A deoxidizer for medium and high pressure boilers and its preparation method

Abstract

The application provides a deoxidizing agent suitable for medium and high pressure boilers and a preparation method thereof, wherein the deoxidizing agent contains the following raw materials in parts by weight: 20-40 parts of an organic reducing agent, 10-20 parts of an amino heterocyclic compound, 4-8 parts of a hydroxylamine compound, 2-8 parts of a dispersing agent, 3-6 parts of a neutralizing agent, 2-6 parts of modified sodium alginate, 1-3 parts of modified lignin and 20-40 parts of deionized water. The deoxidizing agent is high-temperature resistant, has outstanding dissolved oxygen removal capacity, is suitable for a medium and high pressure boiler water supply system, has a corrosion prevention effect, solves the corrosion problem of boilers, pipelines and heat exchangers, and is environmentally friendly, safe, almost non-toxic and harmless, and has a good market prospect.

Description

Technical Field

[0001] This invention belongs to the field of boiler deoxygenating agent technology, specifically relating to a deoxygenating agent suitable for medium and high pressure boilers and its preparation method. Background Technology

[0002] In the continuous development of my country's industrial sector, boilers, as an indispensable and crucial piece of equipment in industrial production, play a vital role in the stability of the entire industrial system through their safe and efficient operation. However, during long-term operation, boilers often face corrosion and scaling problems in key components such as water-cooled walls, economizers, and convection pipes. These problems not only lead to an increase in the thickness of the boiler's metal walls but may even cause perforation of the metal walls, and in severe cases, may lead to safety accidents such as pipe explosions.

[0003] To ensure the safe operation and improve the efficiency of boilers, effective deoxygenation of boiler water is crucial. While traditional thermal deoxygenation methods can prevent oxygen corrosion caused by heating to some extent, their effectiveness is less than ideal in practical applications due to long-term operation and water flow regulation. Against this backdrop, chemical deoxygenators have gradually become a new choice in the industry. Chemical deoxygenators can effectively remove excess nutrients from the water, prevent oxygen from reacting with substances inside the boiler to form deposits, thereby maintaining the quality of the boiler water and ensuring the balance of pH and salinity. However, existing chemical deoxygenators still have some limitations in use, such as numerous restrictions on application conditions and environmental impacts.

[0004] Chinese Patent CN 109928447 A discloses a high-efficiency deoxygenator for boiler feedwater, its preparation method, and its application. It is composed of organic amine-modified lignin, isoascorbic acid, polyepoxysuccinic acid, polyaspartic acid, a pH adjuster, tetramethyl-p-phenylenediamine, carbazide, methyl ethyl ketone oxime, and water. It not only effectively adsorbs dissolved oxygen in water but also forms a protective oxide layer on metal surfaces, improving deoxygenation and corrosion inhibition. Although it exhibits good deoxygenation effects, it is still primarily a traditional deoxygenator. Its suitability for high-pressure boiler water environments requires further investigation, particularly since tetramethyl-p-phenylenediamine may decompose at high temperatures.

[0005] Therefore, there is an urgent need for a special deoxygenating agent for medium and high pressure boilers and its preparation method, which aims to be able to withstand high temperatures, have outstanding ability to remove dissolved oxygen, be suitable for medium and high pressure boiler feedwater systems, and be environmentally friendly and safe. Summary of the Invention

[0006] To address the existing technical problems, the present invention aims to provide a deoxygenating agent suitable for medium and high-pressure boilers and its preparation method. The deoxygenating agent of this invention is resistant to high temperatures, exhibits outstanding dissolved oxygen removal capabilities, is suitable for medium and high-pressure boiler feedwater systems, has anti-corrosion effects, solves the corrosion problems of boilers, pipelines, and heat exchangers, and is environmentally friendly, safe, and virtually non-toxic, with promising market prospects.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] One aspect of this invention is to provide a deoxygenating agent suitable for medium and high pressure boilers. By weight, the deoxygenating agent comprises the following raw materials: 20-40 parts of organic reducing agent, 10-20 parts of amino heterocyclic compound, 4-8 parts of hydroxylamine compound, 2-8 parts of dispersant, 3-6 parts of neutralizing agent, 2-6 parts of modified sodium alginate, 1-3 parts of modified lignin, and 20-40 parts of deionized water.

