A method for controlling a chemical recovery boiler. The method includes measuring concentrations of sodium carbonate, sodium sulfide, and sodium sulfate from green liquor of the chemical recovery boiler, determining a target temperature for smelt, imaging at least an area of a char bed of the chemical recovery boiler, the area being close to a smelt spout, to obtain an image of the area, determining a measured temperature of the char bed using the image of the area. The method further includes determining that the measured temperature of the char bed is less than the target temperature for smelt, and controlling the chemical recovery boiler such that the temperature of the char bed increases. A chemical recovery boiler for the same.

Provided are a gasification furnace operating method, a gasification furnace, a two-stage gasification apparatus, a gasification method for an organic raw material, and a two-stage gasification method for organic waste that make it possible to stably operate a gasification furnace over a long period of time. The present invention provides a gasification furnace operating method including, in a gasification furnace into which an organic raw material is introduced and that produces gas and slag, directly or indirectly introducing an alkali metal-containing compound into the gasification furnace to reduce the viscosity of the slag.

An online monitoring device for fouling and slagging based on capacitance principle differential measurement includes multiple measuring devices arranged at the same height of the boiler heating surface. Each measuring device includes a fixed sleeve and a sensor, one end of the fixed sleeve is fixed on the boiler heating surface, the sensor is connected with the fixed sleeve through screw threads, the end of the sensor near the boiler is equipped with a measuring probe. When measuring the thickness of ash residue on the monitoring surface, three sets of the measuring devices are at the same height of the monitoring surface. Each sensor is adjusted at a different position in the corresponding fixed sleeve to realize the differential measuring on ash residue thickness. Thus, the thickness of ash residue on the monitoring surface can be calculated based on the measured capacitance by applying the capacitance formula of planar capacitor.

An online monitoring device for fouling and slagging based on capacitance principle differential measurement includes multiple measuring devices arranged at the same height of the boiler heating surface. Each measuring device includes a fixed sleeve and a sensor, one end of the fixed sleeve is fixed on the boiler heating surface, the sensor is connected with the fixed sleeve through screw threads, the end of the sensor near the boiler is equipped with a measuring probe. When measuring the thickness of ash residue on the monitoring surface, three sets of the measuring devices are at the same height of the monitoring surface. Each sensor is adjusted at a different position in the corresponding fixed sleeve to realize the differential measuring on ash residue thickness. Thus, the thickness of ash residue on the monitoring surface can be calculated based on the measured capacitance by applying the capacitance formula of planar capacitor.