Gasification Of Plastics Research Articles

Chemical looping gasification of waste plastics for syngas production using NiO/Al2O3 as dual functional material

This study investigates the chemical looping gasification (CLG) of typical waste plastic, polypropylene (PP), using NiO/Al2O3 as a dual functional material, i.e. oxygen carrier (OC) and catalyst. The whole PP-CLG process comprises PP gasification, coke steam oxidation, and OC air regeneration with the first one being the key step for syngas production. Four operation modes for PP gasification were studied and compared, which were distinguished by whether PP and OC were premixed, and whether the heating rate was fast or slow. Significant differences in the product distribution, PP conversion ratio, and the roles that NiO/Al2O3 played were observed under different modes. The highest syngas yield (64.7 mmol/g-PP), carbon conversion (64.9 %), and minimum coke deposition (19.3 %) during PP gasification were achieved through a combination of premixing and fast heating (Type A). Benefitting from its extensive lattice oxygen supply and the effective catalytic cracking capabilities of NiO/Al2O3, Type A accelerated volatile conversion, demonstrated elevated CO selectivity, and reduced tar content, thereby enhancing PP-syngas conversion efficiency. Direct CLG of PP was genuinely realized in Type A, which is different from the traditional pyrolysis-reforming scheme for syngas production. Characterizations further illustrated that the NiO/Al2O3 in Type A produced coke that was the easiest to remove, experienced less sintering, and exhibited the highest lattice oxygen utilization ratio. The findings are expected to provide practical guidance for the choice of a suitable reaction pathway maximizing the waste plastics to syngas conversion.

CO2 intensified supercritical water gasification of waste plastics

To enhance the efficiency and sustainability of the supercritical water gasification of plastic wastes, this study proposed a new approach by introducing CO2 to modify the reaction environment. The gasification performance of waste plastic was comparatively investigated in a mixed fluid consisting of supercritical water and CO2. The results highlighted that gasification efficiency was significantly higher in the mixed fluids than supercritical water alone, with more H2 and CH4 produced through chain reactions initiated by the Boudouard reaction. Increase in key factors, such as reaction temperature, time, and amount of CO2 added, positively influenced plastic gasification. At 700 °C, the carbon conversion rate achieved in mixed fluids was approximately 2.5 times higher than in supercritical water alone. Moreover, the improvement in gasification performance varied among different plastics. Polystyrene exhibited the greatest improvement, followed by polycarbonate, and then polyethylene. These differences stem from the thermal stability of the plastic monomer structures and their interactions with fluid molecules. Simulation results further revealed that the mixed supercritical fluids possess superior solvation ability compared to supercritical water, promoting a more homogeneous reaction.

Experimental Study on Gasification of Banknote Waste: Effects of Torrefaction Pre-Treatment and Co-Gasification on Producer Gas Composition

There is approximately 500,000 tonnes of potential end-of-life banknote waste worldwide, which is increasing by 2-3% per year. This waste consists of cotton and polymer-based banknotes printed on substrates whose raw materials are cotton and polypropylene, respectively. The vast majority of banknotes in circulation are cotton-based banknotes. End-of-life cotton banknotes, which are lignocellulosic biomass, are generally disposed of by landfill and incineration. Studies to reduce the environmental impact of these wastes to find more effective ways of using them is becoming increasingly important. Syngas, which can be used for the production of electricity, energy and chemicals is obtained by gasification of end-of-life cotton banknotes. In this study, DSC and FTIR analysis were performed as part of the characterization tests of the cotton-based banknote sample. As a result of the analysis, the sample was found to have characteristics similar to those of cotton. Within the scope of the investigation of thermal decomposition kinetics, activation energies were calculated as 134-171 kJ/mol by the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. Experiments were performed in a fluidized-bed reactor at 800°C with an inlet H2O/O2 ratio of 25. The content of the producer gas formed during gasification was examined according to the maximum mole fraction achieved. In order to facilitate handling, storage and transportation and to improve fuel quality, the effect of torrefaction pre-treatment on the producer gas content was studied by conducting torrefaction to the cotton-based banknote sample at 250°C for 10 min. To overcome the disadvantages of plastic gasification in terms of operational sustainability, the cotton and polymer-based banknote samples were co-gasified. With the torrefaction pre-treatment, the mole fractions of H2, CO and CH4 increased, while the mole fraction of CO2 decreased. This finding revealed the effects of Boudouard, hydrogasification, water-gas and steam reformation reactions. With the co-gasification of cotton and polymer-based banknote samples, H2, CO and CO2 mole fractions decreased while CH4 mole fraction increased. This result showed that as the proportion of polymer-based banknote samples in the feedstock increased, the conversion efficiency decreased and the hydrogasification reaction became dominant.

