关键词: 风机叶片, 沉降炉, 煤, 掺烧, 一氧化氮, 固废资源化利用

Abstract:

The design lifespan of wind turbines is 20—25 years. The wind turbines put into operation around the year 2000 are about to be retired in China. With the increasing installed capacity of wind turbines year by year, the demand for resource utilization of retired turbines will surge in subsequent years. Due to the long length, light weight, and high strength characteristics, suitable scale recycle methods have not been found for wind turbine blades. Based on the assumptions of the current installed capacity of 440 million kilowatts and a composite material consumption of 16kg per kilowatt, the national wind turbine blade composite material market is approximately 7.04 million tons. The stacking density of wind turbine blades broken to the centimeter level is relatively small, only 39% of that of coal powder, and the transportation cost is relatively high. Based on a transportation distance of 200 kilometers, the transportation cost per ton of blades has reached 1200—1500CNY (excluding costs such as dismantling, cutting, and crushing). From an economic perspective, coupling with coal-fired boilers for co-firing is a promising large-scale recycle route. Wind turbine blades have good ignition and burn out characteristics. Starting at 224℃, weight loss occurs, and the characteristic temperatures during the ignition and burnout stages are 264℃ and 504℃, respectively. The ignition and burnout performance are better than those of coal. The residue of the burned blades is mainly glass fiber, and the elemental composition is mainly silicon, aluminum, calcium, and magnesium in the form of oxides. Wind turbine blades have the characteristics of high nitrogen, and low calorific value. A typical wind turbine blade has a dry nitrogen content of 0.82%, and an air-dry calorific value of 1849kcal/kg. There is a significant difference in the nitrogen structure between coal and wind turbine blades. Coal nitrogen mainly exists in the form of pyrrole nitrogen, accounting for 85%, while wind turbine blade nitrogen is mainly composed of amide structure, accounting for 90.6%. After being heated, amide structure nitrogen is more easily released into gas-phase nitrogen. The results of the co-firing experiment show that there is no significant change in pollutant NO emissions within a 10% co-firing ratio (weight ratio). According to a 10% co-firing ratio, a 300MW coal-fired boiler can tackle with the blade composite materials produced by 3052MW retired wind turbines annually. This means that the current coal-fired boiler can fully tackle with the solid waste generated by future retired wind turbines.

Key words: wind turbine blade, drop tube experiments, coal, co-firing, nitric oxide, resource utilization of solid waste