Fire hole pressure and upward heating
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According to traditional practices, the pressure at the tuyere viewing holes in coke ovens is generally maintained at a slight positive pressure (i.e., 0–5 Pa). But later, it was proposed that increasing the pressure in the viewing hole would help improve vertical heating. What is still true about this claim? How can the principle be explained using fluid dynamics or other sciences?
Increasing the pressure at the tuyere holes of a coke oven can indeed improve upward heating. The main reason for this is that by raising the pressure at these holes, the intensity and speed of the airflow inside the furnace increase, which facilitates better mixing between coke and air. This leads to improved combustion efficiency and heat exchange, while also reducing the emission of harmful gases such as CO and CH4, thus contributing to environmental protection. Specifically, increasing the pressure at the viewing ports can promote the mixing and transfer of coke and air within the furnace, reduce the resistance at the combustion surface, and increase the combustion rate and heat release rate ； It also enhances the stability of the flow field inside the furnace, preventing adverse phenomena such as flow separation and secondary recirculation, thereby improving heating efficiency and thermal balance. From a fluid dynamics perspective, increasing the pressure at the viewing port can boost the momentum and energy of the gas flow within the furnace, thereby enhancing the generation and maintenance of turbulence and vortices there. This promotes the mixing and transfer of gases. At the same time, it increases the pressure and density of the gases in the furnace, resulting in more intense convective heat transfer. It should be noted, however, that excessively high pressure in the fire viewing ports can also have some negative effects, such as increasing fuel consumption and compressor power, as well as potentially causing unstable combustion and damage to the coke. Therefore, in practical applications, comprehensive consideration and optimized control are required based on specific circumstances. -
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Increasing the pressure at the viewing port requires reducing the suction force; does a decrease in suction force increase the gas flow rate? Additionally, this combustion system and coke operate in two separate systems; coke undergoes high-temperature dry distillation in the carbonization chamber, with no contact with air. What model of coke oven are you referring to?
It is true that coke undergoes high-temperature dry distillation in the carbonization chamber, with no contact with air. But the carbonization chamber and the combustion chamber are separated only by a wall, so leakage through the furnace wall is inevitable. If the pressure in the carbonization chamber is higher than that in the combustion chamber, raw gas will flow into the combustion chamber through the gaps between the bricks, resulting in graphite deposits forming in those gaps, which helps to improve the sealing ； If the pressure in the combustion chamber is higher than that in the carbonization chamber, the burning exhaust gases (containing excess oxygen) will flow into the carbonization chamber through the gaps between the bricks, burning the graphite deposited in those gaps and thereby causing even more leakage.
To increase the pressure at the fire viewing hole, it is necessary to reduce the suction in the smoke distribution ducts, that is, to close the flaps of those ducts. If the suction force decreases, how can the flow velocity increase? I don’t understand.