Preliminary analysis of an integrated ICE-gasifier plant for power generation from plastic waste material

Abstract The escalating global production of plastic waste is a challenge that must be rapidly addressed, but it also conceals opportunities. Currently, only a minor portion of the worldwide plastic waste is recycled, with the remainder destined for either incineration or landfill. In this context, gasification emerges as a sustainable alternative to conventional waste management methods, offering a substantial reduction in pollutant emissions. Dioxins and furans emissions, in fact, are drastically reduced when compared to incineration. Additionally, in contrast to landfill disposal, gasification allows for the recovery of chemical energy contained in plastic that would otherwise be wasted. The study of plastic gasification is gaining attention and several studies demonstrated feasibility and effectiveness, despite it is not as established as biomass gasification. The present paper aims at taking a step forward by conceptualizing an integrated gasifier-internal combustion engine power plant, operating in a closed-loop system. This layout offers potential benefits from both energetic and environmental points of view, respectively related to the recovery of engine waste gas and CO2 emission reduction. The proposed plant is based on the steam/CO2 gasification technique, which allows the complete conversion of input CO2 into syngas under certain thermochemical conditions. This feature enables the operation of engine and gasifier in a closed-loop system, directly exploiting the exhaust gas to perform plastic gasification. A thermodynamic feasibility study is performed, accounting for the efficiency of the main components, the heat fluxes and the heat absorbed by the endothermic reactions inside the gasifier. The setup of the proposed power plant shows an energy conversion efficiency up to 18% in a pure electric generation scenario and up to 56% in a cogeneration scenario.

Microwave-assisted chemical looping gasification of plastics for H2-rich gas production

Microwave-assisted heating coupled with chemical looping gasification was first proposed for the recycling of plastics into H2 rich gas, achieving a hydrogen conversion efficiency of up to 84.3%. In the experiment, plastic was initially decomposed into hydrocarbon volatiles, followed by the gasification reactions in the presence of an oxygen carrier under vacuum conditions for 10 min. Subsequently, air was introduced for wax removal and oxygen carrier recovery for another 10 min. This study evaluated the chemical looping gasification performances of polypropylene using oxygen carriers NiaFebOx with different Ni/Fe molar ratios (0, 1:40, 1:20, 1:10, 3:20, and 1:5). NiFe20Ox showed the highest gas yield of 81.3 mmol/gPP with an H2 yield of 46.0 mmol/gPP. Among different microwave powers (590 W, 690 W, 790 W, 890 W, and 990 W), 890 W was identified as the ideal microwave power for maximum gas yield and H2 yield. Microwave-assisted heating exhibited high efficiency, achieving a heating rate of 450 °C/min at 890 W, with the microwave oven consuming only 0.182 kWh of electrical power during the entire experiment. In the chemical looping gasification of various plastics (polypropylene, high-density polyethylene, low-density polyethylene, polystyrene, and plastics mixture) over NiFe20Ox under 890 W microwave power, polypropylene yielded the highest gas and H2 production. This study provides a novel approach for efficiently recycling plastics, alleviating environmental pollution and contributing to energy sustainability.

