Slag monitoring device for coal gasifier and coal gasifier

A slag monitoring device for a coal gasifier, the slag monitoring device comprising:

• a slag-hole observing unit that observes a slag hole from which molten slag flows out;
• a water-surface observing unit that observes a situation in which the slag flowing out from the slag hole falls onto a water surface of cooling water;
• a slag-falling-sound observing unit that observes a sound of the slag falling onto the water surface;
• an underwater-slag observing unit including a first wave transmitting/receiving sensor and a second wave transmitting/receiving sensor that can transmit and receive a detection wave is provided below the slag-falling-sound observing unit;
• and
• a processing device that determines a solidification and adhesion position of the slag based on an opening area of the slag hole observed by the slag-hole observing unit, and falling lines and falling positions of the slag observed by the water-surface observing unit, and changes over a relation of transmission and reception between the first wave transmitting/receiving sensor and the second wave transmitting/receiving sensor to evaluate deposition of solidified slag in the cooling water based on a detected path of the detection wave.