Progress 09/01/11 to 08/31/16
Outputs
Target Audience:Successful development and demonstration of the SRNF technology in Phase II has lead CMS to collaborate with key partners in vegetable oil processing and membrane supply & marketing industries. These collaborations will facilitate CMS to carry out experiments with representative samples of solvent extracted stream from oil plants, rapidly design and fabricate prototype membrane device and do appropriate field testing. If a sufficient business plan can be developed, CMS could scale up the SRNF membrane modules and enhance and optimize the SRNF membrane module performance on a pilot-scale system. A pilot demonstration unit would also be deployed at a vegetable oil refining plant for demonstrating the membrane process capabilities and advantages. In addition, SRNF membrane technology for solvent recovery is expected to be of great value in processing other oil seeds such as corn, cotton seed and canola. Other applications of the proposed SRNF technology include solvent recovery from algae oil extraction process in biofuel production and solvent recovery from solvent-deasphalting process in petroleum refining. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Summer students from University of Delaware and Drexel University Chemical Engineering Departments assisted in the program. How have the results been disseminated to communities of interest?Successful development and demonstration of the SRNF technology in Phase II has lead CMS to collaborate with key partners in vegetable oil processing and membrane supply & marketing industries. These collaborations will facilitate CMS to carry out experiments with representative samples of solvent extracted stream from oil plants, rapidly design and fabricate prototype membrane device and do appropriate field testing. If a sufficient business plan can be developed, CMS could scale up the SRNF membrane modules and enhance and optimize the SRNF membrane module performance on a pilot-scale system. A pilot demonstration unit would also be deployed at a vegetable oil refining plant for demonstrating the membrane process capabilities and advantages. SRNF membrane technology for solvent recovery is expected to be of great value in processing other oil seeds such as corn, cotton seed and canola. Other applications of the proposed SRNF technology include solvent recovery from algae oil extraction process in biofuel production and solvent recovery from solvent-deasphalting process in petroleum refining. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
a) The procedure and technology for fabricating large scale composite flat sheet membranes based on perfluoropolymers has been developed. b) Spiral wound membrane modules based on composite membranes have been successfully developed. c) The large-scale test rig was built to test the membrane modules on a continuous and semi-continuous basis. d) Separation of n-hexane from vegetable oil has been successfully demonstrated on a module scale. e) Performance of the membrane was evaluated across a range of operating conditions with both refined soybean oil and crude soybean oil. Hexane permeation rates increased with both temperature and pressure. No detrimental effects on oil rejection were noted at higher temperatures or pressures. f) The membrane exhibited stable performance over 53 hours of operation with crude soybean oil. g) An economic analysis of the NF membrane separation of hexane from vegetable oil indicates that the benefits significantly outweigh the costs in both greenfield and retrofit applications. Capacity expansion of a plant through the addition of the NF separation process is also economically beneficial. Project Results Composite membrane fabrication: Large sheets of composite membranes based on CMS perfluoropolymer were successfully fabricated on Polyacrylonitrile (PAN) microporous support by both the techniques of gravure coating and spray coating. Membrane module development: Perfluoropolymer composite membranes are supplied to Sepro Membranes Inc. for fabricating them into spiral wound modules (shown in Figure 1a). Stainless steel housing for the spiral wound module (shown in Figure 1b) was built by CMS. Permeate, feed spacers and epoxy for the spiral wound modules are successfully tested for compatibility with oil and n-hexane mixture. Effective surface area of the spiral wound modules is 1.5 sq. ft. Figure 2. Large scale NF test rig Large scale test rig: A large scale NF rig was built to test the spiral wound modules for n-hexane separation from vegetable oil miscella on either continuous or semi-continuous basis (shown in Figure 2). The rig is capable of operating at different operating temperatures (25 to 70°C) and operating pressures (up to 600 psi). It can be operated in a batch mode or continuous mode. The rig is also capable of running in both nanofiltration and pervaporation modes. The rig can also collect and record the data for offline analysis. Characterization of the spiral wound membrane module at 25°C: Spiral wound module was first characterized for its solute rejection behavior by testing with a solution of n-hexane and Oil blue. Oil blue is a molecular weight marker with a molecular weight of 378 g/mol. Membrane module has retained about 95% of oil blue. Pressure Normalized Flux (PNF) (reported in units of liters/m2-hr-bar [LMHB]) of n-hexane across the module was also steady. So, the spiral wound module performed very well during continuous operation at room temperature and 250 psig feed pressure. On completion of this initial screening test, the membrane was evaluated at elevated temperatures and higher pressures with feed solutions having higher vegetable oil concentrations. After testing the spiral wound module on a continuous basis successfully for a number of days, the module was tested on a semi-continuous basis. It was found that it the feed pressure to the membrane is gradually reduced to less than 50 psig before switching off the feed pump and similarly restarting the feed pump with a low pressure setting, the observed reduction in vegetable oil rejection with each cycle is eliminated. This "soft start and soft stop" procedure was adopted for all membrane tests. A second issue that was