Two-stage Reactor Research Articles

Comparative study on pilots between ANAMMOX favored conditions in a partially saturated vertical flow constructed wetland and a hybrid system for rural wastewater treatment

The objective of this research was to evaluate the nitrogen removal in a single stage rural wastewater treatment system. It was a modified subsurface vertical flow (SSVF) constructed wetland. The so-called Anaerobic Ammonium Oxidation(ANAMMOX) process is favored by imposing a saturated zone at the bottom of the basin. The nitrogen removal performances of this modified SSVF were compared to those of a conventional hybrid system where the well-known nitrification-denitrification process is performed. This study was carried out using three lab-scale pilots of constructed wetlands during four months: (1) a hybrid constructed wetlands with a reed-Phragmites australis SSVF bed in serial with a cattail-Typha angustofolia SSHF bed (SSVFp + SSHF). (2) A reed-Phragmites australis SSVF bed partially saturated at 40% of its depth (SSVFPS); (3) A cattail-Typha angustofolia SSVF bed partially saturated at 40% of its depth (SSVFTS). The results showed that the three configurations used in this study were efficient for most of the pollutants reduction. In fact, single-stage reactors have achieved similar chemical oxygen demand (COD) removal in comparison to the two-stage reactor independently of the macrophytes species. However, for Total Kjeldahl Nitrogen (TKN), a slightly higher nitrogen removal efficiency was recorded for (SSVF p + SSHF) with an average removal rate of 53% versus 48% and 51% for SSVF PS and SSVFTS respectively. These findings were highlighted with fluorescent in situ hybridization (FISH) analysis, which demonstrated the presence of major differences in the community composition and abundance of the bacteria involved with denitrification and nitrification in the three systems. In fact, SSVFP of the hybrid system was characterized by highest relative abundance of nitrifying bacteria (13% Nitrosomonas, 11% Nitrosospira, 14% Nitrospira and 10% Nitrobacter). While, the SSHF of hybrid system had larger number of denitrifying species than SSVF, with relative abundances of pseudomonas (3%), Paracoccus (9%), Zoogloea (6%), Thauera (4%), Thiobacillus (2%) and Aeromonas (1%). Interestingly, in the SSVFST (planted with Thypha angustofolia) where the relative abundance of nitrifying bacteria was very low (4% Nitrosomonas, 4% Nitrosospira, 4% Nitrospira and 1% Nitrobacter), we have detected the presence of ANAMMOX bacteria (3%). Accordingly SSVFST in the presence of Thypha angustofolia have favored the development of ANAMMOX activity in comparison to the other configurations.

Volatiles reaction during pyrolysis of corn stalk – Its influence on bio-oil composition and coking behavior of volatiles

Reaction of nascent volatiles is unavoidable during biomass pyrolysis and significantly influences the product yield, bio-oil quality and coking on the reactor wall. However, experimental studies in this aspect are still very limited. This work aims to advance the knowledge in this aspect using a two-stage reactor. Volatiles were generated in-situ from pyrolysis of corn stalk at 540 °C and swept off to the second-stage reactor preheated at 440–650 °C with a residence time of 1.5–4.7 s. The bio-oil quality was evaluated using simulated distillation gaschromatography. Results show that with increasing the volatiles temperature, the bio-oil yield decreases but the quality is improved: the contents of phenols, aldehydes and monocyclic aromatics increase significantly, those of esters and alcohols increase slightly and the contents of ketones, acids and furans decreases. Effect of volatiles residence time on the bio-oil quality depends on the volatiles temperature: becoming worse at 440 °C and better at 600 °C with increasing the residence time. The volatiles reaction also generates a few tetrahydrofuran-insoluble compounds, depositing on the downstream wall of the second-stage reactor (termed coke-wall) or suspending in bio-oil (termed soot-oil). The coke-wall yield increases with increasing volatiles temperature and residence time and is generally higher than the soot-oil yield.

