Selective Control Strategy For Multi Effect Evaporators

Cascade Control Strategy For Multi Effect Evaporators

Continuous Fluid Bead Dryer With Single Loop Controls

Distinguish between ‘Continuous’ and ‘Batch’ Dryers Continuous Dryer The term continuous drying is where grain is continuously flowing though a dryer without stopping. The dryer itself has the same features as that of the mixed grain dryer. Batch Dryer This is the simplest dryer requiring a storage bin with a perforated floor and a blower to move air through the grain. Continuous Dryer for high capacity and fast change-overs Batch Dryer compact and competitive Continuous Dryer The continuous dryer operates by pulling hot air through one or two product beds which are each variable in depth.  Batch Dryer The batch dryer operates by forcing hot air through 5 to 10 product beds. Continuous Dryer New product is continuously fed in through the inlet valve, while the Swivel Valve discharger ensures smooth discharging of dried product to the next drying deck or into the hopper. Batch Dryer New product is continuously fed to the top bed deck which transforms the continuous flow into a series of

 Inferential Control Strategy For Dryers

Compensated Flash Dryer Compensated flash dryer is difficult to measure the wet bulb temperature in the case of hot air contaminated with solids, a program relating To to Ti for a particular ratio of temperature difference To TW/Ti Tw has been established. Linearization results in the following equation To* = RTi + b Where  To* is the desired outlet air temperature, R is the slop of To vs. Ti curve, and  b is the To axis intercept or bias. 

Different Types Of Dryers Rotary Dryer Spray Dryer Flash Dryer  Batch Dryer  Double Drum Dryer Rotary Dryer Rotary dryers work by tumbling material in a rotating drum in the presence of a drying air. They can also be indirectly heated to avoid direct contact between the material and processing medium. The drum is positioned at a slight horizontal slope to allow gravity to assist in moving material through the drum. Spray Dryer A spray dryer takes a liquid stream and separates the solute or suspension as a solid and the solvent into a vapor. The solid is usually collected in a drum or cyclone. The liquid input stream is sprayed through a nozzle into a hot vapor stream and vaporized. Solids form as moisture quickly leaves the droplets. Flash Dryer Flash dryers offer an effective method of removing surface or unbound moisture from a feed product. The technology behind flash drying employs a low residence time within the actual dryer; thus, the unbound moisture is "flashed" off t

Feedback Control Strategy For Evaporator Control

Evaporators Process Variables  Level of Solution, Temperature of Solution, Concentration Density. Input Variables  Dilute feed Solution, Steam Flow. Output Variables  Vapor, Steam, Product. Control Objectives  The main objective of evaporators is to get a concentrated product by vaporizing volatile liquid, Out evaporation process, Evaporation is conducted by non volatile solids and volatile solvent to produce this liquid. Manipulated Variables  Flow Rate of the feed solution, Discrete signal of the outlet value control.

Dryers Process Variables Temperature, Drying Period, Surrounding Temperature. Input Variables   Feed Flow, Input Temperature of Dry Air, Input Moisture of Solid and Feed Flow . Output Variables  Dred Product Moisture Content, Exhaust Air Temperature, The Temperature of Air Product  mixture (for spray dryers), Exhaust air Humidity, Product Quality, Control Objectives  maintenance of Dried Product Quality, Maxima of throughout of optimal, Energy efficiency and minimum cost, Stability of process. Manipulated Variables  Heating rate (e.g., inlet air or steam temperature), Solids feed rate (e.g., screw conveyor speed, discharge rate), Airflow rate (for direct dryers), Rotational speed (for rotary dryers)

Why distillation column is difficult to control The type and magnitude of disturbances affecting a distillation column have a direct effect on the resulting product variability. An analysis of the major types of disturbances encountered in distillation columns follows Feed composition upsets Feed flow rate upsets Feed enthalpy upsets Subcooled reflux changes Loss of reboiler steam pressure Column pressure upsets Feed composition upsets Changes in the feed composition represent the most significant upsets with which a distillation control system must deal on a continuous basis. A feed composition change shifts the composition profile through the column resulting in a large upset in the product compositions. Most industrial columns do not have a feed composition analyzer; therefore, feed composition upsets usually appear as unmeasured disturbances. When a feed composition analyzer is available, a feedforward controller can be applied using the on-line measurements of the feed compositio

