Scale Removal Research Articles

Development of a Unique Organic Acid Solution for Removing Composite Field Scales.

Removal of oil field scales commonly requires low pH acid, which may cause many issues under downhole conditions. Because of the deposition of different scale types and the economic effect, there is a need to develop a remedial descaling fluid that can be effectively used to remove different types of scales at a different position in the well. This paper provides a new scale dissolver that is noncorrosive and has high scale dissolution performance for composite scales. This study shows a series of comprehensive experimental lab tests as scale characterization, equilibrium brine compositional analysis, fluid compatibility and stability, solubility test, precipitation tendency for the dissolved solids, corrosion test, and core flooding. The scale samples contain magnetite, kaolinite, calcium carbonate, and sulfate scales. The results showed that the dissolution rate was higher than 74% for composite field scale samples after 6 h at 70 °C, while the new dissolver completely dissolved the two samples at 100 °C after 5 h. The new dissolver outperformed the common commercial dissolver used in the oil and gas industry. The new dissolver has a pH of 9 and showed safe use regarding the precipitation of dissolved solids that can be produced during the scale treatment and a low corrosion rate of 0.063 kg/m2 at 6.9 MPa and 100 °C for 6 h. Also, the new dissolver was tested through core flooding for Indiana limestone and showed core permeability enhancement; the treatment with the new dissolver enhanced the core permeability from an initial value of 0.67 milliDarcy (mD) to record 1.29 mD.

Experimental Study on Electrochemical Softening for Cooling Circulating Water in Converter Station

In this study, the electrochemical softening method was used to treat the simulated drainage of the converter station, and the treatment effect under different water inlet conditions was investigated. The results show that the hardness removal rate is from 10% to 80% when the residence time is from 0.5h to 4h, and the longer the residence time is, the higher the removal rate is. The maximum scale removal capacity reached 2.67g/h/m2 when residence time was 1h. Through the formula fitting of several groups of tests, it is concluded that the removal effect can be expressed by the formula C0/C=0.9627e(17.73at/V) under different water intake (residence time).

Effects of H2 combustion on scale growth and steel surface quality in reheating furnaces

The use of hydrogen as fuel in the reheating furnaces, to replace (partially or totally) natural gas, causes a modification in the composition of the furnace atmosphere, with low or null concentration of CO2 and an increased concentration of H2O. The new atmosphere may change the scale growth kinetic and may affect the surface properties, in terms of scale removal and formation of decarburized layer. These effects can be studied at laboratory scale simulating the atmosphere generated by H2 combustion considering the working conditions of the burner and the excess oxygen. Hence, the comprehension and quantification of this effect is a fundamental pre-requisite for the use of hydrogen as fuel in reheating and treatment furnaces. For this reason, TenarisDalmine and Rina CSM carried out an experimental activity to simulate reheating and heat treatment process selecting two steels grades: one for line pipe production and one for casing production, two steels in which the more remarkable differences for scale growth and adherence are in the C and Ni content [1,2]. The experimental scenario was defined to verify the effects of the combustion atmosphere simulating the heating of a 20 mm thick pipe at 920 °C and the reheating process at 1230 °C for 180 min. The trials included two possible combustion atmospheres having different H2O concentration and corresponding to 100% natural gas and 100% H2. The steel oxidation and scale formation were studied by TGA (Thermo Gravimetric Analysis) tests. Results showed some increase in scale growth up to 10% during heating at 920 °C and up to 16% in case of re-heating at 1230 °C. The differences between line pipe and casing steel grades were minimal with a slight tendency to higher oxidation for line pipe steel. No decarburization was observed in steel sample heated at 920 °C oxidized in both atmospheres (with 100% natural gas or 100% H2 combustion). Metallographic analysis on TGA samples confirms, for the test with atmosphere form 100%H2, at 1230 °C, the increased thickness of the scale; in these tests, the interface between scale and steel appears more complex and entangled.

Modelling and simulation of ultrasonic descaling in heat exchanger

Heat exchanger is widely used in petrochemical industry, long cycle operation will lead to the generation of scaling and the reduction of heat transfer coefficient, but the traditional scale removal method is not convenient to operate with high cost. In this paper, a kind of ultrasonic descaling technology is designed, and the propagation model of ultrasonic wave in heat exchanger is established by using B-P neural network, including the propagation model of ultrasonic load on tube plate and the propagation model of ultrasonic load in medium. Based on the influence of two different ultrasonic loading modes, the propagation mechanism of ultrasonic load on the tube plate of heat exchanger was obtained by simulation research. Finally, the propagation mechanism model of ultrasonic wave in heat exchanger is established successfully through experimental verification.

