JP3664592B2 - Immobilization method of phosphorus in sludge melting furnace - Google Patents

Description

【００１４】
表１は、脱水機２２に注入するポリ硫酸第２鉄の混合量を、１％ずつ違えて投入した場合の脱水ケーキにおけるリンの固定化率と、溶融炉２１で生成するスラグ３０におけるリンの固定化率を示す。
【００１５】
この結果において、乾燥ケーキ中のリンは、排ガス中へ移行することなく、スラグ３０中に移行する傾向となる。特に、原料汚泥２３に鉄分として乾燥汚泥換算重量（対ＤＳ）の３〜６％のポリ硫酸第２鉄２４を混合した時に有効な効果を得られる。
【００１６】
したがって、溶融炉２１より排出する排ガス中に揮発するリン成分が少ないので、リン酸化合物の生成を抑制でき、煙道３２、輻射式廃熱ボイラ３３および水管式廃熱ボイラ３４の壁面やボイラ水管にリン酸塩が付着して、通気路の閉塞やリン酸腐食を引き起こすことを防止できる。
【００１７】
【発明の効果】
以上述べたように、本発明によれば、脱水機にポリ硫酸第２鉄を注入することにより、溶融に際し、乾燥ケーキ中のリン成分を、排ガス中へ揮発することなく、スラグ中に固定化することができる。特に、ポリ硫酸第２鉄の混合量を、原料汚泥の乾燥汚泥換算重量の３〜６％とすることにより、より有効な効果を得ることができる。このため、リン酸塩の生成を抑制して、排ガスの通気路におけるリン酸塩の付着による閉塞やリン酸腐食を防止できる。
【図面の簡単な説明】
【図１】本発明の実施の形態における溶融炉の構成を示す摸式図である。
【図２】従来の溶融炉の構成を示す摸式図である。
【符号の説明】
２１ 溶融炉
２２ 脱水機
２３ 原料汚泥
２４ ポリ硫酸第２鉄
２５ 脱水ケーキ貯留ピット
２６ ケーキ供給ホッパ
２７ 汚泥乾燥機
２８ 主燃焼室
２９ バーナ
３０ スラグ
３１ 二次燃焼室
３２ 煙道
３３ 輻射式廃熱ボイラ
３４ 水管式廃熱ボイラ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for treating sludge such as sewage treatment sludge in a melting furnace, to fix phosphorus in slag, and to a method for fixing phosphorus in a sludge melting furnace.
[0002]
[Prior art]
The sludge generated at the sewage treatment plant is melted and slag in a melting furnace for the purpose of reducing, stabilizing and reusing the sludge. In this treatment step, for example, as shown in FIG. 2, the sludge 1 generated in the sewage treatment plant is dehydrated to a water content of about 80% in the dehydrator 2, and the dehydrated cake is put into the dehydrated cake storage pit 3 for storage. The dehydrated cake in the dewatered cake storage pit 3 is supplied to the cake supply hopper 4 by a bucket crane, and the dehydrated cake with a moisture content of 80% is fed from the cake supply hopper 4 to the sludge dryer 5 and the moisture content is increased to 20% by indirect heating. dry.
[0003]
The dried cake is put into the melting furnace 6 and subjected to high-temperature treatment at 1300 to 1500 ° C. using the combustion heat of the burner 8 in the main combustion chamber 7 and the combustion heat of organic matter in the sludge as a heat source for melting, and the molten slag is subjected to secondary combustion. It is dripped in cooling water through the chamber 9, and the cooled and solidified slag is discharged. The exhaust gas passes from the secondary combustion chamber 9 through the flue 10 and is led to the radiant waste heat boiler 11 and the water tube waste heat boiler 12 to recover heat of the heat energy of the exhaust gas as steam.
[0004]
[Problems to be solved by the invention]
By the way, in recent years, the phosphorus concentration in the sludge has increased with the advanced treatment in the sewage treatment plant, and when the sludge containing this phosphorus is treated at a high temperature in the melting furnace 6, the phosphorus is not fixed in the slag. Volatilizes into the exhaust gas and becomes a highly sticky phosphoric acid compound 13 which adheres to the walls of the flue 10, the radiant waste heat boiler 11 and the water pipe waste heat boiler 12 and the boiler water pipe, blocking the air passage and phosphorus There was a problem that caused acid corrosion.
[0005]
For this reason, an attempt was made to operate the melting furnace 6 in an oxidizing atmosphere. However, due to an increase in the amount of air, the temperature of the main combustion chamber 7 is lowered, the amount of auxiliary fuel used is increased, and an effect cannot be obtained. It was.
[0006]
The present invention solves the above-described problems, and provides a method for fixing phosphorus in a sludge melting furnace capable of fixing phosphorus in slag in a melting furnace operated with the main combustion chamber set in a reducing atmosphere. With the goal.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the method for immobilizing phosphorus in the sludge melting furnace of the present invention is to mix the iron-based flocculant with the raw material sludge, which is the sludge containing phosphorus, in the dehydrator, and dehydrate the cake. Drying in the sludge dryer, throwing the dried cake into the melting furnace, melting processing in a reducing atmosphere in the melting furnace to slag, suppressing the phosphorus component volatilized in the exhaust gas discharged through the air passage, It prevents phosphate adhesion which causes phosphoric acid corrosion or blockage of the air passages .
[0008]
Preferably, the iron-based flocculant is any one of polyferric sulfate, ferric sulfate, and ferric chloride.
Preferably, polyferric sulfate is used as the iron-based flocculant, and the mixed amount of polyferric sulfate is set to 3 to 6% of the dry sludge equivalent weight of the raw material sludge as iron.
[0009]
With the above-described configuration, the phosphorus in the dry cake is fixed in the slag without being transferred into the exhaust gas during melting. The above was confirmed by experiments.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a melting furnace 21 is intended to reduce the temperature, stabilize and reuse sludge by treating sludge containing phosphorus generated at a sewage treatment plant at a high temperature to form slag.
[0011]
Prior to the melting of the sludge in the melting furnace 21, as a pre-process, the raw material sludge 23 is introduced into the dehydrator 22, and polysulfuric ferric acid 24 is injected as an iron-based flocculant, so that the raw material sludge 23 and the polyferric ferric sulfate are injected. 24 is mixed and dehydrated to a water content of about 80%. The mixing amount of this ferric sulfate is 3 to 6% of the dry sludge equivalent weight (vs. DS) of the raw material sludge 23.
The dehydrated cake is put into the dehydrated cake storage pit 25 and stored, the dehydrated cake in the dehydrated cake storage pit 25 is supplied to the cake supply hopper 26 by the bucket crane, and the dehydrated cake is supplied from the cake supply hopper 26 to the sludge dryer 27. Dry by indirect heating to a moisture content of 20%.
[0012]
The dried cake is put into the melting furnace 21, subjected to high-temperature treatment at 1300 to 1500 ° C. in a reducing atmosphere using the combustion heat of the burner 29 in the main combustion chamber 28 and the combustion heat of organic matter in the sludge as a melting heat source, and melted slag 30 is dropped into the cooling water through the secondary combustion chamber 31, and the cooled and solidified slag 30 is discharged. The exhaust gas passes from the secondary combustion chamber 31 through the flue 32 and is led to the radiant waste heat boiler 33 and the water tube waste heat boiler 34, and heat recovery is performed using the thermal energy of the exhaust gas as steam.
[0013]
[Table 1]

