Refined online control method for excess alkali amount

Abstract

The invention discloses a refined online control method for excess alkali amount, which belongs to the technical field of chlor-alkali industry, and comprises a baffling tank, a front reaction tank, a rear reaction tank, an intermediate tank, a filter and a membrane filtration system which are connected in sequence, setting a sodium hydroxide excess alkali amount control index, calculating a flow value after sodium hydroxide adjustment per hour, issuing control index deviation data, and enabling a sodium hydroxide self-adjusting valve to receive a control instruction for automatic adjustment; setting a control index of sodium carbonate excess alkali amount, calculating a flow value of sodium carbonate after adjustment per hour, issuing control index deviation data, and enabling a sodium carbonate self-adjusting valve to receive a control instruction for automatic adjustment; according to the refined online control method for the excess alkali amount, data are read in real time, the timeliness is improved, the error rate is reduced, the accident occurrence probability is reduced, the labor cost is reduced, and company benefits are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chlor-alkali industry, and particularly relates to a method for fine online control of excess alkali amount. Background Art

[0002] With the rapid development of the chlor-alkali industry, in response to the country's important "green environmental protection" initiative, we must adhere to safe, environmentally friendly and clean production, and continuously improve the utilization and conversion rate of resources. This requires continuously improving the automation level of equipment, and the upgrading and transformation of the online monitoring system is imperative.

[0003] Industrial salt uses a loader to transport solid salt to the salt tank through a belt conveyor according to production needs. The purchased brine is transported to the brine storage tank in the primary brine workshop through a pipeline. The brine is heated by the waste heat system and the hot water unit and enters the water distribution tank. The salt feeding pump sends the salt water in the water distribution tank into the salt tank to dissolve the salt saturated, and overflows to the baffle tank, where sodium hypochlorite, sodium carbonate, sodium hydroxide and other refining agents are added respectively and then enter the reaction tank. The amine salt (ammonium) in the brine is decomposed into volatile monochloramine (dichloramine) under the oxidation of the strong oxidant (sodium hypochlorite). The magnesium ions in the crude brine react with the refining agent sodium hydroxide to form magnesium hydroxide flocs, and the calcium ions in the crude brine react with sodium carbonate to form calcium carbonate crystal precipitation. After the reaction, the crude brine overflows to the middle tank, and is transported to the crude brine filter by the Jiusi membrane filtration feed pump to remove solid impurities, and then enters the Jiusi membrane filtration system through the filtration circulation pump.

[0004] The control of two alkalis in the primary brine workshop is based on the online alkali meter as a reference, combined with quality inspection analysis as calibration to adjust the addition of two alkalis. The current problems are as follows:

[0005] 1) There are errors in the measurement of on-site online alkali meter, and automatic control cannot be achieved.

[0006] 2) The installation position of the online instrument for over-reduction is inappropriate, and it cannot serve as an accurate reference for the control of double alkali.

[0007] 3) The valves for controlling the addition of two alkalis cannot be linked with the over-and-under meters and need to be adjusted in combination with quality inspection and analysis. The accuracy cannot be guaranteed, and the labor intensity of personnel is increased, which increases the safety risk of personnel. Therefore, in response to the above problems, it is necessary to develop a new method for fine-tuning the online control of the amount of over-alkali to solve the existing problems. Summary of the invention

[0008] The purpose of the present invention is to provide a refined online control method for the amount of over-alkali, so as to solve the problem that there are errors in the measurement of the on-site online over-alkali instrument and automatic control cannot be achieved.

[0009] To achieve the above object, the present invention provides the following technical solution: a method for fine online control of the amount of over-alkali, comprising a baffle tank, a front reaction tank, a rear reaction tank, an intermediate tank, a filter and a membrane filtration system connected in sequence;

[0010] Wherein, the baffle tank is connected to the sodium carbonate high-level tank and the sodium hydroxide high-level tank respectively; a sodium hydroxide self-regulating valve and a sodium hydroxide flowmeter are arranged between the baffle tank and the sodium hydroxide high-level tank;

[0011] A sodium carbonate self-regulating valve, a sodium carbonate flowmeter, and a sodium carbonate concentration meter are arranged between the baffle tank and the sodium carbonate high-level tank;

[0012] The input end of the baffle tank is provided with a calcium and magnesium ion analyzer, and the input end of the calcium and magnesium ion analyzer is respectively connected to the crude brine, the sodium carbonate concentration meter, and the sodium hydroxide flow meter;

