Optimization of the wash process and wash water recycling in the preparation of MgZnAl-CO_3 layered double hydroxides

An MgZnAI-CO3 layered double hydroxide （LDH） slurry with Na2 S04 as the by-product has been prepared by a co-precipitation method. The filtrates in the LDH washing process were collected according to their different levels of salinity. Filtrates with lower salinity can be used to wash a LDH slurry with higher salinity in the next cycle. Only in the final stages is pure water used. Recycling of the wash water in this way has been employed in a commercial production process, resulting in a water-saving of over 80%. The resulting MgZnAI-CO3-LDH product has a well-formed crystalline layered structure with a low content of impurities.

Analysis of influence of the power plant ash storage yard on groundwater environment

The fluoride contained in the filter liquor produced by fly ash in the thermal power plant which takes the coal as fuel can lead to groundwater pollution. Therefore, it is of great significance to study the migration characteristics of the pollutants in groundwater, in order to control and prevent the groundwater fluoride pollution. By adopting the numerical modeling method, this paper takes the ash-storage yard of Shahe Power Plant in Xingtai City as an example, to study the characteristics of fluoride migration in phreatic water, and establish a two-dimensional groundwater flow and water quality model on the basis of the hydrogeological condition analysis in this study area. Meanwhile, based on the Vmodflow software, the migration regulation of the fluoride in groundwater has been simulated. Because the phreatic aquifer of this area belonging to the Shahe alluvial-diluvial sediments and with a coarse lithology as well as high permeability, the migration and diffusion ability of the fluoride in this area is relatively strong. It turns out that the longest migration distance in 5 years is 892 m and that within 8 years is 1 515 m.

Tests on Alkali-Activated Slag Foamed Concrete with Various Water-Binder Ratios and Substitution Levels of Fly Ash

To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 400 kg/m3 were tested. Ground granulated blast-furnace slag (GGBS) as a source material was activated by the following two types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The main test parameters were water-to-binder (W/B) ratio and the substitution level (RFA) of fly ash (FA) for GGBS. Test results revealed that the dry density of AA GGBS foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased. With the increase in the W/B ratio, the amount of macro capillaries and artificial air pores increased, which resulted in the decrease of compressive strength. The magnitude of the environmental loads of the AA GGBS foamed concrete is independent of the W/B ratio and RFA. The largest reduction percentage was found in the photochemical oxidation potential, being more than 99%. The reduction percentage was 87% - 93% for the global warming potential, 81% - 84% for abiotic depletion, 79% - 84% for acidification potential, 77% - 85% for eutrophication potential, and 73% - 83% for human toxicity potential. Ultimately, this study proved that the developed AA GGBS foamed concrete has a considerable promise as a sustainable construction material for nonstructural element.

Influence of Fly Ash and Silica Fume on Water-resistant Property of Magnesium Oxychloride Cement

By incorporation of fly ash or silica fume into magnesium oxychloride （MOC） cement, a high water resistance material can be formed for successful industrial applications. The influences of fly ash and silica fume on water-resistant property were investigated by SEM and EDS. It is found that the incorporation of fly ash or silica fume can improve the water-resistance of the MOC. The improvement of the water resistance of the MOC incorporated with fly ash or silica fume may be attributed to the alumino-silicate 5·1·8 gel or silicate 5·1·8 gel.

Application of polymeric flocculant for enhancing settling of the pond ash particles and water drainage from hydraulically stowed pond ash

Delayed settling of the ash particles and poor drainage of water from the pond ash are the major problems faced during the hydraulic stowing of pond ash. In this study the effect of polymeric flocculant on settling of the ash particles and drainage of water during pond ash stowing are investigated. In addition, the parameters, viz. drainage and absorption of water during pond ash stowing are quantified by stowing a mine goaf model with pond ash slurries of five different concentrations added with and without flocculant. The study revealed that addition of only 5 10 6 of Sodium Carboxymethyl Cellulose (Na-CMC) flocculant with the pond ash slurries during stowing offers best result in terms of quicker settling of the ash particles and enhanced water drainage from the hydraulically stowed pond ash. Besides, it resulted in drainage of more than 85% of the total water used in the initial 45 min of stowing. The improvement in drainage is caused due to coagulation and flocculation of the pond ash particles because of charge neutralization and particle-particle bridging. This study may provide a basis for estimating the drainage and absorption of water during the real pond ash stowing operation in underground mines.

