Home >> Industry Knowledge >> Nitrogen Generator (Nitrogen equipment) to drive the course of the problem
Preface
Nanjing Iron & Steel United Co., Ltd. Gas supply companies (to
Short: Nansteel gases) has 5 sets of air separation equipment, by the Hangzhou
Hangzhou Oxygen Company Limited (hereinafter referred to as: Hang oxygen) production. These
ASU only the use of switching process, but also the use of molecular sieve absorption
Attached purification, pressurized expansion of structured packing distillation tower and the whole hydrogen-free argon
Outside the compression and the compression process with 20000m3 / h air separation plant. More
Years, 5 sets of air separation plant has been running normal, the production, purity
To achieve the design specifications.
ASU is a process of driving only consumption, not production
Of time, space industry has adopted a series of measures to reduce the
Drive the process. Hollow points and driving the process equipment of all kinds of it
Impaired, if unable to be effectively addressed, will significantly extend the car
Process, even driving unsuccessful.
For an air separation plant are driving the process into several problems arise
Line analysis, and propose solutions for the peer reference.
1 air compressor export air pressure fluctuations
Now running a large-scale air separation plant DCS control of commonly used
System control, and control of air compressors in two ways: one is empty
In a separate press system, its own anti-surge control system; there is a
Species is an air separation plant by the user DCS control system direct control.
As a result of large-scale air separation plant is now commonly used by molecular sieve Adsorbed Water
Points, carbon dioxide and other impurities in the air compressor has just started, molecular sieve
Absorber with an air separation plant with the boost. Therefore, if a boot
Put pressure on the automatic adjustment, and some air compressor easily lead to pressure wave
Dynamic, and oscillation. This is due to exports from the air compressor to the molecular sieve adsorption
Inlet this relatively small space, short of a closed valve, the pressure is
Quickly increased, and a short, quickly lower the pressure. At this point,
If the guide vane in automatic control of imports, it will transfer frequent
Section, easy to create pressure fluctuations caused by vibration at the same time. At this time
Will import the best short guide vanes and control valves are manually changed.
Boot process in the air compressor, air compressor, air volume and pressure
Larger than the change in power, air compressor guide vane import the best of the opening control
System in the normal opening of about 80%. In this way, the air subsystem
Into the small gas can also be by regulating the emptying valve opening so that air
Press the pressure stability, does not surge into the area to ensure the safety of air compressor
Run.
2 air-cooling tower water level high chain-stopping
The role of air-cooling tower air scrubber to reduce air into the plate-fin
Or zeolite adsorption heat exchanger temperature. To prevent the air-cooled
Air with the water tower failure, air-cooling tower with a high water level alarm, interlock
Functions.
Nansteel gas in the air separation unit to drive the process, there had been empty
Great room temperature water cooling system and then start jumping, air-cooling tower water fast
Higher speed, more than air-cooling tower water level parking limit value chain, resulting in air
Short chain presses, air separation equipment failures forced to stop.
A 20000m3 / h Air Separation Plant in the normal air-cooling tower design work
Value for the water level 1200mm, alarm level value of 1600mm, water
Value chain of parking spaces for the upper limit of 1800mm, this value chain outage air-cooled
System pumps, air compressor short, plate-fin heat exchanger inlet stop.
External power supply as a result of a particular impact of large water pump at room temperature air-cooling system to stop
Transportation, air-cooling tower water by the normal 730mm to 1200mm drop
After, and then automatically return to the design water level. At this point, the operator Kai
Moving large pump room temperature air-cooling system, in only 1 minute of time,
Air-cooling tower water level rose rapidly from 1200mm to 1950mm, more than
Upper limit of air cooling tower water level parking value chain, resulting in short air compressor, air
Separation plant to stop into the gas, oxygen, nitrogen, argon product supply.
The air separation unit air-cooling tower the lower part of the diameter of 3000mm, air-cooled
Pump flow system at room temperature large 420m3 / h, low-temperature flow of a small water pump
50m3 / h. Great room temperature air-cooling system pumps water out of 7t / min,
7t water and air cooling tower water level can rise 1000mm. In the air-cooling tower
The water level rose, the air cooling tower backwater valve will gradually open
Large, due to the delayed adjustment of the valve, the valve open time
Longer, it is not air-cooling tower water level will quickly adjust to the design
Value, caused by air-cooling tower water level is too high and short chain compressor, air separation
Parking equipment.
Improving methods: air-cooling system to run at room temperature in large water before
The water level will be air-cooled tower 1200mm settings changed by 500mm,
In the air-cooling tower when the water level to 500mm large pumps to run at room temperature, do not enter
Operation of any man-made line. Air-cooling tower water levels rise within 1 minute to
1300mm, the callback to automatically set the value, thus avoiding
Open chain points. Tap water in the air-cooled down to below 1200mm, and then
Will set the value of air-cooling tower water level to 1200mm.
3 plate-fin heat exchanger into the gas flow rate fluctuations
Driving an air separation plant in the process, the plate-fin heat exchanger into the beginning of
The rate of gas must be slow, otherwise air can easily cause the entire subsystem
Pressure fluctuations in air flow and processing.
