The mechanistic understanding of the reactions that govern the inhibitor retention and release,modeling,and the state-ofthe-art innovation in squeeze treatment are reviewed.The retention and release are governed by(1)...The mechanistic understanding of the reactions that govern the inhibitor retention and release,modeling,and the state-ofthe-art innovation in squeeze treatment are reviewed.The retention and release are governed by(1)the amount of calcite that can dissolve prior to inhibitor-induced surface poisoning;(2)calcite surface poisoning after^20 molecular layers of surface coverage by the adsorbed inhibitors to retard further calcite dissolution;(3)less base,CO3^2-,is released into the aqueous solution;(4)formation of the more acidic inhibitor precipitates;(5)phase transformation and maturation of the more acidic inhibitor precipitates;and(6)dissolution of the less soluble crystalline inhibitor precipitates.The trend to advance squeeze technologies is through(1)enhancing scale inhibitor retention,(2)optimizing the delivery of scale inhibitors to the target zone,and(3)improving monitoring methods.Lastly,a prototype yardstick for measuring the squeeze performance is used to compare the squeeze life of 17 actual squeeze treatments.Even though the various squeeze treatments appear to be different.all published squeeze durations can be rated based on the normalized squeeze life per unit mass of inhibitors.展开更多
The corrosion inhibition of a green scale inhibitor, polyepoxysuccinic acid (PESA) wasstudied based on dynamic tests. It is found that when PESA is used alone, it had good corrosioninhibition. So, PESA should be inclu...The corrosion inhibition of a green scale inhibitor, polyepoxysuccinic acid (PESA) wasstudied based on dynamic tests. It is found that when PESA is used alone, it had good corrosioninhibition. So, PESA should be included in the category of corrosion inhibitors. It is not only akind of green scale inhibitor, but also a green corrosion inhibitor. The synergistic effect betweenPESA and Zn2+ or sodium gluconate is poor. However, the synergistic effect among PESA, Zn2+and sodium gluconate is excellent, and the corrosion inhibition efficiency for carbon steel is higherthan 99%. Further study of corrosion inhibition mechanism reveals that corrosion inhibition ofPESA is not affected by carboxyl group, but by the oxygen atom inserted The existence ofoxygen atom in PESA molecular structure makes it easy to form stable chelate with pentacyclicstructure.展开更多
Inorganic scale deposits are a major water-related problem encountered in producing oil and gas wells. The harshness of scale deposits is dependent on the field operating conditions. Scale deposits can vary from mild ...Inorganic scale deposits are a major water-related problem encountered in producing oil and gas wells. The harshness of scale deposits is dependent on the field operating conditions. Scale deposits can vary from mild scaling tendencies to extreme. In general, the scale deposit will cause a reduction in formation pores, declining productivity and eventually blockage of the wellbore and hence unexpected downtime if it is allowed to persevere. To overcome this, the productivity of an oil and gas well is ensured by handling scale deposits via removal or prevention methods. Scale prevention is the best and cost-e ective method for handling scale deposits that ensures production continuity. Inhibition through 'threshold' scale inhibitor treatment is the most common method that is proven to prevent or reduce likely deposits. This paper examines the art of synthetic scale inhibitors, in particular, threshold scale inhibitors in oil and gas production. It discusses the chemistry of those inhibitors, inhibition mechanisms, treatment methods and key properties for their applications. It also highlights the chemistry of the synthetic routes often used to produce them in the laboratory and/or industry. Finally, it highlights the environmental concerns for the applicability of threshold scale inhibitors.展开更多
By using acrylic acid copolymer, sodium citrate, hydrolyzed polymaleic anhydride (HPMA), corrosion inhibitor D and Zn2+ synergist as raw materials, a multi-component phosphate-free corrosion and scale inhibitor was de...By using acrylic acid copolymer, sodium citrate, hydrolyzed polymaleic anhydride (HPMA), corrosion inhibitor D and Zn2+ synergist as raw materials, a multi-component phosphate-free corrosion and scale inhibitor was developed. The performance of the composite phosphate-free corrosion and scale inhibitor was evaluated using the rotary hanging sheet corrosion test, the static scale inhibition test and the corrosion electrochemical test. And the surface morphology of the carbon steel was observed by scanning electronic microscope (SEM). Orthogonal experiment results indicated that the optimal mass ratios of amino acid: Zn2+ synergist: HPMA: corrosion inhibitor D: acrylic acid copolymer was 0.5:10:12:1:8. It was also observed that phosphate-free corrosion and scale inhibitor based on an anodic reaction through the electrochemical corrosion experiment, its annual corrosion rate and scale inhibition rate reached 0.0176 mm·a–1 and 98.3%, respectively, showing excellent corrosion and scale inhibition performance.展开更多
