MEC 6450 Assignment The assignment consists of 3 parts (Complete all parts) PART A is a review paper with a required length of 4 pages of A4 text plus diagrams, tables etc. (30 marks) PART B is a coal burner sizing/design exercise for a number of air firing and oxy-coal firing cases. (40 marks) PART C is linked to the calculated flue gas compositions obtained from PART B and requires the calculation of adiabatic flame temperatures under different cases of operation. (30 marks) The assignment will be issued on the 18/3/2016 via MOLE. The assignment should be handed in by 6/05/2016 at 5pm via MOLE in Word or PDF format. MEC6450 Assignment Page | 2 PART A Review paper Title: Review major CCS technologies for power generation from fossil fuel. Also, describe what further research is ongoing to improve the technology. In your discussion outline possibilities for CCS deployment in the UK but also activity at large scale around the world. (Length - 4 pages of A4, 12pt characters and 1.5 line spacing) 30 Marks. PART B Use the spreadsheet developed in the module to calculate the flow of combustion air to a single coal fired burner rated at 63 MW at an excess air level of 20%. The coal has a net CV of 27MJ/kg as received. The combustion air is preheated to 523K and this is assumed to be the temperature of the oxidant in the burner Ta. The composition of the coal that is being fired is as follows. The primary, secondary and tertiary flow velocities at Ta are 20m/s, 15m/s and 50m/s, respectively. The primary air is 20% of the total volumetric flow to the burner. The ratio of secondary air to tertiary air is 15/85 by volume. Assume 15% of the combustion air (by vol) is being used as overfire air (OFA) for NOx control and the core air is set at 5% of the total volume flow. a) Calculate Dt, Ds, Dp assuming that Dc is 75mm, Figure 1. Velocities are considered upstream of the swirl vanes and fuel concentrators for the purposes of this calculation. 10 Marks Coal Composition % by mass Carbon 70.6 Hydrogen 4.4 O (by difference) 11.2 Fuel Nitrogen 2.1 Fuel Sulphur 0.6 Ash 5.3 Moisture 5.8 Total 100.0 MEC6450 Assignment Page | 3 b) Adapt the calculation procedure used above with the fuel compositions and excess oxidant level quoted above to calculate the wet flue gas compositions for the following cases. Assume dry recycle in oxy coal cases and justify or otherwise the inclusion of NO and SO2 in the flue gas product. 1. Case 1. Air combustion (21 mol% O2, balance N2) (5) 2. Case 2. A reference oxy-coal combustion case with 21 mol% O2, balance CO2. This reference case can be taken as equivalent to 100% recycle. (5) 3. Case 3. An oxy coal combustion case where the ratio of recycle flue gas to the burner is 72.4%. What is the concentration of O2 in the oxidant flow to the burner under these conditions. Recycle ratio (simplified) = oxidant enriched/oxidant reference, kmol/100kg coal basis) (5) 4. Case 4 Using Case 3, match the flue gas O2 composition in Case 1. Report how you did that and any changes to the input data that you had to make. (5) 20 Marks c) For Cases 1 to 4 in question B - 1 c). above, compare the individual burner air flow velocities under air and oxy firing Cases for the 63MW burner in the context of flame propagation rate, Sb. Discuss health and safety aspects of operating the same burner under Case 1 and Case 4 conditions. Discuss what modifications, if any, you would make to the burner geometries so that the burner could cope with the duty requirements of Cases 1 and 4 above. 10 Marks Figure 1 Simplified schematic of a modern low-NOx burner. Note absence of fuel concentrators and swirl vanes . MEC6450 Assignment Page | 4 PART C Future power plant operating with coal as the feedstock fuel will be required to operate under air and oxy-firing conditions (CCS configuration). Assuming the total heat lost from the flame is 20% of the net CV in all cases and the oxidant preheat is maintained at 523K; a. Calculate flame temperature for Cases 1, 2 , 3 and 4 using the wet flue gas compositions that you have calculated from 1 c) above. b. Discuss the differences in temperature that you found and the reasons for these differences. c. Which oxy-firing case compares best to the air case for flame temperature? Molar enthalpies for the combustion and oxidant components is available in the attached table. 30 Marks ATTACHMENTS Molar enthalpies Molar enthalpies relative to zero at 298.15K (MJ / kmol) Temperature (K) CO2 H2O O2 N2 298.15 0 0 0 0 400 4.008 3.452 3.029 2.971 600 12.916 10.498 9.247 8.891 800 22.815 17.991 15.841 15.046 1000 33.405 25.978 22.707 21.46 1200 44.484 34.476 29.765 28.108 1400 55.907 43.447 36.966 34.936 1600 67.58 52.844 44.279 41.903 1800 79.442 62.609 51.689 48.982 2000 91.45 72.689 59.199 56.141 END