Objectives of distillation column control The basic objective of distillation is to take a liquid mixture and separate it into two or more streams which have compositions different to the feed stream. In a basic distillation column a feed stream enters in the middle of the column and two streams leave, one at the top and one at the bottom.  Components with lower boiling points are concentrated in the stream leaving the top while components with higher boiling points are concentrated in the stream leaving the bottom. Separation is achieved by controlling the column temperature and pressure profiles to take advantage of differences in the relative volatility of the mixture components and therefore tendency to change phase.  The lighter, lower boiling point components evaporate and travel up the column to form the top product and the heavier, higher boiling point components condense and travelling down the column to form the bottom product.

Reflux ratio in distillation The reflux ratio is defined as the ratio of the liquid returned to the column divided by the liquid removed as product, i.e.  R = Lc/D. Reflux ratio is a most important parameter in distillation column  The Reflux ratio is the ratio between the boil up rate and the take-off rate. Or in other words, it is the ratio between the amount of reflux that goes back down the distillation column and the amount of reflux that is collected in the receiver (distillate). If 5 parts of the reflux go back down the distillation column and 1 part is collected as distillate then the reflux ratio is 5:1. In the case where all the reflux is collected as distillate the reflux ratio would be 0:1. If no distillate is collected then a reflux ratio is not assigned. Instead we call this "total reflux" or equilibration. The higher the reflux ratio, the more vapor/liquid contact can occur in the distillation column. So higher reflux ratios usually mean higher purity of the di

Evaporators  Process variable Level of solution, Temperature of solution, Concentration density Output and Input Variables Input Dilute feed solution, Steam flow  Output Vapor, Steam, Product Control objective The main objective of evaporation  is to get a Concentrated product by vaporization volatile liquid. Out evaporation  process evaporation  is conducted by non relative solids and volatile solvent to produce this liquid  Manipulated Variable flow rate of the feed solution, discrete signal of the outlet valve control

Dryers  Process Variable Temperature, drying period surrounding Temperature  Input and Output variable Input feed flow, input temperature of dry air, input mixture of solid and feed flow Output Dried product, moisture content , exhaust air temperature, The temperature of the air product, Exhaust air , humidity, product quality Control objective Maintaining of dried product quality, Maxima of throughout of optimal, energy efficiency and minimum cost, Stability of process Manipulated variable Heating rate, Solid feed rate, Air flow rate, rotational speed 

Distillation Column Process variables  Pressure, Temperature, level Input and Output Variable Input  variable Feed flow, Steam flow Output variable Distillate, Top and Bottoms product Control objective Liquid level in column base and accumulate distillation and bottom product  complete Pressure and temperature of column Manipulated variables product flow rate, reflux heat input

 Two Element Boiler Drum Level Control Two element boiler drum level control is a effective strategy suitable for boilers. In two drum level controlling (double element level controlling) the swelling and shrinking effect of boiler drum is taken care.  Single Element Boiler Drum Level Control  Three Element Boiler Drum Level Control

Single Element Boiler Drum Level Control Single element boiler drum level control is a simple strategy suitable for small boilers. Two Element Boiler Drum Level Control Three Element Boiler Drum Level Control

Three Element Boiler Drum Level Control A three-element boiler Drum level control system is uses the measured water level, and regulate the flow of water into the boiler. Single Element Boiler Drum Level Control Two Element Boiler Drum Level Control

Shrink and Swell effect in boiler  Shrink Now automatic water level control valve opens and cool water enters the system and bubbles burst leading to decrease in level of water more. this effect is called shrinkage Swell The formation of bubbles inside the boiler makes the level of water looks like increased which in real in not there. this phenomenon is known as swelling