Instrument and method for online detection of purity of p-nitrochlorobenzene

Abstract

The invention belongs to the technical field of analytical instruments, and particularly relates to an instrument and a method for detecting the purity of p-nitrochlorobenzene on line. The instrument mainly comprises a measuring system, a temperature control system and a computer control system. The online detection instrument is controlled by the computer control system to introduce a detected solution into the measuring cell, the cooling crystallization process is realized through cooling air introduced by the temperature control system, the temperature value of a crystallization point is measured by a temperature sensor in the measuring system, and the purity of the p-nitrochlorobenzene solution is calculated according to a regression curve of the crystallization point and the purity. And the measured crystal is heated and melted by the temperature control system and flows out of the measuring system. And circulating the measurement process under the control of a computer system to realize online detection of the crystallization point and the purity of the p-nitrochlorobenzene solution.

Description

Technical Field

[0001] The invention belongs to the technical field of analytical instruments, and in particular relates to an instrument and a method for online detection of the purity of p-nitrochlorobenzene. Background Art

[0002] Nitrochlorobenzene mainly refers to p-nitrochlorobenzene and α-nitrochlorobenzene, which are important basic petrochemical organic raw materials and are widely used in chemical industries such as pesticides, medicines, and rubber additives. The production of nitrochlorobenzene mostly adopts nitration, distillation, and crystallization separation. The finished products of p-nitrochlorobenzene and α-nitrochlorobenzene are separated by the difference in crystallization points.

[0003] At present, the crystallization point of p-nitrochlorobenzene in the nitrochlorobenzene production device is measured by manual sampling, and the crystallization point and purity are determined by observing the sample temperature when the crystals are precipitated through natural cooling of the ambient temperature. This method has the disadvantages of long analysis time, delayed measurement results, large errors, etc., resulting in increased system energy consumption and low product qualification rate. Summary of the invention

[0004] The purpose of the present invention is to provide an instrument and method for online detection of the purity of p-nitrochlorobenzene. Designing an automatic sampling and measuring detector based on a single-chip microcomputer control system can realize the online automatic measurement function and solve the shortcomings of long lag and large error of manual sampling analysis.

[0005] The solution to the problem of the present invention is: an instrument for online detection of the purity of p-nitrochlorobenzene, characterized in that it comprises a measuring system, a temperature control system and a computer control system; the measuring system comprises a measuring cell, the measuring cell is wound with a temperature control coil, a stirring device is arranged inside, a temperature sensor is arranged on the outer wall and the center, and the measuring cell is provided with an inlet and outlet pipeline and a corresponding control valve; the temperature control system comprises a heating box and a cold air inlet pipe respectively connected with an air source, a heating coil, an electric heater and a temperature sensor are arranged in the heating box, an inlet valve and an outlet valve are arranged at both ends of the heating coil and are respectively connected with the air source and the temperature control coil, and a cold air inlet pipe is provided with a cold air inlet valve connected with the temperature control coil; the computer control system comprises a single chip computer system, a multi-channel temperature sensor signal amplification circuit and an analog-to-digital conversion circuit, a valve and stirring control circuit, a parameter storage module and a standard signal output module.

[0006] Furthermore, the measurement system includes 2 temperature sensors, and the temperature control system includes 1 temperature sensor.

[0007] Preferably, the temperature sensors are all PT1000 temperature sensors.

[0008] Furthermore, the measuring cell and the heating box are both provided with a heat-insulating layer.

[0009] Furthermore, the computer control system includes a liquid crystal display screen and independent buttons.

[0010] Preferably, the data storage module is AT24C02, and is remotely transmitted via a 4-20mA standard signal output circuit.

[0011] The present invention also provides a method for online detection of the purity of p-nitrochlorobenzene by using the above-mentioned instrument, which is characterized in that the instrument introduces the p-nitrochlorobenzene solution to be tested into the measuring system under the control of a computer control system, realizes the cooling crystallization process through the cooling air introduced by the temperature control system, collects the temperature signal through the temperature sensor signal amplification circuit and the analog-to-digital conversion circuit, calculates the crystallization point temperature of p-nitrochlorobenzene, and then uses a series of standard p-nitrochlorobenzene solutions of different purities to make a regression curve of the p-nitrochlorobenzene purity and the crystallization point temperature according to the external standard method, and then compares the regression curve with the crystallization point temperature value to obtain the purity corresponding to the p-nitrochlorobenzene solution to be tested.

