Quantification of the composition of pyrolysis oils of complex plastic waste by gas chromatography coupled with mass spectrometer detector.

Waste valorisation through pyrolysis generates solid, liquid and gaseous fractions that need to be deeply characterised in order to try to recover secondary raw materials or chemicals. Depending on the waste and the process conditions, the liquid fraction obtained (so-called pyrolysis oil) can be very complex. This work proposes a method to quantitatively measure the composition of pyrolysis oils coming from three types of polymeric waste: (1) plastic packaging from sorting plants of municipal solid waste, (2) plastic rich fractions rejected from sorting plants of waste of electrical and electronic equipment and (3) end-of-life carbon/glass fibre reinforced thermoset polymers. The proposed methodology uses a gas chromatography (GC) coupled with mass spectrometer detector (MS) analytical technique, a certified saturated alkanes' mix, an internal standard and fourteen model compounds. Validation of the methodology concluded that the average relative error was between -59 wt% and +62 wt% (with standard deviations between 0 wt% and 13 wt%). Considering that the state-of-the-art scenario to quantify complex plastic pyrolysis oils as a whole is almost none and that they are usually evaluated only qualitatively based on the area percentage of the GC-MS chromatograms, the presented quantification methodology implies a clear step forward towards complex pyrolysis oil compositional quantification in a cost-effective way. Besides, this quantification methodology enables determining what proportion is being detected by GC-MS with respect to the total oil. Finally, the presented work includes all the Kováts RI for complex temperature-program gas chromatography of all the signals identified in the analysed pyrolysis oils, to be readily available to other researchers towards the identification of chemical compounds in their studies.

Composite waste recycling: Predictive simulation of the pyrolysis vapours and gases upgrading process in Aspen plus.

Waste generation is one of the greatest problems of present times, and the recycling of carbon fibre reinforced composites one big challenge to face. Currently, no resin valorisation is done in thermal fibre recycling methods. However, when pyrolysis is used, additional valuable compounds (syngas or H2-rich gas) could be obtained by upgrading the generated vapours and gases. This work presents the thermodynamic and kinetic multi-reaction modelling of the pyrolysis vapours and gases upgrading process in Aspen Plus software. These models forecast the theoretical and in-between scenario of a thermal upgrading process of an experimentally characterised vapours and gases stream (a blend of thirty-five compounds). Indeed, the influence of temperature (500 °C-1200 °C) and pressure (ΔP = 0, 1 and 2 bar) operating parameters are analysed in the outlet composition, residence time and possible reaction mechanisms occurring. Validation of the kinetic model has been done comparing predicted outlet composition with experimental data (at 700 °C and 900 °C with ΔP = 0 bar) for H2 (g), CO (g), CO2 (g), CH4 (g), H2O (v) and C (s). Kinetic and experimental results show the same tendency with temperature, validating the model for further research. Good kinetic fit is obtained for H2 (g) (absolute error: 0.5 wt% at constant temperature and 0.3 wt% at variable temperature) and H2O (v) shows the highest error at variable T (8.8 wt%). Both simulation and experimental results evolve towards simpler, less toxic and higher generation of hydrogen-rich gas with increasing operating temperature and pressure.

Production of hydrogen-rich gases in the recycling process of residual carbon fiber reinforced polymers by pyrolysis.

In this work, a novel method to valorize the polymeric matrix of residual carbon fiber reinforced polymers (CFRP) in the recycling process of carbon fibers by pyrolysis is presented. The experiments have been carried out with an expired epoxy-based pre-preg and in a lab-scale installation composed of two reactors. In the first one, pyrolysis and oxidation have been carried out, while in the second one, the gases and vapors resulting from the thermal decomposition of the polymeric resin have been thermally treated. The following operating parameters have been studied in the pyrolysis step: dwell time, the use of N2 (N2 flow, no N2 flow and not even to inert the reaction medium) and the solid bed material of the second reactor. In the oxidation step, temperature and time have been optimized by using the theory of experiments based on 2 k factorial design was used. It has been demonstrated that clean carbon fibers and a gaseous fraction with 75% by volume of H2 can be obtained. This is possible through a combined process of (1) CFRP thermal decomposition at 500 °C, (2) thermal treatment of gases and vapors at 900 °C in a solid bed tubular reactor filled with a waste refractory material and (3) oxidation of pyrolysis solid at 500 °C during 165 min in presence of 1.3 L air min-1.

Possibilities and limits of pyrolysis for recycling plastic rich waste streams rejected from phones recycling plants.

The possibilities and limits of pyrolysis as a means of recycling plastic rich fractions derived from discarded phones have been studied. Two plastic rich samples (⩾80wt% plastics) derived from landline and mobile phones provided by a Spanish recycling company, have been pyrolysed under N2 in a 3.5dm3 reactor at 500°C for 30min. The landline and mobile phones yielded 58 and 54.5wt% liquids, 16.7 and 12.6wt% gases and 28.3 and 32.4wt% solids respectively. The liquids were a complex mixture of organic products containing valuable chemicals (toluene, styrene, ethyl-benzene, etc.) and with high HHVs (34-38MJkg-1). The solids were composed of metals (mainly Cu, Zn, and Al) and char (≈50wt%). The gases consisted mainly of hydrocarbons and some CO, CO2 and H2. The halogens (Cl, Br) of the original samples were mainly distributed between the gases and solids. The metals and char can be easily separated and the formers may be recycled, but the uses of the char will be restricted due to its Cl/Br content. The gases may provide the energy requirements of the processing plant, but HBr and HCl must be firstly eliminated. The liquids could have a potential use as energy or chemicals source, but the practical implementation of these applications will be no exempt of great problems that may become insurmountable (difficulty of economically recovering pure chemicals, contamination by volatile metals, etc.).

