Online viscose bleaching detection control method and device
阅读说明：本技术 一种在线式粘胶纤维漂白检测控制方法及装置 (Online viscose bleaching detection control method and device ) 是由 郑柏山 孙郑军 彭宴星 仲伟峰 张英杰 张建民 郑晓冰 杨双 庞艳丽 熊忠 韩绍 于 2019-11-07 设计创作，主要内容包括：本发明涉及一种在线式粘胶纤维漂白检测控制方法及装置,其检测控制方法包括以下步骤：(1)分别实时检测漂白液循环罐输送至精炼机的漂白液的ORP值和PH值,得到进口ORP值和PH值,同时实时监测精炼机回流至漂白液循环罐的ORP值值,得到出口ORP值；(2)根据实时检测的进、出口ORP值的差值,及时计算出次氯酸钠的消耗量,并自动控制通入漂白液循环罐的次氯酸钠的加入量；(3)根据实时检测的PH值,自动控制通入漂白液循环罐的PH调配介质的加入量,激发次氯酸漂液的活性。本发明的ORP检测控制方法,具有调控及时、测量精确、稳定、可靠、维护量小等优点,替代人工取样分析。(The invention relates to an online viscose bleaching detection control method and a device, wherein the detection control method comprises the following steps: (1) respectively detecting ORP (oxidation-reduction potential) values and PH values of bleaching liquor conveyed to a refiner by a bleaching liquor circulating tank in real time to obtain inlet ORP values and PH values, and simultaneously monitoring ORP values of bleaching liquor returned to the bleaching liquor circulating tank by the refiner in real time to obtain outlet ORP values; (2) calculating the consumption of sodium hypochlorite in time according to the difference value of the ORP values of the inlet and the outlet detected in real time, and automatically controlling the addition of the sodium hypochlorite introduced into the bleaching solution circulating tank; (3) and automatically controlling the addition amount of a pH adjusting medium introduced into the bleaching liquid circulating tank according to the pH value detected in real time, and exciting the activity of the hypochlorous acid bleaching liquid. The ORP detection control method has the advantages of timely regulation and control, accurate measurement, stability, reliability, small maintenance amount and the like, and replaces manual sampling analysis.)
1. An online viscose bleaching detection control method is characterized by comprising the following steps:
(1) respectively detecting ORP (oxidation-reduction potential) values and PH values of bleaching liquor conveyed to a refiner by a bleaching liquor circulating tank in real time to obtain inlet ORP values and PH values, and simultaneously monitoring ORP values of bleaching liquor returned to the bleaching liquor circulating tank by the refiner in real time to obtain outlet ORP values;
(2) calculating the consumption of sodium hypochlorite in time according to the difference value of the ORP values of the inlet and the outlet detected in real time, and automatically controlling the addition of the sodium hypochlorite introduced into the bleaching solution circulating tank;
(3) and automatically controlling the addition amount of a pH adjusting medium introduced into the bleaching liquid circulating tank according to the pH value detected in real time, and exciting the activity of the hypochlorous acid bleaching liquid.
2. The on-line viscose bleaching detection control method according to claim 1, wherein in the step (3), the real-time detected pH value is compared with a preset pH value, and when the real-time detected pH value is not within the range of ± 0.5 of the preset pH value, the adding amount of the pH adjusting medium is controlled to be increased or decreased until the real-time detected pH value is within the range of ± 0.5 of the preset pH value; and when the real-time detected PH value is within the range of the preset PH value +/-0.5, maintaining the adding amount of the current PH blending medium.
3. The on-line viscose bleaching detection and control method according to claim 2, wherein said blending medium is NaOH or H2SO4(ii) a When the PH blending medium is NaOH, controlling to increase the addition amount of the PH blending medium when the real-time detected PH value is less than the preset PH value +/-0.5, and controlling to decrease the addition amount of the PH blending medium when the real-time detected PH value is greater than the preset PH value +/-0.5; when the PH blending medium is H2SO4And when the pH value detected in real time is less than the preset pH value +/-0.5, controlling to reduce the addition amount of the pH adjusting medium, and controlling to increase the addition amount of the pH adjusting medium, wherein the pH value detected in real time is greater than the preset pH value +/-0.5.
4. The on-line viscose bleaching detection control method according to claim 2, wherein the preset pH value is controlled between 9 and 11 according to the ORP value and the viscose variety.
5. The on-line viscose fiber bleaching detection control method according to any one of claims 1 to 4, wherein in the step (2), the difference between the ORP values of the inlet and outlet detected in real time is compared with the difference between the preset ORP values, and when the difference between the ORP values of the inlet and outlet detected in real time is larger than the difference between the preset ORP values, the adding amount of sodium hypochlorite is controlled to be increased; when the difference value of the ORP values of the inlet and the outlet detected in real time is smaller than the preset ORP difference value, controlling to reduce the addition amount of sodium hypochlorite; the preset ORP difference range is controlled to be 50-100 mv.
