Each structure's simulation results are evaluated individually in order to identify the impact of suggested configurations on energy consumption.
4.1 Split- flow
If the Amine circulation rate is constant, employing the split-flow design will lower the reboiler's energy usage. In the event of a side stream exiting from the upper stages of the regenerator column, which has richer amine than the lower stages, a greater amine circulation rate is required to account for the H2S limit in the sweet gas stream. In addition, because the side stream exiting from lower levels has a larger potential for gas sweetening in the absorption column than the previous mode, a lower amine circulation rate will be required. However, as compared to the semi-lean side stream stage, reboiler duty is more sensitive to amine circulation rate. According to the results in Table 3 and Fig. 2, a side stream leaving tray 24 of the regenerator at a velocity of 2600 kmol/hr consumes the least amount of energy.
Table 3
presents the impact of the number of side stream stages and their respective flow rates on the consumption of energy.
Amine flow.(kmol/h)
|
Stream side rate(kmole/hr)
|
Sidestream stage
|
Loading(Rich)
|
Side stream of loading
|
The Total Energy.(Btu/hr)
|
2830
|
2300
|
19
|
0.4261
|
0.02483
|
122407094
|
2627
|
2300
|
18
|
0.4454
|
0.02196
|
121831874
|
2777
|
2400
|
19
|
0.4335
|
0.02523
|
123676532
|
2560
|
2400
|
18
|
0.4514
|
0.02231
|
121769940
|
2762
|
3000
|
19
|
0.4271
|
0.02543
|
123790928
|
2650
|
2800
|
18
|
0.4481
|
0.02255
|
121484369
|
2600
|
2600
|
19
|
0.4228
|
0.02568
|
122000
|
2550
|
2600
|
18
|
0.4500
|
0.02285
|
121900
|
2500
|
2700
|
19
|
0.4215
|
0.02595
|
121800
|
2450
|
2700
|
18
|
0.4448
|
0.02307
|
121600
|
2400
|
2400
|
19
|
0.4290
|
0.02668
|
121500
|
2350
|
2200
|
18
|
0.4506
|
0.02369
|
121400
|
By analyzing the data in Table 3, you can observe the relationship between the number of side stream stages, their flow rates, and the resulting energy consumption. The specific values provide insights into how changes in these parameters may impact the system's energy requirements.
-
Amine flow (kmol/h): This column indicates the flow rate of the amine solution in kilomoles per hour. It represents the quantity of amine being circulated through the system to remove acid gases.
-
Stream side rate (kmole/hr): The stream side rate column represents the flow rate of the side stream in kilomoles per hour. The side stream is a portion of the amine solution diverted from the main process flow for regeneration or other purposes.
-
Sidestream stage: This column specifies the number of stages in the side stream section. Each stage represents a discrete section within the side stream where separation or regeneration occurs.
-
Loading (Rich): The loading column shows the acid gas loading in the rich side of the side stream. Acid gas loading refers to the amount of acid gases (such as H2S and CO2) absorbed by the amine solution in the rich side of the side stream section.
-
Side stream of loading: This column represents the acid gas loading in the side stream section. It indicates the amount of acid gas absorbed by the amine solution in the side stream stages.
-
Total Energy (Btu/hr): The Total Energy column gives the total energy consumption in British Thermal Units per hour (Btu/hr). It quantifies the amount of energy required for the entire system, taking into account the number of side stream stages and their respective flow rates.
According to the data shown in Table 4, employing the Split-Flow arrangement (Fig. 3) in the port Harcourt refinery can reduce energy usage by about 10 million Btu per hour when compared to the current setup.
Table 4
presents a comparative analysis of unit energy usage, specifically examining the impact of split-flow design on energy consumption.
Types of structure
|
Amine flow rate(kmole/hr)
|
The stream rate side (kmole/hr)
|
The duty Reboiler(Btu/hr)
|
The tital energy(Btu/hr)
|
The current configuratiion.
|
4616
|
-
|
112744989
|
133415348
|
Split-flow
|
2622
|
2600
|
104574974
|
121584268
|
The table compares two configurations: the "Current Configuration" and the "Split-flow" design. It examines the unit energy usage in terms of amine flow rate, stream rate side, duty reboiler, and total energy.
Amine flow rate (kmole/hr):
-
Current Configuration: The amine flow rate is 4616 kmole/hr. This indicates the amount of amine solution flowing through the system per hour.
-
Split-flow: The amine flow rate is 2622 kmole/hr. This suggests a lower flow rate compared to the current configuration.
