Energy-saving production method of ethyl chloride

Abstract

The invention discloses an energy-saving production method of ethyl chloride, and belongs to the field of chemical production. Aiming at the problems of high energy consumption, long flow, material transfer risk and the like in the existing two-kettle two-step process, the invention provides an integrated optimization scheme which comprises the following steps: sequentially performing primary chlorination, medium switching and secondary chlorination in a single reaction kettle; in the primary chlorination stage, circulating water with the temperature of 10-35 DEG C is used as a cooling medium to control the reaction temperature to be 70 DEG C or below; after chlorine introduction is finished, a jacket medium is switched to be low-pressure steam, and the materials are heated to 88-90 DEG C for secondary chlorination and heat preservation. According to the invention, circulating water is used for completely replacing a high-energy-consumption frozen brine system, and reaction equipment is combined, so that the production energy consumption and equipment investment are greatly reduced, the production period is shortened by about 10%, meanwhile, the safety and environment-friendly hidden dangers caused by material transfer are thoroughly eliminated, the product purity is stably improved to 99% or above, and the production cost is reduced. The method has the advantages of remarkable energy conservation, safety, reliability, high product quality and the like.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, and more specifically, to an energy-saving production method for ethyl chloride. Background Technology

[0002] Ethyl chloride (O,O-diethylthiophosphoric chloride) is an important intermediate in organophosphorus pesticide production, widely used in the manufacture of various insecticides such as parathion, phoxim, and chlorpyrifos. Its industrial production typically uses ethanol and phosphorus pentasulfide as raw materials, proceeding through sulfidation, chlorination, and distillation processes. The chlorination process is the core and critical step, as it is a strongly exothermic reaction. The control of the reaction's thermodynamics and kinetics directly affects product selectivity, yield, and production safety.

[0003] In existing technologies, the chlorination production of ethyl chloride generally employs a two-step batch process. Specifically: the first step is primary chlorination, where ethyl sulfide is added to a dedicated chlorination reactor, and chlorine gas is introduced at a relatively low temperature (usually controlled at 25-50°C). Due to the intense exothermic reaction, this stage typically relies on a low-temperature chilled brine system (usually maintained below -15°C) for forced cooling of the reactor to remove the heat and prevent temperature runaway. After the primary chlorination reaction is completed, the reactants are pumped through pipelines to another dedicated heated reactor for the second step of secondary chlorination. In the heated reactor, the material is heated to above 90°C to complete the deep chlorination reaction, ultimately yielding qualified crude ethyl chloride.

[0004] While the traditional "two-reactor, two-step" process has been widely adopted, its inherent drawbacks are becoming increasingly apparent: First, the process is lengthy, involving two relatively independent reaction stages and intermediate material transfer steps, resulting in long production cycles and low equipment utilization. Second, the equipment investment and operating costs are high, requiring at least two reaction vessels, supporting pipelines, valves, and two independent temperature control systems. In particular, the large refrigeration units needed to maintain the low-temperature frozen brine (usually calcium chloride or ethylene glycol solution) consume enormous amounts of electricity, representing a major energy drain in the production process. Third, during the transfer of materials from the chlorination vessel to the heating vessel, leaks and spills are prone to occur at connection points such as flanges, pumps, and valves, causing not only material yield losses but also environmental pollution and safety hazards. Finally, the complex intermittent operation places high demands on personnel, and product quality is prone to fluctuations between batches. Therefore, there is an urgent need in this field for a new process for the production of ethyl chloride that can simplify the process, reduce energy consumption, eliminate transfer risks, and improve product quality stability. Summary of the Invention

[0005] In view of the problems existing in the production process of ethyl chloride in the above-mentioned technologies, such as lengthy process, high energy consumption, large equipment investment, safety and environmental risks in material transfer, and complex operation, the present invention provides an energy-saving production method for ethyl chloride. Through process integration and innovative temperature control strategies, the entire chlorination process can be completed safely, efficiently and economically in a single reactor.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An energy-efficient method for producing ethyl chloride includes the following steps:

[0008] S1. Primary chlorination stage: In a single reactor, chlorine gas is introduced into the material containing ethyl sulfide to carry out the chlorination reaction, while a cooling medium is introduced into the jacket of the reactor to control the temperature of the chlorination reaction to be below 70°C.

