Pyrolysis Of Mixed Waste Plastics Research Articles

Optimisation of Process Parameters to Maximise the Oil Yield from Pyrolysis of Mixed Waste Plastics

The study sought to optimise process parameters of thermal pyrolysis of mixed waste plastic (MWP) to maximise pyrolytic oil yield. High-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS) were used as feedstocks for pyrolysis. Response surface methodology (RSM) and Box–Behnken design (BBD) were used to optimise the pyrolysis process. The optimisation was carried out by varying three independent variables, namely, reaction temperature (460–540 °C), residence time (30–150 min), and size of MWP feedstock (5–45 mm), to increase the liquid oil yield. A BBD matrix was used to generate the design of the experiments, and 15 experiments were conducted. The highest liquid oil yield of 75.14 wt% was obtained by optimising the operating parameters, which were a reaction temperature of 535.96 °C, a reaction time of 150 min, and a feedstock particle size of 23.99 mm. A model was developed to determine the relationships among the independent variables, and analysis of variance (ANOVA) was used to investigate their impact on maximising oil yield. ANOVA results showed that the temperature and residence time had the maximum impact on oil yield, followed by feedstock size. Physicochemical analysis of the properties of the plastic pyrolytic oil (PPO) revealed that the crude PPO obtained from the MWP had higher water (0.125 wt%) and sulfur content (5.12 mg/kg) and lower flash point (<20 °C) and cetane index (32), which makes it unsuitable for use as an automobile fuel. However, these issues can be resolved by upgrading the PPO using different posttreatment techniques, such as distillation and hydrotreatment.

Ga-modified zeolites to convert mixed waste plastics to benzene, toluene, ethylbenzene, and xylene (BTEX)-enriched oil through a dielectric barrier discharge plasma-modified reactor

Non-thermal plasma (NTP)-assisted catalytic pyrolysis is a promising technology for producing benzene, toluene, ethylbenzene, and xylene (BTEX) from mixed waste plastics. A primary challenge in this approach is the need to achieve a high selectivity for the target products. To address this challenge, this study focused on the preparation of Ga-modified zeolites. The results showed that Ga loading was effective in increasing BTEX yields for the zeolites of USY, β, and HZSM-5 by 7.49%, 4.72%, and 8.63%, respectively. Among these zeolites, HZSM-5-Ga-N2 was the most suitable for catalyzing the NTP-assisted pyrolysis reaction to produce BTEX hydrocarbons, with a maximum selectivity of 63.19% and a maximum yield of 31.84%. This was because the pore of HZSM-5 matched the ring size of BTEX, and NTP improved the distribution of Ga2O3 active sites, allowing more acidic active sites to participate in the catalytic reaction. This work provides an applicable solution to increase the selectivity and yield of BTEX from NTP-assisted pyrolysis of mixed waste plastics with Ga-loading catalysts.

Uncovering the differences: A comparison of properties of crude plastic pyrolytic oil and distilled and hydrotreated plastic diesel produced from waste and virgin plastics as automobile fuels

Thermal pyrolysis of mixed waste plastics (MWP) and mixed virgin plastics (MVP) containing high-density polyethylene (HDPE), polypropylene (PP) and polystyrene (PS) at 1:1:1 ratio were performed in a 20L pyrolytic pilot-scale batch reactor. The pyrolysis was conducted at 540 °C temperature and atmospheric pressure for 6 h. The properties of the produced crude plastic pyrolytic oil (CPPO or crude PPO), such as higher heating value (HHV), cetane index, lubricity, flash point, etc, obtained by pyrolysis of MWP, and MVP samples, confirmed that the oil was not suitable for direct use as an automobile fuel. Therefore, CPPO was further refined by vacuum distillation to match the properties of standard diesel more closely, herein referred as distilled plastic diesel (DPD). Some of the properties of DPD did not meet the standard diesel criteria, which is why DPD was further refined through a hydrotreatment process to ensure it was directly comparable to standard diesel, herein referred as hydrotreated plastic diesel (HPD). The fuel properties of all crude PPO, DPD and HPD were analysed and compared to standard (consumer) diesel according to Australian, ASTM and EN standards to assess their suitability as automobile fuel. With the aid of a 20L pyrolizer and a pilot-scale distillation and hydrotreatment plant, this comprehensive study demonstrated the importance of distillation and hydrotreatment for CPPO and found that DPD and HPD are well suited for use as drop-in diesel fuels. The results signify that with the right choice in refining technologies, waste plastics can be used as a source of automobile fuel.

