DE4029071C2 - Device for evaporating liquid products, method for operating the device and use of the device as a steam generator or condenser - Google Patents

Description

The invention relates to a device for evaporation of liquid products according to the preamble of claim 1 and a method for operating such a device and its use as a steam generator or condenser.

Devices for vaporizing liquid products are known in many embodiments. In contrast to steam however, they usually serve boilers or steam generators not for the production of steam, but for conversion of liquids or liquid mixtures in steam State because they are in this, for example, too che mix reactions that should be separated or because one Solute again by evaporating the solvent should be won.

The most important factors influencing evaporation are always the boiling temperature of the product, the operating pressure of the evaporator and the heat energy supplied for heating The boiling point of the product is not only per product-specific and from a certain product temperature dependent, but also on the concentration of the product. For example, the boiling temperature rises when thickening of a product with increasing concentration.

Evaporation is generally understood to mean the transition a liquid in the gas (vapor) state. Heated a liquid so far that its surface saturates temperature has reached, so go to this surface  continuously molecules into the vapor state. The necessary Such heat of vaporization can either be of the liquid are fed into the evaporator (heatable evaporators), or but the liquid is before entering the evaporator to any boiling temperature using any heating device warms up, and it can then get inside the evaporator due to the lower operating pressure prevailing there tension and partially evaporate (flash evaporator). The residual liquid is generally the preheater again supplied and the steam is either used as a product and / or condenses when the relaxation process turns off separation of salts or other components of the output purpose of the product.

In addition to the distinctions between heatable and relaxation Evaporators are differentiated from circulation and flow-through evaporators. With the latter, the flow of the liquid product takes place (Mass flow) from top to bottom, one speaks of a downflow or Falling film evaporator. These are used when the Ver because the time of the liquid to be evaporated is very low should, such as in the evaporation of heat sensitivity solutions that only boil for a short time may be used out so that they are not damaged. The need for evaporators with a short stay products used has been relatively strong in the past increased. On the one hand, this is due to the rising Forde improvements in product quality and yield and on the other the ever increasing number of new substances, which ther behave mixed unstable and not seldom also oxidations are sensitive. The mode of operation at relative low temperatures and extremely short residence times therefore in the thermal processing of such products an essential requirement if damage ver should be avoided. Falling film evaporators meet however the above conditions are not always sufficient gung. The fact that in the evaporator the level of the tem temperature and the dwell time during which the product  this is suspended, measured for the degree of its damage give necessarily leads to the requirement for types, where the product is in even less time, if possible as even thinner film that passes through evaporation surfaces and whose mode of operation exceeds the maximum permissible Temperature on the product side prevented. So are that Group of heatable evaporators belonging to so-called Thin film evaporators known in which the liquid film with a correspondingly lower, within certain limits adjustable thickness is generated and moved mechanically. A low film thickness is with liquid films, as they occur in thin film evaporators, as is well known an essential requirement for achieving good warmth transitions.

The evaporation areas are inside the evaporator mostly executed as heating pipes, so that the known Ver steamer to achieve large surfaces and therefore as possible thin film thicknesses have relatively large dimensions. One has gone over to solutions that incrust or the formation of deposits on the pipes tend to exclude the heating pipes to be placed half of the evaporator housing to allow evaporation in the pipes to prevent malfunctions by the formation of deposits can be largely avoided. Due to high flow rates between 2 and 5 m / s may not be one in all cases Crusting prevented, but at least delayed.

Evaporation is no longer found on or in the heater tubes, but in the actual evaporator, the so-called Vapor space, instead, one speaks of flash evaporators. The flash is generated during flash evaporation Vapors by lowering the pressure mostly to boiling temperature preheated solution. A flash evaporator system be therefore consists of a liquid heater and one as a vapor space trained relaxation body as well a vapor condenser.  

From CH-PS 84 062 is a device for evaporation of liquids known to also produce of steam can be used. With this device becomes the liquid to be evaporated or evaporated distributed by a riser on plate-shaped surfaces, to evaporate there. The surfaces are wavy, around the surface without enlarging the plate to be able to increase. The surfaces are from one side heated.

The purpose of this device is evaporation or perform evaporation in the shortest possible time can.

Evaporation takes place in this device in the vapor room and not in the heating pipes, it acts but not a flash evaporator because heating also takes place on the plate-shaped surfaces. The liquid is distributed in the device according to CH-PS 84 062 not in a thin film on the plate-shaped surfaces, but stands or flows in the thickness of the waveform.

This will heat the liquid for a long time exposed than to avoid damage compatible with sensitive liquids is. So it is not a thin film evaporator either.

