A non-stop online cleaning agent for steam turbines

Abstract

The invention discloses an online cleaning agent for steam turbines without stopping, relates to the field of steam turbine cleaning, and aims to solve the problem that online cleaning is impossible in the prior art. The technical scheme adopted is: using neutral or alkaline surfactants, penetrants, dispersants, and corrosion inhibitors, and emulsifying them in pure water. The agent is carried into the steam turbine by steam, and a film is formed inside the turbine flow, penetrating the scale layer, so that the scale layer is softened, loosened, and dispersed into nanometer-scale powder. With the rotation of the steam turbine and the continuous flushing of the steam flow, the dispersed scale layer forms nanometer-scale powder and gradually falls off, and leaves the steam turbine with the steam. When the scale layer is cleaned, the cleaning agent will form a single passivation film on the metal surface, so that the base metal is completely protected. The invention has cleaning and anti-corrosion effects, can realize online cleaning of the steam turbine, descale the steam turbine without stopping the machine, ensure the continuous production, and reduce the economic losses caused by shutdown.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine cleaning, in particular to an online cleaning agent for steam turbines without stopping the machine. Background Art

[0002] During the use of the steam turbine, since the steam produced by the boiler is not absolutely clean (it contains impurities such as sodium and silica), when the steam enters the steam turbine to expand and do work, its parameters decrease and its ability to carry salt gradually weakens. The salt crystallizes and precipitates, tightly adhering to the surfaces of flow parts such as nozzles, blades and steam valves, forming a hard layer of salt scale.

[0003] If the salt scale is not cleaned in time, the flow area in the turbine will be reduced, the turbine load will be reduced, the efficiency will be reduced, the enthalpy drop will be reduced, the reaction degree will be increased, the axial thrust of the rotor will increase, and the displacement and vibration of the unit will increase, which may cause the thrust bearing to overload and overheat and cause an accident; for the valve stem scaling of components such as the quick-closing valve and the speed regulating valve, it may cause the valve to get stuck and fail to cut off the steam inlet under accident conditions, thus causing the unit to overspeed and run away.

[0004] Existing cleaning methods:

[0005] 1. Stop the machine and open the cylinder: Open the cylinder to sandblast and clean the rotor blades and partitions. Stopping the machine and opening the cylinder for cleaning will bring a lot of economic losses. When the production task is heavy, the production cycle cannot leave enough time for cleaning and maintenance, which brings great inconvenience to the company's production.

[0006] 2. Use saturated steam for purging: reduce the load of boilers and turbines, convert superheated steam into saturated steam, reduce the turbine speed to about 1000 rpm, and detect the sodium and silicon content of condensed water during the purging operation. When the content is reduced, the purging is completed. Saturated steam has a high water content. Improper operation may cause water hammer, which may cause blade breakage and lead to major accidents, seriously threatening the safe, stable and economical operation of the turbine. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the existing defects and provide an online cleaning agent for steam turbines without stopping the machine, which can effectively solve the problems in the background technology.

[0008] In order to achieve the above object, the present invention discloses an online cleaning agent for steam turbine without stopping, and the technical scheme adopted is that the cleaning agent comprises the following components in parts by weight:

[0009] 10-25 parts of surfactant, 1-5 parts of penetrant, 1-5 parts of dispersant, 1-5 parts of corrosion inhibitor, 30-60 parts of deionized water;

[0010] The surfactant, the penetrant, the dispersant and the corrosion inhibitor are all neutral or alkaline.

[0011] Neutral or alkaline agents will not corrode the turbine components during the cleaning process.

[0012] As a preferred technical solution of the present invention, the surfactant is one or more of cyclohexylamine, tert-butylamine, triethanolamine, isobutylamine, and 2-ethylhexylamine. The surfactant can reduce the surface tension of the scale layer and penetrate the scale layer, thereby dispersing the scale layer into nano-scale powder, which is convenient for it to fall off from the surface of the equipment.

[0013] As a preferred technical solution of the present invention, the penetrant is one or more of sodium secondary alkyl sulfonate, sodium alkylbenzene sulfonate, fatty alcohol polyoxyethylene ether, sodium octyl succinate sulfonate. The penetrant can penetrate the scale layer and loosen the scale layer.

[0014] As a preferred technical solution of the present invention, the dispersant is one or more of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate. The dispersant can further disperse the scale layer into nano-scale powder.

