Production technology of suspension furnace

The suspension furnace is composed of several vertically arranged cyclone, a roaster and connecting pipes. It can make the raw materials complete all the technological process from preheating to roasting and then to cooling in the suspension state. It is a continuous and stable production equipment. The light roasting of magnesium oxide in suspension furnace is a new technology, which has a relatively short history of only about 20 years. When calcination of magnesite in suspension furnace, it is required that the particle size of raw material is < 2mm and the water content of raw material is 1%-2%. When roasting flotation concentrate, the size of raw materials into the furnace is required to be less than 0.2mm, the water content of raw materials is less than 10%. The fuel for roasting may be either heavy oil or gas. The suspension furnace is suitable for large-scale enterprises to produce high quality light fired magnesium oxide, with the annual output generally between 6000 and 50000T.

The characteristics of suspension furnace are :(1) large production capacity; (2) Low heat consumption; (3) High level of automation; (4) Production adjustment is very flexible; (5) High activity and uniform quality; (6) Small floor space; (7) Maintenance workload is very small.

In suspension furnace system, the motion state of material and gas is the coexistence of parallel flow and counterflow. For the whole system, the material goes down and the gas goes up, both of which are in the countercurrent state, while between two adjacent cyclone, the gas carries the material and flows, and the material particles are suspended in the gas. After entering the cyclone, the material is separated from the gas. The gas goes up and is discharged from the top of the cyclone, while the material goes down and is discharged through the bottom chute. After being preheated by several stages of the cyclone in the preheating section, the raw material particles reach the roasting temperature, slip out of the bottom of the cyclone at the end of the preheating section, enter the roaster from the top of the burner at the bottom of the roaster, and are immediately suspended in the air. The fuel is injected into the roaster by the burner and burned in the mixture of raw material particles and gas. The heat released by the combustion is immediately absorbed by the raw material particles and decomposed. 2~3 burners are installed in the extended part of the lower straight section of the calciner. The fuel is injected into the calciner and burned in the mixture of raw material particles and gas. The fuel combustion and raw material decomposition are completed instantaneously within 1~1.5s at almost the same time. The thermal efficiency is about 58%, and the heat consumption is 4180~5016kJ/kg. The burner used to ignite the roaster in the hot blast furnace is used to continue to provide hot air for the roaster during the normal production process. The fuel used in the hot blast furnace accounts for 10%~20% of the total production amount. The gas temperature will not exceed the decomposition reaction temperature, the raw material will not overburn, and the heat loss will be reduced to a minimum.

The suspension furnace is an assembly, and it has 6 cyclone. The first, second and third stages are the preheating stage, the fourth stage is the roasting stage, and the fifth and sixth stages are the cooling stage. Each level of cyclone is connected in series with gas pipe and material chute and supported on each floor separately. The inlet pipe of the first-stage cyclone is provided with a feeding port and installed with a spiral feeding machine, from which the raw materials are added into the suspension furnace. A roaster is connected to the inlet pipe of the fourth stage cyclone for the roasting of raw materials. The hot air for the roaster is supplied by a hot air furnace installed nearby. The outlet gas pipe of the fifth-stage cyclone is provided with a side passage through which the excess hot air is drawn. After dust removal by the by-pass cyclone, the excess hot air is sent to the lower part of the feeding mouth of the intake gas pipe of the first-stage cyclone for drying raw materials into the furnace.

The upper part of the cyclone is cylindrical, the lower part is conical, welded with steel plates and lined with refractory materials. The upper part of the shell of the cyclone is provided with a check door, and the lower end of the cone is provided with a -ray monitoring instrument to monitor whether the material is arching, and a compressed air blowpipe is installed for regular automatic blowing. In addition, manual purge hole is also provided. Its injection with compressed air from a dedicated air compressor.

The roaster is a 25m long cylinder, welded with steel plate and lined with refractory material. The upper part is made into a "∩" shaped tube, which impedes the suspension fluid mixture and increases the residence time of the physics in the roaster. A check door is left on the straight section. 2~3 fuel burners are installed in the extended part of the straight section. The material inlet is set above the burner, and 2 hot air inlet are connected with the hot air furnace below the burner.

The hot air furnace is a horizontal cylindrical steel structure lined with refractory materials. A burner is installed and equipped with a combustion system. The burner, which is used to ignite the roaster when the hot air furnace is opened, continues to provide hot air for the roaster during the normal production process, and the fuel used accounts for 10%~20% of the total production amount. Connecting pipe lining refractory. The lower end of the pipeline is provided with an expander, the bottom is provided with a feed inlet, and the upper part is provided with a check door on the elbow connecting with the cyclone. A compressed air injection port is set at the elbow and the feed inlet. The material chute housing is steel pipe lined with refractory material. The lower end of the chute is equipped with an electric swing valve or an electric format valve, and an expander is also installed on the chute.

Characteristics of suspension furnace :(1) low heat consumption per unit product; (2) High production intensity and uniform product quality; (3) Three-dimensional layout, less floor space, less spare parts, less maintenance workload, high level of automation; (4) Negative pressure operation, good working conditions, little environmental pollution.