BEE Paper-1 — Chapter 5: Material & Energy Balance

1. 54 kg of water is mixed with 0.34 moles of salt to make a solution. The mole fraction of the solution is ____.

1. 0.1
2. 18.36
3. 158.8
4. none of the above

2. C2H4 + xO2 ----> 2CO2 + yH2O, what is the value of x + y?

1. 2
2. 3
3. 5
4. 8

3. A solution of common salt is prepared by adding 25 kg of salt to 100 kg of water. The weight fraction of solution is ____.

1. 20%
2. 25%
3. 4%
4. none of the above

4. A system uses 100 kg of raw material A, 200 kg of B and 220 kg of C. The mix is heated to 220 deg C. Air carries away on average 60% of A and 30% of B through the chimney. The output product would be

1. 520 kg
2. 400 kg
3. 312 kg
4. 208 kg

5. If feed of 15 tonnes per hour at 6% concentration is fed to an evaporator, the product obtained at 30% concentration is equal to ____ tonnes per hour.

1. 3
2. 9
3. 0.9
4. 4.5

6. 1 kg of wood contains 15% moisture and 5% hydrogen by weight. How much water is evaporated during complete combustion of 1kg of wood?

1. 0.6 kg
2. 200 g
3. 0.15 kg
4. none of the above

7. In a drying process product moisture is reduced from 60% to 30%. Inlet weight of the material is 200 kg. Calculate the weight of the outlet product.

1. 80
2. 120.5
3. 114.3
4. none of the above

8. A mass balance for energy conservation does not consider which of the following

1. Steam
2. water
3. Lubricating oil
4. Raw material

9. Diagrammatic representation of input and output energy streams of an equipment or system is known as

1. mollier diagram
2. sankey diagram
3. psychrometric chart
4. balance diagram

10. Which of the following tool is made use of to assess the input, conversion efficiency, output, losses, quantification of all material, energy and waste streams in a process or system?

1. material balance
2. energy balance
3. material and energy balance
4. Sankey diagram

11. If feed of 100 tonnes per hour at 10% concentration is fed to an evaporator, the product obtained at 25% concentration is equal to ____ tonnes per hour.

1. 25
2. 40
3. 50
4. 62.5

12. 1 kg of wood contains 15% moisture and 7% hydrogen by weight. How much water is evaporated from wood during complete combustion of 1 kg of wood ?

1. 0.78 kg
2. 0.22 kg
3. 0.15 kg
4. 0.63 kg

13. Material and energy balance is used to quantify

1. material and energy losses
2. profit
3. cost of production
4. all of the above

14. The objective of material and energy balance is to assess the

1. input-output
2. conversion efficiency
3. losses
4. all the above

15. In the material balance of a process or unit operation, which component will not be considered on the input side?

1. chemicals
2. water/air
3. recycle
4. by product

16. In material balance of a process, recycle product is always considered as

1. input to process
2. output to process
3. both (a) and (b)
4. none of them

17. In a chemical process two reactants A (200 kg) and B (200 kg) are used as reactants. If conversion is 50% and A and B react in equal proportion, calculate the weight of the product formed.

1. 150 kg
2. 200 kg
3. 250 kg
4. 400 kg

18. In a heat treatment furnace the material is heated up to 800 degC from ambient temperature of 30 degC. Considering the specific heat of material as 0.13 kcal/kg degC, what is the energy content in one kg of material after heating?

1. 50 kcal
2. 250 kcal
3. 350 kcal
4. 100 kcal

19. In a utility steam boiler, heat loss due to radiation normally is in the range of

1. 10%
2. 14%
3. 1%
4. 8%

20. Energy supplied by electricity, Q in kcal is equal to

1. kWh x 8.6
2. kWh x 86
3. kWh x 860
4. none

21. Sankey diagram is a useful tool to represent

1. financial strength of the company
2. management philosophy
3. input and output energy flow
4. human resource strength of the company

22. Which of the following formula is useful to determine the heat duty in conducting heat balance?

1. Q = M Cp deltaT
2. Q = AV
3. PV = nRT
4. none of the above

23. A 230V, 100 W rated incandescent bulb is operated at a constant voltage of 250V. The approximate power consumption of bulb is

1. 100 W
2. 118 W
3. 85 W
4. none of the above

24. A gaseous mixture contains 7.50 gms of H2 and 3.25 gms of O2 and 5.55gms of N2. The Mole fraction of N2 is ____.

1. 0.34
2. 0.03
3. 0.0294
4. 0.049

25. A dry feed contains 7% moisture was feed to a water spray chamber to increase the moisture content to 35% in the dry feed. The output feed quantity coming from the spray chamber is ____.

1. 0.5 kg/kg of input feed
2. 1.43 kg/kg of input feed
3. 1.48 kg/kg of input feed
4. 2.66 kg/kg of input feed

26. Law of conservation of mass can be expressed by the following equation:

1. Products = Raw Materials + Waste Products + Stored Products + Losses
2. Products = Raw Materials + Waste Products + Stored Products - Losses
3. Raw Material = Products + Waste Products + Stored Products - Losses
4. Raw Materials = Products + Waste Products + Stored Products + Losses

27. When the evaporation of water from a wet substance is zero, the relative humidity of air is likely to be ____.

1. 0%
2. 10%
3. 50%
4. 100%

28. 1 mole of sulphur react with X moles of H2SO4 to form Y moles of H2O and Z moles of SO2 then (X/Y) + Z is ____.

1. 2
2. 4
3. 1
4. 3

29. In a drying process, moisture is reduced from 50% to 30%. Initial weight of the material is 100 kg. Calculate the weight of the final product in kg.

