Container for recovering the heat energy of wastewater

Abstract

The invention relates to a container (1) for recovering the heat energy of wastewater. The container (1) comprises a shell (10) and a continuous spiral pipe (2) for conveying wastewater through the container in a vertical direction. A first heat transfer space for a heat transfer liquid is arranged between an outer shell of the spiral pipe (2) and the shell (10) of the container (1), and a second heat transfer space is arranged inside the spiral pipe (2). The shell (10) is provided with at least one openable inspection hatch (6) having fastened thereto a manifold (7) as well as a shell and tube heat exchanger (3) having its inlet and outlet ends coupled to said manifold (7). The spiral pipe (2) consists of acid-proof or stainless steel and its internal surface is adapted to have a higher chromium content than the other parts of the spiral pipe's wall.

Claims

1. A container for recovering the heat energy of wastewater, said container comprising a shell defining the container outwards, a continuous spiral pipe for conveying wastewater through the container in vertical direction, said spiral pipe being in communication with an extra-container wastewater ingress conduit by way of an inlet connection associated with the container shell, and with an extra-container wastewater egress conduit by way of an outlet connection associated with the container shell, a first heat transfer space encircling a shell of the spiral pipe and being confined by an outer shell of said spiral pipe and by the shell of the container, and said first heat transfer space being in communication with a heat transfer fluid ingress conduit by way of at least one heat transfer fluid inlet connection associated with the shell of the container and with a heat transfer fluid egress conduit by way of at least one heat transfer fluid outlet connection associated with the shell of the container, as well as a second heat transfer space left inside the spiral pipe and confined by an outer shell of said spiral pipe, whereby at least a portion of the container is provided as a pressure vessel, wherein the container has its shell provided with at least one, preferably two, operable inspection hatches, at least one inspection hatch having fastened thereto a manifold as well as a shell and tube heat exchanger, preferably a spiral type shell and tube heat exchanger, said shell and tube heat exchanger having its inlet and outlet ends coupled to said manifold which is further provided with means for opening and closing a fluid connection to said shell and tube heat exchanger, as for its material, the wastewater pipe consists of acid-proof or stainless steel and has at least its internal surface treated in such a way that, by means of said treatment, the spiral pipe has at least its internal surface adapted to have an average chromium content higher than the average chromium content of other parts of the spiral pipe's wall.

2. The container according to claim 1, wherein the spiral pipe has its internal surface, and possibly also its outer surface, treated with electrolytic polishing for reducing its surface roughness.

3. The container according to claim 1, wherein the spiral pipe has both its internal surface and possibly also its outer surface treated with an electrochemical method to a surface roughness below Ra=120.

4. The container according to claim 1, wherein the inspection hatch is coupled to a flange of the container with bolted joints or the like and to the inspection hatch is coupled in an operable manner a shell and tube heat exchanger as well as a manifold.

5. The container according to claim 1, wherein the material thickness of the spiral pipe with respect to an average cross-sectional diameter of the spiral pipe is on the one hand selected in such a way that the spiral pipe has a first pressure resistance level, and the material thickness for the container's shell with respect to the container's internal diameter is on the other hand selected in such a way that the container has a second pressure resistance level, whereby the pressure resistance level of the spiral pipe is different from that of the container.

6. The container according to claim 3, wherein the average cross-sectional diameter of the spiral pipe is selected in such a way that the spiral pipe has on the one hand a pressure resistance consistent with pressure classification 10-16, and the material thickness for the container's shell is on the other hand selected to have its pressure resistance consistent with pressure classification −0.5-6.

7. The container according to claim 1, wherein the second heat transfer space, left inside the spiral pipe, has located therein one or more shell and tube heat exchangers, each having such a ratio of its cross-sectional diameter to the pipe's material thickness that the tubular heat exchanger has a third pressure resistance consistent with pressure classification 10-16.

