Reactor Unit Research Articles

The Energy and Exergy Analysis of the Reactor Unit of Boric Acid Production Process with ChemCAD Simulation

Energy and exergy analysis of systems are of great importance to enhance the energy and exergy efficiency of industrial production facilities. With the energy and exergy analyses performed, the energy dependency of the production facilities and their energy consumption can be reduced, the price of the product can decrease, and the profit margin can increase. Additionally, it is ensured that the energy produced based on fossil fuels is used in a controlled way. In the present study, the analysis of energy and exergy has been performed for the production reactor unit of the Boric Acid from Colemanite. The first law of thermodynamics and ChemCAD simulation program was used for energy analysis calculations, and the calculations of exergy analysis were carried out by using the second law of thermodynamics. The total energy loss of the reactor unit and the calculated energy loss per 100 kcal input steam were calculated as 110880 kcal/h and 3.724%, and the losses of total exergy in the reactor units and the losses of exergy calculated per 100 kcal input steam were calculated as 225058.86 kcal/h and 30.095%, respectively. Exergy efficiency for the reactor unit has been determined as 3.3 %. Some suggestions were given for the reactor units of boric acid production plants to minimize system losses.

Volatilization of B4C control rods in Fukushima Daiichi nuclear reactors during meltdown: B–Li isotopic signatures in cesium-rich microparticles

Boron carbide control rods remain in the fuel debris of the damaged reactors in the Fukushima Daiichi Nuclear Power Plant, potentially preventing re-criticality; however, the state and stability of the control rods remain unknown. Sensitive high-resolution ion microprobe analyses have revealed B–Li isotopic signatures in radioactive Cs-rich microparticles (CsMPs) that formed by volatilization and condensation of Si-oxides during the meltdowns. The CsMPs contain 1518–6733 mg kg–1 of 10+11B and 11.99–1213 mg kg–1 of 7Li. The 11B/10B (4.15–4.21) and 7Li/6Li (213−406) isotopic ratios are greater than natural abundances (~4.05 and ~12.5, respectively), indicating that 10B(n,α)7Li reactions occurred in B4C prior to the meltdowns. The total amount of B released with CsMPs was estimated to be 0.024–62 g, suggesting that essentially all B remains in reactor Units 2 and/or 3 and is enough to prevent re-criticality; however, the heterogeneous distribution of B needs to be considered during decommissioning.

Щодо будівництва нових ядерних енергоблоків в Україні

The article provides information on the pace of construction and commissioning of nuclear power units at nuclear power plants in the world over the past 60 years. Nuclear energy is the most important factor in ensuring the energy independence of Ukraine. As of 2022, 80% of the entire fleet of Ukrainian nuclear power units (12 out of 15) have already been in operation for more than 30 years. In the world, this figure is 68%. Two power units with VVER-440 reactors have been in operation for more than 40 years, and by 2028 the number of power units at Ukrainian NPPs, that have been in operation for more than 40 years, will increase to 10. Therefore, the need and importance of introducing a program for the construction of new nuclear power units to ensure energy independence of Ukraine are obvious. The article discusses the most important characteristics of the modern AP1000 reactor unit, which is licensed in the USA, Canada and some other countries. Information is presented on the advantages of the AP1000 project over other modern reactor plants EPR-1750, APR-1400, VVER-1200, as well as issues that need to be paid special attention, when performing the relevant stages of work on the justification and implementation of the AP1000 technology in the nuclear power industry of Ukraine. For example, the installed capacity utilization factor of operating power units with EPR-1750, APR-1400, VVER-1200 is lower than for АР1000. When justifying the decision to choose AP1000, it is necessary to pay attention to the already known problematic issues of implementing Westinghouse technology. It is recommended to involve the institutes of the National Academy of Sciences of Ukraine in the work, related to the scientific and technical substantiation of the choice of promising nuclear installations for Ukrainian NPPs.

