1. Working principle of booster turbine expansion machine
The working medium of this unit is pressurized by the booster first, and then enters into the main heat exchanger after cooling, and then enters into the expansion machine for adiabatic expansion to generate the cooling required by the air separation unit, meanwhile, the mechanical power produced is absorbed by the booster.
2. The working process and structure of the expander
The working medium enters the volute through the inlet pipe, then enters into the working wheel to work through the adjustable nozzle, and then is discharged through the expansion chamber and exhaust pipe.
The air volume adjustment of the expansion machine is realized by the pneumatic film actuator installed on the top of the cold box to drive the blade of the nozzle to rotate, thus changing the sectional area of the channel, the stroke of the valve stem of the actuator reflects the change of the width of the nozzle channel. The total stroke of the valve stem is about 40mm. The downward movement of the valve stem makes the nozzle channel wide, while the upward movement makes it small.
Volute: it is welded with stainless steel structure, fixed on the fuselage, connected to the base through the fuselage, and the content of volute includes nozzle and expander impeller.
Rotor: the two ends are respectively equipped with the impeller of the expansion machine and the impeller of the booster (both of them are closed), which are a rigid rotor, fitted on the bearing of the body.
Bearings: both front and back bearings are radial thrust combined bearings, and clean and sufficient lubricating oil is supplied by the inlet pipe to make the rotor run stably for a long time. Platinum resistance thermometer is adopted to measure the bearing temperature.
Shaft seal: there is a maze seal sleeve on each shaft which is close to the second impeller to control the gas leakage within the minimum range, fill the sealing sleeve near the expansion machine with normal temperature Sealing Gas (dry air or nitrogen) to prevent the low temperature gas flowing through the expansion machine from leaking, and run "cold ", in order to control the pressure difference between the gas at the nozzle outlet and the sealing gas at the expansion machine end to maintain around 0.05MPa, a precise pressure reducing valve is specially set up to fill in the sealing sleeve of the booster end ~ Sealed Air (dry air) with a pressure of 0.5MPa ).
3. Centrifugal booster
The booster consists of air intake chamber, impeller, Vane-free diffuser and volute. The impeller and the impeller of the expander are placed on the same axis, and their rotating speeds are the same. The mechanical power sent by the impeller of the expander drives it to rotate, after entering the impeller, the gas is accelerated and pressurized. After entering the leaf-free diffuser, it further slows down and increases pressure. Finally, it is gathered outside the exhaust machine of the volute and enters into the electric heat exchanger after cooling down, then enter the expansion machine. [Ok3w_NextPage]
4. Oil supply system
The oil supply system is composed of separate systems, mainly including oil tank, three screw oil pump, oil cooler, temperature control valve, capsule accumulator, etc. The lubricating oil enters into the oil pump to boost the pressure, enters into the oil cooler and the switching oil filter, and then enters into each bearing respectively. At last, the inner cavity of the machine body enters into the oil return pipe and returns to the oil tank. In addition, an accumulator is set, automatically filling oil after the oil pump is started, which is used for oil supply for a period of time (about 1 minute) when the unit interlocks and stops after the oil pressure decreases or the oil pump stops to ensure the safety of the bearing.
The lubricating oil adopts N32 transparent oil. In order to ensure the quality of the oil, oil change should be conducted once after 300 hours of operation, and then oil change should be conducted at least once a year on the premise of cleaning the oil filter, only on the premise that the oil has good characteristics after inspection, can the oil changing time be prolonged.
5. Emergency cut-off valve
An emergency cut-off valve is set at the entrance of the expansion machine. When the unit is in a dangerous state, according to the interlocking signal sent by each dangerous point, this valve can be closed in a very short time, thus cutting off the air source, make it stop quickly and play the role of safety protection.
In the critical situation, the interlock of the instrument control system of the expansion machine will cut off the power supply of the solenoid valve, which will make the emergency break valve close quickly. At the same time, the return valve FCV401 of the booster machine will open automatically.
6. Back cooler of booster
In order to cool the outlet high temperature gas of the booster machine to meet the requirement of air separation process, the cooler is set up to cool it with cooling water, and the purpose of adjusting the outlet gas temperature can be achieved by adjusting the water inlet, the control of cooler working condition should be carried out according to its technical parameters and process requirements.
7. Return valve of booster
Setting this valve has the following three purposes:
A. pressure adjustment: according to the requirements of air separation process, it is generally hoped that the outlet pressure of the booster should keep constant, and the opening or closing of the valve should be big or small, which can reduce or increase the pressure, under the automatic control of instrument control system, the valve can achieve the purpose of constant pressure.
B. anti-surge: At a certain inlet flow rate and rotation speed, when the inlet flow rate is small to a certain value, the machine will surge, and the pressure will fluctuate greatly at this time, and make a strong "gasp" sound and vibration, which will cause damage to the machine. To prevent this situation, the valve will open automatically when the inlet flow is small to a certain value. The given anti-surge flow is based on the condition that the inlet pressure, inlet temperature and rotating speed are all rated. When these conditions are different, the anti-surge flow value should be revised.
C. Open the large return valve: it can increase the load of the booster to slow down the expansion machine [Ok3w_NextPage]
8. Maintenance instructions
8.1 nozzle: as long as the supplied gas is clean, even if the luster of the nozzle blade turns dark, the efficiency will not be affected, however, if the gas contains relatively large or even a small amount of solid particles or liquid drops produced by carbon dioxide, the abrasion of nozzle blades will occur, and pits will appear in serious cases, in this way, the efficiency will be significantly reduced. At this time, the nozzle should be replaced. During the start-up of the device, abrasion is the easiest to occur. Therefore, special attention should be paid to the operation of the device.
8.2 The impeller of the expansion machine: the same reason as the Blade of the nozzle may also cause abrasion on the inlet edge of the blade. If the abrasion is serious or even the pits appear, the working wheel should be replaced.
8.3 The sealing cover of the impeller of the expansion machine and the booster is easy to be slightly worn. If the abrasion is serious, it must be replaced, and the Assembly clearance is shown in the figure.
8.4 shaft sealing sleeve: the hole of the shaft sealing sleeve will be slightly worn when running. If the abrasion is serious, the shaft seal should be changed, because excessive abrasion will lower the temperature of the bearing and increase the loss of air leakage. The radial clearance of the shaft seal is 0 ~ When 0.04mm increases to 0.1, it should be replaced.
8.5 bearing: the bearing surface is elaborately designed and guaranteed by machining. Therefore, the inner hole and thrust surface are not allowed to be arbitrarily corrected. If bearing damage is found due to temporary overload or poor lubrication, the bearing should be replaced.
8.6 The impeller of the booster: If the supplied gas is not clean, it will cause abrasion of the blade of the booster, so as to break the balance, which is similar to the damage of the dynamic balance of the impeller of the expander. It should be noted that when the impeller of the expander, the impeller of the booster or other parts need to be replaced, the whole rotor must be replaced instead of the impeller or other parts alone.
8.7 oil cooler is generally cleaned once a year. If the cooling water is not clean, the cleaning times will increase.
8.8 oil filter, if the filter resistance is obviously increased, the filter element should be cleaned or replaced.
8.9 the rear cooler of the supercharger is usually cleaned once a year. If leakage occurs during work, the resistance increases suddenly and the heat exchange effect becomes worse, then the reason should be checked immediately and repaired.
