Insight into the ammonia torrefaction and pyrolysis system of cellulose:Unraveling the evolution of chemical structure and nitrogen migration mechanism

This study aimed to investigate the mechanism of nitrogen doping,migration,and conversion during ammonia torrefaction and also explore the evolution law of the chemical structure of cellulose.The results showed that the ammonia torrefaction pretreatment could significantly optimize the distribution of nitrogen and oxygen elements in cellulose.The carbon skeleton first captured the active nitrogenous radicals to form-NHn-N,and pyridine-N and pyrrole-N originated from the conversion of-NHn-N.The existence of C=O played a major role in the immobilization of nitrogen.The nitrogen in bio-oil exists mainly in the form of five-and six-membered heterocycles.The correlation analysis showed that the main precursors for the formation of nitrogenous heterocyclic compounds were five-membered Oheterocyclic compounds.Finally,the product distribution characteristics in the torrefaction-pyrolysis systems were summarized,and the nitrogen doping and conversion mechanisms were proposed.This study expanded the boundaries of cellulose pretreatment and the production of high-value chemicals.

Effects of Microwave Torrefaction with Mg（OH）2 on Characteristics of Bio-oil from Co-pyrolysis of Straw Stalk and Soapstock

This study investigated the effects of torrefaction with Mg(OH)2 on the properties of bio-oil formed from the microwave-assisted catalytic fast co-pyrolysis of straw stalk and soapstock.The effects of torrefaction temperature and residence time on the yield and composition of bio-oil were discussed.Results showed that the torrefaction temperature and residence time remarkably influenced the yield and composition of bio-oil.With the increase in temperature and time,the bio-oil yield and the proportion of oxygen-containing compounds decreased,while the proportion of aromatic compounds increased.When the feedstocks were subject to torrefaction reaction for 20 min at 260°C,the proportion of oxygen-containing compounds decreased from 29.89%to 16.49%.Meanwhile,Mg(OH)2 could render the deoxidization function of torrefaction process increasingly noticeable.The proportion of the oxygen-containing compounds reached a minimum(14.41%),when the biomass-to-Mg(OH)2 ratio was 1:1.

Upgraded Pellet Making by Torrefaction—Torrefaction of Japanese Wood Pellets

Upgraded wood pellets were produced and evaluated by torrefaction of wood pellets. In this study, conventional wood pellets were initially prepared and subsequently torrefied on a laboratory and then larger scale. During the laboratory scale production, pellets from wooden parts of Japanese cedar (sugi, Cryptomeria japonica) and Japanese oak (konara, Quercus serrata) trees were heat- treated in an inert gas oven under nitrogen atmosphere around 170°C - 320°C. For the Japanese cedar, the calorific values were improved by heat treatment up to 260°C. By heat treatment at 240°C, the upgrade ratio of higher heating value (HHV) was nearly 30% and the energy yield was 97%. For the Japanese oak, the calorific values were improved by heat treatment up to 320°C. By heat treatment at 280°C, the upgrade ratio of HHV exceeded 30% and the energy yield was 84%. On a larger scale, a conventional charcoal oven was modified for torrefied wood pellet production, meaning that torrefied wood pellet with 25 MJ/kg of calorific value was produced during heat treatment at 350°C. A mixture of conventional and torrefied pellets was applied to a commercial pellet stove, and torrefied wood pellets produced in this study might be usable as fuel for conventional pellet stoves.

Fundamental Study on the Production of ＂Hyper Wood Pellet＂——Effect of Torrefaction Condition on Grinding and Pelletizing Properties

In order to upgrade the conventional wood pellet, Japanese softwood and hardwood chips were torrefied at around 200-350℃, and pelletized. The characteristics of the torrefied material/pellets such as their calorific value, grinding energy, pelletizing energy and elemental composition, were also evaluated in this study. The calorific value rose with increasing torrefaction temperature and exceeded 25 MJ/kg （an increase of nearly 40% compared to the untreated state） for torrefaction at around 350℃. The grinding energy greatly decreased with increasing torrefaction temperature, and the reduction was larger for Japanese oak hardwood chips. The pelletization energy for the torrefied material tended to be slightly smaller than in the untreated case. People named such torrefied pellet as ＂hyper wood pellet＂.

