Promote the green, low-carbon and circular development of the biomass power generation industry

One is the lack of clearly enforced flue gas emission standards for biomass power plants. The survey found that at present, there is no separate flue gas emission standard for biomass power generation, and most places refer to coal-fired power generation or natural gas power generation. In 2010, biomass power generation enterprises usually refer to the third period of the "thermal power plant emission standards for air pollutants" with coal gangue as the main fuel of the boiler flue gas discharge standards, its atmospheric particulate matter, sulfur dioxide, nitrogen oxides shall not exceed 50mg/Nm3, 200mg/Nm3, 400mg/Nm3; With the gradual improvement of environmental protection requirements, the flue gas emission standards in 2013 were adjusted to 30mg/Nm3, 200mg/Nm3, 200mg/Nm3; In order to fight the battle of pollution prevention and control, in 2018, the Ministry of Ecology and Environment issued the "Announcement on the Implementation of Special Emission Limits for Air Pollutants in Beijing-Tianjin-Hebei Air Pollution Transmission Channel Cities", and the flue gas emission standards were further adjusted to 20mg/Nm3, 50mg/Nm3, and 100mg/Nm3. The implementation of ultra-low flue gas emission standards for biomass generators has brought greater pressure on enterprises to control the emission of air pollutants.

Second, the ultra-low emission transformation cost of biomass power generation enterprises is relatively high. The "Action Plan for the Comprehensive Control of Air Pollution in the Autumn and Winter of 2018-2019 in Beijing, Tianjin, Hebei and surrounding Areas" issued in 2018 clearly requires: "Biomass boilers should use special boilers, and it is prohibited to mix coal and other fuels, supporting cloth bags and other efficient dust removal facilities; Actively promote the ultra-low emission transformation of biomass cookers in urban built-up areas; Accelerate the low-nitrogen transformation of gas boilers, and in principle, the nitrogen oxide emission concentration after the transformation shall not be higher than 50 mg/cubic meter." The survey found that in order to achieve the ultra-low emission requirements of atmospheric pollutants in biomass direct combustion boilers, the National Energy Company invested a lot of money to carry out desulfurization and denitrification transformation of its power generation projects, and in 2018, the company only invested about 283 million yuan in flue gas treatment. According to the economic analysis of the existing construction projects, the investment of a 30 MW unit desulfurization, denitrification and dust removal integrated technical transformation project is about 17 million yuan, the investment of sewage treatment is about 3 million yuan, the investment of dust screen construction is about 1 million yuan, and the annual operation and maintenance cost of environmental protection facilities is about 10 million yuan. The increase in costs has made it difficult for the biomass power generation industry, which is already at the break-even point.

Third, the treatment of nitrogen oxides in biomass power generation is still facing technical problems. Considering that the raw materials used by biomass power generation enterprises are agricultural and forestry straw, etc., the calorific value, water content, sulfur content and alkali metal content of the fuel are very different from the fuel characteristics of coal power plants, and the ultra-low emission transformation standards of the standard coal power industry are analyzed from the technical level, and there is no obstacle to achieve ultra-low emission of particulate matter and sulfur dioxide. But in the reduction of nitrogen oxides exposed a series of problems, mainly as the current technology is not mature, there are also ozone escape and power consumption and liquid oxygen production and storage security risks and other problems, this is due to the biomass fuel containing chlorine elements and alkali metals, while the fuel ash and water content is high, the furnace temperature can only reach 800 degrees. Far less than coal-burning boilers. At present, non-selective catalytic reduction (SNCR) technology is usually used, because the furnace temperature can not reach the best reaction temperature of SNCR technology, resulting in incomplete reaction, a large amount of ammonia escapes and forms crystallization on the tail heating surface tube row, the bag dust collector box and the induced draft fan impeller, resulting in a decrease in denitrification efficiency and boiler efficiency. At present, Nangong Biopower Co., Ltd. is further implementing the ozone denitrification transformation, but the enterprise reflected in the survey that the operating cost is large, 1 kg of ozone consumes about 8 degrees of electricity, a 30MW biomass generator unit needs an additional power consumption of 1.72 million to 4.6 million degrees per year (according to 300 days of operation time), and there are problems such as liquid oxygen safety risks and ozone escape.

Fourth, the material stacking and covering requirements of biomass power plants should not be simply applied. The investigation found that Nangong Bio-Power Generation Co., Ltd. was repeatedly required to implement the provisions that "the open-air stacking of materials in the material yard should be covered by dustproof nets, and the covered area should be greater than 85%" in the strengthened inspection of air pollution prevention and control. However, enterprises and the government safety production authorities believe that covering the biomass fuel storage field is easy to bring fuel spontaneous combustion and other hidden dangers. This is because the biomass material used by enterprises has a large water content and the size is more than 5 cm. Although it is not easy to generate dust, the black dust filter is easy to absorb heat and the fuel is easy to spontaneous combustion, and there are great hidden dangers in high temperature weather. In addition, in order to avoid dust generation of materials, irregular fog gun dust removal is required according to relevant regulations, but this will correspondingly increase the water content of materials, which is not conducive to full combustion, but will cause more pollutant emissions and other problems.