A device is known from DE-AS 28 15 927 for the continuous concentration of chemical solutions serves. The heating process also occurs here the plate-shaped surfaces on which the Liquid is cascaded from above. The necessary heat is generated in the bars that form the plate Wear surfaces, fed. As in the CH-PS 84 062 are also no measures on the device here provided for evaporation as a relaxation process or to produce a thin film to protect the Product can lead.  

The variety of evaporator types listed above makes it clear that for the different evaporation tasks different evaporator types are used, to meet each specific problem to be able to achieve the best possible efficiency.

Proceeding from this, the invention has the object reasons, the aforementioned and described in more detail above Device for evaporating liquid products in Be train for universal applicability in large operations improve safety and high economic efficiency and a method for operating such a device to sit down. It is also desirable that the device with a simple and compact design for steam generation with a good quality of saturated steam can be used.

This problem is solved with regard to the device by the characterizing part of claim 1 and regarding the procedure by the labeling part of claim 15.

Due to their simple, from a few different Parts existing structure is the inventive Device not only particularly inexpensive, but also can be produced with relatively simple means. this makes possible their construction also in the so-called developing countries, where the Vorrich constructed and operated according to the invention tion for a variety of purposes, such as Desalination plants, in chemical plants, in the textile industry or can be used in power plants.

Another advantage of the device according to the invention is their particularly low susceptibility to failure. During the Evaporation does not require heat, the heat is done by heating in an outside of the device lying heat exchanger applied. The fiction device does not require driven mechanically  rotating parts with the for achieving such parts a uniform film distribution previously necessary high processing quality.

This makes it a particularly compact structure is enough that the housing, the trickle plate and the central tube has a round cross section (Claim 2). According to claim 3, it is the same for one moderate film distribution particularly useful if the trickle surfaces falling outwards from the central tube Expand the frustoconical plate. It is special favorable that the slope of the conical surface of each trickle surface plates between 1: 5 and 1: 20 (claim 4), in particular 1:10 (claim 5), is.

Adequate clearance for the steam produced To provide space for deduction, fill according to Claim 6 the trickle plate between the annular gap Half of the central tube and housing.

A particularly even product distribution the trickle surface plates is achieved in that the Openings in the central tube as horizontally arranged Row of slots, each with several horizontal slots per trickle plate are formed (claim 7).

So that the thin film on the trickle areas plates overflow essentially a constant Keeps width are according to claim 8 on each trickle surface plate provided several guide elements, which in advantageously curved convex upwards can be formed (claim 9). Manufacturing technology it is particularly simple that every trickle plate and the associated guide elements are formed in one piece are (claim 10).

To ensure an even distribution of the central pipe supplied product on the trickle plate Ensure cuts are the guide elements according to claim 11 on each pouring plate and the corresponding openings  arranged in the central tube so that they are in their Correspond to the number and mutual position.

To get entrained in the evaporation Retain liquid particles in the housing according to claim 12 in the area above the ver vaporization surfaces (vapor space) of arranged liquid separator provided.

According to claim 13 is the material for the product leading parts of corrosion-resistant steel, in particular V2A (claim 14) seen.

Due to the particularly high thermal efficiency the device according to the invention, it is also possible these as steam generators, e.g. B. in connection with solar power plants to use (claim 16). While maintaining the basic structure of the invention direction, it is even possible according to claim 17 use as a capacitor.

The aforementioned and the claimed and in the Described embodiments, according to the invention using components or process steps in their size, shape, material selection and tech African conception or the procedural conditions special exceptions, so that in each because of the known application criteria can find limited use; are in particular they also independently of each other to solve the task or at least one subtask can be used advantageously.

There are different teaching options To design and develop the invention for what on the one hand on the subclaims and on the other hand the following explanation is more preferred and in the drawing Reference shown embodiments is referred.

Fig. 1 shows a cross section through the basic design of the inventive device for the evaporation of liquid products;

Fig. 2 shows a horizontal section through the inventive device along the line II-II of Fig. 1;

FIG. 3 shows a section of the arrangement of individual trickling surface plates in a side view along the line III-III from FIG. 2;

Fig. 4 shows - greatly enlarged - an interior view of a portion of the central tube along the line IV-IV of Fig. 2;

Fig. 5 shows the device according to the invention, a set in a flash evaporator system of a solar power plant with a one-step process and

FIG. 6 shows the arrangement according to FIG. 5 in a two-stage work process.

The device according to the invention shown as a whole in cross section in FIG. 1 initially consists of a housing 1 into which a central tube 2 projects from below, which serves as a product inlet. At the upper end of the housing 1 there is a steam outlet 3 through which the resulting steam leaves the housing 1 . Be in the lower area of the device of the invention is in Darge exemplary embodiment illustrated on the left side as product outlet a further opening 4 is provided. The unevaporated part of the product comes out of the housing 1 through this opening.