1. 80
2. 86
3. 71.4
4. 74.3

30. If feed of 100 tons per hour at 5% concentration is fed to a crystallizer, the rate in tons per hour of the product obtained at 25% concentration is equal to:

1. 40
2. 20
3. 25
4. 100

31. A process receives 1000 kg/hr of raw material. The hourly outputs are 700 kg of product, 200 kg of waste, and 50 kg stored. What is the unaccounted loss?

1. 100 kg/hr
2. 150 kg/hr
3. 200 kg/hr
4. 50 kg/hr

32. Calculate the quantity of water evaporated when 100 kg of feed containing 6% solids is concentrated to 30% solids.

1. 600 kg
2. 180 kg
3. 80 kg
4. 800 kg

33. Moles of water in 54 grams:

1. 3
2. 4
3. 5
4. 6

34. Mean molecular weight of air (77% N2, 23% O2 by weight) is ___________ grams.

1. 26.8
2. 27.8
3. 28.8
4. 29.8

35. The number of moles of water contained in 72 grams of water is

1. 2
2. 3
3. 4
4. 5

36. A solution of common salt in water is prepared by adding 25 kg of salt to 100 kg of water. The concentration of salt in this solution as a weight fraction shall be

1. 10%
2. 15%
3. 20%
4. 25%

37. The general material balance equation for a process can be written as:

1. Raw Materials = Products + Waste Products + Stored Products + Losses
2. Raw Materials = Products − Losses
3. Products = Raw Materials + Losses
4. Raw Materials + Losses = Products

38. In a process flow diagram, which of the following is NOT on the INPUT side of the process box?

1. Raw material
2. Recycle stream
3. By-product
4. Combustion air

39. A diagram that visually represents the input and output energy flows of a system, where the width of each arrow is proportional to the magnitude of the flow, is called a:

1. Gantt chart
2. Sankey diagram
3. Pie chart
4. Fishbone diagram

40. Dust-laden gas enters a bag filter at 200,000 m^3/hr carrying 6 g/m^3 of dust. The cleaned gas leaves at 210,000 m^3/hr carrying 0.1 g/m^3. The dust collected in the hopper is:

1. 1179 kg/hr
2. 1200 kg/hr
3. 21 kg/hr
4. 1221 kg/hr

41. A liquor containing 8% solids is concentrated to 40% solids. Starting with 100 kg of feed, the mass of water evaporated is:

1. 32 kg
2. 60 kg
3. 80 kg
4. 20 kg

42. A furnace shell (mass 2000 kg, specific heat 0.2 kcal/kg°C) is cooled from 90°C to 55°C by water whose temperature rises by 5°C. The mass of cooling water required is (Cp_water = 1 kcal/kg°C):

1. 1400 kg
2. 2800 kg
3. 14000 kg
4. 700 kg

43. Boiler feed water has a TDS of 120 mg/l and the maximum permissible TDS in the boiler drum is 3500 mg/l. The required blow-down (as % of feed) is approximately:

1. 29.2%
2. 0.34%
3. 3.43%
4. 12.0%

44. Air is approximately 77% N2 and 23% O2 by weight. Taking a 100 kg basis (N2 = 28, O2 = 32), the mean molecular weight of air is about:

1. 30.0
2. 28.8
3. 32.0
4. 28.0

45. Water flowing at 200 m^3/hr is heated through a temperature rise of 7°C. The heat duty is (1 m^3 water = 1000 kg, Cp = 1 kcal/kg°C):

1. 140,000 kcal/hr
2. 1,400,000 kcal/hr
3. 14,000 kcal/hr
4. 1400 kcal/hr

46. A solid is dried from 55% moisture to 10% moisture. For 60 kg/hr of wet feed, the moisture removed is:

1. 27 kg/hr
2. 33 kg/hr
3. 30 kg/hr
4. 45 kg/hr

47. Electrical energy of 1 kWh is equivalent to how much heat energy?

1. 860 kcal
2. 632 kcal
3. 1000 kcal
4. 427 kcal

48. Coal contains 67.2% carbon and 22.3% ash. The refuse contains 7.1% carbon (rest is ash). Taking 100 kg of coal as basis, the fraction of original carbon left unburnt in the refuse is about:

1. 7.1%
2. 2.5%
3. 1.7%
4. 24%

49. Which of the following will not be a major component of mass balance

1. steam
2. water
3. raw materials
4. lubricating oil

50. The number of moles of water contained in 54 kg of water is ------------

1. 2
2. 3
3. 4
4. 5

51. In a drying process, moisture is reduced from 60% to 30%. Initial weight of the material is 200 kg. Calculate the weight of the product

1. 104
2. 266.6
3. 130
4. 114.3

52. If air consists of 77% by weight of nitrogen and 23% by weight of oxygen, the mean molecular weight of air is

1. 11.9
2. 28.8
3. 17.7
4. insufficient data

53. An oil-fired boiler operates at an excess air of 6%. If the stoichiometric air fuel ratio is 14 then for an oil consumption of 100 kg per hour, the flue gas liberated in kg/hr would be

1. 1484
2. 1584
3. 106
4. 114

54. A process requires 10 Kg of fuel with a calorific value of 5000 kcal/kg. The system efficiency is 80% and the losses will be

1. 10000 kcal
2. 45000 kcal
3. 500 kcal
4. 2000 kcal

55. A centrifugal pump draws 12 m3/hr. Due to leakages from the body of the pump a continuous flow of 2 m3/hr is lost. The efficiency of the pump is 55%. The flow at the discharge side would be

1. 12 m3/hr
2. 10 m3/hr
3. 5.5 m3/hr
4. 6.6 m3/hr

56. 20 m3 of water is mixed with 30 m3 of another liquid with a specific gravity of 0.9. The volume of the mixture would be

1. 47 m3
2. 48 m3
3. 50 m3
4. 53 m3

57. 1 kg of wood contains 15% moisture and 7% hydrogen by weight. How much water is evaporated during complete combustion of 1 kg of wood

1. 0.78 kg
2. 220 grams
3. 0.15 kg
4. 0.63 kg

58. A process requires 120 kg of fuel with a calorific value of 4800 kcal/kg for heating with a system efficiency of 82 %. The loss would be____________.

