Özkan Murat Doğan

HYDRODYNAMICS AND STABILITYOF SLOT-RECTANGULAR SPOUTED BEDS. PART I: THIN BED

Spouted beds of rectangular cross-section with gas entry through bottom slots have been proposed as a means of overcoming scale-up difficulties of conventional spouted beds. A study was undertaken of bed hydrodynamics in a thin slot-rectangular column of width 150 mm and slot width 2 to 20 mm for four types of particles. Flow regimes and bed hydrodynamics are qualitatively similar to those in cylindrical spouted beds, but there are significant quantitative differences caused by the different geometry. Slot width exerts a strong influence on such features as flow regimes, maximum spoutable bed height, minimum spouting velocity, pressure drop and fountain height.

HYDRODYNAMICS AND STABILITY OF SLOT-RECTANGULAR SPOUTED BEDS PART II: INCREASING BED THICKNESS

Tests were carried out with rectangular spouted bed columns of different thickness, i.e., front-to-back dimension, while holding the column width and air-entry slot width constant, to investigate the effects on spoul stability and bed hydrodynamics. For the three sizes of glass beads and one size of polyethylene beads examined, increasing the column thickness led to three-dimensional effects, such as formation of multiple spouts, and affected such hydrodynamics variables as the minimum spouting velocity, maximum spoutable bed depth and maximum pressure drop.

Pyrolysis of Low and High Density Polyethylene. Part I: Non-isothermal Pyrolysis Kinetics

Abstract Thermal decomposition kinetics of low- and high-density polyethylene (LDPE, HDPE) were investigated. Thermal degradation of raw and waste LDPE and HDPE was performed using a thermogravimetric analyzer (TGA) in nitrogen atmosphere under non-isothermal conditions. Heating rates between 5 and 50 K/min were employed in TGA experiments. First-order decomposition reaction was assumed, and for the kinetic analysis an integral method was used. The apparent activation energy (Ea) and the pre-exponential factor (ko) were evaluated. It was found that value of the kinetic parameters and apparent activation energy of HDPE were larger than the LDPE.

Pyrolysis of Low and High Density Polyethylene. Part II: Analysis of Liquid Products Using FTIR and NMR Spectroscopy

Abstract The pyrolysis of low- and high-density polyethylene (LDPE, HDPE) were investigated, and we characterized the liquid pyrolysis products. Pyrolysis experiments were carried out in a lab-scale batch-wise fixed-bed Pyrex® reactor, placed in a vertical furnace, and liquid products of the pyrolysis process were obtained. Nitrogen gas was used as carrier during the experiments, and the temperature was varied from 293 to 823 K. FTIR and 1H, 13C NMR spectra were used to determine structural analysis of pyrolysis product.

Mass transfer enhancement factor for chemical absorption of carbon dioxide into sodium metaborate solution

Hydrogen is getting increasing attention as a medium for energy storage, and sodium borohydride is accepted as a suitable carrier for hydrogen. The main product of the process by means of which hydrogen is produced from sodium borohydride is sodium metaborate. Our aim was to find an alternative use for sodium metaborate and specifically investigating the feasibility to use it for carbon dioxide capture from flue gases. The products of this chemical absorption are sodium carbonate, sodium bicarbonate and boric acid, all of which are industrially important chemicals. A bubble column was used in the experiments. Oxygen desorption technique was employed to determine the liquid side physical mass transfer coefficient. Chemical mass transfer coefficient was determined by absorption of carbon dioxide from its mixture with nitrogen into sodium metaborate solution. Enhancement factor was then calculated and a correlation was developed for it.

KINEMATIC VISCOSITIES OF POLYETHYLENE GLYCOL + DEXTRAN + WATER SOLUTIONS

ABSTRACT The kinematic viscosities of aqueous polyethylene glycol and dextran and polyethylene glycol + dextran + water were measured at temperatures of 30, 50, and 70°C. Polyethylene glycol with relative molecular masses of 200 and 1000 and dextran samples with nominal molecular masses of 37 500 and 2 000 000 were used. A one-parameter Grunberg-like equation proposed earlier by one of the present authors was used for estimating the values of viscosity of polyethylene glycol + dextran + water. A disposable parameter for the temperature range was calculated as 0.96 and 1.05 for PEG 200 + dextran 37 500 + water and PEG 1000 + dextran 37 500 + water, respectively, and as 2.74 and 2.80 for PEG 200 + dextran 2 000 000 + water, and PEG 1000 + dextran 2 000 000 + water, respectively. In view of our results, the proposed model works well for systems containing polyethylene glycol and dextran with different molecular masses.