CENG 301

Material and Energy Balances

Fall 2003

Project Data

Part 1: Design a Sulfur Dioxide Scrubber

  • A flow chart of the sulfur dioxide scrubber can be found here.
  • The average properties of the two coals are given in Tables 1 and 2 below. All other properties are as specified in Chapter 14 of Felder and Rousseau.
  • The sub-bituminous coal comes from the Cordero-Rojo mine in Powder River basin, Wyoming. It costs $4 per ton at the mine.
  • The lignite coal comes from the Calvert mine located near Franklin, Texas. It costs $16 per ton at the mine.
  • The power plant is located in Fort Bend county, near the Brazos Bend State Park.
  • The transportation cost for the coal is 2 ¢ per (ton)(mile) and the cost for limestone is $20 per ton.
  • Note1: In 2000, 52% of the electricity produced in the U.S. came from coal-fired plants.
  • Note 2: In 2001, about 32% of all coal used in the U.S. came from mines in the Powder River basin.

    •  

    Table 1: Average Coal Composition (Ultimate Analysis)

    Coal
    Ultimate Analysis, wt% (dry basis)
    C
    H
    O
    N
    S
    Ash

    Lignite

    55.0
    4.4
    13.0
    1.0
    1.7
    24.9
    Sub-bituminous
    72.5
    6.1
    17.2
    0.7
    0.4
    3.1

     

    Table 2: Average Coal Properties

     

    HHV

    (Btu/lb)

    Moisture

    kg/(100 kg dry coal)
    Source

    Lignite

    9,727
    52.7
    Texas
    Sub-bituminous
    13,606
    48.8
    Wyoming

 

Part 2: Further Reduction of Sulfur Dioxide Emissions by Conservation

  1. Conserve electrical energy by replacing all incandescent bulbs (IB) in our homes with fluorescent bulbs (FB)
    • Find out the amount of electricity for residential use in Houston. Assume that half of this power comes from coal-fired plants.
    • 7% of that amount is used for lighting.
    • Assume that all lighting comes from 60W incandescent bulbs. Calculate how many such bulbs there are in Houston.
    • Find out the price and the lifetime of the 15W FB and the 60W IB, respectively.
    • Calculate how much money can be saved each year if all 60W IB in Houston are replaced with 15W FB. Consider the cost of bulbs and electricity used in both cases.
    • How much SO2 must be released in order to provide the electricity needed to light our homes with incandescent or fluorescent lights?

  2. Conserve electrical energy by replacing all current air conditioning (AC) units with new, higher efficiency units.
    • Find out the amount of electricity for residential use in Houston. Assume that half of this power comes from coal-fired plants.
    • 30% of that amount is used for air conditioning.
    • Assuming that all current units have a 10 SEER rating, calculate how many such AC units there are in Houston.
    • Find out the average price of a 14 SEER AC unit (only the condenser needs to be replaced). What is the total cost of replacing all current AC units with new 14 SEER units?
    • Find the operating cost of a 10 SEER unit for 5 years.
    • Find the operating cost of a 14 SEER unit for 5 years. How much of the replacement cost do we recoup with the energy savings over this period?
    • How much SO2 must be released over 5 years in order to provide the electricity needed to cool our homes with 10 SEER or 14 SEER AC units?

 

NOTES:

  1. An air conditioner’s efficiency is rated according to its seasonal energy efficiency ratio (SEER). SEER is the annualized efficiency of a unit in Btu's removed from a home per W of electricity used.
     
    SEER = (Heat removed, Btu)/(Electricity used, W)

 

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