6. The on-line viscose fiber bleaching detection control method according to claim 5, further comprising the following steps after step (1) and before step (2): comparing the inlet ORP value with a preset inlet ORP value, and manually controlling to increase or decrease the addition amount of sodium hypochlorite when the inlet ORP value is not within the range of the preset inlet ORP value +/-20 mv until the inlet ORP value is within the range of the preset inlet ORP value +/-20 mv; when the inlet ORP value is within the range of +/-20 mv of the preset inlet ORP value, the current adding amount of sodium hypochlorite is maintained; after the actual value is stabilized within the range of +/-20 mv of the preset inlet ORP value, automatic control is carried out; the preset inlet ORP value is controlled between 450 and 600mv according to different varieties of viscose fibers.
7. An online viscose bleaching detection control device is characterized in that a sodium hypochlorite metering pump is arranged between an outlet of a sodium hypochlorite mother liquor tank and a bleaching liquor circulating tank, an ORP detection branch and a PH detection branch which are connected in parallel are arranged on a bleaching pipeline communicated with a refiner at the outlet of the bleaching liquor circulating tank, an inlet ORP detection device is arranged on the ORP detection branch, an outlet ORP detection device is arranged on a backflow pipeline communicated with a backflow port of the bleaching liquor circulating tank of the refiner, and the inlet ORP detection device and the outlet ORP detection device are respectively in electric control connection with the sodium hypochlorite metering pump and used for controlling the adding amount of sodium hypochlorite added into the bleaching liquor circulating tank through the sodium hypochlorite metering pump according to the difference value of ORP values of the inlet and the outlet detected in real time; and a PH adjusting automatic control valve is arranged on a pipeline between an outlet of the PH adjusting medium storage tank and the bleaching liquid circulating tank, a PH detection device is arranged on the PH detection branch, and the PH detection device is electrically connected with the PH adjusting automatic control valve and used for controlling the adding amount of the PH adjusting medium introduced into the bleaching liquid circulating tank through the PH adjusting automatic control valve according to the PH value detected in real time.
8. The on-line viscose bleaching detection control device according to claim 7, wherein the PH detection device comprises a PH electrode and a PH communicator, the PH electrode has a measuring range of 0-14, and is installed in the PH communicator and electrically connected with the PH regulation automatic control valve, an inlet of the PH communicator is communicated with the bleaching pipeline, and an outlet of the PH communicator is communicated with the bleaching liquid circulation tank.
9. The on-line viscose bleaching detection control device according to claim 7, wherein the inlet ORP detection device comprises an inlet ORP electrode and an inlet ORP communicator, the inlet ORP electrode is installed in the inlet ORP communicator, the outlet ORP detection device comprises an outlet ORP electrode and an outlet ORP communicator, the outlet ORP electrode is installed in the outlet ORP communicator, the inlet ORP electrode and the outlet ORP electrode are electrically connected with the sodium hypochlorite metering pump respectively, the inlet ORP communicator is communicated with the bleaching pipeline and the bleaching liquid circulation tank respectively, and the outlet ORP communicator is communicated with the refiner and the bleaching liquid circulation tank respectively.
10. The on-line viscose fiber bleaching detection control device according to any one of claims 7 to 9, wherein the sodium hypochlorite metering pump is a small diaphragm metering pump, an inlet of the sodium hypochlorite metering pump is communicated with the sodium hypochlorite mother liquor tank, an outlet of the sodium hypochlorite metering pump is communicated with the bleaching liquor circulation tank, the PH regulation automatic control valve uses a DN25 pneumatic single-seat valve, an inlet of the PH regulation automatic control valve is communicated with the PH blending medium storage tank, and an outlet of the PH regulation automatic control valve is communicated with the bleaching liquor circulation tank.
Technical Field
The invention relates to an online viscose bleaching detection control method and device, in particular to a method and device for detecting and controlling the bleaching degree of bleaching liquid in a bleaching process on viscose, which is different from the existing method and device used in the chemical fiber industry, and belongs to the field of viscose bleaching process measurement and control.
Background
In the field of measurement and control of bleaching processes in the viscose industry, sodium hypochlorite is generally used for bleaching.
The on-line detection bleaching solution has oxidation-reduction potential characteristics, the composition of the on-line detection bleaching solution contains effective chlorine components, and the chemical equation of the reaction of sodium hypochlorite and water is as follows: NaClO + H2O < ═ HClO + NaOH;
since NaClO is a strong base and a weak acid salt, it can be hydrolyzed, and the solution is alkaline after hydrolysis.
Chemical equation of hydrolysis: NaClO + H2O<＝>HClO+NaOH；
Ionic equation of hydrolysis: ClO-+H2O<＝>HClO+OH-The reaction process is reversible.
