An Aspen plus process simulation model for exploring the feasibility and profitability of pyrolysis process for plastic waste management.

Plastics, integral to various human activities, have led to a surge in production, posing substantial challenges in waste management. The persistent non-biodegradability of plastics, taking over a century to decompose, necessitates exploration into technologies for their conversion into sustainable fuels. Pyrolysis, an oxygen-free thermal decomposition process, emerges as a promising avenue for producing liquid fuels from plastic waste. This study's primary objective is to create and validate an Aspen Plus simulation model, enabling techno-economic evaluation and sensitivity analysis of pyrolysis for converting waste plastics into liquid fuels. Critical parameters-temperature, retention time, and particle size-are examined for their impact on product yield and quality. The methodology involves model development, validation, and subsequent simulations with various waste plastic types under different pyrolysis conditions. Experimental investigation using waste high-density polyethylene (HDPE) in an auger reactor yielded an oil yield of 61.29%, char yield of 10.98%, and syngas yield of 27.73% at 525 °C. Post-validation against this data, the model explored four plastic types, revealing significant influences of plastic type and reactor temperature on product yields. Polystyrene (PS) at 500 °C produced the highest oil content at 83.69%, with temperature affecting yield before secondary cracking. Techno-economic evaluation for a pyrolysis plant processing 10,000 tons of waste HDPE annually indicated a minimum selling price (MSP) of $302.50/ton, a net present value (NPV) of $12,594,659.7, and a 1.03-year payback period. This study provides crucial insights for designing an economically viable and sustainable pyrolysis process, guiding further research and industrial implementation.

Hydrodynamic performance assessment of photocatalytic reactor with baffles and roughness in the flow path: A modelling approach with experimental validation.

Purification of wastewater is essential for human being as well as for the flora and fauna, and sustainable environment. Photocatalytic reactor with TiO2 coated layer can be used to degrade the pollutants but without proper pollutant mass transfer in the reactive surface, photocatalytic reactor decreases its effectiveness. The baffles and rough surface in the flow path can improve the fluid mixing to enhance pollutant mass transfer to improve the reactor's performance. In this study, a computational fluid dynamics (CFD) model has been developed to investigate the effect of four top baffles and three rough surfaces (semi-circular, triangle, and rectangle) on pressure drops, mass transfer and the hydrodynamic performance of the reactor. The experimental investigation was carried out using Formic Acid (FA) as pollutant in feed water for model validation. The simulated result varies only within 5% with the experimental data of FA concentration versus feed flow rate and fluid velocity. The model was run at fluid velocity of 0.15 m/s and 0.5 m/s (Reynolds number of 2150 (laminar flow) and 7500 (turbulent flow), respectively. The simulation result shows that the addition of baffles and roughness on the reactive surfaces increases the turbulent kinetic energy (minimum increase 8%) and consequently increases the mass transfer (maximum increase 37%) of the pollutant. The highest wall shear was observed to be 40 Pa when both square and triangular elements were used as roughness elements at turbulent flow condition. The results also shows that the highest pressure-drop of 8 kPa was found when the square roughness element was used at turbulent flow condition. Overall, the photocatalytic reactor performance is significantly enhanced by the application of combined baffles and roughness elements in the reactive surface.

End-of-life tyre conversion to energy: A review on pyrolysis and activated carbon production processes and their challenges.

The number of end-of-life waste tyres has increased enormously worldwide, which is one of the non-biodegradable Municipal Solid Waste (MSW) piling up in an open space for a long time. Every year, various types of tyres are released in the environment from different vehicles, such as trucks, buses, cars, motorcycles, and bicycles, which negatively impact the environment. Nowadays, waste tyres are treated in several ways, whereas thermochemical conversion is one of them, including combustion, gasification, incineration, and pyrolysis. Many literatures revealed that pyrolysis is a more environmentally friendly process than others since it can convert waste tyres into crude oil, char, and syngas without emitting harmful gases. In this study, the pyrolysis of tyres and the chemical activation of tyres are reviewed in terms of their kinetic behaviour. According to the literature, the most influential factors of the pyrolysis process are reactors, temperature, heating rate, residence time, feedstock size and catalyst. As the main ingredient of the tyre is rubber, tyre pyrolysis starts from 300 °C and completely decomposed nearly 550 °C. It can be found from literature that Pyrolysed tyre can produce 30-65% oil, 25-45% char and 5-20 % gas. It is also explained how the properties of active carbon (AC) are affected by activating conditions, including activation temperature, agent, the ratio of reagent mixture and others. Generally, pyrolytic char has surface area between 20 and 80 m2/g, whereas tyre-derived activated carbon's (TDAC) surface area varied from 90 to 970 m2/g. For large surface area and porous structure, TDAC has large application in purification and energy storage sector. The individuality of this article is to depict the entire pathway of AC production from waste tyres. The findings of this literature review help to improve technologies for producing activated carbon from waste tyres pyrolysed char.

Advancements in algal membrane bioreactors: Overcoming obstacles and harnessing potential for eliminating hazardous pollutants from wastewater.

