| 1. |
|
|
| 2. |
- Ajdari, Sima, 1985, et al.
(författare)
-
Modeling the Nitrogen and Sulfur Chemistry in Pressurized Flue Gas Systems
- 2015
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 54:4, s. 1216-1227
-
Tidskriftsartikel (refereegranskat)abstract
- A rate-based model is developed to elucidate the chemistry behind the simultaneous absorption of NOx and SOx under pressurized conditions (pressures up to 30 bar) that are applicable to the flue gases obtained from CO2 capture systems. The studied flue gas conditions are relevant to oxy-fuel and chemical-looping combustion systems. The kinetics of the reactions implemented in the model is based on a thorough review of the literature. The chemistry of nitrogen, sulfur, and N-S interactions are evaluated in detail, and the most important reaction pathways are discussed. The effects of pH, pressure, and flue-gas composition on the liquid-phase chemistry are also examined and discussed. Simulations that use existing kinetic data reveal that the pH level has a strong influence on the reaction pathway that is followed and the types of products that are formed in the liquid phase. In addition, the pressure level and the presence of NOx significantly affect the removal of SO2 from the flue gas.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Ajdari, Sima, 1985, et al.
(författare)
-
Reduced Mechanism for Nitrogen and Sulfur Chemistry in Pressurized Flue Gas Systems
- 2016
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 55:19, s. 5514-5525
-
Tidskriftsartikel (refereegranskat)abstract
- The gas- and liquid-phase chemistry of nitrogen and sulfur species under pressurized conditions is of high importance to the design and performance of the pressurized flue gas systems in carbon capture and storage (CCS) schemes. Yet, the available description of this chemistry is complex and difficult to apply in design studies for removal of NOx and SOx during the compression. This work proposes a reduced mechanism for engineering calculations of pressurized flue gas systems, a mechanism that is able to describe the relevant gas and liquid-phase chemistry as well as the S/N-product distribution. The reduced mechanism is derived by identifying the rate-limiting reactions using sensitivity analysis. The performance of the mechanism subsets are compared with results of a detailed mechanism. The identified rate-limiting reactions for the formation of key products form the basis for two different types of reduced mechanisms. The sets include one general reduced mechanism (valid for all pH conditions) and sets of pH-specific mechanisms. The general reduced mechanism and the pH-specific mechanisms perform satisfactorily compared to the detailed mechanism under different pH conditions. The results show that depending on the purpose of the modeling, whether it is to predict the pollutant removal (where sulfurous acid and nitrogen acids are mainly important) or capture the liquid composition, for which the N-S chemistry products are also important, different levels of simplification can be made. The number of reactions is reduced from 34 reactions (39 species) in the detailed mechanism to 12 reactions (20 species) in the general reduced mechanism and 7-8 (14-17 species) in the pH-specific mechanisms.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Andersson, Klas, 1977, et al.
(författare)
-
Experiments and modeling on oxy-fuel combustion chemistry during lignite-firing
- 2007
-
Ingår i: The Proceedings of the 32nd International Technical Conference on Coal Utilization & Fuel Systems, Clearwater, USA, 2007.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents experimental and modeling work on the combustion chemistry of the oxy-fuel(O2/CO2 recycle) process with focus on the difference in NO formation between oxy-fuel and air-firedconditions. Measurements have been carried out in a 100 kW test unit, which facilitates oxy-fuelcombustion with real flue gas recycle. These measurements include in-furnace gas concentrations andtemperature profiles from lignite-fired tests. The tests comprise a reference test in air and three oxy-fuel test cases with different oxygen fractions in the recycled feed gas. Additional oxy-fuelexperiments were performed in order to study the sensitivity of the NO formation to bothstoichiometry and air ingress.The results show that for the burner settings used in this work, lignite oxy-combustion with a globaloxygen fraction of 25 vol % in the feed gas results in flame temperature levels close to those duringair-firing. Similar to previous work, it is seen that the NO emission levels in [mg/MJ] during oxy-fueloperation are reduced to less than 30 % of the emission level during air-fired conditions. The resultsfrom the modeling shows that the reduction of NO emissions during oxy-fuel combustion is caused byan increased destruction of formed and recycled NO. Further experimental tests on the OF 27condition show that an increased stoichiometric ratio (from l = 1.18 to 1.41) as well as an increasedN2 content in the feed gas (from about 1% to 15%) only has a small effect on the NO formation duringoxy-combustion.
|
|
| 10. |
- Andersson, Klas, 1977, et al.
(författare)
-
Flame and radiation characteristics of gas-fired O2/CO2 combustion
- 2007
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 86:5-6, s. 656-668
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an experimental study on the flame properties of O2/CO2 combustion (oxy-fuel combustion) with focus on the radiation characteristics and the burn-out behaviour. The experiments were carried out in a 100 kWth test unit which facilitates O2/CO2 combustion with real flue gas recycle. The tests comprise a reference test in air and two O2/CO2 test cases with different recycled feed gas mixture concentrations of O2 (OF 21 @ 21 vol.% O2, 79 vol.% CO2 and OF 27 @ 27 vol.% O2, 73 vol.% CO2). In-furnace gas concentration, temperature and total radiation (uni-directional) profiles are presented and discussed. The results show that the fuel burn-out is delayed for the OF 21 case compared to air-fired conditions as a consequence of reduced temperature levels. Instead, the OF 27 case results in more similar combustion behaviour compared to the reference conditions in terms of in-flame temperature and gas concentration levels, but with significantly increased flame radiation intensity. The information obtained from the radiation and temperature profiles show that the flame emissivity for the OF 21 and OF 27 cases both differ from air-fired conditions. The total emissivity and the gas emissivity of the OF 27 and the air-fired environment are discussed by means of an available model. The gas emissivity model shows that the increase in radiation intensity (up to 30%) of the OF 27 flame compared to the air flame can partly, but not solely, be explained by an increased gas emissivity. Hence, the results show that the OF 27 flame yields a higher radiative contribution from in-flame soot compared to the air-fired flame in addition to the known contribution from the elevated CO2 partial pressure.
|
|
