At the end of the catalyst cycle, the spent catalyst may either be regenerated for reuse or be sent for elimination and metals recovery. In order to optimize the regeneration or metals recovery process, it is important to prepare the shutdown carefully to ensure that the spent catalyst is conditioned optimally for further processing, both for safety and cost reasons. The shutdown procedure may involve a hot hydrogen strip of the reactor to remove volatile hydrocarbons from the catalyst, or even a low oxygen burn to reduce the carbon / coke on the spent catalyst to reduce its reactivity towards air.
After the shutdown, specialized catalyst-handling companies will unload the reactor. It is important to keep track of the location inside the reactor where the catalyst originated. It is a best practice to number the drums per reactor bed and identify the catalyst types, drum number and reactor and bed IDs on a clear label. This will help with cost-effective analysis of the spent catalyst and in distinguishing between a good-quality catalyst for reuse and a contaminated catalyst for elimination. Thorough analysis of the spent catalyst can reveal why the catalyst deactivated, how it got poisoned, or why it caused the pressure drop to increase. This post-cycle analysis can be used to propose improved loading diagrams.
Several companies offer ex-situ regeneration and rejuvenation of spent hydro-processing catalysts. Regeneration is used to remove the carbon and sulphur from the spent catalysts. Rejuvenation is necessary for some catalysts with type II active sites to redisperse the active metals after regeneration. There are several rejuvenation processes on the market, some developed by the fresh catalyst producers, some by the regeneration companies. Catalyst Intelligence can advise on unloading strategy, packaging and labelling of the spent catalyst, plus analysis of the spent catalyst and laboratory analysis and regeneration to determine suitability of the material for reuse. After regeneration and/or rejuvenation, the catalyst destined for reuse should be sampled and analyzed to determine whether the service provider has met the guarantees.
Spent catalyst that can not be regenerated or rejuvenated should be sent for elimination. The purpose of the spent catalyst recycling is to recover valuable metals and to convert hazardous waste into non-hazardous waste or construction material. The metal reclaimers offer either hydro-metallurgical metals recovery or pyro-metallurgical metals recovery, each with its own advantages and disadvantages. For the catalyst user it is important to find a reclaimer that can recover a high percentage of the contained metals and convert the rest of the material in a non-hazardous material. The catalyst user should receive a certificate of save disposal. Catalyst Intelligence can help you find the best reclaimer for your spent catalysts.
Since 2016, we have been involved in several spent catalyst analyses to understand unit performance and to select best reclaim options. In addition, we have been involved in several due diligence projects into spent catalyst reclaim companies, as interest in save disposal and recycling of scarce resources (base metals, noble metals) is increasing.