Biomass Residence Time Research Articles

Ni/N-modulated biomass pyrolysis to make carbon-based catalysts for electrochemical CO2-to-CO conversion

There are tremendous requirements in CO2 electrolysis to produce value-added chemicals, where the functional carbon-based catalysts possess the unique superiorities for CO2 conversion. Pyrolysis kinetics as a theoretical guidance is pivotal to construct the high-activity carbon-based catalysts precisely, which is decoupled urgently. Herein, the pyrolysis behaviors of ipomea batatas leaves were well optimized by Ni/N modulators and unveiled systematically, where the residence time of biomass was prolonged during the pyrolysis process and the emerged out-of-plane orientation sp3 C–N species were increased. Additionally, the presented first-order kinetics revealed that with Ni/N modulators, the higher apparent energy barrier was determined than single biomass, corresponding to an enhanced thermostability. As a guidance, the derivative catalyst with high N content (17.22 at%) can drive electrochemical CO2-to-CO reaction efficiently. The current density was up to 200 mA cm–2 and the CO Faradaic efficiency kept over 95 % at a wide work window (–0.66 to –1.46 V versus reversible hydrogen electrode) in flow cell.

Potential of aerobic granular sludge technology for domestic wastewater treatment of high ammonia from urea fertilizer industry

Fertilizer is the main element that has an essential role in the sector of agriculture. Urea fertilizer has a source of Nitrogen with 46.04%. Ammonia is a chemical complex that is used and produced from the processing of urea fertilizer. A specific domestic wastewater quality standard for industry explains that the maximum level of ammonia allowed in effluent water was 10 mg/l. In the urea fertilizer industry wastewater treatment results were found to be in the range of 19.49 - 42.4 mg/l. Activated sludge technology is considered fairly effective in wastewater treatment but requires a large amount of energy and additional land for handling excess sludge. From the disadvantages, it is necessary to conduct research related to the effectiveness of high ammonia wastewater treatment that is environmentally friendly. Aerobic granule is characterized by a compact and dense structure, high biomass residence time, resistance to shock loading and toxic compounds, and a high settling speed so that it can produce a compact reactor design. Aerobic granule allows ammonia removal to reach more than 97%. This article aims to review the potential of implementing the use of aerobic granular sludge technology for ammonia removal in the wastewater of the urea fertilizer industry.

Development of a Dual-Chamber Pyrolizer for Biochar Production from Agricultural Waste in Sri Lanka

This study investigates the design and development of a pyrolysis reactor for batch-type biochar production from rice husks. The main objective is to develop an appropriate technology to regulate pyrolysis temperature and biomass residence time that can be easily operated under field and household conditions with minimal operational and technical requirements. The designed novel dual-chamber reactor comprises two concentrical metal cylinders and a syngas circulation system. The outer cylinder is for energy generation and the inner one is for pyrolysis. Temperature profiles, energy exchanges, syngas production, and the physicochemical characteristics of biochar were obtained to determine the performance of the reactor. Different trials were carried out to obtain different pyrolysis temperatures under constant amounts of feedstock and fuel. The temperature was monitored continuously at three predetermined reactor heights, the temperature profile varied from 380 °C to 1000 °C. The biochar yield was 49% with an average production rate of 1.8 ± 0.2 kg h−1. The reactor consumed 11 ± 0.1 kg of rice husk as feedstock and 6 ± 1 kg h−1 of wood as fuel. The gaseous products from the pyrolysis were CH4, CO2, H2, CO, and CnHm, which contributed 23.3 ± 2.3 MJ m−3 of energy as fuel for the pyrolysis process. The specific surface area of the biochar was 182 m2 g−1. The achieved operational capacity and thermal efficiency of the reactor show biochar production is a suitable option to convert discarded biomass into a value-added product that can potentially be used in several environmental applications.

