Coupled effects of Fenton-like systems with different concentrations of H2O2/Biochar on diethyl phthalate removal: Dominant role of environmental persistent free radicals (EPFRs).

To investigate the impact of different H2O2 concentrations on the Fenton-like systems of H2O2/biochar, this study examined the mechanism of the physical structure and environmental persistent free radicals (EPFRs) of biochar during diethyl phthalate (DEP) removal by the Fenton-like system. The peak-splitting method was utilized to differentiate EPFRs types in cotton stalk biochar produced at different temperatures. High-temperature environments promote π-electron delocalization, which facilitates phenyl π free radicals and σ-π oxygen-containing free radicals. By analyzing relationships between the removal rate K1 and removal constant Kobs of DEP with the structural properties of biochar, it was discovered that EPFRs concentrations in biochar had a significant positive correlation with K1 (r = 0.92) and Kobs (r = 0.97). Different H2O2 concentrations added to the biochar removal system resulted in varied DEP removal efficiency. Among them, CS500, CS550, and CS600 exhibited superior DEP removal efficiency when H2O2 concentration was 5 mM.

Urea impregnation into fungus pretreated corn stover to perform pyrolysis for production of nitrogen-containing bio-oil and nitrogen-doped biochar.

Urea was introduced into the fungal pretreated corn stover and then the urea soaked materials were subjected to pyrolysis for the production of nitrogen-containing bio-oil and nitrogen-doped biochar. The urea soaking effectively realized the enrichment of nitrogen-containing compounds in the bio-oil and the maximal content of the nitrogen-containing compounds in bio-oils reached up to 66.32% under 4 wt% urea concentration. Among the nitrogen-containing compounds, amines were the most dominant component with the maximal content of 41.17%. The higher urea concentration is beneficial to make more nitrogen be fixed in the biochar. The nitrogen content of the biochar reached up to 12.86 wt% under 8 wt% urea concentration. Nitrogen on the biochar surface existed in the form of pyrrolic-N, pyridinic-N and graphite-N. In conclusion, urea simple soak on fungus pretreated biomass to perform pyrolysis is a promising approach to obtain high value-added nitrogen-containing chemicals and nitrogen-doped biochar with high nitrogen content.

Comparative Assessment of Proportions of Urea in Blend for Nitrogen-Rich Pyrolysis: Characteristics and Distribution of Bio-Oil and Biochar.

This study aimed to investigate the effect of the urea content on the characteristics and distribution of nitrogen-rich bio-oil and nitrogen-doped biochar. Cellulose, cellobiose, and glucose were used as feedstock. Urea was used as the exogenous nitrogen source in nitrogen-rich pyrolysis at 500 °C. The order of the nitrogen increase in the nitrogen-doped biochar was cellulose < cellobiose < glucose. Nitrogen-doped biochar consisted of abundant nitrogen and nitrogenous functional groups, and the stability of biochar was optimal. The nitrogen-doped biochar obtained from cellulose showed the optimal adsorption performance for diethyl phthalate with 50% urea addition. When the proportion of urea was 20%, the content of anhydro-sugars in bio-oil reached the maximum value (61.86%). Furans and other small-molecule oxygenates were intermediates to produce nitrogenous heterocyclic compounds (NHCs) from cellulose. When the proportion of urea was 40%, the bio-oil had the highest selectivity (91.63%) of NHCs. The NHCs in the obtained bio-oil mainly consisted of pyrroles, pyrimidines, pyridines, imidazoles, and pyrazines. Therefore, the excellent proportion of urea in the blend could promote the generation of high-value NHCs and nitrogen-doped biochar from the nitrogen-rich pyrolysis of cellulose (and its model compounds).

Reduced Pollutant Emissions and Slagging Rate of Biomass Pellet Combustion by Optimizing the Multilayer Distribution of Secondary Air.

The utilization of coal and other fossil fuels is becoming increasingly restricted. Biomass, as a clean and renewable energy, plays a significant role in achieving zero carbon emissions. However, biomass is prone to slagging in the combustion process due to its high alkali metal content. The ash slagging rate and pollutant emission level of flue gas can be reduced by optimizing the air distribution, in order to decrease the fuel layer temperature in the combustion chamber. The results reveal opposite change trends of CO and NOx concentrations in the flue gas. The NOx emissions of corn stalk combustion under the multilayer secondary air distribution are obvious compared with those of rice husk combustion. The slagging rate of corn stalks is highly correlated with temperature T 1 of the fuel bed. The silica ratio (G), alkali/acid ratio (B/A), Na content index (Na (index)), and alkaline index (Al c ) cannot accurately predict the slagging tendency when temperature T 1 changes. Therefore, the modified predictive index (Gt ) was proposed to predict the slagging tendency of corn stalks with the combustion zone temperature T 1 effectively. The experimental results can contribute to the efficient combustion and low pollutant emissions of biomass.

