- Email: [email protected]
Application of foam technology for dust control in underground coal mine
International Journal of Mining Science and Technology 24 (2014) 13–16
Contents lists available at ScienceDirect
International Journal of Mining Science and Technology journal homepage: www.elsevier.com/locate/ijmst
Application of foam technology for dust control in underground coal mine Ren Wanxing a,b,c,⇑, Wang Deming a,b,c, Guo Qing c, Zuo Bingzhao c a
State Key Laboratory of Coal Resources and Safe Mining, China University of Mining & Technology, Xuzhou 221008, China Key Laboratory of Gas and Fire Control for Coal Mines, China University of Mining & Technology, Ministry of Education, Xuzhou 221008, China c School of Safety Engineering, China University of Mining & Technology, Xuzhou 221116, China b
a r t i c l e
i n f o
Article history: Received 23 May 2013 Received in revised form 22 June 2013 Accepted 26 July 2013 Available online 6 January 2014 Keywords: Coal dust Dust control Foaming agent Foam generator
a b s t r a c t In order to effectively control the dust in the underground coal mine, this study proposes and develops a new technology for dust control by foam, and briefly demonstrates the advantage of the foam technology for dust control, such as the good isolation performance, large contact area, high wetting ability, strong adhesion and so on. Besides, the details of the technology are introduced, including the foam agent, foam generator, and foam production process. Then the paper studies the relationship between the foaming agent concentration and liquid surface tension, and explains the principle of the foam generator. The technology is applied in heading face. The application results show that the foam has a remarkable effect on dust control in underground coal mines. Ó 2014 Published by Elsevier B.V. on behalf of China University of Mining & Technology.
1. Introduction Dust is one of the main disasters during the coal production [1,2]. The miners chronically inbreathe the coal dust, especially the respirable dust, which does serious harm to the miners’ health and makes them become pneumoconiosis patients. With the popularization of the mechanized coal mining in recent years, the amount of the coal dust increasingly grows in the underground mine, which brings the potential dangers to the safety in mining production. According to the statistics of Ministry of Health, there had been more than 310 thousand coal miners who suffer from pneumoconiosis by the end of 2007, reaching 50% of the whole pneumoconiosis patients in China. Every year, more than 57 thousand miners suffer from the illness of pneumoconiosis, and 6000 miners died on average per year. The report of China State Administration of Work Safety in Eleventh Five-Year Plan of Coal Mine Safety also shows the direct economic loss that reaches 1 billion yuan because of pneumoconiosis in the coal industry every year [3–7]. In addition, coal dust is the main dangerous source of explosive disaster. Statistical data shows that 106 coal dust explosions have taken place in China from 1949 to 2007, resulting in 4613 casualties [8].
⇑ Corresponding author at: State Key Laboratory of Coal Resources and Safe Mining, China University of Mining & Technology, Xuzhou 221008, China. Tel.: +86 13775883564. E-mail address: [email protected] (W. Ren).
To control the coal dust, a number of methods have been widely used. The most popular technologies are ventilation, water spray, water infusion, water/wetting agent spray and dust-collecting fan [9–14]. These technologies had played an important role in dust prevention, but they have limitations. For instance, the water infusion requires complex equipments and a large amount of water. When using water spray, the nozzle is easy to be blocked, and it leads to the reduction of the ratio of dust precipitation. As for using dust-collecting fan to fall dust, the equipment structure is complicated and the volume is also large. What’s worse, the volume of wind which can be dealt with is limited. To overcome these limitations, the authors developed the foam technology and equipment. Practical application shows that the dust hazard of working face is efficiently controlled by the foam technology, so there is great prospect of wide application of this technology. 2. Features of foam technology for dust control The foam used for dedusting is composed of air, water and foaming agent. The surface tension of water reduced when foaming agent was added. Then abundant small and homogeneous foam is produced by the foam generator, and then sprayed in the air or on the surface of dust sources. Compared with traditional technologies, the foam technology for dust control has the following remarkable features. When using water spray, regardless of the fineness of the droplets, there always exist ‘‘empty spaces’’ between the water
2095-2686/$ - see front matter Ó 2014 Published by Elsevier B.V. on behalf of China University of Mining & Technology. http://dx.doi.org/10.1016/j.ijmst.2013.12.003
14
W. Ren et al. / International Journal of Mining Science and Technology 24 (2014) 13–16
droplets. The respirable dust particles will easily ‘‘escape’’ through these ‘‘empty paths’’. In addition, the foam can cover the dust source without ‘‘empty space’’, which can prevent the dust from spreading outside effectively. When the foam is formed, the whole volume and area of foam film will become large rapidly. Compared to water spray, high expansion foam will cover much more space with the same amount of water. It can greatly increase the probability of the collision between foam and dust. The film of the foam contains foaming agent, which can greatly reduce the surface tension of water. And the dust wettability is improved quickly. As a result, the dust will be wetted very efficiently. Moreover the adhesiveness of foam is very strong. Once the foam and dust collide, the dust will adhere to the foam quickly and firmly. Thereby, it will catch the dust particles much more easily [15–19].
