochloric acid solution; the raw materials in the waste acid halogenation reactor 1 include liquid methanol and the product after the reaction in the chloromethane reactor; the feed molar ratio of total methanol to total hydrogen chloride in the two reactors is (1.05-1.1):1.

[0050] In one specific embodiment, the concentration of hydrochloric acid solution in the waste acid halogenation reactor 1 is 6 wt.% to 16 wt.%. The purpose of setting the concentration of hydrochloric acid solution in the waste acid halogenation reactor 1 to be low is to ensure that the amount of hydrogen chloride gas overflowing from the reactor is small, thereby reducing the pressure on the subsequent system for hydrogen chloride recovery. This is because for low-concentration hydrochloric acid solutions, water will preferentially evaporate during the reaction process. As the water evaporates, the concentration of the hydrochloric acid solution increases before a small amount of hydrogen chloride gas is released.

[0051] In one specific embodiment, the reaction pressure of the chloromethane reactor and the waste acid halogenation reactor 1 is 2-5 barg, and the reaction temperature is 125-150℃.

[0052] In summary, compared to current chloromethane synthesis devices using the hydrogen chloride excess method, this invention adds a waste acid halide reactor 1 in series. By adding excess methanol to the waste acid halide reactor 1, the hydrogen chloride excess reaction is converted into a methanol excess reaction, thus avoiding the need for desorption and deep removal of the excess hydrogen chloride from the wastewater. Simultaneously, it retains the hydrogen chloride excess method chloromethane synthesis process using 75% zinc chloride as a catalyst in the preceding chloromethane reactor, which offers a relatively fast reaction rate. This avoids the technical problem of the slow reaction rate of the methanol excess method, which requires a large-volume chloromethane reactor to provide sufficient residence time. Since the reaction load of the waste acid halide reactor 1 is much lower than that of the chloromethane reactor, even with the methanol excess method, an excessively large reaction volume is not required.

[0053] like Figure 1 As shown in a specific embodiment, the chloromethane waste acid treatment device provided by this utility model includes at least a water washing unit, which includes a water washing tower 3 and a double-effect heat exchanger 2; the outlet of the waste acid halogenation reactor 1 is connected to the first inlet of the double-effect heat exchanger 2; the bottom outlet of the water washing tower 3 is connected to the second inlet of the double-effect heat exchanger 2 and the top inlet of the water washing tower 3 respectively through pipes; the first outlet of the double-effect heat exchanger 2 is connected to the bottom inlet of the water washing tower 3, and the double-effect heat exchanger 2 is used to exchange heat between the product in the waste acid halogenation reactor 1 and the material collected from the bottom of the water washing tower 3.

[0054] In one specific embodiment, the chloromethane waste acid treatment device provided by this utility model further includes at least a preheating unit, the preheating unit including a preheater 9, the bottom outlet of the water washing tower 3 is not directly connected to the second inlet of the double-effect heat exchanger 2, and the preheater 9 is connected to the bottom outlet of the water washing tower 3 and the second inlet of the double-effect heat exchanger 2 respectively through pipes.

[0055] In one specific embodiment, the chloromethane waste acid treatment device provided by this utility model further includes at least a cooling unit; the cooling unit includes a cooler 10, which is connected via pipes to the bottom outlet of the water washing tower 3 and the second inlet at the top of the water washing tower 3. Furthermore, the cooler 10 is also connected to cooling water, which cools and washes the methanol and hydrogen chloride from the waste acid halogenation reactor 1 inside the water washing tower 3, thereby ensuring the quality of the chloromethane product extracted from the top of the water washing tower 3.

