Zhu Zhenhua, Wu Zhenghui
Abstract: The prospect of biomass pellet fuel, production technology, premise of forming, production equipment and biomass pellet fuel are introduced.
Stalks fire smoke prevention and control work is the fundamental way out of energy. Straw energy mainly through solidification and gasification 2 ways to achieve, such as the stalks and other biomass raw materials after thermoplastic extrusion molding, and to a certain density can be made Biomass pellet fuel.
Biomass pellet fuel refers to the crushed corn, wheat, cotton, rice, wheat and oil crops such as straw or sawdust, leaves and other agricultural and forestry waste added to the particle molding machine, the crushed material is pressed against the mold and die The resulting biomass pellet fuel can be used as fuel for pellet fuel cooking and heating, and also can be used as a biomass industrial boiler and the main fuel for thermal power generation to replace coal combustion. Fuel is easy to transport, easy to store and has the characteristics of high combustion efficiency and a new topic of "recycling the other half of agriculture." Promoting the use of biomass pellet fuel is a good project for developing a "low-carbon economy" City Construction 'national sustainable development experimental zone' to add brick.
1 biomass pellet fuel development prospects
From the policy perspective, "Renewable Energy Law of the People's Republic of China" clearly requires accelerating the development of biomass energy, biomass products can enjoy local government subsidies, tax relief.NDRC, Ministry of Agriculture in order to accelerate the comprehensive utilization of straw to achieve straw Resources, and Commercialization, Promote Resource Conservation, Environmental Protection and Farmers' Income. On February 9, 2009, the Guiding Opinions on Compiling Plan for Integrated Utilization of Straw was formulated. It was proposed that more than 80% of the comprehensive utilization of straw should be strived for by 2015 The use of large straw is an inevitable choice for agriculture and energy development.
From the perspective of raw materials, the annual output of crop straw in China reaches 700 million tons. There are a large number of kinds of agricultural and forestry wastes, which are widely distributed and widely distributed. However, the recycling rates are low and are not fully utilized, which not only results in the waste of resources but also causes environmental pollution , And even triggered a fire, threatening forest security, threatening transport security Changzhi City, the existing corn, wheat, millet and other food crops 22.67 million hm 2, With an annual output of about 1.55 million tons of straw, combined with a variety of agricultural and forestry waste conservative calculation of up to 3 million t, if 60% can be converted into pellet fuel, then equal to build an annual output of 1200000 t of coal mines.
From the characteristics of straw particulate fuel, there are the following aspects: ①Using the wastes (crop stalks, rice husks, peanut shells, corn cobs, sawdust, twigs, leaves and wood trim etc.) used in agriculture and forestry as raw materials, Environmental protection and energy saving, good safety, good for fire prevention. ② High density, long burning time. The straw is crushed and formed compactly, the volume of pellet fuel is reduced by 4 ~ 6 times, greatly prolonging the burning time of the straw. ③ Burning, storage and transportation are convenient. ④ fuel diameter is generally 4mm, 6mm, 8mm, length of 10 ~ 20mm, points less than 10%, the density of not less than 1100kg / m3, ash content of not more than 0.9%, calorific value of not less than 14,650,500.
From the application situation, foreign biomass solid fuels technology and equipment have matured, forming a complete industrial chain system, such as in South Korea, Japan, the government free to provide fuel for cooking, heating use. China's biomass solid fuels Industrialization of key technologies also become mature, biomass pellet fuel products in the Northeast and Shandong provinces are in full swing to promote the application.
From the use of view, biomass pellet fuel a wide range of applications, you can replace wood, liquefied petroleum gas, etc., are widely used in biomass straw power plants, enterprises boilers, biomass straw gasification station, household gasifier, European-style heating Fireplace and so on.
2 biomass pellet fuel production process
Biomass pellet fuel production process is: raw material recovery → crushing (powder length less than 5mm) → quenching and tempering (moisture content less than 15%) → press molding → output cooling and drying → packaging and transportation.
3 biomass pellet fuel production type
According to the structural characteristics, biomass pellet fuel production patterns can be divided into the roller, spiral, ring mode peace mode.
3.1 pairs of rollers
Roller-type working parts are a pair of pressing rolls with a large number of holes on the surface, and the relative movement of the two rollers during the working process squeezes the powder falling into the nest into granules, which has the disadvantage that the pressing time is short, Low density.
3.2 spiral
Screw-type structure and meat grinder similar to the squeeze screw propeller, compression chamber, die hole and cutting knife composition, the work squeeze the screw propeller to push the powder in the compression chamber forward, so that it through the template Hole into a cylindrical shape, followed by cutting knife cut into granular This structure is mostly used in the production of puffed feed, shortcomings spiral worm life is short.
3.3 ring mode
The working part of the ring mode is a porous thick-walled ring die. The inner cavity of the die is equipped with 2 to 3 pressure rollers, the pressure roller or the ring die rotates during work, the pressure roller drives the powder in the cavity out of the die hole, It is cut into granules by the cutter, the granulating quality is good, the unit structure is big, the cost is high, and it is mostly used for the pellet fuel processing plant of medium size and above.
