Heating assembly, blowback system thereof and control method of blowback system

Abstract

The invention relates to a heating assembly and a back flushing system thereof. An adsorption assembly comprises a plurality of adsorption columns; the inlet end of each adsorption column is provided with a hot-blowing back-blowing outlet path; a cold air outlet path is arranged between the inlet end of the hydrogen tank and the outlet end of each adsorption column; meanwhile, a cold air inlet path is arranged between the outlet end of the hydrogen tank and the inlet end of each adsorption column; the inlet end of the heating assembly is connected to the outlet end of the hydrogen tank, and a hot gas back-blowing inlet path is arranged between the outlet end of the heating assembly and the outlet end of each adsorption column. By controlling the heating frequency and temperature of the heating assembly, thermal damage to the adsorbent, the heating unit and the like can be avoided, so that the long-term stability and the service life are improved.

Description

Technical Field

[0001] The invention relates to the technical field of tail gas recovery of polysilicon, and in particular to the technical field of a back-blowing system. Background Art

[0002] In the polysilicon production process, tail gas recovery is an important link, which aims to improve the utilization rate of raw materials and reduce environmental pollution. In the prior art, adsorption columns are used to recover and purify useful components in tail gas, such as hydrogen and chlorosilane. However, as the adsorbent is used for a long time, a certain amount of impurities will accumulate on its surface, which will reduce the adsorption efficiency, so it is necessary to perform backwashing activation regularly to restore its performance.

[0003] Although the existing back-blowing technology uses hot air back-blowing and cold air technology for energy consumption and cost considerations, the existing technology does not take into account the damage to the heating components caused by hot air back-blowing and cold air. In addition, a considerable part of the back-blowing technology does not fully consider the thermal damage caused by hot blowing. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to achieve the backflushing effect quickly and efficiently while avoiding thermal damage to the adsorbent and the heating component, thereby improving the long-term stability and service life.

[0005] In order to solve the above technical problems, a heating assembly for a backflush adsorption column is provided according to the present invention, comprising:

[0006] A plurality of heating units, wherein the plurality of heating units are connected in series;

[0007] A temperature sensor, wherein the temperature sensor is disposed at the outlet of the heating component;

[0008] A control unit is provided, wherein the control unit is electrically connected to the temperature sensor and all the heating units.

[0009] Furthermore, the control unit is a PLC controller, and the PLC controls all the heating units through pulse width modulation signals.

[0010] A backflush system, including the above-mentioned heating assembly of the backflush adsorption column, includes:

[0011] The adsorption assembly comprises a plurality of adsorption columns; the inlet end of each adsorption column is provided with a hot blow back blow outlet;

[0012] A hydrogen tank, wherein a cold air outlet is provided between the inlet end of the hydrogen tank and the outlet end of each of the adsorption columns; and a cold air inlet is provided between the outlet end of the hydrogen tank and the inlet end of each of the adsorption columns;

[0013] The inlet end of the heating component is connected to the outlet end of the hydrogen tank, and a hot gas back-blowing inlet is provided between the outlet end of the heating component and the outlet end of each adsorption column.

[0014] Furthermore, the inlet end of each of the adsorption columns is connected to the tail gas inlet, and the outlet end of the same adsorption column is connected to the hydrogen tank through the tail gas outlet.

[0015] Furthermore, a first switch valve is provided at the exhaust gas inlet and the exhaust gas outlet; and a boost valve is connected in parallel to the first switch valve.

[0016] Furthermore, all the hot-blow back-blow outlets are connected to the exhaust path, and both the hot-blow back-blow outlets and the hot-blow back-blow inlets are provided with a second switch valve, and the second switch valve is connected in parallel with a pressure relief valve.

[0017] Furthermore, the cold air outlet and the cold air inlet are both provided with a third switch valve.

[0018] Furthermore, pressure sensors are provided in all the adsorption columns.

[0019] A control method for a backflush system, comprising any one of the backflush systems described above, comprising:

[0020] Step 1: The control unit opens the first switch valve of one of the adsorption columns and closes the remaining switch valves of the adsorption column; the adsorption column performs an adsorption process;

[0021] At the same time, the corresponding boost valve of the adjacent adsorption column is opened, and the third switch valve of the adsorption column is opened; the adsorption column performs a boost cooling process;

[0022] At the same time, the corresponding pressure reducing valves of the remaining adsorption columns are opened, and the second switch valves of the adsorption columns are opened; and the adsorption columns perform a hot gas back-blowing process.