3. Key points of foam technology The foam is composed of air, water and foaming agent. The key points of the technology are to develop the foaming agent and foam generator.
3.1. Foaming agent
The foam for dust control is produced by the foam generator. So the foam generator is one of the main components of the foam technology for dust control. The structure of foam generator usually used contains net and filler form. But their working conditions are not suitable to coal mine. Although there are reports about other types foam generator at home and abroad, the foaming multiple is low, and cannot meet the need of dust control [20–22]. In the design process of the foam generator the following four factors should be taken into consideration: first, make the gas–liquid two-phase fluid form turbulent stream as far as possible; second, make the liquid scatter increase the contact superficies with the gas; third, increase stirring intensity of the gas–liquid properly and let them collide with each other to form bubbles; fourth, make sure that there are no internal moving units and keep the pipe unobstructed. According to the four key points mentioned above, new foam generator was developed based on the theory of turbulent jet. The principles of the foam generator are used to make full use of the high pressure of water and compressed air in underground mines, as well as the characteristics of high-speed and low-pressure of venturi tube at its throat. The static pressure of water can be transformed into velocity pressure when the foam solution flows through the foam generator. Because of the entraining effect of the jet, the compressed air was pulled in the jet core. In order to increase the contact surface between gas and liquid, several air holes and the disturber at the diffusion section of venturi tube were set. Then the two-phase gas–liquid jet flow impacted the disturber with high-speed, and the turbulence was formed behind the jet disturber in foam generator, therefore the gas and liquid can be mixed fully. Besides, some barrier boards were set behind the vortex generator to raise the intensity of the gas–liquid mixture. Then the flow run through the baffle area which was the posterior structure of the foam generator. It can make the air and liquid mix further, and then stable and high-quality foams are formed. 3.3. Producing flow of foam Fig. 3 shows the producing flow of the foam for dust control. First, the water was pulled in the pipeline through pump or gravity from the ground surface. The foaming agent was added proportionately
25
80 70 60 50 40 30 20 10 0
3.2. Foam generator
Wetting time (min)
Surface tension (mN/m)
In order to meet the demand of foaming and dust removing, many kinds of surfactants are screened out. The multicomponent experiments are carried out in laboratory, and a certain amount of auxiliary agent was added. The mixed system named new foaming agent was formed and has a good effect on reducing the surface tension of water, and the dust was wetted easily. Meanwhile, the foaming multiples will become larger obviously. Fig. 1 shows that: with the change of the concentration of new foaming agent, the surface tension of the liquid changes respectively. From these curves, the most adoptable concentration of the foaming agent is about 0.5%. The efficiency of dust removing has direct relation with the dust wetting performance of the foaming agent. In order to investigate the wetting performance, rock dust, which weights 10 g and 150– 200 mesh, is selected in laboratory. The wettability of the foaming agent for the dust is evaluated by water film flotation which is by measuring the time of a certain amount of dust sinking into the water or solution. The dust was sprayed on the surface of water (or solution). The experimental procedures are as follows: first, prepare 5 kinds of 200 mL solutions in 500 mL cylinder, and they are clear water, solution A, solution B, solution C and solution of new foaming agent. The concentration of every kind of solution except clear water is 0.5%. Second, take 9 mL every kind of solution with transfer pipette into 5 measuring cups. When the liquid level in the measuring cups keeps stable, 0.2 g rock dust is weighted on the electronic balance with an accuracy of 0.01 g, and then sprinkled them to the measuring cups. Then, the time is measured,
when the dust all is immersed in the clear water or solution. Last, the above steps are repeated three times to take the average. Fig. 2 displays the comparison of surface wettability among clear water, the new foaming agent and the other three surfactants for rock dust. As shown in Fig. 2, it is obvious that the new foaming agent has the best surface wettability for rock dust under the same conditions.