8. The container according to claim 1, wherein the shell and tube heat exchanger boated in the second heat transfer space is fabricated as an independent pressure vessel from which does not occur any material transfer onto a tube side of the container, i.e. into the spiral pipe, or onto a shell side of the container.

9. The container according to claim 1, wherein the container has the internal and external walls of its shell finished with a treatment enhancing the corrosion and wear resistance thereof.

10. The container according to claim 1, wherein the container has its shell and/or cover and/or bottom provided with one or more additional connections, preferably flange connections, for heat exchangers in order to transfer energy into or out of a heat transfer fluid present in the heat transfer space.

11. The container according to claim 1, wherein the spiral pipe has an interior which is continuous for adapting a liquid to travel in said spiral pipe without obstruction.

12. The container according to claim 1, wherein the spiral pipe has its helices designed to have horizontal angles and/or said helices have a fluctuating radius from a vertical center line of the spiral pipe for changing the flow rate of a liquid flowing inside the spiral pipe.

13. The container according to claim 1, wherein the flow rate of a liquid or gas present inside the spiral pipe is adjusted with wastewater flowing arrangements external of the container.

Description

[0044] The invention and benefits attainable therewith will now be described in even more detail with reference to the accompanying figures.

[0045] FIG. 1 shows a vertical section view of a container suitable for recovering the heat energy of wastewaters.

[0046] FIGS. 2 and 3 show from slightly different viewing angles the container of FIG. 1 as seen from outside.

[0047] FIG. 4 shows a tube heat exchanger 3, which is in connection with a manifold 7 and coupled with an inspection hatch. This manifold-tube heat exchanger-inspection hatch assembly is also visible in FIG. 1.

[0048] FIG. 5 shows a heat exchanger 81, which is connectable to a flange 8 visible in FIG. 3 at a lower part of the shell of a tube heat exchanger 3, and which here is a spiral solar heat exchanger. The solar heat exchanger's 81 inlet and outlet connections 82a, 82b are connected with a flange joint to a lower part of the tube heat exchanger's 3 shell, or to a heat transfer space 11, which is internal of the tube heat exchanger 3 and thus lies in the interior 11 of these mini-spirals 3.

[0049] FIG. 6 shows a cross-section of the spiral pipe in a view directly from above.

[0050] FIGS. 1-3 depict a first embodiment for a container 1 of the invention, which relates to a container adapted to recovering the energy of residential and municipal wastewaters.

[0051] FIG. 1 is a lengthwise section view, showing a container 1 according to a first embodiment of the invention, which functions as a shell and tube heat exchanger especially for the recovery of heat energy from black waters. FIGS. 2 and 3 illustrate how wastewaters and heat transfer liquids are supplied into the container or withdrawn from the container.

[0052] As seen from the lengthwise section view of a container 1 shown in FIG. 1, the container functioning as a shell and tube heat exchanger has an outer shell 10 as well as a continuous spiral pipe 2 for conveying wastewater through the container vertically of the container 1. Generally, blackwater travels gravitationally in a top-down direction through the container. The container is equipped with a stand 12.

[0053] The spiral pipe 2 constitutes a tube portion of the heat exchanger and is in communication with a wastewater ingress conduit external of the container by way of an inlet connection 2; 21 associated with the container shell (cf. FIG. 3) and with a wastewater egress conduit external of the container by way of an outlet connection 2; 22 associated with the container shell (cf. FIG. 2).

[0054] The spiral pipe 2 has its shell, i.e. the spiral pipe's outer wall, directly encircled by a first heat transfer space 4, which at the same time makes up a shell portion for the shell and tube heat exchanger. The first heat transfer space 4 is defined by an outer wall of the spiral pipe 2 and by an outer shell (double shell) of the container 1. This first heat transfer space 4 is in communication with a heat transfer fluid ingress conduit (not shown in the figures) by way of at least one heat transfer fluid inlet connection 4; 41 associated with the shell 10 of the container 1 and with a heat transfer fluid egress conduit (not shown in the figures) by way of at least one heat transfer fluid outlet connection 4; 42 associated with the shell 10 of the container 1. Inside the spiral pipe 2 is left a second heat transfer space 5 , which is thereby located in a vertical space confined by helices 2; 2.sup.1 . . . 2.sup.8 of the spiral pipe 2. The container 1 is provided as a pressure vessel.

