Coal blending in coal preparation plant

One of the preparation processes of coking coal. Important preparation process of coal before coking or carbonization. In other words, in order to produce coke that meets the quality requirements, different brands of coking coal are matched in an appropriate proportion. There are many kinds of coking coal. The application of coal blending technology can not only ensure the quality of coke, but also make rational use of coal resources, save high-quality coking coal and expand coking coal resources. Coal blending technology involves many technical characteristics of coal, coking characteristics, coordination characteristics of ash, sulfur and volatile matter, and coking mechanism of coal. For a long time, coal blending test has been an indispensable technical procedure for selecting coal blending scheme and verifying coke quality. There are two methods of coal blending: coal blending in coal blending tank and coal blending in open-air coal blending plant. Brief introduction of coal blending theory: At present, coking coal resources are scarce in the world. With the enlargement of blast furnace, the requirements for coke quality and stability are getting higher and higher, while there are fewer and fewer strong caking coals in coking coal resources, which is particularly prominent in China. Considering the economic benefits and reality, coking plants at home and abroad are committed to the study of coal blending scheme. Although the scheme is ever-changing, the principle of coal blending is nothing more than the principle of colloid layer overlap, interchangeability and carbonization. The principle of 1 colloid layer overlap requires that the colloid softening interval and temperature interval of various single coals in coal blending can overlap well, so that the blended coals can be in a plastic state in a larger temperature range during coking, thus improving the bonding process and ensuring the uniform structure of coke. The typical method is "J method" coal blending technology. "J-method" coal blending technology is a new technology to determine various optimal (practical) coal blending schemes quickly, accurately, simply, economically and randomly. Based on the "determination method of coal binding force" and the uniform change law of coal and coke, the strength of coke is accurately predicted, and the coal quality is evaluated and the "dominant coal" is determined according to Jb-Vdaf "meter" coal blending diagram and its principle. The quality of coke depends on the content of active and inert components in coking coal and the operating conditions of coking. The metamorphic degree of a single coal determines the quality of its active components, and the maximum reflectance of vitrinite average group is the best index to reflect the metamorphic degree of a single coal. At present, coal blending is guided by coal petrology, and many coking plants have their own coal blending schemes, but generally three parameters of vitrinite average random reflectance, reflectance histogram and mirror inertia ratio are used as coal petrology coal blending parameters. According to the principle of interchangeability coal blending, when coal blending has strong cohesiveness, adding a certain amount of coke powder or anthracite is beneficial to improve coke quality. It is technically feasible to add 3% ~ 5% coke powder instead of lean coal for coking, but it is very important to ensure coke quality without adding binder under the same coal quality. 3 *** carbonization principle: adding non-coal binder to coal for carbonization is called * * * carbonization. * * * The study of carbonization provides a theoretical basis for selecting a suitable binder for coking low metamorphic weak caking coal, and also provides the possibility for adding organic residue, plastics, rubber, asphalt, etc. Carbonized coal has made great contributions to solving the current world environmental pollution problem. Foreign Colin Company pyrolyzes waste plastics and coal tar pitch at 400℃, and collects pyrolytic oil and gas products. The residue obtained from the reaction can be coked with weakly caking coal to improve its coking performance. The research work in Ukraine is to use blended coal to coke with plastic fat waste. Because the organic matter with aromatic structure has a good influence on the coking performance of blended coal, the strength of the obtained coke is improved and valuable chemical products are obtained. Li Baoqing of Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences used 10g fixed bed reactor to study the coking characteristics of waste plastics and coal. The experimental results show that when the amount of waste plastics is less than 5%, the yield of coal gas and tar increases, and the aliphatic hydrocarbons and methylated aromatic compounds in tar increase obviously, while the properties of semi-coke are basically unaffected. It is considered that the coking technology of waste plastics and coal is feasible. The composition of several asphalts and Chongqing coking residue was analyzed by corbett method. The results show that vacuum residue and propane deasphalting have high saturated hydrocarbon content and low asphaltene content, so their performance as modifiers is poor. Thermal cracking residue and ethylene tar have higher aromatic hydrocarbon and asphalt content and lower QI content, so they have better performance as modifiers. Coal tar pitch has high aromatic properties, so the solvent performance is good, but the QI content is high, which is not conducive to the development of mesophase in tar process. Prediction of coke quality 1 Prediction of ash and sulfur content of coke Under the condition of stable production, there is a good linear relationship between ash and sulfur content of coke and ash and sulfur content of blended coal. The general prediction model is: Y=aX+b The least square method in mathematical statistics is used to determine the regression coefficients A and B in the equation, so as to control the ash and sulfur content of blended coal, adjust the proportion of single coal, and provide reference for selecting coal sources. 2 Prediction of cold strength of coke (M40 and M 10) The indexes used for cold strength prediction of coke are generally coalification index and caking index. Prediction methods can be basically divided into three categories: the first category takes technical indicators of coal as parameters, such as Vdaf and C.I. MF。 G。 