Crud Formation Research Articles

Efficient recovery of organic phase from crud in solvent extraction unit of Sarcheshmeh copper complex in Iran by powerful water-absorbent reagents

The formation of stable multi-phase emulsions (crud) is a serious problem in almost all commercial solvent extraction (SX) plants. Crud is a mixture of organic and aqueous phases, air, and organic or inorganic solid particles, often found to distribute itself randomly throughout the separating phases of SX plants. Crud formation is encountered in almost all SX units in metal extraction plants. It causes the loss of solvent and thus increases the process costs. Therefore, the removal of crud and recovery of the expensive organic phase including diluent and extracting reagents from it is of great importance. In this research, the applicability of a range of powerful water absorbent reagents was studied for the recovery of organic phase from the crud formed in copper extraction/electrowining unit of Sarchashmeh copper complex (IRAN). The reagents included gypsum, carbomer, sodium polyacrylate, sodium sulfate, magnesium sulfate and calcium chloride. The results showed that gypsum, carbomer and sodium polyacrylate are effective additives which let the organic phase to be recovered with up to 95 % yield. To ensure that gypsum does not cause a negative effect on the copper loading and stripping of the recovered solvent, the extraction/stripping properties of the organic phase separated with gypsum was compared with the organic phase separated by centrifugation without additives. Surface tension analysis of the gypsum-recovered organic phase also confirmed its suitability for recovery of organic phase from crud. Finally, the calcium content of gypsum-recovered organic phase was measured and compared with that of the organic phase separated by centrifugation without any additive.

The Testing Results of ACORGA, LIX Extractants and CR60 Crud Mitigation Reagent Influence during SX-EW Copper Extraction

Research analysis reveals factors influencing third-phase crud formation and composition during metal extraction, including solution composition, solid suspensions, organic compounds, colloidal compounds (e.g., silicic acid), and extractant purity. Compositional analysis of copper-containing sulfuric acid solutions (1.25 g/dm3 copper) identifies principal sulfate-forming components. Copper extraction was studied using extractants LIX 984N, ACORGA M5774, and M5640 at different ratios of the organic phase to the aqueous O:A (from 1:2 to 1:10). Suppressive impact of 10 vol.% CR60 additive on third-phase crud formation during copper extraction with LIX 984N, ACORGA M5774, and M5640 is analyzed, with ACORGA M5774 being the most effective. Physicochemical analysis characterizes CR60’s active substance as poly(sodium 4-styrenesulfonate) with steel-suppression properties, and its structural formula is determined. Optimal copper extraction conditions establish ACORGA M5640’s 24% efficiency, followed by ACORGA M5774 at 15%. CR60 reduces crud formation, with 5 cm3 of ACORGA CR60 added to sulfuric acid solution reducing interfacial crud formation by 2–3 times. Optimal extraction parameters include 1:2 O:A ratio, 20 ± 5 °C temperature, 5 cm3 CR60 additive, 5 min process duration, and 1-day settling time. ACORGA M5774 (10 vol.% in kerosene) is recommended as an extractant, with 2–3 stages of countercurrent extraction.

Effects of metal ion concentration on deposition chemistry of Corrosion Related Unidentified Deposits in PWR fuel cladding

An experimental facility was set up to investigate the effect of metal ion concentration on the formation of CRUD on fuel cladding in simulated pressurized water reactor primary water. The structural and chemical characteristics of the specimens were examined and it was found that the thickness of the CRUD increased with the metal ion concentration. At lower concentrations, a primitive CRUD chimney structures were observed, while higher concentrations led to more developed ones. Chemical analysis indicated more Ni oxide deposition at lower concentrations. Despite thicker CRUD at higher concentrations, enhanced chimney structures improved thermal conductivity by promoting heat transfer through wick boiling behavior.