Reactive molecular dynamics simulations of poly(vinyl alcohol) gasification in supercritical carbon dioxide

Supercritical fluid gasification technology, as an environmentally friendly technology, can convert organic components of plastic waste into fuels and chemical materials. Moreover, the utilization of CO2 as the gasification environment holds significant importance for reducing carbon emissions. To better comprehend the microscopic mechanism of plastic gasification in supercritical environment, this sthdy used the Reactive Force Field (ReaxFF) molecular dynamics method to study the gasification process of long-chain poly(vinyl alcohol) molecule in supercritical H2O/CO2 under different reaction conditions. The result illustrated that during the gasification process, poly(vinyl alcohol) initially depolymerized into multiple long carbon chain (C5+) molecular fragments. Subsequently, these fragments underwent cleavage into short carbon chains and various gaseous small molecules. In this reaction, O radicals generated by CO2 decomposition play a crucial role in promoting the cleavage of plastic C–C bonds. In addition, through the analysis of the products and chemical bonds, we found that increasing temperature and prolonging reaction time significantly enhance the gasification efficiency and hydrogen production of plastics. Conversely, exceedingly high pressure inhibits the gasification reaction.

Technoeconomic feasibility of producing clean fuels from waste plastics: A novel process model

Plastic waste is a problematic issue impacting the environment and human health. A proper recycling of plastics to valuable products is highly needed to meet the increase in energy demand. Plastics have high heating value; therefore, the thermochemical recycling of plastic waste is a valid and feasible approach. Recently, ethanol has attracted wide applications such as the conversion of ethanol to olefins, and hydrocarbons. It burns completely and cleanly, where it reduces the emissions of greenhouses compared to the usual fuels. Hydrogen and other higher hydrocarbons are also crucial in meeting the energy demand. In this study, the plastic waste, mainly polyethylene and polypropylene (due to their availability) were gasified using steam gasification process to produce syngas which then was further processed to hydrogen, ethanol, and other valuable liquid hydrocarbons. An alternative design is constructed integrating steam methane reforming (SMR) with plastic gasification to utilize the heat at the outlet of the gasifier and to enhance the syngas heating value. The two models were compared in terms of syngas heating value, energy analysis and economic analysis. The main parameters that have been evaluated are the production rate of fuel per total feedstock, total required heat, overall process efficiency, and fuel levelized production cost. The results indicated that Case 2 generates syngas with a higher heating value of 55 %, produces four times more H2, and comparable amount of ethanol and other fuels than Case 1. The analysis also revealed that Case 2 has a process efficiency that is 3 % better and a 37.5 % lower fuel production cost than Case 1. Overall, the design of Case 2 was found to be more efficient and cost-effective than the Case 1 design.

Microwave-assisted catalytic gasification of mixed plastics and corn stover for low tar, hydrogen-rich syngas production

The challenge for efficient management of post-consumer plastic and biomass waste has grown over the past few decades due to their dramatic increases. In comparison to conventional gasification, microwave-assisted co-gasification of plastics and corn stover offers many benefits, including increased H2 yield and gas components compared to unfavorable char/tar. Nonetheless, for future commercialization of the process and ease of product separation, further reduction of the undesirable tar is necessary, which can be achieved over the catalytic route. In this work, we studied the catalytic effect of magnetite for microwave-assisted co-gasification of corn stover and plastic to make syngas with higher H2 and lower tar selectivity over non-catalytic conditions. A 1:1:1 ratio of plastic-corn stover-magnetite was used to evaluate the reaction parameters such as temperature, space velocity, heating media, and catalytic cycles under gasification conditions. In comparison with the microwave non-catalytic route, a 100% increase in the total H2 yield with 76% higher H2 production efficiency (mmol/kWh) was achieved in the presence of the magnetite catalyst, while reducing the overall tar formation from 9% to 2%. When magnetite was reduced in situ during the reaction, it coupled with microwave and delivered oxygen radicals that cracked down plastic and corn stover intermediates generated from the synergistic effect under microwave heating. Soon after the oxygen transfer process initiated, magnetite reached its final oxidation state consisting of microwave-active Fe and Fe3C phases that continued coupling with microwaves along with the generated graphitic carbon to maintain the heat necessary to further reduce the generated tar and make additional gaseous products, as confirmed by XRD, Raman, and TGA analyses.

