Coal India takes a look at underground mining and uses punch entry to extract more from surface mines

PSU Coal India (CIL) miner is looking into underground (UG) mining, aiming to take over existing UG operations in the long term, and short term using the punch entry method to go under surface mines depleted (OC) and extract more reserves. Using this method for the first time, CIL virtually converts some OC mines to UG mines.

The company also plans to deploy 10 high-wall machines at four OC mines this fiscal year, with capital expenditure of between 800 and 1,000 crore. Machines extract coal that an open pit leaves as unextractable after reaching its ultimate pit level. A CIL executive told FE that such coal cannot be mined manually.

The expected production potential has been estimated at 5 million tonnes per year. A longwall mining project involving capital expenditure of 200 crore is already underway in the South Eastern Coal Fields (SECL). Three other projects of this type will start this year in the Eastern Coal Basins (ECL).

The executive said contractors hired for the projects will share capital expenditures on a 50/50 basis and CIL will bear half of the costs. Longwall mining could further lead to the entry of punches into coal-depleted surface mines.

“Punch entry will actually make holes in an open pit and could create a horizontal pathway to access underground coal in the open pit. Punch entry could be through a combination of technologies, and CIL plans to identify and implement five of these mines in a phased manner through FY24,” he said.The entire punch entry process would be mechanized and no miners would would go underground, which would ensure operational safety.

Investments for the clocking entry system will be estimated as the project progresses and according to the technology used. But it will likely be on a split basis, the executive said.

The company had closed all the underground mines one by one for non-techno-commercial viability. But it plans to quadruple UG production to 100 million tonnes (MT) by FY30 from 25.6 MT in FY22.

“UG production is clean for the environment, minimally invasive on land degradation and friendly to society. About 70% of the country’s coal reserves are suitable for UG mining,” the CIL executive said, adding that the goal is to make UG production significantly complementary to OC production. At the current rate, exploitable coal reserves at existing OC mines will slowly begin to decline.

Since the nationalization of the mines in 1975, UG production has contracted 57.7% through FY22, while OC production has increased 8.5 times. UG mines suffered losses and had longer gestation periods with a lack of skilled labor, unavailability of local equipment, and high departmental production costs.

But UG production could now become technically-commercially viable with the availability of mass production technologies locally and a well-trained skilled workforce. Outsourcing to subcontractors would reduce production costs and the gestation period is considerably shorter. CIL thus plans to gradually increase the use of stranded UG coal assets, he said.

Paste filling technology, another green frontier that involves high-speed storage, will be compatible with mass production technologies. Instead of conventional sand storage, it uses fly ash to fill the void created by coal mining from UG mines. Such a system is in an advanced stage of implementation at ECL.

Among mass production technologies, CIL will introduce 50 continuous miners by FY25 with a peak production potential of 25 MT per year. Currently, 21 such machines are deployed at ECL, Central Coalfields and SECL, producing 9 MT per year.

Two Powered Support Longwall (PSLW) machines operating at ECL and Bharat Coking Coal (BCCL) produced 1.58 MT in FY22, 40% more than 1.13 MT produced in FY22. ‘EX21. Two other PSLWs with a total capacity of 4.5 MT per year will soon be deployed at BCCL.

About William J. Harris

Check Also

CIL to deploy green mining technologies to reduce emissions

June 20, 2022 C.W. Team Coal India Limited (CIL) plans to deploy green mining technologies …