Device system for energy-saving cold hydrogenation process

Abstract

The utility model provides an energy-saving device system for a cold hydrogenation process. The device system comprises a cold hydrogenation reaction unit, a first-section waste heat recovery heat exchange unit, a gas-solid separation dust removal unit, a washing unit, a second-section waste heat recovery heat exchange unit, a first-stage gas-liquid separation unit, a cooling unit, a second-stage gas-liquid separation unit, a circulation unit, a vaporization unit and an electric heating unit. Reaction tail gas of the cold hydrogenation reaction unit serves as heat sources of the first-section waste heat recovery heat exchange unit and the second-section waste heat recovery heat exchange unit to preheat raw materials, and silicon powder and other impurities are removed through the gas-solid separation dust removal unit and the washing unit. The device system provided by the utility model can fully recycle the heat of the cold hydrogenation reaction tail gas, has higher energy utilization rate, can effectively remove silicon powder and other impurities in the reaction tail gas, and is favorable for improving the product quality.

Description

Technical Field

[0001] The utility model relates to the technical field of polysilicon production, and particularly relates to a device system for an energy-saving cold hydrogenation process. Background Art

[0002] In the process of producing polysilicon by the improved Siemens method, producing polysilicon by disproportionation to produce silane, or producing silane by disproportionation method, trichlorosilane is used as a raw material, and the target product is obtained through thermal decomposition reaction or disproportionation reaction. However, whether it is a decomposition reaction or a disproportionation reaction, a large amount of by-product silicon tetrachloride will be generated while generating the target product. If this part of silicon tetrachloride cannot be reasonably recycled, the production cost of polysilicon or silane will rise sharply.

[0003] To solve the problem of recycling a large amount of by-product silicon tetrachloride, the current production process of polysilicon or silane gas usually converts silicon tetrachloride into raw material trichlorosilane by hydrogenation and uses it in the production of polysilicon or silane gas, that is, a production closed-loop is formed to reasonably utilize silicon tetrachloride and achieve the effect of reducing costs. Currently, the main methods for synthesizing trichlorosilane from silicon tetrachloride are thermal hydrogenation method and cold hydrogenation method. Among them, the thermal hydrogenation method is an important method for treating silicon tetrachloride in the early stage. It mainly uses silicon tetrachloride and hydrogen as raw materials, and is heated by a graphite heating element at a temperature of 1200 - 1250 °C to carry out a thermal reduction reaction to generate trichlorosilane. However, this method needs to carry out the reaction at a temperature of 900 - 1400 °C or even higher and a high pressure of 1 - 35 MPa, with high energy consumption, and the heating device used is an isostatic pressing graphite belt, which is very easy to form gases such as methane under high temperature and high pressure conditions, bringing carbon pollution to the product in the closed-loop production of polysilicon or silane gas.

[0004] Currently, the cold hydrogenation process is a research hotspot in this field because of its advantages such as low cost, high output, environmental friendliness, etc., and avoiding the phenomenon of graphite recrystallization and improving the preparation efficiency of polysilicon or silane gas. It mainly adds silicon powder and hydrogen to a fluidized bed at a temperature of 400 - 800 °C and a pressure of 2 - 4 MPa by using a copper-based or iron-based catalyst to react with silicon tetrachloride to generate trichlorosilane. Currently, the conversion rate of the cold hydrogenation technology has exceeded 35% at most, greatly reducing the production cost. However, with the great development of the industry and the instability of the terminal market price of products, the conversion rate of silicon tetrachloride is no longer the only goal pursued in the cold hydrogenation production process. The safety problems, long-term operation problems and energy consumption problems in its production process have received more and more attention. Especially the energy consumption problem is an important direction for reducing production costs in the next step.

[0005] For example, a method for operating polysilicon cold hydrogenation is disclosed in CN103896280A. In this method, a cryogenic heat exchanger gas-liquid separator is used to freeze to -40 to -55 °C for gas-liquid separation, separating hydrogen and chlorosilane. However, this method has disadvantages such as high refrigeration costs and high energy consumption.

[0006] Therefore, providing a device system for an energy-saving cold hydrogenation process is a technical problem that needs to be solved in the current field. Utility Model Content

[0007] Aiming at the deficiencies of the prior art, the purpose of the present utility model is to provide a device system for an energy-saving cold hydrogenation process. The device system can fully recover and utilize the heat of the cold hydrogenation reaction tail gas, has a high energy utilization rate, and can also efficiently remove silicon powder and other impurities in the reaction tail gas, which is beneficial to improving the product quality.