[0013] A brine flow meter, a brine density meter and an excess alkali analyzer are sequentially arranged between the post-reaction tank and the intermediate tank;

[0014] Set the sodium hydroxide excess alkali control index, calculate the adjusted flow value of sodium hydroxide per hour, send the control index deviation data, and the sodium hydroxide self-regulating valve receives the control command for automatic adjustment;

[0015] Set the control index of the amount of sodium carbonate over-alkali, calculate the adjusted flow value of sodium carbonate per hour, send the control index deviation data, and the sodium carbonate self-regulating valve receives the control command for automatic adjustment.

[0016] Preferably, an online analyzer for excess alkali and an online analyzer for calcium and magnesium ions are provided at the output end of the membrane filtration system.

[0017] Preferably, the sodium hydroxide over-alkali amount control index is 0.2-0.5 g / l.

[0018] Preferably, the control index of the sodium carbonate overbase amount is 0.30-0.45 g / l.

[0019] Preferably, the calculation of the adjusted flow value of sodium hydroxide per hour comprises:

[0020] Calculate the amount of sodium hydroxide added:

[0021] Amount of sodium hydroxide added = amount of sodium hydroxide added calculated by magnesium ions + amount of excess alkali × amount of refined brine delivered × coefficient of sodium hydroxide content = magnesium ion concentration × amount of refined brine delivered × coefficient of sodium hydroxide conversion + amount of excess alkali × amount of refined brine delivered × coefficient of sodium hydroxide content;

[0022] Calculate the sodium hydroxide valve flow rate:

[0023] Initial flow value = (magnesium ion concentration × refined brine delivery volume × sodium hydroxide conversion coefficient + excess alkali amount × refined brine delivery volume × sodium hydroxide content coefficient) ÷ sodium hydroxide content ÷ sodium hydroxide density = (magnesium ion concentration × 3.33 × 10 -3 + target value of excess alkali × 2.35) × brine delivery volume × 2.34 × 10 -3 ;

[0024] Calculate the adjustment value of the sodium hydroxide valve flow rate;

[0025] Flow adjustment value = initial opening of sodium hydroxide valve - [(excess alkali amount display value - target value) × brine delivery volume × sodium hydroxide content coefficient × deviation coefficient] ÷ sodium hydroxide content ÷ sodium hydroxide density = (magnesium ion concentration × 3.33 × 10 -3 + target value of excess alkali × 2.35) × brine delivery volume × 2.34 × 10 -3 - [(excess alkali value displayed value - target value) × brine delivery volume × 2.35 × deviation coefficient] × 2.34 × 10 -3 .

[0026] Preferably, the calculation of the adjusted flow value of sodium carbonate per hour includes:

[0027] Calculate the amount of sodium carbonate added:

[0028] Amount of sodium carbonate added = amount of sodium carbonate added calculated by calcium ions + amount of excess alkali × amount of refined brine delivered × coefficient of sodium carbonate content = calcium ion concentration × amount of refined brine delivered × coefficient of sodium carbonate conversion + amount of excess alkali × amount of refined brine delivered × coefficient of sodium carbonate content;

[0029] Calculate the sodium carbonate valve flow rate:

[0030] Initial flow value = (calcium ion concentration × refined brine delivery volume × sodium carbonate conversion coefficient + excess alkali amount × refined brine delivery volume × sodium carbonate content coefficient) ÷ sodium carbonate concentration = (calcium ion concentration × 2.65 × 10-3 + excess alkali amount target value × 1.76) × refined brine delivery volume ÷ 88.235;

[0031] Calculate the adjustment value of the sodium carbonate valve flow:

[0032] Flow adjustment value = initial opening of sodium carbonate valve - [(excess alkali amount display value - target value) × refined brine delivery volume × sodium carbonate content coefficient × deviation coefficient] ÷ sodium carbonate concentration = (calcium ion concentration × 2.65 × 10-3 + excess alkali amount target value × 1.76) × refined brine delivery volume ÷ 88.23 - [(excess alkali amount display value - target value) × refined brine delivery volume × 1.76 × deviation coefficient] ÷ 88.235.

[0033] Preferably, the sodium hydroxide self-regulating valve receives a control instruction for automatic adjustment including: initial opening, setting the amount of excess alkali, collecting data and calculating the adjustment amount of the valve, if the set value is less than the target value, closing the regulating valve, otherwise opening the regulating valve.

