Plugging Problems Research Articles

Study on adsorption of methylene blue by a novel composite material of TiO2 and alum sludge.

A composite material of TiO2 and alum sludge (TiO2@AS) is reported in this paper. The samples of alum sludge (AS) and TiO2@AS were characterized using a field emission scanning electron microscope (FE-SEM), an energy dispersive spectrometer (EDS) and an Ultima IV X-ray diffractometer (XRD). In order to study the adsorption capacity and the adsorption mechanism of methylene blue by TiO2@AS in aqueous solution, three indexes — pH, adsorbent dosage and initial concentration of methylene blue — were investigated to evaluate the adsorption capacity of TiO2@AS. Moreover, thermodynamic, kinetic and isothermal model analyses of the adsorption process were carried out. The results showed that pH has little effect on the adsorption capacity. The maximum adsorption efficiency occurred at an optimized pH value of 11 for the aqueous solution. The adsorbed amount of methylene blue on TiO2@AS increased with the initial concentration of adsorbate and decreased with an increase in TiO2@AS dosage. The adsorption kinetics of methylene blue by TiO2@AS were in good agreement with the quasi-second-order kinetic model (R2 ≥ 0.9964), indicating that chemisorption is the main rate-controlling step. The Freundlich isotherm equation can best describe the experimental data (R2 = 0.9788). It is revealed that the adsorption is mainly multilayer adsorption. Because ΔG < 0 and ΔH > 0, the adsorption is a spontaneous endothermic process. Furthermore, the TiO2@AS can be regenerated under ultraviolet light, thus prolonging the service life of AS and facilitating a solution to the problem of adsorption plugging.

Preparation of DB film in the channel of SS304 bipolar plate to improve its water liquidity

Flow channel is one of the important design and part of the bipolar plate, and the water management of flow channel is an important problem to affect the actual application of PEMFCs, therefore surface treatment is needed to improve the water liquidity. Because of the hydrophobic property and corrosion resistance of 6-N,N-(dibutyl)-1,3,5-triazine-2,4-dithiol (DB), DB film is obtained by syringe injecting in the flow channel for self-assemble. Tested by XPS and FT-IR, it was found that the channel of SS304 was covered by uniform DB film entirely, and there are bonds of SFe and SNi between DB film and SS304 substrate, makes the combination stable. Different layers of DB film are prepared in the flow channel to compare their property difference. According to the water liquidity test by gravity force, the liquidity degrees decrease as SS304/DB3 > SS304/DB2 > SS304/DB1 > SS304 substrate. While according to the stability test by polarization, the stability for SS304/DB2 and SS304/DB1 are greater than that for SS304/DB3. Further result by EPMA (electron probe micro-analyzer) to flow channel surface discovers that the uniformity of SS304/DB3 is very poor, accompanied by peeling phenomenon, and the uniformity of SS304/DB2 and SS304/DB1 in the flow channel are quite well. Considering the liquidity to solve the problem of water plugging, the SS304/DB2 is the best choice.

Performance of Cooled Cone Grinding Machine in Cocoa Cake Processing

The process of cocoa paste pressing has a function to separate the fatty component of cocoa from its cake. Cocoa paste is further processed into cocoa powder using grinding machine for cocoa cake. The cooled cone type of cocoa grinding machine is used to solve the problem of plug in the maschine caused by melting of fat in cocoa cake due to hot effect as a result of friction in the grinding machine. Grinding machine of cocoa has conical form of cylinder for grinding and stator wall wrapped by source of cold and closed with jacket wool. Research was conducted at Kaliwining Experimental Garden of Indonesian Coffee and Cocoa Research Institute (ICCRI) using cocoa cake containing 26.75% originated from Forastero type of cocoa seed. The capacity and recovery of the machine was influenced by space between rotor cylinder and stator wall. Grinding machine operated at cooling temperature of 25.5oC and space between rotor – stator 0.9 cm and the capacity of 187.5 kg/hour with recovery of 200 mesh cocoa powder as much as 24%. The maximum power of machine required was 2.5 kW with efficiency of energy transfer of 97%. Results of proximate analysis showed that there was no change of protein content, but protein and carbohydrate content increased after processing, i.e. from 5.70% and 59.82% into 5.80% and 61.89% respectively.Key words : cocoa cake, cooling, grinding, cocoa powder

