Continuous Steam Research Articles

Structure and Compositional Changes of Eucalyptus Fiber after Various Cycles of Continuous Screw Extrusion Steam Explosion

A continuous screw extrusion steam explosion (SESE) pretreatment method was used to disrupt the structure of eucalyptus fiber. The effects of increasing numbers of SESE pretreatment cycles on the structure and composition of eucalyptus fiber were investigated. Lignin was isolated from the eucalyptus fiber via the phosphoric acid method under modest reaction conditions (50 °C), and was characterized. The SESE pretreatment led to a decrease in crystallinity and degraded the hemicellulose and cellulose. The surface of the eucalyptus fiber was damaged by SESE pretreatment, and significant surface debris were observed. The isolated lignin was typical of guaiacyl-syringyl (G-S)-enriched lignin of eucalyptus hardwood. The SESE pretreatment led to the cleavage of ether linkages and condensation of lignin, and thus a more heterogeneous structure compared with that of raw lignin. The increased molecular weight of SESE-pretreated lignin showed that condensation was more pronounced with increased numbers of SESE cycles. The thermostability of lignin increased after three SESE cycles and remained stable with further cycles. This corresponded to the trend in the molecular weight of lignin with increased SESE pretreatment. The SESE pretreatment was more efficient for pretreating eucalyptus fiber than conventional batch-type steam explosion, and thus is more suitable for industrial application.

A Convenient Synthesis of Azulene

An improved and scalable synthesis of azulene has been developed by the application of pyrrolidine as a reagent and continuous steam distillation and extraction for workup. Applications for the coloration of perfluorinated media and silicones were demonstrated.

Characteristics and environmentally friendly extraction of cellulose nanofibrils from sugarcane bagasse

This study reports an environmentally friendly process to prepare cellulose nanofibrils (CNFs) from sugarcane bagasse (SCB), by ultrasonication combined with various mechanochemical pretreatments. The pretreatments included continuous steam explosion, dilute alkali-catalyzed (0.4wt% NaOH) hydrothermal treatment, and bleaching with hydrogen peroxide. The morphology and physiochemical properties of the fibers obtained after each stage of treatment were characterized by various techniques. Suspensions of fibers subjected to different pretreatments were prepared by the same mechanical process. The result proved that continuous steam explosion pretreatment could strip the primary wall and the binding materials related to middle lamella, loosen the structure of fiber cell wall, and promote sequent nanofibrillation of the cellulose fibers. Therefore, the total energy consumption is reduced. The current pretreatments effectively removed non-cellulosic constituents of the raw fibers, using very small amount of chemical reagents. Individual CNFs typically had diameters of 20–40nm, high aspect ratios, a fine web-like structure, and good thermal stability.

Durability studies of limonite ore for catalytic decomposition of phenol as a model biomass tar in a fluidized bed

The development of highly active, durable, tar decomposition catalysts is desirable for practical application of biomass gasification at low temperature. In this study, limonite ore calcinated at 900 °C was used as bed material in a fluidized bed for catalytic decomposition of phenol (biomass tar model) at 650 °C. The limonite showed catalytic activity for the decomposition of phenol to produce combustible gases (H2 and CO). A long-term durability test of phenol decomposition with O2 regeneration treatment was conducted for 25 h using the limonite catalyst. The O2 treatment repeatedly removed the deposited carbon, allowing H2 and CO to be generated constantly for 25 h. Steam reforming of phenol using the limonite catalyst was also conducted with various steam/carbon ratios (S/C = 0, 0.4, and 0.8), of which S/C = 0.4 was the best for suppressing carbon deposition and producing higher volumes of H2 and CO gases. Continuous steam reforming for 24 h could be achieved using a limonite catalyst with S/C = 0.4, while maintaining the production of H2 and CO gases, even though carbon deposition occurred steadily. These results indicated that limonite ore is a promising bed material for use in internally circulating fluidized-bed systems for long-term catalytic decomposition of biomass tar.