Recirculation factor as a key parameter in continuous-flow biomass selection for polyhydroxyalkanoates production

The effectiveness of polyhydroxyalkanoates (PHA) production with mixed microbial cultures (MMC) largely depends on the selection of PHA-storing microorganisms, conventionally performed in sequencing batch reactors (SBR). These, although easily allow the establishment of the required feast and famine (FF) regime, can represent a factor of cost increase when the process is scaled up. Here, a novel continuous-flow process for MMC selection under FF conditions has been developed by using two sequentially operated reactors. The feast reactor, having a tubular configuration, was continuously fed with a synthetic mixture of acetic and propionic acids (at an organic loading rate of 2.12 gCOD/L d) and the effluent of this reactor was in part sent to the CSTR famine reactor. The recirculation factor (RC), that is the ratio between the recirculation flow rate and the feeding flow rate to the feast reactor, was the main parameter investigated. Four different runs were performed with the RC varying from 1 to 8 and the increase in its value caused a decrease of the biomass residence time in each reactor. The intracellular PHA content in the feast reactor almost linearly increased up to RC 4 (with a value of 34 ± 2 %, wt/wt) and dropped at the RC 8 condition that, however, showed the maximum PHA content (58 ± 5 %, wt/wt) during the accumulation tests. Indeed, the relative abundance of sequences affiliated with putative PHA-storing bacteria increased up to 90.5 % at RC 8 and were dominated by members of the Alphaproteobacteria class mostly represented by the genus Meganema (74 %).

CFD investigation of the in-situ gasification process of biomass in the chemical looping combustion system

At present, chemical looping combustion has emerged as a promising combustion technology for carbon capture. In this work, the gas-solid reactive flow in the biomass gasification of the fuel reactor of the chemical looping combustion system is numerically studied via the multiphase particle-in-cell approach under the Eulerian-Lagrangian framework. Regarding the model validation, the gaseous products numerically obtained quantitatively agree well with the experimental data in the literature. Then, the gas-solid reactive flow behaviour together with the effect of operating parameters are discussed. The results show that the non-uniform distribution of solid phase along the axial direction results from the size/density-induced segregation, which gives rise to the accumulation of oxygen carrier particles in the bottom and elutriation of biomass particles. The skewed distribution of biomass residence time in the fuel reactor can be observed. The smallest carbon content exists in the region close to the feeding port. Above the feeding position, the increase of carbon content but the decrease of biomass mass can be observed. Compared with oxygen carriers, biomass particles have a larger dispersion coefficient. Small content of CO and H2 appears while a wide range of CO2 exists in the dense region of the reactor.

Experimental investigations on sugarcane bagasse pyrolytic oil production from flash pyrolysis using a rotary screw reactor

AbstractA rotary screw pyro‐oil reactor was designed for powdery biomass for a feeding capacity of 40 kg h−1 with a moisture content of <10%. The pyro‐oil reactor temperature was maintained at 450–550 °C. The pyro‐oil vapors produced were quickly drafted out of the reactor for quenching to yield 16–24 L h−1 from 40 kg h−1 of biomass feed. The flash‐pyrolysis technique, which is capable of directly turning biomass into a liquid fuel, was used to produce liquid fuel (bio‐oil). It was carried out at a pressure at 0.03 bar and at a medium temperature of about 550 °C. The flash‐pyrolysis technique converts the entire biomass matter, excluding the ash. In this method the powdery biomass is converted into three components: bio‐oil (the yield is typically 70% on an energy basis, a powdery biomass feed at a moisture content of 10%); pyrolysis gas (typical yield 14%) and char (typical yield 16%). The temperature of the fixed bed was adjusted in the experiment, but the other variables remained constant, such as the amount of feed, the pyrolysis time of the gas product, the reactor pressure and the bed height. A biomass particle size range of 1–3 mm and a biomass residence time of 20 s in the reactor resulted in optimal bio‐oil production of 70%. This work demonstrated how precise pyrolysis mechanism processes and bio‐oil yields can influence the maximal reaction temperature in the 450–550 °C range. The performance analysis reveals that the fixed bed reaction temperatures of biomass rapid pyrolysis give reliable control over the bio‐oil reactor type and size. This paper provides an overview of the design and thermochemical liquefaction process used to convert powdered biomass to biofuel. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