[0009] S2, Medium switching: When the chlorine flow reaches the set value, stop the chlorine flow and drain the cooling medium in the jacket, switch the medium passage configured on the jacket, and introduce heating medium into the jacket;

[0010] S3, Secondary chlorination and heat preservation stage: The material in the reactor is heated to 88°C using a heating medium to carry out a secondary chlorination reaction. The reaction temperature is maintained in the range of 88-90°C by adjusting the state of the medium in the jacket. The temperature is kept for 2 hours. After the reaction is completed, crude ethyl chloride is obtained.

[0011] The cooling medium is circulating water with a temperature between 10 and 35°C.

[0012] Preferably, in step S1, the temperature of the cooling medium is 15–30°C.

[0013] Preferably, the temperature of the chlorination reaction in step S1 is controlled at 50–70°C.

[0014] Preferably, in step S1, the amount of chlorine gas introduced is 38% to 40% of the mass of the ethyl sulfide.

[0015] Specifically, the jacket of the reactor has a cooling medium passage interface and a heating medium passage interface for connecting to equipment that provides the corresponding medium. The cooling medium passage interface and the heating medium passage interface are equipped with an electronically controlled switching device.

[0016] Specifically, while step S1 is being performed, the hydrogen chloride gas produced by the reaction is drawn out and treated by a three-stage falling film water absorption process to generate hydrochloric acid as a byproduct. The exhaust gas after absorption enters the waste gas treatment system.

[0017] Preferably, in step S2, the heating medium is low-pressure steam with a pressure of 0.6 to 0.8 MPa.

[0018] Specifically, in step S3, the process of maintaining the reaction temperature in the range of 88 to 90°C by adjusting the medium flow state in the jacket includes: after the material in the reactor is heated to 88°C, the heating medium flow is stopped, and then the cooling medium passage in the jacket is switched to the ready state. At the same time, the reaction temperature is monitored, and when the reaction temperature exceeds 90°C, the passage is opened to flow the cooling medium.

[0019] Specifically, in step S3, after the cooling medium is introduced, the opening of the cooling medium passage is adjusted according to the monitored reaction temperature to maintain the reaction temperature within the range of 88 to 90°C.

[0020] Specifically, in step S3, the process of maintaining the reaction temperature in the range of 88 to 90°C by adjusting the state of the medium in the jacket further includes: when the reaction temperature drops to 88°C while the cooling medium is in the state of inlet, stopping the inlet of the cooling medium and switching the heating medium passage in the jacket to the ready state.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) This invention completely replaces the low-temperature frozen brine in the traditional process with room temperature circulating water for primary chlorination cooling, which eliminates the need for the large-scale refrigeration unit and significantly reduces energy consumption and operating costs. According to actual measurements and calculations, this alone can reduce electricity consumption in the production process by more than 90%. Based on the large-scale annual production, it can save hundreds of thousands of yuan in electricity costs every year, demonstrating extremely significant energy-saving benefits.

[0023] (2) The present invention innovatively integrates the "primary chlorination" and "secondary chlorination" reactions that are carried out in two separate reactors in the traditional process into one reactor and carried out in stages in sequence, thereby eliminating the complex intermediate material transfer steps, shortening the process flow, shortening the production cycle by about 10%, and improving production efficiency, reducing the production time from the original 10-12 hours to 9-10 hours, and effectively improving the production capacity of the device under the same equipment conditions.

