Selection of kiln and heat treatment system for heat treatment of mag carbon bricks

During the drying process of magnesia carbon bricks, in order to ensure the heat treatment temperature of 200 ℃, various enterprises have designed many different forms of kilns according to their own characteristics. According to the heating form of the kiln, it can be divided into coal kiln, resistance wire kiln and microwave heat treatment kiln. Each of these three types of kiln has its own characteristics. The selection of heat treatment kiln and heat treatment system will be shared with you below:

1. Selection of heat treatment furnace

Reasonable selection of heat treatment kiln and heat treatment system is very important. Heat treatment is basically the last link of product production. The rest of the selection and packaging can basically not change the quality of the product, so the heat treatment must be well grasped. .

For coal kilns, the heating rate is slow, and the existing coal kilns at this stage are basically very old coal kilns. Many, so the temperature of the coal kiln is very unstable. When the coal kiln reaches the heat preservation stage of 200°C, the kiln workers should frequently check the situation in the kiln and add coal appropriately to ensure that the temperature is stable. Due to the poor thermal insulation of the coal kiln, the temperature drops quickly. Therefore, the heat preservation time of the coal kiln should be slightly extended, generally at 200 ° C for 12 to 14 hours. At present, the newly built heat treatment kilns in magnesia carbon brick factories are basically resistance wire kilns, which are favored by various enterprises because of their mature technology, simple construction and low construction cost. For the resistance wire kiln, the temperature rises quickly, the temperature control is accurate, and it is automatically controlled by electronic equipment. Relatively speaking, it is much simpler, and the temperature rise curve can be formulated. However, due to the huge power consumption of the resistance wire kiln, in order to control the cost, it is best to start the heat treatment kiln at night, because the electricity price is at a "valley" at night, and the electricity price is much cheaper. For the microwave drying kiln, due to the limitations of the enterprise, it does not have the conditions for introduction, so it will not be explained here. Guo Yuxiang and Qu Dianli verified its feasibility through experiments, and industrialization needs to be explored and summarized.

2. Selection of heat treatment system

From the perspective of the curing principle of thermosetting phenolic resin above, the heat treatment system set by the company is roughly 200°C for more than 10 hours. In order to further reduce costs, we have done a series of experiments, including the comparison of pressure resistance, porosity, and density. Take 18 magnesia-carbon sample bricks with carbon content of 8%, 12% and 16% respectively. The sample bricks are different except for the carbon content, and other raw materials are the same. Take 3 pieces of each sample and put them into the coal kiln at 200 °C Keep warm for 10 hours, keep warm for 10 hours at 180°C for coal kiln, keep warm for 10 hours at 160°C for coal kiln; then take 3 pieces of each sample and put them into resistance wire kiln for 10 hours at 200°C, keep warm for 10 hours at 180°C for resistance wire kiln, and keep warm for 10 hours at 180°C for resistance wire kiln. 160°C for 10 hours. After natural cooling, the following data were analyzed.

Table 1: Physical indicators of products after heat treatment at various temperatures

It can be seen from Table 1 that no matter whether the heat treatment temperature is 200°C, 180°C, or 160°C, the porosity and density have no obvious change, and the change does not form an obvious rule. However, the pressure resistance at room temperature changes significantly. From the table analysis, the pressure resistance value after heat treatment at 200°C and 180°C does not change significantly, but once the temperature drops to 160°C, the compressive strength decreases significantly.

It can be seen from the test results that whether it is a product produced by heat treatment in a coal kiln or a resistance wire kiln, lowering the heat treatment temperature from 200°C to 180°C has little effect. However, once the temperature is lower than 160°C, the compressive strength of the product will be significantly reduced, so we suggest that the heat treatment temperature should not be lower than 180°C.