Shenwu Integration Technology for Energy Conservation and Emissions Reduction

Abstract Beijing Shenwu Group Corporation uses self-developed ceramic honeycomb as heat exchange cells instead of metal, with the advantages such as anti-corrosion, anti-erosion and anti-clogging, it can be used for air preheater and gas heater (GGH) in thermal power boiler island, to solving the problem of corrosion and plugging. Meanwhile, setting SCR catalyst in proper temperature region of ceramic honeycomb regenerator can save energy and reduce NOx. This air preheater can further reduce exhaust gas temperature, so as to improving boiler efficiency more than 3%, and achieving the goal of integration of energy conservation and emissions reduction ultimately.

Kinetic model for isopropanol oxidation in supercritical water in hydrothermal flame regime and analysis

Supercritical water oxidation (SCWO) in hydrothermal flame regime has advantages over the oxidation in flameless regime. The main advantage is that the feed can be injected into the reactor at low temperatures, avoiding plugging and corrosion problems in a preheating system. However, there is a lack of kinetic data capable of properly describing the flame regime oxidation. In this study, new global reaction rate parameters for the oxidation of isopropyl alcohol in hydrothermal regime were adjusted from temperature profiles of our group's previous experimental data. The kinetics obey first order rate with regard to the fuel and the oxidant, and follows the Arrhenius law. The parameters are k0=(9.308±3.989)×107(m3s−1kmol−1) and Ea=89.441±2.457(kJmol−1), and the least square error of the fitting was 10.8%. This kinetic model was applied in a parametric analysis of flame formation, and it was used to analyze the behavior of a supercritical water oxidation vessel reactors. The kinetic model is able to describe the behavior of the vessel reactor when working in steady state hydrothermal flame regime at subcritical injection temperatures (246°C). The model predicts both flameless and hydrothermal flame regimes.

Waterproof and Impermeability Technology Strategy of Constructional Engineering

Building leakage is a chronic and stubborn disease to influence the quality of building engineering. The traditional waterproof coiled material such as asphalt has properties of poor weather resistance, easy to crack and large pollution. GT is a kind of green building material with superior performance. GT materials used in building waterproof can fundamentally solve the problem of waterproofing, impermeability and plugging in construction. In this article, the author discuss performance characteristics, construction technical measures and quality testing standards of GT paint, analysis the technical points of GT waterproof paint applied in construction engineering.

Experimental study of hydrothermal flames formation using a tubular injector in a refrigerated reaction chamber. Influence of the operational and geometrical parameters

Experimental results using three different empty tubular injectors into a refrigerated reaction chamber containing a hydrothermal flame as an internal heat source are presented. In the supercritical water oxidation process, one method of avoiding external preheating is injecting the feed at room temperature into a hydrothermal flame. In this way, plugging and corrosion problems produced during transition from subcritical to supercritical conditions in the preheating system can be avoided. The influence of feed flow, injection temperature and diameter and length of the injector has been evaluated by studying the temperature profiles along the reactor, the total organic carbon (TOC) removal and the extinction temperatures at different conditions. It was possible to inject reactants even at room temperature into the hydrothermal flame with organic destruction efficiencies higher than 99.9%, presenting better operational results than other reactors constructed by our research work. The effect of salt addition under subcritical conditions in a hydrothermal flame was also studied. Feeds containing up to 2.5 wt% Na 2SO 4 could be injected in the reactor without plugging problems and a TOC removal of 99.7% was achieved in these conditions. However, only about 10% of the salt introduced in the reactor could be recovered.

