Method for improving steam heating efficiency and papermaking method

Abstract

A method for improving the steam heating efficiency, characterized in that a polyamine represented by the following general formula (1) is present in the steam system for heating, R 1 -[NH-(CH2) m n -NH2…(1), where R 1 represents a saturated or unsaturated hydrocarbon group having 10 to 22 carbon atoms. m is an integer of 1 to 8. n is an integer of 1 to 7. When n is 2 or more, multiple NH-(CH2) m may be the same or different.​

Description

[0001] This application is a divisional application of an application with an application date of July 30, 2018, an application number of 201880054216.2, and an invention title of "Method for Improving Steam Heating Efficiency and Papermaking Method". Technical Field

[0002] The present invention relates to a method for improving steam heating efficiency in a heating process of heating an object to be heated by passing steam through a metal material. The present invention also relates to a papermaking method for improving the production efficiency of a papermaking apparatus by adopting the method for improving heating efficiency. Background Art

[0003] In a papermaking factory or a manufacturing factory of food, beverages, etc., a treatment for drying, concentrating, or sterilizing a manufactured product is carried out by heating the manufactured product with steam. For example, in a papermaking apparatus, a wet paper having a water content of about 50% is dried to a water content of about 5 - 10% by a steam dryer having a rotary cylinder.

[0004] Figure 1 FIG. is a system diagram of a wet paper drying apparatus using a Yankee dryer (a dryer composed of a large-diameter cast iron cylinder) as a steam dryer. Water is supplied to a boiler 5 through a makeup water device 1, a water supply tank 2, a pipe 3, and a water supply head 4. The steam generated in the boiler 5 is supplied into a cylinder 11 of the Yankee dryer through a steam pipe 6, a steam head 7, a pipe 8, a flow control valve 9, and a pipe 10.

[0005] The cylinder 11 is rotationally driven in a clockwise direction in Figure 1 . The wet paper P comes into contact with the outer peripheral surface of the cylinder 11 and is dried, and after being peeled off from the outer peripheral surface, it is sent to a product winding process. The water content of the dried paper and the temperature of the outer peripheral surface of the cylinder are measured by a sensor, and based on this, the steam flow rate is adjusted by a valve 9.

[0006] The condensed water W generated by the condensation of steam in the cylinder 11 is sent to an instantaneous evaporation tank 14 through a siphon 12 and a pipe 13, and is sent back to the water supply tank 2 through a filter 15. In the cylinder 11, the condensed water W is pressed against the inner peripheral surface of the cylinder 11 by the centrifugal force accompanying the rotation of the cylinder 11, and is lifted in the rotation direction of the cylinder 11. Thus, a water film is formed on the inner peripheral surface of the cylinder 11.

[0007] In the paper drying process in a papermaking apparatus, the water content of the wet paper and the temperature of the pulp are slowly increased to evaporate water. In order to dry to a specified water content at a position (dry end) where the paper is peeled off from the outer peripheral surface of the cylinder 11, necessary heat is mainly imparted by steam in each dryer.

[0008] In order to improve the drying efficiency of wet paper and thus increase the paper production volume, it is necessary to effectively discharge the condensed water W generated in the cylinder 11 to reduce the water film.

[0009] As a countermeasure for this, the following methods are implemented: reducing the rotational speed of the cylinder to slow down the paper-making speed, or providing protrusions called spoiler bars inside the cylinder to make the condensed water film accumulated inside the dryer of the cylinder uneven. However, the slow paper-making speed is related to the decrease in the production volume per unit time. The setting of the spoiler bar is an equipment update and requires construction.

[0010] In order to suppress the formation of the condensed water film inside the cylinder without relying on these methods, a method of adding a long-chain aliphatic amine such as octadecylamine as a contact angle increasing agent for increasing the contact angle between the inner circumferential surface of the cylinder and water has been proposed (Patent Document 1).

[0011] The long-chain aliphatic amine proposed in Patent Document 1 is a linear long-chain aliphatic amine represented by the general formula CH3(CH2) m NH2 (m = 9 to 23). However, the polyamine used in the present invention is not disclosed in Patent Document 1.

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-12921.

[0013] By the method of Patent Document 1, the formation of the condensed water film inside the cylinder of the steam dryer is suppressed, and under this effect, an increase in the paper-making speed and an increase in the paper production volume can be achieved. However, especially when the drug is added in excess, blockage will occur in the system, increasing the cleaning frequency. Summary of the Invention

[0014] An object of the present invention is to provide a method for more effectively improving the efficiency of steam heating in a heating process of heating an object to be heated by a metal material using steam, without accompanying a decrease in production efficiency and large-scale equipment updates. Another object of the present invention is to provide a paper-making method for improving the production efficiency of a paper-making apparatus by adopting the method for improving heating efficiency.

