Influence of reactor and condensation system design on tyre pyrolysis products yields

This study investigates the effect the pyrolysis reactor and the condensing system type have on the tyre derived oil (TDO) and DL-limonene yield, as well as benzothiazole concentration in the TDO. All the experiments were performed at 475 °C and three technologies were investigated, fixed bed reactor (FBR), bubbling fluidised bed reactor (BFBR) and conical spouted bed reactor (CSBR), with the latter being the reactor that provided the highest TDO yield (58.2 wt.%). Furthermore, the CSBR enhances DL-limonene production due to its excellent features (low residence time of volatiles and high heat and mass transfer rates), which minimize secondary cracking reactions. Moreover, in order to maximize the TDO retention efficiency and selectively reduce the concentration of certain heteroaromatic species, two types of condensation systems were evaluated: tube-andshell condenser (indirect contact) and quenching condenser (direct contact). The quenching condenser not only promoted the condensation efficiency for DL-limonene, but also reduced the concentration of benzothiazole in the collected TDO. Indeed, the direct contact between water (fed into the quencher) and the hot volatile stream favours the dissolution of some polar heteroaromatic species, thus reducing the nitrogen and sulphur content in the TDO and increasing the applicability of TDO as fuel.This research was supported by the Recycling and Economic Development Initiative of South Africa (REDISA) and the National Research Foundation (NRF). It was also financed by the Ministry of Economy and Competitiveness (CTQ2016-75535-R) and the Ministry of Science, Innovation and Universities of the Spanish Government (RTI2018-101678-B-I00), the European Regional Development Fund (ERDF), the European Commission (HORIZON H2020-MSCA RISE- 2018. Contract No. 823745), the Basque Government (IT1218-19) and the University of the Basque Country (UFI 11/39). The authors acknowledge that any opinions, findings, conclusions or recommendations expressed in this material are the authors' own, and the sponsorscannot accept any liability whatsoever in this regard

