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1. Characteristics of gas composition analysis and problems to be solved In the non-ferrous smelting industry, the most important and most used is the analysis and measurement of gas components. According to the different working principle of the gas composition analyzer, it can be roughly divided into two kinds of measurement methods: The first is the direct measurement method, that is, the probe is directly installed in the process gas pipeline (measurement, transmission device in the probe), such as infrared, ultraviolet And laser gas analyzer, etc.; First, the indirect (sampling) measurement method, that is, the process gas out of dust and other processing, sent to the analysis instrument for measurement (measurement, transmission device in the instrument).
For instruments with indirect analysis and measurement, due to the bad gas conditions such as high temperature, high dust, high moisture, negative pressure, and corrosiveness during the smelting process, the biggest difficulty is how to obtain sample gas suitable for the instrument test conditions. . The only method is to use a pretreatment device to process the sample gas. Due to the fact that some of the imported analyzers have become more mature in their technology, they can meet the needs of industrial analysis. Therefore, selecting (manufacturing) a preconditioner with stable and reliable performance that can adapt to the process conditions is the key to solving the problem of the use of analytical instruments. For instruments using direct analysis and measurement, because it adopts the latest optical technology, it can measure without affecting the state of the measured gas, and has the advantages of accurate measurement and rapid response. In particular, it eliminates the need for pre-treatment devices and eliminates the need for investment in automatic purge devices, which offers significant advantages over traditional thermal conductivity gas analyzers. However, there are also some problems: 1) The price is expensive; 2) It is not suitable for gases with large dust particle size; 3) The gas that is insensitive to working light waves cannot do anything.
2. Application of some on-line analysis instruments Shaoguan smelter is an enterprise that adopts the closed blast furnace (ISP) process for lead-zinc smelting. It is used in the process of material sintering and granulation, acid production, closed blast furnace smelting, gas production, and waste heat power generation. Many process analysis instruments, such as CO, CO2, SO2 gas analyzer, H2SO4 concentration meter and pH meter, infrared moisture meter, calorific value meter and so on. The application of some analyzers is described below.
2.1 OMM3000 infrared moisture analyzer is used to measure the moisture content of the sintering mixture. Because the humidity of the material has an important influence on the quality of the agglomerate, it is very important to use a moisture analyzer with high accuracy and stability to automatically control the moisture content of the material. The IRS-MO-III infrared moisture analyzer was used early in the plant and gradually changed to OMM3000 (replacement product of the former) in the past two years. The biggest advantage of this instrument is that it eliminates the secondary instrument and realizes the integration of measurement and change. It can be checked, calibrated, set, and diagnosed at any time with the PC connection, making the operation easier. The instrument itself has good performance, but due to poor site conditions (high temperature, high humidity, high corrosion), there are still many problems in the use process. For this reason, the author together with the manufacturer made the following improvements to the use of the analyzer: 1) Make a stainless steel protection box, use compressed air to isolate the field air and improve the corrosion resistance of the instrument; 2) Please increase the protection level of the instrument 3) Ask the manufacturer to change the optical path sleeve from hard to soft to avoid the impact of large materials on the instrument and the mounting bracket; 4) Use a new internal cooling structure to eradicate the oil and water in the cooling gas source to the optical device Damage; 5) Install a hood around the field instrument to avoid the effect of sunlight on the meter. Through the above improvements, the instrument's adaptability and usability have been improved.
2.2 Furnace gas composition analyzer The furnace gas composition produced by the blast furnace smelting process is very complex, mainly containing SO2, SO3, CO, CO2, H2, steam, dust, lead, zinc and steam, etc., in which CO, CO2, and H2 are measured. The important parameters of the reaction state of the material in the furnace, the process requires real-time measurement of CO, CO2 and H2. Due to the fact that the complete set of analytical systems that are not yet mature enough to be used under complex conditions employs a thermal conductivity gas analyzer from a domestic plant, only the contents of CO and CO2 are measured and analyzed, and the pretreatment unit is a self-made two-stage filter tank. . Owing to the large dust content of the furnace gas, the poor processing capacity of the filter device and the poor performance of the instrument itself, the analysis of the furnace gas composition has not been able to be used well, causing great inconvenience to the production. There are several mature analytical instruments (systems) in furnace gas analysis that are currently stepping up selection and inspection work to solve the problem of blast furnace gas analysis in the factory as soon as possible.
2.3873 pH Analyzer The plant used 10 sets of 873 pH meters from FOXBRO in the US in the acid production process to measure the pH of 93% and 98% H2SO4 chiller circulating water in order to detect the acid leakage accident of the equipment in time. The instrument is characterized by its stable performance, high precision and low maintenance. It is used successfully on 93% acid coolers. However, the use of 98% acid cooler is not ideal and the sensor is very easy to damage. After careful analysis and analysis of the conditions of use of the 93% acid cooler, it was determined that 98% of the acid cooler outlet circulating water temperature is too high, so that the sensor's glass electrode rupture, is the root cause of sensor damage. For this reason, a cooler designed for the sensor was installed in front of the sensor, completely solving the problem.