[0023] Step 2: Move the adsorption column first controlled by the control unit to the right by one position, and repeat the previous step for the rest;

[0024] Step 3: Repeat step 2 until the operation stops.

[0025] A method for controlling a heating component of a backflush adsorption column, applicable to any of the backflush systems described above, comprising:

[0026] Step 1: When the third switch valve is opened, the control unit reduces the heating frequency of all the heating units to a lower preset value;

[0027] Step 2: when the temperature sensor senses that the temperature gradient is flattened within a preset time period calculated from when the third switch valve is opened, the heating frequencies of all the heating units are increased to normal heating frequencies;

[0028] Step 3: The control unit detects whether the heating frequency exceeds the upper preset value, and stops the heating operation if it exceeds.

[0029] Compared with the prior art, the technical solution provided by the embodiments of the present invention can at least achieve the following beneficial effects:

[0030] First, the present invention can more effectively remove the residues in the adsorption column through the combined use of hot gas backblowing and cold gas forward blowing, thereby improving the adsorption efficiency of the adsorption column.

[0031] Second, the present invention can avoid thermal damage to the adsorbent and the heating unit by controlling the heating frequency and temperature of the heating component, thereby improving their long-term stability and service life.

[0032] Third, the present invention can ensure that the system can operate stably in different operation stages by automatically controlling the switch valves of the heating component and the adsorption column.

[0033] Fourthly, the present invention protects the heating assembly by setting an upper preset value, thereby avoiding greater losses caused by damage to the heating unit, enabling timely repairs and extending the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0035] Figure 1 For the present invention

[0036] In the figure:

[0037] Adsorption column A;

[0038] Adsorption column B;

[0039] Adsorption column C;

[0040] Exhaust gas inlet 111;

[0041] Exhaust gas outlet 112;

[0042] Boost valve 114;

[0043] Pressure relief valve 115;

[0044] Hydrogen tank 2;

[0045] Heating unit 3;

[0046] Heating unit 31;

[0047] Hot blow back blow route 41;

[0048] Hot blow back blow outlet 42;

[0049] A first switch valve 51;

[0050] A second switch valve 52;

[0051] A third switch valve 53;

[0052] Air conditioning outlet 61;

[0053] Air conditioning inlet 62. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment 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.

[0055] Unless otherwise defined, the technical or scientific terms used herein shall have the common meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "a" do not indicate a quantity limitation, but indicate the existence of at least one.

[0056] refer to Figure 1 , this embodiment provides a heating assembly for a backflush adsorption column, comprising:

[0057] A plurality of heating units 31, wherein the plurality of heating units 31 are connected in series;

[0058] A temperature sensor is arranged at the outlet of the heating component;

[0059] The control unit is electrically connected to the temperature sensor and all the heating units 31 .

[0060] The present invention can realize the heating of hydrogen step by step by setting up multiple heating units 31, so as to avoid thermal shock damaging the corresponding parts such as the pipeline; in addition, the present invention sets the temperature sensor at the outlet of the heating component, that is, the end of all the heating units 31, so that the control unit can detect the final temperature in real time; in this way, the present invention can detect the final temperature of the entire heating unit 31 after heating by setting a temperature sensor.

[0061] refer to Figure 1 This embodiment provides a backflush system, including the above-mentioned heating component 3, specifically including:

[0062] The adsorption assembly includes a plurality of adsorption columns A, B and C; each adsorption column A, B or C has a hot blow back blow outlet 42 at its inlet end;

[0063] A cold air outlet 61 is provided between the hydrogen tank 2 and the inlet end of each adsorption column A, B or C; and a cold air inlet 62 is provided between the outlet end of the hydrogen tank 2 and the inlet end of each adsorption column A, B or C.

[0064] The heating component 3 has its inlet end connected to the outlet end of the hydrogen tank 2 , and a hot gas back-blowing inlet 41 is provided between the outlet end of the heating component 3 and the outlet end of each adsorption column A, B or C.