Effect of pretreatment with Phanerochaete chrysosporium on physicochemical properties and pyrolysis behaviors of corn stover.

Fungal pretreatment can selectively degrade partial biomass components, which undoubtedly exerts a significant influence on biomass pyrolysis behavior. The corn stover was pretreated with Phanerochaete chrysosporium, and its influence on the physicochemical properties and pyrolysis behaviors of biomass together with the product characteristics were investigated. The Phanerochaete chrysosporium was more active to degrade hemicellulose and lignin. The hemicellulose and lignin contents in corn stover were decreased by 35.14 % and 31.80 %, respectively, after five weeks pretreatment, compared to the untreated sample. The reaction activation energy decreased from 52.89 kJ·mol-1 for the untreated sample to 40.88 kJ·mol-1 for the sample pretreated for five weeks. The Phanerochaete chrysosporium pretreatment was beneficial to the biochar production but exerted an unfavorable effect on the texture structure. The Phanerochaete chrysosporium also had an obvious influence on the bio-oil compositions. This study can provide a scientific reference for the application of biological pretreatment for biomass pyrolysis technology.

Characteristics of bio-oil and biochar from cotton stalk pyrolysis: Effects of torrefaction temperature and duration in an ammonia environment.

In this study, nitrogen-containing chemicals and nitrogen-rich biochar were prepared using ammonia (NH3) torrefaction pretreatment technology. The effects of temperature and duration of torrefaction on the characteristics of torrefaction and pyrolysis products were evaluated. The results indicated that when the torrefaction temperature was increased to 290 °C, the nitrogen content increased significantly from 0.98% to 6.85%. XPS analysis showed that the raw biomass mainly contained amide-N and pyrrole-N. As the torrefaction temperature and duration increased, quaternary-N formation was promoted, while amide-N, pyrrole-N, and pyridine-N were consumed. Potential nitrogen doping and transformation pathways during the ammonia torrefaction process were proposed. GC-MS analysis showed that ammonia torrefaction promoted the formation of pyridines, while reducing the content of oxygen-containing species. In addition, torrefaction duration had positive effects on the yield of nitrogen-containing chemicals.

Influence of Operating Parameters on Chlorine Release and Pollutant Emission Characteristics of a 130 t/h BCFB Combustion System.

A 130 t/h biomass circulating fluidized bed (BCFB) boiler combustion system model, considering the chloride release and pollutant emissions during the biomass combustion, was established using the Modelica language. The effects of the biomass feed amount, limestone amount, excess air coefficients, and different ratios of primary and secondary air on the boiler furnace temperature and flue gas composition (O2, CO2, SO2, HCl, and KCl) were investigated. Upon the biomass feed amount step change, the variation ranges of NO and KCl concentrations were very large, which were 18.58 and 21.16% of the before step value, respectively. The step change of the limestone input had little effect on b ed temperature in the dense phase zone, but it could obviously reduce the SO2 concentration. The concentration of SO2 in flue gas decreased by 22.56% when the limestone input increased by 50%. The removal rate of SO2 gradually decreased with the increase of the limestone amount. The SO2 desulfurization rate decreased by 68.30% when the amount of limestone increased from 0.0275 to 0.0825 kg/s. More NO would be generated and KCl concentration would be significantly reduced with the increase of the excess air coefficient. When the ratio of primary and secondary air was 4:6, the NO concentration in flue gas was lower than 86.06 mg/Nm3.

A Control Strategy of the Air Flow Rate of Coal-Fired Utility Boilers Based on the Load Demand.

An analysis was conducted on the relationship between the calorific value of different types of coal and the theoretical air requirement. It was found that the theoretical air volume required for generating the same amount of heat during combustion is the same for different types of coal. The concept of the air/coal ratio was improved by proposing the concept of the air/carbon ratio, which refers to the ratio of the mass of air to the mass of carbon during complete combustion; the ratio is approximately 11.5 kg/kg (mass ratio), being roughly constant for different types of coal, unlike the air/coal ratio showing a significant change with coal types. The total air flow rate in a boiler changed with load demand, and the influence of different fuel types can be neglected at the same load level. On this basis, an air flow rate control strategy for coal-fired utility boilers was proposed and implemented in the boiler in which the air flow rate required to the furnace is a function of the unit load. Experiments conducted in a 300 MWe coal-fired utility boiler confirm that the use of the control strategy of the air flow rate for the combustion optimization improves the stability of the main steam pressure and mitigates the fluctuations of the coal flow. These results provide a foundation for the implementation of a new strategy of air/coal decoupling and independent control of boiler combustion.