Skin damage caused by scale loss modifies the intestine of chronically stressed gilthead sea bream (Sparus aurata, L.)

The present study was designed to test if the damage caused by scale loss provokes a change in other innate immune barriers such as the intestine and how chronic stress affects this response. Sea bream (Sparus aurata) were kept in tanks at low density (16 kg m−3, LD) or exposed to a chronic high density (45 kg m−3, HD) stress for 4 weeks. Scales were then removed (approximately 50%) from the left flank in the LD and HD fish. Intestine samples (n = 8/group) were examined before and at 12 h, 3 days and 7 days after scale removal. Changes in the morphology of the intestine revealed that chronic stress and scale loss was associated with intestinal inflammation. Specifically, enterocyte height and the width of the lamina propria, submucosa and muscle layer were significantly increased (p < 0.05) 3 days after skin damage in fish under chronic stress (HD) compared to other treatments (LDWgut3d or HDgut0h). This was associated with a significant up-regulation (p < 0.05) in the intestine of gene transcripts for cell proliferation (pcna) and anti-inflammatory cytokine tgfβ1 and down-regulation of gene transcripts for the pro-inflammatory cytokines tnf-α and il1β (p < 0.05) in HD and LD fish 3 days after scale removal compared to the undamaged control (LDgut0h). Furthermore, a significant up-regulation of kit, a marker of mast cells, in the intestine of HDWgut3d and LDWgut3d fish suggests they may mediate the crosstalk between immune barriers. Skin damage induced an increase in cortisol levels in the anterior intestine in HDWgut12 h fish and significant (p < 0.05) down-regulation of mr expression, irrespective of stress. These results suggest glucocorticoid levels and signalling in the intestine of fish are modified by superficial cutaneous wounds and it likely modulates intestine inflammation.

Application of Electrocoagulation for Printing Wastewater Treatment: From Laboratory to Pilot Scale

This study reports for the first time the application of electrocoagulation (EC) from laboratory to pilot scales for the treatment of printing wastewater, a hazardous waste whose treatment and disposal are strictly regulated. The wastewater was taken from three real printing companies with strongly varying characteristics. The treatment process was performed in the laboratory for operational optimization and then applied in the pilot scale. The weight loss of the electrode and the generation of sludge at both scales were compared. The results show that the raw wastewater should be diluted before EC treatment if its COD is higher than about 10,000 mg/L. Pilot scale removal efficiencies of COD and color were slightly lower compared to those obtained from the laboratory scale. At pilot scale, the effluent CODs removal efficiency was 81.9 – 88.9% (final concentration of 448 – 992 mg/L) and color removal efficiency was 95.8 – 98.6% (final level of 89 – 202 Pt-Co) which proved the feasibility of EC treatment as an effective pre-treatment method for printing wastewater as well as other high colored and hard-biodegradable wastewaters. Keywords: Printing Wastewater, Electro-Coagulation, Laboratory Scale, Pilot Scale, Industrial Wastewater

Applications of cavitating jets to radioactive scale cleaning in pipes

Deposition of scale inside wellbores is causing millions of dollars in damage every year. Any water production or injection in the gas or oil well is creating a possibility of scale formation. It can reduce formation porosity and permeability, it can block flow in the pipes, and it can damage downhole completion equipment. Some mineral scales such as calcium carbonate (CaCO3) can be dissolved with acids but common hard scales such as barium sulfate (BaSO4) are extremely resistant to both chemical and mechanical removal.Another scale problem is natural radionuclides which are contained in rocks and are carried out on the surface during oil production. The cleaning of radioactive scale, is a very complicated and expensive process. In some cases, it is even easier to replace the pipes than to clean depositions of radioactive barium sulfate which generates accumulation of radioactive materials in storage fields.In the current study cavitating jets were used to remove barium sulfate scale from pipes and detailed experimental procedures for cavitating nozzles design and testing were shown. Optimal combination of hydrodynamic nozzles was defined and tested in the field. It was shown that designed combination of hydrodynamic nozzles significantly improved scale removal process.