A computational approach to determine the residence time distribution of biomass particles in rotary drum dryers

Wood pellet manufacturing involves drying of wet biomass from 50% m.c. down to 5%–7% m.c. Rotary drum dryers are the most common dryers in pellet industry. Mis-prediction of biomass residence time leads to fires and low-quality products due to over drying or under drying. The current study uses a CFD and DEM modeling approach to determine the residence time of particles with properties similar to biomass feedstock in a rotating drum. The developed model uses a Lagrangian approach to track the 3D particle trajectory from drum inlet to the outlet. The novelty of the current model is that it includes the contribution of biomass interactions with drum wall and internal baffles, which is mostly missing in the published models. Particles with an increasing mass and aspect ratio stayed longer in the dryer than particles with an aspect ratio closer to unity.

Pyrolysis of Miscanthus: Developing the mass balance of a biorefinery through experimental tests in an auger reactor

Miscanthus is a perennial grass that can be cultivated on marginal lands and used in multiple biobased applications. Through pyrolysis, it can be converted to bio-oil, biochar, and non-condensable gases. This study presents the mass balance and characterization results of Miscanthus pyrolysis in an auger reactor. The response surface methodology was used to identify, from empirical experiments, the optimal process parameters for producing bio-crude oil with the least water content. A response surface model was developed using a Box-Behnken design, allowing to study the impact of a range of pyrolysis temperature (425–575 °C), biomass residence time (80–140 s) and carrier gas flowrate (2–7 Lnitrogen min−1). Results confirmed that the selected approach allowed identifying pyrolysis parameters for producing bio-crude oil with minimal water content. Moreover, the mass balance of the pyrolysis process was established, providing reliable foreground data to be used in life cycle and techno-economic assessments.

CFD Investigation of the In-Situ Gasification Process of Biomass in the Chemical Looping Combustion System

At present, chemical looping combustion has emerged as a promising combustion technology for carbon capture due to the inherent separation of CO2 with other flue gas components. In this work, the gas-solid reactive flow in the biomass gasification of the fuel reactor of chemical looping combustion is numerically studied via the multiphase particle-in-cell approach in the Eulerian-Lagrangian framework. After the model validations with experimental measurements, the gas-solid reactive flow behavior together with the effect of operating parameters are discussed. The results show that the nonuniform distribution of solid phase along the axial direction results from the size-induced segregation, which gives rise to the accumulation of large particles in the bottom and elutriation of fine particles. The skewed distribution of biomass residence time in the fuel reactor can be observed. The smallest carbon content exists in the region close to feeding port. Above the feeding position, the increase of carbon content but decrease of biomass mass can be observed. Compared with oxygen carrier, biomass particles have a larger dispersion coefficient. Small content of CO and H2 appears while a wide range of CO2 exists in the dense region of reactor.

Microbial carbon use efficiency, biomass residence time and temperature sensitivity across ecosystems and soil depths