When vaporization occurs, vapor bubbles and / or high vapor velocities make a liquid separator 5 below the steam outlet 3 necessary to separate the entrained liquid particles from the steam and retain them in the housing.

In order to distribute the product to be evaporated as well as possible in the relaxed space available, a plurality of trickling surface plates 6 are provided around the central tube 2 , closely spaced and parallel to one another, one above the other and with side openings, only a few of which are indicated . In the preferred exemplary embodiment, the trickling surface plates 6 sloping outward widen in the shape of a truncated cone. Preferably, a ratio of 1:10 is selected as the inclination of the conical surface of each giant surface plate 6 , but other inclination ratios are also conceivable in order to obtain other flow velocities of the liquid flowing over the pouring surface plate 6 .

The solid arrows in Fig. 1 represent the direction of flow of the liquid and the dashed arrows represent the direction of movement of the vapor generated by expansion.

From Fig. 1 also shows that the trickle plate 6 fill the annular gap between the central tube 2 and the housing 1 about half.

While in FIG. 1 processing the Vorrich invention shown only schematically, provides a be sondere embodiment of the invention that each Rieselflächenteller 6 is assigned a plurality of vanes 7 in such a manner that the width of the thin-layer film of the flowing across each Rieselflächenteller 6 product between two adjacent guide elements 7 is substantially constant. The in Fig. 1 the better overview because of not Darge presented guide elements 7 can be seen particularly clearly Lich from Fig. 2, where a view of a provided with guide elements 7 trickling surface plate 6 is shown. In the illustrated and in this respect before ferred embodiment, there are ten vanes 7, each of which emanates from a point on the boundary between the central tube 2 and Rieselflächenteller 6, radially extending downwardly of the inclination of the trickling adjuster according to and semi-circularly projects beyond this bottom at its end. The side view shown in FIG. 3 shows that each guide element 7 is convexly curved upwards.

The guide elements 7 aim that - despite the steady increase in the circumference when overflowing each trickling surface plate - the width of the thin film between two adjacent guide elements 7 remains substantially constant.

In order to distribute the liquid to be evaporated as evenly as possible over all sections of the trickle plate 7 , it is particularly advantageous if the openings in the central tube 2 are formed as rows of slots with several slots 8 per trickle plate 6 . It is expedient that the guide elements 7 on each flow plate 6 and the slots 8 in the central tube 2 correspond in their number and mutual position. Fig. 4 shows a greatly enlarged representation of a small portion of the central tube 2 from the inside. Here you can clearly see the horizontal slots 8 , which are bordered up and down by a trickle plate 6 be. Between the slots 8 of a row of slots are so to speak "webs" 9 , the number and location of the guide elements 7 correspond to.

It is easy to see that a ge wrestle number of guide elements the "dead" areas each of the trickle plate greatly increase if the be adjacent edges of the guide elements radially ver out should run. Conversely, too many leaders elements also reduce the "usable space" each of the trickle plate. Tests have shown that the arrangement shown in the embodiment of ten guiding elements per pouring plate as be has proven particularly useful. However, the Teaching of the present invention in no way to this Limit number of guiding elements.  

As already explained above, it is also possible to use the device according to the invention as a steam generator in a power plant. In Fig. 5 the use of the device according to the invention in a solar power plant is shown schematically. By means of solar energy, water in flat-plate collectors 10 is heated to a temperature of 95 ° C. after it has been conveyed from a water reservoir 11 by a pump 12 A to the flat-plate collectors 10 via lines not specified. He heated water is supplied by a further pump 12 B of the device he invented, here referred to as a steam generator 13 . Given the arrangement of the evaporator bottom at a certain height above the water mirror surface of the water reservoir 11 , the operating pressure p = 0.715 bar shown in FIG. 5 corresponds to an outlet water temperature of t _a = 90 ° C. in the steam generator, a water height of 3.0 m above the water level of the water reservoir 11 . The water rises in the central pipe and product outlet to the bottom of the actual evaporator. In order to put the steam generator 13 into operation, the pump 12 B already mentioned must convey the water to the height of the top trickling surface plate, in the example 2.5 m higher. To also overcome the pipeline resistance, an additional pump capacity corresponding to a delivery head of H = 4.0 m must be provided.

