JP2008080309A - Water treating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of a scale on a heat transfer surface by causing no problem when the concentration of those which are corrosion suppression components of the heat transfer surface of thermal equipment and generate the scale on the heat transfer surface is high in raw water while suppressing corrosion of the heat transfer surface of the thermal equipment by using no chemicals. <P>SOLUTION: A water treatment system 1 including a filtration membrane part 4 on a water supply line 3 to a boiler 2 comprises use of a loose RO membrane which removes a corrosion acceleration component of the heat transfer surface of the boiler 2, and a part of those which are the corrosion suppression component of the heat transfer surface of the boiler 2 and generate the scale on the heat transfer surface as a filtration membrane of the filtration membrane part 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water treatment system in which a filtration membrane unit is provided in a water supply line to a thermal apparatus.

  A boiler (for example, a once-through boiler) cited as a representative thermal device includes a heat transfer tube that heats feed water and generates steam. Since this heat transfer tube is formed using a non-passivated metal such as carbon steel, there is a risk of damage if the heat transfer surface in contact with the boiler water is corroded by the influence of the boiler water. For this reason, in order to operate the boiler stably for a long period of time, it is necessary to effectively suppress the corrosion of the heat transfer surface. Then, the chemical | medical agent for suppressing the corrosion of the said heat-transfer surface is added during the feed water to the said boiler.

  However, a part of the chemical added to suppress corrosion of the heat transfer surface may be taken into the steam when the boiler water evaporates. In this case, for example, if the use of steam is cooking or processing food, it may be difficult to directly use it as a heat source because the food may be contaminated.

Therefore, in Patent Document 1, in order to suppress corrosion of the boiler without using a chemical, the corrosion promoting component of the heat transfer surface of the boiler is removed from the water supply line to the boiler, and the heat transfer surface of the boiler is used. There has been proposed a water treatment system provided with a filtration membrane that permeates the corrosion inhibiting component.
JP 2004-238694 A

  Here, a nanofiltration membrane (NF membrane) is used as the filtration membrane. This nanofiltration membrane is a liquid separation membrane that removes most of sulfate ions and chloride ions, which are corrosion promoting components, while passing through most of silica, which is a corrosion inhibiting component.

  Here, although silica acts on the heat transfer surface of the boiler as a corrosion inhibiting component, it is also a scale generating component on the heat transfer surface. For this reason, when the nanofiltration membrane is used for the purpose of suppressing the corrosion of the boiler without using a chemical, when the silica concentration of the raw water is increased, the silica concentration of the boiler water is likely to be increased, and there is a risk of scale generation. Extremely high. When the silica concentration of raw water is high, it is conceivable to provide a filtration membrane portion having a reverse osmosis membrane (RO membrane) in the water supply line as means for suppressing the generation of scale on the heat transfer surface. However, the reverse osmosis membrane can remove most of sulfate ions and chloride ions, which are corrosion promoting components, but also removes most of silica, which is a corrosion inhibiting component. Therefore, the use of the reverse osmosis membrane can reduce the risk of scale generation, while the risk of corrosion increases due to the corrosion promoting components remaining in the boiler feed water. Moreover, in order to suppress generation | occurrence | production of the scale in the said heat transfer surface, although raising the blow rate of the said boiler is also considered, the heat loss in the said boiler becomes large.

  The problem to be solved by the present invention is a component that inhibits corrosion of the heat transfer surface, and generates a scale on the heat transfer surface, even if the concentration in raw water is high, without using a chemical, It is to simultaneously suppress corrosion and scale generation on the heat transfer surface.

  This invention was made in order to solve the said subject, The invention of Claim 1 is a water treatment system which provided the filtration membrane part in the water supply line to a heat | fever equipment, Comprising: Of the said filtration membrane part As a filtration membrane, the corrosion promoting component on the heat transfer surface of the thermal device is removed, and a part of the corrosion inhibiting component on the heat transfer surface of the thermal device that generates scale on the heat transfer surface is removed. A loose RO membrane is used.

