1 Control gas emission method
In order to make the gas concentration of the exhaust gas flow mixed with the full wind pressure flow, the method of controlling the emission of gas must be adopted. The control methods adopted at the site mainly include:
1.1 Increased resistance limit wind method: The essence of increasing the resistance limit wind method is to increase the working wind resistance of the local ventilator to limit the air volume of the local ventilator and achieve the purpose of controlling the discharge of gas, that is, bundled with rope or belt on the wind outlet side of the fan;
1.2 Wind-restricted wind method: The essence of the wind-restricted wind method is to let the wind flow divide, only part of the wind flow enters the single-head roadway through the air duct to discharge the gas, and the other wind flow is diluted with the full-wind pressure airflow. That is, the emission "three links" are set on the wind outlet side of the fan, and the air volume entering the single head roadway is controlled by the "three links" air release;
1.3 Segment-by-segment discharge method: The section-by-segment discharge method is to disconnect the air duct in the single-head roadway, and discharge the gas accumulated in the single-head roadway from the outside to the inside.
The above method is analyzed as follows: the method of increasing the resistance and restricting wind has the fan in the high wind resistance state and the operation is easy to be unstable and the air volume control is difficult to grasp; the segment-by-segment emission method has the exhaust gas in the dirty airflow, and the operation will be improper. Safety hazard; and the wind-restricted wind law is accurately controlled according to the gas concentration at the full-wind pressure mixing. At the same time, according to the actual gas emission amount at the site, the gas concentration of the discharged gas in the mixed airflow with the full wind pressure does not exceed 1.5%. Under the premise, the air volume can be accurately controlled, so that it can not only eliminate the fact that the air volume is too small due to the actual operation, but also can reduce the amount of gas discharged due to excessive air volume during actual operation.
2 About parameter calculation
After the single-track roadway is stopped (including old road reuse), the amount of gas accumulated in the tunnel, the gas concentration, the maximum air supply volume during discharge, the maximum discharge amount and the shortest discharge time must be calculated in the safety technical measures formulated before discharge. come out. First, it is conducive to the discharge of gas personnel in the actual operation, and secondly, it is conducive to properly arrange the work of various departments within the blackout area.
2.1 The amount of gas accumulated in the single lane:
VCH4=KQCH4t, where VCH4—the amount of gas accumulated in a single lane, m3
QCH4——The absolute amount of gas emission from a single lane in normal, m3/min
T——stop time, min
K——The ratio of the absolute gas emission in the single roadway after the wind stop and the absolute gas emission during the normal excavation. The K value is due to the specific conditions of the mine and the single roadway, but the roadway does not dig after the wind stop, CH4 The output is reduced, so K<1, generally 0.3-0.7
2.2 Gas concentration accumulated in the roadway: the C
C=VCH4x100/LS=KQCH4tx100/LS, in the formula
C——the average concentration of CH4 in the roadway, the percentage
L——the length of the single lane, m
S——the average sectional area of ​​the single lane, m2
2.3 Maximum emissions: Q
Q=Q1•1.5%, where Q is the maximum amount of gas that can be discharged per minute from the single lane, m3/min, Q1 – the amount of wind in the full-air pressure ventilation tunnel, m3/min
2.4 Maximum air supply: Qmax
Qmax=Q1•1.5% x100/C=Q•100/C, in the formula
Qmax - the maximum amount of air supply allowed to the single lane, m3/min
C—average gas concentration in a single lane, %
2.5 Emission time: T
T=VCH4/Q, where T is the time required to discharge gas in a single lane, min, Q – the maximum amount of gas allowed per minute from the single lane, m3/min
Strictly speaking, the discharge gas time T should be determined according to the actual operation. The above calculation is calculated according to the maximum emission. In actual operation, the CH4 concentration of the exhaust gas flow and the full wind pressure mixing may not be constant at 1.5%. It should also be considered that after the gas is discharged, it must wait for 30 minutes to confirm that there is no abnormal change before normal gas supply and production can be resumed. Therefore, the actual discharge time can be referred to the empirical value.
