Bark as feedstock for dual fluidized bed gasifiers-Operability, efficiency, and economics

Abstract

Summary The demand for biofuels and biochemicals is expected to increase in the future, which will in turn increase the demand for biomass feedstock. Large gasification plants fueled with biomass feedstock are likely to be a key enabling technology in a resource‐efficient, bio‐based economy. Furthermore, the costs for producing biofuels and biochemicals in such plants could potentially be decreased by utilizing inexpensive low‐grade residual biomass as feedstock. This study investigates the usage of shredded tree bark as a feedstock for the production of biomethane in the GoBiGas demonstration plant in Gothenburg, Sweden, based on a 32 MWth industrial dual fluidized bed gasification unit. The plant was operated with bark feedstock for 12 000 hours during the period 2014 to 2018. Data from the measurement campaign were processed using a stochastic approach to establish the plant's mass and energy balances, which were then compared with operation of the plant with wood pellets. For this comparison, an extrapolation algorithm was developed to predict plant performance using bark dried to the same moisture content as wood pellets, ie, 8%w.b. Plant operation with bark feedstock was evaluated for operability, efficiency, and feedstock‐related cost. The gas quality achieved during the test period was similar to that obtained for operation with wood pellets. Furthermore, no significant ash sintering or agglomeration problems were observed more than 750 hours of operation. The calculated biomass‐to‐biomethane efficiency is 43% to 47% (lower heating value basis) for operation with wet bark. However, the predicted biomass‐to‐biomethane efficiency can be increased to 55%–65% for operation with bark feedstock dried to 8% moisture content, with corresponding feedstock costs in the range of 24.2 to 32.7 EUR/MWh; ie, a cost reduction of about 40% compared with wood pellets.

Analysis of the Physicochemical Characteristics of Biochar Obtained by Slow Pyrolysis of Nut Shells in a Nitrogen Atmosphere

“…Generally, the nut shell samples exhibit similar characteristics and elemental composition. This type of biomass is characterized by a low ash content A d = 0.4-1.1 wt% (except for the peanut shell sample A d = 3.4 wt% [20]) and a high content of volatile compounds V r = 66.4-72.7 wt% and oxygen O d = 40.3-46.7 wt%, which is characteristic of the biomass [21]. In turn, the LHV value (17.5-20.3 MJ/kg) is comparable not only with other types of the biomass but also with low-grade coals (Lignite/brown coal or Sub-bituminous coal) [22].…”

Economic Evaluation of Large-Scale Biorefinery Deployment: A Framework Integrating Dynamic Biomass Market and Techno-Economic Models

“…Several methods aimed at modeling thermochemical biorefinery processes at the conceptual design stage have been suggested [32][33][34]. For processes with robust experimental data, a bottom-up, statistical approach can be used to validate a process model to establish the mass and energy balances of the process [35,36]. However, for processes where available experimental data are not sufficient for statistical evaluations, simulation models accounting for reaction kinetics or thermodynamic restrictions can be used to simulate the processing unit [30,33].…”

Economic Evaluation of Large-Scale Biorefinery Deployment: A Framework Integrating Dynamic Biomass Market and Techno-Economic Models

“…Several methods aimed at modeling thermochemical biorefinery processes at the conceptual design stage have been suggested [26][27][28]. For processes with robust experimental data, a bottom-up, statistical approach can be used to validate a process model to establish the mass and energy balances of the process [29,30]. However, for processes where available experimental data is not sufficient for statistical evaluations, simulation models accounting for reaction kinetics or thermodynamic restrictions can be used to simulate the processing unit [24,27].…”