Effect of Water Washing Pre-treatment on the Properties of Glass-ceramics from Incinerator Fly Ash Using Electronic Arc Furnace

Production of glass-ceramics by sintering the molten slag obtained from electric arc furnace treatment of fly ash was investigated. The effect of washing pretreatment prior to melting the fly ash on the microstructure and properties of the glass-ceramics was examined. The results show that washing pretreatment of fly ash can decrease alkali metal chloride and increase network former in fly ash, which results in the increase of peak crystallization temperature of parent glass and strengthening of properties of bending strength and chemical stability of the glass-ceramics. The optimal heat treatment temperature for parent glass of washed fly ash is 1 173 K, at which the crystalline phase of glass-ceramics is composed of gelignite （Ca2A12SiO7） and akermanite （Ca2MgSi207）. Glass-ceramics produced at optimal heat treatment temperature are excellent in term of the physical and chemical properties and leaching characteristics, indicating attractive potential as substitute of nature materials.

Experimental Study on Fly Ash for Conditioning of Specific Resistance of Sludge Water

Discharge of sludge from water works into waters will result in the increased deterioration of water environment. Therefore, an experimental study was conducted on the addition of conditioning agent to improve sludge dewatering performance. The result shows that coagulation is inadaptable to the treatment of sludge from water works and use of powdered coal ash from power plant as conditioning agent can greatly reduce the specific resistance of sludge and the dewatering performance can be improved. The optimal dosage of fine powdered coal is 20g/100mL and coarse powdered coal is 30g/100mL. Powdered coal is mixed with sludge to form filter cake, which is blended with coal in certain proportion to make into fuel. So that incineration of sludge from water works can be realized.

Separating Performance of Fly Ash in Water Media

The stress state and floating sinking reqularity of various particles in fly ash in water were analyzed. The formula for calculating the floating sinking rate was given. And the formula for calculating the magnetic force needed to separate magnetic beads from magnetic separator was also obtained.

Quality Evaluation of Yi Medicine "Qibujing" Based on Determination of Water Content and Ash Content

[Objectives]To determine the water content,total ash content and acid-insoluble ash content of Yi medicinal material"Qibujing",so as to provide experimental basis for establishing the Quality Standard(Draft)of Yi Medicinal Material"Qibujing"in Sichuan Province.[Methods]According to the second method(drying method)in 0832 water content determination method and 2301 ash content determination method in Chinese Pharmacopoeia(2015 Edition),it was determined,respectively,and the data were processed by IBM SPSS Statistics 26 and DPS 7.05 data processing system.[Results]All the 14 batches of sample met the stipulation that the water content should not exceed 12.0%,the total ash content should not exceed 8.0%,and the acid-insoluble ash content should not exceed 1.5%under"Guan Zhong-(Qibujing)"in the 2005 edition of Yunnan Traditional Chinese Medicine Standard.There was a negative correlation between water content,acid-insoluble ash content and altitude,and a positive correlation between total ash content and altitude.[Conclusions]It is suggested that Quality Standard(Draft)of Yi Medicinal Material"Qibujing"in Sichuan Province stipulate that the water content should not exceed 12.0%,the total ash content should not exceed 8.0%,and the acid-insoluble ash content should not exceed 1.5%.

