Del 5.8 Study on Energy Carrier Use for Entrained Flow Gasification
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www.BioBoost.eu Biomass based energy intermediates boosting biofuel production This project has received funding from the European Union’s Seventh Programme for research, technological development and demonstration under grant agreement No 282873 Deliverable Deliverable 5.8 Study on energy carrier use for entrained flow gasification Workpackage: WP5 Deliverable No: D5.8 Due date of deliverable: 30/09/14 Actual date of delivery: 06/03/15 Version: Final / Vers.1.2 Responsible: KIT Authors: Prof. Dr. Edmund Henrich, Prof. Dr. Nicolaus Dahmen, Andreas Niebel Contact: [email protected] Dissemination level: PU-Public Publishable Summary For biomass gasification, a variety of technologies exist. For large-scale syngas generation with downstream synthesis of organic chemicals or synfuels, pressurized entrained flow (PEF) gasification has emerged as the preferred technology. The technology is flexible and can accommodate many different feedstocks, but at the expense of more technical effort for gasifier feed preparation. The various feed preparation methods and feed properties as well as the gasifier feeding systems are described in context with the other interacting steps in the process network. Gases and liquids (fluids) either with or without an entrained or suspended pulverized fuel are suitable feed forms. The fluid feed can be continuously transferred with pumps or compressors into a highly pressurized gasification chamber. Immediately at the gasifier inlet the fuels are mixed in special nozzles with pure oxygen (and steam) as the gasification agent; liquid and slurry fuels are atomized simultaneously. PEF gasification proceeds at high temperatures >1000 °C and high pressures up to 100 bar or more in a gasifier flame in the course of a second. The total residence time in the gasification vessel is only few seconds and the gasifier volume is correspondingly small. Solid or liquid fuels must be present as small particles or droplets with a sufficiently large surface area for complete conversion in few seconds. Ash is removed as molten slag and their melting behavior determines the minimum gasification temperature. In biofeedstocks – mainly lignocellulose like wood or straw – the cellulose fibers prevent direct milling to a suitable powder and generate fiber muddles. A suitable PEF gasifier feed can be prepared from biomass pyrolysis products; preferred processes are fast pyrolysis or torrefaction. Biomass pyrolysis destroys cellulose fibrils and the chars are brittle and easily pulverized. The pulverized chars can be transferred to a pressurized on-site gasifier either with an inert gas as a dense char particle stream from a pressurized fluidized bed or as a slurry, after char suspension in the pyrolysis liquids or any other combustible (waste) liquid or even as a water slurry, as it is already practiced with pulverized coal. Slurries, especially bioslurries, are not only a suitable PEF gasifier feed form, but also a storage and transport form with a ca. 10 times higher energy density compared to the initial biomass. Bioslurry transport from many regional pyrolysis facilities to a large and more economic gasification/synthesis plant is a unique feed preparation and handling characteristic of the KIT bioliq® process. D5.8 / Study on energy carrier use for entrained flow gasification page 2/38 Table of Content Publishable Summary ................................................................................................................. 2 Table of Content ......................................................................................................................... 3 Report ......................................................................................................................................... 4 1 A suitable gasifier for downstream synthesis of organic chemicals and synfuels .............. 4 1.1 Fixed-bed gasifiers ...................................................................................................... 5 1.2 Fluidized-bed gasifiers ................................................................................................ 5 1.3 Entrained flow gasifiers ............................................................................................... 6 2 Essential operating and design features of PEF gasifiers ................................................... 8 2.1 Operating conditions of PEF gasifiers ......................................................................... 8 2.2 Design characteristics of PEF gasifiers ..................................................................... 11 2.3 Interactions in the total PEF gasification/synthesis process network ........................ 14 3 Suitable feed preparation, feed properties and feeding systems for PEF gasifiers ........... 17 3.1 Gaseous fuel .............................................................................................................. 17 3.2 Liquid fuel, transfer and atomization ........................................................................ 17 3.3 Pulverised fuel, handling and transfer ....................................................................... 17 4 Experience from commercial PEF gasifiers ..................................................................... 20 4.1 Characteristics of commercial gasifiers ..................................................................... 20 4.2 Description of typical fuel feeding techniques .......................................................... 22 4.3 Status of the world gasification technology .............................................................. 26 5 Biomass conversion to PEF gasifier feed ......................................................................... 27 5.1 Focus on lignocellulosic feedstocks .......................................................................... 27 5.2 Torrefaction ............................................................................................................... 27 5.3 Fast pyrolysis ............................................................................................................. 27 6 Pilot projects for large-scale PEF gasification of biomass ............................................... 28 6.1 Lulea university, Sweden (formerly Chemrec): Black liquor feed ........................... 28 6.2 Feeding concept of the Choren Carbo-V process ...................................................... 29 6.3 KIT “bioliq” pilot facilities ........................................................................................ 29 7 Recent process developments ........................................................................................... 30 8 Experience from slurry gasification .................................................................................. 31 9 Summary and conclusions ................................................................................................ 34 10 Sources .......................................................................................................................... 36 D5.8 / Study on energy carrier use for entrained flow gasification page 3/38 Report 1 A suitable gasifier for downstream synthesis of organic chemicals and synfuels Gasification can convert almost all organic feeds with HHV > 10 MJ/kg into syngas, a mix of CO and H2, and consumes only 20-40 % of the O2 required for stoichiometric combustion. Syngas is a very flexible intermediate (platform chemical) and educt for the selective catalytic production of numerous valuable organic chemicals and fuels at certain temperatures and higher pressures [14],[15]. The alternative use as a fuel is syngas combustion in IGCC plants for the generation of electricity or high temperature process heat. All these technical possibilities are already applied commercially. The main gasifier types are depicted in Fig. 1; essential design and operating characteristics are summarized in Tab. 1. Fixed bed gasifier Fluidized bed gasifier Entrained flow gasifier Counter current Stationary Downdraft Solidsolid fuel fuel Rawraw syngas syngas O2 (air) Solid fuel Raw syngas Solid or steam slurry fuel Fuel spray Bed (liquid, slurry, material Bubblingsand bed bed Fuel pulverized..) ( fuel) Ash fluidising gas Ash (slag) ash Fluidization medium Air (O2), steam syngas recycle Molten slag Raw syngas Co-current Circulating Updraft Air (O2) Raw syngas - Raw syngas Solid fuel steam Bed material recirculation Ash Fuel, air, Fuel, air, Fuel O2, steam O2, steam Ash (slag) Raw syngas Fluidization medium Slag Fig. 1: Main gasifier types [8] Tab. 1: Design and operating characteristics of the main gasifier types [14],[22] fixed bed fluid bed entrained flow (EF) gasification conditions: fuel type solid solid powder, liquid, gas fuel size 10-1-10-2 10-2-10-3m ca. ≤ 10-4m pressure 1-30 bar 1-30 bar 1-100 (+) bar residence time 103-104s ca. 102 s 1-few s raw syngas purity low (tar, CH4) low (tar, CH4) high fuel/gas flow countercurrent mixed cocurrent design characteristics: reactor geometry cylinder cylinder cylinder reactor wall refractory refractory membrane, refractory bed material - sand (olivine) - carbon conversion >90% >95% >99% ash dry (solid) dry (solid) molten slag D5.8 / Study on energy carrier use for entrained flow gasification page 4/38 1.1 Fixed‐bed gasifiers In fixed-bed reactors, the feedstock is exposed to the gasifying agent in a packed bed that slowly moves from the top of the gasifier to the bottom, where the ash or slag is discharged. By moving through the reactor, the biomass passes