ReviewObjectivesExperimentalResultsConclusionFuture work A Fundamental Study of Biomass Oxy- fuel Combustion and Co-combustion Timipere S. Farrow Prof. Colin Snape: Supervisor

Presentation overview 1. Introduction  Carbon capture technologies  Detailed oxy-fuel combustion process  Objectives 2. Lab Scale Experimental techniques  Thermo gravimetric Analysis (TGA)/Horizontal Tube Furnace (HTF)  Drop Tube Furnace (DTF) 3. Results I. Combustion reactivity of Biomass Fuel under oxy-fuel and air combustion II. Co-firing sawdust and coal to identify the effect of biomass on coal char burnout III. Co-firing in (DTF), the effect at higher temperature combustion Introduction OverviewObjectivesExperimentalResultsConclusionFuture work

Introduction  The presence of CO 2 and other green house gas emissions in the atmosphere has become more problematic because of their negative environmental impact on climate  Stringent environmental laws on CO ₂ emissions from coal combustion. World energy consumption is predicted to rise to 44% and CO ₂ emissions to 39% in 2030 [1]  Increased interest in power generation industry towards technologies, which help to reduce CO 2 emissions from fossil fuels combustion by means of CO ₂ capturing. 1. International energy outlook, 2009 Introduction ReviewObjectivesExperimentalResultsConclusionFuture work

Leading Techniques for CO ₂ Capture Introduction ReviewObjectivesExperimentalResultsConclusionFuture work  Biomass co-firing Presents a potential technique

Why Biomass and co-firing? Potential option for renewable based power generation  Unlike fossil fuels, biomass fuel is renewable and CO 2 -neutral in the sense that the CO 2 it only releases recently fixed carbon when combusted thereby closing the carbon loop on a short time  Partial substitution of coal for combustion  In the UK, legislation is strong on CO ₂ reduction to meet Kyoto target and EU’s target to reduce CO ₂ emissions by 20% by  Hence the combination of oxy-fuel combustion with biomass fuel become a CO 2 sink for power plants Introduction ReviewObjectivesExperimentalResultsConclusionFuture work

Oxy-fuel combustion Process for cleaner fossil fuel utilisation Introduction ReviewObjectivesExperimentalResultsConclusionFuture work  Fundamental studies of oxy-fuel coal combustion have demonstrated that oxygen concentrations in the range % produced temperature profiles matching those of conventional air firing with lower NO x and SO x emissions.

Objectives 1. To investigate the behaviour of biomass under oxy-fuel conditions in comparison to air fired condition in terms of:  Volatile yield  The associated nitrogen partitioning between char and volatiles in order to monitor NOx emissions.  Kinetic parameters which are useful for design of biomass oxy-fuel combustion system. 2. To investigate how biomass will affect coal char burnout during co-firing under oxy-fuel and air firing with particular emphasis on the catalytic effect of biomass-contained alkali and alkaline metals on coal char burnout Introduction OverviewObjectivesExperimentalResultsConclusionFuture work

Schematic diagram of experimental Approach Thermo gravimetric Analyser (TGA) Horizontal Tube Furnace (HTF) Furnace (DTF) Char Devolatilisation Re-firing Devolatilisation Sawdust Thermo gravimetric analyser Horizontal tube furnace Drop tube Furnace Char Combustion Devolatilisation Combustion Introduction ReviewObjectivesExperimentalResultsConclusionFuture work

Thermo gravimetric analyser (TGA)and horizontal tube furnace (HTF) heating rate of 150 ⁰ C/min Introduction ReviewObjectivesExperimentalResultsConclusionFuture work  TGA Heating rate is miles away from reality yet give fundamental combustion information TGAHTF, replicates TGA char production

Introduction ReviewObjectivesExperimentalResultsConclusionFuture work Drop Tube Furnace, High heating rate, short resident times ( ms) and 1600 ⁰ C  High heating rate and high combustion temperatures, close to reality

Introduction ReviewObjectivesExperimentalResultsConclusionFuture work What Effect does CO ₂ have on volatile yield?  There is no particle size effect at both conditions except for the smallest particle size at 1100 ⁰ C  The impact of oxy-fuel firing is pronounced at 1100 ⁰ C due to volatile –char gasification reaction but low at low temperatures due to Poor thermal conductivity

Why do we need to maximise Nitrogen (N ₂ ) yield in the volatile phase?  Char N ₂ contribute to NOx formation  Beneficial to oxy-fuel due to high transformation of N ₂ into the gaseous state at high temperature Introduction ReviewObjectivesExperimentalResultsConclusionFuture work

TGA Combustion reactivity of biomass chars at 375 ⁰ C  CO2 does not have effect on the combustion reactivity of the chars at low temperature hence the burnout is identical with air fired condition  Insignificant particle size effect is seen in during burnout in both conditions except for the smallest particle size. Introduction ReviewObjectivesExperimentalResultsConclusionFuture work

Impact of low char combustion temperature on kinetic parameters Introduction ReviewObjectivesExperimentalResultsConclusionFuture work  Variation is less due to poor thermal conductivity effect of CO 2 compared with that of N 2

Benefits of Co-firing (TGA Analysis) SamplesNitrogen chars and Air combustion CO ₂ chars and 21%O ₂ /79% CO ₂ combustion 1st order rate constants90% burnout time1st order rate constants90% burnout time (min¯)(min)(min¯)(min) sawdust char 700C Kleinkopje (KK) HTF char 1000C saw/KK char blend 50:50wt%) Predicted sawKK char blend  Improved burnout of blend but slightly more pronounced under oxy- fuel condition  Strong synergetic effect: an indication of interactions Introduction ReviewObjectivesExperimentalResultsConclusionFuture work

Introduction ReviewObjectivesExperimentalResultsConclusionFuture work Moving close to Reality, does biomass char still affect coal char burnout?

Introduction ReviewObjectivesExperimentalResultsConclusionFuture work Improved coal char combustion, effect of catalytic inorganic metals in biomass fuel

Introduction ReviewObjectivesExperimentalResultsConclusionFuture work conclusions  High reactivity observed for CO ₂ at high temperature due to gasification reaction.  No particle size effect, can use bigger particle size for pulverised biomass fuel combustion systems  Biomass improved coal combustion. There is chemical interaction between the two fuels during co-combustion  Inorganic minerals in biomass catalysed coal char combustion

Introduction ReviewObjectivesExperimentalResultsConclusionFuture work Completing PhD, what is left to be done  Devolatilisation of sawdust in DTF at different temperatures and different residence times  DTF char burnout  Co-firing at different temperatures and residence times at the two atmospheres  DTF burnout of blend chars  TGA burnout analysis of DTF chars (sawdust and blend chars) in air and oxy- fuel conditions

Introduction ReviewObjectivesExperimentalResultsConclusionFuture work