Hypochlorous acid, an oxyacid of chlorine element, has the chemical formula of HClO and the structural formula of H-O-Cl, wherein the valence of the chlorine element is +1, and is the lowest-valence oxyacid of the chlorine element, but the oxidability of the oxyacid is extremely strong in the oxyacid of the chlorine element and is the second-highest oxidability acid in the oxyacid of the chlorine element.
And ORP is an abbreviation for oxygen-Reduction Potential, which indicates the Oxidation-Reduction Potential of the solution, and ORP value is a measure of the Oxidation-Reduction capability of the aqueous solution, and is expressed in mV. The ORP electrode is a special instrument for testing the oxidation-reduction potential of a solution, consists of an ORP composite electrode and a mV meter, and is a reference electrode capable of carrying out electron absorption or electron release on the surface of a sensitive layer of the ORP electrode, wherein the sensitive layer is made of inert metal and is usually made of platinum and gold, and the reference electrode is a silver/silver chloride electrode which is the same as a pH electrode. The ORP electrode can measure the oxidation-reduction potential directly, and the oxidation-reduction effect is expressed by MV value.
The detection of the PH value is in the field of measurement and control of bleaching processes in the viscose industry at home and abroad, the detection of the ORP value is generally applied to other technical fields, and the detection is rarely applied in the viscose industry. At present, no system for detecting and controlling the ORP value and the pH value together exists, and the bleaching is difficult to be well controlled. At present, the mode of manually sampling and testing concentration is generally adopted, but the labor cost is higher, the real-time performance is not realized, the measurement precision can not be ensured, and the redox reaction degree of bleaching liquid on the surface of viscose can not be identified, so that the strength of the bleaching effect on the surface of the viscose can not be visually detected, and the better and accurate control of whiteness is not facilitated.
Disclosure of Invention
The invention aims to solve the technical problem of providing an online viscose bleaching detection control method and device, which can detect the bleaching effect of bleaching liquid on viscose in real time on line and form a ratio control system with online PH, so that the bleaching strength of the surface of the viscose is detected intuitively, and the whiteness is controlled better and accurately.
The technical scheme for solving the technical problems is as follows: an online viscose bleaching detection control method comprises the following steps:
(1) respectively detecting ORP (oxidation-reduction potential) values and PH values of bleaching liquor conveyed to a refiner by a bleaching liquor circulating tank in real time to obtain inlet ORP values and PH values, and simultaneously monitoring ORP values of bleaching liquor returned to the bleaching liquor circulating tank by the refiner in real time to obtain outlet ORP values;
(2) calculating the consumption of sodium hypochlorite in time according to the difference value of the ORP values of the inlet and the outlet detected in real time, and automatically controlling the addition of the sodium hypochlorite introduced into the bleaching solution circulating tank;
(3) and automatically controlling the addition amount of a pH adjusting medium introduced into the bleaching liquid circulating tank according to the pH value detected in real time, and exciting the activity of the hypochlorous acid bleaching liquid.
The beneficial effect who adopts above-mentioned scheme is: the detection control method has the advantages of timely regulation and control, accurate measurement, stability, reliability, small maintenance amount and the like, can detect the ORP value on line in real time to judge the strength of bleaching action of bleaching liquid on viscose fibers, forms a ratio control system with on-line PH, replaces manual sampling analysis, reduces production cost, and has important significance for popularization. The detection control method of the invention defines the regulation and control of the ORP value as a target value, the actual value reflects the strong degree of the oxidation effect of the sodium hypochlorite bleaching solution on the surface of the viscose fiber, the regulation and control of the PH value is defined as a secondary parameter, and the actual value reflects the activity of the sodium hypochlorite. According to the current situation of production in the same industry in China, comprehensive analysis is carried out by using ORP and PH detection data, the cost of the bleaching process is effectively reduced compared with manual measurement, the product goodness rate is improved, and experiments prove that the product quality is controllable and stable.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, in the step (3), the real-time detected pH value is compared with a preset pH value, and when the real-time detected pH value is not within the range of +/-0.5 of the preset pH value, the adding amount of the pH adjusting medium is controlled to be increased or decreased until the real-time detected pH value is within the range of +/-0.5 of the preset pH value; and when the real-time detected PH value is within the range of the preset PH value +/-0.5, maintaining the adding amount of the current PH blending medium.
The method has the advantages that the addition amount of the PH blending medium is controlled to be increased or decreased after the pH value of the bleaching solution is detected, so that the PH value is stabilized in a required range, and the pH value is determined by the strength of the bleaching solution in the surface reaction process of the viscose fibers.