This paper offers a comprehensive analysis of algal-based membrane bioreactors (AMBRs) and their potential for removing hazardous and toxic contaminants from wastewater. Through an identification of contaminant types and sources, as well as an explanation of AMBR operating principles, this study sheds light on the promising capabilities of AMBRs in eliminating pollutants like nitrogen, phosphorus, and organic matter, while generating valuable biomass and energy. However, challenges and limitations, such as the need for process optimization and the risk of algal-bacterial imbalance, have been identified. To overcome these obstacles, strategies like mixed cultures and bioaugmentation techniques have been proposed. Furthermore, this study explores the wider applications of AMBRs beyond wastewater treatment, including the production of value-added products and the removal of emerging contaminants. The findings underscore the significance of factors such as appropriate algal-bacterial consortia selection, hydraulic and organic loading rate optimization, and environmental factor control for the success of AMBRs. A comprehensive understanding of these challenges and opportunities can pave the way for more efficient and effective wastewater treatment processes, which are crucial for safeguarding public health and the environment.

Waste plastics pyrolytic oil is a source of diesel fuel: A recent review on diesel engine performance, emissions, and combustion characteristics.

Most waste plastics can be converted into automobile fuel through the pyrolysis process. Plastic pyrolysis oil (PPO) has a heating value comparable with commercial diesel. The properties of PPOs depend on parameters such the plastic and pyrolysis reactor types, temperature, reaction time, heating rate, etc. This study reviews the performance, emissions, and combustion characteristic of diesel engines fuelled with neat PPO, PPO and diesel blends, and PPO with oxygenated additives. PPO has higher viscosity and density, higher sulphur content, lower flash point, lower cetane index and an unpleasant odour. PPO displays a higher delay in ignition during the premixed combustion phase. The literatures reported that diesel engines can run with PPO without any modification to the engine. This paper reveals that the brake specific fuel consumption can be lowered by 17.88 % by using neat PPO in the engine. Brake thermal efficiency can be reduced by 17.26 % while blends of PPO and diesel are used. Some studies say NOx emission can be reduced up to 63.02 %, however, others indicate that it can be increased up to 44.06 % compared to diesel when PPO is used in engines. The highest reduction in CO2 emission was found to be 47.47 % using blends of PPO and diesel; conversely, the highest increase was documented as 13.04 % when only PPO is used as fuel. In summary, PPO has very high potential as a substitute for commercial diesel fuel through further research and by improving its properties through post-treatment processing such as distillation and hydrotreatment.

Thermodynamic Analysis of a Flat Plate Solar Collector with Different Hybrid Nanofluids as Working Medium-A Thermal Modelling Approach.

In this study, the performance of hybrid nanofluids in a flat plate solar collector was analysed based on various parameters such as entropy generation, exergy efficiency, heat transfer enhancement, pumping power, and pressure drop. Five different base fluids were used, including water, ethylene glycol, methanol, radiator coolant, and engine oil, to make five types of hybrids nanofluids containing suspended CuO and MWCNT nanoparticles. The nanofluids were evaluated at nanoparticle volume fractions ranging from 1% to 3% and flow rates of 1 to 3.5 L/min. The analytical results revealed that the CuO-MWCNT/water nanofluid performed the best in reducing entropy generation at both volume fractions and volume flow rate when compared to the other nanofluids studied. Although CuO-MWCNT/methanol showed better heat transfer coefficients than CuO-MWCNT/water, it generated more entropy and had lower exergy efficiency. The CuO-MWCNT/water nanofluid not only had higher exergy efficiency and thermal performance but also showed promising results in reducing entropy generation.

Pyrolytic conversion of waste plastics to energy products: A review on yields, properties, and production costs.

In recent years, about 370 million tonnes of waste plastic are generated annually with about 9 % recycled, 80 % landfilled and 11 % converted to energy. As recycling of waste plastics are quite expensive and labour-intensive, the focus has now been shifted towards converting waste plastics into energy products. Pyrolysis of waste plastic generates liquid oil (crude), gas, char and wax among which liquid oil is the most valuable product. In this review, emphasis has been given on the pyrolysis products yield from both thermal and catalytic pyrolysis and the factors that affect pyrolysis products yield. The use of homogenous catalysts, for example AlCl3, can significantly improve the quality of waste plastic pyrolytic oil (WPPO), reduce time and energy consumption of the process, and help remove the contaminants of waste plastic. This study also thoroughly reviewed physico-chemical properties of WPPO to understand their thermal stability, elemental composition, and functional groups. Although liquid oil exhibits comparable heating value with commercial fuel (diesel/petrol), for example higher heating value of Polypropylene (PP) and Polyethylene (PE) are 50 and 42 MJ/kg which is between 42 and 46 MJ/kg for commercial diesel the other properties depend on several parameters such as plastic and pyrolysis reactor types, temperature, feed size, reaction time, heating rate and catalysts. A techno-economic analysis indicate that the liquid oil production cost could be about 0.6 USD/l if plant capacity is ≥175,000 million litres/year with a breakeven of 1 year. After-treatment of WPPO through distillation and hydrotreatment is recommended for improving the physio-chemical properties comparable to commercial fuel to use in automobile applications. This paper will be a valuable guide for stakeholders, and decision and policy makers for proper utilization of waste plastics.