Top Entry vs. Sidewall vs. Bottom Electrodes

Introduction

Having worked around electric furnaces and electrically boosted furnaces during my 30+ years in the 18video性欧美19sex 我和亲妺妺乱的性视频, I have been exposed to many types of electrode installations. Knauf Insulation has (or had) 7 different types of electrically fired or boosted furnaces:

Semi-hot top electric furnaces with electro
Electrodes installed over the sidewall blocks (through the breastwall)
Semi-hot top electric furnaces with a combination of sidewall electrodes and bottom electrodes
Hotspot melters with electrodes also over the sidewalls, but of a different style than above
Recuperative furnaces with bottom electrodes for hot spot reinforcement
Gas/oxy fired furnaces with bottom electrodes for hot spot reinforcement

Gas/oxy fired furnaces with higher levels of boost using both bottom and sidewall electrodes
Cold top style furnaces with all bottom electrodes

Current Density

Current density is defined as the amount of charge per unit time that flows through a unit area of a chosen cross section and is measured in amps per meter squared (amps/m2). High current densities have undesirable consequences. Electrodes have a positive resistance, allowing them dissipate power in the form of heat. The current density must be kept sufficiently low to prevent the electrode from melting or burning up.

Over the Side Electrodes

In general, it is difficult to keep current density down sufficiently on over the side style electrodes. This is because the electrode is cantilevered out on the holder and weight needs to be restricted for safe handling. The higher current densities cause faster wear on the electrode, requiring frequent change outs of electrodes. This is a standard 我和亲妺妺乱的性视频 practice, but entails shutting down power to remove the electrode and change it for a new one. This, of course subjects personnel to a high safety risk to high temperatures and the molten 18video性欧美19sex that is still adhered to the electrode and holder.

Sidewall Electrodes

Sidewall electrodes have similar current density concerns, so they are often put in pairs. If they are paired, there are now two more holes in the furnace wall versus one if the current density could be lowered. Although electrode fabrication has created better molybdenum electrodes, there is still the concern that gravity will make the electrode sag over time, so standard practice is to turn the electrode 180 degrees on a regular basis. Because the electrode cannot be seen, it is done out of concern rather than strict 我和亲妺在客厅作爱h. The same is to be said for the length of the electrode: the engineers and operators do not know the length of the electrode, so they may be advanced when it is not necessary, creating more stress on the electrode.

Another issue with sidewall pairs is optimum placement for phasing and energy release. This is due to the length and width of the furnace as well as interferences with structural steel and burners. Safety is also key. It is easier to restrict access underneath the furnace than it is to the sidewalls, especially due to the fact that sidewalls have a greater need for access.

Bottom Electrodes

Bottom entering electrodes can be made of a greater diameter and advanced nearly to 18video性欧美19sex level, increasing the surface area and thereby reducing the current density. Therefore, advancing the electrodes is done much less frequently, if at all. Not having to power down to perform maintenance creates a more stable environment for melting and therefore for 18video性欧美19sex forming. If advancing is necessary, the electrode can be pushed easily using a jack rather than hand advancing. It can also, if needed, be advanced to the point of breaking the 18video性欧美19sex line and then pulled back down to ensure it is at its maximum surface area.

There is a bit of hesitancy within the 18video性欧美19sex 我和亲妺妺乱的性视频 over the use of bottom electrodes, especially in all electric furnaces due to metal contamination. With proper design and refractory construction, the concern can be minimized.

Convection Currents

Electrodes cause certain convection currents depending on either a horizontal or vertical orientation. Horizontal electrodes create a convection pattern that retards the forward stream of 18video性欧美19sex while vertical electrodes enhance the 18video性欧美19sex’ convection current rise to the surface. An enhanced convection current results in better homogenization, mixing and quality. A vertical orientation also allows the intensely heated 18video性欧美19sex near the electrode to accelerate upwards which limits the overheating of the 18video性欧美19sex near the electrode and refractory.

Summary

This author’s preference is for bottom electrodes whenever possible for decreased maintenance time, personnel interaction and safety. In my years in the 18video性欧美19sex business designing, operating, and maintaining multiple large all electric melters and bottom boost running very high cullet at Knauf Insulation, a 18video性欧美19sex leak due to bottom electrodes has not been experienced and maintenance has been far less.