1. technical name

Built-in waste heat boiler in main flue of sintering machine in steel plant

2. scope of application

In the field of steel smelting, this technology has little impact on the sintering system. However, considering the complex sintering operating conditions, a residual pressure of 600Pa to 1000Pa from the main sintering exhaust fan is required to meet the overall design needs. In addition, only when the smoke temperature of the main flue is above 150℃, the waste heat can be utilized.

3. technical content

3.1 technical principle

The waste heat recovery of the main flue of sintering mainly recovers the waste heat of high-temperature waste gas generated during the production process of the sintering machine. Corresponding boiler heat exchange surfaces are arranged in the main flue. The heat exchange surfaces of the waste heat boiler realize the heat exchange between the working medium and the flue gas, and generate superheated steam., to provide production use and achieve the purpose of cooling the flue. This technology analyzes the overall flow field and selects a reasonable flue gas flow rate and tube row spacing. The built-in waste heat boiler will basically not affect the system resistance.

3.2 main innovations

(1) Adopt a built-in main flue waste heat boiler to reasonably utilize the heat of high-temperature exhaust gas in the main flue without affecting the system resistance and sinter quality to generate superheated steam, which can be used for other process steam, and can also be used for power generation, while reducing the exhaust gas temperature of the main flue, achieving the purpose of energy conservation and consumption reduction. Compared with external boilers, the built-in waste heat boiler achieves high quality and high utilization of energy, is utilized in stages, has less equipment, and is simple to maintain.

(2) The superheater adopts a low-flow-velocity finned wear-resistant tube design, and the evaporator and economizer adopt a heat pipe structure, which structurally avoids water leakage accidents and operates safely and reliably.

4. Energy conservation and greenhouse gas emission reduction effects

Liuzhou Iron and Steel Company 1#Take the built-in waste heat boiler in the main flue of a 360m2 sintering machine as an example: This waste heat boiler uses high-temperature flue gas at about 350℃ to heat feed water at 40℃, producing superheated steam at 1.9MPa and 310℃, with a steam flow rate of 12t/h, which can save 880kg/h of standard coal. At present, waste heat is not routinely recycled in the main flue of sintering machines, and high-temperature waste gas is directly discharged into the atmosphere. The use of a built-in waste heat boiler in the main flue can effectively utilize the energy of hot exhaust gas and reduce the exhaust gas temperature.

5. Technology demonstration

There have been 4 engineering application demonstrations. For example, the sintering system waste heat utilization project of the nickel-iron smelting project of Guangxi Liugang Zhongjin Stainless Steel Co., Ltd., the comprehensive utilization project of sintering waste heat and energy of the sintering pellet system of the Fangchenggang Iron and Steel Base Project (Phase I), etc. Among them, Liuzhou Steel Group Co., Ltd. 1#The technical transformation project of the smoke and wind system of the power station, with a project scale of 1#360m2 sintering, built-in waste heat boiler and auxiliary machinery in the north and south flue. Since the completion of construction in 2015, the waste heat boiler has an evaporation capacity of 12t/h, saving about 880kg of standard coal per hour. The annual operation time is 7000 hours, and the annual standard coal saving is about 6160 tons.

6. investment estimation

Due to the different sintering capabilities, sintering processes, and equipment wear conditions of various domestic manufacturers, the overall investment in waste heat boiler equipment for the main flue of sintering machines is between 6 million and 12 million yuan depending on different working conditions. Operation and maintenance include desalinated water of 15t/h, variable frequency feed water pump 1 on and on standby, single power of 22kW, daily other lighting power of 2 kW, plus labor costs, equipment depreciation costs (calculated based on 10 years, 5%/year), and overhaul The cost is about 1.5 million yuan.

7. investment recovery period

Liugang 1#The 360m2 sintering flue heat recovery project has an investment payback period of about 1.2 years.

8. Prospects for transformation and promotion of technological achievements

At present, there are more than 1400 steel companies across the country, and about 700 companies can install main flue waste heat boilers. Among them, about 30% have installed main flue waste heat boilers, of which the main flue external waste heat boilers are installed, and the market penetration rate of installing built-in main flue waste heat boilers only accounts for about 8%. The sintering main flue waste heat recovery system has great market promotion prospects.