JP4737019B2 - Boiler feed water treatment system - Google Patents

Description

This invention relates to water boiler feed water treatment system to the heat device.

  A boiler (for example, a once-through boiler) cited as a typical 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 the corrosion generated on the heat transfer surface of the boiler without using a chemical, the corrosion promoting component on the heat transfer surface of the boiler is removed and the corrosion suppression of the heat transfer surface of the boiler is performed. A water treatment system has been proposed in which a filtration membrane part having a filtration membrane that permeates components is provided in a water supply line to the boiler.
JP 2004-290829 A

  However, the filtration membrane has the following problems, for example. That is, some of the filtration membranes are not resistant to chlorine. And when a filtration membrane without chlorine resistance is used in this way, it is impossible to add chlorine as a bactericide to the water supplied to the boiler, so that microorganisms adhere to the filtration membrane and A film may be formed and the filtration membrane may be clogged. Moreover, since the said filtration membrane has the property that the removal rate of a corrosion acceleration | stimulation component changes with the fluctuation | variation of water temperature, there exists a possibility that it may become difficult to ensure fixed water quality.

  The problem to be solved by the present invention is to suppress the corrosion of the thermal equipment without using chemicals without causing problems such as clogging of the filtration membrane and water quality change due to the water temperature.

This invention was made in order to solve the said subject, and suppresses corrosion of a boiler without using a chemical | medical agent by using an electrodialyzer instead of the said filtration membrane. That is, a first aspect of the present invention, the water supply line to the boiler, the boiler feed water processing system in which a configured electrodialysis apparatus with a electrodialysis cell disposed the cation exchange membranes and anion exchange membranes alternately The boiler feed water is passed through the desalination chamber of the electrodialysis tank and the energization amount to the electrodialysis tank is adjusted to form a heat transfer tube of the boiler that exists as ions in the boiler feed water. Removes sulfate ions and chloride ions that promote corrosion of non-passivated metals, and permeates silica that suppresses corrosion of non-passivated metals that exist as non-ions in the feed water and forms the heat transfer tubes of the boiler. It is characterized in that the demineralized water obtained by the above is supplied to the boiler .

In the first aspect of the invention, the electrodialyzer removes ionized substances in the feed water, while non-ionized substances pass through the electrodialyzer. Therefore, the electrodialysis apparatus removes the corrosion promoting components present as ions in the feed water, while the corrosion inhibiting components present as non-ions pass through the electrodialysis apparatus and are included in the feed water to the boiler . Will be.

According to the invention, by using the electrodialysis apparatus in place of the membrane, to the boiler as in the case of using the filtration membranes, corrosion promoting component of the heat transfer surface of the boiler is removed, the boiler It is possible to supply water containing a corrosion inhibiting component. Therefore, corrosion of the heat transfer surface of the boiler can be suppressed without using a chemical without causing problems such as clogging of the filtration membrane and water quality change due to water temperature.

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

In Figure 1, boiler feed water treatment system 1, tap water, industrial water, the water obtained raw water supplied from a water source, such as ground water and water treatment, and supplies to the boiler 2. 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. Then, the in boiler feed water treatment system 1, by the raw water treatment, to obtain a treated water that can suppress the corrosion of the heat transfer surface is a portion in contact with the boiler water in the heat transfer tube as boiler feed water Be able to.

In the said boiler feed water treatment system 1 comprises a water supply line 3 to the boiler 2, electrodialysis device 4 is provided in the water supply line 3. The water supply line 3 is provided with a soft water device 5 and a water supply pump 6 in this order on the upstream side of the electrodialysis device 4, and further on the downstream side of the electrodialysis device 4 with a membrane degassing device 7 and a water supply tank. 8 are provided in this order.

The electrodialysis apparatus 4 includes an electrodialysis tank (not shown) in which a cation exchange membrane (not shown) and an anion exchange membrane (not shown) are alternately arranged between electrodes (not shown). And the said electrodialyzer 4 removes the ionization substance in feed water in the desalination chamber of the said electrodialysis tank, On the other hand, it passes a non-ionization substance. Therefore, in the electrodialysis apparatus 4, the corrosion promoting component on the heat transfer surface of the boiler 2 existing as ions in the water supply to the boiler 2 is removed, and as non-ions in the water supply to the boiler 2. The corrosion inhibiting component of the existing heat transfer surface of the boiler 2 passes therethrough.

  In addition, the electrodialysis apparatus 4 can adjust the removal amount of ionized substances by adjusting the energization amount to the electrodialysis tank. Therefore, the electrodialysis apparatus 4 can adjust the removal amount of the corrosion promoting component existing as ions in the feed water to the boiler 2 by adjusting the energization amount according to the quality of the raw water. Thus, the desired water quality that can suppress the corrosion of the heat transfer surface of the boiler 2 can be stably obtained.

