Stage Dewaxing

A second stage of filtration can be used to reduce the oil in wax and to increase the dewaxed oil yield. Solvent (called repulp or repuddle) is added to the wax from the first stage, t3 ically in the wax scroll or wax boot depending upon the plant design, and pumped to a filter feed drum that feeds the second stage of filters. 

Filtrate from the second stage is lean in oil and can be used in first stage operation. It may be blended with fresh solvent and used as first stage wash, or it may be added as the final increment of dilution in an incremental plant. Recycling the 2nd stage filtrate reduces the overall solvent usage. 

The deoiling process is used to produce a hard wax containing a very low oil content. Waxes produced in deoiling have melting point and needle penetration specifications. Waxes intended for food grade use must also meet UV absorption specifications and require wax hydrotreating. 

In recrystallization deoiling, lean solvent is added to the wax from the dewaxing plant and the resulting slurry is pumped through a heat exchanger where the wax crystals are melted. The wax is then lecrystallized in SSEs and SSCs. Typically two stages of deoiling are used to meet the low Oil in Wax specification. 

DILCHILL dewaxing is ideally suited for Warm-up deoiling. The spherical nature of the crystals facilitates the melting of the softwax and re-crystallization is not required. 

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The process is reported capable of dewaxing any wax-bearing stock, either raw or after selective solvent refining, and waxes with a relatively low oil content may be obtained, by a two-stage operation in which the wax from the primary stage is rerun after further dilution with cold solvent on a second battery of centrifuges. 

Stage 4 - dewaxing. The final process after the tissue sections have been deposited onto the FTIR substrate is the removal of paraffin from tissue that would... 

A common sintering cycle includes several stages, such as dewaxing, presintering, sintering, and cooling. For pressed-to-shape parts, it is customary to combine dewaxing. 

IFP s paper on their Spanish plant described their hydrocracked stocks as having about the same stability to oxidative storage conditions as those from solvent refining. This has generally not been industry experience elsewhere. In fact, unfinished first-stage hydrocracked base oils, waxy or dewaxed, have been found to darken in color over relatively short times and form haze or insoluble deposits, and these effects are accelerated when samples are exposed to high (about 100°C) temperatures or sunlight in so-called window tests, which were later replaced by more specific exposure to ultraviolet (UV) sunlamps. This was... 

Stage hydro-isomerization Vacuum stripper Solvent dewaxer... 

Example 20.1. By extraction with kerosene, 2 tons of waxed paper per day is to be dewaxed in a continuous countercurrent extraction system that contains a number of ideal stages. The waxed paper contains, by weight, 25 percent paraffin wax and 75 percent paper pulp. The extracted pulp is put through a dryer to evaporate the kerosene. The pulp, which retains the unextracted wax after evaporation, must not contain over 0.2 lb of wax per 100 lb of wax-free pulp. The kerosene used for the extraction contains 0.05 lb of wax per 100 lb of wax-free kerosene. Experiments show that the pulp retains 2.0 lb of kerosene per pound of kerosene- and wax-free pulp as it is transferred from cell to cell. The extract from the battery is to contain 5 lb of wax per 100 lb of wax-free kerosene. How many stages are required ... 

Aluminum Phosphate-Based Molecular Sieves. Although still in the early stages of development, aluminum phosphate-based molecular sieves have shown great promise as a microporous catalyst and an adsorbent material. They were first reported in 1982 with a neutral aluminum phosphate (AlP04)-n framework (15), Si, other metals (such as Be, Mg, Ti, Mn, Cr, Fe, Co, and Zn), and other elements (such as Li, B, Ga, Ge, and As) have subsequently been incorporated into the AIPO4 framework these substitutions have allowed additional applications for the catalyst. Some of the applications reported are catalytic dewaxing, hydrocracking, methanol conversion, and toluene alkylation. 

The scroll is an Archimedes screw that moves slack wax from the outer ends of the filter to a center pipe. The slack wax falls down the pipe and may either proceed down a slide where it may be combined with slack wax from other filters into a slack wax drum or into a wax boot or vessel. This is a small drum dedicated to the filter. From the large wax drum or the wax boot the slack wax is pumped to either wax recovery, the second stage of dewaxing or deoiling depending on the plant configuration. 

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