Pyrolysis of polystyrene waste in the presence of activated carbon in conventional and microwave heating using modified thermocouple.
Pyrolysis process was experimented using two types of heating source, namely conventional and microwave. Polystyrene (PS) plastic waste was used as feedstock in a batch reactor for both the conventional (slow pyrolysis) and microwave pyrolysis. The effect of activated carbon to polystyrene ratio on (i) yield of oil, gas and residues (ii) reaction temperature (iii) reaction time were studied. Quality of oil from pyrolysis of polystyrene were assessed for the possible applicability in fuel production. Microwave power of 450 W and polymer to activated carbon ratio of 10:1, resulted in the highest oil yield of 93.04 wt.% with a higher heating value of 45 MJ kg-1 and a kinematic viscosity of 2.7 cSt. Microwave heating when compared to conventional heating method, exhibits a reaction temperature and time of 330 °C in 5.5 min, whereas in conventional heating system it was 418 °C in 60 min. The gas chromatography-mass spectrometry analysis of liquid oil from microwave pyrolysis predominantly yields alkenes of 8.44 wt.%, α-methyl styrene 0.96 wt.%, condensed ring aromatics 23.21 wt.% and benzene derivatives 26.77 wt.% when the polystyrene to activated carbon ratio was 10:1. Significant factor of using microwave heating is the amount of energy converted (kWh) is lesser than conventional heating.
Production of carbon nanostructures in biochar, bio-oil and gases from bagasse via microwave assisted pyrolysis using Fe and Co as susceptors
Abstract In this study, the production of nanostructured biochar from lignocellulosic biomass, sugarcane bagasse, is demonstrated via microwave assisted pyrolysis by using iron (Fe) and cobalt (Co) particles as susceptors. The experiments were performed in a bench scale pyrolysis reactor at 600 W microwave power up to a temperature of 500 °C. The effect of bagasse:susceptor composition on the quality of biochar was evaluated using a range of characterization techniques like scanning electron microscopy, porosimetry, X-ray diffraction, and Raman spectroscopy. The addition of Fe as the susceptor resulted in the formation of nanoparticles and nanotubes of average diameter in the range of 30–120 nm and 20–50 nm, respectively. The addition of more Fe particles resulted in an increase in size of nanoparticles and nanotubes due to enhanced rate of localized heating, which led to fusion of small particles and tubes. The biochar obtained by the addition of Fe susceptor was rich in carbon content compared to that obtained without the addition of susceptor. The addition of a mixture of Fe and Co as susceptor led to the formation of small graphitic flakes and fine nanotubes. Besides biochar, bio-oil and non-condensable gases were also characterized for their composition. The major organic functionalities in bio-oil included furan derivatives, simple phenols, guaiacol, syringol and their derivatives. Maximum energy recovery of 49% was observed in bio-oil when 20 wt.% Fe and 33.3 wt.% of Fe + Co were used as susceptors. The addition of Fe resulted in high yield of H2 and CH4 gases, besides CO2 and CO. Thus, microwave pyrolysis is shown to be a promising technique to tailor the morphological features of biochar by using metallic susceptors, and simultaneously produce good quality bio-oil and gases.
Hygroscopic Expansion of some Casting Investments
CREDIT is generally given to Taggart1 for introducing the cast gold inlay to the dental profession. Although he realized that gold shrinks when cooled from molten state to solid state of room temperature, the investment available to him did not supply sufficient compensation. In 1910, Van Horn2 published a paper dealing with a method by which he obtained the compensation by means of wax expansion. The next major research in connection with this problem was the work of Coleman3 at the National Bureau of Standards. He determined the gold shrinkage to be 1.25 per cent and presented a casting technic with compensation values of quantitative nature. The total compensation for the gold shrinkage was obtained by the combination of the setting and thermal expansion of the mold. This procedure is the general practice followed at the present time for compensation. There are some disadvantages to this method. Skinner has indicated the difficulty of obtaining smooth castings and the improper compensation for the casting shrinkage.4 It has been found by Hollenback5 and Scheu6a that castings made at a high temperature are rougher than those made at a low temperature (450° C.), depending upon the great difference in thermal expansion between plaster of Paris and silica, which causes a poor union of the fine particles. This may also result in friability and there may be some warpage due to the differential expansion. A method which provides sufficient compensation at a low mold temperature is the hygroscopic casting technic.b Wilson7 showed that certain plasters expand as much as 0.0044 inch to the inch by taking up moisture from the air. With this information at hand, Scheula, b tested some commercial investment to determine what results the addition of moisture would have. He found6b: (1) All of the casting investments that were tested expanded. (2) The thicker the mix, the greater the expansion. (3) A mix with hot water expanded more than one with cold water. (4) The time at which the mix is placed in the water is of great importance. It was found that if the mix is placed in the water early, it would not expand so much as when placed in a little later. It was also found that if the mix was placed in the water after a certain time, it could not expand to the maximal amount. (5) The temperature of the water in which the mix is placed is important, for two reasons; (a) the temperature of the water controls slightly the expansion of the investment, and (b) water at a temperature of 1000 F. slightly softens the wax pattern so that the fine margins are not marred while expansion is taking place. The mix should remain in the water at least 20 minutes to obtain the full expansion, after which time no further expansion is obtained.