Biogenic oxygenates in lignite pyrolysis tars and their thermal cracking revealed by two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC-TOFMS)

GC×GC-TOFMS was applied to characterize oxygenates in five lignite tars, which were produced from the pyrolysis of a low-maturity lignite in a two-stage reactor with thermal cracking of volatile matter at a different temperature (500–800 °C) and without thermal cracking. The analysis of the two tars obtained by no cracking and cracking at 500 °C identified 349 and 469 oxygenates with a higher reliability, respectively. Those oxygenates embraced a considerable variety of biomarker species. Many biomarker compounds were the constituents of essential oils or extracts of plants, including long-chain fatty oxygenates (e.g., linolenic acid, erucic acid and 2-hexyldecanol), terpenoids (e.g., cedrenol, caryophyllene oxide and artemisinin) and aromatic compounds (e.g. vanillin, cinnamic acids and flavoniods). Besides, cellulose-degraded primary compounds (e. g., levoglucosenone and furfural) and lignin-derived guaiacols were detected. The results strongly indicated the preservation of various biogenic compositions in the lignite due to the low microbial activity and immature diagenesis. The study also reported the changes of oxygenate classes with cracking temperature by classifying them into chain fatty oxygenates, alicyclic oxygenates and aromatic oxygenates.

Product distribution of the thermal and catalytic fast pyrolysis of karanja (Pongamia pinnata) fruit hulls over a reusable silica-alumina catalyst

The conversion of karanja fruit hulls by fast pyrolysis was investigated using a drop-type two-stage reactor. The ex-situ catalytic fast pyrolysis of karanja fruit hulls over a silica-alumina catalyst was performed at 500 °C and at a catalyst loading of 0.1 g. The obtained bio-oil yield was 41.09 wt%. The bio-oil contained 84.38% carbonyls. The silica-alumina catalyst reduced the liquid yield to 39.73 wt%. The production of aromatics and hydrocarbons in bio-oil was enhanced, whereas the yield of carbonyls was reduced from 84.38% (non-catalytic) to 7.83% (catalytic). After catalyst regeneration, the aromatic yield was increased from 30.08% (1st run) to 52.18% (5th run), and the deoxygenation degree was increased from 35.15% (1st run) to 57.13% (5th run), thereby demonstrating that the silica-alumina catalyst had satisfactory reusability. The amount of catalytic coke was reduced after catalyst regeneration, because less hard coke was formed.

Catalytic performance of scrap tyre char for the upgrading of eucalyptus pyrolysis derived bio-oil via cracking and deoxygenation

Catalytic pyrolysis of biomass is one of the potential routes to convert lignocellulose material to high-value bio-fuels. In this paper, we explored the use of Zn-rich scrap tyre char, a low-value byproduct from the pyrolysis of waste scrap tyre as a catalyst for in-situ upgrading of crude bio-oil derived from the pyrolysis of eucalyptus. Experiments were performed in a two-stage fixed-bed reactor at 500 °C with a catalyst loading of 0–80 wt% on the mass basis of biomass. The characteristics of catalyst and bio-oils were conducted extensively by different facilities, including Karl Fischer titration, XRF, CHNS, FTIR, solvent extraction, and synchrotron C K-edge XANES. A removal of 40.3% oxygen in the form of H2O, CO2 and CO was confirmed upon the loading of 80 wt% scrap tyre char. Simultaneously, the bio-oil yield decreased from 33.4 wt% to 21.1 wt%. The acid-soluble inorganic species in scrap tyre char preferentially cracks the heavy hydrocarbons, thereby decreasing the yields of heavy pitch and coke. The catalyst loading is critical, triggering a rapid increase in the cracking/deoxygenation extent upon increasing the catalyst loading to 40 wt%. Afterwards, the change on the extent of deoxygenation is marginal. Based on the gaseous products, the content of CO2 is the highest, confirming the preferential decarboxylation catalysed by scrap tyre char. In contrast, the amount of CO derived from decarbonylation reaction is nearly unchanged, suggesting an insignificant effect of scrap tyre char on this deoxygenation reaction. The catalytic performance of tyre char was also found comparable to and even slightly better than the zeolitic catalysts tested under the similar conditions in the literature. However, its catalysis mechanism is fully unknown. The abundant ZnS within tyre char has yet to be reported as a catalyst for bio-oil deoxygenation. This inorganic species is even deeply embedded and inaccessible to acid washing within the tyre char. Investigation on its detailed structure and transformation for the catalysis reactions with bio-oil are underway.

