Method for improving efficiency of steam heating, and papermaking method

Abstract

A method for improving the heating efficiency of steam wherein a polyamine represented by the following general formula (1) is caused to be present in a steam system to be used for heating. R.sup.1—[NH—(CH.sub.2).sub.m].sub.n—NH.sub.2 . . . (1) wherein R.sup.1 represents a saturated or unsaturated hydrocarbon group having 10 to 22 carbon atoms; m is an integer of 1 to 8, and n is an integer of 1 to 7; and when n is 2 or more, a plurality of NH—(CH.sub.2).sub.m may be identical or different.

Claims

1. A method for improving heating efficiency of steam, comprising: preparing an aqueous emulsion containing a condensed water film formation-suppressing amine and an emulsifier having hydrophilic-lipophilic balance of 12-16, and adding the aqueous emulsion containing the condensed water film formation-suppressing amine in a heating step of heating a material to be heated by a steam drier via a metallic material, wherein the aqueous emulsion condensing the condensed water film formation-suppressing amine is added in a steam at a steam pipe or a steam header for supplying the steam to the steam dryer that is disposed right before the steam dryer, the condensed water film formation-suppressing amine is added so that a concentration of the condensed water film formation-suppressing amine in the steam is 0.01 to 10 ppm, and two or more neutralizing amines having a pH-adjusting function are concurrently used together with the condensed water film formation-suppressing amine to reduce corrosion rate of the steam drier and steam pipe, the neutralizing amines being added in an amount of 0.1 to 50 ppm based on an amount of steam, wherein the condensed water film formation-suppressing amine is a polyamine represented by the following general formula (1):
R.sup.1—[NH—(CH.sub.2).sub.m].sub.n—NH.sub.2  (1) wherein R.sup.1 represents a saturated or unsaturated hydrocarbon group having 10 to 22 carbon atoms; m is an integer of 1 to 8, and n is an integer of 1 to 7; and when n is 2 or more, a plurality of NH—(CH.sub.2).sub.m may be identical or different.

2. The method for improving the heating efficiency of steam according to claim 1, wherein the metallic material is rotating.

3. A papermaking method comprising a step of heating the steam for improving the heating efficiency of the steam according to claim 1, wherein an amount of the steam to be supplied to the steam dryer is adjusted based on an amount of a papermaking material in the papermaking facility and an amount of the steam used in the steam dryer.

4. The method for improving the heating efficiency of steam according to claim 1, wherein the emulsifier is a polyoxyethylenealkylamine whose alkyl group has 10 to 18 carbon atoms.

5. The method for improving the heating efficiency of steam according to claim 1, wherein the neutralizing amines are volatile amines.

6. The method for improving the heating efficiency of steam according to claim 1, wherein the two or more neutralizing amines consist of monoethanolamine and diethylethanolamine.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a system diagram illustrating one example of a wet paper drying facility.

DESCRIPTION OF EMBODIMENTS

(2) Hereinafter, an embodiment of the present invention will be described in detail.

(3) <Polyamine>

(4) A polyamine to be used in the present invention is represented by the following general formula (1).
R.sup.1—[NH—(CH.sub.2).sub.m].sub.n—NH.sub.2  (1)
wherein R.sup.1 represents a saturated or unsaturated hydrocarbon group having 10 to 22 carbon atoms; m is an integer of 1 to 8, and n is an integer of 1 to 7; and when n is 2 or more, a plurality of NH—(CH.sub.2).sub.m may be identical or different.

(5) The saturated or unsaturated hydrocarbon group of R.sup.1 may be of a straight-chain or a branched-chain, or cyclic. R.sup.1 includes an alkyl group, an alkenyl group, an alkadienyl group and an alkynyl group. R.sup.1 is preferably a straight-chain alkyl group or a straight-chain alkenyl group. The number of carbon atoms of R.sup.1 is preferably 15 to 22.

(6) The integer m is preferably 2 to 6 from the viewpoint of corrosion suppression. The (CH.sub.2).sub.m group includes a methylene group, an ethylene group (dimethylene group), a propylene group (trimethylene group) and a butylene group (tetramethylene group), and is preferably a propylene group.

