JP3334961B2 - Sulfite recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering sulfite from bisulfite using an electrodialyzer using a bipolar membrane.

[0002]

2. Description of the Related Art In combustion of heavy oil and coal, sulfur dioxide is contained in combustion exhaust gas. Various methods for collecting sulfur dioxide in combustion exhaust gas have been studied from the viewpoint of environmental pollution prevention. For example, a method of neutralizing sulfur dioxide with lime milk and collecting it as gypsum is well known. Also, a sulfurous acid gas is absorbed by a sodium hydroxide aqueous solution or a sodium sulfate aqueous solution to form a sodium bisulfite aqueous solution, which is used in an electrodialysis apparatus in which a bipolar membrane and a cation exchange membrane are alternately arranged.
A method of producing a mixed aqueous solution of a sulfate and a sulfurous acid and an aqueous solution of a sulfite by supplying the mixture to both chambers has been proposed (Japanese Patent Publication No. 60-36811).

[0003]

However, in this method, the sulfurous acid discharged from the electrodialysis apparatus is obtained as a mixed aqueous solution with a sulfate, so that an operation for separating the sulfurous acid and the sulfate is required. Therefore, in the above-mentioned document, the mixed aqueous solution of sulfurous acid and sulfate obtained in this manner is supplied to an electrodialysis device using another bipolar membrane to perform separation.

[0004]

Means for Solving the Problems In view of the above-mentioned problems, the present inventors have found that by using an electrodialysis apparatus in which bipolar membranes and anion exchange membranes are alternately arranged, bisulfite and sulfurous acid and sulfurous acid can be used. I found a way to recover salt and
The present invention has been proposed.

That is, the present invention uses an electrodialysis apparatus in which a bipolar membrane and an anion exchange membrane are alternately arranged between an anode and a cathode, supplies an aqueous bisulfite solution to an alkali chamber, and supplies an aqueous solution to an acid chamber. An aqueous sulfurous acid solution is supplied, and the bisulfite ion in the alkali chamber is permeated through the anion exchange membrane and is recovered as an aqueous solution of sulfurous acid by reaction with hydrogen ions in the acid chamber. Wherein a sulfite ion is generated, and the sulfite ion is recovered as an aqueous sulfite solution.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In the present invention, as shown in FIG. 1, an electrodialysis apparatus in which bipolar membranes B and anion exchange membranes A are alternately arranged is used. The bipolar membrane B is
This is a composite ion exchange membrane having a structure in which a cation exchange membrane and an anion exchange membrane are laminated. As such a bipolar film, a known film can be used without any particular limitation. The following is known as a manufacturing method thereof. For example, a method of laminating a cation exchange membrane and an anion exchange membrane with a mixture of polyethyleneimine-epichlorohydrin and curing the mixture (Japanese Patent Publication No. 32-3962).
Publication), a method of bonding a cation exchange membrane and an anion exchange membrane with an ion exchange adhesive (Japanese Patent Publication No. 34-3961)
JP-A-35-14531, a method in which a cation exchange membrane and an anion exchange membrane are coated with a fine powder of an ion exchange resin or a paste-like mixture of an anion or cation exchange resin and a thermoplastic substance and pressed. ), A method in which a paste-like substance comprising vinylpyridine and an epoxy compound is applied to the surface of a cation exchange membrane and irradiated with radiation (Japanese Patent Publication No. 38-16633), the surface of the anion exchange membrane A method in which a sulfonic acid type polymer electrolyte and an allylamine are adhered to the mixture, followed by irradiation with ionizing radiation (Japanese Patent Publication No. 51-4113), a dispersion of an ion exchange resin having an opposite charge on the surface of an ion exchange membrane. For depositing a mixture of a polymer and a base polymer (JP-A-53-3719)
No. 0), a sheet formed by impregnating and polymerizing a polyethylene film with styrene and divinylbenzene is sandwiched between stainless steel frames, one side is sulfonated, the sheet is removed, and the remaining part is chloromethylated, A method of amination treatment (US Pat. No. 3,562,139), and a method of treating the interface between an anion exchange membrane and a cation exchange membrane with an inorganic compound and joining the two membranes (Japanese Patent Laid-Open No.
9-47235).

The anion exchange membrane used in the present invention is not particularly limited, and a known anion exchange membrane can be used.
For example, an anion exchange membrane in which a quaternary ammonium group, a primary amino group, a secondary amino group, a tertiary amino group, and a plurality of these ion exchange groups are mixed can be used. The anion exchange membrane may be of a polymerization type, a condensation type, a uniform type, or a non-uniform type. In addition, the presence or absence of a reinforcing core, a hydrocarbon-based material, a fluorine-based material, and an anion derived from a material / manufacturing method. Any type and type of ion exchange membrane may be used. Further, a 2N-salt solution is subjected to electrodialysis at a current density of 5 A / dm ² and a current efficiency of 70% or more and substantially functions as an anion exchange membrane. Can be used as the anion exchange membrane of the present invention. Since an anion exchange membrane tends to allow an acid to permeate, it is preferable to use an anion exchange membrane that does not easily allow an acid to permeate.

