Other uses of compressed air, what is the nature of compressed air

1. Compressed air as power:

For driving all kinds of pneumatic machinery, the exhaust pressure of pneumatic tools is 7 8 kg square centimeters; It is used for control instruments and automation devices, and the pressure is about 6 kg square centimeter; The vehicle is automatic, the doors and windows open and close, the pressure is 2 4 kg square centimeters; agitation in the pharmaceutical industry, in the winemaking industry, with a pressure of 4 kg cm²; The weft blowing pressure in the air-jet loom is 1 2 kg square centimeter; The starting pressure of medium and large diesel engines is 25 60 kg square centimeters; fracturing of oil wells with a pressure of 150 kg cm²; "Quadratic" oil production, the pressure is about 50 kg square centimeter; The pressure of high-pressure blasting coal mining is about 800 kg square centimeter; It is powered by pressurized compressed air in the defense industry; The sinking and floating of submarines, the firing and driving of torpedoes, and the salvage of wrecks are all powered by compressed air at different pressures.

2. Compressed gas is used for refrigeration and gas separation

The gas is compressed, cooled, expanded and liquefied for artificial refrigeration (refrigeration, air conditioning, etc.) such as ammonia or freon compressors. Its compression pressure is mostly 8 12 kg square centimeters, and this type of compressor is usually called a "chiller" or "ice machine". In addition, if the liquefied gas is a mixture, each component can be separated separately in the separation device to obtain various gases that can be read by qualified lip reading.

For example, pure oxygen, pure nitrogen, and pure xenon, krypton, argon, helium and other rare gases can be obtained after air liquefaction and separation.

3. Compressed gas is used for synthesis and polymerization;

In the chemical industry, gases are compressed to high pressures, which are often beneficial for synthesis and polymerization. For example, nitrogen and hydrogen to ammonia, hydrogen and carbon dioxide to methanol, carbon dioxide and ammonia to urea, etc. In the chemical industry, for example, high-pressure polyethylene has a pressure of 1500 to 3200 kg square centimeter.

4. It is difficult to compress gas for hydrorefining of oil

In the petroleum industry, hydrogen is heated by artificial methods, and reacted with oil after pressurization, which can crack the recombinant components of hydrocarbons into light components of hydrocarbons, such as the lightening of heavy oil, hydrorefining of lubricating oil, etc.

5. Gas delivery

The compressor used to transport gas in the pipeline determines its pressure depending on the length of the pipeline. When sending remote gas, the pressure can reach 30 kg square centimeter. The bottling pressure for chlorine is 10 15 kg sq cm and the CO2 bottling pressure is 50 kg 60 sq cm.

Air occupies a certain space, but it does not have a fixed shape and volume. When pressure is applied to the air in a closed container, the volume of the air is compressed, increasing the internal pressure. When the external force is withdrawn, the air returns to its original volume under the action of internal pressure.

If there is an object in the container that can move, when the air returns to its original volume, the object will be pushed outward by the pressure of the air inside the container. This principle is widely used in production and life. For example:

Compressed air is injected into the ball, and the more air you have, the harder the ball becomes; When compressed air is injected into the tire, the tire can bear a certain weight. In large cars, doors and brakes are opened and closed with compressed air; The hydraulic press uses compressed air to pressurize the water, and in the factory, the compressed air is used to start the air hammer to strike the iron; In coal mines, it can drill holes with a pickaxe. Compressed air is also used in pipelines to transport liquids and granular objects.

Drive all kinds of pneumatic equipment, such as air milling cutters, sand blasting and rust removal and so on.

1. The standard state of the air.

With the change of temperature and pressure, the volume and density of air often change, and the air with a temperature of 20 degrees, a relative temperature of 6%, and an atmospheric pressure of 1 atm (1 atm = is called the standard state, and the density of the air is .

The nature of compressed air.

When the pressure of the air increases, the volume decreases, and in inverse proportion, when the pressure is increased by a factor of 10, the volume shrinks to the original 1 10When the air at atmospheric pressure is compressed into the air tank under the action of mechanical force, its volume shrinks, the pressure rises, and it becomes compressed air. Compressed air has a considerable amount of energy and can do work externally when it is released outward.

The machinery that prepares compressed air is called an air compressor, and the machinery that uses compressed air as a power is called pneumatic equipment. The greater the amount of compressed air with a certain pressure produced per unit of time, the more capable the air compressor will be. Since the volume of compressed air varies with pressure, its pressure must be indicated when expressing the volume for comparison with each other for comparison with each other.

Similarly, the working capacity of pneumatic equipment can be expressed in terms of the consumption of compressed air, and the amount of compressed air that consumes a certain pressure per unit time is called air consumption. Therefore, two indicators are used to express the working capacity of compressors and pneumatic equipment: the volume flow rate is.

Its meaning is that when the gauge pressure is, the air consumption of the device is.

The effect of air conditions on the working capacity of the air compressor.

Since the theoretical working capacity of the air compressor is converted to the volume of air in the standard state, it only has this kind of work efficiency when the air inhaled at the inlet of the compressor is under the standard condition, and when the air is under the actual condition, it has this kind of work efficiency, and the actual situation often has deviations, mainly in the following situations.

Altitude changes.

Since both atmospheric pressure and air density decrease with altitude, compressors produced by using the same compressor at high altitudes produce less compressed air than at lower altitudes. This is due to the fact that the air pressure at the inlet of the air compressor is lower than the standard state value, and the gas production capacity of the air compressor decreases by 3% for every 305 m of altitude gain.

Changes in ambient temperature.

When the air compressor is operating at an ambient temperature 20 degrees higher than the standard state, the actual gas production capacity of the air compressor will decrease because the air inlet of the compressor is less dense than the standard state. When the ambient temperature is above 20 degrees, the compressor's gas production capacity decreases by 2% per liter of height. Working at 37 degrees, its gas production capacity will be reduced by about 6%, so the compressor should be placed in a cool and ventilated place to work in summer.