How waste gasification can clean up its ACT2 April 2018
Can a new waste gasification demonstration facility currently under construction in the UK succeed where so many have failed? James Varley reports
In the UK, waste gasification, classified as an “advanced conversion technology” (ACT), has received significant government support, but has recently been characterised as an area of technology “synonymous with bankruptcies, failures and broken promises”*. One particularly high profile setback was the abandonment in 2016 of the plasma based Tees Valley project (which had been proposing to use waste derived syngas to run two 50 MWe combined cycle units) and the consequent withdrawal of Air Products from the energy-from-waste business, incurring write-down costs in the region of $1 billion. Among the problems have been overoptimism about the technology and underestimating the risks of scale up.
Of considerable potential interest, therefore, is a “commercial demonstrator” 1.5 MWe waste gasification facility currently under construction in Wednesbury, UK, which is planning to produce clean (ie tar free) consistently high quality hydrogen- rich syngas to run a specially built piston-engine-driven genset, with its waste heat system designed for use in a potential district heating network. It is expected to have an input capacity of about 40 tons per day of post-recycle RDF (refuse derived fuel).
The project participants say the facility will “vent nothing to the atmosphere other than clean exhaust gases from the engine generator set” and is “designed to deliver significant carbon benefits through the use of waste to produce power, whilst being more efficient than traditional incineration or pyrolysis based waste-to-energy processes at this scale.” The project also includes a slip stream for trialling other uses for the syngas, eg in other engine types and for processes other than power production (for example aviation fuel production).
Expected to start its operational testing phase around the fourth quarter of 2018, the Wednesbury Sustainable Energy Centre (previously called the SynTech Energy Centre) is employing FluiMax pressurised bubbling fluidised bed gasification technology provided by Frontline Bioenergy of the USA, in conjunction with tar removal (by high temperature thermal cracking) and syngas clean up.
FluiMax is described as proven technology, while the Wednesbury project is said to have “undergone extensive due diligence” with a good deal of effort going into risk mitigation and independent investigations, leading to the conclusions that the “technology has been risk mitigated to an unprecedented extent” and that the analysis of issues impacting plant availability is one of the most comprehensive yet seen in the field of energy-from-waste project development.
The project is being led by KEW Technology, working in partnership with the UK Energy Technologies Institute (ETI). ETI commissioned the project and is providing £8 million funding of the £11.8 million required. Project leadership has recently been transferred from SynTech Bioenergy LLC to KEW Technology, an entity established by Kamal Kalsi, formerly with SynTech Bioenergy LLC and before that Broadcrown.
Otto Simon is principal designer, with Turner Townsend acting as principal contractor.
The Wednesbury gasifier is “about more than just generating clean electricity, although that is an important first step”, says Paul Winstanley, ETI Project Manager, noting that “producing a clean high quality syngas opens up a huge variety of new opportunities in addition to making clean electricity including the generation of hydrogen, jet fuel and even plastics from wastes.”
ETI gasification programme
The project can be seen as the culmination of ETI’s programme on waste gasification, launched in 2012, with the aim of promoting improved small (or “town”) scale (around 5-20 MWe) conversion technologies for waste and biomass, focussing on resource recovery rather than waste destruction, and lending themselves to embedded generation.
The focus of the Energy Technologies Institute was on gasification because of the following perceived advantages over alternatives (such as incineration combined with boiler and steam turbine):
- tolerance of varying feedstock qualities, especially important when dealing with waste;
- production of syngas permits use of power generation technologies that can achieve higher efficiencies, even at small scale (using piston engines, for example), whereas steam turbine efficiencies fall significantly at reduced scale;
- high efficiency at small scale lends itself to distributed generation and integration with local heat networks, and decentralised generation means reduced waste miles; and
- potential ability to produce a range of outputs, not just electricity, increasing resilience to future uncertainties.
A particular emphasis of the ETI programme was what it calls “Type 3” gasification technologies (see panel, right), in which the aim is to produce clean tar-free syngas rather than tar-containing syngas to be combusted for steam raising.
In the first phase of the ETI programme (2012-2014) three technologies/projects, all of Type 3, were identified as being worthy of further consideration in arriving at a design for “the most cost-effective, economically viable and efficient waste to energy plant possible”:
A 7.6 MWe (net), 23 MWt, waste-to- energy IGCC plant using MILENA-OLGA technology (originally developed by ECN, the Dutch national energy research body) to be provided by Dahlman Renewable Technology (now owned by Synova). Site: Grimsby, UK. Gasifier: MILENA indirectly heated fluidised bed (medium temperature). Syngas clean-up: low temp washing (OLGA). Primary power generation: syngas fuelled gas turbine, in combined cycle.
A 5 MWe facility using Advanced Plasma Power’s Gasplasma technology. Site: Tyseley, Birmingham, UK. Gasifier: directly heated, oxygen blown fluidised bed (medium temperature. Syngas clean-up: high temperature plasma treatment. Primary power generation: reciprocating engine.
A 3 MWe facility proposed by piston- engine-based genset provider Broadcrown. Site: Wednesbury, UK. Gasifier: Fluimax directly heated, oxygen blown fluidised bed (medium temperature). Syngas clean-up: high temperature thermal treatment (cracking). Primary power generation: reciprocating engine.
The Broadcrown proposal evolved into the Wednesbury gasification demonstrator. Broadcrown went into administration in 2015 (and was bought by JCB). The Wednesbury project was taken over by SynTech, and then, as already noted, transferred to KEW Technology. The proposed installed capacity was halved.
The other two schemes did not proceed, however, both APP and Dahlman are still working towards deployment of their gasification technologies, with projects underway at Swindon (UK) and Alkmaar (Netherlands), respectively, but with a focus on demonstrating “green gas” production from waste and biomass.
*UK Without Incineration Network (UKWIN) briefing, Gasification failures in the UK
Sources for this article included: presentations at the ETI’s Ten Years of Innovation Conference, London, November 2017 and the ETI Insights Report, Targetting new and cleaner uses for wastes and biomass using gasification, by Geraint Evans (http://www.eti.co.uk/targetting-new-and-cleaner-uses-for-wastes-and-biomass-using-gasification)