Tao Lei 1, 2, Zheng added 1, Martyrdom 3Lvwen Long4
(1.School of Mechanical and Electronic Engineering, Nanjing Forestry University, Nanjing 210037, China; 2. Jiangsu Agricultural Machinery Experimental Station, Nanjing 210017, China; 3. School of Information and Engineering, Huzhou Teachers College, Huzhou 313000, China; 4. Taixing Dingli Technology Co., Ltd. Company, Taixing, Jiangsu 225400)
Abstract: Based on the systematic analysis of the characteristics and existing problems of curing technology of biomass molding equipment at home and abroad, the key technologies such as curing principle and process and curing process in biomass curing molding production line are put forward, and the automatic feeding system, Monitoring and compensation systems and joint control technology system for curing the development of key equipment development recommendations.
The molding fuel is a combination of advanced industrial technology and renewable resources. It is a new type of bio-energy, which can replace wood, coal, fuel, liquefied petroleum gas and so on. It can be widely used for heating, living stove, hot water boiler, Industrial boilers, biomass power generation, etc. In Germany, for the classification of legislation can not be used for the recycling of waste wood, usually as a fuel use, direct use of waste wood materials as fuel, which can be processed for the waste of wood fuel.
Biomass curing equipment is the key equipment for fuel molding. By converting low density, low calorific value and poor combustion performance of agroforestry waste (straw, branchwood, etc.) into high density, high calorific value, burning resistance and easy storage and transportation. Regeneration, cleaning, pollution-free biomass molding of fuel or feed.
Based on the systematic analysis of the characteristics of biomass curing technology at home and abroad, this paper summarizes the existing problems of biomass curing molding, and then puts forward some suggestions on the development of key technologies such as curing technology and the development of key equipment for curing To adapt to China's national conditions of biomass curing fuel molding key technology and equipment to promote the use of development, promote the molding of fuel projects to ease energy tensions.
Analysis on Characteristics of Fuel Molding Technology at Home and Abroad
Japan, the United States and some countries in Europe, biomass curing molding fuel equipment has been stereotypes, and the formation of industry, in the heating, heating, drying, power generation and other fields to promote the application of China's research started late, the research institutes from the molding mechanism, And other aspects of the study, and achieved fruitful results, with the increase in market demand, but also carried out the performance of the fuel combustion of the exploratory research.However, mainly to the laboratory simulation model for molding mechanism and product performance and other deep The main research.
1.1 forming mechanism research
Material characteristics such as material type, crushing particle size, moisture content and additives are the key factors that affect the curing molding. At the same time, the inherent characteristics of curing equipment such as molding temperature, working pressure, working speed or preheating are required to have the corresponding characteristics, Which can affect the mechanical properties such as molding density, strength, durability, elongation and porosity of the molded products, as well as the energy consumption of the molding.The Varun Pan-war and other studies indicate that the molding density is inversely proportional to the particle size, moisture content and forming speed , Is proportional to the molding pressure.
Razuan et al. Used hydraulic piston press molding to suppress palm kernel cake. The results show that molding pressure, temperature, moisture content and binder are the key factors influencing the density and tensile strength of molding. At the molding pressure of 64.38MPa, 80 ~ 100 ℃ and water content of 7.9% under the conditions of forming density of up to 1184 ~ 1226kg / m 3, Tensile strength of 930 ~ 1007kPa, add 1.0% to 2.0% caustic soda additives can increase the tensile strength, and starch additives are invalid. HasanYu-mak and other hydraulic molding equipment to carry out the crushed grass (length ≤ 10mm) 4 molding molds under the molding test, molding conditions are water content of 7% to 10%, pressure 15.7 ~ 31.4MPa and temperature 85 ~ 105 ℃. Chuen-Shii Chou, etc. pointed out that the hot forming temperature is the impact of molding block density and pressure Strength of the key factors, rice husk as an additive in the hot pressing process can promote the densification.Huang Mingquan mouth knock on the basis of the screw forming mechanism of the raw material moisture content, molding temperature, raw material types and screw assembly size of the biomass molding influences.
Yan Wengang and so on in the hydraulic drive piston mold forming test bed lawn pruning residue with different moisture content of different taper mold molding test, the study shows that: with the biomass feedstock moisture content increases, the temperature density of the molding block and compression trends are Is small and then become smaller and smaller.
