## A plant consumes 4,500 tons of furnace oil

## Energy Management

**Questions:**

**Q1.** A plant consumes 4,500 tons of furnace oil per year (GCV =10,200 kCal/kg), as well as 43,000 MWh of electricity per year. Draw the pie-chart of percentage share of each type of energy based on consumption in kCal (1 kWh = 860 kCal)

**Q2.** How much Stream is recuire in a heat exchange to heat 120 kg/ hour of a process fluid From 40o C to 90o C. The specific heat of process fluid is 0.24 kCal/kg oC and the latent heat of steam is 540 kCal/ kg

**Q3. **The following table shows the import bill of fossil fuels in million metric tonnes (MMT) and its cost in Crores Rupees over the last eight years.

#### (i) calculate the average annual percentage increase of fossil fuel imports

#### (ii) calculate the average annual percentage increase of the import bill

#### (iii) calculate the average costs for the last eight years, in Rs. Per metric ton of imported fossil fuels.

**Q4. **Fuel substitution from a high cost fuel to a low cost fuel in boilers is common to reduce energy bill. For the following situations calculate:

#### a) annual reduction in energy costs in Crore Rs.

#### b) annual change in energy consumption in %. (Calorific value of fuels not required for calculations)

__Before substitution:__

#### Steam output = 6 tons/hour

#### Fuel consumption = 1 ton oil per 13 tons of steam.

#### Operating hours = 6400 / Year

#### Fuel costs = Rs.13,000 /ton of oil

#### Boiler thermal efficiency (yearly average) = 82%

__After Substitution:__

#### Steam output = 6 tons/hour

#### Fuel consumption = 3 tons of waste wood per 13 tons of steam

#### Fuel costs = Rs.2,000 / ton of waste wood

#### Boiler thermal efficiency (yearly average) = 74%

**Q5. **A company invests Rs.10 lakhs and completes an energy efficiency project at the beginning of year 1. The firm is investing its own money and expects an internal rate of return, IRR, of at least 26% on constant positive annual net cash flow of Rs.2 lakhs, over a period of 10 years, starting with year 1.

#### a) Will the project meet the firm’s expectations?

#### b) What is the IRR of this measure?

**Q6.** A waste heat recovery system can be installed in a furnace, which will cost Rs. 7,00,000/- to install. This system is expected to have a useful life of 6 years. The salvage value will be Rs. 2,00,000/-. The system will reduce the energy cost by Rs. 2,00,000/- per year, when it operates at full capacity. However the plant will be operating at partial capacity for the first 3 years and the annual energy savings will be at 70% of the energy cost savings at full capacity (Rs. 1,40,000/-). (20 Marks)

#### The new system will entail a maintenance cost of Rs. 10,000/- per year for the first 3 years and Rs.12,000 per year for the next 3 years. A major overhaul is required in the 3rd year, which will cost Rs 1,00,000/-

#### a) If discount rate is 10%, calculate the NPV and find out whether this energy conservation measure is profitable

#### b) What is the profitability index for the project?

**Q7. **An energy auditor undertakes the energy audit of a steam system. The operating data is given as per the schematic diagram given below Key data and assumptions are enunciated below:

#### a) Specific enthalpy of water at 10 kg/cm2 (g) pressure : 186 kCal/kg

#### b) Specific enthalpy of evaporation/latent heat at 10 kg/cm2 (g) pressure : 478 kCal/k

#### c) Dryness fraction of steam generated : 95

#### d) Coal consumption : 840 kg/ hr

#### e) Net calorific value (NCV) of imported coal : 6269 kCal/kg

#### f) Moisture in coal : 5%

#### g) Hydrogen in coal : 4%

#### Other parameters as indicated in the above figure :

#### Based on preliminary data assessment as stated above, calculate the following:

#### a) Feed water temperature to boiler

#### b) Boiler efficiency by direct method on GCV basis

#### c) If the condensate return is enhanced to 6 TPH (steam generation of 7 TPH remaining same) what will be the reduction in coal consumption?

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