ABSTRACT In the past, there has been significant attention devoted to the end-of-the-pipe solutions for wastewater treatment. This is largely due to the complexity associated with an analysis of a entire chemical process as opposed to a limited number of aqueous effluent streams. However, it is often possible to identify much more cost effective solutions for water conservation and reuse when the analysis is not limited to end-of-the-pipe solutions. This paper introduces a holistic methodology called Water Allocation Design and Engineering (WADE). This approach has been used successfully at two large manufacturing sites within Solutia to reduce wastewater discharges and to reduce freshwater usage.
INTRODUCTION Significant progress in the development of design techniques for water conservation has been made over the past decade. These advances have been in response to increasingly stringent environmental regulations and sustained pressure on industry to identify cost-effective pollution prevention strategies. The techniques developed to identify~ cost-effective water conservation designs involve designs for the direct recycle of water, end-of-the-pipe treatment systems to allow the recycle/reuse of water streams, and in-plant modifications for the source reduction of wastewater. These techniques can be classified into three categories. The first category consists of a series of water management tools that target the conservation and reuse of water streams that are not a part of the manufacturing process. The second category~ consists of systems analysis tools which allow the designer to analyze a large system and determine the optimal strategy to address a given water conservation task. Some of these techniques may be graphically represented via the following diagrams: . Component Tracking Diagrams - Source-Sink Stream Representation Diagrams - Source-Sink Mapping Diagrams The third category of design techniques for water conservation focuses on developing robust, cost-effective solutions using interception technologies (unit operations). These design methods apply to end-of-the-pipe and in-plant source reduction systems. They are based on the principle that any water conservation task may be envisioned as the transshipment of a pollutant from a set of unit operations that generate them (sources) to a set of unit operations that can accept them (sinks).
To accomplish this transshipment, the pollutant-rich streams are intercepted by an optimal combination of separation technologies. Some of the end-of-the-pipe design techniques which have been developed are the following: . -Mass Exchange Networks (MENs) - Heat-Induced Separation Networks (HISENs) -Neutralization Network Design Tools - Membrane Network Design Tools
These techniques allow the design engineer to determine, (i) What is the minimum cost to achieve the desired water conservation task, and (ii) What is (are) the optimal technology(s) required to achieve the desired water conservation task. Recently, design approaches for source reduction systems via in-plant modifications have been developed. Some of the source reduction design tools developed to date are: . -Waste Interception and Allocation Networks (WINS) - Heat-Induced Waste Minimization Networks (HIWAMINS) - Energy-Induced Waste Minimization Networks (EIWAMINS)
These tools allow for the identification of a cost-effective system which involves end-of-the-pipe technology(s) and/or in- plant process modifications and for interception process technologies to achieve the desired water conservation task. A holistic approach for using these tools for water conservation and reuse design has been developed and is
ABSTRACT The influence of iron-oxidizing bacteria, Thiobacillus ferrooxidans, grown in a ferrous ion-free medium, on the corrosion of type 304 stainless steel (UNS S30400) was evaluated. Electrochemical measurements were performed, both in the inoculated and in the sterile media. Corrosion potential (Ecorr) for type 304 stainless steel exposed in the bacterial culture was shifted near +230 mVvs S. C.E. Cyclic voltammogram showed significant differences, a reduction peak was detected near -400 mV vs S. C.E. in the presence of the bacterial culture. This effect was most probably due to small quantities of Fe(III) compounds in the culture caused by iron-oxidizing bacteria. These results indicated that bacterial metabolic products affected the corrosion process, although they were able to cause initiation of corrosion of type 304 stainless steel.
