Awni Al-Otoom

Determination of the dosimetric characteristics of InterSource125 Iodine brachytherapy source

The TG-43 recommended dosimetric characteristics of a new 125I brachytherapy source have been experimentally and theoretically determined. The measurements were performed in Solid Water using LiF TLDs. The calculations were performed using Monte Carlo simulations in Solid Water and water. The measured data were compared with calculated values as well as the reported data in literature for other source designs. The dose rate constant this source in water was 1.01 +/- 3% cGy h(-1) U(-1) and the anisotropy constant was 0.956.

Experimental determination of the TG-43 dosimetric characteristics of EchoSeed™ model 6733 125I brachytherapy source

Recently an improved design of a 125I brachytherapy source has been introduced for interstitial seed implants, particularly for prostate seed implants. This design improves the in situ ultrasound visualization of the source compared to the conventional seed. In this project, the TG-43 recommended dosimetric characteristics of the new brachytherapy source have been experimentally determined in Solid Water phantom material. The measured dosimetric characteristics of the new source have been compared with data reported in the literature for other source designs. The measured dose rate constant, A, in Solid Water was multiplied by 1.05 to extract the dose rate constant in water. The dose rate constant of the new source in water was found to be 0.99 +/- 8% cGy h(-1) U(-1). The radial dose function was measured at distances between 0.5 and 10 cm using LiF TLDs in Solid Water phantom. The anisotropy function, F(r, theta), was measured at distances of 2, 3, 5, and 7 cm.

Pyrolysis of poly(vinyl chloride) and-electric arc furnacedust mixtures.

An investigation into the pyrolysis kinetics of PVC mixed with electric arc furnace dust (EAFD) was performed. Mixtures of both materials with varying PVC ratios (1:1, 1:2, 1:3) were prepared and pyrolyzed in a nitrogen atmosphere under dynamic heating conditions at different heating rates (5, 10, 30 and 50 °C/min). The pyrolysis process proceeded through two main decomposition steps; the first step involved the release of HCl which reacted with the metal oxides present in the dust, subsequently forming metal chlorides and water vapor. Benzene was also found to release as detected by TGA-MS. The remaining hydrocarbons in the polymer backbone decomposed further in the second step releasing further volatile hydrocarbons. Different models were used to fit the kinetic data namely the integral, the Van Krevelen, and Coats and Red fern methods. The presence of EAFD during PVC decomposition resulted in a considerable decrease in the activation energy of the reaction occurring during the first decomposition region. Furthermore, iron oxides were retained in the pyrolysis residue, whilst other valuable metals, including Zn and Pb, were converted to chlorides that are recoverable by leaching in water. It is believed that EAFD can be utilized as an active catalyst to produce energy gases such as propyneas evident from the TGA-MS.

Thermal analysis on the pyrolysis of tetrabromobisphenol A and electric arc furnace dust mixtures

The pyrolysis of Tetrabromobisphenol A (TBBPA) mixed with electric arc furnace dust (EAFD) was studied using thermogravimetric analysis (TGA) and theoretically analyzed using thermodynamic equilibrium calculations. Mixtures of both materials with varying TBBPA loads (1:1 and 1:3) were prepared and pyrolyzed in a nitrogen atmosphere under dynamic heating conditions at heating rates of 5 and 10 °C/min. The mixtures degraded through several steps, including decomposition of TBBPA yielding mainly HBr, bromination of metal oxides, followed by their evaporation in the sequence of CuBr3, ZnBr2, PbBr2, FeBr2, MnBr2, KBr, NaBr, CaBr2, and MgBr2, and finally reduction of the remaining metal oxides by the char formed from decomposition of TBBPA. Thermodynamic calculations suggest the possibility of selective bromination of zinc and lead followed by their evaporation, leaving iron in its oxide form, while the char formed may serve as a reduction agent for iron oxides into metallic iron. However, at higher TBBPA volumes, iron bromide forms, which can also be evaporated at a temperature higher than those of ZnBr2 and PbBr2. Results from this work provide practical insight into selective recovery of valuable metals from EAFD while at the same time recycling the hazardous bromine content in TBBPA.

