Multi-layer grouting and rubber injection fire prevention system for coal seam spontaneous combustion and its application

1 Introduction

Wong Nai grout is one of the primary means of fire prevention and control of spontaneous combustion of coal layer [1], since some areas (especially coal spontaneous combustion serious western region) loess lack of resources, it is necessary to adopt some alternative material for filling fire prevention and control, and now The pulping concentration of the grouting and fire prevention system can not be controlled, the water and soil ratio is usually lower, the amount of downhole slurry is large, and the grouting efficiency is low. If the mud concentration is increased, the loess is easy to settle in the pipeline, and the problem of plugging the pipeline occurs. Colloidal fire-fighting technology [2~6] integrates plugging and cooling, and has good fire-proof effect. It has become one of the main technical means for self-ignition fire control of coal seams, but it adopts underground mobile injection-proof fire-extinguishing system, equipment installation and operation. Material transportation can not be quickly implemented, and the injection flow rate is small, and the material transportation amount is large, so that the fire extinguishing efficiency is lowered.

Therefore, it is necessary to establish a multi-functional grouting and anti-fire extinguishing system according to the actual situation of each place, so that it can use various grouting materials such as loess, fly ash, sand, vermiculite, etc., and realize the preparation and high concentration of different concentrations of slurry. The pipeline transportation of the slurry improves the grouting efficiency, and the functions of the injection gel and the composite colloidal material are realized by adding a small amount of the admixture to the grouting system, and the coal seam spontaneous combustion under various conditions is dealt with in a targeted manner.

2 system components and functions

The mine multi-function grouting and anti-fire extinguishing system consists of two parts: the ground and the underground. The system is shown in Figure 1, Figure 2 and Figure 3. For the spontaneous combustion of the surface coal seam, only the downhole part needs to be moved to the ground.

2.1 grouting

The various pulps are sent to the continuous quantitative pulping system through the slurry crushing filtration and conveying system, and are mixed with the water pumped by the water pump (the water-soil ratio is adjustable from 1:1 to 1:0), and the slurry is stirred. , transported to the filter machine for filtration, and then transported by the slurry pump to the underground grouting pipe network system and transported to the grouting site.

2.2 injection thickening colloid

When the concentration of the slurry is large, or when sand or fly ash with a faster settling speed is used, the thickening suspension is added to the slurry by adding the additive A to form a thickened colloid, and then transported to the grouting pipe network. .

The thickened colloid consists of a thickened suspending agent, water and a slurry, see Figure 4. The thickening suspending agent can increase the viscosity of the slurry and suspend the sand, soil or fly ash. The slurry does not secrete water or segregate during use, and is convenient for pumping and pipeline transportation. The addition amount of thickening suspension agent is about 0.06%, and the cost is About 6 to 9 yuan / m3. The thickened colloid has good fluidity, can be transported at a long distance without blocking the tube, and has low cost. It is mainly used for grouting and fire prevention in large area such as stop mining line, cut-eye, and goaf.

2.3 injection gel

The gel is formed by mixing a base material, a coagulant, a slurry and water in a certain ratio, as shown in Fig. 5. The total amount of the base material and the coagulant is 10 to 13%, the slurry is 0 to 30%, and the cost per cubic colloid material is about 60 to 100 yuan. It is mainly used for filling and sealing of fires at the top of coal seams, voids and two closed compartments.

The base material is added to the grouting pipe network through the admixture addition system B at the grouting station, and the coagulant is added to the grouting pipe network through the admixture addition system D near the underground pulping site.

2.4 injection composite colloid

The composite colloid (Fig. 6) consists of a thickened suspending agent, a gelling agent, water and a slurry. The amount of thickening suspending agent is 0.06%, the amount of gelling agent is 0.06%, and the colloidal cost is about 15-18 yuan/m3. The colloid has low cost, has certain stackability, and has viscoelasticity, and is mainly used for prevention and control of underground dynamic pressure belts and large-scale fire areas.

The thickening suspending agent is added to the grouting pipe network through the admixture addition system A at the grouting station, and the gelling agent is added into the grouting pipe network through the admixture adding system C near the slurry site.

3 system application

3.1 Fire area overview

The No. 4 coal seam of 402 fully mechanized mining face in Wuhushan Coal Mine has a length of 1254m and a slope length of 155m. The top is the 1# and 2# coal seam goaf. In May 1999, it was found that the outcrop part of the 2# and 4# coal seams caught fire. The surface distance corresponding to the 402 fully mechanized mining face in the fire area was 900m. At the same time, in the middle of the 402 mining face, the upper 2# coal seam small well was smoked. In March 2002, the high-resolution resistivity method and the ground isotope survey method were combined with the ground geological survey to determine the fire zone and its impact range. The results of the survey showed that the fire zone developed rapidly and the range was large, and the eastern edge of the fire zone invaded. The top of the 402 working face has exceeded 16,000 square meters, and the fire zone affected area is nearly 40,000 square meters.