[0008] To achieve this purpose, the present utility model adopts the following technical solutions:

[0009] The present utility model provides a device system for an energy-saving cold hydrogenation process, and the device system includes a cold hydrogenation reaction unit;

[0010] The gas phase outlet of the cold hydrogenation reaction unit is connected to the heat source inlet of the first-stage waste heat recovery heat exchange unit. The heat source outlet of the first-stage waste heat recovery heat exchange unit is connected to the gas-solid separation and dust removal unit. The gas phase outlet of the gas-solid separation and dust removal unit is connected to the heat source inlet of the second-stage waste heat recovery heat exchange unit through a washing unit. The heat source outlet of the second-stage waste heat recovery heat exchange unit is connected to the first-stage gas-liquid separation unit. The gas phase outlet of the first-stage gas-liquid separation unit is connected to the second-stage gas-liquid separation unit through a cooling unit. The gas phase outlet of the second-stage gas-liquid separation unit is connected to a circulation unit;

[0011] The mixed raw material outlet of the circulation unit is connected to the cold source inlet of the second-stage waste heat recovery heat exchange unit. The cold source outlet of the second-stage waste heat recovery heat exchange unit is connected to the cold source inlet of the first-stage waste heat recovery heat exchange unit through a vaporization unit. The cold source outlet of the first-stage waste heat recovery heat exchange unit is connected to the cold hydrogenation reaction unit through an electric heating unit.

[0012] In the present utility model, the tail gas after the cold hydrogenation reaction first enters a first-stage waste heat recovery heat exchange unit to perform secondary preheating on the mixed raw materials of subsequent batches, and then enters a gas-solid separation and dust removal unit to remove silicon powder and other impurities in the reaction tail gas. After that, it enters a washing unit to wash the reaction tail gas and wash down the remaining silicon powder and other impurities. Then, the washed tail gas enters a second-stage waste heat recovery heat exchange unit to perform primary preheating on the mixed raw materials of subsequent batches, forming condensate and entering a first-stage gas-liquid separation unit to collect the liquid phase. The separated gas phase enters a cooling unit for cooling, forming condensate and entering a second-stage gas-liquid separation unit to collect the liquid phase. The separated gas phase enters a circulation unit and is thus reused for the reaction again.

[0013] In the device system provided by the present utility model, on the one hand, by setting a first-stage waste heat recovery heat exchange unit and a second-stage waste heat recovery heat exchange unit, and using the gas phase generated by the cold hydrogenation reaction to preheat the mixed raw materials, the deep recovery of the heat of the reaction tail gas can be realized, and the energy utilization rate can be improved; on the other hand, by setting a washing unit between the gas-solid separation and dust removal unit and the second-stage waste heat recovery heat exchange unit, the silicon powder and other impurities contained can be pre-washed and removed before the condensate is generated after the secondary preheating, the purity of the finished product can be improved, and the long-term stable operation of the device system can be ensured.

[0014] Preferably, the first-stage waste heat recovery heat exchange unit includes 1 - 4 stages of heat exchangers, for example, it can be 1 stage, 2 stages, 3 stages or 4 stages.

[0015] In the present utility model, any device commonly used for heat exchange in the art can be adopted in the first-stage waste heat recovery heat exchange unit and the second-stage waste heat recovery heat exchange unit, for example, it can be a heat exchanger. Among them, the first-stage waste heat recovery heat exchange unit is used to realize the heat exchange between the reaction tail gas and the raw materials. Preferably, the first-stage waste heat recovery heat exchange unit includes 1 - 4 stages of heat exchangers, more preferably 2 - 4 stages, and even more preferably 2 - 3 stages, which can realize a large temperature change gradient and improve the energy utilization rate. After passing through the first-stage waste heat recovery heat exchange unit, the temperature of the reaction tail gas is reduced to 160 - 280 °C, preferably 180 - 260 °C, and more preferably 200 - 240 °C.

[0016] Preferably, the inlet of the cold hydrogenation reaction unit is also connected to a silicon powder feeding unit; the silicon powder feeding unit includes a silicon powder storage tank and a silicon powder feeding tank; the inlet of the silicon powder feeding tank is connected to the silicon powder storage tank; the outlet of the silicon powder feeding tank is connected to the cold hydrogenation reaction unit.

[0017] In the present utility model, the raw material silicon powder is pre-treated in the silicon powder storage tank, and after completion, it is sent to the silicon powder feeding tank and thus enters the reactor.

[0018] Preferably, the liquid phase outlets of the primary gas-liquid separation unit and the secondary gas-liquid separation unit are respectively connected to the finished product collection unit; the liquid phase outlet of the finished product collection unit is connected to the washing unit.