Human Health Risk Assessment of a pilot-plant for catalytic pyrolysis of mixed waste plastics for fuel production

Dioxins, PCBs and VOCs are the main hazardous chemicals emitted by gaseous streams from catalytic pyrolysis of waste plastics. In this work we propose a methodology to assess toxic and cancer risk under uncertainty, due to inhalation and ingestion of these chemicals by considering complex scenarios, as repeated start-ups and short continuous operation that may occur in a pilot-plant. Different simulation tools are combined to evaluate the expected concentration of pollutants in the environmental compartments and food. Hazard Index and Cancer Risk remain under the threshold for both dioxins (HI < 0.012, CR < 5.03 10−7) and PCBdl (HI < 1.3 10−7, CR < 2.49 10−12) in all the simulated scenarios, also for the worst case of children ingesting vegetables and meat and uncertainty factors up to 1000. Different results are obtained for VOCs since repeated leakages during the pilot-plant operation are possible. All the risk indexes for benzene are under the threshold (HI < 0.175, CR < 1.41 10−7); acute toxic risk due to inhalation and cancer risk due to ingestion of grain/vegetables are over the threshold if all the uncertainties are considered. Lesson learned: HHRA is important also during scale-up; pilot-plants for pyrolysis of waste plastics must always be equipped with all the abatement systems designed for the final plant.

Experimental Study on the Performance of an SI Engine Fueled by Waste Plastic Pyrolysis Oil–Gasoline Blends

Pyrolyzed waste plastic-based green fuel has been reported to be used as an alternate fuel for diesel engines. Some of the main challenges for implementing this in current automotive technology include evaluating engine performance, emission, noise vibration harshness (NVH), and knock characteristics of this fuel. This study focuses on the engine performance of poly-ethylene terephthalate (PET)-based waste plastic oil (WPO) at varying engine speed conditions. The pyrolysis of mixed-waste plastic was carried out at 300 °C in a fixed-bed reactor. Physicochemical properties such as viscosity, density, calorific value, sulfur, and research octane number (RON) of the plastic fuel and its blends with gasoline were analyzed using ASTM standard test methods. The WPO was blended with two different types of gasoline (RON88 and RON90) at 10, 20, and 30%, and was tested in a spark-ignition (SI) engine. The experimental results showed that different WPO–gasoline blends can be used in an SI engine without any engine modifications, and the performance indicators for different blends were found to be close to that of pure gasoline. The brake power and brake specific fuel consumption (BSFC) were found to be 4.1 kW and 0.309 kg/kW h, respectively. The 10% WPO and 90% RON90 blend produced optimal engine performance at 3500 rpm.

The effect of Kankara zeolite-Y-based catalyst on some physical properties of liquid fuel from mixed waste plastics (MWPs) pyrolysis

The effect of Kankara zeolite-Y-based catalyst on some physical properties of liquid fuel obtained from the pyrolysis of mixed waste plastics has been investigated. Combination of zeolite-Y, metakaolin, aluminum hydroxide and sodium silicate all synthesized from Kankara kaolin from Kankara in Katsina State, Nigeria, was used as catalysts. In this study, fifteen experiments were conducted: fourteen set of 200 g of the mixed waste plastics comprising 27 wt% HDPE, 33 wt% LDPE, 13 wt% PP, 18 wt% PS, 9 wt% PET were de-polymerized with catalyst and a set without catalyst (thermal pyrolysis) in a batch reactor. The maximum temperatures for catalyzed and thermal pyrolysis in this study are 350 °C and 490 °C, respectively. The catalyst components were characterized by XRF analysis, while their textural properties were determined from BET technique by N2 adsorption at − 196 °C. A constant catalyst-to-plastic ratio of 1:10 was used for all the catalyzed reactions. The catalyzed liquid sample with the optimum yield of 46.7 wt% was obtained using 10.49 wt%, 32.42 wt%, 27.09 wt% and 30 wt%, of zeolite-Y, metakaolin, aluminumhydroxide and sodium silicate, respectively, while the thermal pyrolysis gave a liquid yield of 66.9 wt%. Furthermore, the liquid products obtained for both thermal and catalytic cracking at optimum yield were characterized for their suitability as fuel. The properties determined were density, viscosity, fire point, and calorific value. The results suggest that catalytic pyrolysis produced liquid products whose properties are comparable to conventional fuels (gasoline and diesel oil) and more suitable for use as liquid fuel than that produced through thermal pyrolysis.

