Retention Of Fines Research Articles

Effect of Raw Material and Process Conditions During the Dry Forming of CTMP Fibers for Molded Pulp Products

ABSTRACT This article provides a concise insight into the thermoforming of airlaid CTMP pulp. First, the airlaid process was studied, showing that fiber fractionation and the retention of fines occurred in the forming head. Then, the effect of temperature and pressure during thermoforming was investigated. Harsher conditions, i.e. higher temperature and pressure, yielded greater densification of the substrate and higher tensile strength. The maximum strength was found at the highest settings tested, that is, 100 MPa and 200°C. The screening of thermoforming conditions was also compared to previously published results on wetforming. Next, the effect of softwood CTMP pulp was delineated, which on average showed the best mechanical properties at elevated freeness and high degrees of bleaching. At last, a comparison between dry forming and wetforming was made for one selected pulp quality. Here, the dryformed substrates were stiffer at low elongation, yet the wetformed substrates yielded a greater extensibility and higher tensile strength. In conclusion, dryformed pulp mostly relies on temperature and pressure for bond formation during thermoforming, which produces materials that are distinctly different from wetformed molded pulp.

Transport and Retention of Coal Fines in Proppant Packs during Gas–Water Two-Phase Flow: Insights from Interface, Pore, to Laboratory Scales

Transport and Retention of Coal Fines in Proppant Packs during Gas–Water Two-Phase Flow: Insights from Interface, Pore, to Laboratory Scales

Study on the Permeability Enhancement of Propped Fractures under the Action of a Coal Fine Plugging Removal Agent.

The retention of coal fines in propped fractures impedes the efficient flow of gas and water, leading to a substantial decrease in coal seam permeability and gas production efficiency. In this article, a coal fine plugging removal agent with good dispersion stability and powerful powder-carrying capacity was developed to study the coal fine plugging removal and permeability enhancement in the propped fracture. The results show that 0.8% SDS + 0.4% NaCl + 0.8% BS-12 was the most effective coal fine plugging removal agent compounding system. Increasing the injection rate of the plugging removal agent and performing recycles of intermittent unblocking when it was used as a plugging agent will effectively enhance the gas-liquid two-phase effective permeability of propped fractures and improve the release of retained coal fines. After three recycles of intermittent unblocking, the coal fine discharging rate can be increased to more than 90%, resulting in a 3.88 times increase of the gas-liquid two-phase permeability compared to that with the single unblocking cycle. This method has important practical significance and theoretical value for solving the problem of coal fine plugging in fractures and ensuring the stable and efficient discharge of coalbed gas-water-coal fines.

Dynamic modelling of reservoir fines retention by mesoporous silica nanofluid to improve oil recovery during low salinity water flooding of a consolidated sandstone

Mesoporous silica (SiO2) nanoparticles (MSNP) was used to stabilize formation fines for increased oil recovery during low salinity water flooding. Likewise, the effect of porous media length on dynamic retention of fines at high temperature reservoir condition was investigated. Breakthrough curves of reservoir fines adsorption by mesoporous SiO2 nanofluid (MSNF) were described using Thomas and Yoon-Nelson models. Similarly, effect of concentration, flow rate, porous media length and temperature on the retention capacity of reservoir fines was modelled using Box Behnken design of experiments. Subsequently, effect of reservoir fines stabilization on oil recovery was evaluated. Formation damage remediation propensity of MSNF was investigated. Finally, the oil recovery mechanisms were determined using the sessile drop contact angle and Wilhelmy plate methods. Experimental results of the dynamic adsorption with coefficient of determination (R2) values between 0.967 and 0.999 signifies that the reservoir fines adsorption by MSNF were well predicted by Thomas and Yoon-Nelson models. Consequently, MSNF stabilized the reservoir fines by attaching onto their surface rather than on the porous media thereby changing the wettability to water-wet, decreasing the contact angle to 16.1°, 17.1° and 20.7° for kaolinite, illite and montmorillonite, respectively. Thus, increasing oil recovery by 22–23% original oil in place.