[0019] In the present utility model, the washing unit can adopt any device commonly used in the art for washing gas phase, generally it can be a washing tower, and the washing tower can be a plate tower or a packed tower, preferably a plate tower. The washing unit can further remove fine silicon powder and intercept other impurities. The washing liquid of the washing unit can be sourced from the finished product collection unit, and the finished product collection unit can be any device commonly used in the art for collecting products, for example, it can be a finished product collection tank.

[0020] Preferably, the inlets of the circulation unit are also respectively connected to the silicon tetrachloride feed pipeline and the hydrogen feed pipeline.

[0021] In the present utility model, the circulation unit can include any device for mixing gaseous raw materials and liquid raw materials in the art, for example, it can include a compressor and a mixer, pressurize the raw material gas and the raw material liquid respectively, and then enter the mixer for mixing. In the circulation unit, fresh raw material gas, fresh raw material liquid and recycled raw material gas are mixed, and then sent into the secondary waste heat recovery heat exchange unit for primary preheating, which can reduce the gas phase partial pressure of chlorosilane, make the mixed raw materials more easily vaporized, and reduce the system energy consumption. After passing through the secondary waste heat recovery heat exchange unit, the temperature of the reaction tail gas is reduced to 80 - 120 °C, preferably 80 - 100 °C.

[0022] Preferably, the cold hydrogeneration reaction unit includes a fluidized bed reactor.

[0023] In the present utility model, the operating pressure of the fluidized bed reactor is 1.0 - 4.0 MPaG, preferably 2.0 - 3.5 MPaG, more preferably 2.5 - 3.0 MpaG, and the reaction temperature is generally 450 - 650 °C, preferably 500 - 600 °C, more preferably 550 - 580 °C. A cyclone separator is preferably configured in the fluidized bed reactor. The cyclone separator is arranged inside the reactor as a part of the reactor set, which can reduce the complexity of the system and simplify the operation. A silicon powder collection tank is arranged at the bottom of the cyclone separator. The silicon powder collection tank collects silicon powder and discharges it to the silicon powder feed tank, so as to send it into the reactor to complete the recovery of fine silicon powder.

[0024] Preferably, the gas-solid separation and dust removal unit includes any one or at least two combinations of a cyclone separator, a microporous filter element filter or a Venturi scrubber.

[0025] Preferably, when a cyclone separator is configured in the fluidized bed reactor, the gas-solid separation and dust removal unit includes any one of a cyclone separator, a microporous filter element filter or a Venturi scrubber.

[0026] Preferably, when no cyclone separator is configured in the fluidized bed reactor, the gas-solid separation and dust removal unit includes a first-stage or second-stage gas-solid separation device; when the gas-solid separation and dust removal unit includes a first-stage gas-solid separation device, the gas-solid separation device includes a microporous filter element filter or a Venturi scrubber; when the gas-solid separation and dust removal unit includes a second-stage gas-solid separation device, the gas-solid separation device includes a first-stage gas-solid separation device and a second-stage gas-solid separation device; the first-stage gas-solid separation device includes a microporous filter element filter or a Venturi scrubber; the second-stage gas-solid separation device includes any one of a cyclone separator, a microporous filter element filter or a Venturi scrubber.

[0027] In the present utility model, by preferably controlling the combination of the gas-solid separation and dust removal unit, the separation efficiency of silicon powder and other impurities can be improved, the product quality can be enhanced, and the long-term and stable operation of the device system can be maintained.

[0028] In the present utility model, the Venturi scrubber is arranged at the rear section of the first-stage waste heat recovery heat exchange unit, and the microporous filter element filter can generally be arranged at the front section, middle section and rear section of the first-stage waste heat recovery heat exchange unit. In the present utility model, it is arranged at the rear section of the first-stage waste heat recovery heat exchange unit.

[0029] Preferably, the filtration accuracy of the microporous filter element filter is 0.05 - 20 μm, for example, it can be 0.05 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable. Preferably, it is 0.05 - 10 μm.

[0030] Preferably, the cooling unit includes any one or a combination of at least two of a waste heat recovery refrigeration unit, an air-cooled heat removal device, a circulating water heat removal device or a chilled water heat removal device. Preferably, it is a combination of a circulating water heat removal device and a chilled water heat removal device or a combination of a waste heat recovery refrigeration unit, a circulating water heat removal device and a chilled water heat removal device.

[0031] Preferably, the chilled water outlet of the waste heat recovery refrigeration unit is connected to the chilled water heat removal device.

