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The aim of this paper is to evaluate the energy self-sufficiency of the tyre pyrolysis process using the pyrolysis gas produced as a heat source. Experimental data on the properties of the tyre and the main pyrolysis products (char, pyrolysis gas, and condensable vapours) have been compiled for a pyrolysis temperature range from 698 to 848 K. The laws of thermodynamics were used to calculate the energy demand of the tyre pyrolysis process, which was divided into heat for the pyrolysis reaction and heat transferred to the carrier gas. The pyrolysis gas was composed of 15 components, and its composition was calculated using a nonstoichiometric equilibrium model. For the temperature range studied, the heat required for the pyrolysis reaction was between 1.41 and 2.16 kJ/g of tyre. In addition, hydrocarbons (71 to 73 wt.%) were the major components in the calculated pyrolysis gas composition. An average lower heating value of 37.3 MJ/kg was calculated for the pyrolysis gas. The heat required for the tyre pyrolysis reaction was provided for burning 30–50% of the pyrolysis gas produced, thus making it self-sustaining. Energy self-sufficiency may not be achieved if the heat losses due to poor reactor insulation are high. However, this problem can be overcome by heating the combustion air using the heat released by the pyrolysis products during cooling. [ABSTRACT FROM AUTHOR]

The aim of this paper is to evaluate the energy self-sufficiency of the tyre pyrolysis process using the pyrolysis gas produced as a heat source. Experimental data on the properties of the tyre and the main pyrolysis products (char, pyrolysis gas, and condensable vapours) have been compiled for a pyrolysis temperature range from 698 to 848 K. The laws of thermodynamics were used to calculate the energy demand of the tyre pyrolysis process, which was divided into heat for the pyrolysis reaction and heat transferred to the carrier gas. The pyrolysis gas was composed of 15 components, and its composition was calculated using a nonstoichiometric equilibrium model. For the temperature range studied, the heat required for the pyrolysis reaction was between 1.41 and 2.16 kJ/g of tyre. In addition, hydrocarbons (71 to 73 wt.%) were the major components in the calculated pyrolysis gas composition. An average lower heating value of 37.3 MJ/kg was calculated for the pyrolysis gas. The heat required for the tyre pyrolysis reaction was provided for burning 30–50% of the pyrolysis gas produced, thus making it self-sustaining. Energy self-sufficiency may not be achieved if the heat losses due to poor reactor insulation are high. However, this problem can be overcome by heating the combustion air using the heat released by the pyrolysis products during cooling.

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Highlights • The residence time distribution of the gas in the pyrolysis plant was studied. • The E curves have been determined for the pyrolysis plant. • Two models have been proposed to simulate the gas flow pattern. • The flow model has been coupled with the kinetic one to study pyrolysis kinetics. Abstract A novel strategy has been proposed for the rigorous kinetic modeling of tyre pyrolysis in a conical spouted bed reactor. A kinetic model coupled with a gas flow model was used in the fitting of experimental results obtained in a bench scale unit in the 425–610 °C range. A gas flow model should be incorporated to account for the delay and mixing phenomena observed in tracer experiments, as these phenomena cause remarkable deviations in the assessment of the kinetic parameters. The gas flow pattern from the reactor to the measuring device was modeled using two different approaches based on ideal flow reactors. Furthermore, two kinetic schemes considering lumped products have been proposed; the first one is based on four parallel independent reactions accounting for the volatile products (gas, liquid, aromatics and tar). The second one considers an additional secondary reaction of aromatic formation from the liquid. The strategy proposed for coupling the kinetics and the flow model led to a suitable fitting of the experimental results, with the performance of the model considering a secondary reaction being slightly better than the simple one. [ABSTRACT FROM AUTHOR]

