JP2008170113A - Method of inhibiting corrosion of condensate passage in steam boiler device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively and economically inhibit corrosion of a condensate passage in a steam boiler device where the condensed water from the condensate passage is mixed with boiler feed-water to be recycled. <P>SOLUTION: In an operation of the steam boiler device 1 for utilizing the steam generated in supplying and heating the boiler feed-water from a water supply tank 40 to the steam boiler 20 through a water supply passage 41, by supplying it to a load device 2, and collecting the condensed water obtained by condensing the steam in the water supply tank 40 through the condensate passage 30 extending from the load device 2 to be recycled, a neutralizer for inhibiting the corrosion of the condensate passage 30 by carbon dioxide gas generated with the steam, is supplied from a chemical agent supply device 60 to the water supply passage 41. A concentration of the free neutralizer in the condensed water collected in the water supply tank 40 from the condensate passage 30 is measured by a chemical agent concentration measuring device 70, and the supply of the neutralizer from the chemical agent supply device 60 is controlled on the basis of the concentration. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for inhibiting corrosion of a condensate path in a steam boiler device, in particular, by storing make-up water in a feed water tank as boiler feed water and supplying the boiler feed water from the feed water tank to the steam boiler through the feed water path and heating it. In a steam boiler apparatus that supplies and uses steam to be supplied to a load device through a steam supply pipe and collects condensate obtained by condensing the steam to a water supply tank through a condensate path extending from the load device and reuses it. The present invention relates to a method for suppressing corrosion of a water path.

  Boiler feed water is supplied to the steam boiler from the feed water tank and heated, and steam generated thereby is used in the load device, and condensate obtained by condensation of the steam is supplied to the feed water tank through the condensate path extending from the load device. Steam boiler devices that are recovered and reused as boiler feed water are known. Such a steam boiler device can reduce the amount of replenishment water used as boiler feed water for condensate recovery to the feed water tank, and enables economical operation of the steam boiler.

  By the way, in the above steam boiler apparatus, the condensate path for collecting the condensate to the feed water tank is often formed using a non-passivated metal such as carbon steel, and is included in the boiler feed water. Corrosion is likely to occur under the influence of hydrogen carbonate and carbon dioxide generated by decomposition of carbonate. This corrosion may cause a hole in the condensate path that hinders smooth recovery of the condensate, and may cause iron ions and other metal ions, which are impurity components in boiler feed water, to elute into the condensate.

  Therefore, in the operation of the steam boiler device, a neutralizing agent for neutralizing carbon dioxide gas that causes corrosion of the condensate passage is usually compared with boiler feed water, steam supplied from the steam boiler to the load device or the condensate route. To suppress the progress of corrosion in the condensate path (for example, Patent Document 1). Here, the supply amount of the neutralizing agent is controlled in accordance with the predicted amount of generated carbon dioxide gas. For example, in the method described in Patent Document 1, it is predicted that the amount of steam generated in a steam boiler is proportional to the amount of carbon dioxide, and the amount of neutralizing agent supplied is controlled according to the amount of steam generated. Yes.

JP 2002-327904 A

  However, the amount of carbon dioxide generated does not necessarily correspond to the amount of steam generated in the steam boiler. This is because the amount of carbon dioxide generated varies depending on the bicarbonate and carbonate concentrations and the operating pressure of the steam boiler. Therefore, even if the amount of generated steam is small, the amount of generated carbon dioxide may be large, and the amount of generated carbon dioxide may be small even though the amount of generated steam is large. In the former case, since the supply amount of the neutralizing agent is reduced with respect to the amount of carbon dioxide generated, corrosion of the condensate pipe is hardly suppressed effectively. On the other hand, in the latter case, the neutralizing agent is excessively supplied, which impairs economic efficiency.

  An object of the present invention is to effectively and economically suppress the corrosion of the condensate path in a steam boiler apparatus that mixes and reuses the condensate from the condensate path with boiler feed water.