NUMERICAL ASSESSMENT OF TWO-CHAMBER MUFFLERS WITH PERFORATED PLUG/NON-PLUG TUBES UNDER SPACE AND BACK PRESSURE CONSTRAINTS USING SIMULATED ANNEALING

Recently, research on new techniques of single-chamber mufflers equipped with perforated tubes has been addressed. However, research work on shape optimization of multichamber silencers hybridized with perforated plug/non-plug tubes along with work on the maximal allowable back pressure of mufflers has been neglected. Therefore, we will not only analyze the sound transmission loss (STL) of a spaceconstrained two-chamber muffler hybridized with perforated plug/non-plug tubes but also optimize the best design shape under a specified pressure drop. In this paper, both the numerical decoupling technique and simulated annealing (SA) for solving the coupled acoustical problem of perforated plug/ non-plug tubes are used. A numerical case in eliminating a broadband fan noise is also introduced. To verify the reliability of SA optimization, optimal noise abatements for the pure tone (500 Hz) are exemplified. However, before the SA operation can be carried out, the accuracy of the mathematical model must be checked using the experimental data. Results indicate that the maximum STL is precisely located at the desired target tones. The optimal result of one case study for eliminating broadband noise also revealed that the overall noise reductions with respect to the muffler, which are under various maximum allowable pressure drops (100, 200, 300, 400, 500 (Pa), and infinity) can reach 68.4, 52.7, 45.4, 40.4, 36.0, and 33.2 dB. Furthermore, both the pressure drop and the acoustical performance increase when the diameters (at inlet tubes as well as perforated holes), the perforated ratio, and the length of perforated tube decrease. Consequently, a successful approach used for the optimal design of the twochamber mufflers equipped with perforated plug/non-plug tubes under space and back pressure constrained conditions has been demonstrated.

Energy Balance of a Staged Process for the Supercritical Water Gasification of a Hydrogen Fermentation Residue of Food Waste

This study was conducted to calculate the energy balance of supercritical water gasification with an activated carbon catalyst for a hydrogen fermentation residue of soybean fiber (SFHFR). To circumvent the problem of plugging, we examined the gasification of SFHFR by a staged operation with alternate feeding of water and feedstock. The calculations were applied to a gasification reaction conducted within a tubular reactor at 600°C and 25 MPa, with an average residence time of 73 s. The calculation results were a cold gas efficiency ηR [(amount of energy recovery from feedstock as product gas, Eg) / (energy supply from feedstock, Ef)] of 0.72 and an energy efficiency ηe, Eg / [(heat supplied by the electric furnace, Ei) + (energy supply from feedstock, Ef)] of 0.30. A comparison between continuous operation and the operation in staged intervals confirmed the effectiveness of the latter.

Treatment of high strength coking wastewater by supercritical water oxidation

Two kinds of coking wastewater were treated by supercritical water oxidation (SCWO) in a continuous-flow reactor using hydrogen peroxide (H2O2) as an oxidant. These wastewater contained high concentrations of ammonia nitrogen (NH3–N), phenol, chemical oxygen demand (COD) and inorganic salts. A salt separator was applied for the separation of salts in the SCWO process to solve the problem of reactor plugging due to salt precipitation. Experiments were conducted to investigate the effects of the temperature, pressure, excess oxygen and residence time on the destruction of pollutants (includes NH3–N, phenol and COD). The efficiency of the salt separator was also investigated. Results showed that both phenol and COD can be easily destructed in SCWO process. NH3–N was inert and its conversion increased noticeably as the temperature and excess oxygen increased. At the condition of 650°C and 300% excess oxygen, the conversions of all pollutants were over 99.94% and the effluent met the first grade discharge standard of China. The results also indicated that the efficiency of salt separation increased with an increasing temperature. By controlling the temperature of salt separator at 600°C, more than 87% of the salts were separated from coking wastewater.