Failure analysis of a carbon steel roller shaft of continuous pad steam machine

This paper presents the failure analysis of carbon steel roller shaft of continuous pad steam machine used in textile industry. The fracture position was located at a stepped diameter. The failed component was the shaft made of carbon steel AISI 1040. Standard procedure for failure analysis was employed in this investigation. Visual examination, chemical analysis, hardness and tensile strength measurements, microstructural characterization, fractography analysis by Scanning Electron Microscopy (SEM) and Finite Element Analysis (FEA) were used for the failure analysis. Using this failure analysis approach, we pinpointed the root cause of failure and developed a means of solving this type of failure in the future. Firstly, the chemical composition of the shaft is done by an Optical Emission Spectroscopy (OES) method, the found chemical composition was matching with required standard value. Mechanical testing consists of two test i.e. tensile test and hardness test and it was found out that the strength and hardness of specimens were within the required capacity. For metallurgical analysis, the microstructure of the shaft was developed by using an optical microstructure. Equal distribution of ferrite perlite shows that heat treatment was performed well and carbon percentage in a material is satisfying the standard values. Thus, it proves that the material used was of good quality and indicates that failure is not due to material property. Further for the fractography, the fractured surface was examined by SEM. The cross-section was taken in a quarter segments and divided into four regions i.e. A, B, C, and D. Fractography morphology mainly showed that the failure of roller shaft was caused due to fatigue. To examine the stress distribution at the fractured surface the Finite Element Method (FEM) was also carried out. Based on the shaft size, a precise ANSYS model was developed. The result of FEM shows that stress concentration was significant at roller shaft step which could reduce the material reliability to some extent. Based on the failure analysis it could be concluded that due to stress concentration a micro crack is initiated along the weak interface and further it converted into the major fatigue failure. Fractography morphology of failed roller shaft also confirms the fatigue failure.

Effects of impregnation of softwood with sulfuric acid and sulfur dioxide on chemical and physical characteristics, enzymatic digestibility, and fermentability

Hydrothermal pretreatment improves bioconversion of lignocellulose, but the effects of different acid catalysts are poorly understood. The effects of sulfuric acid (SA) and sulfur dioxide (SD) in continuous steam pretreatment of wood of Norway spruce were compared in the temperature range 195°C–215°C. The inhibitory effects of the pretreatment liquid on cellulolytic enzymes and Saccharomyces cerevisiae yeast were higher for SD- than for SA-pretreated material, and the inhibitory effects increased with increasing pretreatment temperature. However, the susceptibility to cellulolytic enzymes of wood pretreated with SD was 2.0–2.9 times higher than that of wood pretreated with SA at the same temperature. Data conclusively show that the superior convertibility of SD-pretreated material was not due to inhibition phenomena but rather to the greater capability of the SD pretreatment to reduce the particle size through partial delignification and cellulose degradation. Particle size was shown to be correlated with enzymatic digestibility (R2 0.97–0.98).

Production of Microfibrillated Cellulose by Novel Continuous Steam Explosion Assisted Chemo-Mechanical Methods and Its Characterizations

In this study, microfibrillated cellulose (MFC) was successfully isolated with different time treatments of steam explosion, which were combined with chemo-mechanical stages. The objectives of this study were to isolate and characterize MFC obtained from steam explosion—assisted novel chemo-mechanical methods, and to investigate the effects of different steam explosion times on obtained MFC. Characterizations used were SEM, TEM, PSA, GC–MS, EDS, XRD, FTIR, and STA. The result of this study showed an optimal diameter range of MFC samples was between 23.45 and 77.65 nm at 1 h steam explosion time. However, MFC fibers were aggregated until its particle size distribution by number was about 645.83 nm. That lignocellulose MFC comprised C, N, and O with a dramatic decrease of Si. Most of the samples had many transmittance peaks, indicating the presence of cellulose with –OH, –CH2, C–H, and C–O functional groups whereas IR peaks designated to hemicellulose and lignin were almost absent. The presence of n-heptadecanol-1; n-nonadecanol-1; n-nonadecanol; hexadecanoic acid, ethyl ester; ethyl oleate; and octadecanoic acid, ethyl ester was linked with existance of cellulose and cementing agents (hemicellulose and lignin). There was an increase of cellulose crystallinity along with the increase in steam explosion time. Native cellulose or cellulose I was the initial nature of obtained MFC. The decrease of thermal stability of hemicellulose was correlated with acid treatment and acetyl groups, while the increase of cellulose thermal stability was in accordance with the increase of cellulose crystallinity index.

