Eskom management’s instruction to increase the load of Kusile Power Station Unit 1 to full capacity, against the advice of its engineers, caused the disastrous collapse of a duct which has contributed roughly two stages of load-shedding since late October 2022.

That is according to an internal report by the utility’s assurance and forensics department, which was seen by the Sunday Times.

A section of the flue-gas desulphurisation (FGD) duct, which carries emissions from Kusile Unit 1 into a large chimney, collapsed in October 2022.

Because Unit 2 and Unit 3 are also connected to the chimney, they had to be taken offline to conduct repairs.

That resulted in the loss of a potential 2,400MW of capacity, the equivalent of over two stages of load-shedding.

The report alleges that “unnamed bosses” at Megawatt Park gave verbal instructions to return the unit to service and operate it at its maximum capacity of 800MW.

That was even though a faulty critical component was causing a cement-like sludge to build up inside the flue-gas duct.

Rapport first reported on the cause of the collapse in November 2022.

Citing sources familiar with the breakdown, the report said the faulty components were the baghouse filters meant to capture fly ash from emitted gasses.

They stated that some ash containing high amounts of silica was carried to the desulphurisation facility, where hydrated lime was sprayed through the emitted gasses.

This process helps remove the harmful pollutant gas sulphur dioxide (SO2).

The combination of fly ash, lime water spray, and heat created a hard crust along the sides of the chimney, causing severe strain on its supporting structure, which could no longer bear the weight.

The assurance and forensic team’s report found that the unit had been problematic since 2021 and that partial repairs to rectify the problem were poorly done.

It identified the root cause of the collapse as Eskom management’s decision to continue running the plant at over 500MW while being aware of the sludge build-up.

Because the instruction was reportedly issued verbally and informally, the team could not pinpoint the manager or managers behind it.

“During the investigation, no auditable trail or evidence was provided on the decisions made to continue running the plant with a compromised FGD,” the report stated.

The report found that the unit had been taken offline several times before the collapse, for the same reason.

“From all the facts acquired about the plant design and operation, it is clear that the power station technical staff responsible for the plant predicted the failure,” the report said.

“Continuous decisions taken to favour production above plant health led directly to…failure.”

Eskom anticipates that the FGD’s repair will be completed by September 2024. However, the utility has asked the Department of Environmental Affairs to let it bypass the FGD system to bring the three impacted units back online a year earlier than planned.

The idea would be to build temporary structures that can vent the emissions while repairs are conducted on the duct.

That could help cut down the gap between Eskom’s supply and generation somewhat, and alleviate load-shedding.

According to the lead analyst at the Centre for Research on Energy and Clean Air (CREA), Lauri Myllyvirta, the temporary bypass will increase SO2 emissions at Kusile eightfold — to 80,000 tonnes.

The pollutant is linked to human health problems like asthma and heart attacks, and the CREA estimated that Eskom’s emissions of the gas caused roughly 2,000 deaths in South Africa every year.

Kusile is the first power plant in South Africa to feature the expensive wet FGD technology, but its construction has been delayed by over a decade due to procurement corruption and design defects.

It was scheduled to be finished by 2013, but Eskom’s current timeline will now only see it completed by 2026.

Its original budget of R80 billion has also ballooned to over R226 billion.