Screw Reactor Research Articles

Bio-oil yield potential of some tropical woody biomass

Six tropical biomass samples namely: Ogbono wood (Irvingia wombolu), Mango wood (Mangifera indica), Neem wood (Azadiracta indica), Ogbono shell (Irvingia wombolu), Ogirisi wood (Neubouldia laevis) and Tropical Almond wood (Terminalia catappa) were pyrolyzed in a bench scale screw reactor at 450oC. The physicochemical properties of the samples were determined prior to the pyrolysis experiments. The bio-oil and bio-char produced were similarly characterized using standard procedures established by American Standard and Test Methods (ASTM). The highest bio-oil yield of 66 wt% and least bio-oil yield of 53 wt% were obtained from Neem wood and Tropical Almond wood respectively. The characterization results of the products show that even though the moisture content of the bio-oil was quite higher than those of the original feedstock, their higher heating values were higher than those of the parent feedstock. Both characterization results show that the feedstock and their fast pyrolysis products are good materials for bioenergy production. The Gas Chromatography Mass Spectroscopy (GC-MS) analysis of the bio-oil shows the presence of useful chemicals such as phenols and levoglucosan, which could be harnessed for industrial applications.

Flow Behavior and Aging of Pyrolysis Oils from Different Feedstocks

This work focuses on the flow behavior and accelerated aging of pyrolysis oils produced in a screw reactor from different feedstocks. Beech wood, wheat straw, chicken manure, and sewage sludge were pyrolyzed at 350, 400, 450, and 500 °C, and the viscosity of the corresponding oils was measured at four different temperatures between 20 and 80 °C, with values up to 1 Pa s at 20 °C. Newtonian flow behavior was observed, except for wheat straw pyrolysis oils at temperatures below 50 °C. Absolute viscosity values as well as flow activation energies (EA), covering a range from 38 to 57 kJ mol–1, turned out to be independent of the pyrolysis temperature, except for beech wood oil. In this latter case, a peak in viscosity and activation energy was found at a pyrolysis temperature of 450 °C and is attributed to the low water content of the oil obtained at this temperature. Accelerated aging experiments were conducted for 24 h at 40 and 80 °C. For the latter temperature, the effect of a free surface and an inert ga...

Pyrolysis of Rubber in a Screw Reactor

On the basis of an analysis of thermal methods described in the literature and from the results of experimental investigations of steam conversion, the authors have developed and created a facility for thermal processing of rubber waste. Rubber crumb was used as the raw material; the temperature in the reactor was 500°C; nitrogen, steam, and a mixture of light hydrocarbons (noncondensable part of pyrolysis products) represented the working medium. The pyrolysis yielded 36–38% of a solid fraction, 54–56% of a liquid hydrocarbon fraction, and 6–9% of noncondensable gases. Changes in the composition of the gas mixture have been determined at different stages of processing. Gas chromatography of pyrolysis gases has shown that the basic gases produced by pyrolysis are H2 and hydrocarbons C2H4, C3H6, C3H8, C4H8, C2H6, C3H6O2, and C4H10, and a small amount of H2S, CO, and CO2. Noncondensable gases will be used as a fuel to heat the reactor and to implement the process.

Assessing pretreatment reactor scaling through empirical analysis.