[0065] The present invention can perform adsorption and back-blowing operations simultaneously through the design of multiple adsorption columns, thereby improving the processing efficiency of the entire system. In addition, the present invention realizes the adsorption of tail gas produced by polysilicon through the adsorption component 1, so that the hydrogen after recovery is high-purity hydrogen, which can be stored in the hydrogen tank 2; at the same time, the present invention can more effectively remove the residue in the adsorption column A, B or C by back-blowing the adsorption column A, B or C after heating the hydrogen in the hydrogen tank 2, thereby improving the adsorption efficiency and service life of the adsorption column A, B or C. In addition, the present invention can not only effectively remove the dry residue in the adsorption column A, B or C through the combined use of cold air forward blowing (that is, the direction of cold air passing through the adsorption column is consistent with the direction of tail gas during the adsorption process) and hot air back-blowing (that is, the direction of hot air passing through the adsorption column is opposite to the direction of tail gas during the adsorption process), but also effectively reduce the consumption of back-blowing gas, that is, the efficiency of back-blowing cleaning is improved by hot blowing, and the cooling of the adsorption component 1 is achieved by cold blowing.

[0066] In a preferred embodiment, the heating assembly 3 includes a plurality of heating units 31, specifically electric heaters, all of which are connected in series. The manner in which all the electric heaters are connected in series can ensure that the gas can be evenly heated when passing through the adsorption column A, B or C, thereby improving the efficiency and effect of backflush activation (heating to remove moisture and other impurities on the surface of the adsorbent to improve its adsorption capacity). By connecting the electric heaters in series, the thermal shock to the pipeline can be reduced, thereby reducing the occurrence of situations such as pipeline rupture.

[0067] In a preferred embodiment, the control unit is a PLC controller (Programmable Logic Controller), which controls all heating units 31 through pulse width modulation signals. Specifically, PWM (pulse width modulation) signal control of the power output of the heater is a commonly used power regulation method, which is particularly suitable for resistive loads such as electric heaters. The principle of PWM control is to adjust the ratio of the power-on time of the heater within a certain period of time to the total time by quickly switching the heater on and off, thereby controlling the average power output of the heater.

[0068] In a preferred embodiment, the heating element in the electric heater is electrically connected to a solid-state relay, and the solid-state relay is communicatively connected to a PLC controller. The electrical connection between the heating element and the solid-state relay (SSR), and the communication connection between the solid-state relay and the PLC controller, are to achieve precise control of the heater. Specifically, a solid-state relay is a contactless electronic switch that uses a photocoupler to achieve electrical isolation between input and output.

[0069] In a preferred embodiment, the inlet end of each adsorption column A or B or C is connected to the tail gas inlet 111 , and the outlet end of the same adsorption column A or B or C is connected to the hydrogen tank 2 through the tail gas outlet 112 .

[0070] In a preferred embodiment, a first switch valve 51 is provided between the adsorption column A or B or C and the tail gas inlet 111, and a first switch valve 51 is also provided between the adsorption column A or B or C and the tail gas outlet 112; a boost valve 114 is connected in parallel to the first switch valve 51. The boost valve 114 is connected in parallel with the first switch valve 51, and the pressure of the system can be increased when necessary to meet the needs of a specific operation. Specifically, in order to ensure that the cold hydrogen can effectively penetrate the adsorbent layer and take away impurities, it is usually necessary to maintain a certain pressure so that the cold hydrogen can pass through the adsorbent in the adsorption column with sufficient speed and force.

[0071] In a preferred embodiment, all hot-blow back-blowing outlets 42 are connected to the exhaust path 421, and the hot-blow back-blowing outlets 42 and the hot-blow back-blowing inlet 41 are both provided with a second switch valve 52; the second switch valve 52 is connected in parallel with a pressure relief valve 115. The purpose of the pressure relief valve 115 is to reduce the pressure in the adsorption column, because the gas will expand after heating, so during the hot gas back-blowing process, the pressure of the system is usually reduced to prevent excessive pressure from causing damage to the adsorbent layer or damage to the adsorption column.

[0072] Furthermore, pressure sensors are provided in all adsorption columns A, B and C; the pressure sensors can detect the progress of pressure reduction and pressure increase in real time, thereby avoiding the failure to stop the process in time when the pressure relief valve 115 or the pressure boosting valve 114 fails, thereby causing damage to the adsorption column; accordingly, the pressure sensor is connected to a sound alarm.

[0073] In a preferred embodiment, both the cold air outlet 61 and the cold air inlet 62 are provided with a third switch valve 53 .

