Chemical Engineering Answers

2 tonnes of galena is to be reduced to fine powder by passing through a crusher and a grinder in succession, drawing powder from the same drive. Screen analysis of feed, product from crusher and product from grinder indicated surface areas of 5, 115 and 1000 m²/kg respectively. If the power required by the drive to run the crusher driver assembly is 20 KW and efficiency of crusher is 20%, find the efficiency of grinder. Rittinger's number for galena is 100 m²/kj

] n-heptane (ρ = 39.9 lbm/ft³) at 25 ^oC is being pumped from one tank to another as shown in the figure below. All pipes have 3 in internal diameters. Assume that the overall frictional loss in the pipes is given by:

      V = average velocity in the pipe, ft/s

If the average velocity in the pipe V is 25 ft/s, determine the following:

a)  The power required to drive the pump in kW knowing that it has an efficiency of 75%

b) The pressure at the inlet of the pump (in psia)

c)  NPSH available at the pump inlet knowing that the vapor pressure of n-heptane at 25 ^oC is 10.3 psia. Comment on your result. For simplicity you may ignore the friction in the short length of pipe between the supply tank and the inlet of the pump.

d)  The pressure at the pump exit (in psia)

Three pipes deliver water to a large exit pipe. The velocity at section 2 is 5 ms^-1, and the exit flow rate, Q₄ is 120 m³hr^-1. Find the velocities at 1, 3 and 4 if it is known that Q₃/Q₄ = 0.5

During exponential phase in batch culture, the growth rate of a culture is proportional to the concentration of cells present. When Streptococcus bacteria are cultured in milk, the concentration of cells doubles in 50 min. If this rate of growth is maintained for 8h, what is the final concentration of cells relative to the inoculum level? 

Draw the illustration of main bioreactor types and explain the usage of these reactors in bioprocess engineering applications?(Compare the bioreactor types) 

Water is boiled at the rate of 25kg/h in a polished copper pan, 280mm in diameter at atmospheric pressure. Assuming nucleate boiling conditions calculate the temperature of the bottom surface of the pan.

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Question assume ideal and optimal operating conditions for the cycle and the re-heater. Air enters the cycle at 300K and 100kPa and it leaves the combustor at 975K and 1089kPa.

Calculate the (a) pressure (kPa) of the air leaving the re-heater

A wet organic pigment containing 36% by weight of CCl4 is to be dried to 6% by weight (wet

basis). The drier is to operate adiabatically with fresh plus recycle air entering the dryer with

0.45 kg of CCl4 per kg of dry air. The air leaves the dryer with 0.895 kg of CCl4/kg of dry air. The

capacity of the dryer is 250 kg of bone dry solid per hour. Calculate the ratio of the recycled air

to fresh air.

 The slabs of building boards contain 17% moisture by weight. They are dried to a water content 

of 1% by weight by circulating hot air over them. The fresh air contains 0.17 kg of moisture per 

kg. The exhaust air contains 0.075 kg of moisture per kg. How many cubic metres of fresh air at 

standard conditions must be used per 2000 kg of the wet building boards?

Power required to drive a ball mill with a particular ball load is proportional to (where, D = diameter of ball mill )