Commissioning of the continuous reforming regeneration system
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Hello everyone, I would like to ask: when CCR is started up and black combustion is used to protect the catalyst, is it because there is a high amount of carbon buildup on the catalyst? Does the smoke generated by burning escape from the top? There are also the chlorine adsorption tank and alkali washing options – which one is better? Thank you.
It’s not because there’s a lot of carbon buildup; it’s because the amount of carbon buildup is uncertain or uneven, which is why black burning is used
To achieve uniform carbon deposition, the carbon content in the regenerated coke must be between 3-7%, so as to ensure complete combustion of the catalyst in the coking zone. Flue gas enters from the top and is circulated by the regenerative fan, with the excess being discharged through a pressure differential control valve. Chlorine adsorption can reduce the amount of recycled tetrachloroethylene that needs to be injected, but poor thermal control can cause severe corrosion. Alkaline cleaning is used very rarely these days as it is difficult to control. Fixed-bed dechlorination can be considered.
The black burning of the catalyst is primarily aimed at preventing the catalyst in the regenerator from being damaged due to overheating caused by combustion in high-oxygen areas as a result of carbon content; the flue gas from regeneration flows from the top of the regenerator to the regeneration fan for circulation, with any excess being discharged through a pressure difference control valve. Chlorine adsorption can reduce the amount of recycled tetrachloroethylene that needs to be injected, but poor thermal control can cause severe corrosion. The alkali washing process has issues such as difficulty in controlling the pH of the alkaline solution and crystallization.
Currently, two flue gas dechlorination tanks are installed before the flue gas is released into the atmosphere, one in operation and one as a backup. This approach leads to problems such as non-compliance with environmental standards, difficulties in handling the waste liquid from alkaline cleaning, corrosion issues, and instability that often results in frequent shutdowns
During the regeneration of black burn, there is no air in the heating zone; it is a nitrogen-filled environment. During boiling, air passes through the bottom of the regenerator. If dry burning is used when starting up the regenerator, the carbon-containing catalyst may move down to the chlorination zone, and the high temperature may cause damage to the internal components of the regenerator. Therefore, air is introduced from above at the start of operation; once there is no coke in the catalyst below the burning zone of the regenerator (1. no black substance, 2. no black carbon in the center of the catalyst, 3. catalyst carbon content less than 0.2), the operation is switched to white burning
It’s because the location of the carbon-containing catalyst is unknown
1. When regeneration begins, the main issue is uneven carbon deposition and unstable burning during regeneration; using black burning is relatively safer and easier to control, thus protecting the catalyst and the regenerator. 2. It is recommended to use dechlorination tank technology; alkali treatment is difficult, and alkali scrubbers tend to get clogged.
The dechlorination tank has a simple process, while the washing process is complex and prone to water contamination; however, its effectiveness should be better
During black burning, it can be done quickly; a rough burn is sufficient, and after the carbon buildup on the catalyst has settled, it can be switched to white burning. Burnt gas is discharged from the top of the chlorine adsorption tank or the alkali scrubbing tank. The chlorine adsorption tank results in a high hydrocarbon content in the flue gas, and the adsorbent is difficult to handle. Alkaline water is prone to clogging in winter, and it is not as easy to handle compared to chlorine adsorption!