The energy insecurity from oil and natural gas and increased CO2 emission from fossil fuels is driving societies to look for sustainable and renewable energy supply. The huge coal resources can serve as a potential source for fuels. Bio-energy from biomass has been recognized as renewable energy to reduce CO2 emission. Although fast pyrolysis has emerged as the most promising technology to convert organic materials to liquid fuels at shorter duration but it still faces some technical challenges in improving product yield, its quality and process energy efficiency. Microwave assisted pyrolysis of coal and biomass in the presence of microwave absorber provides distinctive environment to resolve these challenges. The microwave absorber can indirectly heat coal and biomass particles which are relatively microwave transparent and influence product yield and its quality by contributing as a catalytic precursor. The microwave heating of coal or biomass particles with microwave absorber shows efficient heating and sufficient contact of volatile or gas phase species with specific microwave absorber can improve fuel quality.

A review on microwave assisted pyrolysis of coal and biomass for fuel production

As hydrogen fuel cell vehicles move from manifestation to commercialization, the users expect safe, convenient and customer-friendly fuelling. Hydrogen quality affects fuel cell stack performance and lifetime, as well as other factors such as valve operation. In this paper, previous researcher's development on hydrogen as a possible major fuel of the future has been studied thoroughly. Hydrogen is one of the energy carriers which can replace fossil fuel and can be used as fuel in an internal combustion engines and as a fuel cell in vehicles. To use hydrogen as a fuel of internal combustion engine, engine design should be considered for avoiding abnormal combustion. As a result it can improve engine efficiency, power output and reduce NOx emissions. The emission of fuel cell is low as compared to conventional vehicles but as penalty, fuel cell vehicles need additional space and weight to install the battery and storage tank, thus increases it production cost. The production of hydrogen can be ‘carbon-free’ only if it is generated by employing genuinely carbon-free renewable energy sources. The acceptability of hydrogen technology depends on the knowledge and awareness of the hydrogen benefits towards environment and human life. Recent study shows that people still do not have the sufficient information of hydrogen.

An overview of hydrogen as a vehicle fuel

Biomass is relatively cleaner than coal and is the only renewable carbon resource that can be directly converted into fuel. Biomass can significantly contribute to the world’s energy needs if harnessed sustainably. However, there are also problems associated with the thermal conversion of biomass. This paper investigates and discusses issues associated with the thermal conversion of coal and biomass as a blend. Most notable topics reviewed are slagging and fouling caused by the relatively reactive alkali and alkaline earth compounds (K2O, Na2O and CaO) found in biomass ash. The alkali and alkaline earth metals (AAEM) present and dispersed in biomass fuels induce catalytic activity during co-conversion with coal. The catalytic activity is most noticeable when blended with high rank coals. The synergy during co-conversion is still controversial although it has been theorized that biomass acts like a hydrogen donor in liquefaction. Published literature also shows that coal and biomass exhibit different mechanisms, depending on the operating conditions, for the formation of nitrogen (N) and sulfur species. Utilization aspects of fly ash from blending coal and biomass are discussed. Recommendations are made on pretreatment options to increase the energy density of biomass fuels through pelletization, torrefaction and flash pyrolysis to reduce transportation costs.

https://www.mdpi.com/1996-1073/7/3/1098/pdf

A Review of Thermal Co-Conversion of Coal and Biomass/Waste

The objective of this paper is to get an insight into the chemical activation mechanism using KOH and NaOH as activated agents. Three coals have been selected as carbon precursors. It was found that KOH and NaOH develop a similar narrow microporosity, independently of the coal rank, whereas only KOH generates supermicroporosity. Temperature-programmed desorption experiments, carried out with impregnated anthracite, show differences on the gas evolved during the activated carbon preparation using the two activating agents. Thus, whereas hydrogen profiles are quite similar for both activated agents, the CO and H(2)O profiles are different. It is remarkable the high amount of H(2)O evolved at the maximum treatment temperature for both activating agents. The results obtained allow concluding that the chemical activation is due to a combination of different process driving the development of material porosity.

/pdf/insight-into-hydroxides-activated-coals-chemical-or-physical-3ynsf6yr9p.pdf

Insight into hydroxides-activated coals: Chemical or physical activation?

Publisher Summary
This chapter discusses physical structure and properties of brown coal. Brown coal is composed of a poly-dispersed collection of particulate entities ranging from small molecules such as fulvic acids, humic acids, humic acid macromolecules, small plant residues, such as spores, collapsed cells, and pieces of wax and resin right through to xylitic fragments that may themselves range from 1 μm to the size of well-preserved roots, branches, and tree trunks as large as 10 m. Victorian coals contain up to 70% moisture or conversely, the water associated with a seam contains as little as 30% brown coal solids. The water held in the pores is in a state of active interaction with the solid. Upon drying, the physical structure is collapsed and to a large extent its original properties cannot be regenerated by re-wetting. The solids fraction of brown coal is a complex, heterogeneous mixture of plant remains, and each component of the mixture has its own physical and chemical characteristics. Victorian brown coal is very low rank: It has passed through the rotting and humification stages of coalification, but it has not been subjected to the higher temperatures and pressures needed to convert it into higher rank coal. In bed-moist brown coals, or their aqueous dispersions, there is a dynamic equilibrium between the acidic functional groups of the organic matter and the aqueous medium. In its naturally occurring state, brown coal is acidic, owing to the partial dissociation of carboxylic acid groups on the coal surface.

Chapter 4 – PHYSICAL STRUCTURE AND PROPERTIES OF BROWN COAL

Hydrogen production from coal-alkali interaction

Influence of alkali on pyrolysis of coals

Rheological properties of humic acids

Solar tunnel, using solar energy dryers have a great potential for drying large quantities of agricultural products. Open sun drying of Turkey berry fruit (Sundakkai-in Tamizh) is a tedious process that is replaced by Solar Tunnel Dryer. The drying kinetics of turkey berry fruits has been done in the solar tunnel dryer. The experimentation was carried out with the Natural convection mode with turkey berry fruit. The weight of turkey berry sample before drying was 67.85g and after drying the weight was 10.733g in the turkey berry sample. The percentage drop of moisture content of turkey berry fruit was observed to be 81.48%. The coefficient of convective heat transfer was observed to be 7.1104x102W/m2°C. The solar radiation is trapped by the Polyethylene sheet and keeps the inner side of the tunnel dryer hotter than the atmospheric condition, hence the rate of drying is better than the open sun drying. 

Drying kinetics of Turkey berry using solar tunnel dryer: Natural convection

The effect of washing on the texture of silica gel has been investigated in terms of parameters such as porosity, pore size distribution, surface area and absorption of moisture. It was observed that if silica gel (before activation) is washed with water containing dissolved ions such as Ca and Mg wider pores are formed at the expense of smaller ones. This phenomenon has been explained in terms of change in the size distribution of gel particles which is brought about by solution of very fine particles followed by growth, through condensation, of larger particles. The experimental observations have been interpreted to suggest guidelines to control the texture of gels by washing with solutions comaining different cations.

Tripurari Saran

Papers

Hydrogen production from coal-alkali interaction

Influence of alkali on pyrolysis of coals

Rheological properties of humic acids

Drying kinetics of Turkey berry using solar tunnel dryer: Natural convection

Pore Structure of Silica Gel