FEATURE: BIOMASS TO LIQUIDS Feedstock: 120 tpd wood residues Annual capacity: 20 000 m3 bio-oil 4.5 GWh electricity 80 000 tonnes steam Cost: c. EUR 19 million (33% grants, 33% loans & 33 % equity) Main technology suppliers: Belt-dryer: Amandus Kahl Pyrolysis reactor: BTG BioLiquids HRSG Boiler: Stork Thermeq Bioenergy International No 78, 2-2015 19 EMPYRO in figures der 6 percent and the material is transferred to a reactor feed bin inside the main building. – Sufficient excess heat is normally available from the pyrolysis plant to dry biomass from 40–50 percent moisture content to below 6 percent. Here we have a 12-year agreement with AkzoNobel to supply low-pressure high temperature steam for its process, said Muggen. Proprietary rotary cone reactor The heart of the Empyro process is the BTG-BTL proprietary flash pyrolysis modified rotary cone reactor (RCR). Originally researched as a concept with mechanical mixing some 20 years ago at the University of Twente, it was then further developed by BTG who built a pilot plant in 1998 at its R&D facilities in Enschede, the Netherlands. In 2005 BTG built the first commercial 50 tonne per day plant in Malaysia using empty fruit bunches (EFB) as feedstock. In 2007 BTG formed a subsidiary BTG BioLiquids to commercialise its modified RCRpyrolysis technology. Unlike other fluidised bed reactor concepts, no inert gases are needed in the RCR to enable the intensive mixing of the biomass particles with the hot sand bed. Biomass particles are fed near the bottom of the pyrolysis reactor together with an excess flow of 500o C sand, which acts as the circulating heat carrier material. The biomass and sand are mixed within the pyrolysis reactor and converted into pyrolysis oil vapours, gas and char. – The residence time for the reaction is 2 seconds, thereof flash rather than fast, explained Muggen. The produced vapours and gasses pass through several cyclones that separate out the solids, char and sand particles, from the vapours and gases, before these enter the condenser. Here the vapours are condensed by re-circulated bio-oil. The sand and char is transferred to a specially designed fluidised bed combustor, where air is added to combust the char and reheat the sand. The hot sand is then transported back to the reactor to close the loop. The combustor flue gas passes cyclones and bag filter for particle removal before being mixed with uncondensed vapours from the condenser and burnt in an afterburner. A heat recovery steam generator and afterburner provide high temperature steam for a Siemens steam turbine with the post turbine steam supplied to Akzo Nobel as well as the belt-dryer. Defining commercial scale A continuous process the Empyro plant has a design capacity to convert 5 tonnes per hour of woody biomass into 3.3 tonnes of pyrolysis oil, 4.5 MW of steam and 435 kW of electricity with self-consumption of heat and power taken into account. This is deliberately the commercial scale. – It is technically possible to build larger units, the compact design of our modified RCR makes scaling-up to larger capacities straightforward. A 10 tonne per hour plant design just a matter of duplicating the units. If larger outputs are required then additional plants can be set-up in cascade keeping CAPEX low and revenue coming in once the first unit is running, commented Muggen adding that it is much better to transport the bio-oil over longer distances than the raw biomass feedstock. In theory different units could run on different feedstock and it would seem to be relatively easy to dismantle a unit again should a plant need to be decommissioned or moved making it a more liquid asset. According to Muggen due to the simplicity of the rotating cone process, investment costs can be considerably lower in comparison to other pyrolysis technologies that require larger down-stream equipment and in some cases ATEX compliance. – Depending on local conditions energy efficiencies of 85–90 percent can be achieved based on biomass in and oil, heat, electricity out, Muggen said. Valorising bio-oil FrieslandCampina, a major global dairy producer, has agreed a 12-year off-take deal for 80-100 percent of pyrolysis oil allowing Empyro to supply test volumes to other third parties. The bio-oil is being co-fired with fossil gas in a Stork Thermeq steam boiler. – Using this high quality single-phase bio-oil as a fuel is a first step. BTG is looking at other downstream processing such as organic acid extraction and further refining into renewable fuels and chemicals, ended Gerhard Muggen. Text & photos: Alan Sherrard BI78/4781/AS
Bioenergy no 2 - March 2015
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