JPS616106A - Method and apparatus for washing hemihydrate gypsum filter in manufacture of phosphoric acid by wet process - Google Patents

Abstract

PURPOSE:To prevent reduction in the concn. of phosphoric acid, to reutilize waste water after washing, and to improve a washing effect by continuously washing the filter cloth of a belt filter used in the manufacture of phosphoric acid by a wet process with a phosphoric acid soln. and misty washing water in order. CONSTITUTION:In the manufacture of phosphoric acid by a wet process, phosphate ore is decomposed with sulfuric acid or a mixed acid consisting of sulfuric acid and phosphoric acid, and the resulting slurry is filtered with a hemihydrate gyspum filter to separate and recover phosphoric acid. At this time, a belt filter 1 composed of a belt 2 and filter cloth 3 above the belt 2 is used as the hemihydrate gypsum filter. The belt 2 and the cloth 3 are moved together, and after filtering off hemihydrate gypsum, the cloth 3 is separated from the belt 2 at a lower position. The belt 2 and the cloth 3 are separately washed and circulated. The cloth 3 is washed from both front and rear sides with a phosphoric acid soln. spouted from slits cut in pipes 21, 21 for washing filter cloth in the longitudinal direction and openings pierced at both ends of the slits. The cloth 3 is then washed with a small amount of misty washing water from spray nozzle pipes 22, 22 for washing filter cloth. Waste liquor after washing is returned to the system through drip pans 8, 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning a gypsum hemihydrate filter in a wet phosphoric acid manufacturing method, which includes a step of separating hemihydrate 1'j', and a cleaning apparatus therefor.

Wet phosphoric acid production methods that include a step of filtering hemihydrate IT include a hemihydrate method and a hemiwater separation and trihydrite method.

In the hemihydrate method, scale ore is decomposed with sulfuric acid or a mixed acid of sulfuric acid and phosphoric acid to obtain a slurry of gypsum hemihydrate and phosphoric acid, and this is filtered through a gypsum hemihydrate filter to obtain a product of phosphorus 11? This is a method of extracting.

On the other hand, the main purpose of the hemihydrate method is to obtain high-θ degree phosphoric acid as well as high-quality by-product gypsum. In this method, the by-product stone 11 is obtained by summing the mixture and transferring it to dihydrate η, which is then filtered through a water gypsum filter.

In this half-water separation and three-water method, a traveling half-water gypsum filter or a horizontally rotating filter, etc., which is equipped with a cloth and moves to the next degree, is used as the half-water gypsum filter. However, in this filter, gypsum hemihydrate is transferred to dihydrate 1 on the P cloth, and as a result, gypsum scale is generated and grows, clogging the R cloth, or causing a hydration reaction on the pan. to form a block of industrial water gypsum,
There is a problem in that the cake becomes difficult to peel and over-operation becomes impossible.

In other words, for the transition reaction from hemihydrate 1r to dihydrate 1f,
Concentration of phosphoric acid and sulfuric acid in hemihydrate gypsum slurry! In general, the lower the acid concentration, the higher the sulfuric acid concentration, and the lower the temperature, the easier it is to transfer the slurry.Furthermore, if there is gypsum, it is possible to Transfer to gypsum tends to be accelerated, and once stone 1-scale occurs, it rapidly grows and consolidates.

For this reason, in the conventional method, the cloth is washed as much as possible, but because a traveling cloth or a horizontal rotating filter is used, the cloth is fixed and the cloth is washed from one side of the cloth. Moreover, many structures have a structure that makes it difficult to wash away the solid matter that has adhered to the door cloth with a cleaning solution.

Furthermore, in the conventional method, the filtrate of a gypsum filter or, in many cases, water is used as the washing liquid for the P cloth. However, it is said that 1 to 2 solids are generally present in the gypsum filter liquid, and if this is used as a cleaning liquid, it will supply gypsum kernels as described above, and gypsum scale is likely to occur.

