WO2021018331A1

WO2021018331A1 - Heating means for increasing the vaporisation rate of water for thermal and solar water evaporators

Info

Publication number: WO2021018331A1
Application number: PCT/DE2020/000169
Authority: WO
Inventors: Harald Hansmann; Jürgen Renner
Original assignee: Hochschule Wismar
Priority date: 2019-07-27
Filing date: 2020-07-24
Publication date: 2021-02-04
Also published as: DE102019005311A1

Abstract

The invention relates to a heating means for increasing vaporisation rates of water for thermal and solar water evaporators, in particular for sea water desalination plants, in which, for accelerated heating and vaporisation of the liquid to be evaporated by solar thermal radiation as heating means, gel-like substances are used into which energy-absorbing, in particular sunlight-absorbing IR-active substances, are introduced, and porous substances are used which have a high internal microporosity and macroporosity associated with a high capillary action, are in direct contact with the evaporation surfaces and over which the liquid to be heated flows.

Description

Heating agent to increase the evaporation rate of water for thermal and solar water evaporators

The invention relates to a heating means for increasing evaporation rates of water for thermal and solar water evaporators, in particular for

Seawater desalination plants.

Due to the heat movement, the particles of liquid substances, including water, have different speeds according to the Maxwell-Boltzmamn distribution and thus different kinetic energy. The particles that are part of a

The liquid-gas phase interface has a higher energy than that of the

Have binding energy to the surrounding material, can overcome the phase boundary and leave the material structure in the gas space. Their share increases with increasing temperature and is the cause of the increasing vapor pressure of the respective substance. In addition to the transition into the gas phase, particles with lower kinetic energy return from the gas phase to the condensed phase, so that a dynamic equilibrium is established in the vapor pressure. This means that the vapor pressure difference between the liquid and gaseous phase determines the net evaporation that occurs. The vapor pressure increases with increasing temperature. Thus, an increase in temperature of the liquid causes increased evaporation. In addition to the temperature, the evaporation depends on the flow conditions in the liquid and gaseous phase. The movement of the air is responsible for the removal of the air that has been enriched with moisture through the evaporation process. The removal increases the vapor pressure gradient over the

Surface of the liquid and thus promotes the evaporation process.

Accordingly, solutions for increasing the

Evaporation capacities are known that are based on an increase in temperature of the liquids to be evaporated, on an increased air flow for transporting the air laden with water vapor from the evaporation surface and on an enlarged evaporation surface and on systems of a vacuum.

In DE 10 2012 014 560 A1, a substantial increase in the

Desalination of seawater in greenhouses, the amount of water obtained ww through the accumulation of water vapor in the air. The within

Confirmation copy Greenhouses heated air is tested according to a multi-level

Process for desalination of sea water highly humidified. In this process, an air flow is brought to a high moisture content by cascading it with water vapor and at the end of the cascade it is cooled in a condenser in order to recover the salt-free water

DE 16 42 530 A discloses a device for obtaining fresh water from salt water, in which a stream of air is passed along a tubular film, the air being heated in a first part and a condensation on the air hose in a second part to collect the fresh water to be held. The air can be moved by means of fans, with the introduction

mechanical energy to move the air and sea water is consuming. In addition, the device can only be set up in an environment with sea water.

DE 10 2011 121 540 A1 discloses a heating aid with which the solar thermal radiation is used more effectively for accelerated heating and evaporation of the liquid to be heated, which is mechanically and thermally stable and resistant to the liquid to be heated and does not cause any contamination of the liquid. For the accelerated heating and evaporation of the liquid by solar heat radiation, fine-grained solid and porous coke is used as a heating aid, with the liquid to be heated filling the coke bed with little protrusion. The coke is a beneficial one

Heating aid because it absorbs the heat radiation as best as possible due to its black color and the reflection of the heat radiation is low due to its diffuse surface. In addition, the coke quickly releases the heat it has absorbed into the surrounding liquid due to its thermal conductivity. These two properties of strong heat absorption and rapid heat conduction into the surrounding liquid are optimally effective if a fine-grained and polydisperse coke with high internal porosity is used. Furthermore, only dust-free coke is suitable as a heating aid. For the use of coke as a heating aid, coke grains of about 0.1 mm to 10 mm and

preferably 0.2 mm to 2 mm suitable. This polydisperse grain size distribution is necessary for a high packing density of the coke bed, because so the Gap volumes between larger grains can be filled as best as possible by smaller coke grains.

This invention has the disadvantage that the finely divided, solid and porous coke has a very abrasive effect when it is transported through the plant and causes high wear.

In WO 2011/124870 A1, a seawater desalination plant is described, a solar pipeline taking water from the sea and pumping it inland. The sea water is converted into fresh water using solar energy. The rate of evaporation is determined by the use of a vacuum in the

connected solar baths increased. A shallow desalination center further increases freshwater emissions by preheating the seawater before it is pumped into a vacuum. This causes the sea water to evaporate. Urine can also be used when there is no access to the sea.