[0015] As a preferred technical solution of the present invention, the corrosion inhibitor is one or more of benzotriazole, hexamethylenetetramine, and hexadecylamine. The corrosion inhibitor can protect the metal surface from corrosion.

[0016] As a preferred technical solution of the present invention, the pH range of the online cleaning agent for steam turbine without stopping is 7-12.

[0017] The present invention also discloses a method for preparing the cleaning agent, and the technical scheme adopted is to add deionized water into a reaction kettle according to a weight ratio, and then add a surfactant, a penetrant, a dispersant, and a corrosion inhibitor, and then emulsify to obtain a uniformly mixed agent.

[0018] As a preferred technical solution of the present invention, the emulsification temperature is 25-60°C, the emulsification time is 4-8 hours, and the mixture is allowed to stand for 1-4 hours after emulsification.

[0019] The present invention also discloses a method for using the online cleaning agent, and the technical solution adopted is to include the following steps:

[0020] Step 1, when the steam turbine is in normal operation, add the online cleaning agent for steam turbine without stopping into the steam drum; enable steam to carry the agent into the steam turbine; the cleaning agent can be directly added into the steam drum through a dosing device, or the agent can be added into the water supply pipe of the steam drum through a dosing device and enter the steam drum along with the make-up water, or the agent can be added into the deaerator or economizer through a dosing device and then enter the steam drum, or other ways can be used to allow the agent to enter the steam drum;

[0021] Step 2, the online cleaning agent for the steam turbine without stopping is heated and vaporized in the boiler, becomes superheated steam through the superheater, and then is cooled and decompressed by the desuperheater before entering the steam turbine; the agent begins to vaporize when the temperature reaches 100°C, and the superheater heats the steam and the agent to 300-600°C, but the agent will decompose when the temperature reaches 650°C, and the decomposition products are hydrocarbons, nitrogen, etc., so the heating temperature of the superheater should be controlled below 650°C;

[0022] Step 3, the non-stop online cleaning agent for steam turbines is attached to the flow-through part of the steam turbine and forms a film on the surface of the scale layer, producing a special interface penetration effect on the scale layer, penetrating the scale layer, and softening and loosening the scale layer, and at the same time dispersing the scale layer into nano-scale powder, so that it can fall off from the flow-through part;

[0023] Step 4, the scale particles dispersed on the blades of the steam turbine fall off from the blades under the action of the centrifugal force generated during the rotation of the blades; the scale on the non-rotating parts gradually falls off as the steam flow continues to flush, and the scale particles that fall off leave the steam turbine with the steam, and after being condensed in the condenser, they are mixed with condensate and enter the hot well;

[0024] Step 5, when the condensate passes through the fine treatment device, silicon, sodium, iron and other ions are separated from the condensate, and the purified condensate is deoxygenated by the deaerator and returned to the steam drum to realize circulation.

[0025] During the cleaning process, the cleaning results were obtained by monitoring the turbine load, power, speed, wheel chamber pressure, main steam valve opening, vibration, displacement, and the sodium ion and silica content in the condensate. Specifically, the turbine load, power, and speed all increased, the wheel chamber pressure, main steam valve opening, and vibration displacement all decreased, and the sodium ion and silica content in the condensate increased, which shows that the scale layer in the turbine has been peeled off and washed out.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention carries the reagent into the operating steam turbine through steam, forms a film on the scale layer surface inside the blades and other components of the steam turbine, uses a surfactant to activate the scale layer surface, and then penetrates the scale layer through the surfactant itself combined with the auxiliary penetrant, so that the scale layer is softened and loosened, the surfactant and the dispersant can disperse the softened and loosened scale layer into nano-scale particles, the corrosion inhibitor can protect the surface of the equipment from being corroded, and with the rotation of the turbine impeller and the continuous flushing of the steam flow, the dispersed scale layer particles gradually fall off and leave the steam turbine with the steam flow. The present invention can maintain stability below 600°C, and will not corrode the steam turbine components, can realize the online cleaning of the steam turbine, and can descale the steam turbine without stopping the machine, thereby ensuring the continuous production and reducing the economic losses caused by the shutdown; and the present invention is simple to operate, and the experience requirements and operation accuracy requirements of the staff are relatively low, and the cleaning process is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of an existing steam turbine power generation system;

[0028] Figure 2 A schematic diagram of a first embodiment of a steam turbine power generation system using the present invention;

[0029] Figure 3 A schematic diagram of a second embodiment of a steam turbine power generation system using the present invention;

[0030] Figure 4 It is a schematic diagram of a third embodiment of a steam turbine power generation system using the present invention.