Decomposition of soil organic matter by microorganisms is a fundamental mechanism driving the terrestrial carbon (C) cycle. Microbial C use efficiency (CUE), microbial biomass residence time (MRT), and soil C temperature sensitivity (Q10) co-determine the fate of soil C in a changing climate. In order to reveal the effect of soil depth and varying hydrologic properties on CUE, MRT, and Q10 of microbial respiration, we incubated soils from three ecosystems (wetland, grassland, and forest) and soil depths (0–10, 20–30, and 50–60 cm) at two temperatures (10 and 30 °C). Microbial CUE was estimated using a substrate-independent method by incorporating 18O from labeled water into microbial DNA with the simultaneous measurement of microbial respiration. CUE ranged from about 0.2 to 0.7 with a mean value of 0.5 ± 0.1, MRT ranged from 4 to 73 days with a mean value of 26 ± 19 days, and Q10 ranged from 1.8 to 2.9, averaging 2.3 ± 0.3 across all samples. We found that CUE increased but MRT and Q10 decreased along the wetland-grassland-forest hydrologic gradient; and they all increased with soil depth. Moreover, CUE and MRT were lower at 30 °C than that at 10 °C. Although there were some differences in factors regulating the variation in CUE, MRT or Q10 among soil depths and ecosystem types, both within individual ecosystems and depths, CUE, MRT, and Q10 were strongly correlated to available C:N ratios, clay content, and C quality, respectively. In conclusion, our findings emphasize the importance of stoichiometry and C quality of available substrates in predicting the variation in microbial C use efficiency and soil C temperature sensitivity in different soil depths and along a hydrologic gradient.

Development of a Fluidized-Bed Reactor for Oxidative Torrefaction of Biowastes

Torrefaction is considered as a method for producing biofuels with improved characteristics compared to those of the “raw” biomass (higher calorific value, moisture resistance, better grindability). The torrefaction process is an endothermic process that is usually carried out in a gaseous atmosphere in the absence of oxygen. To reduce the required heat input, it is proposed to employ the oxidative torrefaction and conduct the process in a fluidized bed agitated with flue gases containing less than 6% oxygen. Preliminary studies of the oxidative torrefaction of sunflower husks, including thermogravimetric analysis of the treated material, have shown that the heat treatment time for the biomass should be at least 5 min. A fluidized bed is a reactor with ideal mixing of the treated material where uniform treatment of raw material particles cannot generally be attained. To overcome this disadvantage of the fluidization technique and achieve the required residence time for biomass in a fluidized bed during a continuous torrefaction process, it was proposed to equip a torrefaction reactor with a series of vertical baffles spaced at 50 mm. These baffles induce a loop-like flow of the processed biomass from the inlet to the outlet of the reactor. To investigate the residence time for husk particles in the reactor, a tracer, which was colored to husk particles' color with a water-soluble dye which did not change the weight and size of the particles, was injected into the bed of uncolored particles. Tracer samples were taken every 30 s at the outlet of the reactor and were analyzed using a special procedure to determine the fraction of colored particles in each sample. This enabled us to gauge the time during which the colored particles injected into the fluidized bed reached the point of their discharge from the bed. Studies performed in a “cold” model of the reactor showed that a series of vertical baffles in the bed can provide the required residence time for biomass in a reactor including commercial reactors. Plates can provide the necessary biomass residence time in the reactor.

Phosphorus allocation to and resorption from leaves regulate the residence time of phosphorus in above‐ground forest biomass on Mount Kinabalu, Borneo

Abstract The residence time of phosphorus (P) in trees is a consequence of plant adaptation to P deficiency, with longer P residence time on soils with low P availability. P residence time has been studied at the leaf or canopy level but seldom at the whole‐tree level. Whereas P residence time at the leaf or canopy level is largely determined by leaf longevity and the resorption of P before leaf abscission, P residence time at the whole‐tree level will also be influenced by differences in P allocation to different plant parts because leaves and woody organs have distinct longevities. We estimated the residence time of P in above‐ground tree biomass (AGB) as the ratio of P mass (i.e. leaves plus wood) to the annual flux of P via litterfall (i.e. fine litter plus coarse woody debris) for seven tropical rain forests with different soil P availabilities on Mount Kinabalu, Borneo. We analysed the effects of P allocation to and resorption from leaves on P residence time along a soil P gradient. P residence time (2.7–9.8 years) was approximately one‐fifth of biomass residence time (AGB/annual litterfall mass; 19.8–48.8 years). This was due to a disproportionately greater relative allocation of P to leaves (P mass in leaves/P mass in AGB; 0.11–0.46), which had a smaller fraction of biomass (leaf biomass/AGB; 0.02–0.05) but a shorter longevity (1.0–1.8 years). The relative allocation of P to leaves was often high on low‐P soils, and P residence time was expected to be short. By contrast, the resorption rate of P from leaves was also high on low‐P soils, which extended P residence time with P deficiency. Consequently, P residence time was nearly constant across the forests. The short residence time of P relative to biomass indicates that P residence time depends largely on relative P allocation among plant organs. Similar P residence times among sites were maintained because greater P allocation to leaves on low‐P soils was effectively offset by higher P‐resorption efficiency. A free Plain Language Summary can be found within the Supporting Information of this article.