WO 2004/067451 A1 discloses a device for cleaning water, in particular for desalination of salt water, with an evaporator for the water to be cleaned and with a condenser downstream of the evaporator for the water vapor, the evaporator having at least one circumferential textile carrier web for has the water to be evaporated. To be beneficial

To create relationships, it is suggested that the vaporizer and the

Condenser are in a circuit for an air flow serving as a carrier for the water vapor, that the circulating carrier web between deflection rollers

Is guided back and forth in a meandering shape and that the pulleys for the textile carrier web run in the flow direction of the air stream. The textile carrier web has a surface structure, for example knobs, around the

To further enlarge or increase the evaporation surface and thus the water vapor generation. Surface structures with capillary action are also conceivable in order to improve the water absorbed by the carrier web

Promote evaporation to the outsides of the carrier web.

The invention according to DE 19 621 042 A1 relates to a system for desalination of sea or sea water, which is operated exclusively using solar energy for evaporation and recondensation of salty water, with at least one being arranged on or within a floating body Comprises the evaporator space, which is covered with a pane that is permeable to the sun's rays, and a device for discharge in the evaporator space

water vapor-saturated air is arranged with a fan located above it, which is guided through the floors of the evaporator chamber or the float. This is followed by a condenser cooled with seawater

Evaporator chamber return lines for the water vapor-free air, the condenser is followed by a collecting device for the desalinated water, which comprises devices which convey the desalinated water into a container arranged above the water level. Through the bottom of the

Evaporator space or the float is still a than

Heat exchanger unit trained combined device for supply and discharge of salty water out. In the evaporator room there is a device for discharging water vapor-saturated air with a fan located above it, which is guided through the floors of the evaporator chamber and the float, and to which a seawater-cooled condenser with lines for the water-vapor-free air that recirculates into the evaporator chamber is connected, the condenser a collecting device for the desalinated water is connected downstream, which is conveyed with the help of a solar-powered pump into a container 10 arranged above the water level.

Even with the solution proposed in DE 31 19 615 A1

Seawater desalination is the evaporation with subsequent recondensation of seawater using solar energy alone. Here, the air that is supposed to absorb the sea water to be evaporated is natural

Chimney draft between the water surface and a film used as a cover pulled through. The heated and moisture-enriched air is then cooled on surfaces that are below the water level, whereby the condensate precipitates here and drains into a collecting basin connected to the mainland via pipes before the air is discharged to the outside in a chimney. That is what drives the air flow

continuous heating along the inner chimney, due to the

Temperature difference between the deeper sea water and the through

The upper part of the fireplace is heated by solar radiation, but only as long as the temperature level in the fireplace as a whole is higher than in the surrounding area. US Pat. No. 5,053,110 A describes a solar-powered device for purifying and / or desalinating water. Several embodiments are disclosed, each of which essentially derives its heat source from solar energy. The device has a unique design of the

Evaporation collection hood, which is provided with a smooth inner surface to allow the collection of increased amounts of distillate. The exterior of the device has a black surface to act as a black body and so absorb increased amounts of solar energy. In addition, the same exterior is coated with a film of infrared absorbing material (STET) to further increase the absorption of solar energy. To further improve the efficiency of the system, various external pipe designs are used to preheat the load before it enters the vaporization chamber. The distillate receiver is a downwardly extending dome. This increases the volume while reducing re-evaporation by minimizing the exposed surface. The arrangement of the device on a hill or other elevated topography also enables a further increase in the overall system efficiency in that the distillate is forced by gravity through a turbine / generator for the joint generation of electricity.

In DE 10 2017 114 020 A1 a device for evaporation and

Condensation of water, in particular for the production of drinking water

described, which from a closed space that has an evaporator surface, to which a water-containing liquid can be introduced via an inlet. The liquid flows over the at least partially sloping evaporator surface and can then be discharged from the room via a drain. Above the evaporator surface, an inclined film is arranged, on which water can condense on the side facing the evaporator surface and can be diverted from the inclined film via a drain to a collecting device. This allows the extraction of

Condensation from salt or brackish water can be carried out on a large area with simple means.

According to the invention, an inclined film is arranged above the evaporator surface, on which water can condense on the side facing the evaporator surface and can be derived from the inclined film via a drain to a collecting device is. A film for condensation, which can be produced inexpensively and which can also be installed over large evaporator surfaces, can therefore be used in the space. As a result, condensation water can be collected with simple means, whereby both the use of material is low and complex devices such as fans can be dispensed with.