[0031] In the figure: 1. Boiler; 2. Steam drum; 3. Superheater; 4. Desuperheater; 5. Steam turbine; 6. Generator set; 7. Condenser; 8. Hot well; 9. Polishing device; 10. Deaerator; 11. Feed water pipe; 12. Chemical dissolving tank; 13. High-pressure chemical dosing pump; 14. Economizer. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] like Figure 1As shown, the existing steam turbine power generation system includes a boiler 1, which is connected to a steam drum 2. The steam drum 2 contains treated pure water. The pure water in the steam drum 2 is heated by the boiler 1. Under high pressure, steam above 200°C can be generated. The steam in the steam drum 2 is saturated steam. Since the water in the saturated steam will impact and corrode the turbine blades, in order to remove the water in the saturated steam, a superheater 3 is connected to the rear end of the steam drum 2. The exhaust pipe of the boiler 1 is connected to the superheater 3. The steam is secondary heated by the high-temperature flue gas generated by the boiler 1 to 300-600°C (the temperature has a certain relationship with the rated pressure), the moisture in the steam is removed, and then the desuperheater 4 is connected to reduce the steam temperature to 400-550°C, and then the steam enters the steam turbine. 5, pushes the blades to rotate and do work, thereby driving the generator set 6 to generate electricity; then the steam enters the condenser 7 to condense into condensate, which is buffered in the hot well 8, and then the condensate is pumped to the fine treatment device 9 for filtration, and after removing impurities containing sodium, silicon and other elements in the condensate, it is deoxygenated by the deaerator 10, and after preheating by the economizer 14, it returns to the steam drum 2 and enters the cycle; in order to maintain sufficient steam volume, a water supply pipe 11 is also connected to the pipeline at the front end of the deaerator 10, and desalted water is added to the system through the water supply pipe 11. The pH of the added desalted water is adjusted by adding ammonia water to make it alkaline, and then it is deoxygenated by the deaerator 10 and preheated by the economizer 14 before returning to the steam drum 2; at the same time, trisodium phosphate is added to the steam drum 2 for boiler water treatment to prevent boiler scaling.

[0034] Example 1

[0035] This embodiment discloses a first implementation mode of the present invention, firstly discloses an online cleaning agent for steam turbine without stopping, and the technical scheme adopted is that the cleaning agent comprises the following components in parts by weight:

[0036] 25 parts of cyclohexylamine (surfactant), 1 part of fatty alcohol polyoxyethylene ether (penetrant), 1 part of sodium dodecyl sulfate (dispersant), 1 part of benzotriazole (corrosion inhibitor), and 60 parts of deionized water.

[0037] The preparation method of the online cleaning agent for steam turbine without stopping (hereinafter referred to as "agent") is as follows: deionized water is added into a reaction kettle according to a weight ratio, and then a surfactant, a penetrant, a dispersant, and a corrosion inhibitor are added, and the agent is emulsified at 60° C. for 4 hours and allowed to stand for 1 hour to obtain the agent.

[0038] The method of using the drug is as follows: Figure 2 As shown, a drug dissolving tank 12 and a high-pressure drug dosing pump 13 are introduced, the drug is diluted and dissolved in the drug dissolving tank 12, the front end of the high-pressure drug dosing pump 13 is connected to the drug dissolving tank 12, and the rear end is connected to the water supply pipe 11. The specific use method includes the following steps:

[0039] Step 1, after the reagent is dissolved in the reagent dissolving tank 12, it can enter the steam drum 2 through the water supply pipe 11 along with the desalted water added to the steam drum 2 through the deaerator 10 and the economizer 14. The amount of reagent added is 30g per ton of steam;

[0040] Step 2, the reagent is heated and vaporized in the steam drum 2, carried by the steam through the superheater 3 to increase the temperature, and then cooled by the desuperheater 4 before entering the steam turbine 5;

[0041] Step 3, when the agent passes through the pipes, pipe fittings, valves and blades of the turbine 5, it forms a film on the surface of the scale layer and produces a special interface penetration effect. After the surfactant activates the surface of the scale layer, the surfactant and the penetrant penetrate the scale layer and soften and loosen the scale layer. The surfactant and the dispersant then disperse the scale layer into nano-scale powder, and the corrosion inhibitor protects the surface of the equipment from corrosion;