identified in later tests at higher pressures was collapse of the microporous structure of the membrane support material. However, it was found through comparative tests with a pore collapsed membrane at and an unused membrane 250 psig that collapse of the microporous structure does not have a significant impact on either pressure normalized flux of the solvent or oil rejection. Therefore it was not considered a serious technical issue. Impact of Hexane Grade on Membrane Performance Early tests of the membrane performance were carried out with a good quality laboratory grade of n-hexane, 95% purity with a boiling point of 69° C. However, most edible oil extraction processes use a commercial grade of hexane which contains a mixture of hexane isomers, generally boiling in the temperature range of 65-69° C. The results of the tests are summarized in Table 2. Membrane Performance at Higher Pressure and Elevated Temperature The results of the membrane performance tests carried out with laboratory grade n-hexane are summarized in Table 3. The results of tests completed for three feed oil mass fractions, four flow velocities, two temperatures, and two pressures are tabulated. In general, the oil retention was excellent at all test conditions, exceeding 99.9%. High oil rejection is very important because high oil rejection means that the recovered hexane contains very little oil. This minimizes recycle of oil within the oil extraction process as the hexane is reused and maximizes process efficiency. The effect of pressure and feed composition on PNF is illustrated in Figure 6 for a feed temperature of 30° C and a superficial feed velocity of 33.6 cm/s. Additional tests to explore the impact of pressure across a wider range were completed. The results of these tests are not included in Table 3. This would indicate that feed pressures above 600 psig will be economically beneficial. Tests have shown that the membrane is able to withstand operation at this pressure without any significant degradation in performance (flux is stable and oil rejection is high and stable) over the short term. Membrane Performance and Stability with a Crude Soybean Oil Sample After the successful tests separating hexane from refined oil, tests were performed using an actual industrial sample of crude soybean oil. The sample was received from the Perdue Grain & Oilseed, LLC (Salisbury, MD). This test gave a solvent PNF (Pressure Normalized Flux) of 2.26 LMHB and oil retention of 99.9%. Initially, the oil retention was near 100%, essentially a perfect separation. After about 36 hours the retention dropped to high 98% range, a noticeable drop but still an acceptable result. Economic Evaluation of the SRNF Process for Solvent Recovery from Edible Oil The economics of a proposed nanofiltration process to separate edible oils from the extraction solvent (hexane) used in the edible oil production process was evaluated. A solvent recovery system with a crude oil processing capacity of 22,000 lb/hr was chosen as the basis for this analysis. This capacity is representative of a typical edible oil plant. The results of the economic analysis for both greenfield and retrofit plant installations are presented in Table 4. Data for the conventional technology, double-effect evaporators, and SRNF processes are presented. SRNF is a lower cost option than adding an evaporator. SRNF, Case J, offers a 28% lower total annual cost compared the evaporator retrofit, Case I. This amounts to $58,260 less in total annual costs. While SRNF is the superior investment choice, it must also be shown that SRNF provides a sufficient improvement in profitability to justify the investment. The data in rows 7 and 8 indicate that this is so. The retrofit increases the crude oil processing capacity by 4,400 lb/hr, which typically yields about 3,960 lb/hr of finished oil. Bulk soybean oil sells for about $360 per thousand pounds(6) and the typical net margin is 20%. After deducting the total annual cost of the retrofit, the annual cash flow gain is $2,376,680 as reported in row 7. Since the value is positive, the investment is justified.
Publications
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Progress 09/01/11 to 08/31/12
Outputs
OUTPUTS: Compact Membrane Systems (CMS) has successfully developed the SRNF technology and demonstrated feasibility of the SRNF technology for recovering solvent from vegetable oil miscella. The Phase-II program is focused on developing spiral wound membrane module device, evaluating and optimizing the membrane module with a large scale test rig, and field testing the prototype device, followed by engineering and economic evaluation of the technology. As discussed in the following sections, we have successfully developed spiral wound membrane device and evaluated the module using a large-scale test rig. Number of issues associated with module development are successfully addressed. Next, performance of spiral wound module will be optimized at elevated temperatures, and tested in-house with the oil miscella samples (to be supplied by vegetable oil processor). One of the vegetable oil processor with a number of vegetable oil processing facilities, located in the east coast, is very interested in field testing our technology and has agreed to supply is with enough quantities of oil miscella for in-house testing. So, once we complete the module optimization and in-house testing, we are well positioned to field test the membrane device and complete the engineering and economic evaluation. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Success To Date: The procedure and technology for fabricating large scale composite flat sheet membranes based on perfluoropolymers has been developed. Spiral wound membrane modules based on composite membranes have been successfully developed. The large-scale test rig was built to test the membrane modules on a continuous or semi-continuous basis. Separation of n-hexane from vegetable oil miscella has been successfully demonstrated on a module scale. A relationship has been established with a vegetable oil processing plant to field test the membrane separation system.
Publications
- No publications reported this period
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