Slurry digester and capping arrangement for use therein

A capping arrangement for an anaerobic slurry digester of substantially rectangular horizontal cross-section, the capping arrangement comprising:

• a plurality of elongate capping members of inverted channel form comprising wall members having upstanding lateral walls with shoulders which, when said capping members are placed in side-by-side arrangement, define therebetween channels which are upwardly open, said capping members being formed with outlets in upper regions thereof;
• and
• ballast means of substantially letter T-shape in transverse cross-section positioned in said upwardly open channels, such that either side of the heads thereof rests on said shoulders,
• wherein said capping members are connected to each other at their lateral margins in association with said ballast means, said capping members being so formed that the capping arrangement is capable of floating on a body of slurry while being held thereon by said ballast means and being lifted therefrom by gas under pressure thereunder.

An anaerobic slurry digester, comprising:

• a basin of substantially rectangular horizontal cross-section and having a substantially horizontal upper periphery and having a shoulder therearound below the upper periphery thereof;
• inlet means for supply of slurry to said basin below said periphery;
• sludge removal means for removal of sludge from said basin;
• and
• a capping arrangement sized to lie within said basin with its outer margin adjacent the periphery thereof, disposed in an upper region of said basin, which capping arrangement comrises--
• a plurality of elongate capping members of inverted channel form of substantially semi-circular cross-section comprising wall members, including flange sections at their lateral margins, which, when said capping members are placed in side-by-side arrangement, define therebetween channels which are upwardly open, said capping members being formed with gas release outlets in upper regions thereof, and
• ballast means comprising elongate tanks resting on said flange sections in said upwardly open channels, said ballast means being provided with means for supply of water thereto and removal of water therefrom,
• wherein said capping members are connected to each other at their lateral margins in association with said ballast means, said capping members being so formed that the capping arrangement is capable of floating on a body of slurry while being held thereon by said ballast means and being listed therefrom by gas under pressure thereunder, and wherein the endmost of said elongate tanks and the ends of each of said elongate tanks can rest on the shoulders of said basin.

An anaerobic slurry digester, comprising a basin of substantially rectangular horizontal cross-section and having a substantially horizontal upper periphery, inlet means for supply of slurry to said basin below said periphery, sludge removal means for removal of sludge from said basin and a capping arrangement sized to lie within said basin with its outer margin adjacent the periphery thereof, disposed in an upper region of said basin, which capping arrangement comprises

• a plurality of elongate capping members of inverted channel form comprising wall members having upstanding lateral walls with shoulders which, when said capping members are placed in side-by-side arrangement, define therebetween channels which are upwardly open, said capping members being formed with outlets in upper regions thereof;
• and
• ballast means of substantially letter T-shape in transverse cross-section positioned in said upwardly open channels, such that either side of the heads thereof rests on said shoulders,
• wherein said capping members are connected to each other at their lateral margins in association with said ballast means, said capping members being so formed that the capping arrangement is capable of floating on a body of slurry while being held thereon by said ballast means and being lifted therefrom by gas under pressure thereunder.

An anaerobic digester, comprising:

• a basin of substantially rectangular horizontal cross-section and having a substantially horizontal upper periphery;
• inlet means for supply of slurry to said basin below said periphery;
• sludge removal means for removal of sludge from said basin;
• heating means for heating of slurry in said basin;
• a capping arrangement sized to lie within said basin with its outer margin adjacent the periphery thereof, disposed in an upper region of said basin, which capping arrangement comprises
• a plurality of elongate capping members of inverted channel form comprising wall members which, when said capping members are placed in side-by-side arrangement, define therebetween channels which are upwardly open, said capping members being formed with outlets in upper regions thereof, and
• ballast means positioned in said upwardly open channels, said capping members being connected to each other at their lateral margins in association with said ballast means, said capping members being so formed that the capping arrangement is capable of floating on a body of slurry while being held thereon by said ballast means and being lifted therefrom by gas under pressure thereunder;
• duct means for withdrawal of gas from upper regions of said capping members;
• compressor means for the gas;
• and
• return duct means for return of gas to a lower region of said basin, said return duct means being formed at the lower region with a plurality of small apertures for injection of gas under pressure;
• wherein said heating means comprise indirect heat exchangers suspended below said capping arrangement, said heat exchangers having supply ducts for supply of warm water thereto and outflow ducts for removal of water therefrom, and said heat exchangers being in the form of pressed steel panels down a central portion of which passes one of said return duct means and along a bottom region of which branches of the respective said return duct means, formed with small apertures, are provided.