On Fractioning the Tire Pyrolysis Oil in a Pilot-Scale Distillation Plant under Industrially Relevant Conditions.

Tire pyrolysis oil (TPO) is one of the most interesting products derived from the pyrolysis of end-of-life tires. Among others, it contains valuable chemicals, such as benzene, toluene, ethylbenzene, and xylene (BTEX), as well as limonene. In order to recover these chemicals, a pilot-scale distillation plant has been designed, erected, and operated using TPO derived from an industrial-scale pyrolysis plant. The distillation facility consists of a packed column (20 kg/h) and is within the fifth technological readiness level. This work describes for the first time the fractioning of the TPO in a continuous operational mode under industrially relevant conditions. For this purpose, different reboiler temperatures (250-290 °C) and reflux ratios (up to 2.4) were preliminarily assessed on the yields and properties of the resulting products: light fraction (LF) and heavy fraction (HF). Thus, the distillation plant is capable of producing 27.0-36.7 and 63.3-73.0 wt % of LF and HF, respectively. The highest BTEX concentration in the LF (55.2 wt %) was found using a reboiler temperature of 250 °C and a reflux ratio of 2.4. Contrarily, the highest limonene concentration (4.9 wt %) in the LF was obtained at 290 °C in the reboiler without reflux. In this sense, the lower the reboiler temperature, the higher the BTEX, and the lower the limonene concentration in the LF. The main results herein obtained serve to gain key insights to operate packed distillation columns using complex and promising hydrocarbons as TPO in order to recover valuable products. In addition, this work provides significant information for optimizing the recovery efficiencies of both BTEX and limonene, as well as their potential applications including that for the resulting HF.

A pyrolysis process coupled to a catalytic cracking stage: A potential waste-to-energy solution for mattress foam waste.

Pyrolysis coupled to either thermal or catalytic cracking of mattress foam waste was performed in a laboratory-scale facility consisting of a fixed-bed reactor joined to a tubular cracking reactor. The results showed a great potential for the production of syngas specially at high cracking temperatures. Particularly, fixing 800 °C in the cracking reactor, a CO and CH4 rich gas with a remarkable amount of H2 was obtained. The addition of catalysts (dolomite, olivine or HiFUEL®) significantly decreased undesirable tar formation, (below 10 wt%), simultaneously increasing the gas yield and keeping CO and CH4 as the main components in the stream, becoming a preferable route that the non-catalytic process. Accordingly, this stream could be used preferably for further applications in energy generation because its heating value ranged between 15.7 MJ/Nm3 and 19.6 MJ/Nm3. In particular, the gas obtained by the use of dolomite could be advantageous for the production of organic compounds such as dimethyl ether (DME) as well as its use an engine or boiler to generate electricity in small facilities. In addition, the solid fraction obtained after de process could be used as a medium quality refused derived fuel (LHV ~ 12 MJ/kg) in order to support the internal energy requirements of the process.

A combined two-stage process of pyrolysis and catalytic cracking of municipal solid waste for the production of syngas and solid refuse-derived fuels.

Pyrolysis combined to either thermal cracking or catalytic cracking of municipal solid waste was performed in a laboratory-scale facility consisting of a fixed-bed reactor followed by a tubular cracking reactor. The results showed great potential for the production of syngas. The incorporation of inexpensive and widely available dolomite in the cracking reactor (with a constant feedstock to calcined dolomite ratio of 5:1) favoured the catalytic cracking of the primary pyrolysis products towards H2 and CO in a temperature range of 800-900 °C. More particularly, it was possible at 900 °C to achieve a syngas consisting of more than 80 vol% CO and H2 with a heating value of 16 MJ/Nm3. Additionally, a homogeneous solid fuel was obtained as a solid residue, which can be used to provide additional energy to support the process or as a refuse-derived fuel. Thus, the great potential of this process was demonstrated for turning municipal solid waste into a valuable gas fraction that can be used directly as a fuel or as a source of different value-added products.

Porosity-Acidity Interplay in Hierarchical ZSM-5 Zeolites for Pyrolysis Oil Valorization to Aromatics.

