Oil recovery through deemulsification research : separation of water from emulsified oil

In an effort to improve the environment, there is a need to recover and reuse the oil and water components of lubricating emulsions used in copper drawing and rolling processes. The Freeport-McMoRan Copper and Gold Inc. copper rod mill located in El Paso, TX was chosen as the site location for this project. It is one of the largest rolling and drawing operation facilities in the world, and it meets the established criteria set by Project ORDER. A large facility generates an average of 8,400 gallons of spent lubricant per day. The WERC emulsion sample contains 98 v% water and 2 v% lubricating oil and contains metal debris that would negatively impact water quality if it were discharged into surface waters. Oil and water are valuable resources and their maximum recoveries are desired. Project ORDER successfully recovers more than 90 v% of the water and essentially all of the oil. The recovered water could be recycled for fresh lubricant production within the facility, eliminating almost all water discharge and reducing water intake. The recovered oil will be sent to oil recyclers, lowering discharge expenses. Project ORDER has carefully evaluated several water recovery, oil recovery, and metal recovery technologies to design the commercial process. The first processing step of Project ORDER is an ultrafiltration (UF) membrane that recovers 90 v% of the water in the spent emulsion sample. As water permeates the membrane, the concentration of oil in the emulsion increases from about 2 v% to 30 v%. The second processing step removes essentially all of the water from the UF concentrate using an evaporator, which operates by passing low pressure steam through a jacketed, agitated vessel. The third processing step removes metal debris from the oil using a depth filter. The fourth processing step utilizes a reverse osmosis (RO) membrane to purify the UF permeate water for recycle. The fifth processing step reduces the amount of waste from the RO reject using an evaporator, which also operates by passing low pressure steam through a jacketed, agitated vessel. The evaporator removes essentially all of the water in the RO reject and the remaining waste is sent for disposal. The evaporated water from both evaporation units is condensed and combined with the RO permeate to be recycled. Based on a spent emulsion production rate of 8,400 gal/day, it costs $793, 000 per year for current disposal by incineration. For Project ORDER the fixed capital investment is$899,000, the yearly operating cost is $528,000, and the net present worth is$413,000 with a 24% discounted rate of return. After the initial investment is recovered, Project ORDER results in a net savings of $265,000 per year. This project is a promising process to achieve all the goals of Task 5. It produces oil with less than 3% water content, produces maximum water yield, minimizes waste solution, avoids the use of harmful materials and is cost and energy efficient. The health and safety of all individuals involved and the environmental impact of Project ORDER is of utmost importance throughout the construction and life of the project. The facility will ensure that all processes will comply with regulations outlined by the Environmental Protection Agency (EPA), Occupational Safety and Health Administration (OSHA), the Resource Conservation and Recovery Act (RCRA), and Texas State and El Paso County regulations. All operations and company procedures will comply with The Emergency Planning and Community Right-to-Know Act of 1986. The following report provides a detailed proposal for an oil and water recovery system, including experimental research results, process optimization, full-scale design, economic analysis, and environmental, health and safety considerations

