Under the pressure of high energy costs and at the same time ecological sustainability, the chemical industry is increasingly attempting to tap previously untapped potential. The development of appropriate heat transfer systems poses a particular challenge for apparatus and plant engineering. Innovative plant engineering combined with process engineering applications is therefore in demand. One answer to this is head condensers based on thermoshelves with integrated circulation evaporator. These special condensers have enormous advantages over tube bundles in terms of weight, less enclosed space, better cleaning options and thus lower overall investment costs. The use of condensation heat for steam generation in the plates is not widespread so far. However, condensers with steam generation create the possibility to use the released condensation waste heat at a high temperature level as heating steam in other process stages instead of uselessly discharging it via cooling water.
In the circulating evaporator, water is circulated without a circulating pump by natural convection due to the formation of steam bubbles. The heat introduced into the system via condensation superheats the water on the inside of the evaporator. In plate evaporators this leads to the formation of boiling bubbles in the plates. The bubbles rise to the top and create a buoyancy in the mixture of water and steam, which is decisive for circulation. In the steam collector at the upper end of the plates, the steam is separated from the still liquid water, which is then returned to the evaporator via a return line at the lower end. The requirement for a density difference on the steam generation side is accompanied by the requirement for a minimum temperature difference between the condensation temperature and the saturated steam temperature to be generated. If the condensation temperature is about 7 to 10 degrees K above the intended steam generation temperature, the condensation process is suitable for residual heat utilisation with a circulation evaporator.