A method for controlling the concentration of dichlorosilane

Abstract

The present invention discloses a method for controlling the concentration of dichlorosilane, which relates to the technical field of polysilicon production. The present invention is applied in the trichlorosilane refining process. First, under the operating conditions of the trichlorosilane refining process, the actual concentration I of dichlorosilane in the reboiler of the light removal tower III in its recovery distillation process is calculated; secondly, under the existing reduction load and the load of trichlorosilane product I, the required concentration of trichlorosilane product III is set, and the control concentration II of dichlorosilane in the reboiler of the light removal tower III in the recovery distillation process is calculated according to the required concentration; finally, the concentration difference between the actual concentration I of dichlorosilane and the control concentration II of dichlorosilane is calculated, and the light removal tower III in the recovery distillation process is adjusted according to the concentration difference, so as to stably control the concentration of dichlorosilane in the trichlorosilane intermediate product and trichlorosilane product III, and avoid the large fluctuation of the dichlorosilane concentration in trichlorosilane product III from affecting the production of trichlorosilane product III.

Description

Technical Field

[0001] The present invention relates to the technical field of polysilicon production, and more specifically to a method for controlling the concentration of dichlorosilane. Background Art

[0002] In polysilicon production, as Figure 1 shown, it is often necessary to use the synthesis rectification process and the recovery rectification process to produce products, specifically as follows:

[0003] Synthesis rectification process: The products from synthesis, cold hydrogeneration and 191-1 / 3 / 4 / 5 enter the raw material tank V9101AB, and then are pumped into the synthesis rectification column T0301 by pumps P9101A / B / C for separation. The TCS (trichlorosilane) and DCS (dichlorosilane) extracted from the top of T0301 enter the T0302 column to remove light components. The DCS is extracted from the top of the column and sent to reverse disproportionation; the TCS is extracted from the bottom of the column and enters the T0303 column for deweighting. The TCS extracted from the top of the column enters the T0304 column, and the heavy components extracted from the bottom of the column are sent to V9101AB. The TCS enters the T0304 column for removing light components. The light components extracted from the top of the column are sent to V9101AB, and the TCS extracted from the bottom of the column enters the T0305 column for re-deweighting. The TCS product 1 is extracted from the top of T0305 and sent to the V0701AB tank in the 191-5 tank area as the raw material for reduction production.

[0004] Recovery rectification process: The recovered chlorosilane from the 806-4 tail gas recovery process enters V0703A / B at the same time. The materials in V0703A / B are pumped into T03E01 by pumps P0703A / B / C and then separated. The TCS and DCS extracted from the top of T03E01 enter the T03E02 column. The refined DCS extracted from the top of T03E02 is sent for reverse disproportionation use. The TCS intermediate product (mass fraction: containing 5-7% DCS) extracted from the bottom of the column enters T03E03 and T03E04 in parallel operation to remove metal impurities from the bottom of the column. The TCS containing impurities extracted from the bottom of the column is sent to the V0703A / B recovery rectification raw material tank in 191-5 (or sent to V9101AB or T03E01 in 191-6). The TCS product 2 extracted from the top of the deweighting tower of T03E03 / T03E04 is sent to the product storage tank V0701A / B.

[0005] The TCS product 1 and the TCS product 2 are fully mixed through a pipeline to obtain the product 3 (mass fraction: containing 3.5-4.5% DCS).

[0006] The above-mentioned existing technology has the following problems:

[0007] 1. In the recovery rectification column T03E02, part of the DCS is removed from the bottom of the column, and there is a lag in the rectification operation control. The concentration control of DCS in the TCS intermediate product is unstable, affecting the stable control of the DCS concentration in the product 3.