Furthermore, when water is used to wash the cloth, the above-mentioned problems do not occur, but if the water used for washing is returned to Zorocess, the concentration of phosphoric acid in the product decreases, making it impossible to achieve the original purpose of obtaining high-concentration phosphoric acid.

On the other hand, if the water after washing is discharged from the system, the phosphoric acid yield will decrease. For this reason, some fabrics use warm water for washing the cloth, and also use as little amount as possible to prevent a decrease in the phosphoric acid yield and discharge the water after washing to the outside of the system. However, in this case, problems arise in wastewater treatment.

As described above, in the conventional hemihydrate separation method, it is difficult to effectively clean a hemihydrate gypsum filter without reducing the phosphoric acid concentration of the product. This also applies to the half-water method.

In view of these problems, the present inventors have developed a wet-type phosphoric acid production method that can clean gypsum hemihydrate filters without sacrificing the original purpose of obtaining high-concentration phosphoric acid, and that does not cause problems in wastewater treatment. We previously proposed a cleaning method and a cleaning device for hemihydrate filters in accordance with the Japanese Patent Application Laid-open No. 57-20
0211+j).

This method uses a belt filter as a gypsum hemihydrate filter, as shown in FIG. This belt filter 1 includes a belt 2 and a cloth 3, which are separated at the bottom of the filter and circulated separately.The filter cloth 3 is placed on the belt 2 at the top, and the filter cloth 3 is placed at the bottom. belt 2
It is separated and spaced from. Above and below the folded lower part of the p-cloth 3, 1 cloth cleaning senryu 4.5 and 1 cloth cleaning souffle nozzle 6 and 7 are arranged respectively. It's damp. The upper cloth washing gutter 4 has its opening located at the upper part, so that the phosphoric acid solution flows down from the top to the upper surface of the cloth 3. The opening of the lower cloth washing gutter 5 is
from which the acid solution is spouted onto the surface of the cloth 3. These f'J cloth washing gutter 4
At the bottom of the cloth washing area according to ゜5, there is a
is provided to collect the cleaning liquid, and the upper filter 1 cloth cleaning nozzle 6 is for P cloth 3Q! The washing water is sprayed towards the surface, and the bottom 1 fabric washing nozzle 7
is spraying cleaning water towards the surface of 1 cloth 3. A drip gun 9 is provided at the bottom of the area where one cloth is washed by the one cloth cleaning nozzle 6.7 to collect the cleaning liquid. Further, a spray nozzle 10 for cleaning the belt is provided at the bottom of the belt 2, from which cleaning water is sprayed toward the surface of the belt 2. A drip pipe 711 is provided at the bottom of the spray nozzle 10 to collect the cleaning liquid. Note that 12 in the figure is a pan that collects drippings of phosphoric acid on the P cloth.

However, in the method proposed earlier, by using the boric acid solution filtered through a semi-water filter to wash f1 cloth 2),
It is possible to prevent situations such as the occurrence of gypsum scale due to the presence of 6 nuclei of dihydrate η', and it also prevents the possibility that the acid concentration or the yield of 4j'1 acid may decrease as in the case of oxidation using water. do not have.

Furthermore, since the liquid after washing is returned to the system, there is no need for drainage treatment.

In addition, in the belt filter 1, since the belt 2 and the cloth 3 are separated from each other at the opposite side (11) of the filter 1, the e-cloth cleaning gutter 4.5 can be used to clean both sides of the -P cloth 2, improving the cleaning effect. There is an advantage.

However, as shown in FIG. 2, this 'fi cloth cleaning bath 4.5 has a structure in which slits 4g and 5a are provided in the longitudinal direction of the tube, and phosphoric acid solution is supplied from one end.

For this reason, the sludge in the cleaning solution a (for example, the solid content in the cleaning solution is about 5% by weight) is deposited in the gutters 4 and 5 in order from Ill A, and as a result, There is a problem that the liquid ejection port becomes uneven, and the sludge eventually accumulates and accumulates up to the proximal end side B, resulting in a cleaning rate of f1.

