GB2109709A - Apparatus for magnetically removing iron oxides from water in feed water system of thermoelectric power plant - Google Patents

Abstract

Iron oxides can be economically and efficiently removed from feed water through magnetic attraction by providing a magnetic attracting means 48 in a feed water conduit connecting an air separator compartment 9A to an air separator water tank 10 in an air separator in a feed water and condensed water system in a thermoelectric power plant. The magnetic attracting means may be in the downcomer 25 or, as shown, in the distributor therebelow. Numerous arrangements of permanent magnets are described. <IMAGE>

Description

SPECIFICATION Apparatus for removing iron oxides from water in feed water system of thermoelectric power plant The present invention relates to an apparatus for capturing and removing iron oxides contained in water in feed water and condensed water systems, that is, a feed water system and condensed water system, in a thermoelectric power plant or other electric power plant.

Most of main machines, apparatuses and pipe lines in a thermoelectric power plant or other electric power plant are ordinarily formed of iron and steel materials, and high purity water is used as a circulation fluid and the iron concentration in the system water is controlled and maintained by water treatment of adding a minute amount of a chemical to water for preventing corrosion of constituent materials.However, while the system water used for a long time, iron is gradually dissolved out of the iron and steel materials and is accumulated in the system water in the form of iron oxides (mainly ferromagnetic Foe304 and y Fe2O3). These iron oxides are deposited on boiler tube walls, turbine inside, high pressure feed water heaters, feed water flow meters and various valves, and cause various troubles such as (1) over-heating of pipes, (2) reduction of the turbine output, (3) overloading of pumps by increase of the pressure drop and (4) incorrect indication of flow meters. Accordingly, in order to improve the reliability of an electric power plant and increase the output thereof, it is very important to remove iron oxides from water in feed water and condensed water systems.

An electromagnetic filter has been proposed to remove iron oxides from feed water in the feed water system of a power plant (US Patent No.

3841486). That is, the filter comprises a cylindrical-tubular filter container with spheres of ferromagnetic material and an electric coil for the production of a magnetic field. The particles to be magnetized are of steel. The coil for producing the magnetic field is charged with such current that the produced field force is considerably above the saturation field force for the magnetizable particles When the magnetic field is applied, field force gradients occur in the spaces between the arbitrarily arranged spheres, at places where the contact axis of the spheres has a vector in the applied field direction. At these places, a field force density will occur.

It is disclosed that when the electromagnetic filte is so installed into a parallel branch to the feed water tank of the steam power installation, the inlet line to the filter comes from a chamber of the feed water container which is divided by a perpendicular overflow baffle, while the outlet line of the filter ends in the other chamber. It is also disclosed that the filter can be installed between the pre-pump and the main pump of each feed water pump and that the filter can be also provided directly into the f?ed water stream between the high-pressure preheating outlet and the boiler inlet, where the filter must be designed for the full operational pressure of the boiler feed pumps.

However, the electromagnetic filter has such disadvantages as a large power consumption and a requirement for a cooling means for the heat generation.

A filter with a permanent magnet has been also developed, but has not been so popular because of difficulty in removing of attracted iron oxides. In addition, a filter with resin or sintered metal has been also developed, but has such a problem as a decrease in flow rate due to clogging. Especially, a filter with resin has such an inconvenience as decomposition of the resin by hot feed water at about 1 500C. Thus, it is the current practice to manually remove the iron oxides deposited on the inner walls of feed water line in the feed water system of a power plant at the regular inspection of the power plant.

To solve these problems, some of the present inventors investigated iron oxide forming points in a feed water and condensed water system and analyzed the deposition property of iron oxides at high temperatures, and found that especially high effects can be obtained when iron oxides are captured and removed in a high pressure feed water drain system, and proposed that a magnetic attracting means, for example, a permanent magnet, is disposed in a high pressure feed water heater drain system of the feed water and condensed water system, that is, in a drain tank or in an air separator water tank (US Patent Application SN 276,840 filed June 24, 1981; Japanese Patent Application Kokai (Laid-Open) No. 12884/82, laid open January 22, 1982).That is, some of the inventors investigated iron oxide forming points and iron oxide content-increasing points in water systems in an electric power plant with a view to finding out iron oxide capturing and iron oxide removing points which would result in attainment of highest removal effects.

