Chemical Engineering Answers

In order to meet a certain octane number specification, it is necessary to produce gasoline containing 80%w isooctane and 20%w n-heptane. How many liters of a high-octane gasoline containing 90%w isooctane and 10%w n-heptane must be blended with a straight-run gasoline containing 65%w isooctane and 35%w n-heptane to obtain 16625liters of desired gasoline? The specific gravity of each of the liquids is 0.84

You are expected to produce 4000 cases of noodles within your 12hrs shift and you realize that the machine in the production area is malfunctioning. Due to this, you were only able to produce 35 % of the normal production.

(a) How will you approach this situation as a supervisor in a noodle manufacturing company?                                                                                                   

 (b) About 20 packets of noodles are packed in one case (box). If one case is sold for R80, how much production in rands have you achieved during your shift?          

A CSTR is fed with a solution of reactant A of concentration 10 kmol/m3

at a flow rate of 0.02

m3

/s. The product mixture from the first CSTR is fed into a second CSTR of twice the volume

of the first CSTR. The two CSTRs in series are required to achieve an overall conversion of

80%.

The reaction A → B is first order with respect to A (-rA = kCA) with a reaction rate constant of

0.2 s-1

. Assuming constant liquid density, what is the volume of the first CSTR?

T

A second order reaction is carried out at 313 K has an activation energy of 23 000 J/mole and

a rate constant is 2.6. For this reaction, at what temperature would the rate triple? What are the

units of the rate constant?

(NB Use Arrhenius equation)

Question 3 [20 Marks]

The following liquid-phase reaction is carried out in a semi-batch reactor:

A + 2B → C

The reaction is assumed to be zero order with respect to species A and B, and the specific rate

constant is 0.2 mol/dm3

-min.

Initially, the reactor volume is 60 litres and there are 80 moles of species A in the reactor.

Thereafter, a concentration of 12 moles per litre of species B is gradually added to the reactor

at a volumetric flow rate of 2 litres per minutes. How much time does it take to reach a 50%

conversion of species A?

(NB: Start from the general mole balance)

Hydrogen-free carbon in the form of coke is burned:

(a) With complete combustion using theoretical air

(b) With complete combustion using 50% excess air

(c) Using 50% air but with 10% of the carbon burning to CO only

As part of the preliminary design stages, you are required to calculate the gas analysis that will be

found by testing the flue gases on a dry basis.

One of the products of sewage treatment is sludge. After microorganisms grow in the activated sludge

process to remove nutrients and organic material, a substantial amount of wet sludge is produced.

This sludge must be dewatered, one of the most expensive parts of most treatment plant operations.

Disposing off the dewatered sludge is a major problem. Some organizations sell dry sludge for

fertilizer, some spread the sludge on farmland and in some places, it is burned. To burn a dried sludge

fuel oil is mixed with it, and the mixture is burned in a furnace with air.

As part of the design evaluation of the furnace the following analysis for the sludge and product gases

was collected:

Sludge (%) Product gas (%)

S 32 SO2 1.52

C 40 CO2 10.14

H2 4 O2 4.65

O2 24 N2 81.67

CO 2.02

a) Determine the weight percent of carbon and fuel oil

b) Determine the ratio of pounds of dry sludge to pounds of fuel oil in the mixture fed to the

furnace. [20]

The molar volume of (V) a binary mixture of species 1 and 2 having mole fractions.x₁ and respectively is given by V = 220x+180x₂ + x₁x₁₂ (90.x₁ +50.x₂).

The partial molar volume of species 2 at x, = 0.3 is

(A) 183.06

(B) 212.34

(C) 229.54

(D)256.26

A card is drawn from a well shuffled pack of cards what is the probability that it is either spade or an acc A)3/13

(B) 5/13 (C) 4 / 13 D)2/13

The adsorption of pure propane on activated carbon at different temperatures and pressures is given as: T = 311 K T = 338.7 K T = 394 K p q p q p q 2.266 1.044 6 1.069 7.067 0.7099 15.6 2.819 27.2 2.469 38.67 1.677 31.74 3.48 53.2 3.078 83.21 2.238 59.6 3.968 92.67 3.512 98.54 2.37 89.74 4.207 99.97 3.635 99.97 2.4 99.97 4.342 244.8 4.188 303.4 3.251 293 4.94 424 4.475 482.6 3.599 Where, p = partial pressure of propane (kPa); q = amount of propane adsorbed at equilibrium (mmol/g carbon). a. Draw the adsorption isotherms at the above 3 temperatures. (03) b. Determine the isosteric heat of adsorption at constant solute loading of 3.0 and 3.5 mmol/g carbon, respectively.

A drier takes 7 h to dry a wet material from 33% moisture content to 9%. The critical and equilibrium moisture content were 16% and 5%. Determine the time needed to dry a similar material from 37% to 7% under similar drying conditions. All the percentages given above are on dry basis.