Study on Dynamics of Calorific Value, Biomass and Energy in Calamagrostis epigejos Population in Songnen Grassland

There were two peaks of seasonal changes of the calorific value in shoot and leaves of Calamagrostis epigejos in middle June and in the early August respectively. The calorific value in stem presented a single peak curve which appeared in the early August. The calorific values in inflorescence and dead standing showed a fluctuation and the peak value of inflorescence was in the early September and that of dead standing was in middle June. The seasonal changes of energy standing crop on the above-ground part synchronized with that of the biomass, which presented a single peak curve. The energy allocated to each organ in different seasons was in the order as leaves > stem > inflorescence in middle June, leaves > stem > dead standing > inflorescence in early July, leaves > stem > inflorescence > dead standing in middle July, and leaves > stem > dead standing > inflorescence from August to September. The vertical allocation of energy in the parts of above-ground was that the energy value gradually increased from the surface to the 20 cm high level and the maximum value at the 10 - 20 cin high level which made up 26.91% of energy on the above-ground partion, and then it was decreased. In the under-ground portion, the energy value progressively decreased with depth and the maximum value was at 0 - 10 cm depth layer which made up 69.01% of energy of the under-ground portion.

Calorific values and ash contents of different parts of Masson pine trees in southern China

Calorific value of plants is an important parameter for evalu- ating and indexing material cycles and energy conversion in forest eco- systems. Based on mensuration data of 150 sample sets, we analyzed the calorific value （CV） and ash content （AC） of different parts of Masson pine （Pinus massoniana） trees in southern China using hypothesis testing and regression analysis. CV and AC of different tree parts were almost significantly different （P〈0.05）. In descending order, ash-free calorific value （AFCV） ranked as foliage 〉 branch 〉 stem bark 〉 root 〉 stem wood, and AC ranked as foliage 〉 stem bark 〉 root 〉 branch 〉 stem wood. CV and AC of stem wood from the top, middle and lower sections of trees differed significantly. CV increased from the top to the lower sections of the tnmk while AC decreased. Mean gross calorific value （GCV） and AFCV of aboveground parts were significantly higher than those of belowground parts （roots）. The mean GCV, AFCV and AC of a whole tree of Masson pine were 21.54 kJ/g, 21.74 kJ/g and 0.90%, re- spectively. CV and AC of different tree parts were, to some extent, cor- related with tree diameter, height and origin.

Exploring relationships of gross calorific value and valuable elements with conventional coal properties for North Korean coals

Coal in North Korean(NKC)is one of the most important products;however,based on various strategic policies its detail properties remain opaque even for general researchers.Since there are some signs for opening of the North Korea economy,this investigation as a modest effort is going to explore principle relationships among some essential parameters of NKCs such as gross calorific value(GCV),valuable elements and conventional properties by different statistical methods.Correlations indicated that ultimate parameters(carbon,nitrogen,and hydrogen)are the best GCV predictors for NKCs in comparison with proximate parameters(ash,moisture and volatile matter).Multivariable regression demonstrated that predicted GCV based on ultimate properties has a quite accuracy when correlation of determination was 0.99.Descriptive statistics processes showed that on average,the contents of valuable elements such as Ga and V for NKCs are higher than the world coal ranges and they can be considered as byproducts of combustion of NKCs.Pearson correlations indicated that Y may have a mixed organic-inorganic affinity while Ga and V mainly occur in the inorganic part(mineral matter)of NKCs.High inter-correlations between Ga-V and Al showed that aluminosilicates can be considered as their main bring minerals.

