scholarly journals Thermogravimetric Analysis of Coal Semi-Char Co-Firing with Straw in O2/CO2 Mixtures

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1421
Author(s):  
Debo Li ◽  
Ning Zhao ◽  
Yongxin Feng ◽  
Zhiwen Xie
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Ignition Temperature ◽  
Combustion Process ◽  
Stage I ◽  
Stage Iii ◽  
Combustion Behavior ◽  
O2 Concentration ◽  
Three Stages ◽  
The Individual

For coal semi-char as a by-produced of low-temperature pyrolysis, combustion for power generation is one of the effective utilization methods to realize its clean and efficient utilization. However, the coal semi-char combustion process has a difficult ignition, unstable combustion and low burnout rate. The co-firing of the semi-char with biomass under oxy-fuel conditions can improve the combustion behavior and reduce fossil CO2 emissions. In this paper, the combustion behavior of Shenhua coal semi-char (SHC) co-firing with straw (ST) in O2/CO2 mixture is investigated using thermogravimetric analysis. The results show that each curve lays between those of the individual fuels and presents three peaks (i.e., three stages). The thermogravimetric curves of SHC co-firing with ST can be divided into three stages: the volatile combustion of ST, the co-combustion of SHC and ST fixed-carbons and the SHC fixed-carbon combustion and the decomposition of the difficult pyrolytic material of ST. Blending ST into the SHC can significantly decrease the ignition temperature and improve the comprehensive combustion behavior of blended samples. In increasing the proportion of ST from 25 to 100%, the change of the blended ignition temperature is slight, but the burnout temperature decreases greatly. Kinetic parameters of combustion are calculated by using the Coats–Redfern integral method. Compared to that of stage I and stage III, the activation energy of stage II is significantly lower. As increasing blending ratio from 25% to 100%, the activation energy increases at stage I and decreases at stage III. Furthermore, the O2 concentration obviously affects stage III of 50% SHC + 50% ST, and the thermogravimetric curves at this stage are obviously shifted to the lower temperature zone as the O2 concentration increases. The activation energy of 50% SHC + 50% ST increases as the oxygen concentration increases. Besides, the activation energy shows that the combustion characteristics cannot be determined only by the activation energy obtained by the Coats–Redfern method. These findings can provide useful information for semi-char co-firing with biomass.

Mechanisms and kinetics of initial pyrolysis and combustion reactions of 1,1-diamino-2,2-dinitroethylene from density functional tight-binding molecular dynamics simulations

2019 ◽  
Vol 97 (11) ◽  
pp. 795-804 ◽  
Author(s):  
Dong Xiang ◽  
Weihua Zhu
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Density Functional ◽  
Tight Binding ◽  
Combustion Process ◽  
Exponential Factor ◽  
Three Stages ◽  
Dynamics Simulations ◽  
Combustion Processes ◽  
Kinetics Of

The density functional tight-binding molecular dynamics approach was used to study the mechanisms and kinetics of initial pyrolysis and combustion reactions of isolated and multi-molecular FOX-7. Based on the thermal cleavage of bridge bonds, the pyrolysis process of FOX-7 can be divided into three stages. However, the combustion process can be divided into five decomposition stages, which is much more complex than the pyrolysis reactions. The vibrations in the mean temperature contain nodes signifying the formation of new products and thereby the transitions between the various stages in the pyrolysis and combustion processes. Activation energy and pre-exponential factor for the pyrolysis and combustion reactions of FOX-7 were obtained from the kinetic analysis. It is found that the activation energy of its pyrolysis and combustion reactions are very low, making both take place fast. Our simulations provide the first atomic-level look at the full dynamics of the complicated pyrolysis and combustion process of FOX-7.

