1 Overview
Guangdong Province Mining Ltd. Baoshan hole where copper ore is a large multi-metal mine, mainly copper sulfide ore mainly to deposits surrounding rock silicified rocks and skarn-oriented, good condition rock deposits, currently used in large open-air Mining. Due to the high sulfur content of the ore body, spontaneous combustion of the sulfur-bearing ore body is prone to occur, resulting in a higher temperature in some of the blastholes during the production operation. In the north of 757, 769m and other stepped perforation blasting, the individual blasthole temperature is as high as 90 °C. The relevant blasting safety regulations stipulate that when the temperature in the blasthole hole reaches 60 °C, the mine blasting must take corresponding safety measures. Once the temperature in the hole exceeds 140 °C, heat-resistant blasting equipment should be used, but there is no high use condition in China. Mining explosives at 140 °C. Therefore, in order to ensure the safety of mine blasting operations, corresponding safety measures must be taken for high temperature blastholes.
2 causes and hazards of high temperature blastholes
The Fandong Copper Mine is located on the east side of the West-West Depression Area of ​​Yuegui, the southeastern edge of the Qujiang Basin, and the contact zone between the Dadongshan-Guidong East-West tectonic belt and the NE-dongjiang fault zone. By deposit type and spatial location Geological conditions of ore deposits can be divided into an upper limonite Eluvial type deposits, the central volcanic sedimentary - hydrothermal transformation layered siderite deposit, a lower volcanic sink - type layer of a Modification Cu - Zn-shaped lead deposits and western porphyry molybdenum deposit. During the early mining activities of the mine, the open-pit and underground joint mining was carried out. Due to the influence of the underground folk pirates and the lag of the goaf, the mining process could not reach the requirements of the balance of mining and charging. In 2004, the mine experienced three major collapses in the goaf, which seriously threatened the safe production underground. Since then, the mine has stopped underground operations and continuously optimized the open-air production boundary for large open pit mining. Affected by the geological conditions of the mine and the underground goaf, the current presence of the Fandong copper deposit
High temperature blastholes are mainly caused by the following two reasons:
(1) There is an ore body with high sulfur content in the goaf of the original landslide. It is affected by the landslide. The ventilation conditions in the goaf are poor. After the spontaneous combustion of the sulphurous ore body, a large amount of high temperature gas is collected in the landslide area, and the blasthole penetrates through the closed After the collapse of the goaf, the high temperature gas sees the blasthole, as shown in Figure 1;
(2) When the blasthole passes directly through the high-sulfur ore body, the sulphide ore body oxidizes and ignites spontaneously, resulting in an increase in the temperature of the blasthole, as shown in Fig. 2.
Explosives have their own thermal sensitivity, and related detonating equipment, such as detonating cords and detonators, can only be used normally within the specified temperature range. Once the temperature reaches or exceeds the thermal sensitivity of the explosive, it is easy to cause early explosion or spontaneous combustion, thus threatening the life safety of the on-site blasting workers.
At the same time, if the temperature is too high, the explosive may be thermally decomposed, so that the blasting performance is lost and the explosion is prevented. In addition, blasting equipment such as detonating cords and detonators are affected by high temperature, and may also fail, resulting in network refusal, leaving blast safety risks.
The blasting methods currently used in the Fandong Copper Mine are mainly non-electrical detonation networks, with poor blasting between rows. The explosives are mainly 2# rock emulsion explosives. The single hole charge of the rock is about 120kg, the ore consumption is 0.31kg/m3, the rock consumption is 0.29kg/m3, and the detonating equipment is mainly non-conducting detonator detonator and detonation. tube. Among them, 2# rock emulsion explosives failed at high temperature of 130 °C for 6 hours; at 80 °C, the detonator can be detonated normally, but the explosion speed is slightly reduced. It can be seen that if the blasthole with a temperature of up to 90 °C does not take certain treatment measures, it is unfavorable for the blasting operation, and there is also a great safety hazard.
3 high temperature blast hole processing method
In view of the hazards of high temperature blastholes on blasting operations, the current domestic reliable treatment methods are mainly divided into physical cooling and chemical cooling. Among them, physical cooling uses water as coolant to cool the blasthole; chemical cooling uses one. The series of chemical raw materials are chemically reacted with high-temperature ore bodies to make the ore bodies less prone to spontaneous combustion and high temperatures. After a long-term field experiment and analysis of the Fandong Copper Mine, the following treatment methods were summarized and promoted in the mine, which achieved very satisfactory application results.