Extraction of Copper from Pregnant Leach Solution (PLS) and Reduction of Crud Formation

ABSTRACT Presented universal recommendations for the reduction of crud formation, reviewing various aspects affecting the loss of diluent and extractant due to the formation of a third phase (crud), encountered in many hydrometallurgical plants using copper solvent extraction. In this paper introduce the reasons of the crud formation , description of the stable emulsions containing solid particles and choice of technological scheme. An analysis of operations to be considered in the operation of copper solvent extraction plants is presented, due to the deterioration of copper grade below 0.5% in ore and the increase in aluminum content up to 20–25%. Results of use of extraction properties of modified extractants of ACCORGA series and unmodified extractant Lix984N on pregnant leached solution of the most important deposits (Almaly and Aktogay) are given. It is established that for solutions of Almaly deposit, ACCORGA5640 and unmodified Lix984 extractants have high selectivity to copper. Distribution of iron, silica, and copper ions during extraction was studied, and it was found that high selectivity to copper/iron and copper/silica is possessed by extractant Lix 984N, ACCORGA5640. It was found that for solutions of the Aktogay deposit, the ratio of interphase suspension in both extractants is the same, and phase separation in experiments with the use of extractant Lix 984N was 10 s shorter with the use of extractant ACCORGA5640. It was found that the addition of ACCORGACR60 reagent in the amount of 5-10 ppm also leads to a decrease in the volume of crud by 13%, for a stronger suppression of crud.

Insight into the interaction between zirconium dibutyl phosphate complex and diluents: An experimental and computational study

In solvent extraction processes, there are challenges caused by the formation of the third phase or interfacial precipitation. The branched alkanes have been used as diluents to disrupt the third-phase formation, while there is little study about the effect of diluents on the appearance of precipitation. Here, we report the inhibiting effect of the novel hyperbranched alkane diluent (HAD) on the formation of zirconium-dibutyl phosphate (Zr-DBP) precipitation and investigate the formation mechanism by the density functional theory (DFT) theory. The extraction experiments show that HAD as the diluent has a remarkable inhibiting ability to form Zr-DBP precipitation, compared with n-dodecane and kerosene. The spectra show no noticeable difference in the composition and structures of the precipitations formed in the three diluents. The energetics from the DFT calculations suggest the P-OH and P=O ligands on one HDBP molecule can bridge two Zr-DBP complexes into a dimer and then aggregate into the precipitation. Besides, the interactions between diluent-diluent molecules play a significant role in precipitation formation. The straight-chain n-dodecanes have a strong intermolecular dispersion force and tend to attract each other but not the Zr-DBP complex. However, the branched alkanes with weak intermolecular interactions have a better dispersive capacity for Zr-DBP complexes, due to the much higher dispersion force of diluent-complex interaction than that of the diluent-diluent interaction. This work provides a new insight into the formation of interfacial crud from the interactions between solutes and diluents of the organic phase in solvent extraction.

Boron and lithium aqueous thermochemistry to model crud deposition in pressurized water reactors

A comprehensive database of boron and lithium aqueous thermochemistry has been developed for use at elevated temperatures. The Helgeson-Kirkham-Flowers (HKF) formalism provides a framework to describe thermodynamic properties over a broad range of temperatures and pressures. Accuracy at high temperatures is vital to modeling nickel oxide and ferrite fuel deposits that occur in pressurized water nuclear reactors (PWRs). CALPHAD (CALculation of PHAse Diagrams) calculations are performed at PWR crud conditions to predict the stability regions of the solid lithium metaborate (LiBO2) and lithium tetraborate (Li2B4O7) precipitates. In addition, similar calculations are performed using sodium and potassium instead of lithium in order to assess the thermodynamics associated with preventing the formation of such precipitates. This database contributes to understanding of crud formation and composition and will aid in the prediction of phenomena such as Crud-Induced Power Shifts (CIPS).

