Chemical Engineering Answers

A natural gas-fired boiler operates with 20% excess air. Air is fed at 25 °C and contains 21% O2 and 79% N2 on a volume basis. Natural gas composition: 92.6% CH4, 3.6% C2H6, 0.8% C3H8, 0.3% C4H10, 2.6% N2, 0.1% CO2; GCV: 38.6 MJ/m3 . Molecular weights of C, H, O, N are 12 g, 1g, 16 g and 14 g respectively.

(i) During an energy audit, it was proposed to convert this boiler to a condensing boiler. Do you think it is a viable option? Why? In your discussion, consider the main aspects you should look at during the design and operating phases of a condensing boiler.

(ii) Calculate the amount of condensate formed if a condensing section is added to the boiler so that the flue gas exit temperature is 45 °C. Stack pressure is 1.013 bar.

(iv) Calculate the percentage total energy loss with the flue gas and condensate. The specific heat of the dry flue gas and condensate are 1.2 kJ/m3 K and 4.2 kJ/kg K respectively. Assume the molar volume of the gases as 22.4 m3 /kmol

A feed mixture of A and B (45 mole % A and 55 mole % B) is to be separated into a top product containing 96 mole% A and a bottom product having 95 mole% B. the feed is 50 % vapor and reflux ratio is 1.5 times the minimum. What is the equation of the feed line? Determine the number of ideal trays required and the location of the feed tray .Given αAB = 2.8

A mixture of benzene and toluene containing 40 mole % benzene is to be separated continuously in a tray tower at a rate of 200 kmol/h. the top product should have 95 mole% of benzene and the bottom must contain more than 4 mole% of it. the reflux is a saturated liquid and a reflux ratio of 2.0 is maintained. the feed is a saturated liquid (i.e. it is at its bubble point)

a.obtain and plot the operating lines for the rectifying and the stripping sections on the x-y plane.

b.What is the boil-up ratio?

The vapour-liquid equilibrium data at the operating pressure of 101.3 kPa are given below.

X 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Y. 0 0.21 0.38 0.511 0.627 0.719 0.79 0.853 0.91 0.961 1.0

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A mixture of 40 mol% benzene and 60 mol% toluene

is being flash-distilled at a rate of 10 kmol/h at 1 atm

total pressure. The liquid product should not contain

more than 35 mol% benzene. Calculate the amounts

and the compositions of the top and the bottom products.The relative volatility of benzene in the mixture is 3.Solve analytically.

According to Jablonski diagram which transition is more favourable for carrying out a photochemical reaction?

(a)S₁→S₀

(b)S₂→S₀

(c)T₁→S₀

(d)S₁→T₁

In a photochemical reaction A→ B+C , the quantum efficiency with 500nm light is 1.2 x 10^2 mol.einstein^-1. After exposure of 200 millimoles of A to the light, 1.77 millimoles of B is formed.How many photons were absorbed by A?

The density of steam at 1 atm is 0.6 kg/m³, then specific volume of steam at this

pressure is

Calculate ∆G and ∆S when 1 mole of ethanol is vaporized at 65◦C and 1 atm pressure. The latent heat of vaporization of 1g of ethanol is 200 cal

OLED is the one which?

Find the equilibrium constant for the reaction called the water-gas reaction

H2+CO2<--->H2O+CO

at 1200 K