The mixture consisted of benzotriazole (BTA), chitosan (CTS), polyacrylic acid and zinc salt has been investigated as a corrosion and scale inhibitor of A3 carbon steel in cooling water. The scale and corrosion inhibi...The mixture consisted of benzotriazole (BTA), chitosan (CTS), polyacrylic acid and zinc salt has been investigated as a corrosion and scale inhibitor of A3 carbon steel in cooling water. The scale and corrosion inhibition efficiency was evaluated by static anti-scaling teat together with rotary coupon test. Compared with the phosphorus corrosion and scale inhibitor, the corrosion inhibition rate and scale inhibition rate of it increased respectively by 2.51% and 1.16%. As the corrosion and scale inhibitor is phosphate-free, it won’t cause eutrophication, considering the product performance and environmental influence, the phosphate-free corrosion and scale inhibitor is superior to the traditional one.展开更多
The formation of mineral scale is a complex problem during the oilfield operations.Scale inhibitors are widely used to prevent salt precipitation within reservoirs.in downhole equipment,and in production facilities.Th...The formation of mineral scale is a complex problem during the oilfield operations.Scale inhibitors are widely used to prevent salt precipitation within reservoirs.in downhole equipment,and in production facilities.The scale inhibitors not only must have high effectiveness to prevent scale formation,but also have good adsorptiondesorption characteristics,which determine the operation duration of the scale inhibitors.This work is focused on the development of a new scale inhibitor for preventing calcium carbonate formation in three different synthetic formation waters.Scale inhibition efficiency,optical density of the solution,induction time of calcium carbonate formation,corrosion activity,and adsorption-desorption ability were investigated for the developed scale inhibitor.The optimum concentration of hydrochloric acid in the inhibitor was determined by surface tension measurement on the boundary layer between oil and the aqueous scale inhibitor solution.The results show that the optimum mass percentage of 5%hydrochloric acid solution in the inhibitor was in the range of 8%to 10%.The new scale inhibitor had high efficiency at a concentration of 30 mg/L.The results indicate that the induction period for calcium carbonate nucleation in the presence of the new inhibitor was about 3.5 times longer than the value in the absence of the inhibitors.During the desorption process at reservoir conditions,the number of pore volumes injected into the carbonate core for the developed inhibitor was significantly greater than the volume of a tested industrial inhibitor,showing better adsorption/desorption capacity.展开更多
The use of organophosphorus inhibitor is diminishing because of its toxic effects on aquatic and other life. In this study, a composite eco-friendly phosphate-free corrosion and scale inhibitor HS has been developed u...The use of organophosphorus inhibitor is diminishing because of its toxic effects on aquatic and other life. In this study, a composite eco-friendly phosphate-free corrosion and scale inhibitor HS has been developed using hydrolyzed polymaleic anhydride (HPMA), sodium gluconate, Zn2+ synergist and sulfamic acid. And the formula ratio of each component is 9:5:4:2. The performance of the corrosion and scale inhibitor was evaluated by weight loss experiment and the static scale inhibition test, respectively. The results indicated that HS had positive corrosion and scale inhibition effect at a dosage of 40 mg.L–1 or higher. Potentiodynamic polarization curves indicated that HS inhibits the corrosion of steel based on controlling the anodic reaction. And the surface morphology of the carbon steel was studied by scan-ning electronic microscope (SEM). The inhibition effects were due to the formation of protective films.展开更多
Rapid fouling tests were used to investigate the scale-preventing property of ZX type scale inhibitors in
evaporation of salt electrolyte. ZX type scale inhibitors were tested at high temperature under the boiling co...Rapid fouling tests were used to investigate the scale-preventing property of ZX type scale inhibitors in
evaporation of salt electrolyte. ZX type scale inhibitors were tested at high temperature under the boiling conditions.