[0008] 2. The change in the reduction load affects the usage of Product 3 of TCS, and the rectification unit cannot make timely adjustments, resulting in large fluctuations in the DCS concentration in Product 3. SUMMARY OF THE INVENTION

[0009] In order to overcome the defects existing in the above-mentioned prior art, the present invention discloses a method for controlling the concentration of dichlorosilane. The present invention calculates the actual concentration I of dichlorosilane in the reboiler of the light removal tower III in the recovery rectification process, and the controlled concentration II of dichlorosilane in the reboiler of the light removal tower III in the recovery rectification process. Then, according to the concentration difference between the actual concentration I of dichlorosilane and the controlled concentration II of dichlorosilane, the light removal tower III in the recovery rectification process is automatically adjusted to stably control the concentration of dichlorosilane in the trichlorosilane intermediate product and the trichlorosilane product III.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A method for controlling the concentration of dichlorosilane, which is applied to the trichlorosilane refining process. The trichlorosilane refining process includes: obtaining trichlorosilane product I by using the synthesis rectification process, obtaining trichlorosilane product II by using the recovery rectification process, and fully mixing trichlorosilane product I and trichlorosilane product II to obtain trichlorosilane product III.

[0012] In the present invention, trichlorosilane product III is obtained by fully mixing trichlorosilane product I and trichlorosilane product II. The chemical name of the chemical is trichlorosilane; silicoform; silicon chloroform, which is an inorganic substance with the chemical formula SiHCl3. It is a colorless liquid, extremely volatile, soluble in most organic solvents such as benzene and ether, and has stable properties. It is mainly used for the synthesis of organosilanes and alkyl, aryl, and organic functional group chlorosilanes. It is the most basic monomer in organosilane coupling agents and is also a raw material for producing semiconductor silicon and single crystal silicon.

[0013] Preferably, the synthesis rectification process includes: feeding the raw materials cached in the raw material buffer tank into the separation tower I for separation; in the separation tower I, the trichlorosilane and dichlorosilane taken out from the top of the tower enter the light removal tower I to remove their light components; in the light removal tower I, the dichlorosilane is taken out from the top of the tower and sent to the reverse disproportionation, and the trichlorosilane is taken out from the bottom of the tower and enters the heavy removal tower I for heavy removal; in the heavy removal tower I, the trichlorosilane taken out from the top of the tower enters the light removal tower II for light removal, and the heavy components taken out from the bottom of the tower are sent to the raw material buffer tank; in the light removal tower II, the light components taken out from the top of the tower are sent to the raw material buffer tank, and the trichlorosilane taken out from the bottom of the tower enters the heavy removal tower II for re-heavy removal; in the heavy removal tower II, the trichlorosilane product I is taken out from the top of the tower, and the trichlorosilane product I is transported to the refined material buffer tank.

[0014] Preferably, the recovery rectification process includes: feeding the chlorosilane in the recovery rectification raw material tank into the separation column II for separation; in the separation column II, the trichlorosilane and dichlorosilane drawn from the top of the column enter the light component removal column III to remove their light components; in the light component removal column III, the refined dichlorosilane drawn from the top of the column is sent for reverse disproportionation use, and the trichlorosilane intermediate product drawn from the bottom of the column enters the parallel heavy component removal column III and heavy component removal column IV simultaneously for heavy component removal; in the heavy component removal column III and heavy component removal column IV, metal impurities are removed from the bottom of the column and sent to the recovery rectification raw material tank, and the trichlorosilane product II is drawn from the top of the column and transported to the refined material buffer tank.

[0015] Preferably, in the refined material buffer tank, the trichlorosilane product I and the trichlorosilane product II are fully mixed through a pipeline to obtain the trichlorosilane product III, and the trichlorosilane product III contains dichlorosilane with a mass fraction of 3.5 - 4.5%.

[0016] Preferably, the trichlorosilane intermediate product drawn from the bottom of the light component removal column III contains dichlorosilane with a mass fraction of 5 - 7%.

[0017] The dichlorosilane concentration control method includes the following steps:

[0018] I. Calculation of the actual concentration I of dichlorosilane

[0019] S1. Under the operating conditions of the trichlorosilane refining process, calculate the actual concentration I of dichlorosilane at the bottom of the light component removal column III in its recovery rectification process;

[0020] In the above steps, using the chemical engineering principle formula, calculate the actual concentration I of dichlorosilane at the bottom of the light component removal column III in the recovery rectification process under the operating conditions.

