Home >> Industry Knowledge >> Small Nitrogen (Nitrogen equipment) operation
Designed and manufactured by Hangzhou Oxygen Group of KDON. Type 170/350
All low-pressure flow of air separation equipment, it could also extract the oxygen, nitrogen production
Products. The device is designed into the fractionating tower air pressure (gauge pressure, the same below)
Of 0.55 ~ 0.7MPa, processing of the air volume 700 ~ 1500m / h of the
, The use of units according to the local oxygen, nitrogen sales market situation,
Flexibility in matching compressor displacement.
The device in the design, using more advanced "s"
Shaped plate, so that gas-liquid two-phase in the tower of the board have more time to turn
Contacts and continuous distillation. Therefore, oxygen, nitrogen separation is more
Better, more pure, more stable yields. In addition, the device in the configuration
Instruments, measuring instruments are also compared with the same range. In addition to also use the pointer
-Type pressure gauge, the other, such as liquid level, flow, temperature, speed, etc.
All use of electronic digital display. Fractionating tower, instrument panel and operation of boxes
Beautifully designed, clean, generous, easy to operate. It can be said is
More applicable to small-scale domestic energy-efficient air separation unit. KDON. 170/350
Type air separation plant processes shown in Figure 1.
It is expanding with the past, the entire low-pressure flow of air reflux air separation plants
By comparison, in operation there is a larger difference. The following will be the author in Fujian
A Gas Limited KDON. 170/350 type air separation equipment
Operating conditions, making a summary for reference.
l liquid phase of an air separation plant to start operation of
1.1 The operation of the cooling phase of the
Installation of cooling generally can be divided into three steps: ① lower turbine
Expander inlet temperature; ② reduce the turbo-expander exhaust gas temperature; ③
Overall cooling fractionating tower.
1.1.1 reduce the intake air temperature operation of turbo-expander
As the turbo-expander at room temperature when the cooling effects produced relatively poor, must be
Required to fall into the temperature of the first turbo-expander best work and the best
The temperature to achieve efficiency, and therefore the expansion was originally produced by the limited machine
Cold can not be cooled more parts, but only "self-produced their own use."
Kai-V5 and v7 valve, V4, and V6 off valve, the cold all the by-pass
To the main heat exchanger, with cooling capacity expansion to cool the air before expansion.
When the operation point is: give full play to the maximum of two turbo-expander
Cold production efficiency, intake air temperature dropped as soon as possible the requirements of the design value.
1.1.2 reduce the operating temperature of the exhaust turbo-expander
When the expander inlet temperature dropped to 1 120 ℃, has been basically
Expander inlet temperature to meet the job requirements. In order to ensure that the expander
There is a relatively stable intake air temperature, they should expander inlet
From the main heat exchanger in the bottom draw I slowly switched to the central pumping port, but also
Valve V5 is closed and open valve V4. Let the best in the design of an expander into the
Temperature point, to continue to Production of cold in order to reduce exhaust gas temperature.
1.1.3-round operation of the cooling tower fractionation
When the expander exhaust gas temperature dropped to 1 165 ℃, the micro-open-V1
Valve, cooling tower to the next. At the same time, open the valve V6, appropriate Customs
Small v7 valve, right on the cooling tower. At this point the operation of key points are:
With v7 valve opening to ensure an expander inlet temperature 123 ℃ in a left -
Right, the same time with the expander intake valve opening control of exhaust gas temperature in the
One between 165 ~ 1 170 ℃; adjust vl valve opening, so that pre-throttle
A smooth decline in temperature and maintained at between ? 165 170 ℃.
1.2 fluid accumulation phase of the operation of
Fluid accumulation phase is a continuation of the cooling phase. Operation points and
Operation is also based on basically the same. It is noteworthy that the fractionation tower liquid
The emergence of body requirements and frequency of adjustment must be relatively less, to make
Volume to maintain the stable operation of fractionating tower, in order to speed up the accumulation of liquid to create good
Good conditions.