The results indicate that ZX type scale inhibitors have remarkable scale preventing performance during evaporation
of salt electrolyte even at the temperature up to 150℃. Among them, ZX Ⅲ type scale inhibitor is the best with the
rate of scale-preventing reaching to 88.9%. In addition, the scale preventing mechanism of ZX type scale inhibitors
was analyzed and its application prospect in the field of continuous commercial fouling preventing discussed.展开更多
Scale formation due to the mixing of injection water with formation water causes formation damage and reduction in petroleum production.By using scale inhibitors,scale formation/scaling could be prevented.In this work...Scale formation due to the mixing of injection water with formation water causes formation damage and reduction in petroleum production.By using scale inhibitors,scale formation/scaling could be prevented.In this work,static experiments were performed with rapid controlled precipitation tests,which were undertaken using three different scale inhibitors namely Falat scale inhibitor,Scahib 760 scale inhibitor and Scahib 780 scale inhibitor.Results show that parameters such as temperature and pH have significant effects on scale inhibitor efficiency.In this study,at pH of 7.8e9 it was found that an increase in pH can lead to a decrease in SI efficiency.In addition,acquired data shows that Falat scale inhibitor is more efficient at 45C but scale inhibitors(Scahib 760,780)have better efficiencies at 25C.SEM tests were performed to find structure deformation and morphology of precipitation crystals,which indicated that scale inhibitor can have various effects on crystal's shapes.Finally,dynamic tests were performed with coreflood equipment that indicated higher recovery by using the scale inhibitors.The dynamic tests results show that the recovery factor in the presence of Scahib 760 scale inhibitor is about 58%and breakthrough time is 2099(sec).In the absence of scale inhibitor,the recovery factor is about 52%and breakthrough time is 2720(sec).展开更多
A highly efficient and environment-friendly scale inhibitor(MA-VA-VS)was synthesized via free radical solution polymerization method,where maleic anhydride(MA),vinyl acetate(VA)and vinyl sulfonate(VS)acted as monomers...A highly efficient and environment-friendly scale inhibitor(MA-VA-VS)was synthesized via free radical solution polymerization method,where maleic anhydride(MA),vinyl acetate(VA)and vinyl sulfonate(VS)acted as monomers,while ammonium persulfate was used as initiator.The inhibition performance and the structure as well as properties was characterized using static jar measurement and dynamic test,Fourier transform infrared spectroscopy and thermogravimetric analysis.The surface morphology and composition of scale formed in the solution were examined using scanning electron microscopy and Xray diffraction,respectively.The binding energies of inhibitor with calcite(104)face were calculated using Materials Studio 2017(MS)at 323 K.The results show that the inhibition efficiency gradually increases with increasing inhibitor concentration.While as the Ca2þconcentration increases,the efficiency first increases and then decreases.With the increase in temperature or pH,the efficiency generally decreases.It is confirmed that the inhibition efficiency can reach 91.4%when 150 mg/L MA-VA-VS is used in a flow condition.Both the calculated binding energy and inhibition performance evaluation results demonstrate that the scale inhibition performance of MA-VA-VS is better than a commercial scale inhibitor(HPMA).The excellent inhibition performance of this inhibitor is due to its chelation and dispersion properties.展开更多
Precipitation of calcium carbonate(Ca CO3) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect o...Precipitation of calcium carbonate(Ca CO3) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one(scale inhibitor SQ-1211) to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and p H on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca2+was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80°C at p H 8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of Ca CO3 changed from calcite to aragonite.展开更多