[0032] In the present utility model, the cooling method adopted by the cooling unit includes any one or a combination of at least two of waste heat recovery for producing chilled water, air cooling, circulating water cooling, and chilled water cooling. Preferably, it is a combination of circulating water cooling and chilled water cooling, or a combination of waste heat recovery for producing chilled water, circulating water cooling, and chilled water cooling. After passing through the cooling unit, the reaction tail gas is cooled to 10 - 20°C. When a waste heat recovery refrigeration unit is used to produce chilled water, the refrigeration unit can be, for example, a low-temperature heat source refrigeration device such as lithium bromide. Its power source is the reaction tail gas entering the cooling unit, and the produced chilled water is directly used in the chilled water heat removal device as the final cooling of the reaction tail gas by the cooling unit. Additionally, in the device system provided by the present utility model, the temperature level of the cooling unit is raised to 10 - 20°C, avoiding the use of low-temperature units and reducing the low-temperature refrigeration cost, equipment investment, and system operation cost.

[0033] In the present utility model, the vaporization unit can adopt any device commonly used for liquid-phase vaporization in the art, such as a vaporizer. The electric heating unit can adopt any device commonly used for electric heating in the art, such as an electric heater.

[0034] The operation process of the device system provided by the present utility model for cold hydrogeneration reaction is as follows:

[0035] The raw material hydrogen, recycled hydrogen, and raw material trichlorosilane are mixed in the circulation unit to obtain a mixed raw material. The mixed raw material is preheated once to 105 - 135°C in the secondary waste heat recovery heat exchange unit, then vaporized to a temperature of 140 - 170°C in the vaporization unit to achieve complete vaporization and partial superheat of the raw materials. After that, it is preheated twice to 450 - 520°C in the primary waste heat recovery heat exchange unit, and then enters the electric heating unit for electric heating to the reaction required temperature to obtain the raw material gas.

[0036] The silicon powder from the silicon powder feeding unit and the raw material gas are sent into the cold hydrogeneration reaction unit, i.e., the fluidized bed reactor, and a cold hydrogeneration reaction is carried out under the conditions of a temperature of 450 - 650°C and an operating pressure of 1.0 - 4.0 MPaG to obtain the reaction tail gas.

[0037] The reaction tail gas is sent to a primary waste heat recovery heat exchange unit to preheat the raw materials of subsequent batches for the second time until the temperature of the reaction tail gas is 160 - 280°C, and then sent to a gas-solid separation and dust removal unit for gas-solid separation and dust removal. After that, the gas phase is sent to a washing unit for washing. The washing liquid contains silicon powder and other impurities and is discharged for treatment. The washed gas phase enters a secondary waste heat recovery heat exchange unit to preheat the raw materials of subsequent batches for the first time until the temperature of the reaction tail gas is 80 - 120°C, and then enters a primary gas-liquid separation unit for gas-liquid separation. The separated liquid phase enters the finished product collection unit, i.e., the finished product collection tank. The separated gas phase enters a cooling unit for cooling to 10 - 20°C, and then enters a secondary gas-liquid separation unit for gas-liquid separation. The separated liquid phase enters the finished product collection tank, and the separated gas phase, i.e., the recycle gas, enters a recycle unit to be mixed with fresh raw materials.

[0038] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0039] (1) In the device system provided by the present utility model, by setting a primary waste heat recovery heat exchange unit and a secondary waste heat recovery heat exchange unit, and using the gas phase generated by the cold hydrogenation reaction to preheat the mixed raw materials, deep recovery of the heat of the reaction tail gas can be achieved, and the energy utilization rate can reach 80 - 90%. Taking a reactor scale with an annual production capacity of 200,000 tons of trichlorosilane and a feed rate of 120 t / h of silicon tetrachloride as an example, the energy utilization rate can reach more than 83%. Among them, the secondary waste heat recovery heat exchange unit preheats the mixed raw materials from the recycle unit, that is, controls preheating after mixing, which can reduce the gas phase partial pressure of the chlorosilane component, make the raw materials easier to vaporize, improve the efficiency of the heat transfer process, and further reduce energy consumption.

[0040] (2) In the device system provided by the present utility model, by setting multiple heat exchanges in the primary waste heat recovery heat exchange unit and controlling the number of heat exchange stages, the waste heat can be recovered at a deeper level and the system energy consumption can be reduced.

[0041] (3) In the device system provided by the present utility model, more than 99% of the silicon powder in the reaction tail gas can be intercepted by the gas-solid separation and dust removal unit, and a washing unit is arranged between the gas-solid separation and dust removal unit and the secondary waste heat recovery heat exchange unit, which can pre-wash and remove the contained silicon powder and other impurities before condensate is generated after the second preheating, ensure that they are not brought into the subsequent device system in large quantities, improve the purity of the finished product, and ensure the long-term stable operation of the device system.

