Refining caustic

On the other hand, certain types of wood pulp, prepared by se((uences involving both acidic and alkaline treatments, show a linear relationship between gamma-cellulose and non-cellulosic polyoses. This may be illus-strated from the studies of White, Steinman and Work on acetylation pulps. Acetylation-grade pulps are usually prepared from softwoods by sulfite cooking followed by hot-caustic refining. When the total polyose content of a number of such pulps was compared with their gamma-cellulose content, a linear relationship was obtained (see Fig. 3). In spite of this excellent correlation, it cannot be assumed that all of the non-cellulosic polyoses are contained in the gamma fraction of these pulps (see below). 

Phospholipids. These components are better known to oil processors as phospha-tides and are frequently referred to, together with small quantities of carbohydrates and resins, as gums that have adverse effects on product quality and refined oil yield. Phosphatides are emulsifiers, and so hinder the separation of oil and water phases in the caustic-refining process. The phosphatides are broadly separated into hydratable and nonhydratable types. As the name implies, hydratable phosphatides can be removed by treatment with water, and the nonhydratable compounds, which are salts or coordination compounds of calcium and magnesium primarily... 

Re-Refining— In handling dark oils, it frequently happens that no matter how efficient the original caustic refining of a crude cottonseed oil may be, the bleached color is less than desired. Under these circumstances, it becomes necessary to re-refine the oil for additional color removal. Usually, 1% or 2% of a 16°Be caustic treat is sufficient to provide a bleach color of 2.0 to 2.5 Lovibond red color (123). 

Chemical Refining. Also called caustic refining, chemical refining involves three stages (1) gum conditioning and neutralization, (2) bleaching and filtration, and (3) deodorization. 

Soapstock contains fatty acid soaps and, for oil that is caustically refined, ory-zanol (5-10%). The soaps may be acidulated for feed use and the oryzanol isolated (16). Diethyl ether, alumina chromatography, and crystallization are used for purification of the oryzanol. 

The article is directed mainly at conventional caustic refining and related downstream processes with related considerations in physical refining and new... 

Caustic refining with single-stage water wash 27,000 kg/hr nondegummed soybean oil. 

Soapstock Handling. The largest factor affecting wastewater loading is handling of refinery soapstock when caustic refining is employed. Four methods are routinely employed ... 

Caustic refining in particular does not only effectively perform the separation functions described above but is considered more forgiving in operation than alternate physical methods. If the degumming operation has been less than perfect (or is not used), alkali refining will remove the bulk of the phosphatides. If a high amount of metals, particularly calcium and magnesium, are present, these can be... 

The basic processing steps consist of (1) crude oil storage (2) degumming or caustic refining (3) bleaching (4) hydrogenation (5) fractionation or winterization (6) deodorization and (7) finished oil storage. Each step removes specific components from the oil. These materials may be classified as ... 

Caustic refining Free fatty acids Phosphoiipids Trace metais Pigments—coior bodies Pumping Storage tank to iniine mixer to centrifuge 74 (165) Ambient to 50 (122) Nitrogen or air... 

TABLE 1. Hormite vs. Montmorillonite Response to Acid-Activation and Comparison of Bieaching Efficiency in the Treatment of Caustic Refined Soybean Oii (0.5 wt% Ciay Dosage) (31). 

Chemical refining Sequence of process stages, which definitively includes alkali refining (also referred to as caustic refining or neutralization) to remove most of the FFA and, in most cases, also deodorization in the last stage. 

Most seed oils contain 0.2-0.8% nonhydratable phospholipids (5), specifically the magnesium (Mg) and calcium (Ca) salts of phospholipids, which cannot be removed by water degumming. For many years, a common way for nonlecithin producers to degum edible oil was to treat the oil with 0.02-1% of concentrated phosphoric acid at 70-90°C, after water degumming. Then, without the removal of any precipitated solids, the oil is caustically refined. Phosphoric acid chelates the Ca and Mg in the oil so that the nonhydratable phospholipids are converted into the hydratable form. The phosphoric acid pretreatment produces a darker lecithin with lower purity (5). 

Degumming with acetic anhydride. The process is referred to as the Staley 50 process. Acetic anhydride (0.1%) is mixed with preheated oil (60-70°C) for 15 min, and the mixture is stirred for 30 min after the addition of 1.5% water. The degummed oil obtained is claimed to require no caustic refining. However, the Staley process does not work well with highly colored vegetable oils like cottonseed oil (5). 

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