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One of the main challenges in developing a process of continuous steam injection is to control the injection profile. Said profile is strongly affected by steam channeling to “thief zones” and the gravitational effect of override, both are characterized by preventing contact of the steam with reservoir zones containing considerable amounts of hydrocarbons thus decreasing the vertical sweep efficiency. These phenomena are favored by some features of the formation such as large thickness and reservoir heterogeneities and may affect the technical and economic feasibility of the project if they are not controlled and / or monitored properly.Several methodologies have been designed to address this problem. Among them are injecting surfactants for the formation of in situ foam, which seeks to reduce the mobility of steam; using thermal gels, for plugging high permeability channels; injection of solvents, used to enhance oil mobility; and water-alternating-steam injection (WASP) for scavenging of both upper and lower zone of the formation. This article collects relevant aspects of the mentioned methods, and a comparison is made in base of the number of applications, incremental production and implementation cost.Keywords: Steamflooding, In Situ Foams, Solvents, High Temperature Gels, Water Alternating Steam.

Integrated Primary and Thermal Development of a Large Extraheavy-Oil Field

Summary Extraheavy-oil (XHO) reservoirs in South America represent some of the largest hydrocarbon accumulations (>500 billion bbl) in the world. Primary production (PP) that uses long horizontal wells is a commercially proved technology for XHO reservoirs. The expected ultimate recovery with primary production is generally less than 12% of original oil in place (OOIP), and thermal enhanced oil recovery (EOR) is critical for increasing recovery to 30–60% OOIP. Economic and environmentally viable thermal development of these reservoirs will require the use of horizontal steam injectors. Our results reveal that continuous steam injection (CSI) with a horizontal injector placed vertically above a horizontal producer (CSI-HIHP) is a very effective method for XHO reservoirs, with high peak-oil rate and significantly high recovery. This study, the first of its kind for an XHO reservoir, outlines an integrated work flow to evaluate the production potential of a large XHO greenfield with PP followed by thermal exploitation. The work flow, based on a probabilistic framework [involving design of experiment (DOE), proxy methods, and Monte Carlo simulations], evaluates reservoir performance for the whole life cycle of the field under a range of uncertainties, and quantifies the impact of key parameters affecting the reservoir performance. XHO reservoirs usually have significantly higher pressures than typical conventional heavy-oil reservoirs, where CSI has been applied commercially. Therefore, pressure in these reservoirs must be reduced before CSI can begin. Cyclic steam stimulation (CSS) after the initial stage of PP can be used to accelerate pressure reduction in the reservoir, while providing additional recovery. Our results demonstrate that geological features such as shale baffles have a significant impact on delaying pressure reduction during PP and CSS. Under a broad range of conditions investigated in this study, PP for 1 year followed by CSS for 4 years has been found to be successful in reducing pressure to the target pressure for CSI. High pressure drop in the horizontal steam injector can cause pressure near the toe region of the injector to be lower than the producer pressure. This results in poor steam injection and poor steam-chest development in that region, thus greatly reducing the efficiency of the thermal-recovery process. We quantify pressure drop in a horizontal steam injector and its impact on the thermal performance and suggest a novel well configuration that uses two injectors for every long producer during CSI. The proposed configuration with a sequential development plan can significantly improve economics of the projects. A novel probabilistic work flow for a full-field (FF) development plan (PP, CSS, and CSI) of XHO reservoirs provides robust production forecast during the entire life cycle. The work flow developed and the insights obtained would be very valuable in preparing effective exploitation plans and optimal facility design, a key economic variable in large projects of developing giant XHO reservoirs.