Evolution of the chemical form of zirconium in aqueous solution during denitration and its influence on extraction by TRPO

Denitration by formic acid is a process that can reduce the acidity of High-Level Liquid Waste (HLLW) generated by the Plutonium Uranium Reduction EXtraction (PUREX) process, making it compatible with the feed requirements of the TRPO (trialkylphosphine oxide) process. Unfortunately, the denitration leads to the formation of interfacial crud in the TRPO extraction due to the presence of zirconium; however, the mechanism remains elusive. In this work, the evolution of the chemical form of Zr(IV) during the denitration process by formic acid was investigated. The aggregates formed in the Zr(IV) solutions after denitration were characterized by dynamic and static light scattering (DLS and SLS). Afterwards, the solutions were vacuum-dried and the solids were characterized by elemental analysis, scanning electron microscope (SEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Zr(IV) is present in solutions with different forms such as the tetramers of Zr4(OH)8(NO3)8 and Zr4(OH)8(HCOO)8 and their aggregates, depending on the [HCOOH]/[HNO3] ratio. The evolution of the chemical form of Zr(IV) can impact the extraction of Zr(IV) by TRPO and is responsible for the formation of interfacial crud.

An efficient method for recovery of organic phase from crud in solvent extraction unit of Sarcheshme copper complex in Iran by guar gum

One of the problems of all industries that use metal extraction with organic solvents is stable emulsions and finally the formation of crud. The formation of crud is usually accompanied by the loss of a significant amount of the causal solvent and thus increases the process costs. Therefore, the removal of crud and recovery of its organic phase is of particular importance. In this research, the applicability of polysaccharides such as guar gum, xanthane gum, Arabic gum and starch for recovery of organic phase from the crud formed in copper extraction/electrowining unit of Sarchashmeh copper complex (IRAN) was studied. The results showed that guar gum is an effective additive which let the organic phase to be recovered with up to 95% yield. To ensure that gum do not have a negative effect on the system and that the absorption and desorption of copper is done correctly, the extraction/stripping properties of the organic phase separated with guar gum is compared with the organic phase separated without additives. Surface tension analysis of the guar gum-recovered organic phase also confirmed the suitability of guar gum for recovery of organic phase from crud.

Study of the Extraction Process of the Main Components of the Productive Solution (Copper, Iron and Silica) of the Almaly Deposit

The purpose of the research was to study the extraction of the main components of the productive solution of the Almaly deposit with oxyoxime extractants. As the practice of existing plants shows, one of the main drawbacks of the process when implementing the liquid extraction process at various fields is the formation and accumulation of a large volume of the third phase (crud), which leads to a slowdown, in some cases to a stop in the solvent extraction process, thereby reducing the efficiency of the entire production copper by SX-EW technology. One of the main factors leading to the formation of such a phase are harmful metal impurities, solid suspensions in the solution supplied for extraction, improper selection of extractants and the operation mode of the extraction cycle. To prevent such a process, it is important to study the extraction of the main components of productive solutions with different extractants. Studies on the extraction of metals from the productive solution of the Almaly deposit of composition, g/dm3 : Cu 0.235-0.262, Fe 17.97-21.55, SiO2 0.34-0.36 were carried out using reagents Acorga 5640 (10%), Acorga 5640 (5%) with CR60 additive and Lix 984N (10%). It was found that when using the first two, they led to the accumulation of iron and silica ions in the organic phase, and at Lix 984N (10%), the maximum transition of silica ions into the electrolyte, and iron into the raffinate. The accumulation of iron and silica ions in the organic phase is undesirable and may be the cause of crud formation.

A comparison on the use of DEHBA or TBP as extracting agent for tetra- and hexavalent actinides in the CHALMEX Process

The Chalmers Grouped ActiNide EXtraction process is a solvent extraction process for the homogeneous recycling of spent nuclear fuel. The use of TBP for the extraction of tetra- and hexavalent actinides can be problematic for several reasons, including troublesome degradation products causing crud formation, decreased extraction yield and the possibility of explosive red oil reactions. Here, the substitution of TBP by a N,N-dialkyl monoamide, DEHBA, is investigated. The findings suggest that DEHBA can be a suitable extracting agent for use in the CHALMEX solvent, although identified drawbacks need to be further investigated.

