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Content archived on 2022-11-21

Water infusion in thick, steep seams, with high firedamp content and easily caved coal, worked by the horizontal sublevel method

Objective

The main aim of the present project is to study the possibilities of the application of water injection as a dust prevention technique in coal seams worked using the sublevel and 'soutirage' system, also examining the adaptation to the specific conditions of this working method of other dust prevention methods based on ventilation, pulverisation etc.
As a general conclusion to the injectability studies carried out we offer the following:

1. The real possibilities of an effective application of water injection in layers worked by sublevels depend fundamentally on the state of distention and/or alteration of the deposits. Specific analysis should, in each case, be performed using the existing technique, developed in the course of the present Project.

2. The numerous tests carried out call into question earlier criteria regarding the practical implementation of permeability and injectability in deposits neither distended nor altered, confirming our previous experience in unsuccessful attempts to apply injection methods at great depths in such deposits.

3. A priori, panels distended by nearby exploitation of other layers at roof or footwall determine a situation favourable to the application of injection.

4. It is unadvisable to apply high pressures to achieve appreciable injection flow rates. Injection should only be applied in panels where these rates are obtained with moderate pressures (< 40 Kg/cm2).
Over the last few years, the application of the exploitation system of 'horizontal sublevels' (descending horizontal strips with caving) has become more widespread in Spanish coalmining, to work broad and steeply sloping layers (thickness and inclination of over 2.00 and m and 50 degrees respectively), in which the methane-bearing and drawable nature of the coal, and the falseness of the sidewalls mean that both the traditional system of manually worked TESTEROS and conventional mechanisation with shearers, are not viable.

Without doubt, this method of operation, with some variations, will be the most widely used after the restructuring of the mining sector in Spain.

An important problem in this system of exploitation is the large amount of dust produced, especially in the caving or 'soutirage' phase, there being no established system of prevention, given the relative novelty of the application of the method in this kind of deposit.

The characteristics of the coal winning method and the geometry of the exploitation panels require a detailed analysis of the injection conditions, especially in view of the fact that significant differences in behaviour have been observed with water injection in these exploitations as compared with the application commonly used in others. Previous experience in the application of water injection to these exploitations did not yield usable results in practice, nor did it provide information which would explain the reasons for the low level of efficiency obtained using water injection.

It was, on the other hand, of obvious interest that the practical possibilities of injection should be determined, given that adequate humidification of the coal 'in situ' would guarantee, a priori, the prevention of dust throughout the extraction and transport process.

Call for proposal

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Funding Scheme

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Coordinator

INSTITUTO NACIONAL DE SILICOSIS
EU contribution
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Address
Cindad Sanitaria Dr Bellmunt s/n
33006 Oviedo
Spain

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Total cost
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