[0021] Preferably, in the step S1, first obtain the mole fraction of dichlorosilane using the saturated vapor pressure of dichlorosilane and the saturated vapor pressure of trichlorosilane, and then obtain the real-time mass fraction of dichlorosilane using the mole fraction of dichlorosilane.

[0022] Preferably, in the step S1:

[0023]

[0024] The saturated vapor pressure of dichlorosilane is:

[0025]

[0026] The saturated vapor pressure of trichlorosilane:

[0027]

[0028] The mole fraction of dichlorosilane is:

[0029]

[0030] The real-time mass fraction of dichlorosilane is:

[0031]

[0032] Wherein, P 总 is the absolute pressure corresponding to P3; P3 is the on-line display pressure at the bottom of the light removal tower; T3 is the on-line display temperature at the bottom of the tower; P A is the saturated vapor pressure of dichlorosilane; P B is the saturated vapor pressure of trichlorosilane; X a is the mole fraction of dichlorosilane, and M is the real-time mass fraction of dichlorosilane.

[0033] In the present invention, the "real-time mass fraction of dichlorosilane" calculated above is the "actual concentration I of dichlorosilane at the bottom of the light removal tower III" described above.

[0034] II. Calculation of the controlled concentration II of dichlorosilane

[0035] S2. Under the existing reduction load and the load of trichlorosilane product I, set the required concentration of trichlorosilane product III, and calculate the controlled concentration II of dichlorosilane at the bottom of the light removal tower III in the recovery rectification process according to the required concentration;

[0036] Preferably, the step S2 includes the following steps:

[0037] S21. Specify the required concentration A of trichlorosilane product III;

[0038] S22. Set a flowmeter I at the outlet of trichlorosilane product I in the heavy removal tower II of the synthesis rectification, set a flowmeter II and a flowmeter III at the outlets of trichlorosilane product II in the heavy removal tower III and the heavy removal tower IV of the recovery rectification respectively, and set a flowmeter IV and a flowmeter V at the feed inlets of the heavy removal tower III and the heavy removal tower IV of the recovery rectification respectively;

[0039] S23. Collect flow data by using the flowmeter I, the flowmeter II, the flowmeter III, the flowmeter IV and the flowmeter V, and generate the controlled concentration II of dichlorosilane at the bottom of the light removal tower III in the recovery rectification process according to the collected flow data and the required concentration A.

[0040] Preferably, in the step S23, the controlled concentration II of dichlorosilane is:

[0041]

[0042] Wherein, B is the controlled concentration II of dichlorosilane, and A is the required concentration of trichlorosilane product III.

[0043] III. Comparison between concentration I and concentration II and adjustment of the light removal tower III

[0044] S3. Calculate the concentration difference between the actual concentration Ⅰ of dichlorosilane and the controlled concentration Ⅱ of dichlorosilane, and adjust the light-removing tower Ⅲ in the recovery rectification process according to the concentration difference to stably control the concentration of dichlorosilane in the trichlorosilane intermediate product and the trichlorosilane product Ⅲ.

[0045] In the present invention, by using program sequence control, the difference between the actual concentration Ⅰ of dichlorosilane and the controlled concentration Ⅱ of dichlorosilane is automatically compared, and the reflux of the rectification tower (light-removing tower Ⅲ, i.e., T03E02) is automatically adjusted, so that the rectification tower can produce intermediate products with the required DCS concentration and can be automatically adjusted and matched according to the reduction load adjustment and the rectification product Ⅰ load adjustment.

[0046] Preferably, in the step S3, within a set period, when the concentration difference is greater than the upper limit of the set concentration difference value, the main circuit of the light-removing tower Ⅲ increases the adjustment amplitude of the upper limit of the difference; when the concentration difference is less than the lower limit of the set concentration difference value, the main circuit of the light-removing tower Ⅲ reduces the adjustment amplitude of the lower limit of the difference.

[0047] Preferably, in the step S3, the light-removing tower Ⅲ includes a main circuit and a secondary circuit with cascade control.

