Development of Sensible Heat Storage Materials Using Sand, Clay and Coal Bottom Ash

In this paper, the mechanical and thermal properties of a sand-clay ceramic with additives coal bottom ash (CBA) waste from incinerator coal power plant are investigated to develop an alternative material for thermal energy storage (TES). Ceramic balls are developed at 1000°C and 1060°C using sintering or firing method. The obtained ceramics were compressed with a compression machine and thermally analyse using Decagon devise KD2 Pro thermal analyser. A muffle furnace was also used for thermal cycling at 610°C. It was found that the CBA increased the porosity, which resulted in the increase of the axial tensile strength reaching 3.5 MPa for sand-clay and ash ceramic. The ceramic balls with the required tensile strength for TES were selected. Their volumetric heat capacity, and thermal conductivity range respectively from 2.4075 MJ·m-3·°C-1 to 3.426 MJ·m-3·°C-1 and their thermal conductivity from 0.331 Wm-1·K-1, to 1.014 Wm-1·K-1 depending on sand origin, size and firing temperature. The selected formulas have good thermal stability because the most fragile specimens after 60 thermal cycles did not present any cracks. These properties allow envisioning the use of the ceramic balls developed as filler material for thermocline thermal energy storage (structured beds) in Concentrating Solar Power plants. And for other applications like solar cooker and solar dryer.

Vegetation of mono-layer landfill cover made of coal bottom ash and soil by compost application

Monolayer barriers called evapotranspiration (ET) covers were developed as alternative final cover systems in waste landfills but high-quality soil remains a limiting factor in these cover systems. Coal bottom ash was evaluated to be a very good alternative to soil in previous tests and a combination of soil (65% wt.wt-1) and coal bottom ash (35% wt.wt-1) was evaluated to be the most feasible materials for ET cover systems. In our pot test, selected manure compost as soil amendment for the composite ET cover system, which was made of soil and bottom ash at ca. 40 Mg.ha-1 application level was very effective to promote vegetation growth of three plants;namely, garden cosmos (Cosmosbipinnatus), Chinese bushclover (Lespedezacuneata), and leafy lespedeza (Lespedeza cyrtobotrya). To evaluate the effect of compost application on plant growth in an ET vegetative cover system, two couples of lysimeters, packed with soil and a mixture of soil and bottom ash, were installed in a pilot landfill cover system in 2007. Manure composts were applied at the rates of 0 and ?40 Mg.ha-11before sowing the five plant species, i.e.indigo-bush (Amorphafruticosa), Japanese mugwort (Artemisia princeps, Arundinella hirta, Lespedezacuneata, and Lespedezacyrtobotrya). Unseeded native plant (green foxtail,Setaria viridis) was dominant in all treatments in the 1st year after installation while the growth of the sown plants significantly improved over the years. Total biomass productivity significantly increased with manure compost application, and more significantly increased in the composite ET cover made of soil and bottom ash treatment compared to the single soil ET cover, mainly due to more improved soil nutrient levels promoting vegetation growth and maintaining the vegetation system. The use of bottom ash as a mixing material in ET cover systems has a strong potential as an alternative to fine-grained soils, and manure compost addition can effectively enhance vegetative propagation in ET cover systems.

Uranium speciation in coal bottom ash investigated via X-ray absorption fine structure and X-ray photoelectron spectra

Similar to chromium contamination, the environmental contamination caused by uranium in radioactive coal bottom ash（CBA） is primarily dependent on the chemical speciation of uranium. However, the relationship between uranium speciation and environmental contamination has not been adequately studied. To determine the relationship between uranium speciation and environmental contamination, X-ray absorption fine structure（XAFS） and X-ray photoelectron spectra（XPS） analyses were performed to determine the uranium speciation in CBA exposed to different chemical environments and simulated natural environments. The leachability of the different forms of uranium in the CBA was studied via a simulated acid rain leaching experiment, and the results showed that 57.0% of the total uranium was leached out as U（VI）. The results of a linear combination fit（LCF）of the X-ray absorption near edge structure（XANES） spectrum revealed that in the raw CBA, the uranium mainly occurred as U_3O_8（71.8%）. However, in the iron-rich particles, the uranium mainly occurred as UO_2（91.9%） after magnetic separation. Magnetite is a ubiquitous ferrousbearing oxide, and it was effective for the sorption of U（IV）. The result of FeSO_4 leaching experiment indicated that 96.57% of total uranium was reduced from U（VI） to U（IV） when infiltrated with the FeSO_4 solution for 6 months. This result clearly demonstrated the changes in chemical valence of uranium in the coal ash and provided a conceptual principle for preventing uranium migration from ash to the surrounding soil and plants.

