Development of biomass power generation in China



1 History of biomass power generation in China

China's biomass power generation started later than Europe and the United States, but after more than ten years of development, has basically mastered agricultural and forestry biomass power generation, urban waste power generation and other technologies.

Before 2005, large-scale grid-connected power generation projects using agricultural and forestry waste as raw materials were almost blank. In 2006, China approved more than 1 million kilowatts of direct-combustion power generation projects. The installed capacity of biomass power generation exceeds 2.2 million kilowatts, including 1.7 million kilowatts of bagasse power generation, 50,000 kilowatts of rice hulls power generation in rice mills, 400,000 kilowatts of municipal waste incineration power generation, in addition to some small-scale biomass gasification power generation demonstration projects. In 2006, the "renewable Energy Law" and the implementation of relevant supporting policies such as preferential on-grid electricity prices for biomass power generation have made China's biomass power generation industry begin to grow rapidly.

From 2006 to 2009, the installed capacity of straw direct combustion power generation increased at an average annual rate of more than 30%. At the end of 2009, China's total installed capacity of straw direct combustion power generation was 2.65 million kilowatts, accounting for 62% of all biomass power generation; The total installed capacity of waste incineration power generation is 1.25 million kWh, accounting for 29% of all biomass power generation; Other gasification power generation, biogas power generation, and mixed combustion power generation account for a small proportion, accounting for less than 10% in total.

According to the national renewable energy medium - and long-term project plan, biomass power generation will reach 30GW in 2020. At present, there are more than 10 biomass direct combustion power generation projects under construction in the country, with an installed capacity of more than 4 million kWh. However, to reach the 2020 development goals, there is still a need to solve the problem of resource fragmentation and raw material collection difficulties.

2 Status quo of biomass power generation technology in China

2.1 Direct combustion power generation

The domestic direct combustion power generation technology has matured, and the single-unit capacity can reach 15MW. According to the nature of the fuel can be divided into two categories: first, the combustion technology of woody biomass fuel in Europe and the United States. Bagasse and rice husk furnaces in early China belong to this category. The other kind is straw burning technology, China's biomass resources to straw as the main body, so the domestic biomass burning technology research mainly focuses on straw burning technology. Domestic boiler manufacturers according to the actual situation of biomass power generation in China to improve the introduction of Danish technology after manufacturing production. Domestic independent development of fuel pretreatment system, feed system and slag removal system. Many domestic scientific research institutions and boiler manufacturers have developed fluidized bed boilers with independent intellectual property rights, and the technology is relatively mature.

2.2 Hybrid fuel power generation

There are two main types of hybrid fuel power generation. One is biomass directly mixed with coal and then put into combustion, which has higher requirements for fuel processing and combustion equipment; One is the mixed combustion of gas and coal generated by biomass gasification, and the generated steam is sent to the turbine generator set. Hybrid fuel power generation is mainly modified by introducing Danish technology.

There is a precedent for the use of bagasse mixed combustion for power generation in south China. It is only necessary to slightly transform the furnace of the existing coal power plant boiler, and then add the feeding and bag-type dust removal device. The biomass that is less than 20% of the total calorific value is directly mixed in the traditional coal-fired boiler, which has been basically mature in technology.

2.3 Gasification power generation

Biomass gasification power generation refers to the conversion of biomass into gas fuel in the gasifier, and after purification, it is burned in the gas engine for power generation or into the fuel cell for power generation. The gasification technology applied to engineering in China is mainly the biomass circulating fluidized bed gasification technology developed by Guangzhou Energy Institute of the Chinese Academy of Sciences. Other domestic research institutions, such as the Shandong Energy Research Institute, are also carrying out relevant research. In 1998, the first 1MW biomass rice husk gasification power generation system was built in Putian, Fujian Province, followed by the construction of more than 20 biomass gasification power generation systems across the country.

The existing gas internal combustion engine has low efficiency, small installed capacity, and low power generation conversion efficiency (generally only 12 ~ 18%), which can not meet the needs of large-scale industrial applications. The calorific value of gas is low, the tar content in gasification gas is high, and the secondary pollution is serious. Therefore, it is necessary to further research and develop suitable large-scale equipment and technology.

2.4 Biogas power generation

Biogas power generation mainly uses biogas generated by anaerobic fermentation treatment of a large amount of organic waste in industrial and agricultural or urban life to drive generator sets to generate electricity.

China's biogas power generation technology research and development has more than 20 years of history, the current domestic biogas power generation project is mainly combined with high concentration of degradable organic wastewater treatment construction, belongs to the product of wastewater treatment, the largest unit in normal operation in China is 10,000 kW · h, there is no larger biomass biogas generator set.