[0048] Preferably, in the step S3, the value range of the concentration difference is -0.1% - +0.1%.

[0049] In the present invention, for the light-removing tower Ⅲ, the secondary top temperature TI-03E22 (main circuit TIC-03E22) and the reflux flow rate FI-03E21 (secondary circuit FIC-03E21) of T03E02 are in cascade control. The set value of TIC-03E22 is adjusted according to the concentration difference result; FIC-03E21 is in cascade control through the change of the temperature control value of TIC-03E22. The cascade control system consists of two regulators, namely the main regulation loop and the secondary regulation loop. The output of the main regulator is used as the given value of the secondary regulator. The purpose of cascade control is mainly to control the stability of the main controlled variable.

[0050] Advantages of cascade control:

[0051] 1. Compared with single-loop regulation, cascade regulation has an additional secondary regulation loop. The main disturbances of the regulation system are included in the secondary regulation loop. Therefore, the secondary regulation loop can timely detect and eliminate the influence of disturbances on the main regulation parameters, improving the regulation quality.

[0052] 2. In cascade regulation, the amplification factor of the main and secondary regulations (the product of the amplification coefficients of the main and secondary regulators) can be set larger than that of the single-loop regulation system. Therefore, the response speed and anti-interference ability of the system are improved, which is also beneficial to improving the regulation quality.

[0053] 3. In a cascade control system, the change in the characteristics of the controlled object in the secondary loop has little impact on the entire system. For example, in many cases where the secondary loop is formed by using flow rate (or differential pressure) around the regulating valve or baffle, it can overcome the lag and non-linearity effects of the regulating mechanism. When the main regulating parameter changes due to operating conditions or load changes, the main regulator can automatically change the set value of the secondary regulator, improving the adaptability of the system.

[0054] Preferably, the set parameters for the light tower III are set as follows:

[0055] High limit of the main loop TIC-03E22 SP, low limit of the main loop TIC-03E22 SP;

[0056] High limit of the set concentration difference, low limit of the set concentration difference;

[0057] Adjustment range for the high limit of the difference, adjustment range for the low limit of the difference;

[0058] Adjustment period.

[0059] In the present invention, the high / low limit of the main loop TIC-03E22 SP refers to the high / low limit that restricts the setting of TIC-03E22 in the program, preventing over-adjustment and increasing the fluctuation range of the bottom concentration of the tower;

[0060] The high / low limit of the concentration difference indicates that the current concentration has a positive / negative deviation, and the temperature control value needs to be adjusted. Its function is to give the judgment condition for adjustment;

[0061] The adjustment range for the high / low limit of the difference is the high / low limit of the temperature value adjusted each time after it is determined that the concentration difference reaches the high / low limit and adjustment is required, and it is used to output the adjustment value of TIC-03E22;

[0062] The adjustment period refers to the interval time after each determination and adjustment. Its function is to prevent readjustment before the rectifying column has reflected the adjustment change after the control value of TIC-03E22 is adjusted.

[0063] Concentration difference calculation: Concentration difference = DCS concentration (DCS-03E02) - recommended control concentration (DCS-03E021).

[0064] In the present invention, when the program is put into use and the mode of the main loop TIC-03E22 is automatic, the high limit of the loop set value is the high limit of the main loop TIC-03E22 SP, and the low limit of the loop set value is the low limit of the main loop TIC-03E22 SP. When the program is removed, the high limit of the loop set value is 100, and the low limit of the loop set value is 0.

[0065] In the present invention, one adjustment cycle is detected once: when the concentration difference is greater than the upper limit of the set concentration difference, the SP value of the main loop TIC-03E22 increases by (+) the adjustment range of the upper limit of the difference; when the concentration difference is less than the lower limit of the set concentration difference, the SP value of the main loop TIC-03E22 decreases by (-) the adjustment range of the lower limit of the difference.