The reaction behavior of volatiles generated from lignite pyrolysis

The reactions of volatiles generated from coal pyrolysis determined the tar yield and composition. In order to investigate the effect of the reaction behavior of volatiles on the distribution of pyrolysis products, especially the tar yield and composition, the reactions of volatiles generated from the Shengli lignite (SL) pyrolysis using a two-stage fixed-bed reactor, with the first stage for lignite pyrolysis and the second stage for reactions of volatiles, were investigated in this paper. It was found that the reactions of volatiles resulted in an increase in gas and coke yield and a decrease in tar yield during lignite pyrolysis. And the effect of reaction temperature in the range of 700–900 °C on the distribution of light tar is significantly greater than that of the volatiles’ residence time in the range of 4–14 s. Reactions of volatiles shortened the carbon chain length of alkanes and increased the content of arenes and phenols in light tar under certain conditions. When the volatiles’ reaction temperature was 700 °C and the volatile’s residence time was 8 s during coal SL pyrolysis at the heating rate of 10 °C/min, the phenols content was 1.5 times higher than that of raw light tar. It was found that the more heavy components content the volatiles contained, the more heavy components content the final tar contained after the volatiles reaction.

Highly dispersed nickel nanoparticles supported on hydrochar for hydrogen-rich syngas production from catalytic reforming of biomass

The synthesis of carbon-based nanomaterials, ideally produced via facile, inexpensive approaches, using sustainable resources as precursors, with modulated structures, morphologies and functionalities is still challenging for energy applications. This work developed a mild one-step hydrothermal synthesis route for the fabrication of highly dispersed metallic nickel nanoparticles on hydrothermal carbons derived from waste biomass. The roles of precursor nickel ion concentration and calcination temperature in modulating the morphology, location and crystalline size of the nickel nanoparticles as well as the metal-support interactions have been delineated. The average grain size of the metallic nickel nanocrystals on the resultant Ni0.5@HCOp nanocatalysts could be tuned to 8–13 nm by varying the preparation conditions. The catalytic abilities of the Ni-based nanocatalysts towards hydrogen-rich syngas production and tar reduction were then tested in a two-stage reactor system using sewage sludge as biomass feedstock. The catalytic tests showed that the Ni0.5@HCOp catalyst calcined at 700 °C was shown to have stronger metal-support interactions compared to other Ni-based nanocomposites, which provided better suppression of coke deposition and resistance of nickel agglomeration during the catalytic gasification process. This highly active catalyst promoted formation of hydrogen-rich syngas, with up to 109.2 g H2/kg sludge, and tar yields as low as 2.12 mg g−1.

Effect of volatiles’ reaction on composition of tars derived from pyrolysis of a lignite and a bituminous coal

In coal pyrolysis, the reaction of volatiles plays an important role in determination of tar yield and composition but has not been studied in detail in the literature. This work studies the volatiles’ reaction in pyrolysis of a bituminous coal (SM) and a lignite (HLBE) using a two-stage fixed-bed laboratory reactor with the second-stage temperature of 440–700 °C and the residence time of 1.5–6.9 s. The tars were characterized by solvent extraction with tetrahydrofuran (THF) and hexane, and by simulated distillation (SIMDIST) of the THF soluble matter and high performance liquid chromatography (HPLC) analysis of the hexane soluble matter. It was found that the main component of the tars was oil, which was more in the HLBE tar than in the SM tar. As much as >50 wt% oil and tar retained in the chromatograph columns. The volatiles reacted at temperatures as low as 440 °C and the rate was more pronounced at 600 °C in 4.2 s. The volatiles’ reaction reduced the oil yield while increased the pitch yield. The aromatics in the hexane soluble matter were mainly 2-ring compounds and their content increased by the volatiles’ reaction. The major tar fractions have boiling points of 200–538 °C and their content varied systematically in the volatiles reaction. The findings are important for design of efficient coal pyrolysis reactors.

Enhanced production of aromatics from propane with a temperature-shifting two-stage fluidized bed reactor.