1. 576000 kcal
2. 472320 kcal
3. 103680 kcal
4. 480000 kcal

59. 54 kg of water is mixed with 0.34 moles of salt to make a solution. The mole fraction of the solution is

1. 0.1
2. 18.36
3. 158.8
4. none of the above

60. C2H4 + xO2 -----> 2CO2 + yH2O, what is the value of x + y?

1. 2
2. 3
3. 5
4. 8

61. A solution of common salt is prepared by adding 25 kg of salt to 100 kg of water. The weight fraction of solution is

1. 20%
2. 25%
3. 4%
4. none of the above

62. The number of moles in 90 kg of water is

1. 5
2. 18
3. 2
4. none of the above

63. A process requires 100 kg of fuel with a calorific value of 5000 kcal/kg for heating with a system efficiency of 83%. The loss would be

1. 235,000 kcal
2. 85,000 kcal
3. 103680 kcal
4. 415,000 kcal

64. The number of moles of water contained in 27 kg of water is

1. 5
2. 3
3. 4
4. 1.5

65. In a drying process, moisture is reduced from 50% to 30%. Initial weight of the material is 100 kg. Calculate the weight of the final product in kg

1. 80
2. 86
3. 71.4
4. 74.3

66. A gaseous mixture contains 7.50 gms of H2 and 3.25 gms of O2 and 5.55 gms of N2. The Mole fraction of N2 is

1. 0.34
2. 0.03
3. 0.0294
4. 0.049

67. A dry feed containing 7% moisture was fed to a water spray chamber to increase the moisture content to 35% in the dry feed. The output feed quantity coming from the spray chamber is

1. 0.5 kg/kg of input feed
2. 1.43 kg/kg of input feed
3. 1.48 kg/kg of input feed
4. 2.66 kg/kg of input feed

68. 1 mole of sulphur reacts with X moles of H2SO4 to form Y moles of H2O and Z moles of SO2, then (X/Y) + Z is

1. 2
2. 4
3. 1
4. 3

1. State the purpose of carrying out a material and energy (M&E) balance for an industrial process.

2. State the law of conservation of mass and the law of conservation of energy on which M&E balances are based.

3. Write the general material balance equation for a unit operation and explain why a 'Losses' term is included.

4. Write the general energy balance equation for a unit operation and state why energy balances are more complicated than mass balances.

5. In the material balance of a process, where are the recycle stream and the by-product placed — on the input side or the output side?

6. Distinguish between a steady-state process and an unsteady-state process, and between a continuous and a batch process.

7. Describe the different levels at which a material balance can be developed.

8. List the typical steps in carrying out a material balance for a process.

9. What is a process flow diagram and what should it represent when prepared for a material and energy balance?

10. Define the four ways of expressing material concentration used when choosing units for a material balance.

11. What is a heat balance, and why must enthalpy always be referred to a datum?

12. How can energy be 'lost' in a system, and what are the main causes of this loss of usable energy?

13. Apply the law of conservation of energy to a power plant (Rankine) cycle and state the cycle energy balance.

14. Define the thermodynamic efficiency of a process and explain what 'sinks' represent in an energy balance.

15. Using the conservation of energy, explain how a change in stored energy is inferred when the input does not equal the output.

16. Explain the concept of a 'facility as an energy system' and the three areas into which energy/utility systems are classified.

17. Explain the Sankey diagram with an example.

18. What basic data is needed for an energy analysis, and why is the Sankey diagram preferred to present it?

19. State the heat-duty formula used in a heat balance and the relation converting electrical energy to heat (kcal).

20. List the key physical constants used in Chapter-5 material and energy balance calculations.

21. Explain the method (tie-component / dry-solids balance) for solving a drying or evaporation material balance.

22. Explain how to compute the cooling-water requirement to cool a hot body, using a furnace shell as an example.

23. During an air pollution monitoring study, the inlet gas stream to a bag filter was 200,000 m³/hr and the outlet stream was 210,000 m³/hr. Dust load at the inlet was 6 g/m³ and at the outlet 0.1 g/m³. How much dust (kg/hr) was collected in the bag filter bin?

24. A coal sample from the mine contains 67.2% carbon and 22.3% ash. The refuse after combustion contains 7.1% carbon and the rest is ash. Compute the % of the original carbon left unburnt in the refuse.

25. A boiler is fed with soft water containing 120 mg/l dissolved solids. As per IS standards the dissolved solids in the boiler should not exceed 3500 mg/l (boilers up to 2 MPa). A continuous blowdown system is adopted. Find the percentage of feed water that is blown down.

26. A shell-and-tube heat exchanger is cooled with a stream of demineralized water. Evaluate the total heat rejected to the cooling water (kcal/hr) if the water flow rate is 200 m³/hr and the temperature rise is 7°C.

27. An autoclave holds 1000 cans of pea soup heated to 100°C; the cans must be cooled to 40°C. Each can weighs 60 g (Cp 0.50 kJ/kg°C) and holds 0.45 kg pea soup (Cp 4.1 kJ/kg°C). Heat content of the autoclave walls above 40°C is 1.6×10⁴ kJ. Cooling water enters at 15°C and leaves at 35°C. How much cooling water is required (no wall heat loss)?

28. A 10% solids solution (entering at 5.0 kg/s) is mixed with a 25% solids solution; a single output of 20% solids is removed. Find the other flow rates (no accumulation).

29. In a textile mill an evaporator concentrates a liquor containing 6% solids (w/w) to an output containing 30% solids (w/w). Calculate the water evaporated per 100 kg of feed.