Further, the blending medium is NaOH or H2SO4(ii) a When the PH blending medium is NaOH, controlling to increase the addition amount of the PH blending medium when the real-time detected PH value is less than the preset PH value +/-0.5, and controlling to decrease the addition amount of the PH blending medium when the real-time detected PH value is greater than the preset PH value +/-0.5; when the PH blending medium is H2SO4And when the pH value detected in real time is less than the preset pH value +/-0.5, controlling to reduce the addition amount of the pH adjusting medium, and controlling to increase the addition amount of the pH adjusting medium, wherein the pH value detected in real time is greater than the preset pH value +/-0.5.
The method has the beneficial effect that the pH adjusting medium is selected to be acidic or alkaline according to different viscose fiber varieties. The above PH control deviations (+ -0.5) are all referenced to the actual fiber whiteness during production. The mixing medium can be NaOH with the mass fraction of 30 percent or H with the mass fraction of 21 percent2SO4。
Further, the preset pH value is controlled to be 9-11 according to the ORP value and the variety of the viscose.
The method has the advantages that the pH adjusting medium is selected to be acidic or alkaline according to different viscose fiber varieties, the adding amount of the acid and the alkali is controlled, the reactivity of the sodium hypochlorite is excited, and the reaction degree is stabilized. The PH value of the common filament can be set to 11, the bamboo fiber is 9.5, the high white filament is 9.5, etc., and is generally controlled within the range of 9-11 according to the requirement of the process whiteness.
Further, in the step (2), comparing the difference value of the ORP values of the inlet and the outlet detected in real time with the preset ORP difference value, and controlling to increase the adding amount of the sodium hypochlorite when the difference value of the ORP values of the inlet and the outlet detected in real time is larger than the preset ORP difference value; when the difference value of the ORP values of the inlet and the outlet detected in real time is smaller than the preset ORP difference value, controlling to reduce the addition amount of sodium hypochlorite; the preset ORP difference range is controlled to be 50-100 mv.
The method has the advantages that the ORP value of the bleaching solution is detected, the difference value of the ORP values of the inlet and the outlet is detected, and the adding amount of the sodium hypochlorite is controlled, so that the whiteness of the bleaching solution acting on the surface of the viscose fiber reaches a qualified range, the whiteness of the fiber is different according to the variety of the fiber, and is generally controlled to be 90-92%.
Further, the method also comprises the following steps after the step (1) and before the step (2): comparing the inlet ORP value with a preset inlet ORP value, and manually controlling to increase or decrease the addition amount of sodium hypochlorite when the inlet ORP value is not within the range of the preset inlet ORP value +/-20 mv until the inlet ORP value is within the range of the preset inlet ORP value +/-20 mv; when the inlet ORP value is within the range of +/-20 mv of the preset inlet ORP value, the current adding amount of sodium hypochlorite is maintained; after the actual value is stabilized within the range of +/-20 mv of the preset inlet ORP value, automatic control is carried out; the preset inlet ORP value is controlled between 450 and 600mv according to different varieties of viscose fibers.
The further scheme has the advantages that the control range of the ORP value of the inlet is different according to different varieties of viscose fibers, the common fiber is controlled within the range of 450mv +/-20 mv, the common fiber comprises a plurality of varieties, and the high-whiteness fiber is within the range of 600mv +/-20 mv. In the technical scheme of the invention, the initial adding amount of sodium hypochlorite can be determined firstly in a manual control mode according to the inlet ORP value, when the inlet ORP value is stabilized in a proper range, the automatic control state is switched, the adding amount of the sodium hypochlorite is automatically controlled by using the difference value of the inlet ORP value and the outlet ORP value, the change of the pH value is also observed, the pH value cannot exceed the set pH range, and the set pH range is within plus or minus 0.5 of the set value.
The invention also relates to an online viscose bleaching detection control device, wherein a sodium hypochlorite metering pump is arranged between an outlet of a sodium hypochlorite mother liquor tank and a bleaching liquor circulating tank, an ORP detection branch and a PH detection branch which are connected in parallel are arranged on a bleaching pipeline communicated with a refiner at the outlet of the bleaching liquor circulating tank, an inlet ORP detection device is arranged on the ORP detection branch, an outlet ORP detection device is arranged on a return pipeline communicated with a return port of the bleaching liquor circulating tank by the refiner, and the inlet ORP detection device and the outlet ORP detection device are respectively in electric control connection with the sodium hypochlorite metering pump and are used for controlling the adding amount of sodium hypochlorite added into the bleaching liquor circulating tank through the sodium hypochlorite metering pump according to the difference value of the ORP values of the inlet and the outlet detected in real time; and a PH adjusting automatic control valve is arranged on a pipeline between an outlet of the PH adjusting medium storage tank and the bleaching liquid circulating tank, a PH detection device is arranged on the PH detection branch, and the PH detection device is electrically connected with the PH adjusting automatic control valve and used for controlling the adding amount of the PH adjusting medium introduced into the bleaching liquid circulating tank through the PH adjusting automatic control valve according to the PH value detected in real time.