3.1 water injection cooling
The most direct way to solve the high temperature blasthole is to inject water for physical cooling. The water can absorb heat well to achieve the purpose of cooling due to the larger specific heat capacity. However, when water injection is cooled, attention should be paid to the burning of high temperature water and gas to the workers. After the water injection is completed, the temperature and depth of the hole in the blasthole should be re-measured. If the rock in the blasthole hole is broken during the water injection process, it needs to be adjusted. Blasting parameters such as charge amount.
3.2 Add lime water
The high temperature blasthole is filled with acidic oxides, and the constant chemical reaction releases a large amount of heat. Therefore, the method of adding lime water is to inject lime water into the blasthole before the high temperature blast hole is charged, and the alkaline lime water chemically reacts with the acidic oxide to reduce the acidity of the oxide or completely neutralize the acidity. To achieve the purpose of chemical cooling. In addition, the water itself can act as a physical cooling.
3.3 insulated charge
In order to avoid the thermal decomposition of the explosive at a certain temperature and cause failure, when the high temperature blast hole is charged, the explosive is wrapped with the heat insulating material to be isolated from the hole wall, so that the explosive is at a normal temperature state without thermal decomposition. Avoid uncertain accidents.
3.4 assay analysis
This method is a quantitative analysis of the hazard of high temperature blastholes, that is, the use of assays to verify the danger of explosives. The specific operation is as follows: take a certain amount of holes in the high temperature blast hole, and require the sieve to be below 100 mesh, and mix the hole sample number with the explosive, the ratio is 2:1, mix well, put into the small test tube, and then put The small tube is placed in a simulated environment for heating. Generally, the heating should last for about 1 hour. During the period, the laboratory technician should carefully observe the reaction of each test tube. The test tube with intense reaction, such as bubbling, and the large amount of foam and the high frequency, indicate that the blasthole is dangerous and it is strictly prohibited to charge. In addition, it can also be measured by pH test paper. If the pH value is strongly acidic, it indicates that the blasthole is dangerous and cannot be charged.
3.5 lag charge
In order to shorten the contact time between the explosive and the high-calorie environment, the high-temperature blast hole is lagging charge, that is, after all the normal temperature blasthole charges are completed, the high-temperature blasthole is quickly charged, and then immediately detonated (see Fig. 3). This method shortens the contact time of the explosive with the high temperature environment, which is insufficient to form a combustion or explosion, and increases the safety factor.
4 operation process
In order to facilitate the operation and more efficient treatment of high temperature blastholes in the actual production process, a corresponding set of operating procedures has been developed:
(1) All blasthole hole temperatures must be measured before the blasting operation, and the temperature inside each hole is marked;
(2) After injecting lime water into the high temperature blasthole, re-measure the hole depth and the temperature inside the hole after water injection. If the water is caused to collapse, the volume of each hole is adjusted after re-measuring the hole depth;
(3) Determine the number of high-temperature holes according to the actual situation of the explosion area, first install the normal temperature hole and then install the high-temperature hole;
(4) After all the blasthole charges are completed, the mortar can be filled, and the filling time should be strictly controlled during the filling process. After the filling is completed, it will be detonated immediately after the inspection. Once the burned smog has an abnormal phenomenon such as burning and smoking during the operation, all personnel in the working area are immediately evacuated.
5 Conclusions For the high-temperature blastholes encountered in blasting, Fandong Copper Mine has obtained several effective treatment methods in the production practice and learning summary of long-term Qiu Zhenhua: treatment method for high-temperature blasting of open-pit mines, including adding water injection, Lime water, heat-insulating charge, laboratory analysis, lagging charge, and has been well applied in the stope, successfully eliminating the threat of high-temperature blastholes to open-air safety production, providing a treatment for similar high-temperature blastholes in mines. Lessons to learn from.
references:
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[2] Liao Mingqing. Application of common detonating cord in high temperature blasting [J]. Blasting equipment, 1991 (1): 19-21.
[3] Yao Jian. Stability analysis and treatment technology of Dabaoshan underground goaf [D]. Changsha: Central South University, 2006.
[4] Song Jiadong, Wang Jian. Open-pit mining technology of roof ore body in underground goaf [J]. Non-ferrous metals, 2000 (5) 14-18.
[5] Li Xibing. Rock drilling and blasting engineering [M]. Changsha: Central South University Press, 2011.
Source: Mining Technology: 2016, 16(4);
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