JPS58167487A - Method of reducing generation of nitrogen oxide in kiln during manufacture of potassium silicate fertilizer from fly ash - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention uses fly ash as a raw material! ! Nitrogen oxide No. generated in the kiln during the production process of acid potassium fertilizer,
Relating to a method for reducing

Fly ash is a fine powder that floats in waste gas generated from pulverized coal combustion furnaces such as thermal power plants, is discharged together with the waste gas, and is mainly collected by electrostatic precipitators. This fly ash 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 600 ~
When fired at 100°C, potassium reacts with silicon in the fly ash, resulting in quench e11 soluble Ii! It becomes potassium acid and can be used as potassium diacid fertilizer.

The present applicant has already filed many patent applications and utility model registrations regarding the method for producing potassium diate fertilizer using fly ash as a raw material and the equipment used therefor. In the process of obtaining citric acid-soluble potassium silicate, raw materials are
! When firing at 100℃, a considerable amount of nitrogen oxide NO
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 eliminate nitrogen oxides (N) generated in the calcining furnace during the manufacturing process of potassium silicate fertilizer using fly ash as a raw material.
It is an object of the present invention to provide a method for reducing nitrogen oxides that can reduce Ox as much as possible.

First, an example of a method for producing potassium silicate fertilizer using fly ash as a raw material, which is carried out in the nitrogen oxide reduction method of the present invention, will be described with reference to the first FGL.

In FIG. 1, reference numerals 1 to 4 are storage tanks, in which potassium hydroxide aqueous solution (48 ml aqueous solution) 1, fly ash 2, pulverized coal 3, and magnesium hydroxide 4 are stored, respectively. 5&ma mixing tank, this mixing @
ISK potassium hydroxide aqueous solution (48 saliva solution) 1.7
744/kr, fly ash (moisture 0.4 yen) 2.4
u Ill/kr, pulverized coal (moisture 4 saliva) 410I
#/kr, and magnesium hydroxide (3 drops of water) 144
Add Kp/hr and mix. This mixture is.

The slurry is 4.776 p/hr (moisture 1 s*), so this slurry is then sent to the supply tank 6, and further pumped out at a rate of 4,776 h/hr by the slurry metering pump 8 and then transferred to the mixer 9. and sprayed on the nuclide that is fed back from the feedback tank 14, which will be described later. In this case, the amount of feedback from the feedback tank 14 is detected to control the amount of supply from the pump 8. The supply tank 6 is also equipped with a measuring device, which detects the amount of slurry in the supply tank 6, and when the slurry in the mixing ls decreases to a certain amount, new materials are added to the mixing tank 5 and mixed. conduct.

Blender 9 contains water in advance! The slurry supplied from the supply tank 6 is spray-coated onto the surface of the dry granular raw material to form new granules. 9 from the feedback tank 14 at the starting end of the mixer 9. , 5
s 211/hr (Introduce granular raw material with moisture level 1,
While stirring this raw material, a slurry of 4.776 b/hr is poured into it using the metering pump 8, and stirring is continued. Then, this slurry is coated on the surface of the granular raw material from the feedback tank 14, and the particles adhere to each other to form granular materials with a diameter of about 10 to 31 mm. Since the granular raw material from the feedback tank Kame 4 has been dried in advance and is porous as described below,
A part of the moisture contained in the slug IJ- permeates into the granular raw material side, and the average moisture content decreases to 7.234, resulting in particles suitable for granulation and drying.

Subsequently, 14,328 s/hr of this granular material was dried 1111
0° C., and blow hot air at about 400 to SUO° C. to dry it. As this hot air, hot air (←■0 to 1000°C) discharged from a firing furnace 17, which will be described later, is used.

Reference numeral 11 denotes a drying oil burner, which will be described in detail later, which reheats the kerosene and mixes the incompletely combusted gas with the hot air from the firing furnace 17.
By supplying the L imager, nitrogen oxide NOx can be reduced. Dry granules 13. Dry in dryer 10 to reduce moisture content. t58s/hr is pulverization from pulverizer 13 for $2
, 768m1 and transferred to the sieving machine 12 for 9.6 seconds.
s Kp/by ik is supplied, and the remaining 6,238 whips are led to the feedback tank t4 as unsieved portions <, m
The dry granules introduced into the fraction $1Ii2 are divided into - fractions, and those with a particle size of 4 m111/1' or larger2,7 e sKy/br
and particle size 1~41111〆3.875 Q/hr
, and those with a particle size of 1111m or less, 3,015b. Particles having a particle size of 4 or more are sent to the crusher 13 to be crushed and then mixed with the dry granules from the dryer IO and transported. Particles with a particle size of 1 ml 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 fine particles floating therein, and the exhaust gas is sent to an exhaust gas treatment facility (to be described later), and the fine particles 234 [p/hr] are charged into a hafeed back tank 14. The granules put into the feedback tank 14 are sent to the mixer 10 as granular raw materials as described above. The particles having a grain size of 1 to 4 wwap' separated by the separator 12 are sent to the kiln 17 and fired.

