The ash chemistry in fluidised bed gasification of biomass fuels. Part II: Ash behaviour prediction versus bench scale agglomeration tests

This paper is part II in a series of two.  Ash behavior modeling of the gasification of four biomass fuels is compared with pilot-​scale expts. carried out in a pressurized fluidized bed gasifier at the Royal Institute of Technol. (KTH) and an atm. test rig of Termiska Processer AB (TPS)​.  Expts. were provocative with respect to agglomeration of the bed material.  Thus, in the expts., the agglomeration was allowed to happen without any corrective changes in the operation.Small-​scale expts. showed clear defluidization in five cases.  Some degree of bed disturbance or agglomeration occurred in seven out of 13 cases.  In nine of these cases, agglomerates were also found in the samples analyzed with SEM​/EDX analyses.In six out of 13 cases, the thermodn. multi-​phase multi-​component equil. calcns. were in agreement with SEM​/EDX anal., i.e. predicted formation of agglomerates.  In two cases, no or small amts. of agglomerates were predicted, nor were these found with SEM​/EDX anal.  In two cases out of 13, the modeling predicted some degree of agglomeration while no agglomerates could be detected with SEM​/EDX anal.  However, in these cases, agglomerates were found in the pilot-​scale expts. Thus it is shown that the thermodn. multi-​phase multi-​component equil. calcns. are a useful prediction tool for the formation of agglomerates in (pressurized) fluidized bed gasification of biomass fuels thereby enhancing the understanding of the chem. involved.