In this work, a priori error estimates for finite element approximations to the governing equations of heat and mass transfer in fluidized beds are derived. These equations are time dependent strongly coupled system of five semilinear convection-diffusion-reaction equations. The a priori error estimates for all the five variables are obtained for the error measured in L
∞(L
2) and
L
2
(
E
)
${L}^{2}\left(\mathcal{E}\right)$
,
E
$\mathcal{E}$
is the energy norm.