When the liquid oxygen liquid height up to 300ram above, should play
Open sewage nitrogen control valve V8, coolant air cooling device, so that nitrogen pollution has turned out
Cooler temperatures decreased rapidly.
1.3 adjusted net income phase of the operation of valves
When the fluid level to rise to 400ram or more oxygen, nitrogen has turned out
Cooler temperatures, dirt subcooler nitrogen out of the air out of cooler temperature and expansion
When the temperature reached the designed value, started to close the valves adjusted net operation. As
All low-voltage devices using energy-saving condensing evaporator design temperature difference
Relatively small, in the closed valve tone pure process, the liquid oxygen liquid level fluctuation than the
Larger. Therefore, pay special attention to controlling the speed and magnitude of off valves,
Should try to maintain the stability of liquid oxygen or its control in a certain wave
Dynamic range.
1.3.1 In the off valves V2 and V3 valves small, while refined fractionation tower
Distillation conditions continue to improve. At this point, should be based on expansion of aircraft into and out
Mouth temperature drop and liquid oxygen liquid level rise in a timely manner to reduce swelling
Cold will be one of the expander inlet valve slowly off the small straight
To the whole of customs, so that another expander full load operation.
1.3.2 In normal circumstances, the compressor displacement, if the oxygen
Purity and oxygen production reach the design requirements, indicating V3 valve opening
Inappropriate, should continue to be adjusted to the appropriate location. t
1.3.3 When the liquid oxygen, oxygen purity and oxygen production of the basic stability
Are established, in order to further enhance the oxygen production, should be gradually closed the small V7
Valve to increase the expansion of the flow of air into the tower. While slowly
Guan small v8 valve, so that expansion of air in the tower there is sufficient time for
Alternate contact and continuous distillation, in order to increase oxygen production.
1.3.4 When the v7 valve off a small to a certain location, definitely make the expansion
Machine discharge pressure increases. But this time, the main operation is based on liquid
Liquid oxygen, liquid oxygen can be maintained as long as live, V7 valve can continue to
Small or even fully closed off. However, v8 valve not fully closed, and when opening by
As small as 2 to switch should be up to 400ram and other liquid oxygen liquid height above
Then according to the oxygen content of nitrogen pollution situation will be adjusted to fit their
Opening.
2 normal operation of the operation of
2.1 turbo-expander into the gas flow rate and speed of adjustment
The device after expansion of the air directly into the tower, traffic is too large
Have a direct impact on the oxygen purity. At this point can brake fan inlet
Off valve is small, so that expansion of machine speed increase, appropriate reduction in the inlet expander
Gas, with a corresponding opening big v1 valve, so that oxygen purity increased.
2.2 Control of liquid oxygen
According to operation experience, the device liquid oxygen liquid height of 400 ~
500ram, oxygen purity of the best and highest yield of oxygen. Therefore,
Use the expander intake valve and the v1 valve opening, the liquid oxygen liquid height
Between the control 4OO ~ 500ram.
2.3 The purity of oxygen and oxygen production adjustments
Fractionating tower to adjust to normal, oxygen purity and oxygen production are
Stability and, under normal circumstances no longer have to adjust. However, the device uses
Mini air compressor, this compressor is very sensitive to climate change
Sense, in particular the relatively large temperature changes in the weather, the air compressor displacement
Will increase or decrease with temperature changes. In order to stabilize the purity should be based on exhaust
The amount of change, there is predictability to adjust the oxygen flow.
2.4 The normal operation of the parameter values
KDON. 170/350 type air separation plant parameters during normal operation
Values shown in Table 1. The data listed in Table 1, is the initial operation the device
Action values. Compressor Displacement of 1200m / h, a single turbine expansion
Machine (expansion capacity of 247m / h) run.