[0015] The inventors of the present invention have found that a specific polyamine does not cause a blockage problem and can greatly reduce the cleaning frequency compared to the long-chain aliphatic amine proposed in Patent Document 1. In addition, it has been found that by making the polyamine present in the steam system, the heating efficiency of the steam dryer can be improved without accompanying a decrease in production efficiency such as a decrease in the rotational speed of the cylinder of the steam dryer in the paper-making process and large-scale equipment updates.

[0016] The present invention takes the following as the gist.

[0017] [1] A method for improving the steam heating efficiency, characterized in that, in the heating process of passing through a metal material and heating an object to be heated using steam, the efficiency of the steam heating is improved by allowing a polyamine represented by the following general formula (1) to be present in the steam system,

[0018] R 1 -[NH-(CH2) m n -NH2…(1)

[0019] In the formula, R 1 represents a saturated or unsaturated hydrocarbon group having 10 to 22 carbon atoms. m is an integer of 1 to 8. n is an integer of 1 to 7. When n is 2 or more, multiple NH-(CH2) m may be the same or different.

[0020] [2] The method for improving the steam heating efficiency according to [1], characterized in that the aforementioned metal material rotates.

[0021] [3] The method for improving the steam heating efficiency according to [1] or [2], characterized in that the aforementioned heating process is a process of heating the aforementioned object to be heated through a steam dryer, and the aforementioned polyamine is added at a position directly in front of the steam dryer in the steam pipe or steam head for supplying steam to the steam dryer.

[0022] [4] The method for improving the steam heating efficiency according to any one of [1] to [3], characterized in that the polyamine is added so that the concentration of the polyamine in the aforementioned steam becomes 0.01 to 10 ppm.

[0023] [5] A papermaking method, characterized in that, in a steam dryer provided in a papermaking apparatus, the efficiency of steam heating is improved by the method for improving the steam heating efficiency according to any one of [1] to [4], and the amount of steam supplied to the steam dryer is adjusted based on the papermaking amount in the papermaking apparatus and the steam usage amount in the steam dryer.

[0024] According to the present invention, in the heating process of passing through a metal material and heating an object to be heated using steam, preferably in the heating and drying process, the formation of condensed water films can be suppressed, and the efficiency of the steam heating can be further effectively improved without accompanying a decrease in production efficiency and large-scale equipment renewal, nor an increase in the cleaning frequency due to blockages in the application system.

[0025] By the present invention, the formation of water films on the surface of the metal material can be prevented or suppressed, and the heating efficiency can be improved.

[0026] ​One aspect of the present invention is that, by being used in improving the heating efficiency in the steam dryer of a papermaking device, only injecting polyamine into the steam pipe and the steam head can suppress the formation of condensed water film inside the cylinder of the steam dryer without reducing the rotational speed of the cylinder or providing a member for preventing the formation of the condensed water film. Moreover, the thickness of the formed condensed water film can be made thinner, the drying efficiency of wet paper can be improved, thereby significantly improving the production efficiency, the pressure of the supplied steam can be reduced, which contributes to energy conservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a system diagram showing an example of a wet paper drying device.

[0028] The descriptions of the reference signs are as follows:

[0029] 4: Water supply head;

[0030] 5: Boiler;

[0031] 7: Steam head;

[0032] 11: Cylinder;

[0033] 12: Siphon;

[0034] P: Wet paper;

[0035] W: Condensed water. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The embodiments of the present invention will be described in detail below.

[0037] <Polyamine>

[0038] The polyamine used in the present invention is represented by the following general formula (1).

[0039] R 1 -[NH-(CH2) m n -NH2…(1)

[0040] In the formula, R 1 represents a saturated or unsaturated hydrocarbon group having 10 to 22 carbon atoms. m is an integer of 1 to 8. n is an integer of 1 to 7. When n is 2 or more, a plurality of NH-(CH2) m may be the same or different.

[0041] R 1 The saturated or unsaturated hydrocarbon group of may be linear, may have a branch, or may be cyclic. As R 1 , alkyl, alkenyl, alkadienyl, alkynyl, etc. can be cited. Preferred are linear alkyl and linear alkenyl. The carbon number of R 1 is preferably 15 to 22.