Reactive extraction of lactic acid from sweet sorghum silage press juice

• Uncontrolled fermentation broths from biorefineries can be used as lactic acid source. • Reactive extraction is applicable for lactic acid isolation from complex mixtures. • An extraction efficiency of up to 41.1% is reached with amine-based ion exchangers. • Back-extraction efficiency reaches up to 98.2% for 0.3 M NaOH or 0.3 M NaHCO 3. • Crud formation can be reduced to 2.6 vol% by varying the solvent phase composition. Fermentation of residues or side streams can be used to produce valuable products, such as carboxylic acids. Reactive solvent extraction is widely studied as isolation method for lactic acid from fermentation broths. Here, we investigate the reactive extraction of lactic acid from sweet sorghum silage press juice using different extractants, modifiers, and diluents. Besides a high extraction efficiency, a low crud formation with this highly complex raw material is targeted. Depending on the solvent phase composition, an extraction efficiency of up to 41.1 % was reached using DOA/ALIQ:1–octanol: n –nonane. The crud layer was highly influenced by the applied diluent and amounted to 2.6–42.3 vol% of the total mixture volume. The back-extraction experiments showed, that up to 98.2 % of lactic acid were recovered. Summarizing, the results show that reactive solvent extraction of lactic acid is applicable to highly complex process streams, and crud formation can be reduced by adjusting the solvent phase composition.

Recovery of uranium from carbonaceous radioactive waste of the UF6 production line in a uranium conversion plant: Laboratory and pilot plant studies

Carbonaceous radioactive waste is produced by adsorption of effluent gases of UF6 production line, on a bed of charcoal. Current research was aimed at developing a process for recovery of uranium from this waste in a laboratory and at pilot scale. As a first step, leaching of uranium from carbonaceous radioactive waste was undertaken by successive steps using Al(NO3)3 and nitric acid, the former used to eliminate corrosivity of the F− ions. The stoichiometry of reaction between F− and Al3+ ions form complexes ranging from AlF2+, AlF2+ to AlF3 depending upon their molar ratio. The results showed that the increase of NO3−/U ratio increased the uranium leaching efficiency. Presence of some impurities especially silica in leach liquor caused formation of crud during solvent extraction. In order to remove such impurities, first uranium was precipitated as ammonium diuranate, and then it was dissolved in nitric acid to produce uranyl nitrate solution. This solution was purified by extraction with TBP (30 vol%) /Kerosene, followed by stripping with dilute nitric acid. The pilot scale data confirmed the results of the lab scale with minor variations. The purity of the obtained uranyl nitrate solution was acceptable for returning it as a feed to UF6 production plants.

Screening of Reactive Extractants for the Lignosulfonate Extraction from Lignosulfonate Model Solution and Spent Sulfite Liquor

Crud formation during reactive extraction hinders phase separation and makes the application of conventional extraction equipment more challenging. This study investigates the influence of amines a...

Biobased Support Layers for the Fractionation and Selective Extraction of Lignosulfonates

ABSTRACTThe paper presents an experimental study on the preparation and characterization of cellulose films and their use for reactive lignosulfonate extraction. The extraction of lignosulfonates leads to emulsion and crud formation when standard equipment is applied. By using cellulose films as a support layer between the aqueous feed phase and the organic extractant phase, emulsion formation is prevented. The results showed that selective separation and a fractionation of the lignosulfonates can be realized with this novel approach simultaneously.

Scalable Room-Temperature Synthesis of Multi-shelled Na3(VOPO4)2F Microsphere Cathodes

Summary The large-scale application of rechargeable batteries in electric vehicles and energy-storage systems is still hindered by their high cost, particularly from the active materials. Here we proposed a concept of integration of extraction-separation and materials-preparation to further reduce the materials' cost. The power of this concept was demonstrated by the large-scale room-temperature synthesis (150 g per batch) of multi-shelled Na3(VOPO4)2F microspheres based on in situ generated bubbles as soft templates. The as-prepared Na3(VOPO4)2F shows superior rate capability with discharge capacity of 81 mAh g−1 at 15 C current rate and capacity retention of 70% after 3,000 cycles. Ex situ UV-vis was first employed to characterize the variation of oxidation state for vanadium during the charging and discharging process. This is the first report of a rapid and facile large-scale room-temperature controllable synthesis of Na3(VOPO4)2F microspheres, and this approach could be extended to synthesize other similar compounds.

