By-product Of Pyrolysis Research Articles

Relationship between heavy metal consolidation and H2S removal by biochar from microwave pyrolysis of municipal sludge: effect and mechanism.

The synergistic effects of pyrolysis byproduct, biochar (BC) on heavy metal consolidation, and H2S removal during and after from microwave pyrolysis of municipal sludge were studied in this paper. The results showed that above 80% of heavy metals (Zn and Pb) were enriched in the biochar and the leaching toxicity of both heavy metals was lower than the national emission standards. The chemical specification analysis found the sum of acid-soluble/exchangeable fraction (F1) and reducible fraction (F2) for Pb and Zn metals decreased by 26 and 40%; however, the residual fraction (F4) increased 33 and 46%, which contributed to the good stabilization of heavy metals in biochar. Besides, biochar achieved high H2S removal efficiency of 78.4% compared with the commercial activated carbon (AC). Furthermore, the biochar prepared by microwave pyrolysis had excellent adsorption performance, which was attributed to its larger specific surface area of 476.87m2/g under nitrogen atmosphere at 650oC compared with traditional pyrolysis. The mechanism analysis showed that microwave pyrolysis resulted in the high alkaline condition and formation of a large number of microparticles containing large metal elements on the biochar surface, which mainly contributed to the stabilization of heavy metals. The metal oxides adsorbed on the surface of biochar can catalyze the oxidation of H2S absorption, which will change the pH atmosphere of biochar reducing the leaching behavior of heavy metals. This study provided the good application potential of solid waste (biochar) for simultaneous heavy metal stabilization and H2S capture.

Selective Laser Pyrolytic Micropatterning of Stretched Elastomeric Polymer Surfaces

The patterning of surface structures is a critical step for interfacial engineering applications that are based on soft lithography, casting, or imprinting techniques in general. However, photolithography and mold/die fabrication processes are expensive and time-consuming. To solve this problem, we developed a novel laser-based process that exploits the high stretchability of a polymer. In this study, continuous-wave laser-induced pyrolysis was conducted on a pre-stretched Ecoflex polymer substrate to obtain a controllable hydrophobic surface with functional structures at the micro/nanoscale, which were constructed via the facile removal of pyrolytic byproducts. Under the optimum strain rate and laser parameters, periodic wrinkle generation and a proportional channel pitch reduction were observed, which provided hierarchical micro/nanostructures and enlarged the air gaps between the target droplet and the hydrophobic structures. The processed surface exhibited improved hydrophobic properties (WCA ~ 135°) compared with a flat Ecoflex polymer surface (WCA ~ 105°). Thus, a facile manufacturing method for stretchable polymer substrates with hydrophobic patterned surfaces is proposed.

Autocatalytic co-upgrading of biochar and pyrolysis gas to syngas

A new strategy is exploited toward dramatically increased carbon utilization efficiency of biomass fast pyrolysis by implementing co-upgrading of by-products (biochar and pyrolysis gas) of fast pyrolysis. Simultaneous autocatalytic conversion of biochar and pyrolysis gas is demonstrated using a fixed-bed reactor and an isothermal thermogravimetric analyzer. The reaction of corncob char with simulated pyrolysis gas reveals the feasibility of producing valuable CO and H2 under suitable reaction temperature (>800 °C). The reactivity of biochar and simulated pyrolysis gas increases with increasing potassium content. The raw corncob biochar exhibits high reactivity owing to its high indigenous potassium content. Furthermore, kinetic analysis demonstrates that the modified random pore model (MRPM) satisfactorily describes the reaction behavior of corncob biochar and CO2. The activation energy calculation verifies that the co-upgrading of raw corncob biochar and pyrolysis gas for the production of syngas is feasible at suitable temperature without further treatment.

Synthesis and characterization study of solid carbon biocatalyst produced from novel biomass char in a microwave pyrolysis

Biochar is considered to be one of the most significant by-products obtained from biomass pyrolysis. Biochar is of significant importance in soil amendment, catalyst preparation, and activated carbon formation. Microwave pyrolysis is one of the emerging trends in biochar production. Since the residence time in a typical microwave pyrolysis reactor is quite high, biochar is often the major by-product of biomass microwave pyrolysis. Microwave pyrolysis additionally is an extremely energy-efficient method. This present study involves the preparation and characterization of biochar produced from senna pendula seedcake. The biochar produced from the pyrolysis (up to 600 ˚C) is then subjected to sulphonation using fuming sulphuric acid. TG analysis shows that pyrolysis occurred between 200 and 450 ˚C. FTIR analysis results show that upon sulphonation, the biochar has been strongly carbonized. Both FTIR and XRD analyses showed that biochar had been impregnated with carbonyl and sulphonyl groups post sulphonation. SEM micrography results showed that sulphonation had caused a breakdown of existing organic compounds along with an increase in pore diameter.

