Cleaning Up Amine

The iron sulfide particulates circulating in a dirty amine system have built up from a combination of factors. Foremost among these is inadequate filtering.

There are three common types of filters: rotary precoat filters, cartridge filters, and stacked paper plates. In practice, paper plates are best. In particu­lar, Sparkler stacked filters are easy to maintain. Operation of rotary precoat filters is too complex for many refinery applications. Cartridge filters are good, except that the cartridge cost can be high when frequent change-outs are necessary. Stacked paper plate filters are quite simple: The paper is discarded after each use. On one unit it was estimated that 1,000 lb of particulates had accumulated in one 50-plate Sparkler filter.

The trick to successful filter operation is always to filter 10% of the circulating amine. In practice, two filters are piped up in parallel. When one filter cannot pass 10% of the flow without exceeding 50-psi pressure drop, switch filters. Then immediately change the paper in the spent filter.

For a clean, well-designed unit, switching on a one-month cycle is typical. When amine is black, one may be switching filters every day for a month before solution cleanliness is improved. It will take two men three hours to renew a large paper-plate unit. The operating engineer needs to convince the unit superintendent of the necessity to invest in this mainte­nance manpower to change filters regularly on a priority basis.

The purpose of the charcoal filter is not to remove particulates. The charcoal is there to absorb heavy hydrocarbons or soluble materials that have contaminated the amine. Only filtered amine should be charged to the charcoal filter. The effluent from the charcoal filter should be re-filtered in a sock-type filter to remove charcoal particulates or be recirculated back to the primary lean amine filter.

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