Table of Content

28 October 2023, Volume 23 Issue 10

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Contents

Cover and Contents

The Chinese Journal of Process Engineering. 2023, 23(10):  0. 

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Review

Research process of multivesicular liposomes

Xing FAN Hua YUE Xiaojun WANG

The Chinese Journal of Process Engineering. 2023, 23(10):  1371-1380.  DOI: 10.12034/j.issn.1009-606X.222431

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Since 1983, multivesicular liposomes (MVLs), as a member of the liposome family, have been of interest in the biomaterials and medical fields. MVLs have multiple aqueous compartments separated by phospholipid bilayers and an internal aqueous phase of up to 90%. They also have the advantages of reducing the number of injections, extending the duration of drug action, and improving patient compliance. So far, most of the MVLs reported in the literature are above 10 μm in size and have made good progress mainly in the encapsulation of analgesic drugs. This review provides an overview of the preparation methods, characterization methods, and drug release mechanisms of MVLs that have been reported in the literature in the last decade. There are relatively several methods for preparing MVLs, including the double emulsification method, spray atomization technique, and electroforming method. Currently, the main characterization methods used for MVLs are optical/fluorescent confocal imaging, scanning electron microscopy imaging, determination of particle size distribution, entrapment efficiency, and determination of zeta potential. Because of the large volume of the internal aqueous phase of MVLs and the high hydrophilic drug encapsulation rate of the internal vesicles, the individual vesicles gradually rupture and the hydrophilic drug gradually gets released during in vitro release, with a three-phase release pattern of sustained release. This review also summarizes the current status of clinical studies and types of commercialized products. At present, the application of MVLs regarding analgesics has reached stages II-IV, and three commercialized formulations have entered the clinic with satisfactory results. Moreover, this review summarizes the current progress in applied research, mainly in the delivery of anticancer drugs, analgesic drugs, and protein peptides. Last but not least, the challenge and prospects regarding small-sized MVLs, diverse biomedical applications, and scale-up strategies are proposed.

Research progress of flotation activator for complex copper oxide minerals

Haoxiang WANG Peilun SHEN Jinpeng CAI Xiaodong JIA Rong PENG Dianwen LIU

The Chinese Journal of Process Engineering. 2023, 23(10):  1381-1389.  DOI: 10.12034/j.issn.1009-606X.222336

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Copper is widely used in industry because of its excellent physical and chemical properties.At present, with the depletion of copper sulfide resources, the development and utilization of copper oxide resources has gradually become the focus of research. As an important source of copper metal extraction, the key to efficient recovery of copper oxide ore is the activation process. However, the existing copper oxide resources have the characteristics of high oxidation rate, complex mineral composition and easy sludge, which makes the beneficiation more difficult. The classical sulfidization-xanthate flotation method can't meet the current requirements of complex copper oxide ore resource separation. In addition, the mechanism of activator acting on mineral surface and the unclear explanation of crystal structure of activated products restrict the development of the theory and method of copper oxide ore separation to some extent. In recent years, a variety of new activators or combination activators have been reported in reference for the complex and difficult-to-beneficiated copper oxide resources. Scholars have made a deeper research and elaboration on the activation mechanism of copper oxide ore based on the existing activation theory, and put forward a variety of effective and practical new theories and methods, which have solved the problem of complex copper oxide ore beneficiation to some extent. In this review, by combing the development of activator for copper oxide ore in recent years, the application and activation mechanism of new activator and new activation method are summarized, aiming at enriching the theoretical system of efficient flotation of copper oxide ore and providing reference for production practice.

