Type Of Contactor Research Articles

Gasification of waste tires in a fluid bed reactor

Shredded rubber tires were gasified with steam in a 0.23m I.D. fluidized bed reactor over a temperature range of 900–1060K. The results indicated that the gas produced is rich in olefins and the heating value and volumetric yield of the produced gas vary approximately linearly with the gasification temperature. The gas yield decreases and its heating value increases as the gasification temperature is decreased. In the temperature range investigated, the heating value of the produced gas ranged between 39.6 MJ/Nm 3 (1060 Btu/SCF) and 22.2 MJ/Nm 3 (595 Btu/SCF), and the gas yield ranged from 0.21 Nm 3/kg DAF (3.5 SCF/lb DAF) to 0.76 Nm 3/kg DAF (12.1 SCF/lb DAF). The results also indicated that the fluid bed gives a higher gas yield than other types of contactors.

Mass transfer and hydrodynamic characteristics of the Denver type of flotation cells

The rates of gas induction Q, effective interfacial area a, and liquid-side mass transfer coefficient k L a were obtained from 100 × 100, 140 × 140, 172 × 172 and 380 × 380 mm × mm Denver-type flotation cells. The rates of gas induction were measured by a soap-film meter and values of a and k L a were obtained by chemical methods. The effects of impeller speed, liquid submergence and the presence of fine solid particles on the values of Q, a and k L a were investigated. Further, the effects of liquid viscosity and ionic strength on Q were studied. The performance of the Denver type of flotation cells is compared with the conventional mechanically agitated contactors and other gas-inducing types of agitated contactors. Scale-up criteria are discussed.

Crud in solvent extraction processing — a review of causes and treatment

An overview is presented on the various aspects affecting solvent loss through crud formation, encountered in many hydrometallurgical plants that employ solvent extraction processing. This crud, or stable emulsion mixed with solids, can be caused by properties of the feed solution, the solvent and its composition, the type of contactor selected and the method of operation. Cruds differ between plants and therefore treatment schemes and preventative measures are impossible to define without actual testing and evaluation. A summary of items for consideration in solving crud problems is given.

Critical impeller speed for the onset of gas induction in gas-inducing types of agitated contactors

Critical impeller speed for the onset of gas induction in gas-inducing types of agitated contactors

Mass transfer and hydrodynamic characteristics of gas inducing type of agitated contactors

AbstractPower consumption, rate of gas induction (Q), fractional gas hold‐up and mass transfer characteristics of 0.41, 0.57 and 1.0 m i.d. gas inducing type of agitated contactors were studied. The power consumption was measured by a torque table. The values of effective interfacial area (a), and liquid side mass transfer coefficient (kLa) were obtained by using chemical methods. Two types of impellers (pipe and flattened cylindrical) were employed. The impeller speed was varied from 3 to 11.7 r/s.The effects of impeller diameter, baffle position, orifice area on the impeller, number of impeller blades, position of impeller from the bottom and liquid submergence on the values of Q and a were investigated. Further, the effect of liquid viscosity and surface tension on the values of Q was studied.A satisfactory agreement was found between the observed and the predicted value of the minimum impeller speed at which gas induction occurs. The performance of the gas inducing type of agitated contactor has been compared with the conventional mechanically agitated contactor.

Multivariable Cascade Control of Purex Process

A differential-difference equation model is introduced which can describe the dynamics of any type of extractor, whether, mixer settler, pulsed column or rapid contactor. The differential or difference equation models used by several investigators prove to be particular cases of this model. From the results calculated by this model, it is shown that there exist an optimal stage and an optimal component for monitoring the performance in the control of extractors. A computer control system for the solvent extraction step of the Purex process is devised with use made of a generalized version of the classical cascade control law, which the authors have named the Multivariate Cascade Control Law. This law can easily be extended for application to the control of the Purex process as a whole.

Multivariable Cascade Control of Purex Process

A differential-difference equation model is introduced which can describe the dynamics of any type of extractor, whether, mixer settler, pulsed column or rapid contactor. The differential or difference equation models used by several investigators prove to be particular cases of this model. From the results calculated by this model, it is shown that there exist an optimal stage and an optimal component for monitoring the performance in the control of extractors. A computer control system for the solvent extraction step of the Purex process is devised with use made of a generalized version of the classical cascade control law, which the authors have named the Multivariate Cascade Control Law. This law can easily be extended for application to the control of the Purex process as a whole.

The dynamic response of a multiple-mixer solvent extraction column to concentration disturbances

A model is presented which predicts the concentration response of a multiple-mixer solvent extraction column following changes in the concentration of the input streams. Backmixing in both phases and nonequilibrium stages can be catered for. The model has been programmed to allow the dynamic behavior to be represented in step, impulse or frequency response form. Results have been computed to demonstrate the effect of operating parameters on the dynamic behaviour of this type of contactor and the performance of a pilot-scale unit has also been predicted using experimentally determined steady-state parameters for the water—acetic acid—methyl-isobutylketone system. Some experimental results for the transient response of the raffinate for this system are presented and compared with the predictions of the model.