Supercritical Water Gasification Staged at Intervals for Hydrogen Fermentation Residue of Food Waste

To circumvent the problem of reactor plugging in supercritical water gasification (SCWG), we proposed an SCWG process operated at intervals with a continuous-flow system (10 kg/d) configured to feed water and feedstock in alternate steps. Hydrogen fermentation residues of soybean fiber and restaurant food waste (SFHFR and RWHFR, respectively) were employed as feedstock, and fine activated carbon was used as catalyst. Feedstocks of 2.0-10.0% SFHFR were gasified in a tubular reactor at 600 °C, 25 MPa with a residence time of 60-105 s. An 8% concentration SFHSR was gasified with a carbon gasification efficiency of 0.75 without plugging. A 4% RWHFR, a feedstock composed of more diverse substances, was gasified with a carbon gasification efficiency of 0.57.

Experimental study on gasification characteristics and slagging behavior of Chinese typical high ash fusion temperature coal in lab scale downflow gasifier

AbstractIn order to extend the applicability of entrained flow gasification technology by using Chinese high ash fusion temperature (AFT) coal with dry ash extraction, gasification characteristics and slagging behavior of Chinese high AFT coal were studied in a lab scale downflow gasifier. The results showed that under this experimental condition, the optimum temperature window which is suitable for dry ash extraction with high AFT coal ranges from 1573 to 1623 K, as well as the corresponding optimum O2/coal mass ratio ranges from 0.93 to 1.13. The cold gas efficiency and carbon conversion are around 42 and 90%, respectively in this experiment. The slag on the bottom of the gasifier and in the cyclone existed, on the whole, as solid except that some small parts were melted with several micrometers in diameter, while the slag in the bag filter had remained unmelted when continue operating at an optimum condition for 1.5 h. Due to the small percentage of melted parts in the slag, the tendency of plugging is small and the problems of plugging can be avoided at the exit of gasifier by gasifying Chinese high AFT coal at around 1623 K. Copyright © 2009 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Toluene vapor remediation in a continuous packed bed loop bioreactor

AbstractAn external loop airlift bioreactor with a small amount (99% porosity) of stainless steel mesh packing inserted in the riser section was used for bioremediation of a toluene polluted air stream. The packing enhanced VOC and oxygen mass transfer rates and provided a large surface area for cell immobilization. Using a mixed culture, fed‐batch and continuous runs at five different dilution rates were completed with toluene in the polluted air as the only carbon source. Above 99% and 93.6% toluene removals were achieved at toluene loading rates up to 88.1 and 149.1 g/(m3 h), respectively. The bioreactor responded quickly to a toluene load shock of 33 g/(m3 h) at high inlet toluene loadings. After 185.8 days operation, no plugging problems were observed in the column. A mathematical model is shown to accurately predict transient and steady state data. © 2008 American Institute of Chemical Engineers Environ Prog, 2008

Operating characteristics of a transpiring-wall SCWO reactor with a hydrothermal flame as internal heat source

A novel supercritical water oxidation (SCWO) system with a transpiring-wall reactor (TWR) containing a hydrothermal flame as internal heat source has been investigated. This configuration may overcome the problems of corrosion and plugging of reaction vessels and other components. In the TWR, the wall contact of supercritical reaction media is prevented by fluid dynamical means. Subcritical water permanently flows through porous, non-load-bearing transpiring-wall elements and forms a “film” on the inner wall. Precipitated salt particles do not reach the wall because they are either re-dissolved in this film or are swept away by the transpiring water. The waste water reaches reaction temperature without any wall contact, i.e., by mixing with the combustion products of the hydrothermal flame. In the present work, the apparatus design, processing features, and experimental results are presented. Tests with salt-free water–methanol mixtures have been conducted at 250 bar. The influence of the intensity (i.e., mass flux) and temperature of transpiration on the reactor performance has been examined. The temperatures near the transpiring wall remain subcritical which is a quantitative measure for the wall protection from salt adherence. Methanol conversions of higher than 99% were obtained even at comparatively low transpiring water temperatures (125–250 ° C). At typical operating conditions, the mass flow ratio between the total transpiration flow and the core flow is around 65%. Further, it was found that natural convection effects are not negligible in a transpiring-wall reactor for SCWO.