Enabling plastic waste gasification by autothermal chemical looping with > 90 % syngas purity for versatile feedstock handling

The chemical looping gasification of plastics (CLGP) is a process that offers an innovative solution for transforming post-consumer waste plastics into high-value products. The process utilizes a co-current moving bed reducer reactor with iron-titanium-based oxygen carriers to gasify plastic feed and generate syngas autothermally. Its distinguishing feature is its ability to operate over a wide range of feed loadings and co-injection of mixed plastic species without any performance losses. Isothermal bench-scale experiments reveal a syngas purity of ∼95 %, aligning with the thermodynamic simulations. The moving bed reactor facilitates a deeper reduction of the oxygen carriers to the Fe+FeTiO3 phase, leading to the high syngas purity, which is then verified with additional TGA, XRD, and SEM analysis. For an autothermal operation of CLGP process, an active material content of 20 % is found to be sufficient to satisfy the kinetic and thermodynamic constraints. Further integration with downstream production of H2 is presented and compared to a steam gasification process. The process integration simulations show that the CLGP process outperforms the steam gasification system in terms of Cold Gas Efficiency (CGE), Effective Thermal Efficiency (ETE), and H2 yield. CO2 emissions are impressively reduced by ∼30 % in the CLGP system over that in the steam gasification system due to its ability to autothermally operate the process, unlike the highly endothermic steam gasification process.

Integrated production of methanol and biochar from bagasse and plastic waste: A three-in-one solution for carbon sequestration, bioenergy production, and waste valorization

The shift from fossil fuels to renewable energy is a crucial strategy to achieve carbon neutrality. However, the methanol industry relies heavily on fossil fuels. Alternative feedstocks, such as biomass and plastics, still face many challenges. Biomass is hydrogen-deficient and cannot achieve a high methanol yield, while plastic gasification consumes too much energy. Accordingly, this research proposed a new method to synergistically co-produce methanol and biochar from bagasse pyrolysis and plastic waste gasification. This innovative approach was assessed using techno-economic analysis and hybrid life-cycle assessment based on sugarcane bagasse resources in Guangxi province as a case study and compared with the other four scenarios. The results indicated that the novel method exhibits huger economic and environmental benefits with a low payback period of 6.32 years and a low global warming potential of −1875.41 kg CO2-eq/t. However, the high total capital cost is the primary potential obstacle to widespread promotion. Spatial-temporal analysis shows that Chongzuo and Laibin have the most tremendous methanol production potential and economic and environmental benefits due to their high bagasse production. This study contributes to biomass utilization and plastic waste management by proposing a synergistic process and offers multiple benefits for carbon sequestration, energy security, and waste valorization.

Experimental study on CO2 co-gasification characteristics of biomass and waste plastics: Insight into interaction and targeted regulation method

The CO2 gasification of biomass and waste plastics is one of the essential ways to utilize solid waste resources, and it is also potential negative carbon emission technology. The complex interactions in the co-gasification of biomass and waste plastics affect the quality of syngas and the efficient conversion of solid waste. In this study, sawdust, PE and PVC were selected for CO2 gasification. Firstly, the interaction and gasification characteristics were investigated by thermogravimetric experiments. Then, the impact of interaction on syngas generation and quality was studied through fluidized bed experiments. The results indicated that PE, PVC, and sawdust co-gasification exhibits both inhibitory and synergistic. PE inhibits the release of volatiles in sawdust, while PVC promotes the volatiles release. In short, PVC improves the gasification reactivity of sawdust, and PE enhances syngas quality. Adding 75 % PE, the syngas Low Heating Value by 415 % up to 30.05 MJ/kg, and Cold Gas Efficiency by 147 %. The synergistic of the sawdust/PE-PVC was manifested as the superposition and amplification of the synergistic in sawdust/PE and sawdust/PVC. Adjusting the PE and PVC proportion, syngas quality can be targeted to control. The study results exhibit new perspectives on classifying waste plastics for gasification and regulating syngas quality.

