Large air separation FAQ

All low pressure air separation units are usually equipped with nitrogen water precoolers. It mainly uses the unsaturation of nitrogen in sewage to evaporate part of water. As the water evaporates, it absorbs the latent heat of vaporization to lower the temperature of the cooling water, which is then used to cool the treated air and lower the temperature of the air entering the column. Therefore, it includes air cooling column and water cooling column. The basic purpose of setting up nitrogen precooler is to reduce the air temperature entering the air separation column and avoid the temperature fluctuation greatly. Because the inlet air temperature directly affects the operation conditions of the switching heat ex-changer and distillation column, as well as the economy of the whole air separation unit. In the design, the air temperature entering the column is usually set at 30 ° C. When the inlet temperature of the column is higher than the design index during operation, the throttl

What precautions should be taken when using the oil cooler in air separation equipment?

The amount of liquid nitrogen removed from the lower column of the air separation unit will affect the purity of the liquid nitrogen in the lower column and the oxygen enriched liquid air at the bottom of the column. When the liquid nitrogen removal amount of the lower column increases, the reflux liquid participating in the heat and mass exchange of the lower column will be reduced, the temperature rise of the rising steam on the column plate will be correspondingly reduced, the condensation of the rising steam will not be sufficient, the oxygen component will be condensed less, the purity of nitrogen at the column top will be reduced, and the purity of liquid nitrogen will be naturally reduced. At the same time, the temperature rise of the downflow liquid will increase, the liquid evaporation will be more sufficient, more nitrogen components will be evaporated to the top of the column, and the purity of the liquid air at the bottom of the column will be improved accordingly.

Lean alloy steel is often used in special pressure-bearing equipment. The alloying elements often added include manganese, silicon, chromium, nickel, molybdenum, vanadium, boron and rare earth elements. Most of silicon and manganese melt into ferrite, only a small amount into cementite, which are commonly used strengthening elements in lean alloy steel. The amount of chromium and nickel is generally small, and the main role of chromium and nickel is to increase the undercooling degree of austenite and refine the microstructure. Part of chromium is dissolved in ferrite and some in cementite, which can improve the stability of cementite. Molybdenum is dissolved in ferrite slightly, and has the effect of solid solution strengthening. It is a strong carbide forming element, which can improve the high temperature strength of steel and improve the temper brittleness.

Cryogenic air separation nitrogen production uses air as raw material, which is compressed, purified and heat exchanged to liquefy gas air into liquid air. Liquid air is mainly a mixture of liquid oxygen and liquid nitrogen. Liquid oxygen and liquid nitrogen have different boiling points and are separated by distillation to obtain nitrogen. 1. Air compression and purification The air passes through the air strainer to remove dust and mechanical impurities, then enters the air compressor, compresses to the required pressure, and then goes to the air cooler to reduce the air temperature. It then enters the air drying purifier to remove moisture, carbon dioxide, acetylene and other hydrocarbons from the air. 2. Air separation The purified air enters the main heat exchanger in the air separation column, and is cooled to the saturation temperature by the reflux gas (production nitrogen gas, waste gas), and is sent to the bottom of the distillation column. The nitrogen is obtained fr

Under the conditions of certain welding methods, welding materials, welding specification parameters and welding structure, the difficulty of obtaining high-quality welded joints is called steel weldability. Therefore, the weldability should be evaluated from two aspects of manufacturing and application. The weldability of process mainly refers to the possibility of various cracks in welded joints, which reflects the difficulty of manufacturing. Weldability of using mainly refers to the mechanical properties and special properties of heat resistance, corrosion resistance, low temperature resistance and fatigue resistance of welded joints, which reflects the reliability of use.

