COSMO-RS, a general and fast methodology for the a priori prediction of thermophysical data of liquids is presented. It is based on cheap unimolecular quantum chemical calculations, which, combined with exact statistical thermodynamics, provide the information necessary for the evaluation of molecular interactions in liquids. COSMO-RS is an alternative to structure interpolating group contribution methods. The method is independent of experimental data and generally applicable. A methodological comparison with group contribution methods is given. The applicability of the COSMO-RS method to the goal of solvent screening is demonstrated at various examples of vapor–liquid-, liquid–liquid-, solid–liquid-equilibria and vapor-pressure predictions.

Fast solvent screening via quantum chemistry: COSMO‐RS approach

Currently, fossil fuels such as oil, coal and natural gas represent the prime energy sources in the world. However, it is anticipated that these sources of energy will deplete within the next 40–50 years. Moreover, the expected environmental damages such as the global warming, acid rain and urban smog due to the production of emissions from these sources have tempted the world to try to reduce carbon emissions by 80% and shift towards utilizing a variety of renewable energy resources (RES) which are less environmentally harmful such as solar, wind, biomass etc. in a sustainable way. Biomass is one of the earliest sources of energy with very specific properties. In this review, several aspects which are associated with burning biomass in boilers have been investigated such as composition of biomass, estimating the higher heating value of biomass, comparison between biomass and other fuels, combustion of biomass, co-firing of biomass and coal, impacts of biomass, economic and social analysis of biomass, transportation of biomass, densification of biomass, problems of biomass and future of biomass. It has been found that utilizing biomass in boilers offers many economical, social and environmental benefits such as financial net saving, conservation of fossil fuel resources, job opportunities creation and CO 2 and NO x emissions reduction. However, care should be taken to other environmental impacts of biomass such as land and water resources, soil erosion, loss of biodiversity and deforestation. Fouling, marketing, low heating value, storage and collections and handling are all associated problems when burning biomass in boilers. The future of biomass in boilers depends upon the development of the markets for fossil fuels and on policy decisions regarding the biomass market.

A review on biomass as a fuel for boilers

The group contribution method UNIFAC has become very popular because of its large range of applicability and its reliable predictions of vapor−liquid equilibria. With the help of new data stored in the Dortmund Data Bank (DDB), many gaps in the existing UNIFAC parameter matrix have been filled, and many new main groups have been added to the parameter table. In this paper, the parameters for 46 group combinations are provided. Additionally, a new main group for sulfones is introduced, for which the group interaction parameters for eight main groups are fitted.

Vapor-liquid equilibria by UNIFAC group contribution. 6. Revision and extension

Biomass combustion in fluidized bed boilers: Potential problems and remedies

A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus

Investigation of combustion kinetics of treated and untreated waste wood samples with thermogravimetric analysis

Investigation of co-combustion characteristics of low quality lignite coals and biomass with thermogravimetric analysis

The change of the volatiles burn-out time has been investigated for different particle sizes, superficial velocities, volatile matter content and masses charged. The results have shown that the volatiles take about 3–12 sec to burn for the particle size(1.52–3.06mm) and velocity range (0.38–0.58m/s) studied. The radial velocity of the volatiles coming out of a particle was found to be close to Umf. The surface flux of volatiles increases with particle size. The volatiles affect the combustion characteristics of the remaining char.

Combustion of volatile matter in fluidized beds

Combustion and oxy-fuel combustion characteristics of torrefied pine wood chips were investigated by Thermogravimetric Analysis (TGA). Three torrefaction temperatures (250, 300, and 350 °C) and two residence times (15 and 30 min) were considered. Experiments were carried out at three heating rates of 10, 20, and 40 °C/min. The isoconversional kinetic methods of FWO, KAS, and Friedman were employed to estimate the activation energies. The assessment of uncertainty in obtaining the activation energy values was also considered. The obtained results indicated that due to torrefaction, the O/C and H/C atomic ratios decreased, resulting the 300oC-30 min and 350oC-15 min torrefied biomass to be completely embedded in lignite region in van-Krevelen's diagram. Oxy-fuel combustion affected the decomposition of cellulose and lignin components of biomass while the impact on the hemicellulose component was negligible. The kinetic analysis revealed that with the evolution of conversion degree, the activation energy values increased during hemicellulose degradation, remained approximately constant during cellulose decomposition and showed a sharp decrease for lignin decomposition. The activation energy trends were comparable in both air and oxy-fuel combustion conditions, however slight changes in activation energy values were noticed. The highest activation energy value was obtained for 250oC-30 min torrefied biomass at 183.40 kJ/mol and the lowest value was 72.93 kJ/mol for 350oC-15 min biomass. The uncertainty values related to FWO method were lower than KAS and Friedman methods. The uncertainty values for FWO and KAS methods were at the range of 5–15%.

Aysel T. Atimtay

Papers

Investigation of combustion kinetics of treated and untreated waste wood samples with thermogravimetric analysis

Investigation of co-combustion characteristics of low quality lignite coals and biomass with thermogravimetric analysis

Combustion of volatile matter in fluidized beds

TGA and kinetic study of different torrefaction conditions of wood biomass under air and oxy-fuel combustion atmospheres

Comparison of fuel value and combustion characteristics of two different RDF samples.