[0042] (4) In the device system provided by the present utility model, the low-temperature waste heat of the reaction tail gas can be utilized as the driving heat source of the waste heat recovery refrigeration unit, reducing the cooling load of the system. Moreover, the cooling capacity generated by the waste heat recovery refrigeration unit can be used for the final cooling of the reaction tail gas, further improving the energy utilization rate. In addition, in the device system provided by the present utility model, there is no need to adopt a low-temperature cooling unit, the temperature level of the cooling unit is increased to 10 - 20 °C, reducing the low-temperature refrigeration cost and equipment investment. Taking the reactor scale of 200,000 tons / year of trichlorosilane production capacity as an example, when the feed is 120,000 kg / h of silicon tetrachloride, the cooling load of the low-temperature refrigeration unit is generally 1.043 MW. The present utility model can save this part of the cooling load, reducing the system operation cost and cost. Description of the Drawings

[0043] Figure 1 It is a schematic structural diagram of the device system described in Embodiment 1 of the present utility model;

[0044] In the figure: 1 - cold hydrogenation reaction unit; 2 - first-stage waste heat recovery heat exchange unit; 3 - gas-solid separation and dust removal unit; 4 - washing unit; 5 - second-stage waste heat recovery heat exchange unit; 6 - first-stage gas-liquid separation unit; 7 - cooling unit; 8 - second-stage gas-liquid separation unit; 9 - circulation unit; 10 - vaporization unit; 11 - electric heating unit; 12 - silicon powder feeding unit; 13 - finished product collection unit; 14 - silicon tetrachloride feed pipeline; 15 - hydrogen feed pipeline. Detailed Embodiments

[0045] The technical solutions of the present utility model will be further described below in conjunction with the drawings and through specific embodiments.

[0046] The present utility model will be further described in detail below. However, the following examples are only simple examples of the present utility model and do not represent or limit the scope of the patent protection of the present utility model. The scope of protection of the present utility model shall be subject to the claims.

[0047] It should be understood that in the description of the present utility model, the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present utility model. In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present utility model, unless otherwise specified, the meaning of "a plurality" is two or more.

[0048] It should be noted that in the description of the present utility model, unless otherwise clearly specified and limited, the terms "arranged", "connected", "coupled" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood through specific circumstances.

[0049] Those skilled in the art should understand that the present utility model necessarily includes necessary pipelines, conventional valves and general pump equipment for realizing the complete process. However, the above contents do not belong to the main inventive points of the present utility model. Those skilled in the art can add and arrange them by themselves based on the process flow and equipment structure selection. The present utility model has no special requirements and specific limitations on this.

[0050] Specifically, a device system for an energy-saving cold hydrogenation process is provided, as Figure 1 shown, the device system includes a cold hydrogenation reaction unit 1, and the cold hydrogenation reaction unit 1 is a fluidized bed reactor;

[0051] The gas-phase outlet of the cold hydrogeneration reaction unit 1 is connected to the heat source inlet of the first-stage waste heat recovery heat exchange unit 2. The heat source outlet of the first-stage waste heat recovery heat exchange unit 2 is connected to the gas-solid separation and dust removal unit 3. The first-stage waste heat recovery heat exchange unit 2 includes heat exchangers of grades 1-4. The gas-phase outlet of the gas-solid separation and dust removal unit 3 is connected to the heat source inlet of the second-stage waste heat recovery heat exchange unit 5 through the washing unit 4. The heat source outlet of the second-stage waste heat recovery heat exchange unit 5 is connected to the first-stage gas-liquid separation unit 6. The gas-phase outlet of the first-stage gas-liquid separation unit 6 is connected to the second-stage gas-liquid separation unit 8 through the cooling unit 7. The gas-phase outlet of the second-stage gas-liquid separation unit 8 is connected to the circulation unit 9. The liquid-phase outlets of the first-stage gas-liquid separation unit 6 and the second-stage gas-liquid separation unit 8 are respectively connected to the finished product collection unit 13. The liquid-phase outlet of the finished product collection unit 13 is connected to the washing unit 4;

[0052] The mixed raw material outlet of the circulation unit 9 is connected to the cold source inlet of the second-stage waste heat recovery heat exchange unit 5. The cold source outlet of the second-stage waste heat recovery heat exchange unit 5 is connected to the cold source inlet of the first-stage waste heat recovery heat exchange unit 2 through the vaporization unit 10. The cold source outlet of the first-stage waste heat recovery heat exchange unit 2 is connected to the cold hydrogeneration reaction unit 1 through the electric heating unit 11. The inlet of the circulation unit 9 is also respectively connected to the silicon tetrachloride feed pipeline 14 and the hydrogen feed pipeline 15;