[0066] Advantages of the present invention:

[0067] The dichlorosilane concentration control method provided by the present invention is applied to the trichlorosilane refining process. First, under the operating conditions of the trichlorosilane refining process, calculate the actual concentration I of dichlorosilane at the bottom of the light removal tower III in its recovery rectification process; secondly, under the existing reduction load and the load of trichlorosilane product I, set the required concentration of trichlorosilane product III, and calculate the control concentration II of dichlorosilane at the bottom of the light removal tower III in the recovery rectification process according to the required concentration; finally, calculate the concentration difference between the actual concentration I of dichlorosilane and the control concentration II of dichlorosilane, and adjust the light removal tower III in the recovery rectification process according to the concentration difference, stably controlling the dichlorosilane concentration in the trichlorosilane intermediate product and trichlorosilane product III, and avoiding the large fluctuation of the dichlorosilane concentration in trichlorosilane product III affecting the production of trichlorosilane product III. Brief description of the drawings

[0068] Figure 1 is a schematic diagram of the present invention;

[0069] Figure 2 is a schematic diagram of the light removal tower III of the present invention. Detailed implementation manners

[0070] The concept, specific structure and technical effects generated by the present invention will be clearly and completely described below in combination with the embodiments and the drawings, so as to fully understand the purpose, features and effects of the present invention.

[0071] Example 1

[0072] A dichlorosilane concentration control method, as Figure 1 shown, the dichlorosilane concentration control method is applied to the trichlorosilane refining process, and the trichlorosilane refining process includes: obtaining trichlorosilane product I by using the synthesis rectification process, obtaining trichlorosilane product II by using the recovery rectification process, and fully mixing trichlorosilane product I and trichlorosilane product II to obtain trichlorosilane product III;

[0073] The dichlorosilane concentration control method includes the following steps:

[0074] S1. Under the operating conditions of the trichlorosilane refining process, calculate the actual concentration I of dichlorosilane at the bottom of the light removal tower III in its recovery rectification process;

[0075] S2. Under the existing reduction load and the load of trichlorosilane product I, set the required concentration of trichlorosilane product III, and calculate the controlled concentration II of dichlorosilane in the light removal tower III of the recovery rectification process according to the required concentration.

[0076] S3. Calculate the concentration difference between the actual concentration I of dichlorosilane and the controlled concentration II of dichlorosilane, and adjust the light removal tower III in the recovery rectification process according to the concentration difference to stably control the dichlorosilane concentration in the trichlorosilane intermediate product and trichlorosilane product III.

[0077] Example 2

[0078] This example is further elaborated on the basis of Example 1. The synthetic rectification process includes: feeding the raw materials cached in the raw material buffer tank into the separation tower I for separation; in the separation tower I, the trichlorosilane and dichlorosilane extracted from the top of the tower enter the light removal tower I to remove their light components; in the light removal tower I, dichlorosilane is extracted from the top of the tower and sent for reverse disproportionation, and trichlorosilane is extracted from the bottom of the tower and enters the heavy removal tower I for heavy removal; in the heavy removal tower I, trichlorosilane extracted from the top of the tower enters the light removal tower II for light removal, and the heavy components extracted from the bottom of the tower are sent to the raw material buffer tank; in the light removal tower II, the light components extracted from the top of the tower are sent to the raw material buffer tank, and trichlorosilane extracted from the bottom of the tower enters the heavy removal tower II for secondary heavy removal; in the heavy removal tower II, trichlorosilane product I is extracted from the top of the tower, and trichlorosilane product I is transported to the refined material buffer tank.

[0079] Specifically, as Figure 1 shown, the synthetic rectification process: The synthesis, cold hydrogenation, and product liquid of 191-1 / 3 / 4 / 5 enter the raw material tank V9101AB, and then are transported through the P9101A / B / C pumps into the synthetic rectification T0301 tower for separation. The TCS and DCS extracted from the top of the T0301 tower enter the T0302 tower to remove light components, and DCS is extracted from the top of the tower and sent for reverse disproportionation; TCS is extracted from the bottom of the tower and enters the T0303 tower for heavy removal. TCS is extracted from the top of the tower and enters the T0304 tower, and the heavy components extracted from the bottom of the tower are sent to V9101AB. TCS enters the T0304 tower for light removal, the light components extracted from the top of the tower are sent to V9101AB, and the TCS extracted from the bottom of the tower enters the T0305 tower for secondary heavy removal. TCS product 1 is extracted from the top of the T0305 tower to the 191-5 tank area V0701AB tank as the raw material for reduction production.

