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University of Dar es Salaam

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Articles 61 - 75 of 75

Full-Text Articles in Catalysis and Reaction Engineering

Design Approach For Small Scale Continuous, Steady State Plants, O Kaunde Dec 1994

Design Approach For Small Scale Continuous, Steady State Plants, O Kaunde

Tanzania Journal of Engineering and Technology (TJET)

One of the major steps in the design of a process plant is development of an appiopriate flowsheet. At this step, the technical solutions may be con- sidered in relation to the social and economic factors. In this paper, guide- lines for developing a flowsheet for continuous, steady State process in a developing country environment have been proposed. To illustrate the pro- posed guidelines, a case study involving design of an ethanol distillation plant has been used.

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Experimental Investigation On The Use Of Native Biomass As Biosorbents For Metal Pollutant Removal, R Litto Dec 1994

Experimental Investigation On The Use Of Native Biomass As Biosorbents For Metal Pollutant Removal, R Litto

Tanzania Journal of Engineering and Technology (TJET)

Waste water treatment is a perrnunent task. Many novel techniques have emerge in recent years and one of them is using biomass in removing heavy- metals. In this research screening and preliminary optimization experi- ments have identified different types of abundant biomass which can accu- mulate heavy metals such as Fe3*, C03•, Cu2+ and ftvm effluent. Cystoseira Myrica has a high uptake ofCr3+ while Sargassum Polycystum has been found to have a high uptake 0fFe3+. Observed biosorption kinet- ics shows rapid initial stage, followed by slower second stage and the amount of material adsorbed increases linearly as its concentration in …

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Improved Heat Transfer By Means Of Steam Injection In A Shell & Tube Heat Exchanger, O Kaunde Dec 1994

Improved Heat Transfer By Means Of Steam Injection In A Shell & Tube Heat Exchanger, O Kaunde

Tanzania Journal of Engineering and Technology (TJET)

When designing a heat exchanger; one aims at attaining high heat transfer rates SO as to minimise heat transfer area and therefore the overall cost. This paper presents a method of improving the overall heat travsfer coef- ficient of a conventional shell and tube heal exchanger. The method in- volves injecting steam into the process fluid as it enters the heat exchanger thus effecting mixing of fluid as it travels along the exchanger Tests car- • ried out using this technique showed a significant increase in the overall heat transfer coefficient values.

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Polymer Supported Z-N Catalysts For C2h4-Polymerization,I: Development Catalyst Preparation Method, S Mteza Dec 1994

Polymer Supported Z-N Catalysts For C2h4-Polymerization,I: Development Catalyst Preparation Method, S Mteza

Tanzania Journal of Engineering and Technology (TJET)

Substantial improvement of low sensitivity pressure transducers aiming at obtaining a more realistic output signal is discussed. The output signal direct from these transducers has deficiencies of amplitude attenuation and phase lag, thus the measured values are not necessarily the true in- stantaneous values. In order to correct for such shortcomings the unit step response of these transducers is also studied experimentally. A math- ematical model is established based on the experimental results to build up a compensation circuit which is then included in the instrumentation setup to eliminate these deficiencies. The effectiveness of the compensated transducer is demonstrated by …

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Influence Of Arc Discharge Duration On Turbulent Mass Burning Rate, E Mushi Dec 1994

Influence Of Arc Discharge Duration On Turbulent Mass Burning Rate, E Mushi

Tanzania Journal of Engineering and Technology (TJET)

The influence of arc discharge duration on turbulent mass burning rate was investigated for turbulent r.m.s vglocities of u '=1.73 m/s and u'=4.5 nfs. Methane air mixtures were used at equivalence ratios ranging from 0.83 to / .25. Flame size was obtained through schiieren photography while the intensity Of CH chemiluminescence emissions was used to measure mass burning rate. A variable spark duration unit was used for ignition sparks and all the experiments were done in a fan stirred bomb. Discharge duration has no effect when the equivalence ratio is I. For higher values longer duration inoeases the burning rate …