[0056] In one specific embodiment, the product collected from the outlet of the waste acid halogenation reactor 1 enters the double-effect heat exchanger 2 through the first inlet of the double-effect heat exchanger 2. Simultaneously, the material collected from the bottom of the water washing tower 3 enters the double-effect heat exchanger 2 through a pipe from the bottom outlet of the tower and through the second inlet of the double-effect heat exchanger 2. In the double-effect heat exchanger 2, the product carrying a large amount of reaction heat exchanges heat with the material from the bottom of the water washing tower 3, thereby reducing the temperature of the reactor output product and simultaneously increasing the temperature of the material at the bottom of the water washing tower 3 in this step. Furthermore, the product after heat exchange is collected from the first outlet of the double-effect heat exchanger 2, and the first outlet of the double-effect heat exchanger 2 is connected to the bottom inlet of the water washing tower 3. The product collected from the waste acid halogenation reactor 1, after heat exchange in the double-effect heat exchanger 2, enters the water washing tower 3 through the bottom inlet. The water washing in the water washing tower 3 can significantly reduce the water, hydrochloric acid, and methanol in the components coming out from the top of the tower, obtaining relatively clean chloromethane and dimethyl ether, which are then sent to subsequent processes for further purification and drying. Part of the material coming out from the bottom of the water washing tower 3 is cooled by the cooler 10 and then recycled to the second inlet at the top of the tower to enter the water washing tower 3 for washing the crude chloromethane. The other part is heated sequentially by the preheater 9 and the double-effect heat exchanger 2 before entering the methanol recovery tower 4. Fresh water is used for further washing at the first inlet at the top of the water washing tower 3, thereby ensuring the quality of the chloromethane and dimethyl ether collected from the top of the tower.

[0057] In the chloromethane waste acid treatment device provided by this utility model, the function of the water washing unit is to separate the reaction products, including chloromethane, unreacted hydrogen chloride and methanol, and the water and dimethyl ether produced in the reaction. After water washing in water washing tower 3, the components coming out of the top of the tower are mainly chloromethane and dimethyl ether, while the components coming out of the bottom of the tower are mainly acid water and methanol. The temperature of the top of the water washing tower 3 is 15-50℃. The hydrochloric acid content in the acid water at the bottom of the tower is 1 wt.%-3 wt.%, and the methanol content is about 10 wt.%-20 wt.%.

[0058] like Figure 1 As shown in a specific embodiment, the chloromethane waste acid treatment device provided by this utility model includes at least a methanol recovery unit. The methanol recovery unit includes a methanol recovery tower 4, a double-effect reboiler 8, a compression device 5, and a condensation device 6. The second outlet of the double-effect heat exchanger 2 is connected to the inlet located in the middle of the methanol recovery tower 4. The top outlet of the methanol recovery tower 4 is connected to the inlet of the compression device 5 through a pipe. The outlet of the compression device 5 is connected to the first inlet of the double-effect reboiler 8 through a pipe. The bottom outlet of the methanol recovery tower 4 is connected to the second inlet of the double-effect reboiler 8. The first and second outlets of the double-effect reboiler 8 are respectively connected to the inlet of the condensation device 6 and the first inlet at the bottom of the methanol recovery tower 4. The outlet of the condensation device 6 is connected to the inlet at the top of the methanol recovery tower 4. In one specific embodiment, the methanol recovery unit further includes a top reflux tank 7 of the methanol recovery tower 4. The outlet of the condensing device 6 is not directly connected to the inlet of the top of the methanol recovery tower 4. The top reflux tank 7 of the methanol recovery tower 4 is connected to the outlet of the condensing device 6 and the inlet of the top of the methanol recovery tower 4 respectively through pipelines.

[0059] In a specific embodiment, the liquid containing methanol, water, and hydrogen chloride produced from the bottom of the water washing tower 3, after heat exchange in the double-effect heat exchanger 2 described above, enters the methanol recovery tower 4 through the inlet located in the middle of the methanol recovery tower 4, where the components are separated. Specifically, gaseous methanol enters the compression device 5 connected to the top outlet of the methanol recovery tower 4 via a pipeline. The compression device 5 can be a compressor. After being pressurized by the compressor, the temperature of the gaseous methanol is increased, and then it is used as a heat source to provide heat to the double-effect reboiler 8 of the methanol recovery tower 4. The technology of utilizing gaseous methanol for compression belongs to mechanical vapor recompression (MVR) technology. MVR technology consumes a small amount of compressor compression work to upgrade a large amount of low-grade waste heat carried by secondary steam to high-grade heat for reuse, and is therefore also known as MVR heat pump technology. In this utility model, MVR heat pump technology is combined with the traditional distillation production process to fully recover the heat of the top steam and reduce the consumption of cold and hot utilities in the distillation system. After being compressed by the compression device 5, the gaseous methanol is used as a heat source to heat the double-effect reboiler 8 of the methanol recovery tower 4. Then, it enters the condensation device 6 connected to the double-effect reboiler 8 via a pipeline. The condensation device 6 can be a condenser, and the refrigerant can be cooling water or cooling gas. After entering the condensation device 6, the methanol condenses, and a portion is returned to the methanol recovery tower 4. In some specific embodiments, a portion of the condensed methanol is recovered to the top reflux tank 7 of the methanol recovery tower 4, while the remaining methanol is discharged from the current system as a product. Simultaneously, a portion of the material collected from the bottom of the methanol recovery tower 4 is heated by the double-effect reboiler 8 and returned to the tower for further separation. The remainder is treated as wastewater and preheated by the preheater 9 to preheat the material at the bottom of the water washing tower 3 before being discharged from the current system.