In a system of a typical thermoelectric power plant, as shown in Fig. 1, feed water is introduced into a boiler 14 through a condenser 2, a condensed water hot well 3, a condensed water pipe line 4, a condensed water pump 5, a condensed water desalting apparatus 6, a condensed water pressure elevating pump 7, low pressure feed water heaters 8A through SC, an air separator 9 including an air separator water tank 10, a feed water pipe line 11, a feed water pump 12 and high pressure feed water heaters 13A through 13C, and in the boiler 14, steam is generated and this steam passes through a steam pipe 15, drives a turbine 1 and returns to the condenser 2.Incidentally, reference numerals 16A through 16C represent low pressure feed water heater drain pipe lines, reference numerals 1 7A through 1 7C represent high pressure feed water heater drainpipe lines, reference numeral 18 represents a drain pump, and reference numerals 19A through 19F represent bleeding pipes from the turbine.

In order to clarify iron oxide forming points in the system of a thermoelectric power plant, a comprehensive water analysis test was carried out in various thermoelectric power plants to obtain the results shown in Fig. 2, wherein the water sampling points are shown on the axis of abscissa and the content of iron oxides is shown as an iron concentration (ppm) on the axis of ordinate, and the square mark (0) represents a power plant with a 350 MW capacity, the triangle mark (A) represents a power plant with a 350 MW capacity, and the circle mark (0) represents a power plant with a 450 MW capacity.

As obvious from the results shown in Fig. 2, the iron oxide content in the system water is reduced at the outlet of condensed water desalting apparatus 6, but in the down-stream portion, the iron oxide content is increased to the value at the outlet of air separator 9. The iron oxide content is reduced again in boiler 14.

Accordingly, water in the high pressure feed water heater drain to be introduced into air separator 9 was analyzed and a large quantity of iron oxide was detected in the drain water.

Although the iron oxide in the condensed water system is removed by condensed water desalting apparatus 6, since the water with a high iron oxide content is introduced from the high pressure feed water heater drain pipe line into air separator 9, this increased amount of iron oxide deposits as scales in high pressure feed water heaters 13A through 13C, main feed water flow meter and boiler feed water adjusting valve which are disposed between air separator 9 and boiler 14, and the iron oxides which have been carried into boiler 14 are deposited on the water tube wall of the boiler. Thus, formation of iron oxides is due to the corrosion in high pressure feed water heat drain pipe line system.

That is, some of the inventors found that, since iron oxides deposited on the respective parts of the thermoelectric power plant was formed in the high pressure feed water heater drain pipe line system, highest removal effects can be attained when iron oxides were captured and removed in high pressure feed water heater drain pipe lines 1 7A through 1 7C or air separator water tank 10 disposed just downstream of said pipe lines 1 7A through 1 7C, to which tank the drain is recycled.

The present inventors have made further studies on the basis of the foregoing and have found the most effective position for disposing a magnetic attracting means and the most effective structure and arrangement of the magnetic attracting means.

One object of the present invention is to make it possible to provide an apparatus for removing iron oxides contained in water of a feed water and condensed water system in a thermoelectric power plant with an economical and simple operation and maintenance.

Another object of the present invention makes it possible to provide a magnetic attracting means in a feed water conduit communicating an air separator compartment with an air separator water tank in an air separator means comprising the air separator compartment and the air separator water tank, the air separator means being provided in a feed water system of a thermoelectric power plant, thereby removing iron oxides from feed water through magnetic attraction.

A further object of the present invention is to provide a magnetic attracting means which can have the most efficient structure and arrangement in an apparatus for removing iron oxides in water of a feed water and condensed water system in a thermonuclear power plant.

The present invention provides an apparatus for removing iron oxides contained in water of a feed water and condensed water system in a thermoelectric power plant, said feed water and condensed water system including means for desalting condensed water received from a condenser, a low pressure feed water heater for heating the condensed water obtained from the desalting means, an air separator means for separating air from the condensed water connected to said low pressure feed water heater and a high pressure feed water heater for heating condensed water received from the air separator means, said high pressure feed water heater having a drain system for feeding drain liquid into said air separator, which comprises magnetic attracting means disposed in a feed water conduit communicating an air separator compartment with an air separator water tank in the air separator means comprising the air separator compartment and the air separator water tank, where the magnetic attracting means is disposed preferably in a distributor in the feed water conduit, and more preferably in a down-comer in the feed water conduit.

