Angela N. García

Bio: Angela N. García is an academic researcher from University of Alicante. The author has contributed to research in topics: Pyrolysis & Fluidized bed. The author has an hindex of 25, co-authored 48 publications receiving 1443 citations.

Pyrolysis of Polyethylene in a Fluidized Bed Reactor

Abstract: A fluidized sand bed reactor was used to study the production of gases from polyethylene (HDPE) at five nominal temperatures (ranging from 500 to 900°C). Both HDPE primary decomposition and wax cracking reactions take place inside the reactor. Yields of 13 pyrolysis products (methane, ethane, ethylene, propane, propylene, acetylene, butane, butylene, pentane, benzene, toluene, xylenes, and styrene) were analyzed as a function of the operating conditions. The results are compared with the data obtained by pyrolysis of HDPE in a Pyroprobe 1000, where secondary wax and tar cracking is small. Correlations between the products analyzed with those of methane are discussed.

Effect of the temperature in the nature and extension of the primary and secondary reactions in the thermal and HZSM-5 catalytic pyrolysis of HDPE

Abstract: Catalytic pyrolysis of plastic wastes is a promising recycling alternative to the disposal methods currently used for this type of residues (i.e. land filling or energetic valorisation). In order to optimize the yields of compounds obtained with this treatment, the knowledge of the parameters’ influence on the degradation process is of great interest. Pyrolysis temperature and volatiles residence time are the most influential variables in the process, since they affect the primary as well as the secondary reactions. In this work, the pyrolysis temperature effect on the primary and secondary reactions of the thermal and HZSM-5 catalyzed pyrolysis of HDPE is reported and evaluated, in the range 500–800 °C. For this purpose, two different equipments have been used, i.e. a flash coil pyrolyzer (pyroprobe 1000), that allows us to study the primary products, since the extent of secondary reactions can be neglected, and a fluidized bed reactor, where the extent of the secondary reactions is significant. The results of the present study show that 1-hexene is the major product obtained when primary thermal cracking reactions are mainly taking place. However, the major compounds obtained when thermal secondary reactions are present in larger extension are propene at low temperatures and ethene at high temperatures. In catalytic pyrolysis, the effect of HZSM-5 is clearly evident at all temperatures evaluated, increasing the volatile yields in both equipments used. The influence of this catalyst is more significant in the primary cracking reactions showing an increase of the volatile compounds with the degradation temperature. In this case, propene is the main volatile product obtained reaching a yield of 30.6% at the highest temperature evaluated. When the presence of the secondary reactions is evident, using a fluidized bed reactor, the combined effect of generation and possible cracking reactions leads to a low-dependent product distribution on the degradation temperature, propene being the main volatile compound in the range of temperatures studied. It has been observed that branched hydrocarbons are formed mainly from secondary reactions and are quickly destroyed by increasing the temperature. In the zeolite catalyzed pyrolysis the differences between the yields obtained in both equipments are lower than in the thermal case.

Pyrolysis study of polyurethane

Abstract: The thermal decomposition of a polyurethane in an inert atmosphere has been studied. Three different apparatus, a thermobalance, a pyroprobe and a laboratory furnace, were use to study the kinetics of decomposition and the evolution of gas and volatiles. The kinetics were studied using a thermobalance and four heating rates. The experimental results were described satisfactorily by a two parallel reaction models. The kinetic parameters, that is, the pre-exponential factors, activation energies, reaction orders and maximum production of volatiles at infinite time were also obtained. The formation of hydrocarbons at different nominal temperatures was studied using a coil pyroprobe. An increase of the yield of light hydrocarbons (methane, ethylene, etc) was observed as the pyrolysis temperature increased. The secondary products from the formation/cracking reactions of the different primary compounds were identified by passing the pyrolysis products through a furnace prior to detection. The recovery of chemicals from the pyrolytic degradation was then studied. Toxic compounds were determined by carrying out thermal degradation in a Nitrogen atmosphere. Gas chromatography/mass spectrometry (GS/MS) was used to identify volatile and semivolatile organic compounds generated by the thermal degradation reactions.

CO2 activation of olive stones carbonized under different experimental conditions

Abstract: In order to get more detailed knowledge of the possible effect of the carbonization conditions on the pore structure of activated carbons three very different chars from a common precursor(olive stones) have been prepared under three different sets of experimental conditions

Catalytic flash pyrolysis of HDPE in a fluidized bed reactor for recovery of fuel-like hydrocarbons

Abstract: Products obtained in the flash pyrolysis of HDPE in a fluidized bed reactor, in thermal and catalytic conditions (HZSM-5 or HUSY 20% by weight) at four different temperatures (in the range 500–800 °C) have been analyzed in this work focusing on the liquid fraction. The results obtained showed significant differences between condensable compounds generated in presence and absence of catalysts. The liquid fraction obtained without catalyst was composed principally by linear paraffins (C 10 –C 40 ) and almost no generation of aromatic compounds was observed. The presence of low amounts of zeolite (HZSM-5 or HUSY) led to a significant reduction of the saturated and unsaturated condensable hydrocarbons, while it favored the formation of aromatics and branched paraffins. Compared with the results reached with HZSM-5 zeolite, HUSY produces higher amount of aromatics and branched alkanes and a narrower distribution of products, independently of the pyrolysis temperature. The reactor employed in this work was a fluidized bed reactor, very similar to that used in generation of gasoline-range hydrocarbons at large scale, which allows to illustrate a very useful method for the recovery of these hydrocarbons.