Pyrolysis process optimisation to maximise limonene production from waste tyres

Thesis (PhD)--Stellenbosch University, 2018.ENGLISH SUMMARY: Globally, increasing waste tyre generation is a major economic and environmental challenge. Economic challenges include depleting natural resources and rising crude oil prices from which synthetic rubbers are derived. Environmental problems are mainly associated with large piles of the waste tyres. Waste tyres are characterised by resistance to degradation under typical environmental conditions, high pollution emissions from fires, soil and water pollutants leakage, breeding grounds for venomous insects, such as, snakes and spiders. Among conventional methods used to reduce waste tyre stock piles include: i) blending the tyre crumb with asphalt for civil works, such as, road construction, ii) combustion for generation of the electricity and/or steam, iii) and reuse in manufacturing of plastic and rubber products, such as, filler. However, the rate of waste tyre generation surpasses consumption capacity by these techniques. Moreover, these techniques are yet to be commercialised as they are fraught with economic and environmental challenges. These challenges include capital and operating costs of the production facilities and toxic compound emissions elimination requirements. One of the promising processing methods for waste tyres valorisation is to produce valuable chemicals (mainly DL-limonene) through increasing their content in the tyre derived oil (TDO) and then use remaining TDO for energy recovery. In the current study modification of the existing waste tyre pyrolysis processes, and development of the novel methods critical to maximising the DL-limonene yield in the pyrolysis oil, was achieved. Additionally, improvement in the total TDO yield and quality [high quality characterised by high DL-limonene content but less heteroatom compounds (nitrogen-, oxygen- and sulphur-compounds, mainly benzothiazole)] was observed. DL-limonene is a natural occurring compound and its composition is high in citrus fruit peels derived-oil at more than 80 wt.%. The market price of the DL-limonene ranges between 2.5 and 30 US$/kg depending on the purity. DL-limonene is an important component in the industrial formulations of solvents, resins, and adhesives. While benzothiazole is a main component in the processing additives used in the manufacturing of the tyres. The approach of the current study entails investigating i) various means to maximise DL-limonene yield in the pyrolysis reactor, ii) improving the DL-limonene yield from condensation of the hot pyrolysis volatiles, and iii) substantially reducing the production of most of the heteroatom compounds (nitrogenous, oxygenous and sulphurous containing compounds) to obtain TDO consisting high amounts of DL-limonene. This approached allowed study of the effect of i) temperature, ii) heating rate, iii) residence time of the hot volatiles in the hot reaction zones, and iv) condensation type and cooling rate of the hot volatiles. These operating conditions parameters were varied by interchanging slow, and flash pyrolysis reactor as well as tube-and-shell condenser and quenching condenser.ISISHWANKATHELO SESIXHOSA: Emhlabeni jikelele, ukukhiqizeka kwemfucuza yamathayi kuyinselelo enkulu yezomnotho, kanjalo nesimo semvelo. Izinselelo zomnotho zihlanganisa ukufinyelela esiphethweni kwamagugu emvelo nokukhuphuka kwamanani amafutha ambiwa emajukujukwini omhlaba ayisisekelo ekwakheni imikhiqizo ehlukahlukene yenjoloba. Ukwanda komthamo wemfucuza yamathayi iyona mbangela enkulu ezingqinambeni zesimo semvelo. Imfucuza yamathayi ayivuthuluki ngokwemvelo ngaphansi kwesimo esijwayelekile, uma yokheleka ngomlilo kukhiqizeka imisizi engcolisa umoya, kumunceke imisizi eyingozi enhlabathi nasemanzi, aba ikhaya lokukhosela lezinambuzane ezonobuthi, njengezinyoka nezicabucabu. Phakathi kwezinqubo ezivamile ezisetshenziselwa ukwehliswa imithamo yemfucuza yamathayi kufaka: i) ukumbandakanya amathayi acoyiselekile (akhishwe ingxenye ewocingo nesakotini) nemikhiqizo ewomgogodla esetstenziswa emisebenzini yezakhiwo, njengokwakhiwa kwemigwaqo, ii) ukushiswa ekuvulelekeni ukuze kukhiqizwe ugesi nomusi, iii) kanye nokusetshenziswa njengesisekelo ekukhiqizeni amathayi, njengesisekelo somkhiqizo. Kodwa-ke, isivinini sokukhiqizwa kwemfucuza yamathayi singaphezu kwengqalasisinda yokuwamumatha nxa kusetshenziswa lezi zindlela esezibaluliwe. Ngaphezu kwalokho, lezi zindlela kusamele ziphucululwe ukuze zimelane nemithamo emikhulukazi njengoba zisabandanyeka ezinselelweni zezomnotho nezemvelo. Lezi zinselelo zibandakanya izindleko zokwakha kanjalo nokuqinisekisa ukusebenza kwengqalasizinda kanye nezidingo sokuvimbela ukusabalala kwemisizi enobuthi. Enye yezindlela enesasasa elikhulu ekuphenduleni imfucuza yamathayi ekubeni imikhiqizo eletha inzuzo ukuba kukhiqizwe imisizi eyigugu (njenge DL-limonene) ngokuba kwenyuswe inani lawo kumkhiqizo osaluketshezi wethayi (TDO) bese kusetshenziswa i-TDO esele njengesiphehli mandla. Kulolu cwaningo kube impumelelo ukuguqula izindlela ezijwayelekile zokushisa imfucuza