COAL GASIFICATION AND CO 2 CAPTURE

Transcription

1 COAL GASIFICATION AND CO 2 CAPTURE an overview of some process options and their consequences Use this area for cover image (height 6.5cm, width 8cm) Evert Wesker Shell Global Solutions International B.V. February 2013

2 LAY-OUT OF THE PRESENTATION Some on the context Zooming in on Coal Gasification Pre combustion capture (after gasification) Post combustion capture (after powdered coal fired boiler) Further developments A last word... (and food for thought)

3 World energy consumption (2011) ~ 540 Exa-Joule / year = ~ 17 x Watt Copyright of INSERT COMPANY NAME HERE 3

4 MORE THAN 80% OF THE ENERGY IS (STILL ) BASED ON FOSSIL FUELS (Statistics from 2011; total 540 EJ/year) OPEC + Russia: ~60% of the total world conventional oil production Coal: Security of supply plays in the background

5 THE POSSIBLE GLOBAL CLIMATE PERSPECTIVE To what do we owe this good fortune? Nobody knows for sure. However: Business as usual could mean pushing one s luck. roller coaster Stable!

6 SOME MORE NUMBERS Coal reserves: (numbers from BP statistical review of world energy) Bituminous coal & anthracite Sub-bituminous coal & lignite ~500 Gton (~2500 Gbbl oil equivalent) ~400 Gton ( at least, but probably more ) World power production (2008) Total power production Power from fossil fuels Power from coal 73 EJ/year 48 EJ/year 30 EJ/year (about 40% of the total) Worldwide CO 2 emissions (2008) Total (excluding land change) Coal Power from coal 32 Gton/year 13 Gton/year 8 Gton/year!» Coal & coal based power will (still) be with us for quite some decades, so if we want to do something about these CO 2 emissions we will have to look into CCS...

7 CO 2 CAPTURE, THE VARIOUS ROUTES

8 ZOOMING IN ON COAL GASIFICATION Why? Turning coal into a gaseous product enables combined cycle line-ups with a high efficiency (currently ~47%, possible future» 50%) High pressure process enables high pressure removal of CO 2 (after a shift step) This is part of this lecture. Sulphur ends up as H 2 S (and as elemental sulphur after Claus) instead of SO 2 which has to be removed as e.g. CaSO 4. No Ca(OH) 2 with its energy requirement (CaCO 3» CaO requires 3.8 MJ/kg CO 2 ) is needed. The combined production of power and Hydrogen ( poly-generation ) is a distinct possibility. For the Shell process Dry feeding of the coal (no water evaporation losses) leads to a higher cold gas efficiency. (Often >80% of the initial heating value is retained) The design (membrane wall, burners) is highly robust.

9 SHELL SCGP PROCESS LINE-UP

10 FLOWS IN A CC POWER PLANT

11 PRE COMBUSTION CAPTURE: IGCC WITH CO 2 CAPTURE Sulphur GT air Air Coal ASU (max 50% air int.) Coal Milling & Drying Dry Coal VHP/HP/LP N2 GT N2 Oxygen Shell Coal gasifier VHP/HP N2 BFW LP/IP Steam (sh) IP (sh) Steam H 2 S Removal 62.3 Mio Shift Claus + SCOT H 2 S Acid Gas Removal CO 2 Compression POWER Generation CO 2 Power Slag Flyash Waste Water HP (sat) IP (sh) Steam (low purity) H2 GT air

12 FLOWS IN A CC POWER PLANT WITH CO 2 CAPTURE

13 CO 2 FROM SYN-GAS / PRE-COMBUSTION

14 IGCC CCS PRE COMBUSTION OPTIONS

15 PHYSICAL SOLVENTS A PRESSURE SWING PROCESS

16 WATERFALL DIAGRAM FOR SCHP + SHIFT + SELEXOL (Conventional case) Efficiency IGCC, %LHV st drop ~5.5%p (sour shift) nd drop ~1.5%p (Selexol) 42 3 rd drop ~2.5%p (CO 2 compression) No capture Shift CO 2 AGR CO 2 compress TIT reduction

17 POST COMBUSTION CAPTURE: A POWDERED COAL FIRED POWER PLANT...

18 POST COMBUSTION: AN AMINE BASED TEMPERATURE SWING PROCESS

19 PRE VERSUS POST (Conventional cases) Observations from pre-combustion : The biggest losses are in the shift step (~5.5%!!) In the CO 2 removal step little can be gained (loss ~1.5%) The difference between pre and post is relatively small in case the employment of a conventional shift step: %» 36.8% for amine state of the art solvent %» 36.4% for selexol after shift However: We are looking at a moving target. Gas turbine efficiencies go up (good for pre ) Shift process improvements will be pursued (good for pre ) Solvents will be improved (good for post ) Further ultra supercritical boiler development (good for post )