A temperature-shifting two-stage fluidized bed reactor technology was used to convert propane and its intermediate products into aromatics. The first stage served for the aromatization of propane with a Ga/ZSM-5 catalyst at 570 °C. The second stage served for the alkylation of the intermediates of olefins at 300 °C. The increased yield of aromatics was attributed to the effective transformation of C2–C3 olefins as well as due to the suppression of the hydrogen transfer effect of the olefins.

Demonstration of Chemical Looping Combustion (CLC) with Petcoke Feed for Refining Industry in a 3 MWth Pilot Plant

Chemical Looping Combustion (CLC) is a promising combustion technology with inherent CO2 capture. This process consists in use of metal oxides, called oxygen carriers, to transfer oxygen from Air Reactor into the Fuel Reactor for combustion of Fuels. Accordingly, Air and Fuel are not mixed and the produced flue gas is concentrated in CO2 and not diluted with nitrogen. This inherent CO2 capture results in higher energy and carbon capture efficiencies compared to conventional capture technologies. This paper presents recent achievements of TOTAL in collaboration with IFPEN on CLC development for the refining and chemical industry with petcoke feedstock. A novel concept has been developed with a two-stage combustion reactor, an integrated solid-solid separator (Carbon Stripper), and non-mechanical solid flow control devices. These technologies have been demonstrated at different scales up to a 1 MWth equivalent cold flow prototype and in a 10 kWth continuous pilot plant. These experimental works permitted to carry out a full-scale process simulation with steam and electricity cogeneration. Different sections of CLC are represented in this simulation including reactor system, flue gas treatment, CO2 compression, and steam cycle. In addition, the cost of avoided CO2 has been evaluated for power generation with Chemical Looping technology. Finally, CHEERS project is introduced in which CLC process will be demonstrate in 3 MWth scale via an international collaboration including nine partners from Europe and China.

Enhanced debromination by Fe particles during the catalytic pyrolysis of non-metallic fractions of printed circuit boards over ZSM-5 and Ni/SiO2-Al2O3 catalyst

A two-stage fixed-bed reactor was used to investigate the catalytic pyrolysis of non-metallic fractions of printed circuit boards (PCBs) over ZSM-5 and Ni/SiO2-Al2O3 (Ni/SA) catalysts. The addition of Fe particles to the catalyst was evaluated for bromine removal from the pyrolysis products. Results showed that the oil yield was significantly reduced from 50.1 wt% to 41.2 wt% by ZSM-5 catalyst and 36.0 wt% by Ni/SA catalyst, respectively, with corresponding increases of aqueous and gas products. The addition of Fe particles to ZSM-5 catalyst slightly altered the product yields, whereas the mixture of Fe and Ni/SA catalyst largely reduced the oil yield to 25.6 wt%, along with the highest gas yield of 20.3 wt%. The results suggested that the mixture of Fe-Ni/SA catalyst accelerated the cracking of vapor products derived from PCBs rather than the Fe-ZSM-5 mixture. Moreover, ZSM-5 catalyst favored the formation of single ring aromatics in the oils, such as benzene and toluene. The presence of Fe particles increased the concentration of phenol in the oils. The ZSM-5 and Ni/SA catalyst demonstrated great debromination performance for the conversion of organobromine compounds into HBr, reducing the bromine content in oils from 8.74 wt% to 5.96 wt% and 5.46 wt%, respectively. Furthermore, the addition of Fe particles reduced both the organobromine compounds and evolved HBr, which resulted in less than 3.8% of Br being transferred in the oil whereas more than 50% of bromine was fixed in Fe particles.

Catalytic gasification of refuse-derived fuel in a two-stage laboratory scale pyrolysis/gasification unit with catalyst based on clay minerals

