| 1. |
- Allgurén, Thomas, 1986, et al.
(författare)
-
Alkali sulfation during combustion of coal in a pilot scale facility using additives to alter the global sulfur to potassium and chlorine to potassium ratios
- 2021
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:3, s. 4171-4178
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the urgent needs to reduce anthropogenic carbon dioxide emissions there is an increasing interest in the use of alternative fuels. For this reason, there is a need for new knowledge on how to design and adapt existing heat and power plants to biogenic and waste-derived fuels. This work relates to co-firing of biomass and coal and the sulfation of alkali chlorides in coal-fired flames doped with chemical additives. We aim to examine the global time scales of alkali sulfation and chlorination based on combustion experiments that were conducted in a 30-kW coal flame. Temperature, gas and particle composition measurements were conducted. Both experiments and modelling support that the apparent alkali sulfation kinetics are fast in a coal-fired flame and that it is dominated entirely by the presence of SO 2. The availability of oxygen and carbon monoxide, or hydrocarbons, is also critical to sustain the sulfation reaction cycle; low concentrations are sufficient. For industrial boilers this implies that sulfur addition, in combination with reburning, should constitute an efficient strategy to mitigate alkali-chlorination and the related high temperature corrosion.
|
|
| 2. |
- Allgurén, Thomas, 1986, et al.
(författare)
-
The Influence of Alkali, Chlorine and Sulfur on Aerosol Formation
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of low-quality fuels in power generation is typically motivated by a potential reduction in fuel costs or CO2 emissions, the latter in case the fuel is based on biomass. These features make low quality fuels attractive at the same time as such fuels are usually problematic to use in power generation due to fuel composition. One of the main issues is deposition of aerosols upon heating surfaces reducing heat transfer and causing high-temperature corrosion (HTC). The later most often related to alkali chlorides, and these are formed from alkali species and chlorine when released during the combustion process. The present work aims to investigate how the gas phase chemistry are connected to the formation aerosols and their characteristics. This is an ongoing work why only part of the preliminary results is presented focusing on the interaction between alkali, sulfur and chlorine in the gas phase. The results presented here indicate a clear correlation between the S/Cl ratio and the formation of alkali sulfates over chlorides. It is also indicated that the local conditions at which the species are released and available in the gas phase is important for the resulting formation of alkali sulfates.
|
|
| 3. |
- Edland, Rikard, 1990, et al.
(författare)
-
On the nitrogen chemistry in jet and swirled pilot-scale PF flames
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper discusses the differences that may occur in terms of NOx formation while using different suspension-fired technical and pilot-scale units. The aim with the work is to examine the NOx formation and to show how the fuel volatile-composition can be a released and exposed, and, in turn, influence the NOx formation. The flames studied are both jet-type, fully developed turbulent and low-Reynolds number type flames. The units used are located at the University of Utah: the L1500 unit (1.5 MW unit) and the OFC unit (100 kW). The same fuel is used in all tests: Sufco coal. By using these two different units together with three different flame types, we can discuss the influence of both scale and flame type on the formation of NOx. This problem is well-known since previous pilot-scale combustion research (for example the work conducted by the IFRF in the late 1970s). However, the issue is certainly not always recognized in more recent studies. Furthermore, in targeting NOx emission issues in both power plants and industrial units, these scaling issues become critical in todays’ NOx emission research. Therefore, this paper aims to bring this issue some attention. This work demonstrates that NOx formation is closely related to both scale and flame-type. The reason is that the NOx formation is mostly dependent on the time-temperature development combined with oxygen-exposure throughout the suspension. This will be clearly demonstrated in this paper by the experimental results, and then further analyzed by kinetic modelling. In future NOx formation work, these results should be used to create a model fully capable of recreating the differences in scale and flame type in suspension-fired units. Although NOx formation remains a classical combustion problem it is still difficult to tackle in modern large-scale solid-fuel units that cannot use secondary emission control (for process-related or economic reasons). This should prompt new research, related to both fuel-switch in existing units, load-variation in coal PF-units, rotary-kilns, and other coal-based applications; all needing to reduce and control their NOx emissions.
|
|
| 4. |
|
|
| 5. |
- Li, Xiaolong, et al.
(författare)
-
The roles of added chlorine and sulfur on ash deposition mechanisms during solid fuel combustion
- 2021
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:3, s. 4309-4316
-
Tidskriftsartikel (refereegranskat)abstract
- The focus of this paper is on effects of chlorine and sulfur on coal ash deposition rates, under practically relevant but systematically controlled combustion conditions. This problem is important, not so much for coal, but to understand and predict deposition rates for biomass combustion where chlorine contents can be high. To this end, ash deposition rates on a controlled temperature surface were measured for controlled amounts of chlorine and sulfur added to a pulverized coal, doped with potassium and burned in a 100 kW rated combustion rig. Previous work with 35 tests on 11 coal, biomass and petroleum coke fuels burned under a range of operating conditions had strongly suggested that the deposition rate of the tightly bound inside deposits was independent of the ash aerosol composition, and depended only on PM1 in the flue gas. The loosely bound outside deposition rate was dependent primarily on the total alkali content in the flue gas. The new results using chlorine added to the fuel (in the form of ammonium chloride) required these previous conclusions to be drastically revised. They showed that chlorine, not alkali alone, had large effects on the deposition rate of the inside deposits, which now were orders of magnitude higher than without chlorine addition, and did not fit previous (multi-fuel) correlations with PM1. Sulfur addition, together with chlorine, did not affect deposition rates much, although it did lower the chlorine content of the deposit. These results are interpreted in terms of the ash aerosol size segregated composition, which was also measured, and potential sulfation reactions within the deposit.
|
|
| 6. |
- Viljanen, Jan, 1990, et al.
(författare)
-
In-situ monitoring of transient gas phase K-Cl-S chemistry in a pilot-scale combustor
- 2021
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:1, s. 1823-1831
-
Tidskriftsartikel (refereegranskat)abstract
- Biomass and waste derived fuels contain large amounts of sodium, potassium, and chlorine that form NaCl and KCl, that is, compounds that cause operational problems, such as slagging, fouling, and high-temperature corrosion. Therefore, alkali chlorides are the main reasons that explain why steam parameters are less advanced and efficient in biomass and waste-based power generation when compared to coal. These problems can be mitigated by introducing sulphur into the system to form alkali sulphates that are not as problematic on steel surfaces as alkali chlorides. However, the alkali sulphation process in realistic combustion environments needs further exploration. Thus, new diagnostic methods for in-situ monitoring of alkali sulphation kinetics in combustion systems are required. In this work, the simultaneous monitoring of KCl and KOH concentrations in a pilot-scale combustor using Collinear Photofragmentation and Atomic Absorption Spectroscopy (CPFAAS) during stationary and transient operation of the combustor, is introduced. The CPFAAS information is complemented by monitoring SO2 and HCl concentrations using Fourier-transform infrared spectroscopy (FTIR). The temporal performance of the system is demonstrated by measuring the temporal combustor response curves for KCl sulphation for different Cl/K ratios during rapid changes in gaseous SO2 concentrations. The temporal concentration curves obtained imply that the Cl/K ratio has a significant impact on the temporal alkali sulphation behaviour. The measurement system described enables further exploration of K-Cl-S chemistry in realistic large-scale power plant environments.
|
|
