Cold hydrogenation gas-phase silicon powder filtering and recycling system
By introducing baffle sections and high-temperature filters into the cold hydrogenation system, combined with an oscillating ball design, the effective recovery and reuse of large particles and micro silica powder were achieved, solving the problem of silica powder clogging the heat exchanger, improving production efficiency and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-26
- Publication Date
- 2026-04-14
AI Technical Summary
In existing cold hydrogenation systems, silicon powder clogging of heat exchangers leads to reduced heat exchange efficiency, increased system energy consumption, reduced fluidized bed reaction efficiency, limited production capacity, and high operating costs and large amounts of solid waste generated in the slurry section.
A filtration and recovery system including a fluidized bed, baffle sections, a first high-temperature filter, and a second high-temperature filter is adopted. Through the design of the baffle sections and the use of vibrating balls, large silicon powder particles are removed, and micro silicon powder is further filtered by the high-temperature filters and recycled back to the fluidized bed for reuse.
This effectively avoids silicon powder clogging of the tail gas heat exchanger, reduces system energy consumption and solid waste, improves fluidized bed reaction efficiency and capacity, and reduces polysilicon production costs.
Smart Images
Figure CN121846822A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polycrystalline silicon production technology, and in particular to a cold hydrogenation fumed silicon powder filtration and recovery system. Background Technology
[0002] The cold hydrogenation process involves a gas-solid reaction of silicon tetrachloride, hydrogen, and metallic silicon powder in a gas-solid fluidized bed to produce trichlorosilane, a raw material needed for polycrystalline silicon production. Currently, domestic cold hydrogenation systems use cyclone separators to separate large silicon powder particles from the gas phase. This process has very limited silicon powder interception efficiency and lacks the ability to separate micro-silicon powder. Fine micro-silicon powder generated during high-speed fluidization, collision, and reaction within the fluidized bed enters the reaction tail gas heat exchanger with the gas phase, causing blockage, severely reducing heat exchange efficiency, increasing system energy consumption, making process control unstable, and requiring frequent shutdowns for cleaning. The limited bed height further reduces gas-solid reaction efficiency, resulting in limited production capacity. The micro-silicon powder ultimately enters the quench tower and is transported to the slurry section with the residual liquid through the discharge pipeline.
[0003] During the annual planned maintenance phase of the plant, the cleaning and maintenance of heat exchangers, as well as unplanned shutdowns due to blockages and leaks, all result in high maintenance costs and production losses.
[0004] In summary, the existing cold hydrogenation process has the following problems:
[0005] (1) Silicon powder clogs the tubes, severely reducing heat exchange efficiency and leading to increased system energy consumption;
[0006] (3) The slurry section has high operating costs and generates a large amount of solid waste;
[0007] (4) The bed height of current fluidized bed reactors is generally too low, which limits the output. Summary of the Invention
[0008] In view of this, the present invention provides a cold hydrogenated fumed silicon powder filtration and recovery system, the main purpose of which is to filter and recover the fumed silicon powder discharged from the fluidized bed in a timely manner.
[0009] To achieve the above objectives, the present invention mainly provides the following technical solutions:
[0010] This invention provides a cold hydrogenation fumed silica powder filtration and recovery system, the system comprising:
[0011] A fluidized bed, a baffle section, a first high-temperature filter, and a second high-temperature filter are connected in sequence, with the outlet of the second high-temperature filter connected to the exhaust gas heat exchanger.
[0012] The baffle section includes multiple vertical pipes and multiple arc-shaped pipes. The multiple vertical pipes are arranged horizontally in sequence, and the multiple vertical pipes and multiple arc-shaped pipes are connected alternately. The middle part of the arc-shaped pipe located at the lower end of the vertical pipe is connected to the upper end of the recovery pipe, and the lower end of the recovery pipe is connected to the silicon powder feed pipe of the fluidized bed.
[0013] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.
[0014] Optionally, it also includes multiple sleeves, each sleeve being fitted onto one of the vertical pipes. Multiple baffles are axially arranged in the annular space between the sleeves and the vertical pipes to divide the annular space into multiple oscillation spaces. Each baffle is evenly distributed with multiple through holes. Each oscillation space contains multiple oscillating balls. The lower end of the annular space is connected to the intake pipe, and the upper end of the annular space is connected to the exhaust pipe.
[0015] Optionally, the oscillating ball is a hollow steel ball, and the surface of the oscillating ball is evenly distributed with multiple pits.
[0016] Optionally, the filter element of the first high-temperature filter is a sintered metal filter element, and the discharge pipe at the lower end of the first high-temperature filter is connected to the silicon powder inlet pipe.
