Air gasification of biomass and polyethylene using a staged gasifier - - PowerPoint PPT Presentation

Speaker: Yong-Seong Jeong

• Univ. of Seoul

6th International Conference on Sustainable Solid Waste Management

Air gasification of biomass and polyethylene using a staged gasifier in lab scale and pilot scale

• 1. Introduction
• 2. Lab scale experiment

3.Pilot scale experiment

• 4. Summary

Contents

• 1. Introduction

Source: Premium Engineering 2016

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Introduction: Gasification

Tar is one of the main obstacles of gasification

 Typical definition of tar All organic contaminants with a molecular weight larger than that of benzene  Tar problems Tar condenses during gasification at reduced temperatures, thus blocking and fouling process equipments such as engines and turbines

 Tar tolerances for gas engine and turbines

Application Allowable tar Conc. (mg/m3) Reference Gas Engine 50 − 100 Milne & Evans (1998) Gas Turbine 5 Milne & Evans (1998) SOFC 1000 − 10000 Basu (2010) Methanol synthesis via Fischer-Tropsch 0.1 Bui et al. (1994)

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Introduction: Tar

Primary method : Treatments inside the gasifier

• Proper selection of the operating conditions

(temperature, equivalence ratio, pressure)

• Use of a proper bed additives or a catalyst (Ni-based catalyst)
• Proper gasifier designs (fixed bed, fluidized bed)

Fuels Gasifier + Tar Removal Tar free gas Gas cleanup Application Air/Steam/O2 Dust N, S, halogen Compounds

Introduction: Tar removal methods-Primary method

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Secondary method: Gas cleaning after gasifier

• Tar cracking either thermally or catalytically
• Physical methods such as the use of a cyclone, a filter, a scrubber

Gasifier Tar Removal Application Air/Steam/O2 Downstream cleaning (Tar, dust, N, S, halogen Compounds) Tar Tar free gas Fuels Gas cleanup

Introduction: Tar removal methods-Secondary method

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Tar removal apparatus

Installation and

• peration cost is

very high  OLGA tar removal system-ECN

Introduction: Typical tar removal equipment

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Water Air, O2 or Steam Chiller (water) Silo Screw feeder Additives

Fluidized bed reactor

Thermocouples Distributor Distributor Thermocouples Condensers Cyclone Hot filter Pre-heater Electric furnace

Tar cracking reactor

Gas engine

Introduction: Two-stage UOS gasification process

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Introduction: Aims

Aims of the research

1) Production a producer gas with low tar and high H2 from the three-stage dried sewage sludge (DSS) and polyethylene (PE) gasification in lab-scale. 2) In-situ regeneration of activated carbon used as tar removal agent 3) Production a clean producer gas from wood pellet, DSS, and palm kernel shell (PKS) in a pilot-scale two-stage process.

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Introduction: Aims

• 2. Lab scale experiment

 Characteristics of feed materials

Proximate analysis (wt%) Ultimate analysis (wt%) Moisture 7.27 ± 0.01 Carbon 29.88 ± 0.86 Volatile matter 50.30 ± 0.02 Hydrogen 4.61 ± 0.08 Fixed carbon 7.73 ± 0.35 Nitrogen 4.34 ± 0.15 Ash 34.70 ± 0.32 Oxygen 25.41 ± 1.06 Sulfur 1.06 ± 0.03 LHV (MJ/kg) 11.74 LDPE

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Experiment: Feed material

Proximate analysis (wt%) Ultimate analysis (wt%) Moisture 0.1 ± 0.01 Carbon 85.2 ± 0.16 Volatile matter 99.9 ± 0.01 Hydrogen 14.6 ± 0.07 Fixed carbon N.D. Oxygen 0.2 ± 0.01 Ash N.D. Sulfur N.D. LHV (MJ/kg) 40.3 DSS

 Characteristics of AC

Proximate analysis (wt%) Moisture Volatile matter Fixed carbon Ash 0.9 ± 0.02 22.45 ± 0.60 64.95 ± 1.17 17.77 ± 0.73 Ultimate analysis (wt%) Carbon Hydrogen Nitrogen Oxygen Sulfur 78.51 ± 1.06 0.58 ± 0.01 0.43 ± 0.09 2.32 ± 0.02 0.39 ± 0.01 ICP analysis (ppm) Al Ca Fe Mg K 13173 13071 12977 3673 465 BET analysis Surface area (m2/g) Micro pore volume (cm3/g) Total pore volume (cm3/g) Mean pore diameter (nm) 1125.7 0.5380 0.6192 2.2004

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Experiment: Activated carbon

Screw feeders Water Air

Chiller (water, 10)

Additives

Fluidized bed reactor

Thermocouples

Distributor

Sintered distributor Thermocouples Condensers Cyclone Hot filter Burner Clean gas sample : GC-TCD and FID Electrostatic precipitator Pre-heater Electric heater Raw gas sample Silo

Vibrator

gas sample gas sample Thermocouples

Auger reactor Fluidized bed reactor Tar cracking reactor

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Experiment: The three-stage gasifier

Auger reactor Fluidized bed reactor Tar cracking reactor

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Experiment: The three-stage gasifier

 Gasification conditions

• Gasification time: approximately 60 min
• Amount of natural olivine used as the fluidizing bed material: 2200 g, 150−300 μm
• Flow rate of air: 15 NL/min

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Experiment: Gasification conditions

Run1 Run2 Run3 Run4 Run5 Feed material DSS DSS PE PE PE Auger reactor temperature (°C) 645 659 503 495 502 Fluidized bed reactor temperature (°C) 807 811 828 823 820 Tar-cracking reactor temperature (°C) 814 820 811 820 820 Equivalence ratio 0.35 0.34 0.30 0.30 0.32 Feed rate (g/min) 13.11 13.11 4.92 4.92 4.54 AC (g) 1600 1500 1500 Regeneration X X X X O