[0080] The said recovery rectification process includes: feeding the chlorosilane in the recovery rectification raw material tank into the separation tower II for separation; in the separation tower II, the trichlorosilane and dichlorosilane taken from the top of the tower enter the light component removal tower III to remove their light components; in the light component removal tower III, the refined dichlorosilane taken from the top of the tower is sent for disproportionation reaction, and the trichlorosilane intermediate product taken from the bottom of the tower enters the parallel heavy component removal tower III and heavy component removal tower IV for heavy component removal at the same time; in the heavy component removal tower III and heavy component removal tower IV, metal impurities are removed from the bottom of the tower and sent to the recovery rectification raw material tank, and the trichlorosilane product II is taken from the top of the tower and transported to the refined material buffer tank.

[0081] Specifically, as Figure 1 shown, the recovery rectification process: the recovered chlorosilane from the 806-4 tail gas recovery process enters V0703A / B at the same time. The materials in V0703A / B are transported into T03E01 by pumps P0703A / B / C and then separated. The TCS and DCS taken from the top of T03E01 enter the T03E02 tower. The refined DCS taken from the top of T03E02 is sent for disproportionation reaction. The TCS intermediate product (mass fraction: containing 5-7% DCS) taken from the bottom of the tower enters T03E03 and T03E04 in parallel operation at the same time. Metal impurities are removed from the bottom of the tower, and the TCS containing impurities taken from the bottom of the tower is sent to the V0703A / B recovery rectification raw material tank of 191-5 (or sent to V9101AB or T03E01 of 191-6). The TCS product 2 taken from the top of the heavy component removal of T03E03 / T03E04 goes to the product storage tank V0701A / B.

[0082] TCS product 1 and TCS product 2 are fully mixed through a pipeline to obtain product 3 (mass fraction: containing 3.5-4.5% DCS).

[0083] Example 3

[0084] This example further elaborates on step S1 on the basis of Example 2. In step S1, using the chemical engineering principle formula, the actual concentration I of dichlorosilane at the bottom of the light component removal tower III in the recovery rectification process under the operating conditions is calculated.

[0085] As Figure 2 shown, specifically, in the said step S1:

[0086]

[0087] The saturated vapor pressure of dichlorosilane is:

[0088]

[0089] The saturated vapor pressure of trichlorosilane:

[0090]

[0091] The molar fraction of dichlorosilane is:

[0092]

[0093] The real-time mass fraction of dichlorosilane is:

[0094]

[0095] Wherein, P 总 is the absolute pressure corresponding to P3; P3 is the on-line display pressure at the bottom of the light removal tower; T3 is the on-line display temperature at the bottom of the tower; P A is the saturated vapor pressure of dichlorosilane; P B is the saturated vapor pressure of trichlorosilane; X a is the molar fraction of dichlorosilane, and M is the real-time mass fraction of dichlorosilane.

[0096] Example 4

[0097] This example further elaborates on step S2 based on Example 3. The step S2 includes the following steps:

[0098] S21. Specify the required concentration A of trichlorosilane product III;

[0099] S22. Install flowmeter I at the outlet of trichlorosilane product I of the synthesis and rectification heavy removal tower II, install flowmeter II and flowmeter III at the outlets of trichlorosilane product II of the recovery rectification heavy removal tower III and the heavy removal tower IV respectively, and install flowmeter IV and flowmeter V at the inlets of the recovery rectification heavy removal tower III and the heavy removal tower IV respectively;

[0100] S23. Collect flow data using flowmeter I, flowmeter II, flowmeter III, flowmeter IV, and flowmeter V, and generate the control concentration II of dichlorosilane at the bottom of the light removal tower III in the recovery rectification process based on the collected flow data and the required concentration A.

