Diary of an engineer: The tests are OK, but the workers aren't

Submitted by martin on 21 September, 2021 - 6:52 Author: Emma Rickman
Engineering plant

The company that processes the plant’s “Incinerator Bottom Ash” call to return three loads, and say they are quarantining two more. The logistics company who do the deliveries are not able to tip, and they tell their drivers to stop collecting from us. I ask the company if they’re able to separate the unburned waste from the ash and return it to us, at our expense — she says no. This means that the plant is now producing Incinerator Bottom Ash (IBA) continuously with nowhere to send it. The ash bay is very small, and it won’t take long before it’s full. The only way to stop producing ash is to go off-line.

I inspect the IBA and take pictures, feeding information back to the operators. There is unburned waste in it — some remains of plastic bottles, fabric, plastic streamers, cans with labels, remnants of crisp packets... but I’ve never really looked at the IBA on a good day. I have nothing to compare it to.

N, the shift team leader, suggests trying to sift the unburned waste out of the IBA with a jerry-rigged skip and some wire mesh. He and the assistants rig something up, but it doesn’t work. In the end, me and N work out a plan to feed the IBA back into the pit. It means instructing the assistants to fill front-loaders with IBA and tip at designated times, then the crane driver will mix the ash thoroughly with fresh waste, and feed it into the furnace again. This is disruptive for many reasons; it adds traffic to the tipping hall which is already full of bin wagons; it adds waste to the pit which is already full and hard to mix; it uses up all of the assistant’s time; and it puts material on the fire that cannot be burned, essentially dampening the combustion and making all the existing problems worse.

I learn in the first few weeks of my new job as Compliance Technician that there are chemical tests done to ensure the IBA has been burned sufficiently. The labs test for Total Organic Carbon (TOC) content; if over 3% of the sample contains organic carbon, then it has not been burned enough. The other test performed is called Loss On Ignition, where the IBA is heated until any unburned waste in the sample catches fire; if this portion exceeds 5% of the total sample, then it has not been burned enough.

My manager’s first line of attack is to look at the plant’s contract with the IBA processing company. He speaks to his manager and comes back with a definition of “Rejected IBA”.

“IBA shall not exceed 3% TOC or 5% LOI on testing”, G tells me. “It’s extremely unlikely we’re exceeding those limits, but we need to get the ash tested every day to confirm this.”

I write an email to the company director quoting the contract, providing photo evidence and the last report from the lab. He doesn’t respond well — he rings G and they have a very polite and passive-aggressive phone call.

It turns out that the company who process our IBA have had a problem with “black matting”, which originated from Sheffield. Photos show it’s an abrasive carbon-fibre-like webbing that separates into individual fibres which tangle with everything else in the ash. The company have a line of workers on a conveyor belt separating out unburned residue, and they have complained to the Health and Safety Executive that their employer hasn’t provided them with the correct PPE. The company tells me their workers have skin-rashes and cuts from this fibre.

• Emma Rickman is an engineer in a Combined Heat and Power plant

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