Research Paper

Effect of conical distribution plate with slit hole on flow characteristics in fluidized reactor

Tiancheng WANG Gong CHEN Dexi WANG Lixin SHAO

The Chinese Journal of Process Engineering. 2023, 23(10):  1390-1400.  DOI: 10.12034/j.issn.1009-606X.222472

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Water pollution has gradually become one of the prominent problems restricting the harmonious development of urban ecosystem. At present, the development of efficient wastewater treatment technology has important practical significance to alleviate this problem. Wastewater treatment reactor is the core equipment of wastewater treatment, and the internal flow characteristics affected by its structure have an important impact on water treatment efficiency. Fluidization reactor has become a common sewage treatment equipment because of its high heat and mass transfer rate. In view of the liquid phase back mixing and uneven liquid-solid mixing still exist in fluidized reactor for wastewater treatment. Based on the mobile biofilm wastewater treatment technology and the concept of maximizing the space utilization of integrated wastewater treatment equipment, a rectangular fluidized reactor with slit hole conical distribution plate was designed. The orifice area of the distribution plate gradually increased from the center of the reactor to the outside, and the Euler-Euler multiphase flow model and RNG k-ε turbulence model were used for numerical simulation of the fluidized reactor with a conical distribution plate with slit holes. The effect of the distribution plate structure on the distribution of particles in the reactor was studied by the arrangement of the holes and the cone angle of the slit hole conical distribution plate. The results showed that the conical distribution plate with slit holes can solve the problems of liquid-phase backmixing and uneven liquid-solid mixing, form multiple ring core flows in the reactor, improve the uniformity of particle distribution, and strengthen the liquid-solid mixing. Based on the comprehensive evaluation of particle volume fraction, flow rate, and bed density standard difference, the optimal hole distribution mode of the slit conical distribution plate was determined to be perpendicular to the central axis, and the optimal fluidization effect of the reactor appeared under the cone angle of 120°.

Influence of structure of swirlers on fluid field characteristics of main absorption tower

Zhanyu YANG Qiling YIN Tuanliang WANG Yuge LI Wenming SONG Yufu ZHANG Yuan YAN Liping WEI

The Chinese Journal of Process Engineering. 2023, 23(10):  1401-1410.  DOI: 10.12034/j.issn.1009-606X.222384

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The main absorption tower of natural gas with high hydrogen sulfur content purification needs regular welding repair due to corrosion. Before and after repair, the internal combustion integral heat treatment technology can be used to perform hydrogen-eliminating treatment and eliminate stress. The arrangement of swirlers has an important impact on air distribution and flame control during the heat treatment. In this work, the fluid field characteristics of two-stage swirler, single-stage swirler I and II in the absorption tower are simulated, respectively. The results show that there is no obvious recirculation zone above the two-stage swirler and the velocity distribution is uniform. A large tangential velocity is generated above the inner and outer swirler blades. The maximum tangential velocity is 8.33 m/s when the inlet velocity is 9.8 m/s, followed by single-stage swirler II and single-stage swirler I, 4.5 m/s and 3.12 m/s, respectively. The pressure drop in the tower corresponding to the two-stage swirler has the smallest change. These prove that the two-stage swirler can effectively generate low resistance swirling flow field. The proportion of the streamline at the bottom of the tower corresponding to the two-stage swirler changes steadily with the gas mass flow rate, and is kept at about 14%, which is consistent with the percentage of the tower bottom wall in the total surface area of the tower body. It can ensure that enough gas media return to the tower bottom and promote gas convection. The 90% residence time of two-stage swirler increases linearly with the increase of gas mass flow rate. In general, the swirling effect of the two-stage swirler is better than that of the other two swirlers, and this study provides a reference for the optimization design of swirl device of internal combustion integral heat treatment process.

Liquid-liquid heterogeneous mixing characteristics of self-priming jet impeller

Jing ZHANG Jiaxin YUAN Hongye LI Chengsong ZHANG Bin GONG

The Chinese Journal of Process Engineering. 2023, 23(10):  1411-1420.  DOI: 10.12034/j.issn.1009-606X.223040