A novel model for cost performance evaluation of pulverized coal injected into blast furnace based on effective calorific value

The combustion process of pulverized coal injected into blast furnace involves a lot of physical and chemical reactions. Based on the combustion behaviors of pulverized coal, the conception of coal effective calorific value representing the actual thermal energy provided for blast furnace was proposed. A cost performance evaluation model of coal injection was built up for the optimal selection of various kinds of coal based on effective calorific value. The model contains two indicators: coal effective calorific value which has eight sub-indicators and coal injection cost which includes four sub-indicators. In addition, the calculation principle and application of cost performance evaluation model in a Chinese large-scale iron and steel company were comprehensively introduced. The evaluation results finally confirm that this novel model is of great significance to the optimal selection of blast furnace pulverized coal.

Accuracy improvement of quantitative analysis of calorific value of coal by combining support vector machine and partial least square methods in laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy(LIBS) is a potential technology for online coal property analysis,but successful quantitative measurement of calorific value using LIBS suffers from relatively low accuracy caused by the matrix effect.To solve this problem,the support vector machine(SVM) and the partial least square(PLS) were combined to increase the measurement accuracy of calorific value in this study.The combination model utilized SVM to classify coal samples into two groups according to their volatile matter contents to reduce the matrix effect,and then applied PLS to establish calibration models for each sample group respectively.The proposed model was applied to the measurement of calorific values of 53 coal samples,showing that the proposed model could greatly increase accuracy of the measurement of calorific values.Compared with the traditional PLS method,the coefficient of determination(R2) was improved from 0.93 to 0.97,the root-mean-square error of prediction was reduced from 1.68 MJ kg-1 to1.08 MJ kg-1,and the average relative error was decreased from 6.7% to 3.93%,showing an overall improvement.

Effect of tree-age on calorific value and other fuel properties of Eucalyptus hybrid

For determining the effect of tree-age on the fuel properties of Eucalyptus hybrid, the variability in basic density, calorific value, proximate and ultimate parameters of 2-6 years old trees and mature trees （20- year-old）, grown under short rotation forestry regime, were measured and analyzed. Results show that there was no significant variation in the basic density of wood for 2-6 year-old Eucalyptus hybrid, with average value of 0.55-0.58 g.cm-3; the calorific value of mature trees was higher than that of lower age trees, but the ash content was much higher in lower age trees compared to mature trees. No particular trend was observed for volatile matter content and the fixed carbon content with tree-age. In conclusion, the fuel properties of mature tree were marginally better than trees of lower age.

Numerical simulation of UCG process with the aim of increasing calorific value of syngas

The determination of operational parameters in the underground coal gasification(UCG)process should be considered in two aspects:first,the total coal in each UCG panel must be gasified and second,the calorific value of the produced gas should be acceptable.The main aim of this study is to present a model that meets these aspects and increasing the calorific value of syngas during this process.In order to achieve those aims,eight different increasing scenarios were devised for total gasification of coal per panel.These scenarios included:increasing oxygen injection rate(scenario 1),the amount of steam injection(scenario 2),operation time(scenario 3),cavity pressure(scenario 4),increase operation time and cavity pressure simultaneously(scenario 5),increase steam injection speed and oxygen injection rate simultaneously(scenario 6),increase in cavity pressure,operating time,steam injection rate and oxygen injection rate simultaneously(scenario 7)and also simultaneous increase in the operating time and steam injection rate(scenario 8).The results showed that for producing syngas with a higher calorific value,the following parameters had the most positive effects respectively:operation time,cavity pressure,steam injection rate and oxygen injection rate.Finally,the model validation was performed for the Centralia LBK-1 UCG pilot and the results showed that this model is very close to reality.