INTRODUCTION Iron-oxidizing bacteria were implicated in microbially induced corrosion. The organism, Thiobacillus ferrooxidans, has been described as an obligate autotrophic bacterium that can transport ferrous iron into the cell, oxidize it to the ferric state, and transport it out of the cells. Several studies have been conducted to investigate the effect of iron-oxidizing bacteria on the corrosion of various mater ials3?4?5. Traditionally, iron-oxidizing bacteria have been reported to be important in the corrosion process, promoting differential aeration cells and providing oxygen depleted conditions due to their ability to oxidize ferrous ion to ferric ion. However, an investigation into whether iron-oxidizing bacteria accelerate initiation of corrosion has not been conducted. Recently, it has been reported that microbial colonization of passive metals could shift corrosion potential(EMCOR) in the noble direction. The phenomena of ennoblement has been variously ascribed to an increase in cathodic current density7, depolarization of the oxygen reduction react ion8?g, the combined effect of elevate dHz Oz and decreased p Hi, and production of manganic oxidell, etc. From a technical perspective, ennobled potentials can exceed critical pitting potentials for stainless steel, increasing the risk of localized corrosion. Once initiated, localized attack may proceed rapidly due to the enhanced cathodic depolarization.
The purpose of the present study was to investigate the mechanism of initiation of corrosion of type 304 stainless steel in freshwater containing iron-oxidizing bacteria and focusing particularly on the electrochemical phenomenon of ennoblement. Ferrous ion-starved iron-oxidizing bacteria were used to measure corrosion potential. The cyclic voltammetry was applied to evaluate the effect of the bacteria on the corrosion initiation process. Experiments were conducted using type 304 stainless steel immersed both in a sterile and in an inoculated media under two different conditions, air-purge (aerated) and argon-purge (deaerated).
ABSTRACT Localized corrosion such as pitting, crevice and/or under deposit corrosion is the main limiting factor in determining the set-vice life of equipment (such as carbon steel heat exchangers) in industrial water systems. Because of the complexity and dynamic nature of industrial operations, as well as lack of effective monitoring tools, little systematic understanding on the impact of system conditions and process variations on localized corrosion and the inhibition performance profiles of the chemical treatments have been available. As a result, premature failure of equipment occurs, in spite of the use of a relatively large design safety factor. Recently, a localized corrosion monitor capable of on-line real time measurements of localized corrosion rates in industrial systems accurately and reliably was developed, This new monitor has enabled one to conduct performance (in terms of expected equipment service life) based on- line cooling water treatment optimization and control to minimize the damaging effects of process variations. It also permits one to gain a deeper understanding about localized corrosion, and facilitate the development of new inhibitors, treatment programs, and their application methodology to control and minimize localized corrosion. The new mechanistic understanding on the localized corrosion processes thus obtained have speeded up the development of new generations of localized corrosion inhibitors. New chemical treatments containing the new inhibitors were developed and evaluated. The performance of the new treatments against localized corrosion were further optimized with the use of the new localized corrosion monitor both in the lab and in the field. Typical results obtained in several field applications of the localized corrosion monitor in optimization and control of various cooling water treatment programs to minimize localized corrosion while still satisfying or exceeding other system performance requirements are described and discussed. The results serve to demonstrate how one can conduct treatment program optimization and control using the new real time localized corrosion monitor to meet the individual system needs, and to provide more precise and direct information about the treatment cost vs. performance.
INTRODUCTION Ferrous metals such as carbon steel (or mild steel) are among the most commonly used structure materials in industrial systems. It is generally known that in industrial systems having a ferrous metal in contact with an aqueous solution, corrosion of the metal is one of the major problems. It has also long been recognized that the majority of corrosion phenomena encountered in industrial systems is non- uniform or localized. In industrial cooling water systems, pitting, crevice and/or under deposit corrosion are the most commonly observed forms of localized corrosion. 1?2>314A recent Japanese survey shows that more than 70°/0of cooling water side failure of carbon steel heat exchangers are due to pitting corrosion.3 Obviously, reduction of localized corrosion will lead to corresponding extension of equipment service life. data very Hence, controlling localized corrosion is a major concern in-industry~. . . Because of economic restriction on capital investment or insufficient knowledge of the performance on the given materials in the design or selection stage, use of a chemical treatment program with low concentrations (treatment dosages in the order of -100mg/1 product or less5>7?8)is often the most cost-effective approach to reduce localized corrosion-related failures in industrial cooling water systems. A treatment program (chemical dosages, control parameters and contingency counter measures) for a given cooling water system is usua
ABSTRACT The cracking characteristics of Alloy 690 in deaerated 1wt% NaCl solution with different Na2S2Os concentrations, namely 0.01, 0.1, 0.2 and 0.5 M, at controlled anodic potentials was investigated by using slow strain rate testing (SSRT) with a strain rate of 1 x 10-6s . The results showed that the ultimate tensile strength and the ductility increased with increasing the concentration of Na2O3 at the same anodic potential, but decreased with increasing potential at a fixed concentration of Nai%Q. pitting corrosion could occur on AIIoy 690 in 1wt% NaCl solution with the concentration of Na&Os = 0.1M, depending on the potential. The susceptibilities of Alloy 690 to pitting corrosion and environmentally-assisted cracking in 1wt?%0 NaCl solution were inhibited with the concentration of Na2S203 ~ 0.2M, regardless of the potential.