[0034] Preferably, the set value of the excess alkali amount is 0.2 g / l.

[0035] Preferably, the sodium carbonate self-regulating valve receives control instructions for automatic adjustment including: initial opening, setting the amount of excess alkali, collecting data and calculating the adjustment amount of the valve, if the set value is less than the target value, closing the regulating valve, otherwise opening the regulating valve.

[0036] Preferably, the set value of the excess alkali amount is 0.3 g / l.

[0037] The technical effects and advantages of the present invention are as follows: the refined online control method for the amount of excess alkali can read data in real time, improve timeliness, reduce the error rate and thus reduce the probability of accidents, cut down on labor costs and improve company benefits; at the same time, the online excess alkali meter can realize automatic control with the sodium hydroxide self-regulating valve and the sodium carbonate self-regulating valve installed in the two alkali high-level tanks, thereby reducing personnel intervention in instrument control and ultimately reducing the consumption of the two alkalis. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the overall process flow chart of the present invention;

[0039] Figure 2 This is a control flow chart of the present invention;

[0040] Figure 3 This is a schematic diagram of the sodium hydroxide addition amount flow chart of the present invention;

[0041] Figure 4 It is a schematic diagram of the sodium carbonate addition process of the present invention. DETAILED DESCRIPTION

[0042] 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.

[0043] The present invention provides Figure 1 A method for fine online control of the amount of over-alkali as shown in the embodiment comprises the following steps:

[0044] 1) The refined control of the primary brine over-alkali amount requires the installation of a sodium hydroxide over-alkali amount analyzer, a sodium carbonate over-alkali amount analyzer, a calcium and magnesium ion analyzer, a sodium hydroxide self-regulating valve, a sodium hydroxide flowmeter, a sodium carbonate self-regulating valve, a sodium carbonate flowmeter, a brine flowmeter, a brine density meter, and a sodium carbonate concentration meter; Figure 1 Medium alkali content analyzers include sodium hydroxide alkali content analyzer and sodium carbonate alkali content analyzer;

[0045] 2) The sodium hydroxide self-regulating valve and sodium hydroxide flowmeter are installed on the pipeline from the primary sodium hydroxide high-level tank to the baffle tank, the sodium carbonate self-regulating valve and sodium carbonate flowmeter are installed on the pipeline from the primary sodium carbonate high-level tank to the baffle tank, and the brine flowmeter and brine density meter are installed on the pipeline after the post-reaction tank; the initial opening of the regulating valve can be designed with reference to the data of previous experience of feeding and the technical parameters of the valve itself, and the size of the regulating valve is selected according to the conditions of the process pipeline. The specifications and range of the flowmeter are determined according to the process conditions.

[0046] 3) Based on the fact that the cleanliness of brine affects the measurement accuracy and service life of the instrument, the sampling points of the excess alkali amount and calcium-magnesium analyzer are added after the Jiusi membrane filtration system. An analysis cabin is installed at this location, which includes an excess alkali amount online analysis and a calcium-magnesium ion online analysis instrument. The calcium-magnesium ion analyzer can play an auxiliary role in the dual alkali excess alkali analyzer, realize dual monitoring, and ensure that the two alkali amounts of the brine meet the control indicators, thereby ensuring the quality of the primary brine.

[0047] 4) The control index of sodium hydroxide over-alkali amount is required to be set at 0.2-0.5g / l. In order to facilitate the index and accurate control, the control target value of over-alkali amount is 0.2g / l. Figure 3 The adjusted flow value of sodium hydroxide per hour is calculated, and the control index deviation data is sent to the DCS system. The DCS gives the sodium hydroxide self-regulating valve control instructions for automatic adjustment.

