Method of injecting chemicals into a steam system

Abstract

The present invention is a method for feeding a chemical to a steam system that controls the injection of a water treatment chemical to the steam system, the method being for feeding a chemical to the steam system that comprises: a pressure sensor, a temperature sensor, or a steam trap as a steam circulation detection means provided to the steam system; and a chemical feed pump for injecting the water treatment chemical to the steam system, said steam system controlling the injection of the water treatment chemical by means of the chemical feed pump in accordance with the steam circulation detection status of the steam circulation detection means.

Description

Technical Field

[0001] The present invention relates to a chemical injection method for injecting chemicals into a steam system.

Background Art

[0002] In order to maintain or preserve the air supply piping and equipment that utilize the steam generated from a boiler (steam generator), chemicals are injected into the steam system. <00000!15>

[0003] Generally, the purposes of chemical injection into the steam system include corrosion prevention of the steam condensate system of the steam generation equipment and improvement of the heating efficiency of the heat exchanger.

[0004] For the corrosion prevention of the steam condensate system of the steam generation equipment, corrosion prevention components such as volatile neutral amines such as morpholine and film-forming amines are added alone to the boiler feed water, condensate system, and makeup water system, or a boiler chemical in which corrosion prevention components such as volatile neutral amines and film-forming amines are liquefied together with the corrosion inhibitor of the boiler body may be added.

[0005] <00:00023>In this case, since a part of the corrosion inhibitor remains in the boiler water, it is necessary to add an excessive amount of chemicals, which is uneconomical. In addition, the chemical may be entrained in the steam even in a system where it is not desired to have the chemical in the steam (for example, a steam humidification system or a process that performs direct steam heating).

[0006] Therefore, these corrosion inhibitors may be directly added to the steam system (Patent Document 1).

[0007] Here, in many cases, an expensive steam flow meter is not installed in the steam line, and in many cases, a constant amount of corrosion inhibitor is injected without providing an interlock for the chemical injection device. In this case, the corrosion inhibitor continues to be injected even though the target equipment is stopped and no steam is flowing, and when the steam is re-fed, a high-concentration chemical diffuses into the system at a high concentration, which may cause odor troubles and the like.

[0008] Furthermore, even when boiler steam is branched and used, corrosion inhibitors may continue to be injected even when the equipment in question is shut down and no steam is flowing. When steam is then resumed, high concentrations of the chemical may be diffused into the system, potentially causing odor problems.

[0009] To improve the heating efficiency of steam-type heat exchangers, chemicals such as polyamines are sometimes used (Patent Document 2).

[0010] In this case as well, if there is no steam flow meter, the interlock of the chemical injection device may not be released even when the equipment in question is stopped, resulting in the addition of an excessive amount of chemical, which can cause odor problems and strainer clogging due to the generation of sticky substances. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2004-69182 [Patent Document 2] Japanese Patent Publication No. 2019-56524 [Overview of the project] [Problems that the invention aims to solve]

[0012] This invention has been made in view of the above-mentioned conventional circumstances, and aims to provide a chemical injection method that can appropriately inject chemicals into a steam system while suppressing costs. [Means for solving the problem]

[0013] The gist of this invention is as follows:

[0014] [1] A method for injecting chemicals into a steam system, comprising a pressure sensor, a temperature sensor, or a steam trap as a steam flow detection means provided in the steam system, a chemical injection pump for injecting water treatment chemicals into the steam system, and a method for injecting chemicals into a steam system, wherein the injection of water treatment chemicals by the chemical injection pump is controlled according to the steam flow detection status of the steam flow detection means.

[0015] [2] The method for injecting chemicals into a steam system according to [1], wherein the steam flow detection means is a sensor comprising the pressure sensor or the temperature sensor, and the chemical injection pump is activated when the detected value of the sensor is equal to or greater than a threshold, and the chemical injection pump is stopped when the detected value of the sensor is less than the threshold.

