Bubbling fluidised bed gasification of wheat straw–gasifier performance using mullite as bed material

Abstract

The adoption of wheat straw as a fuel for gasification processes has been hindered due to a lack of experience and its propensity to cause bed agglomeration in fluidised bed gasifiers.In this study wheat straw was gasified in a small scale, air blown bubbling fluidised bed using mullite as bed material. The gasifier was successfully operated and isothermal bed conditions maintained at temperatures up to 750 °C. Below this temperature, the gasifier was operated at equivalence ratios from 0.1 to 0.26. The maximum lower heating value of the producer gas was approximately 3.6 MJm -3 at standard temperature and pressure (STP) conditions and was obtained at an equivalence ratio of 0.165. In general, a producer gas with a lower heating value of approximately 3 MJm -3 at STP could be obtained across the entire range of equivalence ratios operated. The lower heating value tended to fluctuate, however, and it was considered more appropriate for use in heat applications than as a fuel for internal combustion engines. The concentration of combustibles in the producer gas was lower than that obtained from the gasification of wheat straw in a dual distributor type gasifier and a circulating fluidised bed. These differences were associated with reactor design and, in the case of the circulating fluidised bed, with higher temperatures.Equilibrium modelling at adiabatic conditions, which provides the maximum performance of the system, showed that the gasifier was operating at suboptimal equivalence ratios to achieve greatest efficiencies. The maximum calculated theoretical cold gas efficiency of 73% was obtained at an equivalence ratio of 0.35.

Fluidized Bed Two-Stage Gasification Process for Clean Fuel Gas Production from Herb Residue: Fundamentals and Demonstration

“…However, for producing industry-use fuel gas, a fluidized bed gasifier is always more promising and suitable with obvious merits of high throughput, wide distribution for raw material size (<10 mm), and small capital investment. 12,13 Bhaird et al 14 gasified wheat straw on a bubbling fluidized bed (BFB) reactor with a feeding rate of 1.8 t/day. The lower heating value (LHV) of the gasified gas and its corresponding tar content were ∼3.6 MJ/Nm 3 and >10 g/Nm 3 , respectively.…”

“…At present, gasification is considered as an attractive technology for efficiently converting carbon-containing solid waste into syngas and fuel gas. − According to the differences in reactor structure, the existing gasification process can be mainly divided into a fixed bed gasifier, − a fluidized bed gasifier, and an entrained-flow bed gasifier. However, for producing industry-use fuel gas, a fluidized bed gasifier is always more promising and suitable with obvious merits of high throughput, wide distribution for raw material size (<10 mm), and small capital investment. , Bhaird et al gasified wheat straw on a bubbling fluidized bed (BFB) reactor with a feeding rate of 1.8 t/day. The lower heating value (LHV) of the gasified gas and its corresponding tar content were ∼3.6 MJ/Nm 3 and >10 g/Nm 3 , respectively.…”

Empirical Design, Construction, and Experimental Test of a Small-Scale Bubbling Fluidized Bed Reactor

“…The conversion efficiency from biomass into syngas in the gasification process was determined based on scientific literature [16,26,33,42,54]. For the calculations, a value of efficiency equal to 70% was chosen.…”

“…In the case of the reactor design, several studies analyzed how is the behavior of the BFB gasification process is and how the reactor design is affected by bed material [15][16][17], bed agglomeration [18][19][20][21][22], gasifying agent [9,10,[23][24][25][26], use of catalysts [20,27,28], hydrodynamics [2,29], biomass segregation [5,30], kind and size of biomass [25,[30][31][32][33][34][35], temperature conditions [32,36], or gasification process [37][38][39]. Results from the experimental test were also studied in [23,24,33,34,[40][41][42], and finally, other publications integrated models and tests to validate simulations [43,44].…”