Dynamic stabilization of formation fines to enhance oil recovery of a medium permeability sandstone core at reservoir conditions

Fines migration has impacted the efficiency of low salinity water flooding at reservoir condition. However, previous studies on the use of nanoparticles to combat this problem were not done at reservoir condition and the effect of porous media length was neglected. Hence, the objective of this study is to use mesoporous silica (SiO2) nanoparticles (MSNP) to stabilize formation fines to increase oil recovery during low salinity water flooding at reservoir condition. Likewise, effect of porous media length on dynamic retention of fines at high temperature high pressure (HTHP) reservoir condition was investigated. The breakthrough curves of reservoir fines adsorption by mesoporous SiO2 nanofluid (MSNF) were described using the Thomas and Yoon-Nelson models. Subsequently, the effect of reservoir fines stabilization on oil recovery was evaluated using a HTHP core flooding equipment. Also, the formation damage remediation propensity of MSNF was investigated. Finally, the oil recovery mechanism was determined using the sessile drop contact angle method. Experimental results of the dynamic adsorption with coefficient of determination (R2) values in the range of 0.967–0.999 signifies that the reservoir fines adsorption by MSNF were well predicted by Thomas and Yoon-Nelson models. Consequently, MSNF stabilized the reservoir fines by attaching onto their surface rather than on the porous media thereby changing the wettability to water-wet, decreasing the contact angle to 16.1°, 17.1° and 20.7° for kaolinite, illite and montmorillonite, respectively. Subsequently, increasing oil recovery by 22–23% original oil in place. Therefore, the use of MSNF to stabilize formation fines at reservoir condition is proffered.

Three-dimensional visualization and characterization of paper machine felts and their relationship to their properties and dewatering performance

Polymeric felts are commonly used in the papermaking process on the paper machine wet end, in the press section, and in the dryer section. They provide an important function during paper manufacturing, including as a carrier or support; as a filter media assisting with water removal on the paper machine; in retention of fibers, fines, and fillers; and in some applications, such as tissue and towel, to impart key structural features to the web. These felts can have highly interwoven complex internal structures comprised of machine direction and cross-machine direction yarns of varying sizes and chemical compositions. Here, we present a non-intrusive three-dimensional (3D) image visualization method using advanced X-ray computed tomography (XRCT). This method was used to characterize the complex 3D felt structure and determine the water removal characteristics of some commonly used paper machine felts. The structural features analyzed include porosity; specific pore-yarn interfacial surface area; 3D pore size distribution; 3D fiber or yarn-size distribution; and their variations through the thickness direction. The top, middle, and bottom layers of the felt have very different structures to assist with water removal and impart paper properties. The size distribution of the yarns, as well as the pores in the different layers of the felt, are also inherently different. These structural features were non-intrusively quantified. In addition, variation in the structural characteristics through the thickness of the felts and its potential role in papermaking is explored. In addition to the 3D structural characteristics, permeability characteristics and water removal characteristics, including rewetting of select felt samples, have also been experimentally determined. It is interesting to observe the relationship between key structural features and permeability and water removal characteristics. These relationships can provide additional insights into press felt design, as well as ways to improve product properties and the dewatering efficiency and productivity of the paper machine.

Effects of Proppant Wettability and Size on Transport and Retention of Coal Fines in Saturated Proppant Packs: Experimental and Theoretical Studies

Hydraulic fracturing is the main stimulation technique that enables the economic production of coalbed methane reservoirs. However, massive invasion and retention of coal fines in proppant packs can clog the pore spaces and lead to an impairment of fracture conductivity. In this study, the effects of proppant wettability and size on retention of coal fines in proppant packs during the dewatering stage were investigated, for their optimization to achieve a long-term and effective control of fines retention. First, a series of transport and retention experiments of coal fines were performed on saturated proppant packs with different proppant sizes and wettabilities. Herein, standard quartz sand was used as the proppant carrier, and its surface wettability was modified to either hydrophobicity or stronger hydrophilicity by treatment with fluorocarbon resin and piranha solution, respectively. The experimental results indicated that both the retained amount and the deposition rate coefficient of coal fines decreased with increasing proppant hydrophilicity (or decreasing proppant hydrophobicity) and size. For the proppants treated with piranha solution, almost no coal fines were retained in proppant packs. Second, the forces/torques acting on coal fines in the vicinity of proppants were analyzed to elucidate the underlying mechanisms responsible for the influence of proppant wettability and size on fines retention. The effective filter surface (EFS) parameter was estimated by analyzing forces/torques to evaluate the filtration performance of proppant packs. Theoretical results illustrated that the EFS value decreased with increasing proppant hydrophilicity and size. The EFS value for proppants treated with piranha solution was near zero, which was due to the chemically “unfavorable” retention condition induced by piranha solution treatment. The EFS exhibited a similar tendency to the retention of coal fines observed in experiments, which validated the model. Finally, the recommendations on fines retention control in proppant packs were provided.