Municipal solid waste (MSW) disposal is a serious environmental issue requiring immediate solution and good waste management strategy. Mechanical-biological treatment (MBT) plants offer the opportunity to reduce the amount of MSW that is, otherwise, disposed of in landfills. Up to 40% of MSW is converted to waste fuel, also called refuse-derived fuel (RDF). Gasification is a promising alternative of RDF processing. It can be defined as high temperature treatment of the feedstock with lower than stoichiometric amount of oxygen resulting mainly in a gaseous product (syngas). High hydrogen content, specific ratio of H2/CO, and low tar content are important parameters of syngas for its application in both energy production and chemical synthesis. Reduction of tar content in syngas can be achieved by catalytic tar cracking. In this work, a catalyst prepared from natural clay was characterised by thermogravimetric, specific surface area, X-ray diffraction, X-ray fluorescence and scanning electron microscopy (SEM) analyses. Catalyst activity was tested in two reactions, namely in decomposition of model tar constituent, p-xylene, and in cracking of tar produced in RDF gasification experiments. Influence of the reaction temperature and the amount of catalyst on the p-xylene conversion and products’ distribution was studied. The results proved high catalytic activity of the prepared catalyst in the decomposition of p-xylene. Coupled RDF pyrolysis and the produced volatiles gasification experiments were carried out in a two-stage laboratory scale reactor using a bed of tar cracking catalyst in the second stage. Tar decomposition experiments were carried out at the reactor temperatures of 700–850 °C applying different amounts of catalyst (0.75 g, 1 g, 1.25 g, 1.5 g, 2 g and 4 g) per 1 g of pyrolised RDF. Results indicate that the presence of catalyst had significant effect on both tar cracking efficiency and gas composition. Loss of the catalyst specific surface area was observed when the experiments were carried out at temperatures exceeding 800 °C.

A two-step method for the integrated removal of HCl, SO2 and NO at low temperature using viscose-based activated carbon fibers modified by nitric acid

Activated carbon fibers (ACFs) have been widely used as cost-effective integrated processes for the removal of nitrogen oxides, sulfur oxides and hydrogen chloride (HCl), while the competitive adsorption behaviors and the detailed interaction mechanisms have not been comprehensively investigated. In the current work, the adsorption capacities with one-step process and two-step method were compared, and the effects of HNO3 modification and ambient O2 concentration were simultaneously studied. Furthermore, the relative ratios of surface nitrogen groups, sulfur and chlorine compounds, as well as the soluble species on the ACFs surface, were respectively characterized by X-ray photoelectron spectroscopy and ion chromatography techniques. The results indicated that HCl, SO2 and NO were not able to be effectively removed with only one reactor due to the strong competitive adsorption behaviors, while the adsorption capacities of HCl, SO2 and NO were significantly improved by 30%, 280%, 230% in the two-stage reactors with HNO3 modification. Further investigation indicated interactions between HCl, SO2 and NO in the two-stage reactors are very complicated. The primary reactor can remove HCl and facilitate the catalytic removal of SO2/NO in the secondary reactor since HCl can severely inhibit the adsorptions of SO2 and NO, yet HCl adsorption can be suppressed by SO2. Simultaneously, nitro/nitroso groups derived of HNO3 treatment and NO oxidation can promote the chemisorption of HCl.

Study on steam reforming of coal tar over Ni[sbnd]Co/ceramic foam catalyst for hydrogen production: Effect of Ni/Co ratio

The effect of Ni/Co ratio on the catalytic performance of NiCo/ceramic foam catalyst for hydrogen production by steam reforming of real coal tar was studied. The NiCo/ceramic foam catalyst was synthesized by deposition-precipitation (DP) method and characterized with different methods. The experiments were conducted in a two-stage fixed-bed reactor. The results showed that the reducibility of the metallic oxides in bimetallic NiCo/ceramic foam catalysts was influenced obviously by the Ni/Co ratio.Both gas and hydrogen yield increased first and then decreased with the decline of Ni/Co ratio, and the highest hydrogen yield of 31.46 mmol g−1 was obtained when the Ni/Co ratio was 5/5. The lowest coke deposition of 0.34 wt% was generated at the same Ni/Co ratio. The lifetime test showed the catalyst maintained catalytic activity after 14 cycles (28 h), indicating the coal tar steam reforming on NiCo/ceramic foam catalyst is a promising method for hydrogen production.