[0012] Furthermore, the method specifically comprises the following steps: (1) Under the control of the computer system, the measuring system follows the workflow set by the analyzer. Step 1: open the feed control valve and close the discharge control valve at the same time. The p-nitrochlorobenzene solution to be measured flows into the measuring cell through the feed pipeline. After the p-nitrochlorobenzene solution fills the measuring cell, the feed control valve is closed. Step 2: introduce air from the temperature control system through the temperature control coil wrapped around the measuring cell to cool the measuring cell. Under the control of the computer system, start the stirring motor to ensure that the temperature of the solution in the measuring cell drops evenly until the crystallization point. Step 3: the computer control system detects and records the temperature data of the p-nitrochlorobenzene solution during the cooling-heating-constant temperature process through the temperature sensor during the measurement process. After optimization, the crystallization point of the p-nitrochlorobenzene solution to be measured is obtained. Step 4: after the measurement is completed, open the discharge control valve. The temperature control coil introduces hot gas from the temperature control system to the measuring cell and the crystallized p-nitrochlorobenzene in the measuring cell to heat and melt it to a liquid state. The molten p-nitrochlorobenzene solution flows out of the detector through the discharge control valve and the discharge pipeline. (2) After the instrument is powered on, the electric heater is first used to heat the heating box. The temperature sensor detects the real-time temperature of the heating box. The computer controls the output power of the electric heater to control the temperature of the heating box to the set value. During the cooling and crystallization process of the measuring system, under the control of the computer system, the heating box inlet control valve and the heating box outlet control valve are closed, the cooling gas control valve is opened, and the gas source gas is sent to the measuring system temperature control coil through the gas source pipe and the cooling gas pipe to cool the measuring pool. During the heating and melting process of the measuring system, the cooling gas control valve is closed, the heating box inlet control valve and the heating box outlet control valve are opened, and the gas source gas is fully heated through the gas source pipe and the heating coil in the heating box and then sent to the measuring system temperature control coil for melting the crystallized and solidified p-nitrochlorobenzene in the measuring pool. (3) After the instrument is powered on, the temperature value of the electric heating box is detected by the temperature sensor of the electric heating box, and after comparing it with the set temperature, the output of the electric heater is controlled to keep the temperature of the electric heating box constant at the set temperature; after the temperature of the electric heating box is constant, the computer system controls the opening of the feed control valve and the closing of the discharge control valve to introduce the test solution into the measuring cell; after the test solution is introduced into the measuring cell, the feed control valve is closed, the cooling gas control valve is opened, and the cooling gas is cooled through the temperature control coil to cool the measuring cell, and the stirring motor is turned on to stir the solution in the measuring cell to cool it evenly; the computer system reads the temperature value of the solution during the cooling and crystallization process to obtain the crystallization point temperature, and calculates the purity through a mathematical model; after completing the crystallization point temperature measurement, the computer system controls the opening of the discharge control valve, the heating box inlet control valve, and the heating box outlet control valve, and introduces the heating gas into the temperature control coil to heat the measuring cell, and heats the measuring cell to above the crystallization point of the solution, so that the crystals in the measuring cell are fully melted and then flow out of the measuring cell; (4) Online purity detection: According to the external standard method, a series of standard p-nitrochlorobenzene solutions with different purities are used to draw a regression curve between the p-nitrochlorobenzene purity and the crystallization point temperature. The crystallization point temperature and the purity corresponding to the p-nitrochlorobenzene solution to be tested are further calculated and displayed.

[0013] Preferably, the method obtains the corresponding purity by measuring the crystallization point temperature with the aid of a regression curve. In the range of 0-102°C, the regression curve of the crystallization point temperature and purity of p-nitrochlorobenzene is y=1.1172x+7.444, wherein y is the purity of p-nitrochlorobenzene and x is the crystallization point temperature of p-nitrochlorobenzene.

[0014] Advantages of the present invention: The analyzer calculates the purity of p-nitrochlorobenzene by measuring the crystallization point, has the advantages of high precision, fast response and good stability, and overcomes the disadvantages of large error and measurement lag caused by manual analysis. At the same time, the measured value of the analyzer can be fed back to the process production in real time, improve the degree of production automation, and thus improve product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of measurement system components in an embodiment of the present invention.

[0016] In the figure: 1: temperature control coil; 2: measuring cell insulation layer; 3: temperature sensor 1; 4: temperature sensor 2; 5: feed control valve; 6: feed pipeline; 7: measuring cell; 8: stirring motor; 9: discharge control valve; 10: discharge pipeline; Figure 2 Schematic diagram of temperature control system components in an embodiment of the present invention.

