煤矿英语-通风

11-1 The Main Functions of Ventilation [1]
Ventilation is one of the most important aspects of longwall mining. The main functions of ventilation in longwall mining is:
A. Supply of fresh air at tolerable heat and humidity levels [2] for the mine workers to breathe.
B. Removal of noxious gasses from the mine atmosphere that are produced from the coal seam and mining equipment.
11-2 Ventilation Systems
The type of ventilation system used in a longwall mine is dependant upon the conditions found at each mine. The most influential factor [3] in the choice of ventilation system is the amount of gas that is present in the mine atmosphere. If the mine is considerably gassy, the gas in the mine has to be removed from the working panel as quickly and safely as possible.
The most common types of ventilation systems found in U.K are:
A.“U” System
This is the simplest form, the mining district [4] is developed using two raises [5], both being maintained in front of the face for retreating mining. Ventilation of the method can employ two, or even three parallel intake and return gates [6]. The intake and return gates are drawn off [7] behind the face. The system is called reverse system as the intake air travels in the reverse direction to the return air. The raises, intake return gates are maintained behind the face in gob area [8] for advancing mining while ventilation flow and pressure distribution across the gob area increasing the air leakage [9]. The system has a smaller air leakage for retreating face, but it has a longer and changing ventilation lines, and a larger air leakage for advancing face. The system is suitable for coal seams that have very low gas emission rates.
B.“U” System with Local Gob Edge [10] Ventilation
This system is used when retreating face with just two gates, the return gate being chocked [11] to keep it open. A duct [12] is installed from the return gate across the support line into the return gate behind the face and the airflow through the duct is usually of the order of 1/3 of the total face quantity, The flow is maintained by the use of a compressed air powered airmover [13]. Such a system merely provides scouring of the gob edge at the return end of the face and it only applicable to low gas emissions.
C."Z" System
With the "Z" system, the lower intake is a pre-formed gate [14], drawn off
behind the face, whilst the upper return gate is developed as the face retreats.
Effectively this may be described as an advance/retreat face, since at the return
end it is identical in behaviour to an advancing face. Again, it requires a return air
raise behind the face. The system is known as homotropal ventilation [15] and
used in coal seams that have a very high gas content because it has a short and
stable ventilation lines.
D. “Y” System
This system involves two gates—the upper gate and the lower gate. Both gates are as air intakes, and the upper return gate is maintained behind the face in the gob area. Again, it requires a return air raise behind the face. The system has enough air quantity to dilute the harmful gases in return gate, which can guarantee that the machines in return gate run safely for the fully mechanized longwall mining.
E. “W” System
When the double-unit faces are used, three gates are pre-formed, drawn off
behind the face for retreating mining. The upper and lower gates are as air intakes and middle gate is as an air return, or the middle gate is as an air intake and the upper and lower gates are as the air returns. “W” system can satisfy th e ventilation requirements of double-unit faces. Therefore, it is advantageous to increase the coal production.
F. Back Return System
This is the most used system for retreating face, with no airways permanently [16] maintained behind the face. A small coal rib [17] some three meters to five meters wide left between the end of the return gate and the gob area is made, supported with a roadside pack [18] (or wood chock). Periodically, a cut-through [19] is made in the coal rib, all returns are stopped off [20], except one open cut-through. In this way, the face airflow is diverted back [21], as with the Z-system, reproducing the conditions of an advancing face at the return end. The system can be used in coal seams with much higher emissions and it is probably the only system to be used successfully retreating to the rise [22].
NOTES TO THE TEXT
[1] ventilation：通风
[2] tolerable heat and humidity levels：可容忍的热和湿度标准
[3] influential factor：有影响的因素，决定性因素
[4] mining districtis：采区
[5] raises：上山
[6] intake and return gates：区段进风和回风平巷
[7] draw off：报废，拆除
[8] gob area：采空区
[9] air leakage：漏风，空气泄漏
[10] gob edge：采空区边缘
[11] gate being chocked：设有木垛区段平巷
[12] duct：导管
[13] airmover：轻便压缩机（应急通风用）
[14] pre-formed gate：预先形成的区段平巷
[15] homotropal ventilation：顺流通风
[16] permanently：永久地
[17] coal rib：窄煤柱
[18] roadside pack：巷旁充填
[19] cut-through：联络小巷
[20] stop off：封闭，隔开（用墙、风布等）
[21] divert back：向后部移动
[22] rise：上山方向。