Conversion catalyst
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This post was last edited by Shuang'er on 2012-4-11 at 11:26. Recently, my sulfuric acid plant underwent major repairs, which involved sorting through the catalysts. During this process, I noticed that some of the catalysts had a green surface, while others were white; a small amount of catalysts had a black surface as well. I would like to ask all experienced colleagues: what could be causing this? :handshake
Whitening: I’m not sure which section of it is turning white; generally, whitening in one particular area is related to an excessively high outlet temperature. Additionally, whitening can be a sign of arsenic poisoning, which leads to a decrease in catalyst activity. Turning green: It is mainly related to the catalyst becoming damp. During the cooling process, when air containing sulfur dioxide was used for blowing or forced ventilation, the sulfur dioxide was not completely removed; as a result, the catalyst turned yellow-green after it was opened. Blackening: One type is the blackening near the converter wall; this usually occurs due to low temperatures on the converter wall, which result in continuous condensation and evaporation of sulfuric acid, leading to a rough surface that becomes blackened on both the inside and outside. Another cause is poor purification parameters and moisture levels that are not within the specified limits; this results in a lower temperature in the latter part of the converter, causing sulfuric acid vapor to condense. Additionally, if hot air is not used to clear away the vapor during cooling, the temperature drops rapidly again, and sulfur trioxide cannot be removed, leading to the condensation of sulfuric acid vapor in the latter part of the system. Thirdly, when the two-stage catalyst is permanently poisoned by arsenic, a black layer forms on its surface and the catalyst turns black; under normal circumstances, the catalyst must be replaced.