Progress in the application of biomass energy power generation technology at home and abroad

0 Introduction

In 2020, the CO2 emissions of China's power industry accounted for nearly 50% of the total emissions of the energy industry, and the emission reduction process of the power industry directly affects the overall process of "carbon peak" and "carbon neutrality". To achieve "carbon peak" and "carbon neutrality", on the one hand, we must gradually reduce the consumption of fossil energy, and at the same time, we must effectively increase the proportion of renewable energy consumption.

As a renewable clean energy, biomass energy is also the fourth largest energy source after coal, oil and natural gas, accounting for about 10.0% of the world's energy consumption. In the 1970s, Nordic countries began to explore biomass energy such as ethanol; In 1993, Japan restarted the "Sunshine Program" to develop renewable energy; In 2000, the European Union adopted the European Policy for Security of Energy Supply to encourage the development of biomass fuels. In 2013, India proposed to double unconventional energy.

According to the "China Renewable Energy Development Strategy Research Report" of the Chinese Academy of Engineering, the total amount of clean energy mined annually in China, including solar energy, is equivalent to 2.148 billion tons of standard coal. Among them, biomass energy accounts for 54.5%, which is 2.0 times of hydropower and 3.5 times of wind power, and is the most promising renewable energy in China.

1 Biomass pure combustion power generation technology

1.1 Introduction of biomass energy heat utilization technology

Biomass energy is the only renewable carbon energy at present, and combustion is an efficient way to clean the use of biomass energy. Biomass energy can be divided into forestry waste, agricultural waste, urban waste and industrial organic waste according to different sources. Biomass energy thermal utilization technology includes physicochemical method, thermochemical method and biochemical method, as shown in Figure 1. Among them, biomass energy direct combustion power generation technology is divided into pure burning biomass and mixed combustion with coal, which can achieve large-scale and efficient utilization of biomass energy, and the technology is gradually developing and improving from basic research to engineering application.

1.2 Biomass fuel combustion characteristics

Biomass fuel has high volatile component content and is easy to burn, and its net emission rate of CO2 after combustion is 0,NOx emissions are only 1/5 of coal, and SO 2 emissions are only 1/10 of coal. The content of N and S elements in biomass fuel is small, but the content of inorganic impurities such as K and Cl is high, which will lead to problems such as slag formation in boiler, ash deposition on heating surface, chlorine corrosion on low temperature heating surface, and high temperature corrosion on superheater tube during direct combustion, especially when the power generation parameters of biomass pure combustion power plant are improved to improve the overall power generation efficiency. The high temperature corrosion caused by superheater surface deposition will seriously affect the normal operation of the power plant. The relationship between the heated surface wall temperature and the metal corrosion rate is shown in Figure 2.

Ash deposition will cause heating surface wear and corrosion, and may lead to reduced power generation, and even unplanned furnace shutdown. Although soot blowing can be used to control deposition, uncontrolled deposition can still occur in locations that are difficult for cleaning equipment to reach. Because the heat transfer coefficient of ash accumulation is 1/40 of steel, when the ash accumulation is serious, it will even lead to pipe explosion, which directly threatens the operation safety of the boiler. The solution to the ash deposition problem has received extensive attention in the world. As shown in Figure 3, the publication of ash deposition theses retrieved by the Web of Science in recent 5 years, it is evident that ash deposition was studied on many subjects in our country in recent years, however, the current research results can not completely solve the ash deposition problem.

1.3 Development status of biomass pure combustion power generation technology abroad

Due to the different energy structure, the research and development of biomass pure combustion power generation technology in foreign countries, especially in European countries, is earlier than our country. A representative biomass boiler company, its combustion technology and application are as follows.

Danish BWE company pioneered the development of straw combustion power generation technology. With the technical support of this energy research and development company, the first straw bio-burning power plant was born in Haslev, Denmark, in 1998, with a capacity of 5.0 MW. At present, 130 straw power plants have been built in Denmark, and some power plants that burn wood chips or waste can also burn straw. The main boiler types are vibrating grate furnace and powder chamber furnace. Compared with the powder chamber furnace, the grate furnace system is simple in structure, easy to operate, easy to control the combustion temperature, can alleviate the phenomenon of ash and slag accumulation, and the investment is relatively low. The biomass burning power plant in Elyan, UK was once the world's largest straw power plant with an installed capacity of 38.0 MW, which also uses BWE's biomass burning power generation technology.