NOx abatement solution for 12 boilers at a large industrial petrochemical plant. Source Babcock
NOx abatement solution for 12 boilers at a large industrial petrochemical plant. Source Babcock

Having successfully implemented one of the first nitrogen oxide (NOx) abatement projects in South Africa, Babcock’s Ntuthuko Engineering business is leading the way in specialist combustion installations.

The project scope required the engineering firm to provide and implement an optimised NOx abatement solution for 12 boilers at a large industrial petrochemical plant. This is in line with complying with the National Environmental Management: Air Quality Act.

The legislation calls for NOx levels to be reduced to 750 mg/Nm3 for each combustion installation with a thermal rating of more than 50MW.

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Final performance tests of the NOx abatement installation indicated that NOx production was reduced to significantly lower than local environmental requirements. These tests were conducted in the first quarter of 2019.

The ongoing boiler plant project has been recognised for its significant contribution to South Africa’s energy environment. The recognition has earned Babcock a South African National Energy Association (SANEA) Energy Project Award for 2019.

The awards recognise projects that positively contribute to the South African energy environment or bring international credibility to the country, through leadership, innovation, initiative and vision.

Juan Gerber, process engineering manager for Babcock, says that as part of the concept design phase, daily coal sample data, as well as future coal mining predictions were processed and analysed in order to establish a design coal specification.

After an extensive technology selection process, the compact Babcock & Wilcox DRB-XCL low NOx burner was found to be the most suitable for the given site constraints, and its widespread international application demonstrated NOx reduction higher than local minimum emission requirements.

Together with Babcock & Wilcox and the customer, Babcock investigated and tested different burner configurations to establish the reaction of the low NOx burner to South Africa’s unique coal conditions.

All the auxiliary boiler systems were also investigated to determine the impact on NOx production and how they could be further optimised.

He explains that it was pivotal to match the correct technology with the project scope, which required integrating high tech burners into a 60-year old boiler plant.

While technology and equipment were selected to have minimal impact, parts of the existing boiler plant required modification or redesign.

This included the pulverised fuel piping, main boiler structure and access platforms, pulverised coal mill plant control philosophy, boiler outlet flue gas sampling grid, fuel oil and atomising burner system, and a burner auxiliary air system. The control logic and combustion management systems were also updated.

Gerber adds that Babcock took a modern engineering approach to a complex project and utilised its in-house 3D scanning and modelling capabilities to facilitate and optimise the design phase.

The 3D modelling enabled all parties, from the customer and engineers through to operators and safety officers, to review the process safely, often without requiring on-site presence.