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As a new type of stirred device, the self-priming jet stirred tank has potential engineering application value in heterogeneous mixing enhanced process. The engineering design and industrial application of self-priming jet stirred tank were restricted by the insufficient research on the mixing characteristics. In this study, the liquid-liquid heterogeneous mixing process in self-priming jet stirred tank was investigated using numerical simulation and experiment. Water and oil were set as continuous phase and dispersed phase, respectively. Realizable k-ε turbulence model and Eulerian-Eulerian multiphase flow model were used to numerically simulate the liquid-liquid heterogeneous flow field in the self-priming jet stirred tank. The enhanced mass transfer mechanism of the self-priming jet impeller was investigated. The results showed that the dimensionless velocity on the axis of self-priming jet pipe was less affected by the stirring speed and the dispersed phase holdup. However, the single-phase flow without oil phase had lower velocity inside the self-priming jet pipe and higher velocity outside the pipe. The flow field and dispersed phase distribution in the stirred tank were significantly influenced by the inclination angle β of self-priming jet pipe. When β<0°, the self-priming flow was formed at lower end of the pipe and the jet was formed at upper end of the pipe, which was unfavourable to the radial mixing of oil and water in the stirred tank. When β=0°, the fluid velocity in pipe was close to the impeller speed, and there was no self-priming and jet flow. The impeller only produced the stirring function, which was not good to axial mixing. When β>0°, the self-priming flow was formed at upper end of the pipe and the jet was formed at lower end of the pipe. The high oil phase fluid was sucked by the self-priming jet pipe, and was jetted downward into the low oil phase fluid. The oil phase moved upward by buoyancy. For the self-priming jet impeller with β>0°, the turbulent kinetic energy at the bottom of stirred tank was effectively increased. β>0° was beneficial to eliminate the flow inhomogeneity and oil-water heterogeneous mixing process was enhanced. When β=30°, the fluid region, which dimensionless phase fraction was 0.95~1.05, accounted for 81.88% of the stirred tank volume, and the oil phase distribution was more uniform along the axial and radial directions.

Comparative study on pyrolysis kinetics of different heavy oil based on distributed activation energy model

Qing'an XIONG Yuming ZHANG Jiazhou LI Wei ZHANG Zhewen CHEN

The Chinese Journal of Process Engineering. 2023, 23(10):  1421-1434.  DOI: 10.12034/j.issn.1009-606X.222469

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The pyrolysis behavior of Dagang slurry oil (DG-SO), Qingdao vacuum residue oil (QD-VR) and Canadian oil sand bitumen (CA-OB) were investigated by thermogravimetric mass spectrometry. The pyrolysis kinetic parameters were obtained by Friedman method, FWO method, and distributed activation energy model (DAEM), respectively. The results showed that DG-SO with relatively high content of saturates and aromatics had the highest pyrolysis reactivity, while QD-VR with relatively high content of resins and asphaltenes had the lowest pyrolysis reactivity. The releasing curves of H2, CH4, CO, and CO2 correspond to the main reaction temperature ranges of heavy oil pyrolysis. The distinctions of the shape, intensity and temperature range of the pyrolysis gases releasing curves between different types of heavy oils were mainly attributed to the corresponding composition and pyrolysis reactivity of each type of heavy oil. It was clearly found that Friedman method could gain more accuracy for description of pyrolysis process of heavy oil compared with FWO method in terms of equal conversion methods. The average activation energies (Ea) of DG-SO, QD-VR, and CA-OB were 80.15, 177.00, and 174.56 kJ/mol within the conversion range of 0.1~0.9, respectively. The one-component Gaussian DAEM could describe the whole process of SARA (saturates, aromatics, resins, asphaltenes), and their Ea were 107.78, 210.88, 268.75, and 285.44 kJ/mol, respectively. The four-component Gaussian DAEM could be used to precisely describe the whole pyrolysis process of heavy oil, and the calculated weighted average activation energies were 148.92, 205.92, and 190.37 kJ/mol, respectively. By comparing the Ea of QD-VR and its SARA components, it was found that the interaction between the SARA during the pyrolysis of heavy oil leaded to the Ea of QD-VR close to the Ea of aromatics in heavy oil. At the same time, it was found that the presence of resins and asphaltenes increased the average activation energy of saturates and aromatics, while saturates and aromatics reduced the average activation energy of resins and asphaltenes.

