Falling Film Evaporation

The falling film evaporator system EFF is used for gentle partial evaporation of liquid mixtures, especially when requirements – e.g. low operating pressures at high evaporation rates – exceed the capabilities of classical evaporators.

The raw solution is fed into the evaporator from a feed batch vessel or continuously and evenly distributed as a thin film over the surface of the evaporator tubes with a special distribution system. The low boilers are partially evaporated from the descending film, flow with the concentrate into the sump of the falling film evaporator and are conducted as steam to the external condenser for condensation. As a result, the distillate flows out of the condenser.

Meanwhile, the non-evaporated liquid flows along the falling film evaporator tubes, is continuously concentrated by the evaporation and finally flows as concentrate into the evaporator sump and from there out of the evaporator. Concentrate and distillate are either collected in a receiver or continuously discharged via a pump.

Vacuum pumps are used to set the desired process conditions such as pressure and temperature, and thermostats (laboratory and pilot scale) are used for heating, evaporation and condensation. On a production scale, classic energy sources such as steam, thermal oil or cooling water, cooling brine and glycol are used. A cold trap is used to reduce the undesired entry of low boilers from the exhaust gas flow into the vacuum pump system.

• Compact evaporation devices and systems with low hold-up and correspondingly short residence time with narrow distribution and gentle operating conditions
  • Laboratory and pilot systems made of stainless steel and borosilicate glass 3.3 in standardized modular design, optional process- and customer-specific adaptations
  • Production systems made of stainless steel in process- and customer-specific design
• Modular supplementary evaporator systems according to process requirements, e.g.
  • Downstream evaporators, e.g. system ETF-ESF
  • Vapour rectification column, EFR system
• Process-specific and customer-specific conditions, e.g. ATEX, DGRL, FDA, GAMP, ASME, UL standards
• Suitable for media with increased demands:
  • Low-viscosity media
  • Heat-sensitive media
  • Solids-containing media
  • Larger feed quantities, especially with a high low-boiling component
• Existing expertise for typical applications or feasibility studies with tests and scale-up verification
  • Food, e.g. coffee and dairy products, but also vitamins
  • Flavours and fragrances
  • Fatty acids
  • Process wastewater
  • Various other products of the fine chemicals and pharmaceuticals sector

For many applications, in addition to the composition of distillate and/or residue or concentrate, product properties such as odour and colour are also relevant. Likewise, possible effects that may occur during evaporation, such as foaming or fouling on the heat transfer surface, must be taken into account. The latter cannot be determined or estimated theoretically, but require a visual evaluation of the evaporation process. This can best be implemented in glass plants from COROSYS, which can be individually assembled in a modular system.

Once the general feasibility has been established, the process parameters for the design of a production plant shall be verified, i.e. heat transfer and maximum area-related evaporation rates or practical number of stages as well as the achievable yields and qualities shall be determined. For this purpose, COROSYS has a standardized series of pilot plants made of stainless steel (optionally also special materials) in various sizes and designs to choose from.

For new evaporation or distillation tasks, COROSYS offers in-house services ranging from literature research, thermodynamic simulations and laboratory tests to piloting of single systems or combinations of falling film (EFF), thin film (ETF) and short path evaporators (ESF), if necessary also in combination with rectification (ERF).

The main objectives and possibilities of preliminary studies/test distillations as well as laboratory and pilot plants are again briefly and clearly summarized in the following table:

For many known applications and also numerous new processes, which have been dimensioned in advance through studies and tests, evaporator systems are realized on a production scale. The production plants are preferably designed as package units, this reduces the planning effort on the one hand and, in particular, the installation and commissioning time on site at the customer’s premises on the other.

The evaporator systems on a production scale are individually dimensioned for the customer processes. The typical and most common evaporator sizes range from 2.5 m² to over 4,000 m². For larger plants, attempts are made to integrate a heat recovery system suitable for the respective process, for example by multi-stage evaporation or mechanical vapour recompression. This is shown as an example in the adjacing diagram for a process with 30 t/h water to be evaporated.

In some cases, specific cyclical cleaning processes are also required, which we would be pleased to develop together with you.

In general, fine machining of the surfaces in contact with the product and the use of alternative materials are also possible.

The construction of the production systems is performed in compliance with the required directives such as DGRL 2014/68 EU or ASME, ATEX 2014/34 EU, UL standards, GMP guidelines, TA-Luft and the machinery directive 2006/42/EG.