JPH04298286A - Method for removing dissolved oxygen in service water - Google Patents

Abstract

PURPOSE:To effectively remove DO in service water. CONSTITUTION:A hydrogen donor is added to the service water contg. the DO and a deoxygenation reaction is effected in the presence of a carrier catalyst at 100 to 250 deg.C and under a pressure at which a liquid phase is maintained. The effective components of the carrier catalyst are Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Au, and W as well as the water-soluble or hardly water-soluble compds. of these metals.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for removing dissolved oxygen in service water, and in particular to a method for removing dissolved oxygen from service water containing dissolved oxygen, such as boiler feed water, using a solid catalyst that has an excellent wet oxidation effect. The present invention relates to a method for efficiently removing (DO).

0002

[Prior art] Soft water is usually used for boiler water supply, but since soft water contains DO, the water supply causes corrosion of the boiler body, the heat exchanger in the front stage of the boiler body, and the economizer. . For this reason, the feed water needs to be deoxidized in advance before being supplied to the boiler.

[0003] Conventionally, methods for deoxidizing water for use mainly include chemical methods: (1) adding a reducing agent (hydrazine, sodium sulfite, hydrogen gas, etc.) to react with DO; (2) adding L-ascorbic acid. (2) A method in which a palladium-adsorbing resin is used to react with hydrazine or hydrogen at room temperature. In addition, ■ a method of reducing DO to around 500 ppb using a (heating, vacuum) degassing device (tower) and then treating with chemicals; ■ a method of degassing using a membrane device;
There is also a method in which this method is combined with methods ① to ① above.

0004

[Problems to be Solved by the Invention] Among the above conventional methods, method (2) has drawbacks such as the toxicity of hydrazine and the poor handling of sodium sulfite and hydrogen gas. Method (2) has the disadvantage that it is difficult to control the concentration of L-ascorbic acid. Since method (2) uses hydrazine or hydrogen, it has the same drawbacks as (2) above. Method (2) has the disadvantage that the efficiency of the degassing tower is low;
The disadvantage of this method is that the processing level of the membrane device is low.

An object of the present invention is to solve the above-mentioned conventional problems and provide a method for efficiently removing DO from water.

[0006]

[Means for Solving the Problems] The method for removing dissolved oxygen in service water of the present invention involves adding a hydrogen donor to service water containing dissolved oxygen, and maintaining the temperature of 100 to 250°C and the service water maintaining a liquid phase. iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum,
One or two selected from the group consisting of copper, gold, tungsten, and compounds of these metals that are insoluble or poorly soluble in water.
It is characterized in that dissolved oxygen and a hydrogen donor are reacted in the presence of a supported catalyst containing at least one species of hydrogen donor as an active ingredient.

The present invention will be explained in detail below. In the present invention, the hydrogen donor added to the water is not particularly limited as long as it can donate hydrogen, but for example, methanol, ethanol, sorbitol, glucose, glycerin, aminoethanol, etc. can be used. can. In general, it is advantageous to use methanol from the viewpoint of chemical costs.

[0008] The amount of such a hydrogen donor added varies depending on the DO concentration of the water to be treated.
It is preferable to add about 0.3 to 20 mg/l per 1 mg/l.

The supported catalyst used in the present invention also contains iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold and tungsten as active catalyst components, as well as water-insoluble or Slightly water-soluble compounds, specifically iron sesquioxide, triiron tetroxide, cobalt monoxide, nickel monoxide, ruthenium dioxide, rhodium sesquioxide, palladium monoxide, iridium dioxide, cupric oxide, tungsten dioxide, etc. oxide,
Furthermore, it contains one or more selected from the group consisting of chlorides such as ruthenium dichloride and platinum dichloride, and sulfides such as ruthenium sulfide and rhodium sulfide.

The supported catalyst according to the present invention is one in which these metals and/or their compounds are supported on a carrier such as alumina, silica, silica alumina, activated carbon, titanium oxide, zirconia oxide, etc. in accordance with a conventional method. The amount of metal and/or its compound supported in the supported catalyst is usually 0% of the carrier weight.
．． 05 to 25% by weight, preferably 0.5 to 3% by weight. Such supported catalysts can be used in various forms such as spheres, pellets, cylinders, crushed pieces, honeycombs, and powders.

