Heat exchanger and installation for extracting heat from waste water

The invention relates to heat exchanger systems and installations for the extraction of heat from wastewater.

Such heat exchanger systems are eg. From <patcit id="pcit0001" dnum="DE19719311"><text>German Patent 197 19 311</text></patcit> and also from the <patcit id="pcit0002" dnum="EP1215460A"><text>EP-A-1215460</text></patcit> known. It has been found that direct contact of a preferably metallic heat exchanger surface is important with the waste water, so that an efficiency can be achieved, in which the economic efficiency is ensured. This, however, that this heat exchange surface is formed due on the one hand, that they do not quickly contaminated, and secondly that it meets the regulatory requirements, ie, for example, that it is accessible and can be cleaned with conventional cleaning nozzles.

Sewer or sewers are naturally highly susceptible to contamination. A layer of dirt on the heat exchange surface naturally has a negative effect on the heat transfer.

particularly troublesome in view of the heat transfer is the so-called Sielhaut. This is a biofilm, which covers items that are exposed to prolonged non-pure water.

It is known that certain alloys of metals affect the formation of biofilms. In particular, it has been found that the tendency to Anlagem biofilms on copper alloys is greatly reduced.

As a material for heat exchangers in sewers or sewers copper alloys do not come with sufficient copper concentration but in question. This firstly because copper in the effluent above a certain concentration affects the operation of sewage treatment plants, and it is not granted for this reason as a building material. Second, copper also relatively rapidly worn away (abrasion). This has a negative effect on the life of the heat exchanger.

The object of the invention to provide a heat exchanger system for extracting heat from a sewage system or a sewer running wastewater disposal, in which there is a reduced tendency to form a sewer slime. It is further object of the invention to provide a corresponding installation.

This object is achieved by the invention as defined in the claims.

According to the invention a heat exchanger system at least one surface region made of copper or a copper-containing alloy. This preferably makes only a small percentage - for example less than 5% or less than 2% -. The heat exchange surface. It is so arranged that over the heat exchange surface of flowing waste water flows as possible before the heat exchange surface or at the beginning of the heat exchange surface on the said surface regions.

The invention is based on the realization that the biofilm-impairing effect of a copper concentration at the surface drains and in a certain range continues in the flow direction behind the said surfaces. This was confirmed in measurements.

According to a preferred embodiment, the surface areas available in the form of at least one replaceable, extending transversely across the channel band. If the length of the entire heat exchange surface exceeds a certain, dependent ligand of the average composition of the wastewater value, more than one band can be present. For example. may be disposed a copper tape of a width of eg. 0.5-5 cm every 1-5 m.

It has also shown that the effect of the copper - possibly due to the incipient formation of less active complexes - decreases in a certain distance from the surface areas. The remaining at most in small sewage copper content is harmless to sewage treatment plants. It is smaller than the copper content, which is caused by copper-containing gutters etc.. He is also much smaller than the maximum copper content according to official regulations. The copper surface is also substantially less than the maximum allowable copper surface of roofs. For example, in Switzerland, a percolation system must be provided when a copper surface of 50 m² is exceeded.

Instead of belts, the surface areas can also have other shapes. You can eg. Also be flat and / or be adapted in its width to the locally expected over it flowing wastewater volume. Preferably, they are arranged so that at least a majority of the existing with minimal wastewater Wassertrajektorien lead over the surface areas. With an assumed as laminar flow, this means approximately that the surface areas in a projection along the direction of flow on a contour line up at least half of a lower portion of the contour line.

In the following, embodiments of the invention will be described in detail with reference to drawings. In the drawings:<ul><li>FIG. 1: A schematic view of a lower half of a sewer pipe, a portion of which is configured as a heat exchange surface and which is provided with copper strips as surface areas according to the invention.</li><li>Fig. 2 is a view analogous to FIG. 1 view, the copper strips have a different length</li><li>FIG. 3 is a schematic plan view of a section of a heat exchanger element</li><li>Fig. 4 is a schematic plan view of a section of another heat exchanger element.</li></ul>

In the <b>Fig. 1</b> only very schematically illustrated sewer pipe 1 flows through sewer in the direction of the arrow. The sewer pipe is usually made of concrete. In a region, however, a heat exchange system is incorporated with at least one heat exchange element where the Betonoberfäche is usually replaced by a metal heat exchange surface or covered by it. Under the heat exchange surface flows a heat exchange medium, which circulates between the heat exchanger and a heat pump.