As the curing process is more complex, high temperature, high pressure with physical and chemical changes, and subject to space constraints, can not directly observe the molding process.Therefore, the establishment of mathematical models and microscopic observation is also an effective research method.
Nalladurai Kaliyanl et al. Studied the relationship between elastic modulus, strength coefficient, strain hardening index, viscous coefficient, friction loss factor and molding pressure, particle size, water content and preheating temperature by establishing constitutive model. Sun Qing et al. , The use of AN-SYS software analysis proposed sub-packing compression can improve the durability of molded products, the use of slow compression and improve the softening of the material and other methods to prevent the molding cracks. Du Hongguang and other biomass molds to establish the friction heat analysis model The results show that the temperature of the inner surface of the mold reaches the lignin softening temperature after 60 min of working temperature, and the temperature is stable at 115 ~ 125 ℃. After controlling the raw material, mold material and structure and productivity, the temperature of the lignin softening point can be shortened , And the quality of molding was improved.Wang Liangkou et al. Used quaternary quadratic regression orthogonal rotation test and response surface analysis method, and the effects of molding pressure, heating temperature, water content and binder addition on rice hull forming were studied by SPSS and Matlab Influence order and optimal molding characteristics of block slack density.
Huo Li-li and so on using the micro-topography to observe the ring mode molding machine forming mechanism for the intermittent stratification.Tian Xiaoyu and other use of electronic stereoscopic microscope to observe the corn stalks after forming the combination of particles and micro-morphology, 60 ~ 90MPa, the material temperature is 75 ~ 100 ℃, the moisture content is 8% ~ 16%, and the mechanical properties of the molding block are better than that of the molding block. Wu Yunyu et al. The geometrical relationship between the positive pressure of the raw material and the bevel of the surface of the biomass particle is determined by the contact geometry model.
Study on Combustion Characteristics of Molding Fuel
Factors affecting the combustion characteristics (calorific value, emission and ash) of the fuel are mainly the physical characteristics of the straw, the forming density, the forming diameter, and the ventilation effect during the combustion process, etc. Varun Pan-war is used to press the hydraulic press Mango leaves, eucalyptus leaves, wheat straw and sawdust molding test and combustion characteristics test showed that these four kinds of molding fuel calorific value were higher than the Indian coal calorific value of 1/2, can be used to replace coal and wood. Chuen-Shii Chou, etc. It was found that the caloric value of the crushed rice straw was directly proportional to the rice husk content and the hot pressing temperature. Stefan and other recommended fuels were 900 kgf / cm 2Pressure under the pressure of the compression of 12.72MJ / kg (moisture content of 15%) and bending strength of up to 150kgf / cm 2Of the molding block A. A. Debdoubi and other studies have pointed out that the stem of Stem Staphylococcus aureus under the greater pressure in the densification can get a higher calorific value.
Ma Hongqin and other studies have shown that the volatilization rate of the initial combustion of the straw is accelerated with the increase of the temperature, but the combustion stability is worse. The increase of the ventilation can reduce the temperature in the furnace and the relative stability of the volatiles. The precipitation rate of the volatile fraction of the molded fuel has a certain inhibitory effect. The average burning rate in the initial stage of combustion increases with the increase of the forming diameter and the molding quality, but the precipitation rate of the volatile matter in the later stage of combustion is relatively stable. The combustion characteristics and pollutant emission characteristics of the biomass particulate fuels indicate that the volatiles content is inversely proportional to the moisture content, the ignition time required for the biomass particulate fuel, SO 2, NO xAnd other pollutants discharge quality concentration is much lower than the national standard, but there are some biomass particles of fuel ash content is too large, serious slagging and other issues.Wang Min and other use of boiling water test on the molding block and pine block combustion characteristics of the parameters Test analysis, the remaining pieces in addition to the evaporation rate of the remaining indicators are better than or equal to pine block.
Study on Storage Characteristics of Molded Fuel
The crushing characteristics, moisture content and working conditions of different materials have great influence on the storage performance of the molding fuel.But because the different curing equipment adapts to different material characteristics, when the moisture content of the pressed material exceeds the adaptation range of the curing machine, the material is not suitable Lucywamukonya and so on at 2O ℃ and 50 humidity conditions, tested after storage for 2 weeks after the formation of straw block moisture content and durability, sawdust and shavings forming The durability of the wheat straw is the worst and the expansion rate is the largest in the longitudinal direction, and the durability of the molding block of the sawdust is improved.