[0053] The inlet of the cold hydrogeneration reaction unit 1 is also connected to the silicon powder feeding unit 12. The silicon powder feeding unit 12 includes a silicon powder storage tank and a silicon powder feeding tank. The inlet of the silicon powder feeding tank is connected to the silicon powder storage tank. The outlet of the silicon powder feeding tank is connected to the cold hydrogeneration reaction unit 1;

[0054] When a cyclone separator is configured in the fluidized bed reactor, the gas-solid separation and dust removal unit 3 includes any one of a cyclone separator, a microporous filter element filter, or a venturi scrubber. When a cyclone separator is not configured in the fluidized bed reactor, the gas-solid separation and dust removal unit 3 includes a gas-solid separation device of grade 1 or 2. When the gas-solid separation and dust removal unit 3 includes a gas-solid separation device of grade 1, the gas-solid separation device includes a microporous filter element filter or a venturi scrubber. When the gas-solid separation and dust removal unit 3 includes a gas-solid separation device of grade 2, the gas-solid separation device includes a first-stage gas-solid separation device and a second-stage gas-solid separation device. The first-stage gas-solid separation device includes a microporous filter element filter or a venturi scrubber. The second-stage gas-solid separation device includes any one of a cyclone separator, a microporous filter element filter, or a venturi scrubber;

[0055] The cooling unit 7 includes any one or a combination of at least two of a waste heat recovery refrigeration unit, an air-cooled heat dissipation device, a circulating water heat dissipation device, or a chilled water heat dissipation device.

[0056] Example 1

[0057] This embodiment provides a device system for an energy-saving cold hydrogeneration process, as Figure 1 shown. The device system includes a cold hydrogeneration reaction unit 1, and the cold hydrogeneration reaction unit 1 is a fluidized bed reactor;

[0058] The gas-phase outlet of the cold hydrogeneration reaction unit 1 is connected to the heat source inlet of a first-stage waste heat recovery heat exchange unit 2, the heat source outlet of the first-stage waste heat recovery heat exchange unit 2 is connected to a gas-solid separation and dust removal unit 3, the first-stage waste heat recovery heat exchange unit 2 includes 3 heat exchangers, the gas-phase outlet of the gas-solid separation and dust removal unit 3 is connected to the heat source inlet of a second-stage waste heat recovery heat exchange unit 5 through a washing unit 4, the heat source outlet of the second-stage waste heat recovery heat exchange unit 5 is connected to a first-stage gas-liquid separation unit 6, the gas-phase outlet of the first-stage gas-liquid separation unit 6 is connected to a second-stage gas-liquid separation unit 8 through a cooling unit 7, the gas-phase outlet of the second-stage gas-liquid separation unit 8 is connected to a circulation unit 9, the liquid-phase outlets of the first-stage gas-liquid separation unit 6 and the second-stage gas-liquid separation unit 8 are respectively connected to a finished product collection unit 13, and the liquid-phase outlet of the finished product collection unit 13 is connected to the washing unit 4;

[0059] The mixed raw material outlet of the circulation unit 9 is connected to the cold source inlet of the second-stage waste heat recovery heat exchange unit 5, the cold source outlet of the second-stage waste heat recovery heat exchange unit 5 is connected to the cold source inlet of the first-stage waste heat recovery heat exchange unit 2 through a vaporization unit 10, the cold source outlet of the first-stage waste heat recovery heat exchange unit 2 is connected to the cold hydrogeneration reaction unit 1 through an electric heating unit 11, and the inlet of the circulation unit 9 is also respectively connected to a trichlorosilane feed pipeline 14 and a hydrogen feed pipeline 15;

[0060] The inlet of the cold hydrogeneration reaction unit 1 is also connected to a silicon powder feeding unit 12, the silicon powder feeding unit 12 includes a silicon powder storage tank and a silicon powder feeding tank, the inlet of the silicon powder feeding tank is connected to the silicon powder storage tank, and the outlet of the silicon powder feeding tank is connected to the cold hydrogeneration reaction unit 1;

[0061] A cyclone separator is configured in the fluidized bed reactor, and the gas-solid separation and dust removal unit 3 is a microporous filter element filter; The cooling unit 7 is provided with a waste heat recovery refrigeration unit, a circulating water heat removal device and a chilled water heat removal device.