[0048] Amount of sodium hydroxide added:

[0049] Amount of sodium hydroxide added = Amount of sodium hydroxide added calculated by magnesium ions + Amount of excess alkali × Amount of refined brine delivered × Sodium hydroxide content coefficient

[0050] = magnesium ion concentration × refined brine delivery volume × sodium hydroxide conversion coefficient + excess alkali amount × refined brine delivery volume × sodium hydroxide content coefficient;

[0051] Then the sodium hydroxide valve flow rate:

[0052] Initial flow value = (magnesium ion concentration × refined brine delivery × sodium hydroxide conversion coefficient + excess alkali amount × refined brine delivery × sodium hydroxide content coefficient) ÷ sodium hydroxide content ÷ sodium hydroxide density

[0053] =(Mg ion concentration × 3.33 × 10 -3 + target value of excess alkali × 2.35) × brine delivery volume × 2.34 × 10 -3 ;

[0054] Adjustment value of sodium hydroxide valve flow:

[0055] Flow adjustment value = initial opening of sodium hydroxide valve - [(excess alkali amount display value - target value) × refined brine delivery amount × sodium hydroxide content coefficient × deviation coefficient] ÷ sodium hydroxide content ÷ sodium hydroxide density

[0056] =(Mg ion concentration × 3.33 × 10 -3 + target value of excess alkali × 2.35) × brine delivery volume × 2.34 × 10 -3

[0057] - [(excess alkali value displayed value - target value) × brine delivery volume × 2.35 × deviation coefficient] × 2.34 × 10 -3 ;

[0058] 5) The control index of sodium carbonate over-alkali amount is required to be set at 0.30-0.45g / l. In order to facilitate the index and accurate control, the control target value of over-alkali amount is 0.3g / l. Figure 4 The adjusted flow value of sodium carbonate per hour is calculated, and the control index deviation data is sent to the DCS. The DCS gives the sodium carbonate self-regulating valve control instructions for automatic adjustment.

[0059] Amount of sodium carbonate added:

[0060] Amount of sodium carbonate added = Amount of sodium carbonate added calculated by calcium ions + Amount of alkali × Amount of refined brine delivered × Sodium carbonate content coefficient

[0061] = calcium ion concentration × refined brine delivery volume × sodium carbonate conversion coefficient + excess alkali amount × refined brine delivery volume × sodium carbonate content coefficient;

[0062] Then the sodium carbonate valve flow rate:

[0063] Initial flow value = (calcium ion concentration × refined brine delivery volume × sodium carbonate conversion coefficient + excess alkali amount × refined brine delivery volume × sodium carbonate content coefficient) ÷ sodium carbonate concentration

[0064] =(Calcium ion concentration × 2.65 × 10 -3 + target value of excess alkali × 1.76) × brine delivery volume ÷ 88.235

[0065] Adjustment value of sodium carbonate valve flow

[0066] Flow adjustment value = initial opening of sodium carbonate valve - [(excess alkali value displayed value - target value) × brine delivery volume × sodium carbonate content coefficient × deviation coefficient] ÷ sodium carbonate concentration

[0067] =(Calcium ion concentration × 2.65 × 10 -3 + (target value of excess alkali amount × 1.76) × brine delivery amount ÷ 88.23 - [(displayed value of excess alkali amount - target value) × brine delivery amount × 1.76 × deviation coefficient] ÷ 88.235;

[0068] In this embodiment, the model of the online analyzer for excess alkali, calcium and magnesium ions is Wantong 2035;

[0069] Technical parameters:

[0070] The control unit composed of IPC+PLC is competent for complex multi-task control; the 15' touch screen is convenient and intuitive to operate, and the operation is stable;

[0071] Flexible and customizable modular design (12 wet-parts) to easily realize different applications;

[0072] Automatically run tiamoTM software, programmable analysis methods. Apply validated laboratory analysis methods to online analyzers;

[0073] High-precision visual titration system Dosino (up to 1 / 10000 resolution) ensures instrument analysis accuracy;

[0074] The adjustable speed peristaltic pump module can realize flexible application on site;

[0075] Editable control software (real-time trend chart, real-time result transmission, database result backup);

[0076] Multi-stream injection analysis, flexible program switching, no cross contamination, and independent result output;

[0077] Flexible interface module, supports analog digital input / output TCP / IP; 4-20mA; 24VDC;

[0078] IP66 / NEMA 4 protection grade;

[0079] USB interface for data transmission;

[0080] The analysis time is about 20 minutes;

[0081] Analysis principle:

[0082] 1) Sodium hydroxide, sodium carbonate: potentiometric titration

[0083] Using the pH electrode as the indicator electrode and hydrochloric acid standard solution as the titrant, the acid-base titration method is used to obtain the concentration of sodium carbonate based on the volume of hydrochloric acid standard solution consumed.

