الفهرس 
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Abstract
The goal of the present work was to develop a new heterogeneous stirred tank reactor suitable for conducting liquid solid diffusion controlled reactions. The agitated vessel was fitted with a fixed bed of copper Raschig rings placed at the bettom of the vessel.
The performance of the reactor in conducting diffusion controlled reactions was evaluated in terms of the mass transfer coefficient. The diffusion controlled dissolution of copper in acidified dichromate technique was used to determine the mass transfer coefficient under different conditions.
Variables studied were:
I. Impeller speed of rotation.
2. Physical properties of the solution (viscosity, density and diffusivity).
3. Geometrical parameters of the bed such as particle size and bed thickness (height).
4. Geometry of the impeller (radial flow impeller and axial flow impeller).
5. The presence of drag reducing polymer (polyox WSR-301).
The present study revealed the following results:
I. The mass transfer coefficient at the agitated fixed bed was found to increase with impeller rotation speed but it decreases with increasing the bed thickness (with increasing number of layers of packed Raschig rings).
2. The mass transfer coefficient was found to increase by decreasing the particle size of the copper Raschig rings used.
3. The productivity of the suggested fixed bed stirred tank reactor with the 45° pitched blade turbine (axial flow impeller) is higher than with the 90° flat blade turbine (radial flow impeller) under the same conditions.
4. The drag reducing polymer (polyox WSR-301) was found to decrease the rate of mass transfer by an amount ranging from 17 to 23% for the 90° flat blade turbine and from 15% to 22% for the 45° pitched blade turbine.
5. Mass transfer data were correlated using the method of dimensional analysis, the following overall mass transfer correlation were obtained:
a. For radial flow impeller: Sh = 0.046 SCO.33 ReO.78 (dIh)0.45
b. For axial flow impeller: Sh= 0.0625 SCO.33 ReO.811 (dIh)0.47
6. The suggested reactor can find applications in conducting heterogeneous liquid solid diffusion controlled catalytic and non catalytic reactions such as :
i. Catalytic removal of organic pollutants by destruction on the surface of a solid
catalyst, such as a destruction of phenol on the surface of copper oxide.
ii. Catalyzed electro organic synthesis.
ill. Immobilized enzyme biochemical reactions.
iv. Photochemical reactions on Ti02 catalyst.
v. Heavy metal removal from waste solutions by cementation on a less noble metal.
7. The potential advantage of using the present reactor for conducting catalytic reactions involving gaseous reactants where the reactor acts simultaneously as a gas