Nitrocotton slurry concentration on-line detection method

Abstract

The invention discloses an online nitrocotton pulp concentration detection method which comprises the following steps: connecting a fine washing machine to be tested with an online cotton pulp concentration meter through a pipeline to form a material circulation loop, sufficiently mixing mixed cotton pulp, detecting by the concentration meter to obtain an average concentration signal value, comparing the concentration value of physical and chemical analysis of a sample, fitting a correction curve, and calculating the concentration of the nitrocotton pulp. When the mixed cotton is prepared again, the correction curve can be used for calculating the accurate dry weight of the cotton material, and the needed mixed cotton is obtained. The accurate configuration of the mixed cotton can ensure that the proportions of various components in each batch of products are consistent, so that the final product has better stability and repeatability in the aspects of performance, appearance and the like. In the continuous production process, stable operation of a production line can be ensured through accurate mixed cotton configuration, the downtime and the rejection rate are reduced, the production process is more stable, the production period can be greatly shortened, and the production efficiency is improved. And unstable factors in the production process can be reduced, and the safety risk is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical cellulose production and relates to an online detection method for nitrocellulose slurry concentration. Background Art

[0002] Nitrocellulose, referred to as NC, is also known as cellulose nitrate, nitrocellulose, nitrocellulose, etc. It is an important polymer energetic material. As an important chemical raw material, nitrocellulose is widely used in explosives, coatings, inks and other fields. The existing production process of nitrocellulose mainly includes cellulose pretreatment, nitration, acid removal, boiling and washing, fine cutting, fine washing, drying and other processes. Nitrocellulose fine washing is a process of finely cleaning nitrocellulose. The fine washing process is crucial to improving the quality and performance of nitrocellulose. Through fine washing, impurities in nitrocellulose can be removed and its purity can be improved, thereby improving its key indicators such as stability and combustion performance.

[0003] The nitrocellulose fine washing machine is a kind of equipment specially used for fine washing of nitrocellulose. The nitrocellulose fine washing machine usually adopts physical washing method, using stirring, filtering, centrifugation and other means to fully mix the nitrocellulose and the washing liquid to separate the impurities from the nitrocellulose. The purpose of mixing and configuring the mixed cotton pulp in the fine washing machine is to obtain better cleaning effect and product quality during the cleaning process. Usually, the mixed cotton is made of nitrocellulose, cleaning agent, additives and other ingredients mixed in a certain proportion. The method of configuring mixed cotton pulp needs to consider multiple factors, including the dry weight of the cotton material, cleaning requirements, product specifications, etc. Generally speaking, the required amount of cleaning agent and additives will be determined according to the dry weight of the cotton material to ensure that the mixed cotton can fully play its role in the cleaning process. Therefore, the dry weight of the cotton material is an important indicator for configuring the mixed cotton pulp in the fine washing machine.

[0004] At present, the commonly used method is to measure the dry weight of cotton in the fine washing machine after the material in the fine washing machine has been clarified for 3 hours, and then select the corresponding measuring scale according to the model of the fine washing machine to measure the volume of the cotton, and then find the unit volume weight of the corresponding cotton at this fineness in the "Nitrocellulose Volume Mass Conversion Table" according to the product number of the cotton in the fine washing machine, the result of the full analysis fineness and the model of the fine washing machine, so as to calculate the dry weight of the cotton in the fine washing machine. In nitrocellulose production enterprises, the concentration of cotton pulp needs to be strictly controlled to ensure the stability of product quality. In particular, when manufacturing specific types of gunpowder or coatings, there are strict requirements on the concentration of nitrocellulose pulp.

[0005] The current measurement method has the following disadvantages: first, operators must perform manual operations on site, and it is impossible to evacuate personnel to the background; second, the fine washing machine is not equipped with a liquid level meter. The mixed cotton that needs to be slurried can only rely on the operator to calculate and tie a rope on the scale before discharging the material, which increases the preparation error. In one large batch of preparation, there are less than two single batches of slurry discharge, and the qualified rate of one preparation is low. It is impossible to achieve accurate preparation of the mixed cotton. In particular, after the fine washing machine is modified, the height of the equipment increases, and the length of the measuring scale increases accordingly, which makes it more inconvenient for employees to operate. Summary of the invention

[0006] The purpose of the present invention is to provide an online detection method for nitrocellulose slurry concentration, which solves the problem of large errors in manual measurement and configuration of mixed cotton in the prior art.

