Neutral Reactor Research Articles

Gypsum Scale Formation in Continuous Neutralization Reactors

An experimental study was carried out to determine the rate and extent of scale formation of gypsum (calcium sulphate dihydrate) on stainless steel surfaces in a continuous hydrometallurgical sulphuric acid-calcium carbonate partial neutralization reactor. The purpose of the study was to determine the effects of pH, temperature, residence time, presence of metal sulphates (Fe, Al, and Ni), addition of surfactants and addition of gypsum seed on scale growth. The rate of scale formation was found to be reduced by lower temperatures, longer residence times and the presence of nickel. pH had no significant effect. The effect of these variables on the rate of scale formation was related to the degree of gypsum supersaturation. Scale reduction through the addition of sulphonated anionic surfactants was found to be effective only under certain conditions. However, gypsum seeding was found to be an effective method of scale reduction. Scale was reduced by 50% or more at a seed concentration of 10 g/LOn a effectué une étude expérimentale afin de déterminer le taux et le degré de formation d'écailles de gypse (sulfate de calcium dihydrate) sur les surfaces en acier inoxydable d'un réacteur de neutralisation partielle en continu d'acide sulfurique hydrométallurgique et de carbonate de calcium. Le but de l'étude consistait à déterminer l'effet de plusieurs variables sur la croissance des écailles, incluant le pH, la température, le temps de séjour, la présence de sulfates de métal (Fe, Al et Ni), l'addition d'agents de surface ainsi que l'addition de semences de gypse. On a trouvé que le taux de formation d'écailles était réduit par des températures plus basses, par des temps de séjour plus longs et par la présence de nickel. Le pH n'avait pas d'effet important. L'effet de ces variables sur le taux de formation d'écailles était relié au degré de sursaturation en gypse. De plus, la réduction d'écailles par addition d'agents de surface anioniques sulfonés était efficace seulement sous certaines conditions. Cependant, on a trouvé que l'ensemencement de gypse était une méthode efficace de réduction d'écailles, avec une diminution de 50% ou plus avec une concentration d'ensemencement de 10g/L.

Gypsum Scale Formation in Continuous Neutralization Reactors

An experimental study was carried out to determine the rate and extent of scale formation of gypsum (calcium sulphate dihydrate) on stainless steel surfaces in a continuous hydrometallurgical sulphuric acid-calcium carbonate partial neutralization reactor. The purpose of the study was to determine the effects of pH, temperature, residence time, presence of metal sulphates (Fe, Al, and Ni), addition of surfactants and addition of gypsum seed on scale growth. The rate of scale formation was found to be reduced by lower temperatures, longer residence times and the presence of nickel. pH had no significant effect. The effect of these variables on the rate of scale formation was related to the degree of gypsum supersaturation. Scale reduction through the addition of sulphonated anionic surfactants was found to be effective only under certain conditions. However, gypsum seeding was found to be an effective method of scale reduction. Scale was reduced by 50% or more at a seed concentration of 10 g/LOn a effectué une étude expérimentale afin de déterminer le taux et le degré de formation d'écailles de gypse (sulfate de calcium dihydrate) sur les surfaces en acier inoxydable d'un réacteur de neutralisation partielle en continu d'acide sulfurique hydrométallurgique et de carbonate de calcium. Le but de l'étude consistait à déterminer l'effet de plusieurs variables sur la croissance des écailles, incluant le pH, la température, le temps de séjour, la présence de sulfates de métal (Fe, Al et Ni), l'addition d'agents de surface ainsi que l'addition de semences de gypse. On a trouvé que le taux de formation d'écailles était réduit par des températures plus basses, par des temps de séjour plus longs et par la présence de nickel. Le pH n'avait pas d'effet important. L'effet de ces variables sur le taux de formation d'écailles était relié au degré de sursaturation en gypse. De plus, la réduction d'écailles par addition d'agents de surface anioniques sulfonés était efficace seulement sous certaines conditions. Cependant, on a trouvé que l'ensemencement de gypse était une méthode efficace de réduction d'écailles, avec une diminution de 50% ou plus avec une concentration d'ensemencement de 10g/L.

