8/10/2019 Simulation of NG Processing Plant http://slidepdf.com/reader/full/simulation-of-ng-processing-plant 1/6 SIMULATION OF NATURAL GAS PROCESSING PLANT FOR BUMPLESS SHIFT Ramzan, N*, Naveed, S, Muneeb, R.*, Tahir, F. M. ^Department of Chemical Engineering, University of Engineering & Technology, Lahore 54890, Pakistan Email:[email protected], [email protected]Phone: +92 42 -9029159, Mobile: +92 342- 5002555 Correspondence Author: [email protected]Abstract: A large fraction of energy supplies in the world are fulfilled through natural gas. The un-even variations in the supply and demand often affect the production process. Modeling and simulation is an effective tool to predict, plan and handle such variations. Often it is desired that a bumpless shift takes place in these situations. In this paper, a LPG/NGL recovery plant, which employs Turbo-expander technology for LPG/NGL recovery, is simulated using a steady state flow sheeting simulator (Aspen H YSYS). All major units such as Turbo-expander, separators, heat exchangers, distillation column, reboiler and condenser in the base case have been simulated. The operating conditions are taken to match the field conditions of a plant in Pakistan PengRobinson (PR) equation of state (EOS) has been employed. The simulation was made offline with different inlet gas composition as if changing wells lined up on the plant. The responses were recorded forvarious changes in the inlet gas composition and pressure. The performance of the plant was studied to ensure that the steady state operation of the plant is not significantly affected (bumpless shift). This shall lead to maximum productionusingcustomercontractual limits. KeyWords: Turboexpander, Process Simulation, AspenHYSYS, LPG/NGL recovery, Steady State Operation 1. Introduction Gas plants have several distinctive features that causeoperation complexity. One unique characteristic is the fact that inlet feed stream conditions do not remain constant. This is due to the combination of feed streams from different well formations, variation of pressure and composition of inlet stream with passage of time and depletion of reservoirs. As a result economic optimum set of plant operating process parameters such as temperature and pressure change. To obtain optimum production and meet required quality standards, mathematical modeling and optimization of gas processing plant is mandatory. Computer Simulation is an important tool for analysis and design of chemical processes. Oil and Gas processing is believed to be an area where Simulation could be used very advantageously because hydrocarbons and other organic compounds do not cause such troubles at calculations as strong polar and ionized compounds. This research is to counter the above mentioned problems of a Natural gas processing plant. At this processing facility, during wells shifting (for any maintenance purpose or to maintain wellhead pressure), fluctuations in operating parameters take place. These fluctuations result (LPG), Natural Gas and NGL. The obj ective of this researchis to obtain optimum and on spec production of Natural gas, LPG and NGL by minimizing the fluctuation during wells shifting. 2. Case Study Figure 1 describes the objectives and strategy for the production dynamics of the plant.The disturbances arrive in the process from feed in the form of variation in inlettemperature,pressure,or composition due to shift in the natural gas source well. These disturbances mainly effect the operation of Turbo Expander, De-Ethanizer Column and LPG/NGLSplitter Column units in the NG processing plant which lead to off spec product. In this situation, the product specifications (see figure 1) are met by controlling the discharge temperature of Turbo Expander,Top and Bottom stream temperatureof De-Ethanizer column and the LPG/NGL Splitter Column. Now the expander PvPM, De-Ethanizer column refrigeration and reboiler loadsand reflux ratio, reboiler and condenser loads for the LPG/NGL splitter column can be manipulated in order to control these temperatures to eventually achieve the control objectives.