In the present invention, when the aqueous solution of bisulfite to be subjected to electrodialysis is obtained by absorbing sulfurous acid gas into an aqueous solution of alkali hydroxide or sulfate, one of the sulfites together with the bisulfite is used. And a mixed aqueous solution of bisulfite and sulfite. When this mixed aqueous solution is supplied to the electrodialysis apparatus, in order to improve the separation of the sulfurous acid obtained from the acid chamber and the sulfite obtained from the alkaline chamber, the mixed aqueous solution is used as an anion exchange membrane without permeating divalent sulfite ions. It is preferable to use a monovalent anion selectively permeable membrane that selectively allows only a monovalent bisulfite ion to permeate. In this case, the permeation coefficient (P ^SO3 _{HSO 3} ) of bisulfite ion and sulfite ion is less than 0.5, preferably less than 0.1 in terms of separation efficiency.

The above-mentioned selective transmission coefficient is a value obtained as follows. 0.5N NaHSO ₃ and Na ₂ S
A 1: 1 mixture of O ₃ was placed on both sides of the monovalent anion permselective membrane and electrodialysis at 5 A / dm ² for 40 minutes to permeate through the monovalent anion permselective membrane. It was determined from the amounts of HSO ₃ ^- and SO ₃ ^2- transferred to the opposite side by the following equation.

P ^SO3 _HSO3 = t _SO3 · C _HSO3 / t _HSO3 · C _SO3 (where t _SO3 is the current efficiency of SO ₃ ^2- of the monovalent anion selective permeable membrane, and t _HSO3 is the monovalent anion. HS of permselective membrane
The current efficiency, C _{HSO3 @} is HSO ₃ before electrodialysis ^{- -} O ₃ concentration of, C _SO3 denotes a SO ₃ ^{2-concentration} before electrodialysis. Examples of such a monovalent anion selective permeable membrane include a resin having an aromatic nucleus having one or more amino groups on the surface of an anion exchange membrane and condensing with an aldehyde group or a methylol group to develop a cross-linking bond. Formed by forming a thin layer of a condensate of a compound capable of forming an aldehyde and an aldehyde (Japanese Patent Publication No. 36-152)
No. 58), a membrane having a thin film of an organic low molecular electrolyte having a cation exchange group or a non-crosslinked linear polymer electrolyte on the surface of an anion exchange membrane (JP-B-45-19980).
No.), a part of the functional group which can be converted to a strongly basic anion exchange group is inactivated in advance with respect to the quaternary amino treatment. Or a quaternary aminated film after contact with a peroxide solution (JP-B-56-47213).

In the above-mentioned electrodialyzer, as the anode 1 and the cathode 2, electrodes used in the electrochemical industry such as water electrolysis and salt electrolysis are used without any limitation. For example, nickel, iron, lead, platinum or graphite can be suitably used as the anode material, and nickel, iron, stainless steel or platinum can be suitably used as the cathode material.

The type of the anolyte supplied to the anode chamber can be appropriately selected according to the type of the anode material. Preferred examples of these combinations are, for example, as follows. Examples include nickel or iron-sodium hydroxide aqueous solution, lead-sulfuric acid aqueous solution, platinum-sulfuric acid or sodium sulfate aqueous solution, and graphite-salt aqueous solution. Preferred combinations of the cathode material and the catholyte are as follows. Nickel, iron, or stainless steel-can include sodium hydroxide, sodium sulfate, or saline solutions.

In the present invention, of the chambers divided by the bipolar membrane B and the anion exchange membrane A of the electrodialysis apparatus,
The chamber where the bipolar membrane B is located on the cathode side is an alkaline chamber 4,
The chamber where the bipolar film B is located on the anode side is called an acid chamber 3.
An aqueous solution of bisulfite 5 is supplied to the alkali chamber 4, and an aqueous solution of sulfite 6 is supplied to the acid chamber 3.

The bisulfite ions in the alkali chamber 5 permeate the anion exchange membrane A and move to the acid chamber 6. In the acid chamber 6, the bisulfite ion reacts with the hydrogen ion supplied from the bipolar membrane B to generate sulfurous acid. This is shown in the reaction formula as follows.

HSO ₃ ⁻ + H ⁺ → H ₂ SO ₃ On the other hand, in the alkaline chamber 5, the remaining bisulfite ions that do not permeate the anion exchange membrane A react with the hydroxyl ions supplied from the bipolar membrane B to form sulfurous acid. Ions are generated. This is shown in the reaction formula as follows.

