Patent DE-102009015257-A1 (DE)
Title: Continuous method for hydrothermal carbonization of biomass, comprises increasing pressure of feedstock to desired pressure level, and carbonizing feedstock by splitting into water and carbon dioxide for converting into carbonized product
Inventor: WOLF BODO M
IPC: B01J3/04
Filed: 2009-04-01
Abstract: The continuous method for hydrothermal carbonization of biomass, comprises increasing the pressure of the feedstock to a pressure level of 5 bar in a first process stage, carbonizing the feedstock by splitting into water and carbon dioxide at the pressure of 5 bar and maximum boiling temperature of water for converting into a carbonized product in a second process stage, vertically transporting the feedstock by gravity, and carrying out the conversion of the feedstock in the upper portion of the second process stage by removing the water from the second process stage. The continuous method for hydrothermal carbonization of biomass, comprises increasing the pressure of the feedstock to a pressure level of 5 bar in a first process stage, carbonizing the feedstock by splitting into water and carbon dioxide at the pressure of 5 bar and maximum boiling temperature of water for converting into a carbonized product in a second process stage, vertically transporting the feedstock by gravity, carrying out the conversion of the feedstock in the upper portion of the second process stage by removing the water from the second process stage and/or partially re-supplying the water into the second process stage, depositing the feedstock as sediment in the lower portion of the second process stage, where the minimum level of the sediment is selected such that the solid content increases to 30% by sedimentation and the maximum height of the sediment layer is limited such that no solid base body is formed by static pressure, regulating the filling height of the water level in the second process stage by removing and supplying water in the second process stage, removing the permanent gas that is accumulated in the second step from the second process stage in counter-flow to the feedstock entering into the second process stage so that the obtained water vapor portion contained in the cold feedstock is partially condensed in a ratio and then the permanent gas is removed from the process, and discharging the sediment from the second process stage, cooling, supplying to a drying step and then discharging as end product in the form of marketable carbon with a water content of less than 15 wt.% by evaporating water at a temperature level of a third process stage, where the drying step is carried out at vapor atmosphere. The temperature of the feedstock in the first process stage is increased by mixing the feedstock with hot waste water and exhaust steam from the succeeding process stages in a ratio to the temperature of the feedstock, where maximum water is again separated from the feedstock before entering the feedstock into the second process stage and maximum water from the separated water is discharged from the process. The maximum water is separated from the feedstock in the succeeding process stages of carbonization and drying and the water supplied in the first process stage remains as circulating water in the process. In first process stage, the pressure increase of the feedstock takes place in presence of the liquid and the conveyance of the feedstock directly before the pressure increase is produced by filling its void volumes with process-internal wastewater (29), where the maximum water is again separated from the feedstock before entering the feedstock into the second process stage before supplying. In the carbonization step, an isothermal process flow is obtained by vapor removal, by removing, heating and re-supplying of water taken for the conversion and if necessary by adding external hot vapor, which condenses in the process stage. The drying step is upstream to a mechanical dewatering, where the concentrate occurring during the mechanical dewatering is introduced in the drying step. The flash steam from the pressure reduction of the water not supplied to the second process stage and the water-containing sediment and the vapor developed during drying are isothermally washed, are condensed for generating fresh steam and then compressed or relaxed in a power process by delivering technical work, where the pressure stages of the compression are determined from the pressure required for heating the dryer and for heating of the second process stage. The water occurring in the isothermal washing of the flash steam and drying vapor is supplied to the feedstock in the first process stage before pressure increase, is again separated from the feedstock after delivering a part of its perceptible heat to the feedstock partially before the second process stage and then supplied to an utilization optionally after concentrating by evaporation. The filtrate occurring in the mechanical dewatering is supplied to the feedstock in the first process stage before the pressure increase, is again discharged from the feedstock after delivering the part of its perceptible heat to the feedstock partially before the second process stage and then supplied to an utilization optionally after concentrating by evaporation. The condensate occurring in the evaporator is supplied to the feedstock in the first process stage before the pressure increase, is again discharged from the feedstock after delivering the part of its perceptible heat to the feedstock partially before the second process stage and then supplied to an utilization optionally after concentrating by evaporation.