This kiln 17 can be of any known type, and since the particle size of the dried granules is set within the range of 1 to 4i*m, it is appropriate to use a fluidized bed kiln. Firing furnace 17K 3.87s! /hr of dry granules are charged and fired in the range of 100 to 1100°C.

(For starting at the start of operation) The temperature is raised to a predetermined temperature using the G-chie 18, and from then on, the pulverized coal in the ingredients becomes the fuel.

Under this temperature condition, the potassium and silicon in the granules react and turn into citric acid-soluble potassium silicate, and at the same time, the coal used as a fuel becomes carbon dioxide gas CO3 and evaporates from the granules. It becomes extremely porous and suitable as fertilizer.

The fired granules of 3,000 KF/kr are taken out as a product S, and the exhaust gas is used as a drying heat source for the dryer 10. Also, some of the exhaust gas is converted into pulverized coal through heat exchange? Use it for drying.

Figures 2 and 3 show the exhaust gas system in the production process of potassium silicate fertilizer, with the same parts as in Figure 1 being designated by the same reference numerals.In addition, in Figures 2 and 3, tS is a cyclone dust collector, 21 is a dust collector , chamber, 22 is *1LF1
A mixing chamber that mixes the hot air from 7 and the incompletely combusted gas produced by reheating the first Ilvana 1N for drying, 23 a cooler, 24 a cyclone dust collector, and 25 a dust collector.

26 indicates a chimney. The exhaust gas from the firing furnace 17 is sent to the cyclone collector 119 to separate and collect fine particles floating there, and the exhaust gas from the cyclone dust collector 19 is sent to the heat exchanger 2.
0, the dust is sent to the dust tank Z21 for heat exchange and dust collection, and then sent to the dryer 10 to be used as a drying heat source for the dryer IO.

Some of it is also used to dry pulverized coal.

The exhaust gas from the dryer 10 is sent to a cyclone collector 114 to separate and collect floating fine particles, and then to a cyclone dust collector 2.
The exhaust gas from 4 is cooled with cold air from a cooler 23 and further sent to a dust collector 25. As the dust collector 25, for example, a wet type collector is used to separate and collect finely rutted particles and release them into the atmosphere from a chimney 26. Also, some of the cold air from the cooler 23 lol
The exhaust gas to the tl dryer 10 is passed through a rail, and the temperature of the exhaust gas to the dryer 10 is adjusted.

By the way, as mentioned above, the dry granules f6 are
Calcination is performed in the range of 0G to 1100°C to react potassium and silicon to obtain citric acid-soluble potassium silicate, which produces a considerable amount of nitrogen oxide NOx.

The present invention was made to reduce this nitrogen oxide (NOx), and according to the present invention, granulated raw material? Before supplying the granules to the kiln and firing them, the dryer is equipped with an oil burner, which reheats the oil and mixes the incompletely combusted gas with the hot air from the kiln for drying. By supplying K to I11, the amount of nitrogen oxide NOx generated in the firing furnace is reduced. Further, according to the present invention, nitrogen oxide NOx is reduced by injecting ammonia N into the top (free gate) of the firing furnace.

Examples of the present invention will be described in detail based on the experimental data shown below. Fig. 4 shows an outline of the fluidized firing furnace used in this experiment. A wind box 31 is provided below the furnace body 3o to inject air into the furnace to form a fluidized bed. A raw material 32 is provided at the bottom, a fired product outlet 33 is provided relatively below, a flue port 34 is provided at the top, and an opening 35, 35 communicating with the furnace top blow fan is provided at the top. 35 is equipped with an inspection window 36.

F indicates free board.

The experiment was conducted under the raw material weight and raw material ratio shown in the above-mentioned values.

Nitrogen oxide NOx reduction test using kerosene.

The kerosene was reheated using a drying oil burner installed in the dryer, and mixed with hot air from the kiln, which is an incompletely combusted gas, and then supplied to the dryer. The drying temperature was 320-340°C. As a measuring device, the non-dispersive infrared absorption 2 Now
An 80B continuous analysis needle and a magnetic dumbbell O2 continuous analysis needle were used.

Figure 5 shows the relationship between the amount of injected air and the concentration of NOx (ppnaL and denitrification rate) when the amount of kerosene is set constant. is the denitrification rate at that time -), and solid line B is the amount of kerosene 2*lA
In this case, the dotted line 1 indicates the denitrification rate S) at that time, and the fixed point Ill is the chimney ■ (see Fig. 3).

In addition, when kerosene is not reheated (BI・), N (h
It was 40 pp ugly.

As can be seen from this graph, when K and the amount of kerosene are set constant and the amount of injection air is increased, the nitrogen oxides Now decreases.

Figure 6 shows kerosene 211/h, injection air 3t ON i+
The concentration of NOx at each point from the firing furnace outlet to the chimney when the drying oil bar is added to l'.
ppm) and denitrification rate Sl&.

