The effect of low or high water-gas moisture ratio on the shift converter

Under normal circumstances, increasing the water vapor ratio can improve the conversion rate of carbon monoxide and reduce its residual amount. Furthermore, an excess water vapor ratio can act as a heat carrier, suppressing the temperature rise in the catalyst layer. However, an excessively high water vapor ratio increases the energy consumption during the reaction process, raises the resistance in the bed layer, and increases the load on the equipment in the waste heat recovery system. :handshake active participation

The conversion reaction of carbon monoxide and water vapor in gas can be expressed by the following equation: CO + H2O = CO2 + H2 + heat; increasing the water vapor ratio favors the shift of the reaction to the right.

Could you please be more specific? How is the water vapor ratio affected? Please explain using a low water vapor ratio as an example, thank you

The water/gas ratio (H2O/dry gas) or water/carbon ratio (H2O/CO) is an important parameter in the shift operation. From the equilibrium relationship, it can be seen that within a certain range, an increase in the water/gas ratio leads to an increased equilibrium conversion rate of CO, which helps to reduce the residual CO content and accelerate the progress of the conversion reaction ； At the same time, a higher water-vapor ratio also has an inhibitory effect on side reactions such as methanation. However, the consumption of water vapor is the main factor of consumption during the conversion process, and minimizing its use is of great significance for the economic efficiency of the process. An excessively high water/gas ratio will also increase the resistance in the catalyst bed, and may even lead to reverse sulfidation ； A shorter CO residence time reduces the reaction rate, leading to adverse consequences such as increased load on subsequent waste heat recovery equipment and more process condensate. A low water vapor ratio (usually below 0.5) poses a risk of methanation. Using a high water-vapor ratio to lower the temperature is a contradictory approach: a higher water-vapor ratio increases the depth of conversion, resulting in more heat being released; more steam is then needed to carry away this heat, so it’s necessary to find a balance point.

The conversion rate is high when the water vapor ratio is higher than the temperature, and vice versa.

This post was last edited by 654262293 on 2013-3-16 07:36. When the water-vapor ratio is too high, the CO level at the outlet of the shift converter decreases, and as a result the temperature of the shift converter drops. At this point, the heat released by the CO due to the increased water-vapor ratio is less than the heat carried away by the additional steam； The water vapor ratio is too low, resulting in increased CO at the converter outlet and higher pressures in subsequent processes.

I agree with the opinion from Floor 5 as well. I’ve heard that to prevent the methanation reaction, the issue is addressed by choosing the right catalyst; currently, there are manufacturers in China that use catalysts suitable for low water-gas ratios, and it seems that their operations are quite good

Our factory is undergoing technical upgrades to increase the water-to-vapor ratio in the converter; we still don’t know what the results will be

For example, whether the water-vapor ratio in the converter is appropriate and what value would be ideal depends on specific circumstances; it cannot be generalized. Factors such as the type of catalyst used, the operating conditions, the lifespan of the catalyst, and the system’s configuration all play a role. Furthermore, when the temperature in the converter rises suddenly, it is necessary to determine the exact situation in order to decide on the appropriate course of action

Sulfur-resistant shift reaction: an excessive water-to-gas ratio can lead to reverse sulfidation