[0042] From the viewpoint of corrosion inhibition, m is preferably an integer of 2 to 6. As the (CH2) m group, methylene, ethylene (dimethylene), propylene (trimethylene) or butylene (tetramethylene) can be cited, and propylene is preferred.

[0043] From the viewpoint of corrosion inhibition, n is preferably an integer of 1 to 3.

[0044] Specific examples of the polyamine include dodecylaminomethylamine, dodecylaminodimethylamine, dodecylaminotrimethylamine (N-stearyl-1,3-propanediamine), or tetradecyl, hexadecyl, and octadecyl compounds corresponding to these polyamines, octadecenylaminotrimethylamine, octadecenylamino-bis-(trimethylamino)-trimethylamine, palmitylaminotrimethylamine, etc. As the polyamine used in the present invention, N-oley-1,3-propanediamine (i.e., N-octadecenylpropane-1,3-diamine) with sufficient purity and easy availability is preferred.

[0045] The polyamine can be dissolved in solvents such as methanol, ethanol, and isopropyl alcohol and then added to steam or feed water. The polyamine is preferably made into an aqueous latex using an emulsifier and added to steam or feed water. As the emulsifier, an emulsifier with a high HLB (hydrophilic-lipophilic balance) value is preferred. The HLB of the emulsifier is preferably 12 to 16, more preferably 13 to 15.

[0046] As the emulsifier, for example, polyoxyethylene alkylamine can be cited, and polyoxyethylene alkylamine with an alkyl carbon number of 10 to 18 is preferred.

[0047] As other emulsifiers, fatty acid alkali metal salts can be preferably used, and saturated or unsaturated fatty acid alkali metal salts with 8 to 24 carbon atoms, especially 10 to 22 carbon atoms, are particularly preferred. Specifically, sodium salts and potassium salts of saturated or unsaturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, erucic acid, linoleic acid, and linolenic acid can be cited. As the fatty acid alkali metal salts, sodium salts and potassium salts of fatty acids produced from edible oils can be preferably used. As the fatty acid alkali metal salts, those containing at least 1 kind of fatty acid selected from unsaturated fatty acids with 14 to 22 carbon atoms such as oleic acid, erucic acid, linoleic acid, and linolenic acid in an amount of 25% by weight or more are particularly preferred. In addition, esters of glycerol and the aforementioned fatty acids can also be preferably used as emulsifiers. An ester with stearic acid is particularly preferred.

[0048] Only 1 kind of emulsifier can be used, or 2 or more kinds can be used in combination.

[0049] When forming an aqueous latex using an emulsifier such as an alkali metal salt of a fatty acid, the mixing ratio of the polyamine to the emulsifier is preferably 40 / 1 to 1 / 1 by weight (polyamine / emulsifier), and particularly preferably around 20 / 1 to 2 / 1.

[0050] Only one type of polyamine can be used, or two or more types can be used in combination.

[0051] Within the range where blockage does not occur, long-chain aliphatic amines such as octadecylamine and oleylamine can be used in combination.

[0052] The polyamine is preferably present in a proportion of 0.01 to 10 ppm relative to the amount of steam, and particularly preferably in a proportion of 0.1 to 1 ppm. When the amount of polyamine is too small compared to this range, the effects of inhibiting the formation of condensate shrinkage films and improving the heating efficiency based on the polyamine cannot be fully obtained. When the amount of polyamine is too large compared to this range, there is a possibility of adhesive deposits being generated in the system.

[0053] Herein, the so-called "ppm" is the weight ratio of the polyamine to the water corresponding to the amount of steam, which is equivalent to "mg / L - water". The same applies to the addition amounts of the neutralizing amine and the deoxidizer described later.

[0054] <Other chemicals>

[0055] Other chemicals can be used in combination with the above polyamine. For example, a neutralizing amine having a pH adjustment function can be used in combination. By using the neutralizing amine in combination, the effect of reducing the corrosion rate of the steam drum and the steam condensate piping before and after the drum can be obtained.

[0056] As the neutralizing amine, volatile amines such as ammonia, monoethanolamine (MEA), cyclohexylamine (CHA), morpholine (MOR), diethylethanolamine (DEEA), monoisopropanolamine (MIPA), 3 - methoxypropylamine (MOPA), 2 - amino - 2 - methyl - 1 - propanol (AMP), and diethylene glycolamine (DGA) can be used. Only one type of neutralizing amine can be used, or two or more types can be used in combination.

[0057] As an alternative to the neutralizing amine, pH adjustment can be carried out using ammonia derived from the thermal decomposition of the following deoxidizer.