BackgroundPretreatment is a critical step in the biochemical conversion of lignocellulosic biomass to fuels and chemicals. Due to the complexity of the physicochemical transformations involved, predictively scaling up technology from bench- to pilot-scale is difficult. This study examines how pretreatment effectiveness under nominally similar reaction conditions is influenced by pretreatment reactor design and scale using four different pretreatment reaction systems ranging from a 3 g batch reactor to a 10 dry-ton/days continuous reactor. The reactor systems examined were an automated solvent extractor (ASE), steam explosion reactor (SER), ZipperClave®Reactor (ZCR), and large continuous horizontal screw reactor (LHR). To our knowledge, this is the first such study performed on pretreatment reactors across a range of reaction conditions and at different reactor scales.ResultsThe comparative pretreatment performance results obtained for each reactor system were used to develop response surface models for total xylose yield after pretreatment and total sugar yield after pretreatment followed by enzymatic hydrolysis. Near- and very-near-optimal regions were defined as the set of conditions that the model identified as producing yields within one and two standard deviations of the optimum yield. Optimal conditions identified in the smallest scale system (the ASE) were within the near-optimal region of the largest scale reactor system evaluated. The maximum total sugar yields for the ASE and LHR were 95,%, while 89,% was the optimum observed in the ZipperClave.ConclusionsThe optimum condition identified using the automated and less costly to operate ASE system was within the very-near-optimal space for the total xylose yield of both the ZCR and the LHR, and was within the near-optimal space for total sugar yield for the LHR. This indicates that the ASE is a good tool for cost effectively finding near-optimal conditions for operating pilot-scale systems. Additionally, using a severity factor approach to optimization was found to be inadequate compared to a multivariate optimization method. Finally, the ASE and the LHR were able to enable significantly higher total sugar yields after enzymatic hydrolysis relative to the ZCR, despite having similar optimal conditions and total xylose yields. This underscores the importance of mechanical disruption during pretreatment to improvement of enzymatic digestibility.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0620-0) contains supplementary material, which is available to authorized users.

A model of pyrolysis in a staged scheme of low-grade solid fuel gasification

The development and evolution of the theory of solid fuel combustion took place in the mid-20th century. The most studied research subject was sized fossil coal. At the same time the research on the fuels with a high yield of volatile matter (biomass) was limited due to insufficient data on kinetics of physical and chemical processes that occur at their heating. Obviously, the creation of a prospective low-tonnage technology for staged gasification of wooden biomass is possible only when a detailed mechanism of these processes is well understood and their kinetic parameters are known. This paper presents the initial results of the development of a model of wood pyrolysis in a screw reactor as the first stage of the multistage gasification process. One of the currently set goals in this research is to develop a mathematical model of heat and mass transfer processes to perform optimization calculations.

Thermal cracking of methyl esters in castor oil and production of heptaldehyde and methyl undecenoate

The main aim of this study was to investigate experimentally the thermal cracking of methyl esters in castor oil with a view to the production of heptaldehyde and methyl undecenoate as precursors for flavors and perfumes for the cosmetics and pharmaceutical industries. Experiments were carried out in a pilot plant with a screw reactor, under isothermal and continuous conditions at temperatures ranging from 475 to 525°C and residence times of 44–104s, with bio-oil production ranging from 48 to 228g/h. Mass balances were obtained by means of mass and chemical species measurements, using gravimetric and GC-FID/GC–MS analysis, respectively. Global bio-oil yields of 50–80wt.% were achieved, of which 2–12wt.% was methyl undecenoate and 14–18wt.% was heptaldehyde. The variations are attributed to the operational conditions in terms of temperature and residence time. The best conditions were a higher temperature and shorter residence time, which provided a mass fraction of 12–18wt.% for both products. In addition, a proposal for the simplified mechanism involved in the thermal cracking of methyl esters in castor oil, showing one pathway for the desired products and two pathways for the undesired products, is presented and discussed. All results were verified by experimental data on the mass fractions of the components in the bio-oil obtained from CG–MS analysis, as a function of the temperature and residence time.

Influence of temperature and residence time in the pyrolysis of woody biomass waste in a continuous screw reactor

