Some thoughts on the oxygen flow regulation issue in four-nozzle gasification furnaces!
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Some thoughts on the regulation of internal oxygen flow in four-nozzle gasifiers: In our company, the regulation of oxygen flow and water-coal slurry flow operates as a dual-cross regulation system with the oxygen-to-coal ratio setting as a fixed value. Theoretically, this regulation system can meet the process requirements while ensuring that the gasifier does not experience an excess of oxygen; that is, when the load increases, the water-coal slurry flow increases first, followed by the oxygen flow； When the load is reduced, the oxygen flow rate decreases first, followed by the coal water slurry flow rate ； Ensure that the water-coal slurry is increased first and decreased later to prevent excess oxygen in the gasifier. Based on our company’s experience, the load of the gasification furnace does not change frequently; therefore, it is also possible to use single-loop control for oxygen regulation and coal-water slurry regulation respectively, in which case the oxygen-to-coal ratio needs to be determined manually. If the water-coal slurry flow rate is set, the oxygen flow rate value is calculated based on the oxygen-to-coal ratio, and then the oxygen flow rate is adjusted.
Does everyone know how to calculate the oxygen-coal ratio?
For calculations in process control systems, a simple configuration based on direct ratios is usually sufficient. Oxygen is typically converted to mass flow rate; the purity level is generally above 0.996, so it can be used directly. The slurry flow rate is determined using a fixed coefficient, and by dividing these two values, the mass ratio of oxygen to coal is obtained for control purposes. If there is a concentration analyzer for the slurry and its output is stable, that value can also be used in the calculations. When the type of coal remains stable, determining the relevant coefficients and incorporating them into the module makes it convenient to carry out approximate calculations in a DCS system
If the coal quality is relatively stable, displaying directly the volume ratio of oxygen to coal slurry is the most straightforward approach:lol
Our company uses the direct volume ratio, that is, the standard volumetric flow rate of oxygen divided by the volumetric flow rate of water-coal slurry. The volumetric flow rate of the water-coal slurry is calculated based on the rotation speed of the diaphragm pump, with reference also being made to the electromagnetic flow meter.
If the coal quality remains stable and the load on the gasifier is constant, it is simple and straightforward to use the volume ratio method: based on the volumetric flow rate of the water-coal slurry, the volumetric flow rate of oxygen is calculated according to the required oxygen-to-coal ratio, and then the volumetric flow rate of oxygen is adjusted accordingly.