[0055] From FIGS. 2 and 3 can be seen in more detail, among others, the construction of the container's 1 shell 10 and the manifold 7 connected to an inspection hatch 6 (a manhole) at an upper part of the container. The upper part of the container's 1 shell 10, visible in FIGS. 2 and 3, is provided with an openable inspection hatch 6, which is fastened with bolts 16 to a collar encircling the container's upper part.

[0056] On top of the inspection hatch 6 is integrated or fixedly secured a manifold 7, and this manifold is coupled with a shell and tube heat exchanger as still discretely depicted in FIG. 4. The manifold 7 includes a first valve system or the like, by which can be opened an inlet path for domestic water or a heat transfer fluid to the manifold 7 from two different directions from outside the container. The manifold 7 is further provided with means, such as a second valve system, for opening and closing a fluid connection from said manifold 7 to a spiral type shell and tube heat exchanger 3 located in a second heat transfer space 5 of the container 1. The shell and tube heat exchanger has its inlet and outlet ends 31, 32 connected to said manifold 7. Hence, the shell and tube heat exchanger-manifold-inspection hatch assembly constitutes in itself a removable entity, facilitating container maintenance. Inside the spiral type heat exchanger is left an additional heat transfer space 11, into which can be introduced a separate spiral heat exchanger 81, wherein circulates a heat transfer fluid which is in communication with the recovery of solar radiation energy or with the condensate liquid circulation of a building's cooling system. It can be seen from FIG. 3 how a flow V1 of heat transfer fluid, such as water, arrives at the manifold 7 and further inside the container. The heat transfer fluid passes by way of a spiral type shell and tube heat exchanger present inside the spiral pipe 2 and delivers its thermal energy at the same time into the heat transfer space 5. After this, the heated or cooled liquid flow, such as a water flow V2, discharges from the manifold 7 of the shell and tube heat exchanger 3 and out of the container 1.

[0057] It is also seen from FIG. 3 how the first heat transfer space 4, i.e. the heat exchanger's shell portion, is in communication with a heat transfer fluid ingress conduit by way of a heat transfer fluid inlet connection 4; 41 and with an extra-container heat transfer fluid egress conduit by way of a heat transfer fluid outlet connection 4; 42.

[0058] The wastewater flow, on the other hand, arrives at an upper part of the container by way of an inlet connection 2; 21 inside the container (cf. FIG. 1). Inside the container, it proceeds along the spiral pipe 2 gravitationally downwards and delivers thermal energy at the same time to the heat transfer fluid present in the shell portion 4. Thereafter, the wastewater discharges from the container by way of a wastewater outlet connection 2; 22.

[0059] The material thickness for a wall of the spiral pipe 2 visible in FIG. 1 with respect to an average cross-sectional diameter of the spiral pipe is selected in such a way that the spiral pipe 2 has a maximum pressure resistance level of 10-16 bar. The material thickness for the container's 1 shell 10 with respect to the container's internal diameter is in turn selected in such a way that the container has a maximum pressure resistance level of 4-10 bar. Hence, the spiral pipe in the container's 1 tube portion has a maximum pressure resistance level which is slightly higher than the highest possible pressure resistance level of the container's shell portion.

