An evaporator, also knowned as concentrator, is the equipment used to reduce the water content from a liquid feed, resulting in a final product also in liquid state but with a higher proportion of total solids. The result can be either an end product by itself, like glucose and fructose syrup or concentrated fruit juice, or an intermediate product such as concentrated milk prior to a spray dryer, which produces milk powder.
SEI Contreras Engineering specializes in the design and construction of falling film, rising film and forced circulation evaporators able to concentrate the widest variety of products, based on a deep knowledge of the heat transfer mechanisms involved and the physical and chemical properties of many products, proven through over four decades of experience.
In an industrial situation of growing economic and environmental demands oriented towards the rational use of energy, multiple effects evaporators optimizes the use of live steam, saving energy and cooling tower water that in most cases play a big part in the payback analysis of the equipment.
Our specialists can determine the optimal number of effects for your process based on the required evaporation capacity and the availability and costs of the utilities involved. In this equipment arrangement, the vapors generated in any given effect are used as heating medium of the next effect in line, and so on, depending on the number of effects the equipment has.
The vacuum generated by the condenser at the end of the evaporator allows to make use of the residual energy of these vapors at a lower evaporating pressure than the previous effect. The result is that the live steam is used as many times as effects the evaporator has.
We offer different alternatives regarding number of effects, arrangement and additional equipment, custom made for your process.
When a product must be highly concentrated, it is advised to include a independent finisher to the evaporator arrangement, so as to have a higher precision and control over the final product. This finisher usually is a falling film evaporator, but it can also be a scraped surface or forced circulation evaporator when viscosity is very high.
The versatility given by a finisher is based on the fact that the heating medium is an independent steam source, not in line with the main evaporator, allowing control over evaporation temperature, steam flow rate and temperature and other variables of the process without altering the operating conditions of the main equipment.
Thermal Vapor Recompression
In most modern evaporators it´s very common to use of steam eyectors to recompress part of the generated vapors using medium pressure live steam, resulting in high energy savings with a very small investment. By using different vapor recompression relations and including more than one effect in the loop open multiple possibilities to be assessed when designing a new equipment or reforming an existent one.
In an evaporator equipped with a thermal vapor recompressor, the vapor generated in a given effect are in part mixed with medium pressure steam and recirculated in the same effect, while the remaining vapors continue to the subsequent effects.
When mixed and recompressed, the vapors increase their temperature and pressure allowing evaporation to take place at a higher temperature. This reduces the required amount of steam for the evaporation in that effect with the corresponding savings in total steam required. As a thumb rule, it is estimated that by adding a thermal vapor recompressor the effect is similar to adding an extra evaporation effect, at a much lower cost.
Mechanical Vapor Recompression
An alternative to thermal vapor recompression y mechanical recompression, that allows reusing part of the vapors generated by means of an electrical compressor. In case of not counting with a medium pressure boiler or being limited in the use of steam, a preconcentrator with mechanical vapor recompression combined with a finisher is an interesting option to generate steam savings whenever electric energy is available and cheap.
Among the auxiliary equipment for evaporators that our company provides you can find:
- Aroma recovery systems
- Heat exchangers and pasteurizers
- Flash coolers
- CIP cleaning systems