An Evaluation of the Calorific Values of the Branches and Stems of 11 Tropical Trees

This work investigated and quantified the calorific values of the main branches and trunks of eleven (11) tropical trees in correlation with their chemical composition in order to assess their suitability for use as credible sources of wood fuel. The determination of the carbon, hydrogen, nitrogen, oxygen and sulphur (CHNOS) content of the samples was done using an organic elemental analyser, while an oxygen bomb calorimeter was used to experimentally determine their corresponding gross heat values. The experimental gross heat values for the branches examined ranged from 18,703.37 kJ/kg in Lophira lanceolata to 21,350.35 kJ/kg in Afzelia africana while that of the trunks ranged from 19,747.74 kJ/kg in Tectonia grandis to 22,408.68 kJ/kg in Prosopis africana. These values were within and about the expected ranges observed for tropical trees and may be considered adequate for wood fuel. The general trend in both branches and trunks was that the higher the carbon content, the higher the gross heat value of sample. The absence of sulphur in almost all the samples except, Prosopis africana, (0.055%) was indicative of the fact that the negative environmental impact with respect to harmful emissions of oxides of sulphur is practically non-existent with respect to these species. In the light of the aforementioned variables, the main branches of Afzelia africana (21,350.35 kJ/kg), Nauclea diderrichii (21,157.30 kJ/kg) and Tectonia grandis (20,257.13 kJ/kg) could be used as credible sources of firewood and charcoal production. With respect to the trunks, the timbers in order of preference would ideally be Prosopis africana (22,408.68 kJ/kg), Nauclea diderichii (21,436.42 kJ/kg) and Brachstigia eurychoma (20,924.7 kJ/kg).

An Experimental Determination of Gross Calorific Value of Different Agroforestry Species and Bio-Based Industry Residues

Solid biomass fuels are useful and cost effective renewable energy source. The energy content of biomass is determined by its calorific value. The objective of this study was to determine experimentally the gross calorific value (GCV) of different agroforestry species and bio-based industry residues that could be used by: a) companies specialized in processing raw biomass solid biofuel production, b) small-scale consumers (households, medium-sized residential buildings, etc.). The fuel samples used were from agricultural residues and wastes (rice husks, apricot kernels, olive pits, sunflower husks, cotton stems, etc.), energy crops and wetland herbs (cardoon, switchgrass, common reed, narrow-leaf cattail), and forest residues (populus, fagus, pinus). The GCV of the bio-mass samples was experimentally determined based on CEN/TS 14918:2005, and an oxygen bomb calorimeter was used (Model C5000 Adiabatic Calorimeter, IKA?-Werke, Staufen, Germany). The GCV of different agroforestry species and residues ranges from 14.3 - 25.4 MJ?kg–1. The highest GCV was obtained by seeds and kernels due to higher unit mass and higher lipid content. Pinus sylvestris with moisture content 24.59% obtained the lowest GCV (13.973 MJ?kg–1).

Effect of Extractive Removal on the Calorific Value of Brazilian Woods Residues

In wood processing, the production of residues is an unavoidable aspect to be considered. The use of wood residues is gaining importance due to the large amount generated and improper disposal, which can seriously harm environment. Burning of wood residues to energy generation is an increasingly usual practice. However, wood residues hold chemical substances that could be recovered before burning. These substances are the wood extractives, which may have many uses as natural dyes for fabrics, foods and cosmetics, as well as potential medicines. Thus, it is of great interest to study the effect of extractive removal on the calorific value of wood residues. In this work, the calorific value of three Brazilian wood species commonly used in sawmills （hymenaeacourbaril, jatoba; cedrelingacatenaeformis, cedroarana; tabebuiasp, ipe） and residues of urban trees pruning （caesalpiniaechinata, Brazil wood） were evaluated before and after extraction in hot water. In woods studied, the calorific value showed three patterns of behavior after removal of extractives soluble in hot water. For Brazil wood, the removal of extractives caused no significant change in calorific value. For cedroarana and jatoba, extractive removal led to a decrease in wood calorific value of 161.3 kcal.kg1 and 40. l kcal.kg^-1, respectively, which indicates that the extractives from these species have a positive energy potential. Finally, for ipe, the removal of extractives resulted in an increase in calorific value of wood （67.6 kcal.kg^-1）, which might encourage the recovery of extractives from wood residues before burning for energy generation.