Recovery of pectic hydrocolloids and phenolics from huanglongbing related dropped citrus fruit

Citrus pre-harvest fruit drop, caused by huanglongbing infection, has increased dramatically concomitant with declining tree health and crop harvest size. This loss of harvestable fruit is damaging to both growers and juice processors. Recovering and converting this fruit to alternative value added products would benefit the citrus industry. Therefore, we have explored the potential of using this fruit as a feedstock in our newly developed pilot scale continuous steam explosion process. Whole fruits were converted to steam-exploded biomass using a continuous pilot scale process. The sugar composition of raw fruit and steam-exploded biomass was determined. Recovered pectic hydrocolloids and phenolic compounds were characterized. Pectic hydrocolloids comprised 78 g kg-1 of the dry material in the dropped fruit. Following the steam explosion process almost all of the pectic hydrocolloids were recoverable with a water wash. They could be functionalized in situ or separated from the milieu. Additionally, approximately 40% of the polymethoxylated flavones, 10% of the flavanone glycosides, 85% of the limonoids and almost 100% of hydroxycinnamates were simultaneously recovered. The continuous steam explosion of pre-harvest dropped citrus fruit provides an enhanced, environmentally friendly method for the release and recovery of valuable coproducts from wasted biomass. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Steam injection gravity drainage as a follow-up process for cyclic steam stimulation

Cyclic steam stimulation (CSS) is an effective method to recover extra heavy oil but it achieves a relatively low recovery factor (~26% before economic limit is reached) and is less energy efficient with higher emissions intensity than that of conventional oil production. After it reaches its economic limit, it remains unclear what is the follow-up recovery process where the energy and emission intensities can be minimized. Here, a detailed examination of the Liaohe extra heavy oil CSS and continuous Steam Injection Gravity Drainage (SIGD) operations is conducted to examine their energy and emission intensities. Further analysis is conducted by using detailed geological and reservoir models and a history match of the CSS and SIGD operations. The results reveal that CSS is an effective thermal recovery method to initiate production from extra heavy oil reservoirs and that SIGD using infill wells is an effective post-CSS recovery process to produce a significant fraction of the remaining oil from the reservoir. For the reservoir studied, the steam-to-oil ratio (energy efficiency) and emissions intensity of SIGD is slightly worse than that of the initial CSS operation.

Solar steam generation through bio-inspired interface heating of broadband-absorbing plasmonic membranes

Efficient solar-enabled evaporation plays a critical role in solar power-based concentration systems, photochemical plants, seawater desalination technologies, etc. However, traditional processes for solar steam generation usually depend on high-temperature heating of the bulk liquid, which requires highly concentrated solar power and suffers from high energy and optical losses. Therefore, the enhancement of solar steam generation by bio-inspired interface solar heating is proposed in this work. In this study, easy-to-prepare, flexible, and reusable plasmonic membranes (PMs) were fabricated for realizing the bio-inspired interface solar heating and continuous steam transportation through the micropores of the membranes. A solar steam generation efficiency of ∼85% was achieved at an illumination power of 10kWm−2. The effects of Au concentration in the membranes and optical power on the steam generation efficiency were systemically studied. The observed high evaporation rate and efficiency were attributed to three main factors: high (∼90%) and broadband solar absorption, efficient photo-thermal conversion due to high plasmon dissipation losses, and fast capillary flow in the membrane micropores. Finally, the application of PMs in a single basin solar still system for seawater desalination was investigated and the PMs exhibited great performance on enhancing the productivity of clean water.