Embodiments of the present invention will be described in detail by way of example below, referring to the accompanying drawings, in which: Fig. 1 is a schematic view of a thermoelectric power plant to which the present invention is applied.

Fig. 2 is a diagram showing the results of a comprehensive water analysis test conducted in thermoelectric power plants.

Fig. 3 is a cross-sectional view of an air separator.

Fig. 4 through to Fig. 6 show one embodiment of an apparatus for removing iron oxides according to the present invention, where Fig. 4 is a vertical cross-sectional view of the apparatus, Fig. 5 is a cross-sectional view along the line V-V of Fig. 4, and Fig. 6 is a cross-sectional view along the line VI-VI of Fig. 4.

Fig. 7 is a cross-sectional view of one embodiment of a magnetic attracting means according to the present invention.

Fig. 8 is a cross-sectional side view along the line Vill-VIll of Fig. 7.

Fig. 9 is a schematic view of a test apparatus for determining relations between the flow speed and the iron oxide removal.

Fig. 10 is a diagram showing results obtained from the test apparatus of Fig. 9.

Fig. 1 1 through to Fig. 13 show another embodiment of an apparatus for removing iron oxides according to the present invention where Fig. 11 is a vertical cross-sectional view of the apparatus, Fig. 12 is a cross-sectional view along the line Xll-Xll of Fig. 1 1, and Fig. 13 is a crosssectional view along the line XlIl-Xlll of Fig. 11.

Fig. 14 through to Fig. 16 show further embodiment of an apparatus for removing iron oxides according to the present invention where Fig. 14 is a vertical cross-sectional view of the apparatus, Fig. 15 is a cross-sectional view along the line XV~XV of Fig. 14, and Fig. 16 is a crosssectional view along the line XVl-XVl of Fig. 14.

Figs. 17 and 18 are cross-sectional views showing still further embodiments of the present invention, where Fig. 17 is a cross-sectional view thereof, and Fig. 18 is a cross-sectional view along the line XVlll-XVlll of Fig. 17.

Fig. 19 is a cross-sectional view showing still further embodiment according to the present invention.

Fig. 20 is a cross-sectional view along the line xX-XX of Fig. 19.

Fig. 21 is a side view of a feed water distributor tray used in the embodiment of Fig. 19.

Fig. 22 is a schematical side view of a magnetic attracting means used in the embodiment of Fig. 19.

Fig. 23 is a schematical view showing an arrangement of magnets in the magnetic attracting means in Fig. 22.

Fig. 24 is a cross-sectional view showing fixing a permanent magnet to a plate in the magnetic attracting means in Fig. 22.

Fig. 25 is a schematical view showing another test apparatus for determining relations between iron oxide removal and time.

Fig. 26 is a diagram showing the results obtained from the test apparatus of Fig. 25.

The present apparatus for removing iron oxides is provided in the feed water conduit in an air separator.

An air separator 9 comprises an air separator compartment 9A and an air separator water tank 10, as shown in Fig. 3 which depicts a crosssection of a typical horizontal type air separator.

Air separator compartment 9A is provided above water tank 10, and also provided with tray compartments 21 in it, a plurality of spray nozzles 22 at the top, inlets 23 for heating steam at the side and inlets 24 for high pressure feed water heater drains.

A down-comer, 25 for feed water and a distributor 27 are provided, as connected to each other, between air separator compartment 9A and water tank 10. Pressure-equalizing pipes 26 are also provided between the air separator compartment 9A and the water tank 10.

The feed water sprayed into air separator compartment 9A through spray nozzles 22 and heated and deaerated by the heating steam, and the drain introduced into separator compartment 9A from inlets 24 for drain are all made to pass through down-comer 25 into water tank 10 and distributed uniformly by a distributor 27, and recycled to the boiler through outlets 28 for feed water.

Non-condensible gases in air separator compartment 9A are discharged into the atmosphere or condenser through orifice A and valve B or C. Orifice A is connected to all of spray nozzles 22 and the non-condensible gases are usually discharged into the condenser.

Details of a feed water conduit in an air separator 9 are shown in Figs. 4 to 6. Fig. 4 is a vertical cross-sectional view of a feed water conduit comprising a down comer 25 and distributors 27, Fig. 5 is a cross-sectional view along the line V-V of Fig. 4, and Fig. 6 is a crosssectional view along the line VI-VI of Fig. 4, where the flow of feed water is indicated by arrows 29.

