Taguchi Optimization of Solvent-Antisolvent Crystallization to Prepare Ammonium Perchlorate Particles

The sphericity and size of ammonium perchlorate (AP) particles significantly influence the properties of composite propellants. As the AP particles become more spherical, the accumulation coefficient increases, the viscosity during casting decreases, and the particle loading and burning rate increase. Hence, the production of micronized AP particles with an average size between 1 and 20 μm is important to increase the loading percentage of AP in the composite propellant. Here, the Taguchi experimental design was used to optimize the solvent-antisolvent crystallization (SAC) process for the preparation of micronized AP particles with higher sphericity. SAC parameters such as the type of antisolvent, the solvent-to-antisolvent ratio, the antisolvent temperature, the stirring speed, and the retention time were investigated at four levels. The type of antisolvent and the solvent-to-antisolvent ratio were found to mainly contribute to improving the sphericity and size of the AP particles, respectively.     

Incorporation of fish by-product into the semi-continuous anaerobic co-digestion of pre-treated lignocellulose and cow manure,with recovery of digestate's nutrients

Norway's fish processing industry generates large amounts of fish waste every year. The high-risk waste fraction with most of its oil removed has not yet been tested for energy production. The stability of an anaerobic digestion process that incorporates this material with steam exploded Salix and cow manure was tested using mesophilic, semi-continuous laboratory-scale digesters. The effects of recycling the liquid digestate fraction were also investigated. The removal of ammonium (NH₄⁺) and phosphate (PO₄³⁻) from the rejected digestate using struvite precipitation and bentonite adsorption were tested to generate a nutrient-enriched, final solid fertiliser. Adding 20% fish by-product (volatile solids basis) increased methane yields by 35%, while recycling the digestate caused a slight increase. The NH₄⁺–N levels reached 4–5 g l⁻¹ in the reactors with recirculation and fish feed. Although these levels may threaten methanogenesis, the stability of the process was maintained during the entire period due to the good balance between the lignocellulose, proteins and fats provided by the co-digestion mixture and the positive effects of recirculation. The NH₄⁺ and PO₄³⁻ were successfully removed from the rejected liquid digestate. The reductions using struvite reached 87% and 60% (pH 9.5 and Mg²⁺:NH₄⁺:PO₄³⁻ ratio of 1.2:1:1), while bentonite achieved 82% and 52%, respectively.     

Biofiltration potential of macroalgae for ammonium removal in outdoor tank shrimp wastewater recirculation system

Shrimp wastewater usually contain high amount of nitrogen that causes eutrophication, a phenomenon of algae bloom. It is harmful for shrimp growth and needs to be addressed if the objective is to improve water quality and make it suitable for shrimp growth. This paper addresses ammonium removal in tiger shrimp wastewater by using two macroalgae species: Ulva lactuca (U. lactuca) and Gracilaria edulis (G. edulis). To achieve this, an outdoor macroalgae with shrimp integrated system was developed. This integration was completed in two shrimp growth periods; 60 days and 120 days. The mean growth rates of G. edulis and U. lactuca were found as 4.0% day⁻¹ and 3.6% day⁻¹, respectively. The mean ammonium removal rates for G. edulis and U. lactuca were found to be 70% and 45%, respectively. Thus, both species are suitable as biofilter and their valuable biomass has a great commercial value. The potential applications of the findings include improvement of shrimp wastewater quality which will ultimately enhance shrimp and macroalgae productivity to meet growing demands of the market.     

Influence of Ammonium Pentaborate (APB) on the Performance of Urea Formaldehyde (UF) Adhesives for Plywood

Ammonium pentaborate (APB) was used to modify urea formaldehyde (UF) resins, in which the formaldehyde to urea molar ratio was set at 1.80, 1.50, 1.25, and 1.05. Some specific properties, including gel time, free formaldehyde content in UF, bond strength, and formaldehyde emission levels from plywood were evaluated. The result showed that APB increased the gel time length, but also decreased free formaldehyde content and emission levels, which was reduced mostly by 79.0% and 81.4%, respectively. The result of bond strength indicated that APB was proper to modify high F/U molar ratio of UF resin regardless of the loading level, but a recommended loading level should be considered to relevantly lower the F/U molar ratio of UF. The suggested loading level of APB to UF is 8.0% to 6.0%, 6.0%, and 4.0% to UF resin with F/U molar ratio of 1.8, 1.5, and 1.25 separately.     

