Mine filling system

(1) Filling process

1. Conveying method of filling materials

(1) hydraulic transmission. At the surface filling preparation station, the water-sand filling material or cemented filling material is sent to the underground stope for filling through the filling pipeline by means of double line dead weight transportation, or by pump.

(2) Wind transport. Generally, filling stations are set up underground to prepare cemented filling or dry filling materials, and then compressed gas is injected into stope through pipelines for filling.

(3) Mechanical filling. Dry filling materials are often filled through the filling well and then transferred to the stope, where they are filled by electric harrows or throwers. Filling is made of concrete or through surface mixing, vertical pipe down the well, or in the underground preparation station, and then sent to the stope, and then filled with electric harrow or thrower.

At present, hydraulic filling is the main method at home and abroad. Whether it is wind filling or mechanical filling, there are auxiliary transport filling problems, many links, more complicated technology. But the wind filling machine and the thrower filling machine have the advantages of high filling density and good top connection. Some mining methods, such as upward and downward filling methods, can fully show their superiority.

2. Hydraulic filling process

1) Determination of fluid type

From the perspective of rheology, hydraulic transport can be divided into heterogeneous flow of Newtonian flow and homogeneous flow of non-Newtonian flow. In the homogeneous flow of non-Newtonian flow, Bingham flow, pseudo plastic flow, yield pseudo plastic flow and time dependent energy variable flow are often seen.

Under certain conditions of conveying material (weight, particle size), concentration is the main factor that determines whether the slurry belongs to the heterogeneous flow of Newtonian flow or the homogeneous flow of non-Newtonian flow.

2) Conveying Newton flow heterogeneous flow fillers

At present, most of the hydraulic conveying water-sand filling materials and cemented filling materials in China's mines are heterogeneous flows. When the tailing is filled, the weight of the tailing is 2.7g/cm³, and the weight concentration is less than 67% ~ 69% (depending on the size gradation). The water-sand filling of coarse sand is all heterogeneous flow. This kind of low-concentration heterogeneous flow transporting water-sand filling requires better permeability coefficient of fillers and good dewatering facilities installed in stope to make it dehydrated in time.

Because of its high water content, cement segregation is easy to occur and the strength of filling body is low when the cemented filling material is transported with heterogeneous flow. Stope dehydration is dominated by overflow. In order to reduce horizontal cement segregation, the filling hose in the stope is moved as quickly as possible during the filling process.

Conveying heterogeneous flow filler, its water content is large, in the water out, often contains more fine-grained solid materials, need to precipitate treatment in time, should try not to make it into the water tank. It is recommended to set up a sedimentation tank in the mining area in the stage, and the solid materials can be cleared in time after settling in the sedimentation tank, and the water can be cleared into the water tank.

3) Conveying non-Newtonian flow homogeneous flow fillers

When the concentration of conveying slurry is increased to a certain extent, homogeneous flow is formed, and homogeneous flow is mainly used for conveying tailing filler, tailing cemented filler and fine sand cemented filler. Its advantage is that it can prevent pipe clogging, reduce pipe wear and reduce underground drainage and pollution. For cemented fillers, the more important advantage is that the strength of the filling body can be greatly improved.

3. Full tailings filling process

The tailings filling in China are all settled sand, and the amount of settled sand is often insufficient. Overflow tailings can not be dammed, need quarrying dam construction, high cost, fine grained overflow tailings will cause pollution to the environment. All tailings filling can avoid and improve the above problems. The difficulty of full tailing filling lies in the settlement and dehydration of fine-grained tailing, and the ideal condition is to make a homogeneous flow with high concentration on the surface and transport it to the mine instead of dewatering the mine. At present, it is mainly used for subsequent filling of goaf.

4. Cemented stone filling process

In this process, after returning to the mining room by the open stope method, the block is filled with stone, and then the cement mortar is injected into the block stone to form block concrete. Or the gravel is poured into the goaf at the same time, the cement mortar is transported by the pipeline to form a block of stone concrete, and then the pillar mining.

(2) Filling system

The mine filling system is a process system in which solid mine waste is used as aggregate, cement and other materials are used as cementing materials, and a certain concentration of filling slurry is prepared by concentrating and stirring, and then transported to the underground stope for filling by means of arteflow or pumping. At present, the common filling aggregate in mines is tailings, and crushed waste stone, Gobi aggregate and other coarse aggregates are also used. The coarse aggregate is transported to the mixing system through the conveyor belt during the mixing stage. The process is relatively simple, so it is not explained in detail. The tailings filling system is mainly introduced here. The tailings filling system is mainly composed of tailings concentration and storage system, cementitious material storage and feeding system, filling slurry mixing system, filling slurry conveying system and automatic filling control system.