Hydrogen-rich carbon recycling complex system establishment and comprehensive evaluation

Hydrogen-rich carbon recycling complex system coupling CO2 reduction with waste heat conversion efficiently is becoming a vigorous horizon stepping forward carbon peak and carbon neutrality with great strides in metallurgical industrial sectors. This article originally proposes an in-situ waste plastics gasification complex system utilizing blast furnace flue gas waste heat for hydrogen-rich preparation and CO2 reduction simultaneously, and the effect of parameters such as temperature, pressure, etc. on syngas yield, CO2 conversion rate, etc. are systemically discussed in detail, furthermore, the techno-economic analysis and priorities of this complex system are obtained through originally comparing intensifying factor and substitution coke ratio. The results show that waste plastics conversion rate, hydrogen and syngas yield have a positive relationship with temperature, but opposite with pressure. Hydrogen preparation is intensifying when water vapor is feeding into, and CO yield is augmented when flue gas is injected. The maximum H2 plus CO preparation efficiency is 61.3–77.4% and H2 yield is 95.9–135.5%,when pressure, temperature, H2O/P ratio and CO2/P ratio should be controlled in 1 bar, 800–1000 °C, 1.5–3.0 and 0.1–0.5, respectively, meanwhile, CO2 conversion rate is 28.4%.Otherwise, this complex system has a maximum CO2 reduction efficiency 73.6–99.0%, when 1 bar, 800–1000 °C, 0.1–0.2, 0.1–3.0 are adopted. Under the optimum conditions above, CO2 reduction efficiency is 171.1 kg/t for an ironmaking sector with capacity 54,000 tons, hydrogen preparation efficiency is 15.6 kg/t at 800 °C, corresponding coke ratio substitution amount is 460.0 kg/t. Besides, the maximum H2 preparation intensifying factor is 8.3% at 1000 °C and the maximum CO2 emission reduction intensity factor is 91.0%, which increases by 49.6–71.3% comparing to predecessors. Through this researches above, hydrogen-rich carbon recycling complex system has unique advantages for CO2 deep reduction and coke ratio decrease, and has a significant contribution suppling with a new horizon and methodology for low-carbon metallurgical process development in the future.

Investigation of hydrogen production via waste plastic gasification in a fluidized bed reactor using Aspen Plus

Plastic waste-to-energy conversion via gasification is a promising method for hydrogen production. In this study, the effects of waste plastic type, equivalence ratio, operating temperature and pressure on the hydrogen production from waste plastics in a fluidized bed reactor were investigated. A precise model of the air gasification process of five different types of waste plastics was developed using modules available in Aspen Plus. Following the model validation, a parametric study was conducted by varying the temperature in the range of 600 °C–1200 °C, the equivalence ratio between 0.05 and 0.50, and the pressure between 1 bar and 50 bar. This study provides valuable information on the impact of different process parameters on the air gasification of various waste plastics which has not been reported extensively. The conversion behaviours of air gasification process for waste plastics were characterized based on syngas composition, syngas lower heating value, hydrogen yield and cold gas efficiency. The simulation results for hydrogen production, which ranged from 15.33 Nm3/ton feed to 284.40 Nm3/ton feed for all plastics, were found to be consistent with experimental results. As a result, the optimal conditions for achieving maximum hydrogen yield in the waste plastic gasification process have been determined and reported.