• Review of the literature on tyre pyrolysis reactors. • A new way of presenting and comparing pyrolytic product yields. • Descriptions and diagrams of various types of reactors for tyre pyrolysis. • An attempted classification of these reactors based on the medium's movement. This article discusses the current use of different pyrolytic reactors, their constructions and operating principles regarding the yields of main products of waste tyre pyrolytic recycling. Whether one makes a larger or smaller profit, or even a loss due to a surcharge being levied on waste tyre recycling, depends on the sale of the pyrolysis products (gas, char, oil), the proportions and market prices of which differ. The cheapest is gas, which can be used as a source of technological heat of energetically self-sufficient pyrolysis or after purification, can be burned in a boiler and converted into heat or electricity. Raw char is not expensive either. It requires upgrading and then, as carbon black, can be re-used for the production of tyres or in the form of improved carbon can be used as an absorber or catalyst. The most expensive is oil, containing mainly aromatic compounds, on the condition that it will not be burned as diesel or liquid fuel. Hence, the oil yields obtained in various types of pyrolysers are given. This review of pyrolysis reactors is organised according to the criterion of charge movement in the reactor and the means of bringing this about. Depending on the method and speed of movement of the load in reactors, they are classified as fixed-bed and movable-bed reactors. The latter group is subdivided, depending on the method of inducing this movement, into pneumatic (bubbling, spouted, circulating or transport fluidised beds), mechanical (rotary kiln, rake, auger, ablative, stirred) reactors and reactors in which the charge moves under gravity. This review focuses on the construction and operating principles of the reactors and the yields of the products of pyrolytic thermal decomposition of scrap tyres. The summary and comparison of main product yields (oil/gas/coal) obtained in different reactors and by different authors, presented in graphical and tabular form, constitute a summary and supplement to this work. [ABSTRACT FROM AUTHOR]

Due to its high total sulphur content and other unfavourable properties, pyrolytic oil obtained as a result of tyres pyrolysis is not suitable for use as motor or heating fuel. Therefore, pyrolytic oil was hydrorefined. Hydrorefined oil was used as a component of light heating oil. A composition was prepared from 30 wt % hydrorefinate with 70 wt % Ekoterm Plus (a commercial oil). Unfortunately, the flash point temperature of the hydrorefinate was too low, and did not allow fuel compliant with the Polish standard PN-C-96024:2011 for L1 light heating oil to be obtained. Therefore, the fraction with boiling point below 180 °C was removed from the hydrorefinate. The residue, with a flash point of 74 °C and a sulphur content of 0.143 wt %, was mixed with Ekoterm Plus and fuels with a hydrorefinate fraction content of 30 and 50 wt % were prepared. The composition containing 30 wt % met the requirements for L1 oil in the whole range of tested parameters. Total sulphur content was 0.092 wt %, specific weight was 856 kg/m3 and closed cup flash point was 64 °C. However, the composition containing 50 wt % hydrorefinate did not meet the requirements regarding sulphur content and specific weight. Sulphur content, specific gravity, and flash point are the parameters limiting the possibility of using hydrorefined pyrolytic oil for composing light heating oils compliant with the mentioned standard.

Waste truck tyre valorization by fast pyrolysis has been performed in a conical spouted bed reactor in the 425–575 °C range. The tyre pyrolysis oil (TPO) yield was found to decrease with increasing temperature whilst the yield of gas increased. The effect of temperature on TPO properties has been studied in order to establish the best possible valorization route. FTIR and chromatographic analysis revealed the presence of some undesired compounds with sulphur, nitrogen or oxygen functionalities (benzotiatholes, nitriles and carboxylic acids amongst others) and an increase of TPO aromaticity with increasing temperature. The carbon and sulphur content and the heating value of the TPO increased with temperature. The simulated distillation showed that approximately 70% of the TPOs produced at 425 and 475 °C correspond to diesel range, whereas that TPO obtained at 575 °C is between diesel and gasoline range. The properties of the TPOs evidenced their potential to substitute conventional fuels. However, some of them need to be improved, i.e., by reduction of the sulphur, nitrogen and aromatic content. Additionally, the TPO obtained at 425 and 475 °C could be an important source of limonene and that at 575 °C of xylenes, although current removal methods present some limitations. [ABSTRACT FROM AUTHOR]