yamathayi endaweni evalelekile, kanjalo nokusungula izindlela ezintsha eziwumgogodla ekwandisweli kokukhiqizwa kwe-DL-limonene. Okunye okuqasheliwe, ukuthuthukiswa komkhiqizo we-TDO kanye nokucwengeka kwayo [ukucwengeka kungamataniswa nobuningi bengxenye ye-DL-limonene kwi-TDO kodwa ibe semazingeni aphansi imisizi enyama nambana (imisizi enesakhiwo se-nitrogen, -oksijini, kanye nesibabule, kakhulukazi i-benzothiazole]. I- DL-limonene ikhiqizeka ngokwemvelo futhi inani layo oketshezini olukhiqizwa emakhasini ezithelo ze-citrus iba ngobuningi ngaphezu kwengxenye engama-80$/kg kuncike ekucwengekeni kwayo. I-DL-limonene iyisici esibalulekile ezimbonini ezikhiqiza uketshezi lokuhlamba, elokwenza amafutha amakha, kanye nezinamathiseli. Ekubeni i-benzothiazole iyingxenye esemqoka ezithathiseleni ezilekelela ukukhiqizwa kwamathayi. Indlela okwenziwe ngayo lolu cwaningo kubandakanya: i) izindlela ezahlukahlukene zokwandisa isivuno se-DL-limonene esitsheni sokushisa amathayi ngokuvalelekile, ii) ukuthuthukisa isivuno se-DL-limonene ngesikhathi isuswa esimweni somusi siya oketshezini, futhi iii) nokwehla ngamandla kokukhiqizwa kwemisi enyama nambana (eyizingxube ne-nitrogen, -oksijini, kanye nesibabule) ukuze kukhiqizeke uketshezi oluqukethe inani eliphakeme le-DL-limonene. Lendlela yocwaningo ivumele ukuba kubonakaliseke umthelela i) wezinga lokushisa noma ukubanda, ii) isivinini sokwenyuswa kwezinga lokushisa, iii) isikhathi esichithwa uketshezi lisesimweni somusi ezingxenyeni zovuthondaba ezishisayo esitsheni sokushisa amathayi ngokuvalelekile, kanye iv) nendlela yokuguqula futhi kupholiswe umkhiqizo osaketshezi lusuka esimweni somusi. Lezizimo zokusebenza ziguquguqulwe ngokushintshanisa izimbiza zokushisa amathayi ekuvalelekeni ngesivinini esincane, kanye ngokushesha kanjalo kusetshenzisw izitsha ezivumela ukuthintana kanye nokungathintani koketshezi lokubandisa noketshezi lwethayi olusesimweni somusi ngesikhathi sokuphendulwa nokupholiswa kwalo.AFRIKAANSE OPSOMMING: Globaal is die toenemende afvalstofopwekking 'n groot ekonomiese en omgewingsuitdaging. Ekonomiese uitdagings sluit in die verswakking van natuurlike hulpbronne en stygende ruolie pryse waaruit sintetiese rubbers afgelei word. Afvalbande word gekenmerk deur weerstand teen afbreking onder tipiese omgewingsomstandighede, hoë besoedeling veroorsaak deur vure, grond- en waterbesoedelingslekkasie, teelareas vir giftige insekte, soos slange en spinnekoppe. Onder die konvensionele metodes wat gebruik word om afvalstortingstowwe te verminder, sluit in: i) die bandkrummel met asfalt vir siviele werke soos padkonstruksie, ii) verbranding vir die opwekking van elektrisiteit en / of stoom, iii) en hergebruik in die vervaardiging van plastiek en rubber produkte, soos vulsel. Die verlagingskoers van afvalmateriaal oorskry egter die verbruikskapasiteit deur hierdie tegnieke. Daarbenewens word hierdie tegnieke nog nie gekommersialiseer nie, aangesien hulle vol ekonomiese en omgewingsuitdagings is. Hierdie uitdagings sluit in kapitaal- en bedryfskoste van die produksiefasiliteite en eliminasievereistes vir giftige verbinding. Een van die belowende verwerkingsmetodes vir valorisering van afvalbande is om waardevolle chemikalieë (hoofsaaklik dl-limoneen) te produseer deur hul inhoud in die bande afgeleide olie (TDO) te verhoog en gebruik dan die oorblywende TDO vir energieherwinning. In die huidige studie aanpassing van die bestaande afvalpyrolyse prosesse, en die ontwikkeling van die nuwe metodes wat krities is om die dl-limonene opbrengs in die pirolise olie te vermeerder, is bereik. Daarbenewens is die verbetering van die totale TDO opbrengs en kwaliteit [hoë kwaliteit gekenmerk deur hoë dl-limonieninhoud, maar minder iseroatomverbindings (stikstof-, suurstof- en swaelverbindings, hoofsaaklik bensotiasool)] is waargeneem . DL-limonien is 'n natuurlike voorkomende verbinding en die samestelling daarvan is hoog in sitrusvrugte, afgeleide olie by meer as 80% weeg. Die markprys van die dl-limonene wissel tussen 2,5 en 30 US $ / kg afhangende van die suiwerheid. DL-limonene is 'n belangrike komponent in die industriële formulasies van oplosmiddels, harpuis en bindmiddels. Terwyl bensotiasool 'n hoofkomponent is in die verwerkingsadditiewe wat gebruik word in die vervaardiging van die bande. Die benadering van die huidige studie behels die ondersoek van i) verskeie maniere om dl-limonene opbrengs in die pyrolysereaktor te vermeerder, ii) die dl-limonien opbrengs te verbeter deur kondensasie van die warm pyrolyse-vlugtige bestanddele, en iii) die produksie van die meeste van die heteroatomverbindings (stikstofagtige, suurstof- en swaelhoudende bevattende verbindings) om TDO bestaande hoë hoeveelhede dl-limone te verkry. Hierdie benaderde studie van die effek van i) temperatuur, ii) verhittingstempo, iii), verblyf tyd van die warm vlugtige stowwe in die warm reaksie sones, en iv) kondensasie tipe en koelsnelheid van die warm vlugtige stowwe. Hierdie parameters vir die bedryfstoestande is gevarieer deur die stadige, flits-pyrolyse-reaktor sowel as die buis-en-dop-kondensor en die sluiting van die kondensator te wissel