(7) The integer n is preferably 1 to 3 from the viewpoint of corrosion suppression.

(8) Specific examples of the polyamine include dodecylaminomethyleneamine, dodecylaminodimethyleneamine, dodecylaminotrimethyleneamine(N-stearyl-1,3-propanediamine) and tetradecyl, hexadecyl, and octadecyl compounds corresponding to these polyamines, and octadecenylaminotrimethyleneamine, octadecenylaminodi-(trimethylamino)-trimethyleneamine and palmitylaminotrimethyleneamine. A polyamine to be used in the present invention is preferably N-oleyl-1,3-propanediamine (that is, N-octadecenylpropane-1,3-diamine), which is easily available in a sufficient purity.

(9) The polyamine may be dissolved in a solvent such as methanol, ethanol or isopropanol, and added to steam or feed-water. It is preferable that the polyamine is made into an aqueous emulsion by using an emulsifier, and added to steam or feed-water. The emulsifier is preferably one having a high HLB (hydrophilic-lipophilic balance) value. The HLB of the emulsifier is preferably 12 to 16 and more desirably 13 to 15.

(10) Examples of the emulsifier include polyoxyethylenealkylamine, and preferable is a polyoxyethylenealkylamine whose alkyl group has 10 to 18 carbon atoms.

(11) As other emulsifiers, fatty acid alkali metal salts, particularly saturated or unsaturated fatty acid alkali metal salts having 8 to 24, particularly 10 to 22, carbon atoms can suitably be used. Specific examples thereof include sodium or potassium salts of saturated or unsaturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, behenic acid, oleic acid, erucic acid, linoleic acid and linolenic acid. As the fatty acid alkali metal salts, sodium salts or potassium salts of fatty acids produced from edible fat and oil can also be preferably used. As the fatty acid alkali metal salts, suitable are alkali metal salts of fatty acids containing 25% by weight or higher of at least one selected from the group consisting of, particularly, unsaturated fatty acids having 14 to 22 carbon atoms, for example, oleic acid, erucic acid, linoleic acid and linolenic acid. As the emulsifier, besides, esters of glycerol with the above-mentioned fatty acids can also be preferably used. Esters with stearic acid can be used especially preferably.

(12) The emulsifiers may be used singly or in combinations of two or more.

(13) When the polyamine is made into an aqueous emulsion by using an emulsifier such as a fatty acid alkali metal salt, it is suitable that the blend proportion of the polyamine to the emulsifier is, in weight ratio (polyamine/emulsifier), 40/1 to 1/1, especially about 20/1 to 2/1.

(14) The polyamines may be used singly or in combinations of two or more.

(15) A long-chain aliphatic amine such as octadecylamine or oleylamine may be used in combination in a range which does not generate clogging.

(16) It is preferable that the polyamine is caused to be present in a proportion of 0.01 to 10 ppm, especially 0.1 to 1 ppm, based on the amount of steam. When the amount of the polyamine is smaller than this range, the effect of suppressing the formation of the condensed water film and the effect of improving the heating efficiency due to the polyamine cannot sufficiently be attained. When the amount of the polyamine is larger than this range, there arises a risk that a tacky adhered material is produced in the system.

(17) Here, “ppm” is a proportion in weight of the polyamine to water corresponding to the amount of steam, and is equivalent to “mg/L-water”. The amounts of a later-described neutralizing amine and deoxidizing agent to be added are similarly defined.

(18) <Other Chemical Agents>

(19) Together with the above-mentioned polyamine, other chemical agents may be concurrently used. For example, a neutralizing amine having a pH-adjusting function may be concurrently used. The concurrent use of the neutralizing amine enables attaining the effect of reducing the corrosion rate of the steam drum and steam condensing piping before and after the drum.

(20) As the neutralizing amine, volatile amines such as ammonia, monoethanolamine (MEA), cyclohexylamine (CHA), morpholine (MOR), diethylethanolamine (DEEM, monoisopropanolamine (MIPA), 3-methoxypropylamine (MOPA), 2-amino-2-methyl-1-propanol (AMP) and diglycolamine (DGA) can be used. The neutralizing amines may be used singly or in combinations of two or more.