SAFETY OF UKRAINE’S NUCLEAR POWER INDUSTRY IN EXTREME OPERATING CONDITIONS

An urgent issue of the state (level) of safety of Ukraine’s nuclear power industry in extreme conditions is the situation of the Zaporizhzhia NPP, the largest in Europe, due to the station’s location in the war zone and difficulties in its management and operation, as well as the safety regulation of the station in the occupied territory. In the proposed article, the possibility of Zaporizhia NPP industrial site flooding is analyzed from the elaborated hydrodynamic model and justifying calculation; the conditions of ZNPP industrial site possible flooding are determined depending on the warhead power producing a corresponding destructive effect. Probabilistic approaches to assessing the Zaporizhia NPP safety objective state (level) in extreme conditions are insufficiently justified taking into account the lessons of the largest nuclear and radiation accidents. On the basis of a deterministic approach, the conditions of Zaporizhia NPP industrial site critical flooding due to extreme military action are identified. Flooding of the plant’s industrial site may cause two initial emergency events: a complete long-term de-energization of power units and violation of heat exchange conditions in spent nuclear fuel dry storage facilities. Prevention of flooding of the Zaporizhia NPP industrial site can be based on the construction of protective flood barriers on the cooling pond coast. Prospective directions to increase the accident management efficiency related to the nuclear power units’ passive safety systems modernization and improvement of operational symptom-oriented emergency instructions/manuals for managing severe (nuclear) accidents have been identified. An effective accident management strategy with complete long-term de-energization of WWER power units can be based on a comprehensive modernization of emergency recharge systems of steam generators with steam driven pumps and natural circulation circuits of passive heat removal systems from the pressurized reactor unit.

Development of circuit model with natural circulation of coolant under conditions of ship motion

Safety is the key requirement to any nuclear power installation. Various factors affect safety during operation of the nuclear power installation. These factors are difficult to study due to the high economic costs. This problem can be solved by developing prototype models to conduct the research of many complex processes. Dynamic impact on the ship installation is one of these processes. The most significant impact is the impact on the natural circulation of the coolant, that is one of the basic emergency safety systems. Also, it is a promising way to ensure movement in the main circulation circuit. The purpose of this paper is to assess the influence of external dynamic forces on the processes of natural circulation. For the study a testing bench has been developed that simulates one of the circulation loops of the reactor unit. The basic method to obtain experimental data is temperature sounding of the specific sections of the circulation route. A mathematical model has been developed that describes this process. The model is based on the equations of momentum conservation and heat balance. In accordance with the experimental data, the calculation of natural circulation for static and dynamic modes has been carried out. A mathematical model to describe this process has been developed. A comparative analysis of the results of calculating the static and dynamic modes has been carried out. It is founded out that the decrease of mass flow rate is about 10 % as compared with the static regime. It confirms the qualitative effect of ship motion on natural circulation. The practical significance of the research is the development of a model under conditions of ship motion, as well as verification of the model at the testing bench. The results show a significant effect of ship motion on the mass flow rate of the coolant in the case of natural circulation. Thus, to ensure the required safety of ship installations, it is recommended to conduct a study of natural circulation in accordance with the developed model under conditions of maximum possible ship motion.

Technological and operating features of the AR-1000 reactors Generation III+ and small modular reactors MR-160

Technological and environmental analysis of the main characteristics of technological, operational and environmental safety in the context of progress in the main areas of development of reactor units such as VVER, MR-160 and AR-1000 for power units currently under development, design and construction is one of the most pressing issues development of world nuclear energy. This urgency in particular is due to the fact that on the basis of these technologies further development of Ukraine's nuclear energy is planned. The tasks of ensuring operational and radioecological safety for new generation power reactors are reduced to obtaining the lowest possible probability of events related to a possible accident, as well as the lowest possible probability of radiation consequences in compliance with all requirements of national and international regulations and recommendations adopted by a particular state and its civil society.