[0024] (3) By optimizing the process, this invention completely avoids the material transfer process between reactors, fundamentally eliminating the risk of leakage that may occur in this step. This not only improves the production environment and reduces the probability of safety accidents, but also reduces the loss of volatile materials. At the same time, based on the simplification of the process and the stable control of temperature, the consistency and selectivity of the reaction are improved. Actual production data show that the purity of the ethyl chloride product obtained by the method of this invention is consistently above 99.2%, which is a significant improvement over the traditional method (approximately 98.5%).

[0025] (4) The process optimization of the present invention also reduces the number of required reactors, connecting pipes, valves and control instruments, etc., reducing the initial fixed asset investment. Since the system no longer includes complex moving equipment such as large refrigeration units, the daily maintenance workload and maintenance costs are also significantly reduced.

[0026] (5) The operation steps of the method of the present invention are clear, and there is no need to carry out dangerous material transfer operations, which reduces the labor intensity of operators and the risk of human error. Based on the reaction heat risk assessment data, the upper limit of the reaction temperature set by the present invention at each stage is far lower than the material thermal decomposition initiation temperature, which has sufficient safety production boundaries. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process flow of an embodiment of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0029] Example

[0030] like Figure 1 As shown, the energy-saving production method of this ethyl chloride includes the following steps:

[0031] S1. Primary Chlorination Stage: Ethyl sulfide is added to a reactor equipped with a heat exchange jacket. Stirring is started, and circulating water at a temperature of 10–35°C is introduced into the jacket as a cooling medium. The temperature of the circulating water is preferably matched to the ambient temperature, for example, 15–30°C, which can be determined based on the actual ambient temperature in different regions and seasons, thereby reducing the energy consumption required for handling the cooling medium. Under the cooling effect of the circulating water, chlorine gas is slowly introduced into the material in the reactor to carry out the chlorination reaction. By controlling the chlorine gas introduction rate (usually 80–120 kg / h), the temperature of the entire primary chlorination reaction stage is maintained below 70°C, preferably within the range of 50–70°C. This step uses ambient temperature circulating water instead of the low-temperature chilled brine in traditional processes, fundamentally eliminating the dependence on high-energy-consuming refrigeration systems. The jacket of the reactor has cooling medium and heating medium interfaces for connecting to equipment that provides the corresponding media (e.g., a circulating water network for cooling and an industrial steam network for heating). These interfaces are equipped with electrically controlled switching devices. The switching devices can be electrically controlled valves or similar devices, working in conjunction with the monitoring and control systems to achieve real-time adjustments to the production process. During the primary chlorination reaction, the generated hydrogen chloride gas is extracted and treated by a three-stage falling film water absorption process to produce hydrochloric acid as a byproduct. The absorbed tail gas then enters the waste gas treatment system.

[0032] S2. Medium Switching: When the amount of chlorine gas introduced reaches the set proportion of ethyl sulfide (e.g., 38%–40%), stop the chlorine supply, marking the end of the first chlorination reaction. At this time, drain the circulating water in the reactor jacket, switch the medium passage configured on the jacket, that is, switch the cooling medium passage to the heating medium passage, and then introduce the heating medium into the jacket. Low-pressure steam with a pressure of 0.6–0.8 MPa can be used as the heating medium.

[0033] S3. Secondary Chlorination and Heating Stage: Utilizing the heat provided by the heating medium, the material in the reactor is heated from the temperature at the end of the primary chlorination (usually around 60°C) to 88°C for secondary chlorination. The reaction temperature is maintained within the range of 88–90°C by adjusting the flow of the medium in the jacket, and held for 2 hours. After the reaction is complete, crude ethyl chloride is obtained. In this stage, the reaction temperature is controlled by adjusting the flow of the medium in the jacket, achieving temperature interlock control and maintaining the reaction temperature within the range of 88–90°C. The process includes: after the material in the reactor is heated to 88°C, the flow of the heating medium is stopped, and then the cooling medium passage in the jacket is switched to the ready state. Simultaneously, the reaction temperature is monitored. When the reaction temperature exceeds 90°C, the passage is opened to introduce the cooling medium to lower the reaction temperature. After introducing the cooling medium, the opening of the cooling medium passage is adjusted according to the monitored reaction temperature to maintain the reaction temperature within the range of 88–90°C. Furthermore, when the reaction temperature drops to 88°C while the cooling medium is being introduced, the introduction of the cooling medium is stopped to avoid the reaction temperature from becoming too low, and the heating medium passage in the jacket is switched to the ready state.

