In recent years, various parts of my country have strictly enforced environmental protection, especially the governance and prevention of industrial pollution emissions, and have achieved initial results. However, at the same time, the impact on some industrial industries is also inevitable. Taking the grain dryer industry as an example, the heat source part is an important part of the grain dryer, and the heat source of traditional grain dryers is mainly coal. With the implementation of the "coal ban" in various places, grain dryers have to seek new heat sources to replace the more polluting coal, which has raised a new issue for grain dryer manufacturers across the country. For a long time, the grain industry has been a low-value-added industry, and the development of the industry has always been in a state of "small profits but quick turnover, winning by quantity". Coal, as a traditional energy source, has always been used as a heat source for grain dryers with its "low price and easy access". However, under the pressure of national environmental protection policies, manufacturers have to develop new alternative energy solutions to ensure the normal use of grain dryers under the premise of meeting environmental protection emissions. At present, the main domestic alternatives are: natural gas, air energy heat pumps, biomass pellets, steam and other methods. The following introduces different energy methods based on the successful experience of Zhengzhou Wangu Machinery Co., Ltd. in focusing on grain dryers for more than 20 years.

Natural gas is a clean energy source. When fully burned, it mainly produces non-toxic carbon dioxide and water. In addition, it produces a very small amount of sulfur dioxide and nitrogen oxides. Because the content is very low, the impact on the environment is very small and can be ignored. Therefore, the combustion exhaust gas of natural gas can be discharged directly without treatment. Therefore, gas hot air furnaces are increasingly used in the grain drying industry. Users usually use fixed natural gas pipelines or natural gas transport vehicles and other non-fixed methods to supply the required natural gas.

Steam heat exchanger is a heat exchange equipment that uses steam to release heat during condensation to heat normal temperature air. It has the advantages of cleanliness, easy control of air temperature, and simple operation. After heating, normal temperature air can be directly used as the drying medium of the grain dryer. This method is generally only suitable for occasions where there are large industrial steam resources near the grain dryer plant, especially some large grain deep processing enterprises self-built grain dryers, because their plants are usually equipped with large steam boilers and have surplus industrial steam available. At present, Zhengzhou Wangu has successfully built dozens of steam grain dryers with a daily output of 1,000 tons in many provinces such as Northeast, Northwest, and Henan.

Biomass pellet fuel is a granular new energy fuel produced by processing straw, rice husk, firewood, peanut shell, corn cob, tea shell, cottonseed shell, etc. Since biomass pellet fuel does not contain sulfur and phosphorus, it does not produce sulfur and phosphorus oxides when burned, does not cause acid rain, and has less pollution to the environment. There is very little ash after the combustion of biomass pellet fuel, which can reduce the site for stacking slag, and the ash after the combustion of biomass pellet fuel is organic potassium fertilizer, which can be recycled to create profits. Usually, biomass pellets have the characteristics of small bulk density, low calorific value, and more fine dust after combustion. Therefore, the furnace structure and exhaust dust removal of the hot air furnace need to be optimized to meet the heating and environmental dust emission standards of the grain dryer.

Air energy heat pump is a drying form that uses electricity as energy and absorbs and converts energy in the air into heat energy. Air energy heat pump technology has been gradually promoted and applied in the field of grain dryers in recent years due to its advantages of cleanliness and pollution-free. However, due to the limitations of the working principle of heat pump technology, this technology is currently mostly used in small grain drying equipment. Moreover, its use is limited by geographical region and is often used in warm areas in the south, mostly as a heat source for low-temperature rice drying.