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A comparative study on syngas production from crude glycerol by utilizing DC arc plasma Dr. Andrius Tamoši ū nas Plasma Processing Laboratory, Lithuanian Energy Institute 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018

Content • Glycerol as a source for energy production • Aim of the work • Use of plasma and its classification • Experimental setup & process parameters • Results & Discussion • Conclusions

Glycerol (C 3 H 8 O 3 ) – a source for energy production Source: http://www.ebb ‐ eu.org/stats.php# Glycerol accounts to 10 wt.% of the total biodiesel production, but in some cases it can amount to 30 wt.%.

Aim of the work • Experimental investigation of crude glycerol conversion to syngas using DC arc plasma. • Process performance quantification in terms of: – Producer gas composition; – H 2 and CO yield; – H 2 /CO ratio; – Lower heating value (LHV); – Carbon conversion efficiency (CCE); – Energy conversion efficiency (ECE); – Specific energy requirements (SER).

What is Plasma? Why Plasma? Use of plasma because of: Limitations of conventional utilization methods (DR, High temperatures (enthalpy) (10 3 – 10 4 K); SR, pyrolysis, PO, AR, SWG, etc.): • High chemical reactivity and kinetics; • Catalyst sensitivity to contaminants; • Neutralization efficiency up to 99.99%; • Its deactivation, expensive materials such as Pt used for • Ecological cleanness; • catalysts preparation; The amounts of unwanted contaminants are • High investment and exploitation costs; • reduced, (NO x , CO x , HC and etc); Requirement of external high ‐ temperature heat sources • No need of catalyst; • inducing thermal absorption reaction; Fast start ‐ up – sut ‐ down of the process; • Requirement of high pressures; • Easy adoption for various materials treatment; •

Classification of plasma Plasma Low temperature High temperature (Non ‐ equilibrium plasma) (Equilibrium plasma) T < 5 x 10 4 K T > 5 x 10 4 … 10 8 Thermal plasma Non ‐ thermal plasma Examples: (quasi ‐ equilibrium) (Non ‐ equilibrium) Sun, T e ≈ T i ≈ T g ≤ 2 x 10 4 K T e >> T i ≈ T g ≈ 300 ~ 10 3 K Stars Universe, etc. Examples: Examples: Direct barrier discharge Arc discharge Corona discharge, etc. RF discharge MW discharge, etc.

Experimental setup & process parameters Fig. 1 Experimental setup of glycerol conversion system: plasma torch (1), chemical reactor (2), plasma ‐ forming gas feeding line (3), electrical circuit (4), glycerol feeding line (5), and product gas analysis (6). Table 1. Experimental conditions for crude glycerol conversion. Parameter/Case Water vapor + glycerol Air + glycerol Arc current, A 160 160 Arc voltage, V 350–390 350 Power, kW 56–62.4 45.6–56 Glycerol flow rate, g/s 5.6 5.6 Gasifying agent flow rate, g/s 2.9–5.15 2.7–4.9 T plasma , K 2800 4400 Plasma torch thermal efficiency ( η ) 0.69–0.76 0.6–0.74

Results & Discussion Producer gas composition, H 2 /CO ratio and LHV • Effect of gasifying agent ‐ to ‐ glycerol ratio was the only one parameter for both cases enabling to compare the obtained experimental results between. H 2 /CO ratio: Water vapour case – 2.07 Air case – 1.07 LHV syngas (MJ/Nm 3 ): Water vapour case – 9.82 Air case – 7.32 Fig 2. Elemental composition of the producer gas and the H 2 /CO ratio.

Carbon conversion & Energy conversion efficiencies              m LHV CO CO CH 2 C H C H C H     syngas syngas      2 4 2 2 2 4 2 6  ECE 100 %, CCE % 12 Y 100 %,      dry gas   P m LHV 22 . 4 C plasma fuel fuel Fig 4. Effect of gasifying agent ‐ to ‐ glycerol ratio on the carbon Fig 5. Effect of gasifying agent ‐ to ‐ glycerol ratio on the energy conversion. conversion efficiency. Carbon conversion efficiency (CCE%): Energy conversion efficiency (ECE%): Water vapour plasma – 100 Water vapour plasma – 70.8 Air plasma – 75.7 Air plasma – 48.46

Specific energy requirements (SER) SER (kJ/mol): Water vapour plasma – 191.6 (or 1.78 kWh/kg) Air plasma – 266.45 (or 2.5 kWh/kg) P SER  , m syngas Fig 6. Effect of gasifying agent ‐ to ‐ glycerol ratio on the specific energy requirements.

Comparison between results Table 1. Summary of the crude glycerol conversion to syngas with various plasma methods. This study This study Parameter/Reference Yoon et al. [1] Zhang et al. [2] (water vapor + glycerol) (air + glycerol) Discharge type DC arc DC arc MW Rotating DC arc Power, kW 62.4 56 2 24.1 Thermal efficiency ( η ), (%) 76.1 74.1 n.d. 40 Gasifying agent Water vapor (83%)/Air Air Air/steam Ar/water in glycerol (17%) H 2 , (vol.%) 51.16 29.00 57 56 CO, (vol.%) 24.74 27.00 35 38 H 2 /CO ratio 2.07 1.07 1.63 1.47 LHV syngas , MJ/Nm 3 9.82 7.32 12 11 CCE, (%) 100 75.7 ~100 100 ECE, (%) 70.8 48.46 62* 66 SER, (kJ/mol) 191.6 266.45 n.d. n.d. *This value was named as the cold gas efficiency. The power of the plasma was not added to the formula presented. If the power were added, the ECE would be lower. 1. Yoon, S.J., Yun, Y.M., Seo, M.W., Kim, Y.K., Ra, H.W., Lee, J.G.: Hydrogen and syngas production from glycerol through microwave plasma gasification. Int. J. Hydrogen Energ. (2013). https://doi.org/10.1016/j.ijhydene.2013.09.001 2. Zhang, M., Xue, W., Su, B., Bao, Z., Wen, G., Xing, H., Ren, Q.: Conversion of glycerol into syngas by rotating DC arc plasma. Energy (2017). https://doi.org/10.1016/j.energy.2017.01.128

Conclusions • Crude glycerol conversion to syngas was investigated using thermal DC arc plasma at atmospheric pressure; • Two separate gasifying mediums were used: water vapor and air; • Crude glycerol gasification in water vapor plasma gave a better process performance and syngas quality over the air plasma gasification in terms of the H 2 /CO ratio, H 2 and CO yield, CCE, ECE, and SER.

Dr. Andrius Tamoši ū nas E ‐ mail: Andrius.Tamosiunas@lei.lt