Home >> Industry Knowledge >> Reduce Nitrogen (nitrogen plant) the practice of energy consumption

Western Gas Co., Ltd. Zhoushan 100 million KDON-IO00Y/IO00
Liquid from Hangzhou, Sichuan Air Separation Plant Air General Equipment Co., Ltd. Design I
Manufacturing, using molecular sieve purification, turbo-expander refrigeration, bath-type
The main condenser and the DCS system control, process shown in Figure 1.
The air separation plant in the June 22, 2004 car test run,
June 24 sunrise oxygen. Product liquid oxygen yield, purity meet the design
Indicators.1.65kW·h/m (
Value, the product converted into gaseous state).
KDON-IO00Y/IO00 liquid air separation plant performance indicators
Table 1. ,
As the operator is basically the novice, for various operating parameters of the control
The system is not entirely reasonable to make our products the higher the energy consumption of liquid oxygen. After continuous exploration
Cable and summary of the operating parameters to optimize the equipment to run up
Better working conditions, increased oxygen extraction rate and oxygen production, the product liquid oxygen
The unit energy consumption significantly lower
Table 1 KDON · 1000Y/1000 liquid air separation plant performance indicators
Design specifications
Condition 1 Condition 2 Purity
Processing air volume / (1113 / h) 14750 1475O f
Liquid oxygen production / (m '/ h) 1O0o 80o 99.6% 0,
Gas oxygen production / (m '/ h), 20o 99.6% 0,
Nitrogen gas production / (m '/ h) 1O0o 1O0o <10 X10 ~ 0,
Note: The liquid has been converted into a gaseous state, the data are the standard state.
An adjustment of air compressor discharge pressure, improve the amount of expansion in cooling
1.1 Analysis
Atlas copco air compressor selected the company's ZH15000 type centrifugal
Type 3 air compressor, from Simens company's high-voltage electric drag
Rated Displacement of 15000m3 / h, rated power of 1600kW, the design
Working pressure 0.8MPa. Pressurized air through the Booster, the most
Points (about 60%) obtained by the swelling mechanism of the cold volume, small portion of Canada
Public air, after the main heat exchanger to enter the next tower.
Put into operation, due to expansion cooling capacity machine is not high, the nozzle opening
Large (80% ~ 85%), so that the compressed air bypass the primary heat exchanger
Large quantity, there are about 9600m3. In order to better reduce the products to
Consumption, increase production, consider amending the process parameters to improve the expansion of the mechanism
Cooling capacity, improve liquefaction rate and lowering the energy consumption of liquid oxygen unit head
1.2 adjustment measures
Because this set of liquid air separation plant using low-pressure air circulation flow
Cheng. Of its own existence than the medium-pressure process on the liquefaction rate is low and high energy consumption of
Phenomenon. If during operation the pressure to improve circulation, can improve
Liquefaction rate.
System pressure, it can only improve the air compressor exhaust pressure, but increase
Compressor discharge pressures to increase energy consumption. On balance, decided to enter
Line experiment.
Compressor discharge pressure limit value of 0.99MPa, out of
Air-cooling tower, the main heat exchanger of the security considerations at the same time, the system pressure
To improve any departure from design conditions, the operation of the main heat exchanger negative, because
Here, a maximum of only up to about 0.85MPa. At this point, the air through the
Booster Booster, the pressure of 1.12MPa, and the pressure of air-cooling tower
Pressure test the value of 1.2MPa. In the compressor discharge pressure of 0.80MPa
When the expander inlet pressure 0.92MPa, outlet pressure 25kPa,
Inlet temperature 1 130 ℃, the temperature difference is 57 ℃. Gradually increase the air compressor
Exhaust pressure, when the compressor discharge pressure is set to 0.85MPa
When the air compressor exhaust flow rate maintained at 14800rn3 / h or so, work
ER about 4%. Air-cooling tower outlet pressure increased from 0.98MPa
To 1.04MPa, expander inlet pressure becomes 1.014MPa, export
Pressure of 23kPa, inlet temperature 1 124 ℃, the temperature difference is 56 ℃, swelling
Expansion of air enthalpy drop larger, cooling capacity increases. Expander nozzle opening by
70%, so that bypass the primary heat exchanger for the air minus 8850rn3 / h.
Expander inlet pressure by the compressor discharge pressure constraints. Increased when,
At the same time, due to the cooling water pipeline compressor selection of water filters are not
Filter resistance is too large, the cooling water inlet pressure deviate from the design of the
Demand. In order to better control the levels of the cooling temperature, cooling water entrance plus
Installed a bypass valve to increase the cooling water flow, so that cooling air compressor
121 into the pressure of the water increased from 0.35MPa to 0.4MPa, so that three cold -
But temperature from 43 ℃, 38 ℃, 41 ℃ reduced to 38 ℃,
36 ~ C, 36 ~ C, in line (long-term running averages). So empty
Press run to reach a better state.
2 air precooling system reduced load operation
2.1 Analysis
The sets of air separation plant is not set to nitrogen and water pre-cooling tower, chilled water from the
Sea-air-conditioned train yard LSB. 230 semi-enclosed water-cooled piston-type water chiller to mention
Supply, two chillers operating in parallel. Chilled water design flow 7t. By
Conditioning load in the freezer can not be put into production, it has been delivered at full capacity
行. At an ambient temperature below 24 ℃, the export of chilled water temperature appears
Through the low, freezer frequent phenomenon of interlocking Bump. This is from the freezer
Unable to adjust the load below the design condition, the freezer too cold
Left caused. To enable stable operation of an air separation plant, had to be chilled water
Flow rate increased to 9.5 ~ 1It, so that pump load increased, energy consumption by
Canada. Winter (October to next May) unit operating costs increased.