3 Safety technical requirements
3.1 Emission requirements:
3.1.1 When the gas concentration in the wind stop area exceeds 1.0% but does not exceed 3.0%, safety measures must be taken to control the airflow emission. Because the amount of gas that needs to be discharged in the wind stop area is not large, strict control measures are taken to ensure safe discharge. Therefore, it is generally unnecessary to formulate special measures for gas emission safety. However, it is necessary for the inspectors, safety inspectors, electricians and other relevant personnel to supervise and manage the site and take measures to control the wind.
3.1.2 When the concentration of gas in the wind-stop zone exceeds 3.0%, technical measures for safe discharge of gas must be formulated and reported to the chief engineer for strict implementation of safety technical measures to discharge gas.
3.2 System adjustment before gas emission: The air volume must be adjusted before discharge, and there must be a dilution air volume that meets the requirements.
3.3 In view of the wind turbine bearing capacity and the difficulty of controlling the airflow operating procedures, in principle, a single-stage local fan discharge gas is used.
3.4 Safety Emissions: First of all, all open discharge “three linksâ€, before the start of the fan, the wind turbines in front of the fan are bundled with belts or ropes to limit the supply of air to the single-head roadway, leaving only the safety aperture and starting the single-stage fan. The wind is supplied to the working face, and part of the wind directly enters the return airway. Gas is exhausted as a whole in the roadway, and is diluted into the full-pressure mixture. In this process, how to optimize and control, objectively eliminate the shortcoming of the air volume to affect the discharge speed, and the air volume is too large to increase the discharge of gas, thus ensuring The gas discharged from the single-head roadway does not exceed 1.5% of the gas concentration and carbon dioxide concentration in the full-wind pressure mixed flow. It is the leading and safety core of our gas emission safety technical measures. How to operate the air cylinder and use the aperture size to ensure Providing safe air flow to the single-headed roadway, the following examples are as follows:
The bundle allows the maximum allowable air supply volume of the single lane: Qmax=Q1•1.5%x100/C=Q•100/C=8.25X100/20=41.25 m3/min, and the air supply volume of the local fan is 400m3/min. The “three-way†discharge directly into the return air passage is 358.75m3/min, and the diameter of the air duct here is 800mm, and the sectional area is 0.5m2, so the control section of the binding duct is 0.057m2, so we know the air duct The control diameter d is 0.269 m, that is, d is 269 mm, which is very safe. After that, according to the change of gas in the actual discharge process, the air volume adjustment will be carried out, and the “three links†will be gradually converged. Until the gas discharge work is completed and the confirmation is correct, the “three links†can be fully tightened. ".
3.5 Safety Precautions: 1 Strict blackout and evacuation range and alert position. No one may enter the area during the discharge period; 2 Clearly discharge gas participants and their division of labor; 3 Set up the discharge base, which should be located in the fresh air flow on the inlet side 4 gas emission methods, steps and wind-restricting measures must be clearly specified in the measures; 5 before the ventilation is restored, the gas, including the electrical equipment (switching cavity) in the roadway, must be inspected to confirm that the power supply system is restored after the error; One of the circumstances does not allow the discharge of gas: a non-approved measures or measures are inconsistent with the site; b emissions measures are not implemented, no responsibility is implemented; c no emission organization personnel or site leaders; d should be involved in the discharge of on-site personnel The e-discharge gas area and the affected area are not fully marked on the emission gas system map.
4 Conclusion
Gas emission itself is a safety measure to eliminate hidden dangers. However, if it is not implemented well, it will cause accidents. Therefore, in the process of discharging gas, we must strictly formulate special safety technical measures and implement “three responsibilitiesâ€, that is, implementation. The evacuation of people, the establishment of warning and power off range and the inspection of electrical equipment and the responsibility of discharging gas on-site command; implementation of the "three principles", that is, the principle of evacuation, power cuts, and limited quantities, strengthen the management of discharge gas work, and ensure the safe production of coal mines. .
Pressure seal bonnet is suggested for better closure in high pressure condition, while bolted bonnet is still available for customer's option.
Pressure Seal Globe Valve, High Pressure Globe Valve Manufacturer, Pressure Seal Valve Supplier, Cast Steel Globe Valve, Stainless Steel Globe Valve Manufacturer
Wenzhou Kolink Valve Co., Ltd. , https://www.kolinkvalves.com