M■ssbauer spectroscopic studies the characterization of three China coal and the corresponding fly-ashes and bottom ashes

Three fresh China coals(lignitie,bituminite and anthracite) from different geo-logical origin and the corresponding fly and bottom ashes were studied by room tempera-ture(RT)M(?)ssbauer spectroscopy(MS).The iron-bearing minerals were characterized tobe mainly pyrite in all coal samples by the hyperfine parameters.Suphate(FeSO_4.nH_2O)was found in bituminite and anthracite coal.The M(?)ssbauer spectra of the fly and bottomashes as a result of pulverised coal combustion(PCC) in Xiaolongtan,Shuicheng andLuohuang Power Plants are comprised of superimposed sextets and doulets of oxides in-cludes maghemite(γ-Fe_2O_3),magnitite(Fe_3O_4),haematite(α-Fe_2O_3),magnesioferite(MgFe_2O_4),Fe^(3+)/Fe^(2+)-mullite,Fe^(3+)-glass silicate and metallic iron.The studies also showthat iron-bearing minerals in coals are largely dependant on geological regions and coalrank,the composition of the corresponding fly and bottom ashes will not only depend onthe type and mineralogy of the feed coal but also on the local nature of combustion.

燃煤锅炉底灰斗机械化捅焦实践

燃煤锅炉底灰斗人工捅焦有很大的人身安全风险,为了消除此安全风险,某电厂提出了底灰斗机械化捅焦方案并进行实施。实施结果表明,此捅焦机械结构简单,运行可靠,可实现机械化捅焦,代替人工捅焦,杜绝人工捅焦的安全风险,并提高劳动生产率和现场文明生产水平。

铝硅比对燃煤炉渣发泡陶瓷的制备与性能的影响研究

以燃煤炉渣为主要原料,通过调控坯料中Al_(2)O_(3)与SiO_(2)含量,系统研究了铝硅比对发泡陶瓷烧成性能、孔结构、体积密度与抗压强度的影响,并通过物相组成分析,揭示了铝硅比对发泡陶瓷性能的影响机理。结果表明,尽管铝硅比增大将提高坯体的发泡温度,导致同一烧成温度制得的发泡陶瓷气孔率减小、体积密度增大,但拓宽了坯体的烧成温度范围,减弱了烧成温度对孔径的影响,并促使晶相量增加。若铝硅比大于0.6,将导致孔径分布变宽、孔结构劣化,降低材料的抗压强度。当坯料中的Al_(2)O_(3)与SiO_(2)总量约为82%,铝硅比为0.41时,可制备出孔结构优异的高强度炉渣发泡陶瓷。

Distribution and mode of occurrence of uranium in bottom ash derived from high-germanium coals

The radioactivity of uranium in radioactive coal bottom ash（CBA） may be a potential danger to the ambient environment and human health. Concerning the limited research on the distribution and mode of occurrence of uranium in CBA, we herein report our investigations into this topic using a number of techniques including a five-step Tessier sequential extraction, hydrogen fluoride（HF） leaching, Siroquant（Rietveld） quantification, magnetic separation, and electron probe microanalysis（EPMA）. The Tessier sequential extraction showed that the uranium in the residual and Fe–Mn oxide fractions was dominant（59.1%and 34.9%, respectively）. The former was mainly incorporated into aluminosilicates,retained with glass and cristobalite, whereas the latter was especially enriched in the magnetic fraction, of which about 50% was present with magnetite（Fe_3O_4） and the rest in other iron oxides. In addition, the uranium in the magnetic fraction was 2.6 times that in the non-magnetic fraction. The experimental findings in this work may be important for establishing an effective strategy to reduce radioactivity from CBA for the protection of our local environment.