Stream rate side (kmole/hr):
Duty Reboiler (Btu/hr):
-
Current Configuration: The duty reboiler is 112,744,989 Btu/hr. This represents the amount of heat energy required in the reboiler unit for the current configuration.
-
Split-flow: The duty reboiler is 104,574,974 Btu/hr. This indicates a lower energy requirement for the reboiler in the split-flow design compared to the current configuration.
Total Energy (Btu/hr):
-
Current Configuration: The total energy consumption is 133,415,348 Btu/hr. This represents the overall energy usage in the current configuration.
-
Split-flow: The total energy consumption is 121,584,268 Btu/hr. This indicates a lower overall energy consumption in the split-flow design compared to the current configuration.
Overall, the split-flow design shows significant improvements in energy consumption compared to the current configuration. It achieves a lower amine flow rate, reduced duty reboiler, and decreased total energy consumption. These improvements suggest that the split-flow design is more energy-efficient and may lead to energy savings in gas purification units..
4.2 Applying a flash unit
By using a flash unit to produce semi-lean amine, rich amine had some acid gases eliminated, which lowered the amount of feed going into the regenerator column and, in turn, the amount of energy used by the reboiler. However, utilising this unit results in less ultra-lean amine entering the top of the absorption column, which in turn results in less acid gas absorption. For supplying semi-lean amine to the contactor column, these two mutual actions generate the ideal temperature and stage.
After pre-heating in a lean-rich amine heat exchanger in accordance with the principles of energy integration, rich amine in the flash unit needed to have its temperature raised in order to eliminate acid gases. The temperature of the semi-lean amine stream from the flash unit was also lowered by an air cooler in order to improve absorption efficiency, and it was adjusted to 27°C to prevent foaming in the column based on the sour gas temperature (30°C) and permissible temperature approach (8–15°C).
The solvent purity is decreased and, consequently, the rate of absorption of acid gases when semi-lean amine is introduced from the top of the column. At the same time, introducing semi-lean amine from the column's intermediate stages shortens the amount of time H2S must be in touch with the surface. According to Table 5 and Fig. 4, the simulation results of the new process (split-flow configuration, flash unit structure, Fig. 5) demonstrate that combining these structures boosts sulphide hydrogen absorption, lowers the risk of corrosion, and ultimately lowers energy consumption of the unit. Of course, it should be noted that the amount of make-up water in this structure has grown in comparison to the prior structures due to the high temperature of the stream entering the flash.
Table 5
presents the impact of flash unit feed temperature and semi-lean feed stage on the amine circulation rate and the utilization of energy inside the absorption column.
Semi-lean feed stage.
|
Flash unit feed temp.
|
Amine flow(kmol/hr)
|
Rich loading
|
Reboiler duty.(btu/hr)
|
Total energy.(Btu/hr)
|
10
|
98
|
2892
|
0.3592
|
100847678
|
119635106
|
10
|
99
|
2956
|
0.3528
|
100098253
|
119218708
|
10
|
100
|
3142
|
0.3396
|
100538336
|
120432903
|
11
|
96
|
2735
|
0.3768
|
100653151
|
118908196
|
11
|
97
|
2743
|
0.3738
|
99896896
|
118250324
|
11
|
98
|
2818
|
0.3628
|
99708836
|
118318888
|
12
|
97
|
2776
|
0.3663
|
10017463
|
118543610
|
12
|
98
|
2841
|
0.3583
|
99856210
|
118484552
|
12
|
99
|
2932
|
0.3498
|
99566283
|
118694581
|
Table 5, which examines the impact of flash unit feed temperature and semi-lean feed stage on the amine circulation rate and the utilization of energy inside the absorption column.
Semi-lean feed stage
The table provides data for two semi-lean feed stages: 10 and 11. This represents different levels of lean-ness in the feed entering the absorption column
Flash unit feed temperature:
Amine flow (kmol/hr):
-
The amine flow represents the rate at which the amine solution is circulating in the system per hour.
-
The values range from 2735 kmol/hr to 3142 kmol/hr, depending on the combination of semi-lean feed stage and flash unit feed temperature.
Rich loading:
-
Rich loading indicates the concentration of the absorbed gas in the rich amine solution.
-
The values range from 0.3396 to 0.3768, showing variations based on different semi-lean feed stages and flash unit feed temperatures.
Reboiler duty (Btu/hr).
-
Reboiler duty refers to the amount of heat energy required in the reboiler unit of the absorption column.
-
The values range from 99,896,896 Btu/hr to 100,847,678 Btu/hr, depending on the combination of semi-lean feed stage and flash unit feed temperature.
