Typical Processing Units Research Articles

Investigation of the impact of hydrodynamic parameters for phosphorus recovery from synthetic anaerobic digester supernatant in a fluidized bed reactor

Recovering phosphorus (P) from wastewater as struvite has been investigated widely as this approach represents a solution to several wastewater-related problems. Some of the typical process units applied in the industry for struvite recovery from wastewater streams include fluidized bed reactors where individual struvite crystals are being agglomerated into spherical granules, or pellets. Various hydrodynamic parameters affect the extent of inter-particle collisions, the intensity of mixing, localized concentrations of ionic species, nature of eddies, etc. which determine the efficiency of the crystal agglomeration. This study evaluated the impact of three key hydrodynamic parameters (up-flow velocity, feed injection nozzle velocity, and nozzle configuration) on P-removal and recovery efficiencies in a newly designed novel fluidized bed reactor (FBR). Lowering up-flow velocities from 60 cm/min to 20 cm/min resulted in higher P-removal and recovery efficiency, whereas high up-flow velocities were favorable for the production of larger pellets and fines. Nevertheless, higher nozzle velocity (18.04 m/s) was responsible for improving P-recovery efficiencies. The nozzle velocity had a strong influence on the morphology of pellets and fines. High nozzle velocity contributed to the formation of the smooth-surfaced pellets and plate-shaped fines. Three different nozzle-configurations generating different flow patterns within the agglomeration zone were studied.

The application of leak detection and repair program in VOCs control in China’s petroleum refineries

ABSTRACT Volatile organic compounds (VOCs) contribute to the formation of ground-level ozone. This causes the phenomena of haze and photochemical smog pollution. Recently, the leak detection and repair (LDAR) program was required to implement in China’s petroleum industry on the background of the huge emissions from equipment leaks. This paper analyzed and compared the application of LDAR program in four petroleum refineries and six typical processing units in these refineries. The results showed that non-flanged connectors, flanges, valves, and open-ended lines were the most common components, which accounted for over 99% in these refineries. And over half were non-flanged connectors. About 0.2% to 0.4% of all components were found to leak and emitted up to 91.8% of VOCs, especially the leaking valves and open-ended lines. And over 88.5% of VOC emissions were from high leaking components. The VOC emissions reduced 42% to 57% by repairing 42% to 81% of leaking components. And 90% of the reduction was achieved by repairing high leaking components. Besides, under the same processing capacity, the gas fractionation unit and continuous catalytic reforming unit have a higher average number of components, leaking components and VOC emissions than the other four units. Finally, this paper proposed some problems and suggestions during the implementation of LDAR program. These findings can enhance and improve the effectiveness of LDAR program, and establish a comprehensive VOCs control system, which provides a scientific basis and technical support for the government and refineries. Implications: Recently, China required industries to implement leak detection and repair (LDAR) program to control volatile organic compound (VOC) emissions, especially the petroleum industry. In this paper, we analyzed and compared the LDAR program implementation in four refineries and six typical processing units in these refineries. The results indicate that the implementation of LDAR program was highly effective in petroleum industry. The comparison helps us to enhance the effectiveness of LDAR program by locating the high VOC emission components and units, which provides technical support for the government and refineries in developing specific regulations and plans.

Insights into the key components of bacterial assemblages in typical process units of oily wastewater treatment plants

To compare the structure of microbial community in the oily wastewater treatment plants (OWWTPs) located in China, and to discern the impacts of environment variables on the variance of microbial community, activated sludge samples from six typical OWWTPs were taken and the structure of microbial community of these six samples were analyzed via Illumina high-throughput sequencing. 18 core genera including Comamonas, Bacillus, Pseudomonas, Thauera, Paenibacillus, etc. were shared by all OWWTPs. Canonical correspondence analysis (CCA) suggested that temperature, oil concentration, DO and pH exhibited significant impacts in shaping the structure of microbial community. Variance partitioning analyses (VPA) illuminated that the most variation in microbial community was contributed to geographic location, explaining 36.4% of the total variations obtained, followed by wastewater characteristics (18.7%) and operational parameters (8.6%). This work offered insights into the structure of microbial community in OWWTPs at different geographic locations and illustrated the correlations between environment variables and microbial community in OWWTPs.

