A recirculation circuit for a processing vessel is configured to process a load with a process fluid. The recirculation circuit includes a first circuit portion configured to recirculate a first portion of the process fluid through the vessel. The first circuit portion includes a first pump having a first flow rate and a first output pressure and a heat exchanger in fluid communication with the first pump. A second circuit portion is configured to recirculate a second portion of the process fluid through the vessel. The second circuit portion includes a second pump having a second flow rate higher than the first flow rate and a second output pressure lower than the first output pressure.

A process and plant for preheating a metal charge fed in continuous to an electric melting furnace through a preheating tunnel provided with side walls, a vault and a horizontal conveyor, wherein the metal charge is enveloped in countercurrent by fumes or exhaust gases exiting from the electric melting furnace, includes causing an air intake from the surrounding environment through openings along the preheating tunnel to complete the combustion of the fumes or exhaust gases. The intake is regulated by acting on suction fans and/or on the openings, based on measurements by temperature sensors and/or the composition of the outgoing gases in or downstream of the terminal part of the tunnel. The metal charge is enveloped by jets of gas ejected through a plurality of nozzles arranged non-uniformly longitudinally on the vault of the tunnel, with a greater concentration on the top of the vault of the tunnel.

The present invention provides an electric furnace including: a cylindrical furnace wall; a furnace cover that is provided at an upper end of the furnace wall; and a furnace bottom that is provided at a lower end of the furnace wall and includes a deep bottom portion and a shallow bottom portion as a region having a height of 150 mm to 500 mm from a deepest point of the deep bottom portion, in which a slag pouring port into which molten slag or a solidified slag lump is capable of being poured from a slag transport container directly or through a tilting trough is provided, the slag pouring port overlaps the shallow bottom portion in a plan view, and the area ratio of the shallow bottom portion to the furnace bottom in a plan view is 5% to 40%.

The present invention provides an electric furnace including: a cylindrical furnace wall; a furnace cover that is provided at an upper end of the furnace wall; and a furnace bottom that is provided at a lower end of the furnace wall and includes a deep bottom portion and a shallow bottom portion as a region having a height of 150 mm to 500 mm from a deepest point of the deep bottom portion, in which a slag pouring port into which molten slag or a solidified slag lump is capable of being poured from a slag transport container directly or through a tilting trough is provided, the slag pouring port overlaps the shallow bottom portion in a plan view, and the area ratio of the shallow bottom portion to the furnace bottom in a plan view is 5% to 40%.

One object of the present invention is to provide a burner which makes it possible to prevent blockage and damage of the nozzle by the molten metal and the slag, and the present invention provides a burner including a combustion supporting gas supply passage which is configured to supply a combustion supporting gas toward a combustion supporting gas outlet provided at the center of the tip end side; a fuel supply passage which is configured to supply a fuel toward a fuel ejection outlet provided around the combustion supporting gas outlet; and a protective nozzle provided from a position surrounding a periphery of the fuel ejection outlet so as to project forward beyond the tip end surface at which the combustion supporting gas ejection outlet and the fuel ejection outlet are provided; wherein the combustion supporting gas supply passage includes a Laval nozzle, and a diameter-enlarged nozzle of which a diameter gradually increases from the tip end of the Laval nozzle toward the combustion supporting gas ejection outlet, and the protective nozzle has a shape which is gradually reduced in diameter forward from the tip end surface.

A process of calcining aluminium hydroxide (Al.sub.2O.sub.3.3H.sub.2O) to form alumina (Al.sub.2O.sub.3), for example in an alumina plant, such as a Bayer process plant, is disclosed. The process comprises combusting hydrogen and oxygen and generating steam and heat 5 and using the heat to calcine aluminium hydroxide and form alumina and more steam. An apparatus is also disclosed.

A process of calcining aluminium hydroxide (Al.sub.2O.sub.3.3H.sub.2O) to form alumina (Al.sub.2O.sub.3), for example in an alumina plant, such as a Bayer process plant, is disclosed. The process comprises combusting hydrogen and oxygen and generating steam and heat 5 and using the heat to calcine aluminium hydroxide and form alumina and more steam. An apparatus is also disclosed.

A method and system for operating a seal gas compressor utilized in a direct reduction process including: monitoring a pH level of a water stream used in the seal gas compressor, wherein the pH level of the water stream is affected by a reformer flue gas stream that comes into contact with the water stream, wherein the monitoring step is carried out one or more of upstream of the seal gas compressor and downstream of the compressor; and adjusting the pH level of the water stream to maintain the pH level of the water stream within a predetermined range based on feedback from the monitoring step. The method includes maintaining the pH level of the water stream upstream of the seal gas compressor in a range between 7.5 and 10 and maintaining the pH level of the water stream downstream of the seal gas compressor in a range between 7.8 and 9.5.

Provided is a high pressure heat treatment apparatus including: an internal chamber accommodating an object to be heat-treated; an external chamber including a high-temperature zone accommodating the internal chamber and a low-temperature zone having a lower temperature than the high-temperature zone; a gas supply module including a process gas line for supplying a process gas for the heat treatment to the internal chamber at a first pressure higher than that of the atmosphere and a protective gas line for supplying a protective gas to the external chamber at a second pressure set in relation to the first pressure; a switch module configured to switch the high-temperature zone and the low-temperature zone into a communication state; and a purge module configured to purge the protective gas in the high-temperature zone to the low-temperature zone in the communication state.

Provided is a high pressure heat treatment apparatus including: an internal chamber accommodating an object to be heat-treated; an external chamber including a high-temperature zone accommodating the internal chamber and a low-temperature zone having a lower temperature than the high-temperature zone; a gas supply module including a process gas line for supplying a process gas for the heat treatment to the internal chamber at a first pressure higher than that of the atmosphere and a protective gas line for supplying a protective gas to the external chamber at a second pressure set in relation to the first pressure; a switch module configured to switch the high-temperature zone and the low-temperature zone into a communication state; and a purge module configured to purge the protective gas in the high-temperature zone to the low-temperature zone in the communication state.