Bioproducts from the pyrolysis of castor seed cake: Basic dye adsorption capacity of biochar and antifungal activity of the aqueous phase

Castor seed cake, a solid residue produced after castor oil extraction, has been used as raw material in the pyrolysis process. Crude biochar (40.6% yield) was subjected to four activation methods; the best activating agent for obtaining activated biochar 1 (AB1) with 603.29 m2 g−1 of a specific area comparable to commercial active carbon in the methylene blue dye adsorption was concentrated sulfuric acid (H2SO4). The adsorption experiments revealed the removal of more than 96% of the dye, kinetic studies showed that a pseudo-second-order (r2 ≥ 0.99) model fitted better with evaluated data and that intraparticle diffusion controls the adsorption rate of the dye by AB1. The aqueous phase (19.2% yield) was lyophilized, and the organic extract contains –N (3%), –O (49%), and –NO (48%) content compounds. The in vitro antifungal activity against the Cryptococcus species was evaluated, and a low concentration of the aqueous phase induced higher growth inhibition in C. neoformans and C. gattii. Therefore, the use of castor seed cake, an environmental waste, in the preparation of an adsorbent material can be considered a low-cost alternative for water treatment when contaminated with the MB dye. Moreover, the aqueous phase, which is a commonly neglected slow pyrolysis by-product, could be an efficient option for decontaminating areas with a high fungal load.

Chemistry Review of Vaping Products and Respiratory Injury

Background: While the Public Health Agency of Canada notes 19 cases from May 2019 to February 2020 relating to e-cigarette or vaping product use-associated lung injury (EVALI) in Canada, there are likely many more unreported cases, including non-hospitalized and asymptomatic cases. E-cigarette use or vaping exposes users to numerous aerosolized chemical species, some of which have proven to be deleterious to health. These chemical species can include vitamin E acetate (VEA), flavourants, base / solvents (propylene glycol or vegetable glycerin), psychoactive substances, pesticides, endotoxins, metals, and pyrolysis by-products from e-cigarette heating coils. Objectives: We aim to review current findings related to EVALI from the standpoint of known chemical species currently used in vaping products. We specifically examine the toxicological profiles of these chemical species and the mechanisms through which they cause lung injury. Methods: A comprehensive literature search was performed with MEDLINE for EVALI-related human studies that were published between January 1, 2010, and May 15, 2020. This search strategy identified 832 case reports, case series, clinical trials, and in-vitro laboratory studies. From this group, 71 records were examined in greater detail. Results and Conclusions: Although the chemical composition and toxicology of vaping products have largely been characterized, the physiological effects of the chemical interactions between various constituents of vaping products and the generation of new species remain inconclusive. Given the rapid increase in the popularity of vaping and e-cigarettes, there is a need for further research. Developing a comprehensive understanding of the chronic health effects of vaping through randomized controlled trials and physiological studies is prudent and necessary to reduce the long-term impacts on users and the health care system.

Metal-organic chemical vapour deposition of lanthana-doped ceria layers at low temperatures

Non-porous, amorphous and nanocrystalline CeO2–La2O3 layers were synthesized by means of MOCVD using Ce(tmhd)4 and La(tmhd)3 as reactants on tubular and planar quartz glass substrates. Different layers were synthesized in the temperature range 500–700 °C using various molar contents of La(tmhd)3, i.e. 10, 15, 26 and 50%, respectively. A mixture of Ar and air was used as a carrier gas. Air was also an oxygen source necessary for carbon oxidation (a solid by-product of reactant pyrolysis). Therefore, the layers should only contain Ce4+ ions. When the synthesis process was controlled by the surface reaction rate, there was no correlation between the chemical composition of reactants and that of the layers. Such a dependence was obtained when the synthesis process was controlled by mass diffusion to the substrate. In addition, it was observed that La3+ ion segregation can occur during layer synthesis between surface areas with lower and higher amounts of a crystalline phase. The molar percent of La2O3 in areas exhibiting less crystallization with smaller grains was higher than in locations with larger grains, because, in this case, intergranular boundary content was lower. X-ray analysis indicates that layers deposited at 500 °C were amorphous, although SEM images show numerous small nuclei of a crystalline phase. It seems that the crystalline phase content was not high enough to be identified by X-ray analysis. Layers deposited at 600 °C consisted of a solid solution of La2O3 dissolved in CeO2. From UV-VIS tests it follows that absorption is very strong up to a wavelength of approximately 320 nm.