[0060] In one specific embodiment, the pressure of the methanol recovery tower 4 is 0.5-2 barg, the top temperature of the methanol recovery tower 4 is 70-85℃, the outlet temperature of the compression device 5 is 140-170℃, and the bottom temperature of the methanol recovery tower 4 is 110-130℃. In the chloromethane waste acid treatment device provided by this invention, the methanol recovery unit aims to recover approximately 15% of the methanol in the waste hydrochloric acid water. As described in the background art, in the preparation process of chloromethane synthesis using the methanol excess method, the steam consumed by the double-effect reboiler 8 of the methanol recovery tower 4 accounts for approximately 60% of the total steam consumption of the chloromethane synthesis unit. This invention utilizes MVR technology, using the compression device 5 to compress the material, and then uses the compressed material as a heat source to heat the bottom material of the tower to 120℃ through the double-effect reboiler 8 for vaporization before returning it to the tower, thus achieving the reboiling function and saving a significant amount of steam.

[0061] In one specific embodiment, to ensure a stable heat source for heating the bottom material of the methanol recovery tower 4 during start-up and shutdown, and fluctuations in the flow rate, pressure, and temperature at the outlet of the compression unit 5, this invention further optimizes the chloromethane waste acid treatment device. Specifically, the chloromethane waste acid treatment device also includes a steam reboiler and a temperature sensor. The steam reboiler is located downstream of the outlet of the double-effect reboiler 8 of the methanol recovery tower 4; the temperature sensor is located at the bottom of the methanol recovery tower 4 to measure the temperature of the bottom material. Furthermore, the chloromethane waste acid treatment device also includes a DCS system. A regulating valve is installed on the steam pipeline of the steam reboiler and connected to the DCS system. A bypass pipeline is installed between the compression unit 5 and the connecting pipeline from the double-effect reboiler 8 to the condenser 6. A regulating valve is installed on the bypass pipeline and connected to the DCS system. Furthermore, the regulating valve is an automatic regulating valve.

[0062] In actual industrial production, when the temperature at the bottom of the methanol recovery tower 4 is lower than the set value, the DCS system automatically opens and adjusts the regulating valve of the steam reboiler, while simultaneously closing the automatic regulating valve on the bypass line of the double-effect reboiler 8, thereby increasing the steam flow to provide more heat. When the temperature at the bottom of the methanol recovery tower 4 is higher than the set value, the DCS system automatically opens and adjusts the automatic regulating valve on the bypass line of the double-effect reboiler 8, while simultaneously closing the steam regulating valve of the steam reboiler, thereby reducing the flow rate of the material from the outlet of the compression unit 5 through the double-effect reboiler 8 to reduce the supply of heat.

[0063] Table 1 shows a comparison of energy consumption and cost for different methods of synthesizing chloromethane.

[0064] Table 1

[0065]

[0066] Note: The above data comes from production practice, journal articles, and Aspen plus V14.

[0067] Roughly calculated, for a chloromethane synthesis unit with an annual output of 350,000 tons, the device provided in this utility model can save 37 million yuan per year compared to the mainstream process of chloromethane synthesis using excess hydrogen chloride. The estimated renovation cost is 20 million yuan, so the investment can be recovered in just over six months.