20 FURTHER DEVELOPMENTS: INDUSTRIAL GAS TURBINES Turbine Inlet Temperature ( C) Turbine Inlet Temperature Efficiency on NG (% LHV) 1993 (E-class) Available for syngas (F-class) Available for natural gas (G/H-class) Pressure ratio Long-term development target 44% 42% 40% 38% 36% 34% 32% Efficiency on NG (% LHV)

21 IGCC COAL-TO-POWER EFFICIENCIES Efficiency IGCC [%LHV] E class (Buggenum) F class - base case G class H class (TIT=1425 C) H+ class (TIT=1525 C) ASU 50% integration High efficiency ASU Hot Gas CleanUp USC with reheat@620 C Basis: El Cerrejon coal with Cold Gas Efficiency ~82%. Site is sea shore in the Netherlands, typical ISO ambient conditions (15 C air, 12 C sea water, temperature range sea water = 8 C), 0 m elevation

22 FURTHER DEVELOPMENTS: WATER GAS SHIFT CO + H 2 O = CO 2 + H Novel low steam WGS 500 Syngas to 1 st reactor: CO (60%), H 2 (30%), N 2 (8%), CO 2 (2%) Conventional HTS/LTS 80 Bed Temperature ( o C) WGS conversion (%) Bed temperature CO conversion H2O conversion Steam : CO ratio (mol:mol)

23 SOUR WGS PROCESS WITH LOW STEAM/CO RATIO Low steam:co sour Water Gas Shift process: + lower import of MP steam, utility-efficient + less unconverted steam in the product gas + capital investment is comparable with conventional HTS/LTS Technology developed in China, applied since 2007 and quickly adopted by SCGP licensees. Presently, 7 plants using low steam/dry gas shift process put into industrial operation, and 4 plants in preparation. A retrofit system has recently been installed at the coal gasification plant in Yueyang, Hunan Province, China. The facility is a 50:50 Joint Venture between Sinopec and Shell Coal Gasification Company Limited.

24 FURTHER DEVELOPMENTS: ADIP-X SOLVENT FOR CO 2 REMOVAL ADIP-X is a mixture of the tertiary amine N-methyl di-ethanol amine (MDEA), the secondary diethylene di-ethanol amine (piperazine) and water. Combines benefits of physical solvent (low amount of heat for regeneration) & chemical solvent (high purity of captured CO 2 ) Staged flash regeneration is applied with pre-heating of the fat solvent at relatively low temperature (<100 C). allows low value heat sources to be utilized (e.g. from the hot syngas ex WGS and the CO 2 compressor intercoolers) maximises the amount of CO 2 flashed-off at around 5 bar, minimising required compression power

25 IGCC WITH TOMORROW S TECHNOLOGY A typical example based on 2 gasification strings + G-class gas turbines Total plant fuel input (MWth, LHV) Gas Turbines power output (MW) Steam Turbines power output (MW) Plant power output, gross (MW) Auxiliary Power (MW) Plant power output, net (MW) IGCC IGCC + 90% CCS Gross Efficiency (%) Net Efficiency (%) % LHV efficiency improvement potential for Future IGCC + CO 2 capture

26 CANSOLV: ANOTHER OPTION CURRENTLY AVAILABLE

27 MAIN RESULTS KEMA CASE STUDIES

28 CONCLUSIONS Technology development pathway for IGCC with CO 2 capture outlined. In medium-term, advanced technology pushes coal-to-power efficiency: above 48% for IGCC above 41% for IGCC with CO 2 capture Other IGCC advantages: ultra-low emissions of NOx and SOx, low cooling water demand, part-load operation with rapid turndown The widening of the gap between pre and post combustion depends on the developments of ultra-supercritical (700 C) powdered coal fired power plants.

29 A LAST WORD (AND FOOD FOR THOUGHT) Imagine: CCS for MW ( 10 EJ/year) Coal based power Efficiency power plants on coal (+CCS): 40%» Ergo: ~2.3 Gton CO 2 /year A density for CO 2 when injected (~200 bar, ~30 C) of ~ 900 kg/m 3 implies: ~2.3 Gton CO 2 /year» 43 million barrel per day To put it in perspective: The present conventional oil production is about ~73 million barrel per day. (1 barrel = 160 litre). So: For CCS, equivalent to about 5% of the current world energy consumption in this case an infrastructure (pipelines, injection wells, etc.) of the size of an order of magnitude of half of the oil production infrastructure is required. This is big stuff (if we decide to go for it)

30 Q & A

31 SCGP TYPICAL ENERGY BALANCE Coal in 100% 2.0% Steam from reactor wall (reused) 12.8% Steam from Syngas cooler (reused) 0.5% Unconverted carbon (fly ash/slag) 2.7% Low-level heat (cooling of slag) 82% 18.0% Total Raw synthesis gas