Kalina & Organic Rankine Cycles: How to Choose the Best - - PowerPoint PPT Presentation
Kalina & Organic Rankine Cycles: How to Choose the Best Expansion Turbine ? Dr Frdric Marcuccilli, Senior Process Engineer Herv Mathiasin, Sales Engineer Electricity generation from Enhanced Geothermal Systems Strasbourg 14-16 th of
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w w w .cryostar.com frederic.m arcuccilli@cryostar.com
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1 .1 Cryostar in figures 1 .2 Cryostar in the m arket place 1 .3 Cryostar new m arkets
2 .1 Radial inflow turbine 2 .2 Expander w heel design 2 .3 Designing for best efficiency 2 .4 Sealing system
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1.1 Cryostar in figures
Skid mounted HC turboexpanders Boil-Off gas reliquefaction unit High pressure reciprocating pump
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1.2 Cryostar in the market place
I ndustrial gases
No.1 in the application of cryogenic and industrial gas pump sectors
Oil & Gas
One major supplier of turbo-expander/ compressors in oil & gas treatment (HC dewpointing, ethylene plants)
LNG carriers
No.1 in « boil-off » gas handling and recovery (90% market share)
Energy recovery
Principal supplier of energy recovery expanders for « geo- pressure » application on natural gas grids (30 MW installed in Europe in the last 20 years plus North America ongoing)
LNG Industrial gas Clean energy Oil & Gas
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1.3 Cryostar new markets
Geotherm al and heat recovery expansion turbines
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2.1 Radial inflow turbine
Main elem ents:
1.A high pressure barrel from which the gas first expands through guide vane arrangement that is located in the circumference of the wheel.
wheel is given to a shaft which runs in high speed bearings. This power can be recovered by driving a compressor or a generator.
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and enters the turbine w heel. It converts the kinetic portion of energy contained in the gas by means of deflection into mechanical energy.
level and is passing afterwards through the discharge diffuser where velocities are reduced to normal pipeline velocities.
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2.2 Expander wheel design
U = tip speed (m/ s) rotating speed of the blades at the furthest extremity from the rotating axe C0 = spouting velocity (m/ s) the magnitude of the absolute velocity vector at nozzle exit under isentropic conditions (i.e no losses in the nozzle passage)
) / ( kg kJ drop enthalpy Isentropic H is ∆
velocity Spouting H c
is
∆ = . 2000
U/ C0 is a m easure of the shape of the velocity triangle in the inter-space betw een nozzle exit and rotor inlet
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2.2 Expander wheel design
Ns = specific speed Links main sizing variables: flow, speed, head Ns is shape factor for the passage of the wheel
Axis of rotation Low Ns at design point High Ns at design point Speed Specific H Q . 1000 N . 76 N
3 is
s
∆ =
) s / m ( Rate Flow . Vol Q ) rpm ( speed Wheel N ) kg / kJ ( drop enthalpy Isentropic H : with
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is
∆
Efficiency U/C0
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2.2 Expander wheel design
tip
4 3 is
s
h
Q N ∆ ⋅ = ω &
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2.2 Expander wheel design
Depending on material Ti alloy > Al 7 Series > Stainless Steel Depending on wheel type (open or closed) Depending on shaft connection type (Hirth or Polygon) Speed corresponding to max Tensile and Yield stresses admissible related to wheel geometry
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2.2 Expander wheel design
Usually expressed in Horse Power per Square Inch [ hp/ in2] Defined the load admissible per unit of wheel surface area Depending on material: Ti alloy > Stainless Steel > Al 7 Series
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2.2 Expander wheel design
Most of the time, tilting pad (also called Michell) bearings are used Maximum sliding speed defined by bearing manufacturer
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2.2 Expander wheel design
At wheel discharge, Ma = 1 causes shock At throat of the guide vanes, flow is limited to Ma= 1 Further downstream, Ma > 1 can give flow distortion, a cause for loss on efficiency
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2.2 Expander wheel design
Inlet Temperature higher than 100-120 degC “Aggressive” working fluid like ammonia- water mixture
Wheel tip speed Power Density
Kalina cycle
84.31%-w NH3, 5.47 kg/s, pout = 7.4 bara 0,7 0,75 0,8 0,85 0,9 2,5 3,5 4,5 5,5 6,5 7,5 Pressure Ratio [-] Isentropic Efficiency [-] Limit High Limit Low
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2.3 Designing for best efficiency
Specific speed Ns Isentropic Efficiency (%) Increasing Wheel diameter Operating range for Cryostar binary cycle expanders
Adimensional Specific speed Ns
From Balje O.E., “Turbomachines, A Guide to…and theory” 1980
Kalina Cycle - Offenbach (design for summer) ORC with iC4-Soultz High Brine Flow ORC with iC4-iC5 Waste heat recovery
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2.3 Designing for best efficiency
Experience show s that efficiency decreases w hen:
0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 Wheel Diam et er Isentropic efficiency for TG
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2.3 Designing for best efficiency
Up to 2 0 0 ° C inlet tem perature Up to 1 2 MW elec radial inflow turbines for binary cycles are …
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2.3 Designing for best efficiency
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2.4 Sealing system
Challenge: Sealing gas for closed cycle. Role of the seal gas: prevent contam ination of process gas by the lubricant Lim it or elim inate gas leakage around the shaft
Use of process fluid im possible: NH 3/ H 20 leads to liquid form ation and corrosion problem s; I nert Nitrogen is often chosen; Needs to lim it the flow of N 2 w hich is lost afterw ards; « Dry Gas Seal » system ; Little losses of process gas unavoidable.
Use of ORC fluid possible: clean & dry iC4 , iC5 , R1 3 4 A… used as seal gas; Oil sealing system w ith drainer or Dry Gas Seal is used; Seal gas m igrating into oil system is cleaned from oil ( coalescing filter) ; Cleaned seal gas is recovered by recom pression to inlet of condenser; No losses of the process gas.
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2.4 Sealing system
Need of external source of Nitrogen; Low flow is necesssary 1 -2 m 3 / h; Polluted N 2 by NH 3 & H 2O needs to be stored before treatm ent; Possibility to « w ash » the NH 3 gas to recover in the storage tank.
N2 + NH3/H2O
recover
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To com pressor
4 5 3 2 34,4 150 125 100 75 50 200,0 137,6 36,9 6 1 0,00 bara 5,00 bara 10,00 bara 15,00 bara 20,00 bara 25,00 bara 30,00 bara 35,00 bara 40,00 bara
0,00 100,00 200,00 300,00 400,00 500,00 Enthalpy (kJ/kg) Pressure (bara)
ORC cycle: Solution for sealing Oil seal + drainer + recom pression
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