A method of monitoring a flame during gas combustion in a combustion chamber (10). A heating unit (1) has an evaluation unit, an extraction line (11) and a sensor (12). The sensor (12) is arranged in the extraction line (11) to detect thermal substance properties of the gas. Thus, it is determined if it is ambient air (B), a non-combusted fuel-air mixture (C) or particularly the hydrogen-air mixture, or a waste gas (A) generated during combustion. The sensor (12) transmits a recorded measured value to the evaluation unit. The evaluation unit uses the measured value to determine whether ambient air (B), the non-combusted fuel-air mixture (C), or waste gas (A) is flowing through the extraction line (11) and thereby determines whether the flame is burning or extinguished.

A direct reduction plant is disclosed. The direct reduction plant includes an oxygen injection system, a reformer, and a shaft furnace. The oxygen injection system includes an oxygen injection reactor and a main oxygen burner. The oxygen injection reactor is adapted to receive a gas mixture. The main oxygen burner is adapted to increase a temperature of the gas mixture by burning a mixture of fuel and oxygen fed to the main oxygen burner. The reformer is adapted to reform the gas mixture with the increased temperature. The shaft furnace is adapted to reduce iron ore using the reformed gas mixture.

In a gas hot water heater, changes of the signal output of an A/F sensor are calibrated in the atmosphere, in which the A/F sensor detects an oxygen concentration in a combustion tube. The gas supplied via a gas supply pipe is injected, together with in-taken air, into a combustion tube, which is incorporated in a hot water supply tank, via an injection unit. A proportional valve controls a combustion state in the combustion tube based on the detected oxygen concentration to thereby heat water supplied in the hot water supply tank. A purging process is performed to supply air into the combustion tube, at a timing between an extinguishment operation first performed after the ignition the gas mixture in the combustion tube and a re-ignition operation. Changes of signal output characteristics of the A/F sensor are subject to the calibration after the purging process.

An in-situ averaging combustion analyzer includes a housing and a probe coupled to the housing at a proximal end. The probe has a distal end configured to extend into a flue and contains a zirconia-based oxygen sensing cell proximate the distal end. Electronics are disposed in the housing and are coupled to the zirconia-based oxygen sensing cell. The electronics are configured to measure an electrical characteristic of the zirconia-based oxygen sensing cell and calculate an oxygen concentration value. An averaging conduit is disposed about the probe and has a plurality of inlets spaced at different distances from the distal end of the probe. The averaging conduit has at least one outlet positioned between the distal end and the proximal end of the probe. The electronics are configured to provide an average oxygen concentration output based on the calculated oxygen concentration value.

The gross or net calorific value of a hydrocarbon-containing fuel gas is determined by using a Raman photometer. A Raman radiation obtained following interaction of laser light with the fuel gas is limited by a bandpass filter to a wavenumber range of the C—H stretching vibrations of the hydrocarbons contained in the fuel gas around 2900 cm.sup.−1 and is supplied to a photomultiplier and integratively detected by the photomultiplier. The gross or net calorific value is determined from the output signal of the photomultiplier.

A combustion system such as a furnace or boiler includes a perforated reaction holder configured to hold a combustion reaction that produces very low oxides of nitrogen (NOx).

A combustion system such as a furnace or boiler includes a perforated reaction holder configured to hold a combustion reaction that produces very low oxides of nitrogen (NOx).

A burner appliance is disclosed. The burner appliance includes a byproduct sensor in an exhaust flue and/or a barometric pressure sensor to detect an environmental pressure at the burner appliance. By calculating concentrations of combustion byproducts in the exhaust with the byproduct sensor, a controller can adjust blower speed and/or fuel rate to modify combustion efficiency. By calculating the environmental pressure at the burner with the barometric pressure sensor, the controller can adjust blower speed and/or fuel rate to modify combustion efficiency. The barometric-pressure data can also be used to adjust blower speed control bands, thereby calibrating the control bands based on environmental pressure. The environmental pressure can be indicative of altitude and/or weather conditions. Methods of operating said burner appliance are also disclosed.

The premixing device includes a first and a second venturi having a pressure reducing portion for air, and a gas supply passage for supplying fuel gas to the venturis, and generates air-fuel mixture by mixing fuel gas with air flowing in the venturi by using a fan and supplies the air-fuel mixture to a burner. A first and a second nozzles for reducing pressure of fuel gas are disposed in the gas supply passage, and the first and the second nozzles are formed in the same nozzle shape as the pressure reducing portion of the first and the second venturis.

The premixing device includes a first and a second venturi having a pressure reducing portion for air, and a gas supply passage for supplying fuel gas to the venturis, and generates air-fuel mixture by mixing fuel gas with air flowing in the venturi by using a fan and supplies the air-fuel mixture to a burner. A first and a second nozzles for reducing pressure of fuel gas are disposed in the gas supply passage, and the first and the second nozzles are formed in the same nozzle shape as the pressure reducing portion of the first and the second venturis.