Efficient natural gas boiler with low-nitrogen emission

Abstract

The invention discloses an efficient natural gas boiler with low-nitrogen emission. As low-temperature waste heat (sensible heat and latent heat) of smoke is recycled based on an evaporative cooling principle, firstly, the problem that the heat exchange loads of high-humidity smoke and low-humidity combustion-supporting air are not matched is solved by humidifying the combustion-supporting air, meanwhile, the heat exchange coefficient of the high-humidity smoke and the low-humidity combustion-supporting air is effectively improved, low-temperature sensible heat and latent heat of smoke are recycled to the greatest extent, and the problem of white smoke of a natural gas boiler can also be eliminated; secondly, the smoke dew point is increased by humidifying the combustion-supporting air, the grade of the low-temperature latent heat is improved, and the smoke latent heat recycling rate can be improved advantageously; and thirdly, the oxygen concentration is reduced by improving the humidity of the combustion-supporting air, the generation amount of thermal NOx in the natural gas burning process can be reduced, meanwhile, part of NOx can be dissolved through direct contact of smoke and heating medium water, and thus nitrogen oxide emission of the gas boiler can be effectively reduced.

Description

technical field [0001] The invention relates to the technical field of boiler flue gas waste heat recovery and NOx pollutant control, in particular to a low-nitrogen emission high-efficiency natural gas boiler. Background technique [0002] Natural gas is a clean fuel, 85-90% of which is methane, and the combustion products are mainly carbon dioxide and water, and the content of water vapor is relatively high. According to calculation, 1Nm 3 The combustion of natural gas produces about 1.55kg of water vapor, and the corresponding latent heat of vaporization can account for about 10% of the low calorific value of natural gas. Therefore, fully recovering and utilizing the latent heat of water vapor in natural gas combustion flue gas is of great significance for the efficient utilization of natural gas. [0003] At this stage, with the adjustment of my country's urban energy structure, a large number of coal-fired heating boilers are replaced by gas-fired boilers. In order t...

AI Technical Summary

Problems solved by technology

This method only needs to add a heat exchanger to the boiler system and use the heating return water as the cooling medium. The system is simple, but the latent heat recovery effect is limited by the heating return water temperature.

Since the return water temperature of the heating system in our country is generally 45-50°C, and the flue gas temperature cannot be lowered below the return water temperature, the low heat transfer temperature difference makes the latent heat recovery rate very low

In addition, some people apply absorption or compression heat pumps to the latent heat recovery of flue gas. This method uses the heat pump to generate a cooling medium lower than the temperature of the heating return water, which improves the latent heat recovery rate. However, the equipment investment and operating costs are relatively high.

The above methods are based on the existing boiler structure, by adding additional devices or systems to realize latent heat recovery, which will undoubtedly increase the complexity of the boiler system and require a larger footprint, and cannot effectively solve the problem of NOx emissions from gas-fired boilers

Moreover, due to the high moisture content in the exhausted flue gas, when the flue gas discharged from the chimney encounters cold air, the water vapor quickly liquefies into small water droplets, forming "white smoke" visible to the naked eye. Harmless, but the white smoke blocks the normal sunlight and affects the visual effect of human beings. At the same time, small water droplets combined with dust in the air fall to the area around the chimney, which also causes certain pollution to the environment.

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