Numerical method for predicting pellet drying process in grate blast drying section

Abstract

The invention discloses a numerical calculation method for predicting the pellet drying process of a grate blast drying section, which comprises the following steps: (1) establishing a two-dimensionalunsteady mathematical model of the pellet layer heat coupling process of the grate blast drying section; One-dimensional unsteady mathematical model of heat transfer in single pellet considering steam condensation as an important process of moisture transfer; (2) In order to improve the calculation speed, the drying process of grate blast drying section is simplified and assumed reasonably; (3) establishing mathematical model, including single pellet drying mathematical model, pellet bed drying mathematical model and so on; (4) calculating a model, according to the mathematical model, determining parameters of heat and mass transfer, geometry structure and the like, and simulating changes of drying process under different drying processes and control parameters of the grate blast drying section; (5) performing model verification, comparing with the actual pellet drying test results, to determine the value of empirical coefficients; (6) Simulation and optimization, adjusting the control and process parameters in the actual drying process, optimizing the pellet drying process.

Description

technical field [0001] The invention relates to the technical field of pellet sintering technology in iron and steel smelting, in particular to a numerical calculation method for predicting the drying process of pellets in the blast drying section of a grate machine. Background technique [0002] Grate machine is one of the key equipment for producing pelletized metallurgical materials, mainly used for drying and preheating green (wet) pellets from pelletizer. It distributes the raw (wet) pellets on the grate plate of the grate bed of the grate machine running at a slow speed through the distributing machine, and blasts the raw (wet) pellets by using the waste heat of the ring cooler and the hot air discharged from the rotary kiln. Drying, air drying and preheating oxidation, and after reaching sufficient compressive strength, it is directly sent to the rotary kiln for roasting to obtain pellets with reliable quality. [0003] The grate machine is composed of blast drying s...

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Problems solved by technology

Young et al. (Ironmaking&Steelmaking, 1979) established a mathematical model for the drying and preheating of pellets in the grate-rotary kiln-circular cooler, and calculated and analyzed the factors affecting the convective heat transfer of the pellets, but the author did not analyze the mathematical model In-depth analysis; Pan Shujing et al. (Steel Research, 2012) considered the mutual coupling effect among mass, energy and momentum in the pellet layer for the drying process of pellets in the blast drying section, and established the drying process The mathematical model of the multi-field coupling transfer process inside the pellet layer does not consider the internal heat conduction of the pellets, and does not study the entire drying process of the pellets; for the condensation of water vapor in the pellet layer, Cumming et al. (Ironmak.Steelmak., 1990 ) thinks that once the gas reaches saturation, water vapor begins to condense, but it ignores the mass transfer process; Dash et al. (Ironmaking steelmaking, 1978) believe that the condensation rate of water vapor is proportional to the difference between the gas humidity and the gas saturation humidity, and the model has certain experience

For the evaporation process of water in pellets, Patisson et al. (Metallurgical Transactions B, 1990) found that the evaporation rate of water in pellets consists of a constant speed section and a slowing speed section; Ljung et al. (SIMULATION, 2006) considered the pellet material layer as For porous media, the temperature distribution of the pellets was calculated by taking the porosity of the material layer into account, but it ignored the water evaporation of the pellets, and the parameters used were based on rough approximations, so there were large errors in the results; Tsukerman et al. (International ...

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