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Pulping Of Sisal Fibres: Effects Of Chemical Concentration, Na-Zs03/Na2c03 Ratio And Fibre To Chemical Ratio, J Katima Jun 1994

Pulping Of Sisal Fibres: Effects Of Chemical Concentration, Na-Zs03/Na2c03 Ratio And Fibre To Chemical Ratio, J Katima

Tanzania Journal of Engineering and Technology (TJET)

This paper reports on pulping of hard fibres extracted from the leaves Of agave sisalana using sodium sulphite buffered with sodium carbonate as pulping chemical. The cooking was carried Out at 1680Cfor a cooking period of 6 hours, with varying chemical concentration, sodium sulphite to sodium carbonate ratio and fibre to chemical ratio. The results show thar boll! the pulp yield and pulp viscosity decæase with increasing chemi- cal concentration, whereas Kappa number of pulp decreases to a limit of about 16.45. Brightness increases significantly with an increase in the ra- rio of Na2S03/Na2C03. The pulp yield obtained indicated the …

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Improvement Of Solar Salt Works Performance, J Katima Dec 1993

Improvement Of Solar Salt Works Performance, J Katima

Tanzania Journal of Engineering and Technology (TJET)

Coal, asphalt, black oil paint, naphthol green b and alkali blue 6b were testedfor improvement Of solar energy utilisation in solar salt manufacture. It was found that the use of alkali blue 6b dye dissolved in raw seawater improves efficiency by 3.6 percent. Both modifications could increase solar salt works with a coal coated surface than one employing raw seawater dyed with alkali blue 6b.

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Thermodynamics And Transport Proper- Ties Analysis Of Natural Gas From Songosongo In Kilwa- Tanzania, G Mrema Dec 1993

Thermodynamics And Transport Proper- Ties Analysis Of Natural Gas From Songosongo In Kilwa- Tanzania, G Mrema

Tanzania Journal of Engineering and Technology (TJET)

Analysis ofthermodynamics and transport properties was carried outfor six natu- ral gas samples from Songosongofield in Kilwa - Tanzania using PRO/II simula- for. Properties of most interest in gas processing (due to their influence on the sales value) such as density, specific gravity, critical parameters, bubble point and dew point, enthalpy, latent heat of vaporisation, molecular weight, boiling point and phase were investigated. In addition composition of the gas was com- pared with that from elsewhere. The gas was assumed to be at a temperature of 30C and a pressme of 150 bar before pressure let down station. Results indicated …

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Development And Testing Of Locally Produced Natural Rubber (Nr) And Pvc Blends, B Mutagahywa Jun 1993

Development And Testing Of Locally Produced Natural Rubber (Nr) And Pvc Blends, B Mutagahywa

Tanzania Journal of Engineering and Technology (TJET)

The mechanical properties of natural rubber - poly(vinyl chloride) blends have been studied. Tensile and tear strengths of the vulcanizates has been shown to increase with increasing proportions of PVC up to about 20 pphr. Abrasion loss and hardness decreases slightly with increasing concentration of PVC. Increased loading Of carbon black lowers the tensile and tear strength while increasing the abrasion loss and hardness values. This may be explained by the fact that PVC exists as a discontinuous rigid phase in the polymer compound. At normal loading of black (37 pphr) PVC improves processability and acts in the same way …

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Absorption Of Nitrogen Oxides Into Sodium Hydroxide Solution In A Packed Column: Effect Of Gas Flowrate And Temperature, J Katima Dec 1991

Absorption Of Nitrogen Oxides Into Sodium Hydroxide Solution In A Packed Column: Effect Of Gas Flowrate And Temperature, J Katima

Tanzania Journal of Engineering and Technology (TJET)