0.5 1.0 1.5 2.0 2.5 Additive concentration of foaming agent (%)
Fig. 1. Relationship between concentration of foaming agent and surface tension.
20 15 10 5 0
Clear water
B
New agent
A
C
Fig. 2. Comparison of surface wettability of clear water, three surfactant and new foaming agent for the rock dust.
15
W. Ren et al. / International Journal of Mining Science and Technology 24 (2014) 13–16
Water
Foaming agent
Water pipe
Foam generator
Proportioner
Dust-control foam
Pressed air
according to water flow in the pipeline by proportioner. Water containing foaming agent flows into the foam generator, while the compressed air is drawn into the foam generator, and then the foam is formed in the generator. 4. Application The Xin’an Coal Mine lies in Zhao Yang Lake district in the west of Tengzhou, Shandong province, China. The recoverable reserves are 35.6071 million tons. Xin’an Coal Mine is newly built, and it can produce 5 million tons per year at present. It is a low gas mine, and its mainly natural disaster is coal dust. The application of the foam technology was conducted at mechanized heading face named 12211 underground Xin’an Coal Mine.
Removal efficiency of total dust (%)
Fig. 3. Producing processes of foam for dust-control.
90 80 70 60 50 40 30 20 10
Efficiency of water spraying Efficiency of foam technology
0 Fig. 5. Comparison of removal efficiency between foam technology and water spraying for total dust.
4.1. Main technical parameters
nozzles connect to the distributor. Finally, the foam was sprayed on the dust source to prevent the spread of coal dust by nozzles.
According to the technological process of controlling dust by foam, the following are the main parameters of this project.
4.3. Analysis of applied result
The The The The The
quantity of water consumption is 1 m3/h; quantity of compressed air supply is 40 m3/h; production of the foam is 40 m3/h; foaming multiple is 40; quantity of foaming agent supply is 5 kg/h.
At the heading face, three measuring points were set near the fully-mechanized digging machine. The light scattering digital conimeter was used to measure the concentration of dust in air when using the foam and spray technology. After measuring, the average
4.2. Installation of equipment Fig. 4 presents the installation of foaming dust control system in underground. The water and air pipelines of the system were connected to the branches of the main water and air pipe respectively. The two branches were joined to the foam generator. And the proportioner was installed in the water branch. The pipeline was highpressure hose whose diameter was 25 mm. The foam generator was fixed on the surface of fully-mechanized digging machine. The foam was produced in the generator and transported to the foam distributor by hose whose diameter was 42 mm. The foam
Removal efficiency of respirable dust (%)
(1) (2) (3) (4) (5)
80 70 60 50 40 30
Efficiency of water spraying Efficiency of foam technology
20 10 0
Fig. 6. Comparison of removal efficiency between foam technology and water spraying for respirable dust.
Control valve Air
Foam distributor
Foaming agent Water
Nozzle Filter
Proportioner
Foaming generaor
Fig. 4. Installed sketch map of foaming dust-control system.
16
W. Ren et al. / International Journal of Mining Science and Technology 24 (2014) 13–16
value was obtained and curves were drawn. Figs. 5 and 6 are the contrastive histogram for the removal efficiency of total and respirable coal dust after the application of foam and spray technology. From Figs. 5 and 6, we can see that the removal efficiency of foam technology for total dust is 2.11 times of that with water spraying, while the removal efficiency of foam technology for respirable dust is 1.72 times of that with water spraying. The application of foam technology for dust control has a great effect on reducing the dust concentration at the heading face. The dust control’s effect is obvious and it can ensure the miners’ health and the safety during mining production. 5. Conclusions This paper presents the key features, principles and application of the foam technology for dust control. The main conclusions reached in this study are as follows: (1) The foam technology, which can control the dust efficiently in the coal mines, has the following advantages: good coverage performance, large surface area, high wetting speed, strong adhesion and so on. (2) Key points of producing high-performance foam are to develop foaming agent and foam generator. After the experiment and application of the foaming agent and foam generator developed in this study, these characteristics are obvious, such as high-efficiency of dust-control, simple operation, good stability and reliability as well as broad application prospect. (3) The foam technology has been applied at the heading face in underground coal mine successfully. From the results, we can conclude that it has a great effect on reducing dust and improving the working environment in coal mine observably.
