Chem Process Systems Ahmedabad, Gujarat

chem process rising film evaporators operate on a thermo-siphon principle. Feed product enters the bottom of the heating tubes and as it heats, steam begins to form. The upward force of this steam produced during the boiling causes liquid and vapors to flow upwards in parallel flow. At the same time the production of vapor increases and the product is pressed as a thin film on the walls of the tubes, and the liquid rises upwards.

this co-current upward movement against gravity has the beneficial effect of creating a high degree of turbulence in the liquid. This is advantageous during evaporation of highly viscous products and products that have a tendency to foul the heating surfaces. Usually there must be a rather high temperature difference between the heating and boiling sides of this type of evaporator. Otherwise the energy of the vapor flow is not sufficient to convey the liquid and to produce the rising film.

Energy efficiency of Chem Process Evaporators and Crystallizers is a crucial consideration during the designing of each customers specific application. Energy efficient systems utilize waste heat, multiple effects, mechanical vapor recompression (MVR) and/or thermal vapor recompression (TVR).

The evaporation duty is separated into stages operating at different temperatures. External heat drives the first effect of the evaporator, with subsequent effects being driven by vapor generated from the previous higher temperature effect. Product may be passed through the evaporator in forward, back or mixed flow configurations. Additional efficiency is achieved with the use of regenerative heaters, condensate heaters and vapor heaters.

In general a Multi-Stage Flash Evaporator is a series of single stage evaporators, where the steam is used for direct heating in one effect only. And the feed flow in a linear way passes through all the single stage evaporators.

The basic fundamental of the multi staging is utilization of the vapors generated in preceding effect heat exchanger or Calandria under negative pressure (vacuum) condition and lowering the boiling point of the feed in the subsequent stages. More the number of effects, lesser is the steam consumption. This helps economize the utility consumption.

How it works

In Multi-Stage Flash Evaporators, the product flows with a positive pressure through the tubes of all the stages i.e. from the last stage to the first stage, where the liquid is heated gradually by the vapor condensed in all the stages. From the last stage the liquid is discharged by the concentrate pump. The distillate is collected from all the condensers to the last stage condenser and from here it is discharged by the distillate pump. The non-condensable gases released in all the stages are discharged by the ejectors.

Chem Process designs and manufactures multi-stage flash evaporation plants, which may be used for producing fresh water from sea water, well water or industrial water. A special advantage of the multi-stage flash technology is that the thermal efficiency can be tailored to the individual client requirements. Chem Process multistage flash evaporation plants are also used for reduction of the volumes of industrial waste waters generated by industries.

Chem Process Forced Circulation Evaporators are normally used for liquids which are prone to fouling, scaling, crystallizing or for those which are inversely soluble or while concentrating thermally de-gradable materials. Here high re-circulation rate allows high liquor velocities through the tubes which help to minimize the buildup of deposits or crystals along the heating surface. The universal type, preferably used for concentration of solutions containing encrusting substances, hardening agents and un-dissolved solids, and for viscose solutions; also suitable for evaporative crystallization.

Forced circulation is required when hydrostatic head prevents boiling at the heating surface. A pump can also be used to avoid fouling that is caused by the boiling of liquid on the tubes; the pump suppresses bubble formation. Other problems are that the residing time is undefined and the consumption of steam is very high, but at high temperatures, good circulation is easily achieved.

How it works

Liquid is circulated at a high rate through the heat exchanger, boiling being prevented within the unit by virtue of a hydrostatic head maintained above the top tube plate. As the liquid enters the separator where the absolute pressure is slightly less than in the tube bundle, the liquid flashes to form vapour.

he Falling Film Evaporators can be operated with a low temperature difference and since the product residence time is very less, they are best suited for liquids which are temperature sensitive, have a high rate of specific heat transfer, particularly for non-crystalline solutions. Having low liquid holding volumes, the falling film evaporators are very easy to operate, clean and are extremely sturdy, thus the most frequently used types.

Caution must be used to ensure a continuous film wetting rate and to prevent nucleate boiling, otherwise the rate of heat transfer will fall off dramatically, and the rate of fouling on the heat transfer surface will increase.

Chem Process Spray Evaporator Crystallizer is a direct contact heat and mass transfer system which works similar to the principle of the induced draft cooling tower. These are for specific purpose sort of crystallization units and stand apart due to their unique operational philosophy, often referred as the granulation and prilling process. These type of crystallizers are generally utilized in the fertilizer segments where the most important aspect of this process is to lower the moisture content and improve the flow-ability of the very fine submicron particles.

How it works

The warm process slurry is sprayed against an ambient air stream, which is humidified through the removal of water from the spray and the sprayed liquid is cooled and concentrated. For increasing the evaporation rate, an external heat exchanger is utilized by adding energy to the recalculating slurry.

This is a tall column in range of 30 m height and around 6 m diameter, where a typical saturated slurry with low water content is sprayed from the top of the tower, and a very high temperature air is blown from the bottom of the tower. The droplets drop concurrently and gather the heat while travelling down and get dried to acceptable moisture level or water content.

If the solubility of a solvent is not decreased by lowering the temperature, the appropriate degree of solution super-saturation can be achieved by evaporating some of the solvent. Evaporative Crystallizers are usually operated under reduced pressure to aid solvent removal, minimize heat consumption or decrease the operating temperature of the solution and these are also described as low pressure evaporative crystallizers. To generate recirculation, an external heat exchanger is used with a high recirculation rate operated pump. Such kind of evaporators are generally used in many sugar refining and salt generation units.

Forced Circulation Crystallizers are of the Mixed Suspension, Mixed Product Removal types and operate either on controlled or natural slurry density, depending upon process requirements and/or unit material balance.These systems can be either of single or multiple effects and with which thermal or mechanical vapor recompression concept is often applied. Usually, they operate from low vacuum to atmosphere pressure. Almost any material of construction can be considered for the fabrication of these crystallizers