PT93989A - PROCESS OF EVAPORATION OF A HOT LIQUID - Google Patents

Description

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Description of the invention patent of A * Ablstrom Corporation, Finnish, industrial and commercial, headquartered in SF-2960G Hoormarkku, Finland, (inventort Histo Saa-ri, residing in Finland) pa- 'tsl' FIOCBSBO Dl EYAFQMClO BE DM DÍQUISO BURNING11.

The present invention relates to a multistage distillation method for the evaporation of liquid by means of thermal energy contained in the liquid. The present invention is suitable, for example, for the concentration of hot waters and liquids wasted by the industry.

Water in the paper pulp industry has in many cases a very low content of wasted material which is harmful to the environment and to remove harmful substances it is necessary to clean large quantities of water. With conventional cleaning methods the process involves considerable costs, which, again, may prevent the cleaning of waters necessary for the protection of the environment *

As is well known, industrial processes consume energy as well as raw material. Energy is discharged as energy wasted by the process generally at a temperature level that is lower than the original level. The said wasted energy is 1

often combined with the waters that are being discharged from the processes by which part of the water may also contain wasted material. The wasted waters of the process are thus, on the one hand, swollen and, on the other, have to be cleaned. Cleaning of rejected water would be more economical if waste heat could be used. The problem is that waste heat is combined in the same water, which must be cleaned, and it is difficult to remove it from the water to allow it to operate as a heat source of a cleaning process * Wasting hot water I, in a certain way, c subject and the object of the cleaning process *

Conventional distillation methods can not use wasted heat because their object is that the primary energy is maintained for the heat effect of the process.

By using the present invention, most of the water containing wasted heat can be evaporated by the wasted heat included in the water itself.

If the temperature of wasted water is, for example, 60 ° C, it is possible to evaporate almost half of it and more than three quarters when the temperature is 80 ° C, if water cooled at about 15 ° C is available. invention is characterized in that the steam originated in each distillation step of a multi-stage distillation process is fully condensed with the evaporation water in a heat exchange in the next distillation step which is carried out at a lower temperature. As can be seen from the following description, it is possible by this method to utilize the heat contained in the liquid itself more efficiently than by conventional methods. The present invention is described below and is compared with known methods by way of example 2.

quot; with reference to the accompanying drawings, which are all sinales and quot; flowchartsquot;

FIG. 14 is a schematic illustration of a known multi-effect distillation method (MED); FIG. 24 is a schematic diagram of another known method, a rapid multi-step method (koE); and Figure 34 is a schematic illustration of a distillation process according to the present invention.

Several different distillation methods have been developed for the needs of the industry and especially for the desalination of sea water, where the energy consumption of distillation has been decreasing. The most important of the methods used are the distillation method of multiple effect (MBD, Big, 1) and the fast multi-step method (HSF * Hg # 2) *

There is shown in Figure 1 that part of the steam 13 originating from one of the distillation stages 11 of a conventional multiple effect distillation plant is condensed in a water heater 16 in communication with each of the distillation stages excess of the remaining part 15 of the steam is condensed in a heat exchanger 17 in a heat exchange with the liquid to be distilled which is then vaporized which is carried out at the lower temperature, the distillation product 14 is condensed in a distillation stage ll is partially vaporized when it flows to the lower pressure of the next distillation stage 12 and also this vapor is condensed in the heater. 16 of the feed water * 3

Thus the energy to be released when the vaporization liquid 19 and also the distillation product 14 are gradually cooled is used to heat the feed water near the temperature of the hotter distillation operation. The latter is carried out by means of the primary energy source 18 introduced in the first stage 10 when the primary energy is gradually transferred with the vapor 15 from the vaporization and condensation to a lower temperature and finally when it is discharged to the condenser of the last step. Figure 2 shows a rapid distillation (MSI *) which is the most commonly used method for the desalination of seawater. In a certain sense, the above-described method is carried out. The liquid 29 is sprayed merely by means of the thermal energy therein, when it flows from a stage 21 to the next stage 22, which has a lower pressure. The vapor is in this case not condensed in the heat exchange with the liquid of the vaporization. * Instead, all the vapor 23 originating in a specific distillation stage 21 is condensed in a condenser 26 at this same stage *