Frontal osteomas: standardising therapeutic indications

2011 ◽  
Vol 125 (10) ◽  
pp. 1020-1027 ◽  
Author(s):  
L M Gil-Carcedo ◽  
E S Gil-Carcedo ◽  
L A Vallejo ◽  
J M de Campos ◽  
D Herrero
Keyword(s):  
Classification System ◽  
Bone Destruction ◽  
Stage I ◽  
Stage Ii ◽  
Stage Iii ◽  
Tumour Mass ◽  
Surgical Indications ◽  
Monitoring Protocol ◽  
Three Stages ◽  
Relationship Of

AbstractBackground:We believe the currently accepted indications for frontal osteoma surgery are inappropriate. We propose a new osteoma classification system, below, in order to standardise surgical decisions.Method:Osteomas were classified based on: relationship of tumour mass to sinus size; tumour proximity to the infundibulum, destruction of sinus walls, and complications. Forty-five osteoma cases were thus classified (1971–2007), 29 of which underwent surgery (64.44 per cent).Results:Three stages were thus derived: I, tumour/air fraction less than one-third, tumour distant from the infundibulum, no sinusitis, and no complications (18 patients (40 per cent)); II, tumour/air fraction one-third to one-half, no infundibular obstruction, no bone destruction, no sinusitis, and no complications (six (13.33 per cent)); and III, tumour/air fraction more than one-half, partial or total infundibular obstruction, sinusitis, bone destruction, and/or complications (21 (46.67 per cent)).Conclusion:Study findings suggest the following surgical indications: stage I, no surgery required, implement monitoring protocol; stage II, implement monitoring protocol, surgery may be required depending on tumour severity and general patient condition; and stage III, surgery always required. This system provides a method of standardising osteoma surgical decisions.

scholarly journals Influences of High-Speed Train Speed on Tunnel Aerodynamic Pressures

2021 ◽  
Vol 12 (1) ◽  
pp. 303
Author(s):  
Jianming Du ◽  
Qian Fang ◽  
Jun Wang ◽  
Gan Wang
Keyword(s):  
High Speed ◽  
Peak Pressure ◽  
Stage I ◽  
Stage Ii ◽  
Stage Iii ◽  
High Speed Train ◽  
Railway Tunnel ◽  
Maximum Peak ◽  
Train Speed ◽  
Three Stages

To comprehensively investigate the characteristics of aerodynamic pressures on a tunnel caused by the whole tunnel passage of a high-speed train at different speeds, we conduct a series of three-dimensional numerical simulations. Based on the field test results obtained by other researchers, the input parameters of our numerical simulation are determined. The process of a high-speed train travelling through a railway tunnel is divided into three stages according to the spatial relationship between the train and tunnel. Stage I: before train nose enters the entrance; Stage II: while the train body runs inside the tunnel; Stage III: after the train tail leaves the exit. The influences of high-speed train speed on the tunnel aerodynamic pressures of these three stages are systematically investigated. The results show that the maximum peak pressure value decreases with increasing distance from the entrance and increases with increasing train speed in Stage I. There is an approximately linear relationship between the three types of maximum peak pressure (positive peak, negative peak, and peak-to-peak pressures) and the power of the train speed in Stage II. These three types of maximum peak pressure values of the points near tunnel portals increase with increasing train speed in Stage III. Moreover, these three types of maximum peak pressure in the tunnel’s middle section at different train speeds are more complex than those near the tunnel portals, and there is one or more turning points due to the superimposed effects of different pressure waves.

scholarly journals Measurement of O2 in the Combustion Chamber of Apulverized Coal Boiler

10.14311/1544 ◽  
2012 ◽  
Vol 52 (3) ◽  
Author(s):  
Břetislav Janeba ◽  
Michal Kolovratník ◽  
Ondřej Bartoš
Keyword(s):  
Combustion Chamber ◽  
Flue Gas ◽  
Combustion Process ◽  
Pulverized Coal ◽  
Or Management ◽  
Pulverized Coal Boiler ◽  
O2 Concentration ◽  
Coal Boiler ◽  
The Individual ◽  
Lambda Probe

Operational measurements of the O2 concentration in the combustion chamber of a pulverized coal boiler are not yet common practice. Operators are generally satisfied with measuring the O2 concentration in the second pass of the boiler, usually behind the economizer, where a flue gas sample is extracted for analysis in a classical analyzer. A disadvantage of this approach is that there is a very weak relation between the measured value and the condition in specific locations in the fireplace, e.g. the function of the individual burners and the combustion process as a whole. A new extractionline was developed for measuring the O2 concentration in the combustion chamber. A planar lambda probe is used in this approach. The extraction line is designed to get outputs that can be used directly for diagnosis or management of the combustion in the boiler.

scholarly journals MORPHOFUNCTIONAL CHARACTERISTICS THYROID GLAND OF WHITE-BREASTED MALE HEDGEHOG IN THE PERIOD OF PUBERTY