To probe the scale inhibition mechanisms,calcium carbonate scale occurring before and after the ad- dition of scale inhibitors was collected.The results from scale SEM confirm that,without scale inhibitor, calcium car...To probe the scale inhibition mechanisms,calcium carbonate scale occurring before and after the ad- dition of scale inhibitors was collected.The results from scale SEM confirm that,without scale inhibitor, calcium carbonate scale shows rhombohedron and hexagon,which are the characteristic feathers of calcite.After addition of inhibitors,morphology of scale is changed,and the more efficient the scale inhibitor is,the more greatly the morphology is modified.To elucidate the scale constitute,they were further analyzed by FT-IR,XRD.Besides calcite,vaterite and aragonite occur in calcium carbonate scale after addition of inhibitors,and the higher scale inhibition efficiency is,the more vaterite presents in scale.It can be concluded that the alteration of morphology is ascribed to the change of crystal form. There are three stages in the crystallizing process including occurrence and disappearing of unstable phase,occurrence and disappearing of metastable phase,development of stable phase.Without scale inhibitors,metastable phases usually transform into stable phase,thus the main constitute of formed scale is calcite.When scale inhibitors are added,both formation and transformation of metastable phases are inhibited,which results in the occurrence of aragonite and vaterite.From the fact that more vaterite presents in scale with a more efficient scale inhibitor added,we can see that the function of scale inhibitor is realized mainly by controlling the crystallizing process at the second stage.展开更多
基金financially supported by Rice University Brine Chemistry Consortium member companies,which are listed in the Acknowledgement section。
文摘The mechanistic understanding of the reactions that govern the inhibitor retention and release,modeling,and the state-ofthe-art innovation in squeeze treatment are reviewed.The retention and release are governed by(1)the amount of calcite that can dissolve prior to inhibitor-induced surface poisoning;(2)calcite surface poisoning after^20 molecular layers of surface coverage by the adsorbed inhibitors to retard further calcite dissolution;(3)less base,CO3^2-,is released into the aqueous solution;(4)formation of the more acidic inhibitor precipitates;(5)phase transformation and maturation of the more acidic inhibitor precipitates;and(6)dissolution of the less soluble crystalline inhibitor precipitates.The trend to advance squeeze technologies is through(1)enhancing scale inhibitor retention,(2)optimizing the delivery of scale inhibitors to the target zone,and(3)improving monitoring methods.Lastly,a prototype yardstick for measuring the squeeze performance is used to compare the squeeze life of 17 actual squeeze treatments.Even though the various squeeze treatments appear to be different.all published squeeze durations can be rated based on the normalized squeeze life per unit mass of inhibitors.
文摘The corrosion inhibition of a green scale inhibitor, polyepoxysuccinic acid (PESA) wasstudied based on dynamic tests. It is found that when PESA is used alone, it had good corrosioninhibition. So, PESA should be included in the category of corrosion inhibitors. It is not only akind of green scale inhibitor, but also a green corrosion inhibitor. The synergistic effect betweenPESA and Zn2+ or sodium gluconate is poor. However, the synergistic effect among PESA, Zn2+and sodium gluconate is excellent, and the corrosion inhibition efficiency for carbon steel is higherthan 99%. Further study of corrosion inhibition mechanism reveals that corrosion inhibition ofPESA is not affected by carboxyl group, but by the oxygen atom inserted The existence ofoxygen atom in PESA molecular structure makes it easy to form stable chelate with pentacyclicstructure.
文摘Inorganic scale deposits are a major water-related problem encountered in producing oil and gas wells. The harshness of scale deposits is dependent on the field operating conditions. Scale deposits can vary from mild scaling tendencies to extreme. In general, the scale deposit will cause a reduction in formation pores, declining productivity and eventually blockage of the wellbore and hence unexpected downtime if it is allowed to persevere. To overcome this, the productivity of an oil and gas well is ensured by handling scale deposits via removal or prevention methods. Scale prevention is the best and cost-e ective method for handling scale deposits that ensures production continuity. Inhibition through 'threshold' scale inhibitor treatment is the most common method that is proven to prevent or reduce likely deposits. This paper examines the art of synthetic scale inhibitors, in particular, threshold scale inhibitors in oil and gas production. It discusses the chemistry of those inhibitors, inhibition mechanisms, treatment methods and key properties for their applications. It also highlights the chemistry of the synthetic routes often used to produce them in the laboratory and/or industry. Finally, it highlights the environmental concerns for the applicability of threshold scale inhibitors.