Compared with the process of Figure 1 the heater 16, the 26 became effectively so wide that the standard heat exchanger 17 decreased. The first distillation stage 20 became the last heater of the feed water, which is heated with the primary energy 28. The flow of feed water increased respectively so that in the HBB distillation is typically double compared to the outlet, while in the MSP distillation is about ten times. If this water stream is cooled by complete vaporization, for example 56 ° C, then 10% of it will evaporate. The method according to the present invention shown in figure 1 is the other end of the process of Figure 1, somewhat opposite to the MSP process of Figure 4,

In this case all the steam 35 originated in a specific distillation step 31 and condensed with the vaporization liquid mm heat exchanger 37 in the next distillation step which is carried out using the lower temperature. There is neither a heater 16 nor a condenser 26 from KSF distillation. the vapor 36 expanding from the condensate distillation product 33 is condensed in the heat exchanger 37 together with the vaporization liquid in the next step. The first stage 30 may simply be an expansion chamber in which part of the hot liquid 38 flowing for the spray-evaporated process and the steam 40 upon being released is condensed in the next step 31 which the vapor-cooled liquid 41 flows into the next step 31 in which due to the low salt pressure prevailing in that stage, part thereof is vaporized by subsequent sparging to a lower temperature. Here it receives the heat of condensation from the vapor 40 of the preceding step 30 * whose heat vaporizes a relative amount of the new vapor. The remaining liquid 33 also flows to the next step where the same process takes place again and so on as needed. In the latter step, the vapor is condensed in a condenser 42 which may for example be a nozzle condenser *

There is described application of an embodiment of the present invention. Full vaporization takes place by means of heat in the liquid to be vaporized. No primary energy is required. The energy to be released in the first stage and the energy to be released in cooling the liquid and of the distillation product at each stage are used again in the next step. This means the output of each step and more than the output of the previous step. In conventional distillation which is used as a comparison, the output of each step is slightly lower than the output of the preceding step and in the distillation MSP 5

In the first step of the process according to the present invention, for example 1% of the water is vaporized and the water is thus cooled to about 60 ° C, another 1% of the water is vaporized during its condensation in the second step. temperature between the steps is 4.5 ° C, 0.8% is further vaporized in the second step by spraying in other words 1,8% in the whole of the third step a corresponding amount of vapor is vaporized and further by spray 0, 8. $ 2.6 total. A further 12-stage steam distillation plant is in the order of steps 1 * 1 * 8, 2 * 6 * 3 * 4 * 4 * 2 * 5 * 0 * 5 * 8 * 6 * 6 * * 7 * 4 * 8 * 2 * 9.0 and 9 * 8 * ie * 64 * 8 $ in total *

Simultaneously, the water cooled to 54%, in other words the same amount as in the above-described distillation example. The amount of water evaporated, and however, 6.5 times the evaporated material with the gradually increased salt, in principle, be carried out in two ways. A large heat exchanger may be constructed as in the preceding step provided that the temperature differences remain approximately the same. It is also possible to construct the heat exchangers of approximately the same size, as in conventional distillation plants, provided that the temperature differences between the steps increase gradually when production increases. The first alternative referred to is more economical, especially when the number of steps increases *

If any extra energy is available, the evaporation process according to the present invention can be intensified by heating the liquid to be evaporated at a temperature which is higher than 6.

Claims (1)

than the original one, before being transferred to the process. If, however, the temperature level is not high enough so that it is possible to vaporize the liquid by means of extra energy in the first stage of the process and in order to add steam, otherwise, by sprinkling. Part of the liquid may also be fed back from the last to the first distillation step through one or more heat exchangers, which are heated by extra energy and which can thus use wasted heat to temperatures. A multi-stage distillation process for evaporating hot liquids, characterized in that the steam generated in each distillation stage is completely condensed in a heat exchanger with the liquid vaporized in the next distillation stage which is carried out at a low temperature. A process according to claim 1, characterized in that part of the waste liquid, which is discharged from the colder distillation phase, is recycled to the hotter distillation stage through one or more subsequent heat exchangers acting at levels of which are heated by means of the heat energy supplied exogenously. Apparatus for carrying out the process according to claim 1 or 2, characterized in that a heat exchanger of each distillation stage is larger than the heat exchanger. heat exchanger to the preceding distillation stage at elevated temperature The applicant claims the priority of the Finnish request lodged on 10 May 1989, 892239 # lisboa, June 9, 1990 @ OSTUILE, © Λ SJÍJSIí 8