Study on the thermal decomposition reaction behavior and kinetic characteristics of millimeter sized magnesite particles in fluidization

Feng GAO Liangliang FU Dingrong BAI Guangwen XU

The Chinese Journal of Process Engineering. 2023, 23(10):  1435-1445.  DOI: 10.12034/j.issn.1009-606X.222470

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Thermal decomposition is the primary step to utilizing magnesite resources. Traditionally, it has been done in the shaft or rotary-type kilns using lumpy bulk raw materials, leaving a substantial amount of small or millimeter-sized particle materials unusable. In this work, the decomposition of millimeter-scale magnesite particles using high-temperature gas-solid fluidized beds is proposed. The thermal decomposition behavior of magnesite particles with four different sizes in the range of 0.3~3 mm at different temperatures using a laboratory fluidized bed reactor of 30 mm in diameter combined with an online mass spectrometry analyzer is reported in this work. The results showed that the thermal decomposition rate of magnesite particles accelerated with the increase in bed temperature and the decrease in particle size. As the decomposition progresses, three characteristic stages can be observed. At the initial stage of decomposition corresponding to conversions of less than about 0.1, the reaction was controlled by the interfacial chemical reaction kinetics, and the apparent activation energy decreased with increasing particle size. In the middle stage of the reaction (the conversion was 0.1~0.9), the decomposition reaction obeyed the shrinking core model, and the activation energy of the decomposition reaction remained almost unchanged with the conversion for the particle of 0.46 mm in diameter but increased with the conversion for other large-sized particles. In the later stage of the thermal decomposition reaction (after the conversion was greater than 0.9), the conversion varied slowly with time, and the reaction was affected significantly by heat transfer and gas diffusion. For each of the decomposition reaction stages, the reaction mechanisms and kinetic parameters were determined based on the experimental data. This study discussed the effects of bed temperature and particle size on the thermal decomposition of magnesite particles for a better understanding of the thermal decomposition behavior of millimeter-sized magnesite particles in fluidized beds. The study provided essential data support for the development of new products for the preparation of magnesite particles in fluidized beds, serving as a critical reference for the preparation of millimeter-sized high-density dead burned magnesia at high-temperature in fluidized beds.

Preparation of calcium-based composite absorbent and simultaneous removal performance of SOx and NOx from flue gas

Yang LI Yang LIU Changming LI Liangliang FU Jian YU

The Chinese Journal of Process Engineering. 2023, 23(10):  1446-1457.  DOI: 10.12034/j.issn.1009-606X.222344

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In order to solve the technical problems of simultaneous desulfurization and denitrification of flue gas at ultra-low temperatures (<120℃) by dry process, this work prepared several calcium-based composite absorbents by coupling different strong oxidants with lime of high specific surface area, which can realize the efficient simultaneous removal of sulfur oxides (SOx) and nitrogen oxides (NOx) from flue gas at ultra-low temperature (<120℃). The results of desulfurization and denitrification performance evaluation of calcium-based composite absorbers with different oxidant types and loadings showed that the addition of strong oxidants not only improved the desulfurization performance of Ca(OH)2 but also achieved simultaneous denitrification with Ca(OH)2. The type and amount of oxidant had a significant influence on the simultaneous desulfurization and denitrification of flue gas, and the appropriate moisture and oxygen contents of flue gas were beneficial to improve the desulfurization and denitrification efficiency. According to the characterization results of crystal structure, thermal decomposition, microstructure, and specific surface area of calcium-based composite absorbers before and after the flue gas purification reaction, it can be found that SO2 and NO are first oxidized by strong oxidants, and then react with hydrated lime to generate corresponding sulfates and nitrates, improving the desulfurization and denitrification efficiency. This study is expected to provide a new purification material and process for the upgrading of the intrinsic engineering process or purification of small industrial boilers to achieve ultra-low emission requirements.