文摘By using acrylic acid copolymer, sodium citrate, hydrolyzed polymaleic anhydride (HPMA), corrosion inhibitor D and Zn2+ synergist as raw materials, a multi-component phosphate-free corrosion and scale inhibitor was developed. The performance of the composite phosphate-free corrosion and scale inhibitor was evaluated using the rotary hanging sheet corrosion test, the static scale inhibition test and the corrosion electrochemical test. And the surface morphology of the carbon steel was observed by scanning electronic microscope (SEM). Orthogonal experiment results indicated that the optimal mass ratios of amino acid: Zn2+ synergist: HPMA: corrosion inhibitor D: acrylic acid copolymer was 0.5:10:12:1:8. It was also observed that phosphate-free corrosion and scale inhibitor based on an anodic reaction through the electrochemical corrosion experiment, its annual corrosion rate and scale inhibition rate reached 0.0176 mm·a–1 and 98.3%, respectively, showing excellent corrosion and scale inhibition performance.
文摘The mixture consisted of benzotriazole (BTA), chitosan (CTS), polyacrylic acid and zinc salt has been investigated as a corrosion and scale inhibitor of A3 carbon steel in cooling water. The scale and corrosion inhibition efficiency was evaluated by static anti-scaling teat together with rotary coupon test. Compared with the phosphorus corrosion and scale inhibitor, the corrosion inhibition rate and scale inhibition rate of it increased respectively by 2.51% and 1.16%. As the corrosion and scale inhibitor is phosphate-free, it won’t cause eutrophication, considering the product performance and environmental influence, the phosphate-free corrosion and scale inhibitor is superior to the traditional one.
文摘The formation of mineral scale is a complex problem during the oilfield operations.Scale inhibitors are widely used to prevent salt precipitation within reservoirs.in downhole equipment,and in production facilities.The scale inhibitors not only must have high effectiveness to prevent scale formation,but also have good adsorptiondesorption characteristics,which determine the operation duration of the scale inhibitors.This work is focused on the development of a new scale inhibitor for preventing calcium carbonate formation in three different synthetic formation waters.Scale inhibition efficiency,optical density of the solution,induction time of calcium carbonate formation,corrosion activity,and adsorption-desorption ability were investigated for the developed scale inhibitor.The optimum concentration of hydrochloric acid in the inhibitor was determined by surface tension measurement on the boundary layer between oil and the aqueous scale inhibitor solution.The results show that the optimum mass percentage of 5%hydrochloric acid solution in the inhibitor was in the range of 8%to 10%.The new scale inhibitor had high efficiency at a concentration of 30 mg/L.The results indicate that the induction period for calcium carbonate nucleation in the presence of the new inhibitor was about 3.5 times longer than the value in the absence of the inhibitors.During the desorption process at reservoir conditions,the number of pore volumes injected into the carbonate core for the developed inhibitor was significantly greater than the volume of a tested industrial inhibitor,showing better adsorption/desorption capacity.
文摘The use of organophosphorus inhibitor is diminishing because of its toxic effects on aquatic and other life. In this study, a composite eco-friendly phosphate-free corrosion and scale inhibitor HS has been developed using hydrolyzed polymaleic anhydride (HPMA), sodium gluconate, Zn2+ synergist and sulfamic acid. And the formula ratio of each component is 9:5:4:2. The performance of the corrosion and scale inhibitor was evaluated by weight loss experiment and the static scale inhibition test, respectively. The results indicated that HS had positive corrosion and scale inhibition effect at a dosage of 40 mg.L–1 or higher. Potentiodynamic polarization curves indicated that HS inhibits the corrosion of steel based on controlling the anodic reaction. And the surface morphology of the carbon steel was studied by scan-ning electronic microscope (SEM). The inhibition effects were due to the formation of protective films.
基金the National Natural Science Foundation of China (No.59504005).
文摘Rapid fouling tests were used to investigate the scale-preventing property of ZX type scale inhibitors in
evaporation of salt electrolyte. ZX type scale inhibitors were tested at high temperature under the boiling conditions.
The results indicate that ZX type scale inhibitors have remarkable scale preventing performance during evaporation
of salt electrolyte even at the temperature up to 150℃. Among them, ZX Ⅲ type scale inhibitor is the best with the
rate of scale-preventing reaching to 88.9%. In addition, the scale preventing mechanism of ZX type scale inhibitors
was analyzed and its application prospect in the field of continuous commercial fouling preventing discussed.