Evaluation of Fuel Properties of Six Tropical Hardwood Timber Species for Briquettes

The fuel potential of six tropical hardwood species namely: Triplochiton scleroxylon, Ceiba pentandra, Aningeria robusta, Terminalia superba, Celtis mildbreadii and Piptadenia africana were studied. Properties studied included species density, gross calorific value, volatile matter, ash content, organic carbon and elemental composition. Fuel properties were determined using standard laboratory methods. The result indicates that the gross calorific value (GCV) of the species ranged from 20.16 to 22.22 MJ/kg and they slightly varied from each other. Additionally, the GCV of the biomass materials were higher than that of other biomass materials like;wheat straw, rice straw, maize straw and sugar cane. The ash and volatile matter content varied from 0.6075 to 5.0407%, and 75.23% to 83.70% respectively. The overall rating of the properties of the six biomass materials suggested that Piptadenia africana has the best fuel property to be used as briquettes and Aningeria robusta the worse. This study therefore suggests that a holistic assessment of a biomass material needs to be done before selecting it for fuel purpose.

基于实测数据的高炉煤气单位热值含碳量推荐值的修正方法

钢铁工业碳排放核算方法依据GB/T 32151.5-2015《温室气体排放核算与报告要求第5部分:钢铁生产企业》所提供的排放因子法,单位热值含碳量(C_(C))作为表征可燃物质在单位热值下碳元素含量的指标,是排放因子法计算碳排放量的重要影响因子。前人对于钢铁工业碳排放研究主要侧重于各种核算方法之间的差异性,而对于单位热值含碳量推荐值准确性鲜有研究。为研究可燃物质单位热值含碳量对于碳排放计算的影响,选择钢铁工业炼铁工序副产气体高炉煤气作为研究对象,基于某钢厂高炉煤气各项指标实测数据,计算得出不同组分(CO和CO_(2))含量下高炉煤气C_(C)实测值,分析不同组分含量高炉煤气低位发热量实测值、全碳组分C_(C)实测值、燃烧过程C_(C)实测值等实测参数变化。结合排放因子法广泛应用的现状,基于C_(C)实测值波动情况,提出3种将C_(C)推荐值修正为燃烧过程C_(C)的方法,在各自适用条件修正值与实测值的偏差均小于5%;最后,用该钢厂高炉炼铁工序2021年有关统计数据,针对高炉煤气C_(C)推荐值修正前后高炉本体碳排放计算结果进行对比分析,修正前高炉本体每吨铁的碳排放量-0.19 t,修正后高炉本体每吨铁的碳排放量0.415 t,修正结果与真实碳排放情况较吻合。研究结果表明,在计算钢铁工业高炉本体二氧化碳排放时,使用实测均值、修正系数w(CO)[w(CO)+w(CO_(2))]和w(CO)—C_(com)拟合曲线修正高炉煤气单位热值含碳量,计算结果与实际相符。

多源低热值燃气无焰燃烧的数值模拟研究

生物质、生活垃圾、低品位煤等原料通过厌氧发酵、热解气化等技术可制备燃气。这既能处理固体废弃物、清洁利用煤,又能产生可利用的燃气,具有能源和环保的双重效益。但制得的燃气热值低、组成复杂、不可燃组分多,且组成受原料、工艺影响变化较大,采用传统燃烧方式存在点火困难、燃烧不稳定、污染物不易控制等问题。无焰燃烧是一种低氧条件下的温和燃烧模式,污染物排放量低、燃烧效率高,有助于解决这些问题。因此,采用详细化学反应机理GRI Mech 3.0和涡耗散概念(EDC)模型,通过湍流与化学反应的耦合计算,对3种低热值燃气无焰燃烧过程进行数值模拟研究。实验数据验证该方法能够准确地模拟实际燃烧器中的无焰燃烧。随后对沼气、生物质气化气、煤气化气进行无焰燃烧数值模拟研究,包括温度场、组分场、OH自由基分布和污染物排放等,并通过对燃烧器的改进成功实现了生物质气化气和煤气化气的无焰燃烧。结果表明,生物质气化气、煤气化气在进行无焰燃烧时温度分布比天然气、沼气的温度分布更加均匀、反应区结构更大,且NO_(x)接近“零排放”;CO_(2)的稀释对于无焰燃烧有促进作用;CH_(4)成分的存在会改变反应区及OH分布,使温度分布更加趋于不均匀。将3种低热值燃气无焰燃烧横向对比发现,即便输入功率一样,燃气热值越低,炉膛整体温度越低,但烟气量更大,因此应加强烟气的余热利用,增大系统的热效率。