Gas-heat-electricity poly-generation system based on solar-driven supercritical water gasification of waste plastics

Energy shortage and environmental pollution make people aware of the need to recycle waste resources and develop environment-friendly energy. The massive plastic waste and clean solar energy provide new solutions to energy and environment issues. In this study, a solar-driven gas-heat-electricity poly-generation system based on supercritical water gasification of plastics was established. Plastic waste and solar energy were converted into electricity, heat and hydrogen-rich gas. A detailed analysis of mass, energy and exergy flow of the system was analyzed under typical operating conditions. The effects of temperature, pressure, plastics to water ratio, etc., on gasification performance, system efficiency, and energy output distribution were investigated. The results showed that the system exergy loss mainly occurred in cooler, reactor and heat exchanger, and their loss account for more than 85% of the total loss. The increase in temperature significantly increased total gas production and H2 molar fraction. At 800 °C, the total gas production reached 77.50 kg/h and the H2 molar fraction was 65.78%. However, increasing temperature had a negative impact on system efficiency. The effect of pressure on the gasification reaction and system efficiency was not significant. Increasing plastics to water ratio was beneficial in improving system efficiency, while each gas production showed varying degrees of growth. However, H2 yield and molar fraction decreased dramatically. The increase of turbine feed water led to a slight decrease of energy efficiency, while the exergy efficiency remained basically unchanged. These can provide theoretical guidance for system optimization and promote the industrial application of the technology.

A review on gasification and pyrolysis of waste plastics.

Gasification and pyrolysis are thermal processes for converting carbonaceous substances into tar, ash, coke, char, and gas. Pyrolysis produces products such as char, tar, and gas, while gasification transforms carbon-containing products (e.g., the products from pyrolysis) into a primarily gaseous product. The composition of the products and their relative quantities are highly dependent on the configuration of the overall process and on the input fuel. Although in gasification, pyrolysis processes also occur in many cases (yet prior to the gasification processes), gasification is a common description for the overall technology. Pyrolysis, on the other hand, can be used without going through the gasification process. The current study evaluates the most common waste plastics valorization routes for producing gaseous and liquid products, as well as the key process specifications that affected the end final products. The reactor type, temperatures, residence time, pressure, the fluidizing gas type, the flow rate, and catalysts were all investigated in this study. Pyrolysis and waste gasification, on the other hand, are expected to become more common in the future. One explanation for this is that public opinion on the incineration of waste in some countries is a main impediment to the development of new incineration capacity. However, an exceptional capability of gasification and pyrolysis over incineration to conserve waste chemical energy is also essential.

Process design and techno-economic analysis of dual hydrogen and methanol production from plastics using energy integrated system

This study has been dedicated towards the conversion of plastics to methanol and hydrogen. The base design (case 1) represents the conventional design for producing syngas via steam gasification of waste plastics followed by CO2 and H₂S removal. The syngas then processed in the methanol synthesis reactor to produce methanol, whereas, the remaining unconverted gases are processed in water gas shift reactors to produce hydrogen. On the other hand, an alternative design (case 2) has been also developed with an aim to increase the H2 and methanol production, which integrates the plastic gasification and the methane reforming units to utilize the high energy stream from gasification unit to heat up the feed stream of reforming unit. Both the cases have been techno-economically compared to evaluate the process feasibility. The comparative analysis revealed that case 2 outperforms the case 1 in terms of both process efficiency and economics.

Experimental study on the gasification characteristics of polyethylene terephthalate (PET) microplastics in supercritical H2O/CO2 environment

Plastic waste can be seen everywhere in our life, while the increasing emission of CO2 is causing concern. The use of supercritical fluids to treat plastic waste is highly efficient and provides a new idea for the green treatment of plastic waste. Green treatment of plastics can be achieved, and the possibility of CO2 consumption can be explored in supercritical fluids. Still, its mechanism has not been clearly explained yet, so it is essential to study its laws carefully. This paper carried out the gasification experiment of polyethylene terephthalate (PET) in supercritical H2O/CO2. The effects of temperature, residence time, initial CO2 volume and seawater on the gasification reaction are discussed. The results showed that: increasing the gasification temperature, extending the reaction residence time, and increasing the amount of carbon dioxide can improve the gasification efficiency, and the metal salts contained in seawater can promote the pyrolytic gasification of plastics. And the temperature change significantly influences the interface of PET plastics. The carbon conversion efficiency of PET plastics reached 40.5% with a certain amount of raw material and water for 20 min at 700 °C in supercritical carbon dioxide and water. At 500 °C, PET plastic has the best thermochemical reduction of CO2. This work provides new ideas for future green treatment of plastic waste and contributes to carbon reduction efforts.