[0009] The reaction mechanism and function of this invention are as follows:

[0010] 1. Sodium alginate, as a component of boiler deoxygenators, interacts with dissolved oxygen in water to effectively reduce the dissolved oxygen content in boiler water, helping to reduce the risk of boiler corrosion and scaling, and extending the service life of the boiler. At the same time, sodium alginate can form a protective film on the boiler metal surface. This film can slow down the contact between the metal and corrosive substances in the water, thus playing a role in corrosion inhibition and protecting the boiler from corrosion. In addition, the viscosity of sodium alginate helps to improve the dispersibility of the deoxygenator in the boiler water, making it more evenly distributed in the boiler water and improving the ability to remove dissolved oxygen.

[0011] However, sodium alginate exhibits relatively poor stability at high temperatures. Medium- and high-pressure boilers typically operate at high temperatures, which can lead to the decomposition or inactivation of sodium alginate in boiler water, thus affecting its deoxygenation performance. Therefore, the applicant utilizes an amidation reaction between the carboxyl and amino groups to introduce fluorenemethyloxycarbonyl-L-aspartic acid-1-tert-butyl ester to modify sodium alginate. On one hand, the introduction of the heat-resistant functional group fluorene improves the overall heat resistance of sodium alginate; simultaneously, the introduction of fluorenemethyloxycarbonyl-L-aspartic acid-1-tert-butyl ester enhances the intermolecular interactions of sodium alginate, such as hydrogen bonding and hydrophobic interactions, which contribute to improving the stability of sodium alginate at high temperatures.

[0012] On the other hand, by introducing aspartic acid groups into sodium alginate, the compatibility of the modified polymer with the system can be improved, and its oxygen removal performance can be better utilized. At the same time, the presence of aspartic acid may also promote the biodegradation of modified sodium alginate, making it easier to decompose in the environment and increasing its environmental friendliness.

[0013] In addition, the modified sodium alginate may have a higher crosslinking density. The increase in crosslinking points can enhance the thermal stability of the material, allowing sodium alginate to maintain its structure and function at high temperatures.

[0014] 2. Lignin, a natural high-molecular polymer found in plant cell walls, contains various active functional groups, such as phenolic hydroxyl groups and ether bonds. These functional groups can react with oxygen in water, helping to remove dissolved oxygen. Due to the large number of phenolic hydroxyl groups in its molecular structure, lignin has a certain degree of water solubility; however, the molecular weight of lignin is usually large, and there are also a large number of non-polar regions in the molecule, which limits its water solubility.

[0015] The applicant modifies lignin with acrylamide and vinyl sulfonic acid. On the one hand, the modified lignin introduces strong chemical bonds and cross-linking networks to improve its thermal and chemical stability, enabling it to maintain its activity in medium and high-pressure boilers. On the other hand, the modified lignin can covalently bond to the boiler metal surface to form a protective film, which not only improves the mechanical strength of the deoxygenator but also enhances its wear resistance and reduces wear under high-pressure environments. In addition, the modification of lignin with acrylamide and vinyl sulfonic acid can enhance its water solubility, increase the chance of reaction with oxygen molecules, and thus improve its ability to remove dissolved oxygen.

[0016] In some embodiments, the organic reducing agent is any one or more of acetone oxime, dimethyl ketone oxime, carbazide, and ethoxyquin.

[0017] Preferably, the organic reducing agent is acetone oxime and carbazide, with a mass ratio of 1:(1.2-1.8).

[0018] In some embodiments, the amino heterocyclic compound is any one or more of 1-aminopyrrolidine, 1-amino-4-methylpiperazine, and 1-aminopiperidine.

[0019] In some embodiments, the hydroxylamine compound is any one or more of diethylhydroxylamine, diisopropylhydroxylamine, and phenylhydroxylamine.

