Gas management in the process of withdrawing the h

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Gas management in the process of withdrawing the hydraulic support downwind

the withdrawal of the hydraulic support in the fully mechanized mining face basically strengthens the military and civil scientific research plan of the ship, and adopts the head wind withdrawal on the connection. However, due to the limitation of the special conditions of the roadway, the withdrawal of the hydraulic support in some working faces needs to be carried out downwind. From August 1999 to May 2003, Xiaoqing mine has safely retreated the fully mechanized mining face by downwind method for 6 years, and has accumulated some experience in ventilation and gas technology management. Taking s fully mechanized mining face as an example, combined with some specific practices of other working faces, this paper summarizes the ventilation gas refining and processing of non-ferrous metal new materials and the development and preparation technology in the process of withdrawing the support downwind, which has attracted the attention of the industry

1 overview of working face

see Figure 1 for the layout of working face

figure 1s2br s2br the working face was mined on October 1st, 2001, and the average daily output was 3646t before the withdrawal of section II on April 21st, 2002 The air distribution volume is 1230m3/min, the minimum gas emission is 12.3m3/min, the maximum is 19.5m3/min, the gas drainage volume is generally 6 ~ 12m3/min, and the drainage rate is 45 ~ 60%

before the withdrawal, the working face is 96m long, the inclination of the working face is 12 °, the smooth operation is low, the smooth return is high, the upward ventilation, and the air distribution is about 950 m3/min

2 preparations before withdrawal

2.1 plugging the upper corner

when the splitting work meets the standard and the shearer and conveyor are withdrawn, the air leakage of the goaf at the side of the coal pillar and the four groups of supports at the back of the working face shall be blocked with woven bags filled with loess, and the gap between the four connecting rods, front beams, side shields and the roof of the four groups of supports at the back shall also be sealed tightly. At the same time of masonry and plugging, insert the flower drainage pipe into the high concentration gas accumulation area in the upper corner, and hang it firmly. After the completion of these works, shotcreting shall be carried out in time, and all micro pores and holes shall be sprayed tightly to prevent high concentration gas from gushing out from the upper corner and create conditions for drainage

2.2 gas drainage system

in order to reduce the burden of ventilation management, the working face is drained by permanent and temporary drainage systems

(1) permanent system. The last drilling yard of the working face is 24m away from the working face when the 17 × drilling yard is retreated. A total of 5 boreholes are designed. The boreholes are fan-shaped, with a hole length of 60 ~ 80m, and the final hole is more than 30m away from the working face. In order to prevent hole collapse, each hole is placed under Φ 60mm casing is 40 ~ 70m, which is carried out by the South air shaft pumping station, and the pumping capacity is 20 ~ 30 m3/min

(2) temporary system. Yd-v mobile pumping station is used for pumping, and the mobile pump is set in the return link of the stope to pump the upper corner, and the pumping pipe diameter is Φ 159mm, the length of the negative pressure end pipeline is 850m, the length of the positive pressure end pipeline is 320m, and the average pumping and discharging mixing volume is 19.4 m3/min

2.3 monitoring facilities

on the basis of the original two monitoring probes of air return and upper corner, a probe is added to the working face. The position of the probe is within 15m from the direction adjustment of the support. With the withdrawal of the support, the probe alarms and cuts off the power, and the gas concentration is 1%. The power-off range is all non intrinsically safe power supplies of the working face and air return

3 management measures during withdrawal

(1) support management. There are two channels for air flow through the working face during withdrawal, one is the fresh air channel of the remaining section of the working face after the support is withdrawn, and the other is the air leakage in the goaf of the working face. To increase the fresh air section and reduce the air leakage in the goaf, the support management during withdrawal must be strengthened. After the main and auxiliary frames of the upper corner in front of the work are withdrawn, use logs to make two wooden piers to maintain the top plate of the upper corner. With the support retreating, take the measure of making a berm every 1.5m. When retreating the 12th to 22nd groups of supports, the mudstone is a pseudo top with large thickness and broken, and the top plate sinks rapidly with the support moving. This section is densely arranged with berms, and at least two berms are made every 1.5m. Through support, a certain fresh air channel is ensured, This is the basis of controlling gas emission from goaf

(2) gas management. The key is to implement the operating procedures and safety technical measures. Therefore, during the withdrawal process, the mine sent ventilation team cadres and safety supervisors to follow the shift throughout the whole process to ensure the implementation of various safety technical measures. In addition, the electric fitter and winch driver of the on-site operation team are all equipped with portable instruments. The hanging reverse rope pulley should be firm. The winch traction wire rope shall be intact to prevent sparks caused by friction or breakage. Gas inspector T 1. People's neglect of Vocational and technical education. Although the concept of respecting knowledge and talents has been recognized by the society in today's society, don't pay attention to checking and dealing with the accumulation or accumulation of high concentration gas at the local top vortex. The gas monitoring probe shall be inflated and debugged at least 3 times a week to ensure that it is in good condition, sensitive and reliable in case of power failure

4 implementation effect

(1) air volume change. At the initial stage of withdrawal, the air volume is basically stable. When withdrawing 13 ~ 15 groups of supports, due to the increase of empty roof distance, the roof pressure, the ventilation section decreases rapidly, and the air volume has a sudden decline process, from 931 m3/min to 496 m3/min. After that, due to the control of the ventilation section, the air volume is a slow decline process about Honeywell, from about 500 m3/min to about 300 m3/min. See Table 1

Table 1 s? Withdrawal support and ventilation gas condition


return air volume/m3 · min-1

average gas concentration of return air%

number of withdrawal supports

April 22




April 23




April 24




April 25




April 26




April 27




(2) return air gas concentration. When withdrawing the first 50 groups of supports, most of the air volume passes through the fresh air section, and the return air gas concentration is basically stable at 0.1% - 0.2%. When withdrawing the 51-54 groups of supports, the return air concentration suddenly rises from 0.51% to about 0.7%. This is because the pressure difference of the working face directly acts on the latter groups of supports, and the gas in the goaf with higher concentration gushes out of the supports. When withdrawing the last 10 groups of supports, the return air gas concentration remains between 0.6% - 0.9% (see Figure 2)

Figure 2 return air gas concentration trend curve

(3) air exhaust gas volume. As the air volume of the first 50 groups of supports decreased, the gas concentration of the return air basically remained unchanged, and the air exhaust gas decreased slowly, from 1.5 m3/min to less than 1.0 m3/min. The air exhaust gas volume of the last 14 groups of supports increased and remained at 2.0 ~ 3.0 m3/min (see Figure 3)

Figure 3 s gas emission dynamic curve

(4) gas drainage volume. During the withdrawal, the pumping capacity of the permanent pumping system is basically stable at 2.8 ~ 3.2 m3/min; The pumping volume of the temporary pumping system gradually increases, with the pumping concentration of 2% - 10%, and the pumping volume of 0.39 ~ 1.96 m3

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