Effect of injection timing on performance and emission characteristics of single cylinder diesel engine running on blends of diesel and waste plastic fuels

Abstract Environmental concern, increasing fossil fuel demands and depleting fossil fuel reserves have caused interests in the search for alternate fuels for internal combustion engines. Waste plastics are indispensable materials in the modern world and application in the industrial field is continually increasing. In this context, waste plastic solid is currently receiving renewed interest. the recycling of the waste plastic for renewable energy generation is receiving more attention nowadays. The present study deals with utilization of waste plastic pyrolysed oil in single cylinder diesel engine with varying injection timing. The pyrolysis of mixed waste plastic was carried out at 400oC-550oC in a fixed bed reactor. The physic chemical properties such as calorific value density, viscosity, cloud point, pour point, flash point of the plastic fuel and its blends with diesel (PF10,PF20,PF30) was analysed using standard methods and found under ASTM standards. To see the effect of injection timing on performance and emission, a single cylinder diesel engine was run on plastic fuel blends at the two different angles (10o retard and the 8o advance before the TDC). The results showed that at advanced condition BTE, CO, UHC, CO2 and smoke increased while BSFC and NOx decreased with the increasing load.

Effect of ZnCl2-activated biochar on catalytic pyrolysis of mixed waste plastics for producing aromatic-enriched oil

ZnCl2-activated biochar produced by one-step (impregnated by a 40% ZnCl2 solution, defined as Zn/C-I) and two-step (impregnated by a 40% ZnCl2 solution and microemulsion, defined as Zn/C-II and Zn/C-III, respectively) methods was used to catalyze the pyrolysis of mixed waste plastics (polyethylene, polyethylene, and polystyrene) to comparatively study their catalytic effect on aromatic-enriched oil production. The catalytic mechanism was discussed. The results show that ZnCl2-activated biochar showed high catalytic selectivity to aromatics during the pyrolysis of plastics at 500 °C, and the content of aromatics was increased to 47.5, 46.8, and 42.4% when respectively catalyzed by Zn/C-I, Zn/C-II, and Zn/C-III. Two-ring aromatics were significantly enriched, which accounted for 90.7, 73.1, and 87.7% of the aromatics in Zn/C-I, Zn/C-II, and Zn/C-III catalytic pyrolysis oils. 1,3-Diphenylpropane was the major component of the oils, and its proportion was 19.4, 11.5, and 15.9% in Zn/C-I, Zn/C-II, and Zn/C-III catalytic pyrolysis oils, respectively. The introduced Zn species could increase the surface acidity by forming Lewis acid sites (Zn-L), which increased aromatic yields by promoting the Diels–Alder reaction, hydrogen transfer, and dehydrogenation processes. Zn-L also promoted the condensation reaction of aromatics. Compared with Zn/C-I, Zn/C-III treated by ZnCl2 microemulsion could reduce 41.8% of coke on the catalysts owing to its larger pore size, while maintaining a relatively high oil quality.

10.2478/s11814-009-0305-5

We did a kinetic analysis of the thermal degradation of wax materials obtained from pyrolysis of mixed waste plastics using the nonisothermal weight loss technique with heating rates of 10, 20, 30 and 40 °C/min. The weight loss data according to degradation temperature were analyzed by using the integral method based on Arrhenius form to obtain the kinetic parameters. To verify the effectiveness of the proposed kinetic analysis method, the experimental values were compared with those of the numerical integration results using kinetic parameters obtained in this work. It was found that the proposed kinetic analysis method gave reliable kinetic parameters of the thermal degradation of wax materials obtained from pyrolysis of mixed waste plastics.

Kinetics of the thermal degradation of wax materials obtained from pyrolysis of mixed waste plastics

We did a kinetic analysis of the thermal degradation of wax materials obtained from pyrolysis of mixed waste plastics using the nonisothermal weight loss technique with heating rates of 10, 20, 30 and 40 °C/min. The weight loss data according to degradation temperature were analyzed by using the integral method based on Arrhenius form to obtain the kinetic parameters. To verify the effectiveness of the proposed kinetic analysis method, the experimental values were compared with those of the numerical integration results using kinetic parameters obtained in this work. It was found that the proposed kinetic analysis method gave reliable kinetic parameters of the thermal degradation of wax materials obtained from pyrolysis of mixed waste plastics.