Fixed bed gasification of coal generate some by-products, such as tar and coal powder. Coal powder obtained because the coal feed for fixed bed gasification reactor must have a size above 20 mm. Meanwhile, tar is a high molecular weight hydrocarbon compounds that will condense at low temperatures, which cause clogging and blocking of pipes. In this study, experiment on combustible gas generation from co-gasification of tar and coal powder was conducted in an auto-thermal reactor to determine the temperature of the process, combustible gas composition, and efficiency of the process. From calculation and experiments about oxidizing reactor operation, 20 kg/hr of tar was more promising to operate and can reach the optimal temperature which was 1900ºC. The energy from oxidizing reactor used for the reduction reaction of tar and pyrolysis of coal powder and produce combustible yield gas. The coal powder that can be conversion was about 14.4 kg/hr and produce approximately 84.52 kg/hr combustible gas. The calorific value of combustible yield gas amounted to 783.62 Cal/g. Combustible yield gas has advantages levels of hydrogen gas (H 2) as high as 19.2%, which is already exceeding the levels of hydrogen gas from coal gasification is only <10%. Cold gas efficiency (CGE) has a value which was still low at 26.31%. It is caused by two factors, namely the calorific value fuel gas produced was still low and the remainder of the conversion of coal powder were still mostly in the form of charcoal.

The biochar utilization reduces CO2 emissions. This study aims to investigate the optimum pyrolysis temperature of lamtoro wood (Leucaena leucocephala) to produce suitable biochar for coal blends as fuel in the steam power plant. The experiment was carried out in a batch process, applied to a fixed bed reactor, 10°C/minute heating rate, three different variables temperature (300, 450, 600°C), and 60 minutes residence time. The biochar yield for each pyrolysis temperature is 61.77%, 26.45%, and 24.89%. This shows that the pyrolysis is carried out at a temperature of 300 to 450 °C, then ramps up to 600 °C. The volatile matter was released during the pyrolysis and raise the fixed carbon content. The fixed carbon content for each pyrolysis temperature is 26.35%, 61.82%, and 65.66%. Fixed carbon content at 450 and 600 °C identical to bituminous coal. The increase in fixed carbon content in biochar leads the heating value to increase. The heating value of lamtoro wood was 19.15 MJ/kg (db), increasing to 22.92, 28.01, and 29.73 MJ/kg (db) for each pyrolysis temperature. The biochar heating value is close to bituminous coal. The biochar energy content of original lamtoro wood for each pyrolysis temperature is 81.72%, 42.77%, and 42.71%. Biochar reaches its optimal point at pyrolysis temperature 450 °C, which has a yield and heating value almost the same at pyrolysis temperature of 600 °C. The biochar characterization results indicate that it can be used as a coal blend for steam power plants.

The Indonesian government has encouraged coal mining companies to expand into coal downstream industries. In response to this policy, PT. Arutmin Indonesia has conducted a pre-feasibility study on the construction of a coal-to-methanol plant. The plant was located in the Pulau Laut Utara Coal Terminal (NPLCT). The plant is designed to produce 3.0 million tons of methanol/year. The raw material is supplied from the Sarongga coal mine, about 5 km away from NPLCT. The coal-to-methanol process was simulated using ChemCad to solve chemical and energy problems. Based on heat & material balance simulation results, the plant requires coal of 6.0 million tons/year as a raw material. Air Product technology was chosen for coal gasification and Davy Technology for methanol synthesis. Air product gasifier requires lower oxygen to produce syngas than other technologies, thereby reducing oxygen production costs. The plant needs an investment cost of USD 3.0 billion. With the assumption of a methanol price of 311 USD/ton and 20 years of tax holiday incentives, the financial analysis results show that the construction of coal-to-methanol plant is financially feasible with an NPV value of 289.7 million USD and an IRR of 13.35%.

Coal gasification is one of coal utilizations that produces less CO2 emission than coal combustion. Coal gasification technology that has been used in Indonesia is generally a fixed bed gasification. Fixed bed is designed for high-rank coal and the majority of Indonesian coal is of a low-rank. Low ash and high moisture content of the Indonesian coal in a fixed bed can affect mechanical and thermal fragmentation, pressure drop, gas and particle flow distribution. The operation of gasifier may cause unstable condition. Another gasification technology is bubbling fluidized bed, which is operated above 1,200°C, so ash can melt. High operating temperature causes agglomeration and makes unstable gasification process. Therefore, in this study, low-rank coal is gasified in bubbling fluidized bed reactor at low operating temperature. The purpose of this study is to determine the optimal conditions of bubbling fluidized bed gasification. The research was conducted in bubbling fluidized bed coal gasification Process Development Unit (PDU) at Coal Utilization Technology Centre of R&D Centre of tekMIRA, Palimanan. Coal was fed continuously as many as 20 kg/hour into a gasifier then was gasified to produce gas using air as a gasifying agent and silica sand as a bed material at 850-950°C. The produced gas from the gasification was analyzed using the Orsat Analyzer. A simulation using a ChemCAD 7.1 CC steady state was applied to validate the experiment result. From the analyzed result of yield gas composition, the produced CO and CO2 were about 10-15 wt%. Gas compositions that are close to criteria of producer gas, no agglomeration, and stable process condition during study indicate that bubbling fluidized bed gasification at low operating temperature is suitable to be applied as gasification technology for Indonesian low-rank coal.