[0017] Optionally, the filter element of the second high-temperature filter is a ceramic filter element, and the discharge pipe at the lower end of the second high-temperature filter is connected to the silicon powder collection tank.
[0018] Optionally, a third high-temperature filter is also included, the lower end of which is fixedly connected to the top wall of the silicon powder collection tank.
[0019] Optionally, it also includes a first hydrogen purge pipe, which is connected to the first high-temperature filter and the second high-temperature filter respectively.
[0020] Optionally, a second hydrogen purge pipe is also included, which is connected to the top wall of the third high-temperature filter.
[0021] Optionally, it also includes a nitrogen purging pipe, which is connected to the side wall of the silicon powder collection tank and the discharge pipe of the silicon powder collection tank.
[0022] Optionally, the top wall of the third high-temperature filter is connected to one end of the air intake pipe, and the other end of the air intake pipe is connected to the lower end of the annular space.
[0023] By employing the above technical solution, the present invention has at least the following advantages:
[0024] After the gas is discharged from the fluidized bed, it flows through the baffle section. In the baffle section, the gas phase component containing silicon powder flows up and down in a meandering manner. The silicon powder rubs against the inner wall of the baffle section, and the kinetic energy of the large silicon powder particles is lost. The large silicon powder particles settle into the arc-shaped pipe at the lower end of the vertical pipe and flow through the recovery pipe to the silicon powder replenishment pipe, ultimately realizing the reuse of large silicon powder particles.
[0025] The gaseous components after removing large silicon powder particles flow through the first high-temperature filter and the second high-temperature filter for further removal of silicon powder.
[0026] Based on the above, the gas phase components entering the tail gas heat exchanger have no silicon powder residue, which can avoid silicon powder clogging the tubes of the tail gas heat exchanger and avoid frequent shutdowns for cleaning the tail gas heat exchanger; it is not necessary to maintain the operating effect of the tail gas heat exchanger at the expense of limiting the bed height of the fluidized bed; the amount of silicon powder received by the quench tower after the tail gas heat exchanger is reduced, which also reduces the amount of solid waste that needs to be treated in the slurry section; at the same time, the silicon powder is recycled to the fluidized bed, which also reduces the production cost of polysilicon. Attached Figure Description
[0027] Figure 1 A diagram of a cold hydrogenation gas-phase silicon powder filtration and recovery system provided in an embodiment of the present invention;
[0028] Figure 2 for Figure 1 Enlarged view of section A;
[0029] Figure 3 for Figure 1 Enlarged view of section B.
[0030] The reference numerals in the accompanying drawings include: fluidized bed 1, baffle section 2, first high-temperature filter 3, second high-temperature filter 4, vertical pipe 201, arc-shaped pipe 202, recovery pipe 5, silicon powder inlet pipe 6, first shut-off valve 7, sleeve 8, partition 9, oscillation space 10, through hole 11, oscillation ball 12, air inlet pipe 13, exhaust pipe 14, second shut-off valve 15, silicon powder collection tank 16, third shut-off valve 17, fourth shut-off valve 18, third high-temperature filter 19, tail gas pipe 20, first hydrogen purge pipe 21, second hydrogen purge pipe 22, and nitrogen purge pipe 23. Detailed Implementation
[0031] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.
[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.
[0033] like Figure 1 As shown, an embodiment of the present invention provides a cold hydrogenation gas-phase silicon powder filtration and recovery system, which includes:
[0034] The fluidized bed 1, the baffle section 2, the first high-temperature filter 3 and the second high-temperature filter 4 are connected in sequence, and the outlet of the second high-temperature filter 4 is connected to the exhaust gas heat exchanger.
[0035] The baffle section 2 includes multiple vertical pipes 201 and multiple arc-shaped pipes 202. The multiple vertical pipes 201 are arranged horizontally in sequence, and the multiple vertical pipes 201 and multiple arc-shaped pipes 202 are alternately connected. The middle part of the arc-shaped pipe 202 located at the lower end of the vertical pipe 201 is connected to the upper end of the recovery pipe 5, and the lower end of the recovery pipe 5 is connected to the silicon powder inlet pipe 6 of the fluidized bed 1.
[0036] The working process of the cold hydrogenation gas phase silicon powder filtration and recovery system is as follows:
[0037] After the gas is discharged from the fluidized bed 1, it flows through the baffle section 2. In the baffle section 2, the gas phase component containing silicon powder flows up and down in a meandering manner. The silicon powder rubs against the inner wall of the baffle section 2, and the kinetic energy of the large silicon powder particles is lost. The large silicon powder particles settle into the arc-shaped pipe 202 at the lower end of the vertical pipe 201, and flow through the recovery pipe 5 to the silicon powder replenishment pipe 6, finally realizing the reuse of large silicon powder particles.
