Exhaust emissions from an EFW plant contain a variety of gaseous compounds which are regulated by the Industrial Emission Directive (IED).
Two of these gaseous compounds are hydrogen chloride (HCl) & sulphur dioxide (SO₂), both of which are acid gases. Under normal operation, both are emitted in small quantities from EFW plants.
Small quantity emissions are the result of very good abatement control technology. Lime is injected into the abatement plant, which effectively ‘scrubs’ any acid components that are present in the gas stream.
However, due to the inhomogeneous nature of the feedstock (black bin waste) the concentration of HCl & SO₂ can vary, so both need to be carefully monitored.
The latest revision of the IED saw emissions limits reduced significantly.
Until now, site operators would estimate how much lime reagent was needed by monitoring the final emission to atmosphere.
A feedscrew would then increase/decrease the amount of lime injected into the gas stream in a bid to reduce emissions.
The problem with this method is the reliance on a ‘feed-back’ technique. Site operators have been frequently adding too much lime.
Overdosing is common but this comes at a cost in both emission limit breaches & lime wastage.
Challenge 1: Achieve precise measurement of raw gas HCl to avoid overdosing dry basic reagent.
Challenge 2: Meet decreasing emissions limits (HCl from 10 mg/m³ to 8 mg/m³ for existing plants).
The Hampshire EFW site turned to ENVEA for a cost-saving solution that can be adjusted to future legislative changes.
The LAS 5000XD TDL was proposed, even though it was limited to HCl measurement only. ENVEA’s knowledge of the EFW process, the known concentration of the raw gas & the ELV proved that if you control the HCl, the SO₂ would be controlled as a byproduct.
The in-situ gas analyser was trialed to measure process HCl gas prior to abatement so accurate amounts of lime could be added.
The LAS 5000XD is a precise, reliable & maintenance free solution. It measures HCl which allows the plant to run in fully automatic mode, where the lime dosing is controlled from the LAS 5000XD readings.
Now, raw gas measurement can be performed by the LAS 5000XD prior to abatement to manage the feed-forward.
This solution has been largely appreciated by the plant operators because it’s the first time since the site became operational that their abatement plant has been fully automated.
✅ Allows the abatement plant to operate fully automated without intervention thus removing guesswork and improving accuracy.
✅ Meets current Emission Limit Values (ELVs) and supports future BREF requirements.
✅ ROI – Lime dosing savings of £21k per stream.
✅ Maintenance free – Reducing downtime otherwise spent servicing parts.
Curious? Learn more about LAS 5000XD here.