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

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