Selective addition of C-PVAm to improve dry strength of TMP mixed tissue paper

Abstract During the manufacture of low basis weight tissue paper, it is difficult to efficiently use the dry strength agent (DSA) because a large amount of DSA adsorbed fines releases in forming roll by centrifugal forces. In this study, cationic polyvinylamine (C-PVAm) was used as a DSA in an environment where the retention of fines was weak. Addition of C-PVAm to the thermomechanical pulp (TMP) or TMP mixed with softwood bleached kraft pulp (SwBKP) improved the turbidity of filtrate from sheet former, however, the strength of handsheet paper was similar to that without C-PVAm. When C-PVAm was selectively added to SwBKP as much as 4 %, the tensile index could be improved by approximately 10.6 % without changing the retention of fines. In addition, C-PVAm added before the beating of SwBKP showed better results than C-PVAm added after the beating in terms of fines retention, tensile index, and formation. In particular, the tensile index was improved about 7.7 % by adding of C-PVAm 4 % as is before beating of SwBKP. Consequently, it was found that C-PVAm with a high reaction rate can be added before beating of SwBKP to improve the physical strength.

Development of Nanofluids for the Inhibition of Formation Damage Caused by Fines Migration: Effect of the interaction of Quaternary Amine (CTAB) and MgO Nanoparticles.

Fines migration is a common problem in the oil and gas industry that causes a decrease in productivity. In this sense, the main objective of this study is to develop nanocomposites based on the interaction of quaternary amine (hexadecyltrimethylammonium bromide—CTAB) and MgO to enhance the capacity of retention of fine particles in the porous medium. MgO nanoparticles were synthesized by the sol–gel method using Mg(NO3)2·6H2O as a precursor. Nanoparticles were characterized by dynamic light scattering (DLS), the point of zero charge (pHpzc), thermogravimetric analysis, and Fourier transform infrared spectroscopy (FT-IR). Different nanoparticle sizes of 11.4, 42.8, and 86.2 nm were obtained, which were used for preparing two system nanofluids. These systems were evaluated in the inhibition of fines migration: in the system I MgO nanoparticles were dispersed in a CTAB-containing aqueous solution, and system II consists of a nanocomposite of CTAB adsorbed onto MgO nanoparticles. The fines retention tests were performed using Ottawa sand 20/40 packed beds and fine particles suspensions at concentrations of 0.2% in a mass fraction in deionized water. Individual and combined effects of nanoparticles and CTAB were evaluated in different treatment dosages. The analysis of the interactions between the CTAB and the MgO nanoparticles was carried out through batch-mode adsorption and desorption tests. The best treatment in the system I was selected according to the fines retention capacity and optimized through a simplex-centroid mixture design for mass fractions from 0.0% to 2.0% of both CTAB and MgO nanoparticles. This statistical analysis shows that the optimal concentration of these components is reached for a mass fraction of 0.73% of MgO nanoparticles and 0.74% in mass fraction of CTAB, where the retention capacity of the porous medium increases from 0.02 to 0.39 mg·L−1. Based on the experimental results, the nanofluids combining both components showed higher retention of fines than the systems treated only with CTAB or with MgO nanoparticles, with efficiencies up to 400% higher in the system I and higher up to 600% in the system II. To evaluate the best performance treatment under reservoir conditions, there were developed core flooding tests at fixed overburden pressure of 34.5 MPa, pore pressure at 6.9 MPa and system temperature at 93 °C. Obtaining critical rate increases in 142.8%, and 144.4% for water and oil flow in the presence of the nanofluid. In this sense, this work offers a new alternative for the injection of nanocomposites as a treatment for the problem of fines migration to optimize the productivity of oil and gas wells.

