Boiler Feed Water Treatment for Industrial Boilers & Power Plants Exhibited by Conventional Membrane a Cost-Effective and Environmentally-Sound Solution Systems
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Application Note Boiler Feed Water Treatment for Industrial Boilers & Power Plants exhibited by conventional membrane A cost-effective and environmentally-sound solution systems. The VSEP membrane system will significantly reduce TDS, TSS, color bodies, silica and hardness from Background Objective influent streams originated from city water, well water, and river/surface In the steam boiler industry, high purity To meet the requirements of both waters, thus minimizing treatment cost. feed water is required to ensure proper ecology and economy, the filtration of operation of steam generation systems. boiler feed water streams allows an The VSEP treatment system uses High purity feed water reduces the use industrial boiler or power plant to meet ultrafiltration or nanofiltration/reverse of boiler chemicals due to less frequent the stringent requirements for more osmosis membrane modules to treat the blowdown requirements (reducing efficient boiler performance. The influent water in order to generate a blowdown frequency by as much as a treatment of the boiler feed water is permeate stream that meets the boiler factor of 10). Lower blowdown required for preventing excessive heat feed water criteria regarding frequency also results in lower fuel transfer equipment fouling and the concentrations of suspended and costs. Scale buildup is reduced due to a erosion of turbine blades. dissolved solids, silica, and hardness. smaller concentration of impurities in After final polishing by ion exchange the boiler feed water to foul heat transfer resins, the clear permeate can then be surfaces. The lower level of impurities Solution used as boiler feed water. Reverse also reduces corrosion rates in the osmosis filtration can be used if boiler. When boiler is used to run a Technological advances in membrane dissolved solids are an issue. In steam turbine, turbine blade erosion is filtration systems have created an summary, the VSEP treatment system reduced due to higher purity steam opportunity for industrial boilers and can be used to treat boiler feed water generated. steam power plants to treat boiler feed with only minor final polishing by ion water streams in order to meet stricter exchange resins. VSEP will eliminate The use of reverse osmosis in feed water system performance. The “Vibratory the pretreatment requirements and can purification systems reduces chemical Shear Enhanced Processing” or substantially reduce chemical usage for costs by reducing the frequency of ion VSEP, developed by New Logic regeneration thus reducing disposal of exchanger regeneration. A complete International makes it possible to filter spent regenerant and the associated system, which includes reverse osmosis influent water or effluent wastewater costs. and ion exchange, typically results in a streams without the fouling problems more cost effective system when compared to systems that do not use reverse osmosis. However, the use of Figure 1 conventional reverse osmosis requires substantial use of pretreatment unit Power Plant Water Cycle operations which also adds costs. Silicate and colloidal deposits decrease Source Water boiler efficiency and also result in Boiler Feed Truck Haul premature failure of turbines. Condensate Recovery Ultrafiltration can remove greater than Municipality Wash Water Wastewater 99% of colloidal silica, as well as Municipality Power Plant - Treatment precipitated iron and aluminum. The Manufacturing Facility reduction in particulate matter, suspended solids and total organic carbon also enhance turbine and boiler efficiency. However, the use of conventional membrane technologies has faced substantial membrane fouling problems. Aquifer Aquifer www.vsep.com Application Note Table 1 Benefits of VSEP when Comparing with Competitive Technologies Technology Benefits of VSEP Chemical • The main advantage of VSEP over a clarifier system is that the settling that Addition/Clarifier a clarifier requires is a great deal of time which leads to clarifiers with a Systems great hold-up volume and thus large space required and cloudy overflow. • VSEP can handle wide variations in feed concentrations • VSEP generates a permeate quality with 0 ppm suspended solids versus about 500 ppm from a clarifier treatment process • VSEP is a one step process where as the clarifier treatment process generally requires pre and post treatment • VSEP can obtain higher quality permeate, typically 10 to 20 mg/L of hardness and less than 1 mg/L of Silica when RO membrane is used • VSEP offers smaller foot print, thus much lower building/facility costs • The chemical consumption for clarifiers is usually high and significant overdose is required