Optimizing bioenergy and by-product outputs from durian shell pyrolysis

Durian shells (DS) constitute an abundant agricultural waste stream with a large yield in Southeast Asia and higher heating value. This study aimed to quantify the bioenergy and by-product outputs of the DS pyrolysis as a function of heating rate (5, 10, 20, and 40 K/min) combining thermogravimetric, Fourier transform infrared spectrometry, and pyrolysis–gas chromatography/mass spectrometry analyses. The joint optimizations of multiple responses were also performed as a function of a changing biofeedstock, heating rate, and temperature. The DS pyrolysis composed of three stages, with the main decomposition stage occurring between 141.2 and 616.5 °C. The increased heating rate promoted the DS pyrolysis, while the pyrolysis reaction was more complete at the low heating rate. Activation energy of the pyrolysis reaction was estimated to vary between 221.58 and 245.71 kJ/mol. The major gases evolved from the DS pyrolysis included CO2, CO, CH4, H2O, carbonyl compounds, acids, and NH3. The major pyrolytic by-products were aromatic and alicyclic hydrocarbons, phenolic substances, and N-containing compounds. Joint optimizations pointed to 999 °C, 5 K/min, and aboveground water hyacinth biomass, or DS as the most optimal operational conditions. Our findings provide insights into the optimization and scale-up for the industrial pyrolytic applications of DS.

Color change and termite resistance of fast-growing tropical woods treated with kesambi (Schleichera oleosa) smoke

Smoke treatment can be used to enhance wood resistance to subterranean termite attack. In this study, kesambi (Schleichera oleosa) wood was pyrolyzed to produce charcoal. The smoke produced as a by-product of pyrolysis was used to treat sengon (Falcataria moluccana), jabon (Anthocephalus cadamba), mangium (Acacia mangium), and pine (Pinus merkusii) wood samples for 1, 2, or 3 weeks. Following the smoke treatment, the wood specimens were exposed to subterranean termites (Coptotermes curvignathus Holmgren) according to the Indonesian standard 7207-2014 in a laboratory. The color change caused by smoke treatment was observed, and chemical analysis of smoke was also done. The results showed that chemical compounds of kesambi smoke predominantly consisted of acetic acid, phenol, ketones, amines, and benzene. The color of smoked wood became darker, less yellow, and a little redder, while a longer smoking period produced a darker color which was more resistant to termite attack. Smoke treatment enhanced the resistance of wood to subterranean termite attack, and the resistance levels were not significantly different based on the duration of the smoke treatment.

Effect of process conditions on the surface properties of biomass chars produced by means of pyrolysis and CO2 gasification

Biomass char is defined as the carbonaceous by-product of biomass pyrolysis or gasification and is an undesired by-product that is disposed as a waste, usually at a very high cost. Chars have interesting characteristics like high carbon content and high porosity. These characteristics can make attractive the utilization of biomass char for alternative and innovative applications, e.g. as precursors for activated carbons or as filtering mediums. In this framework, this present work focuses the attention on the surface properties of char which is a key parameter for the evaluation of its applicability in adsorption applications. The combination of three main variables has been considered: the carrier gas (nitrogen or carbon dioxide), the temperature (set at 500°C, 700°C and 900°C) and the initial heating rate (10°C min−1, 30°C min−1 or 50°C min−1). Maximum heating values are observed at 700°C for the case of inert atmosphere (pyrolysis) and the values reduce slightly for the case of CO2 gasification. On the contrary, CO2 gasification has a positive effect on the porosity of the biomass chars. This present research has the scope to provide a first insight on the effect of operating conditions on the optimal char characteristics for the utilization of biomass char as a cheap alternative for filters and adsorbents. An interesting future potential transition of existing biomass CHP facilities would be the evolution into biorefineries, in accordance with the new mandates about Circular Economy.

