Production of bleaching chemicals on site at a pulp mill

摘要

Non-chlorine bleaching chemicals (e.g. all or most) for a cellulose pulp bleach plant are produced on site. Oxygen and hydrogen are produced by disassociating water (e.g. by electrolysis) and the hydrogen and oxygen. The hydrogen is used (e.g. with bleach plant effluent, and a catalyst such as anthraquinone) to produce hydrogen peroxide which is used in a P bleach stage in the bleach plant. The oxygen is fed to an ozonator to produce a bleaching gas containing oxygen as a carrier gas and about 3 to 12 % by weight ozone as the active bleaching agent, and the cellulose pulp is bleached with the ozone in a Z stage. The oxygen may also be fed directly to an O stage, or the oxygen off gases from a Z stage may be divided, with part let to an O stage, and another part purified and combined with newly produced oxygen. On site production is extremely economical compared to purchase of the non-chlorine bleaching chemicals.