Efficient operation process of polycrystalline silicon tail gas recovery adsorption tower

Abstract

The invention relates to an efficient operation process of a polycrystalline silicon tail gas recovery adsorption tower, which comprises six adsorption towers arranged in parallel, namely a first adsorption tower, a second adsorption tower, a third adsorption tower, a fourth adsorption tower, a fifth adsorption tower and a sixth adsorption tower, the six adsorption towers are interlocked and controlled to operate through a DCS (Distributed Control System), and in the operation process of the six towers, the adsorption towers are connected in parallel. Four towers are in an adsorption process, one tower is in a cooling process, and the other tower is in a heating back blowing process. According to the process, the tail gas treatment efficiency and the adsorption efficiency of each adsorption tower are remarkably improved, the service life of equipment is effectively prolonged, the operation cost is reduced, and the purity and stability of hydrogen recovery are improved.

Description

Technical Field

[0001] The invention relates to the technical field of polysilicon, and in particular to a high-efficiency operation process of a polysilicon tail gas recovery adsorption tower. Background Art

[0002] As a form of single crystal silicon, polysilicon is widely used in the photovoltaic industry and microelectronics industry due to its semiconductor properties. At present, 80% of the world's polysilicon manufacturers use the modified Siemens method to produce polysilicon. The principle is to use high-purity trichlorosilane (SiHCl3) and hydrogen (H2) to reduce high-purity trichlorosilane under high temperature conditions to generate high-purity polysilicon deposited on the silicon core. In the tail gas recovery device, more than 90% of polysilicon manufacturers currently use activated carbon adsorption towers to purify the hydrogen in the mixed gas. In the existing process, the adsorption system is usually composed of three adsorption towers, but there are problems such as low adsorption efficiency and insufficient tail gas treatment volume. Summary of the invention

[0003] The purpose of the present invention is to provide a highly efficient operation process of a polysilicon tail gas recovery adsorption tower, improve the adsorption efficiency and tail gas treatment capacity, and solve the problems in the prior art. The following technical solutions are adopted:

[0004] An efficient operation process of a polysilicon tail gas recovery adsorption tower comprises six adsorption towers arranged in parallel, namely a first adsorption tower, a second adsorption tower, a third adsorption tower, a fourth adsorption tower, a fifth adsorption tower and a sixth adsorption tower. The six adsorption towers are operated by interlocking control of a DCS system. During the operation of the six towers, four towers are in an adsorption process, one tower is in a cooling process, and one tower is in a heating backblowing process.

[0005] Furthermore, the durations of the adsorption process, cooling process, and heating backflushing process of each adsorption tower are 100 min, 80 min, and 100 min, respectively.

[0006] Furthermore, the specific steps include:

[0007] S1, when the first adsorption tower, the second adsorption tower, the third adsorption tower and the fourth adsorption tower are adsorbing, the fifth adsorption tower is cooled, and the sixth adsorption tower is heated and backwashed, and this step lasts for 80 minutes;

[0008] S2, the fifth adsorption tower is controlled by the DCS system to enter the adsorption process, the sixth adsorption tower continues to heat and backwash, and the adsorption process of the first adsorption tower is stopped at the same time, and the heating and backwashing process is entered. At this time, the second adsorption tower, the third adsorption tower, the fourth adsorption tower, and the fifth adsorption tower are adsorbed, the sixth adsorption tower is heated and backwashed, and the first adsorption tower is heated and backwashed. This step lasts for 20 minutes;

[0009] S3, the DCS system controls the sixth adsorption tower to enter the cooling process, at this time, the second adsorption tower, the third adsorption tower, the fourth adsorption tower, the fifth adsorption tower adsorption, the sixth adsorption tower cooling, the first adsorption tower heating backwash, this step lasts for 80 minutes;

[0010] S4, the sixth adsorption tower is controlled by the DCS system to enter the adsorption process, the first adsorption tower continues to heat and backflush, and the adsorption process of the second adsorption tower is stopped at the same time, and the heating and backflush process is entered. At this time, the third adsorption tower, the fourth adsorption tower, the fifth adsorption tower, and the sixth adsorption tower adsorb, the first adsorption tower continues to backflush, and the second adsorption tower heats and backflush. This step lasts for 20 minutes;