Residue Char Derived from Microwave-Assisted Pyrolysis of Sludge as Adsorbent for the Removal of Methylene Blue from Aqueous Solutions

Residue char is the main by-product of the microwave-assisted pyrolysis of activated sludge and it has a high content of fixed carbon and porous structure, but little is known about its character as an absorbent. In this study, residue char of activated sludge with microwave-assisted pyrolysis was used as an adsorbent to absorb methylene blue. The effects of pyrolysis temperature, pyrolysis holding time, contact time, and adsorption temperature on the adsorption ability of residue char were investigated. Kinetics, isotherm, and thermodynamic models were also included to study the adsorption behavior. The results showed that the optimal pyrolysis condition was 15 min and 603 °C, and the adsorption capacity reached up to 80.01 mg/g. The kinetics analyses indicated the adsorption behavior followed the pseudo-second-order kinetics model and the adsorption process was mainly due to chemical interaction. The adsorption isotherm was described by Freundlich model and thus, its process was multimolecular layer adsorption. Furthermore, the thermodynamics parameters (ΔG0, ΔH0, and ΔS0) at different temperatures indicated that the nature of the adsorption process was endothermic and spontaneous.

Pyrolysis GC/MS analysis of improved guayule genotypes

In addition to the commonly known use as an alternative source for natural rubber and hypoallergenic latex, guayule could also be a source of resin and bagasse for use in the pharmaceutical and biofuel industries. Pyrolysis is a method to convert guayule biomass into liquid (condensable gas or bio-oil), which can be an intermediate towards production of biofuels and/or renewable chemicals. In this work, six guayule genotypes that were planted under either well-irrigated or reduced-irrigation conditions were pyrolyzed using a pyrolysis gas-chromatography-mass spectrometry instrument (PY-GC/MS). The products included condensable gas, non-condensable gas and bio-char. Within the condensable gases, selected compounds were divided into nine chemical classes including aromatic hydrocarbons, alkyl phenols, guaiacols, syringols, furans, cyclopentenones, acetic acid and acetol, levoglucosan and limonene groups. As a result, significant variations were observed in the major compounds and prominent sub-constituents of condensable gas among the studied guayule genotypes and under irrigation levels. Strong positive correlations were found between irrigation levels and oxygenated condensable gas components derived from cellulose and lignin, although hydrocarbon components derived from the rubber and resin were found to be negatively correlated with irrigation levels. Results indicated that the genetic variations among guayule genotypes can be used to improve its bioenergy potential, and positive correlations observed among pyrolysis byproducts suggest the possibility to improve several byproducts simultaneously in guayule breeding programs. This research gives an insight to breed for guayule as an economic crop with high bioenergy potential for the development of sustainable agriculture.

Theoretical study of the gas-phase thermal decomposition of urea

Urea is used in Selective Catalytic and Non Catalytic Reduction (SCR and SNCR) methods for NOx abatement in post-combustion processes. The decomposition of urea-water solution in exhaust systems leads to the formation of NH3, which is the NOx reducing agent. However, the decomposition of urea can also lead to the formation of unwanted pyrolysis by-products, particularly in region where the temperature and pressure conditions are not optimal or via wall-spray interactions. In this study, a gas phase kinetic model for urea pyrolysis is proposed to explain the growth of pyrolysis by-products of urea, and in particular, the route of formation of the major product: isocyanuric acid. Systematic theoretical calculations, using electronic structure calculations and transition state theory, were performed to explore all the possible unimolecular and bimolecular reactions of the initial species. Kinetic modeling was used to select the relevant reaction pathways at each growing step, and their rate constants were refined using CCSD(T)/CBS//B2PLYP-D3/cc-pvTZ calculations. Quantum calculations showed that the postulated growing schemes of the literature, based on the successive urea + HNCO ⇆ biuret, biuret + HNCO ⇆ triuret followed by the cyclization of triuret into isocyanuric acid are not energetically favored. It is observed that the most favored reaction route to isocyanuric acid involves carbamimidic acid, the urea tautomer, that first yields biuret in a reaction with HNCO and then is involved in the formation of triuret by reacting with a decomposition product of biuret. Isocyanuric acid is produced from the reaction between HNCO and the same decomposition product of biuret. This new mechanism of formation of isocyanuric acid is tested at different conditions to explore its most favored conditions of formation in the gas phase. Exploratory simulations of a pseudo condensed phase are also performed to qualitatively simulate condensed phase experiments and explain the observed pyrolysis yields.

