Comparison of Tar Samples from Reaction Zone and Outlet in Ex-Situ Underground Coal Gasification Experiment

Tar remaining in the gasification cavity during underground coal gasification (UCG) is an important pollution source, while the reported studies only focus on the tar behavior at the outlet. The present work aims to compare the tar properties from the reaction zone and the outlet, analyze the tar evolution during gasification, and discuss possible measures to control tar pollution. Tar was sampled with a self-developed equipment from an ex-situ underground coal gasification experimental system and analyzed by GC-MS. The gas composition, temperature, and PM10 were also compared for the reaction zone and the outlet. Compared with the tar from reaction zone, the tar from outlet has a smaller percentage of high boiling point content, PAHs, C, O, N, S, Cl, Si, and a larger percentage of H. The PAHs percentage in tar at the outlet in this work is closer to the field data than the lab data from literature, indicating the experimental system gives a good simulation of tar behavior in underground coal gasification. Condensation due to a fast temperature drop is one of the main reasons for PAHs decreasing. Tar cracking and soot formation also cause the decrease of heavy tar, proven by the light gas and particulate matter results.

Techno-economic analysis of producing low heating value underground coal gasification gas in Indonesia

Indonesia is currently reviewing the use of underground coal gasification (UCG) technology to utilize deep-seated coal. UCG may exploit the coal deposit that is not feasible for open-pit mines due to its great depths. In this study, the UCG plant in two coal mines, the Kideco Jaya Agung (KJA) and the Indominco (IMM) coal mines, will be compared their economics in producing low heating value gas with a capacity of 170,000 MJ/hour. The UCG plants implement the linking vertical well (LVW) technique combined with reverses combustion linking (RCL). The discounted cash flow (DCF) method is used for financial analysis to determine the minimum selling price of UCG low heating value gas. The study aims to understand the economic feasibility of applying UCG technology to Indonesia’s different characteristics of coal deposits. The results show the minimum prices of the low heating value UCG gas of KJA and IMM UCG plants are USD 3/MMBTU and USD 3.57/MMBTU, respectively. The operating cost of the IMM UCG is higher than that of the KJA UCG plant due to its thinner and deeper coal seams.

Advantages of underground coal gasification implementation in Indonesia

Underground Coal Gasification (UCG) is an energy manufacturing process whereby coal is gasified or chemically converted into a gas, in-situ. UCG has several benefits in terms of low capital cost, lower environmental impact, high energy density and long-term production certaint y. The objective of this study is to describe the advantages of implementing UCG technology in Indonesia based on UCG gas resources, product market, coal quality and availability of regulation to support UCG projects. UCG gas resources are estimated based on data of CBM resource and coal quality was examined by heat treatment. The size of conservatively estimated potential UCG gas manufacturing volume in Indonesia based on CBM data is 160 TCF which is greater than Indonesia’s natural gas reserves, namely 142.7 TCF. UCG gas markets are available in South Sumatera and East Kalimantan since the natural gas production in the two provinces is declining significantly. UCG in Indonesia is regulated under the mineral and coal regulatory regime, which brings some benefits, including more flexibility in the type of drilling rigs that can be used for UCG, compared to oil and gas drilling.