旋风除尘器流场及浓度场实验与模拟

在研究旋风除尘器内气固两相的运动状况及分离机理方面,计算机模拟替代部分实验的方法能够优化设计旋风除尘器结构参数,提高其对微细颗粒的捕集效率,减少运行压力损失。本研究采用RSM模型和随机轨道模型对旋风除尘器内流场及浓度场进行模拟及实验。研究表明,旋风除尘器压力损失模拟结果与实验结果吻合较好,对于大于5μm的颗粒其捕集效率模拟结果与实验结果基本吻合;旋风除尘器外壁的颗粒浓度呈螺旋带状分布;如将排气管管径减少至原直径0.8倍,可使其对2μm颗粒捕集效率提高6.6%,但压力损失提高36.5%;颗粒的凝并作用有利于提高旋风除尘器微细颗粒的捕集效率。     

烧结烟气脱硫剂性能的研究

为了提高脱硫效率和合理利用烧结过程中产生的机头灰,在半干法烟气脱硫剂生石灰中,加入一定量的烧结机头灰作为脱硫催化剂。在测定机头灰与生石灰化学成分、粒度和比表面积的基础上,研究和分析了机头灰与生石灰的质量配比对于脱硫效率的影响。结果表明,脱硫剂与机头灰在粒径分布和比表面积上都较接近,但经过消化活化后的混合脱硫剂的比表面积明显增大。当机头灰添加量为脱硫剂质量的2%～5%时,脱硫效率提高了2%～3%。机头灰与生石灰的胶凝反应以及机头灰中Fe2O3的催化作用是主要的作用机理。     

湿法烟气脱硫反应过程的实验研究

在石灰石/石膏湿法烟气脱硫中试台上,系统开展了浆液pH值、飞灰浓度、液气比、入口SO2浓度、烟气速度和氧化方式等对脱硫反应过程影响的实验研究。实验表明,脱硫效率随着石膏浆液pH值、液气比的升高而增加,且入口SO2浓度越高,液气比越低,影响效应越明显;脱硫效率随着烟气速度、烟气温度和入口SO2浓度的增加而下降;石膏浆液中飞灰含量对系统脱硫效率具有一定的促进作用:pH值>5.6,飞灰浸出液中Fe3+含量相对较低,Fe3+对脱硫反应过渡态催化氧化影响程度较轻,不同工况脱硫效率差别不大。pH值<5.6,飞灰浸出液中Fe3+含量随pH值降低而增大,增效效果逐渐显著;氧化方式对脱硫反应过程有明显的影响,强制氧化工艺的脱硫效率比自然氧化的高5%左右。     

A-A~2/O工艺脱氮实践运行效果及优化

A-A2/O工艺是预缺氧/厌氧/缺氧/好氧组成的生物脱氮除磷工艺,广州市某污水处理厂采用该工艺处理城市污水,具有同时去除有机物、脱氮除磷能力,但是TN去除率较低。分析了其TN去除率低的原因,并提出相应措施。该水厂针对本厂水质特征以及影响工艺脱氮性能的主要因素,优化了工艺控制参数,提高了TN去除率和TN达标保证率。     

以改性TiO2-SnO2为载体的SCR脱硝催化剂性能

研究以共沉淀法制备TiO2-SnO2复合载体,浸渍负载活性组分CeO2制成SCR脱硝催化剂。以NH3为还原剂,在适当的模拟烟气的实验条件下,考察了不同载体催化剂在150~400 ℃内对脱硝性能的影响。实验结果表明,经过改性的TiO2-SnO2复合载体改性对催化剂的脱硝性能有较大的影响,SnO2的加入大大提高了Ce/TiO2的脱硝效率,并可以在一定程度上抵抗SO2带来的毒害和钝化作用。此外,利用BET、XRD和SEM等表征手段,研究载体改性对催化剂微观结构的影响。表征结果显示,SnO2的掺杂可在一定程度上促进载体及催化剂比表面积的增加,复合载体TiO2-SnO2对于活性组分CeO2有着更好的分散性,活性组分CeO2以高度分散的形式存在或呈无定型状态存在于复合载体TiO2-SnO2的表面,未出现团聚的现象。     

Blue–green water utilization in rice–fish cultivation towards sustainable food production

