Abstract: A spent caustic treatment process addresses the shortcomings with traditional Wet Air Oxidation Systems. The process can treat either refinery or sulphidic spent caustic streams with CODs of up to 50,000 mg/L. The process uses >90% oxygen as an oxidising agent. A horizontal, tubular reactor is operated at pressures between 100 and 170 Bar (ideally 145-165 Bar). The reactor has an operating temperature of between 120° C. and 320° C., ideally 280° C. to 300° C. A closed heat transfer medium circulation loop is utilised for heat recovery from the reactor effluent stream to the spent caustic feed stream. The invention allows for a COD reduction of 75 to 99.9%.

Abstract: A process performed by a plant for oxidation of a waste stream with oxidizable material is described. In a start-up phase, supercritical water is fed to a supercritical water oxidation reactor, heating the process up to supercritical conditions. In a treatment phase, the waste stream is fed to the reactor for supercritical water oxidation treatment, in which sufficient mass of water under supercritical conditions is present in the reactor to retain supercritical conditions with the newly introduced waste stream. Oxygen is used as oxidant and a stoichiometric quantum is added to the reactor. The energy released from the oxidation reaction substitutes the energy provided by the addition of supercritical water up to a point where the reactor achieves near autothermal conditions with supercritical water providing trim heat requirement. The reactor outlet is quench cooled, neutralised and energy is recovered from it. A gas liquid separator ensures that the effluent stream is degassed.

Abstract: An hydrolysis stage of an anaerobic digestion (AD) process includes supercritical treatment in a reactor (R1). The treatment may use sub-stoichiometric oxygen so that there is not full oxidation. Effluent from the supercritical treatment may be used to pre-heat the organic matter in-feed to the supercritical treatment. There may be a second supercritical treatment in a second reactor (R2). This may have full stoichiometric oxygen, to oxidize the solids from the first reactor (R1) effluent. Furthermore, it provides heat for pre-heating its own in-feed and also that for the first reactor (R1). The output from the hydrolysis may be only clarified liquid, leading to particularly efficient downstream AD processes. The second supercritical treatment rector may oxidize also fed-back solids from the final stage of the AD.

Abstract: An hydrolysis stage of an anaerobic digestion (AD) process includes supercritical treatment in a reactor (R1). The treatment may use sub-stoichiometric oxygen so that there is not full oxidation. Effluent from the supercritical treatment may be used to pre-heat the organic matter in-feed to the supercritical treatment. There may be a second supercritical treatment in a second reactor (R2). This may have full stoichiometric oxygen, to oxidise the solids from the first reactor (R1) effluent. Furthermore, it provides heat for pre-heating its own in-feed and also that for the first reactor (R1). The output from the hydrolysis may be only clarified liquid, leading to particularly efficient downstream AD processes. The second supercritical treatment rector may oxidise also fed-back solids from the final stage of the AD.