[0014]
Table 1 shows the immobilization rate of phosphorus in the dehydrated cake when the mixed amount of ferric polysulfate to be injected into the dehydrator 22 is different by 1%, and the amount of phosphorus in the slag 30 produced in the melting furnace 21 The immobilization rate is shown.
[0015]
In this result, phosphorus in the dry cake tends to move into the slag 30 without moving into the exhaust gas. In particular, an effective effect can be obtained when the raw sludge 23 is mixed with 3 to 6% polysulfuric ferric sulfate 24 of dry sludge equivalent weight (vs. DS) as iron.
[0016]
Therefore, since there is little phosphorus component volatilized in the exhaust gas discharged from the melting furnace 21, the production of phosphate compounds can be suppressed, and the walls of the flue 32, the radiant waste heat boiler 33 and the water pipe waste heat boiler 34, and the boiler water pipe It is possible to prevent phosphate from adhering to the air passage and block the air passage and cause phosphoric acid corrosion.
[0017]
【The invention's effect】
As described above, according to the present invention, by injecting polyferric sulfate into the dehydrator, the phosphorus component in the dry cake is fixed in the slag without being volatilized into the exhaust gas upon melting. can do. In particular, a more effective effect can be obtained by setting the mixing amount of polyferric ferric sulfate to 3 to 6% of the dry sludge equivalent weight of the raw material sludge. For this reason, the production | generation of a phosphate can be suppressed and the obstruction | occlusion and phosphoric acid corrosion by the adhesion of the phosphate in the ventilation path of waste gas can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a melting furnace in an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a configuration of a conventional melting furnace.
[Explanation of symbols]
21 Melting furnace 22 Dehydrator 23 Raw material sludge 24 Polysulfuric acid ferric iron 25 Dehydrated cake storage pit 26 Cake supply hopper 27 Sludge dryer 28 Main combustion chamber 29 Burner 30 Slag 31 Secondary combustion chamber 32 Flue 33 Radiation waste heat boiler 34 Water tube waste heat boiler

Claims (3)

In the dehydrator, the raw material sludge, which is phosphorus-containing sludge, is mixed with iron-based flocculant and dehydrated. The dehydrated cake is dried in the sludge dryer, and the dried cake is put into the melting furnace. Melting treatment to form slag suppresses phosphorus component volatilized in exhaust gas discharged through the air passage, and prevents phosphate adhesion that causes phosphoric acid corrosion or blockage of the air passage A method for fixing phosphorus in a sludge melting furnace.   2. The method for immobilizing phosphorus in a sludge melting furnace according to claim 1, wherein the iron-based flocculant is one of polyferric sulfate, ferric sulfate, and ferric chloride.   The polyferric sulfate is used as an iron-based flocculant, and the mixing amount of the polyferric sulfate is 3 to 6% of the dry sludge equivalent weight of the raw material sludge as iron. Immobilization method of phosphorus in the sludge melting furnace.

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