Volume 5 Issue 1

The thin layer drying of pine forest residues consisting of bark, needles, leaves, and chips was experimentally conducted at air temperatures of 40, 50, 60, 70, and 80oC. Physical and chemical properties of fractionated forest residues were determined to evaluate its fuel properties. The experimental data obtained from thin layer drying study were fitted with Lewis, Page, and Henderson and Pabis equations to evaluate the drying behavior of the forest residues. Among the three drying models, the Henderson and Pabis model fitted well with the experimental drying data at the tested temperatures (40, 50, 60, 70, 80oC), achieving R2 values of0.992, 0.994, 0.997, 0.989, and 0.983, respectively. The drying constant k for the forest residues was increased with increase in drying air temperature and was correlated in the form of a second order regression equation. The thin layer drying data developed from this study will be useful for designing low temperature dryers for forest residues.

Starch microcellular foams (SMCF) containing pores in the micron size range may be prepared by pore-preserving drying processes, developing highly porous, high specific surface area materials useful for applications such as opacifying pigments or as adsorbent materials. The objective of this research was to understand how the exchange of water with ethanol, used as a pore preserving step, affected the dimensional properties of the starch material during and after processing. SMCF were prepared from molded aquagels of cooked corn starch that were subjected to ethanol exchanges with different time intervals (6, 12, or 48 hrs) and number of exchanges (1, 2, or 3) and then air dried. To study the transformation of water-swollen starch into precipitated starch foam in ethanol, the volume of the starch material was measured in the wet state after each exchange and after final air drying. As water is replaced by ethanol, the starch material contracts, with the greatest contraction during the first ethanol exchange. The amount of contraction during air drying decreased with decreased starch water content just before air drying, presumably due to less pore collapse of the stiffer cell walls on drying. Interestingly, the minimum density of 0.37 g/cc SMCF was for the 12 hour exchange time, not the longest exchange time. Evidence of a skin-core morphology included SEM images as well as dimensional instability data on dried samples. The results indicate that SMCF of low density with fewer tendencies to deform during drying does not necessarily require extremely long exchange times.

This study aims to understand the mechanism of bio-oil gasification and the influence of operating parameters on the properties of the gas products. Firstly, the pyrolysis/gasification of bio-oil was performed using a thermogravimetric analyzer (TGA). The evaporation of gas products from bio-oil were measured on-line with coupled Fourier Transform Infrared Spectroscopy (FTIR). The main gas products were CO, CO2, CH4, H2O, and light hydrocarbons, etc. Organics mainly evolved out at lower temperature (100-200°C), while the cracking of heavy hydrocarbon components took place at higher temperature (>200°C). Simultaneously, the gasification behavior of bio-oil was investigated in a fixed bed gasification reactor under different temperature and residence time. The gas product evolving was checked using micro-gas chromatography. It was observed that the yield of CO and H2 increased with increasing gasification temperature above 600°C, and the maximum value was obtained at 800°C. Prolonging the residence time was not favorable for the upgrading of syngas quality.

The free fatty acids in waste oil with high acid value were removed and transformed into fatty acid methyl esters by the extraction-reaction coupled process. The de-acidification efficiency and esterification conversion in the extraction-reaction coupled process were studied and compared with those in the stand-alone extraction process and the esterification process, respectively. Compared with cross-current batch extraction, the de-acidification efficiency of the extraction-reaction coupled process was equivalent to that of seven equilibrium stages in the conditions of the oil/methanol mass ratio of 1:1 at 60 oC. Compared with the esterification process, the esterification conversion of the coupled process was 90.3%, which is much larger than 46% in the esterification process at the reaction time of 32 minutes. Based on these findings, it is suggested that the extraction-reaction coupled process is a very effective and promising method for biodiesel production from oils having high acid value.

Mixed hardwood chips were treated with lignin-degrading fungi to study the effect of fungal pretreatment on bleaching characteristics of kraft pulp. Pretreated wood chips were subjected to reduced active alkali doses in comparison to untreated chips. Comparable results were obtained for pretreated chips with reduced alkali dose as was obtained with higher dose of alkali in case of untreated chips. Fungal treatment made the process more energy-efficient, and 4.8% less chlorine was consumed in comparison to the control process. Pretreatment with Ceriporiopsis subvermispora was responsible for reduction of 4.7% in lignin contents, 14.3% permanganate number, and overall reduction of 15.5 kg/T of Cl2 consumption. The pollution load in terms of COD and BOD at the CD stage was reduced by 32.6% and 41.5% respectively, whereas 12% reduction in AOX compounds was observed in effluent of pretreated pulp.