[0007] The technical solution adopted by the present invention is an online detection method for nitrocellulose slurry concentration, which is specifically implemented according to the following steps: S1. Connect the fine washing machine to be tested and the online cotton pulp concentration meter through a pipeline to form a material circulation loop; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

[0008] The present invention is also characterized in that: In S1, a control valve is arranged on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter. The online cotton pulp concentration meter in S1 is an internal rotation type cotton pulp concentration meter.

[0009] The mixed cotton material in S2 includes nitrocellulose and a fine detergent required for fine washing, and the fine washing machine stirs for 30 to 60 minutes.

[0010] The pressure of the discharge from the fine washing machine in S3 is controlled within the range of 0.30MPa to 0.33MPa when it passes through the online cotton pulp concentration meter. The signal of the online cotton pulp concentration meter in S3 is basically stable. When the concentration signal value fluctuates between ±10, the range change is recorded and the signal mean is calculated.

[0011] The detailed steps of sampling in S4 are as follows: use a special sampling tool to continuously sample 10 to 15 times at the discharge port of the fine washing machine, and place all the samples obtained in the same water-free, clean special sampling bucket, and then use a special sampling tool to stir the samples in the special sampling bucket, stirring continuously for 30 to 60 seconds to mix the samples obtained multiple times evenly, use a special sampling tool to take 300 to 350 ml of the sample in the special sampling bucket into a clean and dry wide-mouth bottle with a ground mouth and a stopper, cover the bottle cap, and send it as a test sample for physical and chemical analysis to obtain the cotton pulp concentration.

[0012] The liquid level gauge in S7 is a differential pressure level gauge.

[0013] The beneficial effects of the present invention are: Accurately configuring the blended cotton can ensure that the proportions of various ingredients in each batch of products are consistent, making the final product more stable and repeatable in terms of performance, appearance, etc.

[0014] In the continuous production process, precise blending of cotton configuration can ensure the stable operation of the production line, reduce downtime and scrap rate, make the production process more stable, and do not need frequent parameter adjustment and product testing, which can greatly shorten the production cycle and improve production efficiency. By accurately controlling the proportion of various ingredients, it is possible to avoid product failure or poor performance caused by too much or too little ingredients, thereby reducing the waste of raw materials.

[0015] For flammable and explosive materials such as nitrocellulose, accurate configuration can reduce safety risks. By accurately controlling the content of nitrocellulose, the safety of products during production, storage and transportation can be ensured, and unstable factors in the production process can be reduced, reducing the probability of accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a measuring circulation loop of an online method for measuring nitrocellulose slurry concentration of the present invention.

[0017] In the figure, 1. Online cotton pulp concentration meter, 2. Fine washing machine. DETAILED DESCRIPTION

[0018] The online detection method of nitrocellulose slurry concentration of the present invention is specifically implemented according to the following steps: S1, connecting the fine washing machine to be tested and the online cotton pulp concentration meter 1 through a pipeline to form a material circulation loop; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

[0019] Among them, a control valve is arranged on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter in S1, and the online cotton pulp concentration meter in S1 is an internal rotating cotton pulp concentration meter.

[0020] The mixed cotton material in S2 includes nitrocellulose and a fine detergent required for fine washing, and the fine washing machine stirs for 30 to 60 minutes.

[0021] The discharge of the fine washing machine in S3 is measured by an online cotton pulp concentration meter to control the pressure within the range of 0.30MPa~0.33MPa.

[0022] The signal of the online cotton pulp concentration meter in S3 is basically stable. When the concentration signal value fluctuates between ±10, the range change is recorded and the signal mean is calculated.

[0023] The detailed steps of sampling in S4 are as follows: use a special sampling tool to continuously sample 10 to 15 times at the discharge port of the fine washing machine, and place all the samples obtained in the same water-free, clean special sampling bucket, and then use a special sampling tool to stir the samples in the special sampling bucket, stirring continuously for 30 to 60 seconds to mix the samples obtained multiple times evenly, use a special sampling tool to take 300 to 350 ml of the sample in the special sampling bucket into a clean and dry wide-mouth bottle with a ground mouth and a stopper, cover the bottle cap, and send it as a test sample for physical and chemical analysis to obtain the cotton pulp concentration.