Microbial activity response to hydrogen injection in thermophilic anaerobic digesters revealed by genome-centric metatranscriptomics

BackgroundThe expansion of renewable energy produced by windmills and photovoltaic panels has generated a considerable electricity surplus, which can be utilized in water electrolysis systems for hydrogen production. The resulting hydrogen can then be funneled to anaerobic digesters for biogas upgrading (biomethanation) purposes (power-to-methane) or to produce high value-added compounds such as short-chain fatty acids (power-to-chemicals).Genome-centric metagenomics and metatranscriptomic analyses were performed to better understand the metabolic dynamics associated with H2 injection in two different configurations of anaerobic digesters treating acidic wastes, specifically cheese manufacturing byproducts. These approaches revealed the key-genes involved in methanation and carbon fixation pathways at species level.ResultsThe biogas upgrading process in the single-stage configuration increased the CH4 content by 7%. The dominant methanogenic species responsible for the upregulation of the hydrogenotrophic pathway in this reactor was Methanothermobacter wolfeii UC0008. In the two-stage configuration, H2 injection induced an upregulation of CO2 fixation pathways producing short-chain fatty acids, mainly acetate and butyrate. In this configuration, the abundant species Anaerobaculum hydrogeniformans UC0046 and Defluviitoga tunisiensis UC0050 primarily upregulated genes related to electron transport chains, suggesting putative syntrophisms with hydrogen scavenger microbes. Interestingly, Tepidanaerobacter acetatoxydans UC0018 did not act as an acetate-oxidizer in either reactor configurations, and instead regulated pathways involved in acetate production and uptake. A putative syntrophic association between Coprothermobacter proteolyticus UC0011 and M. wolfeii UC0008 was proposed in the two-stage reactor. In order to support the transcriptomic findings regarding the hydrogen utilization routes, an advanced bioconversion model was adapted for the simulation of the single- and two-stage reactor setups.ConclusionsThis is the first study investigating biogas reactor metatranscriptome dynamics following hydrogen injection for biomethanation and carbon fixation to short-chain fatty acids purposes. The same microbes showed different patterns of metabolic regulation in the two reactor configurations. It was observed an effect of the specialized acidogenic reactor on the overall microbial consortium composition and activity in the two-stage digester. There were also suggested the main species responsible for methanation, short-chain fatty acids production, and electron transport chain mechanisms, in both reactor configurations.

Pyrolysis of sawdust with various Fe-based catalysts: Influence of support characteristics on hydrogen-rich gas production

In the present study, we studied the hydrogen-rich gas production from catalytic pyrolysis of sawdust using various Fe-based catalysts derived from layered double hydroxide (LDH) precursor in a two-stage fixed-bed reactor. Specifically, we investigated the effect of support characteristics (Fe–Mg, Fe–Ca and Fe–Al) on the physicochemical properties and catalytic performances in relation to hydrogen production and coke formation. Various characterization techniques, such as XRD, SEM, BET, H2-TPR and TG-DTG temperature-programmed oxidation (TPO), were employed to thoroughly characterize the fresh and reacted Fe-based catalysts. It revealed that the support characteristics played an important role in determining the iron species form, textural properties and catalytic abilities of the resulting catalysts. The Al-supported Fe-based catalyst was found to be the most effective catalyst for hydrogen-rich gas production with the highest gaseous efficiency of 61.4 wt.%, gas yield of 598 mL/g biomass, H2 yield of 217 mL/g biomass, and H2/CO molar ratio of 2.5 at 700 °C. Based on the results of structural characteristics, this might be attributed to its fine particle, enhanced reducibility, high surface area and generation of surface acidity by introduction of Al form, which could provide efficient active sites for pyrolysis volatiles to crack and reform through a series of catalytic reactions. According to GC–MS experiment results, the Fe–Al catalyst was capable of selectively producing aromatic compounds, with the maximum yield as high as almost 100%. Therefore, the Fe–Al catalyst developed in this work could provide a promising route for hydrogen-rich gas production from catalytic pyrolysis of biomass.

Stability analysis and design of model predictive reset control for nonlinear time-delay systems with application to a two-stage chemical reactor system

This paper presents a systematic Lyapunov-based approach for reset control of nonlinear time-delay system. The reset controller consists of a base controller and a reset law that enforces resets to the controller states. The reset actions are triggered if predefined reset conditions are satisfied and reset law is used to determine reset values of the controller states. A model predictive strategy is proposed to design the reset law by solving a linear matrix inequality optimization problem. Based on Lyapunov–Krasovskii approach, the reset controller with guaranteed asymptotical stability is synthesized. Finally, we apply the developed method to the control design of a two-stage chemical reactor with delayed recycle streams, and the simulation results verify the effectiveness of the main results.

