Study on Prevention of Coal Spontaneous Combustion Technology in Semi-Advance Face by Polymer Compound Swelling Colloid Material

The semi-advanced coal mining face is the mining face of the 揩Z-shaped ventilation system, and the air inlet or return airway is an empty roadway. The wind direction of the inlet and return airways is the same. If conventional methods are used, it will inevitably cause the air flow on the supply work surface to leak through the empty lane to the goaf. It is very difficult to prevent coal spontaneous combustion. Polymer compound refers to a compound with a high molecular weight. It has many special properties, such as high solution viscosity, usually only a viscous liquid or solid state, and regeneration after dehydration. In 2002, Zhangji Coal Mine of Xuzhou Coal Mining Group developed a polymer compound swelling colloidal material due to the continuation of tension, and developed a comprehensive fire extinguishing technology based on the use of polymer compound swelling colloidal material. With measures, good results have been achieved.

2 Zhangji Coal Mine and 7423 Surface Overview Zhangji Coal Mine has a production capacity of 900,000 tons, and it mainly mines 7 layers of coal in the Shanxi Formation. 9-storey coal, mine development method for vertical development of multi-level wells, the current production level is a level of 700m, the production of the mining area has a East. In the East 2nd and West 3rd mining areas, the ventilation pattern of the mine is diagonally opposite to that of the two wings. The coal mining method mainly adopts backward mining, 7, and the former half of the Mf coal, the higher score of the efa, the t Falling over the law. Mine due to Ma Zhongfei et al.: Prevention of coal spontaneous combustion with semi-advanced coal face due to polymer compound swelling colloidal materials. Coal and gas outbursts occurred in the second half of 2001. Coal seams were prominent in 92 coal seams. The gas content of coal seams in the currently produced Xisan and Donger II mining areas is relatively high, the gas emission amount is 0.4~18m3/min, and the gas content in the Dongyi mining area is relatively low; the coal dust has the danger of coal dust explosion and the explosion index is 29.42%. ~38.99%; The 7-layer coal and 9-layer coal of the main mining are spontaneously pyrophoric and belong to the spontaneous coal seam. Since 1990, there have been five spontaneous combustion pyromases for a variety of reasons in the mine, among which, 7 coals 3 times and 9 coals 2 times.

In 700m Dongyi mining area, the thickness of 72 coal seams mined at the working face is 3~4m on average, the working face is 500m long, and the slope is 143~205m. The coal has natural tendency to become angry and belongs to the spontaneous coal seam. The spontaneous combustion period of coal is 3~6. Months passed. The laneway supporting wall is carried on the side of the gob-side gob of the belt conveyor roadway, and the roadside supporting wall is made of crushed coal and cement mixed in a certain proportion. The section of the wall is trapezoidal, and the width of the wall is narrow and wide, and the average wall width is 2 m. The height of the wall is about 4m. The wall-building work is included in the revolving operation of the working face. The wall follows the hydraulic support of the working face and timely supports the wall. The polymer compound swellable grey tape is located on the side of the goaf side of the roadside support wall, and the height is slightly larger than the height of the roadside support wall. The width along the inclined direction is 3~5m. It is composed of fly ash and polymer compound swelling gel of the power plant. The material is formed into grout at a grouting station outside the conveyor belt of the working face and then poured into the side support wall side through the mud pump and grouting system. The composition ratio of the polymer ash, that is, fly ash: polymer compound swelling colloid material: the ratio of water is 0.7:0.002:0.8. The grouting station is built in the alley of Dongyi track downhill and belt down the mountain, the slurry pool Specification 2 is parent 2 to parent 2; injection pump is 8-250/6 type mud pump, diameter of grouting pipe is 50mm, along the 7423 belt machine lane, there are 6m The grouting pipe remained, and the grouting work was carried out in the workshop renovation class, with 4 to 5 people in each shift, responsible for pulping, pumping, piping, and grouting.

3.3 Polymer Compounding Swelling Colloidal Material Technology and Measures for Spraying Gobs of Residual Coal To prevent the spontaneous combustion of coal in the goaf area, apply polymer compound swelling colloid material to the gob area. The spraying method is to add water at a ratio of 1:160 with a polymer compound swelling colloidal material to make a mixture, and spray 10 kg of mixture solution per square meter. Renovate the class on the working surface, use a sprayer for agricultural use, connect a hose with a diameter of 4 minutes, and spray the fire extinguishing polymer compound swelling colloid material to the gob.

China Safety Science 3. Technology and measures for closing roadways with polymer compounding swelling colloid materials. In the material path and contact lane of the 7423 work surface, fire walls with double walls and mud plugs (as shown in the specific locations) are installed to prevent Goaf air leakage; mud from fly ash, polymer compound swelling colloidal material 0.7:0. 002 plus 80% water.