3.4 flat mode
The flat mold is equipped with a pressure roller on the vertical shaft. The pressure roller is closely attached to the porous flat mold plate. When the pressure roller or the flat mold is rotated, the powder can be pressed out of the mold hole to form a columnar shape. Granule quality is better, the unit structure is small, low cost, can be used for small and medium sized pellet fuel processing plant.
Pellet fuel molding machine is the key technology is the feed and extrusion of materials between the cooperation, to 'eat' into the 'spit' drawn material can be fed is the premise of whether extrusion can be fed after molding is The key factors that influence the feeding and extrusion molding are the physical shape of the powder, the radius of the press roll, the feed scraper intermittent, the motor power, the die roll speed, the die stick gap, the material moisture content, the die hole shape, etc. Only these influences When the factors have reached a coordinated and unified, extrusion and forming can be synchronized.
4 biomass pellet molding premise
4.1 smash the raw material unit density as possible
The higher the unit density of crushed raw materials, the better the free-flowing property and the higher the granulated yield.The crop stalks are preferably crushed into granules by a crusher; the crushed raw material filaments crushed and processed by a kneading machine are more likely to be overhead, Feeding performance is poor, granulation yield is low.
4.2 material moisture content should be appropriate
Material moisture content is too high or too low, will affect the yield and quality of granulation.If the material is too high moisture, more than 20%, the quenching and tempering difficulties, easy to cause the material slipping between the ring mold wall and the pressure roller, resulting in If the moisture content is lower than 14%, the friction between the material and the machine will be fierce, the powder will be fined out, the granulation will be reduced, and the granulation will be reduced Output.General requirements before conditioning material moisture should be 15% to 18%.
5 biomass pellet fuel production equipment
Biomass fuel molding equipment selection principle is technologically advanced, affordable, high reliability, safety and durability, high process completeness, energy saving and environmental protection, easy maintenance economy, high production efficiency.Currently, the high reliability of the ring for the machine model With the flat mold machine, according to the individual's economic strength, straw resources and production scale selected.
5.1 large biomass pellet fuel production equipment
Covers an area of about 2000m 2, The complete sets of equipment required for the production of about 180,000 yuan, the host power of about 80kW, supporting equipment power of about 22kW, production capacity of about 1.5t / h, the annual conversion of straw raw materials 4000t. The equipment requires four staff members, ingredients, feeding , Host control, bagging 1. Production plant, product warehouse, office area can be replaced by a simple plant, 1 million yuan working capital can be put into operation.
5.2 small and medium biomass pellet fuel production equipment
Covers an area of about 200m 2, The required equipment for production is about 50 ~ 80,000 Yuan, the main engine power is about 7.5 ~ 15kW, the production capacity is 0.1 ~ 0.3t / h, and the annual biomass material can be transformed into 1000 ~ 3000t.The equipment needs 4 staffs, ingredients, Feeding, host control, bagging of 1. Production plant, product warehouse, office area can be replaced by a simple plant, 100,000 yuan working capital can be put into operation.
6 biomass pellet fuel use
The formed biomass pellet fuel also has good combustion performance similar to briquette, and has the advantages of small sulfur content, less ash content and less environmental pollution compared with coal Biomass pellet fuel Compared with firewood, moisture Low content, specific gravity and calorific value, which will help to improve the thermal efficiency of biomass pellet stove.
Therefore, biomass pellet fuel is widely used in biomass straw power plants, enterprises and institutions boilers, biomass straw gasification stations, household heating stoves for cooking, European-style heating fireplace, and then replace coal, to solve environmental pollution problems.
6.1 Household biomass gasifier
Use of household semi-gasifier for household cooking, heating single or dual use requirements of household biomass stove with stable performance, easy ignition, easy operation, safe and reliable, strong fuel adaptability, the furnace at reasonable prices, And have a service life of more than 3 years.The performance must reach high efficiency and low emission.The biomass fuel is burned directly in the furnace and is rationed with the gasification component called biomass semi gasifier Stoves secondary air effect is very obvious, one oxygen to increase the calorific value, the second is to further enhance the flue gas disturbance, so that combustion more fully.
Currently a lot of use is to make up the air, but also make up steam.The performance of stoves: cooking stove thermal efficiency is greater than 35%, things heating stove thermal efficiency greater than 60%, heating furnace thermal efficiency greater than 65%; soot emissions concentration less than 50g / m 3; Sulfur dioxide emissions concentration of less than 30mg / m 3; NOx emission concentration less than 150g / m 3; Carbon monoxide emissions concentration of less than 0.2%.
6.2 Biomass fireplace
The biomass fireplace is made from biomass pellet raw material, which adopts advanced control technology to achieve automatic ignition and automatic feeding. It has the advantages of energy conservation, environmental protection, cleanness, safety and convenience. It is ideal for home, office and public places The way of heating.
7 Conclusion
Development and utilization of straw pellet fuel provides an effective way for straw conversion.Particle biomass fuel is a new type of environmentally friendly clean renewable energy and is one of the main directions for the development and utilization of biomass and is in line with the current national industrial policy, The market space.
