Early layer formation on K-feldspar during fluidized bed combustion with phosphorus-rich fuel

Review of Phosphorus Chemistry in the Thermal Conversion of Biomass: Progress and Perspectives

“…To understand how phosphates interact with bed material, to potentially cause particle agglomeration and bed defluidization, a number of studies applying model compounds were performed. The model compounds include NH 4 H 2 PO 4 , 9,436 KH 2 PO 4 , 9,436,684,686,688 NaH 2 PO 4 , 9,436,686 H 3 PO 4 (in combination with NaNO 3 ), 685 Ca(H 2 PO 4 ) 2 , 688 CaHPO 4 , 436,610 K 3 PO 4 , 436,610 Na 3 PO 4 , 436,610 Ca 3 (PO 4 ) 2 , 436 and Mg 3 (PO 4 ) 2 . 610 Primarily silica sand 9,436,[684][685][686]688 was used as a bed material, but a single study using K-feldspar was also performed.…”

“…The model compounds include NH 4 H 2 PO 4 , 9,436 KH 2 PO 4 , 9,436,684,686,688 NaH 2 PO 4 , 9,436,686 H 3 PO 4 (in combination with NaNO 3 ), 685 Ca(H 2 PO 4 ) 2 , 688 CaHPO 4 , 436,610 K 3 PO 4 , 436,610 Na 3 PO 4 , 436,610 Ca 3 (PO 4 ) 2 , 436 and Mg 3 (PO 4 ) 2 . 610 Primarily silica sand 9,436,[684][685][686]688 was used as a bed material, but a single study using K-feldspar was also performed. 610 The model compounds NH 4 H 2 PO 4 , KH 2 PO 4 , and NaH 2 PO 4 were used in a fixed bed study to understand the agglomeration mechanism taking place in a large-scale unit converting poultry litter.…”

“…610 Primarily silica sand 9,436,[684][685][686]688 was used as a bed material, but a single study using K-feldspar was also performed. 610 The model compounds NH 4 H 2 PO 4 , KH 2 PO 4 , and NaH 2 PO 4 were used in a fixed bed study to understand the agglomeration mechanism taking place in a large-scale unit converting poultry litter. 9 The agglomeration mechanism was hypothesized to be melting induced, but no characterization of the agglomerates were performed to verify this hypothesis.…”

“…9 However, as stated above, a fluidized bed test showed that defluidization occurred after addition of only 0.5 wt % NH 4 H 2 PO 4 . 436 Faust et al 610 investigated the interaction between K-feldspar and the model compounds K 3 PO 4 , Na 3 PO 4 , CaHPO 4 , and Mg 3 (PO 4 ), in a fixed bed at 830 °C using a holding time of 24 h. The tests with alkaline earth phosphates did not display any interactions with K-feldspar, but agglomeration was observed for the alkali phosphates. 610 The agglomeration mechanism was suggested to be melt induced because the interparticle material in the experiment with K 3 PO 4 had a potassium to phosphorus ratio of about 2.5, which is close to the original composition of K 3 PO 4 .…”

“…436 Faust et al 610 investigated the interaction between K-feldspar and the model compounds K 3 PO 4 , Na 3 PO 4 , CaHPO 4 , and Mg 3 (PO 4 ), in a fixed bed at 830 °C using a holding time of 24 h. The tests with alkaline earth phosphates did not display any interactions with K-feldspar, but agglomeration was observed for the alkali phosphates. 610 The agglomeration mechanism was suggested to be melt induced because the interparticle material in the experiment with K 3 PO 4 had a potassium to phosphorus ratio of about 2.5, which is close to the original composition of K 3 PO 4 . 610 However, K 3 PO 4 and Na 3 PO 4 have melting temperatures of 1619 and 1579 °C, 104 respectively, so some kind of chemical reaction between the bed material and alkali phosphates must have taken place to form a phase with a lower melting temperature.…”