Densification behavior of dry spent coffee ground powders: Experimental analysis and predictive methods

The knowledge of bulk properties and densification behavior of Spent Coffee Ground (SCG) powders can be useful in handling such powders through the typical processing units of the soluble coffee industries. In this paper we measured the bulk densities of SCG mixtures with mean sizes from 225 to 550 μm as a function of tapping and tested a number of selected equations to predict the densification behavior of these mixtures. Densification kinetics of SCG powders was found to be overwhelmingly driven by the mass fraction of fines in the mixture. The equations proposed by Kawakita and Ludde (1971), Knight et al. (1995) and Mallol et al. (2008) predicted well the variation of bulk density of SCG powders throughout tapping. Nevertheless, the Kawakita and Ludde's equation is recommended as the most suitable because the fitted parameters in this equation could be correlated to the powders' mean size and Hausner ratio. Besides, three methods to predict the densification curves were proposed. In the first method, the powders' mean diameter is used to predict the densification kinetics and in the second the angle of repose and the loose bulk density of the samples are used. Finally, the third method is based on coupling the densification equation to the Modified Linear-Mixture Packing Model. The three approaches led to predictions of bulk density with deviations <10% in comparison to the experimental data and can be recommended to estimate the densification kinetic behavior of industrial SCG powders.

Implementation of Unsigned Multiplier Using Area-Delay-Power Efficient Adder

-Multiplication and addition are most widely and oftenly used arithmetic computations performed in all digital signal processing applications. Multiplication is the basic arithmetic operation which is present in many part of the digital computer especially in signal processing systems such as graphics and computation system. It requires substantially more hardware resources and processing time than addition and subtraction. In fact, 8.72% of all the instruction in typical processing units is multiplication. This paper deals with the basic multiplier that is shift and add multiplier. Accurate operation of the shift and add multiplier is mainly influenced by the performance of the adder. So performance of the adder enhances the performance of the multiplier. Hence, to design a better architecture the basic adder blocks must have reduced delay time consumption and area efficient architectures. This paper, involves the implementation of unsigned multiplier using area, delay and power efficient adder. This design will be developed using Verilog programming language and implementing using Field Programmable Gate Array (FPGA) platform.

Delay-Power Performance Comparison of Multipliers in VLSI Circuit Design

A typical processor central processing unit devotes a considerable amount of processing time in performing arithmetic operations, particularly multiplication operations. Multiplication is one of the basic arithmetic operations and it requires substantially more hardware resources and processing time than addition and subtraction. In fact, 8.72% of all the instruction in typical processing units is multiplication. In this paper, comparative study of different multipliers is done for low power requirement and high speed. The paper gives information of “Urdhva Tiryakbhyam” algorithm of Ancient Indian Vedic Mathematics which is utilized for multiplication to improve the speed, area parameters of multipliers. Vedic Mathematics suggests one more formula for multiplication of large number i.e. “Nikhilam Sutra” which can increase the speed of multiplier by reducing the number of iterations.

Evaluation Method and Workbench for APC Strategies

The large number of various advanced control strategies (e.g. Model Predictive Control. Neural Networks or Fuzzy Control) and the lack of a practically usable selection methodology make it very difficult to choose an appropriate strategy for a given plant. In order to support the selection of proper control strategies and products a set of relevant evaluation criteria is developed. A flexible and expandable test environment (workbench) is created aiming at a controller evaluation considering these criteria. The evaluation approach and workbench are demonstrated for PID based and commercial Model Predictive Controllers at some typical process units and plants.

Inhibition of Nickel Precipitation by Gluconate. I: Kinetic Studies and Spectroscopic Analyses

The role of gluconate on nickel precipitation kinetics was evaluated through particle size distribution analyses, and the inhibition mechanisms were explored through spectroscopic studies. Batch kinetic studies showed that nickel precipitation does not achieve equilibrium within the time frame of typical process units. The molar ratio of gluconate to nickel had a profound effect on precipitation kinetics. A complete inhibition of nickel precipitation was observed when the molar concentration of gluconate was high, and a time-dependent resolubilization was observed at lower ratios. Particle size distribution indicated that nickel precipitates were colloidal in nature. Nucleation rates were promoted by the presence of gluconate; however, the removal efficiency decreased due to complexation reactions. Spectroscopic analysis of the solids suggested the presence of a mixture of two solids, a nickel-gluconate complex and a nickel hydroxide. The kinetics of the formation of the precipitates suggests that design of treatment units for the recovery of nickel in the metal finishing industry should be proceeded with advanced oxidation that would oxidize the organic impurities, before nickel recovery is accomplished.