Assessment of Air Quality of Stone Crusher Units in India. M Selvarajan, Anand Bohra, KRP Nath, N K Tiwary and A K Mishra

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1 Assessment of Air Quality of Stone Crusher Units in India M Selvarajan, Anand Bohra, KRP Nath, N K Tiwary and A K Mishra National Council for Cement and Building Materials, India Abstract Stone crusher industry is an important industrial sector in the country engaged in producing crushed stone which is an ingredient for various construction activities like construction of Buildings, Roads, Highways, Bridges, etc. It is considered as one of the most polluting industries of our country due to poor control technologies for dust emissions, less capital intensive and low technology penetration in the industry. The environmental issues associated with stone crusher industry are mainly the dust emissions arising out of it. Emissions of suspended particulate matter (SPM), PM1, and PM2.5 dust emissions are generated from a number of unit operations in stone crushers. The physical properties of atmospheric particulates affect human health either by allowing penetration of the lung and causing irritation to the internal membrane, or by transporting absorbed toxic gases and vapours deeper into the lung. The fugitive dust adversely affects visibility, reduces growth of vegetation and hampers aesthetic view of the area. This paper analyzes the present dust emission level from the stone crusher units based on a detailed study carried out in twelve stone crusher units located in four different zones spread all over India, selected on the basis of location, size, type of technology, capacity, pollution control systems installed at the units etc. The paper also highlights the available dust control technologies adopted in the stone crusher units in India. (Keywords: Stone crusher, dust level, dust control, SPM, fugitive, environment) 1. Introduction Stone crusher industry is an important industrial sector in the country engaged in producing crushed stone which is raw material for various construction activities like construction of Buildings, Roads, Highways, Bridges, etc. The booming demand for concrete resulted in demand of coarse aggregates, thus increasing the number of stone crusher units. However, it is considered as one of the most polluting industries of our country, due to poor control technologies for dust emissions and low technology penetration in the industry. In the present paper, the dust emission level measured at stone crusher units and the available dust control technologies adopted in the stone crushers in our country are highlighted. The data shown is part of a study entrusted to National Council for Cement and Building Materials (NCB) by Department of Industry Policy and Promotion (DIPP), Ministry of Commerce and Industry. 2. Environmental issues related with stone crushers

2 The environmental issues associated with a stone crusher unit are mainly the dust emissions arising out of it. Emissions of suspended particulate matter (SPM), PM1, and PM2.5 dust generated during size reduction and segregation operations in stone crusher units. A substantial portion of these emissions consists of heavy particles that may settle down within the boundary of the unit. Emissions from unit process operations are considered fugitive unless the sources are vented to a bag house or are contained in an enclosure with a forced-air draft vent or stack. Fugitive dust sources generally involve the re-entrainment of settled dust by wind or vehicular movement. Factors affecting fugitive dust generation include the stone size distribution, the surface moisture content of the stone processed, the process throughput rate, the type of size reduction equipment, operating practices used, topographical and climatic factors. Dust settled over the equipment may cause rapid wear and tear of the rotating parts and may lead to frequent breakdowns and higher maintenance costs. The fugitive dust also adversely affects visibility, reduces growth of vegetation by preventing them from photosynthesis. and hampers aesthetic view of the area. The physical properties of atmospheric particulates affect human health either by penetration to the lungs and causing irritation to the internal membrane, or by transporting absorbed toxic gases and vapours deeper into the lungs. The work place environment at stone crusher units have high concentration of respirable particulate matter that may get deposited in lungs. 3. Environmental standards for stone crusher industry Due to the rising complaints of dust emissions to the surrounding areas, Ministry of Environment, Forests and Climate Change (MoEF&CC) and various pollution control boards have framed siting criteria and guidelines for environmental protection for stone crushers. The applicable ambient air quality standards and SPM standard for stone crushers notified by MoEF&CC are: i). The SPM measured between 3 to 1 meters from any process equipment of a stone crushing unit shall not exceed 6 μg/m 3 ii). As per National ambient air quality standards (NAAQS) 29, the daily average concentration of PM1 and PM2.5 should not exceed 1 and 6 μg/m 3 respectively. 4. Field Studies On the basis of location, size, type of technology, capacity and pollution control systems/ installed or adopted at the units, twelve stone crusher units were selected in four different zones (south, north, west and east) for detailed field study. The crusher units studied in north and east zone were located in stone crusher clusters, whereas units studied in west and south zone were isolated units. A few isolated units studied were operating with proper dust control installed in

