  We study, in the ensemble of constant particle number, processes in which a
cluster of particles is annihilated and particles are created catalytically in
active sites. In this ensemble, particles belonging to a cluster of $\ell$
particles jump to $\ell$ distinct active sites. As examples of our
prescription, we analyze numerically three nonequilibrium systems that
annihilate cluster of particles that are identified as conserved versions of
the pair annihilation contact model, triplet annihilation contact model and
pair contact process. We show also how to set up the constant particle number
ensemble from the constant rate ensemble.
