Carbonization of biomass: effect of additives on alkali metals residue, SO2 and NO emission of chars during combustion

The effect of additives (NHHPO, CaCO and CaO) on biomass carbonization was studied in the current paper, including residual K and Na in chars, SO and NO emission of different chars during combustion. Experiment was carried on a tube furnace system. The results show that, CaO and NHHPO reduce the alkali content of chars to different degree. Three additives inhibit SO emission from raw and carbonized biomass remarkably, and SO mass emission is lesser than 0.1\ua0mg\ua0g. Three additives enhance NO emission at different levels, and NO mass emission is from 1.2 to 3.5\ua0mg\ua0g. Both raw and carbonized biomass can be modified by some additives to achieve near zero emissions of SO. Although the additives promote the NO release, the total emission rate (3.8–10.1%) was much lower than that of brown coal combustion, which was reported as 33.5–37.7%. Economic analysis shows that three additives are economy for industry utility. Thus the three additives are good for modifying biomass carbon to attain clean and efficient combustion

Genome-wide identification, characterization, evolution and expression analysis of the DIR gene family in potato (Solanum tuberosum)

The dirigent (DIR) gene is a key player in environmental stress response and has been identified in many multidimensional tube plant species. However, there are few studies on the StDIR gene in potato. In this study, we used genome-wide identification to identify 31 StDIR genes in potato. Among the 12 potato chromosomes, the StDIR gene was distributed on 11 chromosomes, among which the third chromosome did not have a family member, while the tenth chromosome had the most members with 11 members. 22 of the 31 StDIRs had a classical DIR gene structure, with one exon and no intron. The conserved DIR domain accounts for most of the proteins in the 27 StDIRs. The structure of the StDIR gene was analyzed and ten different motifs were detected. The StDIR gene was divided into three groups according to its phylogenetic relationship, and 22 duplicate genes were identified. In addition, four kinds of cis-acting elements were detected in all 31 StDIR promoter regions, most of which were associated with biotic and abiotic stress. The findings demonstrated that the StDIR gene exhibited specific responses to cold stress, salt stress, ABA, and drought stress. This study provides new candidate genes for improving potato’s resistance to stress

The study of sulphur retention characteristics of biomass briquettes during combustion

In the current world, the large consumption of fossil fuel leads to some global environmental problems, using biomass energy is one of the good solutions. However, due to the more strict emission policy, the sulphur releasing during biomass combustion cannot be ignored. In order to study the self-sulphur retention characteristics, the briquetting process of biomass is carried out. In this study, a batch of biomass briquettes combustion experiments are conducted to investigate self-sulphur retention characteristics. Five kinds of biomass powder, biomass briquettes, and briquettes with additive samples are used to carry out the combustion experiments, which are performed in a lab-scale tube furnace system. The influence of the briquetting process, reaction temperature, added coal and additives are studied comprehensively. The briquetting process gives remarkable enhancements on sulphur retention characteristics compare to the raw biomass powder, which is mainly due to the effect of the structural transformation. The enhancement are 35.00%, 76.68%, 36.15%, 27.34% and 31.36% compared to the original biomass samples. The reaction temperature behaves severely on the release of sulphur, that when the reaction temperature reaches 900C, the sulphur release ratio starts to sharply increase. Adding coal into the biomass samples can increase the sulphur retention ability and the caloric value. The effects of different additives on sulphur retention ratios are also studied, exhibiting opposite trends as temperature increased. The organic Ca-based additives show better performance to enhance the self-sulphur retention ability. What's more, the potassium-based additives have a higher improvement than the calcium-based ones. The mechanism on sulphur retention of biomass briquettes with or without additives is also discussed. This study develops insightful understand on biomass self-sulphur retention ability, and its behaviours under the effect of the briquetting process, reaction temperature, added coal or additives, which could use as a guild for biomass briquetting combustion