Application of an iterative identification for control scheme to a neutralization process

Abstract In this paper an iterative scheme for identification and control is discussed. In the identification step a plant model which is suitable for the subsequent controller design step is obtained by estimation of the (dual) Youla-parameter in the time-domain. Using the plant model, the frequency response of the ideal controller, which perfectly realizes the desired closed-loop response for set-point changes is computed. This controller may not be realizable or is of high-order. A realizable, low-order controller is then calculated using frequency-weighted approximation. These steps are repeated until satisfactory performance of the closed-loop system is obtained or cannot be improved further. The proposed scheme is applied to the identification and control of a continuous neutralization reactor.

Hynol—An economical process for methanol production from biomass and natural gas with reduced CO 2 emission

The Hynol process is proposed to meet the demand for an economical process for methanol production with reduced CO 2 emission. This new process consists of three reaction steps: (a) hydrogasification of biomass, (b) steam reforming of the produced gas with additional natural gas feedstock, and (c) methanol synthesis of the hydrogen and carbon monoxide produced during the previous two steps. The H 2-rich gas remaining after methanol synthesis is recycled to gasify the biomass in an energy neutral reactor so that there is no need for an expensive oxygen plant as required by commercial steam gasifiers. Recycling gas allows the methanol synthesis reactor to perform at a relatively lower pressure than conventional while the plant still maintains high methanol yield. Energy recovery designed into the process minimizes heat loss and increases the process thermal efficiency. If the Hynol methanol is used as an alternative and more efficient automotive fuel, an overall 41% reduction in CO 2 emission can be achieved compared to the use of conventional gasoline fuel. A preliminary economic estimate shows that the total capital investment for a Hynol plant is 40% lower than that for a conventional biomass gasification plant. The methanol production cost is $0.43/gal for a 1085 million gal/yr Hynol plant which is competitive with current U.S. methanol and equivalent gasoline prices. Process flowsheet and simulation data using biomass and natural gas as cofeedstocks are presented. The Hynol process can convert any condensed carbonaceous material, especially municipal solid waste (MSW), to produce methanol.

Model predictive control using neural networks

In this article, we present the application of a neural-network-based model predictive control scheme to control pH in a laboratory-scale neutralization reactor. We use a feedforward neural network as the nonlinear prediction model in an extended DMC-algorithm to control the pH-value. The training data set for the neural network was obtained from measurements of the inputs and outputs of the real plant operating with a PI-controller. Thus, no a priori information about the dynamics of the plant and no special operating conditions of the plant were needed to design the controller. The training algorithm used is a combination of an adaptive backpropagation algorithm that tunes the connection weights with a genetic algorithm to modify the slopes of the activation function of each neuron. This combination turned out to be very robust against getting caught in local minima and it is very insensitive to the initial settings of the weights of the network. Experimental results show that the resulting control algorithm performs much better than the conventional PI-controller which was used for the generation of the training data set. >

Neutral Beam Source Design and Beam Kinetic Energy Activated SiO2 Etching

ABSTRACTAn unique method is used to produce a low energy nonthermalized fast neutral radical beam wliich can activate the SiO2 surface for chemical reaction at the desired incident energy. The fast neutral beam energy is continuously adjustable (2eV<Ek<200eV) and the beam flux is typically 5×1015cm−2 sec−1(∼4L). An uniform large diameter plasma is also made for the production of neutral beam covering 5”wafer and larger. Large diameter neutral beam single wafer reactor is feasible with off-the-shelf pumping technology.

Non-Linear Discrete Time Modelling and Control of a Pilot Neutralization Chemical Reactor

Many continuous industrial processes working inside a large operating range can be modelled by variable parameter and/or bilinear continuous state equations. In the case of processes with variable parameters, the state affine models allow to get a discrete approximated representation. An original direct identification method, involving a variable parameter filter, is processed inside the whole operating range in order to estimate the model coefficients. A dual approach leads to state affine control algorithms by gathering a family of linear controllers into a unique control law. In the case of bilinear continuous processes, their discrete model is of linear time-varying type. A way for digitally controlling them can be a closed loop linearization which leads to an implicit control law. An improvement can be obtained by adding integrators. Experimental results got, in each operating case (variable parameter or bilinear system), from a pilot neutralization reactor show the applicability of the methods.