[0016] [3] The method for injecting chemicals into a steam system according to [1], wherein the steam flow detection means comprises the steam trap and a steam flow detection sensor of the steam trap, and the chemical injection pump is activated when the steam flow detection sensor detects steam flow, and the chemical injection pump is stopped when the steam flow detection sensor does not detect steam flow.

[0017] [4] A method for injecting chemicals into a steam system according to any one of [1] to [3], characterized in that a check valve with a siphon stopper is provided in the chemical injection piping that leads the water treatment chemicals from the chemical injection pump to the steam system.

[0018] [5] The method for injecting chemicals into a steam system according to any one of [1] to [4], characterized in that the location of the steam flow detection means in the steam system and the injection point of the water treatment chemicals from the chemical injection pump into the steam system are located on the secondary side of a steam flow control valve provided in the steam system.

[0019] [6] A method for injecting chemicals into a steam system according to any one of [1] to [5], characterized in that at the injection point of the water treatment chemicals from the chemical injection pump into the steam system, the water treatment chemicals are sprayed with a spray nozzle and injected into the steam system. [Effects of the Invention]

[0020] During normal operation of the boiler and heat exchanger equipment, the steam system is always pressurized or heated by steam, so its pressure and temperature are high. However, when the operation of the boiler stops, the temperature of the steam system drops, the volume of steam in the steam system decreases, or the steam condenses into water, resulting in a significant drop in the pressure of the steam system.

[0021] In the present invention, steam flow detection means is provided in the steam system, and the chemical injection of water treatment chemicals is controlled according to the steam flow situation detected by the steam flow detection means.

[0022] In one aspect of the present invention, a pressure sensor or a temperature sensor is installed in the steam system. When the detected value of the pressure sensor or the temperature sensor is above the threshold, the chemical injection pump is operated, and when the detected value of the sensor is below the threshold, the chemical injection pump is stopped.

[0023] In another aspect of the present invention, the steam flow detection means of the steam system comprises a steam trap and a steam flow detection sensor of the steam trap. When the steam flow detection sensor detects the steam flow of the steam trap, the chemical injection pump is operated, and when the steam flow detection sensor does not detect the steam flow, the chemical injection pump is stopped.

[0024] According to the present invention, by stopping the addition of water treatment chemicals to the steam system when the steam supply to the steam system stops, it is possible to prevent troubles caused by excessive addition of chemicals. In addition, excessive chemical addition during equipment shutdown can be prevented, which is advantageous both economically and in terms of practicality.

Brief Description of the Drawings

[0025] [Figure 1] It is a system diagram of a boiler system according to an embodiment. [Figure 2] It is a system diagram of a boiler system according to an embodiment. [Figure 3] It is a system diagram of a boiler system according to an embodiment. [Figure 4] This is a system diagram of the boiler system according to the embodiment. [Modes for carrying out the invention]

[0026] In the present invention, the steam system includes, but is not limited to, piping and headers for supplying steam from boilers, etc., as well as heat exchangers to which steam is supplied.

[0027] In one embodiment of the present invention's method for injecting chemicals into a steam system, a pressure sensor and a temperature sensor are installed in the steam system that supplies steam to the manufacturing process, a chemical injection pump is used to inject water treatment chemicals into the steam system, and a chemical injection control device is used to control the injection of water treatment chemicals according to the signals from the pressure sensor and the temperature sensor, and the amount of chemicals added by the chemical injection pump is adjusted according to the detected value of the pressure sensor or the temperature sensor.

[0028] In one aspect of the present invention, ON / OFF control is performed such that the chemical injection pump is turned ON when the pressure sensor or temperature sensor detected value is above a preset threshold, and OFF when it is below the threshold.

[0029] In another aspect of the present invention, the steam flow detection means for the steam system comprises the steam trap and a steam flow detection sensor for the steam trap, wherein the chemical injection pump is activated when the steam flow detection sensor detects steam flow in the steam trap, and the chemical injection pump is stopped when the steam flow detection sensor does not detect steam flow.

[0030] Any type of steam trap can be used, including mechanical steam traps, thermostatic steam traps, and thermodynamic steam traps.

[0031] Examples of mechanical steam traps include bucket-type mechanical steam traps and lever-type float-type mechanical steam traps.