In addition, ■ or ■ indicates the measurement point, ■ indicates the firing furnace outlet, and ■
is the heat exchanger inlet, ■ is the dust chamber inlet, ■ is the mixing chamber inlet, ■ is the dryer inlet 5 ■ is the dryer outlet,
■ indicates the dust collector inlet, ■ indicates the chimney, and ■ indicates the drying oil burner (see Figure 3).

No reduction in NOx other than near leakage was observed from the kiln outlet ■ to the mixing chamber ■, but a reduction in NOx was observed between the dryer outlet ■ and the chimney ■. According to this experiment, the distance between the firing furnace outlet ■ and the chimney ■ is approximately 3.
01NOx decreased.

Ammonia, 8dH, nitrogen oxide NOx by injection method
A test for reducing NH was carried out by injecting NH into the firing furnace under the following conditions.

■ is the firing furnace exit, G5 is the flue experiment result in front of the dryer (1) Wind box N11ls injection method (Tes
tt, Te5t2) In the wind box NB, injection method, it has been demonstrated that there is local combustion or raw material combustion at a temperature of 1000°C or higher during injection, or that the raw material has catalytic activity to oxidize to NH, t' NCkt. Therefore, the wind box NH1 injection method is not effective as a NOx reduction method.

(z) Freeboard NM, Injection method (Furnace top blower fan ON state, T @ Hatakets) When the furnace top blower 7 fan is ON, the temperature of freeboard F is 770 to 710℃ and the NOx reduction rate is 30 to 30℃. 35'1 (
It was confirmed that the temperature was Ii degree (NH@"e l OOe l/hr injection). At F7.~1 s.°C, it is considered to be low for a single reaction to reduce NOx.

(3) Freeboard 1 is also an injection method (furnace top blowing fan
Status of ff@s T@l t 4) Furnace top blow fan・
In the state of ff, the temperature of freeboard F rises to 8!
The temperature ranged from 50 to 950°C, and NOx increased slightly compared to when the furnace top blower fan OA was used.

At this time, the NOx reduction rate was 4240~@0 (Nu, ?7
00-L 00044r).

The table below summarizes the experimental results of T@st3 and ding/st4, and also shows the experimental results of T@st3 and ding/st4.
and Te5t4, )III, injection volume (4/&r
) and the NOx concentration (ppm) converted to 12 saliva, and the relationship between the NH injection amount (lAr) and the NOx reduction rate. Case Mu and NH.

When injecting 1050^r, the inlet temperature in BK (freeboard temperature in °C) and the breath rate of 0. Relationship with N□x concentration (tP) in conversion and NH, injection amount (l/hr)
The relationship between and the Nox reduction rate is shown.

From the table and FIG. 7, S@, it can be seen that it is most effective in reducing NOx when NH is injected at an inlet temperature of 850 to 1150° C. ()IJ - board temperature "C).

[Brief explanation of the drawing]

FIG. 1-4...Raw material tank 5...Mixing-6...Supply tank 7...Measuring meter 8...Supply pump
9...Mixer 10...Dryer 11...Burner for dryer 12...Sieving machine 13...Powder 1Nll
14... Feedback tank 15...
Cyclone 16... Pack filter 17...
・Firing furnace 18... Starting burner for firing furnace 19・
...Cyclone 20...Heat exchanger 21...
Dust channel 22...Mixing channel (23...Cooler 24...Cyclone 25...
・Dust collector 26... Chimney 31... Wind box 32... Raw material population 33... Fired product outlet 14°... Flue population 35... Opening leading to furnace top blowing fan 36... Inspection window.

Claims (1)

[Claims] (1) A potassium source such as an aqueous potassium hydroxide solution,
Magnesium sources such as fly ash, pulverized coal, and magnesium hydroxide are weighed and mixed in predetermined proportions, granulated into a mixed slurry granule, and dried in a dryer to form a dry granule. In this method for producing potassium silicate fertilizer obtained by firing dry granular materials in a firing furnace, an oil burner is provided in the dryer that uses hot air discharged from the firing furnace as a heat source, and the oil burner burns oil. To reduce the amount of nitrogen oxides generated in the kiln by 1000 tt, than by using a horsefly to blow hot air from the kiln that is incompletely burned. ! A method for reducing nitrogen oxides generated in a firing furnace during the manufacturing process of potassium silicate fertilizer using fly ash raw material as fa. (3) A potassium source such as potassium hydroxide aqueous solution, fly ash, pulverized coal, and A magnesium source such as magnesium hydroxide is weighed and mixed in a predetermined ratio, the mixed slurry is granulated, the granules are dried in a dryer to form dry granules, and the dry granules are fired. In the method for producing potassium silicate fertilizer in which potassium silicate fertilizer is obtained by firing in a furnace, ammonia is injected into the top of the furnace at a temperature of ISO to 950°C, and hot air discharged from the furnace is used as a heat source. 4111 refers to installing an oil burner in the dryer and reheating the oil with the oil burner and mixing the incompletely burned scalpel with the hot air from the kiln to reduce nitrogen oxides generated in the kiln. 7: Method for reducing nitrogen oxides generated in the kiln during production of potash fertilizer using fire ash as raw material.