Experimental study of a trickle-bed reactor operating at high pressure: two-phase pressure drop and liquid saturation

Torrefaction is a thermochemical pretreatment process at 200–300 °C in an inert condition which transforms biomass into a relatively superior handling, milling, co-firing and clean renewable energy into solid biofuel This increases the energy density, water resistance and grindability of biomass and makes it safe from biological degradation which ultimately makes easy and economical on transportation and storing of the torrefied products Torrefied biomass is considered as improved version than the current wood pellet products and an environmentally friendly future alternative for coal Torrefaction carries devolatilisation, depolymerization and carbonization of lignocellulose components and generates a brown to black solid biomass as a productive output with water, organics, lipids, alkalis, SiO2, CO2, CO and CH4 During this process, 70 % of the mass is retained as a solid product, and retains 90 % of the initial energy content The torrefied product is then shaped into pellets or briquettes that pack much more energy density than regular wood pellets These properties minimize on the difference in combustion characteristics between biomass and coal that bring a huge possibility of direct firing of biomass in an existing coal-fired plant Researchers are trying to find a solution to fire/co-fire torrefied biomass instead of coal in an existing coal-fired based boiler with minimum modifications and expenditures Currently available torrefied technologies are basically designed and tested for woody biomass so further research is required to address on utilization of the agricultural biomass with technically and economically viable This review covers the torrefaction technologies, its’ applications, current status and future recommendations for further study

A review on advances of torrefaction technologies for biomass processing

Modelling of the hydrodynamics of the cocurrent gas–liquid trickle flow through a trickle-bed reactor

A study of chemical structure changes of Chinese lignite during fluidized-bed drying in nitrogen and air

Exergy analysis of fluidized bed drying of moist particles

A kinetic model is developed for the drying of solids in fluidized beds, assuming a falling rate period following a constant rate period. Experimental data obtained using batch and continuous single and spiral fluidized beds are satisfactorily matched with the assumed drying kinetics and the residence time distribution of solids appropriate for the type of dryer.

Fluidized bed drying of solids

Pressure drop and liquid saturation are two important design parameters in cocurrent gas-liquid downflow through packed beds. A macroscopic model based on momentum balance is formulated for the condition of no radial pressure gradients. The model includes the effect of bubble formation on the pressure drop and holdup and is compared with the experimental data of the earlier investigators and of the present study. The model provides a functional form for correlating pressure drop and liquid saturation but some parameters have to be determined by fitting the experimental data.

Hydrodynamics of two-phase cocurrent downflow through packed beds. Part I. Macroscopic model

Pressure-drop in cocurrent gas-liquid downflow through packed beds was experimentally measured for nonfoaming, foaming Newtonian, and non-Newtonian liquids. The variables include the column diameter, packing size and shape, flow rates of the phases, and their physical properties. Unified correlations are presented for the data of the present study as well as data available in literature in terms of Lockhart-Martinelli parameters and flow variables and packing characteristics. The data were modeled using a dynamic interaction model.

Pressure drop in gas‐liquid downflow through packed beds

Two-phase pressure drop and dynamic and total liquid saturation are experimentally determined for air-water system under cocurrent downflow through packed beds using packing differing widely in geometry The experimental data of the present study as well as that available in literature is satisfactorily correlated in terms of: (a) Lockhart-Martinelli parameters; and (b) the Reynolds numbers defined for the respective phases and the bed porosity, taking into account the flow behavior of the phases through the packed bed

Y. B. G. Varma

Papers

Fluidized bed drying of solids

Hydrodynamics of two-phase cocurrent downflow through packed beds. Part I. Macroscopic model

Pressure drop in gas‐liquid downflow through packed beds

Hydrodynamics of two‐phase cocurrent downflow through packed beds. Part II: Experiment and correlations

A model for the residence time distribution of liquid phase in trickle beds