Letter Report on: The Blue Grass Chemical Agent Destruction Pilot Plant's Water Recovery System (2012) / Chapter Skim
Currently Skimming:
BACKGROUND
BACKGROUND
Pages 5-43
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 5... ...
Barton, Bechtel Parsons Blue Grass, "Blue Grass Chemical Agent-Destruction Pilot Plant Water Recovery System (WRS) , RO: Addendum," briefing to the committee, July 20, 2011.
|
From page 6... ...
SCOPE OF THE REPORT This report focuses solely on the BGCAPP WRS. The scope of this study is limited to WRS operations, which begin when SCWO effluent and steam and cooling blowdown water enter the pretreatment system and end when the purified water exits the RO units.
|
From page 7... ...
The vendor had never treated anything similar to the unique compositions of the BGCAPP SCWO effluents. In the course of performing its work, the committee obtained details about the SCWO process only insofar as that process affects the process stream that the WRS will treat.
|
From page 8... ...
Tables 1 through 3 show the results of analyses of SCWO effluent performed in 2004. The hydrolysates for these analyses were produced by the neutralization of actual agent at an Army laboratory, were blended with energetics hydrolysate, and were then treated with an SCWO unit at a General Atomics site in its test SCWO unit.
|
From page 9... ...
SOURCE: Adapted from BPBG, 2005. Table 3 Liquid Effluent Analyses for Mustard SCWO Performance Tests 9/25/2004 9/26/2004 9/27/2004 12:30 10:00 06:15 Analyte Units Result Result Result TOC(1)
|
From page 10... ...
The SCWO effluents will have overall salt concentrations similar to those of brackish water, but the specific compositions of the effluents will be unique, coming as they do from the processing of chemical agent and energetics hydrolysates. Therefore, although experience from RO plants that treat brackish water and seawater can provide guidance about the challenges that might be expected in the BGCAPP WRS, such experience is not necessarily directly applicable to the planned BGCAPP WRS.
|
From page 11... ...
DESCRIPTION OF THE WATER RECOVERY SYSTEM The WRS will desalinate SCWO effluents, cooling tower blowdown, and steam boiler blowdown for reuse as quench water in the SCWO process. The system was designed: To operate with an efficiency of 70 percent water recovery with a maximum of 500 mg/L total dissolved solids (TDS)
|
From page 12... ...
SOURCE: Neil D Frenzl, Engineering Manager, Bechtel Parsons Blue Grass, and Surajit Amrit, P.E., Mechanical Engineering Lead, Bechtel Parsons Blue Grass, "Blue Grass Chemical Agent-Destruction Pilot Plant Water Recovery System (WRS)
|
From page 13... ...
This would reduce greatly the amount of water that must be processed by the RO system. The hydraulic design of the RO process targets 70 percent recovery, but a higher recovery might possibly be achieved if the calcium in the ion exchange-treated cooling tower and steam blowdown water effluent is sufficiently low and there is minimal calcium in the SCWO effluent after pretreatment.
|
From page 14... ...
Additional reverse osmosis hydraulic design simulations (e.g., ROSA) should be considered using different levels of calcium in the feed, taking into account the calcium levels anticipated in the SCWO effluents, in order to establish the target level of recovery for each campaign.
|
From page 15... ...
This may become important if other problems accelerate membrane fouling. Coagulation of the Suspended Solids in the SCWO Effluent Overview of Coagulation The use of RO membranes requires some form of pretreatment in order to remove suspended solids and to reduce turbidity and the silt density index (SDI)
|
From page 16... ...
Time should be scheduled to shake down the media filters at the start of each new agent campaign. Choice of Coagulant The committee is concerned about the choice of aluminum sulfate as the coagulant to be used to pretreat the SCWO effluent prior to medial filtration (BPBG, 2009)
|
From page 17... ...
The coagulation system, as currently designed, has a high risk of functioning poorly for two reasons. First, if aluminum coagulant is used, coagulant-phosphate reactions in supercritical water oxidation effluent could lead to excessive filter loading rates.
|
From page 18... ...
Operational Characteristics of Media Filtration Systems Filtration rate and bed loading are the two key characteristics of media filters. Filtration rate is the overall water velocity through the granular media, and bed loading is the total mass of suspended solids removed and retained in the granular media before backwashing is required.
|
From page 19... ...
membranes need to be backwashed when the filter head loss exceeds the design value, or when the quality of the filter effluent is no longer acceptable for the RO system. Granular media filters are typically backwashed at 15 to 20 GPM/ft2 for the range of temperatures found in drinking water treatment (5°C to 25°C/41°F to 77°F)
|
From page 20... ...
Also, approximately 10 to 50 mg/L of titanium dioxide solids are expected in the SCWO effluent, and up to 150 mg/L of aluminum and calcium phosphate precipitates may occur in SCWO effluent when GB and VX are processed. These concentrations may also be reduced as a result of settling in the storage tanks but, again, to an unknown extent.
|
From page 21... ...
Recommendation. The inlets and outlets of the supercritical water oxidation effluent storage tanks and the hydrolysate holding tanks should be designed to maximize solids removal by means of sedimentation to reduce the solids loading of the granular media filter.
|
From page 22... ...