Investigation into role of CO2 in two-stage pyrolysis of spent coffee grounds

As a way of improving process efficiency of pyrolysis of waste biomass, the effect of carbon dioxide (CO2) on pyrolysis of spent coffee grounds (SCGs) was examined using a two-stage pyrolysis reactor consisting of a region with increasing temperature and an isothermal region. It was experimentally validated that CO2 accelerates thermal cracking of organic compounds formed during the pyrolysis of SCGs. The expedited thermal cracking attributed to employing CO2 in pyrolysis of SCGs led to changing pyrolytic products in gas, liquid, and solid phases. The production of gaseous carbon monoxide was increased when using CO2 as the pyrolysis medium. In liquid pyrolytic products, the formation of phenolic compounds was hindered in the CO2-assited pyrolysis. Biochar morphology (solid pyrolytic product) was also changed with different pyrolysis environments. This study shows that CO2 can help improve applicability of pyrolysis of waste biomass by modifying three phase pyrolytic products in a two-stage pyrolyzer.

Effects of HZSM-5 on volatile products obtained from the fast pyrolysis of lignin and model compounds

This study aimed to experimentally investigate the effect of HZSM-5 on the distribution of volatile products, especially carbon monoxide (CO), C1–C5 hydrocarbons and aromatic hydrocarbons (AHs) during catalytic pyrolysis of lignin and lignin model compounds. Catechol was pyrolyzed using a two-stage tubular reactor (TS-TR) connected to a gas chromatography system over HZSM-5 at 550–950 °C. Forty-three products, including four inorganic gases, twenty C1–C5 hydrocarbons, and nine AHs were quantified using three GC-columns. Results indicated that HZSM-5 accelerated the catechol conversion with a large amount of CO and AHs produced. C1–C5 hydrocarbons were formed during non-catalytic pyrolysis of model compounds, and consumed quickly during HZSM-5 catalytic pyrolysis of catechol. Catalytic pyrolysis of phenol, guaiacol and syringol was carried out at 650 °C in the TS-TR over HZSM-5. HZSM-5 obviously promoted the conversion of lignin model compounds, and largely increased the yield of volatile products especially CO and AHs. Three lignin samples were also catalytically pyrolyzed over HZSM-5 in the TS-TR at 650 °C. HZSM-5 increased the yield of C2-C3 hydrocarbons and AHs, and reduced the yield of oxygenated compounds. HZSM-5 could promote the formation of AHs (lower than 10 wt%) during lignin pyrolysis, but not as obviously as during model compounds pyrolysis (higher than 19 wt%). High yields of char and tar would account for the low catalytic efficiency of HZSM-5 during lignin pyrolysis.

System analysis of the ethylbenzene dehydrogenation reactor as a control object

Catalytic dehydrogenation of ethylbenzene charge in a two-stage continuous-action adiabatic reactor is the main stage of the styrene production process. The analysis of this technological process existing automated control systems revealed the following main drawback, that these systems require great efforts from production personnel to ensure a change of the reactor temperature regime in the stages of the reactor in accordance with styrene concentration drop, which is caused by deactivation catalytic layer deactivation. Therefore, the synthesis of the target product concentration at the reactor outlet predictive control system is actual task in the field of technical cybernetics. This article presents the system analysis results of the dehydrogenation reactor as a control object. The main research result is a method choice for controlling of the chemical transformations temperature regime in the reactor, using that, it is possible to increase the energy efficiency and productivity of this device. The general and specific tasks of the control system synthesis are formulated on the basis of the system analysis, the information and functional synthesis of the temperature regime ACS is produced, the information and functional schemes of the reactor unit process equipment control subsystems are developed. As an operating system ACS is selected, which realizes of steam-ethylbenzene mixture temperature change at the reaction zones entrances of the 1st and 2nd reactor sections in accordance with the program control algorithm on the basis of predicting models, describing the heat exchange processes occurring inside the reactor stages as well as the dynamics of changes in such parameters as the concentration of coke deposits, catalyst activity, the basic and by- products concentration of chemical reactions.