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Abstract: A large fraction of energy supplies in the world are fulfilled through natural gas. The un-even variations in the supply anddemand often affect the production process. Modeling and simulation is an effective tool to predict, plan and handle such variations.Often it is desired that a bumpless shift takes place in these situations. In this paper, a LPG/NGL recovery plant, which employsTurbo-expander technology for LPG/NGL recovery, is simulated using a steady state flow sheeting simulator (Aspen H YSYS). All
major units such as Turbo-expander, separators, heat exchangers, distillation column, reboiler and condenser in the base case have been simulated. The operating conditions are taken to match the field conditions of a plant in Pakistan PengRobinson (PR) equationof state (EOS) has been employed. The simulation was made offline with different inlet gas composition as i f changing wells linedup on the plant. The responses were recorded forvarious changes in the inlet gas composition and pressure. The performance of the
plant was studied to ensure that the steady state operation of the plant is not significantly affected (bumpless shift). This shall lead tomaximum productionusingcustomercontractual limits.
KeyWords: Turboexpander, Process Simulation, AspenHYSYS, LPG/NGL recovery, Steady State Operation
1. Introduction
Gas plants have several distinctive features that
cause operation complexity. One unique
characteristic is the fact that inlet feed stream
conditions do not remain constant. This is due to the
combination of feed streams from different well
formations, variation of pressure and composition of
inlet stream with passage of time and depletion of
reservoirs. As a result economic optimum set o f plantoperating process parameters such as temperature
and pressure change. To obtain optimum production
and meet required quality standards, mathematical
modeling and optimization of gas processing plant is
mandatory.
Computer Simulation is an important tool for
analysis and design of chemical processes. Oil andGas processing is believed to be an area where
Simulation could be used very advantageously
because hydrocarbons and other organic compounds
do not cause such troubles at calculations as strong
polar and ionized compounds. This research is to
counter the above mentioned problems of a Natural
gas processing plant.
At this processing facility, during wells shifting (forany maintenance purpose or to maintain wellhead
pressure), fluctuations in operating parameters take
place. These fluctuations result
(LPG), Natural Gas and NGL. The obj ective of thisresearch is to obtain optimum and on spec
production of Natural gas, LPG and NGL by
minimizing the fluctuation during wells shifting.
2. Case Study
Figure 1 describes the objectives and strategy for the
production dynamics of the plant.The disturbances
arrive in the process from feed in the form of
variation in inlet temperature, pressure, or
composition due to shift in the natural gas source
well. These disturbances mainly effect the operation
of Turbo Expander, De-Ethanizer Column and
LPG/NGL Splitter Column units in the NG
processing plant which lead to off spec product. In
this situation, the product specifications (see figure
1) are met by controlling the discharge temperatureof Turbo Expander, Top and Bottom stream
Simulation of Natural Gas Processing Plant for Bumpless Shift
Figure 7 gives the comparison of the entire variables
which have direct response on the specifications of
products. As it can be seen they
remain somewhat constant throughout the changes
to the process indicating that process parameters'
change has been employed successfully.
200
150
100
50
-50
-100
rr
• K -201 out
• V - 2 0 7 b o t t o m
• V - 2 0 7 t o p
• V - 2 0 8 B o t t o m
• V - 208 - T op
Base Case 1 Case 2 Case 3 Case 4
CaseSimulation Case
Fig. 7: Desiredproduct stream temperatures
Conclusions:
The change in inlet conditions (Composition,
pressure and temperature) effect the throughput and
quality o f products. To counter the above mentioned
problem, plant is simulated on HYSYS. From this
simulation work about 80 % of bumps have been
reduced. Different cases of inlet composition
variations verify the possibility of controlling
product quality and
maintaining it at a constant Based on the resultsobtained from the cases study, it should be noted that
the optimum operating parameters change. So,
during wells shifting, to obtain optimum and
References
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[9] Marshal l, W. R., and R. L. Pigford. TheApplication of Differential Equations toChemical Engineering Problems.Universityof Delaware, Newark, Delaware (1947).
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on specs production of the desired products the plant
may be tuned to operating parameters determined
through this simulation.The results obtained through
this simulation will be very useful for
Fluctuation control of plant operating
parameters, resulting in quality improvement
and production enhancement during wells
shifting
Simulation for changing inlet gas composition
and pressure with life of gas field, causing up
to mark recovery of hydrocarbon reserves and
for line up of future wells.
NFC-IEF R Journal of Engineering & Scientific Research