Adaptive Control of a Waste Water Neutralization Process — Control Concept, Implementation and Practical Experiences

The first part of the paper describes a new method for adaptive pH-control of a continous neutralization process in a waste water treatment plant. The waste water which is collected from different laboratories, pilot plants and production plants is fed into a neutralization reactor with a low mean residence time and a dominating time constant of about 30 sec (fast dynamics). As the composition and the concentration of the waste water changes quickly, the nonlinear titration curve alters accordingly. Consequently the gain factor of the neutralization process, depending on the derivation of the titration curve, also tends to alter quickly. In this case, neither conventional fixed PID control (due to the wide range of the process gain) nor adaptive control with recursive parameter estimation (due to the quick alterations of process parameters and nonmeasurable disturbances) can be applied. In order to overcome these problems a new adaptive control which is based on the principle of model reference adaptive control, has been developed. The gain of the main control algorithm will be altered by a superposed adaptive control loop so that in the case of a control deviation the pH-value of the effluence approaches its setpoint by a prescribed trajectory. This adaptive control system was developed in a pilot plant. The algorithms were implemented on a Personal Computer in the programming language BASIC. Many experiments have proved it being very practical for many types of disturbances.The second part of the paper describes the implementation of control scheme in the large neutralization plant. As controller hardware we used a standard programmable digital controller called IAC (Interactiv Controller) from Fisher Controls. The firmware of this controller contains blocks for control functions (e.g. PID) and in addition arithmetic and logic functions which are similar to assembler mnemonics of customary microprocessors.In order to implement the control scheme on this controller, the BASIC program which was developed in pilot operation was carried over to the syntax of the IAC. Only small modifications had to be done due to the different time behaviour of the pilot and large neutralization reactor.The adaptive control scheme is in operation in our large neutralization plant since October 1984. The control behaviour is statisfactorily, even for large disturbances. In the third part the control behaviour is described by showing some representative curves of the effluent pH (controlled variable) and influent pH.

A General Coordination for Multicircuit AC Transmission Studies

A fundamental frecuency phasorial approach for transmission unbalance analysis is presented applied to the two 500 KV parallel lines part of the Alicura transmission expansion. Single-phase autoreclosing magnitudes, near resonance coupling effects and unbalance indicators are investigated by means of a single computer program. Different transposing criteria are considered together with neutral reactor sizing, primary reactor location, load flow, earth resistivity and line sectionalizing including full electromagnetic and electrostatic intra-and inter-circuital couplings.

Implementation and application of microprocessor-based self-tuners

The implementation of a class of self-tuning controllers using a portable microcomputer system is described. The self-tuning control theory is shown to provide a variety of control objectives such as model-reference, optimal Smith prediction and the minimization of a general k-step-ahead cost-function. Hardware and software details of the portable computer, SESAME, are presented with particular reference to the use of a new high-level language, Control Basic. Studies of the application of self-tuning to the control of room-temperature, acid neutralization, and batch chemical reactors in industry are outlined.

Single-Phase Switching Parameters for Untransposed EHV Transmission Lines

Single-phase switching compensation schemes are presented and analyzed for untransposed EHV transmission lines having one, two or three shunt reactor banks. For this purpose modified and simple four-legged shunt reactor banks are utilized. A general method is developed to optimize the neutral reactor values in order to minimize the secondary arc current for different arrangements of the modified and simple four-legged reactors. As an example, a large range of 765kV lines is used and single-phase switching parameters are obtained and analyzed for different ratios between the capacities of simple and modified reactor banks. The optimum neutral reactances as well as the secondary arc current, recovery voltage and neutral reactor voltages are presented as functions of the compensation factor which is varied from 0.6 to 1.0.

Compensation Scheme for Single-Pole Switching on Untransposed Transmission Lines

A Modified Four-Legged Reactor Scheme was developed for high speed, single-pole reclosing on untransposed lines. The new scheme, together with the simple four-legged reactor bank, effectively reduces the secondary arc current and the recovery voltage. Equations were derived to determine optimum neutral reactor values. Efficiency of the compensation scheme and the optimization procedure were verified by an example. The modified four-legged reactor bank includes four switches whose operations are coordinated with the line breakers. Switch parameters and suggestions for neutral reactor protection are given.

Single-Pole Switching - A Study of System Transients with Transposed and Intransposed Lines

Single-pole switching is investigated on a 150 km, 500 kV transmission line using a hybrid computer simulation which has been verified by comparison with field tests. The effects of transpositions along with changes in the neutral and shunt reactors are studied. Also, a detailed representation of a synchronous machine is incorporated with the simulation of the transmission line to study the effects of single-pole switching upon the electrical and mechanical transients of the machine. This method of representation offers a means of predicting the instantaneous torque as well as the couple-frequency rotor currents during single-pole switching.