Effect of Simulated Annealing Conditions on Scale Formation and Neutral Electrolytic Pickling

Scale formation of AISI 304 stainless steel during annealing at temperatures between 1100 and 1200 °C under a water vapor‐containing atmosphere is studied. Characterization of the oxide scale is performed with field‐emission scanning electron microscopy–energy dispersive spectroscopy (FESEM–EDS) and glow discharge optical emission spectroscopy (GDOES) and removal of oxide scale is done via neutral electrolyte pickling. The pickling conditions are kept constant and the effect of the annealing conditions and scale properties on the pickling result are examined. The effectiveness of pickling is evaluated using analysis FESEM images taken on polished sections of pickled surfaces. Research shows that the thickness, morphology, and composition of the oxide scale are dependent on annealing temperature and time. The thicknesses of the scale formed under the established conditions vary from 0.2 to over 30 μm, and morphologies between the chromium rich oxide layer and layered scale structure formed by breakaway oxidation. The pickling response of oxide scales remains good at all annealing temperatures with the shortest exposure time.

Removal of Iron Oxide Scale From Feed-Water in Thermal Power Plant by High-Gradient Magnetic Separation: Scale-Up Effect

In the boiler feed-water system of thermal power plants, iron oxide scale is generated due to the corrosion of piping, which decreases the effectiveness of the heat exchanger in the boiler and contributes to reduced power generation efficiency. Scale removal can prevent this phenomenon, which consequently results in decreased carbon dioxide emission. In a previous study, an iron scale removal system was developed using superconducting magnets, and high-gradient magnetic separation (HGMS) experiments were conducted using the height difference between the inflow and outflow tanks. As a result, particles were intensively captured by the filters at the inflow side. We succeeded in eliminating this capture by properly controlling the applied magnetic field. However, because the suspension also flowed due to the height difference in this experiment, the problems of partial blockage of the filter and the resulting decrease in the flow rate were not resolved even under the controlled magnetic field. In this study, HGMS experiments were conducted under a constant flow rate with a large pump in a large-scale system having a filter diameter of 300 mm to simulate a boiler feed-water system or chemical cleaning line. Furthermore, we investigated the feasibility of the large-scale HGMS system and elucidated the scale-up effect on the amount captured and the spatial distribution of the captured particles on the filters. Based on these results, a plant-scale HGMS system (800 mm filter diameter) was designed.

Dissolution Kinetics of Different Inorganic Oilfield Scales in Green Formulations.

Scale mineral deposition is a critical problem that hinders the daily production of oil and gas fields. Chemical removal of these scales, based on the scale type, is common. In this paper, borax and diethylene tremaine penta acetic (DTPA) acid-based formulations are used for the removal of sulfides, carbonates, and sulfate scales. In particular, the dissolution rates of sulfide (pyrite, pyrrhotite, and galena), sulfate (celestite and barite), and carbonate (calcite) scales were investigated in a rotating disc apparatus at typical well conditions. Scanning electron microscopy–energy-dispersive X-ray and X-ray diffraction analyses were performed for characterizing scale composition and type. The effect of temperature, scale type, and formulation on the dissolution rate is studied. Even though borax formulation has been developed for the sulfide scale removal, it showed a high dissolution rate for the carbonate scale (7.23 × 10–7 mol·L–1·s–1·cm–2). For the sulfide scale, the highest dissolution in borax formulation was obtained with galena (lead sulfide, PbS), followed by pyrrhotite, and the lowest dissolution was reported for pyrite (1.55 × 10–8 mol·L–1·s–1·cm–2). Borax formulation was found to be inefficient in the removal of sulfate scales with a dissolution rate lower than carbonate and sulfide scales by 3 and 2 orders of magnitude, respectively. Similarly, DTPA-based formulation has yielded the highest dissolution for the carbonate scale (7.98 × 10–6 mol·L–1·s–1·cm–2). However, for sulfate, DTPA-based formulation showed better performance than borax. The increase in temperature leads to an increase in the dissolution rate for almost all types of scales; however, DTPA-based formulation showed improved performance with temperature. Both formulations are efficient in removing sulfate- and sulfide-rich scales. The experimental results of DTPA have been validated by density functional theory calculations of binding energies between DTPA and metal ions present in the mixed scale.