[0032] Examples of thermostatic steam traps include bellows-type thermostatic steam traps and bimetallic-type thermostatic steam traps.

[0033] Examples of thermodynamic steam traps include disc-type thermodynamic steam traps and air-insulated thermodynamic steam traps.

[0034] As steam flow detection sensors for detecting the flow of steam through a steam trap, the following can be used: a vibration sensor that detects vibrations caused by the opening and closing of the steam trap; a temperature sensor that detects the rising steam trap temperature due to steam flow into the steam trap; and an acoustic sensor that detects the sound generated from the steam trap due to steam flow into the steam trap.

[0035] In this invention, in order to prevent excess chemicals from being drawn into the steam system even when the steam system becomes negatively pressurized when the equipment is stopped, it is preferable to install a check valve with a siphon stopper in the chemical injection line from the chemical injection pump to the chemical injection point.

[0036] In one aspect of the present invention, the pressure sensor, temperature sensor, steam trap, and chemical injection point are installed on the secondary side (downstream side in the steam flow direction) of a steam flow control valve provided in the steam system.

[0037] Furthermore, when water treatment chemicals are added to the entire steam flow rate from the boiler, rather than just to a portion of the steam system, the boiler may be operated using a DSS (daily nighttime start-up / shutdown) or WSS (weekend start-up / shutdown) system. In this DSS or WSS system, if the addition of water treatment chemicals to the steam system is stopped when the boiler is shut down, pressure sensors, temperature sensors, steam traps, or chemical injection points may be installed in addition to the secondary side of the steam flow control valve. For example, pressure sensors, temperature sensors, steam traps, or chemical injection points may be installed before or after the main steam valve immediately after the boiler body, in the steam header, or immediately before the heat exchanger.

[0038] The pressure sensor and chemical injection point may be located close together or far apart. Furthermore, if multiple heat exchanger systems are installed and each operates independently, it is desirable to install a separate pressure sensor and chemical injection point for each system.

[0039] The drug is preferably in the form of a solution or dispersion and delivered to the injection site by a drug injection pump.

[0040] In one aspect of the present invention, at the chemical injection point, the water treatment chemical is sprayed into the steam system using a spray nozzle and diffused.

[0041] In this invention, in order to prevent check valves and chemical injection piping (hoses) from deteriorating due to heat from the steam system, it is desirable to install them at a sufficient distance from the steam system or to provide a loop section in the middle of the chemical injection piping.

[0042] Examples of water treatment chemicals to be added to the steam system include corrosion inhibitors as described in Patent Document 1 and heating efficiency improvers as described in Patent Document 2, etc.

[0043] Specifically, this corrosion inhibitor can be any of the following: a film-forming corrosion inhibitor that prevents corrosion by forming a film on the pipes; a neutralizing corrosion inhibitor that prevents corrosion by neutralizing acidic substances contained in the water; or a composite corrosion inhibitor that combines a film-forming corrosion inhibitor and a neutralizing corrosion inhibitor.

[0044] Examples of heating efficiency improvers include long-chain fatty acid amines, such as polyamines represented by the following general formula (1).

[0045] R 1 -[NH-(CH2) m ] n -NH2…(1) (1) In the formula, R 1 represents a saturated or unsaturated hydrocarbon group having 10 to 22 carbon atoms, where m is an integer from 1 to 8 and n is an integer from 1 to 7. If n is 2 or greater, multiple NH-(CH2) groups are represented. m They may be the same or different.

[0046] The embodiments will be described in more detail below with reference to the drawings.

[0047] Figure 1 is a diagram showing the configuration of a boiler system to which the chemical injection method for the steam system according to the embodiment is applied.

[0048] In Figure 1, steam from boiler 1 is supplied through pipe 2, passes through flow control valve 3, and is supplied to heat exchanger 5 via pipe 4.

[0049] The chemical solution from the chemical tank 10 is supplied to the chemical injection nozzle (not shown) in the pipe 4 via the chemical injection pump 11, piping 12, check valve with siphon stopper 13, and piping 14, and the chemical is injected by spraying it into the pipe 4.

