Historical Developments of Pyrolysis Reactors: A Review

Developing an effective cleaner process technology for maize-cob biomass wastes is of utmost importance. This work involved the comparison of products yield (bio-oil, biogas, and biochar) from the fast, slow, and flash pyrolysis of maize-cob biomass wastes using a fixed-bed reactor; evaluation of the individual and combined influences of pyrolysis temperature, biomass particle size, and residence time on the yield of product, and the determination of the optimum pyrolysis conditions/products yield of fast pyrolyzed maize-cob. The fast pyrolysis was performed according to the Box-Behnken Design of Experiment with three variables and three levels of the response surface methodology. The bio-oil fuel properties were determined utilizing ASTM methods and chemically characterized using CHNS elemental analyzer, GC/MS, and FTIR. The performance of the three pyrolysis techniques in terms of their product yield is in the following order: Flash pyrolysis > Fast pyrolysis > Slow pyrolysis (for bio-oil); Slow pyrolysis > Fast pyrolysis > Flash pyrolysis (for biochar and biogas). An optimum bio-oil yield of 43.13% with a high heating value (HHV) of 30.59 MJ/kg, biochar yield of 37.18% with HHV of 20.41 MJ/kg, and biogas yield of 26.05% (HHV = 13.19 MJ/kg) was respectively obtained at an optimum temperature of 567.72, 463.71, and 593.17 °C; biomass particle size of 0.51, 3.83, and 2.58 mm; and residence time of 10.01, 15.28, and 18.92 min. The determined physicochemical characterized properties of the maize-cob-derived-bio-oil revealed that the bio-oil can potentially be valued as a biofuel and as a more promising feedstock for value-added chemical production.

Some agro-industrial wastes are currently untreated, resulting in an increase in greenhouse gas emissions. Therefore, in relation to the pollution generated by fossil fuels, the study of the obtained fuels from agro-industrial and forestry residues has been promoted. Rice is a basic product for several families in the world, and its residue is a component that has enormous potential in Colombia due to its consumption. The objective of the present study is to conduct an exergoeconomic evaluation of the production of fuel from rice husks as agro-industrial waste by means of the slow and fast pyrolysis process. Using simulators like Aspen Plus, the simulation of the two processes was carried up, implementing a rigorous kinetic model. The yield values were validated with data from the literature, obtaining values of 42.3% and 41.4% for slow and fast pyrolysis, respectively, for pyrolytic oil. The total investment cost of the process is 2146.45 kUSD. According to the thermodynamic parameters of the simulator, an exergy analysis was conducted for the two processes. Overall exergy percentages of 73.84% and 78.19% were obtained for the slow and fast pyrolysis, respectively. The economic and exergy analysis was coupled to implement a specific exergy costing. The exergoeconomics factors obtained values of 72.21% and 76.78%, for the slow and fast pyrolysis reactors, respectively. The contribution of the present research is related to the rigorous kinetic model, in addition to its implementation in slow pyrolysis, involved in the exergoeconomic study of biomass pyrolysis processes.

The objective of this study is to investigate the effects of slow and fast pyrolysis on the yields and properties of bio-oils using Macadamia nutshell (MNS) as feedstock. A pilot scale auger pyrolysis reactor which had the facilities of conducting both slow and fast pyrolysis was utilized. The pyrolysis processes were carried out at a temperature of 500 ˚C, the heating rate of 5 ˚C/min, a residence time of 60 mins, and a feedstock particle size of 2 mm. The characterization of feedstock and the produced bio-oils was performed by different techniques like elemental analysis, Gas chromatography-mass spectrometry (GC–MS), and physicochemical properties analysis using appropriate ASTM standards. Proximate and ultimate analysis showed promising prospects of MNS as a feedstock for the pyrolysis process. In the case of slow pyrolysis, the bio-oil yield was found to be 39.7%, whereas the bio-oil yield was 49.5% for the fast pyrolysis process. Significant changes in the peak region of GC–MS were observed for bio-oils produced under two different pyrolysis conditions. It was found from the physicochemical properties analysis that calorific value is higher and water content is lower in the bio-oil produced through fast pyrolysis than the bio-oil produced through slow pyrolysis. Comparison with standard biodiesel properties revealed that produced bio-oils were not suitable for use in engines at this stage. Proper upgradation is required to make it suitable for engine application. Based on these results it can be concluded that the produced bio-oils can be used as fuel in other applications such as in boilers and as additives to produce valuable chemicals.