The interest in obtaining alternative fuels from waste sources and at the same time diminishing the impact of waste disposal has drawn attention to scrap tyres' carbon recovery. In order to thermally degrade used tyre rubber, a laboratory pyrolysis system was developed in this work. The installation devised focused on the production of liquid pyrolysates, where shredded rubber was supplied as the feedstock and nitrogen used as the carrier gas to provide an oxygen-free atmosphere. The variables affecting the performance of the process were investigated, including target temperature, heating rate and total residence time. Characterization of the volatile matter released was conducted by means of mass spectrometry to determine the composition of products, and particulate matter analysis to ascertain the aerosol content in the gas stream. The reproducibility of experiments, the influence of the temperature and time, and differences between the vapours before condensation and the exhaust gases are discussed. This work identified that the larger hydrocarbon fragments condense to constitute the oils, whereas the lighter molecules remain as non-condensable gases. This work also identified that the total number of nano-scale particles carried by the exhaust stream varies with temperature; significant changes in the composition of products and particle content were reported at approximately 400°C. The high number of nano-scale solid particulate matter present in the exhaust gases suggests that a thorough treatment for that stream would be required to avoid human health hazards. [ABSTRACT FROM PUBLISHER]

Liquid product from pyrolysis of used tyres has been fractionated in naphtha and residual fraction in a rectification column with 15 theoretical trays. Gas chromatographic analysis of the naphtha indicated that it consisted of: normal + iso paraffins = 7.1%; normal + iso olefins = 8.9%; normal + iso di-olefins = 7.0%; cyclic paraffins = 11.7%; cyclic olefins = 18.6%; cyclic di-olefins = 1.4%; aromatics = 35.6%. The naphtha sulphur was 0.48% from which 0.2% was mercaptane sulphur and the remaining was thiophene sulphur. The most abundant individual hydrocarbon in naphtha was found to be limonene (7.65%). The naphtha research octane number was 93.6, and the motor octane number was 80.0. The physical and chemical properties (sp.gr.=0.937, gross calorific value = 41.4 MJ/kg) of the residual fraction indicated that it can be used as a low sulphur fuel oil (0.81% sulphur) or marine oil. [ABSTRACT FROM AUTHOR]

Abstract: A study has been carried out on the effect of acid catalysts prepared based on HZSM-5, HY and HBeta zeolites on the distribution of volatile products (gas, non-aromatic C5–C10 fraction, aromatic and tar), in the pyrolysis of tyre material carried out in a fast heating microreactor. The results have been compared with those of thermal pyrolysis. The strategies of using the catalyst in situ and reforming the volatiles generated in thermal pyrolysis have also been compared. The use of a catalyst in situ lowers the pyrolysis temperature by 50K (to 723K) and produces a significant increase in the yield of gases and light aromatic , at the expense of a decrease in the yield of non-aromatic . The yield of tar increases only slightly. The shape selectivity of each zeolite has a significant effect and, consequently, HY zeolite leads to the formation of heavier structures that make up the tar and to aromatic , which is favoured by hydrogen transfer capacity. HZSM-5 is more efficient for the formation of gases, although it contributes only to decreasing the molecular weight of aromatic fraction. HBeta zeolite catalyst has an intermediate behaviour. Reforming pyrolysis volatiles at 723K using a HZSM-5 zeolite catalyst efficiently increases (from 2 to 20wt%) the yield of gases, with a high yield of ethene and propene. The yields of BTX fraction are also very high (around 11.5wt%). [Copyright &y& Elsevier]

The increasingly stringent shipping emissions regulations and global decarbonisation movement have prompted the adoption of alternative fuels in the shipping industry. This review presents the performance results and evaluation of alternative fuel engines under low-medium speed operation that has not been considered by existing reviews. This operating regime is typically used in marine propulsion. Relevant articles published by reputable journals were retrieved from scholarly databases and analysed. The evaluated alternative fuels were waste plastic oil (WPO), tyre pyrolysis oil (TPO), biodiesel, ammonia, vegetable oil (VO), and waste lubricant oil (WLO). Neat WPO and TPO demonstrated poorer emissions performances than diesel; alternatively, retarding the fuel injection timing of the WPO engine and blending the TPO with biodiesel had elevated engine performances substantially. As compared to VO degum and blending VO with diesel, VO preheating was a more promising approach to augment engine performance. Ammonia is an attractive candidate owing to its carbon-free chemical composition, but novel technologies are needed to address its terribly high NO x emission. Diesel-like fuel (DLF) derived from WLO produced notably better engine performance than fossil diesel. This review provides insight into liquid alternative fuels performances for low-medium speed engine operation, whose combustion physics is considerably different from high-speed operation. Such understandings are vital to address the current issues regarding marine engine systems, promoting the development of combustion technologies and alternative fuels uptake in marine propulsion. • The low-medium speed alternative fuels engines are reviewed. • Retarding fuel injection timing enhances WPO engine performances. • Nanoparticle's addition suppresses biodiesel NO x formation. • Preheating the VO elevates the overall performances of a low-medium speed engine. • DLF derived from WLO augments overall diesel engine performances. [ABSTRACT FROM AUTHOR]