[0074] A control method for a backflush system, comprising any of the above-mentioned backflush systems, comprising:

[0075] Step 1: The control unit opens all the first switch valves 51 connected to one of the adsorption columns A, and closes the other switch valves of the adsorption column A; the adsorption column performs an adsorption process;

[0076] At the same time, the corresponding boost valve 114 of the adjacent adsorption column B is opened, and the third switch valve 53 of the adsorption column A is opened; the adsorption column B performs a boost cooling process;

[0077] At the same time, the corresponding pressure relief valve 115 of the remaining adsorption column C is opened, and the second switch valve 52 of the adsorption column C is opened; the adsorption column C performs a hot gas backflush process.

[0078] Step 2: Move the adsorption column first controlled by the control unit to the right by one position (i.e., from adsorption column A to adsorption column B), and repeat the previous step for the rest;

[0079] Specifically, the control unit first opens the first switch valve of the adsorption column B, and at the same time opens the first switch valve 51 of the adsorption column B, and closes the remaining switch valves of the adsorption column B; the adsorption column performs the adsorption process;

[0080] At the same time, the corresponding boost valve 114 of the adjacent adsorption column C is opened, and the third switch valve 53 of the adsorption column C is opened; the adsorption column C performs a boost cooling process;

[0081] At the same time, the corresponding pressure relief valve 115 of the remaining adsorption column A is opened, and the second switch valve 52 of the adsorption column A is opened; the adsorption column A performs a hot gas backflush process.

[0082] Step 3: Repeat step 2 until the operation stops.

[0083] Through the above operation, at the same time, one adsorption column is performing adsorption, another adsorption column is performing hot backflush, and the remaining adsorption column is performing cold backflush. In addition, the hydrogen used in backflush is hydrogen filtered after adsorption, which can reduce the use of backflush gas and reduce the backflush cost.

[0084] For ease of understanding, the same adsorption column A is taken as an example to illustrate the stages that the adsorption column A goes through:

[0085] Adsorption process:

[0086] The gas enters the adsorption tower A which is in the adsorption state from the first switch valve 51 at the bottom of the adsorption tower A. Under the selective adsorption of the activated carbon adsorbent, components such as HCL and chlorosilane are adsorbed, and the unabsorbed hydrogen (with a purity of up to 99.999%) is sent to the hydrogen tank 2 through the first switch valve 51 and the filter on the adsorption column. When the adsorbed impurities reach the reserved section at the bed outlet, the two first switch valves 51 of the adsorption tower are closed to stop the adsorption. The adsorption time is 240 minutes, and the adsorption tower A begins to enter the regeneration process.

[0087] Depressurization process:

[0088] After the adsorption process is completed, the pressure relief valve 115 is opened to release the pressure to 0.05 MPa for 15 minutes. After the pressure relief is completed, the pressure relief valve 115 is closed;

[0089] Purge heating process:

[0090] The second switch valve 52 is opened, and the hydrogen is heated by the electric heater 31 and enters the adsorption tower A, and the HC1 and chlorosilane adsorbed on the activated carbon are completely resolved, so that the activated carbon is regenerated. When the temperature at the bottom of the adsorption tower A is greater than 150°C and the timer reaches the preset time of 208min, it can be considered that the heating and purging is completed, and the adsorption column AS then enters the cooling process. The two second switch valves 52 are closed.

[0091] Purge cooling process:

[0092] When the heating and purging process is completed, the two third switch valves 53 are opened. When the top temperature of the adsorption tower is less than 10° C. and reaches the preset time of 208 min of the timer, the pressurization and cooling process is completed, and the two third switch valves 53 are closed.

[0093] Boosting process:

[0094] In order to ensure that the adsorption column A can smoothly switch to the next adsorption and ensure that the pressure of the adsorption column A does not fluctuate during this process, the pressure of the adsorption column needs to be increased to the adsorption pressure. After the cooling of the adsorption tower is completed, the booster valve 114 is opened, and the adsorption tower A starts to be pressurized. When the pressure is 1.25Mpa, the charging time is 15min. After the boosting process is completed, the booster valve 114 is closed.

[0095] After this process, the adsorption column has completed a complete "adsorption-regeneration" cycle and is ready for the next adsorption.

[0096] In the back-blowing route of the present invention, the stage of adsorption by adsorption column A, cold air positive blowing by adsorption column B and hot air back-blowing by adsorption column C is taken as an example. It can be seen that after the cold air positive blowing by adsorption column B, the cold air (i.e., cold hydrogen at a lower temperature) will become heated hydrogen due to passing through the heated adsorption column B. When passing through the heating component 3 again, the already heated heating component 3 may be damaged. In order to avoid this situation, the control of the heating component 3 is adaptively changed.