The effect of gas flow rate and temperature on the absorption rate of nitrogen oxides (NO ) and column absorption eff iciency has been studied using a 2M goåium hydroxide (NaOH) solution in a packed The absorpt ion process was carried out at atmospheric column. pressure, with NOV concentration ranging between 150 and 10000 pp:tt, NO/N02 ratio of O and 1 iquid flow rate of O .8 1/ min. The gas flow rate was varied from 20 to 60 1/17 in and the temperature from 25 to 45 c. It was found that Ehe column absorption efficiency increases with decreasing …

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Energy From Biomass: Combustion And Gasification, G John Dec 1991

Energy From Biomass: Combustion And Gasification, G John

Tanzania Journal of Engineering and Technology (TJET)

Some fundamental facts of the combustion Of BIOMAS are outlined and di scussed . It is suggested that these provide guidelines for rhe development Of successful practical combustors. Furthemore, a realisation Of energy conversion from the same in gasfier is presented.

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Nn Investigation Of Nitrogen Oxide Abscwption In Packed Columns, J Katima Dec 1991

Nn Investigation Of Nitrogen Oxide Abscwption In Packed Columns, J Katima

Tanzania Journal of Engineering and Technology (TJET)

An experimental study was carried out on the performance of a packed column to study the absorption mechanism of nitrogen oxides (NOx). Two packed columns were set up, one with wall wiper rings to reduce wall effects and one without. Both columns were packed with stainless steel lessing rings and operated at fixed gas and liquid flow rates (40 and 8 L/min, respectively), atmospheric pressure, temperature (25°C), and sodium hydroxide concentration (8% w/w). The NOx (NO₂ and N₂O₄) equilibrium concentration and feed concentrations of up to 7000 ppm were used. The results indicated improved performance in the column with wall …

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Density Measurement For Corrosive Solutions At Elevated Temperatures, Kimweri, H Dec 1991

Density Measurement For Corrosive Solutions At Elevated Temperatures, Kimweri, H

Tanzania Journal of Engineering and Technology (TJET)

In this work, apparatus for measuring densities of corrosive solutions at high temperatures was developed and used. Densities of dilute aqueous sulphuric acid solutions, containing different amounts of zinc and iron salts were measured at temperatures up to 185°C. In view of the good agreement between consecutive measurements for each solution and the density of water obtained by using this apparatus with that given in literature, for all experiments, the apparatus is recommended to be used for measuring densities of corrosive solutions at high temperatures.

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Nitrogen Oxides Rbsorption Into Sodium Hydroxide Solution In A Packed Column Column: Effect Of Naoh Concentration, J Katima Dec 1991

Nitrogen Oxides Rbsorption Into Sodium Hydroxide Solution In A Packed Column Column: Effect Of Naoh Concentration, J Katima

Tanzania Journal of Engineering and Technology (TJET)

Experiments have been conducted to evaluate the ettect of sodium hydroxide (NaOH) concentration upon the absorption rate of nitrogen oxides (NO ) and packed column performance. The absorption process using was carried out at atmospheric pressure and 29B K, concentrations between zero and w/ w, NO/ NO ratio of 0.5 and NO concentrations between 150 and 10000 ppm in an air mixture. The performance of the calumn was enhanced by the presence of hydroxyl ions ( 0B - ) relative to the absorption into water, however, The absorption it was found to be independent of NaOH concentration. rate of NO …

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Effects Of Feed Solids Concentration On Dual Functionality Of A Hydrocyclone., Zanzu M Dec 1991

Effects Of Feed Solids Concentration On Dual Functionality Of A Hydrocyclone., Zanzu M

Tanzania Journal of Engineering and Technology (TJET)

The dual functionality, i.e. thickening and classification of a 50.8mm diameter hydrocyclone has been investigated. A metallurgical slime consisting of a 50% mixture of quartz and petroleum coke was used in the tests. It was found that in order to achieve both thickening and classification at the same time, the pressure drop across the hydrocyclone, the underflow diameter and the feed solids content have to be subtly controlled.

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