Method for preparing calcium oxide using a multistage suspension preheater kiln

A method for preparing calcium oxide using a multistage suspension preheater kiln, wherein the method comprises steps of:

• (1) feeding limestone powder to the multistage suspension preheater kiln for preheating to 800° C. to 900° C.;
• (2) feeding a preheated material to a decomposition furnace and calcining at 900° C. to 1100° C. and a negative pressure of −0.9 kPa to −1.5 kPa for 25 s to 35 s;
• (3) feeding a calcined material to a rotary kiln and calcining at 1100° C. to 1300° C. for 25 min to 35 min;
• cooling to obtain calcium oxide having a purity of 90% or greater;
• wherein the multistage suspension preheater kiln comprises six-stage hot flue gas cyclones that are sequentially connected to a hot gas duct;
• the six-stage hot flue gas cyclones comprises a first-stage hot flue gas cyclone, a second-stage hot flue gas cyclone, a third-stage hot flue gas cyclone, a fourth-stage hot flue gas cyclone, a fifth-stage hot flue gas cyclone and a sixth-stage hot flue gas cyclone;
• the hot gas duct conveys hot flue gas upward;
• the first-stage hot flue gas cyclone on the hot gas duct is the topmost hot flue gas cyclone, and a material outlet of the fifth-stage hot flue gas cyclone connects to an inlet of the decomposition furnace;
• an end of the hot gas duct is provided with an exhaust device;
• a material outlet of the first-stage hot flue gas cyclone connects to a hot flue gas outlet duct of the third-stage hot flue gas cyclone, a material outlet of the third-stage flue gas cyclone connects to a hot flue gas outlet duct of the fifth-stage hot flue gas cyclone;
• a material outlet of the second-stage hot flue gas cyclone connects to a hot flue gas outlet duct of the fourth-stage hot flue gas cyclone;
• a material outlet of the fourth-stage hot flue gas cyclone connects to a hot flue gas outlet duct of the sixth-stage hot flue gas cyclone;
• a material at an outlet of the decomposition furnace is fed to a feed pipe of the sixth-stage hot flue gas cyclone through a rising gas flow;
• a material outlet of the sixth-stage hot flue gas cyclone connects to a flue chamber of the rotary kiln;
• a raw material of the limestone powder is fed through the hot gas duct between the first-stage hot flue gas cyclone and the second-stage hot flue gas cyclone;
• wherein a gas temperature in the first-stage hot flue gas cyclone is lower than that in the second-stage hot flue gas cyclone;
• the second-stage hot flue gas cyclone has a gas temperature of 400° C. to 500° C. and a negative pressure of −4 kPa to −5 kPa;
• the third-stage hot flue gas cyclone has a gas temperature of 500° C. to 600° C. and a negative pressure of −3.5 kPa to −4.5 kPa;
• the fourth-stage hot flue gas cyclone has a gas temperature of 600° C. to 700° C. and a negative pressure of −2.5 kPa to −3.5 kPa;
• the fifth-stage hot flue gas cyclone has a gas temperature of 800° C. to 900° C. and a negative pressure of −1.5 kPa to −2.5 kPa;
• the sixth-stage hot flue gas cyclone has a gas temperature of 950° C. to 1130° C. and a negative pressure of −1.0 kPa to −2.0 kPa;
• and
• wherein a particle size of the limestone powder is less than 70 mesh.