Table 1 KDON-170/350 full low-pressure flow type air separation plants
Normal operation of the parameter values
Measurement
Measuring the value of the contents of the actual operation site the value of the original design
The air out of the main heat exchanger temperature of 11 170 ℃ ~ 1 168 1 l69 ℃
Expansion of the primary heat exchanger exit temperature of the air pump a l23 ℃ 1 l24 11 l28 ℃
Win a subcooler nitrogen temperature of a l78 ℃ 1 l7l 11 l72 ℃
Nitrogen pollution has turned out cooler temperature of a l78 ℃ 1 l7l 11 l72 ℃
Inflate the air out of cooler temperature of 11 l68 11 l75 ℃ 1 l70 ℃
Expander inlet temperature of a l23 ℃ ~ 1 125 1 l29 ℃
11 expander outlet temperature 165 ℃ ~ 1 158 1 l66 ℃
Liquid Air surface ≈ l60ITlnl l53 a l56mm
Surface liquid oxygen liquid ≈ 4oOITlnl 4oO a 50oITlnl
Oxygen purity of 99.6% O, 99.6% O
Oxygen purity of 99.6% O, 99.6% O,
Pure
Air Liquide purity of 32% O, 32% ~ 33%
Liquid nitrogen purity of l0 × l0 10, no analysis of
Degree
Nitrogen purity l0 × l0 10, no analysis of
Nitrogen pollution purity l0.3% 0, ll% a l2% 0
Air throttle vl 3 5 switch 35 to switch
Valve
Door Air Liquide V2 4 turn throttle switch 240 ~ l
Open
Throttle V3 2-degree liquid nitrogen to switch 25o turn l
Nitrogen pollution control valve V8, l turn 310o
Expansion of the air flow into the tower, ll0 ~ l30m / h
Flow oxygen flow l70m3 / h 170-190m3 / h
The amount of nitrogen flow rate 350m / h> 465m3 / h
Sewage nitrogen flow 200 570 Ⅲ J / h> 300m / h
The air out of the main heat exchanger pressure 0.645MPa 0.49MPa
Pressure
Under the tower pressure 0.5l7MPa 0.45 ~ 0.49MPa
Li
Pressure on the tower 0. O59MPa 0. O5MPa
Question 3 off oxygen
3.1 Analysis of the feasibility of the implementation of intermittent oxygen
For the medium-pressure process for the implementation of intermittent small-scale air separation plant system
Oxygen is no longer a novelty. But the fact is low-pressure flow of small air separation equipment,
In the design is based on continuous oxygen (nitrogen) as the premise, therefore, can be
Can not be intermittent oxygen? How, after the implementation of intermittent oxygen gymnastics
Make? Are subject to further practice and concluded.
Compared with the medium-pressure process, all low-pressure flow of air separation equipment, the main change
Heaters, condensate evaporator, liquid air and liquid nitrogen cooling device as well as the expansion of space
Air coolers, are used very high heat transfer efficiency of materials and advanced technology
Made, not easy to leak, cold little damage, but the special effect of heat transfer
. These intermittent oxygen for example, are very beneficial to be
Pieces. Therefore, I believe that as long as find a suitable method of operation
The implementation of intermittent oxygen is feasible.
3.2 Method of operation to restore oxygen
According to our operational situation, there are two kinds of time to restore oxygen
How can choose: one is "abandoning surface seeking purity" operation
Law; the other is "protecting surface" operation method.
The so-called "surface seeking homes purity" operation method, is actually a sacrifice
Sacrifice the amount of cold fractionation tower to get the cost of the work of the tower points
Temperature; then fractionating tower according to the consumption of cold, with expansion
Additional cooling capacity to do. As the cryogenic liquid evaporation process always starts from a low-boiling
Components to high-boiling point components, so they can rapidly improve oxygen purity,
To advance the purpose of delivery of oxygen.
This operation method is simple, relatively quick recovery time, oxygen,
Approximately 20 30min or so. However, this method consumes cold fractionation tower
Too large, but the scope of application is also very small. Downtime is slightly longer,
Fractionating tower could be able to run out of low-temperature cold, and when a new cold again
Or not when, but more difficult to operate.
The second method of comparison operation safer. All low-pressure flow
Process characteristics, so that we can not spend the first low temperature distillation tower
Volume, while the standalone expansion machine, the main heat exchanger, thermal insulation material and
Part of the pipe pre-cooling and cold storage of a certain amount; and then
Expansion of cold sent to fractionation tower. On this basis, only consumption of
Some low-temperature cold tower for further cooling on the list overall.