RNSingh in 40% to 85% of the environmental humidity conditions, pointed out that in high humidity environment, storage of biomass molding fuel will not produce any problems.K.erarattananoon and other studies that the formation of particles after the expansion, moisture content and bulk density, True proportion, should be based on the type of material to determine an optimal moisture content to meet the stable production of biomass particles, durability and the needs of the appropriate storage environment.
1.4 molding production process research
Zhang Baoliang introduced the structure, forming principle and application of HPB-I biomass molding machine, which adopts hydraulic drive reciprocating piston bidirectional extrusion molding mechanism, which is extruded through the punching rod at both ends of the double rod Material, in the external force, the biomass particles began to rearrange the position relationship, and the occurrence of mechanical deformation and plastic rheology; Finally, the role of the push rod, the biomass into a rod from the two ends of the sleeve in the extrusion, Become a given shape.
Hydraulically driven reciprocating piston sleeve Two-way extrusion molding mechanism can reduce the efficiency, work is smooth, the design is reasonable, novel structure; it for the development and utilization of straw-based biomass energy provides an effective way to reduce the direct burning of crops Straw caused by environmental pollution, with significant economic benefits and environmental benefits.
The effect of ring-mold compression ratio, raw material type and raw material moisture content on the density of granular fuel was studied by using BIO-C37 biomass particle molding machine. The effects of high density granular fuel on the production of low energy consumption were summarized. Conditions, it is concluded that under the condition of normal temperature, the biomass raw material is deformed in the form of intermeshing in the process of compression molding, and the particle layers are combined with each other in the form of mutual bonding.It is found that the cellulose content in the raw material determines The higher the cellulose content is, the easier the molding is.The raw material particle size and water content have obvious influence on the molding conditions. When the particle size is 1 ~ 5mm and the water content is 12% ~ 18%, the particle density maximum.
YAO Zong-lu and so on, adopt the principle of mold roll forming, and design a production line of biomass solid molding fuel and related equipment. The equipment adopts the raw material mixing pretreatment process of secondary crushing, continuous feeding and adjusting feeding, And the biomass solid molding fuel production line was established. It was pointed out that the productivity of the biomass solidification fuel production line was 17.3% higher than that of the single state, and the biomass solid forming fuel production line was established. The economic efficiency increased by 13.3%, the molding rate reached 98%, the bulk density and the particle density were also significantly higher than the stand-alone, but the test results did not give the most impact on the process line to promote the application of power consumption indicators.
Hou Zhendong and other experiments through the self-made straw curing molding equipment, indicating that the introduction of axial displacement, radial peak displacement, peak pressure and nominal stress and other concepts to measure the mechanical properties of the forming block is feasible.Studies found that the molding pressure, temperature and material moisture The effect of the rate on the slack density, deformation resistance and impermeability of the molded piece is remarkable. The molding mechanism of the corn stalk forming block with excellent performance and easy storage and transportation is when the pressure is 60 ~ 90MPa, the heating temperature is 75 ~ 100 ℃, the material moisture content is 8% ~ 12%, you can produce excellent performance and easy storage and transportation of the molding block.
Wolfgang Stelte studied the effect of particle length, mold temperature, biomass moisture content and particle size on the granulation pressure during the production of biomass fuel granulation.The results show that the granulation pressure increases with the increase of the granule. The results show that the increase of temperature leads to the decrease of granulation pressure, and the effect of granulation pressure on the water content is the same as that of the control. (Diameter from 0.5mm to 2.8mm) were tested. The results showed that the granulation pressure increased with the decrease of particle size, and the effect of granulation pressure on the particle density was determined. The results show that the granulation pressure at 200MPa or more only lead to a slight increase in particle density.
Analysis of the above studies show that: the key factors affecting the formation of biomass curing molding is the molding pressure, water content and material size; to improve the spindle speed and increase the diameter of the die hole is to improve equipment production capacity and reduce energy consumption of the main measures; the same molding pressure, The smaller the particle size, the greater the density of the fuel after molding, the better the molding effect.
