Cold hydrogenation process adopting on-line filtration and back flushing

Abstract

The invention relates to the technical field of cold hydrogenation processes, and particularly discloses a cold hydrogenation process adopting online filtration and back flushing, which comprises the following steps: S10: utilizing steam heating to change liquid STC into gaseous STC; s20, the gaseous STC and hydrogen are mixed in proportion, and the mixed gas is further heated; s30, enabling the preheated STC and H2 mixed gas and silicon powder to enter a cold hydrogenation reaction furnace together, and reacting to generate TCS (SiHCl3); s40, the gas is introduced into a dust removal system, and solid dust particles in the gas are removed; s50, cooling and washing the dedusted gas to obtain condensate and non-condensable gas; s60, conveying the condensate to a rectification system to obtain a TCS product, unreacted STC and a high-boiling residue; wherein in the step S40, a target resistance value P is set for the dust removal system, a resistance value delta P caused by an attached dust layer in the dust removal system is measured, and when delta P is larger than or equal to P, a back flushing regeneration system is triggered, and online dust removal is conducted on the dust removal system. According to the invention, shutdown back flushing is not needed, and the cold hydrogenation reaction efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cold hydrogenation process, and particularly relates to a cold hydrogenation process adopting online filtering and back flushing. BACKGROUND

[0002] In the process of producing polysilicon by improved Siemens method, the cold hydrogenation section is used for hydrogenating by-product silicon tetrachloride (SiCl4) into trichlorosilane (TCS), which is a key to realize material recycling. The high-temperature gas generated in the process contains solid catalyst dust and other impurities, which must be effectively filtered before entering the downstream waste heat boiler and separation and purification system, so as to protect the equipment, improve the heat recovery efficiency and ensure the product purity.

[0003] At present, the section usually adopts a filter provided with a ceramic filter element to perform dry dust removal. However, due to the low gas source pressure of the back flushing system, the back flushing effect is poor, and effective online cleaning cannot be realized. Therefore, the existing technology generally adopts a double-filter configuration scheme of "one online and one standby". That is, when one filter is online for filtering, the other filter is switched to an offline state for back flushing regeneration. This scheme has obvious defects. First, the filter switching process will cause discontinuity of the entire production process, affecting the stability of the system operation. Second, the standby filter and its matched valves and pipelines increase the equipment investment and land occupation. Third, the discontinuity of the process will affect the stable operation of the downstream waste heat boiler, reduce the heat recovery efficiency and cause energy waste. SUMMARY

[0004] In order to solve the problem that the existing filter needs to be offline for regeneration and back flushing, the present application provides a cold hydrogenation process adopting online filtering and back flushing.

[0005] The cold hydrogenation process adopting online filtering and back flushing provided by the present application adopts the following technical scheme: The cold hydrogenation process adopting online filtering and back flushing comprises the following steps: S10: Liquid STC is sent into a vaporizer, and is heated by steam to become gaseous; S20: The gaseous STC is mixed with hydrogen gas in proportion, and the mixed gas is further heated to reach the required temperature for reaction; S30: The preheated STC and H2 mixed gas and silicon powder are introduced into a cold hydrogenation reaction furnace to react to generate TCS (SiHCl3) at a temperature of 450-600 DEG C; S40: The gas from the cold hydrogenation reaction furnace is introduced into a dust removal system to remove solid dust particles in the gas, so as to obtain dust-removed gas and silicon powder dust; S50: The dust-removed gas is introduced into a spray tower for cooling and washing, and then the tower outlet gas is introduced into a condensing system for cooling to obtain condensate and non-condensable gas; S60: delivering the condensed liquid to a rectification system for separation to obtain TCS product and unreacted STC and high-boiling substances; In step S40, a target resistance value P is set for the dust removal system, and a resistance value ΔP caused by the filter assembly and the dust layer attached to the surface of the backflushing regeneration system is measured, and when ΔP≥P, the backflushing regeneration system is triggered, and the dust removal system of the backflushing regeneration system is cleaned online.

[0006] By using the above technical scheme, by using the online backflushing regeneration technology, the cleaning process of the dust removal system is realized simultaneously with the main process filtration, without the need for shutdown switching, so that a single dust remover can be set to realize continuous operation, without the need for configuring a standby dust remover, reducing equipment investment, and reducing the occupied area; by monitoring the differential pressure (ΔP) of the filter assembly in real time and using it as a backflushing trigger signal, the cleaning process is automated and intelligent, and the system only backflushes when needed, avoiding gas waste and filter wear caused by excessive cleaning, and preventing high system resistance caused by insufficient cleaning, realizing precise, energy-saving, and self-adaptive operation and maintenance.

