Several questions regarding the feeding of space furnaces
Thread Content
Some enthusiasts who work with space furnaces would like to ask you a few questions regarding them. 1. In the operation of a space furnace, three coal supply lines share one oxygen line; does this mean that all three coal supply lines must be fed simultaneously during material feeding? 2. There is a curve relationship between the flow control valve of the oxygen pipeline and the load; during material feeding, the oxygen valve is set to a predetermined opening degree. Could this lead to fluctuations in the pressure of the oxygen main pipe, as well as errors between the oxygen flow rate and the desired value? 3. The design requirement is that the pressure in the vaporization furnace should be around 10 kilograms when feeding material by driving the machine; it is necessary to determine whether the actual pressure deviates too much from this required value during material feeding.
1. The three coal dust pipelines must be put into operation simultaneously. This is closely related to the burner structure of the space furnace. The space furnace uses a top-jet structure for the burners, and three coal powder pipelines are provided to ensure a uniform spray velocity at all angles of the cylindrical burners. This is the decisive factor in maintaining the gas-phase flow field and flame shape in the gasification chamber. If inputs are made sequentially, it is easy to cause uneven flame combustion, leading to localized overheating and damage to the water wall. 2. During the driving phase, when the pulverized coal burner is activated, the control valves for oxygen and the three pulverized coal pipelines are set to their predetermined opening levels; this ensures that the burner receives sufficient load and energy to sustain combustion. It also prevents a situation in which the addition of pulverized coal and oxygen occurs at different rates, which could lead to an excessive oxygen-to-coal ratio and thereby cause the system to shut down. The preset opening degree is determined through testing prior to operation, based on the characteristics of the oxygen valve and coal valve at the installation site, as well as the minimum load required according to the furnace design. 3. The value of 1.0 MPa set when the coal powder burner is activated is intended to maintain the temperature in the gasification chamber. As determined through tests, with the startup burner (using natural gas or diesel) at 0–1.0 MPa, the temperature inside the gasification chamber can gradually increase as the load rises. At 1.0 MPa, the temperature inside the vaporization chamber is approximately 800 degrees. This temperature ensures that the energy required for moisture evaporation, coking, and combustion to occur immediately upon adding the pulverized coal is available. Under the conditions of appropriate initial temperature and pressure, if the pressure is insufficient and the temperature inside the gasification chamber is too low, the pulverized coal fed in cannot burn. Of course, for coal with a relatively low ignition point, it is also used at 0.8 MPa.
Thank you very much for your explanation. The coal powder angle valve of the Shell furnace is manually controlled during the coal feeding cycle, and the mass flow rate of coal is regulated after setting the oxygen-to-carbon ratio for a specific burner. This might be a bit different, as after all three are put into use simultaneously, whereas Shell’s can be brought online one by one. Regarding the third point, I would like to share my own opinion. The backpressure control for feeding material into the gasification furnace is intended to ensure an appropriate flow rate of oxygen entering the furnace; if the flow rate is too high, it affects the length of the flame and also increases wear on the burner head. The relationship between the temperature inside the gasification furnace and its pressure isn’t very close, as by the time feeding begins the burner is already lit, and the heat generated at that point is sufficient to ignite the coal burner.