[0020] In some embodiments, the dispersant is polyethylene glycol and / or sodium polyacrylate.

[0021] Preferably, the dispersant is polyethylene glycol and sodium polyacrylate in a mass ratio of 1:(1-3).

[0022] More preferably, the polyethylene glycol is polyethylene glycol 200.

[0023] In some embodiments, the neutralizing agent is cyclohexylamine and / or ethanolamine.

[0024] In some embodiments, the method for preparing the modified sodium alginate includes the following steps:

[0025] (1) Dissolve sodium alginate in deionized water, adjust the pH to 6-7, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide to obtain solution 1;

[0026] (2) Dissolve fluorenyl methoxycarbonyl-L-aspartic acid-1-tert-butyl ester in deionized water, add N,N-dimethylformamide, and obtain solution 2;

[0027] (3) Add solution 2 dropwise to solution 1. After the addition is complete, heat to 40-50℃ and stir to react, and obtain modified sodium alginate.

[0028] In some embodiments, the mass ratio of sodium alginate to fluorenemethyloxycarbonyl-L-aspartic acid-1-tert-butyl ester is 1:(3-5).

[0029] In some embodiments, the method for preparing the modified lignin includes the following steps:

[0030] Lignin and deionized water were added to a reaction vessel, the pH was adjusted to neutral, the mixture was heated to 65-75℃, stirred for 20-30 minutes, an inert gas was introduced, ammonium persulfate was added, and then acrylamide and vinyl sulfonic acid were added dropwise. The reaction was carried out for 6-12 hours, the precipitate was separated, washed, dried, and ground to obtain modified lignin.

[0031] In some embodiments, the molar ratio of acrylamide to vinyl sulfonic acid is 1:(1-4).

[0032] Another aspect of the present invention provides a method for preparing a deaerator suitable for medium and high pressure boilers, comprising the following steps:

[0033] Add some deionized water to the reactor, heat to 40-50℃, add organic reducing agent, amino heterocyclic compound, and hydroxylamine compound, stir for 10-15 min, then add dispersant, modified lignin, and modified sodium alginate, stir for 10-20 min, then add neutralizing agent and the remaining deionized water, stir for 10-20 min, cool to room temperature, and obtain oxygen scavenger.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. The oxygen scavenger of this invention is resistant to high temperature and has an outstanding ability to remove dissolved oxygen. It is suitable for medium and high pressure boiler feedwater systems, has anti-corrosion effect, solves the corrosion problems of boilers, pipelines and heat exchangers, and the oxygen scavenger is resistant to high temperature, environmentally friendly and safe, and almost non-toxic and harmless.

[0036] 2. The principle of the fluorenemethyloxycarbonyl-L-aspartic acid-1-tert-butyl ester modified sodium alginate of the present invention involves introducing heat-resistant functional groups, enhancing intermolecular interactions, improving biocompatibility and biodegradability, and increasing crosslinking density and network structure stability. The modified sodium alginate can be better applied in medium and high pressure boilers, exerting its deoxygenation, corrosion prevention and dispersion properties.

[0037] 3. This invention improves the thermal and chemical stability of lignin by modifying it with acrylamide and vinyl sulfonic acid; simultaneously, it enhances the water solubility of lignin, thereby improving deoxygenation efficiency. Furthermore, the modified lignin can covalently bond to the boiler metal surface, forming a protective film. Detailed Implementation

[0038] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0039] Each oxygen scavenger was prepared according to the proportions and preparation methods of the raw materials specified in the following examples and comparative examples.

[0040] To facilitate implementation of this invention by those skilled in the art, the manufacturers of some raw materials for the embodiments and comparative examples are described below:

[0041] Polyethylene glycol 200: purchased from Wuhan Jixin Yibang Biotechnology Co., Ltd.;

[0042] Sodium polyacrylate: purchased from Renqiu Pengyu Chemical Co., Ltd., with a viscosity of 78 cps at 25℃;

[0043] Sodium alginate: purchased from Hubei Xingdongcheng Chemical Co., Ltd.;

[0044] Lignin: Purchased from Pande (Shanghai) International Trading Co., Ltd.;

[0045] Unless otherwise specified, all other raw materials can be purchased from the market.

