Chemical Engineering: Solutions to the Problems in Volume 1 by J R Backhurst, J H Harker, J.F. Richardson | 9780750649506 | 075064950X | Holooly

Intro to Chemical Engineering

Chemical Engineering: Solutions to the Problems in Volume 1

282 SOLVED PROBLEMS

Question: 7.8

An agitated tank with a standard Rushton impeller is required to disperse gas in a solution of properties similar to those of water. The tank will be 3 m diameter (1 m diameter impeller). A power level of 0.8 kW/m³ is chosen. Assuming fully turbulent conditions and that the presence of the gas does ...

Verified Answer:

(a) Assuming that the depth of liquid = tank diame...

Question: 8.6

In a single-stage compressor: Suction pressure = 101.3 kN/m². Suction temperature = 283 K. Final pressure = 380 kN/m². If each new charge is heated 18 deg K by contact with the clearance gases, calculate the maximum temperature attained in the cylinder. ...

Verified Answer:

The compression ratio = (380/101.3) = 3.75. On the...

Question: 13.3

Wet material, containing 70% moisture on a wet basis, is to be dried at the rate of 0.15 kg/s in a counter-current dryer to give a product containing 5% moisture (both on a wet basis).The drying medium consists of air heated to 373 K and containing water vapour with a partial pressure of 1.0 kN/m² ...

Verified Answer:

The feed is 0.15 kg/s wet material containing 0.70...

Question: 10.42

State the assumptions made in the penetration theory for the absorption of a pure gas into a liquid. The surface of an initially solute-free liquid is suddenly exposed to a soluble gas and the liquid is sufficiently deep for no solute to have time to reach the far boundary of the liquid. Starting ...

Verified Answer:

\frac{C_{A}}{C_{As}} =\text{erfc}\frac{y}{2...

Question: 10.46

Derive the partial differential equation for unsteady-state unidirectional diffusion accompanied by an nth-order chemical reaction (rate constant k): ∂Ca/∂t = D∂²CA/∂y² – kCA^n where CA is the molar concentration of reactant at position y at time t. Explain why, when applying the equation to ...

Verified Answer:

(i) The partial differential equation for unsteady...

Question: 1.2

Compare the costs of electricity at 1 p per kWh and gas at 15 p per therm. ...

Verified Answer:

Each cost is calculated in p/MJ. 1 kWh = 1 kW × 1 ...

Question: 10.33

Explain the basis of the penetration theory for mass transfer across a phase boundary. What are the assumptions in the theory which lead to the result that the mass transfer rate is inversely proportional to the square root of the time for which a surface element has been expressed d?(Do ...

Verified Answer:

(a) Danckwerts age distribution function Dividing ...

Question: 10.21

Experiments have been carried out on the mass transfer of acetone between air and a laminar water jet. Assuming that desorption produces random surface renewal with aconstant fractional rate of surface renewal, s, but an upper limit on surface age equal to the life of the jet, τ, show that the ...

Verified Answer:

For the penetration theory:

\frac{∂C_{A}}{∂...

Question: 10.35

For the diffusion of carbon dioxide at atmospheric pressure and a temperature of 293 K, at what time will the concentration of solute 1 mm below the surface reach 1 per cent of the value at the surface? At that time, what will the mass transfer rate (kmol m^-2 s^-1) be: (a) At the free surface? ...

Verified Answer:

\frac{∂C_{A}}{∂t} =D\frac{∂^{2}C_{A}}{∂y^{2...

Question: 10.24

A large deep bath contains molten steel, the surface of which is in contact with air. The oxygen concentration in the bulk of the molten steel is 0.03% by mass and the rate of transfer of oxygen from the air is sufficiently high to maintain the surface layers saturated at a concentration of 0.16% ...

Verified Answer:

If C′ is defined as the concentration above a unif...

Loading...