Standardization or Ratings of Neutral Grounding Reactors

Standardization or Ratings of Neutral Grounding Reactors

Neutral earthing of three-phase systems, with particular reference to large power stations

The paper reviews the various methods of earthing the neutrals of power systems and gives recommendations illustrating the latter by an example. Methods of analyses are considered, and the simplicity obtained by using symmetrical-component circuits is shown; attention is confined mainly to the zero-sequence circuit which can be varied to suit the earthing condition under consideration. The same circuits can be used also for the determination of restriking voltages. With an insulated neutral the effect of cyclic restriking in building up large neutral displacement voltages is shown. Reactance earthing is considered from a general aspect, particular attention being given to the effects of an unbalanced system and mutual reactance when using arc-suppression coils. The cause of neutral inversion when earthing through 3-phase potential transformers is dealt with. Earthing, both resistance and direct, is considered, special attention being paid to multiple earthing. The necessity of limiting the earthfault current, and methods of reducing the circulation of third-harmonic currents are indicated. Consideration is also given to the secondary effects of the method of earthing the neutral, inter alia, on the interference with communication circuits and insulation stresses. Suggestions are made regarding the ratings of neutral resistors, reactors and circuit breakers.

Temperature Limits for Short-Time Overloads for Oil-insulated Neutral Grounding Reactors and Transformers - II

Temperature Limits for Short-Time Overloads for Oil-insulated Neutral Grounding Reactors and Transformers - II

Temperature limits for short-time overloads for oil-insulated neutral grounding reactors and transformers — II

Temperature limits for short-time overloads for oil-insulated neutral grounding reactors and transformers — II

Temperature Limits for Short-Time Overloads for Oil-Insulated Neutral Grounding Reactors and Transformers

In part I, published in 1938,1 the principal question considered was the effect of ventilating coils on temperature limits for ground faults greater than one minute, for which it was assumed that 160 degrees centigrade based on all heat stored in copper was the correct limit. Since 1938 considerable new data have been obtained. This paper presents the new data and shows that: 1. For heating periods of one minute or less, practically all aging of insulation occurs during the cooling period. It is shown that temperature limits can be based on the rate of cooling rather than on the heating period. 2. In the heating-up period of one minute or less, 25 to 45 per cent of the loss is dissipated from the copper to the insulation and oil. Formulas are developed for calculating the temperatures during the heating and cooling periods. 3. Temperature limits above 160 degrees centigrade for one minute are permissible for both non-ventilated and ventilated coils, being approximately 200 degrees centigrade for windings which cool sufficiently rapidly.

General considerations in grounding the neutral of power systems: The neutral grounding reactor: Operating performance of a Petersen earth coil: Present day practise in grounding transmission systems: Systems transmitting at generated voltage: Systems transmitting at higher than generated voltage

R. W. Atkinson: I want to say a word with regard to the comparison between the condition of a cable system and an overhead open-wire system with regard to the grounding of the neutral. There is a large and important difference for two reasons. The most important reason is the relative cost of insulation of the cable system as compared with the overhead cable for high voltage. The insulation is a very important part of the transmission system, whereas it is a relatively minor part in the overhead system. You can afford in the overhead system to put on insulation to take care of the voltage rise due to abnormal conditions, and you can afford to put on the insulation to take care of service conditions; whereas the same difference in service conditions costs you a whole lot more in insulation of cable systems. Another difference from the standpoint of operation, is the very much greater electrostatic capacity for the cable system.

The Neutral Grounding Reactor

A neutral grounding reactor (Petersen Coil) has been in operation on the system of the Alabama Power Company since October 12, 1921. This is the first of these devices in this country, although there are perhaps several hundred of them in operation in Europe. The present paper discusses the tests made shortly after installation of this reactor. A companion paper by Messrs. J. M. Oliver and W. W. Eberhardt, discusses the operation of the reactor for a period of about a year. It is believed that this device has a somewhat limited use in this country on account of the prevalence and popularity of the solidly grounded neutral. Nevertheless, there are certain installations favorable to the use of the reactor and it is partly the purpose of the present paper to outline the field of this device as well as to show how its rating may be determined for a particular system.