Synthesis of S-containing MAX phase Ti₂SC via the carbo-sulfidation of ilmenite concentrate

Zhenqian ZHANG Sheng PANG Liangwei CONG Youpeng XU Laishi LI Yusheng WU Zhi WANG

The Chinese Journal of Process Engineering. 2023, 23(10):  1458-1468.  DOI: 10.12034/j.issn.1009-606X.223041

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The MAX phase Ti2SC is a potential high-temperature structural material and precursor for titanium extraction by molten salt electrolysis due to its special structure and properties. However, the existing preparation methods all involve the use of high-value Ti powder, TiC powder, and TiS powder, since the synthesis of Ti2SC has always been thought to be through the reaction of TiC and TiS. The preparation of high-purity Ti2SC in a low-cost way is the prerequisite for its large-scale application. In this work, with ilmenite concentrate, pyrite, and graphite spherical tailings as the raw materials, high-purity Ti2SC was successfully prepared via the carbo-sulfidation of ilmenite concentrate. Since it was a new reactant system for preparing Ti2SC, the formation mechanism of Ti2SC in the FeTiO3/FeS2/C system was discussed in detail based on the results of XRD and thermodynamic calculation. A new formation mechanism that Ti3O5, the intermediate product of carbothermal reduction of FeTiO3, was directly reconstructed into Ti2SC in the molten FeS was proposed. Then, the effects of graphite proportion, sintering temperature, and holding time on the purity and morphology of products were determined by the orthogonal experiment. Ti2SC with uniform size and purity of up to 96wt% was obtained from the sample containing 27.4wt% graphite after sintering at 1400℃ for 4 h and subsequent pickling treatment continued based on the results of XRD fine-fitting data and SEM. Furthermore, to reduce the amount of acid used in the purification process, the in-situ physical separation of by-product Fe and Ti2SC was realized under 1700℃ high-temperature sintering by taking advantage of the large density difference between Ti2SC and molten Fe. The amount of acid used for purification was reduced by 72.7% according to the comparison of theoretical and actual acid consumption. The results of this study not only proposed a new pathway to synthesize Ti2SC but also provided valuable references for the industrial production of this MAX phase.

Effect of carbon content on microstructure and graphite precipitation behavior of high silicon and high aluminum steel

Yong WAN Dong MA Lijie TIAN Dongxu LIU Mingqi LIU Yonghong WEN

The Chinese Journal of Process Engineering. 2023, 23(10):  1469-1477.  DOI: 10.12034/j.issn.1009-606X.222456

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Due to its low cost, environmental protection, and excellent machinability, graphite free-cutting steel has attracted extensive attention from metallurgical and materials scholars at home and abroad in recent years. In this work, the effects of two kinds of carbon content (0.20wt% and 0.52wt%) on the microstructure changes of 1.9wt%Si-1.1wt%Al high-silicon and high-aluminum steel during hot-rolling, quenching-tempering process and the precipitation behavior of graphite particles after tempering were studied by metallography microscope, scanning electron microscope and energy spectrum analyzer. The results showed that the microstructure of 0.20wt%C experimental steel after hot rolling→quenching→tempering was transformed into ferrite+pearlite→ferrite+"island" bainite→ferrite+graphite particle+a small amount of cementite. The microstructure of the experimental steel at 0.52wt% C after hot rolling→quenching→tempering changes to ferrite+pearlite→martensite→ferrite+graphite particles+a small amount of cementite. At the same tempering temperature, the quantity and size of graphite particles in 0.52wt% C experimental steel are larger and more precipitated in grain boundary nucleation mode than that in 0.20wt% C experimental steel. When the tempering temperature increased from 680℃ to 710℃, the density of graphite particles precipitated on the grain boundary of 0.20wt% C steel decreased from 2337/mm2 to 1710/mm2, and the average size increased from 1.50 μm to 2.27 μm. At 0.52wt% C, the density of precipitated graphite particles at the grain boundary of the experimental steel decreased from 5244/mm2 to 1938/mm2, and the average size increased from 2.36 μm to 3.45 μm. The increase of carbon content from 0.20wt% to 0.52wt% can effectively promote the nucleation and growth of graphite particles in the tempering process. Compared with the tempering at 710℃, the number of graphite particles in the tempering at 680℃ is more and the distribution is more uniform, which is more conducive to the improvement of the overall machinability of the experimental steel.

