BR-102020018650-B1 - METHOD FOR PREPARING CALCIUM OXIDE USING A MULTI-STAGE SUSPENSION PREHEATING FURNACE

BR102020018650B1BR 102020018650 B1BR102020018650 B1BR 102020018650B1BR-102020018650-B1

Abstract

METHOD FOR PREPARING CALCIUM OXIDE USING A MULTI-STAGE SUSPENSION PREHEATING FURNACE. The disclosure describes a method for preparing calcium oxide using a multi-stage suspension preheating furnace. The steps of the method are: (1) limestone powder is fed into the multi-stage suspension preheating furnace for preheating to 800°C to 900°C; (2) preheated material is fed into a decomposition furnace and calcined at 900°C to 1100°C for 25 to 35 s; (3) calcined material is fed into a rotary furnace and calcined at 1100°C to 1300°C for 25 to 35 minutes, and finally cooled to obtain calcium oxide.

Inventors

Yan Zhuang
Licheng Zhuang
Qiancheng Zhuang

Assignees

GUANGXI SIWEI MATERIALS TECHNOLOGY CO., LTD

Dates

Publication Date: 20260317
Application Date: 20200912
Priority Date: 20190912

Claims (4)

1. Method for preparing calcium oxide using a multi-stage suspension preheater furnace, characterized in that the method comprises the steps of: (1) feeding limestone powder into the multi-stage suspension preheater furnace for preheating to 800°C to 900°C; (2) feeding the preheated material into 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 the calcined material into a rotary furnace and calcining at 1100°C to 1300°C for 25 min to 35 min; cooling to obtain calcium oxide; wherein the multi-stage suspension preheater furnace comprises six-stage hot flue gas cyclones that are sequentially connected to a hot gas duct; The hot gas duct carries the hot combustion gas upwards; a first-stage hot combustion gas cyclone in the hot gas duct is the highest combustion gas cyclone, and a material outlet from a fifth-stage hot combustion gas cyclone connects to an inlet of a decomposition furnace; one end of the hot gas duct is provided with an exhaust device; a material outlet from the first-stage hot combustion gas cyclone connects to a hot combustion gas outlet duct of a third-stage hot combustion gas cyclone, and a material outlet from the third-stage hot combustion gas cyclone connects to a hot combustion gas outlet duct of a fifth-stage hot combustion gas cyclone. A material outlet from a second-stage hot combustion gas cyclone connects to a hot combustion gas outlet duct of a fourth-stage hot combustion gas cyclone; a material outlet from a fourth-stage hot combustion gas cyclone connects to a hot combustion gas outlet duct of a sixth-stage hot combustion gas cyclone; material at a decomposition furnace outlet connects to a feed pipe of the sixth-stage hot combustion gas cyclone via an upward gas flow; a material outlet from a sixth-stage hot combustion gas cyclone connects to a combustion chamber of the rotary kiln. A powdered limestone feedstock is fed through a hot gas duct between the first-stage hot combustion gas cyclone and the second-stage hot combustion gas cyclone; wherein the gas temperature in the first-stage hot combustion gas cyclone is lower than that in the second-stage hot combustion gas cyclone; the second-stage hot combustion gas cyclone has a gas temperature of 400°C to 500°C and a negative pressure of -4 kPa to -5 kPa; a third-stage hot combustion gas cyclone has a gas temperature of 500°C to 600°C and a negative pressure of -3.5 kPa to -4.5 kPa; a fourth-stage hot combustion 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 combustion 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 combustion gas cyclone has a gas temperature of 950°C to 1130°C and a negative pressure of -1.0 kPa to -2.0 kPa; wherein the particle size of the limestone powder is smaller than mesh 70; wherein the first-stage hot combustion gas cyclone has a diameter of 5.67 m and a height of 5.35 m; wherein the second-stage hot combustion gas cyclone has a diameter of 6.58 m and a height of 5.83 m; wherein the third-stage hot combustion gas cyclone has a diameter of 6.96 m and a height of 6.93 m; wherein the fourth-stage hot combustion gas cyclone has a diameter of 7.15 m and a height of 5.58 m; wherein the hot combustion gas cyclone of the fifth stage has a diameter of 7.86 m and a height of 5.91 m; wherein the hot combustion gas cyclone of the sixth stage has a diameter of 7.93 m and a height of 5.98 m.
2. Method according to claim 1, characterized in that the hot combustion gas is a combustion gas that is generated by the decomposition furnace and the rotary kiln.
3. Method according to claim 1, characterized in that the fuel used for calcination in the rotary kiln is petroleum coke.
4. Method according to claim 1, characterized in that the wind pressure in the rotary kiln is 12 kPa and the rotational speed of the rotary kiln is 3.5 rpm.

