Bed agglomeration due to the addition of KCl and K2CO3 - first results from a laboratory fluidized bed reactor

Bed agglomeration in fluidized beds is a severe problem especially today when

more and more difficult fuels such as agrofuels are utilized. These difficult fuels often

contain significant amounts of potassium, which may leave the bed as evaporated KCl, or

with the fly ash in some solid form (e.g. K2CO3, K2SO4) or it may alternatively react with

the bed particles producing a product layer of K‐silicates which may eventually cause

agglomeration. In this work a laboratory scale bubbling fluidized bed reactor has been

constructed primarily to study bed agglomeration. The fluidized bed reactor consists of a

steel tube (Ø 60 mm) with a 300 mm long air‐preheater section at the bottom, a 100 μm

net for keeping the sand bed and a 700 mm long reactor section. The reactor was further

equipped with thermocouples and a micromanometer. The pressure drop was used as an

indication of agglomeration. In the experiments quartz sand was used as bed material and

the tested salt was semi‐continuously fed in small batches into the reactor. Tests were

done at 805°C, 855°C and 875°C. Once agglomeration occurred the experiment was

finished and the reactor was dismantled to remove the bed and take samples for analyses

with a SEM/EDX analyzer. In this paper we present the first agglomeration results from

the newly constructed fluidized bed reactor, for example, it is shown that 0.4 weight‐%

KCl and about 1 weight‐% of K2CO3 was enough to cause defluidization of the quartz bed.