In the industrial field, various type of fuel have been used for product processing facilities. Recent for 10 years, the usage of natural gas (NG) was gradually increased. Because it has many merits; clean fuel, no transportation, storage facility and so on. There are common safety concept that strict explosion protection approaches are needed for facilities where explosive materials such as flammable liquid, vapor and gases exist. But some has an optimistic point of view that the lighter than air gases such as NG disperse rapidly, hence do not form explosion environment upon release into the atmosphere, many parts has a conventional safety point of view that those gases are also inflammable gases, hence can form explosion environment although the extent is limited and present. In this paper, the heating equipments (Hot Oil Heater) was reviewed and some risk management measures were proposed. These measures include hazardous area classification and explosion-proof provisions of electric apparatus, an early gas leak detection and isolation, ventilation system reliability, emergency response plan and training and so on. This study calculates Hazardous Area Classification using the hypothetical volume in the KS C IEC code.

The amount of sewage treatment has been increasing year by year as the small and medium sized cities grow in Korea. Besides, the treatment of sludge has been more significant owing to the total ban on disposal of organic sludge in a landfill since April 2004 and ocean dumping of organic waste since December 2013. In this research, we studied the drying characteristics of sewage sludge by indirect heating device using thermal oil. The indirect heating device operated in a batch for 16 hours according to the variation of drying temperature between 100 and 200oC and the initial input weight of each type of sewage sludge was equally 60 kg. As a result, the moisture content in raw, excess and mixed sludge became lower than 10% under 14 hours at 160oC. The average water loss rate of raw, excess and mixed sludge is 0.436 g-wet/ min, 0.362 g-wet/min and 0.367 g-wet/min respectively at this stage. Therefore, the raw sludge can be dried well, using indirect heating device in sewage treatment plant. Also, it is better to dry raw sludge or excess sludge alone than mixed sludge because each type of sludge does not make synergistic effect but counter effect when they are together.