Modeling chemical and physical processes of wood and biomass pyrolysis

Abstract: This review reports the state of the art in modeling chemical and physical processes of wood and biomass pyrolysis. Chemical kinetics are critically discussed in relation to primary reactions, described by one- and multi-component (or one- and multi-stage) mechanisms, and secondary reactions of tar cracking and polymerization. A mention is also made of distributed activation energy models and detailed mechanisms which try to take into account the formation of single gaseous or liquid (tar) species. Different approaches used in the transport models are presented at both the level of single particle and reactor, together with the main achievements of numerical simulations. Finally, critical issues which require further investigation are indicated.

Thermal stability and flame retardancy of polyurethanes

Abstract: The thermal stability and flame retardancy of polyurethanes is reviewed. Polyurethanes (PUs) are an important class of polymers that have wide application in a number of different industrial sectors. More than 70% of the literature that deals with PUs evaluates their thermal stability or flame retardancy and attempts to provide a structure–property correlation. The importance of studying thermal degradation, understanding the processes occurring during thermal stress as well as the parameters affecting the thermal stability of PUs are essential in order to effectively design polyurethanes having tailor-made properties suitable for the particular environment where they are to be used. A detailed description of TGA, TGA-MS and TGA-FTIR methods for studying the decomposition mechanism and kinetics is also a part of this review. In general, thermal decomposition of PUs begins with the hard segment (HS) and a number of parameters govern a polyurethane's thermal stability. Detailed description of the parameters such as HS, soft segment (SS) and chain extender (CE) structure and molecular weight, NCO:OH ratio, catalyst nature and crosslink density that affect the nature of PU degradation is given. Descriptions of approaches to improve the thermal stability in PUs such as formation of poly(urethane-isocyanurate), poly(urethane-oxazolidone) and poly(urethane-imide) in addition to other methods such as PUs with an s-triazine ring or increased aromatic ring concentration, azomethane linkages as well as use of hyperbranched polyols as crosslinking agents is given. A part of the review is also concentrated on the improvement of thermal stability via hybrid formation such as the incorporation of appropriate amounts of fillers, e.g., nano-silica; Fe 2 O 3 ; TiO 2 ; silica grafting; nanocomposite formation using organically modified layered silicates; incorporation of Si–O–Si crosslinked structures via sol–gel processes; and the incorporation of polyhedral oligomeric silsesquioxane (POSS) structures into the PU backbone or side chain. Incorporation of carbon nanotubes (CNT) into PUs and the use of functionalized fullerenes in PUs are also described as these are the newest tools to obtain good thermal stability and flame retardancy. Part of the review also concentrates on the process that occurs during burning of PUs, flame retardant mechanisms and different additives or reactive type flame retardants used in the PU industry. The use and working function of expandable graphite and melamine as additive type flame retardants are shown. Description of the use of different reactive type organophosphorus compounds, cyclotriphosphazenes, aziridinyl curing agents in aqueous polyurethane dispersions (PUDs), organoboron compounds and organosilicon compounds for improving flame retardancy is also given.

Utilization of sewage sludge in EU application of old and new methods—A review

Abstract: The European Union has made progress in dealing with municipal wastewater in individual countries and as a corporate entity. However, it intends to make still further and substantial progress over the next 15 years. Currently, the most widely available options in the EU are the agriculture utilization, the waste disposal sites, the land reclamation and restoration, the incineration and other novel uses. The selection of an option on a local basis reflects local or national, cultural, historical, geographical, legal, political and economic circumstances. The degree of flexibility varies from country to country. In any case sludge treatment and disposal should always be considered as an integral part of treatment of wastewater. There is a wide range of other uses for sludge, which exploit its energy or chemical content, namely the thermal processes. The present paper sought to review past and future trends in sludge handling, focusing mainly at thermal processes (e.g. pyrolysis, wet oxidation, gasification) and the utilization of sewage sludge in cement manufacture as a co-fuel.

A review on pyrolysis of plastic wastes

Abstract: The global plastic production increased over years due to the vast applications of plastics in many sectors. The continuous demand of plastics caused the plastic wastes accumulation in the landfill consumed a lot of spaces that contributed to the environmental problem. The rising in plastics demand led to the depletion of petroleum as part of non-renewable fossil fuel since plastics were the petroleum-based material. Some alternatives that have been developed to manage plastic wastes were recycling and energy recovery method. However, there were some drawbacks of the recycling method as it required high labor cost for the separation process and caused water contamination that reduced the process sustainability. Due to these drawbacks, the researchers have diverted their attentions to the energy recovery method to compensate the high energy demand. Through extensive research and technology development, the plastic waste conversion to energy was developed. As petroleum was the main source of plastic manufacturing, the recovery of plastic to liquid oil through pyrolysis process had a great potential since the oil produced had high calorific value comparable with the commercial fuel. This paper reviewed the pyrolysis process for each type of plastics and the main process parameters that influenced the final end product such as oil, gaseous and char. The key parameters that were reviewed in this paper included temperatures, type of reactors, residence time, pressure, catalysts, type of fluidizing gas and its flow rate. In addition, several viewpoints to optimize the liquid oil production for each plastic were also discussed in this paper.

Pyrolysis of biomass to produce fuels and chemical feedstocks

Abstract: This review presents the summary of new studies on pyrolysis of biomass to produce fuels and chemical feedstocks. A number of biomass species, varying from woody and herbaceous biomass to municipal solid waste, food processing residues and industrial wastes, were subjected to different pyrolysis conditions to obtain liquid, gas and solid products. The results of various biomass pyrolysis investigations connected with the chemical composition and some properties of the pyrolysis products as a result of the applied pyrolysis conditions were combined. The characteristics of the liquid products from pyrolysis were examined, and some methods, such as catalytic upgrading or steam reforming, were considered to improve the physical and chemical properties of the liquids to convert them to economic and environmentally acceptable liquid fuels or chemical feedstocks. Outcomes from the kinetic studies performed by applying thermogravimetric analysis were also presented.