Before committing to a pyrolysis plant, test your actual waste in an operating one. A trial programme offered to a European client used 10 tonnes of each of two materials, refuse-derived fuel (RDF) and animal flour, run through a working UK pyrolysis and gasification plant. It measured stack emissions, weighed and analysed the ash, and checked that the ash would meet the leaching limits for non-hazardous landfill.
The challenge: proving a feedstock you have never run
The client wanted to build a plant in southern Europe and needed evidence that two feedstocks would behave as expected. Laboratory analysis alone does not show how a material feeds, how much ash it leaves or what ends up in the flue gas. Only a full-scale run does.
The difficulty is that the trial plant was a commercial operation. It was treating waste from hospitals on a fixed programme, and it needed notice to shut down safely, prepare for the trial material and restart on the usual waste afterwards.
The approach: a structured, as-is trial
The two feedstocks
| RDF | Animal flour | |
|---|---|---|
| Moisture | about 20% | about 3% |
| Calorific value (dry) | about 19.5 MJ/kg | about 19.5 MJ/kg |
| Ash | not stated | about 20% |
| Nitrogen | not stated | about 10% |
| Chlorine and sulphur | not stated | about 0.7% and 0.5% |
| Density | not stated | about 600 kg/m³ |
Animal flour is high in nitrogen, so the trial paid close attention to NOx and to the consumption of the ammonia used in the NOx catalyst. Its ash content is also high.
How the trial ran
- 10 tonnes of each material, one after the other, over a continuous two-day period.
- After each test, the plant was shut down, cooled, cleaned and restarted on the next material.
- The programme was set at 6 weeks to deliver the material to site, 24 hours of running for each 10 tonne batch, and a report two weeks after tests finished.
- The client accepted that results were provided as-is. The plant owners took no responsibility for how appropriate the results were for the client’s own design.
What was measured
The test objectives were a high feed rate, maximum energy recovery, maximum mass reduction, compliance with the minimum temperature of destruction and compliance with emission limits.
Emissions
The plant’s continuous emission monitoring system measured hydrogen chloride, volatile organic compounds as total organic carbon, NOx, carbon monoxide, sulphur dioxide and total particles. Hydrogen fluoride was an open question: the client wanted to know whether the existing system could measure it. A good trial plan finds such gaps before the test, not after.
Ash and slag
Ash from the cyclone and slag from the gasifier were to be weighed and sampled separately, and the samples analysed independently. The target was to meet the European criteria for acceptance of waste at landfills for non-hazardous waste. At a liquid-to-solid ratio of 10 l/kg those limits include, for example:
- arsenic 2 mg/kg;
- cadmium 1 mg/kg;
- lead 10 mg/kg;
- mercury 0.2 mg/kg;
- chloride 15,000 mg/kg and sulphate 20,000 mg/kg;
- total dissolved solids 60,000 mg/kg.
The full list is in Council Decision 2003/33/EC. Chlorine in the feed and chloride in the ash are linked, which is one reason the feed analysis matters.
Consumables
The consumption of sodium bicarbonate for acid-gas control and ammonia for the NOx catalyst was to be recorded during the trial. Those two numbers feed straight into operating cost estimates for the full-scale plant.
What the trial does not do
The offer is blunt about its limits. No other tests were included, and any further laboratory work would be at the client’s cost with an independent laboratory of their choice. The trial scope covered accepting and handling the material, shutting down and restarting the plant, ash testing and access to instruments, plus collating and presenting the final report.
What to consider for your own project
- Specify what you want measured before the trial. Missing parameters are expensive to add later.
- Send a representative sample. Ten tonnes only tells you about the material you supply.
- Agree the ash criteria in advance. Know which landfill acceptance limits apply to you.
- Allow for the host plant’s schedule. Trial slots depend on a working plant’s programme.
- Keep the result in context. A trial proves behaviour at one scale on one day, not a guarantee.
In the UK, the Environment Agency sets expectations for waste treatment permits and emissions monitoring.
FAQ
Why test with 10 tonnes?
It is large enough to run the plant at stable conditions for a day, producing meaningful emission and ash data.
Can a trial plant accept any material?
Not without notice and approval. The host plant’s permit and licence limit what it can receive, and the proposal raised animal flour acceptance as a question to confirm.
What is leaching testing for?
It shows whether the ash would release metals and salts into water at levels that would make it hazardous for landfill.
Who pays for extra analysis?
The client, using an independent laboratory of their choice.
Need to prove a feedstock?
Contact us to plan a trial around your waste.