  The method for inhibiting corrosion of a condensate path in a steam boiler apparatus according to the present invention is generated by storing makeup water in a feed water tank as boiler feed water, supplying the boiler feed water from the feed water tank to the steam boiler through the feed water path, and heating it. Condensate is used in a steam boiler apparatus that supplies steam to a load device through a steam supply pipe and collects condensate obtained by condensing the steam to a water supply tank through a condensate path extending from the load device and reuses it. This is to suppress the corrosion of the path. This method includes a step A of supplying a neutralizing agent for suppressing corrosion of the condensate path to at least one of the water supply path, the steam supply pipe, and the condensate path, and the recovery from the condensate path to the water tank. A step B of collecting a part of the condensate as a sample and measuring the concentration of the free neutralizing agent contained in the sample. In step A, the concentration of the free neutralizing agent measured in step B The supply amount of the neutralizing agent is controlled based on the above.

  This method will be described in more detail. When the concentration of the free neutralizing agent measured in the step B is substantially zero, the step A is performed to neutralize carbon dioxide contained in the steam generated in the steam boiler. Therefore, it can be determined that there is a possibility that carbon dioxide gas that is not neutralized is present in the condensate path. Therefore, in such a case, the supply amount of the neutralizing agent is increased in step A to the extent that free neutralizing agent is detected from the sample. Thereby, the supply shortage of the neutralizing agent is solved, and corrosion of the condensate path is effectively suppressed.

  On the other hand, when the concentration of the free neutralizing agent measured in the step B is high, the amount of the neutralizing agent supplied in the step A is generated in order to neutralize the carbon dioxide contained in the steam generated in the steam boiler. It can be judged that it was excessive as compared with the amount of carbon dioxide. Therefore, in such a case, the supply amount of the neutralizing agent is reduced in Step A until the concentration of the free neutralizing agent in the sample is lowered to a predetermined concentration. Thereby, the excessive supply of a neutralizing agent is eliminated and corrosion of the condensate piping can be economically suppressed.

  In the steam boiler apparatus according to the present invention, the method for inhibiting corrosion of the condensate path controls the supply amount of the neutralizing agent based on the concentration of the free neutralizing agent contained in the condensate. Can be effectively and economically suppressed.

  With reference to FIG. 1, the steam boiler apparatus which can implement one Embodiment of this invention is demonstrated. In FIG. 1, a steam boiler device 1 is for supplying steam to a load device 2 that is a steam using facility such as a heat exchanger, a steam kettle, a reboiler, or an autoclave, and includes a water supply device 10 and a steam boiler 20. , A condensate pipe 30, a medicine supply device 60, a medicine concentration measuring device 70, and a control device 80 are mainly provided.

  The water supply apparatus 10 is for supplying boiler feed water to the steam boiler 20, and includes a water supply tank 40 for storing boiler supply water, and a supply path 50 for supplying make-up water used as boiler supply water to the water supply tank. It is mainly equipped with. The water supply tank 40 has a water supply path 41 extending from the bottom thereof to the steam boiler 20. The water supply path 41 communicates with the steam boiler 20, and has a water supply pump 42 for sending boiler supply water stored in the water supply tank 40 to the steam boiler 20.

  The supply path 50 has a water injection path 51. This water injection channel 51 is for supplying makeup water to a water supply tank 40 from a raw water tank (not shown) in which raw water supplied from a water source such as tap water, industrial water or groundwater is stored. A water softening device 52 and a deoxygenation device 53 are provided in this order toward the tank 40.

  The water softening device 52 treats make-up water from the raw water tank with sodium-type cation exchange resin, replaces the hardness contained in the make-up water, that is, calcium ions and magnesium ions with sodium ions, and converts them into soft water. Is for.

  The deoxygenation device 53 is for removing dissolved oxygen in the makeup water treated in the water softening device 52, and is usually of a type that removes dissolved oxygen using a separation membrane. Various types of known types such as a type that removes dissolved oxygen or a type that removes dissolved oxygen by heating treated water are used.

  The steam boiler 20 is a once-through boiler, and as shown in FIG. 2, an annular storage portion 21 capable of storing boiler feed water supplied from a water supply path 41, and a large number of heat transfer tubes 22 rising from the storage portion 21 (FIG. 2). Only two are shown), and mainly includes an annular header 23 provided at the upper end of the heat transfer tube 22, a steam supply pipe 24 extending from the header 23 to the load device 2, and a combustion device 25 such as a burner. The combustion device 25 can radiate combustion gas from the header 23 side toward the storage portion 21 to heat the heat transfer tube 22.