INTRODUCTION Inconel Alloy 690 (UNS N06690) has better corrosion resistance in many aqueous environments because of its higher Cr content (normally between 27 and 31 wt%) with respective to Alloy 600 (UNS N06600) (Cr content: normally between 14 and 17 wt%). Therefore, Alloy 690 has been considered as a substitute. for UNS N06600 as the tubing material for pressurized water reactors (PWRS). However, pitting corrosion or corrosion cracking of Alloy 690 may still occur in some environments 1-3.For Alloy 690, the presence of NazS203 in l wt% NaCl solution greatly affects the pitting corrosion behavior, and the effect of Na2S203 on pitting corrosion is concentration dependent 2.At a lower concentration of Na2S203, pitting corrosion is enhanced, while the detrimental effect is diminished as its concentration increases up to 0.1M. At a much higher concentration of Na2S2Os, greater than 0.2M, pitting corrosion is even inhibited in lwt% NaCl solution, For many alloy/Cl- systems, pitting corrosion always acts as a promoter for stress corrosion cracking 4?5. The effect of Na2S203 on the cracking behavior of Alloy 690 under external stress condition is thus of interest and worth further investigation.
ABSTRACT C-Mn steel is heavily utilized in the oil and gas industry, primarily in upstream operations and downstream refining. Many of these vessels are exposed to wet hydrogen sulfide environments and as a consequence become damaged. Assessment of these damaged vessels is a key point for continued safe operations. This paper addresses several of the key material properties of C-Mn steels required to perform such assessments. Guidelines on the influence of welding, stress relief treatments, crack location and hydrogen charging on the mechanical properties and fracture toughness are detailed. Results showed elongation and reduction in area were greatly affected by hydrogen charging, however, yield and tensile strength were only mildly affected. Regarding toughness, the parent metal and heat affected regions of hydrogen charged material exhibited a factor of three decrease in toughness compared to baseline values, while the toughness of the weld metal remained relatively unchanged.
The oil and gas industry is required to safely manage equipment exposed to a variety of corrosive environments. In the production~ transport and refining stages, HzS arising from crude oil is one of the principal constituents which leads to the deterioration of equipment. The exposure of conventional carbon steel to an aqueous HzS environment leads to the formation of blistering, hydrogen induced cracking (HIC), stress-oriented hydrogen induced cracking (SOHIC) and/or sulfide stress cracking (SSC). Such defects reduce the life of the equipment and can cause catastrophic failure . To properly assess the integrity of equipment, one has to: (1) evaluate the toughness of both parent metal and weldments, develop non-destructive procedures; and set a criteria for the interaction and acceptance of flaws or discontinuities. In accordance with NACE Standard RP0296 , 26 percent of process equipment have HIC and/or SSC. Assessment of damaged equipment is therefore a key point for safe operation in wet H2Senvironments.
Damage produced in wet H2S environments currently is treated in two categories, (1) planar flaws and (2) volumetric flaws. SSC, SOHIC and link-up of HIC damage can all be categorized into planar flaws which can be assessed using conventional fracture mechanics approaches. Two such industry practices which lend themselves nicely to the treatment of planar flaws include BS PD6493  and the proposed API RP 579  assessment procedures. Both utilize a failure assessment diagram incorporating the aspects of brittle fracture and plastic collapse. In order to utilize these approaches effectively, accurate estimations of hydrogen charged material properties are required. With respect to the assessment for brittle fracture, the fracture toughness of hydrogen charged material is needed. With respect to the assessment of plastic collapse, the flow properties of the hydrogen charged/damaged material is required. In the case of the assessment of volumetric flaws, only the later is required.