[0068] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application.

[0069] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0070] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A chloromethane waste acid treatment apparatus characterized by comprising: The chloromethane waste acid treatment device is used for separating materials generated in a chloromethane synthesis process, and is communicated with a reaction unit for synthesizing chloromethane. The waste acid halogenation unit comprises a waste acid halogenation reactor. An outlet of a chloromethane reactor in the reaction unit for synthesizing chloromethane is communicated with a first inlet of the waste acid halogenation reactor. The water washing unit comprises a water washing tower and a double-effect heat exchanger. An outlet of the waste acid halogenation reactor is communicated with a first inlet of the double-effect heat exchanger; a bottom outlet of the water washing tower is communicated with a second inlet of the double-effect heat exchanger and a second inlet arranged at an upper part of the water washing tower, respectively, by pipelines; and a first outlet of the double-effect heat exchanger is communicated with a bottom inlet of the water washing tower, so that the double-effect heat exchanger is used for heat exchange between products in the waste acid halogenation reactor and materials taken out from the bottom of the water washing tower. The methanol recovery unit comprises a methanol recovery tower, a double-effect reboiler, a compression device and a condensing device. A second outlet of the double-effect heat exchanger is communicated with an inlet arranged in a middle part of the methanol recovery tower; a top outlet of the methanol recovery tower is communicated with an inlet of the compression device by a pipeline; an outlet of the compression device is communicated with a first inlet of the double-effect reboiler by a pipeline; a bottom outlet of the methanol recovery tower is communicated with a second inlet of the double-effect reboiler; a second outlet of the double-effect reboiler is communicated with a first inlet of a bottom part of the methanol recovery tower; a first outlet of the double-effect reboiler is communicated with an inlet of the condensing device; and an outlet of the condensing device is communicated with an inlet of a top part of the methanol recovery tower.

2. The apparatus of claim 1, wherein, The device further comprises: A raw material providing unit; The raw material providing unit provides raw materials for the chloromethane reactor in the reaction unit for synthesizing chloromethane, and the raw materials comprise gaseous hydrogen chloride, hydrochloric acid solution and gaseous methanol; The raw material providing unit is communicated with a second inlet of the waste acid halogenation reactor, and the raw material providing unit provides raw materials for the waste acid halogenation reactor, and the raw materials comprise liquid methanol; The raw material providing unit is communicated with a first inlet arranged at a top part of the water washing tower, and the raw material providing unit provides raw materials for the water washing tower, and the raw materials comprise water.

3. The apparatus of claim 1, wherein, The device further comprises: A preheating unit; The preheating unit comprises a preheater, and the preheater is communicated with the bottom outlet of the water washing tower and the second inlet of the double-effect heat exchanger, respectively, by pipelines; A cooling unit: The cooling unit comprises a cooler, and the cooler is communicated with the bottom outlet of the water washing tower and the second inlet arranged at the upper part of the water washing tower, respectively, by pipelines.

4. The apparatus of claim 3, wherein, The bottom outlet of the methanol recovery tower is further communicated with the preheater, and the preheating unit can use heat of materials taken out from the bottom of the methanol recovery tower to preheat materials taken out from the bottom of the water washing tower.

5. The apparatus of claim 1, wherein, The methanol recovery unit further comprises: A methanol recovery tower reflux tank; The methanol recovery tower reflux tank is communicated with the outlet of the condensing device and the inlet of the top part of the methanol recovery tower, respectively, by pipelines.

6. The apparatus of claim 1, wherein, The device further comprises: a steam reboiler arranged downstream of the double-effect reboiler outlet of the methanol recovery column; and a temperature sensor arranged at the bottom of the methanol recovery column for measuring the temperature of the bottom material.

7. The apparatus of claim 6, wherein, The device further comprises: a DCS system, an adjusting valve is arranged on the steam pipeline of the steam reboiler and connected to the DCS system, and a bypass pipeline is arranged between the connecting pipeline of the compression device to the condensing device through the double-effect reboiler, an adjusting valve is arranged on the bypass pipeline and connected to the DCS system.

8. The apparatus of claim 7, wherein, The adjusting valve is an automatic adjusting valve.

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