[0024] The liquid level gauge in S7 is a differential pressure level gauge.

[0025] In the online detection method for nitrocellulose slurry concentration of the present invention: S5 uses a calibration curve between an online cotton pulp concentration meter and the concentration value of physical and chemical analysis to improve the accuracy of preparing nitrocellulose pulp. The concentration changes can be monitored in real time and the cotton pulp can be adjusted in time. The method is simple and easy to operate, eliminating the problem of large errors in manual preparation of nitrocellulose and the need for multiple preparations with large losses.

[0026] Example 1 The online detection method of nitrocellulose slurry concentration in this embodiment is specifically implemented according to the following steps: S1. Connect the fine washing machine to be tested and the online cotton pulp concentration meter 1 through a pipeline to form a material circulation loop, and set a control valve on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter. The online cotton pulp concentration meter is an internal rotation type cotton pulp concentration meter; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

[0027] Among them, the function of the control valve in S1 is to control whether the circulation of the material in the fine washing machine passes through the online cotton pulp concentration meter.

[0028] The internal rotating cotton pulp concentration meter works based on the shear force principle. When the rotating part of the instrument rotates in the cotton pulp, it will be subject to the resistance of the cotton pulp. The magnitude of this resistance is related to the concentration of the cotton pulp. The higher the concentration, the greater the obstruction of the cotton pulp to the rotating part, and the greater the torque required for rotation. By measuring the torque or related mechanical parameters of the rotating part and converting them through a specific algorithm, the concentration value of the cotton pulp can be obtained.

[0029] In addition to the internal rotating cotton pulp concentration meter, the online cotton pulp concentration meter can also be replaced by an ultrasonic concentration meter, a capacitive concentration meter, etc.

[0030] Ultrasonic concentration meter determines the concentration of solution by measuring the propagation speed of ultrasonic wave in solution. The concentration change of nitrocellulose in solution will affect the propagation speed of ultrasonic wave. The concentration can be calculated based on this relationship. It is suitable for measuring various concentration ranges and is not affected by factors such as solution color and turbidity. It is easy to install and can measure online in real time.

[0031] Capacitive concentration meter uses the change of capacitance to measure the concentration of solution. The presence of nitrocellulose in the solution will change the dielectric constant of the solution, thereby affecting the capacitance value. By measuring the change of capacitance value, the concentration of the solution can be determined. It is suitable for the measurement of high and low concentrations and has good stability and reliability.

[0032] Example 2 The online detection method of nitrocellulose slurry concentration in this embodiment is specifically implemented according to the following steps: S1. Connect the fine washing machine to be tested and the online cotton pulp concentration meter 1 through a pipeline to form a material circulation loop, and set a control valve on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter. The online cotton pulp concentration meter is an internal rotation type cotton pulp concentration meter; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

[0033] The mixed cotton material in S2 includes nitrocellulose and a fine detergent required for fine washing, and the fine washing machine stirs for 30 to 60 minutes.

[0034] The fine washing machine can stir the materials to make the nitrocellulose and the cleaning liquid fully contact and mix, so as to more effectively dissolve and separate the acid attached to the nitrocellulose, the unreacted raw materials and other impurities, so as to achieve the purpose of improving the purity and quality of the nitrocellulose.

[0035] The stirring methods in the fine washing machine include mechanical stirring and gas stirring, and mechanical stirring is divided into paddle stirring and anchor stirring.

[0036] Paddle stirring is a common method, and usually suitable paddles are installed inside the fine washing machine, such as flat paddles, inclined paddles or turbine paddles. Flat paddle stirring is relatively gentle, and is suitable for situations where the material stirring uniformity is not extremely demanding and the material is relatively not prone to excessive shearing; inclined paddles can produce a certain axial and radial mixing effect, and the stirring efficiency is relatively good; turbine paddles can form a strong liquid circulation and shearing effect, which can quickly mix the nitrocellulose and the cleaning liquid, but if the speed is not properly controlled, it may have a certain impact on the fiber structure of the nitrocellulose.

