Hydrocarbon condensation modelling to mitigate fluid coker cyclone fouling

FLUID COKING is a continuous process that thermally converts heavy hydrocarbons, such as oil sands bitumen, to lighter and higher‐value products by horizontal spray injection onto a fluidized bed of hot coke particles. The cyclone sections of commercial fluid coker reactors experience fouling during typical operation, which limits unit run lengths. The main objective of this work is to improve fluid coker reliability by proposing cyclone fouling mitigation strategies based on practical operation modifications. This study developed a process simulation in Aspen Plus to establish the combined impact of vapour‐liquid equilibrium, endothermic thermal cracking reactions, pressure changes, and overall fluid dynamics in the selected fluid coker control volumes. The hydrocarbon composition was defined by applying an assay characterization of distillation data for representative hydrocarbon streams. Case studies were performed to determine the sensitivity of the predicted temperatures and hydrocarbon condensate flow rates for: (a) the burner‐to‐fluid coker transfer line temperature; (b) the hot coke flow rate; (c) hot coke entrainment from the freeboard region; and (d) scouring coke flow rate in the horn chamber. The scouring coke flow rate was identified as the most promising process lever to mitigate fluid coker cyclone fouling.     

Studying Fluid Characteristics Atop Surface Patterned Membranes via Particle Image Velocimetry

Surface patterning is a recent promising approach to promote performance of pressure-driven membranes in water treatment and desalination. Nevertheless, knowledge about foulant deposition mechanisms, especially at early stage of filtration, is still lacking. The applicability of particle imaging velocimetry to study fluid characteristics atop surface patterned thin-film composite membranes was investigated at different operating conditions. This work is an important first step toward reliable understanding of the impacts of topographical membrane surface modification on hydrodynamic conditions and foulant deposition mechanisms.     

Surface Modification of Ready-to-Use Hollow Fiber Ultrafiltration Modules for Oil/Water Separation

Reusing wastewater from oil-related industries is becoming increasingly important, especially in water-stressed oil-producing countries. Before oily wastewater can be discharged or reused, it must be properly treated, e.g., by membrane-based processes like ultrafiltration. A major issue of the applied membranes is their high fouling propensity. This paper reports on mitigating fouling inside ready-to-use ultrafiltration hollow-fiber modules used in a polishing step in oil/water separation. For this purpose, in-situ polyzwitterionic hydrogel coating was applied. The membrane performance was tested with oil nano-emulsions using a mini-plant system. The main factors influencing fouling were systematically investigated using statistical design of experiments.     

膜组合工艺应对藻类暴发的能力研究

藻类暴发严重威胁饮用水水质以及供给。试验采用投加混凝剂、粉末活性炭和高锰酸钾作为微滤膜预处理的膜组合工艺,考察应对藻类暴发的能力。研究表明,藻类暴发会引起有机物含量的增加,主要是小分子(相对分子质量低于1 000)的中性亲水组分的大量增加,这类有机物可通过预处理得到有效的去除,因而没有发现藻类暴发会对膜过滤产生严重的影响,粉末活性炭和高锰酸钾可有效延长膜过滤周期。导致膜不可逆污染的有机物主要为中等分子的强疏水和中小分子的中性亲水组分。     

Passive Picoinjection Enables Controlled Crystallization in a Droplet Microfluidic Device

Segmented flow microfluidic devices offer an attractive means of studying crystallization processes. However, while they are widely employed for protein crystallization, there are few examples of their use for sparingly soluble compounds due to problems with rapid device fouling and irreproducibility over longer run‐times. This article presents a microfluidic device which overcomes these issues, as this is constructed around a novel design of “picoinjector” that facilitates direct injection into flowing droplets. Exploiting a Venturi junction to reduce the pressure within the droplet, it is shown that passive injection of solution from a side‐capillary can be achieved in the absence of an applied electric field. The operation of this device is demonstrated for calcium carbonate, where highly reproducible results are obtained over long run‐times at high supersaturations. This compares with conventional devices that use a Y‐junction to achieve solution loading, where in‐channel precipitation of calcium carbonate occurs even at low supersaturations. This work not only opens the door to the use of microfluidics to study the crystallization of low solubility compounds, but the simple design of a passive picoinjector will find wide utility in areas including multistep reactions and investigation of reaction dynamics.     

聚四氟乙烯微孔膜亲水性与抗污性的关系研究

探讨错流过滤中聚四氟乙烯微孔膜亲水性与抗污性的关系。在聚四氟乙烯（PTFE）膜表面引入磺酸基（-SO3H）,通过扫描电镜（SEM）、傅里叶红外光谱（FTIR）、固体表面电位分析仪（SurPASS）等研究-SO3H含量对膜亲水性、Zeta电位、牛血清蛋白（BSA）静态吸附量及水通量的影响。结果表明：疏水的PTFE膜易吸附负离子,Zeta电位〈0,BSA吸附量高,水通量降幅大,抗污性差;经过亲水改性后,由于-SO3H的引入,膜表面不易吸附负离子,Zeta电位升高,BSA吸附量降低,水通量降幅小;随-SO3H含量增加,膜Zeta电位因-SO3H电离而降低,与负电性BSA之间的静电斥力增强,抗污性进一步提高。     

粉末活性炭和超滤组合工艺处理低温低浊水试验研究

通过浸没式超滤试验考察了粉末活性炭和超滤组合工艺对低温低浊水的净水效能以及对膜污染的缓解作用,并对其机理进行探讨.试验结果表明,粉末活性炭和超滤组合工艺处理低温低浊水时,能够降低膜表面的负荷,对可逆污染和不可逆污染具有一定的缓解作用;粉末活性炭投加量为10mg/L时,粉末活性炭和超滤组合工艺出水的浊度低于0.06NTU,对CODMn,UV254的平均去除率分别为20.9%,25%,比单纯的超滤工艺的去除率分别提高了10%,15%.     

膜元件性能变化对反渗透系统的影响

以六支膜单段串联反渗透系统为研究对象，总结了膜污染对膜元件性能影响的主要特征，并结合膜污染的实际特点，分析了膜元件污染对反渗透系统运行性能参数的影响，分别指出了膜压降、膜通量、脱盐率3项元件性能指标变化对反渗透膜系统性能指标的作用。为相关实际工程问题的解决提供了一定的参考依据。     

Characteristics of Air-Side Particulate Fouling Materials in Finned-Tube Heat Exchangers of Air Conditioners

Heat exchangers are used widely in residential, commercial, and industrial HVAC applications. Air-side particulate fouling in the heat exchangers of HVAC applications degrades the performance of cooling capacity, pressure drop across a heat exchanger, and indoor air quality. Indoor and outdoor air contaminants foul heat exchangers. The purpose of this study is to investigate the characteristics of the air-side particulate fouling materials in finned-tube heat exchangers of air conditioners. Air conditioners being used in the field such as inns, restaurants, and offices are collected in chronological order of use. The fouling materials attached on the evaporator heat exchangers consist of particulates and fibers. The particulates mainly originate from indoor dusts and the fibers are separated from clothes, bedclothes, papers, fur of pets, and so on. Typical fouling materials on the heat exchangers include fibers and dusts ranging from 6.6 to 20.9 μm in aerodynamic mean diameter.