The beneficial effect who adopts above-mentioned scheme is: the circulation of sodium hypochlorite mother liquor is regulated and controlled by a sodium hypochlorite metering pump, and the adding amount of acid liquor or alkali liquor is controlled by a PH regulating automatic control valve.
Further, the PH detection device comprises a PH electrode and a PH communicator, the PH electrode measuring range is 0-14, the PH electrode measuring range is installed in the PH communicator and is electrically connected with the PH adjusting automatic control valve, an inlet of the PH communicator is communicated with the bleaching pipeline, and an outlet of the PH communicator is communicated with the bleaching liquid circulation tank.
Further, the inlet ORP detection device comprises an inlet ORP electrode and an inlet ORP communicator, the inlet ORP electrode is installed in the inlet ORP communicator, the outlet ORP detection device comprises an outlet ORP electrode and an outlet ORP communicator, the outlet ORP electrode is installed in the outlet ORP communicator, the inlet ORP electrode and the outlet ORP electrode are respectively in electric control connection with the sodium hypochlorite metering pump, the inlet ORP communicator is respectively communicated with the bleaching pipeline and the bleaching liquid circulation tank, and the outlet ORP communicator is respectively communicated with the refiner and the bleaching liquid circulation tank.
Further, the sodium hypochlorite measuring pump adopts small-size diaphragm measuring pump, and its import intercommunication sodium hypochlorite mother liquor jar, export intercommunication bleaching liquor circulation jar, the PH adjusts the automatic control valve and uses DN25 pneumatic single-seat valve, and the import intercommunication PH allotment medium storage tank, the export intercommunication bleaching liquor circulation jar.
Drawings
Fig. 1 is a schematic structural diagram of an online viscose bleaching detection control device according to the present invention.
In the drawings, the components represented by the respective reference numerals are listed below:
1. the ORP electrode comprises an inlet ORP electrode, 2 an inlet ORP communicator, 3 a sodium hypochlorite metering pump, 4 a PH electrode, 5 a PH regulation automatic control valve and 6 an outlet ORP electrode.
Detailed Description
The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
At present, the detection of the PH value in the field of measurement and control of the bleaching process in the viscose industry at home and abroad is realized, the detection of the ORP value is generally applied to other technical fields, and the detection is rarely applied in the viscose industry. There was no system for measuring and controlling both ORP and pH prior to this application, making it difficult to control bleaching well. The redox reaction degree of the bleaching solution on the surface of the viscose can not be identified only by monitoring the pH value, and the bleaching strength of the surface of the viscose can not be visually detected, which is not beneficial to better and accurate control of whiteness. In the prior art, the ORP value is usually detected by manually sampling and testing the concentration and then manually controlling, but the method has high labor cost and no real-time property. Many ORP online concentration instruments exist in other technical fields, but for bleaching liquid with low concentration in a bleaching process, instrument model selection is limited, the precision is required to be below one ten thousand, model selection difficulty is high, the precision cannot be guaranteed, and if an online analysis instrument is used for sampling and titration, the investment cost is high and the maintenance amount is large.
In the viscose fiber bleaching process, in order to obtain a good bleaching effect on viscose fibers, bleaching solution is usually diluted for use, the sodium hypochlorite adding amount is controlled by measuring the concentration of sodium hypochlorite, the pH value is kept within the range of 9-11, and field experiments prove that the ORP value is introduced into automatic control to form a ratio control system with the pH value, so that the control effect is better.
The invention relates to an online viscose bleaching detection control method, which comprises the following steps:
(1) respectively detecting ORP (oxidation-reduction potential) values and PH values of bleaching liquor conveyed to a refiner by a bleaching liquor circulating tank in real time to obtain inlet ORP values and PH values, and simultaneously monitoring ORP values of bleaching liquor returned to the bleaching liquor circulating tank by the refiner in real time to obtain outlet ORP values;
(2) calculating the consumption of sodium hypochlorite in time according to the difference value of the ORP values of the inlet and the outlet detected in real time, and automatically controlling the addition of the sodium hypochlorite introduced into the bleaching solution circulating tank;
(3) and automatically controlling the addition amount of a pH adjusting medium introduced into the bleaching liquid circulating tank according to the pH value detected in real time, and exciting the activity of the hypochlorous acid bleaching liquid.
The detection control method has the advantages of timely regulation and control, accurate measurement, stability, reliability, small maintenance amount and the like, can detect the ORP value on line in real time to judge the strength of bleaching action of bleaching liquid on viscose fibers, forms a ratio control system with on-line PH, replaces manual sampling analysis, reduces production cost, and has important significance for popularization. The detection control method of the invention defines the regulation and control of the ORP value as a target value, the actual value reflects the strong degree of the oxidation effect of the sodium hypochlorite bleaching solution on the surface of the viscose fiber, the regulation and control of the PH value is defined as a secondary parameter, and the actual value reflects the activity of the sodium hypochlorite. According to the current situation of production in the same industry in China, comprehensive analysis is carried out by using ORP and PH detection data, the cost of the bleaching process is effectively reduced compared with manual measurement, the product goodness rate is improved, and experiments prove that the product quality is controllable and stable.
