Download Quantity of Coal - Environmental Engineering - Old Exam Paper and more Exams Environmental Science in PDF only on Docsity!
CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2009/
Module Title: Environmental and Energy Engineering
Module Code: CIVL
School: Department of Civil, Strutural and Environmental Engineering
Programme Title: Bachelor of Engineering (Hons) in Structural Engineering
Programme Code: CSTRU_8_Y EENEN_8_Y
External Examiner(s): Dr. M. Richardson Mr. J. O’Mahony
Internal Examiner(s): Dr. N. Power
Instructions: Answer any four question All questions carry equal marks
Duration: 2 Hours
Sitting: August 2010
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 750MWe at maximum efficiency. An efficiency of 37% 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 43%. Again the plant operates on average 85% of the time. (a) Determine the quantity of coal and gas that is required to fuel the power plant (in units of tpa and m^3 pa). (10 marks) (b) Calculate the greenhouse gas savings in units of ktCO 2. (10 marks) (c) Estimate a monetary value of this saving based on a carbon tax of €100/t carbon. (2 marks) (d) A wind turbine operates at maximum efficiency 40% of the time; electricity from wind may be considered CO 2 neutral. What size of wind farm (MWe) is required to affect the same greenhouse gas savings? (3 marks)
Modified Dulong formula Energy content of fuel MJ/t = 337C + 1419 (H 2 – 0.125O 2 ) + 93 S + 23.26N where, C is the percentage of carbon, H 2 is the percentage hydrogen, O 2 is the percentage oxygen, S is the percentage sulphur and N is the percentage nitrogen.
Properties of coal 69 % carbon, 6.5% hydrogen, 4.5% sulphur, 10 % oxygen, 2% nitrogen, 8% ash
Properties of natural gas Energy value of natural gas = 43.18MJ/m^3 Density of natural gas (kg/m^3 ): molecular weight divided by 22.412m^3
90 % methane (CH 4 ), 6.4% Ethane (C 2 H 6 ), 2. 1 % Propane (C 3 H 8 ), 1. 2 % Butane (C 4 H 10 ), 0. 3 % Pentane (C 5 H12) Combustion equations: 90 .0% methane CH 4 + 2O 2 → CO 2 + 2H 2 O
- 4 % Ethane C 2 H 6 + 3.5O 2 → 2CO 2 + 3H 2 O 2.1% Propane C 3 H 8 + 5O 2 → 3CO 2 + 4H 2 O
- 2 % Butane C 4 H 10 + 5.5O 2 → 4CO 2 + 5H 2 O
- 3 % Pentane C 5 H 12 + 8O 2 → 5CO 2 + 6H 2 O
Combustion equation C + O 2 = CO 2 Molecular weights: C = 12, O = 16 H = 1
Q4. Biofuels (a) What are the four advantages for locating an ideal niche market for utilising biofuels? ( 4 marks) (b) What are the three ways in which ethanol can be used as a vehicle fuel? (3 marks) (c) Describe briefly the following properties of ethanol: ( 8 marks)
- Toxicology
- Solvent
- Octane
- Volatility (d) What are the by-products of the ethanol process? ( 2 marks) (e) What is the difference between PPO and biodiesel? ( 3 marks) (f) List the five benefits of developing a biodiesel and PPO industry in Ireland. ( 5 marks)
Q5. Sludge treatment A sludge treatment centre treats the sludge from an urban wastewater treatment plant of 450,000pe. It is assumed that 1pe equates to 60gBOD/day and 225L/day. The influent of the wastewater has a Total Suspended Sold concentration of 270mg/L. The Primary sludge arrives on site thickened to 6.0% 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. (a) Estimate the thickened primary sludge, the thickened WAS production and the total thickened sludge production in tDS/day and t/day. (9 marks) (b) Assume 65% of solids in both sludge types are volatile. Assume the anaerobic process destroys 50% of volatiles and produces 1m^3 of biogas per 1kg of volatile solids destroyed. How much biogas is produced per day? Express your answer in terms of m^3 biogas/t of thickened sludge. (4 marks) (c) The sludge is dewatered to 30% solids. What quantity of dewatered sludge is produced (3 marks) (d) The sludge is then dried by evaporation to 95% solids. What quantity of dried sludge is produced? Express your answer in t/day. (3 marks) (e) 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 21MJ/m^3. Assume a thermal energy efficiency of 75% in a boiler. Is there sufficient energy in the biogas to dry the sludge? (6 marks)
Q6. Climate change and sustainability (a) Explain the greenhouse gas effect and list the six main gases which contribute to it. (6 marks) (b) What does DEAP stand for? (1 marks) (c) Explain three ways to design a building for Passive Solar design (3 marks) (d) Discuss renewable energy in Ireland with emphasis on how wind energy has increased in capacity in recent years. (6 marks) (e) Explain the term carbon tax and how it may be used to reduce emissions. (3 marks) (f) Describe in detail the three types of wind turbines and how they operate. ( 6 marks)
