Low Nitrogen Combustion Retrofit of 0.7mw Gas-Fired Central Flashback Hot Water Boiler.

March 09, 2020

There are two aspects to consider in the low nitrogen combustion transformation of the gas-fired central flashback boiler. The first aspect is the structure of the boiler, which makes the fuel burn more fully in the boiler after several times of combustion. The second is the burner. NOx produced by different types of burners is also different.

The combustion forms of gas-fired boiler mainly include diffusion combustion and premixed combustion. Diffusion combustion is that the fuel and air are sent to the burner through different channels, and the fuel and air are mixed and burned at the same time. Diffusion combustion has the advantages of good safety performance, not easy to temper and large regulation ratio, so the commonly used burner in the gas boiler is a diffusion burner. Premixed combustion is that before combustion, the fuel and air are well mixed evenly. In recent years, the metal mesh burners adopt the uniform combustion, which has the advantages of low emission but also has the disadvantages of easy tempering and metal mesh plugging.

1.1

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The combustion process of the central back burning boiler: the fuel is injected into the furnace tank through the burner and burned under positive pressure. The high-speed flame causes the flue gas to flow in the furnace tank, so that the high-temperature flue gas returns from the rear of the furnace tank to the front flue gas box, and then fully exchange from the flue gas tube and finally discharges into the atmosphere through the chimney. In this way, the unburned fuel in the flue gas is combusted again in the process of returning, which makes the combustion more full. At the same time, the flue gas circulation in the furnace is realized and the heat exchange efficiency is increased. The NOx emission is fully reduced.

2.2

The central flashback boiler has the advantages of less heat loss and low NOx emission. However, if the burner and boiler size do not match. The amount of NOx will increase.

At present, the more reasonable boiler configuration is diffusion burner + flue gas return technology. In the range of 30% ~ 100% boiler load, under the premise of full combustion of fuel, low nitrogen emission of NOx ≤ 30mg / M 3 (standard state, 3.5% oxygen content) can be realized.

1. The burner shall make the flame of the boiler slender and rigid according to the furnace size of the central flashback boiler, and match the furnace of the boiler completely.

2. Adopt multi-stage air distribution and multi-stage fuel input to avoid flame superposition and reduce the generation of thermal NOx.

3. Adopt staged jet combustion technology.

4. The burner shall be designed so that the gas and air are fully mixed to avoid the formation of local high-temperature paint.

Flue gas recirculation system. After the flue gas is extracted from the tail of the boiler, it is mixed with air and sent into the boiler for combustion again. NOx generation can be greatly reduced.

Effect after transformation

The CO emission of 0.7mw Gas-fired central combustion boiler is 0 under 30% ~ 100% different load operation, and the NOx emission is lower than 30mg / m3 (standard state). The denitration efficiency is as high as 72.73%.

EPCB boiler is a professional industrial center heating boilers manufacturer, and the gas-fired hot water boilers have higher boiler efficiency.