Effect of granulation on chlorine-release behavior during municipal solid waste incineration.

The preparation of refuse-derived fuel (RDF) is an effective and simple means of rural municipal solid waste utilization. The release of chlorine during RDF combustion is important as it causes high-temperature corrosion and pollutants emission such as HCl, dioxins, etc. In this paper, constant-temperature and increasing-temperature combustion experiments were carried out using an electrically heating furnace to analyse the effects of granulation (pressure and additives) on the release of chlorine in particles. During the constant-temperature combustion below 800 °C, only organic chlorine was released from the RDF. The increase of granulation pressure from 1 MPa to 10 MPa did not affect the total amount of chlorine release, but delayed the organic chlorine release by increasing the gas diffusion resistance. During the constant-temperature combustion above 900 °C, inorganic chlorine was released as well. The increase of granulation pressure enhanced the inorganic chlorine release significantly by promoting the reactants contact. During the increasing-temperature combustion, the increase of granulation pressure delayed the organic chlorine release as well but inhibited the inorganic chlorine release. This was mainly attributed to the slow temperature rise to 900 °C, during which the inherent calcium in the RDF reacted with silicon and aluminium, resulting in less reactants for an inorganic chlorine release reaction. Three calcium-based additives were used to inhibit chlorine release. CaCO3 showed no dechlorination effect, and CaO showed better dechlorination effect than Ca(OH)2. For the constant-temperature combustion at 900 °C, the addition of CaO with a Ca/Cl ratio of 2 achieved a dechlorination efficiency of over 90%, with little influence from the granulation pressure. For the increasing-temperature combustion, the granulation pressure had a significant influence on CaO dechlorination effectiveness. Only at a granulation pressure as high as 10 MPa, did the addition of CaO with the Ca/Cl ratio of 2.5 achieve a dechlorination efficiency of 95%.

Experimental study on adsorption of PbCl2 and CdCl2 on kaolin modified by leachates from municipal solid waste incineration power plant.

Six kinds of waste liquids produced in the treatment process of leachate in a waste incineration plant were used to improve the adsorption effect of raw kaolin on heavy metal chloride. The capture performances of these modified kaolin on PbCl2 and CdCl2 vapor were investigated in a two-stage fixed bed combustor. The results indicated that the adsorption effects of raw kaolin on PbCl2 and CdCl2 were improved in some experimental groups, main effective component was Na+ in the leachate, but the influences did not change regularly with the increase in the concentration of Na + introduced into kaolin. The adsorbents formed by modifying 10 g kaolin with 21.25 ml leachate 2 were the best adsorbents for PbCl2 and CdCl2. The capture efficiencies of PbCl2 and CdCl2 can reach 95% and 63.88%, with the increase of 36% and 53%, respectively. Using leachate as modifying agent had the same effect as directly using Na+. Adsorptions of PbCl2 and CdCl2 were still mainly chemical adsorptions. After adsorption of PbCl2, the modified kaolin not only generated PbA12Si2O8, but also produced other chemical compounds. The adsorption of CdCl2 by modified kaolin did not generate CdAl2Si2O8, but other chemical reactions occurred to generate CdAl2O4 and Pb8Cd (Si2O7)3.

A comparative investigation of fast pyrolysis with enzymatic hydrolysis for fermentable sugars production from cellulose.

In this study, ball milling and ionic liquid pretreatments were utilized to alter cellulose structure prior to fast pyrolysis and enzymatic hydrolysis. The variations in the products distribution of cellulose fast pyrolysis, and their dependence on the structure of cellulose, and the temperature of fast pyrolysis were illustrated. Fast pyrolysis of pretreated cellulose yielded more levoglucosan than crystalline cellulose (14.7%) at 300 °C. Nevertheless, the levoglucosan achieved higher yield (64.3%) from crystalline cellulose at 400 °C. At last, a comparison between fast pyrolysis and enzymatic hydrolysis for cellulose saccharifaction was made. Fast pyrolysis was a promising alternative to liberate levoglucosan from cellulose. Further investigation and development were required to maximize the levoglucosan production.

Highly abrasion resistant thermally fused olivine as in-situ catalysts for tar reduction in a circulating fluidized bed biomass gasifier.

Olivine synthesized by wetness impregnation (WI) and thermal fusion (TF) methods were investigated as in-situ catalysts to reduce the tar content during air-blown biomass gasification in a circulating fluidized bed (CFB). The results showed that the tar content decreases with the increase of reaction temperature. Raw-olivine reduced tar content by 40.6% compared to non-active bed material (silica sand) experiments; after calcination, the catalytic activities of olivine catalysts were further improved due to the migration of Fe from olivine grain to the surface. 1100-WI-olivine could reduce the tar content by up to 81.5% compared with that of raw-olivine because of the existence of Fe2O3, NiO and NiO-MgO. For 1400-TF-olivine, due to the formation of NiFe2O4, the tar content decreased to 0.77 g/Nm3, an 82.9% reduction compared to raw-olivine. Moreover, the TF-olivine had a stronger anti-attrition performance and was more suitable for using in a circulating fluidized bed.