Advanced analytics of self-colmatation in terrigenous oil reservoirs

One of the most significant issues of petroleum engineering nowadays is a decline in productivity and injectivity of wells due to formation damage, which is typically associated with the migration and retention of fines. The prediction of formation damage is a challenging problem due to the lack of information about concentrations and localizations of potential mobile fines in the reservoir. To solve this problem different algorithms of machine learning and data mining were tested: linear regressions, decision trees, random forest, gradient boosting and artificial neural networks. We developed the predictive model of permeability reduction in Vendian deposits (Russia) based on the analysis of rock properties and flooding conditions. This model allowed to describe the dynamic of permeability reduction as a multi-parametric function of injected pore volumes of water. Three defining parameters in the model were unique colmatation characteristics which have been predicted for each core sample. All the features of the self-colmatation process were studied and arranged by their importance. To build the model of permeability reduction we used two approaches. The first one was to discover all possible 2D cross-plot correlations between colmatation characteristics and features (manual analysis). The second is applying machine learning algorithms where all features were taken into account simultaneously. The benefits and disadvantages of both approaches were discussed in details.

Effect of SiO2 nanoparticles on fines stabilization during low salinity water flooding in sandstones

Low salinity water (LSW) flooding is a commonly used technique to recover remaining oil. Efficiency of this method can be improved by decreasing salinity of the injected fluid during LSW flooding. However, the environment of low salinity is unfavorable for fine-sized particles retention, and may result in fines migration and formation damage. In most sandstone reservoirs, migration and production of fines along with fluid is a major problem in oil and gas industry.Several methods can be used to control migration of fine-sized particles. One effective treatment is to use nanofluids. Nanofluids can affect surface charges and increase the attraction between the particles and sand surface. Fines are negatively charged while nanoparticles usually have positive charge. By attracting nanoparticles to surface of the sand, sand surface becomes more positive which leads to retention of fines. In previous studies, effect of nanoparticles on fines migration in aqueous media was investigated. Another parameter which can influence surface charges is presence of hydrocarbon. Crude oil is an organic substance which is negatively charged just like other organic substances. And this charge difference explains why the presence of oil can affect the performance of nanoparticles in fine migration control.The purpose of this experimental study is to investigate the effect of using SiO2 nanoparticles on controlling fines migration caused by LSW injection in presence of hydrocarbon. In addition, the effect of fine particles stabilization on oil recovery was analyzed. A mixture of paraffin and decane was used as hydrocarbon. Experiments have been conducted in three different series. The first series of experiments aimed to select the best nanoparticle among Al2O3, SiO2, and MgO. The results showed that silica nanoparticles had a great potential to control fines migration during LSW flooding. In the second series, the impact of injected nanofluid concentration on fines migration was investigated. And, in the third series, the effect of soaking times of 6, 12, 24, and 48 h was investigated. In addition, recovery of oil is measured in all tests. Silica oxide nanofluid in 0.1% wt. concentration shows the best performance in controlling fines migration and reducing the pressure drop in the porous media. In the third series of experiments, the soaking time of 24 h for the SiO2 nanofluid showed the best results for controlling fines migration. Also, our experiments showed that migration of fines cannot be considered as an effective mechanism of enhanced oil recovery during LSW flooding.

Polyelectrolyte complexes for assisting the application of lignocellulosic micro/nanofibers in papermaking

A novel procedure based on the addition of polyelectrolyte complexes (PECs) onto the pulp containing lignocellulosic micro/nanofibers (LCMNF) is presented. This procedure allows increasing paper strength avoiding an excessive loss in drainability. LCMNF were obtained from partially delignified kraft pine sawdust using a high-pressure homogenizer. Cationic complexes (CatPECs) were prepared by adding the anionic polyelectrolyte solution (polyacrylic acid) on the cationic polyelectrolyte solution (poly(allylamine hydrochloride)). According to turbidity and surface morphology changes, an interaction between CatPECs and LCMNF could be established. Different CatPEC dosages (from 0.3 to 1.0% on pulp) were added on a recycled unbleached softwood kraft pulp containing 3% of LCMNF. For a PEC dosage of 0.75% on pulp, an optimum balances between negatively and positively charged materials [near to zero value of the logarithm of the colloidal titration ratio (logCTR)] was found. Britt Dynamic Drainage Jar test showed a high retention of fines and LCMNF for all PEC dosages. A maximum in retention value was obtained for the addition of 0.75% of PECs on pulp, dosage that was suggested as optimum by the logCTR. In addition, the best drainability value (18°SR) was obtained for this PEC addition level. Papermaking properties were clearly improved for all dosage of PECs. Particularly for a dosage of 0.75% of PECs on pulp, tensile strength was noticeably increased (+48%) and both compressive resistance Concora Medium Test (CMT) and Short-span Compressive Test (SCT) were markedly increased (+64% and +39%, respectively). These results suggest that PECs are a possible alternative to assist the application of LCMNF in papermaking.