Recent Advance on Torrefaction Valorization and Application of Biochar from Agricultural Waste for Soil Remediation

With the increase of global proportion of soil pollution and the number of areas at risk,researchers have sought to develop various pathways to repair or relieve the pollutants in soil.Among them,biochar represents one multi-dimensional soil amendment which has got great deal of attention on its physicochemical properties towards the removal or mitigation of contaminants in soil.A variety of agricultural wastes like straw and manure prepared from different torrefaction process have been employed as feedstock for the production of biochar,which can be applied to the contaminated soil to facilitate the growing environment for crops,and to improve soil fertility and microbial environment.In addition,the utilization of biochar for soil remediation is also considered as a pro-cess of carbon sequestration.The purpose of this review is to summarize the latest research progress in torrefac-tion processes and mechanism of agricultural waste,the effects of different torrefaction methods on the formation and properties of biochar were explained,coupled with the effects of process parameters.Especially,the conver-sion and mechanisms of biochar prepared from agricultural wastes composed mainly with lignocellulosic material were discussed,and the characteristics of biochar prepared for improving soil physical and chemical character-istics,microbial community characteristics,nutrients,and the stability and relief of soil pollutants,especially heavy metals,are compared.Finally,this work discussed the application and future technical challenges of soil remediation based on agricultural waste derived biochar.

Impacts of Torrefaction on PM_(10) Emissions from Biomass Combustion

Typical biomass torrefaction is a mild pyrolysis process under conditions of ordinary pressure,low temperature(200–300°C)and inert atmosphere.Torrefaction is considered to be a competitive technology for biomass pretreatment,but its impacts on the emissions of particulate matter from biomass combustion are worthy of further study.In this paper,three kinds of biomass,i.e.,bagasse,wheat straw and sawdust were selected for torrefaction pretreatment and the impacts of torrefaction on the emission characteristics of PM_(10) from biomass combustion were investigated.The combustion experiments were carried out on a drop tube furnace.The combustion-generated particulate and bulk ash samples were collected and subjected to analyses by various techniques.The results show that torrefaction tends to result in a reduction of PM_(1)(particulates with an aerodynamic diameter less than 1μm)emissions from combustion,but the extent of reduction is dependent on biomass type.The reduction of PM_(1) from the combustion of torrefied biomass is mainly because that the torrefaction process removes some Cl and S from the biomass,thereby suppressing the release of alkali metals and the emissions of PM_(1) during the combustion process.As for PM_(1–10)(particulates with an aerodynamic diameter within 1–10μm),its emissions from combustion of torrefied biomasses are consistently reduced,compared with their untreated counterparts.This observation is primarily accounted for the enhanced particle coalescence/agglomeration in combustion of torrefied biomasses,which reduces the emissions of PM_(1–10).

Design and Testing of a Solar Torrefaction Unit to Produce Charcoal

With increasing crude oil prices, fuels like kerosene and cooking gas have become unaffordable for many ordinary people in developing countries. For millions of Africans who need heat energy to cook their food, biomass like wood remains the easiest and cheapest source of fuel. Charcoal remains the most popular choice compared to wood since it can cook food much faster with very little smoke. Torrefaction of biomass is a mild form of pyrolysis at temperatures typically between 200℃ and 300℃ to produce charcoal. Torrefaction changes biomass properties to provide a much better fuel quality for combustion applications. A simple parabolic trough solar collector to produce charcoal by torrefaction process using solar energy has been designed from first principles. The device was fabricated and various locally available wood species were tested. The yield was found to be 21% to 35% with a production time of 90 minutes. The paper details the design procedure and the test results.

Superhydrophobic and superlipophilic biochar produced from microalga torrefaction and modification for upgrading fuel properties

Torrefaction operation is an essential pathway for solid biofuel upgrading,and good hydrophobicity of torrefied biochar is conducive to its storage.Herein,a two-stage treatment of torrefaction followed by modification by hexadecyltrimethoxysilane was adopted to improve the moisture resistance performance of biochar.This two-stage treatment process led to a longer torrefied microalgal biochar preservation time(60-200%improved)and great superhydrophobicity and superlipophilicity.Therefore,the modified microalgal biochar could significantly adsorb leaking oil for environmental remediation and further improve the calorific value of the biochar.The obtained results indicated that the oil adsorption capacity of modified microalgal biochar was correlated to torrefaction temperature and oil species.Specifically,the oil adsorption capacity was enhanced up to 70-80%from the modification process when comparing to raw microalga.Increasing the torrefaction temperature enhanced the adsorption quantity of the modified microalgal biochar.By adsorbing the oil,the calorific value of oilchar,namely,biochar with adsorbed oil,could be higher than 40 MJ kg^(−1).Furthermore,the pyrolysis and combustion characteristics suggested that biochar stability gradually rose as the torrefaction temperature increased.By comprehensively analyzing and comparing the fuel performance of the modified microalgal biochar with previous literature,the obtained modified microalgal biochar possessed better fuel properties and environmental sustainability.