Acknowledgments The financial support by the National Natural Science Foundation of China (No. 51104153) and the Fundamental Research Funds
for the Central appreciated.
Universities
(No.
2011QNB11)
is
deeply
References [1] Wang DM. Mine ventilation and safety. Xuzhou: China University of Mining and Technology Press; 2007. [2] Yang J, Wu XK, Gao JG, Li G. Surface characteristics and wetting mechanism of respirable coal dust. Int J Min Sci Technol 2010;3(20):365–71. [3] Wang PF, Feng T, Liu RH. Numerical simulation of dust distribution at a fully mechanized face under the isolation effect of an air curtain. J China Univ Min Technol 2011;1(21):65–9. [4] Kissell FN. Handbook for dust control in mining. Pittsburg: US Department for Health and Human Service; 2003. [5] Wu C, Ou JC, Wu GM. Experiment on coupling of wet agents composed with anionic surfactant s and dust of sulfide ores. J China Univ Min Technol 2006;35(3):323–6. [6] Jin L. Mine dust control. Beijing: Coal Industry Press of China; 1993. [7] Li DW, Ma J, Liu HQ. The technology of occupational disease and mine dust control. Xuzhou: China University of Mine and Technology Press; 2007. [8] Zheng YP, Feng CG, Jing GX, Qian XM, Li XJ, Liu ZY, Huang P. A statistical analysis of coal mine accidents caused by coal dust explosions in China. J Loss Prev Process Ind 2009;22(4):528–32. [9] Shi XX, Jiang ZA. Research status and development tendency of dust-control technique in the fully-mechanized mining faces in coal mine. J Saf Sci Technol 2005;2:41–3. [10] Zhao D, Liu WH, Yao LZ, Zhang YH. Synthesis dust-control measures in coal mine. Min Saf Environ Prot 2003;S1(6):111–2. [11] Qian ZX, Li YY. Coal cutter spraies high-pressure spray and falls dust with secondary negative pressure. Shandong Coal Sci Technol 2001;3:31–2. [12] Ma ZS, Wang YF, Zhang L. Application of long-hole water injecting into coal seam at Changgouyu colliery. J Liaoning Tech Univ 2009;28(6):881–3. [13] Xie YS, Fan GX, Dai JW, Song XB. New respirable dust suppression systems for coal mines. J China Univ Min Technol 2007;3(17):321–5. [14] Wei MS, Tong MM, Hao JF, Cai L, Xu J. Detection of coal dust in a mine using optical tomography. Int J Min Sci Technol 2012;4(22):523–7. [15] Page SJ, Volkwein JC. Foams for dust control. Eng Min J 1986;187(10):50–4. [16] Salyer IO, Sun SM, Schwendeman JL, Wrustner AL. Foam suppression of respirable coal dust. Washington D.C.: Department of the Interior Bureau of Mines Open File Report; 1970. [17] Parrett FW. Foam suppressants-an alternative for dust control. Ind Miner 1986;220(1):52–3. [18] Mukherjee SK. Spraying foam helps control longwall dust. Los Angeles: SMEAIME Annual Meeting; 1984. [19] Mukherjee SK. New techniques for spraying dust. Coal Age 1984;89(1):54–7. [20] Shen RC. Summary on the structural design of foam generator. China Pet Mach 1993;5(21):52–5. [21] Zhang JS, Yang H, Liu JH. The study of foaming generator on foam concrete. Concretes 2001;135(1):51–3. [22] Qing BT, Wang DM, Zhang RG. Foaming mechanism and design principles of a three-phase-foam generator. J China Univ Min Technol 2008;37(4):439–42.
