Drax power plant operation 6: biomass pellet production

　　British Drax 6*660MW power plant biomass fuel power generation operation, introduces the relevant parts of power plant operation from multiple angles and multiple links. Section 5 introduces the tipper used for unloading in biomass fuel processing plants. This section introduces the production process of biomass pellet fuel.

　　Biomass fuels may seem trivial, but they are the key to biomass-coupled power generation in large coal-fired power plants, and also the key to power generation from coal to clean renewable energy. Biomass raw materials have been used as energy sources for tens of thousands of years. Although they have not been used for combustion power generation for a long time, the real realization of large-scale power generation applications in large-scale pulverized coal-fired power plants is after 2000. Biomass fuels are not only renewable and sustainable, but they are also very effective and successful when used for direct combustion in large coal-fired power plants.

　　The British Drax 6*660MW coal-fired power plant has completed the 100% biomass fuel conversion transformation of four 660MW coal-fired units. It is the world's largest biomass fuel power plant with an annual biomass fuel consumption of more than 7 million tons. From the perspective of fuel supply guarantee for power plant operations, Drax Power Plant not only purchased biomass fuels, but also invested in the construction of 3 biomass fuel processing plants in the United States, with a capacity of 2 525 thousand tons and 1 450,000 tons, totaling 150 With a production capacity of 10,000 tons, these three fuel processing plants will actually supply more than 1.4 million tons of biomass pellet fuel in 2019. Here is an introduction to the processing process of biomass raw materials from bulk to pellets at the biomass pellet processing plant in Mississippi. The workflow can be divided into the following 9 steps:

　　1, trucks transporting biomass bulk materials enter the factory

　　Biomass bulk materials are transported to the factory by truck, and are transported to 4 different locations according to the physical characteristics of the raw materials: bulk material storage yard, bulk material temporary storage yard, small material or saw foam storage yard, and follow-up directly Processing.

　　2, log peeling

　　The logs are sent to the debarker, which fixes the logs and beats them to remove the bark. After peeling, the bark is put aside and used as fuel for the dryer, which is used in subsequent processing.

　　3, large pieces of material broken

　　Logs or bulk biomass materials-low-value biomass raw materials from sustainably managed forests. These raw materials need to be broken into smaller pieces so that they can be crushed into fine materials needed to make particles . Inside the crusher, multiple blades rotate and cut large pieces of biomass material into small pieces about 10 mm long and 3 mm thick. The broken pieces are sent to the pile of wood chips, ready for screening.

　　4, screening and filtering small pieces

　　Small pieces of material may include sand, leftover bark, stones, and other wastes that affect particle production. These small pieces of material are passed through a sieving machine to screen out the waste, leaving only small pieces of biomass raw material that meet the required size.

　　5, drying

　　Before entering the pellet manufacturing process, the humidity of wood chips has strict requirements, usually around 12%. Too high or too low moisture will affect the quality of biomass pellets. Small pieces of biomass feedstock enter a large drum and are heated by hot air generated by a heater driven by the waste bark collected by the previous debarker. A small piece of biomass material is blown through the drum by a large fan, ready for the hammer mill.

　　6, biomass hammer mill

　　There is a rotating shaft in the hammer mill with a series of hammers. The small pieces are fed into a hammer mill and crushed into fine powder material for making granules.

　　7, making biomass pellets

　　The biomass powder crushed by the hammer mill is sent to the pelletizer. Inside, a rotating arm presses powdered raw materials through a grid with many small holes. The strong pressure heats the biomass powder raw material, helping it to bind together through the holes on the metal ring dye to form compressed biomass particles.

　　 8, cooling

　　The fresh temperature from the pellet machine is relatively high, and it is exposed to moisture. It needs to be placed for a period of time to cool down before being transported from the site. They are transferred to large storage silos at low temperatures so that the pellets can be cooled and hardened, ready for shipment.

　　9, stored in the processing plant

　　In-plant storage is the last stage before shipment. Specially designed and constructed storage domes are used to store finished biomass pellets, which are transported to the Mississippi River, Louisiana, and then across the Atlantic Ocean to England.

　　 The end of this section, the next section introduces the decision-making process of the Drax power plant from coal to biomass fuel.