[0038] The gaseous components after removing large silicon powder particles flow through the first high-temperature filter 3 and the second high-temperature filter 4 for further removal of silicon powder.
[0039] Based on the above, the gas phase components entering the tail gas heat exchanger have no silicon powder residue, which can prevent silicon powder from clogging the tubes of the tail gas heat exchanger and avoid frequent shutdowns for cleaning the tail gas heat exchanger; it is not necessary to maintain the operating effect of the tail gas heat exchanger at the expense of limiting the bed height of fluidized bed 1; the amount of silicon powder received by the quench tower after the tail gas heat exchanger is reduced, which also reduces the amount of solid waste that needs to be treated in the slurry section; at the same time, the silicon powder is recycled to fluidized bed 1, which also reduces the production cost of polysilicon.
[0040] Specifically, the recovery pipe 5 is equipped with two first shut-off valves 7 to facilitate the periodic discharge of large particles of silicon powder that have settled in the baffle section 2 to the silicon powder replenishment pipe 6.
[0041] like Figure 1 , Figure 2 and Figure 3As shown, in a specific embodiment, it also includes multiple sleeves 8, each sleeve 8 being sleeved on one of the vertical pipes 201. Multiple partitions 9 are axially arranged in the annular space between the sleeves 8 and the vertical pipes 201 to divide the annular space into multiple oscillation spaces 10. Each partition 9 is evenly distributed with multiple through holes 11. Each oscillation space 10 contains multiple oscillating balls 12. The lower end of the annular space is connected to the intake pipe 13, and the upper end of the annular space is connected to the exhaust pipe 14.
[0042] In this embodiment, specifically, the lower end of the annular space is connected to the gas supply device through the air inlet pipe 13. When silicon powder flows through the baffle section 2 with the gas phase components, in order to avoid silicon powder adhering to the inner wall of the vertical pipe 201, the gas supply device supplies gas to the annular space through the air inlet pipe 13. The airflow flows through multiple through holes 11, causing the oscillating balls 12 in multiple oscillating spaces 10 to move randomly. The randomly moving oscillating balls 12 hit the outer wall of the vertical pipe 201, causing the pipe wall of the vertical pipe 201 to oscillate slightly, causing the silicon powder adhering to the inner wall of the vertical pipe 201 to fall off, thereby maintaining the radial cross-sectional area of the baffle section 2, thereby maintaining the flow rate of the gas phase components.
[0043] In a specific embodiment, the oscillating ball 12 is a hollow steel ball, and the surface of the oscillating ball 12 is evenly distributed with multiple pits.
[0044] In this embodiment, specifically, the oscillating ball 12 is made of hollow steel ball, which has a certain mechanical strength. The hollow structure of the oscillating ball 12 is relatively light in weight. The impact force of the airflow acts on multiple pits on the surface of the oscillating ball 12, which can cause the oscillating ball 12 to move upward randomly for a certain distance. The oscillating ball 12 then falls down due to its own weight. During the above-mentioned random movement, the steel oscillating ball 12 hits the wall of the vertical tube 201, which does not easily cause the oscillating ball 12 to deform.
[0045] In a specific embodiment, the filter element of the first high-temperature filter 3 is a sintered metal filter element, and the discharge pipe at the lower end of the first high-temperature filter 3 is connected to the silicon powder inlet pipe 6.
[0046] In this embodiment, specifically, two second shut-off valves 15 are installed on the discharge pipe at the lower end of the first high-temperature filter 3. The filtration accuracy of the metal sintered filter element of the first high-temperature filter 3 is 0.5μm. The first high-temperature filter 3 is equipped with a differential pressure gauge. When the differential pressure of the first high-temperature filter 3 exceeds 5KPa, the two second shut-off valves 15 are opened. The silicon powder in the lower conical space of the filter settles into the silicon powder inlet pipe 6 due to its own gravity and enters the fluidized bed 1 to react again.
[0047] In a specific embodiment, the filter element of the second high-temperature filter 4 is a ceramic filter element, and the discharge pipe at the lower end of the second high-temperature filter 4 is connected to the silicon powder collection tank 16.