[0017] In the figure: 11: air source pipe; 12: cooling air pipe; 13: cooling air control valve; 14: heating coil; 15: heating box inlet control valve; 16: temperature sensor 3; 17: heating box; 18: heating box insulation layer; 19: electric heater; 20: heating box outlet control valve; Figure 3 Schematic diagram of a computer control system in an embodiment of the present invention. Implementation

[0018] The present invention is further described below with reference to the accompanying drawings and examples. Example

[0019] Instrument reference for online detection of p-nitrochlorobenzene purity Figure 1-3 , mainly including measurement system, temperature control system, and computer control system. Measurement system (reference Figure 1 ) mainly includes temperature control coil 1, measuring pool insulation layer 2, temperature sensor 1 (3) and temperature sensor 2 (4), feed control valve 5, feed pipeline 6, measuring pool 7, stirring motor 8, discharge control valve 9, discharge pipeline 10; temperature control system (reference Figure 2 ) mainly includes an air source pipe 11, a cooling air pipe 12, a cooling air control valve 13, a heating coil 14, a heating box inlet control valve 15, a temperature sensor 3 (16), a heating box 17, a heating box insulation layer 18, an electric heater 19, and a heating box outlet control valve 20; the computer control system mainly includes a single-chip microcomputer system, a multi-channel temperature sensor signal amplification circuit and an analog-to-digital conversion circuit, a valve and stirring control circuit, a parameter storage module and a standard signal output module, a liquid crystal display and independent buttons, etc.

[0020] Figure 1In the example shown, under the control of a computer system, the feed control valve (5) is opened, the discharge control valve (9) is closed, and the p-nitrochlorobenzene solution to be measured is introduced into the measuring cell (7) through the feed pipeline (6). After the p-nitrochlorobenzene solution fills the measuring cell (7), the feed control valve (5) is closed, and cooling air is introduced through the temperature control coil (1) to cool the measuring cell. The temperature sensor 1 (3) is externally arranged and close to the measuring cell (7). The temperature sensor 1 (3) controls the temperature reduction range of the measuring cell (7) to meet the crystallization requirements of the p-nitrochlorobenzene solution. The temperature control coil (1) introduces cooling air to cool the p-nitrochlorobenzene solution to the crystallization point. According to the principle of thermodynamics, the p-nitrochlorobenzene solution releases heat during crystallization, causing the solution temperature to rise and be kept constant at a certain temperature value. After all the crystals release heat, the temperature continues to be lowered. The computer control system detects and records the temperature data of the p-nitrochlorobenzene solution during the cooling-heating-constant temperature process through the temperature sensor 2 (4), and obtains the crystallization point of the p-nitrochlorobenzene solution to be measured after optimization. During the cooling and crystallization process, the stirring motor (8) is controlled by a computer to ensure that the temperature of the solution in the measuring pool (7) is uniform. After the measurement is completed, the discharge control valve (9) is opened, and the temperature control coil (1) introduces hot air to heat and melt the crystallized and solidified p-nitrochlorobenzene in the measuring pool (7) to a liquid state, and the molten p-nitrochlorobenzene solution flows out of the detection instrument through the discharge control valve (9) and the discharge pipeline (10). The insulation layer (2) of the measuring pool is used to reduce heat loss during the melting process. The detection instrument cyclically runs the above measurement process to achieve online measurement of the crystallization point temperature of the p-nitrochlorobenzene solution.

[0021] Furthermore, a regression curve of nitrochlorobenzene purity and crystallization temperature is drawn using a series of standard nitrochlorobenzene solutions of different purity according to the external standard method, and then the purity corresponding to the nitrochlorobenzene solution to be tested is obtained by comparing the regression curve with the crystallization temperature value. In the range of 0-102°C, the regression curve of the crystallization temperature and purity of p-nitrochlorobenzene is y=1.1172x+7.444, where y is the purity of p-nitrochlorobenzene and x is the crystallization temperature of p-nitrochlorobenzene.

[0022] Figure 2In the example shown, the heating box (17) is heated by the electric heater (19), the real-time temperature of the heating box (17) is detected by the temperature sensor 3 (16), and the temperature value of the heating box (17) is controlled to a set value by controlling the output power of the electric heater (19) by the computer. During the cooling process of the measuring system, under the control of the computer system, the cooling air control valve (13) is opened, the heating box inlet control valve (15) and the heating box outlet control valve (20) are closed, and the air source air is passed into the measuring system temperature control coil (1) through the air source pipe (11), the cooling air pipe (12), and the cooling air control valve (13). During the heating and melting process of the measuring system, the cooling air control valve (13) is closed, the heating box inlet control valve (15) and the heating box outlet control valve (20) are opened, and the air source air is passed into the measuring system temperature control coil (1) after being fully heated through the air source pipe (11), the heating box inlet control valve (15), the heating coil (14), and the heating box outlet control valve (20). The heating box insulation layer (18) is used to keep the heating box (17) warm.

