DE2948541A1 - METHOD AND DEVICE FOR MULTI-STAGE EVAPORATION - Google Patents

Description

79 252 KN

NUKEM GmbH 6450 Hanau 11

Method and device for multi-stage evaporation

The invention relates to a process for co-condensation in multi-stage evaporator systems for concentrating salt-containing Solutions and / or solid suspensions, in particular for the decontamination of radioactively contaminated solutions and suspensions, and a device for carrying out the method.

In multi-stage evaporator systems, the vapors from the previous Evaporator stage are liquefied by mixed condensation in the subsequent evaporator stage. The one with mixed condensation Transferred heat is converted into re-evaporation by reducing the pressure of the fluid in the forced circulation utilized.

In DE-AS 2418045 it is reported that the vapors are perforated Surfaces or similar are introduced into the liquid. However, there is disadvantageous that such mixing condensers are structurally complex, easily clog the perforated surfaces, water hammers cause and require considerable maintenance. When processing radioactively contaminated solutions and suspensions particular difficulties can result from these disadvantages.

A method described in DE-OS 2632910 uses indirect methods Heat exchanger for each stage. This procedure is technically complex, expensive and is particularly useful for radioactive Sewage adverse maintenance problems.

It was therefore an object of the invention to provide a process for co-condensation in multi-stage evaporator systems for the concentration of saline solutions and / or solid suspensions, in particular

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for the decontamination of radioactively contaminated solutions and suspensions, as well as a device for carrying out the process to find that, above all, are easy to maintain, technically not complex and not prone to clogging.

The object was achieved according to the invention in that for co-condensation jet pumps can be used from the second stage.

In the schematic figures I and II vird the invention Method explained using a particularly advantageous device by way of example near.r, where Abbildunn II is a Shows jet pump in detail.

The liquid to be evaporated is transferred via pipe (1) a preheater (3) is fed into an evaporation tank (2) of the first evaporator stage. A circulation pump (4) promotes the Liquid is returned to the evaporation tank (2) via a heat exchanger (5) and a throttle screen (6). A subset of the liquid evaporates when the circulating concentrate is expanded in the throttle orifice (6) Determining the amount of heating steam supplied via a feed line (7) for the throughput of the evaporator system. The vapor is separated from the circulating concentrate in the evaporation tank (2). The waste heat from the heating steam condensate discharged through a pipeline (8) heats up in the preheater (3) the via the pipeline (1) liquid to be fed. The vapors from the first evaporator stage reach a mixing condenser by means of a pipe (9) (10), which is located in the circulation line (11) of a second evaporator stage. In doing so, everyone is made up of the vapors the droplets entrained in the first evaporator stage are injected and incorporated into the concentrate circulation of the second evaporator stage, so that the droplets from the first stage do not contaminate the distillate of the subsequent stage, e.g. radioactively contaminate them. According to the invention, this injection takes place by means of a mixing condenser performing jet pump (10). Jet pumps are small, compact elements for installation in accordance with the invention as mixing condensers eminently suitable, ca they practically a part

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the bypass line. The volume of the previously known voluminous and structurally complex mixing condensers, which is 7 m for an evaporation rate of 6.5 t / h, for example, is reduced to 0.1 m for the same evaporation rate with the design according to the invention, and the material weight to approx. 10%. In the example chosen, the mixed condensation according to the invention takes place in a jet pump with a nominal diameter of approximately 300 mm and a length of approximately 1.5 m. The method according to the invention also has a particularly favorable effect on the assembly effort and on the ease with which it can be decontaminated in the event of the evaporation and decontamination of radioactive waste water. In contrast to previous mixing condensers, multistage evaporator systems according to the invention can also be started up without the known water hammer which adversely affects the apparatus. It is therefore also possible to dispense with indirect heat exchangers that are otherwise required. The jet pump (10) functioning as a mixing condenser is connected to the circulation line (11) and the throttle orifice (17) of the second evaporator stage as well as to the pipe (9) of the vapor supply by means of flanges (12) so that it can be mounted or dismantled. Between the jet pump (10) and the vapors leading pipe (9) a shut-off valve (13) is connected, it is advantageous to further Absperreinrichtungeri between the jet pump (1O) and adapted to the circulation orifice (17) bzwi the circulating line to provide (11). This means that the jet pump (10) can be replaced quickly and safely, and because of the small outer surface, the only slight heat losses are advantageously noticeable. Integrating the jet pump (1O), which represents the mixing condenser, into the circulation line {H) also simplifies the design effort required to take into account the thermal expansion.

The second and optionally the further evaporation stages, respectively equipped according to the invention with the jet pump (10) functioning as a mixing condenser, otherwise work in the same way

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Principle of how the first evaporation stage, i.e. the liquid arrives in forced circulation from the evaporation tank (14) via the circulation ί pump (15) back to the jet pump (10). The vapors are fed into the next stages by means of vapor lines (16) if necessary or further treated in a manner known per se.

The concentrate of the first evaporator stage is via a line (18) drained. The blowdown from the second and further evaporator stage e takes place via lines (19).

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Claims (3)

79 2ί> 2 KN NUKEM GmbH 6450 Hanau 11 Claims /1. Process for mixed condensation in multi-stage evaporator systems for the concentration of saline solutions and / or solid suspensions, in particular for the decontamination of radioactively contaminated solutions and suspensions, characterized in that jet pumps are used for mixed condensation from the second stage. 2. Apparatus for performing the method according to claim 1, consisting of a first evaporator system stage with preheater, evaporation tank, circulation pump, heat exchanger and throttle and one or more further evaporator system levels with evaporation tank, circulation pumps, throttle orifices, pipelines and mixing condensers, characterized in that t that in the further evaporator system stages, the mixing condensers are designed as jet pumps (1O). 3. Apparatus according to claim 2, characterized in that the jet pump (10) is connected to the vapor pipeline (9) via a shut-off valve (13). 130023/0461 ORIGINAL INSPECTED