2021 ◽  
Vol 248 (4) ◽  
pp. 233-237
Author(s):  
D.N. Fiadotau ◽  
◽  
◽  
Keyword(s):  
Thyroid Gland ◽  
Sexual Maturation ◽  
Stage I ◽  
Stage Ii ◽  
Stage Iii ◽  
Three Stages ◽  
Morphological State ◽  
End Of Puberty

The issue of the morphofunctional characteristics of the thyroid gland of male white-breasted hedgehogs during puberty on the territory of Belarus was studied. Material for the study was taken from 15 males, who were divided into three stages of studying the sexual maturation of hedgehogs: stage I - prepubertal period, stage II - the beginning of puberty, and stage III - activation of the gonads and the end of puberty. The results obtained characterize the morphological state of the thyroid gland of male white-breasted hedgehogs during puberty, and thus makes it possible to use morphometric indicators of structures as indicators of the environment and physiological states (for assessing puberty).

Growth of crop communities and the production of yield.

2021 ◽  
pp. 50-88
Author(s):  
Dennis B. Egli
Keyword(s):  
Production Process ◽  
Leaf Area ◽  
Stage I ◽  
Stage Ii ◽  
Stage Iii ◽  
Species Variation ◽  
Seed Number ◽  
Yield Production ◽  
Three Stages ◽  
Community Growth

Abstract This chapter focuses on developing general model of community growth and the production of yield by grain crops. Murata's (1969) three-stage system provides such a model. It is useful because it is simple (only three stages), it applies equally well to all grain crop species (although there are some species variation in minor details), it clearly identifies the sequential nature of the yield production process and the three stages relate to the primary drivers of the yield production process at the community level. First, the crop must accumulate the leaf area that drives community photosynthesis (Stage I), then seed number is determined (Stage II), and finally seed filling occurs (Stage III) and the production of yield is finished. High yield of any variety/location combination requires, at a minimum: (i) the production of enough leaf area index (LAI) during Stage I to maximize solar radiation interception and community photosynthesis; and (ii) an absence of stress during Stage II to maximize seed number and during Stage III to allow the seeds to fill to their maximum potential size. The scheme provides a powerful framework for us to think about how management decisions and environmental conditions affect yield.

Thermogravimetric Analysis of Different Biomass Materials and the Primary Biomass Components

2012 ◽  
Vol 260-261 ◽  
pp. 187-191
Author(s):  
Ya Bo Li ◽  
Xu Ming Zhang ◽  
Lei Qiang Zhao ◽  
Qiang Lu ◽  
Chang Qing Dong
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Combustion Process ◽  
Nitrogen Atmosphere ◽  
Pyrolysis Kinetics ◽  
High Activation ◽  
High Activation Energy ◽  
Pyrolysis Characteristics ◽  
Biomass Components ◽  
Biomass Materials

Thermogravimetric analysis (TGA) was employed to study the pyrolysis and combustion characteristics of three primary biomass components (cellulose, xylan and lignin) and seven different biomass materials under both of nitrogen and air atmosphere. Based on the experimental results, the pyrolysis and combustion kinetics were calculated. The results indicated that the three primary biomass components exhibited different decomposition characteristics and pyrolysis kinetics. Xylan was the least thermal stable component, while the lignin would form much more solid residues than the cellulose and xylan under the nitrogen atmosphere. Moreover, the pyrolytic devolatilization process of the cellulose had high activation energy, so was the char combustion process of the lignin. The seven biomass materials showed similar pyrolysis characteristics, and poplar wood exhibited high activation energy values in both of pyrolysis and combustion processes.

Non-isothermal thermogravimetric analysis of heavy oil in an O2/CO2 atmosphere

2018 ◽  
Vol 16 (6) ◽  
Author(s):  
Zhiqiang Wang ◽  
Ming Liu ◽  
Xingxing Cheng ◽  
Yusheng He ◽  
Yingjie Hu ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Thermogravimetric Analysis ◽  
Low Temperature ◽  
Oxygen Concentration ◽  
Heavy Oil ◽  
Combustion Process ◽  
Molecular Weights ◽  
Diffusion Controlled ◽  
Temperature Activation