Biomass torrefaction in a slot-rectangular spouted bed reactor

Sawdust was subjected to torrefaction in a "semi-batch" slot-rectangular spouted bed (SRSB) reactor at temperatures from 240 to 330℃ and biomass feed rates from 220 to 710g/h.Stable spouting of the sawdust was achieved in the slot-rectangular spouted bed,although the pressure drop across the reactor was observed to oscillate.Compared to the biomass feed rate,the temperature had a greater effect on the biomass weight loss and energy yield.Increases in temperature were found to promote weight loss of the sawdust while decreasing the energy yield.The main solid product was the torrefied sawdust,which remained in the SRSB reactor and was captured by a cyclone.The ratio of the torrefied biomass removed by the cyclone to the total torrefied biomass increased along with both the feed rate and temperature.After undergoing torrefaction,6.7%-39.2% of the original sawdust mass was lost while 67.4%-98.7% of its energy was retained.The torrefied sawdust had a higher carbon content but less oxygen,hydrogen and volatiles,along with a greater higher heating value and increased density compared to the raw sawdust.The size of the sawdust particles also decreased markedly during the torrefaction process.

Effects of operating conditions and pre-densification on the torrefaction products of sorghum straw

The effects of operating conditions and pre-densification on the torrefaction performance parameters and the properties of the torrefied sorghum straw were studied.A full-factor experiment was performed on a fixed tube furnace,in which sorghum straw powder and pellets were heated to 230℃,260℃,280℃ and 300℃ at 2.5℃/min,5℃/min and 7.5℃/min,respectively.The pyrolysis characteristics of the sorghum straw torrefied under various operating conditions were complemented by thermogravimetric analysis.It was observed that the high temperature led to the high calorific value of the torrefied sorghum straw with an acceptable mass and energy yield.The sorghum straw torrefied at a temperature above 280℃ had a higher heating value(HHV)that was comparable to that of the low rank coal while maintaining its energy yield above 85%.The results suggested that temperature was an important factor determining the properties of the torrefied products,and the heating rate would affect the internal temperature of the torrefied biomass by affecting the heat transfer during the torrefaction.The energy densification index of the pellets decreased uniformly as the heating rate increased proportionally,indicating that pre-densification can be used as a potential method to solve the heat transfer delay in the fixed reactors at high heating rates,especially for high temperatures.

Microwave torrefaction of empty fruit bunch pellet:Simulation and validation of electric field and temperature distribution

Microwave simulation is significant in identifying a reactor design allowing the biomass to be heated and processed evenly.This study integrated the radio frequency and transient heat transfer modules to simulate the microwave distribution and investigated the performance of microwave heating in the cavity.The simulation results were compared with the experimental findings us-ing the finite element analysis software of COMSOL MULTIPHYSICS to predict the temperature profile and electric field of microwave in the biomass(empty fruit bunch pellets).The higher temperature distribution was observed at the bottom and centre section of the empty fruit bunch pellet bed in the reactor,showing the uniqueness of microwave heating.According to the simula-tion results,the temperature profile obtained through the specific cavity geometry and dielectric properties agreed with the experimental temperature profile.The simulated temperature profile demonstrated a logarithmic increase of 120°C/min at the first 50 s followed by 50°C/min until 350 s.The experimental temperature profile showed three different heating rates before reaching 300°C,including 78.3°C/min(50-120°C),30.6°C/min(121-250°C),and 105°C/min(250-300°C).The results of this study might contribute to the improvement of microwave heating in biomass torrefaction.

Structural characterization of char during co-gasification from torrefied sludge and Yangchangwan bituminous coal

The present study aims to investigate the physico-chemical structural evolution characteristics of char structure of CO_(2) atmosphere torrefaction pretreated sludge with Yangchangwan bituminous coal(YC)during co-gasification.The co-gasification reactivity of torrefied sludge and YC was measured using a thermogravimetric analyzer.The co-gasification reactivity of torrefied sludge with YC was thoroughly explored in depth by in situ heating stage microscope coupled with traditional characterization means of char sample(Scanning electron microscope,nitrogen adsorption analyzer,laser Raman spectroscopy).The results show that the gasification reaction rate of sludge treated under CO_(2) atmosphere and coal blended char was better than other char samples at 1100–1200℃.The torrefied sludge under CO_(2) atmosphere promoted its thermal decomposition to the maximum extent,so that it eventually was transformed into a large number of small broken particles.The specific surface area and ID1/IG ratio of blended char of torrefied sludge under CO_(2) atmosphere and YC were 1.70 and 1.07 times higher than that of YC,respectively.The in situ technique revealed that YC char with the addition of torrefied sludge undergo gasification by shrinking core modes and the presence of obvious ash melting flow phenomenon.It was more obvious than that of YC.