In the step (3) of the control method, the real-time detected pH value is compared with a preset pH value, and when the real-time detected pH value is not within the range of +/-0.5 of the preset pH value, the addition amount of the pH adjusting medium is controlled to be increased or decreased until the real-time detected pH value is within the range of +/-0.5 of the preset pH value; and when the real-time detected PH value is within the range of the preset PH value +/-0.5, maintaining the adding amount of the current PH blending medium. After the pH value of the bleaching solution is detected, the adding amount of a pH adjusting medium is controlled to be increased or decreased, so that the pH value is stabilized in a required range, and the pH value is determined by the strength of the bleaching solution in the reaction process of the bleaching solution on the surface of the viscose fiber.
The pH adjusting medium is selected to be acidic or alkaline according to different viscose fiber varieties. Specifically, the blending medium is NaOH or H2SO4(ii) a When the PH blending medium is NaOH, controlling to increase the addition amount of the PH blending medium when the real-time detected PH value is less than the preset PH value +/-0.5, and controlling to decrease the addition amount of the PH blending medium when the real-time detected PH value is greater than the preset PH value +/-0.5; when the PH blending medium is H2SO4And when the pH value detected in real time is less than the preset pH value +/-0.5, controlling to reduce the addition amount of the pH adjusting medium, and controlling to increase the addition amount of the pH adjusting medium, wherein the pH value detected in real time is greater than the preset pH value +/-0.5.
The above PH control deviations (+ -0.5) are all referenced to the actual fiber whiteness during production.
The mixing medium can be NaOH with the mass fraction of 30 percent or H with the mass fraction of 21 percent2SO4。
On the basis of the technical scheme, the preset PH value is controlled to be 9-11 according to the ORP value and the variety of the viscose fibers.
The pH adjusting medium is selected to be acidic or alkaline according to different viscose fiber varieties, the addition amount of the acid and the alkali is controlled, the reactivity of the sodium hypochlorite is excited, and the reaction degree is stabilized. The PH of the common filament can be set to 11, the bamboo fiber can be set to 9.5, the high white filament can be set to 9.5, and the PH is controlled to be in the range of 9-11 according to the process whiteness requirement.
In the step (2) of the control method, the difference value of the ORP values of the inlet and the outlet detected in real time is compared with the preset ORP difference value, and when the difference value of the ORP values of the inlet and the outlet detected in real time is larger than the preset ORP difference value, the adding amount of the sodium hypochlorite is controlled to be increased; when the difference value of the ORP values of the inlet and the outlet detected in real time is smaller than the preset ORP difference value, controlling to reduce the addition amount of sodium hypochlorite; the preset ORP difference range is controlled to be 50-100 mv. The method detects the ORP value of the bleaching solution, compares the difference value of the ORP values of the inlet and the outlet, and controls the adding amount of the sodium hypochlorite, so that the whiteness of the bleaching solution acted on the surface of the viscose fiber reaches a qualified range, and the whiteness of the fiber is different according to the variety of the fiber and is generally controlled to be 90-92%.
Presetting an ORP difference value range, wherein the control of the ORP difference value range to be 50-100mv refers to a set difference value selectable range, the ORP difference value can be set to be 50mv, or can be set to be 80mv or 100mv, the difference value of an ORP inlet and an ORP outlet exceeds the preset ORP difference value, the sodium
In the step (2), the prepared bleaching liquid inlet ORP value is detected and compared with the backflow outlet ORP value, the consumption of sodium hypochlorite can be found visually, and in the production process, the difference values of three bleaching systems are different, and are shown in the data in the table (1):
TABLE 1
As can be seen from the data in Table 1, when the bleaching solution enters the bleaching process and undergoes oxidation reaction with the fibers, the ORP value and concentration thereof are greatly changed, and the difference between the outlet ORP value of the backflow and the inlet ORP value becomes large; when being greater than the difference of the preset ORP, the opening of the sodium
Specifically, the invention measures the OPR value of the bleaching liquid after the bleaching circulation tank is blended and the refiner reflows for secondary blending, and the effective chlorine component is found to be dynamically changed through the table 1, the concentration of the supplemented sodium hypochlorite mother liquor is 120-plus 130g/l, the effective chlorine of the finished product sodium hypochlorite is about 12%, the difference value of ORP at the inlet and the outlet participates in the calculation and control of the sodium
In addition, a further preferred technical solution is that the method further comprises the following steps after the step (1) and before the step (2): comparing the inlet ORP value with a preset inlet ORP value, and manually controlling to increase or decrease the addition amount of sodium hypochlorite when the inlet ORP value is not within the range of the preset inlet ORP value +/-20 mv until the inlet ORP value is within the range of the preset inlet ORP value +/-20 mv; when the inlet ORP value is within the range of +/-20 mv of the preset inlet ORP value, the current adding amount of sodium hypochlorite is maintained; after the actual value is stabilized within the range of +/-20 mv of the preset inlet ORP value, automatic control is carried out; the preset inlet ORP value is controlled between 450 and 600mv according to different varieties of viscose fibers. Namely, the sodium hypochlorite mother liquor and the water in the bleaching liquid are prepared according to different proportions in a manual control mode, so that the ORP value at the inlet reaches the range of 450-600 mv. When the automobile is normally opened, the fibers are not in the bleaching process, the manual control inlet ORP value reaches the preset range, the outlet ORP value can be changed after the fibers enter the bleaching process, the fibers can be automatically controlled, and the program can automatically regulate and control according to the ORP difference value.
