Drax Power Plant Operation 4: Biomass Fuel Storage Warehouse

　  British Drax 6*660MW power plant biomass fuel power generation operation, introduced from multiple perspectives and multiple links. Section 3 introduces the biomass fuel transportation train, this section introduces the biomass fuel storage bin in the Drax power plant.

　　The Drax power plant has four white cylindrical storage silos at the bottom + conical storage silos at the top. The storage silo is 50 (cylindrical) + 15 meters (cone) high, with an internal diameter of 63 meters and a wall thickness of 0.35 meters. Each storage silo can hold 75,000 to 80,000 tons of biomass pellet fuel, and the plant can store up to 300,000 tons of fuel. Meet the fuel demand of 4 660MW biomass generating units for about 12 days.

　　 These biomass raw materials are a kind of renewable clean fuel, and the Drax power plant has also realized the upgrade of the production of clean and renewable energy by converting biomass fuel to replace coal.

　　The use of biomass raw materials for power generation has been realized in many countries, but large-scale use of biomass fuels for power generation faces some challenges different from coal power generation. Storing large amounts of biomass fuels in confined spaces will bring risks that must be managed around the clock. The key difficulty in storing these biomass fuels is their chemical volatility. These biomass fuels will release carbon monoxide (CO) under certain temperature conditions. In a confined space, this kind of CO will accumulate, and due to the extreme flammability of CO, it is necessary to adjust the atmosphere in the entire storage tank through a set of highly complex engineering solutions. As long as biomass fuels release more heat into the atmosphere than they naturally generate in a closed environment, there is no danger of burning.

　　A little biomass fuel in the bunker will not cause a fire, and a small pile will not, but when thousands of biomass particles pile up, the pressure increases, causing the biomass fuel to heat up. Gradually, the rate of temperature rise increases and exceeds the critical value of safety. If the oxygen supply in the silo can be removed or restricted, and the flammable CO emitted by the biomass fuel can be removed, the risk is greatly reduced. The challenge for the construction of the dome storage silo at the Drax power plant is to find a way to manage the temperature inside the silo. Neutral N2 nitrogen can do this, reducing the risk by automatically injecting nitrogen into the storage room. Although nitrogen is not a real inert gas, its activity is much smaller than CO and O2, which is a safer environment. In order to obtain a stable supply of N2 nitrogen, conventional air (78% nitrogen) in the atmosphere passes through a molecular filter to filter out larger O2 oxygen molecules. The gas collected at the other end is 96% nitrogen. This nitrogen-enriched air is then injected from below the storage bin and is continuously distributed in the storage bin. This is not only a fire prevention method, but also a method that can be used to extinguish fires when a fire occurs. In addition to the above measures to control the temperature in the storage bin, the storage bin is also equipped with a carbon dioxide (CO2) injection system and a sprinkler system as a fire prevention measure.

　　The next problem facing engineers is how to accurately detect the amount of biomass fuel in the storage bin. In order to achieve this, a sonar system is installed in each storage bin — which sounds a bit like a chirping bird — which continuously reports how full the bin is. The sonar monitoring system provides level, profile, and volume information, which is converted into a three-dimensional image of the stored biomass fuel. This volume measurement method allows the operator to view and monitor the level of the silo in real time during loading or normal operation, as well as to view specific areas in a targeted manner. In addition to the sonar system, multiple thermocouple temperature measurement points arranged in the silo also provide real-time feedback to the operators so that they can evaluate the status of the silo and effectively plan the feeding and discharging of biomass fuel. The gas monitor also detects the CO and CO2 values ​​at the top of the silo in real time, as well as the O2 consumption. The top of the silo is equipped with a two-way valve as a vent to maintain a relatively uniform pressure inside and outside the silo, allowing air to enter during the discharge period, and releasing the gas in the upper space during nitrogen filling. The last problem of atmospheric control is to regulate the pressure. There is a controllable hole at the top of each silo, called a sliding door, which is closed unless the dome is filled to allow material to enter. A dome suction system is installed here to filter and remove the replacement air in the head space during the filling process, while also providing a channel for CO and other degassing products.

　　 All these systems hidden in these four huge white silos enable Drax power plant operators to effectively control the internal gas conditions. The key is to be able to safely store a large amount of volatile biofuels on site.