Combustion Characteristics, Kinetics, SO2 and NO Release of Low-Grade Biomass Materials and Briquettes

The influence of the briquetting process on SO2 and NO release characteristics, combustion properties and kinetic characteristics during biomass combustion was investigated. Two biomass (Wheat straw and Tree bulk) and two obtained briquettes were analysed. The briquetting process helps to prevent the release of SO2 and NO. The experimental results show that once the biomass is made into a briquette, when the reaction temperature is 900 ∘C, the sulphur release ratio for TB was reduced from 34.7% to 4.3% and for WS was reduced from 12.4% to 1.6%. When the reaction temperature increases to 1000 ∘C, the sulphur release ratio for TB was reduced from 73.4% to 30.4%, for WS it was reduced from 58.4% to 10.2%. SEM micrographs show that the compact structure of the TB-Briquette and WS-Briquette reduce the rate of SO2 and NO release during combustion. The thermogravimetry confirmed that the combustion performance of WS-Briquette is the best, while the TB-Briquette is the worst. According to the Coats-Redfern method, the fitting was performed at segments of 250 ∘C to 550 ∘C, and the correlation coefficient of the fitting degree was above 0.99. The effective collision rate of WS-Briquette is much higher than that of other briquettes. Compared to BR-1 and BR-2, trying to mix TB with WS to make a compound biomass briquette can enhance the combustion performance of TB-Briquette. The results may guide the upgrading of biomass briquettes technology and benefit the efficient application of biomass briquettes

Thermogravimetric analysis of the relationship among calcium magnesium acetate, calcium acetate and magnesium acetate

Thermal decomposition characteristic of calcium magnesium acetate (CMA), calcium acetate (CA) and magnesium acetate (MA) are investigated through thermogravimetric (TG) analysis at the heating rates of 5 K min-1, 7.5 K min-1, 10 K min-1 and 15 K min-1. After dehydration, the evaporation of carboxylic radical and carbon dioxide of CMA and CA exist in two separate segments, but for MA, this occurs together in just one segment without clear borderline. The curves of calculated CMA (C-CMA) and the deduced characteristic parameters illustrate the different characteristic of CA and MA from the corresponding components in CMA which may be the reason for the different performances of these sorbents in SO2 and NOx reduction. Also, the kinetic parameters of activation energy and reaction order of the three sorbents are calculated through Vyazovkin method and Avrami theory, respectively.Thermogravimetric (TG) Calcium magnesium acetate (CMA) Activation energy Reaction order

Segmented heating carbonization of biomass: Yields, property and estimation of heating value of chars

To provide preferable operating conditions for biomass carbonization, the carbonization properties of maize straw, cotton stalk and poplar wood were investigated in nitrogen atmosphere by segmented heating process at different final temperatures of 300–800 °C for 1 h. Segmented heating carbonization contributes to higher ratio of mass and energy yields than a constant temperature/linear heating process with final temperature of around 300 °C. The fuel properties and characteristics of raw and carbonized biomass were analysed systematically. Increasing carbonization temperature, the fuel ratios of the obtained chars rise exponentially, and the profile of atomic H/C ratio versus atomic O/C ratio approximately decreases linearly. There are small changes of sulphur and nitrogen content in the chars. To provide an estimation method for higher heating value for torrefied/carbonized biomass, a new correlation is proposed based on ultimate analysis. The correlation is HHV=19.9579+0.1284C+0.3355H−0.1209O−1.3836N−5.4680S, which is validated through experimental data. The correlation has a low level of errors, that the correlation efficient, mean absolute error, average absolute error and average bias error are 0.971, −6.75×10MJ, 1.2% and 0.02% respectively. This work will make a contribution to the biomass pretreatment process

Co-combustion characteristics and kinetics of meager coal and spent cathode carbon block by TG-MS analysis

