Rheology and fuel properties of slurries of char and bio-oil derived from slow pyrolysis of cassava pulp residue and palm shell

Three bio-oil samples, namely, raw bio-oil from pyrolysis of cassava pulp residue (CPR), separated oil phase and aqueous phase of bio-oil from pyrolysis of palm shell (PS), were used as suspending media for preparing slurries of bio-oil and the co-product char. Rheologies of all tested slurries exhibited pseudoplasticity with yield stress and the degree of this non-Newtonian behavior depended on such parameters as slurry type, solid concentration, particle size and slurry temperature. Overall, char/bio-oil slurries gave better fuel properties including higher pH and reasonably high calorific value (18?C32 MJ/kg) as compared to their bio-oil properties. Combustion of char/bio-oil slurries occurred in the temperature range similar to their solid char combustion and without ignition delay.     

Surface modification and adsorption of eucalyptus wood-based activated carbons: Effects of oxidation treatment, carbon porous structure and activation method

The incorporation of oxygen functional groups onto the surface of eucalyptus activated carbon and its surface chemistry were investigated as a function of oxidation conditions, carbon porous properties and carbon preparation method. Under all treatment conditions of increasing time, temperature and oxidant concentration, liquid oxidation with HNO₃, H₂O₂ and (NH₄)₂S₂O₈ and air oxidation led to the increase of acidic group concentration, with carboxylic acid showing the largest percentage increase and air oxidation at the maximum allowable temperature of 350 °C produced the maximum content of both carboxylic acid and total acidic group. Nitric acid oxidation of chemically activated carbon produced higher total acidic content but a lower amount of carboxylic acid compared to the oxidized carbon from physical activation. The increased contents of acidic groups on oxidized carbons greatly enhanced the adsorption capacity of water vapor and heavy metal ions.     

Precisely controlled delivery of plant hormone using poly(vinyl alcohol)/zeolite A hydrofilm composite

Programmable release of a plant hormone, 1-naphthylacetic acid (NAA), could be achieved by using a novel zeolite–hydrofilm (ZHF) composite. The ZHF was prepared using poly(vinyl alcohol) and glutaraldehyde as a cross-linking agent with the addition of different amounts of zeolite A (0, 1.5, 2.0, 2.5, and 3.0 wt%). This reveals that ZHF was formed as a phase-separated microcomposite with chemical interactions between zeolite A and polymer matrix. We found that the composite film with 2.5 wt% zeolite A had the largest pore size, which exhibited the highest water absorbency and the longest water retention time of over 7 h with high thermal and mechanical stabilities. Release profile displayed rapid desorption of NAA from the film at the initial stage, followed by sustained release thereafter. This behavior was explained by the Korsmeyer–Peppas model with a predominant mechanism of simple Fickian diffusion. Additionally, ZHF with NAA could effectively enhance adventitious root formation of Ocimum basilicum Linn. (sweet basil) cuttings due to accurate releasing NAA and time duration for releasing plant hormone. Finally, the NAA released at the film surface could be in a controlled manner with less negative impact on plant and environment.     

Effect of reaction conditions on the catalytic esterification of bio-oil

Studies of bio-oil upgrading via esterification of palm shell bio-oil and alcohols employing acid catalysts were carried out in this work. The effects of esterification conditions on reaction conversion and product quality were investigated. Results indicated that esterification reaction using solid acid catalyst of Amberlyst15 enabled the conversion of organic acids in the bio-oil to esters and could also reduce certain amount of active aldehydes. The utilization of H₂SO₄ liquid catalyst was found to give higher conversion at the same reaction condition. Furthermore, higher reaction conversion to esters was achievable under conditions of higher temperature, longer reaction time, higher amounts of catalyst and alcohol and the use of shorter hydrocarbon chain of alcohol. Bio-oils, after being subjected to esterification, gave moderate heating value of 23–25 MJ/kg and improved fuel properties of decreased density, viscosity, carbon residue content, ash content, pour point and acidity.     

Studies of sintering of coal ash relevant to pulverised coal utility boilers: 2. Preliminary studies of compressive strengths of fly ash sinters

The development of strength of pellets of fly ash with sintering temperature was investigated. Pellets heated below the shrinkage or electrical (Raask) sinter point did not develop strength over several hours. Hot crushing of pellets above the sinter point gave plastic deformation, presumably due to liquid on the particle surfaces. Cooling below the sinter point before crushing gave the same strength as crushing at room temperature, showing strength was due to solidification. Strength as a function of heat treatment temperature (1 h duration) above the sinter point went through a maximum, indicating that liquid is removed at higher temperature. SEM analysis of the cold pellets showed glassy sintering at conditions of maximum strength, and crystallization of mullite as strength decreased with higher heat treatment temperatures. Results suggest that iron silicate compositions increased the maximum sinter strength more than sodium silicate compositions. Water washing of fly ash reduced maximum strength. Addition of Na₂0 or surface films of sodium carbonate to a synthetic mineral mixture reduced the sinter point and led to strength development at lower temperatures: however, too high additions reduced the maximum strength.     