Impact of fast and slow pyrolysis on the degradation of mixed plastic waste: Product yield analysis and their characterization

Valorization of peanut shells has recently gained prominence in the context of thermally converting agricultural waste into biochar, a carbon-rich byproduct with significant potential as a soil amendment. The present study delves into understanding the influence of slow (450°C and 500°C) and fast (550°C and 600°C) pyrolysis temperatures with a resident time of 60 and 30 minutes, respectively, on the physico-chemical properties of peanut shell biochar produced in a low-cost kiln. Results of the Scanning Electron Microscopy analysis revealed that increased pyrolysis temperature increased porosity and surface roughness with crystalline deposits. Thermogravimetric analysis showed that increased temperatures contributed to enhanced thermal stability but reduced biochar yield. Pyrolysis temperatures of 450, 500, 550, and 600°C exhibited 32.19, 29.13, 21.8, and 19.43 percent conversion efficiency with organic carbon content of 11.57, 6.48, 8.64, and 7.76 percent, respectively. The intensities of functional groups (C-H and C-O) declined, whereas the intensity of C=C and stable carbon content increased with the rise in temperatures. The concentrations of heavy metals in all biochar samples were below permissible limits outlined by international biochar initiatives. The study concluded that slow pyrolysis at 450°C for 60 minutes resident time is an ideal pyrolytic condition for producing peanut shell biochar in terms of qualitative and quantitative characteristics.

Biochars produced from groundnut shells at the condition of slow and fast pyrolysis (GB350 and GB700) were used as adsorbents for removal of cadmium (Cd2+), mercury (Hg2+) and lead (Pb2+) ions from aqueous solution. Adsorption experiments were carried out at different solution pH, constant biochar dosage and particle size of 2 mm, variant metal ion concentrations, constant contact time and temperature to determine the adsorption efficiency. The removal efficiency of groundnut shell biochar was greater than 99.60% for Cd2+ under the three maximum contaminants limits. The GB700 was able to ascertain 100% removal efficiency for Cd2+ and Pb2+ in binary mixtures with concentrations of 0.04:0.10, 0.08:0.20 and 0.20:0.50 mg/l. The removal efficiency of GB350 was 100% for Pb2+ and Hg2+ except Cd2+ that showed 99.05, 99.46 and 99.69% at folds one, two and five of the ternary system, respectively. The maximum Langmuir capacity for mono-component system was 0.14 for Hg2+ and 0.18 mg/g for Pb2+, 0.09–0.56 mg/g for binary mixtures, 0.05–0.10 mg/g for ternary mixtures by GB350 and GB700, respectively. The results showed groundnut shell biochar can be used as a cost-effective and effective adsorbent for the removal of heavy metals from aqueous environment. Based on the results, further experiments should be carried out to examine the adsorption of the heavy metal contaminants at higher concentrations, a reduced biochar dosage and different contact time.

Reaction of volatiles – A crucial step in pyrolysis of coals

Energy conversion assessment of vacuum, slow and fast pyrolysis processes for low and high ash paper waste sludge

Slow and fast pyrolysis of Douglas-fir lignin: Importance of liquid-intermediate formation on the distribution of products

With the increasing concern on fossil fuel storage and environmental problems, the utilization of renewable lignocellulosic biomass resources will play an increasing important role in the future. Biomass can be converted to a variety of fuels and chemicals by different technologies, one of them is fast pyrolysis which has received extensive interests in recent years (Bridgwater & Peacocke, 2000; Mohan et al., 2006). Fast pyrolysis of biomass is a thermal decomposition process that occurs in the absence of oxygen, with quickly biomass decomposition and rapid vapor condensation, to convert biomass mainly into a liquid product (know as bio-oil) with the yield as high as 70~80 wt%. The essential principles to obtain high bio-oil yield include moderate pyrolysis temperature (around 500 °C), very high heating rates (103 – 105 °C/s), short vapor residence time (< 2 s) and rapid quenching of pyrolysis vapors. A number of pyrolysis reactors have been developed for the bio-oil production, including bubbling fluidized bed, entrained bed, circulating fluidized bed, rotating cone, screw pyrolysis reactor, vacuum pyrolysis reactor, etc. In recent years, several research institutes (BTG, Dynamotive) have already established demonstration biomass fast pyrolysis plants, suggesting that the fast pyrolysis technique is near commercial. Crude bio-oils, also referred to as biomass pyrolysis liquids, pyrolysis oils, or bio-crude oils, are dark brown, free flowing liquids with an acrid or smoky odor. Chemically, bio-oils are complex mixtures of water and hundreds of organic compounds that belong to acids, aldehydes, ketones, alcohols, esters, anhydrosugars, furans, phenols, guaiacols, syringols, nitrogen compounds, as well as large molecular oligomers (holocellulose-derived anhydrooligosaccharides and lignin-derived oligomers). There are many valuable compounds, and thus, bio-oils have the potential for useful chemicals recovery. However, most of the chemicals are in low contents, making their recovery not only technically difficult but also economically unattractive at present. Therefore, the commercialization of bio-oils for valueadded chemicals requires the production of specific bio-oils with high contents of target products. Selective fast pyrolysis, differed from conventional fast pyrolysis which is usually aimed at the maximum bio-oil yield, is to drive the pyrolysis of biomass towards the products of interest. Since the biomass pyrolytic pathways and the subsequent products are influenced by various factors, and thus, selective fast pyrolysis can be performed in different ways, mostly by catalyst utilization, to (1) maximize the yield of target products and (2) obtain target products with high purity. This manuscript is divided into two sections. The first