  In the first aspect of the present invention, most of the corrosion promoting components contained in the water supply to the thermal equipment are removed by the loose RO membrane. Further, in the loose RO membrane, only a part of the corrosion-inhibiting component contained in the water supply to the thermal equipment that generates scale on the heat transfer surface is removed. Water contains a moderate amount of corrosion inhibiting components. Therefore, since the corrosion promoting component is removed and the water supply containing the corrosion inhibiting component can be supplied to the thermal device, corrosion of the heat transfer surface of the thermal device can be suppressed without using a chemical. . Moreover, even if the concentration of the corrosion inhibiting component of the heat transfer surface, which generates scale on the heat transfer surface, is high in the raw water, a part thereof is removed by the loose RO membrane, so in the permeated water The concentration is reduced to such an extent that corrosion of the heat transfer surface can be suppressed and generation of scale on the heat transfer surface can be suppressed. Therefore, according to the first aspect of the present invention, corrosion and scale generation on the heat transfer surface can be simultaneously suppressed without using a chemical.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing an example of an embodiment of a water treatment system according to the present invention.

  In FIG. 1, a water treatment system 1 supplies water supplied from a water source such as tap water, industrial water, and groundwater to a boiler 2 that is a thermal device. The boiler 2 includes a heat transfer tube (not shown) that heats feed water to generate steam. This heat transfer tube is formed using a non-passive metal such as carbon steel. And in the said water treatment system 1, the treated water which can suppress the corrosion of the heat-transfer surface which is a site | part which contacts the boiler water in the said heat-transfer pipe | tube is obtained as boiler feed water by water-treating raw | natural water. It can be done.

  In the water treatment system 1, a water supply line 3 to the boiler 2 is provided, and a filtration membrane unit 4 is provided in the water supply line 3. Further, the water supply line 3 is provided with a water softening unit 5 and a water supply pump 6 in this order on the upstream side of the filtration membrane unit 4, and a deaeration unit 7 and a water supply tank on the downstream side of the filtration membrane unit 4. 8 are provided in this order.

  The said filtration membrane part 4 is equipped with the filtration membrane module (illustration omitted) which performs the filtration process of water supply. And this filtration membrane module removes the corrosion promoting component of the heat transfer surface of the boiler 2 and is a corrosion inhibiting component of the heat transfer surface of the boiler 2 and generates scale on the heat transfer surface. Some are about to be removed.

  Here, the term “corrosion promoting component” refers to a component that acts on the heat transfer surface of the heat transfer tube formed of a non-passivated metal to promote the corrosion, and is usually sulfate ion, chloride ion and other components. Is included.

  The corrosion inhibiting component refers to a component that acts on the heat transfer surface and can inhibit the corrosion, and usually contains silica (that is, silicon dioxide). Here, the silica also acts as a material that generates scale on the heat transfer surface of the boiler 2. Therefore, silica can be mentioned as a corrosion inhibiting component that generates scale on the heat transfer surface.

  As the filtration membrane constituting the filtration membrane module, a loose RO membrane (not shown) is used. The loose RO membrane in the present invention is a liquid separation membrane having characteristics located between the nanofiltration membrane (NF membrane) and the reverse osmosis membrane (RO membrane) in terms of the removal rate with respect to the corrosion inhibiting component. That is, the corrosion promoting component is set to the same removal rate (sulfate ion removal rate and chloride ion removal rate) as the nanofiltration membrane and the reverse osmosis membrane, but the corrosion inhibiting component is the nanofiltration membrane. The intermediate removal rate (silica removal rate) between the membrane and the reverse osmosis membrane is set. In other words, most of sulfate ions and chloride ions contained in the water supply are removed by the loose RO membrane, but silica is mostly permeated like the nanofiltration membrane or the reverse osmosis. Most of the film is not removed like the film, and only a part is removed by the loose RO film. Thereby, when the silica concentration in raw | natural water is high, while being able to suppress the corrosion of the heat transfer surface of the said boiler 2, the silica concentration of permeate can suppress the generation | occurrence | production of the scale in the said heat transfer surface. The concentration can be adjusted.

  In the filtration membrane section 4, the feed water sent from the feed water pump 6 flows from one side, the feed water is filtered by the loose RO membrane, and the permeated water and the corrosion containing silica as a corrosion inhibiting component are corroded from the other side. Concentrated water containing sulfate ions and chloride ions, which are promoting components, is separated and flows out. The loose RO membrane removes a part of silica contained in the feed water as a corrosion inhibiting component, and the removed silica is contained in the concentrated water. That is, silica is contained in both permeated water and concentrated water.