3 it. However, most of the isolated stone crushers had partial dust containment only. Most of the stone crusher units in clusters studied were operating either with partial dust control or no at all. The various dust control installed at 12 selected stone crusher units are shown in Table-1. S. No. Unit Table-1: Stone Crusher Units selected for detailed study Unit Size 1. SZ-1 Small 2. SZ-2 Small 3. SZ-3 Medium 4. WZ-1 Medium 5. WZ-2 Small 6. WZ-3 Medium Type of Technology VCS and 1 FS 1 SJC, 1 VCS & 1 VFS 1 PJC, 3 SJC, 1 VCS & 1 VFS 3 PJC, 6 SJC & 2 VS 1 PJC & 1 RS Location of Unit Year Isolated 23 Isolated 1997 Isolated 21 Isolated 1965 Isolated 1965 VCS & 1 VFS Isolated NZ-1 Medium VCS & 1 VFS 8. NZ-2 Medium VCS & 1 VFS 9. NZ-3 Medium VCS & 1 VFS Three 1 PJC, 1 SJC, 1 1. EZ-1 Small VCS & 1 VFS Cluster 1957 units 11. EZ-2 Medium VCS & 1 VFS 1 PJC, 2 GC, EZ-3 Large IC, 1 VCS, & 1 Isolated 21 VFS Products (mm Size) 4-2, 2-12, 12-8 >4, 4-2, 2-12, 12-8, 8-4 >4, 4-2, 2-12, , 12-8, 8-4, <4 ¾, ½, ¼ >4, , 12-8, 8-4 Capacity (TPH) Pollution Control System WS, NS, FE, BW/WC WS, PE, BW, GB FE Screens, RS, WS, GB WS, PE, GB, RS, BW 8 PE, WS 4 Cluster NA NA NA PE Cluster NA NA NA PE PE, WS on stockpiles Cluster NA NA NA PE, WS >4, 4-2, 2-12, 12-8, 8-4, <4 25x3 = 75 WS Cluster NA NA NA WS >4, 4-2, 12-8, <4 >1 FE, CCB, WS, RS NZ- North zone, SZ South Zone, EZ East Zone, WZ West Zone, PJC Primary Jaw Crusher, SJC Secondary Jaw Crusher, VCS Vibratory Coarse screen, VFS Vibratory Fine Screen, RS Revolving screen, IC Impactor, WS Water sprinkler, NS Nozzle spray, FE Full enclosures, PE Partial Enclosures, BW Boundary wall, WC Wind Cheaters, GB Green Belt, RS Road sprinkling, CCB Covered conveyor belts, NA Not available. 5. Results and Discussion Field studies carried out at twelve stone crusher units included collection of data on dust control adopted at various stone crusher units and monitoring of the Ambient air quality (near boundary of the unit) for parameters viz. SPM, PM1 & PM2.5 concentration and fugitive dust (near process equipments).

4 The comparison of SPM concentration vis-à-vis dust control installed at the units is shown in Table-2. The concentration of SPM at the boundary of the stone crusher units was found to be in the range of μg/m 3 for isolated units as shown in Figure-1. The average SPM concentration in isolated units having proper dust control was 57 μg/m 3 whereas for units having partial dust control, average SPM concentration was 1168 μg/m 3. For units located in stone crusher clusters/zones, SPM concentration was found to be in the range of μg/m 3 as shown in Figure-2. The higher SPM concentration in the units located in clusters with an average of 55 μg/m 3 was mainly due to inadequate or only partial dust control installed. Table-2: SPM concentration vis-à-vis control Location of unit Isolated Cluster Measures SPM, μg/m 3 MAX MIN AVG With dust control µg/m3 1 5 SZ-1 SZ-2 SZ-3 WZ-1 WZ-2 WZ-3 EZ-3 Figure-1: Concentration of SPM measured at isolated stone crusher units

