Coal-steam electricity generation

In summary, the power plant requires one reheat stage to maintain steam quality above 88.2%. The thermal efficiency of the power cycle is 38/6%. The annual sulfur dioxide emission from this power plant is 18.9216 metric tons.
  • #1
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Homework Statement


A coal-fired steam power plant operates on the ideal Rankine cycle. Feedwater from the
condenser at P1
= 10 kPa is pumped to the boiler at P2
= P3
= 20 MPa, where it is
superheated and exits the boiler at T3
= 550 °C.
The moisture content in the turbine is not to exceed 12% (i.e. steam quality is to be
maintained above x = 0.88 throughout the turbine). Up to two reheat stages can be added to
the steam cycle to satisfy this requirement.
If needed, one stage can be added to reheat the steam to T5
= 525 °C at P4
= P5
= 10 MPa. If
more reheating is required, a second stage can be added to reheat the steam to T7
= 500 °C at
P6
= P7
= 2.5 MPa.

(a). How many reheat stages are required for this power plant (no reheat, single reheat, or
double reheat)? Provide calculations in support of your answer.
(b). What is the thermal efficiency ηth
of the power cycle?
(c). Determine the annual emission of sulfur dioxide, mSO2
, in metric tons, from this power
plant, if the net generating capacity of the plant is 600 MW, and the boiler is 88%
efficient in transferring combustion heat into the feedwater superheat and steam reheat
stages. The boiler burns, to completion, Power River Basin coal that has a heating value
of 22,800 kJ/kg and contains 0.46 wt% sulfur.
Assume that all of the sulfur content of the coal is emitted as SO2
in the combustion flue
gas, and that the coal-burning plant has a capacity factor of 0.85; i.e. the boiler is
operational for 85% of the hours in one calendar year. (1 metric ton = 1000 kg)


Homework Equations


Thermodynamics energy balance equations


The Attempt at a Solution


I completed the first 2 parts of the problem and I found out that one reheating stage is enough to active a steam quality more than 88.2%. I also calculated the thermal efficiency of 38/6% of this power plant.
My question is about part 3. How can I approach?
 
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  • #2
Seems like that's easier than what you've done already - just calculate the total amount of electricity generated, work back through the efficiencies for the heat required, get the mass of coal and multiply out the fraction of sulfur into SO2.
 
  • #3
I am sorry this comes from my bad background in chemistry, I get scared whenever feel that chemistry is involved! So the total electricity generation in a year is 600MW*365*24*3600= 18.9216*10^9 MW/year
I am not sure how to calculate the mass of the coal and as used the efficiencies for the heat required? Can you explain more please?
 

FAQ: Coal-steam electricity generation

1. What is coal-steam electricity generation?

Coal-steam electricity generation is a process in which coal is burned to heat water and produce steam, which is then used to turn turbines and generate electricity. It is a common method of electricity production, accounting for approximately 38% of electricity generated worldwide.

2. How does coal-steam electricity generation impact the environment?

The burning of coal in this process releases carbon dioxide, sulfur dioxide, and other pollutants into the atmosphere, contributing to air pollution and climate change. The extraction and transportation of coal can also have negative impacts on the environment.

3. What are the advantages of coal-steam electricity generation?

One of the main advantages of coal-steam electricity generation is its reliability and affordability. Coal is a relatively inexpensive and abundant source of energy, making it a popular choice for electricity production. It also has a high energy density, meaning that it can produce large amounts of electricity in a relatively small space.

4. What are the disadvantages of coal-steam electricity generation?

The disadvantages of coal-steam electricity generation include its negative impact on the environment and its contribution to climate change. The burning of coal also produces ash and other waste products, which can be harmful if not properly disposed of. Additionally, coal is a non-renewable resource, meaning that it will eventually run out.

5. Are there any alternatives to coal-steam electricity generation?

Yes, there are several alternatives to coal-steam electricity generation, including renewable energy sources such as solar, wind, and hydropower. These sources are cleaner and more sustainable, but they may also have their own limitations and challenges. It is important to consider a mix of energy sources in order to meet our energy needs while reducing our impact on the environment.

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