Both self-baking carbon bricks and pre-baked carbon bricks are one of the commonly used carbon bricks in submerged arc furnaces. The roasting of pre-baked carbon bricks is that the green carbon bricks are heated in the baking furnace with fillers isolated from oxygen and heated at a certain heating rate. Generally, the roasting temperature will not exceed 1200℃, and the heating process of self-baking carbon bricks in submerged arc furnace is different from that of pre-baked carbon bricks, and the final temperature is much higher.

self-baking carbon bricks

1. Different heating methods

The pre-baked carbon bricks are surrounded by fillers in the roasting furnace, and the roasting furnace has the function of multi-sided heating depending on the design of the fire channel, so the pre-baked carbon bricks can be uniformly heated on six sides through the conduction of the filler.

The heat source for carbonization of self-baking carbon bricks in a submerged arc furnace is the temperature of the submerged arc furnace itself. This heat source is conducted from top to bottom. The roasting of self-baking carbon bricks is not actually carried out together, but from top to bottom. Layer by layer roasting.

2, the heating rate is different

Pre-baked carbon bricks have external heat sources during firing, so the heating rate can be controlled, so that different heating curves can be formulated according to the firing stages of carbon bricks. Faster heating before 300℃ is beneficial to reduce the deformation of carbon bricks, slowing down at 300~750℃ is beneficial to coking of asphalt, and above 750℃, the speed can be accelerated again.

When self-baking carbon bricks are roasted, only the temperature in the smelting molten pool is transferred down, and the heating rate cannot be controlled according to several temperature points of asphalt roasting. Since the thermal conductivity of the green self-baking carbon brick 3W/m·k is much smaller than that of the pre-baked carbon brick 16W/m·k, the temperature conduction speed of the carbon brick is very slow, so it can be guaranteed that there is enough Asphalt coking value, but self-baking carbon bricks may increase the possibility of deformation due to too slow heating rate.

3. The roasting of carbon bricks and seam paste is different

The joints between the self-baked carbon bricks are made of carbon cement, generally not more than 1mm, and the prebaked carbon bricks are generally masonry with a wide joint of 40~50mm, and the middle is tamped with cold paste or electrode paste. Furnaces have also started to use charcoal cement on the basis of pre-baked charcoal block finishing.

When the pre-baked carbon brick is heated in the submerged arc furnace, only the interstitial paste will be roasted, and the inter-slit paste will be adsorbed on the pre-baked carbon block during the roasting process. The strength between the seams is the lowest, and it is also the most vulnerable place in the furnace lining to be corroded by molten iron.

The self-baking carbon bricks and seam paste start the baking process at the same time, and the two materials are the same, so they are baked together during the baking process. The self-baking carbon blocks begin to soften when the temperature rises to 100 °C. The plastic deformation of the self-baking carbon brick can fill the place where the gap is too large during the masonry process of the furnace body.

4. Self-baking carbon bricks are fired in a pressurized atmosphere

When coal tar pitch is calcined under normal pressure, more than 30% of the carbon will be lost with the escape of volatile matter, leaving many pores in the carbon brick, which directly affects a series of properties of the carbon brick. Coke content, increase the bulk density of carbon bricks, and improve the internal structure of carbon bricks.

In the submerged arc furnace, self-baking carbon bricks have refractory bricks and furnace shells on the periphery, and the pressure of the charge on the upper part, so the baking of self-baking carbon bricks has the characteristics of pressurization and single-sided heating. It is not easy to be discharged and undergoes a polymerization reaction to generate coke with better performance. The coke reduces the porosity of the carbon brick and improves the performance of the self-baking carbon brick.

Pre-baked carbon bricks do not have such conditions during baking. The atmosphere of seam paste is the same as that of self-baking carbon bricks during baking, but after all, the amount of seam paste is small, so the performance of self-baking carbon bricks after baking is greater than that of pre-baked carbon bricks. Brick performance.