Conversion catalyst
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We are a company that produces methanol from coke oven gas. We replaced the catalyst in the converter in April this year, but after a short period of use, we noticed that its activity was very low. The temperature at the hot spots has been raised to 1100 degrees, yet the methane content in the converted gas remains between 1.2% and 1.5%, which is not within the specified range (<0.6%). The composition of the gas fed into the converter is within the acceptable limits; could anyone help analyze whether this is due to a decrease in catalyst activity? How to maintain catalyst activity in production? (We generally perform parking maintenance once a month. After parking, if there are no maintenance tasks required for the converter, we keep the temperature of the converter at around 500 degrees using steam. Does this have any impact on the catalyst’s activity?) ）
1. Check whether the organic sulfur content after precise desulfurization exceeds the limit; for some types of organic sulfur, such as thiophene, there are generally no testing methods available in standard laboratories. It seems that the sulfur content in the gas entering the converter is within acceptable limits, but in fact it has not been detected. It is sufficient to measure the levels of hydrogen sulfide and sulfur monoxide in the gas at the conversion end. 2. Some sources state that prolonged exposure to high-temperature steam can cause excessive oxidation of the catalyst, affecting its activity. 3. Note that too low a water-to-carbon ratio can also result in a low methane conversion rate, as well as easy carbon deposition, which affects activity. For conversion catalysts, I think Sichuan Tianyi’s ones are better. I wonder which brand you use there? 4. The instruments (flow meter and thermometer) should also be checked at the same time. This is just my personal opinion; I welcome corrections from fellow sailors.
The explanation on the 2nd floor is quite comprehensive; the main reasons for the unsatisfactory methane content in the product gas are those mentioned there, hehe
1. Precautions to be taken when loading the conversion catalyst； 1. Loss of head due to venturi effect; 2. The catalyst needs to be screened; 3. Attention must be paid to the filling height, bulk density, and loss of head. 4 The height difference during loading should be as small as possible. Second, during the nitrogen heating process, the temperature should not be too high; it is generally kept between 180-240 degrees. The heating rate should be 30°C per hour, after which steam is introduced to raise the temperature further, to 650-680°C. The heating rate is 50°C/h. At this point, it switches to natural gas reduction. Third, attention must be paid to ensuring proper desulfurization; the sulfur content should be kept below 0.1 ppm. 4. Increase the water-to-vapor ratio as much as possible when conditions permit. 5. Minimize system pressure as much as possible.
1# **sgs, what is your water-to-carbon ratio? If this ratio is too low, the methane content will also increase. Increasing the water-to-carbon ratio is beneficial for methane conversion from a chemical equilibrium perspective, and it also helps to suppress carbon deposition. However, an increased water-to-carbon ratio means higher steam consumption; the excess steam also needs to be heated in the furnace tubes, which leads to increased energy consumption and a higher thermal load on the preheater. Therefore, while meeting the process requirements, the water-to-carbon ratio should be reduced as much as possible.
Increase the water-to-carbon ratio; introduce a certain amount of hydrogen while passing steam to maintain catalyst activity