  The $N$ site open XXZ quantum spin chain with a right non-diagonal boundary
and special diagonal left boundary is considered. The boundary non-local
charges originally obtained from a field theoretical viewpoint, for the sine
Gordon model on the half line, are recovered from the spin chain point of view.
Furthermore, the symmetry of the open spin chain is exhibited. More
specifically, we show that certain non--local charges commute with the transfer
matrix of the open spin chain, depending on the choice of boundary conditions.
In addition, we show explicitly that for a special choice of the left boundary,
one of the non--local charges, in a particular representation, commutes with
each one of the generators of the blob algebra, and hence with the
corresponding local Hamiltonian.