Abstract Although heavy oil is an abundant and promising energy source, its processing and utilization are complicated due to its high density, low hydrogen/carbon ratio, and high asphaltene content. Fortunately, these problems can be mitigated by the application of oxy-fuel combustion. To gain deeper insights into the above technology, the characteristics of heavy oil combustion in an O2/CO2 atmosphere was investigated using non-isothermal thermogravimetric analysis. We demonstrate that the combustion process consisted of four stages. Low-molecular-weight hydrocarbons reacted at low temperature, whereas heavy ones required a higher temperature. Increasing the concentration of oxygen resulted in increased TGA and DSC peak intensities and decreased peak widths, and these peaks were shifted to lower temperatures. Coat-Redfern and Flynn-Wall-Ozzawa methods were used to evaluate the kinetic parameters (E, A) of the oxidation process, showing that the high-temperature activation energy was much higher than the low-temperature one due to the different molecular weights of the oxidized substrates in each region. The reaction was demonstrated to be diffusion-controlled, as reflected by the lower activation energy at high oxygen concentration and high temperature, with the influence of oxygen concentration on QO processes being much more obvious than that on SO ones.

Preventive effects by intensive restorative treatment against caries in children

2002 ◽  
Vol 26 (4) ◽  
pp. 357-362
Author(s):  
Takanobu Morinushi ◽  
Kouichiro Inoue ◽  
Shozaburo Toyoshima ◽  
Mayumi Morinushi ◽  
Yosiko Araki ◽  
...  
Keyword(s):  
Intensive Treatment ◽  
Stage I ◽  
Stage Iii ◽  
Secondary Caries ◽  
Restorative Treatment ◽  
Pediatric Dentist ◽  
Treatment Stage ◽  
Three Stages ◽  
Preventive Effects

The caries preventive effect of intensive treatment of existing caries was studied in children less than 7 years old living in a district without a dentist. The methods consisted of intensive restorative treatment provided by a pediatric dentist in three stages as follows: Stage I (n=70), two years before initiation of intensive treatment; Stage II (n=80), at initiation of long-term intensive treatment, and Stage III (n=92) three years after initiation of intensive dental treatments. The results were that experience and severity of dental caries and secondary caries rates were significantly lower in stage III than in stage I or II in six year olds. Between-meal consumption of snacks containing sugar and plaque prevalence both were less in stage III than in others. In conclusion, intensive treatment of caries in young children was associated with prevention both primary and secondary caries.

A survey of white mica crystallinity and polytypes in pelitic rocks of Snowdonia and Llŷn, North Wales

1985 ◽  
Vol 49 (352) ◽  
pp. 305-319 ◽  
Author(s):  
R. J. Merriman ◽  
B. Roberts
Keyword(s):  
Regional Metamorphism ◽  
Xrd Analysis ◽  
White Mica ◽  
Stage I ◽  
Stage Ii ◽  
Stage Iii ◽  
North Wales ◽  
Volcaniclastic Rocks ◽  
Three Stages ◽  
Pelitic Rocks

AbstractPelitic rocks in North Wales, ranging in age from late Precambrian to Silurian were sampled. XRD analysis was used to determine the mineralogy and white mica crystallinity of separated < 2 µm fractions. Results show that three stages of metapelite recrystallization can be distinguished. Stage I metapelites are uncleaved or feebly cleaved with crystallinities > 0.43Δ°2θ; the 1Md polytype dominates < 2 µm fractions, occurring as K-and Na-micas. Stage II metapelites show variable cleavage development and crystallinities in the range 0.26-0.43Δ°2θ; 1Md and 2M1 polytypes occur and K- and Na-micas are commonly regularly interstratified. Stage III metapelites are strongly cleaved with crystallinities < 0.26Δ°2θ; the 2M1 polytype is dominant, occurring as K-mica and paragonite. Pelites bearing pyrophyllite, rectorite, and corrensite are found close to plug-like intrusions and were contact altered prior to regional metamorphism. 1M mica is common in deeply buried but relatively undeformed volcaniclastic rocks of the Arfon Group.Contours of equal crystallinity (isocrysts) are plotted with metabasite zones on a metamorphic map. This shows that stage I metapelites are equivalent to the subpumpellyite zone (≡?laumontite zone). Stage II metapelites are equivalent to the prehnite-pumpellyite facies and stage III metapelites to the clinozoisite and biotite zones of the greenschist facies.

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