From the prior art are solutions for increasing the

Evaporation capacities are known that are based on an increase in temperature of the liquids to be evaporated, on an increased air flow to remove the air laden with water vapor from the evaporation surface and on an enlarged evaporation surface and on the application of a vacuum. In order to increase the evaporation rates, all of these solutions require an increased outlay in terms of apparatus with the associated increased costs. When using heating means to increase the evaporation rates, only finely divided coke and charcoal are known from the prior art as heating means. When used in seawater desalination plants in particular, this finely divided coke shows high abrasive properties, which lead to premature wear of the plants.

The object of the invention is to develop heating aids to increase the evaporation rates for solar evaporators in devices for the evaporation and condensation of water, in particular for obtaining drinking water from seawater, the heating means being mechanically and thermally stable and resistant to the liquid to be heated and no contamination causing the liquid.

According to the invention, the object is achieved in that for the accelerated heating and evaporation of the liquid to be evaporated by solar

Heat radiation as a heating aid gel-like substances in which energy-absorbing, in particular sunlight-absorbing, IR-active substances are introduced, or porous substances with a high internal micro- and macroporosity combined with a high capillary effect that are in direct contact with the evaporation surfaces and are overflowed by the liquid to be heated. In one version of the invention, chemically crosslinked gelatin with a foam structure and incorporated IR absorbers, in particular proteins with graphite incorporated into the protein structure, are used as the gel-like substance.

The porous substances have a high internal micro- and macro-porosity and due to the small gap volume in the bed, the stored liquid is divided into small water segments and in this way the

Heat transfer from the porous substance to the liquid is greatly accelerated and rapid heating of the small water segments is achieved.

The invention will now be explained in more detail using examples, FIG. 1 being a schematic representation of an evaporation device according to FIG

DE 10 2017 114 020 A1 with the heating means which is in contact with the evaporator surface, wherein,

1 device for evaporation and condensation

2 side faces of the device (1)

3 basins

4 film for condensation

5 Brackish water inlet

6 Condensate drain

7 Brackish water drain

8 overflow

9 Net with heating agent

10 condensate collector

11 brackish water collector

12 evaporator surface

13 brackish water

mean.

Example 1 :

A device 1 according to DE 10 2017 114 020 A1 for evaporation

and condensation of water, in particular for the production of drinking water, comprises a closed space which has an evaporator surface 12, to which a water-containing liquid can be introduced via an inlet 6, which flows over the at least partially sloping terrace-shaped evaporator surface 12 and can then be derived from the room via a drain 7. Above the

An inclined film 4 is arranged on the evaporator surface 12, on which water can condense on the side facing the evaporator surface 12 and can be diverted from the inclined film 4 via a drain 6 to a collecting device. Furthermore, a plurality of terraced basins 3 are formed on the evaporator surface 12, which are arranged offset in height. On the surface of the basin 3 of the evaporator surface 12 are nets 9 within

Heating aids in the form of gel-like substances, such as gelatin, are placed in the energy-absorbing, in particular sunlight-absorbing, IR-active substances, such as graphite.

An upper basin 3 is each over an overflow 8, in particular one

Overflow bar connected to a lower basin 3. This overflow 8 also serves to secure the networks 9 with the heating means on the

Evaporator surface 12. As a result, the water-containing liquid, in particular salt or brackish water, flows over the heating means over the full area possible. As a result of the action of solar energy, which acts on the evaporator surface 12 through the film 4, the liquid is partially evaporated or evaporated. As a result, water-enriched air with high humidity is formed in the room. This also increases the temperature inside the room. This allows the

Extraction of condensed water from salt or brackish water on a large area can be done with simple means.

Example 2:

Instead of the nets 9 with heating means made of gel-like substances in which energy-absorbing, in particular sunlight-absorbing, IR-active substances are introduced, porous substances with a high internal micro- and macroporosity combined with a high capillary effect, such as mesoporous silica, are placed on the basins 4 , applied in a polydisperse bed and overflowed by the liquid to be heated, heated and partially evaporated or evaporated.

Claims

1. Heating means to increase the evaporation rate of water for thermal and solar water evaporators with evaporator surfaces (12) of the

Evaporator brought into contact and overflowed by the water to be heated and heated, evaporated and / or evaporated, characterized in that the heating means of gel-like substances, introduced into the energy-absorbing, in particular sunlight-absorbing IR-active substances or consists of porous substances.

2. Heating means according to claim 1, characterized in that the gel-like substance is arranged in a network and brought into contact with the evaporator surface (12).

3. heating means according to claim 1, characterized in that the porous

Substance as a polydisperse bed or body is brought into contact with the evaporator surface (12).

4. heating means according to claim 1 and 3, characterized in that the

porous substance has a high internal micro- and macro-porosity.

5. heating means according to claim 1 and 2, characterized in that the

gel-like substance consists of chemically crosslinked gelatin with a foam structure and incorporated IR absorber.

6. heating means according to claim 1 and 2, characterized in that the

Energy-absorbing, in particular sunlight-absorbing, IR-active substances made of protein with graphite incorporated into the protein structure.