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Authors: Ramin Taheri Seresht & Hassan Khodaei Jalalabadi Presented by: Ramin Taheri Seresht

Retrofit of Tehran City Gate Station C.G.S. No.2 by Using Turboexpander Yasun Farayand Company & K.N. Toosi University of Technology. Authors: Ramin Taheri Seresht & Hassan Khodaei Jalalabadi Presented by: Ramin Taheri Seresht. The objectives of presentation:

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Authors: Ramin Taheri Seresht & Hassan Khodaei Jalalabadi Presented by: Ramin Taheri Seresht

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  1. Retrofit of Tehran City Gate Station C.G.S. No.2 by Using TurboexpanderYasun Farayand Company & K.N. Toosi University of Technology Authors: Ramin Taheri Seresht & Hassan Khodaei Jalalabadi Presented by: Ramin Taheri Seresht

  2. The objectives of presentation: • Introduce the conventional natural gas pressure reducing station. • Introduce the turboexpander & its applications. • Express thermodynamically difference between throttle valve and turboexpander. • Select case study. • Exergy analysis on the selected case study. • Simulate the using of turboexpander in the selected case study. • Economical analysis. • Conclusion.

  3. Introduce the conventional natural gas pressure reducing station The different types of the conventional station: • City gate station (C.G.S.). • Town broad station (T.B.S.). • Combinatory station (C.G.S./T.B.S.). • Station for industrial consumptions. • Station for domestic consumptions.

  4. Introduce the conventional natural gas pressure reducing station Comparing the different types of conventional station on the base of pressure:

  5. Introduce the conventional natural gas pressure reducing station The main components of a conventional station: • Ball / Globe valves. • Filter. • Regulator (Throttle valve). • Relief valve. • Safety shut off valve. • Meter. • Heater.

  6. Introduce the conventional natural gas pressure reducing station Please pay attention: All of types of gas stations just differ in size, inlet & outlet pressure, capacity and exitence of some components. But all of them reduce the gas pressure by using throttle valves (regulators).

  7. Introduce the conventional natural gas pressure reducing station Most important roles of the regulator in a conventional station are: • Reducing pressure. • Adjusting pressure.

  8. Introduce the conventional natural gas pressure reducing station How does a regulator (throttle valve) reduce the pressure? • In the throttle-valve gas pressure is reduced in result of the isenthalpic expansion. • In this process not only no energy is produced but also the energy of high-pressure gas is lost.

  9. Could the energy of high-pressure gas be recovered? Yes, of course. Why not? $

  10. How could the energy of high-pressure gas be recovered? It is so easy just by using the turboexpander.

  11. Introduce the turboexpander & its applications What are turboexpanders? • Turboexpanders are expansion turbines, rotating machines similar to steam turbines. • Commonly, the terms “expansion turbines” and “turboexpanders” specially exclude steam turbines and combustion gas turbines. • Turboexpanders can also be characterized as modern rotating devices that convert the pressure energy of a gas or vapor steam into mechanical work as the gas or vapor expands through the turbine. • If chilling the gas or vapor stream is the main objective, the mechanical work so produced is often considered a byproduct. • If pressure reduction is the main objective, then heat recovery from the expanded gas is considered a beneficial byproduct. • In each case, the primary objective of turboexpanders is to conserve energy.

  12. Introduce the turboexpander & its applications The different designing types of turboexpanders: • Axial Type. • Radial Type. That the each of types has three typpes itself: • Impulse. • Reaction. • Complex.

  13. Introduce the turboexpander & its applications The different power absorption methods in turboexpanders: • Direct-connected compressor. • Gear and generator.

  14. Introduce the turboexpander & its applications Turboexpander applications: • Recovering high pressure gas energy & power generation. • Cryogenic process. • Chemical & Petrochemical industries (included: FCC process and producing Nitric acid, Acetic acid, PTA & Terephtalic acid.). • Oil & gas industries (included: LPG & LNG processes.). • Separating air components. • Liquefaction gases (like Helium). • Separating condensable components of natural gas. • Power generation from geothermal energy.