Etherified dicyandiamide condensation copolymer as a wet-end additive for papermaking

Dicyandiamide-formaldehyde condensation copolymer was synthesized and used as a wet-end additive for papermaking. The retention of fibers and fines was used as a performance index. Factors were evaluated governing the performance of the polymer, including polymer dosage, pH and mixing time. The optimum dosage of the polymer was found to be 0.03% under the conditions. Overall, the polymer was effective in improving the drainage, as well as the retention of fibers and fines in papermaking process.

Cationized fibers from pine kraft pulp: advantages of refining before functionalization

AbstractA partial cationization of cellulosic pulps has been suggested to enhance the retention of fillers and fines in the paper and board manufacturing industry. The challenge is the highly crystalline structure of cellulose and the mass transfer limitations of softwood fibers, which are long and resistant to and hinder the chemical reactions. In the present paper, it was demonstrated that refining (leading to decrystallization) and alkaline treatments facilitate the subsequent cationization process with quaternary ammonium groups. Cationization was performed with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) at 120°C for 2 h, and degrees of substitution above 0.3 were achieved. Beating to 4000 or 4500 PFI revolutions was found to be an optimum to achieve these high degrees of substitution. Mixing a small percentage (4%) of cationized pulp (with a charge density of approximately 0.8 meq g−1) with the untreated pulp could compensate for the negative surface charge of the original fibers. In this way, the highest charge density and opacity of the paper and the best retention of fines were achieved. If cationization was implemented in a paper mill, it should follow, not precede, the refining stage.

Application of the Novel Test Machine, Retention and Drainage Analyzer (RDA), for Wet-end Analysis of Papermaking Process (II) : Vibratory RDA and Selection of CaCO3 Filler by Simultaneous Considering of Multiple Assessment Factors

Wet-end where the fibrous components and functional additives are applied is an essential part for determination of properties of the final product and runnability of papermaking process. However, it is difficult to anticipate physical and chemical phenomena in wet-end using some instruments for lab-scale papermaking test. In addition the performance of retention aids and fillers have to be evaluated by overall analysis of retention, drainage, and paper uniformity. With regard to renovate retention and drainage analyzer (RDA), a new analysis of retention, drainage, and paper uniformity using the RDA had been studied. In this study the RDA was modified by equipping air piston vibrator which could delay the consolidation of wet web and reduce the retention of fines. Effects of the varied kinds of fillers on wet-end of fine paper were analyzed by summation of drainage, turbidity (retention), and paper uniformity using the modified RDA. As a consequence, the selection of proper filler for the optimization of wet-end of paper making process for fine paper was made by using the modified RDA.

Application of Cationic Cassava Dregs as a Retention and Drainage Aid in Wet-End System

Cassava dregs contain nearly 38.41% of starch, which has a similar structure to that of a starch. It was found that the cassava dregs would have the same function as the cationic starch if cationic groups were introduced. In this study, cationic cassava dregs were synthesized with the laboratory methods and characterized by FT-IR. The factors affect the retention and drainage was investigated. The result showed that, at a dosage of 1.0% of the cationic cassava dregs, the retention of fines was higher than 90%, best flocculation efficiency occurred at pH 8.5 when the dosage of cationic cassava dregs was 1.5%. Cationic cassava dregs had good resistance against moderate shear force, less affected by the conductivity, and it also showed a good strength properties.