[0101] In the step S23, the control concentration II of dichlorosilane is:

[0102]

[0103] Wherein, B is the control concentration II of dichlorosilane, and A is the required concentration of trichlorosilane product III.

[0104] Example 5

[0105] This embodiment further elaborates on step S3 based on Embodiment 4. In step S3, using program sequence control, the difference between the actual concentration Ⅰ of dichlorosilane and the controlled concentration Ⅱ of dichlorosilane is automatically compared, and the reflux of the rectification column (except for the light removal column Ⅲ, i.e., T03E02) is automatically adjusted to enable the rectification column to produce intermediate products that meet the required DCS concentration, and can automatically perform matching adjustments according to the reduction load adjustment and the rectification product Ⅰ load adjustment.

[0106] In the present invention, for the light removal column Ⅲ, the secondary top temperature TI-03E22 (main loop TIC-03E22) and the reflux flow rate FI-03E21 (secondary loop FIC-03E21) of T03E02 are in cascade control.

[0107] The set parameters for the light removal column Ⅲ are as follows:

[0108] The high limit of the set point SP of the main loop TIC-03E22 and the low limit of the set point SP of the main loop TIC-03E22;

[0109] The high limit of the set concentration difference and the low limit of the set concentration difference;

[0110] The adjustment range for the high limit of the difference and the adjustment range for the low limit of the difference;

[0111] The adjustment period.

[0112] Concentration difference calculation: Concentration difference = DCS concentration (DCS-03E02) - recommended control concentration (DCS-03E021).

[0113] In the present invention, when the program is in use and the mode of the main loop TIC-03E22 is automatic, the high limit of the loop set value is the high limit of the set point SP of the main loop TIC-03E22, and the low limit of the loop set value is the low limit of the set point SP of the main loop TIC-03E22. When the program is removed, the high limit of the loop set value is 100, and the low limit of the loop set value is 0.

[0114] In the present invention, it is detected once in one adjustment period: when the concentration difference is greater than the high limit of the set concentration difference, the value of the set point SP of the main loop TIC-03E22 increases (+) by the adjustment range of the high limit of the difference; when the concentration difference is less than the low limit of the set concentration difference, the value of the set point SP of the main loop TIC-03E22 decreases (-) by the adjustment range of the low limit of the difference.

[0115] The above has specifically described the embodiments of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalents or substitutions are all included within the scope defined by the claims of the present invention.

Claims

1. A method for controlling the concentration of dichlorosilane, characterized in that, The method for controlling the concentration of dichlorosilane is applied to the trichlorosilane refining process. The trichlorosilane refining process includes: obtaining trichlorosilane product I by using a synthesis rectification process, obtaining trichlorosilane product II by using a recovery rectification process, and fully mixing trichlorosilane product I and trichlorosilane product II to obtain trichlorosilane product III; The method for controlling the concentration of dichlorosilane includes the following steps: S1. Under the operating conditions of the trichlorosilane refining process, calculate the actual concentration I of dichlorosilane in the reboiler of the light tower III in its recovery rectification process; S2. Under the existing reduction load and the load of trichlorosilane product I, set the required concentration of trichlorosilane product III, and calculate the control concentration II of dichlorosilane in the reboiler of the light tower III in the recovery rectification process according to the required concentration; S3. Calculate the concentration difference between the actual concentration I of dichlorosilane and the control concentration II of dichlorosilane, and adjust the light tower III in the recovery rectification process according to the concentration difference to stably control the concentration of dichlorosilane in the trichlorosilane intermediate product and trichlorosilane product III; Wherein: In step S1, first use the saturated vapor pressure of dichlorosilane and the saturated vapor pressure of trichlorosilane to obtain the mole fraction of dichlorosilane, and then use the mole fraction of dichlorosilane to obtain the real-time mass fraction of dichlorosilane; Step S2 includes the following steps: S21. Given the required concentration A of trichlorosilane product III; S22. Set a flowmeter I at the outlet of trichlorosilane product I of the heavy tower II in the synthesis rectification, set a flowmeter II and a flowmeter III at the outlets of trichlorosilane product II of the heavy tower III and the heavy tower IV in the recovery rectification respectively, and set a flowmeter IV and a flowmeter V at the inlets of the heavy tower III and the heavy tower IV in the recovery rectification respectively; S23. Collect flow data by using flowmeter I, flowmeter II, flowmeter III, flowmeter IV and flowmeter V, and generate the control concentration II of dichlorosilane in the reboiler of the light tower III in the recovery rectification process according to the collected flow data and the required concentration A; In step S3, within a set period, when the concentration difference is greater than the upper limit of the set concentration difference value, the main circuit of the light tower III increases the adjustment range of the upper limit of the difference value; when the concentration difference is less than the lower limit of the set concentration difference value, the main circuit of the light tower III reduces the adjustment range of the lower limit of the difference value.