  15. Express thermodynamically difference between throttle valve & turboexpander As thermodynamically point of view: • In the throttle-valve gas pressure is reduced in result of the isenthalpic expansion. • In the throttle valve not only no energy is produced but also the energy of high-pressure gas is lost. • In the turboexpander the gas pressure is reduced in the isentropic expansion. • But in the turboexpander the energy of high-pressure gas is recoverd.

  16. Express thermodynamically difference between throttle valve & turboexpander On the other hand:

  17. Select case study The C.G.S. No. 2 of Tehran was selected as case study for following reasons: • Existing enough space for turboexpander installation. • Existing three heaters that they could be heated the entering gas to turboexpander if it was needed. • In this station, the changes of inlet pressure gas is less than the other stations in the country. • In this station, the changes of passed flow rate gas is less than the other stations in the country. • In this station, just for a few days in the year the passed flow of gas is cut off when the annual maintenance operations are done. • This station is next to some residential areas and a few industrial manufacture so that, it might be used of power generation directly if it was needed.

  18. Select case study The chemical compounds of gas that is passed through the C.G.S. No. 2 of Tehran are as table:

  19. Select case study The physical properties of gas that is passed through the C.G.S. No. 2 of Tehran are as following table:

  20. Select case study The monthly average quantities of inlet pressure, outlet pressure, outlet temperature & flow rate of gas that is passed through the C.G.S. No. 2 of Tehran (in 1385) are as table:

  21. Select case study The curves of monthly average inlet & outlet pressure profiles in 1385 for C.G.S No. 2 of Tehran are as follow:

  22. Select case study The curves of monthly average outlet temperature profiles in 1385 for C.G.S No. 2 of Tehran are as follow:

  23. Select case study The curves of monthly average flow rate profiles in 1385 for C.G.S No. 2 of Tehran are as follow:

  24. Exergy analysis on the selected case study At definition: Exergy is maximum work (shaft work) can be obtained from a specified quantity of energy. And exergy is equal to summation of all its components: Where: exK = kinetic exergy. exP = potential exergy. exPh = physical (termomechanical) exergy. exDi = diffusion exergy. exCh = chemical exergy.

  25. Exergy analysis on the selected case study In the selected case stydy: exK = exP = exDi = exCh = 0. And: For calculating CP:

  26. Exergy analysis on the selected case study With substituting the monthly average quantities in the recent relations is obtained:

  27. Exergy analysis on the selected case study The curves of monthly average exergy profiles in 1385 for C.G.S No. 2 of Tehran are as follow:

  28. Simmulate the using of turboexpander in the selected case study Simulation has been done by using the Thermoflow software at two following states: • One turboexpander is installed so as parallel with the station. • Three turboexpanders are installed so as parallel with each unit of the station. So that each of these states has two other states: • Without gas preheating. • With gas preheating.

  29. Simmulate the using of turboexpander in the selected case study The state of one turboexpander and without gas preheating:

  30. Simmulate the using of turboexpander in the selected case study The state of one turboexpander and with gas preheating:

  31. Simmulate the using of turboexpander in the selected case study The state of three turboexpanders and without gas preheating:

  32. Simmulate the using of turboexpander in the selected case study The state of three turboexpanders and with gas preheating:

  33. Simmulate the using of turboexpander in the selected case study The results of simulation has been summarized as following:

  34. Economical analysis Tuboexpander price is obtainable by using following relation or figure:

  35. Economical analysis The local price of electrical energy is as the following table:

  36. Economical analysis The global price of electrical energy is obtained by the following curve:

  37. Economical analysis The results of economical calculations is summarized into the tables:

  38. Conclusion According to that was mentioned, using turboexpanders at natural gas pressure reducing stations not only is economical but also its produced electrical energy in compare of other sources has following advantages: • For producing that doesn’t need to very high investment like power plants & water dams systems. • For producing that doesn’t need to consumption of fossil fuel. • Producing that doesn’t emit any pollutant in environment. • Maintenance cost of its facilities is so less than a power plant or a water dam. • For producing that doesn’t need to a lot personnel. • For producing that doesn’t need to occupy a lot space.

  39. Last Word Using the turboexpanders at the natural gas pressure reducing stations could be a historical opportunity. And if we don’t apply them now, perhaps tomorrow would be too late.

  40. Any Question?

  41. Thanks for your attention.

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