Why should the H2S content in the feed gas be below 0.1 PPM?

The synthetic catalyst is mainly Cu-Zn-Al, among which copper is particularly sensitive to sulfides, not just hydrogen sulfide. The catalyst becomes poisoned and loses its activity when it comes into contact with sulfides. It is permanently invalid.

Catalysts used for the synthesis of methanol are generally copper-based. If the sulfur content in the syngas is too high, it will react with the copper in the catalyst to form stable copper sulfide, thereby rendering the catalyst inactive. This reaction is irreversible, resulting in the permanent loss of catalyst activity.

H2S reacts with the active copper in the catalyst to form copper sulfide, and since H2S cannot be completely removed, an additional meter of catalyst was installed on the tubes of the synthesis tower. On the one hand, it provides heat to bring the gas to an appropriate temperature; on the other hand, it can absorb H2S that has not been completely removed, resulting in high temperatures due to adiabatic effects. This accelerates the thermal aging of the catalyst, causing it to become inactive quite quickly. But it can absorb a certain amount of H2S

In fact, it is to protect the synthetic copper-based catalysts from being damaged by poisons and to extend their service life.

Regarding the excessive parameters of the process gas at the top of the tower: I think it’s possible to rule out potential issues in a step-by-step manner, starting from the simplest ones. First, it’s necessary to rule out problems with the system itself. 1. Eliminate any issues with the instruments, such as instrument failures, data interruptions, transmission problems; most importantly, rule out the possibility of false readings. 2. Address equipment-related problems: 1) The tower may not be installed vertically, or the gas-liquid distributor may not be level. 2) The packing or sieve plates might be damaged. 3) The packing or sieve plates could be clogged, although the sieve plates are in good condition. 4) The gas-liquid distributor might be blocked, resulting in insufficient amounts of lean methanol. 5) Severe fouling on the walls. 6) Leaks in the heat exchanger, allowing gas to mix with the syngas. What remains then are problems related to the process itself. 1. Gas-related factors: 1) High pressure difference in the tower, meaning excessive load, which can also lead to flooding； 2. Changes in the composition of gas: high carbon dioxide content ； II. Temperature factors: 1. High gas temperature leads to poor absorption ； 2. Insufficient cooling capacity of the system, resulting in a reduced absorption capacity ； III. Absorption issues: 1. If the moisture content or other impurities in methanol are too high, the absorption capacity is reduced ； 2. Incomplete regeneration of methanol absorption ； IV. Operational issues: 1. Insufficient methanol absorption circulation rate ； 2. The valve controlling CO2 absorption is opened too wide. 3. Insufficient amount of nitrogen gas, resulting in desorption issues. 4. Incomplete thermal regeneration

To extend the service life of conversion catalysts and synthesis catalysts, they are converted into NiO or synthesized into C307 copper-based catalysts. Excessive hydrogen sulfide levels can cause permanent poisoning and deactivation of the catalysts; furthermore, hydrogen sulfide dissolving in water to form hydrosulfuric acid can also corrode equipment pipelines.

It prolongs the service life of conversion catalysts and synthesis catalysts; it converts nickel catalysts into C307 copper-based catalysts. Excessive hydrogen sulfide levels can cause permanent poisoning and deactivation of the catalysts.

Is purification done by using low-temperature methanol washing to remove sulfides? If so, can the required standards be met?

Sulfides have a significant impact on the service life of methanol synthesis catalysts; zinc-chromium catalysts are more resistant to sulfur, and the sulfur content in the feed gas should be below 50 PPm. Copper-based catalysts have high requirements regarding sulfur; the total sulfur content in the feed gas should be below 0.1 PPm. This is because sulfides react with the metal active components in the catalyst to form metal sulfides, thereby rendering the catalyst inactive (Cu + S = CuS). Therefore, it is essential to remove all sulfides from the syngas before it enters the reactor.

1. Toxic transformation and synthesis catalysts, especially synthetic homocatalysts, are highly sensitive to hydrogen sulfide; their activity can easily be lost if the concentration of hydrogen sulfide exceeds the limit! 2. Corrode pipeline equipment, reducing its service life. 3. Affects product quality.

It must be kept below 0.1PPM; if the limit is exceeded, the operation must be stopped immediately!

It’s not that serious, right? Could you explain why? If it adjusts over time, there’s no need to stop the vehicle!

Catalysts used for conversion and synthesis are very sensitive to sulfides, which can easily lead to a decrease in their activity. This applies not only to H2S; moreover, H2S is also relatively easy to remove. Mild poisoning of the catalysts does not require an immediate shutdown – it is sufficient to detect the problem early and take action promptly, making process adjustments such as increasing the temperature or hydrogen supply in order to reduce sulfur content, as well as adding more process steam. In this way, normal operating conditions can be restored quickly. Moreover, sulfur poisoning is reversible. Of course, if the desulfurization reactor is damaged beyond repair, there is no other choice but to shut down the system urgently and replace the desulfurization catalyst.

The catalyst component used in methanol synthesis is mainly copper! Copper-based catalysts! H2S easily poisons the catalyst, causing permanent poisoning.

Prevents poisoning of the converted nickel catalyst and synthetic copper catalyst, thereby extending the catalyst’s service life.

It is possible to calculate the ratio of the cumulative sulfur atoms to the copper atoms in the catalyst during the estimated production period; this value is likely to be no more than 0.05 percent

Copper-zinc catalysts lose their activity when in contact with sulfides, and they are very sensitive to them; therefore, the concentration must be reduced to 0.1PPM

How can one determine the accumulated sulfur atoms and the copper atoms in the catalyst?

To protect the catalyst, excessive sulfur levels can cause poisoning of copper-based catalysts, leading to permanent inactivation

Prevent catalyst poisoning during the synthesis process, as poisoned catalysts cannot be reversed. Catalysts are extremely expensive, and it is very troublesome to stop the machine in order to replace them. It seems to be asking for the total sulfur content in the feed gas, rather than just the H2S content. In some processing procedures, online monitoring of the total sulfur content is feasible, while in other processes it is not necessary; instead, the total sulfur content is measured offline during startup and commissioning or when there are fluctuations in the process. Once the process becomes stable, there are generally no significant changes.