There are several types of design of heat exchange systems. For example, sewer pipe segments can be replaced in some areas by heat exchange-sewer pipe segments. Heat exchangers can also be introduced into a bed of a dry weather channel, launched, etc. be in the sewer pipe segments. It can supply tubes for supplying the heat exchanger with the heat exchange medium may be provided inside or outside the sewers. Frequently, the heat exchange system has a series of abutting or spaced apart heat exchange elements. For more information on certain aspects of heat exchanger systems can be found in the<patcit id="pcit0003" dnum="DE19719311"><text>German Patent 197 19 311</text></patcit>, Is expressly made to the content with regard to the realization of installations for the extraction of heat from waste water here. The invention relates to any embodiment of heat exchangers for a sewer pipe or -rinne flowing sewage.

The inventive measures can be used in all versions of such heat exchanger systems or yet to be developed.

The heat exchange system according to FIG. 1 is provided with a copper strip, which is mounted upstream of the heat exchange surface and extending across the lower half of the sewer pipe. The copper strip has a width<i>b</i> of 2 cm and a thickness of between 0.5 mm and 5 mm. It may be incorporated into a specially provided groove in a heat exchanger element, is applied to a heat exchanger element or mounted adjacent a heat exchange element or heat exchange between two elements.

In <b>FIG. 2</b> you see a sewer pipe with several heat exchanger elements. In Strömungsrichung above the first heat exchange element and between the heat exchanger elements Cu tapes are attached. The Cu tapes are, for example, in the space between the heat exchanger elements filling mortar inserted. The length of the Cu-bands is selected in this embodiment so that it does not extend over the entire lower half of the sewer pipe. Rather, it only goes up to a waterline which corresponds to the water level at average wastewater flow. In the past most about this waterline partial surface of the heat exchange surface only a small tendency for the addition of a sewer slime is already exist, as they are part surface dries out again. In the illustrated embodiment, a copper strip is mounted in each interspace between two heat exchanger elements. Of course, even made a copper strip between each second, third, etc. Wärmetauscherlelement, or Cu tapes can both on and between the heat exchanger elements or only on heat exchanger elements to be attached. A water analysis and / or the pH of the waste water can be used to determine the necessary Cu surface.

The distance between the Wärmetauscherlementen can be selected depending on the average effluent quality. It has been found that the required distance for the desired function depends on various factors, in particular on the concentration of metals such as Ni, Cr, Zn and Cd in the effluent. Typically, the optimum distance d between two copper bands between 1 m and 10 m, in particular between 1 m and 5 m. When the entire heat exchanger system is not longer than the distance required, a Cu-band ranges.

the Cu tapes are preferably mounted so that they can be removed and replaced easily. Namely, it is to be expected that their life is less than that of the heat exchanger system significantly and that they need to be replaced, for example. All 3-10 years.

At an interface between a noble metal (eg. Cu) and a non-noble metal (eg. Cr in stainless steel), the non-noble metal can corrode rapidly when both metals are in contact with water (voltage range). For this reason, it may be provided that the copper strips or shaped differently Cu elements and the example. Chrome steel assembled heat exchangers do not touch. This can be effected, that between the heat exchanger elements and the Cu-bands, a silicone coating is provided. the bands Alternatively, for example. be narrower than the distance between adjacent heat exchanger elements and placed so that they do not touch them but only come into contact with mortar. Other measures are also conceivable.

Although it is particularly favorable for practical reasons, when the surface areas of Cu or a Cu-alloy is in the form of bands, which is by no means necessary. In<b>Fig. 3</b> is shown in a schematic plan view of an embodiment in which the surface regions having a more or less arbitrarily chosen shape. the surface areas of Cu or a Cu-alloy at a mostly laminar wastewater flow, the surface area is / are chosen so that most of the flow trajectories lead 12 via the Cu. This leads to the approximate condition that in a projection on a contour line 13 along the flow direction or against the flow direction, the surface areas equal to at least half of a lower portion of the contour line. In the drawing, the schematic projection areas is shown by bold lines.

In a turbulent flow, this condition does not apply because there the sewage is mixed by swirling. The embodiment according to<b>Fig. 4</b> has a surface area of ​​Cu or a Cu alloy and then thereto a baffle to generate a swirl. In downstream of the chicane a heat exchange element is mounted. Due to the turbulence ensures that after the chicane, a large part of the waste water has a certain concentration of Cu, which can counteract the formation of a sewer slime.