1. Tailings concentration and storage system

There are two kinds of tailing thickening schemes, namely vertical sand silo scheme and deep cone thickener scheme. The vertical sand silo is generally composed of the top of the silo, the overflow trough, the bottom of the silo and the slurry pipe fittings in the silo. The bin roof structure includes the bin roof room, sand inlet pipe, hydrocyclone (tailing sand classification), material level meter and pedestrian trestle, etc. The overflow groove is located on the inner wall or outer wall of the bin, and the bottom of the groove has a slope towards the overflow pipe interface. The function of the overflow tank is to reduce the overflow speed and improve the utilization rate of tailings. Silo body is the main component of sand storage, generally made of reinforced concrete or steel directly welded. At first, the structure of hemispherical silo bottom was adopted, which had low sand concentration and was easy to plate. Modern vertical sand silos are generally changed to conical sand discharge structure. After the tailing sand is pumped to the vertical sand silo, natural sedimentation or flocculation sedimentation is adopted to achieve dense dehydration of the tailing sand. The overflow water at the top is recycled through the overflow tank, and the concentrated high-concentration tailing mortar at the bottom is filled with sand by fluidizing slurry.

The deep cone thickener is the key equipment for tailings thickening after the vertical sand silo, which is suitable for the treatment of fine and micro-fine particles. Its biggest feature is that it can obtain a higher mass concentration of underflow, and the production capacity is larger. The free settlement principle of the deep cone thickener is basically the same as that of the vertical sand silo, but the mechanical power structure is added. Its structure is center drive type, the main drive is low speed and high torque turbine reducer, the shell is reinforced concrete viaduct elastic structure or steel structure, and the deep cone reinforced concrete self-waterproof structure is adopted. The upper part of the cone is equipped with a control system, a flocculant adding system and a tailings feed port, which are rotated around the central vertical axis. The lower part of the shaft is provided with a spiral, a harrow frame, a mud scraper with a bottom flow cone, and the bottom of the groove is provided with a paste discharge device.

2. Storage and feeding system for cementitious materials

According to the filling capacity, the material of cementitious material is calculated, and then the cementitious material bin is configured in the filling station. The cementitious material in the bin is fed quantitatively through the screw conveying and metering system on the top of the bin. Cement conveying generally adopts double tube screw conveyor, and measurement adopts spiral electronic scale or punching plate flowmeter. In recent years, the micro-powder weigher with aggregate and conveying has been developed greatly. It has the function of preventing cement silo arch and punching, feed stability, and has been widely used in mine filling system.

3. Filling slurry mixing system

Filling slurry mixing system adopts different mixing technology and equipment according to the different properties of filling slurry. In general, filling slurry mixing is divided into one stage mixing and two stages mixing. The primary mixing is mainly for the two-phase slurry, and the vertical mixing tank is generally used. Two-stage stirring is generally for paste or paste filling. Two-stage mixing is commonly configured with a two-axis blade mixer and a two-axis blade mixer, and a two-axis blade mixer and a high-speed activation mixer.

4. Filling slurry conveying system

Filling slurry transport is divided into artesian transport and pumping, and the artesian transport scheme is adopted as far as possible under the condition that the mine has the artesian transport. It is generally required that the filling line of the mine is less than 6. Specifically, the filling slurry stirred evenly by the mixing system is first reached to the middle part of the underground filling through the filling hole, and then the filling of each stope in the middle part is realized through the horizontal pipeline in the middle part and the drilling between the middle part.

When there is no free flow conveying condition or paste filling is to be used, it is necessary to use pumping, and the plunger pump is used for pumping. The homogenously mixed paste filling slurry at the filling station is pumped to the stope through the plunger pump for filling.

5. Automatic filling control system

The automatic filling control system should have the characteristics of reliable and effective operation, complete functions, simple and flexible operation, easy expansion, convenient maintenance, etc., and carry out comprehensive automatic control and operation monitoring of the filling production process. The automatic control system is required to improve the production capacity of equipment as much as possible, reduce the labor intensity of workers, reduce the accident rate of equipment, reduce production costs, and improve economic benefits under the premise of stabilizing the production process and ensuring the filling index. Therefore, advanced automatic control system should be established in the future filling system to improve work efficiency and ensure filling quality.

The main control and regulation loop of filling station is as follows:

① tailings feed flow control.

② Thickener sand discharge flow, concentration monitoring and control.

③ Control of filling slurry ratio.

④ Filling slurry concentration control.

⑤ Constant pressure water supply control.

⑥ Material level monitoring and control of thickener, cement silo, tank and mixing bucket.

⑦ Filling pipeline blockage accident treatment.

To control the filling system, the following process parameters need to be tested

① Thickener, cement bin and mixing bucket material level.

② Concentration and flow of tailings feed.

③ Sand discharge flow and concentration of thickener.

④ cement feed amount.

⑤ Filling slurry flow and concentration.

⑥ Stirring bucket add water flow.

⑦ Water supply pressure.

According to the process characteristics and automatic control requirements of filling station, the key of automatic control lies in how to reasonably adjust the ratio of filling slurry and filling concentration according to filling requirements, realize the sequence control of system equipment and centralized monitoring of system equipment, and improve the filling effect.