[0037] The shape of the stirring paddle of the anchor stirring machine is similar to an anchor, which fits the inner wall of the fine washing machine. This stirring method can effectively scrape off the materials attached to the wall, prevent the accumulation of nitrocellulose on the wall surface and affect the heat transfer and mass transfer effect. At the same time, it can also promote the circulation and mixing of the whole material to a certain extent, which is helpful for maintaining the uniformity of the material properties during the fine washing process, especially suitable for the situation where the material has a certain viscosity and is easy to adhere to the wall surface.

[0038] Gas stirring is to introduce gas (such as inert gas such as nitrogen) into the fine washing machine and use the bubble flow generated by the rising gas to stir the material. Gas stirring is relatively gentle and will not cause excessive shear damage to the nitrocellulose fiber like some high-speed mechanical stirring. In addition, the use of inert gas can also isolate the air and reduce the risk of oxidation to a certain extent. However, when gas stirring is used alone, the stirring efficiency may not be as high as mechanical stirring. It will be used in conjunction with mechanical stirring. On the basis of mechanical stirring, gas is intermittently introduced for auxiliary stirring to further optimize the stirring effect.

[0039] Generally speaking, the time it takes for a nitrocellulose washing machine to stir materials is affected by many factors, and the overall range is approximately 30 minutes to several hours.

[0040] If the initial impurity content of the nitrocellulose is high and the fiber structure is relatively compact, a longer stirring time may be required to ensure that the impurities are fully removed and the cleaning liquid can fully penetrate into the nitrocellulose and replace the impurities. In this case, the stirring time may be 2 to 3 hours or even longer. The nitrocellulose used in this embodiment is of relatively good quality, has fewer impurities and relatively loose fibers, and the stirring time may be shortened to 30 to 60 minutes.

[0041] Different cleaning solution formulas have different abilities to dissolve and remove impurities. If the cleaning solution used has a strong ability to dissolve acids and other specific impurities and can quickly react with the impurities to dissolve them and separate them from the nitrocellulose, then the stirring time can be relatively short; if the cleaning solution has a relatively mild effect, the stirring time needs to be extended to ensure the cleaning effect.

[0042] Example 3 The online detection method of nitrocellulose slurry concentration in this embodiment is specifically implemented according to the following steps: S1. Connect the fine washing machine to be tested and the online cotton pulp concentration meter 1 through a pipeline to form a material circulation loop, and set a control valve on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter. The online cotton pulp concentration meter is an internal rotation type cotton pulp concentration meter; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

[0043] Among them, the discharge of the fine washing machine in S3 is controlled within the range of 0.30MPa~0.33MPa by the online cotton pulp concentration meter.

[0044] Start the pulp discharge pump of the fine washer, open the discharge valve of the fine washer, allow the material in the fine washer to pass through the online cotton pulp concentration meter and then return to the fine washer from the feed port of the fine washer, and control the discharge pressure of the discharge pump to 0.30MPa~0.33MPa.

[0045] The discharge pressure value of the nitrocellulose fine washing machine during normal cycle cleaning may be controlled between 0.5 and 2 MPa. However, when switching to the circulation loop passing through the online cotton pulp concentration meter, in order to protect the precision components of the online cotton pulp concentration meter, ensure measurement accuracy and prevent cotton material from clogging the concentration meter, the discharge pressure needs to be appropriately reduced when the nitrocellulose fine washing machine discharge passes through the online cotton pulp concentration meter.

[0046] Online cotton pulp concentration meters usually measure cotton material concentration based on some specific physical or chemical principles, such as optical principles, electrical principles, etc., and contain many precise sensors, lenses, electrodes and other components. If the discharge pressure is too high, the high-speed flowing nitrocellulose material may cause direct impact and wear on these precise components.

[0047] Appropriate discharge pressure can keep the nitrocellulose in a relatively stable flow state when passing through the concentration meter. If the pressure is too high, the nitrocellulose will flow too fast and unevenly, and unstable phenomena such as turbulence and splashing will occur. This unstable flow state will interfere with the normal measurement of the concentration meter and cause a large deviation in the measurement results.

