Packing Gradation And Characteristics Of Coal Water Slurry From Low Rank Coal

The preparation of coal water slurry(CWS)is a very important technology for the production of Syngas by gasification in modern coal chemical industry.The problems in the practical production of low-rank coal-water slurry include the selection of coal species,the selection of additives and the lack of theoretical support for large-scale coal gasification preparation section.The main work is as follows:(1)Study on the mechanism of low-rank coal-water slurry(CWS)and additivesThrough selecting more than 10 kinds of coal in Ningdong-Yulin-Erdos area,a systematic analysis is made on the mechanism of coal-water-slurry(CWS)additive,the effects of coal-water interfacial tension,coal-water contact angle,coal molecular structure and additive composition on the consistency,viscosity and particle size of coal-water slurry.The process of additive screening based on coal quality and additive characteristic parameters from micro to macro was established.Combined with the actual production of coal water slurry industry,the system has been established from the 100-gram class to the 50-kilogram class,the experimental systems of laboratory dry-test evaluation,wet-test evaluation,wet-test amplification evaluation and mode production evaluation are designed for coal screening and additive screening.A new screening method of industrial CWS additives based on weight analysis was established.Through the feedback to many users of additives,it fit for the actual requirements of industry.The basic process is as follows:By studying the adaptation of different types of additives to coal varieties in Ningxia,Shaanxi,Inner Mongolia and Xinjiang,from the surface adsorption and intermolecular force transfer of coal-water-agent ternary component,etc.a screening method of additives for low-rank coal water slurry(CWS)based on molecular weight,pH value,Critical micelle concentration and intrinsic viscosity of additives was developed.The relative molecular mass,molecular structure and critical micelle concentration of Mu,GNAI and NDF additives were determined by viscometer,FTIR and conductivity meter,respectively.Based on the above determination and analysis,the limiting adsorption capacity and surface tension of the additive and coal were determined and calculated with the ultraviolet-visible photometer and the surface contact angle meter,pH meter.According to the experiment of wet preparation,the screening process of additives for low rank coal preparation was preliminarily established.(2)Study on particle packing gradation and probability algorithm of coal water slurry in wet preparationParticle gradation is the key technology of preparation of coal water slurry.Focusing on the practical problems of larger particle diameter and wider particle distribution in wet preparation of gasification CWS.Based on the fact that the concentration of coal slurry is difficult to predict in the preparation of coal water slurry for gasification under large industrial conditions.An innovative packing model based on multi-void distribution of particles is proposed.The key point of this work is the idea of cutting the coal particle accumulation from three dimensions to two dimensions based on the geometric phase relation of the particle accumulation.The probability algorithm of multi-component particle packing void is constructed by investigating the distribution and occurrence probability of particle packing void,and the stable and unstable state of particle packing are obtained by means of ?PVT,?PST,EPVQ and ?PSQ to evaluate the particle packing density indirectly and Zv is used as the key factor to calculate the particle packing density directly.The basic approach is to use the law of Cosines,Heron formula and Bretschneider formula,the void areas between stable three-particle packing and unstable four-particle packing are calculated respectively.And the probability distribution of packing gradation is derived,the void area and accumulative void areas in different packing gradations were calculated.The study provides a new perspective for understanding the optimization of CWS preparation process and a feasible way for the calculation and analysis of the packing density of infinitely many particles in other fields.The fitting result of this method is consistent with that of the international classical method,and it is better than the international method for the calculation of binary mixture system.(3)Study on steel rod packing gradation and probability algorithm of coal water slurry in wet preparationBased on the actual production of industrial wet CWS and inspired by the model of particle packing gradation,the stable three-steel rod packing gradation and unstable four-steel rod packing gradation were constructed.The void area distribution and probability calculation were carried out,a new evaluation method with the void area index(Smax,Smin)and D was established.Based on the void distribution and probability analysis of steel rod packing gradation,the important function of this method is to establish stable three-steel rod packing gradation and unstable four-steel rod packing gradation,the distribution and size of packing void of steel rods under different packing conditions were quantitatively calculated by using probability analysis,triangle angle relation,Heron formula and Bretschneider formula.By calculating the equivalent diameter De of steel rod packing void,the triangle area Smin and the quadrilateral area Smax of steel rod packing,the probability of void distribution P to build up a evaluation index.On this basis,the CWS particles are divided into coarse particles and fine particles according to the law of particle size distribution,and the packing probability distribution is analyzed,and the method of CWS particle size adjustment is proposed.The relationship between the packing gradation and sieving effect of rod mills is analyzed and discussed.In addition,the relationship between the ratio of probability distribution of void PL/Ps and the ratio of coarse to fine particles was evaluated.On this basis,by means of simulation calculation,simulation analysis and field test,the model algorithm of steel rod gradation,steel rod wear and steel rod adding for wet preparation of rod mill is established systematically,it provides a theoretical support for the preparation of coal water slurry by wet process.(4)Study on rheological mechanism of low-rank coal-water slurry in overflow processThe influence of feed coal size on the particle size distribution,viscosity and concentration of CWS is discussed by analyzing eight factories of CWS production.The relationship between the concentration of overflow coarse particles and viscosity is analyzed,and the relationship between viscosity and effective syngas conversion,CWS concentration and syngas concentration is discussed.This paper summarizes and compares the relationship between coal input and water input,the relationship between concentration and 200 mesh screening rate,the influence of coal input on equipment operation parameters,and the calculation and analysis of mill filling rate.The results show that it is one of the difficulties to effectively control the long-term stable coal slurry concentration and particle size distribution.It is necessary to comprehensively control the technological conditions such as steel rod packing,mill feeding amount and additive amount.The sieving rate of 200 mesh coal slurry particles is between 54%and 57%,which is helpful to the stable operation of coal slurry in the high concentration range.The function of coarse particles in slurry is that its less contact probability decreasing the frictions between particles so that decrease the viscosity of coal slurry.At the same time,the coarse coal particles in feed have the function of self grinding in the grinding process,which is conducive to improving the grinding efficiency and speeding up the production of fine particles.Coal water slurry with high concentration and low viscosity is beneficial to obtain high effective syngas conversion.The quantity of overflowed coarse particle is an important technical factor for CWS concentration control.(5)Study on wear and fracture mechanics of steel rod in overflow rod millThrough the comprehensive analysis of the operating conditions of overflow rod mill for wet preparation,using the principles of fluid mechanics and fracture mechanics,based on the impact of the rod mill on coal particles,the flow behavior of coal particles in the rod mill and the wear behavior of steel rods,the maximum impact force and the wear and fracture action of steel rods in different types of rod mills are analyzed and compared.The stress-strain behavior of steel rods in the process of coal particle fracture was simulated and analyzed by ANSYS.The flow behavior of particles with different packing clearance was simulated and analyzed by Fluent software.The wear and fracture behavior of steel rod was determined by ultrasonic testing,magnetic particle testing,fracture microstructure analysis,hardness analysis and microhardness analysis.Based on the principle of grinding and fracture matrix method,the mechanism of the effect of mill conditions on the formation of CWS particles in wet CWS preparation was studied.Based on the above research work,the interaction mechanism of coal-water-additive-grinding system in the process of coal-water slurry wet preparation for gasification was systematically studied.It provides an important theoretical support for the wet production of CWS in industrial scale.