1. The origin of suspension roasting technology

Twenty years ago, ZK, with its acute market insight and outstanding R&D capabilities, launched the equipment combination of "preheater + rotary kiln + vertical cooler". This innovative achievement was quickly and widely applied within the industry. ZK even drafted relevant equipment standards based on it, setting a benchmark for the standardized development of the industry. However, ZK has always been passionate about technological innovation and has never ceased its exploration in the field of calcination equipment research and development, promoting continuous technological iteration and upgrading

To further reduce energy consumption during the calcination process of white stone and significantly cut carbon emissions, ZK launched a six-year scientific research project, and the suspension calcination technology of ZK was thus born. Guo Shi has joined hands with Zhengzhou University and Chinalco Zhengzhou Research Institute to integrate the scientific research forces of all parties and carry out the research and development of suspension calcination technology. From the repeated verification of fundamental principles in the theoretical research stage, to the brainstorming during the initial design scheme, and then to the meticulous refinement in engineering design; From the arduous exploration of setting up the pilot production line to countless experiments and improvements, the R&D team overcame numerous difficulties and finally achieved results

2. Working Principle of suspension roasting

The powdered materials stored in the raw material silo (such as limestone, dolomite, coal gangue, magnesium carbonate, aluminium hydroxide, etc.) are conveyed and measured by the screw conveyor at the bottom of the silo and the screw metering scale, and then fed into the secondary cyclone preheater (commonly known as the Venturi dryer) by the feeding screw conveyor for initial preheating. The initially preheated materials are carried into the first-stage cyclone separator of the suspension furnace along with the hot gas flowing through the air duct. The mixed gas undergoes gas-solid separation in the first-stage cyclone preheater. The separated solid materials are then blown away by the hot gas (with a gas temperature of approximately 500 to 950℃) coming out of the third-stage cyclone preheater of the suspension furnace and come into full contact with the hot air for further preheating. Then it enters the second-stage cyclone preheater of the suspension furnace with the hot gas flow for gas-solid separation. The hot air coming out of the first-stage cyclone preheater of the suspension furnace enters the subsequent flue gas treatment system for desulfurization, dust removal and denitrification treatment before being discharged. The materials are discharged from the three-stage cyclone preheater and sent to the five-stage suspension furnace for calcination. After five stages of preheating, calcination and three stages of cooling, the products are sent to the finished product storage by the bucket elevator.

After strict calculation and practical verification, the suspension calcination technology has achieved remarkable results in energy conservation and consumption reduction. Compared with the traditional calcination method, this technology can save 30% of standard coal. Originally, 220 kilograms of standard coal were consumed to produce one ton of calcined white, but now it has been reduced to 140 kilograms. Producing one ton of magnesium can save 440 kilograms of standard coal. Calculated at a price of 600 yuan per ton of standard coal, the production cost of one ton of magnesium can be reduced by 264 yuan. Powder calcination takes only over three minutes, which is particularly suitable for dolomite with poor thermal strength. Meanwhile, all the crushed materials from the mine can be fully utilized, turning waste into treasure.

3. Suspension roasting pilot line‌

The designed production capacity of the suspension calcination pilot line is 1-1.5t/h. It takes about 8 hours to complete a full test, and the specific time needs to be adjusted appropriately according to different materials. This test line can only calcine powder materials with a mesh size of 100 or less, and can also calcine mixed powder materials with similar properties. It is not possible to calcine 2-3 kinds of mixed powder materials with significant differences in physical properties, nor can it calcine blocky or small granular materials. Therefore, it is necessary to prepare the corresponding amount of powder materials in advance and store them in the raw material silo, which has an effective storage capacity of approximately 7 m³.


Suspension roasting pilot line: raw material silo and finished product silo

  The pilot line is composed of:

1. Raw Material Storage, Suspension Furnace Calcination, Finished Product Storage System

2. Waste Gas Treatment System

3. Fuel Supply and Utility System

The raw materials of this industrial pilot line complete the entire process from preheating to calcination and then to cooling in a suspended state. It is a continuous and stable production equipment

The ZK suspension calcination system is suitable for the calcination of various powdered materials, such as limestone, dolomite, coal gangue, magnesium carbonate, aluminum hydroxide, etc. For different materials, the requirements for raw materials and product quality are different.

4. Advantages and Disadvantages of Suspension Furnace Calcination:

Advantages:

1. The fine particle high-quality resources that cannot be utilized by rotary kilns and shaft kilns have been fully utilized

2. It has low heat consumption and saves more than 30% energy compared with the traditional rotary kiln production process

3. cover a small area

4. It has a large production capacity, a high level of automation, flexible production adjustment, high product activity and uniform quality

5. It is suitable for large enterprises to produce high-quality products

Disadvantages:

1. The product cannot be directly applied to industries that require blocky materials. It is necessary to add powerful pelletizing equipment

2. If coal powder is used as fuel, it will cause certain pollution to the product