[0046] Preparation Example 1

[0047] The preparation method of modified sodium alginate A includes the following steps:

[0048] (1) Dissolve 1g of sodium alginate in 10ml of deionized water, adjust the pH to 6 with 2mol / L hydrochloric acid, add 15mg of (3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 9mg of N-hydroxysuccinimide to obtain solution 1;

[0049] (2) Dissolve 4g of fluorenemethyloxycarbonyl-L-aspartic acid-1-tert-butyl ester in 40ml of deionized water, add 50ml of N,N-dimethylformamide, and obtain solution 2;

[0050] (3) Add solution 2 dropwise to solution 1. After the addition is complete, heat to 45°C and stir for 24 hours to obtain modified sodium alginate A.

[0051] Preparation Example 2

[0052] The preparation method of modified sodium alginate B is the same as that of preparation example 1, except that the amount of fluorenemethyloxycarbonyl-L-aspartic acid-1-tert-butyl ester added in step (2) is 1.5g.

[0053] Preparation Example 3

[0054] The preparation method of modified lignin A includes the following steps:

[0055] Add 2g of lignin and 40ml of deionized water to a reaction vessel, adjust the pH to neutral with 0.1mol / L sodium hydroxide, heat to 70℃, stir for 25min, introduce nitrogen gas, add 5ml of 5% ammonium persulfate aqueous solution, then add 2.84g of 50% acrylamide aqueous solution and 5.4g of vinyl sulfonic acid dropwise, react for 8h, separate and precipitate with anhydrous ethanol, wash, vacuum dry at 60℃ for 48h, grind for 5min to obtain modified lignin A.

[0056] Preparation Example 4

[0057] The preparation method of modified lignin B includes the following steps:

[0058] 2g of lignin and 40ml of deionized water were added to a reaction vessel. The pH was adjusted to neutral with 0.1mol / L sodium hydroxide. The mixture was heated to 70℃ and stirred for 25min. Nitrogen gas was introduced, and 5ml of 5% ammonium persulfate aqueous solution was added. Then, 2.84g of 50% acrylamide aqueous solution was added dropwise. The reaction was carried out for 8h. The mixture was separated by precipitation with anhydrous ethanol and washed. It was then vacuum dried at 60℃ for 48h and ground for 5min to obtain modified lignin B.

[0059] Example 1

[0060] A deoxygenating agent suitable for medium and high pressure boilers, comprising the following raw materials by weight: 12 parts acetone oxime, 18 parts carbazide, 15 parts 1-aminopyrrolidine, 6 parts diethylhydroxylamine, 1.6 parts polyethylene glycol 200, 3.4 parts sodium polyacrylate, 4.5 parts ethanolamine, 4 parts modified sodium alginate A, 2 parts modified lignin A, and 30 parts deionized water.

[0061] The method for preparing the oxygen scavenger in this embodiment includes the following steps:

[0062] Add 20 parts of deionized water to the reaction vessel and heat to 45°C. Add 12 parts of acetone oxime, 18 parts of carbazide, 15 parts of 1-aminopyrrolidine, and 6 parts of diethylhydroxylamine. Stir for 12 minutes. Then add 1.6 parts of polyethylene glycol 200, 3.4 parts of sodium polyacrylate, 2 parts of modified lignin A, and 4 parts of modified sodium alginate A. Stir for 15 minutes. Then add 4.5 parts of ethanolamine and 10 parts of deionized water and stir for 15 minutes. Cool to room temperature to obtain the oxygen scavenger.

[0063] Example 2

[0064] An oxygen scavenger specifically designed for medium and high pressure boilers, comprising the following raw materials by weight: 9 parts acetone oxime, 11 parts carbazide, 10 parts 1-aminopyrrolidine, 4 parts diethylhydroxylamine, 1 part polyethylene glycol 200, 1 part sodium polyacrylate, 3 parts ethanolamine, 2 parts modified sodium alginate A, 1 part modified lignin A, and 20 parts deionized water.