The combustion and NOx emission characteristics of the ultra-low volatile fuel using the novel pulverized coal self-sustained preheating combustion technology

The pyrolysis semi-char and gasification fly ash, as the by-product of coal pyrolysis and gasification technology, have difficulties in combustion application due to its ultra-low volatile content. As a potential combustion technology, the novel pulverized coal self-sustained preheating combustion technology for the fuel with the ultra-low volatile was developed. The 16 MW novel self-sustained preheating combustion pilot plant was constructed and used for the study. The operation characteristics of the novel internal fluidized bed combustor (IFBC) for pulverized coal preheating and the effects of the secondary air on combustion and nitrogen oxides (NOx) emissions were investigated. The results showed that the fuel could be preheated up to 900 °C continuously and steadily by the IFBC and then fed into the furnace to burn stably. The combustion efficiency was higher than 96% with the lowest NOx emission of 110.0 mg/m3 (@6% O2). The flame images exhibited most areas were red while the marginal area was blue. With the decrease of the secondary air ratio, the flame length and the ignition delay distance decreased, and the flame profile became blurred. Meanwhile, the NOx emissions firstly decreased and then increased with the lowest value at the secondary air ratio of 0.39. The decrease of the momentum ratio of inside secondary air to outside secondary air had a certain effect on inhibiting NOx generation until the ratio dropped to less than 0.6.

The application of comprehensive two-dimensional gas chromatography to the analysis of wildfire debris for ignitable liquid residue

Arsonous wildfires are complex investigations due to the high abundance of natural background compounds and subsequent pyrolysis by-products formed during combustion. These interfering compounds can be present in large concentrations and overwhelm the marker compounds used to identify ignitable liquid residue (ILR). Complex matrix effects often interfere with the identification of ILR, providing ambiguous results. The use of comprehensive two-dimensional gas chromatography with time of flight mass spectrometry (GC×GC-TOFMS) separates natural compounds from interfering with ILR compounds of interest. When compared to standard gas chromatography-mass spectrometry (GC–MS) analysis, GC×GC was able to reduce the number of tentative results by 20%. Certain compounds were determined to be unusable for the identification of ILR in wildfire debris samples, in particular the Three Musketeer Group (ethylbenzene, m,p-xylene, and o-xylene), which are ubiquitous in all samples, as well as long chain n-alkylbenzenes, which are formed in the pyrolysis of organic matter. Conversely, the presence of C1- and C2-alkylnaphthalenes were excellent indicators of the presence of gasoline-type ILR. A sizeable number of background samples were collected that helped to provide additional lines of evidence when classifying samples for ILR. Given the complicated matrices encountered in arsonous wildfires, it is evident that GC×GC provides better capabilities at identifying ILR than the standard GC–MS analytical technique.

Catalytic pyrolysis and bio-products upgrading derived from Chlorella vulgaris over its biochar and activated biochar-supported Fe catalysts

Catalytic and non-catalytic pyrolysis of Chlorella vulgaris microalgae was studied and the temperature, as the primary variable, was assessed to optimize the process. By changing the temperature from 450–850 °C, the highest performance of 58.51 % was achieved in terms of energy recovery (ER) at the optimal temperature of 650 °C. Although known as a useless pyrolysis by-product, the remaining biochar was used as catalyst support to further improve the process efficiency. For this purpose, iron in various concentrations of 2.5, 5.0, and 10.0 wt% was used to impregnate the pristine and KOH-activated biochar. Due to the unique chemical and morphological characteristics of activated carbon, the metallic active sites were loaded more successfully. All catalysts were precisely examined via FT-IR, XRD, FESEM, BET and ICP-OES. Moreover, elemental analysis, GC, GC–MS, and TGA methods were used to investigate the bio-products characterization. Accordingly, in catalytic experiments, the energy recovery factor of biochar based catalyst (CBC), and activated biochar based catalyst (CAC) was increased from 58.51 % (optimum ER in non-catalytic) to 64.46 % and 71.58 %, respectively.

A dual-fuel heating system coupled with negative feedback for fast pyrolysis

To solve the problems that energy consumed excessively, temperature fluctuated largely in the pyrolysis process and pyrolysis by-products can not be used, a novel heating system was designed for pyrolysis, which used liquefied petroleum gas (LPG) and non-condensable gas (NG) to combust simultaneously. The PLC microcontroller utilized the negative feedback to control the pyrolysis temperature within the required temperature range. The experiment apparatus was built to obtain the heating system's temperature rising curve, product yield and input, consumption energy changes. The results showed that the heating system basically satisfied the pyrolysis conditions. The yield of liquid pyrolysis oil was 58.2 %, which was an energy balance but also the most economical point. At this time, the production of NG could provide thermal energy for the heating system to the utmost extent. The thermal energy balance analysis was carried out, finding that the pyrolysis temperature of 500℃ was an ideal condition, where the combustion gas replacement ratio was 76.2 %. Our studies have provided a new design pattern of the heating system for biomass fast pyrolysis with experiment research.