[0034] Thus, through precise temperature control, the secondary chlorination reaction temperature is stably maintained within the target range, allowing the reaction to complete within the specified holding time, ultimately yielding crude ethyl chloride. The hydrogen chloride tail gas produced in the reaction can be continuously extracted and treated by an absorption system.

[0035] The invention will be described in detail below through application examples in industrial production.

[0036] Equipment Preparation: A 3000L glass-lined reactor is used as the core reaction equipment. This reactor is equipped with a switchable media jacket, an anchor agitator, a chlorine distribution pipe, temperature sensors, and pressure sensors. The jacket has two sets of inlet and outlet interfaces: one set connects to the circulating water network (providing circulating cooling water at approximately 15°C), and the other set connects to the low-pressure steam network (providing 0.8MPa steam). The media switching is automatically achieved through an electrically controlled valve and control system. The reactor's gas phase outlet is connected to a three-stage falling film absorption tower to absorb the hydrogen chloride gas produced in the reaction, producing hydrochloric acid as a byproduct. The exhaust gas after absorption is then connected to the factory's centralized waste gas treatment system.

[0037] Feeding and Primary Chlorination: Start the hydrogen chloride absorption system to maintain a slight negative pressure in the reactor system. Add 2000 kg of ethyl sulfide (mainly O,O-diethyl dithiophosphate) to the reactor. Start the agitator, controlling the speed at 60 rpm. Open the electrically controlled valve of the cooling medium passage on the jacket, introducing factory circulating cooling water at approximately 15°C into the jacket. Then, controlled by a mass flow meter, slowly introduce chlorine gas into the liquid phase inside the reactor, with an initial chlorination rate controlled at 120 kg / h. By monitoring the reactor temperature in real time, dynamically adjust the chlorine gas introduction rate to ensure that the reaction temperature inside the reactor is maintained between 60-65°C throughout the chlorination process, with a maximum not exceeding 70°C. The total chlorine gas introduced is controlled at 39% of the ethyl sulfide mass, approximately 780 kg. This primary chlorination stage lasts 6-7 hours. During this process, the generated hydrogen chloride gas is promptly extracted and absorbed.

[0038] Medium switching operation: When the cumulative chlorine flow reaches 780 kg, close the chlorine feed valve to stop chlorination. The first chlorination reaction is complete, and the temperature inside the reactor is approximately 64°C. Subsequently, close the jacket circulating water inlet and outlet valves and open the drain valve to empty the residual circulating water in the jacket. After emptying, switch the valves and open the electrically controlled valve on the heating medium passage to introduce low-pressure steam (0.8 MPa) into the jacket for heating.

[0039] Secondary chlorination and heat preservation: After steam is introduced, the heat of the steam is used to slowly raise the temperature of the material to 88°C for secondary chlorination. The heating process takes about 1 hour. Then, the heat preservation stage begins. In this stage, a temperature interlock control strategy is used to maintain the reaction temperature within the target range of 88-90°C. First, the cooling medium passage is placed in the ready state, and the electronically controlled valve is kept in standby mode for rapid opening. At the same time, the temperature inside the reactor is monitored in real time. If the temperature exceeds the set upper limit of 90°C (for example, reaching 91°C), the cooling medium passage is automatically opened, and circulating water is introduced for cooling. The valve opening of the cooling medium passage can be adjusted according to the temperature monitoring to control the cooling rate of the circulating water and ensure that the temperature is maintained within the target range. When the temperature drops back to 88°C (for example, from 89°C to 88°C), the circulating water is further reduced or shut off, and the heating medium passage is switched to the ready state so that if the temperature drops further from 88°C (for example, from 88°C to 87°C), the circulating water can be stopped in time, drained, and steam added for heating to compensate for the temperature. Under precise control of dynamic temperature equilibrium, the temperature was maintained for 2 hours to ensure the secondary chlorination process proceeded fully. After the maintenance period, samples were taken for analysis.