General large-scale air separation plant in the air into the plate-fin heat exchanger of the tube
Road, the former equipped with regulating valve, such as oxygen production Hang KDON220000 /
30000-based air separation equipment, in the air into the pipes before the cold box with
V111, V112 and V113 3 months control valve. When the export of air-cooling tower
Air pressure is lower than 014MPa and air import and export of molecular sieve adsorber
Pressure greater than 10kPa, the compressor will be short chain, three transfer
Section interlocking valve closed, air-cooling system water pump interlock big outage at room temperature. At
Drove the early, if excessive airway, air compressor valve clearance of the short small as
When the air compressor would be lower than the pressure of 014MPa, which
When the air compressor will be short, V111, V112 and V113 valves automatically
. 014MPa to be higher than when the air compressor pressure, V111,
V112 and V113 valves will automatically open, rapid intake, resulting in
Instantaneous pressure drop in air compressor, air compressor and then emptying the situation, and air
Sub-system pressure and into the plate-fin heat exchanger of the air will appear Week
Period of volatility.
To avoid this phenomenon, in plate-fin heat exchanger Gas
Initially, the V111, V112 and V113 set to manual control valve
System, in accordance with pressure changes in air compressor, the slow-by-turn
V111, V112 and V113 valves. Some with a plate-fin heat exchanger
Outlet air into the tower under the butterfly valve V10 of the air separation unit can also be
Slow opening valve V10 so as to avoid pressure fluctuations in air compressor.
4 while driving the process of fluid transfer pure edge
Air separation plant start-up spend more time, the design value of about 36
~ 48 hours. Drive the process of cooling can be roughly divided into a comprehensive, integrated
Fluid, three stages of tune pure. Of which: full cooling stage to be 14 ~
20 hours, fluid time 15 ~ 24 hours, adjusted net time 2 ~ 4
Hours. Different types of air separation equipment, cold as a result of the expansion mechanism,
Equipment capacity, plate-fin heat exchanger thermal effectiveness of rehabilitation and environmental temperature due to
Su-different, the difference between driving time will be larger, but the process of driving all
Almost.
How to shorten the driving time, the oxygen as soon as possible to reduce the energy consumption is
Are generally concerned about family issues, in addition to filling in the car in back to liquid, to increase
Cooling capacity to reduce driving time, can also be transferred through the side of effusion of pure edge
Ways to shorten the time to drive out oxygen.
Nansteel gas in the 5 sets of air separation plants are used to drive the process
Net transfer fluid side edge approach. Liquid level in the main cold there, the general expansion
Inflation is relatively low gas temperature, when the expansion of gas as far as possible all
Placed on the tower, use of LNG cold or cold recovery device to prevent
Plate-fin heat exchanger cooling, so as to achieve the purpose of speeding up the accumulation of liquid.
At present, the use of molecular sieve adsorption purification, large-scale pressurized flow
Air separation plant in the fluid, they often first appear in the main cooling liquid, when the main
Cold cold liquid up to the main port in the next heat exchanger, the increase in the next column
Gas will be the main cold liquid oxygen to the side heat exchanger, and heat exchangers will
Gases under the condensation tower rising, the main side of the cold liquid oxygen evaporation. With the
Liquid under the tower down, and the rising gas in a heat Trays
And mass transfer, under the distillation tower has already begun working condition. Tap the current liquid
Into the body of a tower, on the distillation tower has also started working condition. In the main cold
Oxygen process, although we do not have a cold, but the amount in advance to allow the main cold
Work place and an important regulator valve can be reached in advance of
The purpose of oxygen.
Some units require fluid phase, the main cold not put into operation in order to put
High on the tower operating pressure, to reduce the principal of evaporative cooling liquid. From the surface
Of view, the main cooling liquid by reducing evaporation, distillation does not occur Trays
Condition, cold air separation plants are concentrated in the main volume of cold oxygen side of the surface
Or faster. But once the product began to regulate the purity, as the tower
Board had no less liquid or liquid, must have a large number of liquid
Board will remain in the tower, causing the rapid decline in the main cold liquid.
Increase the pressure on the tower to reduce the evaporation of liquid cooling the main method of operation
In fact, not science, it will export expander air pressure increased,
The impact of the import and export of expander pressure drop, thus affecting the refrigeration expander
Effect, to extend the drive time. Fluid phase of the above refers to the expansion of gas
Tap into the situation. If the expansion of gas by-pass, it will affect the board
-Fin heat exchanger heat transfer effects, resulting in plate-fin heat exchanger thermal complex
Feet, the same drive time will be extended.
Nansteel gas in the air separation plant start-up process, the use of side plot
Pure liquid side transfer operation, the general in the expander to start a 24-hour
After the purity of product oxygen can be achieved, can be stabilized after 30 hours
Oxygen set.
Concluding remarks
ASU's various systems and parameters closely related, whether it is
Driving or operating normally, there are many technical issues deserve exploration
Discussion, in particular, driving the process, it is a constant over the establishment of working conditions
Cheng, operate and regulate more. To explore the experience of driving, reduce operating
Mistakes and shorten the driving time, there are a lot of work to do.