[0023] Figure 3 In the example shown: the computer control system completes the amplification of the signals of temperature sensor 1 (3), temperature sensor 2 (4), and temperature sensor 3 (16) through the signal amplification circuit, converts the signals into digital signals by the 8-channel analog-to-digital converter, and reads the signals by the processor STC89C516. After the calculation, the crystallization point and purity value are displayed on a 128*64-bit liquid crystal display. The processor STC89C516 outputs signals to drive the feed control valve (5), the discharge control valve (9), the cooling gas control valve (13), the heating box inlet control valve (15), the heating box outlet control valve (20), and the stirring motor (8) to operate according to the detection process. The computer control system is equipped with an AT24C02 data storage module to store the measurement data. The four-digit key is directly recognized and responded by the processor, and the measurement value is remotely transmitted through a 4~20mA standard signal.

[0024] Application Example 1 By measuring a group of p-nitrochlorobenzene crystallization point is 82.4 ℃, according to the regression curve y = 1.1172x + 7.444, where y is the p-nitrochlorobenzene purity, x is the p-nitrochlorobenzene crystallization point temperature, the sample purity is calculated to be 99.50%. The sample purity is 99.51% through chemical analysis, and the error between the measured value and the analyzed value meets the measurement requirements.

[0025] Application Example 2 By measuring a group of p-nitrochlorobenzene crystallization point is 82.0 ℃, according to the regression curve y = 1.1172x + 7.444, where y is the p-nitrochlorobenzene purity, x is the p-nitrochlorobenzene crystallization point temperature, the sample purity is calculated to be 99.05%. The sample purity is 99.00% through chemical analysis, and the error between the measured value and the analyzed value meets the measurement requirements.

[0026] Application Example 3 By measuring a group of p-nitrochlorobenzene crystallization point is 81.5 ℃, according to the regression curve y = 1.1172x + 7.444, where y is the p-nitrochlorobenzene purity, x is the p-nitrochlorobenzene crystallization point temperature, the sample purity is calculated to be 99.50%. The sample purity is 99.48% through chemical analysis, and the error between the measured value and the analyzed value meets the measurement requirements.

[0027] The matters not described in this embodiment are well-known technologies in the art.

[0028] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the field to which the invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0029] The above embodiments are only for explaining the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the present invention. The above embodiments of the present invention are described in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the field without departing from the purpose of the present invention.

Claims

1. An instrument for online detection of the purity of p-nitrochlorobenzene, characterized in that It includes a measuring system, a temperature control system, and a computer control system; the measuring system includes a measuring pool, the measuring pool is wrapped with a temperature control coil, a stirring device is arranged inside, temperature sensors are arranged on the outer wall and the center, and the measuring pool is provided with inlet and outlet pipelines and corresponding control valves; the temperature control system includes a heating box and a cold air inlet pipe respectively connected to an air source, a heating coil, an electric heater and a temperature sensor are arranged in the heating box, an inlet valve and an outlet valve are arranged at both ends of the heating coil, which are respectively connected to the air source and the temperature control coil, and a cold air inlet pipe is provided with a cold air inlet valve connected to the temperature control coil; the computer control system includes a single-chip computer system, a multi-channel temperature sensor signal amplification circuit and an analog-to-digital conversion circuit, a valve and stirring control circuit, a parameter storage module and a standard signal output module.

2. The apparatus according to claim 1, characterized in that The measurement system includes 2 temperature sensors, and the temperature control system includes 1 temperature sensor.

3. The apparatus according to claim 2, characterized in that The temperature sensors are all PT1000 temperature sensors.

4. The apparatus according to claim 1, characterized in that The measuring cell and the heating box are both provided with a heat-insulating layer.

5. The apparatus according to claim 1, characterized in that The computer control system includes a liquid crystal display screen and independent buttons.

6. The apparatus according to claim 1, characterized in that The data storage module is AT24C02, which is remotely transmitted through a 4~20mA standard signal output circuit.