[0011] S5, the first adsorption tower is controlled by the DCS system to enter the cooling process, at this time, the third adsorption tower, the fourth adsorption tower, the fifth adsorption tower, and the sixth adsorption tower are adsorbed, the first adsorption tower is cooled, and the second adsorption tower is heated and backwashed, and this step lasts for 80 minutes;

[0012] S6, control the first adsorption tower to enter the adsorption process through the DCS system, the second adsorption tower continues to heat and backwash, and the adsorption process of the third adsorption tower is stopped at the same time, and enters the heating and backwashing process. At this time, the fourth adsorption tower, the fifth adsorption tower, the sixth adsorption tower, and the first adsorption tower adsorb, the second adsorption tower heats and backwashes, and the third adsorption tower heats and backwashes. This step lasts for 20 minutes;

[0013] S7, the second adsorption tower is controlled by the DCS system to enter the cooling process, at this time, the fourth adsorption tower, the fifth adsorption tower, the sixth adsorption tower, and the first adsorption tower are adsorbed, the second adsorption tower is cooled, and the third adsorption tower is heated and backwashed. This step lasts for 80 minutes;

[0014] S8, control the second adsorption tower to enter the adsorption process through the DCS system, the third adsorption tower continues to heat and backwash, and the adsorption process of the fourth adsorption tower is stopped at the same time, and enters the heating and backwashing process. At this time, the fifth adsorption tower, the sixth adsorption tower, the first adsorption tower, and the second adsorption tower adsorb, the third adsorption tower heats and backwashes, and the fourth adsorption tower heats and backwashes. This step lasts for 20 minutes;

[0015] S9, the DCS system controls the third adsorption tower to enter the cooling process. At this time, the fifth adsorption tower, the sixth adsorption tower, the first adsorption tower, and the second adsorption tower adsorb, the third adsorption tower cools, and the fourth adsorption tower heats and backwashes. This step lasts for 80 minutes;

[0016] S10, the DCS system controls the third adsorption tower to enter the adsorption process, the fourth adsorption tower continues to heat and backwash, and the adsorption process of the fifth adsorption tower is stopped at the same time, and the heating and backwashing process is entered. At this time, the sixth adsorption tower, the first adsorption tower, the second adsorption tower, and the third adsorption tower adsorb, the fourth adsorption tower heats and backwashes, and the fifth adsorption tower heats and backwashes. This step lasts for 20 minutes;

[0017] S11, the DCS system controls the fourth adsorption tower to enter the cooling process, at this time, the sixth adsorption tower, the first adsorption tower, the second adsorption tower, and the third adsorption tower adsorb, the fourth adsorption tower cools, and the fifth adsorption tower heats and backwashes, and this step lasts for 80 minutes;

[0018] S12, the fourth adsorption tower is controlled by the DCS system to enter the adsorption process, the fifth adsorption tower continues to heat and backwash, and the adsorption process of the sixth adsorption tower is stopped at the same time, and the heating and backwashing process is entered. At this time, the sixth adsorption tower, the first adsorption tower, the second adsorption tower, and the third adsorption tower adsorb, the fourth adsorption tower heats and backwashes, and the fifth adsorption tower heats and backwashes. This step lasts for 20 minutes;

[0019] S13, loop through steps S1 to S12 again.

[0020] Furthermore, when one of the adsorption towers fails, the DCS system can control the tower to merge the exhaust gas it needs to treat into the other three adsorption towers in the adsorption process, and automatically switch to the operation mode of three-tower adsorption, one-tower cooling, and one-tower heating backflushing, to ensure that the exhaust gas treatment volume is not affected.

[0021] The beneficial effects of the present invention include at least one of the following:

[0022] Through the reasonable allocation of six adsorption towers and the precise control of the DCS system, each adsorption tower can achieve a cumulative adsorption time of 400 minutes within a 600-minute cycle, thereby effectively improving the adsorption efficiency of the adsorption tower.

[0023] The present invention ensures the full regeneration of activated carbon by optimizing the heating backflush and cooling processes, thereby extending the service life of the adsorption tower and reducing the operating cost.

