# Coal Dust and Methane as a Hazard in Coal Preparation Plants
## 2 Coal Dust Control in Hard Coal Preparation Plants  
Coal dust hazard and methane in hard coal preparation plants is controlled using administrative and legal regulations as well as technical methods. Administrative-legal regulations include the application of directives, laws, orders, recommendations, and regulations and organizational measures. A number of recommendations and orders are of a local nature, related to the conditions prevailing at a particular site. Technical methods aim at eliminating or at least minimizing the amount of dust and methane in the atmosphere surrounding workplaces to non-explosive levels and not exceeding the Maximum Allowable Concentrations (MAC). Technical methods involve dust collection or water spraying on areas where dust is generated and extensive ventilation in case of methane. The following are selected examples that illustrate solutions in this area applied in mechanical processing plants. One such solution is the MB-M-25A circulating dust collector. The results of dust collection tests carried out at a coal preparation plant using this dust collector are described in [15; 16]. It was shown that the operation of the dust collector results in a significant decrease in the amount of dust precipitating on the surfaces around the coal preparation equipment. The largest decreases in the precipitation of the coal dust, more than twofold, were recorded in the vicinity of the screens. As a result of the work carried out at ITG KOMAG, interesting design solutions have been developed that allow them to be used in many places in mining plants where a dust explosion hazard arises [17]. These devices are of four different types. The most popular one, which has been applied in several coal processing plants, is the UO type dust collector [18]. In this device, air mixed with coal dust is sucked in and introduced into the device through a vortex nozzle with a fan. Inside the dust collector, the coal dust introduced into it with the air is mixed with water. The high kinetic energy of the water droplets imparted by the vortex nozzle makes the dust removal highly efficient. Dust removal efficiency is estimated at 99% of the dust of the inhalable dust fraction and 97% of the respirable dust fraction [19]. Another interesting solution that has found application in coal processing plants is the PASAT-type sprinkler system [18]. This system has been installed in one mine above the transfer from the crushers to the belt conveyors, and in another mine above the transfer of the belt conveyor system. The PASAT system can be equipped with several sprinkler batteries, creating a curtain of water mist that dampens and loads the rising dust that falls onto the conveyor. The system uses compressed air, which reduces the use of water needed to reduce the dust concentration. The PASAT system is supplied with water directly from the mine's fire main. The sprinkler unit is equipped with filters, reduction and shut-off valves, and a UV25 type sterilizer. The system is activated by sensors detecting the movement of the conveyor belt. A view of the sprinkler system is shown in Figure 1. PASAT-type sprinkler systems demonstrate reliable operation and high dust reduction efficiency. In the case of methane, technical methods of hazard mitigation involve placing measurement sensors in critical locations (wells, bunkers) that operate within the mine's automated methane monitoring system. The accumulation of methane at a concentration exceeding 1% in these locations triggers the shutdown of the electrical power supply in the hazardous area. One measure to prevent the formation of an explosive atmosphere is to ventilate areas where such an atmosphere may occur. For instance, in some coal processing plants, the start-up of technological processes, including transportation, is preceded by the activation of ventilation fans. A commonly used technical measure to eliminate potential ignition sources from explosion-hazardous areas is the use of electrically powered safety devices in these areas.