2.2 The adjustment measures
In the air cooling tower outlet temperature of air permitted circumstances, an outage
Taiwan refrigeration machines, most of the time a single run. Only the water temperature in summer too
High, out of air-cooling tower the air temperature is higher than 12 ~ C at the same time to open two
Taiwan freezer to ensure that out of the air temperature is lower than air-cooling tower 12 ~ C.
After the above improvements, freezers run smoothly in the design of operating conditions, cold
7t cold water flow remained at about the phenomenon does not appear jumping off the tram and make
Air separation unit power consumption greatly reduced.
3 to extend the molecular sieve purification system switching time, reduce electricity
Furnace heating tubes
3.1 Analysis
The sets of air separation plant molecular sieve adsorber filled with 13X molecular sieve
With activated alumina. Molecular sieve purification system of export dioxide in air
Carbon content of the design value of less than 1 Y 10 ~. Put into operation, in a pure molecular sieve
System of export of carbon dioxide in the air content of 0.7 Y 10 when
Switch adsorber, indicating molecular sieve ample margin may be appropriate to extend the cut
For time.
In addition, the two Taipower heater 1 with a prepared, but the manufacturers mentioned
For the electric heater power is too large (228kW). By design, operating conditions,
The normal production of nitrogen pollution a single heat, and then angry, out of electric heater temperature
To 170oC. In the actual run-time, and then angry outlet temperature up to
220 ~ C (sewage nitrogen 3000m / h), deviation from design conditions, so that power consumption
3.2 adjustment measures
Outlet air purification systems in the molecular sieve carbon dioxide content is not
Exceeding circumstances, to extend the molecular sieve purification system switching time will be
Switching time from 240min changed 271min.
Electric heating pipe the original group of 18 electric three tubes (each
60kW), after repeated experiments, cut off the three heating tubes in the power supply,
That the second group one, the third group of two electric heating tubes power, retaining three groups
15 heating pipes, a furnace temperature of nitrogen pollution is still to reach 175 ℃, so that
Molecular sieve in the design of operating conditions running smoothly. At the same time, reducing the molecular
Sieve purification system switching frequency, reducing the switching loss caused by the air
Loss, thereby reducing the air compressor did a "exercise in futility."
4 Optimization of distillation column operating parameters, improve oxygen extraction rate
4.1 Analysis
A distillation column low purity nitrogen pollution (3.5% o2), shows oxygen extraction
Rate is low. The reasons are:
(1) Air Liquide purity low, about 30% ~ 35% 02;
(2), the tower of liquid nitrogen return valve opening is 30%, the tower of liquid nitrogen
Throttle valve opening is 52%, so that condensation within the cold after the accumulation of nitrogen in the main;
(3) The main cold liquid oxygen liquid is too high (2200mm), so that heat is not
Full, up less than the amount of steam, distillation, and reducing efficiency.
In order to achieve the design output, can only increase the processing of the amount of air distillation
High tower operating pressure, the product unit consumption increased.
4.2 adjustment measures
Distillation cold enough in the circumstances, the right to do distillation column operation
Appropriate adjustments to the success of reducing the oxygen content of nitrogen pollution, increase oxygen to mention
Take rate, lower energy consumption per unit.
(1) full-tower under liquid nitrogen reflux valve;
(2) In the case of nitrogen purity to allow as much as possible to open large sections of liquid nitrogen
Flow valve;
(3) refer to the equipment drawings, will be the main cold liquid oxygen transfer
The whole of 2000mm.
After the above adjustment, distillation column operating conditions to be optimized,
Changes in the specific operating parameters shown in Table 2.5-benefit analysis
To take these measures, to reduce production costs and increase the liquid
Oxygen production. In October 2004 to complete the rectification, air separation plant has been
Smooth operation of 10 months. During the power outage due to causes such as
ASU parking, the operating conditions well. Increase in production of liquid oxygen
12%, to 1.4m / h, unit energy consumption decreased by 5.4%, down
To 1.57kW · h / m.
The system significantly reduces power consumption, shown in Table 3.
Table 3 measures for improving the systems before and after comparison of the power consumption kW
Project pre-cooling system, air compressor system, air purification system, molecular sieve
Adjust the pre-1455 7l 144
Adjusted l462 48 ll5.2
6 rectification experience and ideas
For this liquid air separation did not prepare, if we can in the main heat exchanger
The front plus a cryogenic freezer, will be fully air first through the low-temperature freezing
After cooling to heat transfer machine, you can very well improve the primary heat exchanger temperature
Poor distribution, reduction of cold damage, thereby significantly reducing energy consumption. At the same time, are
In the operation of each system may not be optimal conditions, it should be well hidden
Power to be tapped. Now, if there are more improvements, I would like to with the
Readers to continue to explore.
Meanwhile, a new air separation plant for the enterprise, each piece of equipment and
Selection of the auxiliary equipment must be prudent and take into account all the base
Chu conditions, the impact, so that each piece of equipment to meet the normal operation of the
Environmental conditions.