[0084] 2) Calcium and magnesium ions: photometric titration

[0085] In an alkaline environment (PH=10), calcium and magnesium ions are titrated with EDTA complex. First, a certain amount of HNO3 is added to completely release Ca2+ & Mg2+. In an ammonia buffer solution with PH=10, chrome blue black is used as an indicator, and EDTA is titrated at a wavelength of 620nm using a probe-type LDP electrode. The content of Ca2+ & Mg2+ is obtained based on the volume of EDTA consumed to reach the end point.

[0086] Through refined control, refined management of primary brine can be achieved, which can greatly reduce the excessive calcium and magnesium content caused by analysis intervals, which may affect the quality of secondary brine in a short time and cause irreversible damage to the ion membrane; the stable operation of the excess alkali index will affect the control of calcium and magnesium content, thereby ensuring the quality of brine and improving the stable operation of the electrolytic cell; if the calcium and magnesium content of secondary brine exceeds 50ppb, it will have an irreversible effect on the current efficiency of the ion membrane in a short time. After the implementation of this plan, it is estimated that the annual current efficiency will be increased by more than 0.5%, and the double alkali consumption will be reduced by 30%.

[0087] Taking production data as an example, the cost is calculated as follows:

[0088] Table 1

[0089]

[0090]

[0091] 1. Cost savings of soda ash

[0092] 1) According to Table 1, based on project experience and instrument technology analysis, the consumption of soda ash can be reduced by 30%. The annual cost savings are as follows:

[0093] The cost saved by soda ash = 2825460 / 1000*1948 yuan / ton*2*30%=3302397.65 yuan;

[0094] 2) From the perspective of sodium carbonate control indicators, the control indicators are set at 0.3 as the target value, and the brine flow rate is the average monthly flow rate in the above table. The annual cost savings are:

[0095] (0.45-0.3)g / L*212702.63(brine flow)m3 / h*12*1948÷1000=745820.5 yuan;

[0096] 2. Cost savings of caustic soda

[0097] 1) Based on the above table, if the consumption of caustic soda is reduced by 30%, the annual cost savings are:

[0098] Cost savings of caustic soda = 2251162.89 ÷ 1000 tons * 925 yuan / ton * 2 * 30% = 1249395.4 yuan;

[0099] 2) From the perspective of sodium hydroxide control indicators, the cost that can be saved each year is:

[0100] (0.45-0.2)*212702.63(brine flow)m3 / h*12*925÷1000=590249.8 yuan.

[0101] This refined online control method for the amount of excess alkali can read data in real time, improve timeliness, reduce error rate and thus reduce the probability of accidents, cut labor costs and improve company benefits. At the same time, the online excess alkali meter is automatically controlled by the sodium hydroxide self-regulating valve and sodium carbonate self-regulating valve installed in the two alkali high-level tanks, reducing personnel intervention in instrument control, thereby ultimately reducing the consumption of the two alkalis.

[0102] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for fine online control of the amount of over-alkali, comprising a baffle tank, a front reaction tank, a rear reaction tank, an intermediate tank, a filter and a membrane filtration system connected in sequence; in, The baffle tank is connected to the sodium carbonate high-level tank and the sodium hydroxide high-level tank respectively; it is characterized in that a sodium hydroxide self-regulating valve and a sodium hydroxide flowmeter are arranged between the baffle tank and the sodium hydroxide high-level tank; A sodium carbonate self-regulating valve, a sodium carbonate flowmeter, and a sodium carbonate concentration meter are arranged between the baffle tank and the sodium carbonate high-level tank; The input end of the baffle tank is provided with a calcium and magnesium ion analyzer, and the input end of the calcium and magnesium ion analyzer is respectively connected to the crude brine, the sodium carbonate concentration meter, and the sodium hydroxide flow meter; A brine flow meter, a brine density meter and an excess alkali analyzer are sequentially arranged between the post-reaction tank and the intermediate tank; Set the sodium hydroxide excess alkali control index, calculate the adjusted flow value of sodium hydroxide per hour, send the control index deviation data, and the sodium hydroxide self-regulating valve receives the control command for automatic adjustment; Set the control index of the amount of sodium carbonate over-alkali, calculate the adjusted flow value of sodium carbonate per hour, send the control index deviation data, and the sodium carbonate self-regulating valve receives the control command for automatic adjustment.

2. A method for fine online control of over-alkali amount according to claim 1, characterized in that: The output end of the membrane filtration system is provided with an online analysis instrument for excess alkali and an online analysis instrument for calcium and magnesium ions.