  The permeated water flows through the water supply line 3 and is stored in the water supply tank 8 through the deaeration unit 7. On the other hand, the concentrated water flows out to the concentrated water line 9 connected to the filtration membrane part 4.

  The water softening unit 5 removes the hardness of the water supply, that is, calcium ions and magnesium ions, with an ion exchange resin. Specifically, the water softening unit 9 is configured to exchange the hardness contained in the water supply into monovalent cations such as sodium ions and potassium ions by an ion exchange reaction, thereby converting the water supply into soft water. ing. Thereby, the softened water supply can be supplied to the boiler 2, and it is possible to prevent the scale due to the hardness from being generated on the heat transfer surface of the boiler 2.

  The deaeration unit 7 is a membrane type deaeration device provided with a gas permeable membrane module having a large number of gas permeable membranes and a water-sealed vacuum pump (each not shown). In this case, dissolved oxygen is sucked by the water-sealed vacuum pump through the gas permeable membrane module. Thereby, the water supply from which the dissolved oxygen which causes the corrosion of the heat transfer surface of the boiler 2 is removed can be supplied to the boiler 2.

  In the water supply tank 8, the water supply that has passed through the water softening unit 5, the filtration membrane unit 4, and the deaeration unit 7 is stored by operating the water supply pump 6. The water supply stored in the water supply tank 8 is supplied to the boiler 2 by operating a pump (not shown) provided in the water supply line 3 between the water supply tank 8 and the boiler 2. It has become so.

  Now, in the said water treatment system 1, the water supply which flows through the said water supply line 3 first passes through the said water softening part 5, and is softened. And when this softened water supply passes the said filtration membrane part 4, most of the corrosion acceleration | stimulation component contained in the water supply to the said boiler 2 by the said loose RO membrane (illustration omitted), ie, concrete Most of sulfate ions and chloride ions are removed. In addition, due to the loose RO membrane, a part of the corrosion inhibiting component included in the water supply to the boiler 2 that also acts as a scale generating on the heat transfer surface, specifically, included in the water supply A portion of the silica is removed. At this time, the concentrated water containing sulfate ions, chloride ions and silica flows out to the concentrated water line 9. Part of silica contained in the water supply passes through the loose RO membrane and is contained in the permeated water from the filtration membrane unit 4. Then, sulfate ions and chloride ions are removed, and the permeated water from the filtration membrane part 4 containing silica is deaerated in the deaeration part 7. And the water supply from this deaeration part 7 is stored in the said water supply tank 8, and is supplied to the said boiler 2 from this water supply tank 8. FIG.

  According to the water treatment system 1 described above, since the sulfate ions and chloride ions, which are corrosion promoting components, are removed and the feed water containing silica, which is a corrosion inhibiting component, can be supplied to the boiler 2. Corrosion of the heat transfer surface of the boiler 2 can be suppressed without using chemicals. Moreover, even if the concentration of silica contained in the feed water is high in the raw water, a part of the silica is removed by the loose RO membrane, so the silica concentration in the permeated water is suppressed from corroding the heat transfer surface of the boiler 2. In addition, the concentration can be made such that scale generation on the heat transfer surface can also be suppressed. Therefore, according to the water treatment system 1, even when the silica concentration of the raw water is high, the corrosion on the heat transfer surface is performed without using a chemical agent as in the case of the water treatment system using the nanofiltration membrane. And a water treatment system that suppresses the generation of scale at the same time.

  As mentioned above, although this invention was demonstrated by embodiment, it cannot be overemphasized that this invention can be variously implemented in the range which does not change the main point. For example, in the said embodiment, although the said boiler 2 is mentioned as an example and demonstrated as said thermal apparatus, it is not restricted to this.

It is a schematic explanatory drawing which shows an example of embodiment of the water treatment system which concerns on this invention.

Explanation of symbols

1 Water treatment system 2 Boiler (thermal equipment)
3 Water supply line 4 Filtration membrane

Claims (1)

A water treatment system provided with a filtration membrane part in a water supply line to a thermal device,
As the filtration membrane of the filtration membrane part, it removes the corrosion promoting component of the heat transfer surface of the thermal device and is a corrosion inhibiting component of the heat transfer surface of the thermal device, which generates scale on the heat transfer surface. A water treatment system characterized by using a loose RO membrane for removing a part.

Images