| Roasting is one of main unit operations to vanadium directly in short flow which vanadium-titanium magnetite as raw materials, which determines the conversion rate of vanadium. Roasting furnace is a new type of roasting equipment that drawing steel sector Pelletizing Shaft Furnace (PSF). There ane many advantages such as less initial investment, better sodium-oxidation and lower energy consumption. From the thermal aspect of view, roasting furnace is one of direct-contact gas-solid heat exchangers, which belongs to particle moving beds, and it is approximately a fixed bed, the scientific support is the problem of gas-solid flow and heat transfer. In which, the gas flow in the PSF is the main factors of gas-solid heat exchange inside the material layers. Therefore, the study on the direction, flow rate and distribution of gas flow in the PSF is of great significance for intensifying the heat exchange and enhancing the output and quality of pellets.A pair of gas outlets are set in vanadium-titanium magnetite roasting furnace, which makes the boundary conditions of inlet and outlet flow in the PSF more complicated to determine, and it is the biggest difficulty of calculation. Firstly, basic experimental were conducted to identified a number of key parameters of numerical calculation. Secondly, gas distribution characteristic test in the completed pilot PSF were made to identified the needed boundary conditions of numerical calculation. On this basis, three-dimensional steady gas flow velocity and pressure fields in the PSF were calculated in this paper and got the basic flow distribution laws of the gas inside the material layers, and then made an analysis of the main factors and affecting laws of the gas flow. The results show that:(1) When the guide outlet on the IVAC is open (State I), there are four gas flow trends in the PSF:The majority of the roasting gas from the crater into the PSF oblique outflow through the preheating-roasting zones, small part of the gas flows downwards to the IVAC through the lower guide outlet directly, the other flows downwards into the IVAC through the lower guide outlet. Most of the cold cooling gas into the furnace inlet flows into the IVAC through the cooling zone and lower guide outlet, small part of the flow into the furnace inlet flows into the IVAC through the soaking zone and lower guide outlet, and another small part flows upwards through preheating-roasting zone directly,3kinds of gas distribution modes and2critical conditions can present in the PSF. When the guide outlet on the IVAC is open (State2), there are six gas flow trends in the PSF:The majority oblique outflow through the roasting zone and the preheating zone, small part of the gas flows downwards into the IVAC through the lower guide outlet. Most of the cold cooling gas flows into the IVAC through the cooling zone and lower guide outlet, small part flows upwards through roasting preheating zone directly,2kinds of gas distribution modes and1critical conditions can present in the PSF.(2)Among the operation parameters, inflow velocity ratio is the most important factor of gas distribution pattern. State I, roasting speed remains unchanged, when adjusting the velocity of the cooling gas, when the inflow velocity odds ratio k*=1.13, the gas distribution pattern is in the critical state I in the PSF, when the inflow velocity odds ratio k*=2.8, the gas distribution pattern is in the critical state II in the PSF. The velocity of the cooling gas remains unchanged, when adjusting the roasting speed, when the inflow velocity odds ratio k*=1.01, the gas distribution pattern is in the critical state I in the PSF, when the inflow velocity odds ratio k*=3.2, the gas distribution pattern is in the critical state Ⅱ in the PSF. It can be concluded that when the inflow velocity odds ratio k*≈1.1, the gas distribution pattern is in the critical state I, when the inflow velocity odds ratio k*≈3, the gas distribution pattern is in the critical state II. When in state II, cooling speed remains unchanged, when adjusting the velocity of the roasting gas, when the inflow velocity odds ratio k*=1.29, the gas distribution pattern is in the critical state II in the PSF. The velocity of the cooling gas remains unchanged, when adjusting the roasting speed, when the inflow velocity odds ratio k*=1.18, the gas distribution pattern is in the critical state III in the PSF. It can be concluded that when the inflow velocity odds ratio k*≈1.2, the gas distribution pattern is in the critical state III.(3)Among the structural parameters, the size of guide outlet, the preheating-roasting zone width b1, the preheating-roasting zone height h1, the soaking zone width b1and the soaking zone height h2are main factors of gas distribution, when in state I, the size of lower guide outlet decreases, the size of higher guide outlet increases, the preheating-roasting zone width b1increases, the preheating-roasting zone height h1decreases, the soaking zone width b2 increases and the height of soaking zone height h2decreases, the proportion of the cooling gas which flows upwards increases, the proportion of roasting gas which flows downwards decreases. When in state II, the size of lower guide outlet decreases, the preheating-roasting zone width b1decreases, the preheating-roasting zone height h1increases, the soaking zone width b2decreases and the height of soaking zone height h2increases, the proportion of the cooling gas which flows upwards increases. |
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