[0024] The present invention adopts a six-tower linkage control system, so even if one adsorption tower fails, the other adsorption towers can still maintain normal operation, thereby ensuring the continuity and stability of tail gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the operation of the four-tower adsorption technology of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Reference Figure 1This embodiment proposes an efficient operation process of a polysilicon tail gas recovery adsorption tower, including six adsorption towers arranged in parallel, namely, the first adsorption tower T1, the second adsorption tower T2, the third adsorption tower T3, the fourth adsorption tower T4, the fifth adsorption tower T5, and the sixth adsorption tower T6. The six adsorption towers are operated by the DCS system interlocking control. During the operation of the six towers, four towers are in the adsorption process, one tower is in the cooling process, and one tower is in the heating backwash process. The duration of the adsorption process, cooling process, and heating backwash process of each adsorption tower is 100 minutes, 80 minutes, and 100 minutes, respectively.

[0028] The following takes T1 as an example to illustrate the DCS control of the adsorption tower in each process:

[0029] Hydrogen and trichlorosilane undergo a vapor phase chemical deposition reaction on the silicon core to form polysilicon, wherein the hydrogen and trichlorosilane do not react completely, and the hydrogen chloride generated by the reaction and other side reaction products together constitute the reducing tail gas.

[0030] During the adsorption process, the hydrogen in the reduced tail gas enters the adsorption tower under the adsorption process from the bottom of the adsorption tower. Under the selective adsorption of the activated carbon adsorbent, the components such as chlorosilane and hydrogen chloride are adsorbed, and the unadsorbed hydrogen is sent from the top of the tower to the H2 buffer tank after passing through the H2 filter. Figure 1 At this time, the DCS controls the air inlet valve 1 and the hydrogen outlet valve 2 of T1 to open, and at the same time, the cold water inlet valve 3 and the cold water outlet valve 4 are opened, and the activated carbon in the adsorption tower is cooled with cold water (temperature 40°C) to ensure that the activated carbon has a good adsorption effect (the pressure of the adsorption tower in this process is 0.9MPa);

[0031] During the regeneration process, after the adsorption is completed, the activated carbon is heated with hot water (temperature 180°C) to keep the temperature of the activated carbon at 180°C, and hot H2 is used to back-blow the hydrogen chloride and chlorosilane adsorbed on the activated carbon (the pressure of the adsorption tower in this process is 0.05MPa). At this time, the DCS controls the air inlet valve 1 and the hydrogen outlet valve 2 of T1 to be closed, and the adsorption is stopped. At the same time, the cold water inlet valve 3 and the cold water outlet valve 4 are closed, and the hot water inlet valve 5 and the hot water outlet valve 6 are opened. The adsorption tower is heated by hot water, and the hot hydrogen inlet valve 7 and the regeneration tail gas outlet valve 9 are opened, and the activated carbon is back-blown with hot H2. The hot H2 in this process comes from the H2 buffer tank and is obtained by heat exchange with the reduced tail gas;

[0032] During the cooling process, the activated carbon is cooled with cold water (temperature 40°C) and back-flushed with cold H2 (the pressure of the adsorption tower is increased to 0.9MPa during this process to prepare for the next step of adsorption). At this time, the hot hydrogen inlet valve 7 and the regenerated tail gas outlet valve 9 of T1 are controlled by DCS to stop the hot hydrogen back-flushing, and the hot water inlet valve 5 and the hot water outlet valve 6 are closed at the same time. The cold water inlet valve 3 and the cold water outlet valve 4 are opened, the hot hydrogen inlet valve 7 is closed, and the cold hydrogen inlet valve 8 is opened. After the activated carbon in T1 is cooled, the cold hydrogen inlet valve 8 and the regenerated tail gas outlet valve 9 are closed to enter the adsorption process again.

[0033] The detailed operation process of the process provided in this embodiment is as follows:

[0034] S1, this step is the initial state of a cycle, at this time, T1~T4 are in the adsorption process, T5 is in the cooling process, T6 is in the heating backwash process, after 80 minutes, T5 cooling process is completed, and enter the next step. The cumulative adsorption time of T1~T6 in this process is: 80min, 80min, 80min, 80min, 0min, 0min respectively.