Selection of a synergistic solvent extraction system to remove calcium and magnesium from concentrated nickel sulfate solutions

Synergistic solvent extraction of Ca and Mg from concentrated Ni sulfuric solutions was assessed using extractants Cyanex 272, D2EHPA, and naphthenic acid. D2EHPA has a strong preference for extracting Ca; however, Ca was crowded out by Ni at pH>3.5. Cyanex 272 has a higher affinity for Mg at pH>5, while both earth alkaline metals are rejected by naphthenic acid at pH=2–6 as well as by the system Cyanex 272+naphthenic acid. The system D2EHPA+naphthenic acid has affinity only for Ca. The system D2EHPA+Cyanex 272 can extract Ca and Mg simultaneously; however, selectivities Ca/Ni and Mg/Ni are dependent on the liquor pH and D2EHPA concentration in organic mixture solution. In this system, a strong synergistic effect was found for Ca and Mg, whereas contradictory behavior was observed for Ni. To avoid crud formation, the selective extraction of Ca and Mg should be performed at pH<6. Ni can be selectively stripped from the loaded D2EHPA+Cyanex 272 using diluted H2SO4 solution, whereas Ca and Mg can be completely stripped with concentrated H2SO4 solution.

Comparison in the aggregation behaviour of amide extractant systems by dynamic light scattering and ATR-FTIR spectroscopy

The aggregation behavior of N,N,N’,N’-tetraoctyldiglycolamide (TODGA) in n-dodecane was studied in the presence of two different phase modifiers, N,N-di-hexyloctanamide (DHOA) and 1-octanol using dynamic light scattering (DLS) spectroscopy. The results were compared with the aggregation behavior of a modifier free extractant system N,N-di-octyl-2-hydroxyacetamide (DOHyA) in n-dodecane. Aggregation studies were done as a function of concentration of nitric acid and Nd (III) ions in the aqueous phase. The size distribution of reverse micellar aggregates revealed different aggregation mechanisms in the presence and absence of phase modifiers. For TODGA-modifier systems, the sizes of reverse micellar aggregates were bigger than DOHyA and among the two phase modifiers studied, use of 1-octanol resulted in the formation of bigger aggregates compared to DHOA. The observations from DLS measurements were co-related with the results from ATR-FTIR spectroscopy for all the three extractant systems. The sizes of reverse micellar aggregates increased with increase in extraction of nitric acid and/or Nd (III) ions and no third phase was visible in all the three systems even under very high loading conditions. The aggregation studies under co-current extraction conditions from fast reactor simulated high level waste solution (FR-SHLLW) showed the formation of smaller reverse micellar aggregates and third phase or crud formation after 3–4 successive contacts for all the three systems.

Multi-Dimensional Simulation of LWR Fuel Behavior in the BISON Fuel Performance Code

Nuclear fuel operates in an extreme environment that induces complex multiphysics phenomena occurring over distances ranging from inter-atomic spacing to meters, and times scales ranging from microseconds to years. To simulate this behavior requires a wide variety of material models that are often complex and nonlinear. The recently developed BISON code represents a powerful fuel performance simulation tool based on its material and physical behavior capabilities, finite-element versatility of spatial representation, and use of parallel computing. The code can operate in full three dimensional (3D) mode, as well as in reduced two dimensional (2D) modes, e.g., axisymmetric radial-axial (R-Z) or plane radial-circumferential (R-θ), to suit the application and to allow treatment of global and local effects. A BISON case study was used to illustrate analysis of Pellet Clad Mechanical Interaction failures from manufacturing defects using combined 2D and 3D analyses. The analysis involved commercial fuel rods and demonstrated successful computation of metrics of interest to fuel failures, including cladding peak hoop stress and strain energy density. In comparison with a failure threshold derived from power ramp tests, results corroborate industry analyses of the root cause of the pellet-clad interaction failures and illustrate the importance of modeling 3D local effects around fuel pellet defects, which can produce complex effects including cold spots in the cladding, stress concentrations, and hot spots in the fuel that can lead to enhanced cladding degradation such as hydriding, oxidation, CRUD formation, and stress corrosion cracking.