[0048] In this embodiment, specifically, the discharge pipe at the lower end of the second high-temperature filter 4 is equipped with two third shut-off valves 17, and the discharge pipe at the lower end of the silicon powder collection tank 16 is equipped with two fourth shut-off valves 18. The filtration accuracy of the ceramic filter element of the second high-temperature filter 4 is 0.3μm. The microsilica powder passing through the filter element of the first high-temperature filter 3 arrives at the second high-temperature filter 4 along with the gas phase components. The second high-temperature filter 4 is equipped with a differential pressure gauge. When the differential pressure of the second high-temperature filter 4 exceeds 5KPa, the two third shut-off valves 17 are opened, and the microsilica powder in the lower conical space of the second high-temperature filter 4 settles into the silicon powder collection tank 16 due to its own gravity.
[0049] When the level of microsilica powder in the silicon powder collection tank 16 reaches the upper limit, the two fourth shut-off valves 18 are opened to discharge the microsilica powder.
[0050] In a specific embodiment, a third high-temperature filter 19 is also included, the lower end of which is fixedly connected to the top wall of the silicon powder collection tank 16.
[0051] In this embodiment, the filter element of the third high-temperature filter 19 is also a ceramic filter element. The upper end of the third high-temperature filter 19 is connected to the exhaust pipe 20. When the silicon powder collection tank 16 collects the micro silicon powder discharged from the second high-temperature filter 4, the high-pressure gas in the silicon powder collection tank 16 can enter the exhaust pipe 20 through the ceramic filter element of the third high-temperature filter 19, and finally enter the hydrogen-containing exhaust gas treatment unit for deep cooling to recover the chlorosilane in the gas phase.
[0052] Specifically, the structures of the first high-temperature filter 3 are basically the same, including a shell, a mounting plate and multiple filter elements. The lower space of the shell is a conical space, the edge of the mounting plate is fixedly connected to the inner wall of the shell, and multiple filter elements are evenly distributed and installed on the lower surface of the mounting plate.
[0053] Specifically, this system requires only a small increase in equipment investment to achieve long-term stable operation of the tail gas heat exchanger, reduce the operating load of downstream processes, reduce solid waste generation, increase the height of the fluidized bed 1 reaction bed, and improve production capacity.
[0054] In a specific embodiment, a first hydrogen purge pipe 21 is also included, which is connected to the first high-temperature filter 3 and the second high-temperature filter 4 respectively.
[0055] In this embodiment, specifically, the first hydrogen purge pipe 21 is connected to the top wall of the first high-temperature filter 3 and the side wall of the lower conical space, and the first hydrogen purge pipe 21 is connected to the top wall of the second high-temperature filter 4 and the side wall of the lower conical space. This facilitates reverse purging of the filter element's pores, maintains the filter element's long-term usability, and at the same time, prevents silicon powder from bridging and accumulating in the lower conical space, thereby ensuring that the silicon powder in the lower conical space can fall smoothly due to its own weight.
[0056] In a specific embodiment, a second hydrogen purge pipe 22 is also included, which is connected to the top wall of the third high-temperature filter 19.
[0057] In this embodiment, specifically, the second hydrogen purge pipe 22 is connected to the top wall of the third high-temperature filter 19, which facilitates reverse purging of the filter element of the third high-temperature filter 19.
[0058] In a specific embodiment, a nitrogen purging pipe 23 is also included, which is connected to the side wall of the silicon powder collection tank 16 and the discharge pipe of the silicon powder collection tank 16.
[0059] In this embodiment, specifically, the nitrogen purging pipe 23 is connected to the side wall of the lower conical space of the silicon powder collection tank 16 to prevent silicon powder from bridging and accumulating in the conical space; the nitrogen purging pipe 23 is connected to the discharge pipe of the silicon powder collection tank 16 to prevent the discharge pipe from being blocked by micro silicon powder; at the same time, when it is necessary to discharge the micro silicon powder in the silicon powder collection tank 16, nitrogen can be introduced first to displace the internal space of the silicon powder collection tank 16, so as to facilitate the safe discharge of micro silicon powder.
[0060] Specifically, clean gaseous components enter the tail gas heat exchanger from the top of the second high-temperature filter 4 for heat recovery. The intercepted silicon powder is temporarily stored at the bottom of the filter cone. The operating pressure of the second high-temperature filter 4 is 2.8 MPa, and the operating pressure of the silicon powder collection tank 16 is 2.7 MPa. Every 8 hours, the second high-temperature filter 4 discharges silicon powder into the silicon powder collection tank 16. The silicon powder collection tank 16 is purged with nitrogen at the bottom, and the powder is discharged from the system after passing the purging. The silicon powder interception rate is over 99.99%. Since the tail gas heat exchanger no longer experiences blockage, the heat exchange effect is good. The cold hydrogen chemical section saves 1000 kW / h of electricity per hour. The bed height of fluidized bed 1 is increased from 120 kPa to 135 kPa. The ratio of silicon tetrachloride to hydrogen is increased from 1:2 to 1:2.4. The daily production of trichlorosilane increases by 80 tons. The load of the slurry and waste treatment sections is reduced by more than 45%, and the amount of solid waste generated is reduced by 65%.