Integrated rice–fish culture is a competitive alternative to rice monoculture for environmental sustainability and food productivity. Compared to rice monoculture, rearing fish in rice field ecosystems could increase food (rice and fish) production from this coculture. Moreover, the water productivity of rice–fish coculture is considerably higher than that of rice monoculture, because of double cropping. Despite these benefits, rice–fish coculture has not yet been broadly practiced. One of the potential challenges for the wider adoption of rice–fish coculture is water management. There are two forms of water involved in rice–fish cultivation: (1) blue water–surface and groundwater, and (2) green water–soil water from rainfall. The aim of this article is to focus on key factors determining the adoption of rice–fish cultivation through the effective utilization of blue–green water. We suggest that the efficient application of blue and green water in rice–fish coculture could help confronting water scarcity, reducing water footprint, and increasing water productivity.     

聚苯胺基复合吸收剂对烟气中SO2的吸附

聚苯胺（PANI）作为吸收剂,可有效地吸附烟气中的SO2。不同于其他吸收剂的是聚苯胺具有较高的热稳定性。但聚苯胺本身为团聚结构,在脱硫过程中颗粒之间会相互融合,使其脱硫效率降低。采用凹凸棒、硅藻土、蛭石与苯胺复合制备聚苯胺基复合吸收剂,对烟气中的SO2进行吸附,可有效减少聚苯胺颗粒之间的相互接触,避免聚苯胺颗粒在脱硫过程中颗粒之间的融合。实验结果表明,聚苯胺基复合吸收剂吸附SO2实质上是其中的聚苯胺对SO2的吸附,吸附原理主要为化学吸附,当吸附温度为100~180 ℃时,吸附效果较好;吸附剂可循环使用,且仍然具有优良的吸附容量;相对于纯的聚苯胺,聚苯胺与凹凸棒、硅藻土和蛭石复合之后的吸收剂对SO2的吸附效果显著提高。     

对柴油机集成后处理系统催化性能的数值模拟

为研究柴油机集成后处理系统的催化性能,应用CFD软件建立包括尿素水溶液分解、一氧化氮氧化和NOx选择性催化还原化学反应的数值计算模型,计算在SCR催化器上游加装DOC和CDPF催化器后不同排气温度和氨氮比时系统的催化效率。结果表明：当温度达到300℃以上时,尿素分解效率可达81%左右;NO的氧化效率基本维持在45%~60%,系统具有很好的低温催化性能,200℃时NOx催化效率可达76.6%;当氨氮比为1.0时,大多数工况下NOx催化效率均高于90%,最高可达98.7%。通过台架实验验证了模拟结果与实验数据绝对误差在5%以内,表明模拟计算结果可靠,可为后处理系统的设计提供理论指导。     

旋流场超细颗粒聚集实验研究

不同粒径分布和浓度的催化裂化(FCC)三旋回收超细催化剂颗粒在旋流场中经过50 h循环回流,颗粒中值粒径变化明显。物料中分散相越多、颗粒粒径越小时,颗粒碰撞越频繁,其聚集趋势越明显。颗粒聚集体在旋流场内不够稳定,通过对比不同进料速率下的旋流场聚集效果,得到最适合颗粒聚集的旋流场雷诺数为20 000。颗粒聚集体存在聚集极限粒径,其最佳聚集时间约为40 h,颗粒聚集后的旋流分离效率提高近5%。     

The removal of Polycyclic Aromatic Hydrocarbons in the wastewater treatment process: experimental calculations and model predictions

The removal of PAHs during the wastewater treatment process was examined in an activated sludge mode conventional facility. Concentrations reported are taken from an earlier measuring campaign. Removals of PAHs ranged between 28 and 67% in the primary, <1-61% in the secondary stage, and 37-89% in the whole process. Significant positive relationships were observed for removal efficiencies and the log K(ow) of PAHs in the primary and the log K(H) of PAHs in the secondary stage. Experimental removals were compared to those obtained from the FATE model. In the primary stage, predicted removals were lower than those experimentally calculated while in the secondary stage were higher. Predicted removals were apportioned mainly to sorption with negligible contribution from volatilization and biodegradation. Remarkable consistency between experimental and modeled removal efficiencies (-20-+20%) was observed for almost all PAHs in the whole treatment process.