Pyrolysis of water hyacinth biomass parts: Bioenergy, gas emissions, and by-products using TG-FTIR and Py-GC/MS analyses

This study aimed to quantify the pyrolytic bioenergy potential of water hyacinth roots (WHR), stems and leaves (WHSL) by assessing their physicochemical properties, pyrolysis performances, kinetics, and thermodynamics. Their gas emissions and other by-products were also detected using thermogravimetry-Fourier transform infrared spectroscopy and pyrolysis–gas chromatography/mass spectrometry analyses. The WHR and WHSL pyrolysis consisted of the three consecutive stages of the moisture removal, devolatilization, and the decomposition of residuals. The main pyrolysis temperature varied between 200 and 600 °C. The elevated heating rate raised both initial devolatilization and peak temperatures and shortened the reaction times of the thermochemical conversions of both samples. According to the comprehensive pyrolysis index, WHSL outperformed WHR. The average activation energy estimates pointed to a lower decomposition cost for WHSL (172.09–173.09 kJ/mol) than WHR (230.11–232.06 kJ/mol). The fluctuating thermodynamic parameters indicated a complicated pyrolysis mechanism for WHR and WHSL. The main gases evolved from the WHR and WHSL pyrolysis in decreasing order were CO2, CO, C–O, SO2, CC, H2O, CH4, and CO. The main pyrolytic by-products were phenols (19.2%), and furans (12.4%) for WHR and nitrides (11.9%), and phenols (10%) for WHSL. Our results provide insights into scaling-up bioenergy potential, value-added by-products, and emission controls based on the pyrolysis of the water hyacinth biomass parts.

Linking biochars properties to their capacity to modify aerobic CH4 oxidation in an upland agricultural soil

Aerobic soils are the largest biotic sink for atmospheric methane (CH4). Although agricultural intensification is known to adversely impact soil CH4 uptake, the application of organic amendments (e.g. composts, green residues) in agricultural soils has been found to stimulate the activity of CH4 oxidizers. However, little is known about the influence of biochar (a carbonaceous by-product of biomass pyrolysis) on the soil CH4 sink function. This study analyzes, through a series of laboratory incubation assays, how ten well-characterized biochars with contrasting properties influence CH4 oxidation rate constants (k) in an aerobic high-pH agricultural soil. Through the use of 13C-CH4, we demonstrated that both CH4 soil oxidation and CH4 assimilation were responsible for the decrease in CH4 concentration. A principal component regression (PCR) of the results suggested that the physico chemical properties of biochars were directly linked to their ability to enhance or inhibit the oxidation of CH4. Biochars from wood feedstocks and pyrolysed at 600 °C, characterized by a high pore area, led to the highest CH4 oxidation rates whereas biochars with high ash concentrations and electrical conductivity significantly diminished CH4 oxidation rates. Biochar redox properties were not found to be relevant for CH4 oxidation in soil.

Influences of temperature, waste size and residence time on the generation of polycyclic aromatic hydrocarbons during the fast pyrolysis of medical waste

Mismanagement of Medical wastes can lead to human health and environmental risks. Currently, new pyrolysis technologies are being used to treat medical waste that can reduce the amount of landfilled waste, make it safe, and eventually convert it to a hydrocarbon fuel. Polycyclic aromatic hydrocarbons (PAHs) are pyrolysis by-products and major environmental pollutants. In this study, hazardous medical wastes were pyrolyzed using a semi-industrial pilot scale fast pyrolysis reactor with the purpose of improving the quality of the char for its recovery or use as fuel. The generation of total 4-6 rings PAHs was studied in char product from hazardous medical waste fast pyrolysis under different pyrolysis conditions variables including a vast temperature range (300-700°C), different residence times (100-190 s) and various waste particle sizes (1-3 cm). GC analyzer coupled with a FID detector was used to detect and measure the PAH compounds in char residues. The results demonstrated that the PAHs are present in significant concentrations in char product (54-1184 mg kg-1). Generation of total 4-6 rings PAHs varied by temperature, residence time and waste size. Significant interaction was observed between residence time and temperature that influenced the PAHs generation. By optimizing the pyrolysis operating conditions it is possible to minimize the amount of PAHs generation in the char.