The control of ice slurry systems: an overview

This article outlines some typical control strategies for the basic components of an ice slurry system. From this review it became apparent that the control of terminal units is not fundamentally different from the control of classical single-phase secondary cooling systems, except from the fact that it must be based on the use of local pumps and the ON–OFF operation of actuators to avoid ice plugging problems. The safe control of the ice generator can be ensured with a simple thermostat, although the resulting ice concentration control would be approximate. It was also demonstrated that any ice accumulation in the storage tank would not prevent the ice slurry system from functioning safely. As a final precaution, it was not recommended to operate an ice slurry generator at low solute concentrations and temperatures greater than −3/−4 °C due to the risk of plugging up the distribution loop and causing mechanical wear to the ice generator.

A NEW IDEA IN MARSH CORING

Standard coring techniques are often ineffective in the unconsolidated and vegetated soils and sediments of marsh environments. In this paper, a novel coring device is presented that minimizes the problems of compaction, core plugging, and root disturbance to allow the collection of intact 35+ cm cores from densely vegetated marsh areas. The simple concept uses a sharpened main body and cover plate that are inserted sequentially to obtain a wedge‐shaped soil or sediment slice. In a typical application, the corer is transferred to the field laboratory where sectioning can occur. Removal of the cover plate exposes a large surface area of soil or sediment for visual inspection and sampling. The advantages of the wedge corer design are described in relation to its use in a Spartina alterniflora salt marsh.

Predicting the Potential of Engulfment Using an On-Farm Grain Storage Hazard Assessment Tool

The goal of this research was to address the problem of engulfment in flowing grain in on-farm metal grain storage bins. This was accomplished using a systems approach to identify contributing factors to engulfment, which were then used to develop a 28-question Farm Grain Hazard Assessment Tool (FGHAT). A numerically weighted high- and low-risk response accompanied each question, the sum of which resulted in a potential-risk-of-engulfment score for a given on-farm grain handling and storage system. The assessment tool was pilot tested on a sample of 47 farms. The difference between the mean scores of farms with a history of engulfment (n = 14) and the mean scores of farms with no prior reported engulfment incident (n = 33) was significant (p < or = 0.001). This finding suggests that it is possible, using the hazard assessment tool, to predict the increased likelihood of an engulfment in a specific on-farm grain storage and handling system. It was also found that the management of grain during storage and an individual's perception of risk and willingness to avoid flowing grain hazards had the most significant impact on reducing the potential for an engulfment. In contrast, a history of grain plugging problems was not found to make a considerable difference in scores between the two groups of farms. The presence of stirring devices in bins, accommodation for lockout devices on electrical controls, and using grain storage bins smaller than 20, 000 bu capacity also had little impact on the difference in scores. Based upon the level of significance of each of the 28 questions'ability to predict an increased risk of engulfment, it was concluded that a valid response could be obtained with as few as eight questions. Recommendations concerning continued study and application of the tool were formulated, including the effectiveness of the tool in changing the farmers' behavior, and the findings also contributed to the revision of a potential engineering standard for on-farm grain storage structures.