(21) In place of the neutralizing amine, pH adjustment may be carried out by ammonia originated from thermal decomposition of the following deoxidizing agent.

(22) In the case of the concurrent use of the neutralizing amine, it is preferable that the amount of the neutralizing amine to be added is caused to be 0.1 to 50 ppm, especially 5 to 15 ppm, based on the amount of steam, though depending on the amount of the polyamine to be used, the kind of material to be heated, the type of the steam dryer, and the like.

(23) A deoxidizing agent may be used concurrently together with the polyamine.

(24) The concurrent use of the deoxidizing agent enables attaining the effect of reducing corrosion of the steam drum and the like as in the case of the neutralizing amine.

(25) As the deoxidizing agent, hydrazine derivatives such as hydrazine and carbohydrazide can be used. As non-hydrazine-based deoxidizing agents, carbohydrazide, hydroquinone, 1-aminopyrrolidine, 1-amino-4-methylpiperazine, N,N-diethylhydroxylamine, isopropylhydroxylamine, erythorbic acid or salts thereof, ascorbic acid or salts thereof, tannic acid or salts thereof, saccharides and sodium sulfite can also be used. The deoxidizing agents may be used singly or in combinations of two or more.

(26) In the case of the concurrent use of the deoxidizing agent, it is preferable that the amount of the deoxidizing agent to be added is caused to be 0.01 to 3 ppm, especially 0.05 to 1 ppm, based on the amount of steam, though depending on the amount of the polyamine to be used, the kind of material to be heated, the type of the steam dryer, and the like.

(27) The above-mentioned chemical agents to be concurrently used may be added to the same place as for the polyamine, or may be added to a different place. In the case of adding two or more chemical agents to the same place, the chemical agents to be added may be previously mixed and then added, or may be added separately.

(28) <Application to a Steam Dryer>

(29) When the material to be heated is heated by steam via a metallic material, the above-mentioned polyamine, and further, as required, other chemical agents such as the neutralizing amine and the deoxidizing agent are caused to be present in the steam system.

(30) The metallic material is preferably one excellent in the durability and high in the heat-transfer efficiency. The metallic material may be an iron-based material or a copper-based material.

(31) The material to be heated is not especially limited. The present invention is suitable for heating and drying of wet paper in papermaking facilities. Further, the present invention is suitable for heating and drying wet paper having gone out from press and water-squeeze sections in production facilities for household raw paper materials for tissue paper, toilet paper, kitchen paper and paper diapers, one side-glazed packing paper, and the like.

(32) The present invention can also be applied to a heating or cooling step using steam in usual heat exchangers like plate type heat exchangers.

(33) The above-mentioned polyamine suppresses the formation of the condensed water film. Therefore, the method of the present invention is suitably applied to a steam dryer. In a steam dryer, when the material to be heated is steam heated, since the metallic material interposed between the material to be heated and the steam rotates, a condensed water film is easily formed by a centrifugal force. According to the present invention, this formation of the condensed water film is prevented or suppressed. The steam dryer includes various types of rotary papermaking machine dryers such as the Yankee dryer illustrated in FIG. 1 and multi-cylinder type dryers.

(34) In the case of adding the polyamine to the steam dryer, the addition place is not especially limited. The polyamine is added preferably to a steam piping or a steam header right before a dryer drum. Thereby, the exhaustion of the polyamine before the polyamine reaches the steam dryer is prevented, and the needed amount of the polyamine to be added is reduced. However, the polyamine may be added to the feed-water of the steam generating facility.

(35) Addition of the polyamine to be used in the present invention is not limited to the steam dryer, and may be to steam of a black liquor evaporator of the papermaking facility. The black liquor evaporator is a concentrator for concentrating a dilute black liquor to a concentration of from 20% to about 70 to 80%, and the concentrate is used as a fuel for a recovery boiler. In the black liquor evaporator, steam and the dilute black liquor exchange heat in a plate type heat exchanger, and condensed water generated is transferred along on plates of the heat exchanger, and discharged. By adding the polyamine to steam of the black liquor evaporator, the formation of condensed water films on plate surfaces is suppressed, improving the heating efficiency.