30. In continuous centrifuging, 35,000 kg of whole milk containing 4% fat is separated over 6 hours into skim milk (0.45% fat) and cream (45% fat). Find the flow rates of the two output streams.

31. Skim milk made by removing fat from whole milk contains 90.5% water, 3.5% protein, 5.1% carbohydrate, 0.1% fat and 0.8% ash. If the original whole milk contained 4.5% fat (only fat removed, no losses), find the whole-milk composition.

32. A textile dryer consumes 4 m³/hr of natural gas (CV 800 kJ/mole) and dries 60 kg/hr of wet cloth from 55% to 10% moisture. Estimate its overall thermal efficiency (latent heat of evaporation only).

33. A paper machine produces 340 TPD; inlet/outlet dryness is 40%/95%; evaporated moisture at 80°C (enthalpy 632 kcal/kg); steam supplied at 35 kg/cm² (latent heat 513 kcal/kg). Find (a) moisture evaporated and (b) steam required per hour.

34. An evaporator is fed 10,000 kg/hr of 1% solids solution (feed at 38°C), concentrated to 2% solids. Steam enters at enthalpy 640 kcal/kg, condensate leaves at 100°C; enthalpies: feed 38.1, product 100.8, vapour 640 kcal/kg. Find the vapour formed and the steam used per hour.

35. 20 kg of salt is dissolved in 100 kg of water giving a solution of density 1323 kg/m³. Express the salt concentration as (a) weight fraction, (b) weight/volume fraction, (c) mole fraction, (d) molar concentration. (Mol wt: salt 58.5, water 18.)

36. In a chemical process two reactants A (200 kg) and B (200 kg) react in equal proportion. If the conversion is 50%, calculate the weight of product formed.

37. In a heat-treatment furnace, material is heated from an ambient 30°C to 800°C. Taking the specific heat as 0.13 kcal/kg°C, what is the energy content of one kg of material after heating?

38. Using the milk pasteurizer as an example, show how an energy (heat) balance can be applied to a whole process and to only a part of a process.

39. At what stages of a process is a material balance used, from concept to production?

40. If no chemical changes occur in a plant, how does the law of conservation of mass apply to each individual component? Illustrate with a sugar plant.

41. Air consists of 77% by weight nitrogen and 23% by weight oxygen. Calculate (a) the mean molecular weight of air and (b) the mole fraction of oxygen. (Mol wt: N₂ = 28, O₂ = 32.)

42. A coal sample contains 64% carbon and 24% ash. The refuse after combustion contains 8% carbon and the rest ash. Compute the % of the original carbon left unburnt in the refuse.

43. Steam heats 5 kL/hr of furnace oil from 30°C to 90°C. Furnace-oil Cp = 0.22 kcal/kg°C, sp. gravity 0.95. (a) Steam per hour needed if steam latent heat is 510 kcal/kg. (b) If steam costs Rs 3.40/kg and electricity Rs 6/kWh, which is more economical?

44. Explain how a process or unit operation is represented as a 'box', and what must be true of the mass crossing the box.

45. Distinguish between a gross (overall) material balance and a constituent (component) material balance.

46. What is specific energy consumption (SEC), and how does an energy balance help establish it?

47. In a heat exchanger the inlet and outlet temperatures of the cooling water are 30 oC and 36 oC. The flow rate of cooling water is 400 litres/hr. The process fluid enters the heat exchanger at 60 oC and leaves at 45 oC. Find out the flow rate of the process fluid? (Cp of process fluid is 0.8 kCal/kg oC).

48. A cotton mill dries 1200 kg of wet fabric in a drier from 54% initial moisture to 9% final moisture. How many kilograms of water are removed during drying operation?

49. In a heat exchanger the inlet and outlet temperatures of the cooling water are 30 oC and 36 oC. The flow rate of cooling water is 500 litres/hr. The process fluid enters the heat exchanger at 60 oC and leaves at 45 oC. Find out the flow rate of the process fluid? (Cp of process fluid is 0.8 kCal/kg oC).

50. A cotton mill dries 2000 kg of wet fabric in a drier from 54% initial moisture to 9% final moisture. How many kilograms of water are removed during drying operation?

51. A Diesel Generator performance trial gives specific generation of 3.5 kWh per liter of diesel. The cooling water loss and exhaust flue gas loss as percentage of fuel input are 28% and 32% respectively. The calorific value of diesel is 10,200 kcal/kg. The specific gravity of Diesel is 0.85. Calculate unaccounted loss as percentage of input energy.

52. A Diesel Generator performance trial gives specific generation of 3.5 kWh per liter of diesel. The cooling water loss and exhaust flue gas loss as percentage of fuel input are 29% and 31% respectively. The calorific value of diesel is 10,200 kcal/kg. The specific gravity of Diesel is 0.85. Calculate unaccounted loss as percentage of input energy.

53. A gas fired water heater heats water flowing at a rate of 20 litres per minute from 25 0 C to 85oC. If the GCV of the gas is 9200 kcal/kg, what is the rate of combustion of gas in kg/min (assume efficiency of water heater as 82%)

54. In a process plant, an evaporator concentrates a liquor containing solids of 6% by w/w (weight by weight) to produce an output containing 30% solids w/w. calculate the evaporation of water per 500 kgs of feed to the evaporator.

55. In a chemical factory where dyes are made, wet cake at 30 OC consisting of 60% moisture is put in a dryer to obtain an output having only 5% moisture, at atmospheric pressure. In each batch about 120 kgs of material is dried. a. The quantity of moisture removed per batch. b. What is the total quantity ( sensible & latent) of heat required to evaporate the moisture, if the latent heat of water is 540 kcal/kg at atmospheric conditions, Ignore heat absorbed by the solids c. Find the quantity of steam required for the drying process (per batch), if steam at 4 kg/cm2 is used for generating hot air in the dryer and the dryer efficiency is 80%. Latent heat of steam at 4 kg/cm2 is 520 kcal/kg.

