Kalina & Organic Rankine Cycles: How to Choose the Best - PowerPoint PPT Presentation

Kalina & Organic Rankine Cycles: How to Choose the Best Expansion Turbine ? Dr Frédéric Marcuccilli, Senior Process Engineer Hervé Mathiasin, Sales Engineer Electricity generation from Enhanced Geothermal Systems Strasbourg 14-16 th of September, 2006 w w w .cryostar.com frederic.m arcuccilli@cryostar.com 1

Contents 1 . General Presentation 1 .1 Cryostar in figures 1 .2 Cryostar in the m arket place 1 .3 Cryostar new m arkets 2 . Radial Turbines for Binary Cycles 2 .1 Radial inflow turbine 2 .2 Expander w heel design 2 .3 Designing for best efficiency 2 .4 Sealing system 3 . ORC Cycle Optim isation 4 . Conclusion 2

1. General Presentation 1.1 Cryostar in figures Who is Cryostar ? 3 5 0 em ployees 1 4 5 Million € turnover in FY 2 0 0 6 9 0 % export 1 5 Million € investm ents in 2 0 0 5 -0 7 Skid mounted HC turboexpanders Part of the new Boil-Off gas reliquefaction unit High pressure reciprocating pump 3

1. General Presentation 1.2 Cryostar in the market place Recognised as worldwide experts in the following areas: 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 Oil & Gas LNG No.1 in « boil-off » gas handling and recovery (90% market Clean energy share) Energy recovery Industrial gas 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) 4

1. General Presentation 1.3 Cryostar new markets Geotherm al and heat recovery expansion turbines TG: Turboexpander generator type In construction: one TG500 delivering ca 3.3 MWelec for Siemens Kalina cycle in Unterhaching (Bavaria/ Germany) Ongoing project: other TG500 for Siemens Kalina cycle in Offenbach/ Bellheim Pre-selected for Soultz Hot Dry Rock ORC Project Pre-selected for Innamincka Kalina Project 5

2. Radial Turbines For Binary Cycles 2.1 Radial inflow turbine Main elem ents: 1.A high pressure barrel from which the gas first expands through guide vane 1 arrangement that is located in the circumference of the wheel. 2. The gas is accelerated in the guide vanes and enters the turbine w heel . It converts the kinetic portion of energy contained in the gas by means of deflection into 2 mechanical energy. 3. The gas leaves the wheel axially at the low pressure level and is passing afterwards through the discharge 3 diffuser where velocities are reduced to normal pipeline velocities. 1 2 4. The power generated by the wheel is given to a shaft which runs in high speed bearings . This 3 power can be recovered by driving a compressor or a generator. 6

2. Radial Turbines For Binary Cycles 2.2 Expander wheel design The expander wheel must be designed at optimum ratio of blade tip speed and spouting velocity = U/C 0 U = tip speed (m/ s) rotating speed of the blades at the furthest extremity from the rotating axe C 0 = spouting velocity (m/ s) the magnitude of the absolute velocity vector at nozzle U exit under isentropic conditions (i.e no losses in the nozzle passage) = ∆ c 2000 . H Spouting velocity 0 is ∆ H is Isentropic enthalpy drop ( kJ / kg ) U/ C 0 is a m easure of the shape of the velocity triangle in the inter-space betw een nozzle exit and rotor inlet 7

2. Radial Turbines For Binary Cycles 2.2 Expander wheel design The expander wheel must be designed at optimum specific speed Ns Ns = specific speed 76 . N Q = out N . Specific Speed s ∆ 1000 3 H is Links main sizing variables: flow, speed, head with : ∆ H Isentropic enthalpy drop ( kJ / kg ) Ns is shape factor for the passage of the wheel is N Wheel speed ( rpm ) 3 Q Vol . Flow Rate ( m / s ) out Low Ns at design point High Ns at design point Efficiency U/C 0 Axis of rotation 8

2. Radial Turbines For Binary Cycles 2.2 Expander wheel design Designing for the best efficiency Optimum Ns for known Optimum U/C 0 process data C 0 given by process data Calculation of angular velocity Calculation of tip (wheel) speed ( ) ⎛ ⎞ & ⋅ U N Q out ⎜ ⎟ = × ω = s optimum U C ⎜ ⎟ tip 0 3 ∆ ⎝ C ⎠ h 4 is 0 optimum ω too high ? U tip too high ? Yes Yes Decrease Q exit Decrease C 0 Machines in serie Machines in // No No Optimum wheel speed Optimum wheel diameter ⎛ ⎞ d tip = 2 U ω ⋅ ⋅ 2 ⋅ ∆ h is ⎜ ⎟ ⎝ ⎠ C 0 optimum 9

