Coal Mine Thermal Damage Prevention and Control

1 The air temperature of the underground mining face and the electromechanical chamber shall comply with the current "Coal Mine Safety Regulations".

2 When newly constructing or expanding the design of mines, the temperature forecasting method for mines shall be used according to the well field exploration geological report and the relevant information provided by the construction unit.

3 For temperature-exceeding mines, comprehensive cooling measures should be taken.

4 The use of non-artificial cooling to reduce temperature should be based on the specific conditions of the mine, comprehensive use of natural cooling sources, increase the amount of air supply or increase the local wind speed in the operator's concentration area, down ventilation or ventilation and other favorable cooling ventilation, avoid underground Heat sources, insulation, or reducing the heat source to heat the air into the air flow, discharge or block hot water, personal protection and other measures.

5 The use of artificial cooling to reduce temperature should be based on the mine geological conditions, open up mining systems, roadway layout, mine ventilation system, refrigeration cooling range, mining depth, cooling load, mine water volume and water quality and temperature, return air volume and temperature, mining mechanization The heat source and conditions are similar to those of mines. After technical and economic argumentation, local cooling measures such as underground mobile air conditioning or compressed air cooling, ground centralized air conditioning systems, and ground and downhole joint air conditioning systems are used.

6 Downhole air handling should meet the following requirements:

(1) Downhole air treatment equipment and facilities shall be based on the air conditioning system and the amount of air to be treated and the cooling load, etc., and shall adopt a direct evaporative type, a water-cooled surface type, a spray chiller or a spray chamber.

(2) Downhole air treatment can be handled centrally or separately at each cooling site;

(3) When the amount of air to be treated is large, the cooling load is large or the difference between the natural air temperature of the narrow space is greater than 10°C, and when a single air treatment facility or facility is difficult to achieve an effect or uneconomical, a comprehensive air treatment method should be adopted.

(4) The air volume handled by the air handling equipment should be determined based on the difference between the cooling load and the supply air temperature, but it must not be greater than the air volume at the supply roadway. For the driving face, the amount of air to be treated must not exceed 70% of the total air volume at the site.

7 The condensing heat removal method of the chiller shall be determined according to factors such as the cooling mode, condensation heat, water quality and water quantity of the water source, water temperature, mine return air volume and temperature, and depth of mining, and shall comply with the following provisions:

(1) Cooling towers or natural water bodies may be used when the ground excludes heat of condensation;

(2) When using downhole centralized air conditioning system cooling method, if the downhole water quality, water quantity, water temperature is suitable or properly processed, underground water should be used preferentially to exclude the condensation heat; when underground water is not applicable, the coal mine air return shall be used to exclude condensation heat, Cooling water discharged from the condenser to the ground for cooling treatment, etc.

(3) When using the return air to remove heat of condensation, the return air wet bulb temperature should not be higher than 29°C.

8 The choice of refrigerant should meet the requirements of fire protection, non-explosion, non-toxic, high condensing temperature, low condensing pressure, low cost, and environmental protection.

9 The chiller cold load backup factor can be taken from 110 to 120, and the number of refrigeration equipment should not be less than two. When the cooling load is large, a large-scale refrigerator should be used.

10 When the refrigerating station is set on the ground, the design and layout of the refrigerating machine room shall comply with the relevant provisions of the current national standard "Code for the design of heating, ventilation and air-conditioning" GB 50019. The position of the refrigerating room should not be less than 50m away from the air inlet, and it should be under the dominant wind direction in summer.

11 When a refrigeration station is located downhole, the location and layout of the refrigeration chamber should be conducive to cooling and heat removal and to the requirements for equipment handling, installation, maintenance, operation, and safety.

12 When the well depth is greater than 600m, there must be a coupling device for the cold transmission using the ground centralized air conditioning system. The selection of coupling methods should consider factors such as safety, energy saving, high efficiency, and convenient maintenance and management. After technical and economic demonstration, shell and tube type high and low pressure heat exchangers, water recovery devices, and multi-cavity heat-pressure converters are selected.

13 The water supply pipe of the cold transfer pipe should be insulated. Whether the return pipe is insulated or not should be determined according to the ambient temperature of the return pipe. Cold transfer should meet the following requirements:

(1) The pipeline insulation materials and structures shall be capable of preventing fire, moisture, gas and non-toxic, avoiding the occurrence of “cold bridge”, and the temperature rise shall not be higher than 06°C/1000m;

(2) The pipeline can be laid in the form of wall-hanging, overhead or trench, and the cold-pipe should not be placed in the return-air lane;

(3) The low temperature refrigerant should adopt the aqueous solution of calcium chloride solution, ethylene glycol aqueous solution or glycerin according to the source of raw materials, corrosivity, water solubility, temperature and price of the refrigerant, and the concentration of the solution should be determined according to the temperature of the refrigerant.

14 The network of cooling system and cooling water system in the mine cooling system should be calculated by hydraulic balance. The hydraulic system design shall comply with the relevant provisions of the current national standard "Code for the Design of Building Water Supply and Drainage" GB 50015 and "Code for the design of heating ventilation and air conditioning" GB 50019.

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