Nov 22 2017
After 10 years of research, NRRI now delivering “instant coal”
Starting at the bench scale in 2003 and fiddling with mixture after mixture, NRRI laboratory in Coleraine is now able to produce solid biofuels with a torrefaction process that perform at comparable energy values to coal. The production is 3 – 4 ton a day. The material, coined ‘instant coal’ is made up of agricultural waste including wood and plants.
“What’s really exciting, and what we’ve been working so hard on, is being able to produce this product at a commercially-relevant scale,” said Don Fosnacht, NRRI initiative director for Renewable Energy.
NRRI has also monitored a significant trial of solid biofuel at a Portland electric plant in 2017. They completely replaced the fossil coal with 3,500 tons of biofuel with only minor mechanical changes. This trial demonstrated that this similar biofuel provides roughly 2,500 BTU per pound increase over typical output for Powder River Basin coals.
NRRI, are developing large-scale demonstrations of biomass pretreatment processes to provide industry-relevant data and support. At the NRRI-Coleraine site facility capabilities will include the three techniques.
The first process line is torrefaction a “light to dark roast” of woody biomass chips in an oxygen-deprived environment to deliver a uniform, dry solid fuel that contains approximately 90% the BTU content as an equal weight of western coal. NRRI is commissioning a rotary kiln based system capable of producing 10-12 t/d of torrefied material from 27-32 t/d green wood chips. In 2017, NRRI will also have a moving bed torrefaction system that will be capable of producing 3 t/d of torrefied product.
Hydrothermal Carbonisation (HTC)
The second process Hydrothermal Carbonisation (HTC) process takes “wet” biomass such as agricultural waste or invasive water plant species and processes it in a process similar to a pressure cooker to produce an aqueous “energy mud” that has energy content similar to the dry torrefied fuel. This material is an excellent binder for the dry fuel to be compressed into briquettes for shipment. NRRI’s HTC process is anticipated in 2017.
The third process is called steam explosion, it is a technique of treating woody biomass with high pressure steam followed by rapid release of pressure. This action explodes the wood structure, opening it up for more efficient processing, extraction or torrefaction. NRRI looks forward to having this capability in the Renewable Energy Laboratory in 2017/2018.
NRRI’s renewable energy research is funded by grants from Xcel Energy, Minnesota Next Generation Energy Board/MN Dept. of Agriculture, Minnesota Power, Heetway, K.R.Komarek, Inc. and the Consortium for Advanced Wood to Energy Solutions.