Apparatus for burning materials of cement and the like

Claim 1

A suspension type rotary kiln apparatus for burning the materials of cement, comprising a. a calcinating furnace (1) having at its bottom a combustion air inlet and at its top a feed inlet (5) and an exhaust gas outlet, said furnace including also a plurality of burners (2, 3, 4) for establishing a given burning ratio; b. suspension preheater means including a plurality of cyclones (8, 9, 10) for feeding preheated raw meal to the feed inlet of said furnace; c. a cyclone (11) having an inlet connected with the exhaust gas outlet of said furnace, said cyclone having an exhaust gas outlet connected with the lower portion of said suspension preheater means, and a raw meal outlet; d. exhaust fan means (23) connected with the upper portion of said suspension preheater means for drawing exhaust gases therethrough; e. rotary kiln means (16) having at one end an inlet chamber (15) provided with an inlet connected with the raw meal outlet of said cyclone, said inlet chamber including also an exhaust gas outlet, said rotary kiln means including at its other end an outlet; f. cooler means (18) having an inlet connected with the outlet of said kiln means for receiving the burnt materials produced thereby, said cooler means including also a combustion air outlet; g. a secondary air duct (6) connecting the combustion air outlet of said cooler means with the combustion air inlet of said calcinating furnace; h. a branch duct (21) containing a reduced portion defining an orifice (25) for connecting the exhaust gas outlet of said inlet chamber with said secondary air duct adjacent said furnace, whereby the high temperature exhaust gas from the kiln is mixed with the high temperature combustion air from the cooler; and i. damper means (26, 27) in said secondary air duct intermediate said cooler and said branch duct for regulating the quantity of the combustion air from the cooler that is mixed with the high temperature exhaust gases from the kiln and is supplied to the furnace, said damper means being so adjusted and the restriction of the orifice in said branch duct being so dimensioned that tHe pressure loss in the secondary duct system substantially equals the pressure loss in the kiln system, the capacity of said exhaust fan means being so selected relative to the burning ratio of the burners that the velocity of the combustion air introduced into the furnace from the secondary air duct is higher than the flame propagation speed, whereby almost no flame is generated and the finely divided fuel particles which are floating with the finely ground raw material are burnt at a relatively low temperature and without the formation of a high temperature zone in the furnace.