Where does the air for the cooling zone and drying zone come from after reshaping, regeneration, darkening, and burning?
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I have been learning about the process of *reforming units recently. In the normal operation mode, air is introduced from below (that is, into the cooling and drying zones), while in the black combustion mode, air is introduced from above; in this mode, the air goes directly into the regenerative electric heater. So, after switching from reforming/regeneration mode to black combustion mode, where does the air for the cooling and drying zones come from? It’s also possible that I misread the diagram; I hope the experts here can give me some guidance. Finally, it would be great if someone could provide a simple diagram showing the processes for black-braising and white-braising. Thank you
During black burning, the lower air valve is closed while the upper air valve is open; the nitrogen valve and the valve for mixing nitrogen with air are also open, allowing gas to enter the cooling zone and then the drying zone. For black burning, the upper air valve (black burning air line) is used to control the oxygen content
During black burning, oxygen injection is stopped at the lower part, and instead oxygen is injected at the entrance of the charring zone. During black burning, the oxygen content in the oxychlorination zone is very low, and water and chlorine injection for oxychlorination are also halted.
I don’t see any nitrogen valves on the DCS; so how is it ensured that the regenerating gas in the drying zone is free of oxygen?
Why black-braise? It’s the uncertainty about whether the burning area can reduce the carbon content to the required level. For example, if regeneration is stopped, high-carbon catalysts accumulate; when these high-carbon substances enter the oxychlorination zone, the high oxygen concentration there can cause excessive temperature rise and damage to the equipment. To avoid this, in the case of black burning, air is introduced into the burning zone while nitrogen is introduced at the lower part. In this way, it doesn’t matter if all the carbon in the burning zone isn’t completely burned up, as the nitrogen environment prevents excessive temperature rise.