Well resourced Steel Plants commonly use Blast Furnace route for iron production which accounts for over 60 % of global iron output.
Blast Furnaces usually run for ten to twenty years without repairing hearth walls and tap holes. The tap hole is an outlet for hot metal produced in a Blast Furnace and runs from the shell of the furnace into the interior allowing access to the molten material.
Tapping is the term used for drilling a hole through the tap hole which allows the molten iron and slag to flow out. In steel manufacturing operation, removal of liquid iron from furnace and sending it for steel making is known as cast house practice.
Monitoring of blast furnace tap hole can be categorised into two
Active monitoring during the tap process and
Temperature monitoring ( in the control room and offsite).
In active monitoring during the tap process, the cast operator who is responsible for the opening and closing the tap hole with a drill and mud gun strictly monitors the taphole during tapping durations for any anomaly and takes very drastic steps to deal with it. In this regard, he must monitor the angle at which hot metal and slag flows from the tap hole, splashy casts, when the furnace starts blowing during the tapping process and the condition of the tap hole whether it is fully opened or otherwise.
The angle of the stream of hot metal and slag flowing out the furnace is defined by the liquid pressure and gas pressure inside the furnace. High tapping angles pose a serious safety risk. Hence hot blast volumes into the furnace must be reduced to control the tapping angle and flow. Possible splashing of the tap hole at any time during the tapping poses not only a safety risk but also an operational risk. Splashy tapping practices can result in an increase in the amount of cleaning work required after the tapping, prior to the next tapping. Blowing of the tap hole which is indicated by sparks being emitted is a sign of the furnace being dry and ready for plugging. Before taking the plugging action, the operator needs to ensure that the furnace is actually blowing and that it is not a false blow.
Temperature monitoring is done on two levels. In the control room and off-site. In the control room, the temperature can be monitored on a 24-hour basis by the operator using a digital control system (DCS). Schematics are used to represent the temperatures in an easily understandable way. Off-site temperature monitoring can be done over a longer period. The maximum monitoring periods which spans for weeks or months can then be used and the worst wear can be calculated. With this information, predictions can be made as to possible problem areas. The hearth life can then be predicted in order to safeguard safe furnace operation.
If the blast furnace temperature is not properly monitored, the risk exists that the hearth or tap-hole wear will continue until it reaches the shell where it cannot be contained. This situation would result in a burn-through with molten iron spilling down the side of the shell, causing very serious damage to the shell. This can cause explosions when it comes into contact with water. The explosions can damage thermocouples, and even cause more extensive damage such as hydraulic rooms overheating and catching fire when located directly above such a burn-through. Such a situation is extremely hazardous and injuries and fatalities can occur in a steel plant.
HPE Equipment for Tap Hole Efficiency and Protection
The HPE Mudgun machine guarantees effective closure of tap holes, which is one of the most important and critical operations required for protecting blast-furnaces and also ensuring efficiency in its operation. – closing tapholes.
The special design of HPE Mudguns ensures that any blast furnace operation with modern heavy-duty tapholes are effective and secured. Our Mudguns are developed specifically for critical heavy-duty and non-heavy-duty operations, and their design and technical parameters fully comply with the requirements of modern technological processes of blast-furnace operations.
We offer two types of Mudgun for suitable applications: a high volume low pressure unit with a 154 litre capacity and a low volume high pressure unit with a 70 litre capacity. Both Mudguns use the same hydraulic drive and control which incorporates an essential loading door safety lockout to prevent clay piston movement when the door is open. Our Mudgun loading doors are large enough to enable the use of economically sized pre-packed taphole material or for the easy loading of loose bulk materials. Both Mudguns are fully water cooled right to the tip to prevent heat damage and baking of the taphole fill materials in the barrel nozzle. The Clay pressure in the high pressure gun is 56 bar and in the low pressure gun 28 bar. The robust design makes it highly tolerant to metal splatter and heat radiation.
HPE Mudguns are very easy and cheap to maintain. Their low and short disposable end pieces further reduce taphole damage costs.
Furnace tap hole is considered as one of the most important and critical areas of the blast furnace. Significant loss of time and money occur when it develops malfunctions. This is why it is very important to protect this area as much as possible through accurate, gentle drilling and correct plugging.
The HPE Taphole Drill technology covers the complete performance range, from pneumatic through hydro-pneumatic to fully hydraulic drilling. It has a high drilling torque plus an optional hammer with adjustable frequency and impact force to guarantee that the tap hole can be perfectly drilled as gently as possible. The Taphole Drill is a high powered pneumatic drill which is capable of drilling 100mm holes at 5 bar air pressure.
The HPE Taphole Poker is highly efficient in breaking the last bit of clay when a hole is drilled in the furnace. It clears the hole during tapping operations and ensures that any blockade at the hole entrances is displaced for effective drainage of liquid iron and slag.
The HPE Taphole poker delivers high impact operation at a high speed. It then retracts quickly to minimise heating of the rod. A specially unique retract reverse impact mechanism of the Taphole Poker helps dislodge the rod should it become stuck. This distinguishes our Taphole poker from all others in the market.