56. In a heat treatment shop, steel components are heat-treated in batches of 80 Tons. The heat treatment cycle is as follows;  Increase temperature from 30 OC to 850 OC in 3 hours.  Maintain 850 OC for 1 hour (soaking time).  Cool the material to 60 OC in 4 hours. a) Calculate the efficiency of the furnace, if the specific heat of steel is 0.12 kcal/kg OC and fuel oil consumption per batch is 1400 litres.  GCV of fuel oil - 10200 kcal/kg,  Cost of fuel oil - Rs. 46,000/kL,  Sp. gr. of fuel oil - 0.92. b) Due to high cost of oil, the plant management decides to convert to a lower operating cost LPG fired furnace lined on the inside with ceramic fibre insulation and with an operating efficiency of 80%, for same requirement. The investment towards installation of the new furnace is Rs. 50 lakhs. Calculate the Return on Investment, if the plant operates two batches per day and 250 days in a year.  Cost of LPG - Rs. 75/kg,  GCV of LPG - 12500 kcal/kg.

57. In a 100 TPD Sponge Iron plant, the sponge iron is fed to the Induction melting furnace, producing molten steel at 88% yield. The Energy consumption details are as follows: Coal Consumption : 130 TPD GCV of coal : 4500 kcal/kg Power Purchased from Grid : 82400 kWh / day Specific Energy consumption for Kiln producing Sponge Iron: 120 kWh / ton sponge iron 82400 kWh/day from Grid Factory Boundary Electricity for Induction Melting 130 TPD Coal Furnace 4500 kcals/kg 100 TPD Sponge Induction Melting Iron Ore Iron Molten Sponge Iron Kiln Furnace steel Grid Electricity Yield: 88% 120 kWh/t of Sponge iron Calculate the following 1. Specific Energy Consumption of Induction melting furnace in terms of kWh/ton of molten steel 2. Specific Energy Consumption of the entire plant, in terms of kcal/kg of molten steel (product). 3. Total Energy Consumption of Plant in Tons of Oil Equivalent (TOE )

58. In a 100 TPD Sponge Iron plant, the sponge iron is fed to the Induction melting furnace, producing molten steel at 86% yield. The Energy consumption details are as follows: Coal Consumption : 130 TPD GCV of coal : 4500 kcal/kg Power Purchased from Grid : 82400 kWh / day Specific Energy consumption for Kiln producing Sponge Iron: 120 kWh / ton sponge iron 82400 kWh/day from Grid Factory Boundary Electricity for Induction Melting 130 TPD Coal Furnace 4500 kcals/kg 100 TPD Sponge Induction Melting Iron Ore Iron Molten Sponge Iron Kiln Furnace steel Grid Electricity Yield: 86% 120 kWh/t of Sponge iron Calculate the following 1. Specific Energy Consumption of Induction melting furnace in terms of kWh/ton of molten steel. 2. Specific Energy Consumption of the entire plant, in terms of kcal/kg of molten steel (product). 3. Total Energy Consumption of Plant in Tons of Oil Equivalent (TOE ).

59. In a chemical factory where dyes are made, wet cake at 30 OC consisting of 60% moisture is put in a dryer to obtain an output having only 8% moisture, at atmospheric pressure. In each batch about 120 kgs of material is dried. a. The quantity of moisture removed per batch. b. What is the total quantity (sensible & latent) of heat required to evaporate the moisture, if the latent heat of water is 540 kcal/kg at atmospheric conditions, Ignore heat absorbed by the solids c. Find the quantity of steam required for the drying process (per batch), if steam at 4 kg/cm2 is used for generating hot air in the dryer and the dryer efficiency is 70%. Latent heat of steam at 4 kg/cm2 is 520 Kcal/kg.

60. In a heat treatment shop, steel components are heat-treated in batches of 80 Tons. The heat treatment cycle is as follows;  Increase temperature from 30 OC to 850 OC in 3 hours.  Maintain 850 OC for 1 hour (soaking time).  Cool the material to 60 OC in 4 hours. a) Calculate the efficiency of the furnace, if the specific heat of steel is 0.12 kcal/kg OC and fuel oil consumption per batch is 1400 litres. GCV of fuel oil - 10200 kcal/kg, Cost of fuel oil - Rs. 46,000/kL, Sp. gr. of fuel oil - 0.92. b) Due to high cost of oil, the plant management decides to convert to a lower operating cost LPG fired furnace lined on the inside with ceramic fibre insulation and with an operating efficiency of 75%, for same requirement. The investment towards installation of the new furnace is Rs. 50 lakhs. Calculate the Return on Investment, if the plant operates two batches per day and 270 days in a year. Cost of LPG - Rs. 75/kg, GCV of LPG - 12500 kcal/kg.

61. A paint drier requires 75.4 m3/min of air at 93°C, which is heated in a steam-coil unit. How many kg of steam at 4 bar does this unit require per hour? The density of air is 1.2 kg/m3 and specific heat of air is 0.24 kcal/kg°C. The ambient temperature is 32°C. Steam table data: Pressure 4 bar, Temperature 143 °C, Enthalpy of water 143 kcal/kg, Enthalpy of evaporation 510 kcal/kg, Enthalpy of steam 653 kcal/kg.

62. A continuous centrifuge separates 36,000 kg of whole milk containing 4% fat in 6-hour period into skim milk with 0.40% fat and cream with 40% fat. Find out the flow rates of whole milk, cream and skim milk using mass balance.

63. A conveyor delivers coal with a width of 0.9 m and coal bed height of 0.15 m at a speed of 0.8 m/s. Determine the coal delivery in tons per hour considering the coal density as 1.1 ton/m3.

