Alaqua, Inc
Evaporator (Falling Film / Rising Film)
Product Description
Falling Film Evaporators:
Falling Film Evaporators Print Send link Home / Evaporation & Crystallization / Evaporator Systems / Falling Film Evaporators In falling film evaporators the liquid product (A) usually enters the evaporator at the head (1) of the evaporator. In the head the product is evenly distributed into the heating tubes. A thin film enters the heating tube are it flows downwards at boiling temperature and is partially evaporated. In most cases steam (D) is used for heating the evaporator. The product and the vapor both flow downwards in a parallel flow. This gravity-induced downward movement is increasingly augmented by the co-current vapor flow. The separation of the concentrated product (C) form its vapor (B) is undergoing in the lower part of the heat exchanger (3) and the separator (5).
In falling film evaporators the liquid product (A) usually enters the evaporator at the head (1) of the evaporator. In the head the product is evenly distributed into the heating tubes. A thin film enters the heating tube are it flows downwards at boiling
temperature and is partially evaporated. In most cases steam (D) is used for heating the evaporator. The product and the vapor both flow downwards in a parallel flow. This gravity-induced downward movement is increasingly augmented by the co-current vapor flow. The separation of the concentrated product (C) form its vapor (B) is undergoing in the lower part of the heat exchanger (3) and the separator (5).
Falling film evaporators can be operated with very low temperature differences between the heating media and the boiling liquid, and they also have very short product contact times, typically just a few seconds per pass. These characteristics make the falling film evaporator particularly suitable for heat-sensitive products, and it is today the most frequently used type of evaporator.
However, falling film evaporators must be designed very carefully for each operating condition; sufficient wetting (product film thickness) of the heating surface by liquid is extremely important for trouble-free operation of the plant. If the heating surfaces are not wetted sufficiently, dry patches and incrustations will occur; at worst, the heating tubes will be completely clogged. In critical cases the wetting rate can be increased by extending or dividing the evaporator effects, keeping the advantages of single pass (no recirculation of product) operation.
The proper design of the product distribution system in the head of the evaporator is critical to achieve full and even product wetting of the tubes.
Because of the low liquid holding volume in this type of unit, the falling film evaporator can be started up quickly and changed to cleaning mode or another product easily.
Falling film evaporators are highly responsive to alterations of parameters such as energy supply, vacuum, feed rate, concentrations, etc. When equipped with a well designed automatic control system they can produce a very consistent concentrated product.
The fact that falling film evaporators can be operated with small temperature differences makes it possible to use them in multiple effect configurations or with mechanical vapor compression systems in modern plants with very low energy consumption.
Rising Film Evaporators:
These operate on a "thermo-siphon" principle. Feed product (A) enters the bottom of the heating tubes and as it heats, steam begins to form. The ascending 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. The length of the boiling tubes will typically not exceed 23 ft (7m).
This type of evaporator is often used with product recirculation, where some of the formed concentrate is reintroduced back to the feed inlet in order to produce sufficient liquid loading inside the heating tubes. A number of different designs have been developed using this basic principle. A good example is the Roberts evaporator, which is the oldest type of circulation evaporator. This type of evaporator has a wide circulation tube in the center of the heating tube bundle through which concentrate flows back to the bottom of the tube bundle. The Roberts evaporator is still widely used in the sugar industry.
Company Info:
ALAQUA is a US corporation. We manufacture process equipment. Our engineers have over 20 years experience in the engineering of sanitary and ASME code evaporators, crystallizers, spray dryers, solvent recovery and distillation systems. Alaqua was established in 1989, and incorporated in 1993.
Our evaporators, crystallizers, distillation systems have proven themselves time after time in application after application. We supply world wide equipment to meet your processing requirements.
We supply equipment for installation by customer, skid mounted, or as turnkey projects.
The economics of your particular process and location will dictate the evaporator type and model best suited for your needs.
We offer complete project management capability for process installation. Single source responsibility stakes care of total project activity from initial consultation and design, through engineering and installation to final start-up and commissioning.
Who we are:
ALAQUA is an original equipment manufacturer. We design and manufacture calandrias, evaporators, distillation plants,
crystallizers, ethanol plants classification equipment, solvent
recovery systems, and other process equipment for the Chemical, Dairy, Environmental, Food and Beverage industries.
Our engineers have over 20 years experience in designing these systems.
Our Chairman and Director of Engineering was the founder of major corporations such as HPD, and the Unitech Div. of Ecodyne. He was a senior lecturer on evaporation and evaporation at the University of Wisconsin.
We have extensive experience in engineering and fabricating salt and wastewater evaporators and crystallizers. We will be pleased to have you inspect our fabrication in Wisconsin, and/or to arrange for you to contact directly some of our customers.
What We Do:
We design and manufacture to ASME code, EVAPORATORS, CRYSTALLIZERS, DISTILLATION PLANTS, SPRAY DRYERS AND SOLVENT RECOVERY SYSTEMS for the Chemical, Environmental, Food, Dairy, Beverage and Pharmaceutical industries.
Professionals at your Service:
Alaqua`s nucleus of highly skilled engineers and technicians, most of whom have over 20 years experience in the industry developing outstanding products, serve a national and international base of customers.
- We provide engineering, fabrication, installation, start-up and personnel training for every application. We respond to any troubleshooting call rapidly.
- We guarantee operation to specifications.
- We provide engineering and consulting services
- We are with you 24 hours a day, no matter where you are.
To learn more about our evaporator systems & crystallizer systems, please contact us today