Soil Properties Control Microbial Carbon Assimilation and Its Mean Residence Time

Microbial assimilation and stabilization of soil organic carbon (SOC) is an important process in global carbon cycling. For an improved understanding of climate-induced changes in ecosystem C dynamics, it is important to know the group-specific turnover of microbial C. Consequently, we wanted to answer the questions if fungi store newly assimilated C longer than bacteria and if climatic and edaphic properties of different regions affect microbial C assimilation and its subsequent release. This study presents results from a 112-day long field experiment where endogenous soil microorganisms were labelled with 13C labelled glucose to follow the dynamics of newly assimilated C in two study regions (Kraichgau and Swabian Alb). Whereas microbial assimilation of newly added C was higher in Kraichgau than in Swabian Alb, the opposite result was obtained for the mean residence time (MRT) of microbial biomass C (76 days in Kraichgau and 93 days in Swabian Alb). The accelerated turnover rates of microbial C in the warmer soils of Kraichgau with lower clay content might be an important mechanism explaining the differences in SOC content between both regions. Gram-positive bacteria assimilated more 13C-glucose into their biomass than fungi and the MRT of C was higher in bacteria as compared to fungi in both regions. Beside these dynamic substrate utilization strategies, we could proof cross feeding by gram-negative bacteria. Carbon MRT in fungi was region specific and was best represented by a two-pool model; the initial MRT ranged between 5 to 39 days and was, in the end, higher than 4 years. This provides evidence of a possible shift in fungal community composition; fast growing fungi dominant in the early phase and internal redistribution of C in the second phase of decomposition. Our study identified microbial group and region specific MRT of freshly assimilated C as an important parameter, which might help to explain the commonly found variation in soil respiration and SOC stabilization.

Visual Experimental Analysis of the Residence Time of Flexible Biomass Particles in a Baffled Rotating Cylindrical Tube

Drying of biomass or biofuels is a major issue during pretreatment because of a high initial moisture content, which results in low energy efficiency and combustion temperature and high emission of hydrocarbons. As the motion behaviors of biomass fuels play an important role in the drying process, it is of great significance to investigate the motion of biomass. In this study, visualization experiments on the motion of flexible nonspherical biomass particles in a baffled rotating cylindrical tube were performed. The residence time of biomass particles was obtained and analyzed by taking into account gas velocity, mass flow rate of flexible biomass, initial moisture content of biomass particles, slope and rotational speed of the cylindrical tube, and other parameters under several operational conditions. The results indicated that the mean residence time of flexible biomass increased with the increase in the mass flow rate and initial moisture content and decreased with the increase of the cylindrical tube’s rotational speed and slope and the velocity of the gas phase. Despite the quite small sliding friction coefficient between the tube’s inner wall and biomass particles, a larger slope could lead to stronger sliding friction force in the axial direction when these biomass particles moved to the bottom of the tube. Mean residence time is observed to decrease significantly and gradually decrease with the increase in rotational speed from 6 to 9 rpm and from 9 to 18 rpm, respectively. In addition, the mean residence time increased from 78.5 to 99.4 s when the inlet mass flow rate increased from 60 to 240 kg/h without the gas phase, but it increased from 57.4 to 78.5 s within the same range of the inlet mass flow rate at a gas velocity of 0.3 m/s.