Modeling and simulation challenges pursued by the Consortium for Advanced Simulation of Light Water Reactors (CASL)

The Consortium for the Advanced Simulation of Light Water Reactors (CASL), the first Energy Innovation Hub of the Department of Energy, was established in 2010 with the goal of providing modeling and simulation (M&S) capabilities that support and accelerate the improvement of nuclear energy's economic competitiveness and the reduction of spent nuclear fuel volume per unit energy, and all while assuring nuclear safety. To accomplish this requires advances in M&S capabilities in radiation transport, thermal-hydraulics, fuel performance and corrosion chemistry. To focus CASL's R&D, industry challenge problems have been defined, which equate with long standing issues of the nuclear power industry that M&S can assist in addressing. To date CASL has developed a multi-physics “core simulator” based upon pin-resolved radiation transport and subchannel (within fuel assembly) thermal-hydraulics, capitalizing on the capabilities of high performance computing. CASL's fuel performance M&S capability can also be optionally integrated into the core simulator, yielding a coupled multi-physics capability with untapped predictive potential. Material models have been developed to enhance predictive capabilities of fuel clad creep and growth, along with deeper understanding of zirconium alloy clad oxidation and hydrogen pickup. Understanding of corrosion chemistry (e.g., CRUD formation) has evolved at all scales: micro, meso and macro. CFD R&D has focused on improvement in closure models for subcooled boiling and bubbly flow, and the formulation of robust numerical solution algorithms. For multiphysics integration, several iterative acceleration methods have been assessed, illuminating areas where further research is needed. Finally, uncertainty quantification and data assimilation techniques, based upon sampling approaches, have been made more feasible for practicing nuclear engineers via R&D on dimensional reduction and biased sampling. Industry adoption of CASL's evolving M&S capabilities, which is in progress, will assist in addressing long-standing and future operational and safety challenges of the nuclear industry. • Complexity of physics based modeling of light water reactor cores being addressed. • Capability developed to help address problems that have challenged the nuclear power industry. • Simulation capabilities that take advantage of high performance computing developed.

한울1호기 17주기 연료 크러드의 노내 체류시간 평가

발전소 구조재료의 일반부식에서 기인된 부식생성물은 연료 표면에 침적되어 방사화되고, 다시 노외로 방출되어 계통 선량율을 증가시킨다. 본 연구에서는 방사화된 크러드의 생성과정에 대한 이해를 높이고자 연료 크러드의 비방사능 값과 노내 체류시간을 계산하였다. 노내 체류시간 계산시 모핵종이 조사기간 동안 지속적으로 일정한 양만큼 침적되는 것으로 가정하였다. 본 연구에 활용된 연료 크러드 시료는 한울1호기 17차 O/H시 fuel scraping을 통해 채취되었으며, 본 연구를 위해 원소성분 분석과 핵종 분석이 수행되었다. Corrosion products are released to the primary coolant in the corrosion process of structural materials. They are deposited on fuel surfaces and activated on exposure to a neutron flux with formation of radionuclides that can become incorporated into out-of-core surface films. To get a clear understanding of activated crud formation process, the specific activity and core residence time of fuel cruds was calculated as a function of exposure time to the core neutron flux on the assumption that parent nuclide is being deposited continuously. Fuel cruds were sampled in the fuel scraping campaign from Hanul Unit 1 Cycle 17 and analyzed for elemental concentration and radioisotope activity.