Post on 21-May-2015
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- 1. Blast Furnace Operations Fig 1.
- Operating a blast furnace refers to making decisions regarding the process of iron making.
- These decisions alter the inputs to the furnace in order to obtain the desired operating conditions and material outputs.
- Many different process factors play into ideal operations and equipment limitations can also play a large role.
Fig 2. 3. Cost vs. Production
- The main goals in iron making can be simplified to either cost or production quantity.
- Since a blast furnace is usually part of an integreated steel making process, the demands place on operations can change quickly.
- These demands can shift from making the least costly iron to producing as much iron as possible.
- While these goals often go against one another, they share the same process and equipment limitations.
Fig 3. 4. Cost Limitations
- When cost is the primary concern, efficiency and low cost of operation are sought.
- Efficiency is achieved by running the furnace at steady reasonable rates and not pushing it to it limits.
- Low cost operations are achieved by inputting the lowest cost burden materials.
- Increasing the amount of hot blast injected into the furnace increases efficiency and lowest the cost of production.
Fig 4. 5. Problems with Low Cost Materials
- There are operational issues associated with using low cost materials.
- These lower cost materials have more fine materials in them. These fines plug up the furnace, impede gas flow, and cause erratic burden descent.
- Low cost materials can also contain unwanted materials that will be present chemically in the iron that is produced. These unwanted chemicals require further processing to be removed from the iron.
Fig 5. 6. Problems with Efficient Operation
- Efficient operation requires smooth and stable process conditions within the furnace.
- While efficiency means a high utiliztion of the resources put into the furnce, it cannot always be complished with lower quality materials and it will not give the highest amount of production.
- Typically the lowest cost of operation is achieved by blalacing the input of low cost materials and maintaining efficient operation
Fig 6. 7. Production Limitations
- Any furnace will have a physical limit of how much iron it can produce in a given time frame.
- Certain metallic materials can be used in the burden to increase production. These metallics are iron bearing materials that have less oxygen in them. They typiclly are forms of processed scrap materials. They are very expensive compared to iron ore.
- Production can be increased by driving the furnace harder. This is accomplished by pushing more hot blast in and increasing the amount of material charged in the top of the furnace. This strains the furnace reactions and generally causes instability and operational issues.
Fig 7. 8. Environmental Concerns
- Since a blast furnace is a closed and pressurized system, it has pressure relief valves in order to prevent any sort or explosion should the pressure inside get too high.
- These valves, known as bleeders, let the gas flow coming out of the burden to vent directly to atmosphere n the event the internal pressure exceeds a set point.
Fig 8. 9. Environmental Concerns
- Since these bleeder events release chemicals into the environment they are avoided as much as possible.
- Pushing too much hot blast through the furnace can leads to pressure issues. Having a burden that is not permeable also causes pressure issues. Any internal furnaceinstability can cause the burden to slip down and cause a spike in pressure. These issues all factor into operational decisions such as burden selection and hot blast injection rate.
Fig 9. 10. Summary
- Many factors such as cost, production rate, and environmental concerns determine the operational parameters of the blast furnace.
- These goals often push the furnace to the boundaries of when it can accomplish given the limitations inherent to the equipment and materials input.
- The manipulation of the operating parameters to achieve the given production goals is at the heart of blast furnace operation.