Overview of desulfurization gypsum

Overview of desulfurization gypsum

With the increasing awareness of environmental protection, China's control over the emission of sulfur dioxide in the coal-fired flue gas of power plants is becoming more and more tight, and the desulfurization of power plants is imperative. At present, the treatment process and equipment of desulfurized gypsum are not completely the same as that of natural gypsum, such as material transportation, dust treatment, calcination process, etc.: there are also differences between desulfurized gypsum and natural gypsum in terms of physical properties, such as high purity of desulfurized gypsum, large free water, and fine particle size; The particle size and particle size distribution are uniform, the grading is poor, the water consumption for standard consistency is large, and there are many water-soluble salts; It is also worth noting that the sources of desulfurization gypsum and natural gypsum are different. The main impurities in desulfurization gypsum are unreacted calcium carbonate and calcium sulfite that has not been completely oxidized. The existence and impurity state of the impurities are quite different. In addition, the different technical treatment in desulfurization production process, the different raw material composition of limestone, and the different fineness of processed limestone will affect the quality of desulfurization gypsum.

Drying and exercise process and technology of desulfurized gypsum dryer

The main application of desulfurized gypsum is to use it as a retarder of cement after drying; Or semi-hydrated gypsum, which is used for making gypsum board, gypsum block and plastering gypsum. Building gypsum processing can be divided into direct method and indirect method according to different heat transfer methods:

1. Indirect method (two steps of drying and calcination)

According to the energy situation and environmental protection requirements of the power plant, the two-step method of drying and calcination is to separate the free water that is easy to be separated from the crystal water that is difficult to be separated in two sets of equipment, which makes it more reasonable and convenient for product structure adjustment and quality control. The device can produce dry gypsum dihydrate (used for cement retarder) and super excellent products β Gypsum.

2. Direct method (drying and calcination one-step method)

The one-step drying and calcination process is a set of gypsum calcination process device developed and designed by using the three-layer drum drying technology with high heat and mass transfer efficiency. The process unit can produce dry dihydrate gypsum (for cement retarder) and hemihydrate gypsum. The air temperature for producing dry dihydrate gypsum is only 120. The low-temperature flue gas from thermal power plants can be fully utilized.

Utilization and development prospect of desulfurized gypsum

Desulfurized gypsum is widely used in the building materials industry. It can basically replace most building materials products produced with natural gypsum through different means of treatment. The comprehensive treatment and application of desulfurized gypsum in China has started, and the utilization prospect contains huge market opportunities, especially in economically developed areas where natural gypsum is scarce and desulfurized gypsum resources are rich. The application practice has proved that desulfurized gypsum is a valuable resource with high grade, and it can be suitable for the production of gypsum building materials for different purposes. The treated desulfurized gypsum is a better cementing material than natural gypsum. Desulfurized gypsum is dried and dehydrated to become anhydrite, which can be divided into cast gypsum, plaster gypsum, gypsum for ceramic industry, gypsum for casting industry, dental plaster, orthopedic bandage medical plaster, gypsum for coal mine fire prevention reinforcement roadway wall, gypsum for soil improvement, and so on.

Working principle of desulfurization gypsum dryer

The working principle of the desulfurized gypsum dryer is as follows: the desulfurized gypsum enters the inner layer of the multi-layer drum from the feeding device to realize the downstream drying. The desulfurized gypsum is continuously copied under the inner plate and scattered in a spiral way to realize the heat exchange. The material moves to the other end of the inner layer and enters the middle layer for countercurrent drying. The material is continuously lifted in the middle layer repeatedly, in a way of two steps forward and one step backward, The material in the middle layer not only fully absorbs the heat emitted by the inner layer drum, but also absorbs the heat of the middle layer drum. At the same time, the drying time is extended, and the material reaches a good drying state here. The material moves to the other end of the middle layer and falls into the outer layer. The material moves in a rectangular multi-circuit way in the outer drum. The material that has reached the drying effect moves quickly under the action of hot air and is discharged from the drum. The wet material that has not reached the drying effect cannot move quickly because of its own weight. The material is fully dried in this rectangular sheet, so as to achieve the drying effect and complete the drying process.

Features of desulfurized gypsum dryer

1. Desulfurized gypsum dryer has strong overload resistance, large processing capacity, low fuel consumption and low drying cost;

2. Desulfurized gypsum dryer adopts the downstream drying method. Hot air and wet materials enter the dryer from the same side. High evaporation intensity can be obtained by using high temperature air. The outlet temperature of the dryer is low and the thermal efficiency is high;

3. The desulfurized gypsum dryer can change the operation parameters according to the different material properties, so that the material can form a stable full-cut fabric curtain in the dryer cylinder, and the mass and heat exchange is more sufficient;

4. The desulfurized gypsum dryer adopts a new type of feeding and discharging device, which eliminates the blocking, discontinuity, nonuniformity and material return of the vertical dryer, and reduces the load of the dust removal system;

5. The desulfurized gypsum dryer realizes "zero horizontal thrust", greatly reduces the wear of the retaining roller, and the cylinder operates stably and reliably;

6. The desulfurized gypsum dryer adopts a "self-aligning supporting roller device", which makes the matching between the supporting roller and the rolling ring always in linear contact, thus greatly reducing the wear and power loss;

7. Desulfurized gypsum dryer can control product moisture according to user requirements.