JPS58159833A - Method for reducing nitrogen oxide generated in calcining furnace in production stage for potassium silicate fertilizer using fly ash as raw material - Google Patents

Abstract

PURPOSE:To reduce the content of NOX in waste gases from a calcining furnace in the stage of adding KOH, Mg(OH)2 and pulverized coal as raw materials to fly ashes and producing a potassium silicate fertilizer, by adding ammonia to the calcining furnace. CONSTITUTION:KOH 1, fly ashes 2, pulverized coal 3 and Mg(OH)2 4 are put into a mixing tank 5, and water is added thereto to make these materials into a slurry. The slurry is thoroughly aqitated in a tank 6 and is then supplied to a mixer 9, where the slurry is mixed with the granular raw materials returned from a feedback tank 14 so that the slurry sticks to the surfaces of the granular raw materials. The granular raw materials stuck with the slurry are dried with the high temp. waste gases from a calcining furnace 17 in a dryer 10, whreby a potassium silicate fertilizer is produced. Ammonia is fed into the furnace 17 at 850-950 deg.C in the furnace top part to reduce the NOX generated by the high temp. calcination in the furnace 17 to N, whereby the content of harmrul NOX in the waste gases is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to reducing nitrogen oxides (MOx) generated in a firing furnace during the production of potassium silicate fertilizer using
O 7y related to O reduction method O 7y is a fine powder that floats in the waste gas generated from the SO molded coal combustion furnace of a thermal power plant, is discharged together with the waste gas, and is mainly collected by an electrostatic precipitator. This 72 Iatsushie is mainly composed of silicon dioxide, and is a relatively stable substance chemically, but as mentioned above, since it is a fine powder, potassium salt is added to it and it is heated in a chewing furnace. 600-
When fired at a temperature of 11,000 ℃, potassium and 7 liter gourd react to form potassium silicate containing citric acid, which can be used as a potassium silicate fertilizer.

The present applicant has already filed many patent applications and utility model applications for the production method of potassium silicate fertilizer using fly ash as a raw material and the equipment used therefor. In line 1 to obtain soluble potassium silicate, the raw material is heated in a kiln to 6H to 1
When firing at 100°C, a small amount of nitrogen oxide Mo
Generate x.

On the other hand, the current situation is that environmental standards for nitrogen oxides are becoming increasingly strict.

The present invention has been made from such a viewpoint, and its purpose is to reduce as much as possible the iim*fluride NOx generated in the calcination process during the production process of potassium silicate fertilizer using fly ash as JI. To provide a method for reducing nitrogen oxides that can reduce nitrogen oxides, an example of a method for producing potassium silicate fertilizer using fly ash as a raw material, in which the method for reducing bulk oxides of the present invention is carried out, will be described with reference to Figure M1. 0 In Fig. 1, 1 to 4 are storage tanks, each containing a hydroxide-TTV aqueous solution (4816 bottles, 111 m).
117 Liacuse 2, powder-like stone and magnesium hydroxide 4 are mixed in. 5 is a warming machine, and this warming tank 5 is filled with potassium hydroxide aqueous solution (48-aqueous solution) L.
774kg/, fly ash (moisture turtle 41G) &4
・Ik! E, fine powder stone (moisture 14$・'Ql/
hr, AD Magnesium Hydroxide (Water Hatake) 144”
/kr and mix. This mixture is 417.
Next, this slurry is sent to the supply tank, and further this slurry is pumped out at a moderate rate of 4 mm kg/h using a metering pump 8, and then supplied to the mixing horizontal line. In this case, feed/(feedback amount from the feed tank 14 is detected and the pump 80 supplies violet to 11111IllIil. 0 Mixer 9 The slurry supplied from the supply tank 6 is spray-coated onto the surface of nine granular raw materials that have been previously dried to a moisture content of 15K to form new granules. tss
* 'Q/1 = (moisture 11) granular raw material is put in, and while stirring this raw material, 477 s% slurry 9-1 is poured into it using the metering pump 8 and stirring is continued. Slurry is in feedback tank 14
The granular raw material from the feed batter tank 14 is dried in advance as described later, and the particles are attached to each other to form a granular material of about 1 (h-10rmψ). Since the slurry contains water and has a high concentration of water, the water contained in the slurry permeates into the -sF1 granular Mkasen, and the average water content is reduced to the average water content, resulting in particles suitable for granulation and drying.