[0062] Taking the reactor scale of 200,000 tons / year of trichlorosilane production capacity and the feed rate of 120 t / h of tetrachlorosilane as an example, the operation process of the device system provided in this embodiment for cold hydrogeneration reaction is as follows:

[0063] Mix the raw material hydrogen, recycled hydrogen, and raw material trichlorosilane in the circulation unit 9 to obtain a mixed raw material. The mixed raw material is preheated to 120°C at once in the secondary waste heat recovery heat exchange unit 5, then vaporized to a temperature of 147°C and superheated to 170°C in the vaporization unit 10. After that, it is preheated a second time to 500°C in the primary waste heat recovery heat exchange unit 2. The primary waste heat recovery heat exchange unit 2 uses 3-stage heat exchange, and the temperature between cascade heat exchanges can vary freely. In principle, the temperature difference between cascade heat exchangers is made to be evenly distributed. Then it enters the electric heating unit 11 for electric heating to the reaction required temperature to obtain the raw material gas;

[0064] Feed the silicon powder from the silicon powder feeding unit 12 and the raw material gas into the cold hydrofluorination reaction unit 1, i.e., a fluidized bed reactor, and carry out the cold hydrofluorination reaction under the conditions of a temperature of 560°C and an operating pressure of 3 MPaG. Convert the silicon tetrachloride in the raw material gas into the raw material trichlorosilane required in the production process to obtain the reaction tail gas. A cyclone separator is configured in the fluidized bed reactor for preliminary gas-solid separation; Feed the reaction tail gas into the primary waste heat recovery heat exchange unit 2 to preheat the subsequent batch of raw materials a second time until the temperature of the reaction tail gas is 210°C, and then send it into the gas-solid separation and dust removal unit 3 for gas-solid separation and dust removal. A microporous filter element filter is set in the gas-solid separation and dust removal unit 3 with a filtration accuracy of 10 μm. After that, send the gas phase into the washing unit 4 for washing. The washing liquid contains silicon powder and other impurities and is discharged for treatment. The washed gas phase enters the secondary waste heat recovery heat exchange unit 5 to preheat the subsequent batch of raw materials at once until the temperature of the reaction tail gas is 95°C, and then enters the first-stage gas-liquid separation unit 6 for gas-liquid separation. The separated liquid phase enters the finished product collection unit 13, i.e., the finished product collection tank, and the separated gas phase enters the cooling unit 7 for cooling to 10°C. In the cooling unit 7, first use the reaction tail gas as the heat source to drive the refrigeration unit to produce chilled water, reduce the tail gas temperature to 88°C, and then the tail gas continues to enter the circulating water heat removal device and the chilled water heat removal device for cooling. The chilled water of the chilled water heat removal device comes from the refrigeration unit, and the insufficient part is provided by the outside; Then enter the second-stage gas-liquid separation unit 8 for gas-liquid separation. The separated liquid phase enters the finished product collection tank, and the separated gas phase, i.e., the recycle gas, enters the circulation unit 9 to be mixed with the fresh raw materials. The liquid in the finished product collection tank enters the next process.

[0065] In this embodiment, the deep recovery of the heat of the reaction tail gas can be realized. Taking the reactor scale of 200,000 tons / year of trichlorosilane production capacity and the silicon tetrachloride feed rate of 120 t / h as an example, the energy utilization rate can reach more than 83%.

[0066] In this embodiment, by setting up a gas-solid separation and dust removal unit and a washing unit between the gas-solid separation and dust removal unit and the secondary waste heat recovery and heat exchange unit, the silicon powder and other impurities carried out from the reactor can be effectively separated and intercepted, ensuring that they are not introduced into the subsequent device system, thereby guaranteeing the product quality and ensuring the long-term stable operation of the device system.

[0067] In this embodiment, the reaction tail gas is used as the driving heat source to produce chilled water and is used in the chilled water heat removal device, which can reduce the cooling load required at the terminal, further reducing the energy consumption of the system. And in this embodiment, the tail gas is only cooled to 10 °C by the cooling unit without using a low-temperature refrigeration unit. Compared with the cooling load of a low-temperature refrigeration unit, which is generally 1.043 MW, the present utility model can save this part of the cooling load, reducing the operation cost and cost of the system.

[0068] Embodiment 2

[0069] The difference between this embodiment and Embodiment 1 is only that there is no cyclone separator configured in the fluidized bed reactor, and the gas-solid separation and dust removal unit is provided with a first-stage gas-solid separation device, which is a microporous filter element filter with a filtration accuracy of 5 μm.

[0070] Embodiment 3

[0071] The difference between this embodiment and Embodiment 1 is only that there is no cyclone separator configured in the fluidized bed reactor, and the gas-solid separation and dust removal unit is provided with a two-stage gas-solid separation device. The first-stage gas-solid separation device is a microporous filter element filter with a filtration accuracy of 10 μm; the second-stage gas-solid separation device is a Venturi scrubber.

[0072] In Embodiments 1-3, through the setting of the cyclone separator and the gas-solid separation and dust removal unit inside the reactor, more than 99% of the silicon powder in the reaction tail gas can be intercepted, ensuring that it is not introduced into the subsequent device system, thereby guaranteeing the product quality and ensuring the long-term stable operation of the device system.