DNAPL remediation with in situ chemical oxidation using potassium permanganate: II. Increasing removal efficiency by dissolving Mn oxide precipitates

In situ chemical oxidation (ISCO) schemes using MnO 4 − have been effective in destroying chlorinated organic solvents dissolved in ground water. Laboratory experiments and field pilot tests reveal that the precipitation of Mn oxide, one of the reaction products, causes a reduction of permeability, which can lead to flow bypassing and inefficiency of the scheme. Without a solution to this problem of plugging, it is difficult to remove DNAPL from the subsurface completely. In a companion paper, we showed with batch experiments that Mn oxide can be dissolved rapidly with certain organic acids. This study utilizes 2-D flow-tank experiments to examine the possibility of nearly complete DNAPL removal by ISCO with MnO 4 −, when organic acids are used to remove Mn oxide. The experiments were conducted in a small 2-D glass flow tank containing a lenticular silica-sand medium. Blue-dyed trichloroethylene (TCE) provided residual, the perched and pooled DNAPL. KMnO 4 at 200 mg/l was flushed through the DNAPL horizontally. Once plugging reduced permeability and prevented further delivery of the oxidant, citric or oxalic acids were pumped into the flow tank to dissolve the Mn oxide precipitates. Organic ligands removed the Mn oxide precipitates relatively quickly, and permitted another cycle of MnO 4 − flooding. Cycles of MnO 4 −/acid flooding continued until all of the visible DNAPL was removed. The experiments were monitored with chemical analysis and visualization. A mass-balance calculation indicated that by the end of the experiments, all the DNAPL was removed. The results show also how heterogeneity adds complexity to initial redistribution of DNAPL, and to the efficiency of the chemical flooding.

Destruction efficiencies and dynamics of reaction fronts associated with the permanganate oxidation of trichloroethylene.

Although potassium permanganate (KMnO4) flushing is commonly used to destroy chlorinated solvents in groundwater, many of the problems associated with this treatment scheme have not been examined in detail. We conducted a KMnO4 flushing experiment in a large sand-filled flow tank (L x W x D = 180 cm x 60 cm x 90 cm) to remove TCE emplaced as a DNAPL in a source zone. The study was specifically designed to investigate cleanup progress and problems of pore plugging associated with the dynamics of the solid-phase reaction front (i.e., MnO2) using chemical and optical monitoring techniques. Ambient flow through the source zone formed a plume of dissolved TCE across the flow tank. The volume and concentration of TCE plume diminished with time because of the in situ oxidation of the DNAPL source. The migration velocity of the MnO2 reaction front decreased with time, suggesting that the kinetics of the DNAPL oxidation process became diffusion-controlled because of the pore plugging. A mass balance calculation indicated that only approximately 18% of the total applied KMnO4 (MnO4- = 1250 mg/ L) participated in the oxidation reaction to destroy approximately 41% of emplaced TCE. Evidently, the efficiency of KMnO4 flushing scheme diminished with time due to pore plugging by MnO2 and likely CO2, particularly in the TCE source zone. In addition, the excess KMnO4 used for flushing may cause secondary aquifer contamination. One needs to be concerned about the efficacy of KMnO4 flushing in the field applications. Development of a new approach that can provide both contaminant destruction and plugging/ MnO4- control is required.

A pilot study for oil refinery wastewater treatment using a fixed-film bioreactor

Biological treatment of industrial oil refinery wastewater is a well-established method for remediation of these wastes. We have designed a new bioreactor system to increase the efficiency of biological treatment systems by (1) allowing greater organic loads, (2) minimizing production of sludge waste by-products, and (3) increasing process stability and resistance to shock loading. A fixed-film bioreactor system was constructed with a highly porous polyurethane foam to incubate microorganisms at concentrations up to 8000 mg/l. The support frame of the bioreactor system was built from cylindrical plastic pall rings to form a packed bed of ‘mixed-media’. The frame support provides a high surface area-to-volume ratio (210 ft 2/ft 3), and reduces potential problems of plugging and channeling, distribution of air and water, and mass-transfer limitations. Performance data for fixed-film bioreactors with 8-h hydraulic retention time (HRT) demonstrated chemical oxygen demand (COD) removal rates of 85–90%, and near 100% degradation of phenol from industrial oil refinery wastewater. Furthermore, the pilot bioreactor only generated one-third of the sludge waste compared to the traditional activated sludge process.