[0007] In some embodiments, in step S40, the silicon powder dust removed by the dust removal is re-entered into the cold hydrogenation reaction furnace in step S20 as a reaction raw material for recycling.

[0008] In some embodiments, in step S50, the non-condensable gas obtained after cooling is returned to the cold hydrogenation reaction furnace in step S20 as a reaction raw material for recycling.

[0009] In some embodiments, in step S50, the unreacted STC is returned to step S10 to participate in the reaction again.

[0010] In some embodiments, one side of the filter assembly is the gas inlet side, and the other side is the gas outlet side, a differential pressure gauge is arranged at the filter assembly, and the differential pressure gauge is connected to the gas inlet side and the gas outlet side respectively, and the differential pressure gauge detects and calculates the pressure difference between the two pressure points in real time, that is, the resistance value ΔP=Pin-Pout.

[0011] In some embodiments, in step S40, the dust removal system includes a dust removal tower, the dust removal tower is provided with a gas inlet at the bottom and a gas outlet at the top; a plurality of groups of filter assemblies are vertically arranged in the dust removal tower, and each group of filter assemblies includes a plurality of filter pieces arranged vertically.

[0012] In some embodiments, the filter assembly further comprises a mounting plate, mounting racks and air pipes, the mounting racks and the air pipes are fixed on the mounting plate, a plurality of mounting racks are mounted on each mounting plate, the mounting racks are mounted side by side on the mounting plate, a plurality of mounting cavities are vertically arranged on each mounting rack, each mounting cavity is used for embedding a filter element, and the air pipes are arranged on one side of the mounting plate, the air pipes correspond to the mounting racks one by one, and each air pipe is in communication with the mounting cavities on the mounting rack.

[0013] In some embodiments, the backflushing and regenerating system comprises a storage tank and a blowpipe, the storage tank is arranged outside the dust removal tower, one end of the blowpipe is connected with the storage tank, the other end of the blowpipe is arranged in the dust removal tower, the blowpipe corresponds to the filter assembly one by one, and one end of the air pipe close to the blowpipe is provided with a connecting pipe, the connecting pipe comprises a contraction section, a throat and an expansion section, the throat is connected with the contraction section, and the expansion section is connected with one end of the throat away from the contraction section.

[0014] In some embodiments, the width of each air pipe gradually decreases from top to bottom.

[0015] In some embodiments, the side of the mounting cavity away from the air pipe is obliquely arranged towards the side of the air inlet.

[0016] Compared with the prior art, the present application has at least one of the following beneficial technical effects: 1. The traditional "one active and one standby" filter scheme inevitably leads to process interruption during switching, the present application realizes that the dust removal process of the filter is synchronized with the filtering process of the main process through the online backflushing and regenerating technology, without the need for switching during shutdown, which enables seamless continuous operation from the cold hydrogenation reaction to the downstream waste heat recovery, condensation rectification and other processes, eliminates production fluctuations and interruptions caused by dust removal, and helps to improve processing efficiency; 2. By returning the collected silicon powder dust, condensed non-condensable gas and unreacted STC to the system for recycling, the conversion rate and utilization rate of raw materials are greatly improved, the consumption of fresh silicon powder and hydrogen is reduced, and the waste treatment cost is also reduced; 3. By arranging the connecting pipe, a large flow and high kinetic energy backflushing gas flow can be generated based on the Venturi principle, achieving a strong, uniform and thorough dust removal effect. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a flow chart of the cold hydrogenation process in the embodiment of the present application.

[0018] Figure 2 is a schematic diagram of the overall structure of the dust removal system and the backflushing and regenerating system in the embodiment of the present application.

[0019] Figure 3 is a partial schematic diagram of the filter assembly in the embodiment of the present application.

[0020] Figure 4 Figure is a structural schematic diagram of the air pipe and mounting frame in the embodiment of the present application.

[0021] In the figure: 1, dust removal system; 11, dust removal tower; 12, air inlet; 13, air outlet; 14, filter assembly; 141, filter element; 142, mounting plate; 143, mounting frame; 144, air pipe; 145, mounting cavity; 2, back flushing regeneration system; 21, storage tank; 22, blow pipe; 23, connecting pipe; 24, contraction section; 25, throat; 26, expansion section. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0023] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the term “and / or” in this paper is only to describe the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character “ / ” in this paper generally represents an “or” relationship between the front and rear associated objects without special explanation.

