Professional Engineering

What is the attraction of building the plant for Air Products, a company known as a manufacturer of industrial gases? “We have a history in terms of energy from waste,” says Jordan. “It is part of the business’s strategy to be involved in power generation. Cleaning up syngas and putting it into a gas turbine is something we’re already familiar with. What’s unique here is that it’s the first time all these components have been put together on this scale. The plant will be the largest of its type globally.”

Jordan suggests that projects such as the Teesside plant could become commonplace. “It is the need to divert waste from landfill and the need to generate renewable power. This type of project helps the UK to fulfil both of those aims. We have publicly talked about plans to invest in other projects, and can see a future for a number of these across the UK. This is just the start.”

One British company working on its own waste-to-energy technology is Swindon’s Advanced Plasma Power (APP), which has developed a gasification type of plant that relies on a technology called Gasplasma. Said to be low in emissions, the process is compatible with recycling, and produces a hydrogen-rich syngas and a solid vitrified product known as Plasmarok, which can be used as a construction material or as road aggregate. Heat from the process can 
be captured.

The plant can deal with up to 150,000 tonnes a year of municipal solid waste. Rolf Stein, chief executive officer of APP, says: “What we’ve done is to combine conventional gasification – in our case a fluidised bed gasifier – with conventional plasma treatment. We put the conventional gasifier at the front end to do the donkey work of actually creating a gas, which gasifiers do exceptionally efficiently, while the plasma technology does two things: thermally cracks the syngas into constituent hydrogen and carbon monoxide, and vitrifies the gasifier residues into a rock-like substance, 
which is a safe, environmentally inert building material.”

The Japanese have been doing something similar with incinerator bottom and fly ash for decades to make road aggregate, says Stein. The APP process uses a combination of oxygen and steam, or “oxysteam”, in the gasification stage, meaning the resulting syngas isn’t diluted with nitrogen. “The gas flows are kept to a minimum, and we achieve quite an energy-dense syngas, of about 12 megajoules per normal metre cubed. That is about a third of the energy level of natural gas.” The energy-intense syngas can be fed directly into a gas engine or gas turbine to produce electricity. “That’s significantly more efficient from an electrical energy conversion perspective than a steam cycle,” he says.

Stein says the stage before the waste even enters the plant – the separating out of the recyclables – is critical. “We see no merit in putting recyclable materials, especially inert or inorganic recyclable materials, into a thermal process. It makes no sense – there’s no energy value to them, and you end up losing them. 

“So we prefer to take the recyclates out at the front end. Our plant has a materials recycling facility, or a ‘fuel preparation plant’, as it might be called. We have the standard kind of equipment you see for removing recyclates from household waste, such as eddy current separators. We dry the refuse to be used as fuel with heat from the plant – you want to get the moisture content down, because then you create a more
energy-intensive gas.”

The typical ash content of a “refuse-derived fuel” is about 15%. So handling 100,000 tonnes of fuel a year would produce around 15,000 tonnes of the Plasmarok construction material. Stein says APP is working on several projects. A demonstrator plant in Swindon will be followed by a full-scale commercial operation, although it is not certain this will be in this country.

“The first commercial plant will probably be in the UK, but it may be that an international enquiry will lead to it being established overseas. We are experiencing a high number of enquiries from all over the world.”

He adds: “The ‘hot button’ item at the moment is mass burn incineration, which is typically not acceptable to the public in many cities. No one wants an incinerator. You need a solution that embraces resource management rather than just waste management, to use the resource effectively and also to recover material.”

Much like Jordan, Stein is aware of the potential of the syngas to be used for other means. APP is engaged in a project to develop a fuel comparable with natural gas, with the aim of introducing it to the grid. This project involves converting the syngas to methane. “The syngas is clean and can be used for power generation on site, or it can be turned into biofuels or water gas, shifting all the way through to pure hydrogen,” he says.

“All over the world, syngas is being converted into liquid fuels at petrochemical plants. There are hundreds of installations using gasification, coal, crude oil and biomass to create syngases for feedstocks into plastics plants and chemicals plants.

“It’s a tried and tested methodology – we just do it with waste, which requires a slightly different approach. We are one of a small number of emerging technology companies that are doing this globally. We’re proud to be doing it here. This technology has massive potential.”