[0058] When the neutralizing amine is used in combination, the addition amount of the neutralizing amine varies depending on the amount of polyamine used, the type of the object to be heated, the form of the steam dryer, etc., but is preferably 0.1 to 50 ppm relative to the amount of steam, and particularly preferably 5 to 15 ppm.

[0059] A deoxidizer can be used in combination with the polyamine.

[0060] By using the deoxidizer in combination, the effect of reducing the corrosion of the steam drum, etc., can be obtained in the same way as the neutralizing amine.

[0061] As a deoxidizer, hydrazine derivatives such as hydrazine and carbohydrazide can be used. As a non-hydrazine-based deoxidizer, carbohydrazide, hydroquinone, 1-aminopyrrolidine, 1-amino-4-methylpiperazine, N,N-diethylhydroxylamine, isopropylhydroxylamine, isoascorbic acid or its salts, ascorbic acid or its salts, tannic acid or its salts, saccharides, sodium sulfite, etc. can be used. The deoxidizer can be used alone or in combination of two or more.

[0062] When using a deoxidizer in combination, the addition amount of the deoxidizer will vary depending on the usage amount of the polyamine, the type of the object to be heated, the form of the steam dryer, etc. Relative to the steam amount, it is preferably 0.01 to 3 ppm, and particularly preferably 0.05 to 1 ppm.

[0063] The above-mentioned combined chemicals can be added at the same position as the polyamine or at different positions. When adding two or more chemicals at the same position, the chemicals to be added can be pre-mixed and then added, or added separately.

[0064] <Application in Steam Dryer>

[0065] In the present invention, when heating the object to be heated by a metal material using steam, the aforementioned polyamine, and further other chemicals such as neutralizing amine and deoxidizer as required are present in the steam system.

[0066] The metal material is preferably a metal material with excellent durability and high heat transfer efficiency. The metal material can be an iron-based material or a copper-based material.

[0067] There is no particular limitation on the object to be heated. The present invention is suitable for the heating and drying of wet paper in a papermaking apparatus. In addition, the present invention is applicable to the heating and drying of wet paper from the press dewatering section in the manufacturing apparatuses of household paper raw papers such as tissue paper, toilet paper, kitchen paper, diaper paper, and single-sided colored wrapping paper.

[0068] The present invention is applicable to heating or cooling processes based on steam in general heat exchangers such as plate heat exchangers.

[0069] The above polyamine inhibits the formation of condensate water films. Therefore, the method of the present invention is applicable to steam dryers. In a steam dryer, when steam-heating the object to be heated, a condensate water film is easily formed by centrifugal force through the rotation of the metal material between the object to be heated and the steam. According to the present invention, the formation of this condensate water film can be prevented or inhibited. The steam dryer includes Figure 1 Various rotary papermaking machine dryers such as the Yankee dryer and multi-cylinder dryer shown.

[0070] When adding polyamine to a steam dryer, there is no particular limitation on the addition position. The polyamine is preferably added to the steam piping or steam head directly in front of the dryer cylinder. Thereby, the consumption of polyamine before reaching the steam dryer is prevented, and the necessary addition amount of polyamine is reduced. However, the polyamine can also be added to the water supply of the steam generating equipment.

[0071] The polyamine used in the present invention is not limited to the steam dryer, and can also be added to the steam in the black liquor evaporator of the papermaking equipment. The black liquor evaporator is a concentrator for concentrating dilute black liquor from a concentration of 20% to about 70 - 80% for use as fuel in a recovery boiler. In the black liquor evaporator, steam and dilute black liquor are heat-exchanged using a plate heat exchanger, and the generated condensed water is transferred to the plates of the heat exchanger and discharged. By adding polyamine to the steam in the black liquor evaporator, the formation of the condensed water film on the plate surface is suppressed, and the heating efficiency is improved.

[0072] The method for improving the steam heating efficiency of the present invention is applicable to the steam dryer provided in the papermaking equipment. In this case, it is preferable to adjust the steam amount supplied to the steam dryer according to the papermaking amount in the papermaking equipment and the steam usage amount in the steam dryer. By adjusting the steam amount according to the necessary amount, the steam consumption per unit can be reduced and the production efficiency can be improved. In addition, the papermaking amount can be increased while the steam amount supplied to the steam dryer is fixed.

[0073] Examples

[0074] Examples and comparative examples are described below.