[0065] The method for preparing the oxygen scavenger in this embodiment includes the following steps:

[0066] Add 15 parts of deionized water to the reaction vessel and heat to 40°C. Add 9 parts of acetone oxime, 11 parts of carbazide, 10 parts of 1-aminopyrrolidine, and 4 parts of diethylhydroxylamine. Stir for 10 minutes. Then add 1 part of polyethylene glycol 200, 3 parts of sodium polyacrylate, 1 part of modified lignin A, and 2 parts of modified sodium alginate A. Stir for 20 minutes. Then add 3 parts of ethanolamine and 5 parts of deionized water and stir for 10 minutes. Cool to room temperature to obtain the oxygen scavenger.

[0067] Example 3

[0068] An oxygen scavenger specifically designed for medium and high pressure boilers, comprising the following raw materials by weight: 14.3 parts acetone oxime, 25.7 parts carbazide, 20 parts 1-aminopyrrolidine, 8 parts diethylhydroxylamine, 200 parts polyethylene glycol, 6 parts sodium polyacrylate, 6 parts ethanolamine, 6 parts modified sodium alginate A, 3 parts modified lignin A, and 40 parts deionized water.

[0069] The method for preparing the oxygen scavenger in this embodiment includes the following steps:

[0070] Add 25 parts of deionized water to the reaction vessel and heat to 50°C. Add 14.3 parts of acetone oxime, 25.7 parts of carbazide, 20 parts of 1-aminopyrrolidine, and 8 parts of diethylhydroxylamine. Stir for 15 minutes. Then add 200 parts of polyethylene glycol, 6 parts of sodium polyacrylate, 3 parts of modified lignin A, and 6 parts of modified sodium alginate A. Stir for 10 minutes. Then add 6 parts of ethanolamine and 15 parts of deionized water and stir for 20 minutes. Cool to room temperature to obtain the oxygen scavenger.

[0071] Example 4

[0072] A deoxygenating agent suitable for medium and high pressure boilers and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that an equal amount of modified sodium alginate B is used instead of modified sodium alginate A.

[0073] Example 5

[0074] A deoxygenating agent suitable for medium and high pressure boilers and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that an equal amount of modified lignin B is used to replace modified lignin A.

[0075] Comparative Example 1

[0076] A deoxygenating agent suitable for medium and high pressure boilers and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that an equal amount of commercially available sodium alginate is used to replace modified sodium alginate A.

[0077] Comparative Example 2

[0078] A deoxygenating agent suitable for medium and high pressure boilers and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that an equal amount of commercially available lignin is used to replace the modified lignin.

[0079] Effect evaluation:

[0080] The oxygen scavengers prepared in Examples 1-5 and Comparative Examples 1-2 were tested and analyzed. The specific results are shown in Table 1.

[0081] Performance testing:

[0082] Demineralized water was used as the simulated high-pressure boiler water. A 5000 mL Erlenmeyer flask was purged with carbon dioxide for 2 minutes, and then 5000 mL of demineralized water was added. The flasks were then placed in a water bath and heated to 80°C and 180°C, respectively. For each group of Erlenmeyer flasks, 60 ppm of the oxygen scavenger prepared in the examples and comparative examples was added. After reacting for 2 minutes, the dissolved oxygen content was measured using a portable dissolved oxygen detector. The results are shown in Table 1. The dissolved oxygen content of the blank group was 3.50 ppm.

[0083] Table 1

[0084] Serial Number Dissolved oxygen content at 80℃ / ppm Dissolved oxygen content at 180℃ / ppm Example 1 0.0012 0.0034 Example 2 0.0021 0.0040 Example 3 0.0019 0.0035 Example 4 0.0037 0.0077 Example 5 0.0048 0.0055 Comparative Example 1 0.0079 0.0183 Comparative Example 2 0.0067 0.0899

[0085] As can be seen from the results in Table 1, the oxygen scavengers prepared in Examples 1-3 have outstanding high temperature resistance and ability to remove dissolved oxygen.