The combination of y generally adopts the combination of Vdaf and G, because these two factors play a decisive role in coke quality. Generally, Vdaf is 28%~32%, g is 88%~72% or y is14 ~18 mm. When the volatile matter of coal blending increases, the crack of coke increases and the strength decreases, especially in M40. When the volatile matter of coal blending changes 1%, M40 changes by 2.0% and M 10 changes by 0.2%. The second type is to predict with coal and rock indexes as parameters; In the third category, the preparation of coking coal and coking process conditions are also considered while considering the blended coal index. 3 Prediction method of thermal properties The thermal properties of coke are usually expressed by reactivity index (CRI) and strength after reaction (CSR). There are three kinds of prediction methods: (1) coke cold index prediction methods: these methods are mainly based on coke cold index, such as coke strength (M40, M 10), porosity and pore distribution, optical structure, etc. (2) Index prediction method of blended coal: This method predicts blended coal according to its reflectivity, cohesiveness, inert content and other properties, such as ash, volatile matter and ash composition. Most forecasting models are limited to the statistical analysis of production practice data or experimental data, and their application scope is also limited to their respective coking coals. (3) Prediction method of single coal properties: Feng Anzu and others studied the relationship between coalification index (volatile matter, vitrinite maximum reflectivity), caking index, ash composition and coke thermal properties of different single coals. It is considered that the volatile matter of coal is closely related to the reactivity and post-reaction strength of coke. The volatile fraction is 22%~26%, and Rmax is about 1. 1~ 1.2. Single coke has the best thermal performance. There are basically the same regularity between the caking index (G), the thickness of colloidal layer (Y), the total expansion (a+b) and the Giemsky fluidity (lgMF) of single coal and the thermal reactivity and post-reaction strength of coke. The application of artificial intelligence and expert system, such as Baosteel coal blending expert system, consists of coal resource information system, single coal information system, coal blending information system, coke quality prediction system and production control system. Including the forward reasoning process from single coal to blended coal and from blended coal to coke and the corresponding backward reasoning process, each process contains deterministic relations and the experience of experts in this field. The expert coal blending system in this study is mainly composed of optimization control subsystem, information management subsystem and fault diagnosis subsystem. The optimization control subsystem mainly completes three functions: coke quality prediction, coal blending ratio calculation and expert self-learning. Because there is not a simple linear relationship between blended coal and coal quality characteristics of single coal, but a complex nonlinear relationship, neural network is used to establish coke quality model. It is necessary to calculate the coal blending ratio by using the conventional model. Self-learning is to automatically modify the mathematical model or form a new regular model according to the actual values detected and various intermediate results calculated. The information management subsystem includes the property parameters of single coal, coal blending and coke quality objectives, coal blending process design parameters, system optimization parameters, mathematical model calculation parameters and so on. The fault diagnosis subsystem consists of five modules: lock control, real-time monitoring, fault diagnosis and alarm processing, parameter adjustment and remote monitoring. The goal is to enable the system to query, extract, combine, compare and print various indicators at will, and draw a trend chart. Files can be exchanged and transmitted with different permissions, and there are interfaces such as online inquiry for other departments to connect. Suggestions on Developing Coal Blending Coking Technology (1) Developing coal blending coking technology has always been the main measure to rationally utilize coking coal resources and improve coke quality in China. However, there is no new breakthrough in the research and development of coal blending technology, especially no great progress in production, which is one of the main crux of the low quality of coke in China. The development of coal blending technology involves many technologies and requires certain conditions. At present, all coking plants, research institutes and design institutes in China do not have the ability to independently develop coal blending technology. Therefore, it is necessary to carry out unified planning and coordination, combine scientific research, design and production, concentrate a group of outstanding scientific and technological personnel, and obtain sufficient funds. Only after several years of hard work can we hope to succeed. (2) Another main measure to improve coke quality is to adopt coal pretreatment technology. Except for some enterprises such as Baosteel, most coking plants in China do not adopt coal pretreatment technology, which is one of the main reasons for the generally low coke strength in China. Various coal pretreatment processes are suitable for different coking coals, and the required conditions are also different. Therefore, according to the characteristics and conditions of coking coals in our factory, the appropriate coal pretreatment process should be selected through experiments. A large number of experimental results show that coking plants in East China, Northeast China and North China can adopt pre-treatment technologies such as tamping, briquette blending, coal drying (humidity control) and pneumatic selective crushing. These technologies have been industrialized in the world. While supporting individual qualified enterprises to introduce these technologies, it is necessary to organize scientific research, design and production units to digest them together and further research and develop them into technologies that can be popularized and applied to other enterprises. Use of coal blending tool software: The traditional coal blending calculation is mainly done manually. With the development of computer technology and software technology, people write fixed coal blending calculation methods into software, and use computer technology to realize coal blending calculation and analysis conveniently and quickly. The main uses are: 1 to reduce the complexity of manual calculation; 2. The whole coal blending scheme provides a reference for optimizing the coal blending scheme and expanding the idea of manual coal blending, thus effectively reducing the cost. Mainstream software includes Shenglong coal blending quantitative analysis system and Shenglong coal blending system software.