Analysis of Problems in Biomass Molding Fuel Curing Equipment
At present, China's molding fuel processing to extensive type, low degree of automation and poor production stability. Operators exposed to dust, especially crushing links, poor working environment. 1t / h curing molding production line, for example, continuous production needs 2 the operator to feed, the use of or shovel will be crushed / chopped material continuously thrown into the conveyor.When the material moisture content is lower than the molding requirements, relying on the experience of the use of spray or direct spill the way for water compensation operations, water content So that the production process is unstable, the continuity is poor, the productivity is low, the energy consumption is high and the equipment life is short, and the maintenance cost is high. The average productivity is the same as that of the other Can only reach 60%.
Abroad in the curing technology is relatively mature, supporting the biomass material pre-treatment technology is also more perfect, but the price is high, and due to the surrounding biomass materials and their pre-treatment technology is also the existence of material for bulk material technology adaptability And other issues.
Key Technology of Molding and Its Research Suggestions
In view of the current technology is still confined to the curing molding machine forming mechanism research, and to laboratory simulation, and the actual production of large differences, and business owners are more concerned about the economic benefits of curing equipment, that is, production capacity and product quality, Lack of theoretical support, so the need for molding technology and molding technology and equipment to carry out a comprehensive study.
3.1 curing molding principle and process research
The principle of biomass curing is mainly composed of cold pressing and compact molding, hot pressing and compact molding and carbonization compact molding.Carbonization compacting is mainly used because of the complicated process and high energy consumption.There are less tight compression molding, Molding and punching compact molding, screw molding machine to solve the screw and forming sleeve wear serious mocking, short life of technical problems; piston / stamping molding is characterized by the requirements of raw material moisture content is small, to solve the molding fuel expansion, loose, or even Dangerous 'blasting' phenomenon and the former process of grinding power consumption and other issues.
The cold-press dense molding includes three kinds of structures: horizontal axis ring mold, vertical shaft ring mold and flat mold.High-level ring ring mold structure to solve the material easy to uneven distribution in the mold cavity, the lower part of the material and the upper part of the material caused by mold The uneven load and the pressure roller, the mold wear unevenness, the low productivity, the relative energy consumption and so on.The vertical shaft ring mold structure through the ring mold flat to solve the horizontal axis ring mold structure of the uneven distribution of materials, And the mold structure models become the mainstream market products.
Therefore, the actual production should strengthen the ring mold flat and flat die curing molding equipment curing molding principle and process research, for different material types, crushing characteristics, material moisture content and the corresponding spindle speed to determine the adaptability of curing equipment.
3.2 Analysis of curing process
Curing process is more complex, high temperature, high pressure accompanied by physical and chemical changes, and subject to space constraints, can not directly observe the molding process.For the current laboratory simulation models, computer software simulation, microscopic observation after forming the main way, The effects of material types, material size, moisture content, molding pressure and molding temperature on the molded products are very important, but there are still some differences in the actual production, but there are very different factors such as the actual production of granularity and moisture content , Molding pressure and temperature should not be measured and other factors.Therefore, it is necessary to carry out curing process analysis, for different raw materials, respectively, after crushing / chopping different particle size, different water content conditions, monitoring spindle speed, current and die hole temperature , And take the molding sample, measuring the density and the use of microscopic observation of the sample structure and other methods to analyze the actual production of the curing process.
4 Development and analysis of critical equipment for curing
The supply is an integral part of the process of curing equipment, which directly affects the automation, stability, reliability and efficiency of the equipment, as well as the safety of the work environment.Therefore, the need to develop automatic feeding system, and moisture monitoring and Compensation system and control system, etc. Figure 1 is a block diagram of the automation control system proposed in this paper.Through the automatic feed, water compensation and monitoring spindle speed (pressure roller speed) or current changes, adjust the feed speed, etc., to achieve curing molding equipment Of the automated production, reduce labor intensity, reduce production costs, to ensure stability, continuous production.
5 Conclusion
This paper analyzes the characteristics of biomass curing equipment and fuel molding technology at home and abroad, and some problems such as the production environment safety, the production automation and the quality of the products in the biomass control fuel curing production. At the analysis of the biomass fuel molding system engineering On the basis of the following recommendations:
1) In the actual production, the study of material type, crushing particle size, material moisture content and the corresponding spindle speed to determine the adaptability of curing equipment, biomass fuel curing molding principles and processes.
2) to develop for the biomass curing molding production line development of automatic feeding system, and water monitoring and compensation systems and joint control technology system.
3) gradually apply the system to the biomass curing molding production line, test the application before and after the application of curing equipment, stability, continuity, and the working environment and economic benefits.