Subsequently, this granular material (14s1 g/hr) is supplied to a drying machine and is dried by sending hot air of 40e to 10Os degrees to it.・・Use O~5oona). The burner 11 for the dryer is usually turned on at the start of operation or at the beginning of the firing furnace 1.
G drying 1i1 used when the hot air temperature from 7 is insufficient
Dry granules dried to 0 and 1 s of moisturetttis'Q!
/hr is transported from the crusher 813 together with the O-pulverized appetizer γ・shag, and ILsss''g/, is supplied to the sieving machine 12.1 The remaining 11,258 kg is led to the feedback tank 14 without being crushed.1 The dry granules led to the separator 12 are sieved, and those with a particle size of 4 mmφ or more are
, and those with a particle size of 1 to 4 mmφ 71 kg /,,
and those with a particle size of innφ or less are divided into &011 and -.

Those with a particle size of 4 mmφ or more are sent to the crusher 13 to be pulverized, and then the dry granules from the dryer 10 are conveyed again by a person K1114.Those with a particle size of 1 mmφ or less are put into the feedback tank 14.

The exhaust gas discharged from the dryer 10 is passed through the cyclone dust collector 1
5 and a pack filter 16 to separate and collect the fine particles floating therein, and the exhaust gas is sent to the exhaust gas treatment equipment described later, where 21 kg of particles are collected in 1IA1.7. , is put into the feedback tank 14. The granules input into the feedback tank 14 are sent to the mixer 10 as granular raw materials as described above. The particle size sieved by the sieving machine 12 is 1 to 4! The one with u1ψ is sent to the firing furnace 17 and fired.

As this kiln 17, a known kiln can be used, and since the grain size of the dried granules is arranged in the range of 1 to 4 m1lψ, it is appropriate to use a fluidized bed kiln. tayskg/, of dry granules were put into the firing furnace 17, and -
・Fire within the range of 0 to 11・QC. At the start of operation, the temperature is raised to a predetermined temperature using the starting banner 18, and from then on, the pulverized coal in the ingredients becomes the fuel. Under this temperature condition, potassium and silicon in the granules react to produce citric acid * * S, At the same time, the coal used as a fuel becomes carbon dioxide OQJ and dissipates from the granules, making the granules extremely porous and suitable as fertilizer. Granules &0...klI/kr#i are taken out as product 1, and the exhaust gas is used as a heat source for drying in the dryer 100. A part of the exhaust gas is also used for heat exchange and drying of pulverized coal.

Figures 2 and 3 show the exhaust gas system in the production process of the above-mentioned potassium silicate fertilizer, and the same part as JIIK 1 shows the exhaust gas system.
Attach the code ・So0*j1ml and 3rd-, 19 is a cyclone dust collector, 20 is a heat exchanger, 21 is a denitrification device, 2
2 is a cooler, 23 is a cyclone dust collector, 24 is a dust collector,
25 indicates a chimney. The exhaust gas from the forming furnace 17 is sent to a cyclone dust collector 19 to separate and collect fine particles floating therein, and the O exhaust gas from the cyclone dust collector 19 is sent to a heat exchanger 20 and a denitrification device 21 for heat exchange and denitrification. conduct,
Subsequently, it is sent to the dryer IO and used as a drying heat source for the dryer 10. Some of it is also used to dry fine powdered stone. Exhaust gas from the dryer 10 is passed through the cyclone dust collector 23
The exhaust gas from the cyclone dust collector @ 23 is cooled with cold air from the cooler 22 and further sent to the dust collector 24r (for example, a wet dust collector is used as the collector 24). Further, fine vIL particles are collected separately and released into the atmosphere from the chimney 25.Also, a portion of the cold air from the cooler 22 is sent to the exhaust gas line to the dryer 10 to control the humidity of the exhaust gas to the dryer 10. By the way, as mentioned above, dry granules are heated in a firing furnace...
Potassium and silicon are sintered to obtain citric acid-soluble potassium silicate, which produces a large amount of nitrogen oxide Hog.

In general, a method of injecting ammonia NH3 is conventionally known as one of the methods for reducing nitrogen oxide NOx by 1. The present invention is a method for reducing nitrogen oxide NO
This ammonia MHI injection method is applied as a method for reducing
i! generated in the firing furnace (by injecting ammonia Mal into the top of the furnace at Is00). It has been found that the amount of I bulk oxide MOx can be significantly reduced.