[0086] Compared to Example 1, Example 4 changed the mass ratio of sodium alginate to fluorenemethyloxycarbonyl-L-aspartic acid-1-tert-butyl ester during the preparation of modified sodium alginate. The lack of the heat-resistant fluorene group resulted in poorer temperature resistance and poorer dispersibility, which reduced its ability to remove dissolved oxygen.

[0087] Compared to Example 1, in Example 5, vinyl sulfonic acid was not added during the preparation of modified lignin, which reduced the water solubility of lignin and decreased the ability of the oxygen scavenger to remove dissolved oxygen.

[0088] Compared to Example 1, Comparative Example 1 used an equal amount of commercially available sodium alginate to replace the modified sodium alginate, which reduced the heat resistance and caused the sodium alginate to decompose or become ineffective in the boiler water, thereby affecting its deoxygenation performance.

[0089] Compared to Example 1, Comparative Example 2 used an equal amount of commercially available lignin to replace the modified lignin, which reduced its dispersibility in water and thus affected its oxygen removal performance.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present application in any way. Although the present application discloses the preferred embodiment as described above, it is not intended to limit the present application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A deaerator specifically designed for medium and high pressure boilers, characterized in that, The oxygen scavenger comprises the following raw materials in parts by weight: 20-40 parts organic reducing agent, 10-20 parts amino heterocyclic compound, 4-8 parts hydroxylamine compound, 2-8 parts dispersant, 3-6 parts neutralizing agent, 2-6 parts modified sodium alginate, 1-3 parts modified lignin, and 20-40 parts deionized water. The preparation method of the modified sodium alginate includes the following steps: (1) Dissolve sodium alginate in deionized water, adjust the pH to 6-7, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide to obtain solution 1; (2) Dissolve fluorenyl methoxycarbonyl-L-aspartic acid-1-tert-butyl ester in deionized water, add N,N-dimethylformamide, and obtain solution 2; (3) Add solution 2 dropwise to solution 1. After the addition is complete, heat to 40-50℃ and stir to react, to obtain modified sodium alginate. The mass ratio of sodium alginate to fluorenemethyloxycarbonyl-L-aspartic acid-1-tert-butyl ester is 1:(3-5); The method for preparing the modified lignin includes the following steps: adding lignin and deionized water to a reaction vessel, adjusting the pH to neutral, heating to 65-75℃, stirring for 20-30 minutes, introducing an inert gas, adding ammonium persulfate, and then adding acrylamide and vinyl sulfonic acid dropwise. The reaction is carried out for 6-12 hours, the precipitate is separated and washed, dried, and ground to obtain the modified lignin.

2. The deaerator for medium and high pressure boilers according to claim 1, characterized in that, The organic reducing agent is any one or more of acetone oxime, dimethyl ketone oxime, carbazide, and ethoxyquin.

3. The deaerator for medium and high pressure boilers according to claim 1, characterized in that, The amino heterocyclic compound is any one or more of 1-aminopyrrolidine, 1-amino-4-methylpiperazine, and 1-aminopiperidine.

4. The deaerator for medium and high pressure boilers according to claim 1, characterized in that, The hydroxylamine compound is any one or more of diethylhydroxylamine, diisopropylhydroxylamine, and phenylhydroxylamine.

5. The deaerator for medium and high pressure boilers according to claim 1, characterized in that, The dispersant is polyethylene glycol and / or sodium polyacrylate.

6. The deaerator for medium and high pressure boilers according to claim 1, characterized in that, The neutralizing agent is cyclohexylamine and / or ethanolamine.

7. A method for preparing a deaerator suitable for medium and high pressure boilers as described in any one of claims 1-6, characterized in that, The preparation process includes the following steps: adding a portion of deionized water to a reaction vessel, heating to 40-50℃, adding an organic reducing agent, an amino heterocyclic compound, and a hydroxylamine compound, stirring for 10-15 minutes, then adding a dispersant, modified lignin, and modified sodium alginate, stirring for 10-20 minutes, then adding a neutralizing agent and the remaining deionized water, stirring for 10-20 minutes, and cooling to room temperature to obtain an oxygen scavenger.