Climate change undermines the global functioning of marine food webs.

Sea water temperature affects all biological and ecological processes that ultimately impact ecosystem functioning. In this study, we examine the influence of temperature on global biomass transfers from marine secondary production to fish stocks. By combining fisheries catches in all coastal ocean areas and life-history traits of exploited marine species, we provide global estimates of two trophic transfer parameters which determine biomass flows in coastal marine food web: the trophic transfer efficiency (TTE) and the biomass residence time (BRT) in the food web. We find that biomass transfers in tropical ecosystems are less efficient and faster than in areas with cooler waters. In contrast, biomass transfers through the food web became faster and more efficient between 1950 and 2010. Using simulated changes in sea water temperature from three Earth system models, we project that the mean TTE in coastal waters would decrease from 7.7% to 7.2% between 2010 and 2100 under the 'no effective mitigation' representative concentration pathway (RCP8.5), while BRT between trophic levels 2 and 4 is projected to decrease from 2.7 to 2.3years on average. Beyond the global trends, we show that the TTEs and BRTs may vary substantially among ecosystem types and that the polar ecosystems may be the most impacted ecosystems. The detected and projected changes in mean TTE and BRT will undermine food web functioning. Our study provides quantitative understanding of temperature effects on trophodynamic of marine ecosystems under climate change.

Bridging particle and reactor scales in the simulation of biomass fast pyrolysis by coupling particle resolved simulation and coarse grained CFD-DEM

Efficient utilization of biomass is challenging due to the complexity of the feedstock at molecular, particle, and reactor scales. Direct coupling of particle scale model and reactor scale simulation is computationally infeasible. In this research, the results from a particle resolved simulation were used to calibrate the heat transfer and reaction kinetics of particles. A hybrid drag model was used to consider the different fluidization properties of sands and biomass particles. The computation cost was reduced using a coarse-grained Discrete Element Method (DEM). The simulated conversion rate, char yield, tar yield, and pyrolysis gas yield compare well with experiment. The residence time and axial distributions of biomass were also analyzed. This novel multi-scale method provides an efficient and accurate tool for the modeling of biomass pyrolysis reactors.

Measurement and characterization of biomass mean residence time in an air-blown bubbling fluidized bed gasification reactor

Gasification of biomass in bubbling fluidized beds can be limited by accumulation of unconverted char particles during the process. The amount of unconverted biomass depends on the residence time of the fuel particles. This study demonstrates a method for measuring the biomass residence time over the conversion period at a given air flowrate and a given amount of biomass in a bubbling bed using the variation of bed temperature and fluid pressure recorded over time. The results show that biomass conversion is characterized by the devolatilization and extinction times. The two biomass residence times increase with decreasing air flowrate and increasing amount of biomass charged in the bed. The amount of unconverted char between the two characteristic times also increases with decreasing air flowrate and increasing biomass load. The total heat loss during the devolatilization is observed to increase with increasing air flowrate and amount of biomass in the bed. Correlations are proposed for predicting the mean biomass residence time, the amount of unconverted char particles and the devolatilization heat loss at a given operating condition. The results of this study can be used in determining the bubbling bed properties and solid circulation rate required to decongest the accumulated char particles in the bed.

A generic pixel-to-point comparison for simulated large-scale ecosystem properties and ground-based observations: an example from the Amazon region

