Appropriate temperature for shell-and-tube methanol synthesis catalyst

Is the crude methanol of good quality? Is the alcohol content high? Are there any problems with distillation?

The activity of synthetic catalysts gradually decreases as the temperature rises, and this decrease in activity requires an increase in reaction temperature, which is inherent to the catalyst. The timing for replacing the catalyst depends mainly on the conversion rate of methanol synthesis, the system pressure, as well as the methanol content and impurity levels in the crude methanol. It is these factors that determine whether it is still beneficial to continue using the catalyst in that reactor.

I think the analysis upstairs is quite accurate. Another point is: is the catalyst used by the original poster domestic or imported? The quality difference is significant. I’ve seen factories that are fairly good at the moment; it took them almost three years to achieve one degree of growth.

We are from C307 at the South China University of Chemical Technology. Today, the ethanol content in crude alcohol is around 950PPM. The quality of the distilled product is excellent, with ethanol levels below 10PPM. The CO conversion rate has dropped from 48% at startup to around 35% today, with an alcohol content at the exit of the synthesis tower of 3.5%. It’s just that currently, the CO content at the outlet of the synthesis tower fluctuates significantly with the fresh gas flow; the optimal temperature right now should be somewhere lower in the tower. The outlet temperature has only just reached 236 degrees now

As far as I know, the active temperature of the copper-based catalyst C307 from Nanhua Institute is between 190 and 300 degrees. The temperature at which it is currently being used is not very high; considering raising the bed temperature to 240 to 250 degrees should yield the best level of activity. The service life of a catalyst is primarily determined by the content of harmful substances such as sulfur and chlorine in the feed gas. Catalyst poisoning is the most direct factor affecting its performance; other factors include pressure and the operations related to starting up and shutting down the system, which can also accelerate catalyst degradation. . .

What is the scale of the methanol owned by the poster? The capacity is similar to ours; the amount of catalyst used is 15 cubic meters more than ours. What model of catalyst is being used? Why want to change it after just one year?

It seems that the activity of C307 is not high enough. They also submitted a bid for our project, but suggested that the number of catalyst designs proposed was insufficient. Do you experience severe waxing during use? Are there many side effects (the yield of fusel oils)?

Ours is C306; it’s been in use for almost one and a half years now, and the temperature is only 237. I think it can still last another two years. Was the temperature very high from the start for yours? Ours started at 215. Yours must be damaged, otherwise the temperature wouldn’t rise so quickly

1. What is the reason for replacing the catalyst? 2. The operation regarding the temperature of the synthetic catalyst bed is mainly aimed at controlling the drum pressure; given your current situation, the drum pressure has already reached 2.7 MPa. It is recommended that you maintain a stable drum pressure – no further questions needed – and the system can still be used for another year.

The operating temperature is 230–260°C; generally, the catalyst needs to be replaced when the temperature exceeds 260 degrees.

The catalyst has been in use for almost two years; it was put into operation in April 2007. Since a major repair is scheduled for July this year, I want to replace it in advance. If we don’t change it this time, there’s no absolute guarantee that it will still be usable by the end of next year. Some time ago, due to issues with the previous processing unit, the H2S content in the feed gas remained around 0.2PPM; now everything is back to normal. The by-product fusel oil is removed at a rate of 0.9 cubic meters per hour in three towers. The waxing problem was quite severe three months ago; after a thorough wax removal process along with insulation of the ends, it’s much better now

Solution: After the gas preheater before the tower, a protection tank is added in front of the synthesis tower; the protective layers, from top to bottom, are molecular sieve (for dust removal) – zinc oxide (desulfurizer) – dechlorinating agent – arsenic removal agent. For the synthesis catalyst, XNC-98 from the Southwest Research Institute or NC-309 from the Nanjing Chemical Industry Institute is used; the exit temperature during synthesis is maintained between 210 and 265 degrees, while the inlet temperature is above 195 degrees. The water supply to the steam drum is set at 140 degrees plus or minus 5 degrees. As long as the operation is smooth, the average yield, calculated on an absolute alcohol basis, can exceed 0.55 tons per cubic meter per hour; the recycle ratio can be maintained between 4 and 5.5, while the concentration of carbon monoxide and carbon dioxide in the recycle gas can be kept at 5% plus or minus 2%. During the first four to five months of use of the catalyst, the outlet temperature reached 228 degrees plus or minus 1 degree ； Used for three to six months in the final stage, at temperatures above 250 degrees ； The remaining time is in the active intermediate phase; at least one catalyst tower lasts for 2.5 to 3 years. Following this plan, as long as the catalyst is properly maintained, it is expected to last for two maintenance cycles – five to six years. You can send messages or emails to QQ: 51266974 for communication.