Nanoparticle Catalysts Upgrade Heavy Oil for Continuous-Steam-Injection Recovery

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 179699, “Heavy-Oil Upgrading and Enhanced Recovery in a Continuous Steam-Injection Process Assisted by Nanoparticulated Catalysts,” by C.A. Franco, L. Cardona, S.H. Lopera, J.M. Mejía, and F.B. Cortés, National University of Colombia at Medellín, prepared for the 2016 SPE Improved Oil Recovery Conference, Tulsa, 11–13 April. The paper has not been peer reviewed. The production of heavy and extra-heavy oil is difficult because of its rheological properties caused by high asphaltene content. Upgrading these unconventional oils requires large amounts of energy, decreasing the production’s cost-effectiveness. Nanoparticulated catalysts have been shown to improve enhanced recovery of these oils by altering their physicochemical properties, including asphaltene content. This paper presents an investigation into the effect of catalytic nanoparticles on the efficiency of recovery from continuous steam injection. Introduction Several in-situ techniques have been used to enhance heavy- and extra-heavy-oil recovery with the objective of upgrading the oil and improving its viscosity and mobility. These techniques include thermal processes, such as steam-assisted gravity drainage, and cold techniques, such as treatments with diluents. Cold processes improve the crude oil by dilution or destabilization and deposition of asphaltene components in the reservoir with solvents that have a direct effect on viscosity. This paper evaluates the use of nanoparticulated catalysts in steamflooding. The nanoparticles were selected through batch-adsorption experiments. A methodology was developed for evaluating the effect of the nanoparticulated catalyst in continuous vapor injection. Oil recovery was evaluated by use of a slimtube filled with a nonconfined sandpack in steam-injection scenarios in the absence and presence of a water-based nanofluid. A displacement test was conducted by (1) constructing the base curves, (2) estimating the oil recovery by continuous injection of vapor in the absence of the nanofluid, and (3) identifying the influence of the nanoparticles on the enhanced recovery of oil. Results suggested that functionalized nanoparticles lead to higher adsorption of asphaltenes, higher degrees of asphaltene self-association, and lowered temperature of n-C7 asphaltene steam gasification. Oil recovery increased to 46% for the system assisted by nanoparticles in comparison with that from vapor injection without the nanoparticles. The °API value of the oil increased from 7.2 to 12.1 °API. A reduction of 59% in oil apparent viscosity was also observed. Additionally, analysis of n-C7 asphaltene and residue content demonstrated that nanoparticles are an excellent alternative for heavy- and extra-heavy oil upgrading in processes involving vapor injection. n-C7 asphaltene content decreased by 5.2 percentile points after vapor injection in the presence of nanoparticles com-pared with the unaltered extra-heavy oil. Also, residue content decreased 47%. Improved oil recovery by nanoparticle injection could be attributed to three main reasons: (1) wettability alteration of the porous media, (2) viscosity reduction because of reduction of the asphaltene aggregate, and (3) crude-oil upgrading.

Influence of the Iron Oxide Phases in Steam Oxidation on the Mechanical Properties and Abrasive Wear of Sintered Iron Materials

The objective of this research work was to study the influence of the iron oxide phase resulted during steam oxidation of the sintered steels specimens obtained by powder metallurgy (P/M) route. Steam oxidation is a surface treatment applied to sintered iron parts, as an economic way to reduce the interconnected pores. In powder metallurgy products, the networks of pores are specific, who can be stress concentraions and can produce cracks in material. By steam oxidation treatment the interconnected porosity is closed by sealing them with iron oxides phases. Also, other properties of sintered PM steels are improved. The specimens analyzed in this paper were produced from atomised iron powders, compacted at room temperature at pressures of 600 MPa, sintered for 120 minutes at 1150o C in a laboratory furnace and then subjected to a continuous steam oxidation at 550o C for 60 minutes. Investigations on the structural, mechanical and abrasive wear properties were performed. The microstructure and the pore morphology of the sintered and steam oxidation samples were studied on using optical microscope.