[0024] The traditional cold hydrogenation process includes a fluidized bed reactor for the hydrogenation reaction of silicon tetrachloride and hydrogen, a condensation and separation system including a condenser, a washing tower, a heat exchanger, etc. for the cooling, separation and purification of gas, and a tail gas treatment system including an absorption tower and an adsorber, etc. for treating unreacted gas and by-products. The traditional cold hydrogenation process uses a filter equipped with a ceramic filter element for dry dust removal. Because the back flushing gas pressure is low, the filter is set as one open and one standby, that is, the filter is online filtering, but needs to be cut off for offline back flushing regeneration, which leads to a non-continuous process. Therefore, the present application provides a cold hydrogenation process using online filtering and back flushing, which is described with reference to Figure 1 and Figure 2 A cold hydrogenation process using online filtering and back flushing includes the following steps: S10: Liquid STC is sent into a vaporizer, and is heated by steam to become gaseous; S20: The gaseous STC is mixed with hydrogen (H2) in proportion, and the mixed gas is further heated to reach the required reaction temperature; S30: The preheated STC and H2 mixed gas and silicon powder enter the cold hydrogenation reaction furnace to react to generate TCS (SiHCl3) at a temperature of 450-600°C; the reaction equation is: SiCl4+H2→SiHCl3+HCl S40: The gas from the cold hydrogenation reaction furnace is introduced into the dust removal system 1 to remove solid dust particles in the gas to obtain dust-removed gas and silicon powder dust; S50: The dust-removed gas enters the spray tower for cooling and washing, and then the tower outlet gas is introduced into the condensation system for cooling to obtain condensate and non-condensable gas; S60: The condensate is transported to the rectification system for separation to obtain TCS product and unreacted STC and high-boiling substances; In step S40, a target resistance value P is set for the dust removal system 1, and the resistance value ΔP caused by the attached dust layer in the dust removal system 1 is measured, and when ΔP≥P, the backflushing regeneration system 2 is triggered to perform online dust cleaning of the dust removal system 1.

[0025] The cold hydrogenation process provided in the application includes steps such as vaporization, mixing, reaction, dust removal, cooling and separation, and can realize a continuous process. By setting a target resistance value and triggering the backflushing regeneration system 2, automatic dust cleaning control is realized, online backflushing is performed in real time to maintain filtration efficiency, reduce manual intervention, and ensure continuous and stable operation of the system. Through the online filtration and backflushing mechanism, the process interruption caused by traditional double filters is avoided, the stability of system operation is improved, and equipment investment and floor area are reduced.

[0026] Further, in step S40, the silicon powder dust obtained by dust removal reenters the cold hydrogenation reaction furnace in step S20 as a reaction raw material for recycling. By returning the collected silicon powder dust to the cold hydrogenation reaction furnace for recycling, raw material waste is reduced, production cost is reduced, resource utilization rate is improved through recycling of silicon powder dust, and process sustainability is enhanced. In step S50, the non-condensable gas obtained after cooling is returned to the cold hydrogenation reaction furnace in step S20 as a reaction raw material for recycling. By returning the non-condensable gas to the cold hydrogenation reaction furnace for recycling, waste gas emission is reduced, raw material conversion efficiency is improved, environmental impact is reduced, and energy utilization is optimized through gas recycling. In step S50, the unreacted STC is returned to step S10 to participate in the reaction again. By returning the unreacted STC to the vaporization step to participate in the reaction again, the utilization rate of the reactants is improved, the consumption of fresh raw materials is reduced, thereby reducing the overall process cost, and promoting the recycling of materials.

[0027] Reference Figures 2 to 4Specifically, in the embodiment, in step S40, the dust removal system 1 comprises a dust removal tower 11, the bottom of the dust removal tower 11 is provided with an air inlet 12, and the top is provided with an air outlet 13; a plurality of groups of filter assemblies 14 are vertically arranged in the dust removal tower 11, and each group of filter assemblies 14 comprises a plurality of filter pieces 141 arranged vertically. Specifically, the filter assembly 14 further comprises a mounting plate 142, a mounting frame 143 and a breather pipe 144, the mounting frame 143 and the breather pipe 144 are fixed on the mounting plate 142, a plurality of mounting frames 143 are mounted on each mounting plate 142, the mounting frames 143 are mounted side by side on the mounting plate 142, a plurality of mounting cavities 145 are vertically arranged on each mounting frame 143, one filter piece 141 is fixedly mounted in each mounting cavity 145, and the filter piece 141 is specifically a mesh filter element in the embodiment; the breather pipe 144 is arranged on one side of the mounting plate 142, the breather pipe 144 corresponds to the mounting frame 143 one by one, and each breather pipe 144 communicates with the plurality of mounting cavities 145 on the mounting frame 143. The width of each breather pipe 144 gradually decreases from top to bottom. The arrangement mode of the filter assembly 14 optimizes the internal structure of the dust removal tower 11, improves the space utilization rate and the dust removal efficiency, facilitates the maintenance and back blowing operation of the filter assembly 14, and enhances the compactness and operability of the system.