64. In a textile industry, 25,000 kg/hr water is currently being heated from 28 °C to 80 °C by indirect heating of steam in dyeing machines. It is proposed to recover heat from the hot effluent and generate hot water at 45 °C which would be further raised to 80 °C by steam. Estimate the reduction in steam in kg/hr considering the latent heat of steam as 520 kcal/kg in both the cases.

65. A sample of coal is found to contain 64% carbon and 24% ash. The refuse obtained at the end of combustion is analyzed and found to contain 8% carbon and the rest is ash. Compute the percentage of the original carbon unburnt in the refuse. (5 Marks)

66. A continuous centrifuge separates 36,000 kg of whole milk containing 4% fat in a 6-hour period into skim milk with 0.40% fat and cream with 40% fat. Find out the flow rates of whole milk, cream and skim milk using mass balance. (5 Marks)

67. A food dryer processes 1,000 kg/hr of wet material with an initial moisture content of 55% (wet basis) and dries it to a final moisture content of 10% (wet basis). Steam Flow: 2,500 kg/hr at 3.5 bar (enthalpy = 660 kcal/kg); Latent heat of water vaporization = 540 kcal/kg; Specific heat of dry material = 0.45 kcal/kg deg C; Drying temperature rise = 60 deg C; Ignore heat loss and assume 100% steam use for moisture removal and solid heating. (Each 1 Mark) a) Calculate the mass of bone-dry solid in the feed b) Calculate the mass of water removed per hour c) Estimate the energy required to evaporate the moisture d) Estimate the energy required to heat the dry solids e) Calculate the total energy input from steam

1. An evaporator is fed with 10,000 kg/hr of a solution having 1% solids. The feed is at 38 degC and is to be concentrated to 2% solids. Steam enters at a total enthalpy of 640 kcal/kg and the condensate leaves at 100 degC. Enthalpy of feed = 38.1 kcal/kg, enthalpy of product (thick liquor) = 100.8 kcal/kg and enthalpy of vapour = 640 kcal/kg. Find (i) the mass of vapour formed per hour and (ii) the mass of steam used per hour.

2. Production rate from a paper machine is 340 tonnes per day (TPD). Inlet and outlet dryness to the paper machine are 40% and 95% respectively. Evaporated moisture temperature is 80 degC. To evaporate the moisture, steam is supplied at 35 kg/cm2 (latent heat = 513 kcal/kg). Assume 24 hours/day operation and enthalpy of evaporated moisture = 632 kcal/kg. Estimate (a) the quantity of moisture to be evaporated per hour and (b) the input steam quantity required for evaporation per hour.

3. A wet scrubber removes fine dust from an inlet gas stream with a spray of water so that the outlet gas meets emission standards. Stream 1 (recirculation liquid back to the scrubber) = 4.54 m3/hr. The liquid withdrawn for treatment and disposal (stream 4) = 0.454 m3/hr. The inlet gas (stream 2) is completely dry and the outlet gas (stream 6) carries 272.16 kg/hr of moisture evaporated in the scrubber. Make-up water is added as stream 5. How much make-up water must be continually added to keep the unit running?

4. An autoclave contains 1000 cans of pea soup heated to an overall temperature of 100 degC. The cans are to be cooled to 40 degC before leaving the autoclave. How much cooling water is required if it enters at 15 degC and leaves at 35 degC? The specific heats of the pea soup and the can metal are 4.1 and 0.50 kJ/kg degC respectively. Each can weighs 60 g and contains 0.45 kg of pea soup. The heat content of the autoclave walls above 40 degC is 1.6 x 10^4 kJ, and there is no heat loss through the walls.

5. A bag filter is used to remove dust from a gas stream in a cement plant. Inlet gas to the bag filter is 1,69,920 m3/hr with a dust loading of 4577 mg/m3. Outlet gas from the bag filter is 1,85,040 m3/hr with a dust loading of 57 mg/m3. What is the maximum quantity of ash that will have to be removed per hour from the bag filter hopper?

6. A furnace shell has to be cooled from 90 degC to 55 degC. The mass of the furnace shell is 2 tonnes and its specific heat is 0.2 kcal/kg degC. Water is available at 28 degC and the maximum allowed increase in water temperature is 5 degC. Calculate the quantity of water required to cool the furnace. Neglect heat loss.

7. A textile dryer consumes 4 m3/hr of natural gas with a calorific value of 800 kJ/mole. The throughput of the dryer is 60 kg of wet cloth per hour, drying it from 55% moisture to 10% moisture. Estimate the overall thermal efficiency of the dryer, taking into account the latent heat of evaporation only. (1 mole of gas occupies 22.4 litres at STP; latent heat of evaporation of water = 2257 kJ/kg.)

8. In a continuous centrifuging of milk, 35,000 kg of whole milk containing 4% fat is to be separated in a 6 hour period into skim milk with 0.45% fat and cream with 45% fat. What is the flow rate of the two output streams from the continuous centrifuge?

9. Skim milk is prepared by removing some fat from whole milk. The skim milk contains 90.5% water, 3.5% protein, 5.1% carbohydrate, 0.1% fat and 0.8% ash. If the original whole milk contained 4.5% fat, calculate the composition of the whole milk, assuming that only fat was removed and there are no processing losses.

10. A solution which is 80% oil, 15% usable by-products and 5% impurities enters a refinery. One output is 92% oil and 6% usable by-products. The other output is 60% oil and flows at 1000 lit/hr (assume no accumulation, percentages by volume). Find (a) the flow rate of the input, (b) the percent composition of the 1000 lit/hr output, and (c) what percent of the original impurities are in the 1000 lit/hr output.

11. Prepare the energy balance of a Diesel Generator and draw a Sankey diagram. Given: calorific value of diesel = 10,000 kcal/litre; average energy generated = 4.07 kWh/litre; alternator efficiency = 96%; stack (flue gas) losses = 33%; coolant losses = 24%; and the balance is radiation losses. (1 kWh = 860 kcal.)