Abstract. Comparing model output and observed data is an important step for assessing model performance and quality of simulation results. However, such comparisons are often hampered by differences in spatial scales between local point observations and large-scale simulations of grid cells or pixels. In this study, we propose a generic approach for a pixel-to-point comparison and provide statistical measures accounting for the uncertainty resulting from landscape variability and measurement errors in ecosystem variables. The basic concept of our approach is to determine the statistical properties of small-scale (within-pixel) variability and observational errors, and to use this information to correct for their effect when large-scale area averages (pixel) are compared to small-scale point estimates. We demonstrate our approach by comparing simulated values of aboveground biomass, woody productivity (woody net primary productivity, NPP) and residence time of woody biomass from four dynamic global vegetation models (DGVMs) with measured inventory data from permanent plots in the Amazon rainforest, a region with the typical problem of low data availability, potential scale mismatch and thus high model uncertainty. We find that the DGVMs under- and overestimate aboveground biomass by 25 % and up to 60 %, respectively. Our comparison metrics provide a quantitative measure for model–data agreement and show moderate to good agreement with the region-wide spatial biomass pattern detected by plot observations. However, all four DGVMs overestimate woody productivity and underestimate residence time of woody biomass even when accounting for the large uncertainty range of the observational data. This is because DGVMs do not represent the relation between productivity and residence time of woody biomass correctly. Thus, the DGVMs may simulate the correct large-scale patterns of biomass but for the wrong reasons. We conclude that more information about the underlying processes driving biomass distribution are necessary to improve DGVMs. Our approach provides robust statistical measures for any pixel-to-point comparison, which is applicable for evaluation of models and remote-sensing products.

Experimental study of ferrocement downdraft gasifier engine system using different biomass feedstocks in Ghana

In this study, experimental analyses of a Ferrocement Downdraft Gasifier (FDG) coupled to a 20 kW engine was conducted using different feedstocks. Feedstocks used were Anogeissus Leiocarpus (Kane charcoal), Bambusoideae (bamboo charcoal), Tectona grandis (teak charcoal) and wood pellets. The effects of several parameters including operating moisture content, temperature, gasifying agents, biomass residence time on producer gas flowrate and yield were assessed. The gas generated was used to run a gas engine system. Analysis of the experimental results showed maximum producer gas output from the FDG to be 55, 44, 45 and 37 Nm3/hr for bamboo charcoal, Kane charcoal, teak charcoal and wood pellets, respectively, with bamboo generating more stable engine runs. Highest engine speed on producer gas was determined to be 2300 revolutions per minute (RPM), at a bamboo charcoal consumption rate of 8 kg/h. Stable temperature range of 38–50 °C was recorded across the various cylinders in the system with a maximum gasifier temperature of 1045 °C. Based on the outcomes of the study, bamboo charcoal, teak charcoal, Kane charcoal and wood pellets in that order, were found to be suitable feedstock for gasification and electricity generation based on the corresponding syngas flowrate, tar production and performance when used for electricity generation.

Soot formation during biomass pyrolysis: Effects of temperature, water-leaching, and gas-phase residence time

Soot particles from biomass incomplete combustion, as a major source of particulate matter, arouse significant concerns due to its harmful impacts on environment and human health. In this paper, the effects of pyrolysis temperature, volatile residence time and water-leaching of biomass on soot formation during biomass pyrolysis were studied in a lab-scale furnace. The physicochemical characteristics of soot particles were comprehensively analyzed. Results show that soot is formed by the secondary reactions of volatiles from biomass thermal-cracking requiring a certain high temperature and long volatile residence time. With a short volatile residence time of 0.2 s, no soot is formed at 900–1200 °C. When the residence time increases to 2 s, soot is significantly formed at >1000 °C, when onion-like shell/core structures is observed. With pyrolysis temperature increasing, the soot particle size decreases and becomes uniform, the carbon content in soot increases, and the ordered structure of carbonization is enhanced, which leads to the degradation of soot oxidation reactivity. The water-leaching pretreatment for biomass leads to the increases of soot yield, particle size, and carbon content, as well as the KCl absence in soot and significantly lowered oxidation reactivity of soot. This indicates strong catalysis of potassium on soot production and consumption. Both gas and tar analyses support soot formation mechanism: (1) H2 yield increases due to formation of soot, but C2H2 yield reaches peak at 1000–1100 °C; (2) tar is dominated by PAHs, which molecules grow with the increase of temperature and residence time.