  The heat transfer tube 22 is formed using a non-passivated metal. A non-passivated metal refers to a metal that does not passivate naturally in a neutral aqueous solution, and is usually a metal other than stainless steel, titanium, aluminum, chromium, nickel, zirconium, and the like. Specifically, carbon steel, cast iron, copper, copper alloy, and the like. Carbon steel may be passivated in the presence of a high concentration of chromate ions even in a neutral aqueous solution. This passivation is due to the influence of chromate ions, and the neutral aqueous solution. It's hard to say that it's a natural passivation inside. Therefore, carbon steel belongs to the category of non-passivated metals here. In addition, copper and copper alloys are considered to be metals that are unlikely to corrode due to the influence of moisture due to their noble position in the electrochemical column (emf series), but they are naturally passive in neutral aqueous solutions. Since it does not become a non-passivated metal, it belongs to the category of non-passivated metals.

  The condensate pipe 30 extends from the load device 2 to the water supply tank 40 and has a steam trap 31. The steam trap 31 is for separating steam and water. In general, the condensate pipe 30 is preferably constructed so as to be isolated from the outside air in order to prevent air from being caught in the boiler feedwater stored in the feedwater tank 40. Specifically, it is preferable that the condensate pipe 30 has a tip portion disposed in the boiler water supply, and particularly preferably disposed in the vicinity of the bottom of the water supply tank 40. The condensate pipe 30 is formed using a non-passivated metal, like the heat transfer pipe 22 of the steam boiler 20.

  The chemical supply device 60 communicates with the water supply path 41 and supplies chemicals to the boiler feed water supplied from the water supply tank 40 to the steam boiler 20. The medicine supply device 60 includes a medicine tank 61 for storing medicine, a supply path 62 extending from the medicine tank 61 to the water supply path 41, and a supply pump 63 provided in the supply path 62. The supply pump 63 sends out the medicine stored in the medicine tank 61 to the water supply path 41 through the supply path 62, and can control the flow rate.

  The chemical | medical agent used here is for suppressing the corrosion of the condensate piping 30 by the influence of the carbon dioxide gas mentioned later, and the neutralizing agent which can neutralize a carbon dioxide gas, specifically, a morpholine, a cyclohexylamine, etc. Of volatile amine compounds.

  The drug concentration measuring device 70 mainly includes a branch path 71 and a measuring device 72. The branch path 71 is for collecting a part of the condensate, which will be described later, collected in the water supply tank 40 through the condensate path 30 as a sample. In addition, a flow control valve 73 is provided. The measuring device 72 is for automatically measuring the concentration of the free neutralizing agent contained in the condensate sample collected from the condensate path 30 through the branch path 61. For example, the measuring device 72 makes the amount of free neutralizing agent contained in a predetermined amount of condensate sample, that is, the amount of free volatile amine compound, volatile to the acid consumption (pH 8.3) of the condensate sample. It is measured by a method of multiplying by a coefficient α corresponding to the type of amine compound. Here, the coefficient α is for correcting the basic strength of the volatile amine compound. The measuring device 72 measures the amount of free volatile amine compound contained in a predetermined amount of condensate sample by a method of subtracting IC (inorganic carbon amount) from the acid consumption (pH 4.8) of the condensate sample. You may do.

  The control device 80 is an electronic information processing organization for controlling the medicine supply device 60 and the medicine concentration measuring device 70, and as shown in FIG. 3, a central control device 81, a read-only recording device 82, and a rewritable recording device 83. And an input / output port 84. The central control device 81 is for controlling the operation of the entire control device 80. The read-only recording device 82 mainly records the operation programs of the medicine supply device 60 and the medicine concentration measuring device 70. The rewritable recording device 83 is for temporarily recording various electronic data. Further, the input / output port 84 is for inputting / outputting information in the control device 80, and an input device 85 for manually inputting an operation command or the like on the input side and the measuring device 72 communicate with each other. A supply pump 63 communicates with the output side.

