Glycerine recovery from spent soap lye

Thesis Overview

<p> </p><p><strong>1.0 INTRODUCTION</strong></p><p><strong>1.1 BACKGROUND OF THE STUDY</strong></p><p>Glycerine, (otherwise known as propan 1, 2, 3 triol) is found dissolved in the soap lye and also as an impurity in the crude soap during the saponification of fats and oils with caustic soda. Customarily, the process of soap manufacture, from fats and oil yields glycerol to about 10% of the value of the soap formed and due to its varied uses, its recovery is pertinent to the manufacturing cost analysis for any soap making business. Glycerol being an important bye product of soap manufacture, many small scale and medium scale soap manufacturers normally discards the lye as an unwanted product.</p><p>Glycerol occurs in nature combined in the form of triglycerides (fats and oil) and is obtained during the saponification of these triglycerides. This process was the only means of producing glycerol commercially, until 1949 when synthetic glycerol was produced as the compound recovered as by-product from the soap manufacture was sufficient for the world consumption. Alternatively, glycerol is synthesized from propene by the alternate chlorination and hydroxylation process. It is also obtained from the fermentation of various sugars. Glycerine is also produced by various routes from propylene. The epichlorohydrin process is the most important; it involves the chlorination of propylene to give ally chloride which is oxidized with a strong base to give epichlorohydrin. This epichlorohydrin is then oxidized to give glycerine.</p><p>In biodiesel, glycerine is a waste, as a result, the market for glycerol is depressed and the old epichlorohydrin process for glycerol synthesis is no more economically viable.</p><p>Fats and oils are esters of glycerine with long-chain fatty acid such as stearic acid (C17H35COOH) Palmitic acid (C15H31COOH) and oleic acid (C17H33COOH). Since glycerine contains three –OH groups, it can form three series of esters thus;</p><p>Mono-ester di-ester and tri-esters</p><p>CH2.OH CH2.OH CH2.O.OC.R</p><p>CH.OH CH.O.OC.R CH.O.OC.R</p><p>CH2.O.OC.R CH2.O.OC.R CH2.O.OC.R</p><p>Mono=-ester di-ester tri-ester</p><p>Some of the major industrial applications of glycerol include the manufacture of alkyd resins and flexible polyurethane for the plastic industry. It is also an important ingredient in cosmetics and adhesive manufacture. Many pharmaceutical preparations such as glycerol phenol mixture which serves as tranquilizers utilize glycerol.</p><p>Glycerol residue has been reported to contain 20.2% glycerol, 6.6% fatty acids (as soap) and 64.3% salt. Thus 91.1% of it is potentially useful. It is obviously advantageous, both environmentally and economically, to recover the glycerol in the waste material from soap industries as a potential alternative for the production of glycerol using chemical methods.</p><p><strong>1.2 PROBLEM STATEMENT</strong></p><p>The method of analyzing glycerine is greatly varied due to the fact that glycerine contained impurities which acted so much like glycerine as to introduce serious errors in the determination of crude glycerine. This however led to the appointment of committees in the United States and Europe to investigate the method of glycerine analysis. It was concluded in the meeting of the International Committee set for this purpose, that acetin method should control the buying and selling of glycerine, but the more convenient bichromate method in a standardized form might be used in factory control and other technical purposes.</p><p>The quantity of recovered residual salt is dependent on the point of recovery and nature of lye treatment. Neutralizes of the acid and alkaline content of the soap lye helps to reduce the amount of salt originally combined with soap by precipitation, coagulation and flocculation. This is done through their pH adjustments.</p><p>The whole process becomes entirely cumbersome as absolute care is taken to ensure that glycerine passes through all the stages required to obtain pure glycerine devoid of impurities.</p> <br><p></p>