[0061] In a specific embodiment, the top wall of the third high-temperature filter 19 is connected to one end of the air inlet pipe 13, and the other end of the air inlet pipe 13 is connected to the lower end of the annular space.
[0062] In this embodiment, specifically, the exhaust pipe 20 at the top of the third high-temperature filter 19 is connected to one end of the intake pipe 13, and the other end of the intake pipe 13 is connected to the lower end of the annular space. The exhaust pipe 14 at the upper end of the annular space is connected to the hydrogen-containing exhaust gas treatment unit. After being filtered by the third high-temperature filter 19, the gas entering the exhaust pipe 20 does not contain silicon powder. The gas is a mixture of hydrogen and chlorosilane. Moreover, the hydrogen entering the third high-temperature filter 19 through the second hydrogen purge pipe 22 is also depressurized through the exhaust pipe 20, thus providing the intake pipe 13 with a sufficiently pressurized flow of gas. This flow of gas drives the oscillating balls 12 in each oscillating space 10 to move randomly, and finally reaches the hydrogen-containing exhaust gas treatment unit through the exhaust pipe 14.
[0063] By using the above method, the random movement of the oscillating ball 12 is avoided by setting up a separate air supply device. The oscillating ball 12 is driven by the exhaust gas after purging, which prevents silicon powder from adhering to the inner wall of the baffle section 2.
[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A cold hydrogenation fumed silica powder filtration and recovery system, characterized in that, include: A fluidized bed, a baffle section, a first high-temperature filter, and a second high-temperature filter are connected in sequence, with the outlet of the second high-temperature filter connected to the exhaust gas heat exchanger. The baffle section includes multiple vertical pipes and multiple arc-shaped pipes. The multiple vertical pipes are arranged horizontally in sequence, and the multiple vertical pipes and multiple arc-shaped pipes are connected alternately. The middle part of the arc-shaped pipe located at the lower end of the vertical pipe is connected to the upper end of the recovery pipe, and the lower end of the recovery pipe is connected to the silicon powder feed pipe of the fluidized bed.
2. The cold hydrogenation gas-phase silicon powder filtration and recovery system according to claim 1, characterized in that, It also includes multiple sleeves, each sleeve being fitted onto one of the vertical pipes. Multiple baffles are axially arranged in the annular space between the sleeves and the vertical pipes to divide the annular space into multiple oscillation spaces. Each baffle is evenly distributed with multiple through holes. Each oscillation space contains multiple oscillating balls. The lower end of the annular space is connected to the intake pipe, and the upper end of the annular space is connected to the exhaust pipe.
3. The cold hydrogenation gas-phase silicon powder filtration and recovery system according to claim 2, characterized in that, The oscillating ball is a hollow steel ball, and its surface is evenly distributed with multiple pits.
4. The cold hydrogenation gas-phase silicon powder filtration and recovery system according to claim 1, characterized in that, The filter element of the first high-temperature filter is a sintered metal filter element, and the discharge pipe at the lower end of the first high-temperature filter is connected to the silicon powder inlet pipe.
5. The cold hydrogenation gas-phase silicon powder filtration and recovery system according to claim 2, characterized in that, The filter element of the second high-temperature filter is a ceramic filter element, and the discharge pipe at the lower end of the second high-temperature filter is connected to the silicon powder collection tank.
6. The cold hydrogenation gas-phase silicon powder filtration and recovery system according to claim 5, characterized in that, It also includes a third high-temperature filter, the lower end of which is fixedly connected to the top wall of the silicon powder collection tank.
7. The cold hydrogenation fumed silica powder filtration and recovery system according to claim 1, characterized in that, It also includes a first hydrogen purge pipe, which is connected to the first high-temperature filter and the second high-temperature filter respectively.
8. The cold hydrogenation fumed silica powder filtration and recovery system according to claim 6, characterized in that, It also includes a second hydrogen purge pipe, which is connected to the top wall of the third high-temperature filter.
9. The cold hydrogenation fumed silica powder filtration and recovery system according to claim 6, characterized in that, It also includes a nitrogen purging pipe, which is connected to the side wall of the silicon powder collection tank and the discharge pipe of the silicon powder collection tank.
10. The cold hydrogenation gas-phase silicon powder filtration and recovery system according to claim 8, characterized in that, The top wall of the third high-temperature filter is connected to one end of the air inlet pipe, and the other end of the air inlet pipe is connected to the lower end of the annular space.