2.5 Waste-to-Power generation

Waste power generation includes waste incineration power generation and waste gasification power generation, which can not only solve the problem of waste disposal, but also recycle the energy in the waste and save resources. The waste incineration technology mainly includes layer combustion technology, fluidized bed combustion technology, rotary combustion technology and so on. The gasification and melting incineration technology developed in recent years includes the gasification of garbage at a temperature of 450 ° C ~ 640 ° C and the melting combustion of carboniferous ash residue above 1300 ° C. The waste treatment is thorough, the process is clean, and some resources can be recovered, which is considered to be the most promising waste power generation technology.

By the end of 2009, the total number of waste incineration plants in China had reached more than 80, the daily waste incineration treatment capacity exceeded 55,000 tons, and the total installed capacity of waste incineration power generation reached 1.25 million kW · h. In eastern China, especially in coastal cities, waste disposal is gradually changing from landfill to incineration. With the continuous development of waste recycling, treatment, transportation, comprehensive utilization and other aspects of technology, waste incineration power generation has a broad market prospect.

3 Problems and development prospects of biomass power generation in China

3.1 Problems in biomass power generation

From the construction and operation of domestic biomass power plants, it can be seen that the factors restricting the development of China's biomass power generation industry are mainly as follows.

(1) High construction and operation costs. The unit cost of biomass power plant is 10,000 to 15,000 yuan /kW · h, and the cost of combustion equipment is high. At the same time, due to the low energy density, the cost of pre-processing, transportation and storage of biomass fuel is also high. In addition, the effective tax rate of biomass power plants is 11%, while traditional thermal power plants are about 6% to 8%, and small hydropower is about 3%.

(2) There are technical problems, biomass power generation complex fuel supply system and boiler combustion technology, completely different from conventional thermal power units, biomass power generation main equipment - boiler body and other auxiliary machinery have achieved localization, but there are still problems in the biomass pretreatment and feeding system, the straw straw and other soft straw broken uneven serious. Often causes problems with the feeding system. And then directly affect the operation of biomass power plants. At present, the operating hours of the equipment are short, mainly due to the problems of the fuel handling feeding system (fuel quality factors are mostly) and the maturity of the combustion equipment is not high.

The development of biomass power generation projects in China is relatively late, and the technology is not perfect enough. How to choose feasible process flow according to different fuel components is related to the stable and reliable operation of the units after the completion of the project. In order to adapt to the situation that the same biomass boiler must burn a variety of straw, there is a problem of further technical transformation for the equipment imported from abroad.

(3) Policy issues, although existing laws and policies have provided a favorable environment for biomass power generation, these incentive policies and measures are not enough. The subsidies given by the government for the on-grid price of biomass power generation are based on desulfurization coal, and biomass fuel is different from coal, and the policy is unreasonable. Biomass plants no longer enjoy subsidies after 15 years of operation. And renewable power plants after 2010 enjoy a subsidy of 2% a year. In addition, because the Kyoto Protocol on greenhouse gases only provides for the emission reduction target by 2012, the CDM sales revenue of biomass power generation projects can only be included until 2012, affecting the efficiency.

3.2 Development prospect of biomass power generation

Due to the price disadvantage of biomass power generation and coal power, hydropower and so on, the lack of market competitiveness, the state adopts a price subsidy policy to support the development of biomass power generation. The feed-in price of biomass power plant is the benchmark feed-in price of desulfurization coal-fired units plus 0.25 yuan /kW · h subsidy price. Mixed-combustion power generation projects that consume more than 20% of the heat generated by conventional energy do not enjoy subsidized electricity prices. In addition, biomass power generation can enjoy a 10% income tax deduction, and straw biomass power generation can enjoy a VAT tax refund policy.

A major driving force for the development of biomass power generation in China is to avoid social problems such as pollution caused by farmers burning straw through power generation, and on the other hand, to support farmers through power generation. With the increase of biomass power generation projects, the purchase price of raw materials is still rising, and the loss has forced some biomass power plants to stop production, so it is very important for the state to further increase support in taxation and other policies.

By the end of 2011, more than 170 biomass power generation projects had been approved by governments at all levels in China, with a total investment of more than 60 billion yuan. Renewable energy "Twelfth Five-Year Plan" clearly states that by 2015, the installed capacity of domestic biomass power generation will not be less than 13 million kilowatts. The state has given a series of preferential policies in related industries. With the gradual improvement of industrial policies, biomass power generation will enter a period of rapid development.

In terms of the development status of the domestic biomass power generation industry, technology introduction and independent development have become the main theme of China's biomass power generation. However, it is necessary to clearly realize that striving to take the road of independent development is the ultimate way out, and constantly improving domestic technology will eventually dominate the Chinese market. The development, maturity and perfection of auxiliary systems are essential

Material power generation is the key to continuous development. And domestic related systems, such as collection, storage, transportation, pretreatment and feeding systems, there are certain problems. The perfection and maturity of these systems will determine the development direction of China's biomass power industry.