Multilayer adsorption of benzene on graphitised thermal carbon black—The importance of quadrupole and explicit hydrogen in the potential model

Grand Canonical Monte Carlo (GCMC) simulation was used to study multilayer adsorption of benzene on graphitised thermal carbon black over a range of temperature between 273 K and 373 K. Three potential models for benzene were compared: TraPPE-UA-9, OPLS-AA and TraPPE-EH, in order to study their capability to correctly describe the adsorption isotherms and isosteric heats. In the sub-monolayer region, there is no difference between the simulation results obtained with the three models, which all describe the experimental data well. However, in the multilayer region only the TraPPE-EH model, that includes the quadrupole moment and explicit modelling of the hydrogen, is able to describe the experimental data accurately; the other two models significantly under-predict the data. The TraPPE-EH model was then used to investigate the microscopic behaviour of the adsorbed phase: the local density distribution and the orientation of various layers, particularly the change in orientation of benzene in the first layer with increase in loading from sub-monolayer to multi-layer. It was found that the orientation of benzene molecules in the first layer is affected by the presence of molecules in the higher layers, but that most benzene molecules remain in an orientation parallel to the surface, which is favoured by the interaction with the surface, while a smaller population takes 60° and verical orientations to the surface which maximises the entropy. The ratio of the number of molecules having parallel orientation to that having 60° and vertical orientations decreases in higher layers due to the weaker influence of the adsorbate–adsorbent interaction. Detailed study of the orientation shows that most slant and vertical molecules have two of their hydrogen atoms closer to the surface.     

Thermogravimetric analysis of longan seed biomass with a two-parallel reactions model

The kinetic analysis of pyrolysis process of longan seed was performed in a thermogravimetric analyzer. All experimental runs were carried out by using an initial sample mass of 15 mg and final temperature of 650 °C under the inert atmosphere of nitrogen. Particle sizes in the range from 0.05–2.1 mm and the heating rates from 5–100 °C/min were employed to investigate their effects on the thermogram and the kinetic parameters. The TG curves generally showed sigmoid shape and displayed one major peak in DTG curve. The main devolatilization of longan seed occurred over the temperature range of 210–330 °C. It was found that heat transfer resistance in a particle could be reduced either by decreasing the size of particle or increasing the heating rate. The thermal decomposition of longan seed could be well described by the two-parallel reactions kinetic model. This analysis of reaction kinetic gave the values of activation energy for the decomposition of the two fractions in the model corresponding closely to those of hemicellulose and lignin.     

Nature of the surface involved in fly ash adhesion on boiler steel

Adhesion strength tests were performed in order to test whether the adhesion of slag drops to an oxidized steel surface was due to chemical compatability with the surface or due to a mechanical anchoring in the micropores of the oxide. Since adhesion was negligible or weak on a reduced microporous surface it was concluded that the adhesion was due to chemical compatibility with oxide not mechanical anchoring in microporosity.     

Characterization of products from slow pyrolysis of palm kernel cake and cassava pulp residue

Slow pyrolysis studies of palm kernel cake (PKC) and cassava pulp residue (CPR) were conducted in a fixed-bed reactor. Maximum liquid yield (54.3 wt%) was obtained from PKC pyrolysis at 700 °C, heating rate of 20 °C/min, N₂ gas flow rate of 200 cm³/min and particle size of 2.03 mm. Fuel properties of bi-oils were in following ranges: density, 1.01–1.16 g/cm³; pH, 2.8–5.6; flash point, 74–110 °C and heating value, 15 MJ/kg for CPR oil and 40 MJ/kg for PKC oil. PKC oil gave main contents of n-C₈–C₁₈ carboxylic acids, phenols, and esters, whereas CPR oil gave the highest amount of methanol soluble fraction consisting of polar and non-volatile compounds. On gas compositions, CPR pyrolysis gave the highest yield of syngas produced, while PKC pyrolysis offered the highest content of CO₂. Pyrolysis chars possessed high calorific values in range from 29–35 MJ/kg with PKC char showing a characteristic of reasonably high porosity material.     

Water adsorption in activated carbons with different burn-offs and its analysis using a cluster model

This work presents the behavior of water adsorption in the activated carbons with different porous structure derived by varying the level of char burn-off. Water adsorption isotherms of activated carbons prepared from longan seed at three different burn-offs (19, 26 and 60%) were measured gravimetrically. These obtained carbons were different in terms of their pore size distribution and also the surface functional group properties by showing an increasing of total pore volume and the concentration of surface functional groups with increasing in the burn-off level. The water adsorption isotherms showed that the behavior and amount of water uptake could be divided into three consecutive ranges of relative pressure, 0.0–0.3, 0.3–0.7 and 0.7–0.94, corresponding to adsorption in ultramicropores, supermicropores, and mesopores, respectively. The isotherm data were simulated by a cluster model proposed by Do and Do. The correlation was found to be satisfactory over the entire range of relative pressure only with the lowest burn-off carbon which contained mainly micropores. For higher burn-off carbons, which showed increasing proportions of mesopores, the model needed to be modified by increasing the cluster size of the adsorbed water molecules from 5 to 20 for adsorption at relative pressures greater than about 0.7.