Hence, the goal of this program was to determine the appropriate values of both mechanical properties and fracture toughness of several grades of hydrogen charged / damaged C-Mn plate steels used in the construction of equipment in the oil and gas industry.
ABSTRACT Three flexible PVC sheets were evaluated to determine their suitability as liners to protect existing steel tanks handling treated brine at 55°C in a membrane technology Chlor- Alkali plants. The evaluation included: characterization of liners and plasticizers (by Soxhlet technique, Infrared Spectroscopy (IRS), Secondary Ion Mass Spectroscopy (SIMS) and Gel Permeation Chromatography (GPC); quantification of brine pollutants by Atomic Emission Spectroscopy (AES) and weight-loss/volume ratios; observation of the superficial damage produced by extended immersion in acid hot brine by Scanning Electron Microscopy (SEM); and the estimation of remaining properties in high temperature oxidative atmospheres (per ASTM D 30451). As a result of this evaluation, remaining property curves as a function of time and temperature are presented for high temperature atmospheric exposure. These curves are related to actual service and to changes in liner hardness. Economics of using flexible PVC liners are compared to flake glass filled thermosetting coatings. The conclusions are that, even though flexible PVC linings are disposable, they protect steel against hot acid brine corrosion, and they are economically attractive compared to flake glass filled coatings. In addition PVC linings may be more reliable because remaining PVC properties can be measured using nondestructive hardness measurements. PVC linings are not recommended above 65°C in corrosive service because life is notably reduced.
BACKGROUND Steel tanks in brine treatment areas of Chlor-Alkali plants must be protected against corrosion. Historically this has been achieved by lining the tanks with thermosetting flake-glass filled coatings using resins such as polyesters, vinyl esters, and epoxy-phenolics.
These linings require considerable labor and cost for installation and maintenance, since they are expensive and must be repaired or retouched annually. Each repair or touchup involves sandblasting, chloride removal, application of many coats and thickness measurement for each coat, environmental conditioning (temperature and humidity), and relatively long times for curing. Repair times are so long that they usually determine the minimum plant shut down time.
For these reasons a drop-in lining was considered. Flexible PVC was selected because it is economical and can be installed quickly with no metal surface preparation.
ABSTRACT Traditional vapor phase corrosion inhibitors (VCIS) were developed for short-term protection of steel I articles. VCIS have been applied for protecting metallic structures between stages of manufacturing, between manufacturing and deployment, and in enclosed service environments. Some f the problems associated with this corrosion inhibiting application include: protecting dissimilar metal ic structures, avoiding toxic materials such as nitrite salts and formaldehyde emitting compounds, an the need for longer duration corrosion protection. Several types of organic compounds were derivatives for temporary volatility and formulated to yield materials with sufficient ambient temperature vapor pressure for VCI application. The ability of these new VCIS to prevent vapor phase metallic corrosion w investigated by an accelerated hydrothermal exposure method. Metals investigated included an aluminum aircraft alloy, cold rolled steel, brass and a copper-nickel alloy. Potentiodynamic slow scan electroch micro analysis and SEM were also used to study the surface behavior and corrosion processes for metallic specimens treated with experimental and control VCIS. Several of the new compounds showed significant vapor phase corrosion inhibition on all four metal alloys.
