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Is it possible to use the waste gas, exhausted from Cold Box (Nitrogen process), for combustion purposes in, for instance, fire heaters? Now, the oxygen supply in fire heaters is the atmospheric air while the waste gas, as oxygen rich gas, can be used during the revamp procedure.
26/06/2011 A: Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
The waste as from Cold box is nothing but enriched Oxygen. Enriched oxygen can be tried out for injection in to the catalyst regeneration systems. In FCCs etc., this injection of enriched oxygen can reduce the load of Main Air Blowers.
27/05/2010 A: SUNDEEP GUPTA, BECHTEL, sundeepgupta1@rediffmail.com
If you try to use enriched Oxygen in your Heater; you will need quantity of Air for the combustion needs. You need to be careful, that the Heater is designed for Air. When flue gas side flow reduces, it will impact heat transfer in the Convection zone..it will come down. You will also need to be careful with Burners' operation, check with the vendor.
26/05/2010 A: keith bowers, B and B Consulting, kebowers47@gmail.com
In theory you CAN use the cold box purge which is oxygen enriched. HOWEVER, the devil is in the details. It will have to be compressed some to pipe to the furnace location and the maximum oxygen content determined so material and cleaning procedures used are compatible with that higher oxygen content and not hazardous. Then you must design an air mixing system to blend regular air and this oxygen enriched stream to a uniform composition and then distribute the mixture to all the gas burners. You must also consult with the burner vendor/designer and determine if the burners will tolerate the much higher flame temperature. The same question must be asked of the furnace designer. Without the cooling effect of the diluent nitrogen, the flame temperature is much higher, combustion gas products much lower in mass and volume, and poor heat transfer may result in very hot spots on tubes and rapid failure. ID fans will be operating with much lower volume and may 'surge' or be unstable. Convection section transfer will be adversely impacted.
In the end, I very much doubt the economics will be favorable unless it results in higher unit capacity and the upgrading margin is significant. The added complexity must be considered as the necessary safety interlocks and high speed oxygen analyzers may reduce operating reliability.
26/05/2010 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
In theory the reject oxygen from a nitrogen plant could be used in a fired heater. Flame temperature would go up and there would be numerous safety and materials issues that would need to be addressed. I am not aware of this being done commercially so a lot of extra effort would be required to get a safe workable design.
Generally a more valuable place to use such a stream would be to enrich the oxygen concentration of the make up air to the sulfur plant or FCC. Oxygen enrichment, especially for sulfur plants, is a well proven technology for debottlenecking sulfur plants.