The Contribution of Pyrolysis of Water Hyacinth to South Africa’s Low-carbon and Climate Resilient Economy Transition: A Mini Review

South Africa is a carbon-intensive country, with coal dominating the indigenous energy resource base; however, targets have been set to reduce the national carbon emissions. The transition from coal to cleaner sources of energy generation can be encouraged by the administration of new technologies. Hence, the study aims to review research progress on the pyrolysis of water hyacinth as a tool for the smooth transition to low carbon and climate-resilient economy. Water hyacinth is suitable for energy recovery due to its high carbon content and heating value. The outcome shows that pyrolytic products such as liquid, char and non-condensable gas fractions are beneficial. This paper contributes to policy and research deliberations on promoting and adopting pyrolysis technology in addressing South Africa’s energy crisis and water hyacinth invasion

Methodological Approaches to Optimising Anaerobic Digestion of Water Hyacinth for Energy Efficiency in South Africa

Anaerobic digestion has been identified as a feasible fragment of a bioeconomy, yet numerous factors hinder the adoption of the technology in South Africa. Apart from its energy recovery, other nonmarket advantages support the technology. Though it may be challenging to have a price tag, they provide clear added worth for such investments. With a growing energy demand and global energy transitions, there is a need to sustainably commercialise the biogas industry in South Africa. Most studies are at laboratory scale and under specific conditions, which invariably create gaps in using their data for commercialising the biogas technology. The key to recognising these gaps depends on knowing the crucial technical phases that have the utmost outcome on the economics of biogas production. This study is a meta-analysis of the optimisation of anaerobic digestion through methodological approaches aimed at enhancing the production of biogas. This review, therefore, argues that regulating the fundamental operational parameters, understanding the microbial community’s interactions, and modelling the anaerobic processes are vital indicators for improving the process stability and methane yield for the commercialisation of the technology. It further argues that South Africa can exploit water hyacinth as a substrate for a self-sufficient biogas production system in a bid to mitigate the invasive alien plants