for proper control of the clarifier effluent. Cross-flow • Product recovery is poor with cross flow systems, with cross flow at e.g. Filtration/ Spirals 60% to 75% versus 80 to 90% typical for VSEP • Cross flow filtration normally requires substantial pretreatment • VSEP offers higher end point concentrate stream • Frequent membrane replacement for the cross flow system can become expensive • Cross flow membranes will plug up with higher solid streams • Hold-up volume of cross flow system is high • Need larger feed/working tank with cross flow filtration • Larger piping is required for cross flow filtration • VSEP offers 2 to 3 times higher flux • VSEP offers one pass operation • VSEP can handle wide variations in feed concentrations • VSEP can obtain higher quality permeate, typically 10 to 20 mg/L of hardness and less than 1 mg/L of Silica when RO membrane is used • VSEP offers much lower power requirement. • VSEP offers smaller foot print, thus much lower facility cost www.vsep.com Application Note Figure 2 V✧SEP Nano/RO Filtration influent in one step. For Boiler Feed Water Treatment Another issue for power plants is the VSEP disposal of waste streams such as Treatment scrubber effluent. Of course, several System methods already exist that can perform City Water all of the above functions. Again, a Chemical Injection Ion Exchange multistep process is often employed. A (Optional) Concentrate Polishing Units typical wastewater treatment process to Disposal might include chemical addition, then a clarifier, then a filter press, and finally ion exchange. VSEP technology is unique in that it rolls the whole operation into one machine. All of the Boilers systems mentioned could be replaced using a single VSEP machine equipped Storage Tank with 0.2 m Supply with nonporous membranes, which Post Filter Sterile Vent Filter Pump would remove everything from the large ash particles to the individual gypsum molecules. The resultant water quality Several technologies are currently being power plant, treatment of boiler would be as high as that produced by used for boiler feed water treatment. condensate and its recovery, and the multi-stage filtration and chemical Table 1 presents a summary of the treatment of waste water generated from addition. benefits of VSEP when compared to flue gas treatment scrubbers are selected competitive technologies such additional important water treatment A process schematic for treatment of as chemical addition/clarifier systems challenges. For boiler feed water boiler feed water using a VSEP and cross flow filtration/ spiral treatment, depending on its treatment system is presented in Figure membranes. VSEP offers significant requirements, a number of processes can 2. This system is using nano or reverse advantages over these technologies, as be utilized which include chemical osmosis membrane filtration system to presented in Table 1. treatment/lime softening, dual media replace the entire pretreatment step that filtration, carbon adsorption, would be usually required, i.e. lime or For the industrial boilers and power conventional reverse osmosis cation softening, dual media filters, plant systems, as well as the membranes, and final ion exchange resin carbon adsorbers, and conventional cogeneration industry, VSEP membrane polishing. Significant waste is reverse osmosis units. City water is systems can now be utilized where generated from these unit operations, treated in a single step VSEP treatment traditional cross-flow membrane including spent carbon and spent system followed by a final ion exchange technologies faced substantial regenerant chemicals from the ion polishing unit. The treated boiler feed membrane fouling problems in the past. exchange resins. water is then fed to the boiler via a The VSEP is an attractive alternative to supply pump. conventional filtration methods due to In the setting of a power plant, the its vibrational, shear-enhanced design. Vibratory Shear Enhanced Processing Figure 3 is a process block flow diagram (VSEP) has two major applications. showing the integration of VSEP with Process Conditions The first is the processing of boiler water boiler feed water treatment at an influent. To avoid scale in their boilers, industrial manufacturing facility. This Figure 1 presents a schematic of a power power plants usually utilize a multistep diagram also includes the overall plant water cycle. The influent water to process to remove the hardness of the material balance for the water treatment a power plant may come from a incoming water, including either process and illustrates its performance. groundwater well (aquifer), surface chemical treatment or ion exchange and waters, or a municipality. The influent several less advanced methods such as As presented in Figure 3, city water is water would have to be treated to meet multimedia filtration. These multi-step