The control range of the ORP value of the inlet is different according to different varieties of viscose fibers, the common fiber is controlled within the range of 450mv +/-20 mv, the common fiber comprises a plurality of varieties, and the high-whiteness fiber is within the range of 600mv +/-20 mv. In the technical scheme of the invention, the initial adding amount of sodium hypochlorite can be determined firstly in a manual control mode according to the inlet ORP value, when the inlet ORP value is in a proper range, the automatic control state is switched, the adding amount of the sodium hypochlorite is automatically controlled by using the difference value of the inlet ORP value and the outlet ORP value, the change of the PH value is also observed, the PH value cannot exceed the set PH range, and the PH value is within the range of plus or minus 0.5 of the set value.
In the manual control of the invention, the detected ORP value of the inlet is directly checked by the staff, the ORP value of the inlet is directly compared with the preset ORP value, and after the ORP value is judged, the opening of the sodium
The automatic control of the invention is realized by detecting corresponding parameter values by corresponding detection devices, comparing and judging the parameter values with preset values stored in a controller, and finally controlling corresponding execution mechanisms (a sodium
As shown in fig. 1, the invention also relates to an online viscose bleaching detection control device, wherein a sodium hypochlorite metering pump 3 is arranged between an outlet of a sodium hypochlorite mother liquor tank and a bleaching liquor circulating tank, an ORP detection branch and a PH detection branch which are connected in parallel are arranged on a bleaching pipeline communicated with a refiner at an outlet of the bleaching liquor circulating tank, an inlet ORP detection device is arranged on the ORP detection branch, an outlet ORP detection device is arranged on a return pipeline communicated with a return port of the bleaching liquor circulating tank of the refiner, and the inlet ORP detection device and the outlet ORP detection device are respectively in electric control connection with the sodium hypochlorite metering pump 3 and are used for controlling the adding amount of sodium hypochlorite added into the bleaching liquor circulating tank through the sodium hypochlorite metering pump 3 according to the difference value of the ORP values detected in real time; and a PH adjusting automatic control valve 5 is arranged on a pipeline between an outlet of the PH adjusting medium storage tank and the bleaching liquid circulating tank, a PH detection device is arranged on the PH detection branch, and the PH detection device is electrically connected with the PH adjusting automatic control valve 5 and used for controlling the adding amount of the PH adjusting medium introduced into the bleaching liquid circulating tank through the PH adjusting automatic control valve 5 according to the PH value detected in real time.
Specifically, the PH detection device comprises a
Specifically, the inlet ORP detection device comprises an
The ORP electrode can directly measure the oxidation-reduction potential under the working condition that sodium hypochlorite is used as a main bleaching agent, the MV value represents the oxidation-reduction effect, and the oxidation strength can be used as a process parameter in the bleaching process of viscose fibers to effectively control the whiteness and the strength. The detection of the ORP value is used for better protecting the whiteness and the strength of the bleached viscose, and replacing manual sampling monitoring data, so that the process parameters are automatically and finely controlled on line.
Specifically, sodium
The inlet of the bleaching liquid circulating tank is connected with a soft water inlet pipeline for introducing soft water into the bleaching liquid circulating tank as a main body of the bleaching agent. Still be provided with the liquid level detector on bleaching liquid circulation tank for detect the liquid level in the bleaching liquid circulation tank, and set up soft water switch valve on the soft water admission pipeline, the liquid level detector is connected with soft water switch valve electricity, is used for the entering volume of the liquid level control soft water in the bleaching liquid circulation tank according to detecting.
The outlet of the bleaching liquid circulating tank is communicated to a bleaching pipeline of the refiner, and is also provided with a bleaching circulating pump, the outlet of the bleaching liquid circulating tank is communicated with the inlet of the bleaching circulating pump, and the outlet of the bleaching circulating pump is communicated with the refiner. Specifically, two bleaching circulating pumps are arranged in parallel, so that the two bleaching circulating pumps can run simultaneously or any one of the bleaching circulating pumps can be switched out through opening and closing of a valve on a pipeline for cleaning or maintenance. And the PH detection branch and the ORP detection branch are connected to the bleaching line at a position after the outlet of the bleaching cycle pump, as shown in fig. 1.