Study on gasification characteristics and kinetics of polyformaldehyde plastics in supercritical water

Supercritical water (SCW) treatment technology has been applied in the field of waste plastics recycling due to its advantages of clean, high efficiency and low carbon. Previous research has focused on liquefaction of plastics to produce oil, mainly for some general-purpose plastics. Different plastics have different structures, which will affect their gasification behavior in SCW. As one of the five engineering plastics, polyoxymethylene (POM) plastics will also become one of the main sources of waste plastics recycling industry in the future. In this paper, the supercritical water gasification (SCWG) experiment of POM plastics was carried out. The effects of temperature, residence time, feedstocks concentration, pressure on the gasification reaction were discussed. The carbon balance of the products under different working conditions was investigated. The optimum condition for SCWG of POM plastics was determined. On this basis, the gasification kinetics of POM plastics were studied. It was found that the gasification efficiency of plastics was significantly improved by temperature increase. The total carbon content of gas and liquid phase products increased gradually. At 700 °C, the total conversion rate reached 99.79%. With the prolongation of the reaction time, the organic carbon in the liquid phase was gradually converted into gas and the gasification reaction proceeds more completely. The increase in concentration reduced the contact area between the raw material and the gasification agent. At the same time, the diffusion of organic matter was hindered, resulting in a lower gasification rate. The effect of pressure on the plastics gasification reaction was not significant. Under the optimum gasification reaction conditions, the carbon gasification efficiency reached 97.15%. Finally, a gasification kinetic model was established, and the activation energy of paraformaldehyde was 160.38 kJ/mol.

Feasibility of gasifying mixed plastic waste for hydrogen production and carbon capture and storage

Waste plastic gasification for hydrogen production combined with carbon capture and storage is one technology option to address the plastic waste challenge. Here, we conducted a techno-economic analysis and life cycle assessment to assess this option. The minimum hydrogen selling price of a 2000 oven-dry metric ton/day mixed plastic waste plant with carbon capture and storage is US$2.26–2.94 kg−1 hydrogen, which can compete with fossil fuel hydrogen with carbon capture and storage (US$1.21–2.62 kg−1 hydrogen) and current electrolysis hydrogen (US$3.20–7.70 kg−1 hydrogen). An improvement analysis outlines the roadmap for reducing the average minimum hydrogen selling price from US$2.60 to US$1.46 kg−1 hydrogen, which can be further lowered to US$1.06 kg−1 hydrogen if carbon credits are close to the carbon capture and storage costs along with low feedstock cost. The life cycle assessment results show that hydrogen derived from mixed plastic waste has lower environmental impacts than single-stream plastics.

Comparing different syngas for blast furnace ironmaking by using the extended operating line methodology

This paper assesses the injection of different syngas in air-blown blast furnaces, oxygen blast furnaces, and advanced oxygen blast furnaces. The selected types of syngas come from biomass gasification, plastic gasification, CO2 electrolysis, and reverse water–gas shift reaction. An Aspen Plus model, based on the new extended operating line methodology, was used for the simulation. This methodology is a generalization of the conventional Rist diagram, to extend its application to cases in which the injected gases have large contents of CO2 and H2O, and also to cases in which injections take place at the middle or upper zone of the blast furnace. The base cases were elaborated and validated with data from literature, with a discrepancy below 3.5%. A total of 7 key performance indicators were defined for the study (mass flow of syngas, coke replacement ratio, gas utilization, percentage of direct reduction, blast furnace gas temperature, flame temperature, and net CO2 emissions). In practice, the amount of syngas that can be injected is limited to 92 – 264 kgsyngas/tHM because of the drop in the flame temperature. The lowest net CO2 emissions are achieved in oxygen blast furnace with injection of syngas from reverse water–gas shift reaction.