The applicability of a special pilot-scale installation (Short Circulation Device) was studied for demonstrating the enrichment of selected resin and fatty acids in process waters when increasing water reuse during the manufacture of paper. The traditional gas chromatography with flame ionization detection (GC-FID), turbidity, and online sample enrichment (solid phase extraction, SPE) for atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) measurements were used for the analysis of the resin and fatty acids. The data from all the measurements with unbleached thermomechanical pulp (TMP) process waters were in a good agreement, and correlation coefficients (R2) > 0.9 were obtained in each case. Rapid information about the levels of wood extractives in papermaking process waters is of great importance, and it offers a suitable way to predict oncoming pitch problems. It was concluded that the routine control of the extractives level in papermaking process waters is possible by all these methods.

Three methods for improved deresination of sulphite pulps were evaluated, namely, alkaline washing, enzyme treatment, and pulp fractionation. Alkaline washing appears to come at a high cost, because caustic is expensive and affects cellulose chain length, as indicated by lower viscosity of the pulps. Thus this is not a viable option for pulps that are sensitive to changes in viscosity. Enzyme treatment did not completely degrade the glycerides under the mill conditions used. Fibre fractionation studies showed that the fines fractions contained 8 to 13 times more residual lipophilic extractives than the whole pulps. Removing this fraction, which represents only a small percentage of the whole pulp, could reduce by about a half the amount of lipophilic extractives in the remaining pulp. Thus pulp fractionation appears to be a viable option to achieve further deresination of sulphite pulps.

Chelation of unbleached and oxygen bleached hardwood and softwood kraft pulps with EDTA was studied. The main focus was on the desorption of magnesium, manganese, and iron due to their impact in TCF-bleaching. Desorption of other metal ions present were also studied in order to get an over-all estimation of the metal ion concentrations and their desorption during chelation. By using the concept of side reaction coefficients, an estimation of the chelating strength of EDTA at different pH can be made. Metal ion concentrations were determined by DCP-AES and ICP-MS techniques. Mn, Zn, and Cd were the metal ions that could almost completely be chelated with EDTA. Most of the metal ions were found to be desorbed from the pulps at low pH values by ion exchange with hydrogen ions. With EDTA chelation 50 to 70% of the iron was desorbed. By EDTA chelation the highest Mg/Mn concentration ratios were obtained in the pH range 4 to 6. For oxygen-bleached softwood pulp the ratio was over 7000. Our study showed that both unbleached and bleached pulps can quite successfully be chelated by EDTA.

Desorption of metal ions from oxygen-bleached hardwood and softwood kraft pulps by different chelation treatments were studied. The main focus was on desorption of manganese, iron, and magnesium ions, but also on desorption of some other common metal ions. The metal ion concentrations were determined by the DCP-AES and ICP-MS techniques. Acid treatments with nitric and oxalic acids removed manganese and magnesium very effectively and partially iron as well. Some potential complexing agents such as triethanolamine (TEA), citric acid, oxalic acid, and formic acid were also tested. By using the concept of side reaction coefficients, a comparison of the chelating strengths between different chelating agents can be made. TEA is a strong chelant for iron and did remove part of iron at pH 10. The effect of chemical reduction simultaneously with EDTA was studied by using sodium borohydride, sodium dithionite, and sodium bisulfite as reducing agents. The reducing environment improved desorption of manganese but did not improve removal of iron. The measured redox potentials indicated that the reducing effect with the used agents was not enough to convert iron(III) to iron(II). The effect of the reducing agents was decreased by their decomposition during the chelation experiment.

A modification of “AATCC Test Method 100-1999” was used for assaying for bacteriostatic/antibacterial properties of denim containing various flax concentrations. Since no direct evidence that increasing the flax content of fabric imparted the fabric with increased bacteriostatic properties was found against the control bacteria, Staphylococcus aureus and Klebsiella pneumoniae, other possible explanations for the long held presumption that flax fabric exhibited antibacterial properties was sought. Because the appearance of having antibacterial or bacteriostatic properties might be imitated if the flax content would decrease the time fabric would be moist enough for bacterial growth, the effect of drying was evaluated. When flax fabric was saturated and the moisture lost during incubation was measured, there was no improved drying associated with increased flax content. When untreated nonwoven flax was evaluated as possibly containing more ‘antibacterial’ or bacteriostatic components than scoured nonwoven flax material, the population densities increased. This increase suggests that the unscoured nonwoven flax contain compo-nents that support bacterial growth to the extent that bacteriostatic or antibacterial components, if any, are overwhelmed by the components that support bacterial growth. In tests involving the control bacteria, Staphylococcus aureus and Klebsiella pneumoniae, increasing the flax content of flax fabric did not demonstrate increased antibacterial properties.