Environmental assessment and nano-mineralogical characterization of coal,overburden and sediment from Indian coal mining acid drainage

The deterioration of environmental conditions is the major contributory factor to poor health and quality of life that hinders sustainable development in any region.Coal mining is one of the major industries that contribute to the economy of a country but it also impacts the environment.The chemical parameters of the coal,overburden,soil and sediments along with the coal mine drainage(CMD)were investigated in order to understand the overall environmental impact from high sulphur coal mining at northeastern coalfield(India).It was found that the total sulphur content of the coal is noticeably high compared to the overburden(OB)and soil.The volatile matter of the coal is sufficiently high against the high ash content of the soil and overburden.The water samples have a High Electrical Conductivity(EC)and high Total Dissolve Solid(TDS).Lower values of pH,indicate the dissolution of minerals present in the coal as well as other minerals in the mine rejects/overburden.The chemical and nano-mineralogical composition of coal,soil and overburden samples was studied using a High Resolution-Transmission Electron Microscopy(HR-TEM),Energy Dispersive Spectroscopy(EDS),Selected-Area Diffraction(SAED),Field Emission-Scanning Electron Microscopy(FE-SEM)/EDS,X-ray diffraction(XRD),Fourier Transform Infrared Spectroscopy(FTIR),Raman and Ion-Chromatographic analysis,and Mossbauer spectroscopy.From different geochemical analysis it has been found that the mine water sample from Ledo colliery has the lowest pH value of 3.30,Tirap colliery samples have the highest electrical conductivity value of5.40 ms cm^(-1)Both Ledo and Tirap coals have total sulphur contents within the range 3-3.50%.The coal mine water from Tirap colliery(TW-15 B)has high values of Mg^(2+)(450 ppm),and Br^-(227.17 ppm).XRD analysis revealed the presence of minerals including quartz and hematite in the coals.Mineral analysis of coal mine overburden(OB)indicates the presence both of pyrite and marcasite which was also confirmed in XRD and Mossbauer spectral analysis.The presented data of the minerals and ultra/nano-particles present shows their ability to control the mobility of hazardous elements,suggesting possible use in environmental management technology,including restoration of the delicate Indian coal mine areas.

Economic overview of a two-agent process for underground coal gasification with Fischer-Tropsch- based poly-generation

Underground Coal Gasification(UCG)is a mining-gasification process that produces synthesis gas from in situ coal by injecting air(or oxygen and steam)and extracting the produced gas via boreholes.The resulting synthesis gas(‘syngas’)produced by UCG can be used directly as a fuel-gas or deep-cleaned to produce many other products like chemicals,liquid fuels,hydrogen and synthetic natural gas.UCG has significant environmental,safety and practical advantages over conventional coal mining and utilization,foremost being cost and emissions reductions.In South Africa,facilities of an industrial-scale Fischer-Tropsch(FT)have been operating for decades on coal-to-liquid and gas-to-liquid conversion.Oxygen-blown UCG produces syngas,which contains a mixture of carbon monoxide(CO)and hydrogen,and these molecules can be conditioned to serve as feed for synthetic-crude-oil(‘syncrude’)conversion technologies based on the FT process.African Carbon Energy(Pty)Ltd.(Africary)completed a study integrating its UCG technology with mini gas-to-liquids plant.Syngas from Africary’s Theunissen Underground Coal Gasification(TUCG)project will be used for power production and synthesis of liquid fuels in a unique poly-generation configuration.The TUCG process will consist of two parallel gasifiers,operated on different agents,making the component parts of UCG and coal-to-(any product)(CtX)tightly linked and interdependent,but reducing both cost and emissions.UCG-CtX offers a lower capital investment to conventional underground mining and surface gasification due to the removal of the surface gasifier and coal-mine operations.The gas clean-up systems will remove undesirable components from each gasifier and blend the cleaned syngas for H2:CO ratio control and provide implementation of carbon capture and sequestration.This study has minimized the complexity and optimized the process flow to provide own-use electricity and about 4000 barrels/day equivalent fuels at a capital cost estimate(2017)of about US$350 million and operating cost of around 28 US$/barrel.