Don’t miss! Atlas Copco 12 Principles of single machine selection

Principle of single machine selection

1. Principle of single machine selection

1.1 Air volume selection

Generally, when choosing the gas volume, it is recommended to comprehensively consider the fluctuation of gas consumption, the distribution of gas consumption during the day and night, the maximum and minimum gas volume, pipeline loss, capacity expansion and other factors. When the overall gas volume has been determined, it is recommended to use as many as possible joint control, power frequency + frequency conversion and other schemes. It is recommended to use the frequency conversion machine as far as possible to use the constant voltage after the frequency fluctuation range is between 60-100%, which can take into account the efficiency and adjustment function.  When selecting models, some dealers will have a misunderstanding: they can choose one machine instead of two, and they can choose as many machines as they can within the range that customers can afford. This will result in the situation that a single machine does not have a spare machine in use; if the machine is selected too often, frequent loading and unloading will cause water analysis and lead to the failure of oil emulsification, which will affect the life of the main engine in severe cases.

1.2 Pressure selection

It is recommended to select the pressure according to the principle of high and low pressure and separation of lines. For example, 5bar takes the low pressure pipeline, and 8bar takes the normal pressure pipeline. Partial pressure gas supply can avoid waste caused by secondary “pressurization” and “decompression” at the gas terminal. Now most users will choose a general machine between 6-8bar, but the “over-compression” and “under-compression” machines will consume extra energy, resulting in the unit not saving energy.

1.3 Start method selection

Due to market hype, it is not advisable to recommend variable frequency screw machines. Just like a car, only idling within a certain range is the most energy-saving working condition. The high loading rate of the power frequency screw machine and the moderate frequency of the constant pressure of the variable frequency screw machine can ensure that the compressor is in the best working condition. Taking this as the selection principle, it is recommended that multiple machines choose the power frequency + frequency conversion, and multiple joint control methods.

1.4 Control mode selection

Common control methods for compressors are: on/off, loading/unloading, throttle control, variable speed control, and multiple air compressors. Users can choose the control method or make a special model. A good control method can reasonably control no-load loss and differential pressure loss. These losses mostly occur in the case of high unloading rate and higher operating pressure.

2. Station room selection

2.1 Selection of the whole machine

Choose an energy-saving compressor with low specific power, and choose an appropriate type of compressor according to the range of gas volume, fluctuations, and intermittent gas consumption. Generally more than 4 compressors are not recommended to use variable frequency regulation for all or too many compressors.

2.2 Post-processing selection

There are many types of post-processing equipment currently used: refrigeration dryers, heating regeneration dryers, heatless vacuum dryers, blast heating vacuum dryers, etc. The parameters of power consumption and air consumption should be comprehensively compared, and energy-saving post-processing devices should be selected reasonably. Processing equipment, preferably post-processing equipment controlled by frequency conversion.

2.3 Pipeline selection

The right-angle elbow at the pipe connection has a great detrimental effect on energy efficiency. The right-angle elbow causes the flow resistance to increase, forming an additional work point; High air pressure and easy to unload. Reasonable optimization of pipeline connection points can significantly reduce energy loss, and this part of the loss can be almost eliminated. After the compressed air is sent from the unified air storage tank, it is transported to the gas-consuming link through various pipelines. The efficient delivery forms include single-point daisy chain and multi-point ring. However, in general, users consider saving one-time investment because of the consideration of one-time investment. For other reasons, the direction of the air pipeline is often unreasonable, resulting in excessive pressure loss, resulting in the need to supply a higher gas pressure. The pipeline should meet the user’s requirements for flow and pressure. Under the condition of comprehensive consideration of cost factors in the whole life cycle, the pressure loss of the pipeline should be minimized, and the application of elbows, valves and reducing diameters should be minimized. Generally, it is better to control the exhaust pressure loss from the whole machine to the terminal within 10% as much as possible.

2.4 Selection of gas storage tank

Usually the screw air compressor is already equipped with an after-cooler, and the exhaust of the air compressor is saturated compressed air. The conventional configuration is to equip an air storage tank and a pre-filter between the dryer and the air compressor, then the compressed air will have condensed water after cooling in the air storage tank, so it is best to put the air storage tank in a cool place and remove the condensed water. Efficient discharge. The capacity of the gas storage tank is jointly determined according to the adjustment range of the output of the compressor and the changing demand of the gas consumption.

In the application site, the problem that often occurs is that the capacity of the gas storage tank is insufficient. Due to the small capacity, poor energy storage effect, and large pressure fluctuations, the compressor is repeatedly loaded and unloaded, resulting in a large amount of energy waste. By increasing the air storage tank, if the single unloading time exceeds a certain period of time, the unloading power consumption of the compressor will be reduced, and the energy saving effect will be achieved.

2.5 Compressor waste heat utilization

The production process of compressed air is relatively complicated. In the process of gas compression, the degree of heat generation is relatively high. The oil-free compressor can reach more than 100 degrees Celsius. Only about 20% of the electric energy consumed by the compressor is converted into compressed air power, and the remaining 80% is converted into compressed air power. All are converted into heat, so the utilization value of waste heat of the compressor is often high.

The hot oil and hot air during the operation of the compressor are used for heat exchange, and the heat is transferred to the soft water medium, and then the heat of the soft water medium is exchanged again and transferred to the hot water used by the user to realize the utilization of waste heat. Use the heat energy during the operation of the compressor to generate high-temperature hot water, and then use the high-temperature hot water as a heat source to drive the lithium bromide unit for refrigeration, which can generate chilled water to supply the production process.

3. Intelligent energy saving

3.1 Monitoring items

Compressor exhaust volume, exhaust pressure, power; dryer output air volume, dew point, pressure drop; cooling water system inlet/outlet water temperature and pressure, energy consumption of fans and pumps; pipe network pressure, pressure drop, leakage, etc. .

3.2 Energy saving control points

Energy saving can be achieved through the combination of flow control technology, frequency conversion speed regulation, single-point/multi-point pressure regulation control, centralized control system, drying process improvement, heat recovery, pipe network optimization, leakage monitoring, waste gas recovery and other methods. degree of energy saving.

3.3 Energy saving control

A huge database is established through data collection, and then a mathematical model is established for analysis to find out the internal logical relationship and mutual connection. The system can accurately calculate the energy efficiency level of the air compressor station through the collected data. According to the continuous data extraction and analysis, which time period is the peak of gas consumption, what is the fluctuation range of gas consumption, the fluctuation of pressure dew point, etc., using big data calculation to give early warning, and provide a reasonable adjustment report, set a certain range of compressors The parameters such as the air volume and the water inlet and outlet can be adjusted, so that accurate energy saving can be achieved. If it exceeds the predetermined adjustment range, it will be pushed to the user for automatic adjustment after obtaining consent. Energy conservation is a profound “knowledge” that requires the support of multi-disciplinary expertise. The theory and logic are relatively easy to understand, but in order to be practical and continue to tap the potential, it requires the accumulation of technology and the collection and transformation of application data.

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