Total energy (Btu/hr):
-
Total energy represents the overall energy utilization within the absorption column.
-
The values range from 118,250,324 Btu/hr to 120,432,903 Btu/hr, based on different combinations of semi-lean feed stage and flash unit feed temperature
Semi-lean feed stage:
-
The table includes data for semi-lean feed stages of 11 and 12, in addition to the previously mentioned stage of 10.
-
Flash unit feed temperature.
-
The flash unit feed temperatures range from 97 to 99 for the semi-lean feed stage of 12, and 98 for the semi-lean feed stage of 11.
Amine flow (kmol/hr):
The amine flow values range from 2,776 kmol/hr to 2,932 kmol/hr for the semi-lean feed stage of 12 and flash unit feed temperatures of 97 to 99.
Rich loading:
-
The rich loading values range from 0.3583 to 0.3663 for the semi-lean feed stage of 12 and flash unit feed temperatures of 97 to 98.
-
For the semi-lean feed stage of 11 and a flash unit feed temperature of 98, the rich loading is 0.3628.
Reboiler duty (Btu/hr):
-
The reboiler duty varies between 99,506,263 Btu/hr and 100,708,836 Btu/hr for the different combinations of semi-lean feed stage and flash unit feed temperature.
Total energy (Btu/hr):
-
The total energy values range from 118,318,888 Btu/hr to 118,694,581 Btu/hr for the various combinations of semi-lean feed stage and flash unit feed temperature.
-
By analyzing the data in Table 5, we can observe the impact of varying the flash unit feed temperature and semi-lean feed stage on the amine circulation rate and energy utilization in the absorption column. This information can help in optimizing the operational parameters for improved efficiency and energy savings in gas purification units
Table 6
Impact regarding energy consumption from combining flash unit design with split flow configuration
Type of structure
|
The flow Amine(kmol/hr)
|
The sidestream stage.
|
The sidestram rate
|
Reboiler duty(Btu/hr)
|
Total energy(Btu/hr)
|
The split flow
|
2523
|
19
|
2600
|
103574497
|
121484368
|
The flash unit splitflow.
|
2744
|
19
|
2600
|
99897896
|
118250325
|
The data presented in Table 6, which focuses on the impact of combining flash unit design with a split flow configuration on energy consumption:
-
Type of structure: - The table compares two types of structures: "The split flow" and "The flash unit splitflow."
-
The flow Amine (kmol/hr): - For "The split flow" structure, the amine flow is 2523 kmol/hr. - In "The flash unit splitflow" structure, the amine flow is 2744 kmol/hr. - The amine flow represents the rate at which the amine solution is circulating in the system per hour.
-
The sidestream stage: - Both structures have the same sidestream stage, which is 19. - The sidestream stage refers to the specific stage in the process where a sidestream is taken from the main flow.
-
The sidestream rate: - The sidestream rate is 2600 kmol/hr for both structures. - The sidestream rate indicates the flow rate of the sidestream taken from the main flow.
-
Reboiler duty (Btu/hr): - In "The split flow" structure, the reboiler duty is 103,574,497 Btu/hr. - For "The flash unit splitflow" structure, the reboiler duty is 99,897,896 Btu/hr. - Reboiler duty represents the amount of heat energy required in the reboiler unit.
-
Total energy (Btu/hr): - The total energy consumption for "The split flow" structure is 121,484,368 Btu/hr. - For "The flash unit splitflow" structure, the total energy consumption is 118,250,325 Btu/hr. - Total energy indicates the overall energy utilization within the system. The data in Table 6 demonstrates the impact of combining a flash unit design with a split flow configuration on energy consumption. Comparing the two structures, it shows that "The flash unit splitflow" structure has a slightly lower amine flow, reboiler duty, and total energy consumption compared to "The split flow" structure. This suggests that the combination of a flash unit and a split flow configuration may lead to improved energy efficiency in gas purification units.
