Reduction in CO Emission from Small Reciprocating Engine Operated with Wood Gasifier by Mixture LHV Changing

Hiroshi Enomoto () and Ryo Nakagawa
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Hiroshi Enomoto: Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan
Ryo Nakagawa: Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan

Energies, 2023, vol. 16, issue 6, 1-14

Abstract: In order to exchange the wood biomass energy for electric power with small capacity and high efficiency, it is most effective to use a reciprocating engine operated with a wood gasifier. On the other hand, such a small-capacity system is often installed in urban areas. Therefore, strict emission regulation should be observed. Normally, as the low heating value (LHV) of bio-syngas is small, the engine should be operated with a stoichiometric mixture to achieve a maximum power density. However, the emission with a stoichiometric mixture contains much unburned CO. This means that a stoichiometric mixture operation shows low efficiency and can’t observe the regulations. In this report, a mechanism of the unburned CO is considered, and a method to reduce the unburned CO ratio is shown with experimental results. In the experiment, a commercial reciprocating engine (4-stroke, modified single cylinder) is used. The bio-syngas, a producer gas from a fixed bed gasifier, is produced by a self-made wood pellet gasifier (fixed bed, auto thermal down-draft). The bio-syngas flow rate is calculated with the nitrogen ratio between input air and bio-syngas. The LHV is adjusted with the city gas (as an alternative to methane) and hydrogen. The CO volume ratio of the exhaust from the engine is more than 3 v% when the excess air ratio of bio-syngas/air mixture is 1.3, as the LHV of bio-syngas is less than 5.0 MJ/m 3 -LHV. On the other hand, the CO volume ratio of the exhaust under operation of the mixture, the bio-syngas, and methane with more than 7.0 MJ/m 3 -LHV was less than 0.2 v%. The CO in the exhaust with low LHV fuel means that the combustion is not finished in the chamber. The unburned ratio could be predicted in consideration of the gap/clearance as crevice, the temperature boundary layer, and the quenching distance.

Keywords: thermal boundary layer; extinction distance; excess air ratio; bio-syngas; low heating value (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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