Features of methods for monitoring the fuel cladding tightness in lead-cooled fast breeder reactors

To timely detect failed fuel elements, a reactor plant should be equipped with a fuel cladding tightness monitoring system (FCTMS). In reactors using a heavy liquid-metal coolant (HLMC), the most efficient way to monitor the fuel cladding tightness is by detecting gaseous fission products (GFP). The article describes the basic principles of constructing a FCTMS in liquid-metal-cooled reactors based on the detection of fission products and delayed neutrons. It is noted that in a reactor plant using a HLMC the fuel cladding tightness is the most efficiently monitored by detecting GFPs. The authors analyze various aspects of the behavior of fission products in a liquid-metal-cooled reactor, such as the movement of GFPs in dissolved and bubble form along the circuit, the sorption of volatile FPs in the lead coolant (LC) and on the surfaces of structural elements, degassing of the GFPs dissolved in the LC, and filtration of cover gas from aerosol particles of different nature. In addition, a general description is given of the conditions for the transfer of GFPs in a LC environment of the reactor being developed. Finally, a mathematical model is presented that makes it possible to determine the calculated activity of reference radionuclides in each reactor unit at any time after the fuel element tightness failure. Based on this model, methods for monitoring the fuel cladding tightness by the gas activity in the gas volumes of the reactor plant will be proposed.

Module coordination control of multi-modular lead-based reactor systems

The multi-modular reactor, which connects multiple reactor units to drive a single turbine, is considered to be an innovation in the nuclear energy system. Since multiple reactor units are coupled together by the common secondary loop, the load change of any reactor will affect its own coolant temperature, and also the power of other reactor units. It is obviously that module coordinated control is significant for the safe and stable operation of the multi-modular reactor, which induces the necessity of the study in module coordination. Motivated by this, this paper proposes the method of decoupling between each module to realize the coordinated control of the multi-modular reactor. An operation and control simulation of the multi-modular lead-based reactor based on the China lead-based research reactor (CLEAR-I) is performed. The frequency domain identification method combined with the multivariable frequency response method is proposed to realize the effective decoupling of the system. The purpose of this method is to reduce the complexity of the control system design and make full use of the computer aided design technology. The transfer function matrix of the system is identified through the frequency response experiments. The pseudo diagonal dominance method is adopted to develop the constant diagonal dominant compensation matrix for the inverse transfer function, and then the inverse Nyquist array (INA) method is adopted to design controller for the compensated system. The design of the multiple-input multiple-output system is simplified to a series of single-variable system designs. The numerical results show the feasibility and satisfactory control performance.

Synthesis and Performance of Photocatalysts for Photocatalytic Hydrogen Production: Future Perspectives

Photocatalysis for “green” hydrogen production is a technology of increasing importance that has been studied using both TiO2–based and heterojunction composite-based semiconductors. Different irradiation sources and reactor units can be considered for the enhancement of photocatalysis. Current approaches also consider the use of electron/hole scavengers, organic species, such as ethanol, that are “available” in agricultural waste, in communities around the world. Alternatively, organic pollutants present in wastewaters can be used as organic scavengers, reducing health and environmental concerns for plants, animals, and humans. Thus, photocatalysis may help reduce the carbon footprint of energy production by generating H2, a friendly energy carrier, and by minimizing water contamination. This review discusses the most up-to-date and important information on photocatalysis for hydrogen production, providing a critical evaluation of: (1) The synthesis and characterization of semiconductor materials; (2) The design of photocatalytic reactors; (3) The reaction engineering of photocatalysis; (4) Photocatalysis energy efficiencies; and (5) The future opportunities for photocatalysis using artificial intelligence. Overall, this review describes the state-of-the-art of TiO2–based and heterojunction composite-based semiconductors that produce H2 from aqueous systems, demonstrating the viability of photocatalysis for “green” hydrogen production.