[0035] S2, through the DCS system control T5 to enter the adsorption process, the sixth adsorption tower continues to heat and blow back because the 100min heating backwash process is not completed, and the first adsorption tower adsorption process is stopped at the same time, and the heating backwash process is entered. At this time, the second to fifth adsorption towers are in the adsorption process, and the sixth adsorption tower and the first adsorption tower are in heating backwash. After 20 minutes, the heating backwash process of the sixth adsorption tower is completed, and regeneration is completed, and the next step is entered. The cumulative adsorption time of the first to sixth adsorption towers in this process is respectively: 80min, 100min, 100min, 100min, 20min, 0min.

[0036] S3, the DCS system controls the sixth adsorption tower to enter the cooling process. At this time, the second to fifth adsorption towers adsorb, the sixth adsorption tower cools, and the first adsorption tower heats and blows back. After 80 minutes, the cooling process of the sixth adsorption tower is completed and enters the next step. The cumulative adsorption time of the first to sixth adsorption towers in this process is 80 minutes, 180 minutes, 180 minutes, 180 minutes, 100 minutes, and 0 minutes, respectively.

[0037] S4, the sixth adsorption tower is controlled by the DCS system to enter the adsorption process. Since the 100-min heating backwashing process of the first adsorption tower is not completed, the heating backwashing continues, and the adsorption process of the second adsorption tower is stopped at the same time, and the heating backwashing process is entered. At this time, the third to sixth adsorption towers are in the adsorption process, and the first adsorption tower and the second adsorption tower are in heating backwashing. After 20 minutes, the heating backwashing process of the first adsorption tower is completed, and regeneration is completed, and the next step is entered. The cumulative adsorption time of the first to sixth adsorption towers in this process is respectively: 80min, 180min, 200min, 200min, 120min, and 20min.

[0038] S5, the first adsorption tower is controlled by the DCS system to enter the cooling process. At this time, the third to sixth adsorption towers are in the adsorption process, the first adsorption tower is cooled, and the second adsorption tower is heated and backwashed. After 80 minutes, the cooling process of the first adsorption tower is completed and the next step is entered. The cumulative adsorption time of the first to sixth adsorption towers in this process is respectively: 80min, 180min, 280min, 280min, 200min, and 100min.

[0039] S6, the first adsorption tower is controlled by the DCS system to enter the adsorption process. Since the 100-minute heating backwashing process of the second adsorption tower is not completed, the heating backwashing continues, and the adsorption process of the third adsorption tower is stopped at the same time, and the heating backwashing process is entered. At this time, the fourth to sixth adsorption towers and the first adsorption tower are in the adsorption process, and the second adsorption tower and the third adsorption tower are in the heating backwashing process. After 20 minutes, the heating backwashing process of the second adsorption tower is completed and enters the next step. The cumulative adsorption time of the first to sixth adsorption towers in this process is: 100min, 180min, 280min, 300min, 220min, 120min, respectively.

[0040] S7, the second adsorption tower is controlled by the DCS system to enter the cooling process. At this time, the fourth to sixth adsorption towers and the first adsorption tower are in the adsorption process, the second adsorption tower is cooled, and the third adsorption tower is heated and backwashed. After 80 minutes, the cooling process of the second adsorption tower is completed and enters the next step. The cumulative adsorption time of the first to sixth adsorption towers in this process is: 180min, 180min, 280min, 380min, 300min, 200min respectively.

[0041] S8, the second adsorption tower is controlled by the DCS system to enter the adsorption process. Since the 100-minute heating backwashing process of the third adsorption tower is not completed, the heating backwashing continues, and the adsorption process of the fourth adsorption tower is stopped at the same time, and the heating backwashing process is entered. At this time, the fifth to sixth adsorption towers and the first to second adsorption towers are in the adsorption process, and the third adsorption tower and the fourth adsorption tower are in heating backwashing. After 20 minutes, the heating backwashing process of the third adsorption tower is completed and enters the next step. The cumulative adsorption time of the first to sixth adsorption towers in this process is: 200min, 200min, 280min, 380min, 320min, 220min respectively.

