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How to distinguish between biomass fuel coking and Incomplete burning

The coking is as hard as a rock, and the incomplete burning is as loose as crisp Angle, a crack on the break!

How to distinguish between biomass fuel coking and Incomplete burning(图1)

The main factor of coking. Biomass fuel furnace coking mainly refers to the ash produced after fuel combustion, which is mostly melted into liquid state or in a softening state at high temperature. If the ash still remains in a softening state when it touches the heating surface, it is bonded to the heating surface due to cooling, forming coking.

01 Boiler coking is generally considered to be:

1.The ash of the fuel itself and the coking formed after the doping.

The main factor affecting the melting point of ash is the chemical composition of the ash and the surrounding high-temperature environmental medium. The two interact with each other. Once the fuel furnace is adjusted and not in place, incomplete combustion products will appear, making the surrounding medium show weak reducibility, reducing ash fusibility and causing coking in the furnace.

At the same time, biomass fuel is generally mixed into the mixed fuel situation into the furnace, while fuel incorporate a large amount of soil and fine sand into the fuel. The presence of these impurities changes the composition, form and melting temperature of the fuel, aggravating the coking in the heating surface

2.The temperature level of the surface of the heated surface in the furnace.

Under the condition of a certain ash melting point, the temperature level in the furnace and its distribution become an important factor in whether or not coking occurs.

Experience shows that the coking of the fuel furnace is mostly on the surface of the flue and superheater. The liquid or soft ash particles are subjected to inertia and move to the heated surface. Due to the fast moving speed of the ash particles, the cooling effect is poor, and the molten ash particles are very easy to adhere, so that the slag layer quickly accumulates and grows up. Temperature has a very important influence on coking in the furnace. Studies show that as the temperature increases, the degree of coking will increase exponentially.

02 Reasons of Incomplete burning

1.High enough temperature: a temperature high enough to ensure the heat required for the fire, while ensuring an effective burning rate.

The ignition point of biomass pellet fuel is about 250℃. The temperature is increased with a well-burned subsequent fuel supply. During the ignition process, the heat gradually accumulates, making more fuel to participate in the reaction, and the temperature also rises. When the temperature reaches above 800 ° C, the biomass burns well.

2.Appropriate amount of air: If the amount of air is too small, the combustible components cannot be fully burned, resulting in incomplete combustion loss; however, if the amount of air is too much, the combustion chamber temperature will be lowered, the degree of complete combustion will be affected, and the amount of flue gas will be large, reducing boiler thermal efficiency.

3.Sufficient combustion time: The fuel burns at a certain speed and reaches the maximum degree of combustion, so that it takes a certain time to complete the combustion. The biggest problem of combustion adjustment is to keep the residence time of burning in the furnace as much as possible. With enough burning time, complete combustion can be achieved.

4.The timely mixing of oxygen: the primary air is sufficient to blow and penetrate the agitated fuel; the secondary air is strong and fast to enter, and the oxygen can not be deficient in the most intense combustion center, and the oxygen in the upper part of the furnace is maintained, and the upper layer is maintained. The secondary wind is as large as possible, and the tertiary superheater is not overheated to use the boundary line. After the flame center in the furnace, a decreasing temperature field is formed.

The biomass particles can be fully burned as long as they satisfy the above four points during the combustion process. Sometimes when we encounter problems, do not simply think that the problem is the product, but also to analyze their own combustion engine conditions and other reasons, only a variety of inspection can really solve the problem.

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