Pike River Recovery Agency secures nitrogen plant
17 August 2018
Te Kāhui Whakamana Rua Tekau mā Iwa Pike River Recovery Agency has hired a nitrogen plant that should be up and running at the Pike River Mine site at the start of October.
The BOC New Zealand plant is made up of several containers of equipment, including compressors and other machinery. It is expected to be in use for about a year and will be shipped from its current location in Australia, Chief Operating Officer Dinghy Pattinson says.
“This particular plant has been used in Greymouth before – both at Pike River and at Spring Creek. Part of the contract specifies that the company supplying the plant will also provide a back-up liquid nitrogen system, train our staff in operating the plant and back-up, and have technicians available should anything be amiss,” he says.
The nitrogen plant works by taking filtered and compressed air which passes through a carbon filter leaving nitrogen-enriched gas. The plant will be set up opposite the administration buildings at the mine site, and nitrogen fed into the portal 1.1km up the hill via a steel pipeline.
The plan for purging the mine of methane gas is to pump nitrogen into the mine drift via a pipe through the 30metre seal, while at the same time drawing the methane out through existing boreholes above the mine, using a “venturi” – which Mr Pattinson describes as akin to a fan, without the blades.
Two plastic pipelines will also be laid up on the hill above the mine portal, to borehole 47 (about 3.5km), so nitrogen can also be pumped into the top end of the mine.
Initially, the plant will be set up so tests can be run to ascertain if a stable environment can be achieved within the mine.
There are two distinct areas of the mine: The mine drift and the mine workings. The drift is a 2.3km access tunnel from the portal (entrance) to the workings. The mine workings, where coal was being extracted, contain approximately 5.5km of tunnels. The workings are the last estimated location of the 29 workers who were in the mine when a methane explosion occurred in November 2010. The workings are blocked by a large rockfall at the very end of the drift.
The Agency has been tasked by the Government to develop a safe plan to re-enter and recover the mine drift, to promote accountability for this tragedy, to give the Pike River families closure and to help prevent future mining tragedies.