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During the cupola melting process, due to the combustion of coke, the preheating, melting, and superheating of the metal charge, the movement of furnace gases, as well as the addition and descent of the charge, and also as a result of chemical, thermal, and mechanical effects, the flue gases emitted by the cupola contain large amounts of gaseous and solid harmful substances. These substances are not only harmful to humans but also cause severe damage to the natural environment. With the development of industry and advancements in science and technology. People are also gradually becoming more aware of its harmful effects. In recent years, our country has also attached great importance to work in this area. And corresponding provisions were made. Therefore, flue gas dust removal and purification devices have become one of the essential auxiliary devices in the structure of cupola furnaces, as well as a necessary condition for the survival and performance assessment of enterprises. We have not been working in this area for long, but we have carried out a large number of certifications and tests, achieving some results; we have modified some cupolas and obtained fairly satisfactory outcomes. Composition of blast furnace flue gas: For each ton of molten iron produced by a blast furnace, the amount of flue gas emitted (i.e., the gas released from the charging port) is approximately 700–900 Nm3 per ton of iron. The main harmful gases in the exhaust fumes are sulfur dioxide, carbon monoxide, hydrogen fluoride, etc., along with a large amount of solid matter—soot. The statistics show 3-10 Kg/t of iron. These harmful gaseous and solid substances are released into the atmosphere through chimneys along with the flue gas, causing pollution to the environment. Governance must be implemented. Currently, there are not many dust collectors suitable for cupolas. Based on their working principle, they can be divided into two main categories: dry dust collectors and wet dust collectors. A dry dust collector captures dust and particles by utilizing gravity, inertia, centrifugal force, or the electrostatic attraction generated by an external electric field, as well as through the action of filtering media, thereby achieving the purpose of removing dust and purifying the exhaust gas. There are many types of main structures. But it cannot remove harmful gases from the smoke. A wet dust collector makes use of the relative movement between water and flue gas in a cupola furnace. During the contact between the dust and harmful gas molecules in the flue gas and the water, processes such as inertial collision, interception, diffusion and dissolution, as well as the aggregation of water molecules occur, causing the dust particles in the flue gas to stick together (either between the dust particles and water or between particles themselves), thereby forming larger particles that can be captured. At the same time, the harmful gases in the flue gas dissolve in the water and are also captured. There are various types of wet dust collectors, but few of them are suitable for use in cupola furnaces. In summary, dust collectors come in a wide variety of structural forms, and their characteristics vary greatly. Therefore, when selecting a dust removal device for a cupola, factors such as technical requirements, cost-effectiveness, reliability, and meteorological and hydrological conditions must be taken into account. Under these circumstances, after numerous tests, we adopted a multi-stage composite dust collector system. A high-efficiency, reliable, and low-cost dust collector system is formed, and its system block diagram is as follows: Flue gas is discharged. As summarized in the above block diagram, the flue gas emitted from the cupola passes through a gravity sedimentation chamber, where dust particles larger than 50μm are removed. It then enters an impact water bath via a fan, where the particles and harmful gases in the flue gas are washed, allowing them to mix thoroughly; small particles are combined into larger ones. Finally, separation is carried out using a high-efficiency gas-liquid separation device. This allows the treated clean gas to pass through, while the water-containing particles and harmful gas droplets dissolved in water are separated out. Emit clean gas that meets **the standards**. Design values for relevant parameters: The design wind speed in the pipeline from the cupola to the gravity settling chamber is generally around 10 m/s, while the wind speed inside the gravity settling chamber is 2.5–4 m/s. Only in this way can a better sedimentation effect be achieved. The water volume for the impact-type water bath is 0.5–0.8 L/m3 (air volume). The wind speed through the high-efficiency gas-liquid separation device is 1.5–2.5 m/s. The dust removal and purification system designed for these operating conditions can achieve a dust removal efficiency of 98–99%, as well as a removal rate of 60–70% for harmful gases such as sulfur dioxide. The multi-stage composite dust removal system for the aforementioned cupola is also a dynamic dust removal system; it can be designed with significant adjustments based on the technical requirements of the object to be treated from dust, as well as the surrounding environment. The structure of various components can be adjusted appropriately, thereby achieving the best treatment results with minimal investment. This requires less investment than using a single dust collector, occupies less space, has lower operating costs, and delivers better results. Taking a 3-ton cupola furnace in the general foundry industry as an example, the total investment for the entire setup is around 60,000. Therefore, this is a relatively advanced solution currently used in China for the dust removal and purification of flue gases from small and medium-sized furnaces, in terms of both performance and cost. We generally recommend using a cement brick structure to build gravity settlement chambers and impact water baths, as this offers advantages such as corrosion resistance, reliability, a long service life, and low costs. To ensure that this composite flue gas dust removal and purification system operates properly, correct daily use and maintenance are also very important. The following tasks should be carried out: 1. Before starting the furnace at the beginning of each shift, it is necessary to check whether the fans, pipes, and impact tanks are functioning properly. In the event of any abnormalities, repairs should be carried out immediately. 2. Before starting each shift, check whether the gas-liquid separator (composite wire mesh plate) is clogged. If present, it should be rinsed off. 3. Fill the water tank 5 minutes before starting the furnace. After shutting down the furnace, wait until its temperature drops to room temperature before stopping the water supply. During use, attention should be paid to the water level in the tank. When excessive water levels occur, the debris in the overflow pipe should be removed promptly. 4. Every four to five furnace operation cycles, the water should be drained to remove the dust accumulated in the impact tank. Then clean water is injected. After each injection of clean water, 5-10 kilograms of edible soda should be added to neutralize the acidic harmful substances in the water. The smoke dust removal and purification device for cupolas has been successfully applied to cupolas, melting furnaces, boilers, and vertical cement kilns of various capacities, achieving excellent results in all cases.