[0028] The back blowing regeneration system 2 comprises a storage tank 21 and a blowing pipe 22, the storage tank 21 is arranged outside the dust removal tower 11, one end of the blowing pipe 22 is connected with the storage tank 21, the other end of the blowing pipe 22 is arranged in the dust removal tower 11, and the blowing pipe 22 corresponds to the filter assembly 14 one by one. The breather pipe 144 close to one end of the blowing pipe 22 is provided with a connecting pipe 23, the connecting pipe 23 comprises a contraction section 24, a throat 25 and an expansion section 26, the throat 25 is connected with the contraction section 24, and the expansion section 26 is connected with one end of the throat 25 away from the contraction section 24. By arranging the connecting pipe 23, the back blowing gas accelerates when passing through the connecting pipe 23, forms a high-speed jet, generates negative pressure in the filter assembly 14, blows off the dust attached to the filter piece 141, and falls into the bottom of the dust removal tower 11, thereby enhancing the flow efficiency and energy utilization of the back blowing gas, ensuring complete dust removal, reducing the pressure demand of the back blowing gas source, and improving the overall performance of the dust removal effect. In the embodiment, the back blowing gas is preheated inert gas or clean process gas produced by the system.

[0029] Further, in the embodiment, the pulse valve is arranged on the injection pipe 2, one side of the filter assembly 14 is the air inlet side, and the other side is the air outlet side, a differential pressure meter (not shown in the figure) is arranged at the filter assembly 14, the differential pressure meter is provided with pressure taking points at the air outlet side and the air inlet side, the differential pressure meter detects and calculates the pressure difference between the two pressure taking points in real time, that is, the resistance value ΔP = P in - P out, the differential pressure meter transmits the pressure difference value information detected and calculated to the controller (in the form of a current signal or a field total signal, continuously transmitted to the controller such as a PLC or a DCS), when ΔP ≥ P, the back flushing regeneration system 2 is triggered, the controller sends an electric signal from a digital output (DO) channel, the electric signal is transmitted to and acts on the pulse valve, the pulse valve is opened after receiving the signal, and the dust removal system 1 is cleaned online. In addition, a closing pressure P close is preset, when the monitored pressure drops to the preset closing pressure P close, the controller sends a closing instruction to the back flushing regeneration system 2, and the back flushing regeneration system 2 is closed. After the back flushing regeneration system 2 is closed, the system returns to the closed state, and waits for the resistance value to reach the preset value P again. The differential pressure meter provides accurate filter state monitoring, can identify the blockage of the filter assembly 14 in time, thereby optimizing the back flushing time, prolonging the service life of the assembly, and improving the reliability of the dust removal system 1.

[0030] Further, the installation cavity 145 is arranged to be inclined toward the air inlet 12 side away from the air vent pipe 144. The installation cavity 145 arranged to be inclined can reduce the accumulation of dust in the filter 141, and the installation cavity 145 arranged to be inclined helps the back flushing gas flow to pass through, achieving better back flushing regeneration effect.

[0031] The implementation principle of the embodiment of the application is as follows: the high-temperature dust-containing gas from the reaction furnace enters the dust removal tower 11 from the air inlet 12 at the bottom of the dust removal tower 11, passes through the vertically arranged multiple filter assemblies 14 upwards, the dust in the gas is intercepted by the filter 141, and a dust layer is formed on the surface of the filter 141, and the clean gas passes through the filter assembly 14 and is discharged from the air outlet 13 at the top of the tower to enter the downstream process. In the filtering process, as the dust layer accumulates, the air flow resistance increases, the differential pressure meter monitors the resistance value ΔP in real time, the system presets a target value P, and when the resistance value ΔP ≥ P, the system controls the back flushing regeneration system 2 to start, the gas in the storage tank 21 is released through the injection pipe 22, when the gas passes through the connecting pipe 23, a negative pressure area is formed at the throat 25, the negative pressure induces the surrounding gas to be introduced, the mixed high-speed large flow passes through the expansion section 26, the kinetic energy is further converted and concentrated, and then the back flushing gas flow vertically and uniformly blows to the filter assembly 14 through the air vent pipe 144. The direction of the back flushing gas flow is opposite to that of the air flow during filtering, the instantaneous pulse gas flow makes the filter screen produce micro deformation and vibration, breaks and blows off the dust layer adhered to the surface, and the dust falls into the tower bottom to be collected and reused. After the back flushing ends, the filter assembly 14 restores the filtering capacity, and the whole process has no any interruption to the main process flow.

