Deoiling of slack waxes using a pulsed crystallizer

Abstract

A process was developed for deoiling of slack waxes with a pulsed crystallizer which proposes totally eliminating scraper crystallizers -regenerative and evaporative -from the process scheme.Exhaustively deoiled waxes are obtained with significantly simplified implementation of the process and reduced operating costs.The oil blocks in domestic oil refineries (OR) basically consist of raffinate dewaxing units. Combined dewaxing-deoiling and slack wax deoiling units are encountered much less frequently.As the price of paraffin wax products has increased, organizing production in enterprises with no specialized capacities has become urgent. One way of solving this problem is to convert one dewaxing unit to deoiling the slack waxes obtained in other dewaxing units. When the refinery has a slack-wax deoiling unit, the problem is simplified.The flow chart of a dewaxing or deoiling unit operating after incorporation of a pulsed crystallizer in conditions of production of solid waxes is shown in Fig. 1. Feedstock (slack wax) I, previously mixed with part of filtrate II from the second filtration stage, enters temperature stabilization heat exchanger 1 and then pulsed crystallizer 2, and wet solvent IV, cooled in evaporative (propane or ammonia) condenser 8, is fed into the lower collector. Wet solvent VII is first cooled in heat exchanger 5 with some of the filtrate from the second filtration stage that dilutes the feedstock. Some of wet solvent V cooled in condenser 8 goes to the filters for washing and dilution of residues.Filtrate IX from the first filtration stage (solution of deoiling filtrate) cools dry solvent VI in heat exchanger 6, and solvent VI is then cooled to the required temperature in evaporative condenser 7 and moved to the upper collector in the pulsed crystallizer.A balanced amount of filtrate VIII from the second filtration stage enters for dilution of feedstock suspension X from the pulsed crystallizer before filters 3 from the first filtration stage. The residue of wax XI (missed with the solvent) after second filtration stage filters 4 goes to the solvent regeneration second, like the solution of deoiling filtrate III after heat exchanger 6. The basic process parameters and operating indexes of the dewaxing (deoiling) units in production of exhaustively deoiled waxes are reported in Table 1.