Investigation of the pollution risk of residues from a laboratory-scale underground coal gasification of Malkara (Turkey) lignite

  • Y. Fallahi
  • A. A. Aydın
  • M. Gür
  • H. OkutanEmail author
Original Paper


The aim of this study was to examine the risk of heavy metal, ammonia and sulfate transition from underground coal gasification (UCG) chars and process water of Malkara lignite to the groundwater around the UCG cavity. The residues were collected during laboratory-scale underground coal gasification studies of Malkara lignite in ex situ gasification simulator. In order to compare gasification with combustion in terms of water pollution, ash samples were obtained by combustion of Malkara lignite. To determine the leaching behavior of the char and ash samples, two leaching tests (EPA TCLP and EN 12457-2 methods) were applied. The concentration of heavy metals in char, ash and process water samples was determined by ICP-OES. Additionally, ammonia and sulfate analyses were conducted for process water. Based on the results of this study, it has been found that the concentration of some elements, such as B, Sb and Al in char and ash eluates exceeded the maximum level of drinking water standards. However, there is no landfill concern about char samples according to EU Landfill Directive. A significant increase in B concentration was observed in ash samples. Considering B and some other elements combustion residues were identified with much higher water contamination ability, compared to gasification residues. Ammonia concentration was observed extremely high in process water of the gasification tests. UCG technique may be more environmentally applicable technology compared to combustion for Malkara lignite reserves. However, further detailed studies are necessary in the early stage of the UCG field test design and application.


Underground coal gasification Char Ash residue Metal elution Groundwater pollution 



Acknowledgement is made to the TÜBİTAK (The Scientific and Technological Research Council of Turkey) Project No: 113M038 for their financial support. Authors also thank Dr. Cemile Yerlikaya and Esra Engin for their suggestions and technical supports in conducting this research.

Supplementary material

13762_2018_1746_MOESM1_ESM.docx (42 kb)
Supplementary material 1 (DOCX 42 kb)


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Copyright information

© Islamic Azad University (IAU) 2018

Authors and Affiliations

  1. 1.Chemical Engineering DepartmentIstanbul Technical UniversityMaslak, IstanbulTurkey
  2. 2.Mechanical Engineering DepartmentIstanbul Technical UniversityGümüşsuyu, IstanbulTurkey

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