7. A method for online detection of the purity of p-nitrochlorobenzene using the instrument according to any one of claims 1 to 6, characterized in that the instrument, under the control of a computer control system, introduces a p-nitrochlorobenzene solution to be tested into a measuring system, realizes a cooling crystallization process through cooling air introduced by a temperature control system, collects temperature signals through a temperature sensor signal amplification circuit and an analog-to-digital conversion circuit, calculates the crystallization point temperature of p-nitrochlorobenzene, and then uses a series of standard p-nitrochlorobenzene solutions of different purities to make a regression curve of the p-nitrochlorobenzene purity and the crystallization point temperature according to an external standard method, and then compares the regression curve with the crystallization point temperature value to obtain the purity corresponding to the p-nitrochlorobenzene solution to be tested.

8. The method according to claim 7, characterized in that The specific steps include: (1) Under the control of the computer system, the measuring system follows the workflow set by the analyzer. Step 1: open the feed control valve and close the discharge control valve at the same time. The p-nitrochlorobenzene solution to be measured flows into the measuring cell through the feed pipeline. After the p-nitrochlorobenzene solution fills the measuring cell, the feed control valve is closed. Step 2: introduce air from the temperature control system through the temperature control coil wrapped around the measuring cell to cool the measuring cell. Under the control of the computer system, start the stirring motor to ensure that the temperature of the solution in the measuring cell drops evenly until the crystallization point. Step 3: the computer control system detects and records the temperature data of the p-nitrochlorobenzene solution during the cooling-heating-constant temperature process through the temperature sensor during the measurement process. After optimization, the crystallization point of the p-nitrochlorobenzene solution to be measured is obtained. Step 4: after the measurement is completed, open the discharge control valve. The temperature control coil introduces hot gas from the temperature control system to the measuring cell and the crystallized p-nitrochlorobenzene in the measuring cell to heat and melt it to a liquid state. The molten p-nitrochlorobenzene solution flows out of the analyzer through the discharge control valve and the discharge pipeline. (2) After the instrument is powered on, the electric heater is first used to heat the heating box. The temperature sensor detects the real-time temperature of the heating box. The computer controls the output power of the electric heater to control the temperature of the heating box to the set value. During the cooling and crystallization process of the measuring system, under the control of the computer system, the heating box inlet control valve and the heating box outlet control valve are closed, the cooling gas control valve is opened, and the gas source gas is sent to the measuring system temperature control coil through the gas source pipe and the cooling gas pipe to cool the measuring pool. During the heating and melting process of the measuring system, the cooling gas control valve is closed, the heating box inlet control valve and the heating box outlet control valve are opened, and the gas source gas is fully heated through the gas source pipe and the heating tube in the heating box and then sent to the measuring system temperature control coil to melt the crystallized and solidified p-nitrochlorobenzene in the measuring pool. (3) After the instrument is powered on, the temperature value of the electric heating box is detected by the temperature sensor of the electric heating box. After comparing it with the set temperature, the output of the electric heater is controlled to keep the temperature of the electric heating box constant at the set temperature. After the temperature of the electric heating box is constant, the computer system controls the opening of the feed control valve and the closing of the discharge control valve to introduce the test solution into the measuring cell. After the test solution is introduced into the measuring cell, the feed control valve is closed and the cooling air control valve is opened. The cooling air cools the measuring cell through the temperature control coil. The stirring motor is turned on to stir the solution in the measuring cell to evenly cool it down. The computer system reads the temperature value of the solution during the cooling and crystallization process to obtain the crystallization point temperature, and calculates the purity through a mathematical model; after completing the crystallization point temperature measurement, the computer system controls the opening of the discharge control valve, the heating box inlet control valve, and the heating box outlet control valve, and introduces the heating gas into the temperature control coil to heat the measuring cell, and heats the measuring cell to above the crystallization point of the solution, so that the crystals in the measuring cell are fully melted and then flow out of the measuring cell; (4) Online purity detection: According to the external standard method, a series of standard p-nitrochlorobenzene solutions with different purities are used to draw a regression curve between the p-nitrochlorobenzene purity and the crystallization point temperature. The crystallization point temperature and the purity corresponding to the p-nitrochlorobenzene solution to be tested are further calculated and displayed.

9. The method according to claim 8, characterized in that The corresponding purity is obtained by measuring the crystallization point temperature with the aid of a regression curve. In the range of 0-102°C, the regression curve of the crystallization point temperature and purity of p-nitrochlorobenzene is y=1.1172x+7.444, where y is the purity of p-nitrochlorobenzene and x is the crystallization point temperature of p-nitrochlorobenzene.

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