The advantage of this operation is: to keep low temperature fractionation tower
Volume, although a longer recovery time for oxygen (about 50-60rain
Or so), but the condition is very stable, very safe, but the scope of application is very
Canton, stopping a few hours or even more than a day are available to this method of operation.
3.3 How to restore oxygen and steps for the specific
3.3.1 "Level homes seeking purity" Operation Law
According to operating instructions of the "recovery operations after an emergency shutdown," Fang
Method (abbreviated).
3.3.2 "Security Level" operation method
3.3.2.1 full-V4, V7 valve and expander exhaust valve due to open
Large nitrogen venting valve and nitrogen pollution discharge valve. V5 valve opening 2-3 turn, V2
And v3 the normal valve opening, all customs V1, V6, V8 valve.
3.3.2.2 aspirated into the fractionating tower and after the air pressure rose into the tower
0.5MPa when the valve is opening a v1, so that a small amount of air flow in the tower,
Then start the expander. If the shutdown takes longer, it is necessary to open two-expandable
Inflation machine.
Operation at this time point is: In the expander inlet, exhaust pressure and
Speed allowed as far as large expander intake valve opening to increase the
Cold expansion; air compressor into the column of air venting valve to maintain pressure in the
0.65MPa; when an expander inlet temperature dropped to a 120 ~ C, the slowly
V5 valve tightly closed.
3.3.2.3 When the expander exhaust gas temperature dropped to 1 170 ℃, when, according to
Times to be adjusted as follows: ① with the expander intake valve opening control of exhaust
The temperature between 1 170 11 180 ℃; ② slowly open the valve V6,
Properly close down small V7 valve, right on the pre-cooling tower and use v7 valve open
Degree of control the expander intake air temperature, so that no less than 1 140 ℃; ③
Open V8 valve, coolant air cooling device, so that dirt out of subcooler nitrogen temperature
Degree of decrease; ④ due to open big v1 valve, so that the temperature drop before throttling and
Under the cooling tower; ⑤ oxygen is opening a venting valve, to control its flow in the 5oIn3 / h
So, let inflation air cooler to work.
3.3.2.4 When the throttle before the temperature dropped to a 165 oC, the progressive off
A small air compressor venting valve, and the corresponding opening big v1 valve, until the increase
Fractionating tower into the air all the work to maintain the pressure into the tower
0.65MPa.
3.3.2.5 When the nitrogen out of subcooler temperature, pollution out of subcooler nitrogen temperature
Degree and expansion of air out the cooler when the temperature drops to normal, indicating
Fractionation of various parts of the cooling tower has been basically completed. At this point, can be closed
Small nitrogen nitrogen pollution discharge valve and venting valve, to keep the pressure on the tower.
3.3.2.6 When the liquid oxygen began to rise, if you opened two
Expander, should be gradually closed the small one of the intake valve opening, until the whole
Off. Another expander inlet gas should rise under the surface of liquid oxygen
Circumstances, the appropriate reduced; and the corresponding valve opening big v1, step-down.
After the delivery of oxygen above 1.3.3,1.3.4 and 2.1,2.2,
2.3,2.4 section method.
According to our practical situation, stop before the liquid oxygen liquid
Surface height of 450mm or so, shut down after about 5h, according to the first party
Method is, 20 30rain will be able to get oxygen, liquid oxygen liquid down to
Recovery of about 200mm. Down about 10h later, the second method according to exercises
For, 50 60rain and carries oxygen, liquid oxygen liquid down to about 100ram
Began to rise; stands about 20h after ,90-120rain send oxygen, liquid oxygen
Surface down to 60mm or so began to rise. Two kinds of operation methods
Do not need to open large V2 and V3 valves valve.
Although the above operation than the old 150m / h air separation plant to restore oxygen to
Slow, but a preliminary indication of the device to implement the basic oxygen break
Is feasible.