Slow pyrolysis of cassava peel by using a top-lit up-draft pyrolysis (TLUD-Pyro) reactor

Publication Type

Poster

Authors

Latif, S; Intani, K; Müller, J

Year of publication

2016

Published in

Books of Abstracts

Page (from - to)

49

Conference name

6th International Symposium on Energy from Biomass and Waste

Conference location

Venice, Italy

Conference date

14-17 November 2016

Keywords

Biochar, cassava peel, Pyroplysis, Slow-pyrolysis, TLUD

Cassava (Manihot esculenta) is widely grown in the tropical countries for its starchy root. Cassava is an important source of calories for human and is often cultivated for starch production, which is a high value commodity for various industries such as brewing, paper, adhesives, plastics and chemicals. Cassava peel generated from the starch manufacturing industries is of great concern to the environment due to cyanogenic glucosides contents. It is usually considered as waste. The residue is abundant but underutilized. Therefore, this huge amount of biomass residue can be converted to biochar, bio-oil and pyrolysis gas using a low-cost slow pyrolysis unit. This can improve the resource use efficiency and help farmers to generate additional income by selling the valuable products from the pyrolysis process.

In the present study, a laboratory-scale top-lit up-draft pyrolysis (TLUD-Pyro) reactor was used for the slow pyrolysis of dried cassava peel from Tanzania. The TLUD-Pyro stove was designed using SolidWorks CAD software and constructed with ST 12.03 steel. This system combined micro-gasification and pyrolysis technology for the thermochemical conversion of biomass. The system is thermally self-sustainable for biomass conversion. The energy for pyrolysis reaction was provided by the excess heat (up to 680 °C) from the gasification process (TLUD). A pyrolysis reactor was attached to the after-burner of the TLUD. The pyrolysis chamber was filled with 500 g chopped cassava peel (<1 cm particle size) and sealed with a heat resistant silicone. Woodchips were used as a fuel for the gasifier (TLUD). Type K Thermocouples were used to monitor the temperature profiles during the gasification and pyrolysis processes. In this study, the gaseous products coming out of the pyrolysis chamber were condensed at 0 ^°C while the non-condensable pyrolysis gas was combusted by using a burner. Temperature was continuously monitored and reached to a maximum level 985, 704 and 444 ^°C for gasifier, combustion zone (After-burner) and pyrolysis reactor, respectively. When the pyrolysis temperature reached above 100 ^°C, the pyrolysis gas was combustible for about 30 min providing heat measured above the flame up to 860 °C. The energy from the pyrolysis gas showed its potential to be used as an alternative source of heat for cooking activities. During the slow pyrolysis of cassava peel an average yield of biochar, condensate, and pyrolysis gas were found to be 36%, 25%, and 39%, respectively. The valuable products obtained from the prototype TLUD-Pyro stove including the biochar, condensate (bio-oil and wood vinegar) and pyrolysis gas can be used for agricultural, environmental and energetic applications. Biochar can be used as a solid fuel or soil improver. It can also be activated and used as an adsorbent for the removal of pollutants. Aqueous fraction of the condensate (wood vinegar) has potential uses as food additive and pest repellent. Bio-oil can be extracted from the condensate and converted to both energetic (heat, electricity, synthesis gas) and chemical products (acids, alcohols, phenols, etc.). Pyrolysis gas can be used for energetic applications (heat and electricity generation). Cassava peel was found to be a good feedstock for the TLUD-Pyro reactor in order to produce biochar, bio-oil and pyrolysis gas. However, it was found that the biomass from cassava peel had a high thermal stability during the thermochemical conversion. This might be explained by the high content of starch (up to 35%) in the biomass. A detailed characterization of the biochar, condensate and pyrolysis gas is required in order to exploit their utilization.