[0042] Step 4, the dispersed nano-scale powder falls off from the blades under the centrifugal force generated during the rotation of the blades of the steam turbine 5, and the salt scale powder on the non-rotating parts and pipes, pipe fittings, valves and other equipment is flushed by the steam flow and leaves the attachment surface with the steam, and after condensation in the condenser 7, it is mixed with the condensate and enters the hot well 8, so that the scale layer is gradually peeled off;

[0043] Step 5, when the condensate passes through the fine treatment device 9, the silicon, sodium, iron and other ions are separated from the condensate, and the purified condensate is deoxygenated by the deaerator 10 and then returned to the steam drum 2 to form a cycle;

[0044] Step 6: During the cleaning process, the boiler water in the drum 2, the generated superheated steam, and the condensate in the hot well are tested. The test items, qualified standards, and test frequencies are as follows:

[0045] Main steam index:

[0046] project Eligibility criteria Analysis frequency Sodium ion <15μg / L Every 4 hours Silicon dioxide <20μg / L Every 4 hours

[0047] Boiler water indicators:

[0048] project Eligibility criteria Analysis frequency pH 9.0—11.0 Once every hour Phosphate 2-10mg / L Every 4 hours

[0049] During the cleaning process, the salt scale falls off and dissolves into the condensate, which will cause the increase of sodium ions, silicon dioxide and other detection indicators in the condensate. This is a normal phenomenon in the cleaning process, and it can also reflect that the salt scale in the equipment such as the steam turbine is being peeled off.

[0050] If the pH of boiler water is not within the range of 9.0-10.0, the injection rate of trisodium phosphate should be adjusted in time. At the same time, if the pH is higher than 11.0, the blowdown of drum 2 should be increased;

[0051] Step 7, the cycle of the entire steam turbine online cleaning without stopping is more than 30 days, and the entire cycle is divided into three stages, the first week is the first stage, the second week is the second stage, and the remaining period is the third stage. The amount of reagent added in step 1 is the amount added in the first stage, the amount added in the second stage is twice that of the first stage, and the amount added in the third stage is 2.5 times that of the first stage;

[0052] Step 8, by monitoring the load, steam flow, speed, turbine chamber pressure and main steam valve opening of the steam turbine 5, the cleaning effect of the steam turbine is obtained.

[0053] Example 2

[0054] The difference between this embodiment and embodiment 1 is that:

[0055] The medicine comprises the following components by weight:

[0056] 10 parts of tert-butylamine (surfactant), 5 parts of sodium alkylbenzene sulfonate (penetrant), 5 parts of sodium dodecylbenzene sulfonate (dispersant), 5 parts of hexamethylenetetramine (corrosion inhibitor), and 30 parts of deionized water.

[0057] In the preparation method of the drug, the emulsification conditions are: emulsification at 25°C for 8 hours, and then standing for 4 hours to obtain the drug.

[0058] The method of using the drug is as follows: Figure 3 As shown, the rear end of the high-pressure dosing pump 13 is connected to the steam drum 2. In the specific method of use, in step 1, the reagent can enter the steam drum 2 after being dissolved in the dissolving tank 12. The amount of reagent added is 37.5 g per ton of steam.

[0059] Example 3

[0060] The difference between this embodiment and embodiment 1 is that:

[0061] The medicine comprises the following components by weight:

[0062] 10 parts of isobutylamine (surfactant 1), 10 parts of triethanolamine (surfactant 2), 2 parts of sodium secondary alkyl sulfonate (penetrant 1), 2 parts of sodium succinate octyl sulfonate (penetrant 2), 2 parts of sodium dodecyl sulfate (dispersant 1), 2 parts of sodium dodecylbenzene sulfonate (dispersant 2), 2 parts of urotropine (corrosion inhibitor 1), 2 parts of hexadecylamine (corrosion inhibitor 2), and 50 parts of deionized water.

[0063] In the preparation method of the drug, the emulsification conditions are: emulsification at 40°C for 6 hours, and then standing for 3 hours to obtain the drug.

[0064] The method of using the drug is as follows: Figure 4As shown, the rear end of the high-pressure dosing pump 13 is connected to the economizer of the boiler 1. In the specific method of use, in step 1, the agent can enter the steam drum 2 through the economizer after being dissolved in the dissolving tank 12. The amount of agent added is 35g per ton of steam.

