| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 104 === Carbon accumulation occurs significantly on the walls of inside a coke oven and it may cause serious blocking problems during the coke-making operation. Therefore, the coke oven is scheduled regularly to burn the accumulated carbon under maintenance. Due to the slow combustion rate of deposited carbon, the maintenance time is often long and reduces the yield rate.
The study focused on a 3D unsteady coke oven burning model to simulate the real coke oven including heat blocking materials It simulated different convection conditions, which were natural convection, force convection by air blower and force convection by a nozzle pipe, to assist field personnel to select the best operating mode.
The burning rate of solid carbon is dominated by the oxygen diffusion, so a forced inflow is proposed to increase the carbon-burning rate. However, if the air inflow rate is too high, it will lower the oven wall temperature and consequently the carbon-burning rate may be slowed down, even terminated.
The results showed that more fresh air flow could increase coke burning rate. When flow rate was too high and cool down the oven wall temperature, it may be below the brick safety temperature and the wall brick was damaged. Comparing the simulation results of force convection by air blower and a nozzle pipe, it showed that when the mass flow rate of force convection by a nozzle pipe was 33% smaller than that by air blower, the coke burning rate was 13% higher than force convection by air blower and the burning location was closer to the thicker coke zone. Thus, the method using the forced convection by a nozzle is more time-efficient to coke burning operation.
In these three conditions natural convection resulted in an unstable flow field and the coke burning position will change a lot, while the flow field of force convection by air blower could quickly reach a relatively stable state. As a result, a steady state simulation of forced convection by air blower can be used to evaluate the coke burning rate and shorten the simulation time.
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