The aim of this paper is to study the influence of temperature and residence time in the quality of the charcoal obtained in the pyrolysis of biomass waste, in order to be used as a reducing agent in metallurgical applications. Woody biomass waste (pinus pinaster) coming from forest activities carried out in the north of Spain has been pyrolyzed in a laboratory scale screw continuous reactor connected to a second reactor where the pyrolysis vapors have been thermally treated to promote further cracking, with the aim of diminishing tars and improving the composition of the gas phase.Both the peak temperature and the exposition time at peak temperature have an impact in the pyrolysis fractions yields and composition, however it is at 1173 K where the bigger changes occur both in pyrolysis products yield and composition. In all cases the solids obtained (charcoal) fulfill the requirements to perform as metallurgical reducers. The higher the peak temperature the greater the charcoal quality but the lower the pyrolysis solid yield since secondary pyrolysis reactions consume charcoal. The pyrolysis gases obtained are valuable products rich in CO (22–35 vol%) and hydrogen (35–50 vol%); on the contrary, the pyrolysis liquids obtained are mainly worthless products composed of water and some aromatic compounds (e.g. naphthalene, fluorene & antrhacene).

Thermocatalytic Reforming of Biomass Waste Streams

AbstractA thermocatalytic reforming (TCR®) unit patented by Fraunhofer UMSICHT was tested to convert lignocellulosic biomass and three organic wastes, digestate, paper sludge, and sewage sludge, into enhanced pyrolysis products. The TCR® reactor is an intermediate pyrolysis screw reactor connected to a reformer. hawse have explored the TCR® of four feedstocks in a 2 kg h−1 laboratory‐scale plant. The aim of the work was to compare the product yields and qualities (biochar, bio‐oil, and syngas) obtained by using TCR® under the same pyrolysis conditions (pyrolysis at 400 °C and postcatalytic reforming at 700 °C). Finally, paper sludge bio‐oil was distilled at several temperatures to obtain the oil fractions. High‐quality bio‐oil and syngas from four different kinds of biomass were obtained and compared to that from traditional intermediate pyrolysis and fast pyrolysis. The bio‐oil showed a high higher heating value (HHV) (35–38 MJ kg−1) independent of the kind of biomass used, and the total acid number was 1.8–5.4 mgKOH g−1. Fractional distillation led to a gasoline‐like light fraction and an overall distillation rate of 74 %.

Fast pyrolysis of lignocellulosics in a twin screw mixer reactor

A process development unit (PDU) with 10kg/h biomass capacity was designed, built and operated for fast pyrolysis of biomass. A twin-screw type reactor, in earlier applications used for treatment of coal, oil shale, oil sand and oil refinery residues, was used. Test campaigns with a variety of biomass types were performed. The results with hard-wood, softwood, wheat straw and wheat bran are reported and discussed in this paper, verifying the suitability of the twin screw reactor along with a new product recovery procedure. Liquid pyrolysis condensate, termed bio-oil, is the main product of FP and the yields are about 65±10wt.% for wood but only about 50±10wt.% for cereal straw, which is a typical result for all fast growing types of biomass with higher ash content. These product yields and properties are similar to those found for other FP reactor types and recovery procedures.

Continuous pyrolysis of pine sawdust at different pyrolysis temperatures and solid residence times

In this work, the continuous pyrolysis of pine sawdust is performed with a screw reactor to investigate the influence of pyrolysis temperature and solid residence time on products and energy distribution. Gas chromatograph/mass spectrometer (GC/MS) and Fourier transform infrared spectroscopy (FTIR) were used to confirm the identities of bio-oil. The combustion kinetics of bio-char had analyzed by thermo-gravimetric (TG). The results of gas chromatograph showed that carbon monoxide is the main component in produced gas, and the maximum gas yield of 54.5% was obtained at the temperature of 900°C. Compositional analysis of the oil products showed that phenols were the major components, and its proportion increased at higher temperatures and longer solid residence times. The activation energy of bio-char combustion is 461.10kJmol−1 and 108.45kJmol−1 in the ranges of 290–314°C and 314–518°C, respectively. The maximum of energy profit rate is 6.49% obtained at the temperature of 900°C with the solid residence time of 6min.