The Influence Mechanism of Magnesium Ions on the Morphology and Crystal Structure of Magnetized Anti-Scaling Products

Magnetization technology has been widely used in various transportation pipeline anti-scaling and descaling processes due to its simple equipment, low operating cost and low secondary pollution. To resolve structural pipeline issues in concentrations, the effects of magnesium salt concentration on conductivity, pH value and calcium ion concentration of a magnetized calcium chloride sodium bicarbonate mixed solution were studied. The results indicated that 4.0% MgSO4 had the greatest anti-scaling effect under dynamic water conditions, which increased the calcium concentration of the mixed solution by 5.93%. Furthermore, the synergistic effects of 5.0% magnesium carbonate on the scaling of calcium carbonate were the largest, which reduced the calcium concentration of the mixed solution by 22.19%. Scanning electron microscope (SEM) and Raman spectra showed that magnesium carbonate reduced the effects of magnetization because it inhibited the formation of vaterite-type calcium carbonate and promoted the formation of calcite-type calcium carbonate. Magnesium sulfate can improve the anti-scaling effects of magnetization because it promotes the formation of vaterite calcium carbonate with high solubility. The results of this study can provide a theoretical basis for the scaling process and dissolution behavior regulation of calcium carbonate and have an important reference significance for scale prevention and scale removal in concentrator pipelines.

Energy-Efficient Cooling and Hydraulic Descaling Systems

Determination of real boundary cooling conditions is a fundamental requirement for numerical models and simulations to optimize and control selected processes in metallurgy. To obtain these boundary conditions, a special method has been developed. The input temperature history of cooling is obtained from experiments. The measured data are then mathematically evaluated. Realistic boundary conditions, as the heat transfer coefficient between hot surface and the coolant, allow optimization of the cooling sections and the design of their configurations. To realize the cooling test, unique laboratory equipment was developed. It allows setting of cooling conditions close to the plant conditions. The paper presents examples of optimization of work roll cooling, examples of design of sections for in-line heat treatment of metals and procedure for designing new high-pressure descaling sections. The methodology proposed by the Heat Transfer and Fluid Flow Laboratory of the Brno University of Technology is typically used to determine the heat-transfer coefficient on the surface of high-temperature material in the applications of heat treatment, cooling of rolls of hot rolling mills, and high- pressure descaling. The methodology enables identifying the effect of nozzle water jets on the heat-transfer coefficient or on removal of high-temperature scale and leads to cooling and descaling optimization for industrial partners.

Using Microwave Energy for the Removal of Hardness from Groundwater: Continuous Flow Lab-Scale System

The present study investigates the characteristics of calcium hardness removal from water using a continuous flow microwave (MW) radiation system with heat exchange. The effects of initial calcium concentration, detention time, and initial temperature were investigated by the study. About 97% of calcium hardness removal was achieved at a detention time of 12.5 minutes. It was concluded from the experiments performed that the optimum conditions for this system use a detention time of 12.5 minutes. This leads to an initial temperature of 70°C when using the heat exchanger. These conditions are valid for the range of Ca initial concentrations between 92 and 204 mg/L as CaCO3. The residual concentrations under optimum conditions were 2.4, 2.5, 2.6, and 3 mg/L as CaCO3 for initial concentrations of 92, 141, 172, and 204 mg/L as CaCO3, respectively. The developed system proved to be practical in the continuous flow mode that simulates the actual operations in water treatment plants. It was concluded that MW energy could be one of the most effective methods for large scale removal of hardness from water.

Formation of highly Zn-enriched sulfide scale at a deep-sea artificial hydrothermal vent, Iheya-North Knoll, Okinawa Trough

