Production of building gypsum powder by calcining sulphur gypsum with Sder calciner

I. Overview

Power plants, thermal power plants and large boilers use wet desulfurization to produce a large amount of by-product sulfur gypsum. The desulfurized sulfur gypsum is filtered by a suction filter. The surface water content is 10-15%, the particle size distribution is about 10-100 μm, and the calcium sulfate content is generally greater than 90% to 95%.

Various tests have shown that the desulfurized gypsum can be dried and calcined to produce high-quality building gypsum powder. Since the production of hemihydrate gypsum with desulfurized gypsum has just started in my country, there is no special drying and calcining production equipment for calcining sulfur gypsum into building materials, and the production process of sulfur gypsum with natural gypsum production equipment is quite different. A domestic company introduced foreign equipment to rapidly calcine sulphur gypsum to produce building material gypsum. There are still technical problems in use and continuous improvement and adjustment. Beijing Xingda Kaiyuan Desulfurization Gypsum Co., Ltd. adopted the "Side calciner" designed and manufactured by Liaoning Dongda Powder Engineering Technology Co., Ltd. for calcining sulfur gypsum to produce building gypsum powder. It started debugging and put into production in April 2006. In the debugging process, a reasonable calcination process system is formulated according to the characteristics of sulfur gypsum, and the produced hemihydrate gypsum meets the (GB9776-88) standard and reaches and exceeds the performance of the first-class product. The successful application of this calciner in the calcination of sulfur gypsum provides advanced and reliable process data and equipment for the production of building gypsum from sulfur gypsum.

2. The process and basic principle of sulfur gypsum calcination

According to the above-mentioned calcination system process, the system equipment is mainly composed of heat source, Sder calciner, gas-solid separator, aging bin and storage bin.

Sid calciner is the main equipment in the above system. Sid calciner is a kind of rapid calcining equipment. The hot air heated by the combustion chamber enters the gas distribution chamber of the Sder calciner, and the feeder sends the material to be calcined into the Sder furnace. The movement makes the material quickly disperse, forming a larger specific surface, the heat carrier and the material quickly transfer heat, and the drying and calcining process is completed in an instant.

The system uses coal as the fuel for the heat source and uses a machine-fired coal-fired flue gas hot blast stove, and the high-temperature flue gas generated by the combustion is directly used as the heat source for drying and calcination after dust reduction treatment.

The process of calcining sulfur gypsum in the calciner is as follows: the sulfur gypsum is sent to the feeder of the calciner by the lifting conveyor, and enters the calciner, and is mechanically dispersed in the calciner and the high-temperature flue gas generated by the heat source part It enters the calciner to conduct rapid heat transfer with the dispersed sulfur gypsum. The surface water of the sulfur gypsum is rapidly vaporized in the drying area, and the material temperature rises rapidly and enters the calcining area. The drying and calcining process is completed in 5 to 10 seconds. The gypsum powder converted into hemi-water enters the gas-solid separator for gas-solid separation from the outlet of the Sid calciner. The collected hemi-hydrate gypsum is sent to the aging bin by the conveyor, and the tail gas is further purified and discharged into the atmosphere through bag dust removal.

3. Main features and process data of Sder calciner

To calcine sulfur gypsum in a Sder calciner, it is necessary to combine the operation process of the calciner with the calcining process of sulfur gypsum to determine the basic operating procedures. During the commissioning process, by adjusting the inlet and outlet temperatures of the Sder calciner, adjusting the feed rate of materials in the system and the interface factors between drying and calcining, find out the relevant conditions that affect the initial and final setting, compression resistance and bending resistance, and determine the basic operating procedures. . The following data are the relevant results reflected in the debugging.

SamplingHost import ℃Host outlet °CAdd water %Initial setting time/minFinal setting time/minFlexural strength

After completing the commissioning and determining the basic operating procedures, the equipment entered normal production. Through comparison and summary, the main characteristics of calcining sulfur gypsum by using the Sid calciner are as follows:

1. Drying and calcination are completed in one step

The characteristic of the Sder furnace is that drying and calcination are completed at one time. The surface water of sulphur gypsum is generally about 10-15%, and the material is in a viscous and agglomerated state. It must go through the drying and pulverizing process before, forming a long production process line and a large equipment area. Steer furnace occupies only 1/2 of the above process. The process does not require crushing, the process route is simple, the production capacity is large, the annual output is 50,000 to 100,000 tons, and the equipment and operation space covers an area of more than 200 square meters.

2. After calcination, the material particles can form a good gradation

The particle size of the sulfur gypsum calcined in the Sder calciner becomes smaller, the surface area increases, the activity increases, and the product performance is enhanced. This is the outstanding feature of Sder calcination. After calcination, the grinding process can be omitted. The particle size of the product is obviously reduced, and the specific surface area can be increased by 5 to 10 times. (See the particle size distribution diagram of sulphur gypsum before and after calcination)

3. Continuous production, stable product quality.

It can be seen from the relevant data monitored during the production and operation of the equipment that the corresponding initial and final setting times can be obtained by adjusting the relevant temperature parameters during the operation. The initial setting time can be arbitrarily adjusted within 5 to 7 minutes, and the final setting time can be Adjust within 20 minutes. The flexural strength is greater than 3.2MPa/cm2. After calcination, the product is placed for 1, 3 and 7 days and tested, and the performance is stable. The main factor for the stable product quality is the stable calcination temperature. The heat source and control method adopted by the Sder furnace can make the temperature change within the range of ±5℃. The moisture content of the material is unstable and has little effect on the product performance.

Another reason for the stable quality of the product is that the material is heated evenly, there is no dead angle in the calcination, no raw burning and over-burning, and continuous production can achieve the purpose of rapid aging.

The partial pressure of wet air formed during drying is used to balance the escape rate of crystal water to form a reasonable air humidity, so that the product is not overheated and the phase composition is stable.

4. High production efficiency and low energy consumption.

The outstanding features of the calciner are rapid calcination, high production efficiency and low energy consumption. During rapid calcination, the decomposition temperature of the material is 20-30°C lower than that of low-temperature slow calcination, so that energy consumption can be saved by about 15%.

According to production statistics and equipment operation testing, the energy consumption per ton of building gypsum powder is shown in the table below.

NameSurface water W0%Power consumption kwh/ton productEnergy consumption 1×104kcal/ton product
Sulfur gypsum10~12%18~20


Equivalent to coal (standard coal) 55~58kg/ton product

5. It is easy to operate and can be controlled automatically.

Set the temperature of the inlet and outlet of the furnace, and use automatic and manual methods to control the temperature range, so that qualified products can be produced continuously and stably.

6. Less investment and low operating cost.

Since the one-step drying and calcination process is simpler and simpler than the traditional calcining method, from the investment analysis, the one-step process is compared with the comprehensive investment of the two-step process, the investment is reduced by more than 30%, the operating cost is reduced by 20%, and the equipment failure rate is reduced by more than 30%. Low, no pollution to the environment, conducive to civilized production.

Simple and simple, from the perspective of investment analysis, the one-step process is compared with the comprehensive investment of the two-step process, the investment is reduced by more than 30%, the operating cost is reduced by 20%, the equipment failure rate is low, the environment is not polluted, and it is conducive to civilized production. .