2. Radial Turbines For Binary Cycles 2.2 Expander wheel design Expander lim itations: Circum ferential ( Tip) w heel speed 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 1 0

2. Radial Turbines For Binary Cycles 2.2 Expander wheel design Expander lim itations: Pow er Density 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 1 1

2. Radial Turbines For Binary Cycles 2.2 Expander wheel design Expander lim itations: Bearing ( sliding speed) speed Most of the time, tilting pad (also called Michell) bearings are used Maximum sliding speed defined by bearing manufacturer 1 2

2. Radial Turbines For Binary Cycles 2.2 Expander wheel design Expander lim itations: Sound velocity or Mach Num ber 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 1 3

2. Radial Turbines For Binary Cycles 2.2 Expander wheel design Expander lim itations: Application to turboexpanders for binary cycle Most of the tim e Titanium alloy Kalina cycle w heels m ust be used because of: 84.31%-w NH 3 , 5.47 kg/s, pout = 7.4 bara 0,9 Inlet Temperature higher than 100-120 degC “Aggressive” working fluid like ammonia- water mixture Isentropic Efficiency [-] 0,85 Consequently it gives higher Limit High m argin for: 0,8 Limit Low Wheel tip speed Power Density 0,75 … so higher efficiency 0,7 2,5 3,5 4,5 5,5 6,5 7,5 Pressure Ratio [-] 1 4

2. Radial Turbines For Binary Cycles 2.3 Designing for best efficiency Kalina Cycle - Offenbach ORC with iC4-Soultz High (design for summer) Brine Flow Operating range for Cryostar binary cycle expanders Isentropic Efficiency (%) Increasing Wheel diameter Adimensional Specific speed Ns ORC with iC4-iC5 Waste heat recovery From Balje O.E., “Turbomachines, A Guide to…and theory” 1980 Specific speed Ns 1 5

2. Radial Turbines For Binary Cycles 2.3 Designing for best efficiency Experience show s that efficiency decreases w hen: - Pressure ratio increases - % liquid at outlet of expander increases Expander efficiency of Turboexpander-Generators ( TG) at design points 1 0,9 0,8 Isentropic efficiency for TG 0,7 0,6 0,5 0,4 TG for binary cycles : 0.82 < efficiency < 0.9 0,3 0,2 0,1 0 Wheel Diam et er 1 6

2. Radial Turbines For Binary Cycles 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 … …Standard m achines for CRYOSTAR … Standard m achines for CRYOSTAR Installed base : � More than 1600 turbo-expanders & -compressors in operation � ca 150 TG machines generating more than 80 MW electricity 1 7

1 8 TG300/ 60 delivering 4MWe 2.3 Designing for best efficiency 2. Radial Turbines For Binary Cycles TG m achines

2. Radial Turbines For Binary Cycles 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 Kalina cycle: ORC cycle: Use of process fluid im possible: Use of ORC fluid possible: clean & dry iC4 , NH 3 / H 2 0 leads to liquid form ation and iC5 , R1 3 4 A… used as seal gas; corrosion problem s; Oil sealing system w ith drainer or Dry Gas I nert Nitrogen is often chosen; Seal is used; Needs to lim it the flow of N 2 w hich is Seal gas m igrating into oil system is cleaned lost afterw ards; from oil ( coalescing filter) ; « Dry Gas Seal » system ; Cleaned seal gas is recovered by recom pression to inlet of condenser; Little losses of process gas unavoidable. No losses of the process gas. 1 9

2. Radial Turbines For Binary Cycles 2.4 Sealing system Kalina cycle: Dry Gas seal N 2 + NH 3 /H 2 O recover Need of external source of Nitrogen; Low flow is necesssary 1 -2 m 3 / h; Polluted N 2 by NH 3 & H 2 O needs to be stored before treatm ent; Possibility to « w ash » the NH 3 gas to recover in the storage tank. 2 0

2. Radial Turbines For Binary Cycles 2.4 Sealing system ORC cycle: Solution for sealing Oil seal + drainer + recom pression 40,00 bara 150 1 2 3 35,00 bara To com pressor 30,00 bara 125 Pressure (bara) 25,00 bara 20,00 bara 100 15,00 bara 75 10,00 bara 50 5,00 bara 4 Ex. Compression of iC4 5 6 200,0 36,9 34,4 137,6 0,00 bara -400,00 -300,00 -200,00 -100,00 0,00 100,00 200,00 300,00 400,00 500,00 Enthalpy (kJ/kg) 2 1