Jeong Hwan Lim

Development and evaluation of multilayer air filter media

Three types of multilayer air filter media were developed and evaluated. Two other existing filters were also used for comparison of filter performance. The pressure drop, the collection efficiency, and the dust-holding capacity of the tested filters were measured, and the internal structure of the filter media was analyzed by using a scanning electron microscope. The multilayer filters tested in this study are composed of pre-surface layer, surface layer, and substrate layer. Among those layers, the surface layer is mainly responsible for particle collection. As a test result, it was found that the thickness of a surface layer has the greatest effect on filtration performance of a multilayer air filter. Additionally, filtration velocity and electrostatic forces should be considered together as important parameters for multilayer air filter design.

Pilot-Scale Studies on Upgrading of an Indonesian Low-Rank Coal Using Palm Oil Residues

In the present study, a method was developed to upgrade low-rank coal using palm oil residues. The upgrading process consisted of pulverization, mixing, drying, coating, and briquetting. A palm oil residue (palm fatty acid distillate [PFAD]) was used to upgrade an Indonesian low-rank coal. Pores generated in the low-rank coal due to the evaporation of moisture were coated with the PFAD. The inhibitory effect of the PFAD was investigated by measuring the crossing-point temperature (CPT) of the upgraded coal. The amount of moisture re-adsorbed by the upgraded coal was compared to the raw coal with several methods. The CPT of the upgraded coal increased 10°C, and the moisture re-adsorption decreased by less than 60% compared with the raw coal. The upgraded coal briquettes were hydrophobic and had high compressive strength. This makes the upgraded coal sufficiently stable for long-term storage and long-distance transportation.

Characteristics of coal upgraded with heavy oils

We investigated the ability of an oil coating to upgrade Indonesian low-rank coal, which has a low ash content and a moisture content of approximately 30%. Proximate and ultimate analyses of the characteristics of coal samples containing different amounts of asphalt (ASP) and palm fatty acid distillate (PFAD) were studied, including the samples’ calorific values, crossing-point temperatures (CPT), specific surface areas, pore sizes, structural changes, and moisture readsorption. The results showed that the 0.5% PFAD-coated coal was the highest quality. This coal showed few physical and chemical changes, and it had a low surface area and a high CPT value.

Upgrading Indonesian Low-Rank Coal with an Oil Coating

ABSTRACT In the present work, feasibility to upgrade Indonesian low-rank coal by oil coating was investigated. The low-rank coal (LRC) was upgraded by addition of bio tar, tallow, crude cashew nutshell liquid, refined cashew nutshell liquid, and waste lubricant. Two types of Indonesian low-rank coal samples were pulverized, mixed, dried, coated and briquetted by mixing of the aforementioned materials. Heat calorific values, crossing point temperatures, and moisture re-adsorption characteristics of raw and upgraded coal were evaluated. Heat calorific values of upgraded coals were significantly improved compared to raw coal. Upgraded coals showed a medium tendency to spontaneous combustion and resistance to moisture re-adsorption. Isothermal oxidation characteristics of raw and upgraded coal were assessed by means of the carbon-dioxide-formation rate in the exhaust gas. Upgraded coal showed less susceptibility to isothermal oxidation due to the suppression of active functional groups to oxygen in air by oil coating. Results of the study indicate that these additives are potential candidates for upgrading Indonesian LRC.

Experimental Analysis of Propensity for Spontaneous Combustion of Low-Rank Coal Upgraded by Spray Coating with Heavy Oil

Upgrading technology has been studied for efficient utilization of low rank coal. Spray coating of heavy oil was applied on the upgrading process in order to stabilize low rank coal against spontaneous combustion. Low rank coal, which contains more than 30wt% of moisture, was upgraded to high calorific coal and stabilized by spray coating of heavy oil. It was identified that spray coating of heavy oil after drying coal is the optimum procedure of upgrading low rank coal. The experimental results show that more than 2wt% of heavy oil should be adsorbed on the coal in order to stabilize sufficiently for spontaneous combustion.

Fry-Drying Process Simulation and Optimization for Low-Rank Coal

Process simulation and optimization for fry-drying of low-rank coal was carried out. The operating conditions of the evaporator was set so that the coal moisture would decrease from 33% to 10% during the drying process. Through process simulations, the heat duty supplied and power consumption were calculated under each operating condition. From the simulation results, the amount of enthalpy supplied and operating costs were calculated on the basis of prices in Indonesia as a coal-producing country and South Korea as a coal-importing country. Cases where thermal energy was reused through MVR showed an effect of reducing enthalpy and operating costs by around 50%. The results indicated that the amount of enthalpy supplied to fry-drying process was minimized at the evaporator pressure of 100 kPa and temperature of 120°C. However, the results of optimum operating conditions in terms of operating costs showed a different tendency to depend on the steam and electricity costs. The optimum operating conditions were evaporator pressure 500 kPa and temperature 168°C in Indonesia. On the other hand, the optimum operating conditions were evaporator pressure 250 kPa and temperature 138°C in South Korea.