Process Optimization of Biogas Upgrading with AMP Using Pilot Plant Data and Simulations with ...

124 Pages·2016·2.14 MB·English

Process Optimization of Biogas
Upgrading with AMP Using Pilot Plant
Data and Simulations with Aspen Plus
Hans-Ulrik Lingelem
Industriell kjemi og bioteknologi
Innlevert: juni 2016
Hovedveileder: Hanna Knuutila, IKP
Norges teknisk-naturvitenskapelige universitet
Institutt for kjemisk prosessteknologi

Abstract
Biogasisconsideredasapotentialsourceofenergytoreplacefossilfuels. Besides
methane(CH ),othergaseouscomponentssuchascarbondioxide(CO )andhy-
4 2
drogensulfide(H S),maybegeneratedinbiogasproductionprocesses. Thecon-
2
centrationofsuchcomponentsneedstobereducedtoincreaseheatingvalue,avoid
corrosion, eliminate toxicity (H S, in particular) and to conform to common gas
2
specifications,allinordertoefficientlyutilizethebiogas. Thepurificationprocess
isoftenreferredtoas"upgrading". Intheupgradingprocess,chemicalabsorption
with amines has been identified as one of the most attractive processes. One of
the major limitations of implementing amine based CO removal from biogas, as
2
for post-combustion flue gas capture pf CO , is the high energy loss in the pro-
2
cess. Better process design and new solvents are developed in order to minimize
the energy loss. The development of new solvents with enhanced characteristics
has been an area of focus in recent times. 2-amino-2-methyl-1-propanol (AMP)
isamongthesolventswhichhaveshowngoodresultsincomparisontootherwell
established solvents. The development of more efficient process design has been
lessstudied. However,thisareahasalsogainedmoreattentionwiththeincreased
interestincarboncaptureandsequestration(CCS),andforreducedcostofimple-
mentationofCCS.Keyareasofoptimizationforthechemicalabsorptionprocess
of CO have been identified as: a) Absorption enhancement, b) Heat integration,
2
andc)Heatpumps
InthisstudytheimplementationofaprocesssimulationmodelinAspenPlusV8.6
withAMPhasbeenstudiedasapotentialsolventforbiogasupgrading. Thesim-
ulation model is compared to experimental data for both vapor liquid equilibria
(VLE)andlaboratoryscalepilotplantstudies. Ithasbeenestablishedthatthesim-
ulation model, developed as part of this work, is well suited for simulation. For
concentrations around 30[wt%] AMP in aqueous solution, and for temperatures
typical for processes with CO absorption using amines, 30-120 [◦C]. The devi-
2
ationbetweensimulateddataandexperimentaldatafrompilottestsforabsorption
anddesorptionperformance,were12.8%and8%respectively.
I
Itwasfoundthatthesimulationmodelunderestimatedthedesorptionrate.
Thesimulationmodelhasbeenusedforbiogasupgradingsimulationswith30[wt%]
AMP. Six process modifications have been applied to the conventional amine ab-
sorption process: a) Intercooled absorber (ICA), b) Rich solvent recycle (RSR),
c) Feed gas compression (FGC), d) Lean vapor compression (LVC), e) Rich va-
por compression (RVC), and f) Rich solvent split (RSS). From the simulations of
the modifications it has been shown that significant reductions in the energy re-
quirementoftheprocesscanbeachieved. Itwasfoundthattheabsorptioncolumn
had a large requirement for cooling in order to operate optimally. The simulation
resultsindicated64%reductionfortheoptimalsolventflowrateforICA,andfur-
therworkmaydemonstrateevenhigherreductions. LVCgavethelargestdecrease
in reboiler duty with a reduction of 33%. The reduction in equivalent electricity
(converted to equivalent thermodynamic work, i.e. how much electricity can be
produced with the same amount of energy) for LVC was lower than the reboiler
dutyduetoadditionalcompressionwork,andcalculatedto8.0%. RSSgavea16%
reductionintheequivalentelectricityrequirement.
II
Preface
This Master’s thesis was written during the spring of 2016. It is the final part
of the Chemical Engineering and Biotechnology study program at the Norwe-
gian University of Science and Technology, leading to the degree of M.Sc in
ChemicalEngineering. ThethesiswasperformedincollaborationwiththeEnvir-
onmental Engineering and Reactor Technology group, with Associate Professor
HannaKnuutilaassupervisor.
I hereby declare that this is an independent work according to the exam regula-
tionsoftheNorwegianUniversityofScienceandTechnology(NTNU).
Trondheim,20thofJune2016.
Hans-UlrikLingelem
III

Acknowledgements
Iwouldfirstandforemostliketoexpressmysinceregratitudetowardsmysuper-
visor Associate Professor Hanna Knuutila, for her valuable guidance and support
during the work of this thesis. Her constructive attitude and encouragement has
madetheworkwiththisMaster’sthesisatrulyinspiringexperience.
I would also like to thank my friends in Trondheim for five memorable years.
Last but not least, I would like to tank my family for their invaluable support and
encouragement.
V

Contents
Abstract I
Preface III
Acknowledgements V
ListofTables XIV
ListofFigures XVII
ListofSymbols XIX
Abbreviations XXI
1 Introduction 1
1.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 OutlineofThesis . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3.1 ReducedEnergyConsumptionandReductionofEmission
ofGreenHouseGases . . . . . . . . . . . . . . . . . . . 2
VII
VIII CONTENTS
1.3.2 Biogas . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.3 BiogasUpgrading . . . . . . . . . . . . . . . . . . . . . 6
1.3.4 BiogasUpgradinginNorway . . . . . . . . . . . . . . . 7
2 CO AbsorptionUsingAMPasaSolvent 9
2
2.1 GeneralProcessDescription . . . . . . . . . . . . . . . . . . . . 9
2.2 2-amino-2-methyl-1-propanol(AMP). . . . . . . . . . . . . . . . 11
2.3 ChemicalReactions . . . . . . . . . . . . . . . . . . . . . . . . . 12
3 LiteratureReview 15
3.1 OtherIndustriallyRelevantUpgradingTechniques . . . . . . . . 15
3.1.1 WaterScrubbing . . . . . . . . . . . . . . . . . . . . . . 15
3.1.2 Organicphysicalabsorption . . . . . . . . . . . . . . . . 16
3.1.3 PressureSwingAdsorption . . . . . . . . . . . . . . . . . 17
3.1.4 MembraneTechnology . . . . . . . . . . . . . . . . . . . 18
3.1.5 ComparisonofUpgradingMethods . . . . . . . . . . . . 18
3.2 ProcessModifications . . . . . . . . . . . . . . . . . . . . . . . . 20
3.3 StudiedProcessModifications . . . . . . . . . . . . . . . . . . . 20
3.3.1 BaseCase . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.3.2 AbsorptionEnhancement . . . . . . . . . . . . . . . . . . 21
3.3.3 HeatIntegration . . . . . . . . . . . . . . . . . . . . . . 24
3.3.4 HeatPumps . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.5 SummaryofModifications . . . . . . . . . . . . . . . . . 27
4 SimulationModeloftheCO Absorption/DesorptionProcessinAspen
2
Plus 29
4.1 PilotCampaignSimulatedinThisThesis . . . . . . . . . . . . . 29
4.2 AspenPlusTemplate . . . . . . . . . . . . . . . . . . . . . . . . 30