Contents lists available at ScienceDirect
International Journal of Mining Science and Technology journal homepage: www.elsevier.com/locate/ijmst
Application of foam technology for dust control in underground coal mine Ren Wanxing a,b,c,⇑, Wang Deming a,b,c, Guo Qing c, Zuo Bingzhao c a
State Key Laboratory of Coal Resources and Safe Mining, China University of Mining & Technology, Xuzhou 221008, China Key Laboratory of Gas and Fire Control for Coal Mines, China University of Mining & Technology, Ministry of Education, Xuzhou 221008, China c School of Safety Engineering, China University of Mining & Technology, Xuzhou 221116, China b
a r t i c l e
i n f o
Article history: Received 23 May 2013 Received in revised form 22 June 2013 Accepted 26 July 2013 Available online 6 January 2014 Keywords: Coal dust Dust control Foaming agent Foam generator
a b s t r a c t In order to effectively control the dust in the underground coal mine, this study proposes and develops a new technology for dust control by foam, and briefly demonstrates the advantage of the foam technology for dust control, such as the good isolation performance, large contact area, high wetting ability, strong adhesion and so on. Besides, the details of the technology are introduced, including the foam agent, foam generator, and foam production process. Then the paper studies the relationship between the foaming agent concentration and liquid surface tension, and explains the principle of the foam generator. The technology is applied in heading face. The application results show that the foam has a remarkable effect on dust control in underground coal mines. Ó 2014 Published by Elsevier B.V. on behalf of China University of Mining & Technology.
1. Introduction Dust is one of the main disasters during the coal production [1,2]. The miners chronically inbreathe the coal dust, especially the respirable dust, which does serious harm to the miners’ health and makes them become pneumoconiosis patients. With the popularization of the mechanized coal mining in recent years, the amount of the coal dust increasingly grows in the underground mine, which brings the potential dangers to the safety in mining production. According to the statistics of Ministry of Health, there had been more than 310 thousand coal miners who suffer from pneumoconiosis by the end of 2007, reaching 50% of the whole pneumoconiosis patients in China. Every year, more than 57 thousand miners suffer from the illness of pneumoconiosis, and 6000 miners died on average per year. The report of China State Administration of Work Safety in Eleventh Five-Year Plan of Coal Mine Safety also shows the direct economic loss that reaches 1 billion yuan because of pneumoconiosis in the coal industry every year [3–7]. In addition, coal dust is the main dangerous source of explosive disaster. Statistical data shows that 106 coal dust explosions have taken place in China from 1949 to 2007, resulting in 4613 casualties [8].
⇑ Corresponding author at: State Key Laboratory of Coal Resources and Safe Mining, China University of Mining & Technology, Xuzhou 221008, China. Tel.: +86 13775883564. E-mail address: [email protected] (W. Ren).
To control the coal dust, a number of methods have been widely used. The most popular technologies are ventilation, water spray, water infusion, water/wetting agent spray and dust-collecting fan [9–14]. These technologies had played an important role in dust prevention, but they have limitations. For instance, the water infusion requires complex equipments and a large amount of water. When using water spray, the nozzle is easy to be blocked, and it leads to the reduction of the ratio of dust precipitation. As for using dust-collecting fan to fall dust, the equipment structure is complicated and the volume is also large. What’s worse, the volume of wind which can be dealt with is limited. To overcome these limitations, the authors developed the foam technology and equipment. Practical application shows that the dust hazard of working face is efficiently controlled by the foam technology, so there is great prospect of wide application of this technology. 2. Features of foam technology for dust control The foam used for dedusting is composed of air, water and foaming agent. The surface tension of water reduced when foaming agent was added. Then abundant small and homogeneous foam is produced by the foam generator, and then sprayed in the air or on the surface of dust sources. Compared with traditional technologies, the foam technology for dust control has the following remarkable features. When using water spray, regardless of the fineness of the droplets, there always exist ‘‘empty spaces’’ between the water
2095-2686/$ - see front matter Ó 2014 Published by Elsevier B.V. on behalf of China University of Mining & Technology. http://dx.doi.org/10.1016/j.ijmst.2013.12.003
14
W. Ren et al. / International Journal of Mining Science and Technology 24 (2014) 13–16
droplets. The respirable dust particles will easily ‘‘escape’’ through these ‘‘empty paths’’. In addition, the foam can cover the dust source without ‘‘empty space’’, which can prevent the dust from spreading outside effectively. When the foam is formed, the whole volume and area of foam film will become large rapidly. Compared to water spray, high expansion foam will cover much more space with the same amount of water. It can greatly increase the probability of the collision between foam and dust. The film of the foam contains foaming agent, which can greatly reduce the surface tension of water. And the dust wettability is improved quickly. As a result, the dust will be wetted very efficiently. Moreover the adhesiveness of foam is very strong. Once the foam and dust collide, the dust will adhere to the foam quickly and firmly. Thereby, it will catch the dust particles much more easily [15–19].