[0075] Hereinafter, the steam consumption per unit is calculated using the ratio of the steam usage amount (t) to the paper production amount (papermaking amount) (t), and the paper production amount is the paper production amount after removing the defective parts.

[0076] [Example 1]

[0077] In Figure 1 the shown papermaking and drying equipment, the cylinder diameter of the Yankee dryer is set to 3 m, the supply steam pressure is set to 0.6 MPa, the steam supply amount is set to about 900 kg / h, and the steam supply amount to the Yankee dryer is controlled by a flow control valve 9 so that the outer surface temperature of the cylinder becomes 100 °C, and the moisture content of the dried product (paper) becomes 20 - 30%.

[0078] N-octadecenylpropane-1,3-diamine is used as the polyamine.

[0079] The polyamine is added after being emulsified with polyoxyethylene coconut amine. The compounding amount of polyoxyethylene coconut amine is set to 15 parts by weight relative to 100 parts by weight of the polyamine.

[0080] When polyamine was added to the steam header 7 in such a way that the polyamine was 0.4 ppm relative to the amount of steam, the original steam unit before addition was 2.94, but it improved to 2.81 after the addition of polyamine. During the test, the filter of the paper drying equipment did not become blocked.

[0081] [Example 2]

[0082] In Example 1, together with polyamine, 3.2 ppm of MEA and 2.2 ppm of DEEA as neutralizing amines were added in combination. Otherwise, the operation was the same as in Example 1, and the original steam unit before and after the addition of the agent and whether the filter was blocked were investigated. The results are shown in Table 1.

[0083] [Comparative Example 1]

[0084] In Example 1, instead of N-octadecenylpropane-1,3-diamine, octadecylamine was used and 0.1 ppm was added relative to the amount of steam, and 3.8 ppm of AMP as a neutralizing amine was added. Otherwise, the operation was the same as in Example 1, and the original steam unit before and after the addition of the agent and whether the filter was blocked were investigated. The results are shown in Table 1.

[0085] In Table 1, N-octadecenylpropane-1,3-diamine is recorded as "polyamine". The decrease ratio of the original steam unit after the addition of the agent relative to the original steam unit before the addition of the agent is recorded in Table 1 as the "decrease rate of the original steam unit (%)".

[0086] Table 1

[0087]

[0088] ※The content in parentheses is the addition amount (ppm) relative to the amount of steam

[0089] It can be seen from Table 1 that according to the present invention, by using a specific polyamine, the efficiency of steam heating can be further improved. In addition, it is known that since the filter does not become blocked, the production efficiency can be improved and the stable operation can be continued for the paper-making equipment, etc.

[0090] The present invention has been described in detail using a specific method, but those skilled in the art can make various changes without departing from the intention and scope of the present invention.

[0091] This application is based on Japanese Patent Application No. 2017-181476 filed on September 21, 2017, and the whole text thereof is incorporated herein by reference.

Claims

1. A method for improving the steam heating efficiency, characterized in that, in the heating process of passing through a metal material and heating an object to be heated with steam, the efficiency of the steam heating is improved, an emulsifier, a neutral amine, and a polyamine represented by the following general formula (1) are present in the steam system, the emulsifier contains a polyoxyethylene alkylamine having an alkyl group with 10 to 18 carbon atoms, the addition amount of the neutral amine is 0.1 to 50 ppm relative to the steam amount, the concentration of the polyamine in the steam is 0.01 to 10 ppm, R 1 -[NH-(CH2) m n -NH2…(1),​ In the formula, R 1 represents a saturated or unsaturated hydrocarbon group having 10 to 22 carbon atoms; m is an integer of 1 to 8; n is an integer of 1 to 7; when n is 2 or more, a plurality of NH-(CH2) m are the same or different.

2. The method for improving steam heating efficiency according to claim 1, wherein, the HLB (hydrophilic-lipophilic balance) value of the emulsifier is 12 to 16.

3. The method for improving steam heating efficiency according to claim 1, wherein, The metal material rotates.

4. The method for improving steam heating efficiency according to claim 1, wherein, The heating process is a process of heating the object to be heated by a steam dryer, and the polyamine is added at a position directly in front of the steam dryer in the steam pipe or steam head for supplying steam to the steam dryer.

5. A papermaking method, characterized in that, In a steam dryer provided in a papermaking apparatus, the efficiency of steam heating is improved by the method for improving the steam heating efficiency according to any one of claims 1 to 4, and the steam amount supplied to the steam dryer is adjusted based on the papermaking amount in the papermaking apparatus and the steam usage amount in the steam dryer.

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