In the embodiment shown in Figs.4~6, iron oxide-removing plates 31, which will be described later with reference to Figs. 7 and 8, are provided, as a magnetic attracting means, in distributors 27 in a feed water conduit from air separator compartment 9A to water tank 10, through which the feed water flows as indicated by arrows 29.

The plates 31 are so arranged that their longitudinal directions may be in parallel with the axial direction of distributor 27.

Fig. 7 shows the detail of the iron oxideremoving plate 31 in cross-section along the flow direction, and Fig. 8 is a cross-sectional view along the line VIll-VIll of Fig. 7.

The iron oxide-removing plate 31 comprises a rectangular sheath 34 of non-magnetic material with a flanged end and a plurality of disk permanent magnets 32 encased therein through spacers 33. The disk permanent magnets 32 are arranged in the sheath 34 so that a maximum magnetic flux density can be obtained on the entire surfaces of the plate 31 in the flow direction. A plurality of openings 27a for inserting the plates 31 are provided on the upper sides of the distributor 27 at an appropraite distance, and the plates 31 are inserted into the openings 27a so that the flange ends of sheaths 34 can be fixed to the upper side of distributor 27. If necessary, gaskets (not shown in the drawing) are inserted between the flanged ends and the upper side of the distributor and fixed with bolts, etc.

In the present embodiment, the feed water in air separator compartment 9A, whose iron oxide content has been increased by joining the high pressure feed water heater drain with a higher iron oxide content, is made to pass through the distributor 27 of feed water conduit, and the iron oxides in the feed water are removed by magnetic attraction by the iron oxide-removing plates 31 provided in the distributor 31. The iron oxides are deposited on the plates 31 by magnetic attraction, and the deposited plates 31 can be readily cleaned by withdrawing the plates 31 from the distributor 27 through the openings 27a.

That is, the plates 31 with the iron oxides thereon can be removed through the openings 27a by removing the bolts, etc. and manually pulling up the flanged edges of sheaths 34. Thus, the cleaning work can be readily carried out by workers who will enter the water tank 4 and work at the shut-down of a power-plant for regular inspection.

In order to obtain basic data for actually designing an apparatus for removing iron oxides more efficiently and economically, the present inventors conducted the following test with a test apparatus shown in Fig. 9. Feed water containing iron oxides, actual scales, samples from an actual thermoelectric power plant, was passed through the line provided with a permanent magnet of BaO-ferrite system with 1.5 K Gauss to investigate relations between the iron oxide removal and the flow speed. The results are shown in Fig. 10, where it is obvious that the iron oxide removal can exceed 80% when the flow speed is set to less than 0.5 m/sec.

In Fig. 11 through to Fig. 13, another embodiment of the present invention is shown, which is different from the embodiment shown in Fig. 4 through to Fig. 8 in that in the present embodiment the longitudinal directions of plates 31 are arranged in a direction perpendicular to the axial direction of distributor 27 and the plates are disposed in a staggered position to one another in the axial direction of distributor 27.

With this arrangement, the feed water takes a zigzag flow, so that the contact time of feed water with the plate 31 can be increased, and consequently the iron oxide removal can be improved.

Fig. 14 through to Fig. 16 show further embodiment of the present invention, which differs from the foregoing two embodiments in that in the present embodiment the magnetic attracting means is circular cylinders 35 arranged in a staggered position in the distributor 27 in place of the rectangular plates 31.

As shown in Fig.16, the circular cylinder 35 comprises a cylindrical sheath 37 of nonmagnetic material with a flanged end, and spacers 36 and permanent magnets 32' being stacked therein alternately.

With this structure, there is less local fluctuation in the performance of removing iron oxide in the distributor 27.

Figs. 17 and 18 show still further embodiment of the present invention, where the plates 31 are arranged in the down-comer 25 so that the longitudinal directions of the plates 31 can be in parallel with the axial direction of down comer 25.

As described above, the feed water with an increased iron oxide content by joining the high pressure feed water heater drain with a higher iron oxide content is all to pass through the downcomer 25, and a similar ratio iron oxide removal to that of the foregoing embodiments can be obtained by the arrangement of plates 31 in the down-comer 25. Furthermore, a large number of plates 31 can be provided at one place in the present embodiment, and thus maintenance and control can be carried out much more easily.

