Solid-Liquid Extraction for Pharmaceutics, Food Processing and Pulp Industry

W.M. Zadorsky

1. Introduction

Vegetable oils, sugar, instant coffee, medicines from medicinal plants, etc. are made by processing solid starting material using extraction with liquid solvent(s).

Its initial step is passing the extractant through bulk of the solid in a possibly intimate contact. The contact, however, may be inhibited by air present in interstices between and pores within the pieces to be contacted with the extractant. The air will block penetration of the extractant into some of such cavities. This results in slow and incomplete extraction.

It is therefore desirable to provide a method to remove air blocks in the material to be processed and/or increase the diffusion rates.

High pressure equipment is conventionally used to do this. However, it is expensive, energy-consuming and not always efficient.

The project is aimed at developing a rapid, effective, environmentally friendly and low-cost method to ensure complete extraction of valuable components from solid materials.

2. Project Description
2.1. Process Development

The method requires only minor additions to the existing equipment and may make expensive high-pressure equipment unnecessary. It relies on a simple three-step treatment of the starting material directly before contacting. The pretreatment removes all air trapped in the open pores and involves the following short-time steps carried out in quick succession:

heating the charge,
introducing a specific non-reactive gas, and
desorption of the gas.

It activates every interstice and open pore and results in their quick and complete filling during the contacting step.

An advantage of the pretreatment is that it can be conveniently combined with other means of activation like self-excited oscillations, pulsed pressure and acoustic fields.

2.2. Materials and Equipment

The non-reactive gas characteristics and the timing are unique to each solid/extractant system. This necessitates their tailoring to the system at hand. The gas will invariably be selected among those inexpensive and readily available ones.

2.3. Process and Product Characteristics

Laboratory experiments and commercial use with medicinal plants demonstrated that the method is both effective and readily adaptable to various production routes. The contacting step as such was effected very rapidly and resulted in complete contact between the solid and the solvent. This increased production rate, enhanced product quality and reduced wastes.

3. Novelty

The method is believed to be patentable because it has not been disclosed and no analog to it has been found in the literature.

4. Marketing

The demand for foods is ever growing worldwide and especially in the developing countries. One aspect of the problem is more nearly complete extraction of the nutritional components from raw materials. Another is the absence of low-cost and effective equipment enabling extraction on a small to medium to large scale.

The cost of equipment needed to carry out the new method is small as is the running cost for the new appliances.

The method was recently commercialized for purposes of medicinal plant processing in Ukraine. This demonstrates its engineering attractiveness and economic viability even in a low-income country like this.

Another advantage is that the method is readily implemented in a flexible manufacturing form. Such a flexible manufacturing system may be used for processing a wide variety of starting materials found in a rural community.

5. Applications

Food processing, namely production of vegetable oils, sugar, instant and decaffeinated coffee, instant cocoa, etc. is a major field of application.

In pulp industry, the method may increase the rates of pulp cooking processes and extraction of tannin from bark, etc.

Contact:
Prof.William Zadorsky
PEF&PCPC

Information supplied by the Author October 1999.  Page last updated: July 03, 2005