A Review of Fluidized Bed Gasification Technology

Transcription

1 4 th International Freiburg Conference on IGCC & XtL Technologies May 3-6, 2010 Dresden, Germany A Review of Fluidized Bed Gasification Technology Todd Pugsley a and Nader Mahinpey b Department of Chemical Engineering a University of Saskatchewan b The University of Calgary

2 Outline of Presentation What is fluidization? Basic concept Geldart classification; flow regimes Applications of fluidization Advantage and challenges associated with fluidization Fluidized bed gasification technologies Concluding remarks

3 What is fluidization? TDH Cyclone ECT Windbox Fluidizing medium (e.g. air) enters the bed through the windbox and the distributor Upward flowing air creates a gas-solid suspension with fluid-like properties Entrained solids are separated and returned in the disengagement section (TDH) and cyclone Complex multiphase flow measured with techniques such as electrical capacitance tomography (ECT) Air in

4 What is fluidization? Video shows vigorous mixing, splashing and entrainment

5 What is fluidization? Fluidized bed behavior depends on: Particle properties (Geldart classification) Fluidizing gas velocity (fluidization regimes) Vessel geometry including cross-section, section, diameter, height (scale-up) The nature of the two-phase flow in a fluidized bed is a complex combination of these parameters

6 Regimes of fluidization

7 Geldart Classification

8 Advantages of Fluidized Beds High rates of heat/mass transfer and efficient gas-solid solid contacting Temperature control; effective use of catalysts; good mixing; fuel flexibility including opportunities for co-feeding Continuous addition, removal, circulation of solids for catalyst capture and regeneration; circulation of sorbents Immersion of heat transfer surfaces and semi-permeable membranes

9 Challenges with Fluidized Beds The overarching issue is scale-up Lab to pilot to demonstration to commercial Scale up of existing commercial units Complex multiphase flow Different particles scale-up differently No direct control of the fluidized state Defluidization or non-optimal optimal fluidized state a distinct possibility

10 Challenges notwithstanding, there are many successful applications of fluidized bed technology.

11 Applications of Fluidization 1920s Winkler coal gasifier 1940s Fluid Catalytic Cracking 1950s Sasol Synthol Process 1960s SOHIO process (acrylonitrile) 1970s Fluid coking (Syncrude) 1980s CFB combustors 1990s Dupont maleic anhydride process; methanol to olefins (Exxon)

12 Fluidized Bed Gasification There are 6 main fluidized bed technologies for coal gasification: KBR Transport Gasifier CFBs IDGCC process (Australia) BHEL process High-Temperature Winkler (HTW) KRW or U-Gas U process GreatPoint Energy BFBs KBR, U-Gas, GreatPoint are the highest profile technologies

13 Fluidized Bed Gasification KBR Transport Gasifier T = 1700 F; P = 200 psi Demonstration plant at Southern Co s Wilsonville site; commercial units in design for Mississippi Power and in Guandong Province, China Lower cap and op costs; designed for low-grade coals, including lignite

14 Fluidized Bed Gasification IDGCC integrates drying of brown coal; CFB process

15 IDGCC Process IDGCC = Integrated Dryer Gasification Combined Cycle Hot syngas is used to dry wet brown (lignite) coal Purports to achieve lower CO 2 emissions, cooling water usage and cost-of of-electricity per MWh 550 MW commercial-scale demonstration scheduled for 2013 start-up

16 Fluidized Bed Gasification KRW or U-Gas process agglomerating bubbling fluidized bed

17 U-Gas Process Synthesis Energy Systems purchased technology license from GTI Operating in Shandong Province, producing syngas for a methanol plant; two other projects under development in China Key to operation is removal of ash in the form of agglomerates controlled agglomeration in a single-stage stage fluidized bed

18 Fluidized Bed Gasification GreatPoint Energy catalytic gasification direct to methane

19 GreatPoint Energy Catalytic gasification process based on US Patent No. 4,077,778 filed by Exxon in 1978 Low T, high P process goes straight to methane Alberta Energy Research Institute (AERI) supported pilot testing with Alberta feedstocks Economics unclear given current low NG prices

20 Feedstock Considerations Fluidized beds the leading technology for biomass due to aggressive biomass slag as well as variability of feed physical and chemical characteristics Fluidized bed application to coal tends to be for lignite and sub-bituminous bituminous with operation below or near the ash softening temperature; low-grade coal has higher reactivity

21 Conclusions What is the future of fluidized bed gasification technology? Large worldwide reserves of low-grade, highly-reactive coals Such coals are good fuels for lower- temperature fluidized bed processes Announcements of new projects using fluidized beds show the technology is maturing At this point in time, fluidized bed gasification appears to have a positive future

22 Conclusions (cont.) What are the challenges? Complex multiphase flow and scale-up challenges continue to present significant technical and economic risk What are the opportunities/r&d needs? Catalytic gasification to lower capital and operating costs of entire plant (not just the gasification island) Continued development of chemical looping gasification

23 Carbon Management Canada A National Centre of Excellence funded by the Canadian government $25 million over 5 years with additional investment from provinces Key focus will be gasification and its application to Western Canada feedstocks (lignite and sub-bit coal and petroleum coke) Emphasis on fluidized bed technology reflects Canadian fluidization expertise

24 Thank you for your attention Any Questions?