Composition (vol%) Run1 Run2 Run3 Run4 Run5 N2 51.6 46.3 69.5 52.5 52.8 CO2 14.5 9.1 11.1 5.0 4.7 H2 14.1 28.5 6.9 26.72 26.8 CO 10.3 12.3 2.8 7.8 8.1 CH4 6.4 3.8 8.7 7.9 7.7 C2H2 0.15 0.005 N.D. N.D. N.D. C2H4 2.13 0.023 5.9 0.002 0.001 C2H6 0.18 N.D. 0.4 0.001 N.D. Benzene 0.39 0.014 1.1 0.002 0.002 >Benzene 0.069 0.004 0.1 N.D. N.D. LHV (MJ/Nm3) 6.81 5.63 9.48 6.25 6.12 Impurities in producer gas Tar contents (mg/Nm3) 2573 142 4528 N.D. 2 NH3 in producer gas (ppmv) − 521 H2S in producer gas (ppmv) − 670  Compositions of producer gas

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Results: Gasification results

N.D.: not detected, −: beyond detection range (NH3: 3000, H2S: 2000 ppmv)

 Tar removal mechanism on AC

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Results: Tar removal mechanism over activated carbon

• Thermal or catalytic cracking reaction: pCnHx → qCmHy + rH2
• Steam reforming reaction: CnHx + nH2O → (n+x/2)H2 + nCO
• Dry reforming reaction: CnHx + nCO2 → (x/2)H2 + 2nCO
• Carbon formation reaction: CnHx → nC + (x/2)H2

Tar cracking reactor Fluidized bed reactor Distributor Feed material Activated carbon Adsorption Cracking & Reactions

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Results: Tar-free producer gas

Tar Tar Tar Tar Tar

 In-situ regeneration method Simply stopping feeding → oxidation of coke on activated carbon Gasifying agent (air) will react with tar & coke on AC Textural properties of activated carbon will be recovered

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Experiment: In-situ regeneration

Pore diameter (nm)

1 10 100

dVp/dlog(dp) (cm3/nm/mg)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 Virgin AC Regenerated AC (Run5) Spent AC (Run4)

 Textural properties of virgin and regenerated ACs

Surface area (m2/g) Micropore volume (cm3/g) Total pore volume (cm3/g) Mean pore diameter (nm) Virgin 1125.7 0.5380 0.6192 2.2004 Run4 573.86 0.2597 0.2820 1.9505 Run5 938.75 0.4471 0.4792 1.9322

 Pore size distributions of ACs

• Large numbers of micro- and mesopores

disappeared after gasification

• The AC after regeneration considerably recovered

textural properties

micropores mesopores

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Results: Regeneration results

• 3. Pilot scale experiment

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Experiment: Pilot scale equipment

Quenching system Fluidized bed reactor Tar cracking reactor Flare stack

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Experiment: Feed materials

Feed materials Wood pellet DSS PKS Proximate analysis (wt%) Moisture content 8.34 ± 0.24 7.07 ± 0.31 1.1 ± 0.06 Volatile matter 91.32 ± 0.28 51.53 ± 1.39 86.5 ± 0.23 Fixed carbon 0.18 ± 0.10 3.99 ± 0.28 10.1 ± 0.07 Ash 0.16 ± 0.07 37.41 ± 1.02 2.4 ± 0.22 Ultimate analysis (wt%) Carbon 55.26 ± 0.05 31.32 ± 0.11 49.7 ± 0.02 Hydrogen 7.28 ± 0.01 4.56 ± 0.08 5.9 ± 0.02 Nitrogen 0.32 ± 0.02 4.72 ± 0.02 0.7 ± 0.01 Oxygen 36.96 ± 0.08 20.72 ± 0.31 36.5 ± 0.09 Sulfur 1.27 ± 0.01 LHV (MJ/kg) 18.5 13.2 20.5

 Characteristics of feed materials

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Results: Composition of producer gas

Composition (vol%) Wood pellet DSS PKS N2 42.2 43.2 43.4 CO2 13.0 13.6 14.6 H2 23.5 20.3 20.5 CO 15.9 17.0 18.0 CH4 5.2 5.8 3.61 C2H2 0.03 0.04 N.D. C2H4 0.04 0.07 0.03 C2H6 0.001 0.001 0.01 Benzene 0.05 0.05 0.06 >Benzene 0.001 0.01 0.001 LHV (MJ/Nm3) 6.07 6.09 5.71 Tar contents (mg/Nm3) 42 37 34  Composition of producer gas

N.D.: not detected

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Results: Auto-thermal operation

Time (min)

100 200 300 400 500 600 700

Temperature (oC)

200 400 600 800 1000 1200 Fluidized bed reactor Tar cracking reactor

 Auto-thermal operation

Start feeding Turn off preheater

Maintain ~800 °C

• 4. Summary

Summary

 Effect of AC on tar removal and the hydrogen production

• Tar content in producer gas: 2573 → 142 mg/Nm3 (DSS)

4528 → 0 mg/Nm3 (PE)

• Hydrogen content: 14.1 → 28.5 vol%(DSS)

6.6 → 26.7 vol% (PE)  In-situ regeneration method recovered textural properties of AC

• Surface area: 1125.7 (virgin) → 938.75 m2/g
• Micropore volume: 0.5380 (virgin) → 0.4471 cm3/g

 Pilot scale

• Production of a producer gas with low tar and high H2 without scrubber & EP
• Auto-thermal operation during test

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6th International Conference on Sustainable Solid Waste Management

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