Based on the experimental data shown below, Kamoto IAnows Confucianism! 1lK-Makisuru 0rei 4-The Takiki fl used in this experiment
altP011tlHt indicates s p body 30 o lower-B
A wind box 31 that injects air to form a fluidized bed is installed in the tc hull 9. At the bottom of the main body 300 of the reactor 300 there is a JI department population 32, and at a relatively lower part there is a wind box 31.
3, the upper 11 Ktj - road population 34, the top 11 is equipped with a 1st ss, ss that communicates with the furnace top blower 7, and the - mouth 35 is equipped with an inspection 3.%Ah. 1 indicates free board.

*The raw material weight and raw material weight shown in O value are shown below.
Conduct the experiment under the following conditions: 1I for the ζOgA experiment
De-II shown in X2#A and JI3 diagram! The II device was not activated and heat exchanged, and the exhaust gas was passed through the dryer.Fixed points in the experimental method section: ■Kiln outlet, ■Flue in front of the dryer burner (Figures 2 and 3) Reference) Experimental results (1) Windhox) IMs injection method (T@st
1, Te5t2) In the wind box MHI injection method, there was a tendency for Kaetsu-CNOx to increase during injection. This means that even if the temperature in the bed is 926~■・t, there is local combustion or raw material combustion where the actual firing temperature is 160・C or higher, or that the raw material has catalytic activity to oxidize MHI to NOz K. Therefore, the wind box 1iH1 injection method is not effective as a NOx reduction method.

(3) Freeboard NHa injection method (furnace top blowing fan ON state T/stl) When the furnace top blowing fan is ON at 7 am, the NOx reduction rate is 30-35%@H
It is certain that it is about the same level as when injecting a
It is considered that the reaction temperature for reducing 1 Ioz is low for t7O to 78@O.

(1) Freeboard MMs injection method (state of furnace top blowing fan OFF, d-t4) In the state of furnace top blowing fan OFF, the temperature rises to 79-+1-d1, and l--C NOx 11 Furnace top injection 7 An〇-state 110 o'clock) When the core increases and 9 is ζO, the NOx reduction rate is 40 to 801 (Mi bond? @I~1
＠＠＠4(1) Also, T・-t2. MHI injection amount (A/hr) and 12 at T・-13 tail・t4
0 which shows the relationship between IOX concentration If (ppm) in 1102 conversion and the relationship between MHI injection amount (j/kr) and NOx reduction rate. The inlet temperature in the case of Lumuken $ 81/hr injection is 0 (121
The relationship between yOx concentration (ppm) in i02 subtraction and the relationship between MHI injection f[(t/hr) and M1 reduction rate are shown.

From the table and FIGS. 5 and 6, it can be seen that injecting MHI at injection port temperature a (y9-board temperature a) SS.about.Gi.C is most effective in reducing 1iox.

[Brief explanation of the drawing]

Figure 1 is a flow sheet showing an example of the method for producing potassium silicate fertilizer according to the present invention, Figure M2 and Figure 3 are diagrams showing the exhaust gas M in the method for producing potassium silicate fertilizer shown in Figure 1, and Figure 4 is Cross-sectional view showing the outline of the forming furnace, Figures 5 and 11
FIG. 6 is a graph showing the results of an experiment carried out according to the present invention. l~4・Fist・Raw material tank 15・Mixture type 6・Supply tank 7・・Fist measuring meter 8・・Fist supply pong 9
...Mixer 10...Dryer 11...0 Burner for dryer 12--Sieving machine 13-...Crusher 14
... Φ feedback tank 15 ... cyclone 16 ... pack filter 17 - ... firing furnace 1
8... Starting burner for firing furnace 19, Φ, cyclone 20@-, heat exchanger 21 fist, @ denitrification device 2
2- @, Cooler 23...Cyclone 24*.
-Dust collector 25@・-m projection 31...Wind box 32・War・Raw material population 33@・Fired product outlet 149
... Flue inlet 35 ... Opening leading to furnace top blowing fan 36 ... Point window

Claims (1)

[Claims] A potassium source such as potassium hydroxide water **, a magnesium source such as fly ash, pulverized coal, and hydroxide V rim O are weighed and combined at a predetermined O, warm and heated to form nine trees and dried. This is made into granular 11 dried material, which is then fired to produce potassium silicate I! In the 11th passage to obtain the department,
Furnace O for firing granular 41 materials O furnace top 5oIL degree 850
At ~95OO, an amount of air was injected into the top of the furnace to reduce the amount of nitrogen oxides generated in the furnace. Method for reducing nitrogen oxides 0