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Technical | Ventilation  >  Thermal

Section under development

Early forms of ventilation took advantage of the difference in temperature and hence the density of the air in the mine relative to that outside.  Provided the air in the mine was warmer, a natural air flow would establish itself, but since the mines at that time were fairly shallow, seasonal variations of the outside temperature could prevent this occurring. Unfortunately, this would also coincide with the period of minimal rainfall, the optimal time for the miners since the  workings would be at their driest.

Daily variations of the outside temperature could also disrupt the airflow and, when it did reestablish itself, the direction it adopted was unpredictable. It was eventually realised, however, that the preferred direction of flow could be reestablished by artificially warming the air in one of the shafts and use then began to be made of fire-baskets which could be lowered down into the shaft until the air circulation commenced.

As the need for improved productivity increased, the slow and unreliable fire-basket method became inadequate and, with shafts and workings becoming deeper, the volumes of gas encountered became to great for natural ventilation to cope with. Some means of artificially increasing the airflow in a controlled manner became essential. The principle of thermally induced ventilation had been demonstrated by the use of fire-baskets so enhancements to this method were clearly a technical route to explore.

  • surface furnaces..... 

One apparently promising idea was to take advantage of the draft created by a furnace with a large chimney.  By  closing the top of one of the shafts and connecting it to the bottom of the chimney the natural airflow could be both maintained and enhanced by the hot flue gases from the furnace. Unfortunately, although the technique was theoretically correct, it was, in practice, limited by the height of the chimney itself and whilst it worked reasonably well for small mines it was unable to scale up to the needs of larger collieries.

...therefor superseded by:

  • furnaces at the shaft bottom.....  TBD

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