Fig. 1 9 shows a cross-sectional view of an air separator with an apparatus for removing iron oxides according to still further embodiment of the present invention, and Fig. 20 is a crosssectional view along the line XX-XX of Fig. 19, where the lower end of down-comer 25 is positioned above normal water level (NWL) of feed water in the water tank 10, and a water distributor tray 46 is provided below the downcomer 25 to distribute the feed water flowing down through the down-comer 25 uniformly in the longitudinal direction of water tank 10 and a magnetic box 45 encasing permanent magnets 48 which will be described in detail later, is provided integrally with and under the tray 46 as a magnetic attracting means to form a feed water conduit.

In the present embodiment, the magnetic box 45 is a topless and bottomless rectangular frame of steel, and the upper ends of the box are fixed to the upper side of water tank 10.

The tray 46 has V-notched weirs 46a at the side ends of steel trough with U-shaped crosssection, as shown in Fig. 21, and orifices 46b are provided at the bottom of the tray. The bottom of the tray is positioned at a level somewhat higher than NWL of water tank, and the two ends of the tray are fixed to the two short end plates of magnetic box 45. In the magnetic box 45, a plurality of magnet plates 47 shown in Fig. 22, are fixed to the frame of the magnetic box 45.

In the present embodiment, the magnet plates 47 are vertically juxtaposed between the frame, but can be provided in an inclined state. The magnet plates 47 can be fixed to the frame, as desired, but readily detachable arrangement and structure are preferable.

In Fig. 22, details of magnet plate 47 are shown, which comprises a non-magnetic plate (for example, austenite stainless steel plate) and short disk permanent magnets 48 being fixed thereon in a staggered position. With the short disk permanent magnets as in the present embodiment, diameters dof disk magnets must be equal to the minimum clearance between the magnets, as shown in Fig. 23, whereby the magnetic flux 50 around the magnets can take a maximum density and thus the iron oxideattracting performance can be improved.

To fix the short disk magnets 48 to the plates 47, the permanent magnet 48 is covered with a non-magnetic lid 49, which is fixed to the plate 48 by an appropriate means such as rivets, etc.

With this structure, the iron oxides deposited on the permanent magnet 48 through the lid 49 can be readily cleaned, and also protected from any damage.

In the present embodiment, the feed water flowing down through the down-comer 25 as shown in Fig. 19 falls onto the feed water distributor tray 46 with V-notched weirs 46a and orifices 46b, as shown in Fig. 21, and then the feed water is uniformly distributed along the full length of the tray 46 into the magnetic box 45 while keeping a tentative water level (TWL) depending upon the shape, dimension, and number of the V-notched weirs 46a and orifices 46b and also upon the flow rate of feed water.

The feed water distributed into the magnetic box 45 passes between the magnet plates 47 provided in the box 45 and flows into the water tank 10.

Since the short disk magnets 48 are arranged in a staggered position on the plates 47, as shown in Fig. 22, the feed water proceeds in a zigzag manner therebetween. The feed water is agitated by the zigzag flow, and the iron oxides contained in the feed water can be efficiently captured onto the short disk magnets 48 by attraction.

The iron oxides of the disk magnets 48 can be readily cleaned by injecting high pressure cleaning water thereto.

According to the present invention, particularly by providing a magnetic attracting means in the feed water conduit between the air separator and the air separator water tank, the following advantages can be obtained.

1. Higher iron oxide removal can be obtained, for all the feed water passes through the feed water conduit into the water tank, and thus contacts the magnetic attracting means in the feed water conduit.

2. The magnetic attracting means is provided in one place. When it is provided outside the feed water conduit, for example, in the water tank, it must be provided in a considerably extended area, resulting in difficulty in maintenance and control of the magnetic attracting means, such as cleaning of deposited iron oxides. When it is provided in ne place in the feed water conduit, such difficulty is considerably improved.

3. The magnetic attracting means is provided in a simple manner. When it is provided outside the feed water conduit, for example, in the water tank, a special heavy supporting structure is needed for it, whereas when it is provided in the feed water conduit, it can be provided in a simple manner by utilizing the structure of the feed water conduit.