[0042] S9, the DCS system controls the third adsorption tower to enter the cooling process. At this time, the fifth to sixth adsorption towers and the first to second adsorption towers are in the adsorption process, the third adsorption tower is cooled, and the fourth adsorption tower is heated and backwashed. After 80 minutes, the cooling process of the third adsorption tower is completed and enters the next step. The cumulative adsorption time of the first to sixth adsorption towers in this process is: 280min, 280min, 280min, 380min, 400min, 300min respectively.

[0043] S10, the third adsorption tower is controlled by the DCS system to enter the adsorption process. Since the 100-minute heating backwashing process of the fourth adsorption tower is not completed, the heating backwashing continues, and the adsorption process of the fifth adsorption tower is stopped at the same time, and the heating backwashing process is entered. At this time, the sixth adsorption tower and the first to third adsorption towers are in the adsorption process, and the fourth adsorption tower and the fifth adsorption tower are in the heating backwashing process. After 20 minutes, the heating backwashing process of the fourth adsorption tower is completed and enters the next step. The cumulative adsorption time of the first to sixth adsorption towers in this process is: 300min, 300min, 300min, 380min, 400min, 320min respectively.

[0044] S11, the DCS system controls the fourth adsorption tower to enter the cooling process. At this time, the sixth adsorption tower and the first to third adsorption towers are in the adsorption process, the fourth adsorption tower is cooled, and the fifth adsorption tower is heated and backwashed. After 80 minutes, the cooling process of the fourth adsorption tower is completed and enters the next step. The cumulative adsorption time of the first to sixth adsorption towers in this process is: 380min, 380min, 380min, 380min, 400min, 400min, respectively.

[0045] S12, the fourth adsorption tower is controlled by the DCS system to enter the adsorption process. Since the 100-minute heating backwashing process of the fifth adsorption tower is not completed, the heating backwashing continues, and the adsorption process of the sixth adsorption tower is stopped at the same time, and the heating backwashing process is entered. At this time, the first to fourth adsorption towers are in the adsorption process, and the fifth adsorption tower and the sixth adsorption tower are in heating backwashing. After 20 minutes, the heating backwashing process of the fifth adsorption tower is completed and enters the next step. The cumulative adsorption time of the first to sixth adsorption towers in this process is: 400min, 400min, 400min, 400min, 400min, 400min, 400min, respectively.

[0046] S13, looping the above steps S1 to S12, ensuring that the adsorption, cooling and heating backflushing processes of each adsorption tower are reasonably allocated time to maintain efficient operation of the system.

[0047] According to the above operation process, each set of adsorption device is operated in a cycle of 600 minutes, and the adsorption time of each tower is 400 minutes. This process operation mode further improves the adsorption efficiency of each tower, and the adsorption efficiency is 66.67%.

Claims

1. An efficient operation process of a polysilicon tail gas recovery adsorption tower, comprising six adsorption towers arranged in parallel, namely a first adsorption tower, a second adsorption tower, a third adsorption tower, a fourth adsorption tower, a fifth adsorption tower, and a sixth adsorption tower, wherein the six adsorption towers are operated by a DCS system interlocking control, characterized in that: During the operation of the six adsorption towers, four of them are in the adsorption process, one is in the cooling process, and one is in the heating backflushing process.

2. The efficient operation process of a polysilicon tail gas recovery adsorption tower according to claim 1, characterized in that: The durations of the adsorption process, cooling process and heating backflushing process of each adsorption tower are 100 minutes, 80 minutes and 100 minutes respectively.