• Simulation model for tyre pyrolysis in indirectly heated rotary kilns is presented. • Simulation model is validated by comparison against measurement data. • Suitable kiln design for tyre pyrolysis is developed for laboratory-scale mass flow. • Obtained kiln design is successively upscaled by two orders of mass flow magnitudes. • Heat- and mass-transfer characteristics of process are preserved during scale-up. This paper shows how a design of an indirectly heated rotary kiln for the pyrolysis of waste tyres can be developed based on numerical simulation results. The design is up from a laboratory scale tyre particle mass flow to an industrial scale tyre particle mass flow, preserving the heat- and mass-transfer characteristics. This ensures that findings from the laboratory scale mass flow kiln, which is relatively cheap to build and to operate, are meaningful and representative for the industrial scale mass flow kiln. Due to high cost the scaled-up industrial scale design cannot be tested in advance. The development process based on numerical simulation minimizes the risk that scaled up designs do not reach desired performance values. A one-dimensional simulation model is described, enabling simulation of the temperature and mass flow profiles of the particle bed and the gas phase along the axis of the indirectly heated rotary kiln. The simulation considers the bed height development and the influence of fouling. The model is successfully validated against experimental measurements. It is then used to develop several rotary kiln designs covering a tyre particle mass flow range of two orders of magnitude, from laboratory up to industrial scale, fulfilling a variety of pre-formulated requirements. It is found that the kiln designs increase in slenderness as the bed particle mass flow increases, while the inclination and rotational speed can be kept constant. [ABSTRACT FROM AUTHOR]

• Conical Spouted Bed Reactor provided the highest TDO and dl -limonene yield. • Higher residence time of volatiles led to a lower benzothiazole concentration. • Quenching condenser promoted the condensation efficiency for dl -limonene. • TDO collected using the quenching condenser has a lower S and N content. • Quenching condenser is preferred for cooling and condensing the hot volatile stream. 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-and-shell 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. [ABSTRACT FROM AUTHOR]

Due to its high total sulphur content and other unfavourable properties, pyrolytic oil obtained as a result of tyres pyrolysis is not suitable for use as motor or heating fuel. Therefore, pyrolytic oil was hydrorefined. Hydrorefined oil was used as a component of light heating oil. A composition was prepared from 30 wt % hydrorefinate with 70 wt % Ekoterm Plus (a commercial oil). Unfortunately, the flash point temperature of the hydrorefinate was too low, and did not allow fuel compliant with the Polish standard PN-C-96024:2011 for L1 light heating oil to be obtained. Therefore, the fraction with boiling point below 180 °C was removed from the hydrorefinate. The residue, with a flash point of 74 °C and a sulphur content of 0.143 wt %, was mixed with Ekoterm Plus and fuels with a hydrorefinate fraction content of 30 and 50 wt % were prepared. The composition containing 30 wt % met the requirements for L1 oil in the whole range of tested parameters. Total sulphur content was 0.092 wt %, specific weight was 856 kg/m3 and closed cup flash point was 64 °C. However, the composition containing 50 wt % hydrorefinate did not meet the requirements regarding sulphur content and specific weight. Sulphur content, specific gravity, and flash point are the parameters limiting the possibility of using hydrorefined pyrolytic oil for composing light heating oils compliant with the mentioned standard. [ABSTRACT FROM AUTHOR]

Every year about 1.5 billion tyres are discarded worldwide representing a large amount of solid waste, but also a largely untapped source of raw materials. The objective of the method was to prove the concept of a novel scrap tyre recycling process which uses molten zinc as the direct heat transfer fluid and, simultaneously, uses this media to separate the solids products (i.e. steel and rCB) in a sink-float separation at an operating temperature of 450-470 °C. This methodology involved: •construction of the laboratory scale batch reactor,•separation of floating rCB from the zinc,•recovery of the steel from the bottom of the reactor following pyrolysis.