HSO ₃ ⁻ + OH ⁻ → SO ₃ ²⁻ + H ₂ O The sulfurous acid generated in the acid chamber 6 is recovered as an aqueous solution 7, and the sulfite ion generated in the alkaline chamber 5 is converted into a sulfite aqueous solution 8.
Will be collected as

In the above electrodialysis, a monovalent anion selective permeable membrane is used as the anion exchange membrane A, and a mixed aqueous solution of bisulfite and sulfite is used as an aqueous solution of bisulfite to be subjected to electrodialysis. In this case, only the monovalent bisulfite ion in the mixed aqueous solution supplied to the alkaline chamber 5 selectively passes through the monovalent anion selective permeable membrane A and moves to the acid chamber 6, where the divalent sulfite ion Remains in the alkaline chamber 5. In the acid chamber 6, as shown in the above equation, the bisulfite ion transferred from the alkali chamber 5 reacts with the hydrogen ion to generate sulfurous acid. In the alkali chamber 5, the bisulfite ion reacts with the hydroxyl ion. Sulfite ions are produced. Since the sulfite ion supplied to the alkali chamber 5 is a divalent ion and does not permeate the acid chamber 6, the supplied sulfite ion and the remaining bisulfite ion and hydroxyl ion that have not moved to the acid chamber 6 The total amount with the sulfite ion generated by the reaction is recovered as an aqueous salt solution.

As a method of electrodialysis in the present invention,
The acid chamber 6 and the alkali chamber 5 are provided with a tank for the liquid to be supplied to each chamber, and the liquid is circulated between the respective chambers and the tank for the liquid. A method of supplying a liquid, a method of circulating a liquid to be supplied to one of an acid chamber and an alkaline chamber, and a method of supplying a liquid to the other chamber in one pass can be arbitrarily adopted.

In the present invention, the cations constituting the sulfites and bisulfites are typically ions of alkali metals such as sodium ion, potassium ion and lithium ion.
It may be a sulfonium ion or the like.

[0021]

According to the present invention, sulfurous acid and sulfite can be respectively recovered as aqueous solutions from bisulfite. Heating the aqueous sulfurous acid solution generates sulfurous acid gas, and further oxidizing the sulfurous acid gas produces sulfuric acid. Therefore, sulfurous acid is effective as a raw material for producing sulfuric acid. On the other hand, the aqueous sulfite solution can be reused as a sulfurous acid gas absorbing solution in the flue gas desulfurization step.

[0022]

【Example】

Example 1 A bipolar membrane (manufactured by Tokuyama Soda Co., Ltd.,
Trade name: Neosepta BP-1) and monovalent anion selective permeable membrane (manufactured by Tokuyama Soda Co., Ltd., trade name: Neosepta ACS)
(P ^SO3 _{HSO 3} = 0.1)), an electrodialysis tank (manufactured by Tokuyama Soda Co., Ltd., effective membrane area ² dm ² ) partitioned into an acid chamber and an alkali chamber was used. Na ₂ SO ₃ 5 in the alkaline chamber
An aqueous solution containing 0 g / l and 200 g / l of NaHSO ₃ and an aqueous solution of 5 g / l of sulfurous acid were supplied to the acid chamber, and the operation was performed at a film surface speed of 6 cm / sec and an average current density of 5 A / dm ² . As a result, 180 g of Na ₂ SO _{3 was} discharged from the alkaline chamber.
/ L, an aqueous solution containing NaHSO ₃ 3.1 g / l was obtained. 56.6 g / l of sulfurous acid, Na ₂ SO ₃ 1.
An aqueous solution containing 5 g / l was obtained.

Example 2 A monovalent anion selective permeable membrane manufactured by Tokuyama Soda Co., Ltd.
Product name: An electrodialysis tank using Neosepta AMX (P ^SO3 _{HSO 3} = 0.8) was used.
₃ Aqueous solution containing 200g / l, sulfuric acid 5g / l in acid chamber
Are supplied respectively, and the film surface speed is 6 cm / sec.
The operation was performed at an average current density of 5 A / dm ² . As a result, 113 g / l of Na ₂ SO ₃ and NaHSO ₃ 2
An aqueous solution containing g / l was obtained. Sulfurous acid 70 from acid chamber
g / l, an aqueous solution containing 1 g / l of Na ₂ SO ₃ was obtained.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration example of an electrodialysis apparatus of the present invention.

[Explanation of symbols]

 A Anion exchange membrane B Bipolar membrane 1 Anode 2 Cathode 3 Acid chamber 4 Alkaline chamber 5 Bisulfite aqueous solution 6 Sulfite aqueous solution 7 Sulfite aqueous solution 8 Sulfite aqueous solution

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification code FI C02F 1/46 ZAB B01D 53/34 125R 1/469 C02F 1/46 103 C25B 1/22 (56) References JP-A-49- 58082 (JP, A) JP-A-52-5689 (JP, A) JP-A-7-31842 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 17/62 B01D 53 / 34 C25B 1/22

Claims (1)

(57) [Claims] An electrodialysis apparatus comprising a bipolar membrane and an anion exchange membrane alternately arranged between an anode and a cathode,
An aqueous solution of bisulfite is supplied to the alkali chamber, an aqueous solution of sulfite is supplied to the acid chamber, and bisulfite ions in the alkaline chamber are allowed to pass through the anion exchange membrane, and are recovered as an aqueous solution of sulfurous acid by reaction with hydrogen ions in the acid chamber. A sulfite ion produced by a reaction between bisulfite ion and hydroxyl ion in an alkaline chamber, and recovering the sulfite ion as an aqueous sulfite solution.