In the case of the operating pressure of the steam generator 13 given in brackets with p = 0.483 bar, corresponding to a water outlet temperature of t _a = 80 ° C., the water in the pipeline and in the steam generator 13 rises to a height of H = 5.17 m above the water level of the Water storage 11 . In order to put the steam generator 13 into operation in this case, the water from the steam generator 13 must be pressed back into the water reservoir 11 by means of a third pump 12 C. A delivery height H = 4.0 m is also required in this operating state.

In all other operating states with operating pressures in the steam generator between p = 0.7 and 0.4 bar, both pumps 12 B and 12 C operate at correspondingly lower speeds, so that each trickle plate of the evaporator can be supplied with the required amounts of water, and that the resulting cooled water at the bottom of the steam generator 13 is pressed back into the water reservoir 11 , which serves in this way as a heat store.

The steam generated in the steam generator 13 is fed in a known manner to a turbine set 14 and generator 15 be standing turboset, then beat in a condenser 16 with a degree of 5 ° C. and is returned to the water reservoir 11 by means of a pump 12 D .

Fig. 6 shows the inventive device in a two-stage working process. Here, the water heated in flat collectors 10 to 125 ° C is fed to a first steam generator 13 A with an operating pressure of p = 2.025 bar and partially evaporated there. In this exemplary embodiment, the water portions which have not evaporated to about 120 ° C. are not returned to the water reservoir 11 but to the flat-plate collectors 10 . The steam produced is fed in a known manner to the turbine set consisting of turbine 14 and generator 15 . This is followed by a capacitor 16 A, which can have essentially the same structure as the device according to the invention. In this condenser 16 A, the steam is struck by means of relatively cooler water at a temperature of about 90 ° C., which is heated to 95 ° C. by the condensation and fed to the water reservoir 11 serving as a heat store by means of a pump 12 C.

At the same time, 95 ° C. warm water is removed from the water reservoir 11 and fed to the steam generator 13 B. Steam is generated here, water is recirculated, electricity is generated, condensation and condensate are recirculated as in the exemplary embodiment in FIG. 5.

The previously described low temperature solar power works can already do so today - using known ones Technologies - in the so-called developing countries getting produced. This allows a constant flow supply can be guaranteed. To get the energy Sunshine becomes conventional suns collectors with a simpler glass cover. they are present in almost all developing countries machine equipment can be produced.

Such collectors are easy to clean, so that even with high levels of dust in the air, like this e.g. B. is given in Egypt, properly for a long time remain operational.

The uninterrupted and all load fluctuations ge rightful heat supply of the planned low Pressurized steam power plant is created by the installation of a warm water heat storage ensured. This memory be is made of such simple components that it is also in most developing countries can be manufactured. The same applies - with minor restrictions - to the intended low-pressure steam turbines, generators, Motors and heat exchangers.

When looking for the cheapest maximum process temperature for solar power plants with flat-plate collectors based on realistic system components (collector diagram and steam turbine efficiency) demonstrated that these most favorable process temperature is between 95 ° C and 80 ° C.

Finally, a numerical example should underline the above statements:
With a water throughput of 0.5 m ³ / s and a (selected) flow rate of 1 m / s, the required flow cross-section is 0.5 m ² . With a diameter of the central tube 2 of 0.8 m, the order is about 2.5 m. In the wall of the central tube 2 there are ten 5 mm high slots 8 of 200 mm in length, to which webs 9 of 50 mm in length are connected, the slots and webs being arranged alternately distributed over the entire circumference of the tube.

In order to achieve the required flow cross section A = 0.5 m ² , fifty rows of slits one above the other are required. Each row of slots ends on a trickle surface plate 6 , which is designed to maintain the flow speed frustoconical with an inclination of 1:10. To draw off the steam formed, the trickling surface plates 6 are arranged one above the other at a height distance of 40 mm. With the proposed mean plate diameter of 2.0 m, the flow length of the water is 0.6 m, so that there is a residence time of 0.6 seconds at the water speed of 1.0 m / s. A total cross-section of A = 9.42 m ² is available to the extracting steam in the clear height between two trickling surface plates 6 of 30 mm.

With an amount of steam generated per evaporator of
= 14.89 g / h = 4.136 kg / s
and the specific volume V of the steam of 2.365 m ³ / kg at 0.7 bar, the outflow velocity w _{D of} the steam from the trickling surface plates 6

is therefore extremely low, so that entrainment of water drops is largely avoided. The Dampfge speed increases in the jacket space between Ver steamer and housing 1 . With a housing diameter of 3.5 m there is a flow cross section of

a steam speed of about 1.5 m / s.  

The steam outlet 3 to the turbine 14 is designed for a Dampfge speed of 20 m / s and thus also receives a diameter of 0.8 m.