文摘Scale formation due to the mixing of injection water with formation water causes formation damage and reduction in petroleum production.By using scale inhibitors,scale formation/scaling could be prevented.In this work,static experiments were performed with rapid controlled precipitation tests,which were undertaken using three different scale inhibitors namely Falat scale inhibitor,Scahib 760 scale inhibitor and Scahib 780 scale inhibitor.Results show that parameters such as temperature and pH have significant effects on scale inhibitor efficiency.In this study,at pH of 7.8e9 it was found that an increase in pH can lead to a decrease in SI efficiency.In addition,acquired data shows that Falat scale inhibitor is more efficient at 45C but scale inhibitors(Scahib 760,780)have better efficiencies at 25C.SEM tests were performed to find structure deformation and morphology of precipitation crystals,which indicated that scale inhibitor can have various effects on crystal's shapes.Finally,dynamic tests were performed with coreflood equipment that indicated higher recovery by using the scale inhibitors.The dynamic tests results show that the recovery factor in the presence of Scahib 760 scale inhibitor is about 58%and breakthrough time is 2099(sec).In the absence of scale inhibitor,the recovery factor is about 52%and breakthrough time is 2720(sec).
基金by 111 Project[D18016]Application and Fundamental Research of Sichuan Province[grant number 2017JY0171]Scientific and Technological Innovation Team for the Safety of Petroleum Tubular Goods in Southwest Petroleum University[grant number 2018CXTD01]。
文摘A highly efficient and environment-friendly scale inhibitor(MA-VA-VS)was synthesized via free radical solution polymerization method,where maleic anhydride(MA),vinyl acetate(VA)and vinyl sulfonate(VS)acted as monomers,while ammonium persulfate was used as initiator.The inhibition performance and the structure as well as properties was characterized using static jar measurement and dynamic test,Fourier transform infrared spectroscopy and thermogravimetric analysis.The surface morphology and composition of scale formed in the solution were examined using scanning electron microscopy and Xray diffraction,respectively.The binding energies of inhibitor with calcite(104)face were calculated using Materials Studio 2017(MS)at 323 K.The results show that the inhibition efficiency gradually increases with increasing inhibitor concentration.While as the Ca2þconcentration increases,the efficiency first increases and then decreases.With the increase in temperature or pH,the efficiency generally decreases.It is confirmed that the inhibition efficiency can reach 91.4%when 150 mg/L MA-VA-VS is used in a flow condition.Both the calculated binding energy and inhibition performance evaluation results demonstrate that the scale inhibition performance of MA-VA-VS is better than a commercial scale inhibitor(HPMA).The excellent inhibition performance of this inhibitor is due to its chelation and dispersion properties.
基金supported by the Major Bidding Projects in Shandong Province (No. SDZS-2012-SHBT01)
文摘Precipitation of calcium carbonate(Ca CO3) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one(scale inhibitor SQ-1211) to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and p H on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca2+was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80°C at p H 8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of Ca CO3 changed from calcite to aragonite.
文摘To probe the scale inhibition mechanisms,calcium carbonate scale occurring before and after the ad- dition of scale inhibitors was collected.The results from scale SEM confirm that,without scale inhibitor, calcium carbonate scale shows rhombohedron and hexagon,which are the characteristic feathers of calcite.After addition of inhibitors,morphology of scale is changed,and the more efficient the scale inhibitor is,the more greatly the morphology is modified.To elucidate the scale constitute,they were further analyzed by FT-IR,XRD.Besides calcite,vaterite and aragonite occur in calcium carbonate scale after addition of inhibitors,and the higher scale inhibition efficiency is,the more vaterite presents in scale.It can be concluded that the alteration of morphology is ascribed to the change of crystal form. There are three stages in the crystallizing process including occurrence and disappearing of unstable phase,occurrence and disappearing of metastable phase,development of stable phase.Without scale inhibitors,metastable phases usually transform into stable phase,thus the main constitute of formed scale is calcite.When scale inhibitors are added,both formation and transformation of metastable phases are inhibited,which results in the occurrence of aragonite and vaterite.From the fact that more vaterite presents in scale with a more efficient scale inhibitor added,we can see that the function of scale inhibitor is realized mainly by controlling the crystallizing process at the second stage.