  Here, the corrosion promoting component of the heat transfer surface of the boiler 2 refers to a component that acts on the heat transfer surface of the heat transfer tube made of non-passivated metal to promote the corrosion, and is usually sulfate ion. Contains chloride ions and other ingredients. Therefore, sulfate ions and chloride ions can be cited as corrosion promoting components present as ions in the feed water to the boiler 2. Incidentally, sulfate ions and chloride ions are important substances as corrosion promoting components. Therefore, the corrosion of the heat transfer surface of the boiler 2 can be effectively suppressed by removing these ions in the electrodialysis tank.

  Moreover, the corrosion inhibiting component of the heat transfer surface of the boiler 2 refers to a component that acts on the heat transfer surface and can suppress the corrosion, and usually contains silica (that is, silicon dioxide). Therefore, silica can be mentioned as a corrosion inhibiting component that exists as non-ions in the feed water to the boiler 2.

  In the electrodialysis apparatus 4, when the water supplied from the water supply pump 6 flows in from one side, desalted water containing a corrosion inhibiting component and concentrated water containing a corrosion promoting component flow out from the other side. . Demineralized water flows through the water supply line 3, passes through the membrane deaerator 7, and is stored in the water supply tank 8. On the other hand, the concentrated water flows out to the concentrated water line 9 connected to the electrodialyzer 4.

  Here, the ion exchange membrane used in the electrodialysis apparatus 4 has a relatively high chlorine resistance compared to a filtration membrane (for example, a nanofiltration membrane or a reverse osmosis membrane). Therefore, it is possible to add chlorine as a disinfectant in the water supply. In addition, the ion exchange membrane is less susceptible to changes in temperature than the filtration membrane, and the amount of energization is easy to adjust. Stable water quality without being affected by.

  The electrodialyzer 4 may be a polarity inversion electrodialyzer that inverts the polarity of the electrodes at regular intervals. In this case, generation of scale in the electrode and the ion exchange membrane can be effectively prevented.

  The water softener 5 is provided with a resin cylinder (not shown) filled with an ion exchange resin (not shown) that removes the hardness of the water supply, that is, calcium ions and magnesium ions. And in the said resin cylinder, the water | moisture content of feed water is softened by replacing | exchanging the hardness part in feed water to monovalent cations, such as a sodium ion and potassium ion, by ion exchange. Thereby, the softened water supply can be supplied to the boiler 2, and scale adhesion to the heat transfer surface of the boiler 2 can be prevented.

  The membrane deaerator 7 includes a gas permeable membrane module having a large number of gas permeable membranes, and a water-sealed vacuum pump (each not shown). The membrane degassing device 7 is configured to vacuum the dissolved gas in the feed water, specifically, dissolved oxygen through the gas permeable membrane module with the water ring vacuum pump. 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 soft water device 5, the electrodialysis device 4, and the membrane deaeration device 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, the in boiler feed water treatment system 1, water flowing through the water supply line 3 is first softened by passing through the water softener 5. And when this softened water supply passes the said electrodialysis apparatus 4, the corrosion acceleration | stimulation component which exists as an ion in water supply is removed. At this time, the concentrated water containing the corrosion promoting component flows out to the concentrated water line 9. On the other hand, corrosion inhibiting components present as non-ions in the water supply pass through the electrodialyzer 4. The demineralized water from which the corrosion promoting components including the corrosion inhibiting component are removed flows out from the electrodialysis apparatus 4 to the water supply line 3 and flows through the water supply line 3 and is deaerated by the membrane deaerator 7. . The water supply from the membrane deaerator 7 is stored in the water supply tank 8 and supplied from the water supply tank 8 to the boiler 2.

According to the boiler feed water treatment system 1 described above, by using the electrodialysis apparatus 4 instead of the filtration membrane, it said to the boiler 2 similarly to the case of using the filtration membranes, corrosion promoting component is removed It is possible to supply water containing a corrosion inhibiting component. Therefore, according to the boiler feed water treatment system 1, the filtration membrane without causing problems such as water quality changes due to clogging or the water temperature with is possible to suppress the corrosion of the heat transfer surface of the boiler 2 without using the agent Can do.

  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.

Is a schematic illustration showing an example of an embodiment of boiler feed water treatment system according to the present invention.

Explanation of symbols

1 boiler feed water treatment system 2 boilers <br/> 3 waterlines 4 electrodialysis apparatus

Claims (1)

The water supply line to the boiler, a boiler feed water processing system provided with electrodialysis apparatus configured with a electrodialysis cell disposed the cation exchange membranes and anion exchange membranes alternately,
Passing the boiler feedwater to the desalination chamber of the electrodialysis tank, and adjusting the amount of current supplied to the electrodialysis tank, so as to form a heat transfer tube of the boiler that exists as ions in the boiler feedwater It is obtained by removing sulfate ions and chloride ions that promote the corrosion of metals and passing through silica that suppresses the corrosion of non-passivated metals that exist as non-ions in the feed water and form the heat transfer tubes of the boiler. A boiler feed water treatment system characterized in that the demineralized water is supplied to the boiler.