Artificial hydrothermal vents, created by boreholes that discharge hydrothermal fluids and useful for observing secular changes in mineral precipitates and the chemical compositions of hydrothermal fluids, are periodically cleaned of scale deposits. Here, we report petrographic and geochemical features of hydrothermal scale with a concentric structure and extreme enrichment in Zn, recovered as an intact plug from an artificial hydrothermal vent pipe in the Okinawa Trough. The scale consists of sphalerite with accessory galena and chalcopyrite, and minor cotunnite (PbCl2), barite, an unidentified Zn sulfate, and Bi-rich minerals. It comprises at least five concentric layers alternating between thin, reddish-brown porous layers composed of relatively Fe-rich sphalerite accompanied by galena and chalcopyrite, and coarse-grained, dark gray layers dominated by relatively Fe-poor sphalerite. Cotunnite occurs only in the innermost reddish-brown layer, and barite occurs only in the uppermost and innermost layers. The scale is composed of > 50 wt% Zn, several wt% Fe and Pb, and < 1 wt% Cu, Mn, and Cd, a composition consistent with the solubility of Zn and Cu in a hydrothermal fluid at 304–311 °C and pH 4.7–5.0. We suggest that the concentric layers are related to periodic scale removal operations through which (1) mostly clogged pipe conditions and weak hydrothermal discharge alternate with (2) fully open pipe conditions and vigorous hydrothermal discharge, thus affecting sulfur fugacity and [Cl−] and [SO42−] activities in the hydrothermal fluid and leading to the formation of concentric layers of precipitated minerals.

FABRICATION AND TESTING OF A SEMI-MANUALLY OPERATED FISH SCALE REMOVER

Commercial fish scale removers are very expensive. This study was conducted in order to fabricate and test the performance of a low cost, stand-alone semi-manually operated fish scale remover. The randomized complete block design (RCBD) quasi-experiment was used to test the capacity and efficiency of the semi-manually operated fish scale remover. Three (3) different kinds of fish in Northern Samar (Bangus, Sagision and Kirawan) with three (3) different sizes of scales (Large, Medium and Small) were used in the testing of the fabricated fish scale remover at three (3) different speeds of the scaling drum (High, Medium and Low). The results revealed that the higher the speed of the scaling drum, the higher is the scaling capacity of the manually-operated fish scale remover. Likewise, the bigger the scales of fish being descaled, the higher is the scaling capacity of the manually-operated fish scale remover. The average scaling capacity of the fish scale remover is higher than the average scaling capacity of an experienced fish vendors for kirawan and sagision but is lower than that of the experienced fish vendors for bangus. On the other hand, the average scaling efficiencies of the machine for all the fish used in testing the machine were highest at medium speed setting of the scaling drum. The cost and return analysis on the operation of the semi-manually operated fish scale remover revealed that it will have an annual net income of P 48,724.37, a payback period of 50 days, and a rate of return of 3.82. The actual cost of constructing the semi-manually operated fish scale remover is ₱ 12,756.00.

Real-time monitoring of calcium sulfate scale removal from RO desalination membranes using Raman spectroscopy

Chemical characterization of scaling and removal processes was performed in real time via Raman spectroscopy in a bench-scale reverse osmosis (RO) system. A custom RO cross-flow cell was integrated with a Raman microscope objective, allowing for analysis of localized membrane scaling and scale removal. Permeate flux was also measured to provide a real-time metric for comparison. A commercial flat sheet, thin-film composite reverse osmosis (TFC RO) membrane was scaled using a calcium sulfate (CaSO4·H2O) feed solution. Upon CaSO4 scale detection, the feed was switched to DI water, which served as a cleaning agent to remove the CaSO4 scale from the membrane. In addition to the real-time local (Raman) and global (permeate flux) measurements, membrane samples were characterized post-mortem using Raman spectroscopy, gravimetric analysis and scanning electron microscopy to provide important scaling and scale removal metrics. Results from real-time measurements indicated that changes in Raman intensity were a more sensitive indicator of local scale removal than changes in permeate flux, a standard cleaning performance metric; these findings were corroborated by the post-mortem analyses. Overall, the membrane cleaning experiments showed that Raman spectroscopy provided crucial real-time chemical composition and spatial distribution information, which can inform more effective antiscaling and cleaning strategies.

Structure and some physicochemical and functional properties of water treated under ammonia with low-temperature low-pressure glow plasma of low frequency

AbstractDeionized, tap and two kinds of commercially available mineralized water, after supplementation with ammonia, were treated with low-pressure, low-temperature glow plasma (GP) of low frequency. Treating hard water with ammonia provided the removal of permanent and temporary water hardness already at room temperature. On such treatment, mineralized water supplemented with ammonia was partly demineralized. Precipitated rhombohedral deposit from hard water did not turn into scale even when maintained in suspension for 3 days at around 90°C. In such manner, the use of other chemicals for prevention from the scale formation and/or for the scale removal is entirely dispensable. The rate and yield of precipitation depended on the concentration of admixed ammonia and the GP treatment time. Ammonia served as a ligand of calcium, magnesium and ferric central atoms of corresponding salts constituting the hardness. Moreover, ammonia constituting the atmosphere of the treatment was arrested inside aqueous clathrates. So, stabilized ammonia solutions could potentially be utilized as an environmental-friendly nitrogen fertilizer. The precipitate could also be utilized for the same purpose.