Next, operation | movement of the above-mentioned steam boiler apparatus 1 is demonstrated.
In the operation of the steam boiler device 1, first, makeup water is supplied from the raw water tank to the feed water tank 40 through the water injection channel 51, and this makeup water is stored in the feed water tank 40 as boiler feed water.

  At this time, makeup water from the raw water tank is first processed in the water softening device 52 to become softened water. As a result, the makeup water is less likely to generate scale in the steam boiler 20. In this water softening process, the makeup of the makeup water is changed from dissolved salts to sodium salts. For example, hydrogen carbonate and carbonate also change to sodium salt.

  The makeup water that has become softened in the water softening device 52 is then deoxygenated in the deoxygenation device 53. Thereby, the dissolved oxygen which accelerates | stimulates corrosion of the heat exchanger tube 22 etc. in the steam boiler 20 is removed from makeup water.

  As a result, the dewatered softened water is stored in the feed water tank 40 as boiler feed water.

  When the feed water pump 42 is operated in a state where the makeup water is stored in the feed water tank 40, the makeup water stored in the feed water tank 40, that is, the boiler feed water is supplied to the steam boiler 20 through the feed water path 41. Boiler feed water supplied to the steam boiler 20 is stored as boiler water in the storage unit 21. The boiler water rises in the heat transfer tubes 22 while being heated by the combustion device 25 through the heat transfer tubes 22 and gradually becomes steam. The steam generated in each heat transfer tube 22 is collected in the header 23 and supplied to the load device 2 through the steam supply pipe 24.

  The steam supplied to the load device 2 passes through the load device 2 and flows to the condensate pipe 30, where it loses latent heat and partially changes to condensed water, and the steam and water are separated in the steam trap 31, resulting in a high temperature. It becomes the condensate. The condensate thus generated is mixed with the makeup water collected and stored in the feed water tank 40 through the condensate pipe 30 and reused as boiler feed water. At this time, since the boiler feed water stored in the feed water tank 40 is heated by the high-temperature condensate, the heating burden on the steam boiler 20 is reduced. Therefore, the steam boiler apparatus 1 can suppress the fuel cost for operating the steam boiler 20, and can be operated economically.

  During the operation of the steam boiler apparatus 1 as described above, in the steam boiler 20, the bicarbonate and carbonate contained in the boiler water are decomposed when heated to generate carbon dioxide. The carbon dioxide gas is discharged to the condensate path 30 through the steam supply pipe 24 and the load device 2 together with the steam. For this reason, the condensate path 30 is susceptible to corrosion due to the influence of the carbon dioxide gas.

  Therefore, the steam boiler device 1 supplies the neutralizing agent from the chemical supply device 60 to the water supply path 41 during operation.

  Next, a method for supplying a corrosion inhibitor from the chemical supply device 60 will be described according to the operation flowchart shown in FIG. This supply method is executed based on an operation program recorded in the read-only recording device 82 of the control device 80.

  First, in step S1, the operation program determines whether the operator has turned on the operation start switch. When the operator turns on the operation switch, the operation program proceeds to step S2 and waits for the operator to input the initial supply amount of the neutralizing agent. Here, the initial supply amount is a neutralizer necessary to neutralize the amount of carbon dioxide gas that is expected to be discharged from the steam boiler 20 to the condensate path 30 based on the steam supply amount of the steam boiler 20. Supply amount (supply amount per unit time).

  When the operator inputs the initial supply amount, the operation program moves to step S3 and starts the initial supply of the neutralizing agent. Here, the control device 80 operates the supply pump 63 according to the initial supply amount input in step S <b> 2, and continuously supplies the neutralizing agent stored in the chemical tank 61 to the water supply path 41 through the supply path 62. To do. The neutralizing agent supplied to the water supply path 41 is mixed into the boiler feed water supplied from the water supply tank 40 to the steam boiler 20 and is heated and volatilized by the steam boiler 20. Thereby, the neutralizing agent volatilized in the carbon dioxide gas generated in the steam boiler 20 acts, and the carbon dioxide gas is neutralized.

  Next, in step S4, the operation program determines whether or not the elapsed time t from the start of supply of the neutralizing agent has reached a predetermined time t1. The predetermined time t <b> 1 here is usually a time required for the condensate derived from the steam treated with the neutralizing agent to be stably recovered into the water supply tank 40.