INTRODUCTION Traditional vapor phase corrosion inhibitors (VCIS) were developed for short-term protection of steel articles. VCIS have been applied for protecting metallic structures between stages of manufacturing, between manufacturing and deployment, and in enclosed service environments.1 Effective vapor phase organic inhibitors typically have a vapor pressure between about 10-2to 10-7mm Hg.z-3 Dicyclohexylamine nitrite (DICHAN) has been found especially effective as a vapor-phase inhibitor for steel surfaces but increases attack on copper alloys.z Universal VCIS, based on nitro benzoate and melamine-formaldehyde compounds that simultaneously protect ferrous, copper, and other alloy systems, have been reported.4 VCIS based on molydate salts of organic amines have also been reported to provide multi-metal protections-b
Some of the problems associated with this corrosion inhibiting application include: protecting dissimilar metallic structures, avoiding toxic materials such as nitrite salts and formaldehyde emitting compounds, and the need for longer duration corrosion protection. There are many organic compounds with low toxicity that have been used successfully as corrosion inhibitors but have negligible vapor pressures at ambient temperature. The proposed research sought to derivative candidate organic corrosion inhibitors for inducing transient volatility and employ blends of these compounds as VCIS.
ABSTRACT Many factors, including pH, temperature, make-up water quality, and heat exchanger metallurgy, influence the performance of polymeric inhibitors in treating recirculating cooling water systems. The availability of good quality make-up water and the imposition of stringent wastewater discharge regulations have forced many cooling systems to operate at increasingly higher cycles of concentration. The severity of these operating conditions often results in waters that have higher scale formation potential. Presented here is information regarding the influence of impurities, such as suspended matter and metal ions, on the performance of polymeric inhibitors used in phosphate-based treatment programs.
INTRODUCTION Historically, water is one of the most common heat transfer fluids used in industrial processes The unique combination of high thermal conductivity, heat capacity, and large useable temperature range make water ideally suited as an heat transfer fluid for industrial processes. Governmental regulations and economic considerations often dictate that cooling tower operators increase the cycles of concentration of their cooling water. When this happens, the ionic constituency of the cooling water may increase dramatically and the volubility of certain scale forming salts may be exceeded. As super saturation is achieved, thermodynamics dictates that precipitates will form. Deposit control polymers (DCPS) including poly(acrylic acid) and acrylate-based co- and terpolymers are often used in water treatment applications to reduce the formation of these scales. These DCPS affect the scale formation kinetics by extending the precipitation induction time beyond the holding time of the tower2 which is a property known as threshold inhibition. These DCPS have also been shown to modify~ the crystal structures such that the precipitates formed are less adherent and to disperse particles that would otherwise agglomerate.
Phosphates and phosphonates are essential components of stabilized-phosphate and all-organic cooling water treatment (CWT) programs. However, the performance of multifunctional DCPS is the key to the efficacy of these CWT programs. These high performance DCPS control the thickness of the calcium- phosphate film on metal surfaces and prevent precipitation of the calcium-phosphate and calcium- phosphonate salts in the recirculating water.2?3?4Various polymers are used in these CWT programs to minimize scale formation and for deposit control. The performance of polymers used in recirculating cooling water has been shown to depend on the quality of the water in the system.
Factors governing the performance of polymers can be divided into two distinct categories: (1) those that affect the volubility of the scale-forming salts and (2) those that affect the action of the polymer. Solution pH affects the deprotonization of polymers, the affinity of polymers towards ionic species, and the adsorption of polymers onto growing crystal surfaces. Solution ionic strength also affects polymer performance.5 Additionally, all open cooling towers using natural waters contain certain level of contaminants such as transition metal ions and particulate matter can affect deposit control polymer performance. Transition metal ions are known to significantly effect the performance of these polymers. 4?6-8This is a particular concern because metallic materials are typically the materials of choice for cooling tower piping and heat transfer surfaces. All open cooling towers using natural waters contain particulate contaminants (e.g., clay) which adsorb DCPS and thereby reduce the availability of DCPS for the other desired functions.
ABSTRACT Foreign and domestic test and research reactor fuel is currently being shipped from locations over the world for storage in water filled basins at the Savannah River Site (SRS). The fuel was provided to many of the foreign countries as a part of the Atoms for Peace program in the early 1950?s. In support of the wet storage of this fuel at the research reactor sites and at SRS, corrosion surveillance programs have been initiated. The International Atomic Energy Agency (IAEA) established a Coordinated Research Program (CRP) in 1996 on Corrosion of Research Reactor Aluminum-Clad Spent Fuel in Water and scientists from ten countries worldwide were invited to participate. This paper presents a detailed discussion of the IAEA sponsored CRP and provides the updated results from corrosion surveillance activities at SRS.