Improvements of Strength and Retention of Cotton Handsheet by Additives(I)- Characteristics of Strength and Retention by Additives -

Various properties of cotton handsheet were measured to solve the problem of deformation while storing guar gum(natural polymer) and to improve strength and retention by synthetic polymers(A-PAM, C-PAM, CMC). The results of this study were summarized as follow. The cotton handsheet with 0.2% of A-PAM showed the best tensile index and folding endurance. Retention of fines and fillers in pulp slurry with 0.2% and 0.3% of A-PAM were more excellent than that with guar gum.

Experimental Method to Simulate Coal Fines Migration and Coal Fines Aggregation Prevention in the Hydraulic Fracture

A simple and effective experimental method is proposed to simulate coal fines migration through the proppant pack; such migration inevitably occurs during the process of fracturing fluid flowback or dewatering and gas production in coalbed methane (CBM) reservoirs. The damage to conductivity caused by coal fines migration in the pack and the factors affecting such migration are analyzed. A dispersion agent of coal fines applicable to hydraulic fracturing in CBM is optimized, consequently solving the problem of coal fines aggregation and retention in the proppant pack. Discharging coal fines with water or water-based fracturing fluid from the proppant pack can be difficult because of the adsorption and hydrophobicity of coal fines. Thus, coal fines are likely to aggregate and be retained in the proppant pack, thereby resulting in pore throat plugging, which causes serious damage to fracture conductivity. Two percent coal fines can reduce propped fracture conductivity by 24.4 %. The mobility and retention of coal fines in the proppant pack are affected by proppant size, proppant type, flowback rate, and coal fines property. When flowback rate exceeds the critical value, coal fines can be discharged from the pack, consequently reducing damage to propped fracture conductivity. More importantly, the steady discharging of coal fines requires steady dewatering and gas production to avoid flow shock, which causes pressure disturbance to drive coal fines in a remote formation. The optimized dispersant FSJ-02 employed in this paper can effectively change the wettability and surface potential of coal fines to improve their suspension and dispersion in water-based fracturing fluid. The recovery rate of coal fines increased by 31.5 %, whereas conductivity increased by 13.3 %.

반응표면분석법에 의한 양이온성 옥수수전분 생산의 최적화

Cationic starch is widely used in the paper-making process as a wet-end additive to improve sheet strength and to provide better retention of fines as well as fillers. Cationic corn starch is generally used in most grades of paper because of its cheapness and opulency. Low-substituted cationic starch which has a degree of substitution (DS) of below 0.03 is widely used but regulations pertaining to the total amount of lead present in anionic waste have made paper companies leery about its continued use. As a result, the need for a high-substituted cationic starch which has a DS above 0.04 has been growing. On the basis of the results of the alkali gelatinization initiation concentration (AGIC) of corn starch suspension, the optimization of corn starch cationization was performed by response surface methodology (RSM). When 8% (w/w) cationic reagent was added to the starch suspension with 1.89% (w/w) of Na2SO4 and NaOH, after which 6.75 meq/g-starch of AGIC was added at 38.48°C. It appears that cationic starch can be produced with a reaction yield of 67.28% (DS 0.0302) over the course of 18 h. If the cationic reagent is increased to 20% (w/w), more than 24 h was needed to reach the maximum reaction yield. Within 24 h, the optimized cationization process produced cationic corn starch which has a DS of 0.064.

치환도별 양이온성 옥수수전분의 물리화학적 특성

Cationic starch is widely used in the paper-making process as a wet-end additive to improve sheet strength and to provide better retention of fines as well as fillers. Cationic starches of different origins are available with various degree of substitution (DS). The physicochemical properties of cationic corn starches are characterized as having degree of substitution that range from 0.02 to 0.06. With the increase of DS, the water holding capacity of cationic starch increased to more than three times that of a natural starch. On the other hand, iodine absorption ability decreased as DS increases, possibly because the intensity of starch granules decreased, although the X-ray diffraction pattern displayed little changes in the peak intensity of the cationic corn starch. This suggested that the decreased integrity of starch granules was due to the substitution of cationic groups concentrated in the amorphous region. Rheological characterization showed that 1% gelatinized cationic corn starch was a pseudoplastic fluid, whereas natural corn starch was a Newtonian fluid. The viscosity of the cationic corn starch increased with increments in the DS, but decreased with rising electrical conductivity of the solution. The viscosity was proportional to the DS at a constant shear rate and swelling power sharply increased around the gelatinization temperature region.