[0040] Product post-processing: After confirming the completion of the reaction, the obtained crude ethyl chloride is sent to the subsequent distillation section for purification to obtain high-purity 0,0-diethylthiophosphoric chloride. The reactor is then prepared for the next batch production.

[0041] The key operational data of the embodiments of the present invention (taking 4 consecutive batches) are shown in Table 1.

[0042]

[0043] Table 1 Key operational data of the embodiments of the present invention (after modification)

[0044] Experimental verification and data comparison

[0045] To objectively and quantitatively evaluate the effectiveness of the method of the present invention, a comparative test was conducted in the same factory area using the traditional two-reactor two-step process.

[0046] This comparative example demonstrates a traditional two-stage, two-reactor process using two independent reactors (a chlorination reactor and a heating reactor). The primary chlorination stage is cooled using chilled brine at approximately -15°C. The process is as follows: 2000 kg of ethyl sulfide is added to the chlorination reactor, stirring is started, and the associated chilled brine system is activated. Chilled brine at approximately -15°C is introduced into the jacket for cooling. Chlorine gas is slowly introduced into the chlorination reactor, controlling the temperature inside at 48-52°C. When approximately 780 kg of chlorine gas (39% chlorine concentration) has been introduced, chlorination is stopped, and the jacket chilled brine valve is closed. This process takes 6-7 hours. Next, all material is transferred from the chlorination reactor to the heating reactor via a system consisting of pumps, pipes, and valves. This transfer process takes 1-2 hours and involves multiple dynamic and static sealing points. Then, in the heating reactor, stirring is activated, the steam trap valve is opened, and the jacket steam is turned on. The temperature is raised to 88-90°C for approximately 1 hour, followed by a 2-hour holding period to complete the secondary chlorination process.

[0047] Key operational data for the comparative analysis (4 consecutive batches) are shown in Table 2.

[0048]

[0049] Table 2 Key operational data for the comparative example (before modification)

[0050] The results of comparing the data from the embodiments of the present invention with the comparative data described above are as follows:

[0051] 1. This invention directly eliminates the need for refrigeration units, resulting in a significant reduction in power consumption. Each batch saves approximately 221 kWh of power. Based on this production volume and an annual production of 500 batches, the estimated annual power savings are approximately 221 kWh * 500 * 0.45 yuan ≈ 50,000 yuan. If the production capacity of a single batch is increased, this power consumption can be saved even more, demonstrating significant economic value.

[0052] 2. The production cycle of this invention is shortened by an average of about 1 hour, and efficiency is increased by about 10%, thereby improving equipment capacity. This is mainly due to the elimination of intermediate transfer time such as pumping and pigging, and the fact that the heating process is more efficient because it can start without waiting for all materials to have been transferred.

[0053] 3. The purity of the product of this invention is increased by an average of about 0.83 percentage points, all exceeding 99%. Analysis suggests that this is mainly due to two factors: first, it avoids volatilization losses and potential contamination during material transfer; second, it is carried out in a single reactor, resulting in a more consistent and stable temperature control curve, reducing side reactions caused by sudden changes in the reaction environment.

[0054] 4. This invention completely eliminates the material transfer process, with no odor or potential leakage points on site, significantly improving intrinsic safety and environmental friendliness.

[0055] 5. Risk Assessment Evidence: Reaction calorimetry and adiabatic accelerated calorimetry tests conducted on the materials used in this process show that the thermal decomposition initiation temperature TD24 (the temperature at which the maximum reaction rate is reached in 24 hours under adiabatic conditions) of the primary chlorination material is 105.1℃. This invention strictly controls the temperature below 70℃ during the primary chlorination stage, far below TD24, providing an extremely high safety margin. The temperature during the secondary chlorination stage is controlled at around 90℃, also far below its corresponding TD24 (121.5℃). This theoretically confirms the feasibility of using circulating water cooling and the safety of the entire process.

