Design, construction and commissioning of a counter-flow rotary pyrolyser

Abstract

Biochar is a sustainable carbon sequestrate and a strong contender for renewable carbon based materials. Biomass is a key commodity which should be exploited in the pursuit of the energy transition due to the wide variety of fossil fuel-like derivatives it can produce. The conversion of biomass to value-added products usually focuses on pyrolysis vapour and noncondensable gases because of their properties and possible use cases. In general, biochar is typically consumed in the process, via combustion, to improve the energy efficiency of these processes. Biochar has a variety of uses that are often is regarded/sacrificed in favour of the aforementioned pyrolysis products, and therefore further analysis and research into biochar would not only benefit the biochar value chain but also aid in understanding the technical and economic uses of the solid pyrolysis product.

Extensive research has been done on biochar and its potential usage, but further practical research into biochar reactor design, construction, and commissioning allows the exploration of biochar generation and the quality of the final product. This will also allow the evaluation of the commissioned experimental apparatus and what further may be modified to produce increased product generation rates and higher product quality. Ignoring biochar as a value-adding product could result in research that develops a suboptimal solution to the energy transition. While biochar may not pose immediate benefits to the pyrolysis process besides additional energy-generating capacity via combustion the resulting product has potential in various areas of great value and therefore additional research into the manufacturing of this value-adding product would be of great benefit.

For the investigation of biochar as a value-adding product, the requirement to produce a potentially large amount of repeatable samples was identified and therefore the requirement for a biochar-focused pyrolysis reactor was identified. The Rotary Kiln Pyrolyser (RKP) In-situ Activation (ISA) was designed, constructed, commissioned and operated.

Throughout the exploration of this research topic the design, construction, commissioning and operation of a biochar-focused reactor was a major objective. This objective was much more difficult to achieve due to the complexities of the processing material and the products produced. Therefore, three prototype versions of the reactor (RKP-ISA) were constructed. The first rendition was prototype 1 where areas of improvement were identified and the lessons learnt from the execution of the first prototype were implemented on the second prototype. Thereafter the second prototype was analysed and further modifications were made to improve the operation and quality of the products produced.

An investigation of the reactor performance was completed via the analysis of the produced biochar samples. Experimental runs were completed utilising the prototype 2 reactor and the quality of the resulting biochar was determined through thermogravimetric and elemental analyses. The biochar analysis indicated that further improvement to the prototype 2 reactor could be implemented to produce improved samples. The modifications made to the reactor resulted in improved biochar stability and quality. The body of work completed demonstrates the advancement of the reactor design and operation, but further investigation can still be completed regarding the modification of biochar for specific use cases and the scaling up of the established process for industrial application.