Bishnu Acharya

Chemical-Looping Gasification of Biomass for Hydrogen-Enriched Gas Production with In-Process Carbon Dioxide Capture

The research presents an innovative idea of developing a continuous H 2 production process employing fluidized-bed technology from agricultural biomass with in situ CO 2 capture and sorbent regeneration. Novelty of the process lies in the generation of relatively pure H 2 from biomass with CO 2 as a byproduct using steam as the gasifying agent. Another unique feature of the process is internal regeneration of the sorbent, fouled in the gasifier. Thus, the technology will serve the twin purpose of regenerating the sorbent and generation of N 2 -free H 2 and C0 2 . This work reports theoretical energy analysis and experimental investigation of the process. The system efficiency of the chemical-looping gasification process at an ideal scenario is found to be 87.49% with biomass as fuel. A sensitivity analysis for system efficiency is also conducted by varying carbon-capture and regeneration efficiencies. The experiments conducted in a batch-type fluidized-bed steam gasifier using CaO as the sorbent shows a 71 % concentration of H 2 and nearly 0% concentration of CO 2 in the product gas when sawdust was used as the feedstock. In a separate test using a circulating fluidized-bed reactor as the regenerator, a 40% regeneration of CaO is also achieved at a calcination temperature of 800 °C.

A Comprehensive Review on Biomass Torrefaction

Biomass is a versatile energy resource that could be used as a sustainable energy resource in solid, liquid and gaseous form of energy sources. Torrefaction is an emerging thermal biomass pretreatment method that has an ability to reduce the major limitations of biomass such as heterogeneity, lower bulk density, lower energy density, hygroscopic behavior, and fibrous nature. Torrefaction, aiming to produce high quality solid biomass products, is carried out at 200-300 °C in an inert environment at an atmospheric pressure. The removal of volatiles through different decomposition reactions is the basic principle behind the torrefaction process. Torrefaction upgrades biomass quality and alters the combustion behavior, which can be efficiently used in the co-firing power plant. This paper presents a comprehensive review on torrefaction of biomass and their characteristics. Despite of the number of advantages, torrefaction is motivated mainly for thermochemical conversion process because of its ability to increase hydrophobicity, grindability and energy density of biomass. In addition to this, torrefied biomass could be used to replace coal in the metallurgical process, and promoted as an alternative of charcoal.

The Effect of Torrefaction Pre-Treatment on the Gasification of Biomass

Biomass is favoured as an alternative renewable fuel for heat, power and liquid fuel production (Svoboda et al. 2009). Gasification is being considered for the thermochemical conversion of biomass to produce clean and quality heat, power and liquid fuels from biomass (Bhagavatula 2014). It could facilitate the use of biomass for co-firing in large coal-fired plant, distributed power generation using diesel Abstract

Eggshell as a potential CO2 sorbent in the calcium looping gasification of biomass

This work presents an investigation into the potential use of eggshell as a CO2 sorbent in the calcium looping gasification of biomass to enhance carbon negativity. Calcination reaction was studied in a quartz wool matrix reactor and a thermogravimetric analyser coupled with a Fourier transform infrared spectroscopy. The resulting sorbent was characterised with a scanning electron microscope, colourimeter, inductively coupled plasma optical emission spectroscopy, and nitrogen sorption analyser. The pore structures of the samples are of Type II isotherm. Results show that increasing the calcination temperature enhances decomposition and improves the calcium content and specific surface area of the sorbent. As compared to nitrogen, calcination in a CO2 environment is not effective due to the increased CO2 partial pressure. Samples with low particle size displayed higher carbonation conversion. Increasing the carbonation temperature to an extent enhances the carbonation conversion. The carbonation conversion by the sorbent in multiple calcination-carbonation cycles was also studied. Initial CO2 uptake by the sorbent was highly encouraging. A conversion of 76.41% was realized after the first cycle, but due to sintering and attrition, the conversion reduced with increasing cycle. The sorbent exhibited a low conversion of 18% after the seventh cycle and this corresponds to a decay extent of 76.65%.

Biochar: a sustainable solution for solid waste management in agro-processing industries

ABSTRACT Agro-processing is a major industry in Canada. The processing of an agricultural product generates an enormous amount of water and solid waste. Appropriate management of these waste streams has become a challenging issue. The present study proposes a concept of circular bio-economy whereby solid waste from one agro-processing industry is used as a feedstock for producing biochar, which is then used in another agro-processing industry for wastewater treatment. The biochar after wastewater treatment can be used for agricultural soil applications. This article describes a study on the pyrolysis of oilcakes from crambe and meadowfoam seeds. The pyrolysis of oilcakes obtained from crambe and meadowfoam seeds is conducted in a furnace-heated reactor at 450 °C and 550 °C and the properties of char, oil and gas are studied. The biochar is then used for wastewater treatment. This article discusses the results.

2-D modeling of torrefaction of a large biomass particle

ABSTRACT A two-dimensional (2-D) model is developed to predict the torrefaction behavior of a large wet biomass particle. Although one-dimensional (1-D) model is found to be adequate for L/D ≥ 6, the necessity of using 2-D model at lower L/D ratios and higher torrefaction temperature is established. Errors up to 18% are observed in predicted mass fractions between 1-D and 2-D models. The center temperatures differed more, up to 96%, between z = 0 and z = L/2 in 2-D model which is not captured by the 1-D model. The model predictions agree well with the experimental results of the present authors and others. The evolution of the temperature profile is found to govern the mass fraction profile. At higher reactor temperature, three distinct zones are visible in the contour plots: peripheral fully torrefied zone, intermediate torrefying zone, and core with unreacted virgin biomass zone. Simulation studies show the formation of two symmetric annular hot spots at the ends, which move inward axially and subsequently merge at the center, the rate being faster for smaller L/D ratio. However, 1-D model does not provide such insight. The effects of reactor temperature, particle size, the residence time, and the initial moisture content on the torrefaction behavior are investigated.

Modeling of torrefaction of small biomass particles

ABSTRACT A simple single-step kinetic model consisting of two parallel reactions is proposed for torrefaction of small biomass particles. The model is validated against experimental data on torrefaction of poplar wood fines. Comparison of experimental data and model prediction shows that the results predicted by the proposed simplified model are as accurate as those from the models of Di Blasi and Lanzetta (1997) and Rousset et al. (2006) which involve larger numbers of model parameters – eight and sixteen, respectively – compared to four in the proposed model. This makes it suitable for incorporation into the overall reactor model. At 493 and 553 K, the relative mean errors are found to be 0.056, 0.080, 0.051 and 0.050, 0.100, 0.048 for the proposed model, Rousset et al.’s (2006) model and Blasi and Lanzettas (1997) model, respectively. The effect of particle size, temperature and residence time on torrefaction of biomass is investigated. A transformation of rate-controlling regime from kinetic to heat transfer is identified with an increase in particle size and temperature. Sensitivity analysis shows that the dimensionless groups such as pyrolysis number, dimensionless heat of reaction and dimensionless activation energy have significant influence on the particle temperature and torrefaction behaviour.