Real-Time Monitoring of Reverse Osmosis Membrane Integrity

Reverse osmosis (RO) membrane desalination is the primary technology for seawater and brackish water desalination, agricultural drainage desalting, as well as municipal wastewater recycling for potable water reuse applications. RO membranes achieve high salt rejection (>95%) and in principle should provide a complete physical barrier to nanosize pathogens (e.g., waterborne enteric viruses). However, in the presence of imperfections and/or membrane damage, membrane breaches as small as 20-30 nm in diameter can allow nanosize pathogens to pass through the membrane and contaminate the product water stream. In order to demonstrate that the level of removal of these contaminants by RO processes will assure rigorous public health protection, there is a need for real-time RO membrane integrity monitoring (MIM). However, at present, reliable real-time RO membrane MIM methods are unavailable for the detection of membrane or module breaches. Given the above needs, a Pulsed Marker Membrane Integrity Monitoring (PM-MIM) approach was developed for real-time assessments of RO membrane integrity, based on characterization of fluorescent molecular marker passage across an RO membrane. This approach involves monitoring the dynamic change in marker concentration in the RO permeate (product) stream in response to a pulsed marker injection into the RO feed stream. The presence and characteristics of membrane integrity loss is identified by decoupling marker diffusive and convective transport through the RO membrane. The approach was first evaluated the passage of a molecular marker through intact and compromised RO membranes (with micron-size membrane breaches) in a bench-scale, plate-and-frame (PFRO) system. It was demonstrated that while marker passage through intact RO membranes was governed by diffusive transport, enhanced marker passage for compromised membranes was associated with convective transport through the breached areas. Therefore, detection of enhanced molecular marker passage was indicative of membrane integrity loss. One of the potential causes of RO membrane integrity loss in RO plants is oxidation of the polyamide RO membrane surface by chlorinated disinfectants, which are typically introduced into the RO feed stream to prevent biofouling. The suitability of the PM-MIM approach for quantification of the extent of membrane integrity loss due to oxidation was evaluated for flat-sheet RO membranes that were degraded via exposure to sodium hypochlorite (NaOCl) solution at various exposure conditions (i.e., NaOCl concentration and exposure time). Upon membrane exposure to 50-200 mg/L NaOCl for a period of 2.5 to 10 hours, there was a significant increase in marker solution-diffusion and convection across the RO membrane as a result of changes in membrane surface physicochemical properties (surface roughness, chemical composition, and wettability) and structural damage (as evident from the presence of micron-size breaches). The severity of membrane integrity loss, represented by an equivalent breach size, increased with chlorine feed concentration and exposure time, with the latter having a more pronounced impact on membrane integrity. In order to implement the PM-MIM approach in full-scale RO plants, which typically consist of multiple spiral-wound RO (SPRO) elements, an analytical framework was developed for characterization of marker passage through RO membranes in each individual SPRO element in multi-element SPRO systems. The approach is based on monitoring and analyzing the dynamic change in the marker concentration in the combined permeate stream (from multiple SPRO elements), in response to a pulsed marker injection into the RO feed. Subsequently, marker convective transport, across the RO membrane in each SPRO element, was be resolved via data fusion of dynamic marker response with online water flow, feed salinity, and pressure data, combined with the estimated marker residence time for each SPRO element. Experimental evaluation, which was carried out with intact and compromised SPRO elements (with mechanically induced membrane breaches), demonstrated enhanced marker passage for compromised SPRO elements, with increased marker passage that correlated with increased breach size. The PM-MIM approach was shown to be both technically and economically suitable for multi-element Ro system and through the proposed protocol for its implementation can serve to quantify the severity and identify the approximate location of membrane integrity loss in a multi-element SPRO plant

Analysis of Nanoparticle Agglomeration in Aqueous Suspensions via Constant-Number Monte Carlo Simulation

A constant-number direct simulation Monte Carlo (DSMC) model was developed for the analysis of nanoparticle (NP) agglomeration in aqueous suspensions. The modeling approach, based on the “particles in a box” simulation method, considered both particle agglomeration and gravitational settling. Particle–particle agglomeration probability was determined based on the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory and considerations of the collision frequency as impacted by Brownian motion. Model predictions were in reasonable agreement with respect to the particle size distribution and average agglomerate size when compared with dynamic light scattering (DLS) measurements for aqueous TiO₂, CeO₂, and C₆₀ nanoparticle suspensions over a wide range of pH (3–10) and ionic strength (0.01–156 mM). Simulations also demonstrated, in quantitative agreement with DLS measurements, that nanoparticle agglomerate size increased both with ionic strength and as the solution pH approached the isoelectric point (IEP). The present work suggests that the DSMC modeling approach, along with future use of an extended DLVO theory, has the potential for becoming a practical environmental analysis tool for predicting the agglomeration behavior of aqueous nanoparticle suspensions