Improving hydrocarbons production via catalytic co-pyrolysis of torrefied-biomass with plastics and dual catalytic pyrolysis

To increase the low yield and selectivity of aromatic hydrocarbons during the biomass pyrolysis process,we torrefied the biomass and then co-pyrolyzing with plastics such as high-density polyethylene(HDPE),polystyrene(PS),ethylene-vinyl acetate(EVA)and polypropylene(PP)and also single and dual catalyst layouts were investigated by Py-GC/MS.The results showed that non-catalytic fast pyrolysis(CFP)of raw bagasse(RBG)generated no aromatics.After torrefaction non-CFP of torrefied bagasse(TBG)generated low aromatic yield.Indicating that torrefaction would enhance the proportion of aromatics during the pyrolysis process.The CFP of TBG_(200℃)and TBG_(240℃)over ZSM-5 produced the total aromatic yield of 1.96 and 1.88 times higher,respectively,compared to non-CFP of TBG.Furthermore,the addition of plastic could increase H/Ceff ratio of the mixture,consequently,increase the yield of aromatic compounds.Among the various torrefied-bagasse/plastic mixtures,the CFP of TBG/EVA(7:3 ratio)mixture generated the highest the total aromatic yield of 7.7 times more than the CFP of TBG alone.The dual catalyst layout could enhance the yield of aromatics hydrocarbons.The dual-catalytic co-pyrolysis of TBG_(200℃)/plastic(1:1)ratio over USY(ultra-stable Y zeolite)/ZSM-5,improved the total aromatics yield by 4.33 times more than the catalytic pyrolysis of TBG_(200℃)alone over ZSM-5 catalyst.The above results showed that the yield and selectivities of light aromatic hydrocarbons can be improved via catalytic co-pyrolysis and dual catalytic co-pyrolysis of torrefied-biomass with plastics.

Emission Behaviors of Submicron Particles(PM_(1))Generated by the Combustion of Sesame Stalk after Combined Water Washing and Carbonization Pretreatment

Pretreatment before biomass combustion is significant for its efficient utilization and that combined water washing and carbonization can be efficient.An agricultural processing residues sesame stalk was selected and carried out two pretreatments separately,i.e.,water washing-torrefaction(W-T)and torrefaction-water washing(T-W),to explore the effect on the fuel properties,combustion characteristics and particulate matter(PM)emission.The obtained biochar was also combusted under air and oxy50(CO_(2):O_(2)=50:50)conditions for the sake of investigating the effect of pretreatment and combustion atmosphere.The results indicate that,W-T and T-W both not only have great effect on the improvement of fuel properties but also reduce the content of water-soluble elements like K,Cl,etc.Due to the difference in hydrophobicity,the biochar obtained by W-T have the optimal fuel properties.At the same time,the pretreatment also hinder the combustion in a certain extent in which the comprehensive combustion characteristics(SN)show a downward trend.Furthermore,both two pretreatments have obvious benefit on the reduction of PM_(1)emission and W-T have the best effect related to the higher removal efficiency of inorganic elements(especially K+Na+Cl+S).Under oxy50 condition,the oxygen concentration and combustion temperature is higher,improving the sulfation of K and vaporization of Ca,P and Mg which result in weakening in the pretreatment reduction effect on PM_(1)emission.

Assessment of the Influence of Torrefied Biomass Physical Characteristics, Design and Operating Variables on Gasification Efficiency

Gasification efficiency is an important factor that determines the actual technical operation as well as the economic viability of using a gasifier system for energy production. In this study, the impact of the physical properties of torrefied bagasse and the influence of gasifier design and operating variables were investigated in a computer simulated downdraft gasification system. Results obtained from the study indicated an interrelationship between feedstock characteristics, especially with regard to feed size, design variables such as throat angle and throat diameter as well as gasifier operating conditions such as temperature of input air and feed input. These variables influenced the efficiency of the gasification process of sugarcane bagasse because of increased enhancement of combustion zone reactions, which liberated huge amount of heat that led to a rise in the temperature of the gasification process. This condition also created increased tar cracking within the gasification system, contributing to reduction in the overall yield of tar.