Although this modification will not reduce the solids that are formed during coagulation, it will ensure good removal of solids that readily settle out of the SCWO effluent, thereby decreasing the solids loading on the media filters. The conversion into clarifiers would involve inlet and outlet design, as well as other factors such as consideration of solids accumulation, removal, and appurtenances to improve solids removal.
|
From page 23... ...
clarifier and clear well tank is covered by this trend. Deletion of the clarifier requires increasing the size of the multi-media filters located upstream of the Reverse Osmosis (RO)
|
From page 24... ...
Microbial growth downstream of the supercritical water oxidation reactor and prior to the reverse osmosis system is not likely. If microbial growth does occur and is deemed a problem, adding a chlorination system would be a simple solution.
|
From page 25... ...
Finding. Several different risk-mitigation approaches are available to minimize the risk of the multimedia filtration system's performing poorly.
|
From page 26... ...
Finding. If none of the risk-mangement efforts suggested for the multimedia filters can be employed, or if analyses demonstrate multimedia filtration to be ineffective, a prepackaged ultrafiltration membrane system would be the best available alternative to multimedia filtration for providing adequate prefiltration.
|
From page 27... ...
Finding. Membrane filtration systems tend to have smaller footprints than those of media filters; a smaller footprint may offer additional logistical and space allocation advantages for the supercritical water oxidation facility.
|
From page 28... ...
= 1 – Cprod/Cfeed, where Cfeed and Cprod are the concentrations of the target contaminant (e.g., dissolved solids for RO, turbidity or suspended solids for MF, etc.) in the feedwater and product water, respectively.
|
From page 29... ...
The SCWO effluents from the GB and VX campaigns, and possibly from the mustard agent campaign, may or may not be saturated with calcium and/or aluminum solids following media filtration, depending on what amount of softened water, if any, has been blended in. This level of saturation will increase during the RO process, causing the precipitation of additional solids.
|
From page 30... ...
Based on information provided to the committee, the membranes selected by the vendor will produce less than 200 mg/L of total dissolved solids in the reverse osmosis permeate, given the feedwater quality and 70 percent recovery.
|
From page 31... ...
The design basis used for the ROSA calculations for the BGCAPP reverse osmosis system does not reflect the actual anticipated compositions of the various supercritical water oxidation effluents. Recommendation.
|
From page 32... ...
The RO membranes in the design should provide consistently low TDS effluent, as they are rated for a seawater influent of about 3.5 to 3.9 percent dissolved solids content, whereas the SCWO effluent has a range of 1 to 3 percent dissolved solids content. This conservative design should meet the design objectives of 500 mg/L TDS content necessary for the reuse of WRS effluent as quench water.
|
From page 33... ...
SOURCE: Neil D Frenzl, Engineering Manager, Bechtel Parsons Blue Grass, and Surajit Amrit, P.E., Mechanical Engineering Lead, Bechtel Parsons Blue Grass, "Blue Grass Chemical Agent Destruction Pilot Plant Water Recovery System (WRS)
|
From page 34... ...
SOURCE: Neil D Frenzl, Engineering Manager, Bechtel Parsons Blue Grass, and Surajit Amrit, P.E., Mechanical Engineering Lead, Bechtel Parsons Blue Grass, "Blue Grass Chemical Agent Destruction Pilot Plant Water Recovery System (WRS)
|
From page 35... ...
Intergranular corrosion of the weld heat-affected zone can result if the alloy has a high carbon content. In this heat-affected zone, the carbon combines with the chromium and molybdenum in an alloy, such as type 316 stainless steel, to produce on either side of a weld a band in which the alloy content is seriously reduced, especially at the grain boundaries.
|
From page 36... ...
The nearest archetype systems with which the committee members have experience are seawaters and brackish waters. In these cases, both 316 and 316L have marginal corrosion resistance, and their use has been largely replaced by duplex stainless steels such as 2205.
|
From page 37... ...
In general, the crevice corrosion occurrence rate in cast duplex stainless steels decreases linearly with increased PRE number. 9 Malik et al.
|
From page 38... ...
refers to test methods and procedures to determine pitting and crevice corrosion resistance of stainless steels and related alloys when they are exposed to oxidizing chloride environments. These tests are designed to cause localized corrosion more quickly than in most natural environments.
|
From page 39... ...
is not completely borne out in practice. Experience with SCC of austenitic stainless steels (e.g., 304 and 316)
|
From page 40... ...
Given that the committee is not aware of any other water recovery systems that treat effluents similar to those expected from the BGCAPP supercritical water oxidation system, the bases for the present material selections are not well supported. Finding.
|
From page 41... ...
These corrosion tests should be conducted in a chemical environment similar to that expected in the supercritical water oxidation effluents and the reverse osmosis reject. Candidate alloys for evaluation include type 316 stainless steel, a duplex alloy such as 2205, a super duplex alloy, and perhaps a super austenitic stainless steel.
|
From page 42... ...
B, February 22. Richmond, Ky.: Blue Grass Chemical Agent Destruction Pilot Plant Project.
|
From page 43... ...
2005. Interim Design Assessment for the Blue Grass Chemical Agent Destruction Pilot Plant.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.