Pyrolysis behavior of different type of materials contained in the rejects of packaging waste sorting plants.

In this paper rejected streams coming from a waste packaging material recovery facility have been characterized and separated into families of products of similar nature in order to determine the influence of different types of ingredients in the products obtained in the pyrolysis process. The pyrolysis experiments have been carried out in a non-stirred batch 3.5 dm(3) reactor, swept with 1 L min(-1) N(2), at 500°C for 30 min. Pyrolysis liquids are composed of an organic phase and an aqueous phase. The aqueous phase is greater as higher is the cellulosic material content in the sample. The organic phase contains valuable chemicals as styrene, ethylbenzene and toluene, and has high heating value (HHV) (33-40 MJ kg(-1)). Therefore they could be used as alternative fuels for heat and power generation and as a source of valuable chemicals. Pyrolysis gases are mainly composed of hydrocarbons but contain high amounts of CO and CO(2); their HHV is in the range of 18-46 MJ kg(-1). The amount of COCO(2) increases, and consequently HHV decreases as higher is the cellulosic content of the waste. Pyrolysis solids are mainly composed of inorganics and char formed in the process. The cellulosic materials lower the quality of the pyrolysis liquids and gases, and increase the production of char.

Pyrolysis of plastic packaging waste: A comparison of plastic residuals from material recovery facilities with simulated plastic waste.

Pyrolysis may be an alternative for the reclamation of rejected streams of waste from sorting plants where packing and packaging plastic waste is separated and classified. These rejected streams consist of many different materials (e.g., polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), aluminum, tetra-brik, and film) for which an attempt at complete separation is not technically possible or economically viable, and they are typically sent to landfills or incinerators. For this study, a simulated plastic mixture and a real waste sample from a sorting plant were pyrolyzed using a non-stirred semi-batch reactor. Red mud, a byproduct of the aluminum industry, was used as a catalyst. Despite the fact that the samples had a similar volume of material, there were noteworthy differences in the pyrolysis yields. The real waste sample resulted, after pyrolysis, in higher gas and solid yields and consequently produced less liquid. There were also significant differences noted in the compositions of the compared pyrolysis products.

Pyrolysis of municipal plastic wastes II: Influence of raw material composition under catalytic conditions.

In this work, the results obtained in catalytic pyrolysis of three plastic waste streams which are the rejects of an industrial packing wastes sorting plant are presented. The samples have been pyrolysed in a 3.5 dm(3) reactor under semi-batch conditions at 440 °C for 30 min in nitrogen atmosphere. Commercial ZSM-5 zeolite has been used as catalyst in liquid phase contact. In every case, high HHV gases and liquids which can be useful as fuels or source of chemicals are obtained. A solid fraction composed of the inorganic material contained in the raw materials and some char formed in the pyrolysis process is also obtained. The zeolite has shown to be very effective to produce liquids with great aromatics content and C3-C4 fraction rich gases, even though the raw material was mainly composed of polyolefins. The characteristics of the pyrolysis products as well as the effect of the catalyst vary depending on the composition of the raw material. When paper rich samples are pyrolysed, ZSM-5 zeolite increases water production and reduces CO and CO(2) generation. If stepwise pyrolysis is applied to such sample, the aqueous liquid phase can be separated from the organic liquid fraction in a first low temperature step.

Deactivation and regeneration of ZSM-5 zeolite in catalytic pyrolysis of plastic wastes.

In this work, a study of the regeneration and reuse of ZSM-5 zeolite in the pyrolysis of a plastic mixture has been carried out in a semi-batch reactor at 440°C. The results have been compared with those obtained with fresh-catalyst and in non-catalytic experiments with the same conditions. The use of fresh catalyst produces a significant change in both the pyrolysis yields and the properties of the liquids and gases obtained. Gases more rich in C3-C4 and H(2) are produced, as well as lower quantities of aromatic liquids if compared with those obtained in thermal decomposition. The authors have proved that after one pyrolysis experiment the zeolite loses quite a lot of its activity, which is reflected in both the yields and the products quality; however, this deactivation was found to be reversible since after regeneration heating at 550°C in oxygen atmosphere, this catalyst recovered its initial activity, generating similar products and in equivalent proportions as those obtained with fresh catalyst.

Pyrolysis of municipal plastic wastes: Influence of raw material composition.

The objective of this work is the study of pyrolysis as a feedstock recycling process, for valorizing the rejected streams that come from industrial plants, where packing and packaging wastes are classified and separated for their subsequent mechanical recycling. Four real samples collected from an industrial plant at four different times of the year, have been pyrolysed under nitrogen in a 3.5dm(3) autoclave at 500 degrees C for 30min. Pyrolysis liquids are a complex mixture of organic compounds containing valuable chemicals as styrene, ethyl-benzene, toluene, etc. Pyrolysis solids are composed of the inorganic material contained in the raw materials, as well as of some char formed in the pyrolysis process, and pyrolysis gases are mainly composed of hydrocarbons together with some CO and CO(2), and have very high gross calorific values (GCV). It has been proved by the authors that the composition of the raw material (paper, film, and metals contents) plays a significant role in the characteristics of pyrolysis products. High paper content yields water in the pyrolysis liquids, and CO and CO(2) in the gases, high PE film content gives rise to high viscosity liquids, and high metals content yields more aromatics in the liquid products, which may be attributed to the metals catalytic effect.