PVC synthesis conversion
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After the hydrogen chloride/acetylene ratio for synthetic conversion was adjusted, there was a significant difference in the acetylene and hydrogen chloride contents at the outlet of the second converter. There are usually those reasons; how to make adjustments?
It is mainly caused by the different activity of the catalysts in the converter and the varying operating times of the converter. Generally, this is resolved by adjusting the inlet valves of each converter according to their respective temperatures.
It is mainly due to factors such as catalyst activity, reaction time, and resistance
It is mainly related to catalyst activity (including whether caking occurs, which increases system resistance) and valve opening degree (which is essentially the flow rate). With high catalyst activity and low spatial velocity, the conversion rate is high; the acetylene content is low, so the hydrogen chloride content should also be low. (Is the inference correct? Please advise.)
Adjusting the ratio cannot rely solely on orifice plate metering for acetylene and hydrogen chloride, as there will be some deviations in the measurements. Moreover, due to differences in the purity of hydrogen chloride, the ratios used by different companies also vary. The basis for our adjustment of the ratio is that the hydrogen chloride concentration at the second-stage outlet is 3 to 8 percentage points higher than that of acetylene; an excessive amount of hydrogen chloride increases the level of the by-product dichloroethane, as well as the load on the purification processes. If the conversion rate is low, the levels of outlet acetylene and hydrogen chloride will be high.
The duration of catalyst use varies, and its activity is not consistent, which in turn leads to differences in reaction temperature; as a result, the components at the outlet of the rear converter differ.
Check the internal structure of the converter to see if there is any uneven distribution of the catalyst; it is essential to prevent gas from taking short circuits (for example, at the location of the temperature sensing sleeve)
The operation of each converter varies
It is normal for the hydrogen chloride content at the second-stage outlet to be higher than that of acetylene, mainly due to the different purities of the two feed gases. Generally, the composition analysis results at the second-stage outlet show a hydrogen chloride content of 4–8%, while the acetylene content is below 1%. With such data, the conversion rate should not be very poor.
Can the ratio of converters before and after be adjusted?
Everyone has already analyzed the reasons quite thoroughly, so I won’t say more. From the perspective of control angle, there are two cases: 1. An excessively high HCL content is very dangerous; it is necessary to drastically reduce the flow rate. Because all subsequent equipment will be at risk of corrosion and even penetration! 2. Excess acetylene levels are a manageable issue; it is sufficient to slightly reduce the flow rate of the feed gas and monitor the effects, while also adjusting the reflux ratio for compounds with high and low boiling points. . . In short, once the system is stable, reduce the load on each unit one by one to check the catalysts! This post was last edited by shizhiyong001 on 2009-2-23 10:44.]