In addition, the bleaching liquid circulating tank and the two bleaching circulating pumps can be externally connected with a drain pipe.
After the ORP and the PH parameters enter the control program, the control program preferentially adjusts the ORP value, at the moment, the opening degree of the PH adjustment self-control valve 5 is kept unchanged, and after the difference value of the ORP at the inlet and the outlet exceeds the preset ORP difference value, the opening degree of the sodium
The ORP value is taken as a parameter for representing the oxidability of the bleaching solution, can visually participate in blending control, avoids damage to the surface of the viscose fiber caused by over bleaching, controls the pH value by inhibiting or releasing the oxidation of hypochlorous acid, better protects the whiteness requirement of the viscose fiber, and can stabilize the ORP value.
Experiments show that when the pH value is 1-5, the ORP value shows 950-1200mv, the bleaching rate is high, the damage to viscose fibers is small, but a large amount of chlorine can escape from an acidic solution to cause environmental pollution, and meanwhile, the bleaching rate is high and is not easy to control, so that bleaching under an acidic condition is not generally adopted in production. When the pH value is 7, the ORP value shows 800-867mv, the bleaching rate is higher, but the polymerization degree of the viscose fiber is the lowest, the damage to the viscose fiber is the most serious, and therefore, the sodium hypochlorite bleaching is not carried out under the neutral condition. When the pH value is 9-11, the ORP value shows 400-600mv, the damage degree of the cotton viscose fiber is small, and although the bleaching rate is slow, the bleaching whiteness can be effectively controlled. When the pH value is continuously increased (pH > 11), the ORP value shows 400mv and below, the bleaching rate is gradually slowed down along with the increase of the pH value, and the bleaching efficiency is obviously reduced.
Comprehensive analysis shows that different viscose ORP set values are slightly different and are set according to the requirements of mother liquor concentration and bleaching whiteness, for example, high white silk is set at 600mv +/-20 mv, ordinary silk is set at 450mv +/-20 mv, and modal is set at 430mv +/-20 mv; the pH value of the sodium hypochlorite bleaching liquid is preferably controlled to be 9-11. In the bleaching process, the pH value of the bleaching solution is gradually reduced due to the fact that the viscose absorbs alkali generated by hydrolysis of sodium hypochlorite, and the pH value is ensured to be the same when the ORP is adjusted due to the effects of acidic substances generated by viscose, pectic substances and the like during bleaching and carbon dioxide gas in air. And the ORP value of an outlet in the return pipeline is used for determining the reaction change and the concentration change of the bleaching solution, and a small difference value indicates that the reaction consumption is low, otherwise, the difference value is large.
For example, high whiteness is required in the range of 90-92%; the PH value is set to 9.5, the opening of the PH adjusting automatic control valve 5 with acid or alkali is in the range of 2-6% (manually adjusted according to the whiteness value); the opening value of the sodium
And when the whiteness meets the requirement, the value displayed at the outlet of the pump is 50-100mv greater than that displayed at the backflow outlet ORP, which indicates that the sodium hypochlorite part has been reacted and needs to be supplemented with the sodium hypochlorite.
As shown in fig. 1, the online viscose bleaching detection control device is used for controlling bleaching whiteness of viscose surface by bleaching liquid, the difference of measured values of the
Wherein, the ORP electrode is made of platinum inert metal materials, and the oxidation-reduction potential is expressed by an nernst equation:
wherein E0-standard redox potential (i.e., [ Ox ] ═ Red ] E)
R-gas constant, R-8.314J/K.mol
T-Absolute temperature in K
F-Faraday constant, 9.649X 104c/mol
n-number of electrons participating in the reaction
In the activity ratio term of formula (1), the molecule is the activity of the oxide participating in the reaction [ Ox]The denominator being the activity of the reaction to form the reducing substance [ Red]。
The ORP value is analyzed and calculated according to
Specifically, the
The parts and procedures of each detection device for realizing the control function are all the prior art, and common equipment and procedures are adopted.
In the description of the present invention, it is to be understood that, unless otherwise specifically defined or limited, the terms "OPR", "PH", "bleach liquor", "whiteness", "strength", "sodium hypochlorite", "redox potential", "control", "double closed loop", "nernst", "activity", "reaction", "strength", and the like are to be understood in a broad sense, and for example, they may be bleach, bleach liquor, applied principle, formula, controlled individually, or controlled as a double closed loop system, control within two variables, or interaction of two variables, unless otherwise specifically defined. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "communicate," "dispose," "connect," "mount," and the like are to be construed broadly, e.g., as meaning fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
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