As a hazardous waste, the spent cathode carbon block (SCCB) has a high calorific value while it is difficult to fire, its harmless disposal is a major difficulty at present. Herein, a method of mixed combustion of meager coal and SCCB in a pulverized coal furnace for disposal of SCCB is proposed, and thermogravimetric mass spectrometry (TG-MS) is used to characterize the combustion and gas release characteristics. The effects of the heating rate and mixing ratio on combustion are analyzed as well. The result shows that the comprehensive combustibility index and combustion stability index of SCCB-5 at a heating rate of 50 °C/min are both the highest. Abundant oxygen-containing groups in SCCB promote the co-combustion process. The release of hydrogen fluoride is relatively low below 1000 °C so that the use of pulverized coal boilers meets the temperature requirement for disposal of SCCB. The good melting characteristics of ash after mixing sintering also confirm this point. Finally, the kinetic calculation results show that the combustion activation energy is the lowest when the mixing ratio is 5%, which is in good agreement with the experimental results. The highest activation energy values for the combustion of meager coal, SCCB and SCCB-5 are 46.90, 89.39, 59.87 kJ mol−1, respectively

Study on Slagging Characteristics of Co-Combustion of Meager Coal and Spent Cathode Carbon Block

The harmless disposal of spent cathode carbon blocks (SCCBs) has become an urgent issue in the primary aluminum industry, and the disposal of SCCBs by co-combustion in pulverized coal boilers is expected to be the most effective treatment method. A muffle furnace at 815 °C was used in this study to perform a co-combustion experiment of meager coal and SCCBs. The ash fusion characteristics (AFTs), microscopic morphology, and minerals composition of co-combustion ash were characterized. The interaction mechanism of different mineral components and the change in AFTs and viscosity-temperature characteristics were investigated using FactSage software. Results show that the change in the ash deformation temperature (DT) is correlated linearly with the SCCB addition ratio, whereas other characteristic temperatures exhibit a nonlinear relationship. The contents of SiO2, Al2O3, and Na2O collectively determine the DT in the ash, and the influence degree from high to low is in the order of SiO2, Na2O, and Al2O3. The phase diagram of Na2O–Al2O3–SiO2 is used to accurately predict the changing trend of the melting point of co-combustion ash. The ratio changes between refractory and fusible minerals in the ash, as well as the degree of low-temperature eutectic reaction between sodium- and calcium-containing minerals, are the main factors affecting the melting point of ash. When the blending amount of SCCBs is 5%, mostly complete combustion is achieved, and slagging does not occur easily. The optimal blending ratio of SCCBs is obtained using the co-combustion method from the aspect of AFTs and viscosity-temperature characteristics. This work lays a theoretical foundation for industrial application

Investigation of potassium transformation characteristics and the influence of additives during biochar briquette combustion

Low energy density and ash fusion problem were problems that limit biomass widespread utilization. To avoid these, maize straw (MS) was blended with two additive –NHHPO (ADP) and Ca(HPO) (CPM)-respectively, and the production chain of mixing additive-briquetting-pyrolysis was put forward to produce MS char briquettes (MSC, MSC-ADP and MSC-CPM). Ash fusion characteristics of MS char briquettes after combustion was investigated by XRF, XRD, SEM-EDS and simulation. Results show that the softening temperature increased with the enhanced ratio of PO/KO until 0.2, and CaO/KO until 0.9. The higher amount of CaO and PO, the lower amount of KO, the better ash fusion characteristics. The PO had larger influence on softening temperature. The surfaces of MSC ashes formed at 1000 °C were fusion and smooth in micro observation, while surfaces of MSC-ADP and MSC-CPM ashes were coarse and the particles were much looser. Both SEM-EDS and XRD results illustrated that phosphorus in additives combined with potassium to produce high melting temperature potassium phosphates rather than low melting temperature potassium silicates. The potassium fixation ability of ADP was better than that of CPM. The calcium silicates and calcium phosphates produced by CPM could improve ash characteristics