In May 1998, a number of news articles around the world reported stories that microbiologically influenced corrosion (MIC) was active on the aluminum-clad spent fuel stored in the Receiving Basin for Offsite Fuels (RBOF) at SRS. This assessment was found to be in error with details presented in this paper. A biofilm was found on aluminum coupons, but resulted in no corrosion. Cracks seen on the surface were not caused by corrosion, but by stresses from the volume expansion of the oxide formed during pre-conditioning autoclaving. There has been no pitting caused by MIC or any other corrosion mechanism seen in the RBOF basin since initiation of the SRS Corrosion Surveillance Program in 1993.
INTRODUCTION Foreign and domestic test and research reactor fuel is currently being shipped from locations over the world for storage in water filled basins at the Savannah River Site (SRS). The fuel was provided to many of the foreign countries as a part of the Atoms for Peace program in the early 1950?s. Now, as part of the U.S, Department of Energy 's non-proliferation policy on foreign research reactor spent nuclear fuel, much of this fuel is coming back from research and test reactors in Europe, Asia, and Latin America. This fuel has been in water storage at the reactor sites for times ranging from a few years to over 40 years, The majority of fuel is manufactured horn uranium-aluminum alloy and is clad with aluminum. The quality of water in the fuel storage basins ranges from highly deionized to untreated and circulated water. In these extreme environments, the aluminum-clad fuel is very susceptible to pitting corrosion. In the early 1990?s corrosion of this aluminum-clad fuel was an issue at several of the storage basins in the U.S. and has been seen on Materials Test Reactor (MTR) type foreign research reactor fuel scheduled for shipment back to SRS. ]
In late 1989, processing of aluminum clad production fuel was suspended at SRS for safety upgrades to the canyon reprocessing facilities and issues related to U.S. non-proliferation concerns. The irradiated fuel and target materials were caught in back end of the nuclear pipeline with no plans for processing imminent. Normal water storage times of 9-18 months soon became years. With less than optimum water quality during the early 1990?s, pitting corrosion of the fuel became an issue at SRS and at other Department of Energy sites.2 An expansive program was initiated at SRS to clean up the water storage basins and to install new and improved water purification equipment. As a part of these activities, a corrosion surveillance program was started at SRS to monitor corrosion of the fuel stored in the basins and to measure the effectiveness of the cleanup activities. Results of these surveillance activities through 1997 have been reported in previous NACE publications.3-5
ABSTRACT Carbon dioxide corrosion has been widely studied in the field and laboratory. It is recognized that flow regime and metallurgy are important factors that influence in-situ corrosion rates but there are relatively few documented case studies that are able to separate the individual contributions of corrosion, flow regime and metallurgy on the observed corrosion damage. This paper deals with failure of a pipeline where high quality inspection data together with comprehensive as-built records and stable production conditions allowed the separate influences of flow and metallurgy on corrosion to be studied. The flow regimes in the pipeline ranged from low velocity, stratified flow to high velocity, slug flow. The inspection data showed that the affect of turbulent flow was to increase the frequency of corrosion pits and, in the case of weld corrosion, the mean corrosion rate. The pipeline was constructed from two grades of steel and welded using two types of welding consumable. One grade of pipeline steel corroded at a significantly higher rate and with a higher frequency of corrosion pits than another, apparently similar steel. However, no significant relationship was found between weld metallurgy and corrosion rate or frequency,
INTRODUCTION Wytch Farm oilfield is located on England?s South Coast and is the largest onshore oilfield in Western Europe. In 1997, one of the Wytch Farm production pipelines failed due to internal corrosion. After repair, the pipeline was returned to service but failed again, almost immediately. The failure locations were significantly different in terms of their metallurgy as well as the flow regimes. The second failure prompted a thorough re-assessment of the condition of the pipeline. This involved large scale excavations for inspection and repairs as well as re-analysing intelligent pig data gathered several months earlier. These data, combined with knowledge of the materials of construction, flow regimes and fluid properties, produced a rare insight in to the relationships between metallurgy, flow regime and the corrosion mechanism.