3. Key points of foam technology The foam is composed of air, water and foaming agent. The key points of the technology are to develop the foaming agent and foam generator.
3.1. Foaming agent
The foam for dust control is produced by the foam generator. So the foam generator is one of the main components of the foam technology for dust control. The structure of foam generator usually used contains net and filler form. But their working conditions are not suitable to coal mine. Although there are reports about other types foam generator at home and abroad, the foaming multiple is low, and cannot meet the need of dust control [20–22]. In the design process of the foam generator the following four factors should be taken into consideration: first, make the gas–liquid two-phase fluid form turbulent stream as far as possible; second, make the liquid scatter increase the contact superficies with the gas; third, increase stirring intensity of the gas–liquid properly and let them collide with each other to form bubbles; fourth, make sure that there are no internal moving units and keep the pipe unobstructed. According to the four key points mentioned above, new foam generator was developed based on the theory of turbulent jet. The principles of the foam generator are used to make full use of the high pressure of water and compressed air in underground mines, as well as the characteristics of high-speed and low-pressure of venturi tube at its throat. The static pressure of water can be transformed into velocity pressure when the foam solution flows through the foam generator. Because of the entraining effect of the jet, the compressed air was pulled in the jet core. In order to increase the contact surface between gas and liquid, several air holes and the disturber at the diffusion section of venturi tube were set. Then the two-phase gas–liquid jet flow impacted the disturber with high-speed, and the turbulence was formed behind the jet disturber in foam generator, therefore the gas and liquid can be mixed fully. Besides, some barrier boards were set behind the vortex generator to raise the intensity of the gas–liquid mixture. Then the flow run through the baffle area which was the posterior structure of the foam generator. It can make the air and liquid mix further, and then stable and high-quality foams are formed. 3.3. Producing flow of foam Fig. 3 shows the producing flow of the foam for dust control. First, the water was pulled in the pipeline through pump or gravity from the ground surface. The foaming agent was added proportionately
25
80 70 60 50 40 30 20 10 0
3.2. Foam generator
Wetting time (min)
Surface tension (mN/m)
In order to meet the demand of foaming and dust removing, many kinds of surfactants are screened out. The multicomponent experiments are carried out in laboratory, and a certain amount of auxiliary agent was added. The mixed system named new foaming agent was formed and has a good effect on reducing the surface tension of water, and the dust was wetted easily. Meanwhile, the foaming multiples will become larger obviously. Fig. 1 shows that: with the change of the concentration of new foaming agent, the surface tension of the liquid changes respectively. From these curves, the most adoptable concentration of the foaming agent is about 0.5%. The efficiency of dust removing has direct relation with the dust wetting performance of the foaming agent. In order to investigate the wetting performance, rock dust, which weights 10 g and 150– 200 mesh, is selected in laboratory. The wettability of the foaming agent for the dust is evaluated by water film flotation which is by measuring the time of a certain amount of dust sinking into the water or solution. The dust was sprayed on the surface of water (or solution). The experimental procedures are as follows: first, prepare 5 kinds of 200 mL solutions in 500 mL cylinder, and they are clear water, solution A, solution B, solution C and solution of new foaming agent. The concentration of every kind of solution except clear water is 0.5%. Second, take 9 mL every kind of solution with transfer pipette into 5 measuring cups. When the liquid level in the measuring cups keeps stable, 0.2 g rock dust is weighted on the electronic balance with an accuracy of 0.01 g, and then sprinkled them to the measuring cups. Then, the time is measured,
when the dust all is immersed in the clear water or solution. Last, the above steps are repeated three times to take the average. Fig. 2 displays the comparison of surface wettability among clear water, the new foaming agent and the other three surfactants for rock dust. As shown in Fig. 2, it is obvious that the new foaming agent has the best surface wettability for rock dust under the same conditions.
0.5 1.0 1.5 2.0 2.5 Additive concentration of foaming agent (%)
Fig. 1. Relationship between concentration of foaming agent and surface tension.
