The Filtration of Process Water and Its Importance in the Petroleum Industry; Section 3: Cooling and Amine Systems
Petroleum Industry Cooling Systems and how they can affect system instrumentation and efficiency.
(PRWEB) August 14, 2005 -- Cooling Systems: Cooling systems accumulate airborne dirt and other contaminants that can affect system instrumentation and efficiency. Dirt and iron fouling can rob the system of the required heat transfer capacity and increase frictional hydraulic losses. Cooling systems with inefficient filtration can result in the need for labor-intensive tower cleanouts and heat exchanger refurbishing. Efficient systems will extend equipment life and maintain maximum heat transfer. Removal of 98% of particles of 10 µ and larger is recommended for effective cooling water filtration.
Tubular backwashing systems provide economical method of automated solids removal with minimal backwash volumes. Clean cooling water reduces manual cleanouts, reduces chemical consumption, helps eliminate instrument plugging, and maximizes cooling efficiency. If space is at a premium, tubular systems are available in a nonlinear configuration. For example, the Ronningen-Petter AFR Series tubular backwashing pressure filter has a 1m² footprint.
Amine Systems: Amine systems require filtration to remove contaminants such as pipe scale, iron sulfide, and salt precipitants from the process. If the amine is dark amber to greenish in color, the stream is dirty. For maximum efficiency, the amine stream should be as clear as fresh water. Contaminant removal greatly increases amine efficiency and reduces the system's operating costs.
Problems created by dirty or unfiltered mine include iron sulfides that cause foaming in towers. Contaminants that collect on tower trays reduce efficiency and increase pressure drop across the tower. Solids that build up in the flash drum reduce the available liquid area, which results in incomplete separation of hydrocarbons and amine. Contaminants in the surge drum result in a constant supply of new solids in the flow. When particles settle out, they collect in piping, tanks, heat exchangers, and reboilers causing increasing corrosion, plugging, and fouling of the equipment and poor heat transfer.
Typically, disposable media are used on the lean amine loop and backwashing filters on the rich amine loop. When considering disposables, proper media selection will have the most direct effect on system efficiency and therefore cost effectiveness. For example, nominal efficiency media are not effective because too much dirt passes through the filter. Polypropylene media traps oils and can become blind before the full dirt holding capacity is reached.
For a typical 20% side stream, base the filter system size on flow rates recommended for the type of media used. The optimum flowrate is a compromise between cost and dirt holding. The slower the flowrate, the more dirt the media will hold. If there are oils in the amine or if the temperature exceeds 180˚ F (82˚ C), cellulose or polyester media are recommended; cellulose will generally cost less.
If the amine system has not been filtered or if there are signs of high dirt loading (again, a green or amber color) filtration is highly recommended. To reduce costs, stage the cleaning process. Begin with media that will eliminate larger µ particulate, and step the process gradually into smaller retentions with each change out, ending ultimately with retentions in the 5 - 10 µ range. To keep the system at optimum performance, use high efficiency, absolute rated media at a maximum of 10 µ.
Although more prevalent on the sulfur rich side, backwashing, or self-cleaning tubular systems are ideal for both the rich and lean sides of the amine loop because they eliminate operator exposure and disposal of often-hazardous spent bags or cartridges. The closed system benefits of a backwashing filter are especially important when on the rich side of the amine loop because of the elimination of operator exposure to the highly toxic sulfur being removed.
Backwashing filters should be sized at a flux rate of approximately 4 - 8 gpm/ft². The filter media should be 5 or 10 µ, high efficiency (+98%) filter elements constructed of single layer sintered wire mesh. When the filter is installed on a dirty system, it will typically backwash continuously for the first two to three days. Then, the backwash interval will start to increase and within a week, the amine will be clean and the backwash interval will increase to eight hours or more.
Backwashing filters are self-correcting during and after upsets. During upset conditions, the filter will start backwashing continuously. Once the process returns to normal, backwash interval times will also return to normal. The next article (section 4) will examine how to select the right filter for your process requirements.
by Ask Filter Man
For questions about industrial filtration, please visit the Ask Filter Man at http://wwwRonningen-Petter.com/Ask-Filter-Man-Blog.asp
If you would like to discuss this filtration solution with one of Ronningen-Petter's highly-trained Applications Specialists, please contact us at http://www.Ronningen-Petter.com/ContactUs/Contact-Us.asp
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