Live Energies, along with partners, proposes to demonstrate the BSP process at a suitable emerging market location with a plant of 2000 t/year input capacity. The project has been initiated in Quarter 3, 2016.
Background on the BSP Process
The complete use of carbohydrate-based organic residues, such as straw, wood scrap and waste, grass clippings, vegetable waste or of sewage sludge or digestate as an energy source is necessary for the success of aspirations of a bio-economy. Our demonstration project concentrates especially on waste and by-product biomass with a high moisture content, where the technical barriers towards an energy efficient conversion is highest.
Biomass has a high content of chemically bound water and often has high moisture content. This results in low mass-related energy content. In order to increase the energy density of biomass, various methods are available. Depending on parameters such as temperature, pressure, reaction time and biomass fraction, solid, liquid or gaseous carbonaceous materials can be gained. With increasing severity of the reaction conditions, especially temperature and reaction time, the tendency for the formation of gas is increased, and smaller organic molecules are formed.
Carbon is a versatile and effective energy storage. Processes that target the conditioning of biomass carbon as a solid, encounter growing interest. During carbonization the carbon content of the biomass is converted into solid carbon by thermal treatment in an inert gas atmosphere (pyrolysis) or with auxiliaries, such as hot and pressurized liquid water (hydrothermal carbonization – HTC). Both pyrolysis and HTC require long reaction times to achieve high carbon contents in the coal.
In order to circumvent the procedural disadvantages of HTC and pyrolysis, a group of researchers headed by Prof. Bockhorn at the Engler-Bunte-Institute, Division of Combustion Technology, at the Karlsruhe Institute of Technology (KIT) investigated an alternative method in the project “Green Coal” – the atmospheric steam conditioning. In “Biomass Steam Processing” (BSP) the feedstock is treated under atmospheric pressure with steam at temperatures between 250 °C and 400 °C for reaction times from minutes up to a few hours. This produces a biochar similar to lignite with substantially lower process complexity than the HTC and at much shorter reaction times than pyrolysis. The BSP reaction conditions can be better controlled and the elemental composition of the biochar is variable.
BSP Pilot plant
The project group theoretically and experimentally investigated the BSP process with model and real biomasses such as straw, wood, grass, orange peels, vegetable wastes and sewage sludge. As an experimental plant a number of laboratory reactors and pilot reactors from gram to kilogram scale were used. After initial attempts to the BSP process in a laboratory reactor a continuously operated small pilot plant for the BSP method has been developed. The pilot plant with a throughput of up to 50 kg/h, which is the last stage before a market launch, has been successfully put into operation (see pictures).
BSP Process Scheme
The calorific value of untreated straw or wood is circa 15 and 18 MJ/kg respectively; typical calorific values of lignite are approximately 20 to 28 MJ/kg. In a typical BSP experiment with wood pellets with a reaction time of 34 minutes and a temperature of 350 °C, about 54 percent of the employed chemical energy can be found in the biochar, whereby the calorific value increased by over 60 percent. With wheat straw as a feedstock and milder conditions (temperature 300 °C and reaction time 56 min) similar energy efficiencies can be reached. A part of the input energy is recovered as chemical energy in the condensable organic molecules and can be recycled in the process. Depending on moisture content of the input biomass and biomass-mixtures, a varying share of chemical energy has to be spent to heat up biomass and moisture to reaction temperature.