  When the elapsed time t reaches the predetermined time t1, the operation program moves to step S5 and starts measuring the concentration of the neutralizing agent contained in the condensate. Here, first, the flow rate control valve 73 is controlled so that a part of the condensate flowing through the condensate pipe 30 toward the water supply tank 40 flows continuously to the branch path 71 as a sample for analysis. And the density | concentration of the free neutralizer contained in the condensate sample which flowed into the branch path 71 is continuously measured by the measuring device 72.

  Next, the operation program proceeds to step S6 and determines whether or not the concentration C of the free neutralizing agent measured in step S5 exceeds a predetermined concentration X. Here, the predetermined concentration X can be arbitrarily set in a range larger than 0, but it is usually preferable to set it to a level slightly larger than 0.

  When the concentration C of the free neutralizing agent is higher than the predetermined concentration X, the operation program moves to step S7 and reduces the supply amount of the neutralizing agent. Specifically, the supply pump 63 is controlled to reduce the amount of neutralizing agent supplied from the chemical tank 61 to the water supply path 41. As a result, in the steam boiler device 1, excessive supply of the neutralizing agent is prevented, and corrosion of the condensate passage 30 can be economically suppressed.

  On the other hand, when the concentration C of the free neutralizing agent is equal to or lower than the predetermined concentration X, the operation program moves to step S8 and increases the supply amount of the neutralizing agent. Specifically, the supply pump 63 is controlled to increase the amount of neutralizing agent supplied from the chemical tank 61 to the water supply path 41. As a result, in the steam boiler device 1, insufficient supply of the neutralizing agent is prevented, and corrosion of the condensate passage 30 can be effectively suppressed.

  After steps S7 and S8, the operation program moves to step S9, and determines whether the operator has turned the operation switch OFF. When the operator turns off the operation switch, the operation program is completed and operations such as the supply of neutralizing agent are stopped. On the other hand, when the operator does not turn off the operation switch, the operation program returns to step S6 and repeats steps S6 to S9. As a result, in the steam boiler apparatus 1, the supply amount of the neutralizing agent is continuously controlled based on the concentration of the free neutralizing agent in the condensate.

[Modification]
(1) In the above-described embodiment, the concentration of the free neutralizing agent in the condensate sample is automatically measured by the drug concentration measuring device 70, and the concentration from the drug supply device 60 to the water supply path 41 is determined based on the result. Although the supply amount of the summing agent is automatically controlled, the measurement of the concentration of the free neutralizing agent in the condensate sample and the control of the supply amount of the neutralizing agent can also be performed manually.

(2) In the above-described embodiment, the neutralizing agent is supplied to the water supply path 41, but the neutralizing agent can also be supplied to the steam supply pipe 24 or the condensate pipe 30.

1 is a schematic diagram of a steam boiler apparatus according to an embodiment of the present invention. The partial cross section schematic of the steam boiler used in the said steam boiler apparatus. Schematic of the control apparatus used in the said steam boiler apparatus. The operation | movement flowchart of the said control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steam boiler apparatus 2 Loading apparatus 20 Steam boiler 24 Steam supply piping 30 Condensate path 40 Water supply tank 41 Water supply path 60 Chemical supply apparatus 70 Chemical concentration measuring apparatus

Claims (1)

While supplying makeup water as boiler feed water in a feed water tank and supplying the boiler feed water from the feed water tank to the steam boiler through the feed water path and heating it, the steam is supplied to the load device through the steam supply pipe and used. The steam boiler apparatus recovers and reuses the condensate obtained by condensing the steam to the water supply tank through a condensate path extending from the load device, and is a method for suppressing corrosion of the condensate path. And
Supplying a neutralizing agent for inhibiting corrosion of the condensate path to at least one of the water supply path, the steam supply pipe and the condensate path; and
Collecting a part of the condensate collected from the condensate path to the water supply tank as a sample, and measuring the concentration of the free neutralizing agent contained in the sample;
In step A, the supply amount of the neutralizing agent is controlled based on the concentration of the free neutralizing agent measured in step B.
A method for inhibiting corrosion of a condensate path in a steam boiler device.

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