A new application of giant reed waste material for ammonium removal

Excess nitrogen is one of the main causes of eutrophication in water bodies. In this study, the undesirable agricultural lignocellulosic material giant reed was used to remove ammonium ions from aqueous solutions. Batch experiments were conducted to investigate the effect of various parameters such as contact time, initial ammonium concentration, adsorbent dosage, pH, particle size, agitation rate and phosphate coexisting during the ammonium adsorption process. The ammonium sorption capacity of fibrous giant reed (FGR) at equilibrium was 12.49?mg?N/g with a maximum removal efficiency of 76% observed within 30?min at pH range of 6.5–9.5. Results revealed that the Freundlich isotherm model fitted better with the sorption process than the Langmuir model, and the adsorption process was well described by pseudo-second-order kinetic model. FT-IR analyses indicated that complexation and ion exchange could be the main mechanisms for the ammonium removal by FGR. Results revealed that FGR has a sorption capacity comparable to that of other natural sorbents with the advantage of greater availability with no cost.     

硝基复合肥生产系统优化改造

对硝酸-硫酸混酸法硝酸磷肥生产装置进行改造,添加硫酸钾生产三元硝基复合肥。介绍三元硝基复合肥的生产工艺流程、装置特点。生产的三元复合肥料产品水溶率高,深受用户好评,提高了公司市场竞争力。     

单次降温条件下硫酸盐渍土盐冻胀试验研究

为研究单次降温条件下不同压实度、含水率、含盐量对宁夏地区硫酸盐渍土盐冻胀的影响,进行了室内配置试样试验。结果表明:在单次降温条件下,该地区硫酸盐渍土的起胀温度随含盐量增加而增大。随着温度变化,盐冻胀过程表现为4个阶段:35 ℃~ 5 ℃之间属于纯盐胀阶段,5 ℃~-5 ℃之间属于调整阶段,-5 ℃~-10 ℃之间属于盐冻胀阶段,-10 ℃~-25 ℃之间属于稳定阶段。当压实度较低、且含盐量在2%以内时,盐冻胀率随含盐量增加有所增大;当含盐量超过2%后,盐冻胀率随含盐量增加呈先增大后减小发展趋势,并在含盐量5%时达到峰值。当压实度为100%时,盐冻胀率随含盐量增加而增大。当含盐量较小时,达到最优含水率时盐冻胀率较大;而随含盐量逐渐增大,盐冻胀率随含水率增加呈先减小后增大变化趋势。总体来看,压实度越高、含盐量越大、越接近土体最优含水量时,盐冻胀率也越大。该研究可为硫酸盐渍土地区的工程建设提供参考。     

硫酸盐-干湿循环下高延性纤维增强水泥基材料的自愈合

采用1.0%,1.5%和2.0%预加拉伸应变,使养护7,28d龄期的高延性纤维增强水泥基复合材料(ECC)试件产生裂缝,研究其在经历10,20和30次硫酸盐-干湿循环后的裂缝特性、自愈合后的拉伸性能及自愈合产物.结果表明:带裂缝试件在经历不同循环次数后均表现出了良好的自愈合效果,残余裂缝的最大宽度和数量明显减少;养护7d试件经历10次循环后的残余裂缝最大宽度由愈合前的80μm降至25μm,养护28d试件经历30次循环后的残余裂缝最大宽度由愈合前的100μm降至50μm;67%以上带裂缝试件自愈合后的单轴拉伸应变能力接近甚至超过同样经历的对比用无裂缝空白试件;养护7d试件自愈合后的最终应力可分别恢复至75%以上,养护28d试件可恢复至131%以上;层状结构的CaCO_3晶体是ECC试件的主要自愈合产物.     

Treatment of Acid Leachate from Coal Discard using Calcium Carbonate and Biological Sulphate Removal

Abstract.   An integrated approach is proposed for treating acidic coal discard leachate, consisting of CaCO₃ handling and dosing, CaCO₃-neutralization, and biological sulphate removal. It was found that: powdered CaCO₃ can be slurried to a constant density and used to neutralize the acid water, remove Fe (II), Fe (III), and Al, and partially remove the sulphate (to saturation level); biological sulphate removal can be used to lower the sulphate to less than 200 mg/L using ethanol as the carbon and energy source; CO₂ produced during calcium carbonate treatment can be used for H₂S-stripping and; H₂S gas recovered in the sulphate removal stage can be used for iron removal.     

氨-异丙醇溶液中磷石膏制备硫酸钾新工艺

针对氨溶液中磷石膏制备硫酸钾工艺存在的问题 ,考察了甲醇、氨 甲醇等溶剂对反应过程氧化钾收率的影响 ,筛选出氨 异丙醇作为适宜的添加溶剂 ,并对氨 异丙醇溶液中磷石膏直接制备硫酸钾的工艺进行了研究