The properties of crude bio-oils attained by the pyrolysis of lignocellulosic biomass can be greatly enhanced by means of catalytic upgrading. Here, we demonstrate an efficient process concept coupling the production of pyrolysis oil from pine wood with a consecutive catalytic upgrading step over hierarchically structured ZSM-5 zeolites to attain aromatic-rich bio-oils. The selective upgrading of these complex mixtures is shown to be tightly connected to the extent of mesopore development and the density of Brønsted acid sites at the mesopore surface. A full product analysis enables elucidation of the impact of mesopore introduction and the acidic properties on the complex reaction network. The preferential occurrence of decarbonylation reactions in hierarchical zeolites versus dehydration transformations in the bulk counterparts is believed to be decisive in promoting increased aromatics formation.

Source apportionment of atmospheric PM2.5-bound polycyclic aromatic hydrocarbons by a PMF receptor model. Assessment of potential risk for human health.

One year sampling (2011-2012) campaign of airborne PM2.5-bound PAH was performed in Zaragoza, Spain. A source apportionment of total PAH by Positive Matrix Factorization (PMF) was applied in order to quantify potential PAH pollution sources. Four sources were apportioned: coal combustion, vehicular emissions, stationary emissions and unburned/evaporative emissions. Although Directive 2004/107/EC was fulfilled regarding benzo(a)pyrene (BaP), episodes exceeding the limit value of PM2.5 according to Directive 2008/50/EC were found. These episodes of high negative potential for human health were studied, obtaining a different pattern for the exceedances of PM2.5 and the lower assessment threshold of BaP (LATBaP). In both cases, stationary emissions contributed majority to total PAH. Lifetime cancer risk exceeded the unit risk recommended by the World Health Organization for those episodes exceeding the LATBaP and the PM2.5 exceedances for the warm season. For the cold season, the risk was higher for the LATBaP than for the PM2.5 exceedances.

BaP (PAH) air quality modelling exercise over Zaragoza (Spain) using an adapted version of WRF-CMAQ model.

Benzo(a)pyrene (BaP) is one of the most dangerous PAH due to its high carcinogenic and mutagenic character. Because of this reason, the Directive 2004/107/CE of the European Union establishes a target value of 1 ng/m(3) of BaP in the atmosphere. In this paper, the main aim is to estimate the BaP concentrations in the atmosphere by using last generation of air quality dispersion models with the inclusion of the transport, scavenging and deposition processes for the BaP. The degradation of the particulated BaP by the ozone has been considered. The aerosol-gas partitioning phenomenon in the atmosphere is modelled taking into a count that the concentrations in the gas and the aerosol phases. If the pre-existing organic aerosol concentrations are zero gas/particle equilibrium is established. The model has been validated at local scale with data from a sampling campaign carried out in the area of Zaragoza (Spain) during 12 weeks.

Study of Pb sources by Pb isotope ratios in the airborne PM(10) of Zaragoza, Spain.

Lead is a toxic trace element which produces harmful effects on human health, even at low concentrations, and it can be useful as ambient pollution tracer because the relative abundance of its four stable isotopes (204, 206, 207 and 208) depends on the emission source. This study was focused on the lead concentrations and isotope ratios in the PM10 of Zaragoza, in order to determine the main Pb pollution sources and to check whether the influence of the prohibition of leaded fuel was worthwhile. Two sampling campaigns from 2001 until 2004, the first one in which leaded gasoline was still effective and the second one with the phase-out, were carried out by using a high-volume air sampler able to trap the particulate matter equal to or less than 10 microm (PM10) on Teflon-coated fibre glass filters. Firstly, the Pb concentrations for the two sampling campaigns were analysed by inductively-coupled plasma optical emission spectrometry (ICP-OES). No statistically significant decrease in the Pb average concentration was obtained from the first to the second sampling. Enrichment factors showed that anthropogenic sources were prevalent during both samplings, in particular during 2001-2002. Afterwards, only those samples with higher concentrations than the limit of quantification of Pb were analysed to determine the lead isotopic composition by inductively-coupled plasma quadrupole mass spectrometry (ICP-QMS). To apply this analytical technique successfully, it was necessary to optimize the parameters affecting the measurement accuracy and precision. Differences were found regarding the lead isotope ratios for both periods finding that anthropogenic sources related to industrial processes were reflected on both campaigns. The gasoline contribution for the first campaign was 23% whereas for the second sampling this contribution was negligible, corroborating the success of the lead policies on the quality of the environment.