A blast furnace system is used wherein the coke rate is decreased by recycling upgraded top gas from the furnace back into its shaft section (which upgraded top gas is heated in a tubular heater prior to being recycled). The top gas, comprising CO, CO.sub.2 and H.sub.2, is withdrawn from the upper part of the blast furnace; cooled and cleaned of dust, water, and CO.sub.2 for increasing its reduction potential and is heated to a temperature above 850 C. before being recycled thus defining a first gas flow path used during normal operation of the blast furnace. Uniquely, a second gas flow path for continued circulation of top gas selectively through the heater and a cooler during operation interruptions of the blast furnace allows time for gradual controlled cool down of the heater in a manner to avoid heat-shock damage to the tubular heater.

A method for producing burnt end products from an educt (starting raw materials) of carbonate-containing materials involves preheating the educt using heat recovered from the reaction. The educt and a fluidizing medium including steam are input into a first reaction zone. Heat is transferred to the first reaction zone using mechanical components so as to heat the first reaction zone to a predetermined temperature range for a predetermined time period. The educt is burned in the first reaction zone over the predetermined time period during which the first reaction zone is maintained within the predetermined temperature range. The hot gases that form in the first reaction zone include CO.sub.2 and steam. Hot end product is discharged from the first reaction zone after the predetermined time period elapses. Heat contained in the hot gases and end product that are discharged from the first reaction zone is used to preheat the educt.

The present discloses a thermal energy recovery auxiliary system for temperature detection of molten steel in a steelmaking process, comprising an electric arc furnace, a water supply device, a power generation system, a piston type oxygen compression device, and one or more non-contact temperature measurement devices. A flue communicates with a side wall of the electric arc furnace. The water supply device includes a water supply tank, a water supply pipeline of an electrolytic cell, and a thermal energy recovery component. The power generation system includes a Seebeck-effect thermoelectric power generation component and an electrolytic cell. The piston type oxygen compression device forms a steam containment chamber and an oxygen containment chamber through a piston isolation. One end of each of the one or more non-contact temperature measurement devices communicates with the oxygen containment chamber and the other end of each of the one or more non-contact temperature measurement devices communicates with an interior of the electric arc furnace.

The present discloses a thermal energy recovery auxiliary system for temperature detection of molten steel in a steelmaking process, comprising an electric arc furnace, a water supply device, a power generation system, a piston type oxygen compression device, and one or more non-contact temperature measurement devices. A flue communicates with a side wall of the electric arc furnace. The water supply device includes a water supply tank, a water supply pipeline of an electrolytic cell, and a thermal energy recovery component. The power generation system includes a Seebeck-effect thermoelectric power generation component and an electrolytic cell. The piston type oxygen compression device forms a steam containment chamber and an oxygen containment chamber through a piston isolation. One end of each of the one or more non-contact temperature measurement devices communicates with the oxygen containment chamber and the other end of each of the one or more non-contact temperature measurement devices communicates with an interior of the electric arc furnace.

Systems and processes for external combustion air preheating for providing preheated combustion air to a furnace. The furnace systems convective heating section includes multiple heating coils for waste heat recovery. The heating coils may be used for preheating a feed (feed preheat coils), heating a boiler feed water, superheating steam, or heating or superheating a feed stream prior to the feed being fed to the radiant coil. The waste heat in the combustion gas is also used to heat a heat transfer fluid, which may be used to pre-heat combustion air or for other purposes within the plant.

A jet-type direct-fired preheating system, comprising a direct-fired furnace and a preheating furnace. The direct-fired furnace comprises a furnace casing, a direct-fired heating area being provided in the furnace casing. The preheating furnace comprises: a furnace body, wherein the upper portion of the furnace body is connected to the upper portion of the direct-fired furnace by means of a communicating pipe, the bottom of the furnace body is provided with a strip steel inlet, a sealing apparatus and a steering roller, an upper collection chamber of direct-fired waste gas and a secondary combustion chamber of direct-fired combustion waste gas are provided at the upper portion in the furnace body, and a lower collection chamber of the direct-fired waste gas is provided at the lower portion in the furnace body; and a plurality of heat exchange and jet bellows units, provided in the furnace body in the height direction of the furnace body, a threading channel being formed in the middle. Each heat exchange and jet bellows unit comprises: a bellows body, a heat exchange pipe being provided in the bellows body, and a nozzle being provided on the side surface opposite to the threading channel; a secondary waste gas mixing chamber provided between the bellows bodies; and a circulating fan, an inlet pipeline port being formed in the threading channel, and an outlet pipeline port being located in the bellows body. According to the present invention, strip steel can be quickly preheated to 350 or above and quickly heated to 750 or above; and waste heat of the waste gas is fully utilized, such that an over-thick oxide layer can be prevented from being generated on the surface of the strip steel.

A jet-type direct-fired preheating system, comprising a direct-fired furnace and a preheating furnace. The direct-fired furnace comprises a furnace casing, a direct-fired heating area being provided in the furnace casing. The preheating furnace comprises: a furnace body, wherein the upper portion of the furnace body is connected to the upper portion of the direct-fired furnace by means of a communicating pipe, the bottom of the furnace body is provided with a strip steel inlet, a sealing apparatus and a steering roller, an upper collection chamber of direct-fired waste gas and a secondary combustion chamber of direct-fired combustion waste gas are provided at the upper portion in the furnace body, and a lower collection chamber of the direct-fired waste gas is provided at the lower portion in the furnace body; and a plurality of heat exchange and jet bellows units, provided in the furnace body in the height direction of the furnace body, a threading channel being formed in the middle. Each heat exchange and jet bellows unit comprises: a bellows body, a heat exchange pipe being provided in the bellows body, and a nozzle being provided on the side surface opposite to the threading channel; a secondary waste gas mixing chamber provided between the bellows bodies; and a circulating fan, an inlet pipeline port being formed in the threading channel, and an outlet pipeline port being located in the bellows body. According to the present invention, strip steel can be quickly preheated to 350 or above and quickly heated to 750 or above; and waste heat of the waste gas is fully utilized, such that an over-thick oxide layer can be prevented from being generated on the surface of the strip steel.