Characterization of Novel Torrefied Biomass and Biochar Amendments

Nutrient management is vital for food, feed, fiber, and fuel production. However, excessive application and loss (volatilization, leaching, run-off, etc.) of inorganic and organic sources of nutrients have detrimental environmental impacts, while increasing prices for petroleum-based and mined fertilizers further limit opportunities for their utilization in developing nations. This study evaluated a novel, alternative type of nutrient source through pretreatment processes of torrefaction and pyrolysis by converting high-biomass feedstocks into renewable soil amendments. Napiergrass (Pennisetum purpureum Schumach., [cv. Merkeron]) and pearl millet—napiergrass (Pennisetum glaucum [L.] R. Br. × P. purpureum Schumach.) (PMN) were converted under atmospheric pressure with minimal oxygen at 250°C and 400°C, ground to 1 millimeter (mm) and 2 mm particle sizes, and compared to urea in a full-season field trial and short-season nursery trial growing maize (Zea mays L.) and PMN for fertility response. When compared to urea in the field trial, the torrefied biomass amendment (TBA) and biochar had similar responses despite lower nitrogen (N) application rates. The nursery trial also produced equivalent responses from urea and TBA regardless of lower N application with the exception being phosphorus (P). Finally, maize and PMN had higher P uptake with the TBA in both trials.

First Measurements with a Linear Mirror Device of Second Generation

In 2011, an innovative technique for concentrating solar light has been introduced in the market—the Linear Mirror. It is a very simple device, and it works well also in winter and in northern climates. In 2012, it was certified with the Solar Keymark. Based on this technology, a further improved device was developed and was presented here—the Linear Mirror of second generation (or Linear Mirror II). This is a multi-purpose machine, which overcomes some of the limitations of the previous device. First measurements with the Linear Mirror II are presented in this paper.

Heat Transfer within Direct Heating Integrated Moving Bed Torrefier by Method of Lines

This work deals with the determination of the temperature profile within a direct heating moving bed torrefier in order to determine its minimum column height. A thermal model based on eulerian-eulerian two-phase solid-gas theory was performed and solved with the method of lines. In addition, this study allows to investigate the effect of the biomass particle size on the minimum torrefier column height. This investigation was performed by changing, simultaneously, the diameter of particles and the minimum fluidization velocity of the bed. Then, the calculations were made for a counter-current torrefaction reactor of 30 cm in diameter and for 5 kg/h of the feed rate of raw sugarcane bagasse. Results show that the height of the reactor column must be at least 30 cm for that are 1 mm in diameter and 108 cm for particles that are 2 mm in diameter.

Torrefied Pellets as Fuel for Two-Stage Technology of Biomass Conversion into Synthesis Gas

One of the most important properties of the torrefied pellets, along with high calorific value, is their hydrophobicity. Inability to absorb moisture and self-destruct under its influence determine possibility of using of pellets in the pyrolysis reactor. For the technology of two-stage thermal processing of biomass, developed at the Joint Institute for High Temperatures, the amount of synthesis gas which can be obtained from one kilogram of torrefied pellets is also important. A construction of the pilot torrefaction reactor powered by flue gas is shown. The results of experimental investigations of hydrophobicity of torrefied pellets produced by the reactor and quantity of synthesis gas which can be obtained by two-stage thermal processing of the pellets are presented. It is shown that torrefaction allows simplifying the process of conversion of pellets into synthesis gas without significant reduction in the volume of the gas.

A sustainable preparation strategy for the nitrogen-doped hierarchical biochar with high surface area for the enhanced removal of organic dye

Biochar is a potential porous carbon to remove the contaminants from aquatic environments.Herein,N-doped hierarchical biochar was produced by the combined approach of ammonia torrefaction pretreatment(ATP)and alkali activation.ATP could not only incorporate N element into poplar wood,but obtain the loose structure of poplar wood.The highest surface area of N-doped hierarchical biochar was 2324.61 m^(2) g^(−1) after ammonia wet torrefaction pretreatment,which was higher than that of activation carbon(1401.82 m^(2) g^(−1))without torrefaction pretreatment,the hierarchical biochar(2111.03 m^(2) g^(−1))without ammonia atmosphere.The N-doped hierarchical biochar presented the highest adsorption capacity(564.7 mg g^(−1))of methyl orange(MO),which was 14.64-fold of that on biochar without N doping.In addition,the pseudo-second-order and Langmuir model fitted well with the adsorption kinetics and isotherms of the N-doped hierarchical biochar.The incorporation of nitrogen element could not only tune the distribution of surface electrons on biochar,but optimize the ambient condition of adsorption active sites as well.The adsorption of MO might occur on the N-/O-containing functional groups through the electrostatic interaction,theπ-πdispersion interaction,and the hydrogen bonding.The density functional theory showed that the graphitic-N and pyridinic-N were the dominant adsorption active sites.