2. The dichlorosilane concentration control method according to claim 1, characterized in that In step S1: ； The saturated vapor pressure of dichlorosilane is: ； The saturated vapor pressure of trichlorosilane: ； The mole fraction of dichlorosilane is: ； The real-time mass fraction of dichlorosilane is: ； Among them, P 总 is the absolute pressure corresponding to P3; P3 is the on-line display pressure at the bottom of the light tower; T3 is the on-line display temperature at the bottom of the tower; P A is the saturated vapor pressure of dichlorosilane; P B is the saturated vapor pressure of trichlorosilane; X a is the mole fraction of dichlorosilane, and M is the real-time mass fraction of dichlorosilane.

3. The method for controlling the concentration of dichlorosilane according to claim 1, wherein In step S23, the control concentration II of dichlorosilane is: ； Wherein, B is the control concentration II of dichlorosilane, and A is the required concentration of trichlorosilane product III.

4. The method for controlling the concentration of dichlorosilane according to claim 1, characterized in that, The synthesis and rectification process includes: feeding the raw materials cached in the raw material buffer tank into the separation column I for separation; in the separation column I, the trichlorosilane and dichlorosilane taken from the top of the column enter the light component removal column I to remove their light components; in the light component removal column I, the dichlorosilane is taken from the top of the column and sent for reverse disproportionation, and the trichlorosilane is taken from the bottom of the column and enters the heavy component removal column I for heavy component removal; in the heavy component removal column I, the trichlorosilane taken from the top of the column enters the light component removal column II for light component removal, and the heavy components taken from the bottom of the column are sent to the raw material buffer tank; in the light component removal column II, the light components taken from the top of the column are sent to the raw material buffer tank, and the trichlorosilane taken from the bottom of the column enters the heavy component removal column II for heavy component removal again; in the heavy component removal column II, the trichlorosilane product I is taken from the top of the column, and the trichlorosilane product I is transported to the refined material buffer tank.

5. The method for controlling the concentration of dichlorosilane according to claim 4, characterized in that, The recovery and rectification process includes: feeding the chlorosilane in the recovery rectification raw material tank into the separation column II for separation; in the separation column II, the trichlorosilane and dichlorosilane taken from the top of the column enter the light component removal column III to remove their light components; in the light component removal column III, the refined dichlorosilane taken from the top of the column is sent for reverse disproportionation use, and the trichlorosilane intermediate product taken from the bottom of the column enters the parallel heavy component removal column III and heavy component removal column IV for heavy component removal at the same time; in the heavy component removal column III and heavy component removal column IV, the metal impurities are removed from the bottom of the column and sent to the recovery rectification raw material tank, and the trichlorosilane product II is taken from the top of the column and the trichlorosilane product II is transported to the refined material buffer tank.

6. The dichlorosilane concentration control method according to claim 5, characterized in that, In the refined material buffer tank, the trichlorosilane product I and the trichlorosilane product II are fully mixed through a pipeline to obtain the trichlorosilane product III, and the trichlorosilane product III contains dichlorosilane with a mass fraction of 3.5 - 4.5%.

7. The method for controlling the concentration of dichlorosilane according to claim 5, wherein The trichlorosilane intermediate product taken from the bottom of the light component removal column III contains dichlorosilane with a mass fraction of 5 - 7%.

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