Swedish Energy Agency Report Small Scale Gasification: Gas Engine CHP for Biofuels Jan Brandin, Martin Tunér, Ingemar Odenbrand Växjö/Lund 2011-05-30 Content Preface ..................................................................................................................................................... 5 Summary ................................................................................................................................................. 6 1. Introduction ..................................................................................................................................... 7 1.1 Project description ........................................................................................................................ 7 1.2 References to chapter 1 ................................................................................................................ 9 2. Biomass ............................................................................................................................................. 10 2.1 Use of biomass for energy production in Sweden ...................................................................... 10 2.2 Total potential for biofuel in Sweden .......................................................................................... 13 2.3 Summary biofuel use in Sweden ................................................................................................. 15 2.4 Pretreatment of biomass............................................................................................................. 15 2.4.1 Introduction .......................................................................................................................... 15 2.4.2 Growth of biomass ............................................................................................................... 16 2.4.3 Harvesting ............................................................................................................................. 17 2.4.4 Storage and pre‐drying ......................................................................................................... 17 2.4.5 Transportation ...................................................................................................................... 18 2.4.6 Conventional pelletization ................................................................................................... 18 2.4.7 Torrefaction and compacting ............................................................................................... 19 2.4.8 Drying ................................................................................................................................... 20 2.5 References to chapter 2 .............................................................................................................. 20 3. Gasification ....................................................................................................................................... 21 3.1 Gasification chemistry ................................................................................................................. 21 3.2 Tars .............................................................................................................................................. 22 3.3 Minor contaminants: H2S, NH3, COS, and HCN............................................................................ 24 3.4 References to chapter 3 .............................................................................................................. 25 4. Gasifiers ............................................................................................................................................ 26 4.1 Fixed-bed gasifiers ...................................................................................................................... 26 4.1.1 Updraft gasifiers ................................................................................................................... 26 4.1.2 Downdraft Gasifiers .............................................................................................................. 27 4.1.3 Crossdraft gasifier ................................................................................................................. 27 4.2 Fluidized beds .............................................................................................................................. 28 4.2.1 Bubbling Fluidized bed (BFB) ................................................................................................ 29 4.2.2 Circulating fluidized bed (CFB) ........................................................................................... 30 4.3 Entrained-flow gasifier (EF) ....................................................................................................... 30 1 4.4 Multi-bed Gasifiers ...................................................................................................................... 32 4.4.1 Indirect heating ..................................................................................................................... 32 4.4.2 Separate pyrolysis and char gasification solutions ............................................................... 33 4.5 References to chapter 4 .............................................................................................................. 35 5. Gas cleaning ...................................................................................................................................... 37 5.1 Dust and ash ................................................................................................................................ 37 5.2 Tar cleaning ................................................................................................................................. 38 5.2.1 Removal and use .................................................................................................................. 39 5.2.2 In situ conversion ................................................................................................................. 40 5.3 Minor contaminates .................................................................................................................... 44 5.3.1. Sulphur ................................................................................................................................ 44 5.3.2 Ammonia .............................................................................................................................. 45 5.3.3 Alkali ..................................................................................................................................... 45 5.4 References to chapter 5 .............................................................................................................. 46 6 Combustion engine ............................................................................................................................ 47 6.1 Gas engines: an introduction....................................................................................................... 47 6.2 History of gas engines ................................................................................................................. 50 6.3 Fundamental definitions ............................................................................................................. 54 6.3.1 Basic engine operating principles ......................................................................................... 54 6.3.2 Combustion principles .......................................................................................................... 58 6.3.3 Engine out emissions and aftertreatment ........................................................................... 61 6.4 Producer gas quality versus engine performance ....................................................................... 66 6.4.1 Typical components of producer gas ................................................................................... 67 6.4.2 Contaminants ....................................................................................................................... 70 6.4.3 Heating value and air/fuel ratio ........................................................................................... 71 6.5 Commercial engines .................................................................................................................... 72 6.6 Research on producer gas engines .............................................................................................. 73 6.6.1 Overview of research in the last decade .............................................................................. 73 6.6.2 Recent research at Lund University ..................................................................................... 75 6.6.3 Research on engines directly fuelled with wood powder .................................................... 85 6.6.4 Future research .................................................................................................................... 86 6. 7 Referenses to Chapter 6 ............................................................................................................. 87 7 Case studies ........................................................................................................................................ 90 7.1 Introduction ................................................................................................................................