CZESTOCHOWA UNIVERSITY OF TECHNOLOGY Faculty of Environmental Engineering and Biotechnology Institute of Advanced Energy Technologies 3rd Oxyfuel Combustion Conference September 9-13th 2013 – Ponferrada, Spain The Effect of Excess Oxygen on Nitrogen Conversion in OxyOxy--FuelFuel CFB Environment Tomasz CZAKIERT, Grzegorz KRAWCZYK, Waldemar MUSKALA, Pawel BORECKI, Sylwia JANKOWSKA, Lukasz JESIONOWSKI, Wojciech NOWAK NCR&D Project Advanced T ech nol ogi es for E nergy G enerati on: Oxy-combustion technology for PC and FBC boilers with CO2 capture Budget: • RhkitidhifResearch on kinetics and mechanisms of oxy-flfuel com btibustion • Bench-scale experiments ~25 mln USD • Small pilot-scale investigations (0.1MWth CFB, 0.2MWth PCFB, 0.5MWth PC) • Oxygen production issues (incl. mobile ASU) •CO• CO2 capture issues (incl. mobile CCU) Period: • General modeling work 2010-2015 • Feasibility study for a full chain demo-scale oxy-fuel plant with CCS Academies Czestochowa University of Technology Silesian University of Technology Wroclaw University of Technology R&D Centers Institute for Chemical Processing of Coal Institute of Power Engineering Industry Tauron Wytwarzanie Lagisza Power Plant PGE GiEK Turow Power Plant Foster Wheeler Energia Polska Eurol Innovative Technology Solutions Experimental Conditions: • inlet gas: O2 + CO2 • O2 fraction: 35%-vol. • PG/SG ratio: 70/30 • ggyas velocity: 1.81 m/s (↓SG) – 3.05 m/s (↑SG) • excess oxygen: 1.05, 1.15, 1.25, and 1.35 • fuel: bituminous coal Properties of Fuel kJ lower heating value (LHV) ( /kg) 21888−22728 Proximate Analysis Polish bituminous coal moisture (wt %) 15.0−16.0 volatile matter (wt %) 30.6−32.7 fixed carbon(by difference) (wt %) 39.7−42.5 ash (wt %) 10. 3−13. 8 Ultimate Analysis C (wt %) 55.6−58.0 Scomb (wt %) 1.25−1.31 H (wt %) 3.74−3.86 N (wt %) 0.85−0.90 O(by difference) (wt %) 8.82−10.01 Temperature and pressure • Pressure loop remains in agreement with • The oxy-fuel CFB test rig is not equipped with typical pressure balance around CFB loop any internal or external heat exchangers that (Basu P., Fraser S.A., 1991) could be employed to control the temperature in the CFB loop. • Total pressure drop in combustion chamber • The temperature of inlet gas and the (P2-P9) is kept at level of 2500Pa thickness of thermal insulation on the return leg remained unchanged during the experiment. • Pressure transition (+/-) is established at level of fuel feed point • An increase in excess oxygen from 1.05 to 1.35 results in a temperature drop of 100 K. Calculations • Conversion Ratio of fuel-N to NO • molar ratio of N (fixed in NO)/ C (fixed in CO2 & CO) in flue gas • molar ratio of N/ C in fuel Calculations N → NO, NO2, N2ONHO, NH3, HCN General assumptions: Main advantages: • distributions of N & C independence from: within volatile matter as well • changes in moisture and as char is uniform ash contents in fuel • CR of C to CO2 + CO • changes in volatiles-char corresponds to burn-out ratio ratio of combustible matter • incomplete combustion of fuel losses • no other source of N than • measurements of fuel flux fuel and O2 & CO2 flows CO2 in flue gas is considered • fuel behavior is more to derive from both: transparent • oxidation of C • data can be compared • CO2 in inlet gas directly Results CbCarbon Convers ion λ=1.05 C → Carbon monoxide (CO) C → Carbon dioxide (CO2) • progress in burn-out of combustible matter can be observed • high value of CRC (≈65%) at level of FG1 (0.43m) • further fuel burn-out; no oxidation of CO between FG1- FG2 (0.43-1.45m) • carbon conversion gets slower above FG2 • low value of CRC→CO Results CbCarbon Convers ion λ=1.15 C → Carbon monoxide (CO) C → Carbon dioxide (CO2) • results are quite similar • increased value of CRC at level of FG1 (>70%) • carbon conversion to CO v remains low Results CbCarbon Convers ion C → Carbon monoxide (CO) C → Carbon dioxide (CO2) • increase of CRC at level of FG1 (>80%) • higher value of CRC→CO at level of FG1; drops down in upper part of combustion chamber λ=1.25 Results CbCarbon Convers ion C → Carbon monoxide (CO) C → Carbon dioxide (CO2) • results remain similar • value of CRC ultimately exceeds 85% at level of FG1 • oxidation of CO is almost completed at level of FG2 λ=1.35 Results Nitrogen CiConversion λ = 1.05 N → Nitrous oxide (N2O) N → Nitrogen monoxide (NO) N → Nitrogen dioxide (NO2) N → Hydrogen cyanide (HCN) N → Ammonia (NH3) • low value of CRN (<10%) • nitrogen converts mainly to NO • no CRN->NH3 observed • slight amount of HCN (~1%) • reduction of NO2 to N2 in the upper part of combustion chamber • NO2 appears at the bottom of combustion chamber Results Nitrogen CiConversion λ = 1.15 25%O2 @CO2 N → Nitrous oxide (N2O) N → Nitrogg()en monoxide (NO) N → Nitrogen dioxide (NO2) N → Hydrogen cyanide (HCN) N → Ammonia (NH3) • higher value of CRN (<20%) • nitrogen converts mainly to NO • no CRN->NH3 observed • slight amount of HCN (~1%) • higher reduction of NO & NO2 to N2 in the upper part of combustion chamber • NO2 appears at the bottom of combustion chamber Results Nitrogen CiConversion N → Nitrous oxide (N2O) N → Nitrogg()en monoxide (NO) N → Nitrogen dioxide (NO2) N → Hydrogen cyanide (HCN) N → Ammonia (NH3) • value of CRN >20% • nitrogen converts mainly to NO • no CRN->NH3 obdbserved λ = 1.25 • slight amount of HCN (~1%) • higher reduction of NO & NO2 to N2 in the upper part of combustion chamber, however, it stats in the lower part of the furnace Results Nitrogen CiConversion N → Nitrous oxide (N2O) N → Nitrogg()en monoxide (NO) N → Nitrogen dioxide (NO2) N → Hydrogen cyanide (HCN) N → Ammonia (NH3) • value of CRN ≈25% • nitrogen converts mainly to NO • significant conversion to N2O λ = 1.35 • no CRN->NH3 observed • slight amount of HCN (~1%) Conclusions Generally, fuel-nitrogen conversion (CRN) does not exceed 25% and decreases with a decrease of excess oxygen. The decrease of excess oxygen is associated with an increase in temperature, and hence, the excess oxygen seems to be a crucial factor regarding the formation mainly of NO and N2O. Thevalues of CRN→N2O are the hig hes t at the ltlowest tttemperature regardless of the highest excess oxygen. The reduction of NO was also observed, which affects the final emissions of NOX. The nitrogen conversion to NO2 was found to be much lower compared with the conversion to NO and N2O. Ammonia was not detected at any level of the combustion chamber. HCN appears only locally, and it is to be considered as a residual impurity rather than a flue gas component. THANK YOU FOR YOUR ATTENTION 3rd Oxyfuel Combustion Conference September 9-13th 2013 – Ponferrada, Spain.