Gas boiler exhaust heat recovery
Coal as the main fuel for industrial boilers still dominant. With the rapid development of natural gas industry, such as a clean energy boiler fuel will gradually increase. Compared with coal, natural gas emitted simultaneously emits very little sulfur dioxide and nitrogen oxides, reducing the pressure on the environment. However, after combustion, a large amount of water vapor is generated and high temperature flue gas is discharged into the environment, resulting in serious energy waste. Condensing gas boiler can be used for recovering high-temperature sensible heat and latent heat in the flue gas, the full use of energy and reduce operating costs.
When the flue gas in the channel passes through the heat exchange surface, the temperature drops below the dew point temperature to condense the water vapor gas in the flue to release the latent heat to the refrigerant, Can draw a lot of energy recycling, so as to achieve the effect of energy saving and environmental protection. With the continuous development of the manufacturing industry, a variety of new and efficient condensing heat exchangers are emerging continuously, and the structure and actual waste heat recovery effects have greatly improved.
Flue gas characteristics
The vast majority of natural gas components are hydrocarbons, and gas-fired boilers have high levels of moisture and moisture. Analysis shows that the latent heat of vaporization accounts for a considerable share of the heat generated by heat rejection. 1 cubic meter of natural gas combustion can produce 1.55 kg of water vapor, latent heat of evaporation, about 3700 kJ / m3, accounting for 10% of the low calorific value of natural gas. In the traditional boiler, flue gas temperature is generally 160-250 degrees Celsius, flue gas steam is still in overheating, it is impossible to condense into liquid water, the release of latent heat of vaporization. Therefore, the theoretical thermal efficiency of conventional natural gas boilers is generally only 95%. As long as the flue gas temperature falls below the dew point of the flue gas, the flue gas with sensible heat and water vapor condensation is recovered, and based on the net calorific value, the thermal efficiency of the natural gas boiler can be achieved And more than 110%.
Thermal efficiency analysis
The heat in the flue gas exists in the forms of sensible heat and latent heat, and the heat loss of the boiler consists of the significant heat loss and latent heat loss of the flue gas. However, the apparent heat loss depends on the flue gas temperature and the heat capacity of the flue gas components, and the latent heat loss depends on the amount of water in the flue gas.