JPS61276617A - Burning of phosphorus-containing substance - Google Patents

Abstract

PURPOSE:To obtain a method of burning and treating sludges containing great amounts of phosphorus by adding a calcium compound to the phosphorus- containing substances until at least burning time. CONSTITUTION:In a fluidized bed incinerator, sludges 1 containing great amounts of phosphorus are mixed with a calcium compound 3, e.g., calcium carbonate, etc., in a mixer 2 set on the former stage of the incinerator and then charged into a fluidized bed furnace 4. The sludge 5 is crushed by the fluidizing movement of a fluidizing fluid 6 in the internal lower side of the incinerator, dried, and burned at high temperatures above 600 deg.C. When the heat quantity of the sludge is low, an auxiliary fuel 7 is used in the burning. Phosphoric acid compounds are changed into calcium phosphate and are allowed to incinerate without lowering of the melting point of the ash of the sludge and also any increase in the adhering amount of the ash. The incinerating treatment of the sludges can thus be stably attained without the adherence of the fluidizing mediums, occurrence of clinker, and the adherence of the ash to waste gas processing installation 9.

Description

[Detailed description of the invention] <Industrial field of application> The present invention relates to a combustion method using a fluidized bed, and in particular to a combustion method that can perform good combustion even for incinerated materials with a high phosphorus content. .

<Prior art and its problems> Fluidized bed incinerators are increasingly being used for the incineration treatment of sewage and industrial wastewater sludge due to their excellent incineration performance. Fluidized bed incinerators break up muddy and clumpy water-containing sludge through the fluidization movement of the fluidized medium inside the furnace.

Dry and burn. The drying and combustion efficiency as well as the combustion stability all depend on the active fluidizing movement of the fluidizing medium. Usually, river sand or silica sand containing 5 iOz as a main component is used as the fluid medium when gas treatments such as desulfurization and dehydrochlorination are not required.

However, depending on the composition of the sludge, it may be difficult to maintain the above-mentioned active fluidization.

For example, when incinerating sludge containing a large amount of phosphorus components generated in the treatment of food industry wastewater, etc., there are the following problems when incinerating it in a fluidized bed furnace.

(1) Phosphorus compounds (P compounds) contained in sludge
In the high-temperature atmosphere inside the furnace, pyro and trite occur.

It is sequentially dehydrated and condensed in the form of trapenta. When converted to such condensed phosphoric acid, the viscosity increases, resulting in increased adhesion of sludge ash, resulting in adhesion between media and fly ash entrained in exhaust gas to the furnace wall or post-throttling gas treatment equipment. Adhesion occurs.

(2) During incineration, the above-mentioned phosphorus compound and 8102 in the fluid medium react at high temperatures of approximately 600°C or higher to form phosphate glass, and as a result, the medium undergoes eutectic melting to produce glassy talinka. liquidation becomes impossible.

OBJECTS OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and provide a method for incinerating sludge with a high phosphorus content without causing problems such as problems with the talin force of the medium. It is.

Summary of the present invention> FIG. 1 shows the flow of an embodiment of the present invention.

To explain specifically, sludge 1 with a high phosphorus content is
Calcium compounds 3 such as calcium carbonate are added and kneaded in a kneader 2 installed in the front stage of the furnace, and then transferred to a fluidized bed furnace 4.
will be put into. The introduced kneaded sludge 5 is crushed and dried by the fluidization movement of the fluidized medium 6 in the lower part of the furnace.
Burns at high temperatures above 00℃. If the calorific value of the sludge is low, auxiliary fuel 7 is used during combustion. In the example of the present invention, the following (1
) A reaction like (2) occurs.

50a-) 40H''+3HPCk -5-Oas(O
H) (Po4)s +3H20・・・・・・(1) 01L (OH)4 + 2H3PO4→Oa (H
l PO4)z' 2H20 (2) That is, the phosphoric acid compound changes to calcium phosphate, and as a result, it becomes possible to incinerate the sludge without lowering its ash melting point or increasing its adhesion. . As a result, adhesion between the media and formation of slag do not occur, and stable incineration processing is also possible without adhesion of ash in the exhaust gas equipment 9 that processes the exhaust gas 8 containing fly ash shown in Fig. 1. Become.

In addition, the present invention eliminates the formation of phosphate glass due to the reaction between phosphorus compounds and SiO in the fluidized medium, which has been a problem in conventional fluidized bed furnaces, by changing it to calcium phosphate as described above.
This eliminates the problem of the media becoming tarnished.

In practicing the present invention, the amount of calcium compound added to the sludge should depend on the amount of phosphorus contained. However, continuous analysis of the amount of phosphorus in sludge is not possible with current measurement techniques, and other means are desired.

FIG. 2 shows an example of a control method.

The temperature of a fluidized bed with good fluidization) is almost uniform throughout the fluidized bed, and in the experience of the inventors, the temperature is approximately +10°C.
There is only a slight deviation. On the other hand, if the fluidization of the medium deteriorates due to media adhesion or tarinka formation, etc., especially on the fluidized bed,
As the temperature difference at the bottom increases and this condition progresses, the fluidization movement eventually stops. In other words, when fluidization deteriorates, the temperature of the soil layer increases due to combustion, and the lower layer is cooled by fluidizing air, resulting in a larger temperature difference between the layer and the lower layer.

FIG. 2 shows an example of a method for supplying calcium compounds,
The fluidized bed upper temperature signal 11 and the fluidized bed lower temperature signal 12 are detected, and if the temperature difference 13 between them is larger than the set value, the amount of calcium compound 3 is increased by the supply amount controller 15 via the determiner 14. On the other hand, if it is within the set value, the amount of calcium compound 3 added is gradually decreased. This makes it possible to always optimize the amount of calcium compound added.

Experimental Example> When food wastewater sludge containing 2% phosphorus (water content basis) is incinerated, the fluidized bed temperature is approximately 400°C at approximately 800°C in the conventional method without adding calcium compounds (calcium carbonate).
After incineration for a period of time, some parts of the fluidized bed were observed to have a fixed bond of media. On the other hand, in the operation according to the present invention, that is, when 0.1 kg of calcium carbonate is added per 1 kg of water-containing sludge and then incinerated, the fluidized medium after 4 hours does not exhibit any adhesion or tarinka state, and even after a long period of time, It was possible to drive.

<Effects> Since the present invention has the above-mentioned groove structure, it is possible to prevent adhesion of fluidized media to each other and to prevent molten tarlinker, and stable fluidized incineration operation is possible.

In addition, the adhesion of fly ash is alleviated, and adhesion and clogging of ash to the furnace wall and subsequent gas treatment equipment is prevented.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a fluidized bed combustion method showing an embodiment of the method of the present invention, and FIG. 2 is a control system diagram showing a method of adjusting the supply amount of calcium compounds. 1... Sludge 3... Calcium compound 4... Fluidized bed furnace 6... Fluidized medium 11... Fluidized bed top temperature 12... ...Fluidized bed lower temperature Figure 1 Figure 2 Figure 12 np tolerance

Claims (1)

[Claims] 1. A method for burning a phosphorus-containing substance in a fluidized bed furnace, characterized in that a calcium compound is added to the phosphorus-containing substance at least before combustion. How to burn substances. 2. The phosphorus-containing device according to claim 1, characterized in that the temperature difference between the upper layer and the lower layer of the fluidized bed is detected, and the amount of calcium compound added is adjusted in accordance with the magnitude of this temperature difference. How to burn substances.