基于正交试验的外加剂对混凝土力学性能的试验研究

为了探究复掺外加剂对混凝土的韧性和抗裂性能的影响规律,以期解决工程防护和加固过程中的混凝土开裂、剥落等工程实际问题,通过正交试验研究了速凝剂、早强剂、膨胀剂和粉煤灰对混凝土的抗压强度和劈裂抗拉强度的影响规律。试验结果表明:速凝剂能显著改善混凝土的抗压强度和劈裂抗拉强度;复合早强剂能有效提高混凝土的劈裂抗拉强度;粉煤灰和膨胀剂对混凝土28d抗压强度和劈裂抗拉强度没有显著影响。通过方差分析和数据拟合,可得早强剂和速凝剂的建议掺量分别为4%和1.5%,膨胀剂的最优掺量为3%,粉煤灰的最优掺量为25%。

纳米SiO_(2)改性粉煤灰混凝土力学性能及吸水特性研究

为了探索粉煤灰混凝土的高性能,开展了纳米SiO_(2)改性粉煤灰混凝土的力学和吸水试验,研究了粉煤灰取代率和纳米SiO_(2)掺量对混凝土力学性能(抗压强度、劈拉强度、动弹性模量)和吸水特性的影响。结果表明:粉煤灰混凝土的力学性能指标均随纳米SiO_(2)掺量的增加先增大后减小;当纳米SiO_(2)掺量从0%增加至2%时,粉煤灰混凝土28 d抗压强度、劈拉强度和动弹性模量分别提高了12.90%、7.53%和5.85%,可见纳米SiO_(2)对抗压强度影响更显著;当粉煤灰取代率从10%增加至30%时,混凝土28 d抗压强度、劈拉强度和动弹性模量分别降低了7.24%、2.61%和9.87%,可见粉煤灰对动弹性模量影响更显著;随纳米SiO_(2)掺量增加,粉煤灰混凝土的毛细吸水系数呈现出先下降后上升的趋势;随粉煤灰取代率增加,混凝土毛细吸水系数增大,且纳米SiO_(2)对混凝土毛细吸水系数影响也越显著;粉煤灰取代率和纳米SiO_(2)掺量对混凝土力学性能与毛细吸水系数之间的相关性无显著影响,混凝土抗压强度、劈拉强度以及动弹性模量与毛细吸水系数均呈现负相关性,其中抗压强度与毛细吸水系数相关性最好。

自密实全再生混凝土单轴受压性能及强度指标换算关系研究

为深入了解自密实全再生混凝土单轴受压力学性能,以水胶比(0.36、0.40、0.45)与粉煤灰掺量(20%、30%、40%、50%、70%)为变化参数,设计并制作11组(共99个)自密实全再生混凝土试件对其立方体抗压强度、轴心抗压强度和弹性模量进行试验研究,观察试件受压破坏过程及破坏形态,获取各力学性能指标的变化趋势,基于试验结果及现有文献成果,建立强度指标换算关系,并提出自密实全再生混凝土的本构方程。研究表明:自密实全再生混凝土受压破坏过程及破坏形态与普通混凝土相似,总体上自密实全再生混凝土立方体抗压强度、轴心抗压强度及弹性模量随水胶比、粉煤灰掺量的增加而降低,所提计算式可较好预测自密实全再生混凝土的单轴受压性能指标及本构关系。

稳定化垃圾飞灰的力学特性及填埋体稳定性分析

垃圾飞灰颗粒细、堆积密度较小、易吸水,与一般的固体废弃物具有完全不同的力学特性.针对南京某垃圾飞灰填埋场工程,对稳定化飞灰的力学特性和填埋体的稳定性进行了研究.结果发现,稳定化飞灰的黏聚力随着含水率的增加而先增大后减小,而摩擦角呈现单调减小的趋势;随着初始含水率的增加,飞灰填埋体的稳定性逐渐降低,提出了最优化的飞灰初始含水率建议;降雨对飞灰堆体的稳定性具有一定程度的影响,通过对本地区暴雨工况的模拟,在降雨5 d的情况下,填埋体稳定性系数降低了0.13~0.26,但填埋体仍能保证稳定状态;填埋体底部渗滤液对填埋体的稳定性具有较大影响,在渗滤液深度超过3 m的情况下,填埋体即有发生失稳破坏的可能性.研究结果可以为飞灰填埋的设计和施工提供参考.

