Variable orifice for pulverized coal pipe of pulverizer

A variable orifice for a pulverized coal pipe of a pulverizer comprising:

• a pipe body connected to and installed on a pipeline of the pulverized coal pipe for supplying a pulverized coal from the pulverizer to a boiler and comprising a diameter expansion portion having a diameter expanded more than a diameter of the pulverized coal pipe;
• an opening and closing portion installed inside the diameter expansion portion of the pipe body such that a pair of an inner opening and closing plate and an outer opening and closing plate having curved shapes are arranged to face each other and mutually overlapped to be a hemispherical shape as a whole, and the inner opening and closing plate and the outer opening and closing plate are opened together to extend a cross-sectional area of the pipe body or the inner opening and closing plate and the outer opening and closing plate are closed together to reduce the cross-sectional area of the pipe body;
• a rotation actuating portion configured to rotate the inner opening and closing plate and the outer opening and closing plate in mutually different directions such that the inner opening and closing plate and the outer opening and closing plate are opened or closed together to extend or reduce the cross-sectional area of the pipe body;
• and
• an opening and closing plate protection member coupled to an inner circumferential surface of each of the inner opening and closing plate and the outer opening and closing plate so as to protect the inner circumferential surface of each of the inner opening and closing plate and the outer opening and closing plate from an impact of the supplied pulverized coal,
• wherein the opening and closing plate protection member is formed of a ceramic material which is molded as a main raw material of one or more kinds selected from the group consisting of nitrides, carbides, oxides, complex nitrides, complex carbides, complex oxides, carbonitrides, oxynitrides, and carbonates of aluminum (Al), silicon (Si), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chrome (Cr), molybdenum (Mo), and tungsten (W),
• wherein each of the inner opening and closing plate and the outer opening and closing plate comprises:
• a cutting plate having a cut certain part of upper end portions which face each other;
• and
• a main body plate that is a remaining part of the cutting plate,
• wherein the cutting plate is detachably coupled to the main body plate,
• wherein the opening and closing plate protection member comprises:
• a cutting plate protection member coupled to each of the inner opening and closing plate and the outer opening and closing plate such that the cutting plate protection member is fitted to an inner circumferential surface of the cutting plate of each of the inner opening and closing plate and the outer opening and closing plate;
• and
• a main body plate protection member coupled to each of the inner opening and closing plate and the outer opening and closing plate such that the main body plate protection member is fitted to an inner circumferential surface of the main body plate of each of the inner opening and closing plate and the outer opening and closing plate,
• wherein the main body plate protection member has a uniform thickness,
• wherein the cutting plate protection member is formed to gradually increase from the thickness of the main body plate protection member toward an upper end.