In the proposed method, water is ejected from the spray nozzles 6 and 7 only when the filter operation is stopped or in an emergency.
Solids remaining on the cloth are removed, and due to the water balance in the process, it is difficult to effectively wash the P cloth continuously with a small amount of water.

The present invention was made to solve such problems,
To provide a method for cleaning a gypsum filter in a wet type J14 acid production method and a cleaning percentage f'4 in which the cleaning liquid is always spouted uniformly and effective cleaning can be performed by continuously cleaning with a small amount of water. It is something to do.

That is, the first invention is to obtain a slurry of gypsum hemihydrate and phosphoric acid by decomposing phosphate rock with sulfuric acid or a mixed acid of (;4n and Hoehn), and then convert the gypsum hemihydrate and phosphoric acid in the slurry into gypsum hemihydrate and phosphoric acid. In a wet phosphoric acid manufacturing method in which filtration is performed using a gypsum filter, a belt filter is used as the hemihydrate gypsum filter, and one of the belt filters is
Wet type 4 pz〒 characterized by continuously washing the cloth with a phosphoric acid solution filtered through a belt filter and also continuously washing the filter cloth of the belt filter with a mist of washing water.
Is it the I-making method? 1) How to clean the filter.

1. The second filter has a cloth and a belt, and a belt filter in which the cloth in the upper part passes through the belt, and the filter cloth in the lower part circulates between the belt and the belt, and the lower part. P cloth cleaning pipes each arranged to spout a fluoric acid solution onto the filter cloth at the bottom, an F cloth cleaning nozzle pipe that jets a mist-like cleaning liquid onto the filter cloth at the bottom, and a cloth cleaning nozzle pipe arranged to spray a mist-like cleaning liquid onto the filter cloth at the bottom, and a pipe for cleaning the door cloth. The Δ1 fabric cleaning pipe is provided with a slit in its longitudinal direction, and both ends are opened in the spouting direction of the slit, and the fabric cleaning spray nozzle pipe is a mist jet that is complicated in its longitudinal direction (P
They are installed in parallel toward the right, and when the belt filter filters gypsum hemihydrate and phosphoric acid, phosphoric acid is continuously ejected from the P cloth cleaning pipe to perform the first stage cloth cleaning. This is a cleaning device for a gypsum hemihydrate filter in a wet phosphoric acid manufacturing method, in which a mist of cleaning water is spouted from a cloth cleaning spray nozzle pipe to perform a second stage of cleaning of one cloth.

The present invention will be described below with reference to embodiments shown in FIGS. 3 to 7.

The present invention provides a cloth cleaning side pipe 21.2 shown in FIG.
1, and R fabric cleaning spray nozzle pipes 22 and 22 shown in FIG. 5 are used in place of the P fabric cleaning streak nozzles 6 and 7. Note that the other structures in FIG. 3 are the same as those in FIG. 1, so the same reference numerals are given here and the explanation will be omitted.

As shown in FIG. 4, each of the cloth cleaning pipes 21 and 21 has a slit 23 (for example, a slit width of 5 to 8 cm) in the longitudinal direction, and both ends are made thinner. )2.9 Spout port 24.24 opened in the spout direction
The cleaning liquid is supplied from the center of the tube.

The r fabric cleaning streak nozzle pipes 22, 22 are the fifth
As shown in the figure, compressed gas such as compressed air (
or steam) and a cleaning water supply pipe 26 are connected, and a plurality of mist spray nozzles 27 are installed in the longitudinal direction.
are arranged in two rows in parallel facing the direction of the filter cloth 3, and these nozzles 27... are arranged so that a mist of washing water is spouted by the action of compressed gas.