The polymer-comprising swelling colloid was used as a plugging agent to block the return air well of the material path of the 7423 work surface. That is, the small well is covered with a small shed in the tunnel of the lower well, and then floating coal and floating concrete are added to the polymer compound swelling colloidal material as a plugging agent (water ash is 30:1 ratio). The bottom of the well is filled with a 2 m thick sealing layer and then filled with vermiculite or floating coal; 2 m above the small well and filled with a sealing layer.

Other supporting measures to speed up the work surface to ensure that the work surface monthly promotion rate of not less than 50 from the mining process to take measures to improve the coal recovery rate of the work surface.

After the production of the working face began, the material outside the 7423 work surface was closed in time.

The supporting wall at the side of the road always follows the work surface support to prevent the wind from flowing from the back of the support to the goaf.

When carrying out support along the lanes and lanes along the working face, strictly follow the requirements specified in the mining operation procedures. The height and width of the supporting wall around the roadway comply with relevant regulations and requirements, and a 5m wall is embedded in the wall every 6m. The long 2-inch steel pipe is used for grouting in the goaf.

When the gob area sprays polymer compound swelling colloids, strictly according to the requirements of the measures, a full range of spray shall be applied to the prescribed areas to ensure the prevention of fire extinguishing effects.

As the working face is laid down along the direction of advancement, a reliable drainage system is established within the conveyor belt path of the working face to prevent the goaf from flooding the roadway.

The 7423 belt conveyor is often cleaned and maintained to prevent the roadway from being repaired and the ventilation section is reduced to reduce the air leakage to the goaf.

Before the grouting work in the gob area of ​​the shift was completed, the person in charge of the grouting construction was always able to arrange personnel to rinse the grouting pipeline with clean water as required to prevent the pipeline from being blocked by mud.

In strict accordance with the fire inspection system, a comprehensive inspection of the 7423 work surface at the upper corner, return air flow, and the inside and outside of the CH4CO2CO gas concentration and temperature and other conditions, found problems, timely reporting and treatment to prevent spontaneous combustion accidents.

Strengthen the management of ventilation facilities in the area, connect the air intake door to the air door and arrange special personnel to ensure the stability and reliability of the ventilation system.

4 Fire-prevention effect Fire-fighting and plugging effect To measure the effect of fire-plugging, the SF6 tracer gas method was used in September 2002. The SF6 tracer gas release point is 5m on the air intake side and 5m on the return air side. The sampling point is set on the belt conveyor and is set every 100m. After fixed-point and quantitative release of pure SF6 tracer gas for 30 minutes, gas samples were simultaneously collected at the above five sampling points. Then analyze the SF6 concentration at each sampling point and calculate the amount of air leakage. The calculation results are shown in the table below. It is not difficult to see that the total air leakage rate at the work surface is 4.35%, indicating that the effect of fire prevention and plugging is better.

Fireproof plugging wind effect measurement table Item Sampling point 1 Sampling point 2 Sampling point 3 Sampling point 4 Sampling point 5 Remarks SF6 concentration Total air volume Total air leakage (measured by anemometer) Total air leakage rate 4.2 Coal spontaneous combustion control effect 7423 Surface since 2002 3 On the 22nd of the month, it began to stop mining. By adopting comprehensive anti-fire extinguishing technology measures based on polymer compound swelling colloidal materials and ending the recovery on November 28, 2002, the emergence of hidden dangers of coal spontaneous combustion was eliminated, and the coal was safely retrieved for coal mining 46.9. Tens of thousands of tons, and eased the tense situation in the mine production, won the production initiative, achieved good social and economic benefits, and effectively promoted the mine safety production.

5 Conclusion The theory combined with practice, the use of polymer compound swelling colloidal materials to successfully prevent and control the accidental coal spontaneous combustion of the No. 7423 surface mining in Zhangji Coal Mine, and ensured the safety of production. The material shows that the polymer compound swelling colloid material has strong water-solidity, slow dehydration, reproducible water after dehydration, strong adhesion to coal, can form a coking layer, good fluidity and permeability, and is non-toxic and odorless. No corrosion, high temperature and smoke-free characteristics. It changed the situation of poor control of coal spontaneous combustion in semi-progressive mining. This also shows that, under similar conditions, it is feasible to use semi-advanced mining methods as long as the coal spontaneous combustion comprehensive prevention and control measures based on polymer compound swelling colloidal materials are adopted.

(Received: December 2002; First Author Address: No. 301 Xuefu Road, Zhenjiang City, Jiangsu Province; Department of Safety Engineering, College of Biological and Environmental Engineering, Jiangsu University; Zip Code: 212013; Second Author Address: Xuzhou City, Jiangsu Province; Xuzhou Mine Group Zhangji Coal Mine (Zip Code: 221147)