Preparation of nitrogen-containing heterocyclic amphoteric resin and its separation performance toward succinic acid

Junwei ZHANG Zexiao DONG Miaoxin YUAN

The Chinese Journal of Process Engineering. 2023, 23(10):  1478-1487.  DOI: 10.12034/j.issn.1009-606X.222373

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In order to study the performance of an amphoteric resin with hydroxyl group and nitrogen-containing heterocycle used for the separation of succinic acid (SA), a weak acid-weak base resin, shortly called 4-VMVH resin, the copolymerization of 4-vinylpyridine with methyl acrylate and vinyl acetate, was prepared, then the physicochemical property, performance and adsorption mechanism of the resin was explored. The results indicated that more meso- and micro-pores and less macro-pore were determined inside the resin, and the adsorption of SA on the resin was an exothermic process and could be described by Freundlich model. The distribution of adsorption site on the resin was inhomogeneous, and the isosteric adsorption enthalpy of the resin decreased with increasing the fractional loading of SA. The total acid-base exchange capacity and the hydroxyl group content of the 4-VMVH01 resin were 4.607 mmol/g and 114.21 mg KOH/g and higher than that of the 2-VMVH resin. Moreover, the resolution of SA and acetic acid (AcOH) was 0.92 while the recovery rate of SA reached to 84.67% at a ratio of the column height to its diameter of 15/1 with only hot water as eluent, and the reusability of the 4-VMVH resin basically remained constant. The interaction energy between the heterocyclic N atom and the carboxyl H atom of SA was higher than that between the heterocyclic N atom and the carboxyl H atom of AcOH. The interaction energies between hydroxyl O atom and the carboxyl H atoms of SA and AcOH were respectively -26.531 kJ/mol and -25.094 kJ/mol, which belonged to the hydrogen-bonding adsorption, and therefore the retention force of SA on the 4-VMVH resin was stronger than that of AcOH.

Study on the difference of enzymatic hydrolysis performance of long fibers and short fibers by straw steam explosion classification

Changhong YAO Lan WANG Hongzhang CHEN

The Chinese Journal of Process Engineering. 2023, 23(10):  1488-1496.  DOI: 10.12034/j.issn.1009-606X.222452

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Reducing the consumption of cellulase was the key factor to overcome the economic problem in the refining process of lignocellulose. In this study, the enzymatic hydrolysis performance of long fibers and short fibers fractionated by steam explosion classification and the possibility of using steam explosion classification to reduce the consumption of cellulase were investigated. The results showed that the enzymatic hydrolysis difficulty of short fiber was significantly lower than that of long fiber. The enzymatic hydrolysis rate of cellulose in short fiber was 1.62 times that of long fiber after 48 h of enzymatic hydrolysis at the enzyme dosage of 20 FPU/g DM. Under the enzyme dosage of 5 FPU/g DM, the enzymatic hydrolysis rate of cellulose in short fiber was 58.23% after 36 h. Under the enzyme dosage of 20 FPU/g DM, the enzymatic hydrolysis rate of cellulose in long fiber was only 51.54% after 36 h. The consumption of cellulase was reduced by 75%. The difference in enzymatic hydrolysis difficulty was due to the fact that long fiber and short fiber came from different tissues of corn straw. Due to the difference in mechanical strength, the tearing effect generated by the steam explosion crushed the husk and core into diverse particle sizes. The variety of volumes and shapes provided the basis for classification. Short fibers were mainly composed of parenchyma cells from the core, while long fibers were mainly composed of fiber cells from the husk. The crystallinity of cellulose in short fiber was lower, so the enzymatic hydrolysis difficulty was lower than that of long fiber. In addition, during the enzymatic hydrolysis of short fiber, the release of bound water was more sufficient. The liquefaction time of short fiber was shorter than that of long fiber. This indicated that mass transfer efficiency was improved during the enzymatic hydrolysis of short fiber, which was conducive to reducing the negative effect of product inhibition on enzyme activity and improving the enzymatic hydrolysis efficiency. This study provided an effective method for improving the homogeneity of lignocellulosic materials. The steam explosion classification technology effectively changed the difficulty of enzymatic hydrolysis of corn straw and saved the cost of cellulase. This was of great significance to the exploitation of lignocellulosic resources.