4. The magnetic attracting means is protected from flashing of water in the water tank. At some occasion, the water in the water tank is flashed due to a fluctuation in load, etc. in the water tank, and an external force is applied to the structure in the water tank. The magnetic attracting means can be protected therefrom when provided in the feed water conduit.

The inventors investigated relations between the iron oxide removal and the time with a test apparatus shown in Fig. 25, when iron oxides were magnetically removed. The results are shown in Fig. 26. Feed water containing iron oxides, actual scales, samples from an actual thermoelectric power plant, was tested in the test apparatus of Fig. 25 under the same conditions as in the actual plant, that is, 900C, pH 9.2, with a permanent magnet of BaO-ferrite system with 3 K Gauss and an initial iron oxide concentration of 10 ppm, where changes in clearness of feed water with time was measured and iron oxide concentrations were calculated therefrom.

As is obvious from Fig. 26, the iron oxide removal reached substantially 100% after about 15 minutes.

There is such a restriction that a permanent magnet should not be used under a coercive force-reducing condition, when it is used for removing iron oxides from feed water, but in the case of using a ferrite magnet in the foregoing embodiments, the following advantages can be obtained.

a) Demagnetization due to shock, mechanical strain, vibration, or change in material structure is practically negligibly small, (b) change due to aging is practically negligibly small, and (c) demagnetization by temperature occurs at Curie point (4500 C), but no such problem appears because the feed water temperature is about 1 500C in the feed water conduit.

The ferrite magnet is relatively brittle, but can be used in the present invention by encasing it in a sheath as shown in the foregoing embodiments or covering it with a lid with the result of an improved durability with no fear of damage or inclusion of fragments into feed water, even if damaged.

As described above, in the present invention iron oxides can be economically and efficiently removed from feed water through magnetic attraction by providing a magnetic attracting means in a feed water conduit connecting an air separator compartment to an air separator water tank in an air separator in a feed water and condensed water system in a thermoelectric power plant.

Claims (14)

Claims

1. An apparatus for removing iron oxides contained in water of a feed water and condensed water system in an electric power plant, said feed water and condensed water system including means for desalting condensed water received from a condenser, a low pressure feed water heater for heating the condensed water obtained from the desalting means, an air separator means for separating air from the condensed water connected to said low pressure feed water heater and a high pressure feed water heater for heating condensed water received from the air separator means, said high pressure feed water heater having a drain system for feeding drain liquid into said air separator, which comprises magnetic attracting means disposed in a feed water conduit communicating an air separator compartment with an air separator water tank in the air separator means comprising the air separator compartment and the air separator water tank.

2. The apparatus according to Claim 1, wherein, the magnetic attracting means is disposed in a distributor of the feed water conduit.

3. The apparatus according to Claim 1, wherein the magnetic attracting means is disposed in a down-comer of the feed water conduit.

4. The apparatus according to Claim 1 , wherein the magnetic attracting means is disposed in magnetic box provided below a distributor of the feed water conduit.

5. The apparatus according to Claim 1,2 or 3, wherein the magnetic attracting means is in a form of a plurality of plates, each of the plates comprising a rectangular sheath and a plurality of magnets encased therein in a predetermined arrangement.

6. The apparatus according to Claim 5, wherein the longitudinal directions of the plates are arranged in parallel with the flow direction of the feed water.

7. The apparatus according to Claim 5, wherein the longitudinal directions of the plates are arranged perpendicular to the flow direction of the feed water and in a staggered position to one another.

8. The apparatus according to Claim 1,2 or 3, wherein the magnetic attracting means is in a form of a plurality of circular cylinders, each of the circular cylinders comprising a circular cylindrical sheath and a plurality of magnets and spacers stacked alternately therein.

9. The apparatus according to Claim 8, wherein the circular gylinders are arranged in a staggered position to one another.

10. The apparatus according to Claim 5 or 8, wherein the magnetic attracting means is detachable.

11. The apparatus according to Claim 4, wherein the magnetic attracting means is in a plurality of plates, each of the plates comprising a plate and a plurality of short disk magnets, each covered with a non-magnetic lid, and arranged in a predetermined pattern.

12. The apparatus according to Claim 4, wherein the magnetic attracting means is detachable.

13. An apparatus for removing iron oxides substantially as any herein described with reference to and as shown in the accompanying drawings.

14. A thermoelectric power plant having apparatus for removing iron oxides according to any one of the preceding claims.