Transcript
NOVEL SCHEME FOR SMALL SCALE LNG PRODUCTION in POLAND
W.H. Isalski
Presentation Overview ¾The history of gas de-nitrogenation in Poland ¾Changes in feed gas ¾Changes in market conditions ¾Expanding market for small scale liquefaction ¾Land-based remote locations
¾The technical challenges ¾The results of modifications and their effects
10th TGE Symposium June 10, 2005
The KRIO Nitrogen Rejection Plant Location
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History of Polish KRIO Nitrogen Rejection Plant ¾ ¾ ¾
Located South-Western Poland Constructed in the 1970s Original design feed gas composition : Helium 0,4 vol% Nitrogen 42,7 vol% ( now 30 – 35%) Methane 56,0 vol% Ethane 0,5 vol% Propane+ 0,1 vol% CO2 0,3 vol% Water Saturated at inlet conditions Pressure 5,1 - 5,6 Mpa Temperature 10-25 C deg Flow 136 000 NCMH 10th TGE Symposium June 10, 2005
Process Elements in Nitrogen Rejection Units (NRUs)
Nitrogen contaminated gas / low BTU gas undergoes pre-treatment : CO2 removal (amine unit) H2O removal (molecular sieve) aromatics & C5+ removal (activated carbon) Filtration of dust & mole sieve particles A typical NRU is a highly integrated process comprising : plate-fin heat exchangers pumps cryogenic distillation columns Joule-Thomson (J-T) valves for refrigeration Product Compression
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Block Flow Diagram for Nitrogen Rejection Plant
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History of Polish KRIO Nitrogen Rejection Plant Product Requirements : product gas
< 4% N2 at 1,8MPa compressed to grid downstream
waste gas < 1% CH4 vented to atmosphere crude helium > 85% He pure helium > 99,999% Flexibility to produce some liquid CH4 & N2 Base load Product is pipeline quality gas.
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Changes in Feed Gas & Waste Gas Ä
33 - 35%
Ä
0,18%
5,6 MPa
Ä
5,3 MPa
CO2 content :
0,3 %
Ä
0,4%
Waste gas CH4
<1%
Ä
3–4%
Original Plant lost flexibility.
Nitrogen content :
Helium content :
Pressure :
43% 0,4%
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Main effects of changes in feed composition The environmental impact of increased methane content in the waste gas The economic loss as the consequence of methane emissions Inability to produce liquid products. Reduced flexibility when changing from LNG to liquid nitrogen by-product. Less helium in feed means reduced revenue from liquid helium Less stable operation of the cryogenic unit
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Growing Market for Small LNG liquefiers
Small gas reserves in remote areas can be monetised. Countries with un-reliable or non-existent gas network need gas supplies. a
Scotland, Poland, China, USA, Norway
Rising cost of gas/LNG.
Greater volatility in prices.
LNG transport vessels produce boil-off gas (BOG – covered in previous paper). 10th TGE Symposium June 10, 2005
History of natural gas liquefaction ¾ Cryogenic industry started in early 1900s ¾ Liquefaction of LNG began in the 1940s ¾ First base load Plant in the 1960s ¾ LNG Peak Shaving plants in the 1970s ¾ Base load train size increased dramatically ¾ Ship BOG re-liquefaction patents in 1970s ¾ Stranded gas exploitation gathers momentum in late 1990s ¾ GTL, mid-sized LNG plants, small scale units
¾ Machinery well developed with high efficiencies ¾Mature technology. ¾Innovations still possible. ¾Modifications to existing plants.
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LNG Liquefaction Train Capacities Type of LNG Liquefier
Capacity tonnes/day
Gas Input MMSCFD
Plants & Location
Peak Shaving Units
50 – 300
3 – 15
Mid-sized units
1000 – 4000
55 – 220
Over 100 units,USA, UK, Europe, since 1940s. Less than 10 Kenai, Algeria, China.
Base Load Plants
7000 – 10000
400 – 550
Over 100 units worldwide.
Newer Base Load Plants 11000 – 15000
600 – 850
several built, worldwide, a few planned even larger at >20000 tonnes/day.
Under development
1000 – 1250
Planned
20000 – 25000
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Variety of LNG liquefaction Cycles
Classical APCI C3 pre-cooled MRC.
Dual MRC, Shell, TEAL & Linde.
Cascade Cycle, Phillips.
Single Fluid, multi-stage Mixed Refrigerant.
Single Stage Mixed Refrigerant, Prico.
Gas expander cycles & Nitrogen Expander cycles.
Novel systems: Acoustic, Vortex Tubes.
