A heat exchanger includes a housing that includes an inlet for receiving bulk solids and an outlet for discharging the bulk solids. A first heat transfer plate bank is disposed between the inlet and the outlet. The first heat transfer plate bank includes a plurality of horizontally spaced apart, substantially parallel heat transfer plates for cooling the bulk solids that flow from the inlet, through spaces between adjacent plates. A second heat transfer plate bank is disposed between the first bank and the outlet. The second bank includes plurality of horizontally spaced apart, substantially parallel heat transfer plates for cooling or heating the bulk solids that flow from the spaces between adjacent plates of the first bank, through spaces between adjacent plates of the second bank, to the outlet. The plates of the second bank are horizontally offset from the plates of the first bank such that the plates of the second bank are not in vertically aligned with the plates of the first bank.