Torrefaction of pine in a bench-scale screw conveyor reactor

Numerous works are reported in the literature regarding the torrefaction of biomass in batch processes. However, in industrial applications, continuous reactors and processes may by more interesting as this allows for the integration of continuous mass and heat flows. To shed light on the operation of continuous torrefaction processes, this work presents the findings of continuous, bench-scale (2.5 kg h−1) torrefaction experiments using pine wood particles as a feed material in a screw conveyor reactor. The shifts in product mass yields were in line with theoretical expectations for changes in reactor temperature and reactor residence times whereas the degree of filling within the screw reactor and the flow of the nitrogen purge gas were found to be negligible. The process allowed for the measurement of the particle surface temperatures throughout the length of the reactor and significant temperature differences where measured between the wall of the reactor and the reactor screw. The proximate composition and the higher heating value of the torrefied biomass were found to be correlated to the ratio of the mass of dry biomass feed to the mass of the torrefied biomass produced. Important observations regarding the operability of such a process, also relevant to larger-scale processes, include the need to prevent the occurrence of torrefaction vapour condensation (which leaves the torrefaction reactor in the form of a saturated vapour) in the presence of fine, solid particles as this leads to rapid particle agglomeration and process blockage.

Continuous alkaline pretreatment of Miscanthus sacchariflorus using a bench-scale single screw reactor

Miscanthus sacchariflorus ‘Goedae-Uksae 1’ (GU) was developed as an energy crop of high productivity in Korea. For the practical use of GU for bioethanol production, a bench-scale continuous pretreatment system was developed. The reactor performed screw extrusion, soaking and thermochemical pretreatment at the following operating conditions: 3mm particle size, 22% moisture content, 140°C reaction temperature, 8min residence time, 15g/min biomass feeding and 120mL/min NaOH input. As a result of minimizing NaOH concentration and enzyme dosage, 90.8±0.49% glucose yield was obtained from 0.5M NaOH-pretreated GU containing 3% glucan with 10FPUcellulase/g cellulose at 50°C for 72h. The separate hydrolysis and fermentation of 0.5M NaOH-pretreated GU containing 10% glucan with 10–30FPU for 102h produced 43.0–49.6g/L bioethanol (theoretical yield, 75.8–87.6%). Thus, this study demonstrated that continuous pretreatment using a single screw reactor is effective for bioethanol production from Miscanthus biomass.

Pyrolysis of Medium Density Fiberboard (MDF) wastes in a screw reactor

Medium Density Fiberboard (MDF) wastes were undergoes via a thermal treatment through of a pyrolysis process. Pyrolysis was carried out in a pilot scale reactor with screw conveyor at two reaction temperatures (450 and 600°C) and, for each one, three solid residence times (9, 15 and 34min) were evaluated. Products (char/bio-oil/fuel gas) of the pyrolysis process were characterized and quantified. Results revealed that the products yields were influenced by pyrolysis temperature, as well as by solid residence time. Char yield ranged between 17.3 and 39.7 (wt.%), the bio-oil yield ranged between 23.9 and 40.0 (wt.%), while the fuel gas yield ranged between 34.6 and 50.7 (wt.%). The samples surface area at 450 and 600°C in 15-min residence time were surprisingly high, 415 and 593m2g−1, respectively, which are compatible with the superficial area of commercial activated carbons. Energetic efficiency of process was estimated from energetic content present in the reaction products and the energetic content of MDF wastes, and the following results were obtained: 41.4% (fuel gas), 35.5% (char) and 29.2% (bio-oil). The contribution of this work is the development of a detailed study of the MDF pyrolysis in a pilot reactor with screw conveyor that supports the biorefineries concept.

Screw pyrolysis with integrated sequential hot gas filtration

In this study, the pyrolysis of beech wood chips has been investigated by means of intermediate pyrolysis in a screw reactor with integrated hot gas filtration. Temperatures between 350°C and 500°C have been applied to characterize the yields and properties of the pyrolysis products. The yield of the char decreases with increased temperature from 31wt.% to 18wt.% whereas, the yield of the oil phase reaches a maximum value of 13,2wt.% at 450°C. The viscosity of the oil changed with temperature in the range of 74,6mPa s to 163,4mPas. Acetic acid, furfural and acetaldehyde have been selected to monitor the degradation of the holocellulose derived products, while guaiacol and phenol for that of the lignin-derived ones, showing that it may be possible to treat the pyrolysis of the wood main components adopting a relative small number of liquid organic species. Furthermore, the configuration of the reactor allows the sequential filtration and extraction of the vapors, as well the direct access to the partially pyrolyzed char. The sequential extraction appears as a promising route to concentrate valuable products. Among the results, it has been found that the heating rate in the range of 100°C/min to 210°C/min does not play a major role on the characteristics of the produced char.

