Detailed process modeling of a wood gasification combined heat and power plant

We provide the first process simulation able to depict a complete life cycle inventory of a biomass gasification combined heat and power (CHP) plant. The model predicts the detailed mass and energy balances, minor compounds emissions (such as NOx, SOx, aromatics, etc.). It is based on a phenomenological approach for dryer, reactors (gasification and combustion) and scrubber modeling. Process units are modeled with Aspen Plus® models completed with dedicated Fortran sub-models when more details are required. The gasifier is a Dual Fluidized Bed (DFB). It is decomposed in three sections, describing the three main mechanisms occurring in the reactor: wood pyrolysis, secondary reactions and char combustion. At the outlet of the gasifier, the complete composition of the syngas is predicted, which includes water, permanent gases, inorganics, particles and tars (phenol, benzene, toluene, styrene, indene, naphthalene, acenaphthylene, anthracene, phenanthrene, pyrene). Simulation results were validated against measurements from a pilot plant and other literature data. A wet conventional syngas cleaning system for gasification plant, including cyclone, catalytic tar cracker, syngas cooler, bag filters, water scrubber and wastewater treatment was considered and modeled. The complexity of tar composition allows a reliable determination of tar dew point. At the outlet of the cleaning system, syngas is burned in gas engines. Gaseous emissions (NOx, SOx, etc.) of the gas engines and the DFB combustor are also handled by the model as well as ashes and liquid waste. The predicted electrical and thermal efficiencies are 27 and 39% respectively.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A new model of a biomass gasification combined heat and power plant is presented. ► The whole gasification process is modelled under Aspen Plus from dryer to gas engine. ► Heat streams are integrated for internal needs and district heating. ► Tar and inorganic compounds are predicted. ► A detailed life cycle inventory is obtained including mass and energy balances and pollutant emissions.