[0048] Example 4 The online detection method of nitrocellulose slurry concentration in this embodiment is specifically implemented according to the following steps: S1. Connect the fine washing machine to be tested and the online cotton pulp concentration meter 1 through a pipeline to form a material circulation loop, and set a control valve on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter. The online cotton pulp concentration meter is an internal rotation type cotton pulp concentration meter; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

[0049] Among them, the signal of the online cotton pulp concentration meter in S3 is basically stable. When the concentration signal value fluctuates between ±10, the variation range is recorded and the signal mean is calculated.

[0050] When the mixed cotton cycle passes through the online cotton pulp concentration meter, the concentration meter signal is always changing. It is necessary to judge the reasonable fluctuation range of the signal value to obtain the concentration signal mean that can reflect the actual situation. If it is found that the average values ​​of the concentration signal values ​​in each time period are similar, the fluctuation range is roughly the same, and there is no obvious increasing or decreasing trend, then it can be judged that the concentration signal value is basically stable throughout the production process.

[0051] Therefore, this embodiment sets that when the signal value fluctuation of the online cotton pulp concentration meter changes between ±10, the change range at this time is recorded, so as to calculate the mean value of the concentration meter signal.

[0052] Example 5 The online detection method of nitrocellulose slurry concentration in this embodiment is specifically implemented according to the following steps: S1. Connect the fine washing machine to be tested and the online cotton pulp concentration meter 1 through a pipeline to form a material circulation loop, and set a control valve on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter. The online cotton pulp concentration meter is an internal rotation type cotton pulp concentration meter; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

[0053] Among them, the detailed steps of sampling in S4 are: use a special sampling tool to continuously sample at the discharge port of the fine washing machine for 10 to 15 times, and place all the samples obtained in the same water-free, clean special sampling bucket, and then use a special sampling tool to stir the samples in the special sampling bucket, stirring continuously for 30 to 60 seconds to mix the samples obtained multiple times evenly, use a special sampling tool to take 300 to 350 ml of the sample in the special sampling bucket into a clean and dry wide-mouth bottle with a ground mouth and a stopper, cover the bottle cap, and send it as a test sample for physical and chemical analysis to obtain the cotton pulp concentration.

[0054] In order to ensure that the samples taken can accurately reflect the overall situation of the nitrocellulose concentration in the fine washing machine, it is necessary to take samples at intervals multiple times at the discharge port to avoid the lack of representativeness of the samples due to local differences.

[0055] The sampling tools must be absolutely clean before use, and must not contain any impurities that may affect the purity of the sample or the analysis results. The samples should be immediately placed in a suitable container for storage. For nitrocellulose samples, a well-sealed glass or metal container should be selected. The container should be cleaned and dried in advance to ensure that there are no impurities and moisture.

[0056] After sampling, the sampling time, sampling location, washing machine number and other relevant information should be clearly marked on the sample container so that the source and background of the sample can be accurately understood during subsequent analysis.

[0057] Example 6 The online detection method of nitrocellulose slurry concentration in this embodiment is specifically implemented according to the following steps: S1. Connect the fine washing machine to be tested and the online cotton pulp concentration meter 1 through a pipeline to form a material circulation loop, and set a control valve on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter. The online cotton pulp concentration meter is an internal rotation type cotton pulp concentration meter; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

[0058] Among them, the liquid level gauge in S7 is a differential pressure level gauge.

[0059] After the renovation of the fine washing machine, the height of the equipment increased, and the length of the measuring scale increased accordingly. Manual operation and measurement have become difficult to achieve. Therefore, a suitable level meter is needed to replace manual operation to make the measurement process simpler and the measurement data more accurate.

[0060] In this embodiment, the liquid level gauge is a differential pressure liquid level gauge. The differential pressure liquid level gauge is a device that uses the pressure generated by a liquid column to measure the liquid level. It can measure the liquid level of high-temperature, high-viscosity, easy-to-crystallize, easy-to-precipitate and highly corrosive media, and is more suitable for the characteristics of nitrocellulose pulp.

[0061] The liquid level meter can also be a radar level meter or other liquid level meter that meets the use conditions.

[0062] The radar level meter emits electromagnetic waves. When the electromagnetic waves hit the liquid surface, they are reflected back and received by the receiving device. The liquid level height is calculated based on the propagation time and speed of the electromagnetic waves.