基于实测数据的地铁车站强电设备发热量影响因素分析

如果地铁车站强电设备管理用房的空调系统设计缺少可靠的设备发热量参数,不利于地铁空调系统的优化设计和节能减排。提出一种地铁车站强电设备管理用房空调设备发热量计算与分析方法,并在郑州地区4种地铁车站中进行应用,研究室内空气温度、地铁是否运营、设备额定功率和车站类型等因素对地铁强电设备管理用房设备发热量的影响。结果显示:室内气温虽然对设备外表面温度有较大影响,但是对设备外表面热流密度和设备发热量的影响较小。地铁运营期间的设备发热量大于非营运期间的设备发热量,设备发热量低于设备额定功率。

基于仿真模型的复杂管网计量方法及应用

为实现天然气管网从体积计量转为能量计量,减少计量站设置在线色谱仪的数量,降低投资和运行成本。基于TGNET软件建立了复杂环状管网模型,通过设置合理的初始条件和边界条件,实现了不同节点、不同时间组分浓度及发热量的赋值,并通过稳定条件下的运行结果对模型实施校准,最后对比了能量计量和体积计量的销售价格差异。结果显示,仿真模型对稳定条件及气质浓度变化条件时,具有良好的适应性,可以真实反映分输用户处的组分浓度;发热量赋值方法中ISO 6976法较平均摩尔法的准确度更高,相对误差范围更小;多气源分输用户较单气源分输用户相比,发热量的赋值结果存在一定误差。研究结果可为能量计量和计价的尽快实施提供实际参考。

天然气中掺氢对计量物性参数的影响分析

在天然气管道中掺入氢气是进行大规模天然气输送的有效途径,但氢气会对管输水力和热力特性造成影响,进而影响与计量相关的物性参数。基于此,以常规天然气、页岩气及伴生气等三种典型气质组成为基础,系统分析了不同掺氢条件对管输温度、压力的影响及天然气物性参数的变化规律,探讨了天然气掺氢对计量分析的影响。结果表明,掺氢浓度与掺氢天然气温度呈反比,升高温度或降低压力可以减少掺氢天然气的沿程温降;采用GERG-2008方程计算压缩因子的结果准确度明显高于AGA8-92DC方程,随着温度降低、氢气浓度增加,计算结果误差明显增大。建议管道中掺氢浓度不应超过10%;并从改造气相色谱仪、加速标准气体制备、完善量值溯源和标准体系建设等方面入手,逐步实现掺氢天然气计量的标准化和工业化。

基于仿生算法联合优化BP的燃煤发热量预测

【目的】燃煤发热量的精准预测和评价是煤质分析和热工计算的重要基础,目前神经网络预测燃煤发热量的模型虽能有效拟合非线性关系,但存在易陷入局部最小值、收敛速度慢等问题。【方法】为精准预测煤炭在工业锅炉燃烧过程中的发热量,提出一种由仿生算法FA-GA联合优化BP神经网络的燃煤发热量预测方法。将774组燃煤锅炉常用煤的工业分析及元素分析数据进行预处理,根据平均影响值对煤质指标进行特征变量筛选,最终建立FA-GA-BP的发热量预测模型,并从误差评价指标、迭代次数等方面对优化算法寻优能力和模型预测精度进行了检验。【结果】经过特征变量筛选后模型的预测精度提升至0.956 1;FA-GA联合算法与单一优化算法FA、GA、PSO相比,迭代次数显著减少,算法的全局搜索能力得到有效提升;FA-GA-BP模型与单一优化模型FA-BP、GA-BP、PSO-BP以及目前常用的发热量模型MLR和SVR相比,精度更高,相关系数可达0.984 5.【结论】FA-GA算法优化BP模型,针对燃煤锅炉中来自不同地区、不同煤种的发热量预测具有良好的效果,在理论上满足了工业误差要求。改进后的燃煤发热量预测模型可为有效监测入炉煤质实时变化提供一种新方法。