煤渣粉对高性能混凝土性能的影响

用煤渣粉作为矿物掺合料制备C50高性能混凝土,并与Ⅱ级粉煤灰复掺,研究煤渣粉掺量对水泥凝结时间、混凝土流动性、抗压强度及耐久性的影响。结果表明:煤渣粉替代部分水泥可以提高高性能混凝土的抗压强度和抗氯离子渗透性,对混凝土性能的影响优于Ⅱ级粉煤灰;煤渣粉掺量为20%时,混凝土抗压强度达到最大值,为空白样的120%;煤渣粉与粉煤灰复掺可以改善混凝土的流动性。结果显示,煤渣粉可作为高性能混凝土的掺合料。

煤及其燃烧产物飞灰和底灰中稀土元素地球化学特征及集散规律

采用ICP-MS法测试了褐煤、肥煤和无烟煤以及在不同燃烧条件下获取的飞灰、底灰等29个样品的稀土元素含量;分析了稀土元素地球化学特征。结果表明,不同煤种的稀土元素含量不同,相同煤种在不同燃烧条件下获取的飞灰、底灰中的稀土元素含量也不同;褐煤、肥煤、无烟煤及其燃煤产物飞灰、底灰的稀土元素分布模式呈左高右低的宽缓的“V”型曲线;Eu存在明显负异常。研究了燃煤过程中稀土元素的分布及集散规律,稀土元素在飞灰、底灰中的含量比原煤有明显提高,其增加幅度为几倍至20多倍不等,表明煤炭燃烧后稀土元素在飞灰、底灰中进一步聚集;飞灰和底灰中稀土元素含量、飞灰和底灰对煤的稀土元素含量比和富集因子以及飞灰对底灰的稀土元素含量比和富集因子等,不仅与原煤中稀土元素有直接关系,而且还受锅炉燃烧方式、燃烧温度(炉温)等人为因素的影响。

煤中微量元素镉对环境造成的影响

通过测定原煤、飞灰、底灰及煤堆附近土壤中微量元素镉含量,并对原煤、底灰进行淋滤实验,研究煤中微量元素镉对环境造成的影响。结果显示:大多数煤中镉的含量较高,进口煤中镉含量高于我国主要煤产地平均含量水平,最高达1.90μg/g。

燃煤产物中多环芳烃赋存规律及环境意义

利用GC—MS（色-质谱）对华北4个矿区燃煤电厂的炉前煤、飞灰和底灰的氯仿抽提液中多环芳烃进行了比较研究。结果表明，燃煤产物中所含多环芳烃种类以烷基芳烃居多，母核芳烃相对较少，其中飞灰中低环（2～3环）芳烃含量高，而底灰中4—5环的芳烃含量相对较高。煤中的多环芳烃在其燃烧过程中，一部分直接以气态方式释放到大气中，一部分残留在飞灰和底灰中，其余则经高温热裂解分解为其他种类的多环芳烃。飞灰和底灰中具有致癌、致突变作用的多环芳烃种类较多，其对人类的危害及环境的污染不容忽视。

污泥/煤流化床混烧底灰中的重金属毒性研究

研究了污泥与煤按不同质量比例混烧后,底灰中的重金属形态分布与浸出毒性.结果表明:30∶70的泥煤比使底灰中重金属硫化物及有机态和残渣态所占比例最大,即生物无效部分比例最大;在浸出毒性实验中,30∶70的泥煤比使底灰重金属浸出量最小.由此推出,对环境毒害程度最小的泥煤质量比为30∶70即该实验条件下最优泥煤质量比为30∶70.

宝鸡燃煤电厂原煤及粉煤灰中天然放射性水平

本文调查测量了宝鸡电厂原煤(3个样品)、粉煤灰(17个样品)、底灰(6个样品)中天然放射性核素226Ra、232Th和40K的比活度,分析了燃煤产生的底灰和粉煤灰中上述核素的含量特征,及其与原煤相比的浓集倍数。宝鸡电厂原煤和粉煤灰样品中天然放射性核素226Ra、232Th和40K的比活度水平与北京电厂和上海电厂的接近。依据国家标准(GB 6566-2001),对宝鸡电厂粉煤灰用作建筑材料的可行程度进行了评价,得出当建材原料100%为粉煤灰时,约有29%的样品超过国家标准的限制值。所以,应对用作建材原料的粉煤灰作放射性检测,选用合格的部分,控制高比活度粉煤灰在建材原料中的配比,以确保达到合理使用的效果。

