On slurry filtration technology
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In our facility, the catalytic slurry is filtered through a slurry filter before being sent to delayed coking. However, the requirements for the filtered slurry are very strict, with an ash content of less than 0.1%. However, the quality of the slurry is quite poor; its density is over 1.1, and the solid content in the slurry before filtration ranges from 6g to 8g. We use MOTT’s slurry filters, and these filters often experience blockages and damage. The filter needs to be serviced almost every half month, with the filter elements being replaced; around 150 such elements are replaced in a year. The maintenance costs are incredibly high. Our factory has also been researching technologies for slurry filtration. Recently, a colleague told us about a technique that involves using vane filters; before filtering, a layer of diatomaceous earth is applied to the filter vanes first, and then filtration is carried out using the resulting filter cake. After filtration, the filter cake is discarded, and the vanes are coated again before starting the filtration process once more. It is said that this approach is being used in China. I think it’s pretty reliable; at least the filter elements won’t get clogged. Are there any of you who are familiar with this technology, or who find it promising and interested? Let’s discuss it together.
This post was last edited by altpage on 10/9/2019 at 15:26. There’s no issue with the filter itself, but consideration needs to be given to what to do with the filter cake – that is, how to handle diatomite, catalyst dust, and oil sludge residues. Should it be treated as solid waste?
What mesh size have you chosen for your filter elements? If the pore size is too large, pre-filtration is necessary in order to achieve effective filtration; once the catalyst enters the filter elements, backwashing becomes ineffective. It is possible to consider not using metal powder sintered filters; doing some research might yield surprising results. We are also conducting research at the moment
Yes, this technology enables the oil content in the filter cake to be reduced to very low levels through nitrogen purging. Additionally, catalyst dust must always be dealt with; this technology increases the cost associated with diatomaceous earth as waste material. However, when considered overall, its cost advantage is still significant compared to existing methods.
If the level of precision is not too high, could we try using a fully automatic cleaning filter with a wedge-shaped filter screen? If the medium is viscous, a scraper-type cleaning method can be used inside. . . It can be used as a reference.
Pre-coated cellulose would be more suitable; after incineration for waste treatment, only catalyst powder remains, which makes subsequent processing easier. For filtering elements, blade-type and bundled types can be used to compress the gas.
There are too many impurities; it’s clear that no pre-filtering was done, and the required filtration precision is quite high, so blockages are inevitable. In such cases, multi-stage filtering should be employed – removing larger solid particles at the initial stage, followed by a second filtering step – which would help to reduce waste of filter elements.
Personally, I think the solid content before filtration is still too high. It may be necessary to adjust the operation of catalytic cracking. Another option to consider is installing a coarse filter at the front. It is said that domestic filters are available, which can significantly reduce the cost.
If the filter element used for filtering the slurry is a wire mesh, it will get clogged very easily; try using a metal powder filter element instead