Effect of carbon on isothermal reduction of high-strength steel oxide scale in 30%H2–N2 atmosphere

To replace the traditional pickling process, an environmentally friendly gaseous reduction method was used for the removal of the oxide scale of steel in this work. Isothermal hydrogen reduction of high-strength steel was investigated in the temperature range from 500 °C to 800 °C in 30%H2–N2 atmosphere. The obtained results revealed a clear relationship between the oxide phase composition and the holding temperature during the heating stage, prior to hydrogen reduction. With increasing temperatures, the Fe2O3 and Fe3O4 components of the oxide scale gradually transform into FeO. When the sample was reduced under H2–N2 atmosphere, the surface morphology of the high-strength steel was different from that of the traditional hot-rolled steel strip. It was observed that the surface pore size and porosity increased with increasing temperatures and internal and external oxidation occurred simultaneously in the reduction layer. The addition of carbon to the reduction system decreased the water pressure and clearly promoted the reduction at 800 °C. The surface of the sample was reduced to irregular but uniformly distributed small particles of pure iron. Defects in the oxide scale such as cracks and gaps and carbon reacting with water play a vital role in the reduction process. Since the use of hydrogen reduction of hot-rolled strip eliminates the need for the acid pickling pollution process and the pre-oxidation process in the annealing of cold-rolled strips, it can significantly reduce the energy consumption of steel production and improve the production line efficiency. Thus, this approach is a promising green production technology in hot-dip galvanizing.

Scale characteristics and removal

Scaling, fouling of heat exchange surfaces, may significantly reduce heat transfer and thus affects the energy-efficiency of a sugar factory. Particularly lime salts and silica are known as the main components of scale, but fouling by deposition of insoluble organic substances may occur too. This paper summarizes the different causes of scaling in both beet and cane factories as well as the average composition of scale found at the different process stages. The process chemicals generally applied for removal of scale from heat exchange surfaces will be briefly discussed.

Scale-Prediction/Inhibition Design Using Machine-Learning Techniques and Probabilistic Approach

Summary This paper presents a data-driven methodology to predict calcium carbonate (CaCO3)-scale formation and design its inhibition program in petroleum wells. The proposed methodology integrates and adds to the existing principles of production surveillance, chemistry, machine learning (ML), and probability theory in a comprehensive decision workflow to achieve its purpose. The proposed model was applied on a large and representative field sample to verify its results. The method starts by collecting data such as ionic composition, pH, sample-collection/inspection dates, and scale-formation event. Then, collected data are classified or grouped according to production conditions. Calculation of chemical-scale indices is then made using techniques such as water-saturation level, Langelier saturation index (LSI), Ryznar saturation index (RSI), and Puckorius scaling index (PSI). The ML part of the method starts by dividing the data into training and test sets (80 and 20%, respectively). Classification models such as support-vector machine (SVM), K-nearest neighbors (KNN), gradient boosting, gradient-boosting classifier, and decision-tree classifier are all applied on collected data. Prediction results are then classified into a confusion matrix to be used as inputs for the probabilistic inhibition-design model. Finally, a functional-network (FN) tool is used to predict the formation of scale. The scale-inhibition program design uses a probabilistic model that quantifies the uncertainty associated with each ML method. The scale-prediction capability compared with actual inspection is presented into probability equations that are used in the cost model. The expected financial impact associated with applying any of the ML methods is obtained from defining costs for scale removal and scale inhibition. These costs are factored into the probability equations in a manner that presents incurred costs and saved or avoided expenses expected from field application of any given ML model. The forecasted cost model is built on a base-case method (i.e., current situation) to be used as a benchmark and foundation for the new scale-inhibition program. As will be presented in the paper, the results of applying the preceding techniques resulted in a scale-prediction accuracy of 95% and realized threefold cost-savings figures compared with existing programs.