Slag discharge system, gasifier, and slag filtration method

A slag discharge system, comprising:

• a slag bath disposed at a bottom portion of a gasifier that gasifies via pyrolysis a carbonaceous feedstock, the slag bath receiving slag produced from the carbonaceous feedstock and storing a slag cooling water for rapidly cooling and fragmenting the slag;
• a slag cooling water circulation line that removes a mixture of fragmented slag and the slag cooling water from the bottom portion of the slag bath and circulates the slag cooling water with the slag removed to the slag bath;
• a coarse slag separator device connected in the slag cooling water circulation line, the coarse slag separator device separating coarse slag contained in the slag cooling water;
• a fine slag separator device connected to the coarse slag separator device downstream side, the fine slag separator device separating fine slag contained in the slag cooling water;
• and
• a circulator pump connected to the fine slag separator device downstream side, the circulator pump creating a water flow in the slag cooling water circulation line for pumping out a mixture of the slag and the slag cooling water from the slag bath;
• wherein
• a normal pressure line is connected to the slag cooling water circulation line, the normal pressure line branching from the slag cooling water circulation line at a branching point between the coarse slag separator device and the circulator pump and again joining the slag cooling water circulation line at a joining point between the branching point and the circulator pump, and
• in order from the branching point, a pressure reducing portion that reduces pressure coming into from the slag cooling water circulation line to a normal pressure, the fine slag separator device, and a pressure increasing portion that again increases pressure reduced by the pressure reducing portion are disposed in the normal pressure line.

A slag filtration method, comprising:

• discharging a slag cooling water stored in a slag bath together with a slag produced from a carbonaceous feedstock that falls into the slag cooling water, from a bottom portion of the slag bath disposed at a bottom portion of a gasifier that gasifies via pyrolysis the carbonaceous feedstock;
• performing first filtration to separate coarse slag contained in the slag cooling water, then circulating the slag cooling water towards the slag bath;
• extracting at least a portion of the slag cooling water after first filtration;
• reducing pressure of the at least a portion of the slag cooling water being extracted from a pressure of inside the gasifier to a normal pressure, then performing second filtration to separate fine slag contained in the portion of the slag cooling water;
• and
• increasing pressure of the portion of the slag cooling water after second filtration back to the pressure of inside the gasifier, then joining the portion of the slag cooling water after second filtration back to the slag cooling water after first filtration.