A feedforward-feedback-based reactor power decoupling control strategy for multi-modular nuclear power plants

Multi-modular nuclear power plants (MMNPPs) comprise of several SMRs working in parallel, a common steam header and one or more steam consuming units. The reactor units in this type of plant may share different portion of load and their power may interfere with each other due to a coupling effect through the common steam header. Hence, the load following characteristics of MMNPPs are different from that of single reactor plants. Investigation results show that the coupling effect between load following reactors (LFRs) and fixed power reactors (FPRs) affects the operation of the latter ones during load following or power compensation process. This is not favorable due to the extra movement of the control rods and valves may increase the risk of related accidents. In this research, a setpoint feedforward-feedback header steam pressure control method is proposed to decouple the power output of LFR units and FPR units. Control performance of the decoupling control method is evaluated and made comparison to that of conventional header steam pressure control method. Results demonstrated that the proposed reactor power decoupling control method shows better control performance than the conventional control method, with faster load following speed of the LFR and smaller overshoots of the header steam pressure, eventually keeping the FPR barely disturbed during the transients. This proposed reactor power decoupling control strategy will improve the operation performance, safety and reliability of the MMNPPs.

Separation of the 235U and 239Pu Prompt Energy Spectra in NEOS-II

The NEOS searches for sterile neutrinos by detecting reactor antineutrinos at a very short baseline in Korea. The NEOS detector (1-ton Gd-LS) is deployed at the tendon gallery of the Hanbit reactor unit 5 (2.8 GW thermal power), 23.7 m away from the reactor core. In NEOS-I, we measured the prompt energy spectrum from inverse beta decay using 180 days of reactor-on data and observed the “5 MeV excess”. To understand the origin of the “5 MeV excess”, NEOS-II has taken 368 (120) days of reactor-on (-off) data from September 2018 to October 2020, covering a whole burnup cycle of the reactor. We tested a method for the extraction of the prompt energy spectra for 235U and 239Pu from the whole burnup cycle using pseudo data.

Current state of development of industrial power complexes with fast neutron reactors

The report provides the description of the main demands, approaches and results of the design of the industrial energy complex (IPC) with fast nuclear reactors. A conceptual design (‘outline design’) of the IPC has been developed, which combines industrial reactor units with power output of 1200 MW and closed nuclear fuel cycle facilities. The main solutions and technical and economic indicators are defined. To get higher results with minimum resource spend, we implemented the way of consideration of different solutions, extensive use of digital technologies in designing, applying better solutions well-known both in the nuclear and other industries. The issue of the influence of preferred type of nuclear reactor on IPC design solutions was discussed. The perspective ways of further developments were defined.

Conservation of natural Uranium by inter unit transfer of fuel in PHWRs

For better utilization of land and infrastructure, multiple power reactor units are preferably constructed at same site. In the life of reactor, at some stage, it will undergo either major upgradation for plant life management or de-commissioning which requires whole reactor fuel to be discharged irrespective of burn-up. This includes a large amount of fuel, which has not achieved target discharge burn-up. In this paper, novel methodologies are explored and innovative techniques are proposed for ex-core fuel management (ECFM) and in-core fuel management (ICFM) to utilize low burn-up bundles in a twin unit PHWR by inter-unit transfer. This is achieved without any reprocessing of fuel. Using the proposed modified fuel management, a net economic benefit of equivalent fuel saving of ∼23% NU of the initial full core load of 37-element bundles in an PHWR-700 is achieved. Additionally, reactor operation of ∼60FPDs without using any fresh fuel is also accomplished.