[0065] The steam turbine 5 was cleaned without stopping using the reagent and method disclosed in Example 1, and the state of the steam turbine 5 after cleaning was compared with that before cleaning. The results were as follows: (Steam turbine of refinery hydrogenation unit)

[0066] Before cleaning: When the processing capacity of steam turbine 5 is 180-185t / h, the exhaust pressure is 0.020-0.028Mpa, and the speed is 8600rpm, the wheel chamber pressure is 3.0-3.5Mpa, and the main steam valve opening is 60-77%;

[0067] After cleaning: Under the conditions of processing capacity of steam turbine 5 of 180-185t / h, exhaust pressure of 0.020-0.028Mpa, and rotation speed of 8600-8800rpm, the wheel chamber pressure is 2.6-3.0Mpa, and the main steam valve opening is 46-62%;

[0068] By comparison, it can be seen that after cleaning, while maintaining the original working conditions, the wheel chamber pressure dropped by 0.4-0.5Mpa and the main steam valve opening dropped by 14%.

[0069] It can be seen from the above comparison results that the present technical solution can effectively clean the inside of the steam turbine 5 without shutting down the steam turbine 5.

[0070] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A non-stop online cleaning agent for steam turbines, characterized in that: The components include the following by weight: 10-25 parts of surfactant, 1-5 parts of penetrant, 1-5 parts of dispersant, 1-5 parts of corrosion inhibitor, 30-60 parts of deionized water; The surfactant, the penetrant, the dispersant and the corrosion inhibitor are all neutral or alkaline.

2. The on-line cleaning agent for steam turbines without stopping according to claim 1, characterized in that: The surfactant is one or more of cyclohexylamine, tert-butylamine, triethanolamine, isobutylamine and 2-ethylhexylamine.

3. The on-line cleaning agent for steam turbines without stopping according to claim 1, characterized in that: The penetrant is one or more of sodium secondary alkyl sulfonate, sodium alkylbenzene sulfonate, fatty alcohol polyoxyethylene ether, and sodium octyl succinate sulfonate.

4. The on-line cleaning agent for steam turbines without stopping according to claim 1, characterized in that: The dispersant is one or more of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

5. The on-line cleaning agent for steam turbines without stopping according to claim 1, characterized in that: The corrosion inhibitor is one or more of benzotriazole, hexadecanamine and hexadecylamine.

6. The on-line cleaning agent for steam turbines without stopping according to claim 1, characterized in that: The pH range of the online cleaning agent for steam turbine without stopping is 7-12.

7. A method for preparing an online cleaning agent for steam turbines without stopping the machine based on any one of claims 1 to 6, characterized in that: Deionized water is added into a reaction kettle according to a weight ratio, and then a surfactant, a penetrant, a dispersant and a corrosion inhibitor are added, and the mixture is obtained after emulsification.

8. The method for preparing an online cleaning agent for steam turbines without stopping the machine according to claim 7, characterized in that: The emulsification temperature of the emulsification is 25-60°C, the emulsification time is 4-8 hours, and the mixture is allowed to stand for 1-4 hours after emulsification.

9. A method for online cleaning of a steam turbine without stopping the machine based on the online cleaning agent for steam turbine without stopping the machine according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1, when the steam turbine (5) is in normal operation, adding the online cleaning agent for steam turbine without stopping the machine into the steam drum (2); Step 2, the online cleaning agent for the steam turbine without stopping is vaporized under heating, passes through a heater (3) to remove moisture, and then is cooled and decompressed by a desuperheater (4) before entering the steam turbine (5); Step 3, the non-stop online cleaning agent for steam turbines is attached to the flow-through part of the steam turbine (5), and forms a film on the surface of the scale layer, producing a special interface penetration effect on the scale layer, penetrating the scale layer, softening and loosening the scale layer, and dispersing the scale layer into nano-scale small particles; Step 4, the scale particles dispersed on the flow-through part of the steam turbine (5) fall off from the flow-through part under the action of the centrifugal force generated during the rotation of the blades, leave the steam turbine (5) along with the steam, and after being condensed in the condenser (7), are mixed with condensate and enter the hot well (8); Step 5, during the process of the condensate passing through the fine treatment device (9), silicon, sodium and iron ions are separated from the condensate, and the purified condensate is deoxygenated by the deaerator (10) and then returned to the steam drum (2).

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