(36) The method for improving the heating efficiency of steam according to the present invention is suitably applied to a steam dryer installed in a papermaking facility. In this case, it is preferable that the amount of steam to be supplied to the steam dryer is adjusted based on the amount of papermaking in the papermaking facility and the amount of steam used in the steam dryer. By adjusting the amount of steam according to the needed amount thereof, the steam consumption unit can be reduced and the production efficiency can be raised. Further, with the amount of steam to be supplied to the steam dryer being fixed, the amount of papermaking can be improved.

EXAMPLES

(37) Hereinafter, Examples and Comparative Example will be described.

(38) In the below, the steam consumption unit was calculated as a proportion of an amount of steam used (t) to an amount of production (amount of papermaking) (t) of paper excluding paper having generated defects.

Example 1

(39) In the papermaking and drying facility illustrated in FIG. 1, the drum diameter of the Yankee dryer was set to 3 m; the pressure of water vapor supplied was set at 0.6 MPa; the amount of the water vapor supplied was set at about 900 kg/h; and the amount of the water vapor supplied to the Yankee dryer was controlled by a flow rate regulating valve 9 so that the outer surface temperature of the drum became 100° C. and the moisture content of a product (paper) after drying became 20 to 30%.

(40) As the polyamine, N-octadecenylpropane-1,3-diamine was used.

(41) The polyamine was emulsified with polyoxyethylenecocoamine and added. The amount of the polyoxyethylenecocoamine blended was 15 parts by weight per 100 parts by weight of the polyamine.

(42) Although the steam consumption unit was 2.94 before addition of the polyamine, when the polyamine was added to the steam header 7 so that the amount thereof became 0.4 ppm to the amount of the steam, the steam consumption unit after the addition thereof was improved to 2.81. During the test, no clogging of the strainer of the papermaking and drying facility occurred.

Example 2

(43) The steam consumption units before and after the addition of the chemical agents, and presence/absence of clogging of the strainer were examined as in Example 1, except for that 3.2 ppm of MEA as a neutralizing amine and 2.2 ppm of DEEA were concurrently added together with the polyamine in Example 1. Results are shown in Table 1.

Comparative Example 1

(44) The steam consumption units before and after the addition of the chemical agents, and presence/absence of clogging of the strainer were examined as in Example 1, except for that octadecylamine was used in place of N-octadecenylpropane-1,3-diamine and added in 0.1 ppm to the amount of steam; and 3.8 ppm of AMP as a neutralizing amine was added, in Example 1. Results are shown in Table 1.

(45) In Table 1, N-octadecenylpropane-1,3-diamine is described as “polyamine”. The reduction rate of the steam consumption unit after the addition of the chemical agents to a steam consumption unit therebefore is together indicated as “steam consumption unit reduction rate (%)” in Table 1.

(46) TABLE-US-00001 TABLE 1 Steam Consumption Steam Units before and Consumption Chemical after Addition of Unit Agents the Chemical Agents Reduction Strainer Added※ before the addition after the addition Rate (%) Clogging Example 1 polyamine (0.4) 2.94 2.81 4.4 absent Example 2 polyamine (0.4) 3.14 2.95 6.1 absent MEA(3.2) DEEA(2.2) Comparative octadecylamine 3.60 3.41 5.3 present Example 1 (0.1) (cleaning) AMP(3.8) ※A number indicated in parentheses is an amount added based on the amount of steam (ppm)

(47) It is clear from Table 1 that according to the present invention, by using a specific polyamine, the heating efficiency of steam could further be improved. It is also clear that since no clogging of the strainer was present, stable operation in which the production efficiency had been raised could be continued in the papermaking facility and the like.

(48) The present invention has been described in detail by way of the specific aspect, but it is obvious to those skilled in the art that various changes and modifications may be made without departing from the aim and the scope of the present invention.

(49) The present application is based on Japanese Patent Application No. 2017-181476, filed on Sep. 21, 2017, the entire of which is incorporated by reference herein.

REFERENCE SIGNS LIST

(50) 4 FEED-WATER HEADER 5 BOILER 7 WATER VAPOR HEADER 11 DRUM 12 SIPHON P WET PAPER W CONDENSED WATER