The design and engineering of the boiler emissions abatement (BEA) plant at Impala Platinum’s refinery complex in Springs, east of Johannesburg, is now 42% complete, while the procurement, being pursued concurrently, is 58% complete.

The plant will be capable of efficiently and effectively removing pollutants – not only fly ash particulate matter (PM) but also sulphur dioxide (SO2) and nitrogen oxides (NOx) – from the boiler flue gas, exceeding the requirements of the Air Quality Act.

The design and engineering contract was awarded to Tenova Mining & Minerals South Africa, previously Bateman Africa, in July.

“After the completion of the design, engineering and procurement, the next step in the turnkey project will be to fabricate, supply, install and commission the BEA plant,” says Tenova Mining & Minerals Air Environmental senior product engineer Theo Nkisimane, who is also the BEA plant project manager.

Site work, which will take place in greenfield and brownfield environments, is expected to start in April 2014 and be completed in December 2015.

Impala Platinum Refineries uses a steam-driven process across its base metals and precious metals refinery for matte conversion and purification into marketable products and is equipped with an electrostatic precipitator (ESP) to reduce PM of the flue gases discharging from the six-boiler steam plant.

Nkisimane says this plant configuration no longer complies with the requirements of the National Environmental Management Air Quality Act and, as a result, the existing ESP will be decommissioned and replaced with the new BEA plant.

Major components of the BEA plant will include a catalytic gas cleaning system, supplied by Swiss company ELEX, with ammonia injec- tion for the removal of NOx gases; a dry flue gas cleaning system (DFGCS) with four pulse-jet bagfilter modules and a lime reagent storage and dosing system for SO2 and PM removal supplied by Denmark-based Simatek A/S; three economisers for boiler heat recovery and a new boiler-feed water system; and a dry particulate waste pneumatic transfer system.
Although design and engineering work will be carried out in collaboration with major subcontractors, it will be controlled in-house, while the fabrication of specialised equipment will take place overseas, with the bulk of the general equipment being fabricated in South Africa.

Nkisimane believes the BEA plant project is the first of its kind to be installed in South Africa because, while existing plants reduce either SO2 or NOx gases but not both, the BEA plant will be an integrated plant that will be capable of reducing NOx gases, including SO2 and PM from flue gases, using a Simatek DFGCS.

The BEA plant project is also the largest air environmental plant order that Tenova Mining & Minerals South Africa has received to date, he says.

The BEA plant is being designed to provide the most economical solution, while maintaining a low degree of technical risk and using scarce resources optimally.

Complying with Occupational Health and Safety Act and ISO 9000 and ISO 14000 standards, the plant will reduce PM from the boiler flue gas to less than 25 mg/Nm3, SO2 to less than 200 mg/Nm3 and NOx to less than 150 mg/Nm3.

The BEA plant will also improve existing boiler heat recovery and boiler-feed water systems and will produce a minimal amount of waste residual, reducing the environmental impacts from waste handling or disposal.

One of the challenges of the project is the need to limit plant downtime, as the plant operates 24 hours a day throughout the year, with a planned shutdown lasting only 60 hours once a year.

The plant configuration will ensure mini- mal downtime work, with only two major tie-ins, scheduled for the June 2014 planned shutdown.

“Strategic by-passes and equipment redun- dancy have also been provided for, where applicable, to ensure that the new BEA plant does not lead to any stoppages to the existing steam plant, says Nkisimane.

Tenova Mining & Minerals, as Bateman Africa, has installed more than ten ESPs at Implats’ various mining locations.