[0011] The method of the present invention is carried out, for example, by adding a predetermined amount of a hydrogen donor such as methanol to water containing DO, and passing this through a fixed bed reaction bed filled with the above-mentioned supported catalyst. be able to. In this case, the reaction layer volume,
It is preferable to set the catalyst loading amount and the liquid passing rate so that the contact time between the water and the supported catalyst is 18 to 72 seconds, particularly 30 to 45 seconds. The particle size of the supported catalyst used in the fixed bed reaction bed is usually 3 to 50 mm, particularly 5 to 25 mm.
It is preferable that the degree of

The reaction conditions of the present invention are a reaction temperature of 100 to 3
The temperature is 00°C, preferably 150 to 250°C, and the pressure is such that the water treated at the reaction temperature can maintain a liquid phase. The higher the reaction temperature, the higher the removal rate of DO and the shorter the residence time of water in the reaction tower, but on the other hand, the equipment cost increases, so the required treatment level, operating cost, construction It is best to decide by comprehensively considering costs, etc. Further, the pressure during the reaction may be any pressure that maintains the water in a liquid phase at the minimum predetermined temperature.

[0013] In the method of the present invention, an alkaline agent such as sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, etc. or a volatile alkanolamine such as monoethanolamine, isopropanolamine, cyclohexylamine, etc. is added to the reaction system. It is extremely effective to coexist with amines. That is, in the present invention, since CO2 is generated by the deoxidizing reaction, corrosion can be prevented by removing CO2 by reaction with an alkaline agent or amines. In this case, it is preferable to add about 1.0 to 500 mg/l of the alkaline agent or alkanolamine to the hydrogen donor.

[0014] The water to be treated by the present invention is mainly boiler feed water, but the present invention can also be effectively applied to other water supplies such as hot water supply and hot water for heating.

[0015]

[Operation] The supported catalyst used in the present invention is extremely effective in oxidative decomposition of organic substances. In the presence of such a supported catalyst, a hydrogen donor corresponding to the DO concentration in the water is allowed to coexist in the water, and the temperature is maintained at a temperature sufficient for the reaction, so that the deoxygenation reaction proceeds efficiently and the DO is removed. Incidentally, while the conventional membrane degassing method has a removal efficiency of approximately 0.2 mg-O2/l-element volume/sec, the method of the present invention has a removal efficiency of approximately 4 mg-O2/l-catalyst volume/sec. se
It is possible to achieve a high removal efficiency of approximately c or more.

[0016] Furthermore, the hydrogen donor used is safer than hydrazine, etc., and moreover, it
Since OC) also participates in the reaction, it is sufficient to add a small amount of hydrogen donor. Furthermore, since the present invention is a liquid phase reaction,
The oxygen concentration in the vapor phase is extremely low.

[0017]

[Examples] The present invention will be explained in more detail with reference to Examples below.

Example 1 Soft water with the average DO concentration shown in Table 1 was used as raw water, the chemicals shown in Table 1 were added as hydrogen donors, and 25 ml of a spherical catalyst of ruthenium as an active ingredient was filled as a supported catalyst in a reaction bed.
The treatment was carried out by supplying water at a flow rate of 2.5 l/Hr. Note that the reaction temperature was 150 to 250°C, and the pressure was such that the raw water could maintain a liquid phase. Average D of the obtained treated water
The O concentrations are shown in Table 1. For comparison, the same treatment was performed in the case where no catalyst and hydrogen donor were used (No. 1) and the case where no hydrogen donor was used (No. 2), and the results are shown in Table 1. From Table 1, it is clear that according to the method of the present invention, DO can be efficiently removed. In addition, in the method of this example, the treated water DO could be further lowered by lowering the liquid passing rate or increasing the amount of catalyst.

[0019]

[Table 1]

[0020]

Effects of the Invention As detailed above, according to the method for removing dissolved oxygen in service water of the present invention, DO in service water can be removed easily, efficiently, and at low cost with good work safety. It is possible to remove it with

Claims (1)

[Claims] Claim 1: A hydrogen donor is added to water containing dissolved oxygen, and while the temperature is maintained at 100 to 300°C and the pressure is such that the water remains in a liquid phase, iron, cobalt, nickel, ruthenium, rhodium, and palladium are added to the water. , iridium, platinum,
One or two selected from the group consisting of copper, gold, tungsten, and compounds of these metals that are insoluble or poorly soluble in water.
1. A method for removing dissolved oxygen in water, which comprises reacting dissolved oxygen with a hydrogen donor in the presence of a supported catalyst containing at least one species of hydrogen donor as an active ingredient.