The solution to our energy crisis may lie in rocks

Only around 15% of India's coal reserves is recoverable by the current mining methods. Imagine what our energy scenario could become if we find a way to access the remaining 85%.

Nikhil Sirdesai, a research scholar with the IITB-Monash Research Academy, is working on a project titled 'Numerical and experimental study of rocks under very high temperature conditions: Underground coal gasification' that might present us with an option to do this.

The IITB-Monash Research Academy is a collaboration between India and Australia that endeavours to strengthen scientific relationships between the two countries, and graduate research scholars like Nikhil study for a dually-badged PhD from both IIT Bombay and Monash University, spending time at both institutions to enrich their research experience.

Picture of In-situ Coal Gasification by the Linked Vertical Well Method
(Modified after Shirsat, 1989) (Picture Credit:Shirsat Vijay, Modeling of cavity growth
in Underground Coal gasification, Master of Science Dissertation,
Texas Tech. University, 1989.)

Research suggests that 2500 m3 of syn-gas could be produced from gasifying one tonne of coal. Thus, if only 10% of the un-mineable reserve, i.e. 25.7 BT, is extracted using Underground Coal Gasification (UCG), the syn-gas produced would be equal to 6.17 Trillion m3 of Natural Gas!

The only limitation in tapping this vast energy source is the public perception of underground coal gasification. Research and previous case studies on the pilot UCG projects have indicated the occurrence of ground subsidence (sinking or settling of the ground surface) over the coal seam being gasified. When applied commercially, the scale of subsidence could increase, and contaminants such as heavy metals and toxic gases could migrate through these cracks and pollute the groundwater sources, thus causing further damage. Therefore, it is necessary to study the behaviour of rock properties under thermal variations. And this is why Nikhil's research study becomes so crucial.

Overview of the experimental analyses and the application of the constitutive equations
acquired from the data analyses for numerical modelling (Picture Credit:Nikhil Sirdesai)

Explaining his work so far, Nikhil says, "A mixture of high pressure steam and oxygen is pumped into the seam through the injection well/s triggering the gasification reaction and the resultant syn-gas is recovered through the production well/s. The reaction, however, exposes the rock strata surrounding the coal seam to high temperatures (700 °C to 1500 °C) for a long duration. In such conditions, the geotechnical properties of the rock, namely physical, mechanical and thermal, undergo drastic change. Additionally, the burning of the coal seam leaves behind a cavity which causes the strata to collapse leading to a subsidence on the ground surface. The aim of my study is to characterise the changes through experimental analyses and to simulate the rock strata using numerical modelling techniques."

While most studies have been conducted on igneous rocks, very few have been done on changes induced in sedimentary rocks when exposed to high temperatures, and this makes Nikhil's work special. Besides underground coal gasification, this study also finds its application in areas such as building fires, enhanced oil recovery and the extraction of geothermal energy.

Prof Murali Sastry, CEO, IITB-Monash Research Academy, is delighted at the prospects. "The IITB-Monash Research Academy is an opportunity for industry in Australia and India, as well as for IIT Bombay and Monash University, to train the next generation of rich talent in India by focusing on grand challenges such as energy. What can be more compelling than figuring out innovative technologies for valorizing currently inaccessible coal reserves. The 'Academy' has the potential to be a significant research institution and a source of talent that is slowly becoming much sought after around the globe."

Adds Nikhil, "Our goal is to not only add to the existing pool of knowledge dedicated to thermo-mechanical study, but also help in exploiting the country's locked energy reserves. We aim to propose design parameters for the underground coal gasification reactors. The optimum dimensions can only be proposed if the behaviour of the rocks is characterised and projected by a constituent equation. These equations will help in numerical models where the shape and size of the reactor/s can be tweaked and the resultant damage to the strata can be recorded."

When this begins to contribute to reducing India's energy crisis, researchers like Nikhil Sirdesai could take a bow.

Research scholar: Nikhil Sirdesai, IITB-Monash Research Academy

Project title: Numerical and experimental study of rocks under very high temperature conditions: Underground coal gasification

Supervisors: Prof. Trilok Nath Singh (IITB) and Prof. Ranjith Pathegama Gamage (Monash University)

Contact details: nikhil.sirdesai@gmail.com

This story was written by Mr Krishna Warrier based on inputs from the research student and IITB-Monash Research Academy. Copyright IITB-Monash Research Academy.