Investigation on Effect of Equivalence Ratio on the Performance of a Downdraft Gasifier – An Experimental Approach

Md. Sanowar Hossain, Mujahidul Islam Riad, Showmitro Bhowmik, Sanjay Paul, Sadman Soumik Nuhash
Abstract

Biomass renewable energy is an important and diverse choice for transitioning towards a more sustainable energy system. It makes use of organic waste materials, reduces greenhouse gas emissions, and provides a source of energy that is both renewable and reliable. Using a biomass gasification device to make combined heat and power has become more popular because it is seen as one of the most promising ways to use renewable energy. Downdraft gasifiers that use only biomass as fuel have already been the subject of a lot of studies. Downdraft gasifiers are preferred to other gasifiers due to their simple construction, low cost, and minimal tar production, especially in developing countries for power and thermal applications. The equivalence ratio is one of the many factors that contribute to the performance of a gasifier. In this study effect of the equivalence ratio on the performance study of a small-scale downdraft gasifier has been investigated. The cold gas efficiency shows an increasing pattern with an increasing equivalence ratio in the range of 0.16 to 0.38 and was found to be optimum at 0.345. At an equivalence ratio of 0.345 the LHV was found to be 5.95 MJ/m3 and the cold gas efficiency was 43.19%. In this investigation, Mango wood (Mangifera indica) pellets of size 50-60 mm are used as biomass feedstock.

Conclusion

In this study, the impact of the equivalency ratio on the air flowrate, lower heating value, and cold gas efficiency in a pilot 5 KW gasifier was examined. In this study, it was discovered that maintaining an equivalence ratio between 0.199 and 0.345 was crucial for improved gasification efficiency and LHV. Due to the altered composition of CO, H2, and CH4 gas, the gasifier's effectiveness declines when the gasification process occurs outside of this specific ratio. However, the impact of temperature, moisture content on cold gas efficiency and LHV is not taken into account in this study. Furthermore, because the gasifier unit is a lab scale downdraft gasifier, additional advancements in the feeding system and gas cleaning system must be implemented in order to obtain a much better result. From this study it is clear that gasification of mango wood shavings and pellets is a cheap but good alternative source of energy with its moderate LHV. The downdraft gasifier is also proven to be a reliable but cheap energy conversion device. So it can be employed to small scale

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