Next Generation Water Recovery for a Sustainable Closed Loop Living

In order to facilitate extended human space travel, solutions and innovations are required to enable habitation in microgravity spacecraft habitats such as International space station (ISS), with limited supply availability. At present, the Environmental Control and Life Support System (ECLSS) within the ISS recovers and recycles 90% of the water from human waste. However, their efficiency decreases during their lifetime owing to unmanageable process contaminants, requiring ground support to supply complex hazardous chemicals to treat these system components such that they maintain their targeted performance[i] ,[ii],[iii]. As human missions travel further into the solar system, the availability of ground support will be diminished. Therefore, next-generation systems to recycle water are required to reduce waste and improve system efficiency. Within this context, Faraday Technology Inc. and the University of Puerto Rico (UPR) are developing a bio-electrochemical waste water treatment system. Within this system, a bioreactor will convert urea from the waste water to ammonia by hydrolysis:NH2(CO)NH2 + H2O → 2NH3 + CO2 (1)Next the effluent of the bioreactor will flow through the ammonia oxidation reactor:2NH3 → N2 + 3H2 (2)Thus, generating urea free waste water effluent for further filtration and enhancement. The developed technology has the potential to be compatible with existing ECLSS systems and be an integral part of the closed loop living systems required for long term life support on NASA’s manned space missions.Ongoing activity between Faraday Technology and UPR has demonstrated an 85% conversion of urea to ammonia in a bioreactor and a near complete conversion of ammonia in an electrochemical reactor in a laboratory set-up utilizing a synthetic urine electrolyte[iv] ,[v]. Based on the studies, Faraday has designed and built an alpha scale reactor to process 6 L volume of urine per day as per NASA specifications. The next step in reactor demonstration activities is to understand the effects of zero-gravity on the ammonia reactor. The electrochemical reactor and components are assembled in an electrochemical microgravity laboratory setup (Figure 1). Optimized conditions from ground-based performance data will be implemented during the zero-gravity flight test to evaluate the feasibility of ammonia oxidation in zero-gravity environment. The flight test is scheduled for May 2021.In this talk we will be discussing the ongoing developments at Faraday, where we have (1) leveraged existing knowledge to design and test the bio-electrochemical reactor under zero gravity conditions; (2) evaluated electrocatalyst for ammonia oxidation reactor; (3) optimized the electrocatalytic efficiency and waste water treatment rate with urine simulants; (4) designed and built a demonstration-scale bio-electrochemical reactor unit capable of meeting NASA required specifications; and (5) will be validating operation under zero gravity conditions during the May 2021 zero gravity test flight. Acknowledgements: The financial support of NASA Contract No. NNX17CA30P and 80NSSC18C0222 is acknowledged.

Performance evaluation of the integrated hydroponics-microbial electrochemical technology (iHydroMET) for decentralized domestic wastewater treatment

Here we report on the performance of the integrated drip hydroponics-microbial electrochemical technology (iHydroMET) for decentralized management of domestic wastewater at the household level. The study focused on optimizing the iHydroMET reactor components, followed by its performance evaluation for domestic wastewater treatment at different feed volumes. Based on the reactor components optimization work, granular activated charcoal:cocopeat (20:80) combination for bed matrix, 75% immersed cathode in effluent configuration, and Catharanthus roseus plant were selected for further experiments. The iHydroMET system with the optimized reactor components achieved efficient removal of organic matter (up to 93%) and turbidity (up to 98%) but minimal total nitrogen (<24%) and total phosphorous (<8%) removal after 24 h with 10 L of feed volume. It also removed the contaminants of emerging concern, such as sterols, at >95% efficiency. The UV-treated effluent (<2 MPN/100 mL) with considerable concentrations of N (∼34 mg/L) and P (∼5 mg/L) nutrients qualifies the standards for agricultural use and landscape irrigation purposes and contribute to lowering the burden on freshwater usage. The system also produced a power density of 30.3 mW/m2. Cultivation of evergreen C. roseus, a high aesthetic value ornamental and medicinal plant, further adds to ecological and environmental benefits of the iHydroMET technology. Further modifications in system operation like creating a saturation zone in the reactor units might improve the electric output and result in sufficient removal of nutrients, making the use of effluent for flushing and other purposes possible in households.