[0063] The advantages are non-contact measurement, which is not affected by the physical properties of nitrocellulose, high measurement accuracy, and can adapt to complex working conditions such as high temperature and high pressure; it can realize remote monitoring and automatic control, and is convenient for operation and management. However, the price is relatively high, and the measurement may be affected to a certain extent in some occasions where there is a lot of steam, foam or large fluctuations in the liquid level.

Claims

1. An online detection method for nitrocellulose slurry concentration, characterized in that: Follow the steps below to implement it: S1, connecting the fine washing machine to be tested and the online cotton pulp concentration meter (1) through a pipeline to form a material circulation loop; S2. Select a liquid level gauge that matches the model of the fine washing machine to be measured, measure a certain amount of mixed cotton material within the capacity range of the fine washing machine, and fully stir it in the fine washing machine to form a mixed cotton pulp; S3, circulating the mixed cotton pulp in the fine washing machine through the online cotton pulp concentration meter, and when the concentration signal value on the display screen of the online cotton pulp concentration meter is basically stable, calculating and recording the current average concentration signal value; S4. After the signal of the online cotton pulp concentration meter is basically stable, samples are taken continuously multiple times at the outlet of the fine washing machine, and all the samples taken are mixed and stirred evenly. Samples are taken from the evenly mixed samples and sent for physical and chemical analysis to obtain the concentration of the mixed cotton pulp; S5. Compare the obtained laboratory physicochemical analysis values ​​with the corresponding online cotton material concentration signal values, and according to the grades, viscosity and fineness of nitrocellulose A, B, C, D, respectively, prepare calibration curves for the rational analysis concentration values ​​and the online concentration meter signal values; S6, repeat S2 to S3 to obtain the average signal value of the online concentration meter, select the corresponding calibration curve according to the specific grade, viscosity and fineness of the nitrocellulose, and convert the average signal value of the concentration meter into the corresponding concentration value; S7. Determine the liquid level height and calculate the volume of the pulp to be tested by using a liquid level meter. Then calculate the volume of the mixed cotton in the fine washing machine based on the mixed cotton concentration value obtained in S6. Look up the unit volume weight of the corresponding cotton material at this fineness in the "Nitrocellulose Volume Mass Conversion Table", thereby calculating the dry weight of the cotton material in the fine washing machine and preparing the mixed cotton.

2. The method for online detection of nitrocellulose slurry concentration according to claim 1, characterized in that: In S1, a control valve is provided on the circulation pipeline between the discharge port of the fine washing machine and the online cotton pulp concentration meter.

3. The method for online detection of nitrocellulose slurry concentration according to claim 1, characterized in that: The online cotton pulp concentration meter described in S1 is an internal rotation type cotton pulp concentration meter.

4. The method for online detection of nitrocellulose slurry concentration according to claim 1, characterized in that: The mixed cotton material in S2 includes nitrocellulose and a fine detergent required for fine washing, and the fine washing machine stirs for 30 to 60 minutes.

5. The method for online detection of nitrocellulose slurry concentration according to claim 1, characterized in that: The discharge of the fine washing machine in S3 is measured by an online cotton pulp concentration meter to control the pressure within the range of 0.30MPa~0.33MPa.

6. The method for online detection of nitrocellulose slurry concentration according to claim 5, characterized in that: The signal of the online cotton pulp concentration meter described in S3 is basically stable. When the concentration signal value fluctuates between ±10, the range change is recorded and the signal mean is calculated.

7. The method for online detection of nitrocellulose slurry concentration according to claim 1, characterized in that: The detailed steps of sampling in S4 are as follows: use a special sampling tool to continuously sample 10 to 15 times at the discharge port of the fine washing machine, and place all the samples obtained in the same water-free, clean special sampling bucket, and then use a special sampling tool to stir the samples in the special sampling bucket, stirring continuously for 30 to 60 seconds to mix the samples obtained multiple times evenly, use a special sampling tool to take 300 to 350 ml of the sample in the special sampling bucket into a clean and dry wide-mouth bottle with a ground mouth and a stopper, cover the bottle cap, and send it as a test sample for physical and chemical analysis to obtain the cotton pulp concentration.

8. The method for online detection of nitrocellulose slurry concentration according to claim 1, characterized in that: The liquid level gauge described in S7 is a differential pressure liquid level gauge.

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