Issues regarding coking in gasoline hydrogenation catalysts
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The gasoline hydrogenation unit in our facility began operations in November 2009, and the startup went smoothly. The raw material used at that time contained a relatively high sulfur content of 1200–1400 ppm; after hydrogenation and refining, the sulfur content in the product was reduced to below 150 ppm. During operation, an interruption in the supply of dry gas caused the unit to operate at reduced capacity, but this interruption lasted only about an hour. At that time, the temperature of the reactor bed was 70°C lower than the normal operating temperature. There was also another instance when a power outage lasted half an hour, which led to an emergency shutdown. As a result, after the unit resumed operation, the pressure drop across the reactor bed increased day by day, and the catalyst began to coking. We had no choice but to shut down the unit in order to carry out maintenance on the catalyst. Ask colleagues if they have encountered similar issues, and also seek advice from experts on how to reduce coking in catalysts
Coking may cause the feed diene to polymerize and coker; it is recommended to install a dediene reactor!
If it is caused by diene coking, and your plant carries out hydrogen mixing before the heating furnace, you can add a hydrogenation reactor before the heating furnace; low-temperature hydrogenation using a nickel-based catalyst will suffice, with the heat from the heat exchanger being adequate!
Such rapid coking is likely due to the high content of dienes in the gasoline, which causes coking to form at the top of the catalyst. Check whether there is coking in the heating furnace and heat exchanger. Does your factory use Fuyan’s OCT-M technology? The OCT-M process does not include a pre-hydrogenation de-dienol unit, which is why this result occurs. A diene-removal reactor can be added in front of the fractionation tower, or a diene-removal reactor can be added in front of the hydrogenation reactor for the heavy gasoline fraction.
The modified device feeds material directly, eliminating the storage and transportation process and preventing dienes from coming into contact with air.
Our company uses the OCT-M technology developed by Fuyan. The process based on this technology does not include a step for pre-hydrogenation to remove dienes. The refineries in our vicinity all use a single reactor, and their operation efficiency is poor; they tend to suffer from coking issues
Reply to 5# Canghai Hengliu: This has nothing to do with dienes coming into contact with air. In the pipeline, gasoline and air have little opportunity to come into contact. Dienes themselves tend to polymerize into gum-like precursors at high temperatures, leading to coking.
Reply to 1# Tianshan Wangyue: We are from the Fuyan Institute’s OCT-MD team; we were the first to experience coking, and we are currently preparing to add a low-temperature hydrogenation protection reactor.
This is already the second time we’ve turned our heads; this time we also plan to replace the existing protective agent with a new one
It is changed to two-stage hydrogenation: selective low-temperature hydrogenation at the front to saturate dienes, and high-temperature hydrogenation at the back for deep desulfurization. If you don’t want to make major changes, then focus on the raw materials and catalysts
Is the quality of raw materials strictly controlled?~~~~