掺粉煤活性粉末混凝土基本力学性能研究

为探究在掺粉煤灰情况下,养护制度、水胶比、钢纤维掺量对活性粉末混凝土(Reactive Powder Concrete, RPC)基本力学性能的影响规律,文中完成了78个100 mm立方体和26个100 mm×100 mm×300 mm棱柱体掺粉煤灰RPC试件的单轴受压试验,基于试验结果考察了RPC立方体抗压强度与棱柱体抗压强度之间的关系,建立掺粉煤灰RPC弹性模量、横向变形系数、峰值应变、峰值应力等基本力学参数的预测模型。试验结果表明,粉煤灰的加入明显提升了RPC的基本力学性能。

钢铁含铊高盐固废/废水协同水洗技术研究

钢铁烧结工序会产生大量烧结机头灰和脱硫废水,盐含量高,且含有剧毒重金属铊,其消纳问题成为制约钢铁行业可持续发展的关键问题之一。提出含铊高盐固废与高盐废水协同处置的思路。结果表明,当利用1/4浓度活性炭法脱硫废水用于洗灰时,洗灰水中铊含量低于5 mg/L,且钙、镁的溶出量也有所降低。重点研究了活性炭法脱硫废水中各组分对烧结机头灰水洗过程铊溶出行为的影响,发现水洗过程SO_(3)^(2-)的存在及适宜的pH对铊的溶出有明显抑制作用。

刨花板纹清水混凝土研究与应用

为制备优质刨花板纹清水混凝土,研究了纤维素醚、水胶比、粉煤灰微珠以及引气剂+消泡剂对刨花板纹清水混凝土的影响。发现纤维素醚能提高保水性和工作性能,但若过量会使和易性变差;降低水胶比可提高保水性,但减少用水量会使流动性变差;粉煤灰微珠能更有效地减水润滑、提高抗氯离子渗透性,但降低保水性;引气剂+消泡剂可改善混凝土外观质量。

化学激发淤泥焚烧灰制备生态透水砖性能研究

通过CaO、NaOH、NaAlO2和Na2SiO3激发淤泥焚烧灰化学活性后与水泥复合作为胶凝材料制备生态透水砖,通过正交试验研究了不同化学激发剂对水泥净浆抗压强度的影响,探究了骨胶比对淤泥焚烧灰制备的生态透水砖劈裂抗拉强度、渗透性、抗冻性及保水性的影响。结果表明:复合化学激发剂可以改善淤泥焚烧灰制备的生态透水砖的力学性能,但将降低淤泥焚烧灰制备的生态透水砖的透水性、保水性。骨胶比与透水砖的透水系数呈正相关,当骨胶比从3.0增大到3.4时,未掺淤泥焚烧灰的对照组透水系数增大了153%,掺淤泥焚烧灰的试验组透水系数增大了184%。为满足工程要求,淤泥焚烧灰的掺量不宜超过30%。

基于灰关联理论的混凝土抗压强度影响因素分析

基于灰色关联分析具备的发现系统中各因素对系统结果影响差别的特性,运用灰色关联分析方法,分析了粉煤灰掺量、砂率和水灰比等因素对混凝土抗压强度影响的显著程度。结果表明,粉煤灰掺量对混凝土抗压强度的影响最为显著,与实际实验结果基本一致。分析得出,灰关联分析方法具备一定的结果分析优势,对于现场混凝土试配具有较好的参考意义。

利用湖泊淤泥制备轻质保水陶粒的研究

随着城市化进程的加快和经济的发展,河道、湖泊、水库等水域的淤泥量越来越大,淤泥的资源化处置需要有技术上的突破。本文通过实验探讨利用湖泊淤泥制作陶粒的可行性,并对其制备工艺、性能和应用前景进行深入分析。实验结果显示:与商品陶粒相比,湖泊淤泥烧成的淤泥陶粒不仅吸水性能更好,而且抗压强度也能满足保水陶粒的要求。因此,利用湖泊淤泥这种市政废弃物制备保水陶粒代替黏土陶粒,可实现经济效益、社会效益和环境效益的多方位提升。