5 NZ-1 NZ-2 NZ-3 EZ-1 EZ-2 Figure-2: Concentration of SPM measured at stone crusher units in clusters The comparison of PM1 concentration vis-à-vis dust control installed at the stone crusher units is shown in Table-3. The concentration of PM1 in ambient air at the boundary of the isolated stone crusher units was found to be in the range of 4 41 μg/m 3 as shown in Figure-3. The average PM1 concentration in isolated units having proper dust control was 78 μg/m 3, lower than the NAAQS limit of 1 μg/m 3 whereas for units having partial dust control, average PM1 concentration was 193 μg/m 3. In the stone crusher units located in clusters, PM1 concentration was found to be in the range of μg/m 3 as shown in Figure-4. The higher dust concentration with an average of 194 μg/m 3 at units in clusters was mainly due to inadequate dust control SZ-1 SZ-2 SZ-3 WZ-1 WZ-2 WZ-3 EZ-3 Figure-3: Concentration of PM1 measured at isolated stone crusher units Table-3: PM1 concentration vis-à-vis control Location of unit Measures PM1, μg/m 3 MAX MIN AVG

6 Isolated Cluster With dust control NZ-1 NZ-2 NZ-3 EZ-1 EZ-2 Figure-4: Concentration of PM1 measured at stone crusher units in clusters The comparison of PM2.5 concentration vis-à-vis dust control installed at the stone crusher units is shown in Table-4. The concentration of PM2.5 in ambient air at the boundary of the isolated stone crusher units was in the range of μg/m 3 as shown in Figure-5. The average PM2.5 concentration in isolated units having proper dust control was 37 μg/m 3 lower than the NAAQS limit of 6 μg/m 3 whereas for units having partial dust control, average PM2.5 concentration was 81.4 μg/m 3. For the stone crusher units located in clusters, the concentration of PM2.5 was in the range of μg/m 3 as shown in Figure-6. The higher PM2.5 concentration with an average of 361 μg/m 3 at units located in clusters, was mainly due to inadequate or only partial dust control installed. Table-4: PM2.5 concentration vis-à-vis control Location of unit Isolated Cluster Measures PM2.5, μg/m 3 MAX MIN AVG With dust control

7 SZ-1 SZ-2 SZ-3 WZ-1 WZ-2 WZ-3 EZ-3 Figure-5: Concentration of PM2.5 measured at isolated stone crusher units NZ-1 NZ-2 NZ-3 EZ-1 EZ-2 Figure-6: Concentration of PM2.5 measured at stone crusher units in clusters The concentration of fugitive dust near process equipments of the stone crusher units, measured near process equipments was found to be in the range of μg/m 3 for isolated units as shown in Figure-7 and μg/m 3 for units located in stone crusher clusters/zones as shown in Figure-8. The comparison of fugitive dust concentration vis-à-vis dust control installed at the units is shown in Table-5. The average fugitive dust concentration in isolated units having proper dust control was 2166 μg/m 3 and in units having partial dust control, average fugitive dust concentration was 6 μg/m 3. In the stone crusher units located in clusters, fugitive dust concentration was found to be very high with an average of 194 μg/m 3, mainly due to inadequate or partial dust control installed. Table-5: Fugitive dust vis-à-vis control Location of Measures Fugitive dust, μg/m 3