[0050] A pressure sensor 15 is installed in the piping 4, and its detection signal is input to the controller 16, which controls the chemical injection pump 11.

[0051] The controller 16 performs ON / OFF control, turning on the chemical injection pump 11 when the value detected by the pressure sensor 15 is above a preset threshold, and turning off the chemical injection pump 11 when it is below the threshold.

[0052] Furthermore, one chemical injection pump may be controlled based on the detection signal of one pressure sensor, or multiple chemical injection pumps may be controlled based on the detection signal of one pressure sensor.

[0053] The same applies when a temperature sensor is used instead of the pressure sensor 11.

[0054] Figure 2 is a diagram showing the configuration of a boiler system to which a chemical injection method according to another embodiment is applied.

[0055] In the embodiment shown in Figure 2, the pressure sensor 15 is omitted. In this embodiment, a steam trap 18 is installed in the steam piping 17 on the secondary side, i.e., downstream side, of the heat exchanger 5. A steam flow detection sensor 19 is provided in the steam trap 18, and the detection signal from this steam flow detection sensor 19 is input to the controller 16. The controller 16 operates the chemical injection pump 11 when the steam flow detection sensor 19 detects steam flow in the steam trap 18, and stops the chemical injection pump 11 when the steam flow detection sensor 19 does not detect steam flow.

[0056] As mentioned above, the steam flow detection sensor 19 can be a vibration sensor that detects vibrations caused by the opening and closing of the steam trap 18, a temperature sensor that detects the temperature of the steam trap 18 rising as steam flows into the steam trap 18, or an acoustic sensor that detects the sound generated from the steam trap 18 due to the steam flow into the steam trap 18.

[0057] The other components of Figure 2 are the same as those in Figure 1, and the same reference numerals indicate the same parts.

[0058] Figure 3 is a diagram of a boiler system to which a chemical injection method according to yet another embodiment is applied. In the boiler system of Figure 3, the pressure sensor 15 and controller 16 are omitted from the boiler system of Figure 1, and a pressure switch 22 is installed instead.

[0059] In Figure 3, one end of the siphon tube 20 is connected to the pipe 4, and the other end of the siphon tube 20 is connected to the pressure switch 22 via the pipe 21.

[0060] A pipe 23 branches off from pipe 21, and an air release valve 24 is provided at the end of pipe 23. Although not shown in the diagram, a pressure gauge is provided on pipe 21.

[0061] The piping 14 that carries the chemical solution from the chemical injection pump 11 is connected to this piping 21.

[0062] The siphon tube 20 is provided to reduce the heat transmitted from the piping 4 to the pressure switch 22 and check valve 13, thereby protecting them.

[0063] The other components of Figure 3 are the same as those in Figure 1, and the same reference numerals indicate the same parts.

[0064] In Figure 3, when the pressure transmitted to the pressure switch 22 via the piping 21 is equal to or greater than a predetermined pressure, the pressure switch 22 activates the chemical injection pump 11, and when the pressure is lower than the predetermined pressure, the chemical injection pump 11 is deactivated.

[0065] In Figure 3, the chemical injection pipe 14 is connected to pipe 21, but as shown in Figure 4, pipe 14 may be configured to directly inject the chemical into pipe 4 via a siphon pipe 25. The siphon pipe 25 is provided to reduce the transfer of heat from pipe 4 to the check valve 13.

[0066] The other configurations and control method of the chemical injection pump 11 in Figure 4 are the same as in Figure 3, and the same reference numerals indicate the same parts. [Examples]

[0067] [Example 1] A boiler system having the configuration shown in Figure 1 is operated Monday through Friday with a steady steam generation rate of 10 t The boiler was operated at a normal operating pressure of 0.78 MPa per hour. The boiler was shut down on weekends (Saturday and Sunday).

[0068] The water treatment chemical in the chemical tank 10 was an 80% by mass aqueous solution of aminomethylpropanol. A diaphragm pump was used as the chemical injection pump 11.