[0060] The material thickness for a wall of the spiral coil 3 visible in FIG. 1 with respect to an average cross-sectional diameter of the spiral pipe is selected, on the other hand, in such a way that the spiral coil 3 has a maximum pressure resistance level of 10-16 bar. Inside the spiral coil 3 can be conveyed domestic water, which is heated by means of a heat transfer fluid traveling in a vacant interior of the container 1, i.e. in the first heat transfer space 4. With regard to its part extending inside the container 1, the spiral coil 3 lies in its entirety in the second heat transfer space 5 and is enveloped from every direction by said heat transfer fluid flowing/present in the container's 1 vacant interior. Consequently, the domestic water traveling in the spiral coil is not at any point in contact with the spiral pipe 2, in which is flowing the dirty blackwater.

[0061] Regarding its material, the spiral pipe 2 intended for wastewater and visible in FIG. 1 is made of acid-proof or stainless steel and has its internal surface treated, preferably by electrolytic polishing, to a low surface roughness, for example to below surface roughness Ra=120. In addition, the treatment for an internal surface of the spiral pipe 2 is selected in such a way that, by means of said treatment, the internal surface of the spiral pipe 2 has its average chromium content adapted to be higher than the average chromium content of other wall parts (especially a core part of the wall) of the spiral pipe. The spiral pipe 2 has also its outer surface treated the same way as the internal surface, whereby its average chromium content which is also higher than the average chromium content of other wall parts of the spiral pipe (excluding the spiral pipe's internal surface).

[0062] Electrolytic polishing levels electrochemically the microscopically small irregularities on an internal surface of the spiral pipe 2, whereby the dirt does not adhere to the spiral pipe's internal surface as the heat energy is recovered for example from blackwater. On the other hand, increasing the chromium content on an internal surface improves the corrosion resistance of the internal surface. Increasing the chromium content on an outer surface of the spiral pipe deters calcification of the spiral pipe and maintains thermal conductivity (heat penetration) of the spiral pipe at a high level.

[0063] As mentioned above, the inspection hatch-manifold-tube heat exchanger 7, 6, 3 make up a single entity, which is easy to lift away all at once, thus facilitating considerably maintenance of the container's 1 interior.

[0064] Such an inspection hatch-manifold-tube heat exchanger 7, 6, 3 entity is presented in FIG. 4, but is also visible in FIG. 1.

[0065] It is with the section view of FIG. 6 that horizontal angles for helices of the spiral pipe 2 are illustrated. A helix 2.sup.1 of the spiral pipe 2, i.e. a thread of the spiral pipe, has a helical radius R1 outside bends t. The radius is measured as a distance from a vertical center line H of the spiral pipe to the center line of a helix. As opposed to that, at each horizontal angle, i.e. at the bend t, the distance or the radius of curvature is R1′ as measured again as a distance from the vertical center line H of the spiral pipe 2 to the center line of the helix. The helical angles t make an impact on the traveling speed and turbulence of wastewater J in helices 2.sup.1 . . . 2.sup.8 and therefore on the transfer of heat from liquid flowing inside the spiral pipe 2 to a heat transfer fluid L enveloping the helix 2.

[0066] In the foregoing embodiments there are presented just a few implementations for the invention defined in the claims, and it is obvious for a skilled artisan that there are a multitude of other possible implementations for the invention.

LIST OF REFERENCE NUMERALS (MAIN COMPONENTS)

[0067] 1 container [0068] 2 spiral pipe [0069] 21, 22 inlet and outlet connections (for spiral pipe) [0070] 3 shell and tube heat exchanger [0071] 31,32 inlet and outlet ends (for shell and tube heat exchanger) [0072] 4 first heat transfer space [0073] 4; 41 heat transfer fluid inlet connection [0074] 4; 42 heat transfer fluid outlet connection [0075] 5 second heat transfer space [0076] 6 inspection hatch [0077] 61 top inspection hatch (cover) [0078] 7 manifold [0079] 8 flange connection [0080] 81 spiral heat exchanger [0081] 9 wastewater ingress conduit [0082] 9; 92 wastewater egress conduit [0083] 10 (container's) shell [0084] 11 additional heat transfer space inside mini-spiral [0085] 12 (container's) stand