Investigation Of Sintering And Energy Storage Characteristics Of Particle Packed Bed

To cope with the shortage of traditional fossil energy and the aggravation of environmental pollution,China proposes to achieve carbon peak in 2030 and carbon neutral in 2060,which undoubtedly puts forward higher requirements for the green developments of all walks of life in China.In the iron and steel industry,sintering plants in China are faced with the problems of shortage of high-grade ore resources and high energy consumption.To respond to the changes of sintered raw materials,sintering plants must continue to optimize the production process to meet the development requirements of energy conservation and emission reduction in the iron and steel industry.Research on the effects of different granulation methods and different adhesion layer structures on the green bed properties and sintering characteristics can guide sintering production.In the energy and electric power industry,China’s solar thermal power generation industry is rapidly developing.Solar thermal power generation can be combined with a high-temperature heat storage system,which has unique development advantages among various renewable energy sources.Due to the lower construction and operation costs and wider operating temperature range,air-particle packed bed sensible heat storage technology has been favored by more and more scholars.Choosing low-cost solid materials that can meet the storage requirements is the key to researching packed bed energy storage.Based on the above background,this paper focused on particle packed beds and studied the permeability and sintering characteristics of sinter green beds and sensible heat storage characteristics of particle packed beds.Firstly,we conducted granulation and packing tests under a high proportion of magnetite concentrate replacement level and studied the effects of drying after high-moisture granulation on the granule characteristics and packed bed properties.The results show that the fine particles in the quasi-particles can be concentrated by drying after high-moisture granulation,and thus the liquid bridging force can be increased.Therefore,this granulation method can improve particle strength and bed stiffness,and finally improve bed permeability.When the moisture after granulation is excessive,a thick but weak adhesive layer will be formed inside the particles.The improvement of drying on the strength of the adhesive layer is weakened,which may weaken the adhesion between fine particles and core particles due to the loss of moisture,so the quasi-particles will fracture in subsequent collisions and lead to particle degradation.In this case,the final bed permeability depends on the combined effect of increasing the bed stiffness and decreasing the average particle size.Hydrated lime,as a binder,can promote greater cohesion between particles,significantly inhibit particle degradation,improve granulation efficiency,and further improve bed permeability.Secondly,using magnetite concentrate and hydrated lime as binders,the fuel particles are coated in different adhesive layers by pregranulation.The influence of coating structure on iron ore sintering was studied by pilot-scale sintering pot tests.The results showed that when charcoal replaced coke powder,the flame front speed increased considerably,and the bed temperature decreased significantly,which eventually led to sharp declines in the sinter yield and productivity.No matter what fuel is used,pregranulation can coat the fuel particles inside the quasi-particles,thus inhibiting the diffusion of oxygen into the particles and slowing down the reaction rate of the fuel particles.So this method can reduce the flame front speed and increase the peak bed temperature,thus improving the sinter quality.Because of the oxidative exothermic effect of magnetite concentrate,the bed temperature increases the most and the sinter quality is improved the most when magnetite concentrate is used as adhesive layer material.Mineralogy and microstructure analyses show that pregranulating fuel and magnetite concentrate can reduce the sinter porosity,promote the formation of calcium ferrite,and thus improve the sinter quality.Thirdly,considering the low cost,high-temperature resistance,high strength,non-toxic nature of sinter,and the background of waste heat utilization of sintering cooling bed,this paper innovatively proposes to use sintered ore particles as packed bed sensible heat energy storage material.The pilot-scale energy storage testbed was independently designed and built,and the airflow resistance characteristics and energy storage characteristics of sintered ore particles packed bed were experimentally studied.The study shows that the specific heat of the sinter is 0.86-0.98 J/(g·℃)in the range of200-380℃,which increases with temperature.The permeability index JPU,which is widely used in iron ore sintering,was first introduced into the field of energy storage to study the airflow resistance characteristics of particle packed beds,and its feasibility was verified.The parametric experimental study of energy storage tests shows that the sinter bed using smaller particles has better thermal stratification characteristics and a higher energy storage cycle efficiency because of the smaller bed voidage and larger specific surface area.Higher charging temperature leads to sharper thermoclines but has no significant effect on cycle efficiency.The larger air flow speeds up the energy storage cycle,conducive to improving the cycle efficiency.Fourthly,the above sinter particles were compared with two other common storage materials(alumina ball and rock),and the applicabilities of the three materials as packed bed storage materials were systematically evaluated.The volumetric heat capacity of the sinter at 200℃is 3253.7 k J/(m~3·K),which is between alumina and rock.Sinter and alumina have good thermal stability from 100℃to 1000℃,while rock has poor thermal stability above 600℃.Considering the heat storage properties and costs of the three materials,rock is the preferred material for heat storage applications below550℃,while sinter is a good alternative for ultra-high temperature storage above600℃.The experimental results of energy storage tests show that the bed heat capacity and voidage related to bulk density and specific heat are the key factors affecting the bed thermal behaviors,while the thermal conductivity has little effect.The thermocline characteristics of a packed bed are affected by the thermophysical properties of materials and the bed structure.Larger bed heat capacity and smaller bed voidage are favorable to the formation and maintenance of sharp thermoclines.Finally,the paper proposes to use the slags from a liquid slagging furnace of a coal-fired power plant as packed bed sensible heat energy storage material,and evaluates the applicabilities of three kinds of coal slags(Fukang coal slag,Fukang coal granulated slag,Hongshaquan coal granulated slag)as storage materials.At 380℃,the three materials’energy storage density per unit volume is 1037 MJ/m~3,986 MJ/m~3 and920 MJ/m~3,respectively,indicating good energy storage density.Fukang coal slag with a high crystallization degree,has superior thermal stability and durability,can be directly used for 1000℃ultra-high temperature energy storage.Its broad operating temperature range makes the new generation of 1000℃ultra-high temperature energy storage system more competitive and attractive.However,the two granulated slags have low crystallization degrees and need to be treated at high temperatures to improve their thermal stabilities and durabilities before being used as energy storage materials.