CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 7 Examinations 2008/09
Module Title: Environmental and Energy Engineering
Module Code:
CIVL 8008
School:
Department of Civil, Structural and Environmental Engineering
Programme Title:
Bachelor of Engineering (Hons) in Structural Engineering
- Award
Programme Code:
CSTRU_8_Y4
External Examiner(s): Prof. P. O’Donoghue
Mr. P. Anthony
Internal Examiner(s): Dr. N. Power
Instructions: Answer any four question
All questions carry equal marks
Duration:
2 Hours
Sitting:
Winter 2008
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the
correct examination paper.
If in doubt please contact an Invigilator.
Q1.
Energy from Coal
A coal burning plant produces 900MWe at maximum efficiency. An efficiency of 38% is
obtained. The plant operates on average 85% of the time. It is proposed to convert the plant
to natural gas operating with an electrical efficiency of 41%. Again the plant operates on
average 85% of the time.
1.1
Determine the quantity of coal and gas that is required to fuel the power plant (in
units of tpa and m3pa).
(10 marks)
1.2
Calculate the greenhouse gas savings in units of ktCO2.
(10 marks)
1.3
Estimate a monetary value of this saving based on a carbon tax of €100/t carbon.
(5 marks)
Modified Dulong formula
Energy content of fuel MJ/t = 337C + 1419 (H2 – 0.125O2) + 93 S + 23.26N where,
C is the percentage of carbon, H2 is the percentage hydrogen,
O2 is the percentage oxygen, S is the percentage sulphur and N is the percentage nitrogen.
Properties of coal
Ultimate analysis of coal:
67% carbon, 7% hydrogen, 3% sulphur, 11% oxygen, 2% nitrogen, 10% ash
Properties of natural gas
Energy value of natural gas = 42.26MJ/m3
Density of natural gas (kg/m3): molecular weight divided by 22.412m3
89% methane (CH4), 7% Ethane (C2H6), 2.5% Propane (C3H8), 1.2% Butane (C4H10), 0.3%
Pentane (C5H12)
Combustion equations:
89.0% methane
7.0% Ethane
CH4
C2H6
+ 2O2
+ 3.5O2
→ CO2 + 2H2O
→ 2CO2 + 3H2O
2.5% Propane
1.2% Butane
C3H8 + 5O2
C4H10 + 5.5O2
→ 3CO2 + 4H2O
→ 4CO2 + 5H2O
0.3% Pentane
C5H12 + 8O2
→ 5CO2 + 6H2O
Combustion equation
C
+
O2
=
Molecular weights:
C = 12, O = 16 H = 1
CO2
2
Q2.
Solid waste management
2.1
Discuss the increase in waste generation from the construction and demolition
sector, and describe how the waste hierarchy could be used effectively to reduce
waste from this sector.
(5 marks)
2.2
Describe in detail the site selection process for a non-hazardous municipal waste
landfill.
(5 marks)
2.3
Discuss the environmental conditions and how they affect the anaerobic digestion
process .
(6 marks)
2.4
Explain three methods of composting and state whether these methods comply with
the Animal-By-Product Regulations.
(6 marks)
2.5
Explain the following terms and give and example of each:
(3 marks)
(i)
Waste prevention
(ii)
Waste reuse
(iii)
Waste recycle
Q3.
Incineration
An area has a population of 450,000pe. The MSW production is 575kg/pe, 36% of which is
incinerated. The incinerated waste has an energy value of 12.5GJ/t. Electricity is produced
at an efficiency of 27%; 30% of the electricity produced in used in the plant. Thermal
energy is produced at an efficiency of 48%; 25% of the heat produced is used in the plant.
3.1
How much electricity may be exported from the incinerator? Express your answer in
kWhpa. An average house uses 2628kWhpa. How many houses may be served by
this incinerator?
3.2
(8 marks)
How much thermal energy may be exported from the incinerator? Express your
answer in kWhpa. If an average house uses 66GJpa of thermal energy, how many
houses may be served by this incinerator?
3.3
(5 marks)
Estimate the quantity of kerosene that would be saved if the heat from the incinerator
were used to heat houses. Kerosene has an energy value of 42GJ/t, a density of
808kg/m3 and operates at 90% efficiency. Express your answer in units of Lpa.
(4
marks)
3.4
The capital cost of the incineration process is €670/tpa. The lifetime of the plant is
20 years; a return on investment of 10% is required. The maintenance and operating
cost of the plant are expected to be €55/t. The asset value of the electricity is
€0.072/kWh and heat is €0.02/kWh. Determine the minimum gate fee required with
and without a market for heat.
(8
marks)
3
Q4.
[
]
p r (1 + r )
(1 + r )n − 1
Where R is annual payment, P is principle, r is return on investment (decimal), and
n is the number of years of investment
Biofuels
Formula:
1.1
R=
n
Discuss the Biofuels Directive and explain how the targets set out in this Directive
could help Ireland reduce its reliance on imported fossil fuels.
1.2
(5 marks)
Discuss the main barriers to a biofuel industry in Ireland and describe in detail at
least three methods of promoting a biofuel industry.
1.3
(10 marks)
Explain the ethanol production process from sugar and starch feedstocks.
(5
marks)
1.4
Describe the feedstocks used to produce PPO and biodiesel, and explain how PPO
and biodiesel are used as a vehicle fuel.
Q5.
(5 marks)
Sludge treatment
A sludge treatment centre treats the sludge from an urban wastewater treatment plant of
500,000pe. It is assumed that 1pe equates to 60gBOD/day and 220L/day. The influent of the
wastewater has a Total Suspended Sold concentration of 280mg/L. The Primary sludge
arrives on site thickened to 6.5% dry solids. Assume that Primary treatment removed 50% of
TSS and 25% of BOD. Waste activated sludge (WAS) arrives on site at 3% dry solids.
Assume 0.6kg dry solids per kg BOD removed, and 95% removal efficiency in the aeration
process.
5.1
Estimate the thickened primary sludge, the thickened WAS production and the total
thickened sludge production in tDS/day and t/day.
5.2
(9 marks)
Assume 65% of solids in both sludge types are volatile. Assume the anaerobic
process destroys 45% of volatiles and produces 1m3 of biogas per 1kg of volatile
solids destroyed. How much biogas is produced per day? Express your answer in
terms of m3biogas/t of thickened sludge.
5.3
The sludge is dewatered to 30% solids. What quantity of dewatered sludge is
produced
5.4
(3 marks)
The sludge is then dried by evaporation to 95% solids. What quantity of dried sludge
is produced? Express your answer in t/day.
5.5
(4 marks)
(3 marks)
The quantity of thermal energy required to evaporate water is 2.5GJ/t. Assume
biogas is used in the drier to the dry the sludge. Biogas has an energy value of
4
21MJ/m3. Assume a thermal energy efficiency of 75% in a boiler. Is there sufficient
energy in the biogas to dry the sludge?
Q6.
(6 marks)
Climate change
1.5
Describe three of the main greenhouse gases that Ireland must reduce to meet its
targets under the Kyoto Protocol include in your answer the global warming
potential of the greenhouse gases.
1.6
(7 marks)
Emissions from the transport sector have increased dramatically over the last
number of years. Discuss two reasons for the increased in emissions
(5 marks)
1.7
Discuss the various levels of the Building Energy Rating (BER) and give two
examples of how to reduce the rating of a domestic house.
1.8
(8 marks)
List a policy which could be implemented to encourage the integration of
sustainable development
(5 marks)
5