[0097] A control method for a heating component of a backflush adsorption column, applicable to any of the above-mentioned backflush systems, comprising:

[0098] Step 1: When the third switch valve 53 is opened, the control unit reduces the heating frequency of all heating units 31 to a lower preset value, which is 10 ms.

[0099] Step 2: When the temperature sensor senses that the temperature gradient of the third switch valve 53 is flattened within the preset time period, the heating frequency of all heating units 3 is increased to the normal heating frequency;

[0100] The purpose of this step is to reduce the impact of heating the cold hydrogen on the heating component 3, and to start increasing the heating frequency of the heating component 3 to a normal heating frequency, so as to avoid heating exceeding the bearing limit of the heating component 3 as much as possible.

[0101] Step 3: The control unit detects whether the heating frequency exceeds the upper preset value, and stops the heating operation if it exceeds the upper preset value, which is 20ms.

[0102] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the protection scope of the present invention. The protection scope of the present invention is determined by the appended claims.

Claims

1. A heating assembly for a backflush adsorption column, characterized in that: include: A plurality of heating units, wherein the plurality of heating units are connected in series; A temperature sensor, wherein the temperature sensor is disposed at the outlet of the heating component; A control unit is provided, wherein the control unit is electrically connected to the temperature sensor and all the heating units.

2. A heating assembly for a backflush adsorption column according to claim 1, characterized in that: The control unit is a PLC controller, and the PLC controls all the heating units through a pulse width modulation signal.

3. A backflush system, comprising a heating assembly for a backflush adsorption column according to claim 1 or 2, characterized in that: include: The adsorption assembly comprises a plurality of adsorption columns; the inlet end of each adsorption column is provided with a hot blow back blow outlet; A hydrogen tank, wherein a cold air outlet is provided between the inlet end of the hydrogen tank and the outlet end of each of the adsorption columns; and a cold air inlet is provided between the outlet end of the hydrogen tank and the inlet end of each of the adsorption columns; The inlet end of the heating component is connected to the outlet end of the hydrogen tank, and a hot gas back-blowing inlet is provided between the outlet end of the heating component and the outlet end of each adsorption column.

4. A backflush system according to claim 3, characterized in that: The inlet end of each adsorption column is connected to the tail gas inlet, and the outlet end of the same adsorption column is connected to the hydrogen tank through the tail gas outlet.

5. A backflush system according to claim 4, characterized in that: The exhaust gas inlet and the exhaust gas outlet are both provided with a first switch valve; and the first switch valve is connected in parallel with a boost valve.

6. A backflush system according to claim 5, characterized in that: All the hot blow back blow outlets are connected to the exhaust path, and the hot blow back blow outlets and the hot blow back blow inlets are both provided with a second switch valve, and the second switch valve is connected in parallel with a pressure relief valve.

7. A backflush system according to claim 6, characterized in that: The cold air outlet and the cold air inlet are both provided with a third switch valve.

8. A backflush system according to claim 6, characterized in that: All the adsorption columns are provided with pressure sensors.

9. A method for controlling a backflush system, comprising the backflush system according to any one of claims 1 to 8, comprising: Step 1: The control unit opens the first switch valve of one of the adsorption columns and closes the remaining switch valves of the adsorption column; The adsorption column performs an adsorption process; At the same time, the corresponding boost valve of the adjacent adsorption column is opened, and the third switch valve of the adsorption column is opened; the adsorption column performs a boost cooling process; At the same time, the corresponding pressure reducing valves of the remaining adsorption columns are opened, and the second switch valves of the adsorption columns are opened; and the adsorption columns perform a hot gas back-blowing process. Step 2: Move the adsorption column first controlled by the control unit to the right by one position, and repeat the previous step for the rest; Step 3: Repeat step 2 until the operation stops.

10. A method for controlling a heating assembly of a backflush adsorption column, applicable to a backflush system according to any one of claims 1 to 8, comprising: Step 1: When the third switch valve is opened, the control unit reduces the heating frequency of all the heating units to a lower preset value; Step 2: when the temperature sensor senses that the temperature gradient is flattened within a preset time period calculated from when the third switch valve is opened, the heating frequencies of all the heating units are increased to normal heating frequencies; Step 3: The control unit detects whether the heating frequency exceeds the upper preset value, and stops the heating operation if it exceeds.

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