2.4 CW95digital calorimeter Using the UNION CW95 digital system in Germany to measure the calorific value of self-produced gas. The pretreatment device of this system cannot be said to be bad because it can be used in other industries such as steel and chemical industry. However, because of the poor quality of self-produced gas, there are many impurities such as water, tar, coal ash and so on, making the system's pretreatment device ineffective. Due to the harsh conditions of use of calorific value meter, the pretreatment part is often blocked and the filter core and valve are easily damaged, which leads to high maintenance costs (expensive parts are expensive) and large maintenance workload, which seriously affects the measurement and liquefaction of gas calorific value. Gas blending regulation. In response to this situation, a dedicated research team was established to tackle this issue. After careful analysis and repeated trials, the original treatment unit was improved in two ways: 1) An additional filter was added to the original pretreatment unit: the filter was divided into two layers. The lower floor is a washing room, equipped with two stainless steel plates drilled with pores, so as to minimize the formation of gas bubbles in the water to achieve a full washing effect, thereby removing most of the oil and dust impurities; the upper layer of glass fiber filter Is used to further remove impurities in the gas. The self-made filter also has an automatic flushing function, which can continuously bring the impurities in the washing room out of the tank, greatly prolonging the use period of the filter and reducing the maintenance amount. 2) After the instrument is compressed and treated with compressed air, it is sent to the calorific value meter bottom box to isolate the on-site air and ensure the quality of the combustion air. After improvement, the analysis system has been able to operate normally for a long time under the meticulous maintenance of maintenance personnel.
2.5MW31-1SO2 Concentration Analyzer This device is used to monitor the concentration of SO2 emitted by dust collection fumes. The analyzer uses ultraviolet light as the detection light source. The concentration of SO2 is measured by measuring the attenuation of the light through the measuring tube section. Since the sensor is plug-in mounted, the gas sample does not need to be pretreated, so the measurement is real-time, accurate, and the maintenance amount is small. After using it for a period of time, it was found that there are still two unsatisfactory points in the device: 1) The effect of purging the air unit is not good, the lens is easily dirty; 2) The probe is too bulky (more than 5kg) to give the reflector The cleanliness caused great inconvenience. Two measures were taken for the above situations: 1) Compressed air was introduced to replace the original purged air unit after further purification; 2) The installation method was changed to the extension type, so that the front end of the probe protruded from the process piping (the measurement section was still in process piping Inside) to facilitate the cleaning of reflective lenses. After the improvement, good results were achieved and basically maintenance-free was achieved.
3, analysis instrumentation (system) selection should pay attention to the problem Analysis instrument (system) selection is the key to successful application, improper selection will cause the instrument can not be used normally or increase the difficulty of maintenance. Many companies have encountered the situation that the instrument is not good or even impossible to use due to improper selection. Therefore, the following points should be noted when selecting the type:
(1) Whether the process conditions are consistent with the applicable conditions of the instrument The process must provide the most detailed characteristics of the measured object (taking the gas composition analysis as an example): composition, temperature, humidity, dust particle size, crystallization conditions and corrosivity In order to allow manufacturers to study the design and production process conditions to match and adapt to the analysis and measurement instruments and to focus on solving. If the object is not fully considered, unexpected situations may occur. The MW31-1 analyzer mentioned earlier was originally used to measure the SO2 concentration of flue gas emitted at the outlet of the tailing tower of an acid plant. However, due to insufficient attention to the (NH4)2SO4 crystals in the exhaust gas, the probe was installed after installation. Produce crystals and can not work, resulting in errors in selection.
(2) Processing capacity and reliability of pre-processing equipment The pre-processing part is an important part of the analysis system. Its importance is no less than the instrument itself, because more than 90% of the failures of the analysis instrument (system) occur in the pre-processing part. Good pre-processing equipment not only has strong processing capacity, but also has good reliability, otherwise it will greatly increase the cost of spare parts or maintenance workload.
(3) The advanced nature of instrumentation technology and the follow-up development and service capabilities of manufacturers. Analytical instruments that use advanced technologies are often introduced for certain defects or deficiencies of similar instruments. When selecting models, they can be considered. Large, powerful manufacturers or agencies are more assured in the analysis of instrument maintenance, maintenance and spare parts supply.
(4) It is undeniable that the imported instruments are selected as far as economic conditions permit, and the performance of imported analytical instruments is indeed better. Therefore, the analysis of the components in the important production process should be selected as far as possible imported analysis instruments, and the pretreatment device is best to use domestic products, because the pretreatment device of domestic manufacturers is more targeted, and can be designed according to the user's specific requirements and site conditions .
(5) Case Study Indispensable Analytical instruments (systems) of different manufacturers have their own advantages. Some pretreatment devices are very successful, some are good for sampling and analysis, but almost all parts of the manufacturers are the best. Therefore, by selecting one or two instruments (systems) and then visiting its users, the most realistic information can be obtained, which will contribute to the final shaping.
4. Concluding remarks From the above analysis we can see that most of the analytical instruments (systems) can be used well instead of buying them back. Even advanced, expensive imported analytical instruments often appear to be “satisfied with water and soilâ€. In addition to good selection and attention to the selection of the instrument suitable for its own process conditions, in the use of the process for the site conditions to properly improve the instrument and equipment, and strengthen the maintenance work, is the key to using online analytical instruments (systems).
Application of On-line Analytical Instruments in Non-ferrous Smelting Process
Analytical instrumentation is difficult to apply, and those who are engaged in automation instrumentation have a deep understanding. Especially in the non-ferrous smelting industry, the difficulties and problems faced in the process analysis are many: high temperature, high dust, high moisture, negative pressure and crystallization, corrosive and other bad gas conditions; poor pretreatment equipment; process, pretreatment Large delays caused by analyzers and other links; high requirements for protection against dust, splashes, corrosion, etc.; higher degree of automation and less maintenance workload. All of these have brought a lot of difficulties to the application of process component analysis and environmental monitoring and analysis instruments (systems).