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Effects of ammonium sulfate and ammonium carbonate as contaminated ammonia in fly ash on properties of mortars |
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| รหัสดีโอไอ | |
| Title | Effects of ammonium sulfate and ammonium carbonate as contaminated ammonia in fly ash on properties of mortars |
| Creator | Shayapa Roongruangsarn |
| Contributor | Warangkana Saengsoy, Advisor |
| Publisher | Thammasat University |
| Publication Year | 2564 |
| Keyword | Fly ash, Contaminated ammonia, Ammonium sulfate, Ammonium carbonate, Low CaO fly ash, High CaO fly ash, High free lime fly ash, Mortar |
| Abstract | Post-coal combustion process with SCR or SNCR technologies is widely used to reduce NOx gas in coal power plants. This is done by NH3 injection to convert NOx gas to N2. Some unreacted ammonia left in the process can cause ammonia- contaminated fly ash which are mostly found in forms of ammonium sulfate ((NH4)2SO4) and ammonium carbonate ((NH4)2CO3). The objective of this study is to investigate the effects of (NH4)2SO4 and (NH4)2CO3 in fly ash on the properties of mortars with varied ammonia concentrations in the ammonium salts which are 0, 100, 200, 600, and 1000 ppm. As the ammonia contaminated fly ash does not contain only a single type of ammonium salt, this study also investigates the blended ammonium salts of (NH4)2SO4 and (NH4)2CO3. The varied ratios of (NH4)2SO4 to (NH4)2CO3 are 0, 0.25, 0.5, 0.75, and 1 at the total ammonia concentration in the ammonium salt of 200 ppm. The types of fly ash which are used in the tests are fly ashes having low CaO (FAR), high CaO (FAA), and high CaO with high free lime (FAB) contents at the total ammonia concentration of 200 ppm. The high free lime fly ashes which contain total free lime contents of 5% and 10% are also investigated at the total ammonia concentration of 200 ppm. Mortar specimens with 30% replacement of fly ash and w/b of 0.5 were prepared. The ammonia contamination was prepared by dissolving ammonium salts in water. The test results show that the workability of fresh mortars containing ammonium salts was improved. Setting times of cement pastes containing ammonium salts were delayed. Compressive strength of mortars containing (NH4)2SO4 decreased when compared to that of mortars with no ammonium salts. On the other hand, the compressive strength of mortars containing (NH4)2CO3 increased. Total shrinkage of mortars containing (NH4)2SO4 increased when compared to that of mortars with no ammonium salts. On the other hand, total shrinkage of mortars with (NH4)2CO3 decreased. The test results of properties of mortars containing both ammonium salts with different ratios of (NH4)2SO4 to (NH4)2CO3 were in between the properties of the mortars containing (NH4)2SO4 or (NH4)2CO3 separately. For the test results of properties of mortars containing different types of fly ash, the effects of ammonium salts show the same tendency as in the above explanation. Quantitively, the differences of results come from the differences in chemical compositions of the fly ashes. For properties of mortars containing high contents of free lime, the results show that the workability of fresh mortars containing fly ash with high free lime content decreased while the compressive strength of mortars containing fly ash with high free lime content increased when compared to mortars containing low free lime fly ash. |