Energy efficiency and emission assessment of a continuous rice husk stove for rice parboiling

The study presents a performance evaluation of an integrated rice parboiling stove (IRPS) fuelled with either rice husk or wood in comparison with the three stone fire (TSF) stove currently being used. The stoves were initially tested using the water boiling test. The efficiency, fire power and specific fuel consumption of IRPS were found to be 29%, 16 kW and 0.14 kg/kg rice husk, respectively. To enhance continuous steam production, a heat exchanger extension was made to the IRPS and the efficiency re-evaluated using the indirect boiler efficiency estimation approach, together with pollutants emission factors and safety. The stove efficiency after the extension increased to 46%. The emission factors for CO, CO2 and CxHy were in ranges from 10.6 to 12.0, 785–793, 0.4–2.2 g/kg of rice husk, respectively. Comparison between rice husk and wood combustion in IRPS shows that emission factors for rice husk were significantly lower than wood but decrease with stove fire power.

A New Steam Assisted Gravity Drainage Process Utilizing Vertical Wells

A novel process utilizing vertical wells to enhance heavy oil recovery during steam assisted gravity drainage has been developed. In the vertical well steam assisted gravity drainage (VWSAGD) process shown in Figure 1, the vertical well includes two production strings which are separated by three packers (one dual and two single packers): the short injection string (SIS) is attached to the bottom of the annulus and completed in the top quarter of the perforated formation, while the long production string (LPS) is attached to the bottom of the production tubing and completed in the bottom quarter of the perforated formation. The new process (VWSAGD) requires an initial start-up period (warm-up stage) where the steam is injected into both of the injection strings and production string for a specified period of time of about 14-30 days; then both strings are closed to injection for a specified time period of approximately 7 - 10 days (soaking period). After the initial warm-up and the soaking period, the long production string is opened for production, and the short injection string is opened to continuous steam injection for the rest of the specified simulation time. A commercial simulator (CMG-STAR Simulator) was used to study the performance of the new VWSAGD process. A sensitivity analysis was performed for the grid density, soaking time, steam quality, bottom hole producing pressure, steam injection rate, reservoir thickness, reservoir area, and horizontal to vertical permeability anisotropy. The results of this study have shown that the new VWSAGD process is more preferable for reservoir conditions such as high horizontal to vertical permeability ratio and thick reservoir oil zones.

Friction and wear behavior of steam-oxidized ferrous PM compacts

This study determines density effect by assessing sintering temperature and graphite content on the dry sliding wear characteristics of steam-treated iron materials using a pin-on-disk wear test. The specimens were prepared from atomized premixed iron base powders and contained 0.1 to 1.0 wt.% carbon compacted at different densities (5.9 g/cc to 6.8 g/cc). The specimens were sintered for 1 h at different sintering temperatures (1090°C to 1130°C), and then subjected to continuous steam treatment at 540°C for 95 min through in situ Powder metallurgy (PM) technique. Steam treatment was proposed to improve the wear performances of the components of PM. Wear tests were conducted using a pin-on-disk-type machine. Load ranged from 20 N to 60 N. Sliding distance and sliding velocity of 312 m and 0.26 m/s, respectively, were adopted for all tests. Scanning electron microscope was used to analyze wear surface. Increased density and graphite content reduced the wear rate of steam-treated materials. Hardness increased with increasing graphite content. Wear mechanism, wear rate map, and wear maps were drawn for the test result data. Wear transition map identified mild, severe, and ultra-severe wear regimes as functions of applied load.