3.2 Selection of fire extinguishing materials

The small kiln in the upper kiln of the 402 working face has a large number of hollows and a large number of hollows. It is necessary to release the accumulated heat energy in the fire area, fire the fire extinguishing area, block the small kiln passage, and it is difficult to use conventional water injection grouting technology. There is a large amount of water in the area, which may cause a water inrush or a slurry collapse in the working face. The use of high-concentration colloids with large water content and poor fluidity to infuse the fire zone can increase the accumulation of mud, greatly alleviate the phenomenon of "ditching" and avoid the massive collapse of the slurry. Due to the large area of ​​the fire area, the required fire-extinguishing materials are large, and the amount of engineering is large. Through comparison, it is decided to use the fly ash composite colloid fire-extinguishing technology to control the large-area fire area on the working surface of 402.

The fly ash colloid has a slow dehydration speed and good durability. It can stay in the easy-fired part for a long time and reduce the possibility of re-ignition of the coal. Due to the existence of a large amount of solid material, even the dehydration can block the air leakage passage. At the same time, in Wuhu Mountain The fly ash material in the mining area has a wide source of resources and a small amount of transportation. It is especially suitable for the treatment of large-area fire areas in coal-rich areas such as Wuhushan Mine.

3.3 injection drilling arrangement

In order to effectively control the fire area at the top of the working face, along the inclined direction of the working face, 4 rows of boreholes are drilled from the ground to the underground, with a drilling distance of 15m and a depth of 40~60m. A total of 70 injection holes are drilled. The drilling position is shown in Figure 7. It is mainly divided into high temperature hole, medium temperature hole and low temperature hole. The order of injection is to first inject the high temperature hole, and then to inject the medium temperature hole and the low temperature hole, and focus on the drilling in the high temperature area, followed by the drilling in the affected area.

3.4 injection molding process

Due to the strict requirements of the water-cement ratio of the colloidal material, a special grouting and grouting slurry system must be established to ensure stable and continuous pulping effect and system process flow.

The grouting and injection molding system has simple process, realizes continuous pulping, controllable glue forming time, stable and adjustable water-cement ratio, and the system cost is about 300,000 yuan. The pulper is made into a pulverized coal mortar according to the ratio of water-cement weight ratio of 1:1 to 3:2, and is injected into the borehole through the slurry pipeline. The FHJ16 composite colloid additive is applied by the colloidal injection machine 10m before the drilling. Feed into the grouting pipeline at a certain ratio.

From July 30th to November 16th, 2002, a total of 35255m3 of fly ash composite colloid was injected into the fire area. The total area covered by colloid was about 10292m2, including the area covered by high temperature area of ​​about 8732m2, covering the area of ​​affected area of ​​about 1560m2. A colloidal barrier with a length of about 400 m and a width of about 60 m is formed in the top of the surface and in the west side of the return air duct. During the whole fire-fighting project, a total of 17 tons of FHJ16 colloidal additive was used, and the amount of material used per cubic meter was about 0.05%, and the material cost was only 8 yuan/m3 higher than that of the fly ash.

3.5 effect analysis

In order to analyze the effect of drilling the glue, the temperature of the unfilled hole adjacent to the injection hole is measured once a day, and the other holes are measured every ten days. According to the actual measurement, the drilling temperature before and after injection is shown in Table 1.

It can be seen from Table 1 that the drilling temperature in the high temperature zone and the affected zone is basically restored after the injection, and the fire zone within the injection range is effectively controlled and extinguished. The colloid is at the top of the working face and west of the return airway. An isolation belt is formed to inhibit the intrusion of the fire zone into the working surface. Because the fly ash colloid solidified in the loose coal, there was no “collapse phenomenon” on the working surface during the propulsion process.

4 summary

The multi-functional grouting and anti-fire extinguishing system can use sand, fly ash, loess, vermiculite and other grouting materials to easily realize the local material of grouting material; the system can prepare various concentrations of slurry (water and soil ratio up to 1: 1) to adapt to different conditions of grouting; by adding a suspending agent to the high-concentration slurry, the high-concentration slurry can be smoothly transported to the pulping site through the colloidal anti-fire extinguishing system without blocking the pipeline; only the admixture needs to be changed Through the system, a variety of new fire-fighting materials such as thickened colloid, gel, composite colloid and solidified filling material can be injected into the system to improve the utilization rate of the system; the perfect automatic control system can ensure multi-function grouting injection. The stable operation of the rubber fire prevention system reduces the influence of human factors and improves the operability of the system.

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