城市生活垃圾固体替代燃料的制备技术及应用

针对城市生活垃圾等固废产生量日益增多、组分复杂,处置时易产生温室气体,对其有效管理和碳减排成为当前关注的热点。介绍了城市生活垃圾处理现状及国内外固体替代燃料标准,叙述机械生物处理技术中包含的生物干化、机械分选技术等工序,分析了固体替代燃料燃烧过程中存在的潜在问题,结合城市生活垃圾常规处理和机械生物处理工艺效果,获得机械生物处理后的固体替代燃料热值达到10536 kJ/kg,比原生垃圾热值提升了3倍,且不需要添加辅助燃料进行燃烧。固体替代燃料在水泥、电力等行业应用能提高资源有效再利用,减少化石燃料的使用,对节约成本、保护环境以及推进我国垃圾分类和碳中和进程具有重要意义。

我国车用压缩天然气质量指标探讨

目的针对中国目前车用压缩天然气(CNG)产品标准与相关标准不协调的问题,提出相对科学合理的质量指标,以促进CNG产业的高质量发展。方法综合国内CNG气质现状和国内外CNG质量指标,确定GB 18047《车用压缩天然气》质量指标及在各个阶段的优化修订情况,并与国际上CNG质量指标进行对标分析。结果当前CNG质量指标不能体现天然气清洁属性,且作为商品,CNG质量等级未进行分类,不利于公平公正的市场贸易发展。结论从使用安全、环保、经济适应性和促进产业发展的视角提出了CNG质量指标建议:①根据高位发热量、总硫含量、H_(2)S含量和氧气含量将CNG分为一类气和二类气;②增加一类气,建议其质量指标为:高位发热量34.0 MJ/m^(3)、总硫质量浓度20 mg/m^(3)、H_(2)S质量浓度6 mg/m^(3)、氧气体积分数0.1%;③保留GB 18047—2017质量指标作为二类气质量指标,保障特殊气源作为CNG利用;④水露点指标修改为“在汽车驾驶的特定地理区域内,在操作压力和环境温度低于−13℃的条件下,车用CNG中不应有液态水析出”。

填埋场陈腐垃圾筛上物热值及掺烧对焚烧炉运行工况影响研究——以云南省某市陈腐垃圾掺烧为例

依托新建成的生活垃圾焚烧厂开展了较长时间的陈腐垃圾筛分和掺烧可行性试验。通过对生活垃圾填埋场中的陈腐垃圾开挖、“滚筒筛+风选”预处理,对获得的筛上物进行组分特性分析,发现筛上物(干基)中塑料等轻物质类占比约53%,且与筛上物含水率呈负线性关系。将筛上物运至焚烧厂按一定设计比例与原生垃圾掺烧,根据各组分入炉垃圾量、吨蒸发量等数据,利用能量守恒定律计算得出筛上物的热值约6258 kJ/kg。掺烧会导致烟气处理系统中消石灰日均单耗量显著增加,但不影响尿素的日均单耗量,也会显著增加炉渣和飞灰的日均产生量。基于自动化程度较高的烟气处理系统,掺烧不会显著增高烟气污染物小时平均浓度,也未显著增加尾气排放的不稳定性,所有浓度最高值均满足相关排放标准的要求。