Gas treatment systems and processes for reducing tail gas emissions such as SO2, SO3, H2SO4, NOx, HC, CO, and other pollutants are provided. The processes include transferring tail gas from at least one source of tail gas to at least one destination sulphuric acid plant via a tail gas transfer system, wherein the tail gas replaces or supplements one or more of the combustion gas, air feed, dilution gas, and quench gas used by the destination sulphuric acid plant. The systems include at least one destination sulphuric acid plant and a tail gas transfer system for transferring tail gas from at least one source of tail gas to the at least one destination sulphuric acid plant. The systems and processes described herein may be used to eliminate start-up emissions and/or convert sulphur-containing species present in tail gas emissions into commercial H2SO4.