12. A foundry has an induction furnace of 5 TPH with a specific energy consumption of 620 kWh/tonne of liquid metal. The yield of foundry castings is 60%. The castings are heat treated in an oil-fired furnace consuming 75 kg oil/tonne of castings. Find the energy consumption per tonne of finished product in terms of oil equivalent. (GCV of oil = 10,000 kcal/kg; 1 kWh = 860 kcal.)

13. (a) A fuel used in a boiler contains 40% carbon and 23% ash. The refuse obtained after combustion is analysed and found to contain 7% carbon and the rest ash. Compute the percentage of the original carbon in the fuel that remains unburnt in the refuse. (5 marks) (b) During an ESP performance study, the inlet gas stream to the ESP is 2,89,920 Nm3/hr with a dust loading of 5500 mg/Nm3, and the outlet gas stream is 3,01,100 Nm3/hr with a dust loading of 110 mg/Nm3. How much fly ash is collected in the system in kg/hr? (5 marks)

14. In a Chlor-Alkali plant, an evaporator was designed to concentrate 500 kg of liquor containing 7% w/w solids to 45% solids w/w in the output. Presently the output from the evaporator has 30% solids w/w. The energy manager suggested overhauling the evaporator to achieve the design solids in the output. Calculate the percentage improvement in water removal in the evaporator after overhauling.

15. Saturated steam at 1 atm is discharged from a turbine at 1200 kg/h. Superheated steam at 300 degC and 1 atm is required as feed to a heat exchanger. To produce it, the turbine discharge is mixed with superheated steam at 400 degC, 1 atm (specific volume 3.11 m3/kg). Calculate the amount of superheated steam at 300 degC produced and the volumetric flow rate of the 400 degC steam. (Enthalpies: saturated steam at 1 atm = 2676 kJ/kg; 400 degC steam = 3278 kJ/kg; 300 degC steam = 3074 kJ/kg.)

16. In a drying operation, the moisture content of the feed to a calciner must be held at 15% (w/w) to prevent lumping and sticking. This is achieved by mixing the fresh feed (30% moisture w/w) with a recycle stream of dried material (3% moisture w/w). What fraction of the dried product must be recycled?

17. A paper drying machine has a production capacity of 500 TPD and currently operates at an output of 480 TPD. The dryness of the paper is 60% at the inlet and 95% at the outlet. Steam is supplied at 4 kg/cm2 with a latent heat of 510 kcal/kg. The evaporated moisture is at about 100 degC with an enthalpy of 640 kcal/kg. The plant operates 24 hours per day. Assuming only the latent heat of steam is used for drying and neglecting the enthalpy of moisture in the wet paper, estimate (i) the quantity of moisture to be evaporated per hour and (ii) the input steam quantity required per hour.

18. The production through a paper machine is 300 tonnes per day (TPD). The inlet and outlet dryness to the paper machine are 50% and 95% respectively. The evaporated moisture temperature is 80 degC. Steam is supplied at 3.5 kg/cm2 (latent heat 513 kcal/kg). Assuming 24 hours/day operation and enthalpy of evaporated moisture = 632 kcal/kg, estimate (i) the quantity of moisture to be evaporated in kg/hr and (ii) the steam quantity required for evaporation in kg/hr.

19. An evaporator is fed with 5000 kg/hr of a solution having 0.5% solids at 38 degC, and is concentrated to 1% solids. Steam enters at total enthalpy 640 kcal/kg and condensate leaves at 100 degC. Enthalpy of feed = 38.1 kcal/kg, product solution = 100.8 kcal/kg, vapour = 640 kcal/kg. Find the mass of vapour formed per hour and the mass of steam used per hour.

20. An evaporator is to be fed with 10,000 kg/hr of a solution having 1% solids. The feed is at 38 oC. It is to be concentrated to 2% solids. Steam is entering at a total enthalpy of 640 kCal/kg and the condensate leaves at 100 oC. Enthalpies of feed are 38.1 kcal/kg, product solution is 100.8 kCal/kg and that of the vapour is 640 kCal/kg. Find the mass of vapour formed per hour and the mass of steam used per hour.

21. An evaporator is to be fed with 6000 kg/hr of a solution having 1% solids. The feed is at 38 oC. It is to be concentrated to 2% solids. Steam is entering at a total enthalpy of 640 kCal/kg and the condensate leaves at 100 oC. Enthalpies of feed are 38.1 kcal/kg, product solution is 100.8 kCal/kg and that of the vapour is 640 kCal/kg. Find the mass of vapour formed per hour and the mass of steam used per hour.

22. A bag house is being used to remove dust from an air exhaust stream flowing at 100 m3/min. The dirty air contains 15 g/m3 of particles, while the cleaned air from the bag house contains 0.02 g/m3. The industry's operating permit allows the exhaust stream to contain as much as 0.9 g/m3. For various operating reasons, the industry wishes to bypass some of the dirty air around the bag house and blend it back into the cleaned air so that the total exhaust stream meets the permissible limit. Assume no air leakage and negligible change in pressure or temperature of the air throughout the process. Draw a schematic diagram and calculate the flow rate of air through the bag house and the mass of dust collected per day in kg. [refers to a figure in the original paper]

23. a) A furnace heating steel ingots is fired with oil having a calorific value of 10,500 kCal/kg and efficiency of 75%. Calculate the oil consumption per hour when the throughput of the furnace is 50 TPH and the temperature of the finished product is 600 oC. Take ambient temperature as 30 oC and Specific Heat of Steel as 0.12 kCal/kg oC b) In Steel industry, different types of gases are generated during steel making process. Volumetric Flow rate and Calorific Values of each gases are: Type of Gas Flow (SM3/hr) CV (kCal/SM3) Coke Oven Gas 75,000 4,000 COREX Gas 50,000 2,000 BOF Gas 55,000 1,500 Blast Furnace Gas 80,000 700 All these gases are mixed in the gas mixer before combustion. Find out the Calorific Value (in kCal/SM3) of mix gas.