浅谈煤中微量元素铅对环境的危害

通过测定原煤、飞灰、底灰及煤堆附近土壤微量元素铅含量,并对原煤、底灰进行淋滤实验,考察煤中铅对环境的危害。结果显示:大多数煤中铅的含量较高,且在煤堆附近土壤、飞灰和底灰中得到富集,飞灰粒度越小,铅富集程度越高。在酸性条件下,铅的淋出率较高。在自然环境由于酸雨以及长期累积效应下,煤中铅对环境及地下水造成的污染不容忽视。

燃煤底灰-微波法降解亚甲基蓝的研究

燃煤底灰中含有丰富的金属,这些金属在微波作用下可以对有机物进行有效降解,燃煤底灰-微波法降解亚甲基蓝溶液主要是通过羟基自由基来降解有机物的。底灰中的金属及稀有金属可以作为深度氧化有机物的催化剂,可降低处理成本、减少环境污染。考查了燃煤底灰用量、H2O2用量、以及微波时间对亚甲基蓝降解效率的影响,并测定了亚甲基蓝溶液处理前后的紫外可见光谱。结果表明,亚甲基蓝在燃煤底灰与H2O2微波条件下降解率接近100%。燃煤底灰的用量增加可以加快反应进程,增加亚甲基蓝的降解;H2O2的增加可以提供更多的.OH,加快反应进程,但当增加到一定量后,对反应进程的影响减弱;微波时间的加长可以提高反应温度,促使亚甲基蓝完全降解。对于0.125g.L-1的亚甲基蓝,加入1.0g燃煤底灰、5mLH2O2在中温微波下反应4min即可全部降解。

含铀煤燃烧底灰中铀的形态分布及其影响因素研究

以云南临沧的含铀褐煤为研究对象,在实验室模拟燃烧试验,考察了不同温度、时间、原煤粒径和是否加入CaO4种燃烧控制条件下煤的燃烧过程,并采用逐级提取法分析了燃煤底灰中铀的赋存形态,讨论了不同燃烧条件下燃煤底灰中不同赋存形态铀的含量及其相互转化关系。结果表明:燃煤底灰中铁锰氧化物结合态铀和残渣态铀的含量随燃烧温度的升高而增加,碳酸盐结合态铀的含量随燃烧温度的升高而减小;在600℃、不同条件下的原煤燃烧过程中,燃煤底灰中碳酸盐结合态铀和铁锰氧化物结合态铀的质量随燃烧时间的增加逐渐增加,有机物结合态铀和残渣态铀的质量随燃烧时间的增加逐渐减少;原煤粒径较小时,在燃烧过程中易形成飞灰而降低各种赋存形态铀在燃煤底灰中的含量;在原煤燃烧过程中,加入适量CaO会提高燃煤底灰中除离子交换态铀外的各种赋存形态铀的含量,使燃煤底灰中的铀富集。

燃煤电厂炉渣综合利用现状分析

燃煤发电产生的炉渣是工业固废物的主要来源之一。如果大量炉渣没有充分利用,就会占用土地资源,污染环境。本文首先概述了燃煤电厂炉渣的基本性能和综合利用的发展现状,然后总结了燃煤电厂炉渣目前主要的利用方式,最后分析了综合利用过程中存在的问题并提出建议,以期更好地进行炉渣综合利用。

炉底灰—煤矸石基煤矿充填材料的制备及性能测试

为实现固体废弃物资源化利用并降低充填开采成本,以炉底灰、煤矸石为原料制备煤矿充填材料,研究了颗粒级配、充填料浆质量分数、胶凝材料质量分数对充填材料各项性能的影响,并采用X射线衍射、扫描电镜、能谱分析手段对充填材料水化产物进行分析。结果表明:当煤矸石最大粒径为4.75 mm,煤矸石与炉底灰质量比为1∶1,充填料浆质量分数为77%,胶凝材料质量分数为20%时,充填材料各项性能均能满足充填开采要求。随着养护龄期增长,充填材料中的活性二氧化硅参与水化反应被消耗,钙矾石、水化氯铝酸钙、水化硅酸钙和水化硅铝酸钙凝胶生成量增加。在充填材料水化产物中,片状水化氯铝酸钙晶体与钙矾石交错生长,包裹于水化硅酸钙凝胶中,形成致密的整体,提高了充填体的单轴抗压强度。