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In the manufacturing process for a fine chemical, a manufacturer makes use of a pressure filter, initial cost $110,000, for a product isolation under hot, acid conditions. As a result of the latter, the operating cost (including maintenance) rises sharply with time and the salvage value of the equipment falls correspondingly sharply. The process is expected to operate for 7 years. Operating costs and salvage values as a function of time are given in the table below. It is suggested that the filter be replaced by a new unit before the end of the period of manufacture, in order to reduce equipment and maintenance costs. Since services, pipe work etc. are all in place, this can be done within the period of annual maintenance and it is anticipated that there will be no loss of production or other extra expenses. Using the Net Present Worth criterion at a MARR of 15%, and assuming that the pattern of expenditure with the replacement filter would follow that of the original:
Assuming flotation is a first order rate process, if a bank of 6 flotation cells gives a recovery of 88% with a cell residence time of 5 minutes, what additional recovery would be expected by the addition of 4 cells each of the same design as the 6 cells? Assume the new cells perform as the original cells? (10 marks)
Given that a ball mill is being fed at 250 tonnes per hour for a certain zinc sulphide ore and 80% of the ore passes 1.5mm and that after grinding at 70% solids, 80% of the mill discharge passes 125microns.
(i) If the Bond work index for this size reduction is measured as 14.5kWh/t, calculate the energy consumption for the ore. (10 marks)
(ii) What are the limitations of this energy approach? (5 marks).
A Carnot engine receives 250 kJ/s of heat from a heat-source reservoir at 525degree Celcius and rejects heat to a heat-sink reservoir at 50degree Celcius.
1. What are the powers developed?
2. Calculate the heat rejected?
. In a gas power plant, liquid normal Butane is used as the fuel in the
combustion chamber. The fuel enters the combustion chamber at 25°C and 10 atm at
a rate of 0.7 kg/min. The fuel is burned with 180% excess air that is compressed to 10
atm and preheated to 500 K before entering the combustion chamber. The products of
the combustion are used as the working fluid in a gas power plant and enter the
turbine at 1400 K and 10 atm. The gas leaves the turbine at 800 K and 1 atm. The
adiabatic efficiency of the turbine is 80% and the surrounding temperature is 25°C.
The combustion process is complete.
Draw a schematic diagram of the system and determine:
a. The rate of heat transfer from the combustion chamber.
b. The rate of entropy generation (the net rate of change of entropy).
c. The rate of irreversibility (exergy destruction) during the whole process.
d. Show these processes schematically on a T-s diagram
a. The feed (17000 kgmole) to a distillation column is a 55.0 weight % CH3OH – 45.0 weight % water (nonvolatile) liquid mixture. The water stream leaving the bottom of the column, which contains 96.0 mole % water. The liquid stream leaving the bottom of the column goes to a reboiler. Part of the stream is vaporized; the vapor is recycled to the bottom of the column as boilup, and the distillate liquid is withdrawn as top product as 9582 kgmoles. Calculate the percentage moles of volatile component in the distillate. Given Atomic weight Carbon -12 g/g-atom, Hydrogen – 1 g/g- atom. b. 8 barrels per metric ton is used for the storage of North Sea Crude oil. Calculate the density of North Sea crude oil in lb/gallon and classify the type of oil.
a.
The feed (17000 kgmole) to a distillation column is a 55.0 weight % CH3OH – 45.0 weight % water (nonvolatile) liquid mixture. The water stream leaving the bottom of the column, which contains 96.0 mole % water. The liquid stream leaving the bottom of the column goes to a reboiler. Part of the stream is vaporized; the vapor is recycled to the bottom of the column as boilup, and the distillate liquid is withdrawn as top product as 9582 kgmoles.
(i) Draw the distillation column and mention the streams.
(ii) Calculate the percentage moles of volatile component in the
distillate. Given Atomic weight Carbon -12 g/g-atom, Hydrogen – 1 g/g- atom.
b. 8 barrels per metric ton is used for the storage of North Sea Crude oil. Calculate the density of North Sea crude oil in lb/gallon and classify the type of oil.
The wing on the aircraft in Figure below is subjected to a drag FD
created by airflow over its surface. It is anticipated that this force is a function of the
density and viscosity of the air, the characteristic, length of the wing, and the velocity
of the flow. Show how the drag force depends on these variables by using FLT
system.
Air and fuel enter a furnace used for home heating. The air has an enthalpy of 320 kJ/kg and the fuel has an enthalpy of 43027 kJ/kg. The gases leaving the furnace has an enthalpy of 616 kJ/kg. There are 17 kgair/kgfuel, water circulated through the wall furnace receiving heat. The hose required 17.02 kW of heat, what is the fuel consumption per day. (41 kg/day)
The stack gas from a boiler furnace contains 10.8 % CO2, 0.2 % CO, 9.0 % O2 and 80.0 % N2. These gases enter the stack at 400 oC; 500 kg of coal are burnt per hour. The proximate analysis of the coal as fired is 1.44 % moisture, 34.61 % volatile mater, 57.77% fixed carbon, and 6.18 % ash, and the heating value is 33.3 kJ/g. An analysis for carbon and sulfur shows these to be 78.76 % and 0.78 % respectively. Furthermore, it is known that coal from the same field averages 1.3 % N. The volatile matter of the refuse (dry) is 4 % and fixed carbon 21 %. Air in the boiler room has a temperature of 25 oC
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