Production and characterization of a new quality pyrolysis oil, char and syngas from digestate – Introducing the thermo-catalytic reforming process

A 2kg/h laboratory scale thermo-catalytic reforming (TCR®) unit was designed and commissioned at Fraunhofer UMSICHT to convert digestate into enhanced pyrolysis products. The TCR® reactor is an intermediate pyrolysis screw reactor connected to a reformer. In the experimental series reported, digestate pellets were used as feedstock. The aim herein was to test and characterize the TCR® reactor for the feedstock digestate and its products for syngas applications and decentralized power production. Prior to the pyrolysis experiments thermal gravimetric analysis was used to analyze the weight loss over temperature. The digestate was pyrolyzed at a constant temperature of 400°C, whereas the reformer temperature was varied between 500 and 750°C. Following the cooling and condensation of pyrolysis vapors, these separated into bio-oil, an aqueous phase and permanent gases. Hydrogen concentration increased together with increased reforming temperatures and reached a maximum of 35vol% at 750°C. The bio-oil generated at 750°C had a higher heating value of 33.9MJ/kg, 1.7wt% water content and a total acid number of 4.9mgKOH/g. It was possible to convert over 91% of the energy content of the biomass into usable products. These results are analyzed together with the extensive feedstock and product characterization and the experimental parameters and discussed.

Residence time distributions of coarse biomass particles in a screw conveyor reactor

Rotating screw conveyors can be utilized in the application of heat to granular materials: the mechanical motion of the rotating screw provides a controlled means of transferring the product through different thermal sections. This is particularly interesting for thermochemical biomass reactor applications such as slow pyrolysis and torrefaction. To understand the transfer of heat to the biomass, it is necessary to predict the residence time distribution of the material within the rotating screw reactor. Experiments were performed using a bench-scale (2.5kg/h) rotating screw conveyor. In this work, it has been shown that an empirical mathematical model is sufficient for predicting the mean residence time of various materials (pine chips of different sizes, rice and sand) if the rotational frequency of the screw conveyor and the volumetric throughput rate are both known. The model parameters obtained in this work were found to be independent of material selection but are specific to the geometry of the screw reactor. The form of the mathematical model proposed in this work may be applied to similar applications. Unlike the mean residence times, the axial dispersion calculated from the experimental data showed greater variability and this precluded any predictive modeling.

Applied thermal pyrolysis of cogongrass in twin screw reactor

Thermal pyrolysis by heat transfer model can be solved the control temperature in twin screw feeder for produce bio-oil from Cogongrass by novel continuous pyrolysis reactor. In this study, all yield were expressed on a dry and their values were taken as the average of the thermal controlled. Thermal of pyrolysis were carried out at 400–500°C. The products yield calculation showed that the liquid yield of Cogongrass by pyrolysis was higher than that solid and gas yield, as highest of 52.62%, at 500°C, and the other of liquid yield obtained from Cogongrass were 40.56, and 46.45%, at 400, and 450°C, respectively. When separate liquid phase be composed of the bio-oil was highest 37.39%, at 500°C. Indicated that biomass from Cogongrass had good received yields because of low solid yield average and gas yield and high liquid yield average. The compounds detected in bio-oil from Cogongrass showed the functional group, especially; Phenol, Phenol 2,5-dimethyl, Benzene 1-ethyl-4-methoxy, 2-Cyclopenten-1-one, 2,3-dimethyl, Benzene 1-ethyl-3-methyl.