Scale-up of high-pressure F-T synthesis in 3D printed stainless steel microchannel microreactors: Experiments and modeling

Scale-up of Fischer-Tropsch (F-T) synthesis using microreactors is very important for a paradigm shift in the production of fuels and chemicals. The scalability of microreactors for F-T Synthesis was experimentally evaluated using 3D printed stainless steel microreactors, containing seven microchannels of dimensions 1000 µm × 1000 µm × 5cms. Mesoporous silica (KIT-6), with high surface area, containing ordered mesoporous structure was used to incorporate 10% cobalt and 5% ruthenium using a one-pot hydrothermal method. Bimetallic Co-Ru-KIT-6 catalyst was used for scale-up of F-T Synthesis. The performance of the catalysts was evaluated and examined for three different scale-up configurations (stand-alone, two, and four microreactors assembled in parallel) at both atmospheric pressure and 20 bar at F-T operating temperature of 240 °C using a syngas molar ratio (H2:CO) of 2. All three configurations of microreactors yielded not only comparable CO conversion (85.6–88.4%) and methane selectivity (~14%) but also similar selectivity towards lower gaseous hydrocarbons like ethane, propane, and butane (6.23–9.4%) observed in atmospheric F-T Synthesis. The overall selectivity to higher hydrocarbons, C5 + is in the range of 75–82% at 20 bars.A CFD model was used to investigate the effect of different design features and numbering up approaches on the performance of the microchannel reactor. The effect of the reactor inlet, the mixing internals and the channel designs on the dead zone %, the quality index factor, the cooling requirement and the maximum dimensionless temperature within the microreactor were quantified. There is no significant effect of increasing the channel width on the microreactor performance and operation of the microchannel reactor at lower Nusselt number that results in higher CO conversion. Increasing the channel width reduced the maximum temperature exhibited in the channel. Finally, the effect of increasing the y/x stacking ratio, i.e. having more reactor units in parallel compared to series, was investigated. Increasing the y/x ratio increased the cooling requirement and the maximum dimensionless temperature increase within the unit decreased the productivity. To minimize the productivity losses, numbering up in series is the better approach; however further analysis must be done to delineate heat removal requirements.

STATE'S READINESS MOBILITY IN APPLYING NUCLEAR TECHNOLOGY AS ENERY DEVELOPMENT IN LEGAL PERSPECTIVE

The states Nuclear Program is a program to build and utilize nuclear science and technology both in the non-energy sector and in the energy sector for peaceful purposes. Utilization of non-energy in Indonesia has developed quite advanced. The use of nuclear power in every countries covers various fields such as health, research and industry. Indonesia's readiness in implementing nuclear energy is carried out by ratifying international conventions, issuing laws, and issuing regulations from the Nuclear Energy Supervisory Agency, readiness in the field of infrastructure used to strengthen technology, and in Indonesia is committed to reducing 26% of greenhouse gas emissions in the year 2020. A nuclear power plant or nuclear power plant is a thermal power plant that uses one or more nuclear reactors as a heat source. The working principle of a nuclear power plant is almost the same as a steam power plant, using high pressure steam to turn a turbine. The rotation of the turbine is converted into electrical energy. The difference is the heat source used to generate heat. A nuclear power plant uses uranium as its heat source. The fission reaction (fission) of the uranium nucleus produces enormous heat energy. The power of a nuclear power plant ranges from 40 MWe to 2000 MWe, and a nuclear power plant built in 2005 has a power distribution from 600 MWe to 1200 MWe. As of 2015 there are 437 nuclear power plants operating in the world, which in total generate about 1/6 of the world's electrical energy. To date, around 66 nuclear power plants are being built in various countries, including China with 28 units, Russia with 11 units, India with 7 units, the United Arab Emirates with 4 units, South Korea with 4 units, Pakistan and Taiwan with 2 units each. Nuclear power plants are categorized based on the type of reactor used. However, in some plants that have several separate reactor units, it is possible to use reactor types that are fueled such as Uranium and Plutonium.

