Controlled Pyrolysis of Cotton-gin Trash Froilan L. Aquino and Sergio Capareda Biological and Agricultural Engineering Texas A&M University, College Station, TX.

Pyrolysis Process Definition Pyrolysis – thermal conversion under complete absence of oxidant Typical product yields at different pyrolysis modes. Mode Conditions Liquid (%) Char Gas Fast Moderate temperature, around 500C, short hot vapor residence time ~ 1 second 75 12 13 Intermediate Moderate temperature, moderate hot vapor residence time ~ 10-20 s 50 20 30 Slow Low temperature, around 400C, very long residence times 35 Source: EIA, 2007

Objectives To determine the effect of temperature and reaction time on the solid, liquid and gaseous products of CGT; To evaluate the quality of the solid, liquid and gaseous products by proximate and HHV Analysis; To identify conditions to maximize the solid (char), liquid and gaseous products from the pyrolysis of CGT; and To perform a simple energy and mass balance on the biomass after pyrolysis.

Methodology Pyrolysis Tests A) Sample preparation (Drying and Grinding) B) Pyrolysis Runs Temperature: 500, 600, 700, 800C Reaction Time: 30 min Purge Gas Flow rate: 1000 cm3 min-1 Biomass used: 50 g

Pyrolysis Set-up The modified pyrolysis setup used for cotton-gin trash. (A) Purge gas (N2), (B) Gas flow meter 1, (C) Digitally-controlled furnace, (D) tar/moisture trap, (E) Condenser, (F) Thermocouple reader, (G) Liquid collector, (H) moisture trap, (I) Gas flow meter 2, (J) Sampling/exhaust port, and (K) Gas analyzer. Pyrolyzer/Reactor B C A D E G H I J K F Hood

Results and Discussion Pyrolysis Products Solids/Char Liquid Products Gaseous Product

Results - Char 1. Solid (Char) Analysis:

Results - Char Char Analysis (HHV in MJ/kg): HHV-1 = ave. high heating value of char from preliminary tests. HHV-2 = ave. high heating value of char from the modified tests. Note: Both HHV measured at pyrolysis period of 30 min. Note: CGT has heating value of 15.5 MJ/kg Temp (ºC) HHV-1 HHV-2 500 - 19.23 600 16.90 20.33 700 21.96 21.64 800 18.30 19.70

Results - Bio-oil 2. Liquid (Bio-oil) Analysis Temperature (°C) ρave – average density (including water and char) Temperature (°C) ρave[a] (g cm-3) Average pH HV (MJ kg­1) 500 0.982 4.7 2.430 600 0.992 5.7 2.336 700 1.015 6.6 2.011 800 1.009 7.6 2.020

Results - SynGas 3. Gaseous Product Analysis

Results - SynGas Gaseous Product Analysis – Total Hydrocarbon (THC) 500 °C 600 °C 700 °C 800 °C C1 = methane C4 = butane C2 = ethane C5 = pentane C3 = propane C6 = hexane

Results - SynGas Pyrolytic gas production from CGT. 500 30.060 1.229 Temperature (°C) MWn (g mol-1) ρ (kg m-3) at STP Mave (g) VG (m3) VG (L) GP (L kg-1) 500 30.060 1.229 17.29 0.0141 14.072 281.27 600 29.682 1.213 14.69 0.0121 12.105 241.82 700 27.908 1.141 19.31 0.0169 16.928 338.52 800 27.033 1.105 19.98 0.0181 18.086 361.59

Maximum Conditions Char production: 43 wt.% - 600ºC, 30 min* 2) Liquid Production: 36 wt.% - 800ºC, 30 min 31 wt.% - 600ºC, 30 min

Maximum Conditions 3) Gas production: 58 wt.% - 800ºC, 60 min 35 wt.% - 800ºC, 30 min (no loss) 28 wt.% - 800ºC, 30 min (20 % loss)

Energy and Mass Balance Modified Test The heating values of each pyrolytic product from CGT at different pyrolysis temperatures Temperature (°C) HHV (MJ kg-1) Total HHV (MJ kg-1) Gas HHV (MJ m-3) Char Liquid Gas 500 19.23 2.43 2.74 24.40 3.37 600 20.33 2.34 5.28 27.94 6.41 700 21.64 2.01 6.78 30.43 7.73 800 19.70 2.02 4.26 25.98 4.71

Energy and Mass Balance A. Input Process/Material Energy (kJ) 1) Preparation, EG 139 2) Pyrolysis, EP 5184 3) Biomass, EB 774 TOTAL 6097 B. Output Temperature (°C) Energy (kJ) E output (kJ) Char Liquid Gas 500 367.84 33.27 47.11 448 600 370.60 40.04 77.59 488 700 365.74 27.60 131.43 525 800 300.75 29.84 85.10 416

Energy and Mass Balance Modified Test (mass balance) Typical mass balance for CGT pyrolysis at different temperatures.

Summary and Conclusions Product yield as affected by pyrolysis temperature and time. The production of char decreased with increased pyrolysis temperature and time. The gaseous product yield increased with increased pyrolysis temperature and time. The bio-oil yield increased at a certain temperature and then leveled off (with slight changes) as the temperature was further increased. Longer pyrolysis period resulted to decreased bio-oil yield.

Summary and Conclusions The highest char yield of almost 40 wt.% was observed at lower pyrolysis temperature and shorter reaction time. The highest liquid yield of approximately 30-35 wt.% was determined in the lower pyrolysis temperature and shorter reaction time. The highest gaseous product yield of around 35-58 wt.% was observed at higher pyrolysis temperature and longer reaction time. The Temperature and Time can be Programmed Depending on the Desired Output Product.

Summary and Conclusions Both pyrolysis process resulted to an improved liquid production of up to 36 wt.% which was not determined in previous studies using CGT as feedstock. The process was considered energy intensive due to the high amount of energy input (6100 kJ) while generating a maximum energy output of only 10%. After disregarding the energy used for preparation and pyrolysis, the energy losses ranged from 30-46% while the energy of the output represent between 55-70% of the input energy from CGT.

Acknowledgement Cotton Foundation TAMU Texas AgriLife Research TAMU Cotton Chair (Dr. Parnell) Varisco Court Gin Co. Bryan, TX Jimmy Ropolo, El Campo, TX Co-majors (Joan Hernandez) BAEN Student Workers (Ordway, Bert, Jared & Greg)