Description

TECHNICAL FIELD [0001] The disclosure relates to the field of a method for preparing calcium oxide by calcination, particularly to a method for preparing calcium oxide using a multi-stage suspension preheater furnace. BACKGROUND [0002] Currently, two main methods are used for the production of calcium oxide (lime). One method uses a vertical kiln for calcination, the other method uses a single-stage preheating rotary kiln for calcination. [0003] The vertical kiln is for calcining large quantities of limestone with a particle size of 100 mm to 300 mm. During the calcination process, a suitable fuel must be used; the fuel and limestone enter the kiln simultaneously and burn. This process requires large quantities of limestone to allow for ventilation and combustion, resulting in slow combustion, low efficiency, high energy consumption, low yield, and low product quality. Furthermore, desulfurization and denitrification equipment is necessary for environmental protection, resulting in high production costs. [0004] The single-stage preheater rotary kiln is for calcining limestone with a particle size of 40 mm to 80 mm. The material enters the rotary kiln slowly, and fuel is injected into the kiln from the top for combustion. The residual heat generated during combustion in the rotary kiln flows upwards and enters a single-stage preheater at the end of the kiln. Although the material is preheated to a certain degree, it has slow heat absorption and a large particle size, resulting in unsatisfactory combustion, a long calcination and decomposition time, poor ventilation, and other problems. These problems lead to low yield, high energy consumption, and low product quality; in addition, desulfurization and denitrification equipment is also necessary for environmental protection. [0005] These two conventional methods involve treating limestone chunks of different sizes by calcining them at high temperature to transform them into lime lumps, followed by grinding, hydration, and other processes to further process the lime into lime powder, lime mass (slaked lime), and other materials. The production capacities of these conventional processing methods are low: currently, the production capacity of a single machine is 100 to 800 tons per day. In addition, energy consumption is high: 3350 kJ/kg (200 kg of standard coal) of energy and 50 kWh of power are consumed. SUMMARY [0006] The objective of this disclosure is to overcome the disadvantages of the prior art and provide a method for preparing calcium oxide using a multi-stage suspension preheater furnace. [0007] In order to achieve the disclosure objective, the technical solution of the present disclosure includes a method for preparing calcium oxide using a multi-stage suspension preheater furnace, comprising the steps of: Method for preparing calcium oxide using a multi-stage suspension preheater furnace, characterized in that the method comprises the steps of: (1) feeding limestone powder to the multi-stage suspension preheater furnace to preheat to 800°C to 900°C; (2) feeding a preheated material to a decomposition furnace and calcining at 900°C to 1100°C for 25 s to 35 s; (3) feeding a calcined material to a rotary furnace and calcining at 1100°C to 1300°C for 25 min to 35 min; cooling to obtain calcium oxide. [0008] In the present disclosure, instead of adopting the prior art method of directly calcining limestone in large quantities, powdered limestone is preheated in suspension, calcined and decomposed in the decomposition furnace, calcined and quenched in the rotary kiln to produce powdered calcium oxide. This process has a high production capacity and is energy-efficient and environmentally friendly. According to actual needs, the multi-stage suspension preheater furnace can be divided into 2 or more stages, preferably 5 to 7 stages. Cooling can be carried out in a cooler; the cooling method can be cold air cooling. [0009] As a preferred embodiment of the method for preparing calcium oxide using a multi-stage suspension preheater furnace of the present disclosure, the multi-stage suspension preheater furnace comprises six-stage hot flue gas cyclones that are sequentially connected to a hot gas duct; the hot gas duct carries the hot flue gas upwards; a first-stage hot flue gas cyclone in the hot gas duct is the highest hot flue gas cyclone, and a material outlet from a fifth-stage hot flue gas cyclone connects to an inlet of a decomposition furnace. [0010] As a preferred embodiment of the method for preparing calcium oxide using a multi-stage slurry preheater furnace of the present disclosure, the gas temperature in the first-stage hot combustion gas cyclone is lower than that in a second-stage hot combustion gas cyclone; the second-stage hot combustion gas cyclone has a gas temperature of 400°C to 500°C and a negative pressure of -4 kPa to -5 kPa; a third-stage hot combustion gas cyclone has a gas temperature of 500°C to 600°C and a negative pressure of -3.5