The purpose of this project was to prepare and operate a fast pyrolysis process development unit (PDU) that can validate experimental data generated at the bench scale. In order to do this, a biomass preparation system, a modular fast pyrolysis fluidized bed reactor, modular gas clean-up systems, and modular bio-oil recovery systems were designed and constructed. Instrumentation for centralized data collection and process control were integrated. The bio-oil analysis laboratory was upgraded with the addition of analytical equipment needed to measure C, H, O, N, S, P, K, and Cl. To provide a consistent material for processing through the fluidized bed fast pyrolysis reactor, the existing biomass preparation capabilities of the ISU facility needed to be upgraded. A stationary grinder was installed to reduce biomass from bale form to 5-10 cm lengths. A 25 kg/hr rotary kiln drier was installed. It has the ability to lower moisture content to the desired level of less than 20% wt. An existing forage chopper was upgraded with new screens. It is used to reduce biomass to the desired particle size of 2-25 mm fiber length. To complete the material handling between these pieces of equipment, a bucket elevator and two belt conveyors must be installed. The bucket elevator has been installed. The conveyors are being procured using other funding sources. Fast pyrolysis bio-oil, char and non-condensable gases were produced from an 8 kg/hr fluidized bed reactor. The bio-oil was collected in a fractionating bio-oil collection system that produced multiple fractions of bio-oil. This bio-oil was fractionated through two separate, but equally important, mechanisms within the collection system. The aerosols and vapors were selectively collected by utilizing laminar flow conditions to prevent aerosol collection and electrostatic precipitators to collect the aerosols. The vapors were successfully collected through a selective condensation process. The combination of these two mechanisms has created the ability to effectively fractionate the bio-oil into distinct fractions with improved characteristics. The fractions of bio-oil each contained different properties. Bio-oil properties that were improved included the energy content, water content, acid content and distribution of certain carbohydrates (levoglucosan and acetic acid). The improved properties that are associated with the fractionated bio-oil could allow bio-oil to be used in new markets, preferably without further upgrading. The decreased water and acid contents in the first four (of five) fractions could allow for easier upgrading of the bio-oil into transportation fuels or other valuable products. Char and solid particulate content of bio-oil must be minimized. Solid particulate can erode surfaces, leading to decreased equipment and component life and increased maintenance. Char can contribute to the instability of bio-oil by acting as a catalyst and causing secondary reactions. To continuously remove char from the pyrolysis reactor product stream, two cyclonic gas separators (cyclones) were designed and constructed. The design of the two gas cyclones was based on gas flow rate, particulate density, desired efficiency and desired pressure drop.

In this study, kinetic parameters of fast and slow pyrolysis is compared. For fast pyrolysis, cylindrical wood pieces of 20 mm diameter and 50 mm length is pyrolysed in a tube furnace at temperatures ranging from 300°C to 500°C. Solid, liquid and gas products are collected and the yields are calculated. For slow pyrolysis, thermogravimetric analysis (TGA) is used using sawdust from the same biomass. Using the experimental data from two different methods the kinetic parameters are calculated such as activation energy and pre-exponential factor for the two different pyrolysis methods. For fast pyrolysis the parameters are found to be E = 32.5 kJ/mol andA= 35/min and for slow pyrolysis Es= 50.48 kJ/mol andAs= 3179.86/min. The large difference between the values show that kinetic studies and modelling work using thermogravimetric analysis data is not suitable for commercial scale simulation. Also, the pre-exponential value for fast pyrolysis shows that the kinetic equation used from flash pyrolysis is not exactly suitable for this situation. Therefore, it is recommended that more studies on the kinetic parameters of fast pyrolysis of thermally thick biomass need to be done.

Development of a generalized numerical framework for simulating biomass fast pyrolysis in fluidized-bed reactors

Biomass pyrolysis has been the focus of study by several researchers as a viable means of producing biofuels and other useful products. This paper gives a comprehensive, elaborate and updated review of pyrolysis technology as an efficient thermochemical route for biomass conversion. Pyrolysis products include pyrolytic gas, bio-oil, and solid biochar. Depending on the operating conditions, pyrolysis is usually classified as slow, intermediate, fast, and flash pyrolysis. The utilization of special catalysts can help facilitate pyrolytic gas production, while specific pretreatment processes can help facilitate bio-oil production. The efficiency of the pyrolysis process is affected by a number of factors such as temperature, heating rate, residence time, particle size, biomass type, and biomass pretreatment method. In this review, thermogravimetric analysis and kinetic modelling of biomass pyrolysis were also emphasized while the various constraints encountered during biomass pyrolysis have been highlighted and suggestions made to address them. More recently, more advanced experimental methods have been developed for biomass pyrolysis research, and these include Py-GC–MS/FID, TG-MS/TG-FTIR, in situ spectroscopy for reaction progress analysis, isotopic labelling, and intermediate product analysis techniques that enable the monitoring of the biomass devolatilization process as well as identification of the functional groups of the volatiles and monitoring of the changes in the functional groups on the surface of biomass in the course of pyrolysis. No doubt, biomass pyrolysis will continue to provide several benefits and serve as a sustainable means of producing biofuels, biochemicals, and other valuable products with far-reaching areas of applications.

Influence of fast pyrolysis temperature on biochar labile fraction and short-term carbon loss in a loamy soil