24. The production capacity of a paper drying machine is 500 TPD and is currently operating at an output of 480 TPD. To find out the steam requirement for drying, the Energy Manager measures the dryness of the paper both at inlet and outlet of the paper drying machine which found to be 60% and 95% respectively. The steam is supplied at 4 kg/cm2, having a latent heat of 510 kCal/kg. The evaporated moisture temperature is around 100 0C having enthalpy of 640 kCal/kg. Plant operates 24 hours per day. Assume only latent heat of steam is being used for drying the paper and neglect the enthalpy of the moisture in the wet paper. i) Estimate the quantity of moisture to be evaporated per hr. ii) Input steam quantity required for evaporation per hr.

25. Saturated steam at 1 atm is discharged from a turbine at 1200 kg/h. Superheated steam at 300 0C and 1 atm is needed as a feed to a heat exchanger. To produce it, the turbine discharge stream is mixed with superheated steam at 400 0C, 1 atm and specific volume of 3.11 m3/kg. Calculate the amount of superheated steam at 300 0C produced and the volumetric flow rate of the 400 0C steam.

26. Saturated steam at 1 atm is discharged from a turbine at 1000 kg/h. Superheated steam at 300 0C and 1 atm is needed as a feed to a heat exchanger. To produce it, the turbine discharge stream is mixed with superheated steam at 400 0C, 1 atm and specific volume of 3.11 m3/kg Calculate the amount of superheated steam at 300 0C produced and the volumetric flow rate of the 400 0C steam.

27. In a Chlor-Alkali plant, an evaporator was designed to concentrate 500 kg of liquor containing solids of 7% w/w (weight by weight) to 45% solids w/w in the output. Presently the output from evaporator has 30% solids w/w. The energy manager suggested overhauling the evaporator to achieve the design rate of solids w/w in the output. Calculate the percentage improvement in water removal in the evaporator after overhauling of the evaporator.

28. A medium size chemical plant receives electricity from grid and also generates electricity from coal based Captive Power Plant (CPP). Coal is also used for process requirements. The fine coal from CPP is sold to neighboring plant. The annual energy details are given below: Electricity purchased from grid 5 MU; Electricity exported to grid 11 MU; Power generation from CPP 36 MU; Power supplied from CPP to Process plant 25 MU; Fine coal sold to neighboring unit 1000 ton; Coal used for process plant 5000 ton; GCV of coal 4500 kcal/kg; Heat rate of CPP 3500 kcal/kWh; Annual Operating Hours 7200. Calculate a. Energy usage in TOE (Tons of oil equivalent) (5 Marks) b. Coal used in CPP (3 Marks) c. Calculate the CPP operating power in MW. (2 Marks)

29. a) A sample of fuel being used in a boiler is found to contain 40% carbon and 23% ash. The refuse obtained after combustion is analyzed and found to contain 7% carbon & the rest is ash. Compute the percentage of the original carbon in fuel which remains as unburnt in the refuse. (5 Marks) b) During an ESP performance evaluation study, the inlet gas stream to ESP is 2,89,920 Nm3/hr and the dust loading is 5,500 mg/Nm3. The outlet gas stream from ESP is 3,01,100 Nm3/hr and the dust loading is 110 mg/Nm3. How much fly ash is collected in the system in kg/hr? (5 Marks)

30. The production through a paper machine is 300 tonnes per day (TPD). Inlet and outlet dryness to paper machine is 50% and 95% respectively. Evaporated moisture temperature is 80 deg C. To evaporate moisture, the steam is supplied at 3.5 kg/cm2. Latent heat of steam at 3.5 kg/cm2 is 513 kcal/kg. Assume 24 hours/day operation and estimate the following (Each 5 Marks): i) Quantity of moisture to be evaporated in kg/hr ii) Steam quantity required for evaporation in kg/hour. Note: Consider enthalpy of evaporated moisture as 632 kcal/kg.

31. A) In an industry, de-humidified air containing 0.0089 kg H2O/kg air is required to be fed to a dryer for textile drying. The atmospheric air has a specific humidity of 0.02 kg H2O/kg air. The atmospheric air is to be passed through a de-humidifying system that reduces the absolute humidity to the desired level. The de-humidifying system installed has the capacity to reduce the absolute humidity to 0.0005 kg H2O/kg air. Therefore, to get the desired humidity of 0.0089 kg H2O/kg air at the de-humidifying system outlet, a part of fresh atmospheric air by-passes and mixes at the outlet of the de-humidification system. Find out the mass of water removed per 100 kg of air fed to the dehumidifier and the percentage of by-passed air. (4 Marks) B) The waste acid contains 30% H2SO4, 35% HNO3 and 35% water. The waste acid is to be concentrated to contain 39% H2SO4 and 42% HNO3 by addition of concentrated Sulphuric acid containing 98% H2SO4 and concentrated Nitric acid containing 72% HNO3. Calculate the quantities of three acids to be mixed to get 1000 kg of desired mixed acid. (6 Marks) [refers to a figure in the original paper]

32. An evaporator is to be fed with 5000 kg/hr of a solution having 0.5% solids. The feed is at 38 deg C and is to be concentrated to 1% solids. Steam is entering at a total enthalpy of 640 kcal/kg and the condensate leaves at 100 deg C. Enthalpies of feed are 38.1 kcal/kg, product solution is 100.8 kcal/kg and that of the vapour is 640 kcal/kg. Find the mass of vapour formed per hour and the mass of steam used per hour. (10 Marks)