Analysis and Solution to Abnormity of DNBR Indicated by ICIS of a WWER Unit

To analyze the reason of difference between the departure from nucleate boling ratio (DNBR) indicated by the upper-level software and lower-level software of the in-core instrumentation system (ICIS) at a certain water-cooled water-moderated power reactor (WWER) unit under its first thermal test during raising power, an investigation was made on the critical heat flux (CHF) correlations adopted in the reactor thermal and hydraulic design and accident analysis of WWER unit. On the above basis, the reason behind the difference was found to be the use of different CHF correlations by the upper-level software and the lower-level software of ICIS through the simulation of thermal tests under 50%, 75% and 90% power level using WWER accident analysis code DINAMIKA-97, calculation of DNBRs and comparison with the ones measured in thermal-hydraulic tests. DNBR under 100% power level was predicted, which coincided with the measured DNBR very well and proved the correctness of the guess further. It is suggested that the CHF correlations adopted by the upper-level software and the lower-level software shall be modified to the same conservative CHF correlation to get a conservative DNBR.

Analysis of the Consequences of a Large Leak in a Steam Generator in a Two-Circuit Lead-Cooled Reactor Unit

Analysis of the Consequences of a Large Leak in a Steam Generator in a Two-Circuit Lead-Cooled Reactor Unit

Catalytic fast pyrolysis of beech wood lignin isolated by different biomass (pre)treatment processes: Organosolv, hydrothermal and enzymatic hydrolysis

Lignin is one of the three main structural components of lignocellulosic biomass and is considered as the most abundant source of aromatic and phenolic compounds. Lignin is produced as side-stream in the pulp/paper industry or as residue in the production of second-generation bioethanol. More recently, novel biomass fractionation processes in biorefineries have been developed aiming at the production of high quality/purity lignin towards its more efficient down-stream catalytic conversion to chemicals, monomers, and fuels. Within this context, in this work, we studied the thermal (non-catalytic) and catalytic fast pyrolysis on a Py/GC–MS system and a fixed-bed reactor unit of three types of lignin, all originating from the same biomass (beech wood sawdust) but with different isolation processes: organosolv lignin derived by the organosolv pretreatment/fractionation of biomass, surface extracted lignin derived by the mild Soxhlet extraction (with ethanol or acetone) from the hydrothermally (HT) in pure water pretreated biomass, and the enzymatic hydrolysis lignin derived as a lignin-rich solid residue from the enzymatic hydrolysis of the HT pretreated biomass. Conventional microporous ZSM-5 and mesoporous ZSM-5 zeolites (with intracrystal mesopores, ˜ 9 nm) were used as catalysts in the pyrolysis experiments. Both zeolites were very active in converting the initially produced via thermal pyrolysis methoxy-substituted phenols, benzenes and benzaldehydes mainly towards BTX mono-aromatics, such as 1,3-dimethylbenzene/p- and o-xylenes, toluene and trimethylbenzenes, as well as polycyclic aromatic hydrocarbons (PAHs, mainly naphthalenes). The mesoporous ZSM-5 induced higher dealkoxylation reactivity compared to the microporous ZSM-5 leading to higher concentration of BTX aromatics without a consequent increase of PAHs. The pronounced dealkoxylation/aromatization reactivity of both ZSM-5 zeolites resulted to lower yields (but highly aromatic) organic bio-oils (e.g. from 32−35 wt.% to 15−22 wt.%) compared to thermal pyrolysis, increased non-condensable gases (mainly CO, CO2, methane, ethylene and propylene) and formation of relatively low amounts of coke on catalysts (e.g. 3−5 wt.% on lignin) in addition to thermal pyrolysis char. The observed moderate variations in the characteristics of the three types of beech wood lignin, i.e. molecular weight (GPC), S/G ratio, inter-unit linkages (2D HSQC NMR) and elemental composition, did not induce a systematic/substantial differentiation in the thermal and catalytic fast pyrolysis product yields and composition.