20 15 10 5 0
Clear water
B
New agent
A
C
Fig. 2. Comparison of surface wettability of clear water, three surfactant and new foaming agent for the rock dust.
15
W. Ren et al. / International Journal of Mining Science and Technology 24 (2014) 13–16
Water
Foaming agent
Water pipe
Foam generator
Proportioner
Dust-control foam
Pressed air
according to water flow in the pipeline by proportioner. Water containing foaming agent flows into the foam generator, while the compressed air is drawn into the foam generator, and then the foam is formed in the generator. 4. Application The Xin’an Coal Mine lies in Zhao Yang Lake district in the west of Tengzhou, Shandong province, China. The recoverable reserves are 35.6071 million tons. Xin’an Coal Mine is newly built, and it can produce 5 million tons per year at present. It is a low gas mine, and its mainly natural disaster is coal dust. The application of the foam technology was conducted at mechanized heading face named 12211 underground Xin’an Coal Mine.
Removal efficiency of total dust (%)
Fig. 3. Producing processes of foam for dust-control.
90 80 70 60 50 40 30 20 10
Efficiency of water spraying Efficiency of foam technology
0 Fig. 5. Comparison of removal efficiency between foam technology and water spraying for total dust.
4.1. Main technical parameters
nozzles connect to the distributor. Finally, the foam was sprayed on the dust source to prevent the spread of coal dust by nozzles.
According to the technological process of controlling dust by foam, the following are the main parameters of this project.
4.3. Analysis of applied result
The The The The The
quantity of water consumption is 1 m3/h; quantity of compressed air supply is 40 m3/h; production of the foam is 40 m3/h; foaming multiple is 40; quantity of foaming agent supply is 5 kg/h.
At the heading face, three measuring points were set near the fully-mechanized digging machine. The light scattering digital conimeter was used to measure the concentration of dust in air when using the foam and spray technology. After measuring, the average
4.2. Installation of equipment Fig. 4 presents the installation of foaming dust control system in underground. The water and air pipelines of the system were connected to the branches of the main water and air pipe respectively. The two branches were joined to the foam generator. And the proportioner was installed in the water branch. The pipeline was highpressure hose whose diameter was 25 mm. The foam generator was fixed on the surface of fully-mechanized digging machine. The foam was produced in the generator and transported to the foam distributor by hose whose diameter was 42 mm. The foam
Removal efficiency of respirable dust (%)
(1) (2) (3) (4) (5)
80 70 60 50 40 30
Efficiency of water spraying Efficiency of foam technology
20 10 0
Fig. 6. Comparison of removal efficiency between foam technology and water spraying for respirable dust.
Control valve Air
Foam distributor
Foaming agent Water
Nozzle Filter
Proportioner
Foaming generaor
Fig. 4. Installed sketch map of foaming dust-control system.
16
W. Ren et al. / International Journal of Mining Science and Technology 24 (2014) 13–16
value was obtained and curves were drawn. Figs. 5 and 6 are the contrastive histogram for the removal efficiency of total and respirable coal dust after the application of foam and spray technology. From Figs. 5 and 6, we can see that the removal efficiency of foam technology for total dust is 2.11 times of that with water spraying, while the removal efficiency of foam technology for respirable dust is 1.72 times of that with water spraying. The application of foam technology for dust control has a great effect on reducing the dust concentration at the heading face. The dust control’s effect is obvious and it can ensure the miners’ health and the safety during mining production. 5. Conclusions This paper presents the key features, principles and application of the foam technology for dust control. The main conclusions reached in this study are as follows: (1) The foam technology, which can control the dust efficiently in the coal mines, has the following advantages: good coverage performance, large surface area, high wetting speed, strong adhesion and so on. (2) Key points of producing high-performance foam are to develop foaming agent and foam generator. After the experiment and application of the foaming agent and foam generator developed in this study, these characteristics are obvious, such as high-efficiency of dust-control, simple operation, good stability and reliability as well as broad application prospect. (3) The foam technology has been applied at the heading face in underground coal mine successfully. From the results, we can conclude that it has a great effect on reducing dust and improving the working environment in coal mine observably.
Acknowledgments The financial support by the National Natural Science Foundation of China (No. 51104153) and the Fundamental Research Funds
for the Central appreciated.
Universities
(No.
2011QNB11)
is
deeply
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