Modifications added to existing processes – gas expanders, additional cycles bolted on to existing facilties. 10th TGE Symposium June 10, 2005
Peak Shaving LNG Plants in 1970s - Belgium 240 TPD LNG Peak Shaver using nitrogen Cycle
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Tractebel project - Mid-sized LNG Plant, China 1200 TPD LNG Plant – Urumqi, China Status: Plant in operation since Q4/2004.
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Cascade Reliquefaction System.
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Cascade Re-liquefaction System.
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Cryogenic section of Nitrogen Rejection Unit
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Plate-fin Heat Exchanger.
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Process Concept Development Options considered
Likely Cost/Benefit
Lowering Pressure in Upper Column with Blower
High Capital and operating Cost, limited benefit.
Adding Separate cycle to provide refrigeration
High Capital and operating Cost, moderate benefit.Complex solution.
Importing liquid Nitrogen to assist in cold production.
High operating cost. Simple implementation and with good benefit.
Modification of methane pump control scheme to VSCF controller.
Low, with good benefits, with limited scope for LNG production.
Application of gas expanders in various locations.
Difficult to provide cold at correct temperature level. Quite expensive.
Application of liquid expanders in various locations.Feed to lower column, rich liquid & poor liquid
The 2nd & 3rd options provide cold at the appropriate temperature level. Limited sources of machinery. Testing required.
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LNG Production using turbo-expander.
• TGE Project to increase cold production in a nitrogen rejection plant. • Novel process scheme.
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Process Concept Development Decided to implement - Two-Phase expander! Reasoning based on: ¾ Previous site experience with canned pumps ¾ Previous site experience of VSCF control in a pump modification(Variable Speed Constant Frequency) ¾ Knowledge that trials were done & no cavitation ¾ Compact nature of modification. ¾ MAIN WORRY WAS CAVITATION 10th TGE Symposium June 10, 2005
Example of Cavitation. • Propeller rotation is anticlockwise. • Bubbles collapse & erode blades. • Odolanow situation is opposite: bubbles form and fluid expands.
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The challenges in 2-phase turbines.
Cavitation in turbine(95% vapour volume after flash). 2-phase flow instability in vertical direction. Bearing fluid. Control of turbine. Local space constraints. Maintaining plant flexibility: a
LNG & nitrogen production depending on market
Varying feed composition & need for low CH4 loss in waste gas Internal motor or external motor. 10th TGE Symposium June 10, 2005
LNG liquefaction experience in Poland
Tractebel Project to increase cold production in two nitrogen rejection plants. Result is 60 TPD LNG.
Novel process scheme. A first in the world!!
More difficult than BOG re-liquefaction.
EBARA Expansion turbine with flashing flow on two units. Successful project with test run completed in 2004.
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Main Elements of the Expander (EBARA) ¾Generator Submerged generator on a common shaft insulated / superior dielectric ¾Expander nozzle ring (rotational fluid flow) runner (radial flow) two-phase jet exducer symmetrical flow with vertical rotational axis - assures low vibration level lubrication for the bearings from simple internal system Thrust Equalisation Mechanism (TEM) provides complete thrust balance through whole range from 1- to 2-phase flow ¾Full Containment in pressure vessel rated at inlet pressure 10th TGE Symposium June 10, 2005
Exducer wheels in Aluminium (EBARA)
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Model of initial expansion wheel (EBARA)
Expansion across a jet exducer with helical fluid passages for vapour formation 10th TGE Symposium June 10, 2005
3-D View of 2-Phase expander (EBARA)
Exducer 1st Expander Wheel
Electric Motor
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Turbine before insertion into casing (EBARA)
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Location of Turbine.
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2-phase flow upwards 30 metres.
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Assessment of Power/Cold Production. • Hydraulic Power available is about 65kW • In practice 79kW – 85kW extracted at generator terminals. • In Two-phase terms vapour expansion also contributes energy. • HYSYS simulation suggests potential power available is over 100kW. • Therefore, could do even better!
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Incremental LNG Production Economics. ¾ Assumptions: • LNG cost is at least 5$/MMBtU 2-trains produce 60 TPD LNG • Power Produced is about 80kW per train i.e. 160kW. • Investment is less than 4$ million.
¾ LNG Production yields over 2 million $/year. ¾ Payback in the region of 1 year. ¾ Greater Plant flexibility. ¾ Reduced emissions.
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Conclusions.
Economics was favourable for LNG production and overall plant flexibility. Several different tests were done for expander wheels to improve efficiency. Gas expansion energy from flashing flow can be effectively converted to power/cold production. TGE has an economic solution and broad technical experience to implement such schemes elsewhere. There is scope for improving the efficiency. 10th TGE Symposium June 10, 2005
Truck loading at small land-based LNG plants.
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Thank you for your attention. Questions welcome
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