3. The efficient operation process of a polysilicon tail gas recovery adsorption tower according to claim 2, characterized in that: The process also includes the following steps: S1, when the first adsorption tower, the second adsorption tower, the third adsorption tower and the fourth adsorption tower are adsorbing, the fifth adsorption tower is cooled, and the sixth adsorption tower is heated and backwashed, and this step lasts for 80 minutes; S2, the fifth adsorption tower is controlled by the DCS system to enter the adsorption process, the sixth adsorption tower continues to heat and backwash, and the adsorption process of the first adsorption tower is stopped at the same time, and the heating and backwashing process is entered. At this time, the second adsorption tower, the third adsorption tower, the fourth adsorption tower, and the fifth adsorption tower are adsorbed, the sixth adsorption tower is cooled, and the first adsorption tower is heated and backwashed. This step lasts for 20 minutes; S3, the DCS system controls the sixth adsorption tower to enter the cooling process, at this time, the second adsorption tower, the third adsorption tower, the fourth adsorption tower, the fifth adsorption tower adsorption, the sixth adsorption tower cooling, the first adsorption tower heating backwash, this step lasts for 80 minutes; S4, the sixth adsorption tower is controlled by the DCS system to enter the adsorption process, the first adsorption tower continues to heat and backflush, and the adsorption process of the second adsorption tower is stopped at the same time, and the heating and backflush process is entered. At this time, the third adsorption tower, the fourth adsorption tower, the fifth adsorption tower, and the sixth adsorption tower adsorb, the first adsorption tower continues to backflush, and the second adsorption tower heats and backflush. This step lasts for 20 minutes; S5, the first adsorption tower is controlled by the DCS system to enter the cooling process, at this time, the third adsorption tower, the fourth adsorption tower, the fifth adsorption tower, and the sixth adsorption tower are adsorbed, the first adsorption tower is cooled, and the second adsorption tower is heated and backwashed, and this step lasts for 80 minutes; S6, control the first adsorption tower to enter the adsorption process through the DCS system, the second adsorption tower continues to heat and backwash, and the adsorption process of the third adsorption tower is stopped at the same time, and enters the heating and backwashing process. At this time, the fourth adsorption tower, the fifth adsorption tower, the sixth adsorption tower, and the first adsorption tower adsorb, the second adsorption tower heats and backwashes, and the third adsorption tower heats and backwashes. This step lasts for 20 minutes; S7, the second adsorption tower is controlled by the DCS system to enter the cooling process, at this time, the fourth adsorption tower, the fifth adsorption tower, the sixth adsorption tower, and the first adsorption tower are adsorbed, the second adsorption tower is cooled, and the third adsorption tower is heated and backwashed. This step lasts for 80 minutes; S8, control the second adsorption tower to enter the adsorption process through the DCS system, the third adsorption tower continues to heat and backwash, and the adsorption process of the fourth adsorption tower is stopped at the same time, and enters the heating and backwashing process. At this time, the fifth adsorption tower, the sixth adsorption tower, the first adsorption tower, and the second adsorption tower adsorb, the third adsorption tower heats and backwashes, and the fourth adsorption tower heats and backwashes. This step lasts for 20 minutes; S9, the DCS system controls the third adsorption tower to enter the cooling process. At this time, the fifth adsorption tower, the sixth adsorption tower, the first adsorption tower, and the second adsorption tower adsorb, the third adsorption tower cools, and the fourth adsorption tower heats and backwashes. This step lasts for 80 minutes; S10, the DCS system controls the third adsorption tower to enter the adsorption process, the fourth adsorption tower continues to heat and backwash, and the adsorption process of the fifth adsorption tower is stopped at the same time, and the heating and backwashing process is entered. At this time, the sixth adsorption tower, the first adsorption tower, the second adsorption tower, and the third adsorption tower adsorb, the fourth adsorption tower heats and backwashes, and the fifth adsorption tower heats and backwashes. This step lasts for 20 minutes; S11, the DCS system controls the fourth adsorption tower to enter the cooling process, at this time, the sixth adsorption tower, the first adsorption tower, the second adsorption tower, and the third adsorption tower adsorb, the fourth adsorption tower cools, and the fifth adsorption tower heats and backwashes, and this step lasts for 80 minutes; S12, the fourth adsorption tower is controlled by the DCS system to enter the adsorption process, the fifth adsorption tower continues to heat and backwash, and the adsorption process of the sixth adsorption tower is stopped at the same time, and the heating and backwashing process is entered. At this time, the sixth adsorption tower, the first adsorption tower, the second adsorption tower, and the third adsorption tower adsorb, the fourth adsorption tower heats and backwashes, and the fifth adsorption tower heats and backwashes. This step lasts for 20 minutes; S13, looping through step S1.

4. The efficient operation process of a polysilicon tail gas recovery adsorption tower according to claim 1, characterized in that: When any of the adsorption towers fails, the DCS system can control the tower to merge the tail gas to be treated into the other three adsorption towers in the adsorption process.

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