Shell and tube air separation heat exchanger is the most representative wall heat exchanger. It has a long history of application and is still dominant in all heat exchangers. Shell and tube heat exchanger is mainly composed of shell, tube bundle, tube sheet and head. Most of the shell is round, and there are parallel tube bundles inside. Both ends of the tube bundle are fixed on the tube plate. In shell and tube heat exchanger, there are two kinds of fluids for heat exchange. One kind of fluid flows in the tube, and its stroke is called tube side. The other flows outside the tube and its stroke is called shell side. The wall of tube bundle is the heat transfer surface. In order to improve the heat transfer coefficient of the fluid outside the tube, a certain number of transverse baffles are usually installed in the shell. The baffle can not only prevent the short circuit of the fluid and increase the velocity of the fluid, but also force the fluid to flow through the tube bundle man

When the exhaust temperature of the piston compressor is higher than the design value, the most direct impact is that the lubricating oil is carbonized, which leads to the compressor parts burned out because of not getting good lubrication. If the temperature of the compressor is too high during actual operation, the cause should be analyzed in time and corresponding preventive measures should be taken. The following methods can be used for reference in practice. 1. Reducing the inlet air temperature can directly reduce the exhaust temperature. Check the intercooler to ensure the cooling effect of the intercooler. 2. The installation of the valve and the selection of the spring should be standardized to ensure the normal operation of the valve and minimize the loss of inlet and outlet pressure. 3. Strengthen the cooling of cylinder to ensure the normal compression process index. 4. Internal leakage is the main reason for the increase of exhaust temperature. 5.For multist

Generally, the main reason for the vibration of piston type oxygen compressor is the action of alternating load. There are two kinds of alternating loads: one is the unbalanced inertia force, the other is the interference force caused by the strong gas pressure pulse in the gas pipeline caused by the discontinuous gas supply of the compressor. The vibration caused by unbalanced inertia force can be eliminated and reduced from the structure of the machine itself. The specific methods are as follows: reasonably arrange the crank stagger angle; properly select the mass configuration of reciprocating parts. In addition, the basic design and manufacturing process of the compressor should also strictly comply with the technical specifications. For the vibration caused by air flow pressure pulse, a buffer can be installed near the cylinder exhaust pipe nozzle; the appropriate installation position of orifice plate should be selected on the gas flow channel; the shock absorber should be

When the main condenser evaporator leaks seriously, a large amount of high-pressure nitrogen will leak to the low-pressure oxygen side, and the pressure of the upper and lower columns and the purity of the product will change significantly until normal production cannot be maintained. When the main condenser evaporator leaks slightly, the pressure of the upper and lower columns will not change significantly, and the purity of liquid oxygen in the main condenser evaporator will not decrease significantly. The common phenomenon is that the purity of the gas and liquid oxygen in the main condensing evaporator is very different, and the gas concentration is lower than that in equilibrium with liquid oxygen. For example, the concentration of liquid oxygen is 99% and that of gaseous oxygen is 96%, that 7 main cooling pipes were found to be leaking during maintenance. The common causes of leakage are as follows: 1. Pipes are worn due to mutual vibration. For long tube condensing evap

Expander is a kind of mechanical equipment that uses compressed gas to expand and depressurize, so that the gas temperature can be reduced to obtain the cooling capacity. In the air separation unit, the expander is an important equipment to provide cooling capacity for the air separation unit, and its cooling capacity accounts for 80% - 90% of the cooling capacity of the air separation unit. The main structural forms of expander are piston type and turbine type. The piston expander is suitable for air separation process with large pressure drop and small flow rate because of its convenient manufacture and low speed. Turbine type has the characteristics of large gas flow, high efficiency, stable and reliable operation and no friction parts. Due to the low pressure air separation process used in large air separation units, the pressure drop and unit cooling capacity are very small, and because the expansion air is sent to the upper column for rectification, the expander is requi

Generally, the actual cooling capacity of expander is always less than the theoretical cooling capacity. Under the same inlet and outlet pressure and inlet gas temperature, the lower the efficiency of expander, the smaller the unit refrigerant cooling capacity and the smaller the temperature drop efficiency of expander. The efficiency of expander depends on the size of various losses inside the expander. Due to the existence of various losses, the ability of gas to do external work is reduced in varying degrees. To sum up, the losses mainly include the following aspects: 1. When the air flow passes through the work wheel and the deflector, the loss caused by friction and air flow impact on the runner surface is called flow loss. 2. When the impeller is rotating, the friction heat generated by the gas around the wheel disc will increase the temperature of the gas, which is called friction blast loss. 3. When the gas passes through the deflector, the leakage from the gap bet