Extracting oil from used auto tires at low temperature after chemical treatment

This study presents an alternative tactic to pyrolysis of auto tires avoiding the use of high temperature and increasing the yield of oil produced. It depends on a simple chemical treatment of auto tires with sodium carbonate at low temperature (50°C) followed by solvent extraction. This treatment produced two folds of the yield that can be obtained using normal solvent extraction. The experimental results suggests that sodium carbonate is responsible for breakage of CS bond in the main structure of auto tires making solvent extraction easier. Additionally, the sulphur content of the extracted oil using the sodium carbonate treatment is reduced significantly (by about 28%) making the product more favorable energy/fuel source. This technique allows about 30wt.% of oil to be extracted from the used auto tires at 50°C under atmospheric pressure resulted from the breakage of the sulphur cross-linking by the sodium carbonate.

Semicontinuous solar drying of sludge from a waste water treatment plant

This study presents a newly developed system to utilize solar energy to dewater the sludge in a semicontinuous mode. The semicontinuous dryer mainly consists of a moving belt on which aluminum bars are fixed to hold the sludge and a fan is used to drive the air at the required speed. The effects of operating conditions, such as air velocity, belt speed, and mode of contact between the sludge and air, on the drying rate of water were investigated. The drying rate of water was measured under the effects of different operating conditions, including air velocity, belt speed, and mode of contact between the sludge and air. The experimental results proved the technical feasibility of the developed solar drying system to efficiently evaporate water. The achieved drying rates were 2.02 kg water/m2 h and 0.49 kg water/m2 h in September and February, respectively. Under a given insolation rate, a high evaporation rate is achieved at large air velocity and slow motor speed. An empirical relationship to predict the m...

Effect of solar area concentration ratio on performance of a conventional solar still with air humidification-dehumidification

The high demand for drinking water increased the need to develop new economic methods for water desalination. Conventional solar stills suffer from latent heat losses resulting from water-vapor condensation on the inner surface of the glazing. Using open humidification-dehumidification process with conventional solar stills is a potential area in water desalination nowadays. Integrating a vertical duct to the still for generating a natural draft and solar-air preheater improved its performance. The effect of the solar area concentration ratio on the still performance with heater was studied thoroughly compared to no heater as a reference. Using a condenser in the duct prevents latent heat losses on the inner surface of the glazing and utilizes it to preheat the feed water. This arrangement improved the still productivity. A model was generated to describe the efficiency of the system using three area concentration ratios: 0.5, 0.625, and 0.75. The results showed that the still productivity increased propo...

The use of oil shale ash in the production of biodiesel from waste vegetable oil

Oil shale ash obtained from combustion of local oil shale deposits was used in this study as a heterogeneous catalyst to produce biodiesel from waste vegetable oil (WVO). Two alcohols with high and low boiling points, ethanol and ethylene glycol, were used for oil shale catalytic esterification of the WVO. Results show that the esterification of wastes of oil utilizing wastes of oil shale combustion can be used to produce biodiesel. Additionally, it was found that in order to make the oil shale ash an effective catalyst for transesterification, high reaction temperature is required. Therefore, the results have indicated that high biodiesel yield is obtained when using ethylene glycol at high temperature, while the yield is low when solid catalytic reaction is performed using ethanol at low temperature. The maximum obtained yield was 75 wt. % utilizing ethylene glycol at 150 °C, whereas this yield decreased to 69.9 wt. % as the operating temperature was reduced to 100 °C. On the other hand, when using ethanol, the yield of biodiesel was relatively low (11 wt. % at 60 °C and 9 wt. % at 80 °C).

Biodiesel production from waste soybean oil using jordanian oil shale ash

Biodiesel, an alternative diesel fuel derived from vegetable oil, animal fat, or waste vegetable oil (WVO), is obtained in this work by reacting waste vegetable soybean oil using oil shale ash as a heterogeneous catalyst in addition to two alcohols ethylene glycol and ethanol. Results have indicated that high biodiesel yield is obtained when using ethylene glycol at high temperature, while the yield is low when solid catalytic reaction is performed using ethanol at low temperature. This indicates that heterogeneous catalytic reaction is favored at a high temperature using alcohol with a high boiling point. Maximum yield was 75% wt using ethylene glycol at 150°C and the yield dropped to 69.9% wt as the operating temperature was reduced to 100°C. The increase in yield by 5% wt as the temperature increased from 100°C to 150°C is not significant. Using ethanol, the biodiesel yield is as low as 11% wt at 60°C and 9% wt at 80°C.