3. A method for fine online control of over-alkali amount according to claim 1, characterized in that: The control index of the amount of sodium hydroxide over-alkali is 0.2-0.5 g / l.

4. The method for fine online control of over-alkali amount according to claim 1, characterized in that: The control index of the sodium carbonate overbase amount is 0.30-0.45 g / l.

5. The method for fine on-line control of the amount of over-alkali according to any one of claims 1 to 4, characterized in that: The calculation of the adjusted flow value of sodium hydroxide per hour includes: Calculate the amount of sodium hydroxide added: Amount of sodium hydroxide added = amount of sodium hydroxide added calculated by magnesium ions + amount of excess alkali × amount of refined brine delivered × coefficient of sodium hydroxide content = magnesium ion concentration × amount of refined brine delivered × coefficient of sodium hydroxide conversion + amount of excess alkali × amount of refined brine delivered × coefficient of sodium hydroxide content; Calculate the sodium hydroxide valve flow rate: Initial flow value = (magnesium ion concentration × refined brine delivery volume × sodium hydroxide conversion coefficient + excess alkali amount × refined brine delivery volume × sodium hydroxide content coefficient) ÷ sodium hydroxide content ÷ sodium hydroxide density = (magnesium ion concentration × 3.33 × 10 -3 + target value of excess alkali × 2.35) × brine delivery volume × 2.34 × 10 -3 ; Calculate the adjustment value of the sodium hydroxide valve flow rate; Flow adjustment value = initial opening of sodium hydroxide valve - [(excess alkali amount display value - target value) × refined brine delivery volume × sodium hydroxide content coefficient × deviation coefficient] ÷ sodium hydroxide content ÷ sodium hydroxide density = (magnesium ion concentration × 3.33 × 10 -3 + target value of excess alkali × 2.35) × brine delivery volume × 2.34 × 10 -3 - [(excess alkali value displayed value - target value) × brine delivery volume × 2.35 × deviation coefficient] × 2.34 × 10 -3 .

6. The method for fine on-line control of the amount of over-alkali according to any one of claims 1 to 4, characterized in that: The calculation of the adjusted flow value of sodium carbonate per hour includes: Calculate the amount of sodium carbonate added: Sodium carbonate addition amount = calcium ion estimated sodium carbonate addition amount + over-alkali amount × refined brine delivery amount × sodium carbonate content coefficient = calcium ion concentration × refined brine delivery amount × coefficient of sodium carbonate conversion + over-alkali amount × refined brine delivery amount × sodium carbonate content coefficient; Calculate the sodium carbonate valve flow rate: Initial flow value = (calcium ion concentration × refined brine delivery volume × sodium carbonate conversion coefficient + excess alkali amount × refined brine delivery volume × sodium carbonate content coefficient) ÷ sodium carbonate concentration = (calcium ion concentration × 2.65 × 10-3 + excess alkali amount target value × 1.76) × refined brine delivery volume ÷ 88.235; Calculate the adjustment value of the sodium carbonate valve flow: Flow adjustment value = initial opening of sodium carbonate valve - [(excess alkali amount display value - target value) × refined brine delivery volume × sodium carbonate content coefficient × deviation coefficient] ÷ sodium carbonate concentration = (calcium ion concentration × 2.65 × 10-3 + excess alkali amount target value × 1.76) × refined brine delivery volume ÷ 88.23 - [(excess alkali amount display value - target value) × refined brine delivery volume × 1.76 × deviation coefficient] ÷ 88.

235.

7. The method for fine online control of over-alkali amount according to claim 1, characterized in that: The sodium hydroxide self-regulating valve receives control instructions for automatic adjustment, including: initial opening, setting the amount of alkali excess, collecting data and calculating the adjustment amount of the valve, if the set value is less than the target value, closing the regulating valve, otherwise opening the regulating valve.

8. A method for fine online control of over-alkali amount according to claim 7, characterized in that: The set value of the excess alkali amount is 0.2 g / l.

9. The method for fine on-line control of over-alkali amount according to claim 1, characterized in that: The sodium carbonate self-regulating valve receives control instructions for automatic adjustment including: initial opening, setting the alkali excess amount, collecting data and calculating the valve adjustment amount. If the set value is less than the target value, the regulating valve is closed, otherwise the regulating valve is opened.

10. A method for fine online control of over-alkali amount according to claim 9, characterized in that: The set value of the excess alkali amount is 0.3 g / l.

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