(WO9703927-A1)      The method of contacting a gas and a liquid comprises introducing at least some of the gas and/or liquid into an elongate cylindrical reactor (1), which has an inlet region (4) of reduced cross-sectional area near a first end, in a direction tangential to the longitudinal axis of the reactor to cause rotational flow of the gas/liquid mixture within the region and into the remainder of the reactor at such a velocity as to cause more intimate mixing.    Also claimed are:    (i) the method of contacting a gas and a liquid comprising introducing at least some of the gas and/or liquid into an elongate cylindrical reactor (1), and introducing a gas stream, opt. mixed with further liquids, through a second inlet at an intermediate region of the reactor, such that the gas flows in a longitudinal or rotational direction;    (ii) the apparatus for contacting gas and liquid using the first method; and    (iii) the apparatus for contacting gas and liquid using the second method.    USE -   Used for contacting a gas and a liquid, such as for a fermentation or bioreaction process, and for treating sewage sludge or other organic waste (all claimed).    ADVANTAGE -   The contact between the gas and liquid, which may include a solid phase, is improved to enable the reaction to be carried out in and subsequent to the reactor.    (EP839120-A1)      This method contacts gas and liquid in a novel, long cylindrical reactor. At one end is an inlet region of reduced cross section, where gas and/or liquid is introduced tangentially to the long axis, hence causing rotational flow throughout the reactor, with sufficient velocity for intimate mixing.    Also claimed are: a gas/liquid contacting appts, essentially of the form described; and a bioreactor for gas and liquid, generally as described, using the two-reactor configuration with recirculation, secondary gas introduction and means of stirring.    USE -   A long vortex liquid and/or gas contactor which is used e.g. for bioreactions, esp. for treatment of sewage sludge or other organic waste (claimed).    ADVANTAGE -   The appts. may be used for the aerobic treatment of sewage sludge, or for other totally unrelated chemical or biological reactions using different materials. The speed of reaction is increased by the turbulent mixing, with heating if appropriate, and the plant volume required is reduced. The problems of froth production occurring in other reactors are absent. The flow is sufficient to sweep bubbles from the top of the column, and to prevent them rising to collect there. A horizontal arrangement is equally possible. Swirl flow in the reactor base holds up gas providing improved contact, with 100% utilisation even at high column flow rates.    (GB2303314-B)      This method contacts gas and liquid in a novel, long cylindrical reactor. At one end is an inlet region of reduced cross section, where gas and/or liquid is introduced tangentially to the long axis, hence causing rotational flow throughout the reactor, with sufficient velocity for intimate mixing.    Also claimed are: a gas/liquid contacting appts, essentially of the form described; and a bioreactor for gas and liquid, generally as described, using the two-reactor configuration with recirculation, secondary gas introduction and means of stirring.    USE -   A long vortex liquid and/or gas contactor which is used e.g. for bioreactions, esp. for treatment of sewage sludge or other organic waste (claimed).    ADVANTAGE -   The appts. may be used for the aerobic treatment of sewage sludge, or for other totally unrelated chemical or biological reactions using different materials. The speed of reaction is increased by the turbulent mixing, with heating if appropriate, and the plant volume required is reduced. The problems of froth production occurring in other reactors are absent. The flow is sufficient to sweep bubbles from the top of the column, and to prevent them rising to collect there. A horizontal arrangement is equally possible. Swirl flow in the reactor base holds up gas providing improved contact, with 100% utilisation even at high column flow rates.    (EP839120-B1)      This method contacts gas and liquid in a novel, long cylindrical reactor. At one end is an inlet region of reduced cross section, where gas and/or liquid is introduced tangentially to the long axis, hence causing rotational flow throughout the reactor, with sufficient velocity for intimate mixing.    Also claimed are: a gas/liquid contacting appts, essentially of the form described; and a bioreactor for gas and liquid, generally as described, using the two-reactor configuration with recirculation, secondary gas introduction and means of stirring.    USE -   A long vortex liquid and/or gas contactor which is used e.g. for bioreactions, esp. for treatment of sewage sludge or other organic waste (claimed).    ADVANTAGE -   The appts. may be used for the aerobic treatment of sewage sludge, or for other totally unrelated chemical or biological reactions using different materials. The speed of reaction is increased by the turbulent mixing, with heating if appropriate, and the plant volume required is reduced. The problems of froth production occurring in other reactors are absent. The flow is sufficient to sweep bubbles from the top of the column, and to prevent them rising to collect there. A horizontal arrangement is equally possible. Swirl flow in the reactor base holds up gas providing improved contact, with 100% utilisation even at high column flow rates.    (US6238912-B1)      This method contacts gas and liquid in a novel, long cylindrical reactor. At one end is an inlet region of reduced cross section, where gas and/or liquid is introduced tangentially to the long axis, hence causing rotational flow throughout the reactor, with sufficient velocity for intimate mixing.    Also claimed are: a gas/liquid contacting appts, essentially of the form described; and a bioreactor for gas and liquid, generally as described, using the two-reactor configuration with recirculation, secondary gas introduction and means of stirring.    USE -   A long vortex liquid and/or gas contactor which is used e.g. for bioreactions, esp. for treatment of sewage sludge or other organic waste (claimed).    ADVANTAGE -   The appts. may be used for the aerobic treatment of sewage sludge, or for other totally unrelated chemical or biological reactions using different materials. The speed of reaction is increased by the turbulent mixing, with heating if appropriate, and the plant volume required is reduced. The problems of froth production occurring in other reactors are absent. The flow is sufficient to sweep bubbles from the top of the column, and to prevent them rising to collect there. A horizontal arrangement is equally possible. Swirl flow in the reactor base holds up gas providing improved contact, with 100% utilisation even at high column flow rates.