8 unit MAX MIN AVG With dust control Isolated Cluster µg/m SZ-1 SZ-2 SZ-3 WZ-1 WZ-2 WZ-3 EZ-3 Near Primary Crusher Near Secondary Crusher Near Coarse Screen Near Fine Screen Figure-7: Fugitive dust emissions from unit operations of isolated stone crusher units NZ-1 NZ-2 NZ-3 EZ-1 EZ-2 Near Primary Crusher Near Secondary Crusher Near Coarse Screen Near Fine Screen Figure-8: Fugitive dust emissions from unit operations of stone crusher units in clusters After assessing the air quality data generated at stone crushers located in different zones of India and the present dust control systems that are installed to achieve desired level, it is recommended that the following dust containment should be implemented at every stone crusher unit at the earliest. In order to control fugitive dust, the main dust generating operations like screening and crushing should be properly enclosed and an efficient pollution control system like bag filter and multi cyclones should be installed along with an induced draft fan so that the major part of dust emissions could be arrested and the remaining emissions be discharged through chimney. Boundary wall/wind cheaters should be installed along the boundary of the unit to arrest the transportation of dust particles to nearby places. The approach road to site of stone crusher (including the storage site

9 as well as to the hopper of the primary crusher) from the nearest metalled public road for the transportation of raw material/final products must be paved. The haulage roads inside the stone crusher unit should be continuously wetted by sprinkling of water manually or using sprinklers mounted on trucks. It is to be ensured that raw material should be completely wetted before unloading from the truck into the crusher hopper. At the crusher units, water sprinklers may be installed to keep the raw material wet and results in minimal dust generation. Water Sprinklers may be installed along haulage road or on top of stockpiles or around crushers and screen to arrest the dust generated from the crushing operations. Wetting agents should preferably be added in the water used in the spraying systems so that water consumption is reduced. Nozzle sprayers help in formation of aerosols which results in suppression of dust by combination of dust particles with water droplets that result in making the dust particles heavier and finally settling down. For better control of dust generated from transfer points and conveying systems, all the conveyors should be covered by steel enclosures and all transfer points to and from conveyors should also be enclosed. A row of trees should be planted along the boundary of stone crusher units. However, the width, density, number of the trees varies widely in different zones of the country as well as from one stone crusher unit to another. A high standard of house keeping should be maintained at the stone crusher units. Any piles of materials accumulated in or around the plant should be cleaned up regularly. The surface of all stockpiles of crushed aggregates should be kept sufficiently wet by water spraying. 6. Conclusion It was observed that isolated stone crusher units are equipped with adequate dust control as compared to units located in clusters/zones. In recent years, the stone crusher industry in India has been taking several in adopting environment friendly for dust control. However, there exists a great scope for further improvement of dust containment and suppression in stone crusher units in India. For units operating in stone crusher zones, due to lack of adequate dust control and lack of awareness, a combined effort of stone crusher industry and pollution control board is required to implement dust control. Acknowledgement The authors have freely drawn upon completed R&D works/status reports and some of the published as well as unpublished work of NCB. This paper is being published with kind permission of Director General, National Council for Cement and Building Materials.

10 References 1. Report on Study on present dust emission levels and available technologies for reducing dust emissions at Stone crushers by NCB. 2. Comprehensive Industry Document: Stone Crushers, Comprehensive Industry Document Series: COINDS/78/27-8, Central Pollution Control Board Crushed Stone Processing and Pulverized Mineral Processing, AP-42 Section , US EPA, OAR, Office of Air Quality Planning and Standards (OAQPS)" 4. Environmental guidelines for setting up of a stone crusher unit in Gujarat, 211, Gujarat Pollution Control Board 5. Environment Guidance Manual, Sector: Stone Crushers, Administrative Staff College of India Hyderabad, 211 Rajasthan Pollution Control Board 6. Environment Guidance Manual, Sector: Stone Crushers, Administrative Staff College of India Hyderabad, 211 Rajasthan Pollution Control Board 7. Environmental Study of Stone Crusher, Chaurasia, S., Singh, R., and Pathak, V., IJEP 29 (7): (29) 8. Gazette Notification G.S.R. 46 (E) dated , The Environment (Protection) Rules, Ministry of Environment & Forests, GoI 9. Guidelines for abatement of [pollution in stone crusher industry, Rajasthan Pollution Control Board, "National Ambient Air Quality Status 28", Central Pollution Control Board, Ministry of Environment & Forest, GoI. 11. Pollution Control acts, rules and notifications issues thereunder, Central pollution control board ----