[0069] When the pressure detected by the pressure sensor 15 was 0.5 MPa or higher, the drug solution was injected at a rate of 200 mL / hr; when it was below 0.5 MPa, the drug injection pump 11 was stopped.

[0070] In this embodiment 1, when the boiler was shut down on Saturdays and Sundays, the chemical injection pump 11 was stopped along with the pressure drop in the steam system.

[0071] As a result, no chemicals were added during the weekend when the steam equipment was shut down, and therefore there was no odor in the steam or condensate when it was restarted.

[0072] [Example 2] In Example 2, the operation was carried out in the same manner as in Example 1, except that the check valve 13 with siphon stopper was not installed.

[0073] In this second example, when the boiler was shut down on weekends, the chemical pump stopped along with the pressure drop in the steam system. However, because there was no check valve with a siphon stopper, some of the chemicals in the chemical tank were sucked in by the negative pressure as the pressure in the steam system dropped, resulting in 1 liter of chemical being added to the system. As a result, the steam and condensate had a slight odor when the system was restarted.

[0074] [Comparative Example 1] In Comparative Example 1, the pressure sensor 15 detected chemicals regardless of pressure, and the chemical injection pump 11 consistently injected chemicals at 200 mL / hr, even when the boiler was stopped. As a result, chemicals were continuously injected even when the boiler was stopped on Saturdays and Sundays (weekends). Furthermore, because the boiler operation stopped along with the equipment shutdown on weekends, the pressure in the system dropped to negative pressure, and some of the chemicals in the chemical tank 10 were drawn into the system. Consequently, when the boiler equipment was restarted on Monday, the steam and condensate were odorized. In addition, when the amount of chemical liquid in the chemical tank 10 was examined, it was found that 13 liters of chemicals had been added to the system over just two days (Saturday and Sunday), despite the boiler equipment being shut down.

[0075] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications are possible within the scope of achieving the effects of the invention.

[0076] This application is based on Japanese Patent Application No. 2023-032905, filed on 3 March 2023, which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0077] 1 Boiler 5 Heat exchanger 10 chemical tanks 11. Chemical injection pump 13. Check valve with siphon stopper 15. Pressure Sensor 16 Controllers 18 Steam Traps 19. Steam flow detection sensor 20, 25 Siphon tube 22 Pressure switch

Claims

1. A method for injecting chemicals into a steam system, which controls the injection of water treatment chemicals into the steam system, A pressure sensor, temperature sensor, or steam trap is provided in the steam system as a means for detecting steam flow, A chemical injection pump for injecting water treatment chemicals into the steam system, Includes a chemical injection control device, The chemical injection control device is a chemical injection method into a steam system that controls the injection of the water treatment chemical by the chemical injection pump according to the steam flow detection status of the steam flow detection means, The location of the steam flow detection means in the steam system, and the injection point of the water treatment chemicals from the chemical injection pump into the steam system, are located on the secondary side of the steam flow control valve provided in the steam system. Method for injecting chemicals into a steam system.

2. The steam flow detection means is a sensor comprising the pressure sensor or the temperature sensor, and the method for injecting chemicals into a steam system according to claim 1 is characterized in that the chemical injection pump is activated when the detected value of the sensor is equal to or greater than a threshold, and the chemical injection pump is stopped when the detected value of the sensor is less than the threshold.

3. The steam flow detection means comprises the steam trap and a steam flow detection sensor for the steam trap. The method for injecting chemicals into a steam system according to claim 1, characterized in that the chemical injection pump is activated when the steam flow detection sensor detects steam flow, and the chemical injection pump is stopped when the steam flow detection sensor does not detect steam flow.

4. The method for injecting chemicals into a steam system according to claim 1, characterized in that a check valve with a siphon stopper is provided in the chemical injection piping that leads the water treatment chemicals from the chemical injection pump to the steam system.

5. A method for injecting chemicals into a steam system according to any one of claims 1 to 4, characterized in that, at the point where the water treatment chemicals from the chemical injection pump are injected into the steam system, the water treatment chemicals are sprayed with a spray nozzle and injected into the steam system.

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