[0056] In summary, this invention integrates two chlorination reactions into a single reactor and achieves temperature program control through ingenious medium switching, successfully solving the problems of high energy consumption, long process, and high risk in traditional processes. It achieves multiple goals such as energy saving, consumption reduction, quality improvement, efficiency enhancement, and safety, and has outstanding industrial application value.

[0057] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any changes made based on the design principles of the present invention, or any non-creative modifications made thereon, shall fall within the scope of protection of the present invention.

Claims

1. An energy-saving production method for ethyl chloride, characterized in that, Includes the following steps: S1. Primary chlorination stage: In a single reactor, chlorine gas is introduced into the material containing ethyl sulfide to carry out the chlorination reaction, while a cooling medium is introduced into the jacket of the reactor to control the temperature of the chlorination reaction to be below 70°C. S2, Medium switching: When the chlorine flow reaches the set value, stop the chlorine flow and drain the cooling medium in the jacket, switch the medium passage configured on the jacket, and introduce heating medium into the jacket; S3, Secondary chlorination and heat preservation stage: The material in the reactor is heated to 88°C using a heating medium to carry out a secondary chlorination reaction. The reaction temperature is maintained in the range of 88-90°C by adjusting the state of the medium in the jacket. The temperature is kept for 2 hours. After the reaction is completed, crude ethyl chloride is obtained. The cooling medium is circulating water with a temperature between 10 and 35°C.

2. The energy-saving production method of ethyl chloride according to claim 1, characterized in that, In step S1, the temperature of the cooling medium is 15–30°C.

3. The energy-saving production method of ethyl chloride according to claim 1, characterized in that, In step S1, the temperature of the chlorination reaction is controlled at 50–70°C.

4. The energy-saving production method of ethyl chloride according to claim 1, characterized in that, In step S1, the amount of chlorine gas introduced is 38% to 40% of the mass of the ethyl sulfide.

5. The energy-saving production method of ethyl chloride according to claim 1, characterized in that, The jacket of the reactor has a cooling medium passage interface and a heating medium passage interface for connecting to equipment that provides the corresponding medium. The cooling medium passage interface and the heating medium passage interface are equipped with an electronically controlled switching device.

6. The energy-saving production method of ethyl chloride according to claim 1, characterized in that, While step S1 is being performed, the hydrogen chloride gas produced by the reaction is drawn out and treated by a three-stage falling film water absorption process to generate hydrochloric acid as a byproduct. The exhaust gas after absorption enters the waste gas treatment system.

7. The energy-saving production method of ethyl chloride according to claim 1, characterized in that, In step S2, the heating medium is low-pressure steam with a pressure of 0.6 to 0.8 MPa.

8. The energy-saving production method of ethyl chloride according to any one of claims 1 to 7, characterized in that, In step S3, the process of maintaining the reaction temperature in the range of 88 to 90°C by adjusting the medium flow state in the jacket includes: after the material in the reactor is heated to 88°C, the heating medium flow is stopped, and then the cooling medium passage in the jacket is switched to the ready state. At the same time, the reaction temperature is monitored, and when the reaction temperature exceeds 90°C, the passage is opened to allow the cooling medium to flow in.

9. The energy-saving production method of ethyl chloride according to claim 8, characterized in that, In step S3, after the cooling medium is introduced, the opening of the cooling medium passage is adjusted according to the monitored reaction temperature to maintain the reaction temperature within the range of 88 to 90°C.

10. The energy-saving production method of ethyl chloride according to claim 9, characterized in that, In step S3, the process of maintaining the reaction temperature in the range of 88 to 90°C by adjusting the medium flow state in the jacket further includes: when the reaction temperature drops to 88°C while the cooling medium is flowing, stopping the flow of the cooling medium and switching the heating medium passage in the jacket to the ready state.

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