Several Key Factors Affecting the Output and Energy Consumption of Vacuum Extruder
Vacuum extruder is the main equipment in brick and tile industry for producing hollow brick, and its performance directly affects the economic benefit of enterprise. The are four key factors that affect the performance: mud cylinder, auger, head and die of extruder. As long as these four factors are properly configured, combined with a well-designed production process, the extruder can achieve its optimal performance.
At present, there is an opinion that a shorter mud cylinder is better, as it reduces load and increases output. In fact, the length of the mud cylinder should depend on different raw materials and the nature of finished product. For material with high plasticity, the cylinder should be shorter; conversely, it should be appropriate longer. For standard brick, the cylinder should be shorter, whereas for hollow brick, it should be appropriate longer. Generally, the number of auger turns in sealing section should meet the turns required to generate pressure.
2.Auger
The length of mud cylinder is not the only key factor in determining output, the arrangement of the auger pitch is equally important. It’s worth noting that the arrangement should be tailored to different raw materials. For example, there is a JKR45/45-2.0 vacuum extruder in a brick plant in Jieshou city, Anhui province, has a mud cylinder length of 550 mm, sealing section length of 725 mm, and an auger pitch arrangement of 380, 360×1.76, 380×1/2. The raw material used is plain sedimentary soil. During the test run, the output of KP1 was 6 strips/min, the mud cylinder and the head of the extruder overheated, the mud strip lacked toughness, and severe spiral grain occurred. After analysis, the issue was attributed to an unreasonable pitch arrangement. A new auger was designed with a pitch arrangement of 380, 33x1.92, and 380x1/2, which extended 4 cm into extruder head. It increased the output to 14 strips/min, while reducing the temperature of the head and mud cylinder. It can be seen that the pitch arrangement should be designed based on the characteristics of the raw materials. It is best to analyze the composition and plasticity of the materials before test run and then manufacture the auger accordingly to avoid delays.
3.The die of extruder
The quality of the die directly impacts both the quality and output of product. Our approach is to design the KP1 die and the extruder die for non-load-bearing hollow brick based on the composition and plasticity of the local raw materials, as well as the actual condition of the die for standard solid brick. Generally, the taper of the die should be controlled at around 7 - 8. When the plasticity is high, the taper should be enlarged appropriately; when it is low, the taper should be reduced. For example, in a brick factory in Changsha using soft shale with good plasticity, the KP1 die has a length of 155 mm, with an outlet of 250×122 mm and an inlet of 300×185 mm. In another factory in Jieshou, Anhui, the die for non-load-bearing 8-hole hollow brick is made directly from δ=30 steel plate without a taper. Additionally, in Hexian, Anhui, the JKR50/50-2.0 features a KP1 double outlet design with a length of 140 mm, and outlet and inlet of 250×250 mm and 285×285 mm.
4.The head of extruder
The shape of the head varies among different manufacturers, but the general structure is the same. It is usually equipped with two types of heads (for sand material, the head is longer, and for material with good plasticity, the head is slightly shorter). In addition, there is another type of internal head that features the die embedded inside the cavity of extruder head, with adjustable length and size of the die. For hollow brick, the manufacturing of the head is divided into two types: combined type and main auger insertion type. In short, the diversity of extruder head also reflects the diversity of raw materials.
In conclusion, the above four are the main factors affecting the performance of the extruder, and their optimal combination for different raw materials can make the extruder achieve its best performance. Therefore, preliminary research is crucial for different production lines. For each client, it is important to first study their raw material characteristics before determining the optimal design. At the same time, on-site personnel should possess good skills and be able to come up with best solution for any issues that arise during testing to ensure client satisfaction.
The extruder (including both non-vacuum and vacuum extruders) is the main equipment in brick production line. The article discusses the energy-saving measures of extruder from the perspective of installing a reactive power compensator, rational selection of vacuum pump, and the design of auger and mud cylinder, etc:
（1）Installing a reactive power compensator in extruder can save energy
Installing an energy-saving compensator at the main circuit terminal of extruder motor can improve the power factor of the motor (generally increasing the COSΦ to around 0.95) and save more than 15% of energy, especially in location with low load or where the motor is far from the transformer, where its effect is more significant.
（2）The vacuum extruder should be equipped with suitable vacuum pump
In the past, vacuum extruder was typically equipped with high-power vacuum pump, leading to significant energy waste. Due to poor sealing, a 450mm vacuum extruder had to be paired with a 22KW vacuum pump, and the vacuum level often failed to meet requirement. In recent years, some brick manufacturers have improved the sealing component of the vacuum system, and the performance of vacuum pump has significantly improved. Now, a 5.5KW mechanical vacuum pump can fully meet the need of 500 mm or even larger vacuum extruder, while maintaining a high vacuum level over the long term.
（3）The vacuum extruder should be equipped with optimally designed auger
Auger is the core component of the extruder, and its quality plays a decisive role in extruder’s performance. For some extruders, simply improving components such as the auger can reduce electricity consumption by 20% - 30%, while also increasing output by 20% - 30%. The energy-saving effect is significant.
（4）Improving the mud cylinder of extruder can reduce energy consumption
The length of mud cylinder is also an important factor. Some brick manufacturers believe that a longer mud cylinder is better. However, it not only consumes excessive power but also causes the cylinder to overheat, resulting in a decline in brick quality. Generally, the enclosed length of the auger should not exceed 3 pitches.
（5）The vacuum extruder is most energy-saving at its optimal speed.
Some brick manufacturers believe that higher extruder speed leads to higher output and lower energy consumption per 10,000 bricks. In fact, with the same material and condition, there is only one optimal speed. Test has shown that the extruder consumes the least energy and achieves the highest output at its optimal speed. Exceeding this speed result in higher energy consumption without any increase in output.
（6）Improving production management can make the extruder energy-saving
Some brick manufacturers with same conditions have significantly different energy consumption per 10,000 bricks, primarily due to poor management. For example, in production process, the material supply may sometimes be insufficient, causing the extruder to operate inefficiently with low output. At other times, the material supply may be excessive, resulting in the extruder being “overloaded” and requiring frequent shutdown for cleaning, which reduces hourly output. Additionally, poor coordination in production, such as insufficient raw material supply or delay in brick conveyance can lead to shutdown and low output, thereby increasing energy consumption. Furthermore, some manufacturers neglect regular maintenance, failing to replace worn mud cylinder liner or repair gap greater than 20 mm between the auger and the liner, all of which lead to higher energy consumption.
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