Pyrolysis of cassava rhizome in a counter-rotating twin screw reactor unit

A counter-rotating twin screw reactor unit was investigated for its behaviour in the pyrolysis of cassava rhizome biomass. Several parameters such as pyrolysis temperature in the range of 500-700°C, biomass particle size of <0.6mm, the use of sand as heat transfer medium, nitrogen flow rate of 4-10 L/min and nitrogen pressure of 1-3 bar were thoroughly examined. It was found that the pyrolysis temperature of 550°C could maximise the bio-oil yield (50 wt.%). The other optimum parameters for maximising the bio-oil yield were the biomass particle size of 0.250-0.425 mm, the nitrogen flow rate of 4 L/min and the nitrogen pressure of 2 bar. The use of the heat transfer medium could increase the bio-oil yield to a certain extent. Moreover, the water content of bio-oil produced with the counter-rotating twin screw reactor was relatively low, whereas the solids content was relatively high, compared to some other reactor configurations.

The intermediate pyrolysis and catalytic steam reforming of Brewers spent grain

Brewers spent grain (BSG) is a widely available feedstock representing approximately 85% of the total by-products generated in the brewing industry. This is currently either disposed of to landfill or used as cattle feed due to its high protein content. BSG has received little or no attention as a potential energy resource, but increasing disposal costs and environmental constraints are now prompting the consideration of this. One possibility for the utilisation of BSG for energy is via intermediate pyrolysis to produce gases, vapours and chars. Intermediate pyrolysis is characterised by indirect heating in the absence of oxygen for short solids residence times of a few minutes, at temperatures of 350–450°C. In the present work BSG has been characterised by chemical, proximate, ultimate and thermo-gravimetric analysis. Intermediate pyrolysis of BSG at 450°C was carried out using a twin coaxial screw reactor known as Pyroformer to give yields of char 29%, 51% of bio-oil and 19% of permanent gases. The bio-oil liquid was found to separate in to an aqueous phase and organic phase. The organic phase contained viscous compounds that could age over time leading to solid tars that can present problems in CHP application. The quality of the pyrolysis vapour products before quenching can be upgraded to achieve much improved suitability as a fuel by downstream catalytic reforming. A Bench Scale batch pyrolysis reactor has then been used to pyrolyse small samples of BSG under a range of conditions of heating rate and temperature simulating the Pyroformer. A small catalytic reformer has been added downstream of the reactor in which the pyrolysis vapours can be further cracked and reformed. A commercial reforming nickel catalyst was used at 500, 750 and 850°C at a space velocity about 10,000L/h with and without the addition of steam. Results are presented for the properties of BSG, and the products of the pyrolysis process both with and without catalytic post-processing. Results indicate that catalytic reforming produced a significant increase in permanent gases mainly (H2 and CO) with H2 content exceeding 50vol% at higher reforming temperatures. Bio-oil yield decreased significantly as reforming temperature increased with char remaining the same as pyrolysis condition remained unchanged. The process shows an increase in heating value for the product gas ranging between 10.8–25.2MJ/m3 as reforming temperature increased.

Production of charcoal as an alternative reducing agent from agricultural residues using a semi-continuous semi-pilot scale pyrolysis screw reactor

Nowadays there is widespread concern regarding the CO2 emissions derived from fossil fuels due to the contribution of this gas to the greenhouse effect. Many metallurgical processes use fossil carbonaceous materials like e.g. petroleum coke as a reducing agent involving the emission of substantial amounts of carbon dioxide. One interesting alternative is the substitution of the mentioned fossil-based reducing agents with biomass derived charcoal. Typical carbonization processes are operated between 623 and 773K, but this charcoal does not fulfill the required quality for metallurgical processes. In the present paper a (semi-) continuous carbonization process was developed at high temperatures in order to produce charcoal to be used as a reducing agent. The effect of the temperature, residence time, moisture content and grain size were studied in an auger pyrolysis reactor, and the charcoal quality was tested carrying out reactivity tests, CHN+S as well as calculating the fixed carbon percentage.