Discussion on the tendency of cake collapse in rammed coke ovens!
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For rammed coke ovens, it is crucial to control the particle size and moisture of the blending coal. The former is generally between 89 and 92, with a moisture content of around 12 being ideal. However, with the arrival of the rainy season and the corresponding increase in the moisture content of coal, are there any ways to reduce this increase in moisture?
For rammed coke ovens, a fineness of around 90% and a moisture content of 9–11% are optimal!
Provided that all parameters meet the requirements, attention should be paid to the time taken for compacting the coal; it should not take too long. In a furnace of 4.3 meters in size, 4 cars with 12 hammers are used per shift, and it takes no more than 8 minutes to compact coal with a height of 3.9 meters. The thickness of the underlying coal layer should not be too great – 600–800 millimeters is the ideal value. After the underlying coal layer is compacted, the upper layer can be compacted either in layers according to the quality of the coal or in a continuous manner.
When the coal-bearing bottom plate moves forward to its position, it deviates by about 20 mm; when the coal is delivered to the coke side, it tends to press against the furnace wall, causing the coal pile at the back to collapse.
The compaction of coal briquettes, and whether they collapse or not, depends on three key factors: first, the fineness and cohesion of the coal； The second is the moisture content of the coal fed into the furnace, and the third is the proper control of the ramming time; this can also be considered as the accumulation of operational experience, such as the weight of the hammer, the number of rams used, and the number of layers of coal fed in, etc
For rammed coke ovens, a coal fineness of over 86% is sufficient; too high a fineness is not necessarily advantageous. The moisture content should be kept between 9% and 12%. As for the ramming process, it is particularly important to have a low layer of coal, usually around 600–1000 mm thick, and this layer needs to be compacted properly. The ramming time and the number of blows required are all matters that depend on empirical knowledge.
To prevent the coal cakes from collapsing, it is first necessary to find ways to increase their strength; this requires strict control over the moisture and fineness of the coal. The moisture level should be kept between 9% and 11%, while the proportion of coal with a particle size of less than 3 millimeters should be between 90% and 93%. High performance from the ramming machine is also essential, as it needs to compress the coal cakes firmly so that their density reaches over 1.05 tons per cubic meter. Additionally, the side walls must be smooth. For ramming boxes that are being used for the first time, oiling them regularly is necessary to improve their sliding properties. There should be as few welds as possible on the side walls, and those welds need to be smoothed out to prevent peeling when the coal cakes are fed through. If necessary, some straw or similar materials can also be added during the compaction of the coal cake to improve its strength.