In recent years, China ’s air haze weather has been frequent and air pollution is serious. This has become one of the most serious and urgent environmental problems in China. In order to reduce the impact of heating and heating in northern towns on air haze weather, efficient and environmentally friendly heating methods can be used instead of traditional coal-fired heating. The emergence of air-source heat pumps, while saving energy, also avoids direct emissions of pollutants. Its promotion and application will ease the current situation of air haze weather.
There are many types of heating methods and technical forms in China. Among them, according to the heat source fuel, it can be divided into coal burning, fuel oil, gas and electric heating methods. This article will compare the energy consumption and emissions of pollutants produced by coal-fired boilers, gas-fired boilers, electric boilers, solar electric heating, and air-source heat pumps with the same heating capacity.
Figure | Driven by Beijing's "Clean Air Plan" and "Coal to Electricity", more than 200 households in a village in Miyun switched to air-source heat pumps for heating. The picture was originally taken by this reporter.
Pollutant emissions per unit energy consumption
The energy consumption of the heating system is one of the main sources of air pollution. It has two types of direct and indirect pollution to the environment and the atmosphere. Direct pollution refers to the pollutants emitted by the combustion of various fuels, mainly including soot, SO2, NOx and CO2. In addition, although electric heating has no direct pollution, indirect pollution still exists because more than 70% of China's electricity is coal-fired power generation.
Table 1 Pollutant emissions when various fuels are consumed
Basis for the value of pollutant emissions when various fuels are consumed:
(1) Standard coal: Take a chain furnace as an example, smoke and dust account for 25% of ash, average ash content is 20%, and the dust removal rate is calculated as 85%. If combustibles in smoke and dust are taken as 20%, 1 tce can emit 7.5 kg of smoke and dust; The state stipulates that the sulfur content of standard coal is 1%, then 1 tce can emit 16 kg of SO2; the nitrogen content is taken as 1.5%, and the nitrogen conversion rate is taken as 25%, and 1 tce can be replaced to emit 7.6 kg of NOx; 1 tce is completely burned The amount of CO2 produced is 2.62 t.
(2) Light diesel and natural gas dust, SO2 and NOx emission indicators are calculated according to the GB13271-2001 "National People's Republic of China National Standard Boiler Air Pollutant Emission Standard". The CO2 emission indicators are based on the general technical conditions of fuel use. Statistical average.
(3) From the analysis in Table 1, it can be seen that the emissions of pollutants from power plants are far less than those from direct coal combustion. The reason is that the use of large and extra large boilers for power generation will generally be treated after de-dusting, desulfurization and denitrification, and then discharged. These measures are difficult to burn in small and medium boilers such as self-provided boiler rooms and regional boiler rooms Do it, or the cost is high.
At the same time, the pollution caused by the burning of bulk coal in the vast rural areas of China is even more serious. As far as China is concerned, electricity is the sector that can cleanly use coal. Therefore, the use of coal for combustion in large and extra large boilers to generate electricity, and the promotion of air source heat pumps as an efficient indirect electric heating technology in the project, can effectively improve the current situation of air haze due to winter fuel combustion.
Analysis of pollutant emissions under heating conditions
Table 2 lists the energy consumption and environmental pollution of various heat sources when producing 1000 kW of heat. In order to facilitate the comparison of the energy consumption of each scheme, each energy source is converted into equivalent standard coal. The energy calorific value, thermal efficiency of the equipment, and the discounted coal coefficient of each energy are shown in Table 2. Among them, the equivalent conversion coefficient is the ratio of the equivalent heating value (theoretical calorific value) of the fuel to the calorific value of the standard coal; the equivalent conversion coefficient refers to the ratio of the equivalent heating value of the secondary energy to the standard heating value.
Table 2 Comparison of energy consumption of various heating methods
Figure 2 shows the quantitative comparison results of various schemes. From Table 2 and Figure 2, it can be seen that the energy consumption of the air source heat pump is the least among the six heating methods when the same heat is obtained. If converted into equivalent standard coal, the air-source heat pump saves 69.04 kg of standard coal, which is about 36.5%, than coal-fired boilers.
Figure 2 Comparison of energy consumption of different heating methods
According to the calorific value calculated in Table 2, the energy consumption of each fuel and the amount of pollutants per unit energy consumption in Table 1 result in Table 3, that is, the total amount of pollutants produced by various heating methods to produce the same heat.
Table 3 Emissions of the same thermal pollutants
It can be seen from Table 3 that the total pollution emission of air-source heat pumps is not much different from that of gas-fired boilers, but far less than that of several other heating schemes that use electric energy as their energy source. It also produces 1,000 kW of heat, and the pollutant emissions of air-source heat pumps reduce 90.6% of soot, 29.5% of SO2, 46.2% of NOx, and 53.2% of CO2 compared with coal-fired boilers; compared with electric boilers, it is equivalent To reduce 68.3% of soot, SO2, NOx, and CO2 emissions.
If electric energy is not used for coal-fired power, but clean energy is used for power generation, such as nuclear power, hydropower, solar photovoltaic power generation or wind power generation, air source heat pump heating must be the best environmental protection solution.