The evaporator described above has an off steam area of

So there will be

evaporates, a numerical value that, based on the evaporation areas of low pressure steam boilers, as very low can be designated. Due to the proportionate large evaporation area can be used without Carrying water drops is an excellent one Achieve efficiency.

The findings described above are used in the Calculation and construction of a solar power plant, which provide an installed capacity of 4 MW as an example should be used.

The power plant consists of
Collectors with an area of 270,000 m ² ,
a water storage tank with a volume of 1.57 million m ³ ,
four steam generators with a total area of 528 m ² ,
four low-pressure steam turbines, each with 1,250 KVA and
four capacitors with a degree of 5 ° C.

The total cost of the plant was DM 51.8 million determined. If the capital is made available without interest and annual repayment of 3%, the electricity price is off Factory 0.30 DM / kWh.

From the radiation energy of the sun with the planned plant 5% converted into electricity.

In contrast to all other previously known solar Power plants can be proposed with the invention device using the device in accordance with the device sunless periods up to one month full be powered.

Reference list

1 housing
2 central tube
3 steam outlet
4 product outlet
5 liquid separators
6 trickle plates
7 guide element
8 slot
9 bridge
10 flat collectors
11 water reservoirs
12 A pump
12 B pump
12 C pump
12 D pump
13 steam generators
13 A steam generator
13 B steam generator
14 turbine
15 generator
16 capacitor
16 A capacitor
16 B capacitor

Claims (17)

1. Device for vaporizing liquid products by relaxing at boiling temperature before heated products, with a housing having at least one product inlet, steam outlet and product outlet, in the interior of which a large number of evaporation surfaces is arranged, characterized in that the steam outlet ( 3 ) arranged in the uppermost part of the housing ( 1 ) and that as evaporation surfaces a plurality of in close spacing and parallel to each other, one above the other and around a vertically protruding into the housing, provided with side openings and supplying the product central tube ( 2 ) to ordered and to the outside sloping trickling surface plates ( 6 ) is provided. 2. Device according to claim 1, characterized in that the housing ( 1 ), the trickling surface plate ( 6 ) and the central tube ( 2 ) have a round cross section. 3. Apparatus according to claim 1 or 2, characterized in that the from the central tube ( 2 ) to the outside from falling trickle plate ( 6 ) expand frustoconically. 4. The device according to claim 3, characterized in that the inclination of the conical surface of each trickling surface plate ( 6 ) is between 1: 5 and 1:20. 5. The device according to claim 4, characterized in that the inclination of the conical surface of each trickling surface plate ( 6 ) is 1:10. 6. Device according to one of claims 1 to 5, characterized in that the trickling surface plate ( 6 ) half fill the annular gap between the central tube ( 2 ) and housing ( 1 ). 7. Device according to one of claims 1 to 6, characterized in that the openings in the central tube ( 2 ) are designed as rows of slots, each with a plurality of slots ( 8 ) per trickling surface plate ( 6 ). 8. Device according to one of claims 1 to 7, characterized in that on each trickle plate ( 6 ) a plurality of guide elements ( 7 ) is arranged such that the width of the thin film of the product flowing over each trickle plate ( 6 ) between two adjacent guide elements ( 7 ) is constant. 9. The device according to claim 8, characterized in that each guide element ( 7 ) is convexly curved upwards. 10. The device according to claim 8 or 9, characterized in that each trickling surface plate ( 6 ) and the associated guide elements ( 7 ) are integrally formed. 11. Device according to one of claims 8 to 10, characterized in that the guide elements ( 7 ) on the trickling surface plate ( 6 ) and openings in the central tube ( 2 ) correspond in their number and mutual position. 12. Device according to one of claims 1 to 11, characterized by a liquid separator ( 5 ) arranged in the region above the evaporation surfaces (vapor space). 13. The device according to one of claims 1 to 12, characterized in that as material for the product-carrying Parts of corrosion-resistant steel is used. 14. The apparatus according to claim 13, characterized in that as material for the product-carrying parts V2A steel is used. 15. A method of operating the device according to claim 1, characterized in that by means of a Pump fed and to the operating pressure in the housing appropriate boiling temperature warmed liquid product through openings in a vertically protruding into the housing Central tube over at a close distance and parallel to each other, one above the other and concentrically around the central tube arranged and sloping downwards trickle plate flows and evaporates there by relaxation, the Steam through the one arranged in the uppermost part of the housing Steam outlet fed for further utilization and that non-evaporated liquid product at the bottom of the case collected and subtracted from there. 16. Use of the device according to one of the claims 1 to 14 as a steam generator. 17. Use of the device according to one of the claims 1 to 14 as a capacitor.