[0073] In summary, the device system provided by the present utility model can fully recover and utilize the heat of the cold hydrogenation reaction tail gas, has a high energy utilization rate, and can also efficiently remove the silicon powder and other impurities in the reaction tail gas, which is beneficial to improving the product quality.

[0074] The applicant declares that the above is only the specific implementation manner of the present utility model, but the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present utility model fall within the protection scope and the disclosure scope of the present utility model.

Claims

1. An energy-saving cold hydrogenation process system, characterized in that: The device system includes a cold hydrogenation reaction unit; The gas phase outlet of the cold hydrogenation reaction unit is connected to the heat source inlet of the first stage waste heat recovery heat exchange unit, the heat source outlet of the first stage waste heat recovery heat exchange unit is connected to the gas-solid separation and dust removal unit, the gas phase outlet of the gas-solid separation and dust removal unit is connected to the heat source inlet of the second stage waste heat recovery heat exchange unit through the washing unit, the heat source outlet of the second stage waste heat recovery heat exchange unit is connected to the first stage gas-liquid separation unit, the gas phase outlet of the first stage gas-liquid separation unit is connected to the second stage gas-liquid separation unit through the cooling unit, and the gas phase outlet of the second stage gas-liquid separation unit is connected to the circulation unit; The mixed raw material outlet of the circulation unit is connected to the cold source inlet of the second-stage waste heat recovery heat exchange unit, the cold source outlet of the second-stage waste heat recovery heat exchange unit is connected to the cold source inlet of the first-stage waste heat recovery heat exchange unit via the vaporization unit, and the cold source outlet of the first-stage waste heat recovery heat exchange unit is connected to the cold hydrogenation reaction unit via the electric heating unit.

2. The energy-saving cold hydrogenation process system according to claim 1 is characterized in that: The first stage waste heat recovery heat exchange unit includes 1-4 stage heat exchangers.

3. The device system of the energy-saving cold hydrogenation process according to claim 1 is characterized in that: The inlet of the cold hydrogenation reaction unit is also connected to the silicon powder feeding unit; The silicon powder feeding unit comprises a silicon powder storage tank and a silicon powder feeding tank; The inlet of the silicon powder feeding tank is connected to the silicon powder storage tank; The outlet of the silicon powder feed tank is connected to the cold hydrogenation reaction unit.

4. The energy-saving cold hydrogenation process system according to claim 1 is characterized in that: The liquid phase outlet of the primary gas-liquid separation unit and the liquid phase outlet of the secondary gas-liquid separation unit are respectively connected to the finished product collection unit; the liquid phase outlet of the finished product collection unit is connected to the washing unit.

5. The energy-saving cold hydrogenation process system according to claim 1 is characterized in that: The inlet of the circulation unit is also connected to a silicon tetrachloride feed pipeline and a hydrogen feed pipeline respectively.

6. The energy-saving cold hydrogenation process system according to claim 1, characterized in that: The cold hydrogenation reaction unit includes a fluidized bed reactor.

7. The energy-saving cold hydrogenation process system according to claim 6, characterized in that: The gas-solid separation and dust removal unit includes any one of a cyclone separator, a microporous filter element filter or a venturi scrubber, or a combination of at least two of them.

8. The energy-saving cold hydrogenation process system according to claim 7, characterized in that: When a cyclone separator is arranged in the fluidized bed reactor, the gas-solid separation and dust removal unit comprises any one of a cyclone separator, a microporous filter element filter or a venturi scrubber.

9. The energy-saving cold hydrogenation process system according to claim 7, characterized in that: When the fluidized bed reactor is not equipped with a cyclone separator, the gas-solid separation and dust removal unit includes a 1st or 2nd stage gas-solid separation device; When the gas-solid separation and dust removal unit includes a first-stage gas-solid separation device, the gas-solid separation device includes a microporous filter element filter or a Venturi scrubber; When the gas-solid separation and dust removal unit includes a two-stage gas-solid separation device, the gas-solid separation device includes a first-stage gas-solid separation device and a second-stage gas-solid separation device; The first-stage gas-solid separation device includes a microporous filter element filter or a venturi scrubber; The second-stage gas-solid separation device includes any one of a cyclone separator, a microporous filter element filter or a venturi scrubber.

10. The energy-saving cold hydrogenation process system according to claim 1, characterized in that: The cooling unit includes any one of a waste heat recovery refrigeration unit, an air cooling heat removal device, a circulating water heat removal device or a chilled water heat removal device, or a combination of at least two of them.

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