Changes in the Microstructure and Components of Eulaliopsis binata Treated by Continuous Screw Extrusion Steam Explosion

Eulaliopsis binata (EB) was pretreated by continuous screw extrusion steam explosion (SESE), with the aim of converting EB into useful materials on an industrial scale. The three main chemical components were characterized by component analysis using the Van Soest fiber detergent system, ultraviolet (UV) absorption spectrophotometry, gel permeation chromatography (GPC), and carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy. Changes in the contents of detergent soluble species in the Van Soest process revealed the partial degradation of hemicellulose and cellulose, and the partial removal of lignin. GPC indicated that the molecular weight of lignin decreased from 4194 to 3710 g/mol over the first three SESE pretreatment cycles, but then increased to 4592 g/mol following the fourth SESE pretreatment cycle. UV absorption and 13C-NMR results indicated the partial removal of lignin and the depolymerization and repolymerization of lignin during SESE pretreatment. Scanning electron microscopy (SEM) showed that the epidermis and parenchyma of EB were almost completely desquamated. X-ray diffraction (XRD) revealed that the crystallinity of EB initially increased and then subsequently decreased slightly, with increasing number of SESE pretreatment cycles. The varying physicochemical properties of EB resulting from different numbers of pretreatment cycles may find use in more diverse applications.

Experimental studies into the processes accompanying an intercircuit steam generator break in the safe operating limits in HLMC reactor facilities

The paper presents the results of the processes accompanying an “intercircuit steam generator (SG) break” emergency in the safe operating limits in reactor facilities with lead and lead-bismuth coolants (HLMC). The flow rate of the water and the steam entering the coolant through the break corresponded to the bubble and, in part, to the flare outflow patterns with simulation of the steam generator operating conditions. Varied patterns were used to simulate the water and steam outflow via SG tube holes of various geometries, including through a side hole, into an ejector's neck and into the working clearance of a labyrinth screw pump, with simulation of different degrees of the light phase bubble dispersion in the coolant. The lead melt temperature was 400–550°C, the pressure was 0.1 to 4.0kgf2/cm, the water temperature at the test segment inlet was 20°C, the water pressure was 0.2–8.0kgf2/cm, the flow rate of the water injected into the liquid metal coolant was 0.5–200kg/h, and the continuous steam load on the lead coolant free surface was up to 10.0.The geometry of the channels for the current of two-component flows (HLMC-water, steam) and that of the structural elements immersed in a two-component flow was varied.

Erratum to: Characterization of biochars produced from peanut hulls and pine wood with different pyrolysis conditions

Application of modern biomass pyrolysis methods for production of biofuels and biochar is potentially a significant approach to enable global carbon capture and sequestration. To realize this potential, it is essential to develop methods that produce biochar with the characteristics needed for effective soil amendment. Biochar materials were produced from peanut hulls and pine wood with different pyrolysis conditions, then characterized by cation exchange (CEC) capacity assays, nitrogen adsorption–desorption isotherm measurements, micro/nanostructural imaging, infrared spectra and elemental analyses. Under a standard assay condition of pH 8.5, the CEC values of the peanut hull-derived biochar materials, ranging from 6.22 to 66.56 cmol kg−1, are significantly higher than those of the southern yellow pine-derived biochar, which are near zero or negative. The biochar produced from peanut hulls with a steam activation process yielded the highest CEC value of 66.56 cmol kg−1, which is about 5 times higher than the cation exchange capacity (12.51 cmol kg−1) of a reference soil sample. Notably, biochar produced from peanut hulls with batch barrel retort pyrolysis also has a much higher CEC value (60.12 cmol kg−1) than that (12.45 cmol kg−1) from Eprida’s H2-producing continuous steam injection process. The CEC values were shown to correlate well with the ratios of oxygen atoms to carbon atoms (O:C ratios) in the biochar materials. The higher O:C ratio in a biochar material may indicate the presence of more hydroxyl, carboxylate, and carbonyl groups that contribute to a higher CEC value for the biochar product. In addition, the increase in surface area can also play a role in increasing the CEC value of biochar, as in the case of the steam activation char. Comparison of characterization results indicated that CEC value is determined not only by the type of the source biomass materials but also by the pyrolysis conditions. Biochar with the desirable characteristics of extremely high surface area (700 m2/g) and cation exchange capacity (> 60 cmol kg) was created through steam activation.