Small air separation FAQ

Internal compression air separation process is a process form in which liquid products are pressurized by liquid pump in the cold box, and then sent out of the cold box after reheating by high-pressure heat exchanger. The working pressure of internal compression process generally exceeds the critical point of oxygen and nitrogen. Heat transfer of liquid in supercritical state is a major feature of internal compression process. In the distillation process, due to the difference of product types and acquisition methods, there is a big difference between the material import and export of internal equipment and external compression process. In the internal compressed air separation process, the pressure of oxygen is not limited, the maximum output of nitrogen can reach 2.8 times of that of oxygen, and the extraction rate of argon can reach about 85%. The internal compression air separation process is generally composed of internal compression system, air precooling system, molecular sie

When the cryogenic method is used for air separation, the whole process is carried out in closed containers and pipelines from the air compressor to the final gas and liquid products such as oxygen, nitrogen, argon and so on. During the start-up, shutdown and normal operation of the equipment, the values of relevant parameters must be strictly controlled in each process, including pressure, temperature, flow, resistance, liquid level, rotate speed, voltage, current, component analysis, etc. The following introduces some instrument control components for measuring temperature, pressure and flow for reference. 1.Temperature measurement: In the temperature measurement of air separation plant, the main measuring elements are platinum thermistor thermometer, temperature transmitter and bimetal thermometer. Platinum thermistor thermometer is widely used in air separation plant due to its high measurement accuracy at low temperature (13.81K) and no temperature compensation at cold end.

Which is more costly, the internal compression process or the external compression process in an air separation plant?

After the air separation equipment stops, when the equipment does not discharge liquid, the basic temperature of the cold box will be reduced to more than - 100C in many cases. Most air separation plant users customers concern about this situation which will lead to a illusion of equipment leakage for the sake of safety.

The amount of expansion air entering the upper column increases, and the reflux ratio of the rectification section decreases correspondingly. In order to achieve the required purity of the nitrogen product, more trays need to be provided. When the reflux ratio is reduced to the point that countless trays need to be set to make the nitrogen purity reach the required value, the reflux ratio at this time is called the minimum reflux ratio. The amount of expansion air entering the tower is first lim...

The air contains 0.932% argon. When 99.6% oxygen is to be produced from the upper tower, 1.05% argon must be contained in the nitrogen discharge. From the perspective of separation process, the distillation section of the upper tower (below the liquid inlet) is basically oxygen-argon separation, while in the distillation section (above the liquid inlet) then it is basically nitrogen-oxygen (argon) separation. The boiling point of argon and oxygen is relatively close (the boiling point of oxygen is-182.97 ℃ at 0.1013MPa, and the boiling point of argon is-185.7 ℃), so it is relatively difficult to separate. In the distillation section, such a situation often occurs. In the process of nitrogen-oxygen separation, the oxygen component is not separated clean, and the argon component basically escapes together with the oxygen component in the nitrogen discharge, reduce the purity of nitrogen. If it is required to produce high purity nitrogen, the oxygen component should be completely separ...

Reducing the high pressure of small air separation equipment with medium pressure expansion machine can reduce the energy consumption of air separation equipment. Here is a simple analysis of the influence of the temperature before the expansion machine on the high pressure. Under the condition that the total cooling loss and the gas temperature before expansion are fixed, from the perspective of the heat balance of the total unit, increasing the high pressure can reduce the expansion gas; but from the perspective of ensuring the working condition of the cold section heat exchanger, with the increase of high pressure, it is required to increase the expansion amount and reduce the air flow into the cold section heat exchanger. Therefore, the selection of working pressure and expansion amount of the process should meet both requirements. When the total cooling loss and working pressure of the process remain the same, increasing the temperature of expansion forward gas can increase the...

The three-point temperature of the low temperature of the air separation tower is: T3 temperature refers to the temperature before the high pressure air throttles; T2 temperature refers to the temperature of the air after expansion; t1 refers to the temperature after the first heat exchanger and before the expansion machine. The function of the three-point temperature is mainly to control the gas distribution between the expansion machine and the joint-1 valve during the start-up stage of the air separation tower. There is no need to control the normal and stable operation. If only one or two of the thermometer is out of order, we can speculate the working condition according to the intact temperature point. When the three-point temperature is completely out of order, it can be operated according to the temperature difference between the Heat end of the heat exchanger (namely the temperature difference between the air inlet device of processing air and the outlet temperature of oxyg...

Small air separation equipment consists of air compressor, purifier, air separation Tower, expander, oxygen compressor and other main parts. Before starting, all parts of the equipment should be ensured to be in good condition and can be put into operation at any time. (1) The start-up preparation of piston air compressor after the installation of air compressor, it should be tested according to the instruction manual. The daily preparation work before driving should remember the words "water, oil, gas, electricity and safety", and check according to these five aspects. 1) Water: Open the cooling water, oil cooler cooling water and inlet valve of cylinder liner and cooler at all levels, and check whether the cooling water is unblocked and adjusted properly; 2) oil: it includes the lubricating oil of the cylinder and the lubricating oil of the running part. Shake the plunger oil pump by hand until the oil flows out of the check valve of each oil injection point is opened, and fill up...

Air cooling tower is also a hybrid heat exchanger. In order to make the cooling water fully contact and strongly mix with the air to enlarge the heat transfer area and strengthen the heat transfer, the "stuffing Tower" or "sieve plate Tower" are usually used, and hollow spray tower is also used. The stuffing Tower is a round container made of steel, which is filled with stuffing (porcelain ring, or plastic ring, etc ). The cooling water sprays down from the tower top and is mixed with the bottom-up flowing air for heat and mass exchange. Air transmits heat to cooling water to lower the temperature itself and raise the water temperature. In order to prevent the air from dripping out of the water, the upper part of the tower is usually equipped with laxige ring (or stainless steel wire mesh) stuffing separator (also called capture layer) and mechanical water separator (inertial separation ). The cooling water sprayed out by the spraying device flows downward along the stuffing layer t...

The newly installed distillation column must be thoroughly heated and blown off before starting and returning to work after long-term parking. After being put into operation, when the liquid suspension failure of the distillation column can not be eliminated, or the pressure difference before and after the heat exchanger pressure at the end of the operation period is more than 0.5MPa, or the purity of oxygen and nitrogen and the output decrease, it should be heated and blown off. First of all, make preparations before heating: 1) discharge the liquid in the tower; 2) dismantle the flow meter and thermometer at the outlet of oxygen, nitrogen and distillation, dismantle the upper and lower joints of the liquid air and liquid oxygen level gauge, and dismantle all the pressure gauges except the low pressure gauge; 3) close the high pressure air General inlet valve, joint-1 valve, oxygen and nitrogen products outlet valve, and the heating inlet main valve; 4) open the top rod of the inle...

The load adjustment range of low pressure air separation plant is related to the adjustment performance of raw material air compressor, the adjustment performance of expansion machine, the structural characteristics of distillation column and other factors. At present, the flow regulation range of the turbine air compressor equipped with imported guide blades is 75% ~ 100%; the adjustment range of turbine expansion machine with adjustable nozzle can be 65% ~ 100%. The key is how much room for adjustment of the distillation column is. At present, the load regulation range of the distillation column with regular stuffing can reach 50% ~ 100%, while the best adjustment range of traditional screen tower is 70% ~ 100%, no matter how low the load is, the leakage may be caused by the low speed of steam passing through the sieve hole. When oxygen is rich and needs to reduce the output of oxygen, the output of oxygen products should be reduced first, then the air flow should be reduced corre...