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Abstract:The exponential increase of plastic production produces 100 million tonnes of waste plastics annually which could be converted into hydrocarbon fuels in a thermal cracking process called pyrolysis. In this research work, a direct current (DC) thermal plasma circuit is designed and used for conversion of low density polyethylene (LDPE) into diesel oil in a laboratory scale pyrolysis reactor. The experimental setup uses a 270 W DC thermal plasma at operating temperatures in the range of 625 • C to 860 • C for a low density polyethylene (LDPE) pyrolysis reaction at pressure = −0.95, temperature = 550 • C with τ = 30 min at a constant heating rate of 7.8 • C/min. The experimental setup consists of a vacuum pump, closed system vessel, direct current (DC) plasma circuit, and a k-type thermocouple placed a few millimeters from the reactant sample. The hydrocarbon products are condensed to diesel oil and analyzed using flame ionization detector (FID) gas chromatography. The analysis shows 87.5% diesel oil, 1,4-dichlorobenzene (Surr), benzene, ethylbenzene and traces of toluene and xylene. The direct current (DC) thermal plasma achieves 56.9 wt. % of diesel range oil (DRO), 37.8 wt. % gaseous products and minimal tar production. The direct current (DC) thermal plasma shows reliability, better temperature control, and high thermal performance as well as the ability to work for long operation periods.

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This paper demonstrates an RF thermal plasma pyrolysis reaction apparatus that achieves 89 wt.% reaction conversion yield with no tar content. The demonstrated experimental apparatus consists of a 1100 W RFVII Inc. (104 Church St, Newfield, NJ 08344, United States) @ 13.56 MHz RF thermal plasma generator, a Navio matching network, intelligent feedback controller, and an 8-turn copper RF-ICP torch embedded in a 12 L thermochemical reactor. The intelligent feedback controller optimizes the thermal performance based on feedback signals from three online gas analyzers: CO, CO2 and NOx. The feedback controller output signal controls the RF thermal plasma torch current that provides real-time temperature control. The proposed reaction system achieves precise temperature profiles for both pyrolysis and gasification as well as increases end-product yield and eliminates undesired products such as tar and char. The identified hydrocarbon liquid mixture is 90 wt.% gasoline and 10 wt.%. diesel. The 8-turn RF-ICP thermal plasma torch has an average heating rate of +35 °C/min and a maximum operating temperature of 2000 °C and is able to sustain stable flame for more than 30 min. The reaction operating parameters are (550–990 °C τ = 30 min for pyrolysis and (1300 °C τ = 1 sec) for the gasification process. The identified hydrocarbon liquid products are 90 wt.% of a n-butyl-benzene (C6H5C4H9) and oluene (C7H8) mixture with less than 10 wt.% decane diesel fuel (C10 H22). Comsol simulation is used to assess the RF-ICP thermal plasma torch’s thermal performance.

Thermochemical processes use heat and series of endothermic chemical reactions that achieve thermal cracking and convert a wide range of solid waste deposits via four thermochemical processes to hydrocarbon gaseous and liquid products such as syngas, gasoline, and diesel. The four thermochemical reactions investigated in this research article are: incineration, pyrolysis, gasification, and integrated gasification combined cycle (IGCC). The mentioned thermochemical processes are evaluated for energy recovery pathways and environmental footprint based on conceptual design and Aspen HYSYS energy simulation. This paper also provides conceptual process design for four thermochemical processes as well as process evaluation and techno-economic analysis (TEA) including energy consumption, process optimization, product yield calculations, electricity generation and expected net revenue per tonne of feedstock. The techno-economic analysis provides results for large scale thermochemical process technologies at an industrial level and key performance indicators (KPIs) including greenhouse gaseous emissions, capital and operational costs per tonne, electrical generation per tonne for the four mentioned thermochemical processes.

Thermoplastics are converted to hydrocarbon fuels in a chemical reaction called pyrolysis. The work highlights the energy consumption using Aspen HYSYSV8.8 simulations in each process stage starting with granulation, preheating, pyrolysis reactor and condensation as major process steps concluding that the highest required heat duty which is around 61% in the pyrolysis reactor thus having the highest operating cost. Aspen HYSYS is used to calculate energy consumption in each stage. The design is 10 tonne/hour of thermoplastic mixture. Pyrolys is reactor operating temperatures are 550°C at atmospheric pressure. The condensation system shows recovery duty of 3.4 MW of which can be used to heat cold streams. Pinch analysis was also carried out to design a heat exchanger network (HEN) between hot and cold streams in order to reduce energy consumption. Heat recovery from pyrolysis reactor effluent gases shows possible3.439 MW recovery in a 10 tonne per hour pyrolysis plant.

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