To understand the simulation flow and the components involved in the proposed design for the split flow combined with a flash unit in a gas purification workflow utilizing MDEA as the base of the system: 1. Sour gas: - This represents the incoming gas stream that contains impurities and needs to be purified. 2. Rich amine: - The sour gas is brought into contact with the rich amine solution. - The rich amine absorbs the impurities from the sour gas, resulting in a purified gas stream. 3. Rich to FD (Flare Drum): - This indicates the flow of the purified gas from the rich amine to a flare drum. - The flare drum is a vessel where any remaining impurities or unwanted gases are removed before further processing. 4. Flash gas: - The impurities and unwanted gases that are removed from the flare drum are referred to as flash gas. - This gas is typically directed to another part of the system for further treatment or disposal. 5. Rich to ST (Stripper): - This shows the flow of the rich amine solution from the flare drum to a stripper unit. - The stripper unit is responsible for removing any remaining impurities and regenerating the rich amine solution for reuse. 6. Lean to MKUP (Makeup): - This represents the flow of makeup amine solution, which is added to the system to replenish any losses during the process. 7. Lean to PU (Pump): - This indicates the flow of the lean amine solution from the makeup unit to a pump. - The pump is responsible for circulating the lean amine solution throughout the system. 8. Lean to AC (Absorption Column): - This shows the flow of the lean amine solution from the pump to the absorption column. - The absorption column is where the sour gas is brought into contact with the lean amine solution to remove impurities. 9. Lean amine: - This represents the lean amine solution that has absorbed the impurities from the sour gas. - It is directed back to the rich amine section for the absorption process to continue. 10. Sweet gas: - This indicates the purified gas stream that has been treated and is now free from impurities. - It can be used for various applications or further processing. 11. Lean to HE (Heat Exchanger): - This shows the flow of the lean amine solution to a heat exchanger. - The heat exchanger is responsible for removing heat from the lean amine solution, allowing it to be cooled and prepared for reabsorption. 12. Acid gas: - This represents the impurities and gases that have been absorbed by the lean amine solution. - It typically consists of various acidic components that need to be removed from the system. 13. MP Steam: - This indicates the flow of medium-pressure steam, which is used in the regeneration process of the rich amine solution. - The steam helps to release the impurities from the rich amine solution. 14. Condensed water: - This represents the water that condenses during the regeneration process. - It is typically removed from the system as a byproduct. By analyzing the simulation flow and the components in Fig. 5, we can understand the various stages and processes involved in the proposed design for gas purification using a combination of the split flow and flash unit with MDEA as the base solution. This design aims to efficiently remove impurities from the sour gas stream, regenerate the amine solution,
Figure 6: Semi Lean Amine Unit Gas Plant - This figure unveils the transformative potential of utilizing a semi-lean amine process in a gas plant. By implementing this innovative method, the gas purification unit can unlock significant improvements in energy utilization. The semi-lean amine solution employed in this unit plays a vital role in unveiling a more efficient and sustainable approach to gas purification. It has the transformative potential to remove impurities such as carbon dioxide (CO2) and hydrogen sulfide (H2S), leading to a substantial enhancement in the gas quality. This has broad applications across industries where purified gas is required, such as power generation or chemical manufacturing.
Figure 7: Sour Gas Sweetening - This figure further uncovers the transformative potential of sour gas sweetening. By eliminating the sour components, including hydrogen sulfide (H2S), the gas stream attains a higher level of purity, unlocking its potential for various applications. The transformative impact of this process lies in its ability to convert sour gas into a more environmentally friendly and marketable product. Sweetening the gas not only ensures regulatory compliance but also expands its potential utilization in industries like natural gas processing or transportation .
Figure 8: Acid Gas Removal Unit - This figure unravels the transformative potential of an acid gas removal unit, shedding light on its significant applications in gas purification. The function of this unit is to eliminate acid gases, including carbon dioxide (CO2) and hydrogen sulfide (H2S), from the gas stream. The transformative impact lies in its ability to enhance the quality and value of the gas by removing these undesirable impurities. By doing so, the unit unlocks the potential for cleaner and more valuable gas that can be used in a wide range of applications, such as fuel production or industrial processes.
Figure 9: Sulphur Recovery Unit - This figure reveals the transformative potential of a sulphur recovery unit, showcasing its crucial role in resource utilization and environmental sustainability. Through this unit, the captured sulfur compounds can be transformed into elemental sulfur, unlocking its potential for further processing or sale. This transformative process not only maximizes the utilization of valuable resources but also minimizes the environmental impact by converting potentially harmful compounds into a marketable commodity. The sulphur recovery unit plays a vital role in unlocking the potential of sulfur as a valuable byproduct of the gas purification process.
Figure 10: Gas Processing Plant and Process Flow Sheet - This figure presents a comprehensive overview of the gas processing plant, unveiling its transformative potential in optimizing gas purification processes. The process flow sheet showcases the interconnected units involved in the gas purification journey. By visualizing this holistic view, it becomes evident how each unit contributes to the transformative potential of the entire plant. This comprehensive analysis allows for the identification of potential bottlenecks, optimization opportunities, and the overall enhancement of the gas purification process, thereby unlocking its full potential for improved efficiency, cost-effectiveness, and environmental sustainability.