[0032] The above are all preferred embodiments of the present application, and do not limit the protection scope of the present application, so that: all equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A cold hydrogenation process employing online filtration and backflushing, characterized in that, Includes the following steps: S10: Liquid STC is fed into a vaporizer and heated by steam to turn it into a gaseous state. S20: Gaseous STC is mixed with hydrogen in a certain proportion, and the mixed gas is further heated to reach the temperature required for the reaction. S30: The preheated STC and H2 mixture enters the cold hydrogenation reactor together with silicon powder to react and generate TCS (SiHCl3); S40: The gas from the cold hydrogenation reactor is introduced into the dust removal system (1) to remove solid dust particles from the gas, and the gas and silicon powder dust are obtained after dust removal. S50: The gas after dust removal enters the spray tower for cooling and washing, and then the gas exiting the tower is passed into the condensation system for cooling to obtain condensate and non-condensable gas. S60: The condensate is sent to the distillation system for separation to obtain TCS product and unreacted STC and high-boiling substances; In step S40, a target resistance value P is set for the dust removal system (1), and the resistance value ΔP caused by the dust layer attached to the dust removal system (1) is measured. When ΔP≥P, the backflushing regeneration system (2) is triggered to perform online dust removal on the dust removal system (1).

2. The cold hydrogenation process employing online filtration and backflushing according to claim 1, characterized in that: In step S40, the silicon powder dust obtained from dust removal is reintroduced into the cold hydrogenation reactor in step S20 and recycled as a reaction raw material.

3. The cold hydrogenation process employing online filtration and backflushing according to claim 1, characterized in that: In step S50, the non-condensable gas obtained after cooling is returned to the cold hydrogenation reactor in step S20 and recycled as a reaction raw material.

4. The cold hydrogenation process employing online filtration and backflushing according to claim 1, characterized in that: In step S50, the unreacted STCs return to step S10 to participate in the reaction again.

5. The cold hydrogenation process employing online filtration and backflushing according to claim 1, characterized in that: In step S40, the dust removal system (1) includes a dust removal tower (11), which has an air inlet (12) at the bottom and an air outlet (13) at the top; the dust removal tower (11) is vertically filled with multiple sets of filter components (14), each set of filter components (14) including multiple vertically arranged filter elements (141).

6. A cold hydrogenation process employing online filtration and backflushing according to claim 5, characterized in that: The filter assembly (14) has an air inlet side on one side and an air outlet side on the other side. A differential pressure gauge is installed on the filter assembly (14). The differential pressure gauge is connected to the air inlet side and the air outlet side respectively. The differential pressure gauge detects and calculates the pressure difference between the two pressure points in real time, that is, the resistance value ΔP = Pin - Pout.

7. A cold hydrogenation process employing online filtration and backflushing according to claim 5, characterized in that: The filter assembly (14) also includes a mounting plate (142), a mounting bracket (143), and an air duct (144). The mounting bracket (143) and the air duct (144) are both fixed on the mounting plate (142). Each mounting plate (142) has multiple mounting brackets (143) installed on it. The mounting brackets (143) are installed side by side on the mounting plate (142). Each mounting bracket (143) has multiple vertically arranged mounting cavities (145). Each mounting cavity (145) is used for embedding the filter element (141). The air duct (144) is located on one side of the mounting plate (142). The air duct (144) corresponds one-to-one with the mounting bracket (143). Each air duct (144) is connected to multiple mounting cavities (145) on the mounting bracket (143).

8. A cold hydrogenation process employing online filtration and backflushing according to claim 5, characterized in that: The backflushing regeneration system (2) includes a storage tank (21) and a blowpipe (22). The storage tank (21) is located outside the dust removal tower (11). One end of the blowpipe (22) is connected to the storage tank (21), and the other end is located inside the dust removal tower (11). The blowpipe (22) corresponds one-to-one with the filter assembly (14). A connecting pipe (23) is provided at the end of the vent pipe (144) near the blowpipe (22). The connecting pipe (23) includes a contraction section (24), a throat (25), and an expansion section (26). The throat (25) is connected to the contraction section (24), and the expansion section (26) is connected to the end of the throat (25) away from the contraction section (24).

9. A cold hydrogenation process employing online filtration and backflushing according to claim 7, characterized in that: The width of each of the vent tubes (144) gradually decreases from top to bottom.

10. A cold hydrogenation process employing online filtration and backflushing according to claim 7, characterized in that: The mounting cavity (145) is inclined toward the air inlet (12) on the side away from the vent pipe (144).

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