Ramin Azargohar

Breakthrough CO2 adsorption in bio-based activated carbons

In this work, the effects of different methods of activation on CO2 adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO2 activation and Potassium hydroxide (KOH) activation. CO2 adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25-65°C and inlet CO2 concentration range of 10-30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N2 and CO2 adsorption at 77 and 273 K, respectively. Central composite design was used to evaluate the combined effects of temperature and concentration of CO2 on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm(3)/g and surface area of 1400 m(2)/g had the highest CO2 adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO2 and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO2 activated carbons remained remarkably stable after 50 cycles with low temperature (160°C) regeneration.

Elemental Mercury Capture Using Activated Carbon: A Review

Elemental mercury in the atmospheric environment has been identified as a significant environmental issue. The primary reason is the increased anthropogenic emissions of this metal into the global atmospheric environment in recent years. This paper provides a review for elemental mercury uptake in a flue gas stream. The objectives are to provide a summary of the carbon materials and effective parameters involved in an elemental mercury emission flue gas stream control system for industry. Activated carbon injection systems into emission stacks of coal fired power plant have been credited with providing a significant elemental mercury emission control technology. Various chemicals including sulfur, halogens and others species have been identified as key capture agents for elemental mercury emission control on an activated carbon. With the successes of the past several years, there is in place an excellent frame work in the literature to build an activated carbon injection control system to further increase the efficiency of uptake for elemental mercury from mixed gas streams.

Densification of Agricultural Wastes and Forest Residues: A Review on Influential Parameters and Treatments

Biomass densification is an effective process to overcome specific biomass application limitations such as low density, nonuniform particle size and shape, and cost of transportation. Lignocellulosic materials (e.g. agricultural wastes and forest residues) are the main precursors used for pelletization. The quality of fuel pellets is determined based on their mechanical strength, hydrophobicity, heating value, and density. These properties are influential in handling, transportation, storage, and fuel applications of this product. There are several parameters affecting the quality of fuel pellets: precursor chemical structure, pelletization operating conditions, precursor pre-treatments, and pellet posttreatments. Formation of a strong binding structure in biomass pellet depends on the internal structure of precursors (e.g. lignin, cellulose, hemicellulose, extractives, moisture), particle size range of precursor, additives (e.g. binders, lubricants, plasticizers, and moisture), and pelletization operating conditions. Pre-treatments such as steam explosion and torrefaction can be used to facilitate the pelletization process or improve some precursor properties such as energy content or hydrophobicity. Post-treatments such as coating and torrefaction are applied to biomass pellets to improve their hydrophobicity or heating value. This chapter provides an overview of the parameters affecting the quality of biomass fuel pellets, biomass pre-treatments, and pellet post-treatments, as well as safety aspects related to transportation and storage of fuel pellets.