There is provided a cement plant including a chlorine bypass apparatus capable of efficiently reducing the chlorine concentration in a cement kiln due to exhaust gas extraction by a small amount, by preventing calciner exhaust gas low in chlorine concentration from contamination and extracting a part of kiln exhaust gas high in chlorine concentration. In the invention, a baffle wall 20 which protrudes, on a lower face 16a of an exhaust duct 16 of a calciner connected to the pipe inclination part 14 of an exhaust gas pipe 9 rising from a kiln inlet part 2 of a cement kiln 1, toward a pipe inclination part 14 side at an inclination angle within a range of 20 to 60 relative to the horizontal plane, and a spacing between a lower end edge 20a of the baffle wall and an opposite wall plane 14a of the pipe inclination part is configured such that an average flow rate of the exhaust gas between the both falls within a range of 15 to 35 m/s.

There is provided a cement plant including a chlorine bypass apparatus capable of efficiently reducing the chlorine concentration in a cement kiln due to exhaust gas extraction by a small amount, by preventing calciner exhaust gas low in chlorine concentration from contamination and extracting a part of kiln exhaust gas high in chlorine concentration. In the invention, a baffle wall 20 which protrudes, on a lower face 16a of an exhaust duct 16 of a calciner connected to the pipe inclination part 14 of an exhaust gas pipe 9 rising from a kiln inlet part 2 of a cement kiln 1, toward a pipe inclination part 14 side at an inclination angle within a range of 20 to 60 relative to the horizontal plane, and a spacing between a lower end edge 20a of the baffle wall and an opposite wall plane 14a of the pipe inclination part is configured such that an average flow rate of the exhaust gas between the both falls within a range of 15 to 35 m/s.

A method and a corresponding plant for denitrifying bypass exhaust gases in a cement clinker production plant. Raw meal is sintered in a rotary kiln and deacidified in a calciner. A rotary kiln inlet chamber is connected to the calciner directly or by a riser duct. Bypass exhaust gas is drawn off near the inlet chamber. This exhaust gas is guided into a first mixing chamber, in which the exhaust gas is cooled to between 800 and 950 degrees C., then the exhaust gas is guided through a reaction pipeline segment, wherein the dwell time is between 0.5 and 3 seconds and ammonia, aqueous ammonia solution, or ammonia-releasing substances are injected for denitrification. Then the exhaust gas is guided into a second mixing chamber, in which the exhaust gas is cooled to between 150 250 degrees C. Then the exhaust gas is guided to a filter for dust removal.

A method for industrial refining of coal ash created in power plants and carbonaceous ashes produced in other combustion processes by separating coal from said ashes and returning it to use and by recovering a substantially coal-free ash fraction obtained in the refining. In the method, coal ash and at least one ash fraction created by gasification technique in combustion plants are carefully proportioned in relation to one another and formed into a slurry mixture by means of an efficient dispersion technique, the slurry being then led to a flotation step, where a fraction rich in coal and a siliceous fraction poor in coal and a fraction dissolving in the process water are separated by flotation. The coal ash is arranged to have the highest proportion in the mixture to be taken to flotation, the ashes from combustion plants being dosed into said mixture in an amount that does not cause the maximum amounts of harmful substances to be exceeded in the qualities of the carbonaceous product and the silicate product poor in coal to be obtained.

A method for industrial refining of coal ash created in power plants and carbonaceous ashes produced in other combustion processes by separating coal from said ashes and returning it to use and by recovering a substantially coal-free ash fraction obtained in the refining. In the method, coal ash and at least one ash fraction created by gasification technique in combustion plants are carefully proportioned in relation to one another and formed into a slurry mixture by means of an efficient dispersion technique, the slurry being then led to a flotation step, where a fraction rich in coal and a siliceous fraction poor in coal and a fraction dissolving in the process water are separated by flotation. The coal ash is arranged to have the highest proportion in the mixture to be taken to flotation, the ashes from combustion plants being dosed into said mixture in an amount that does not cause the maximum amounts of harmful substances to be exceeded in the qualities of the carbonaceous product and the silicate product poor in coal to be obtained.

In accordance with the present invention, there is provided a treat chlorine bypass dust while preventing increases in chemical cost and concentrations of heavy metals in clinker, and ensuring stability in quality of cement. In a chlorine bypass facility 1 extracting a part G of combustion gas, while cooling it, from a kiln exhaust gas passage, which runs from an inlet end of a cement kiln to a bottom cyclone, and recovering a high chlorine concentration chlorine bypass dust D5 from the extracted gas G1, a slurry S containing chlorine bypass dust and SO2 gas or/and CO2 gas are contacted with each other to obtain solid content. The slurry containing chlorine bypass dust and an exhaust gas from the chlorine bypass facility or/and the exhaust gas from the cement kiln can be contacted with each other, and the solid content can be fed to a cement finishing process, which allows cement with low CaO and Ca(OH)2 contents and with stable property such as setting time to be produced.

In accordance with the present invention, there is provided a treat chlorine bypass dust while preventing increases in chemical cost and concentrations of heavy metals in clinker, and ensuring stability in quality of cement. In a chlorine bypass facility 1 extracting a part G of combustion gas, while cooling it, from a kiln exhaust gas passage, which runs from an inlet end of a cement kiln to a bottom cyclone, and recovering a high chlorine concentration chlorine bypass dust D5 from the extracted gas G1, a slurry S containing chlorine bypass dust and SO2 gas or/and CO2 gas are contacted with each other to obtain solid content. The slurry containing chlorine bypass dust and an exhaust gas from the chlorine bypass facility or/and the exhaust gas from the cement kiln can be contacted with each other, and the solid content can be fed to a cement finishing process, which allows cement with low CaO and Ca(OH)2 contents and with stable property such as setting time to be produced.

Process for the purification of a residue containing solids and mother liquor and having a chloride ion content greater than 5000 ppm by weight relative to the weight of the residue which comprises (a) piston washing said residue with a washing fluid and (b) recovering a purified residue.

Process for the purification of a residue containing solids and mother liquor and having a chloride ion content greater than 5000 ppm by weight relative to the weight of the residue which comprises (a) piston washing said residue with a washing fluid and (b) recovering a purified residue.