ABSORPTION IN A ROTATING-DISK GAS-LIQUID CONTACTOR

Rates of oxygen absorption into water were studied in a rotating-disk gas-liquid contactor, in which liquid films were formed on the surface of disks rotating around the horizontal axis. When plain disks were used, values of the liquid-phase mass transfer coefficient kL were lower than those predicted from the penetration model. However, with disks made of appropriate wire mesh, kL, values agreed quite well with prediction by the penetration model for the range of gas-liquid contact time from 0.2 to 1.5 seconds.This type of gas-liquid contactor equipped with wire mesh disks seems to be a useful apparatus for studies of liquid-phase mass transfer in gas absorption.

Superconductive Rectifier

The rectifier system where a small alternating current is fed into the dewar vessel, transformed and rectified into a large direct current may present a method to reduce the liquid helium vaporization during the operation of a superconducting magnetTwo kinds of superconductive rectifiers were tested. One of them has Nb Zr wires as its rectifier elements, whose S-N transition for rectifier operation is caused by pulse heating. The other is a contactor type rectifier with Indium-Tin contacts which are also superconductive.The S-N transition type rectifier showed more vaporization of liquid helium than the counter flow leads in 100mV operation, but this vaporization may be reduced comparable, if the design is optimized.The contactor type rectifier was tested in the output of 500mV and 150A, and showed much less vaporization, which will mean the possibility of the superconductive rectifier of several volts and several thousand amperes.

CO<SUB>2</SUB> Gas Absorption by a Rotating Wetted Wall of Water

In the Piazza centrifugal gas absorber or centrifugal gas-liquid contactor which has been developed by us, mass transfer may be carried out in both liquid flow patterns of spray and wetted wall.In this report, pure CO2 gas absorption by a rotating wetted wall whose water travelling length is short is considered theoretically and experimentally.Theoretically, the surface velocity of a rotating aqueous wetted wall is defined by Eq.(23). And if the surface velocity and the average velocity of liquid is found, the Murphree absorption efficiency is calculated from Eq.(33).Experiment of absorption is proceeded in pure CO2 gas and water at 20°C, CO2 gas is sent countercurrently contacting with a rotating wetted wall flow of water.It is shown that experimental results correspond with the results of theoretical calculations which are based on a wellknown unsteady diffusional equation.It is concluded that in such type of contactor the amount of mass transfer in the flow at the wetted wall is comparatively smaller than in the flow of spray.

Motor-operated switch for space heating control

Resistance load (electric heaters, incandescent lights, etc.) can be switched most satisfactorily by a relatively slow moving motor-operated type of switch. Noise, contact wear, and general maintenance are all less than with the ordinary type of magnetic contactor, which is designed for switching inductive loads.

The design of contactors with regard to their industrial application

Modern contactor design is reviewed and reference is made to the influence which various applications of contactor type control gear have had on design and development.After a general survey the special considerations appertaining to motor-control duty are examined in detail, having due regard to the extreme cases which frequently occur in practice. Arc control and contact developments are mentioned, and a short discussion of the oil-immersed contactor follows with particular reference to its use in chemical plants and for high voltage. Some special contactor designs are discussed, as well as the problems arising in connection with the control of electric furnaces. A short résumé of the desirable features of contactor auxiliary switches concludes the paper.

Application of phase sequence principles to relaying of low-voltage secondary networks

The authors present an improved network relaying system utilizing a conventional single-phase relaying element and contactor type overcurrent elements excited by symmetrical phase sequence components to represent completely power flow conditions and control protector operation on a threephase four-wire secondary network system. The low-voltage alternating-current network was conceived and developed to meet the need for an alternating-current system of distribution that would provide high quality service and compete with the direct- current system in reliability and economy. In its present form, it consists of a distribution network, served by a plurality of feeders, with intermediate voltage transformation and network protectors. The use of the present arrangement dates from the development of the network protector which fulfilled several functions and may be described as a means to connect and disconnect each of the feeders to the network under proper conditions. The protector consists of a circuit breaker and necessary operating relays located in each of the feeds to the network. Each main feeder provides a multiplicity of feeds to the network through low-capacity transformers, (50 to 1,000 kva) and it is the function of the protector to connect to or disconnect from the feed to the network under proper conditions. For discussion of this paper see page 626.

A sequence relay for network protectors

USELESS operations of protectors on low voltage distribution networks are practically eliminated when controlled by a relay that has been designed in accordance with the principles laid down in the companion paper “Application of Phase Sequence Principles to Relaying of Low Voltage Secondary Networks.” This relay consists of a single phase induction disk directional element, 2 overcurrent control elements of the contactor type, and suitable current and voltage filters to make it operative on 3-phase circuits. All parts, with the exception of 2 resistors and a phasing lamp, are mounted in a standard relay case.