Here, the phosphoric acid solution flowing into the r fabric washing pipe 21.21 is as follows:
It is supplied from a tank containing phosphoric acid as shown in FIG. 6 or 7. The filter shown in FIG. 6 is provided with a first seal tank 3 and a second seal tank 32 corresponding to the one-material filtration zone z1 and the cake r filtration zone z2 of the belt filter 1.
Pump 3 the phosphoric acid solution stored in the first sealed tank 3
3 is poured as a cleaning liquid 34 into the p-cloth cleaning pipe 21.21, and the f-cloth 3 is washed with this phosphoric acid solution.
will be returned to.

Further, the phosphoric acid solution in the first sealed tank 3 is sent by a pump 35 and used as circulating acid 36.

The phosphoric acid solution in the second sealed tank 32 is sent as a product acid 38 by a pump 37. The phosphoric acid solution in the second sealed tank 32 is designed to flow into the first sealed tank 31 when it overflows.

In the case shown in FIG. 5, the phosphoric acid solution in the first seal tank 31 is used only as the circulating acid 36 and is not used as a cleaning liquid, similar to the case in FIG. 4. 2nd seal tank 3
The first liquid (phosphoric acid solution) in 2 is pumped into cleaning liquid 3 by the pump 33.
4 is sent to the r-cloth washing pipe 21.21, and after washing the r-cloth 3, it is returned to the first seal tank 3 through the discharge nozzle 13. In addition, the phosphoric acid solution in the second seal tank 32 is
7 as product acid 38. Note that the r-material filtration zone z1 is a state in the initial stage of r-filtration in which no cake is formed on the shioko cloth 3, and the r-liquid contains some solid content. Further, the cake Ff passing zone z2 is a state in the latter stage of the r passing when a cake is formed on the f fabric 3, and the r liquid contains only a negligible solid content.

However, in the present invention, a slurry 41 of gypsum hemihydrate and phosphoric acid is filtered through a belt filter 1, and a gypsum hemihydrate cake 4 is separated by P.
2 is treated in a separate process, while the separated phosphoric acid solution is converted into product acid 3.
8. It is used as a circulating acid 36 and as a cleaning liquid. By using this phosphoric acid solution to clean the P cloth 3,
It is possible to prevent the occurrence of gypsum scale due to the presence of gypsum trihydrate nuclei, and there is no fear that the acid concentration of the product will decrease, unlike when water is used instead of phosphoric acid solution.

Furthermore, since the liquid after washing is returned to the system, there is no need for wastewater treatment.

In addition, in this device, in order to remove the solid content remaining attached to the filter cloth after peeling off the half-water cake, a phosphoric acid solution is spouted from the r-cloth cleaning side pipe 21 in the first stage of cleaning the filter cloth. No right angles are deposited on either side or one side of the Further, since the cleaning liquid is supplied from the center, the cleaning liquid is uniformly jetted from the spout ports 24 and 24. Because of this, the F cloth can always be cleaned uniformly without the accumulation of slazo, resulting in high cleaning performance.

Next, in the second stage of V-cloth cleaning, mist-like cleaning water is spouted from the r-cloth cleaning spray nozzle pipe 22.22 by the pressure of compressed gas. In this case, since the cleaning water is in the form of a mist, continuous cleaning can be performed using a small amount of cleaning water even during filter operation. Therefore, the F cloth can be effectively cleaned and the life of the P cloth can be extended. Furthermore, since the washing water is sent to the subsequent hydration process, there is no need for wastewater treatment equipment.
There is no loss of 2O5.

The belt 2 is cleaned using the belt cleaning spray nozzle pipe 22.
Spray with cleaning water.

In this case, it is sufficient to wash the belt intermittently, for example every 5 to 6 UV days, while the belt 2 rotates 2 to 3 times. The filtrate after washing is collected by a drip hook 711 so as not to mix with the f-liquid washing liquid, and returned to the hydration tank gutter. In this case, the amount of belt washing water is extremely small (about 0.5 to 1.0 m'/day in the above case) and its influence on the f process can be ignored.

If the filtrate in the first seal tank 3 is used as the cleaning liquid in the filter cloth cleaning pipes 21 and 21 of the filter cloth 3 as shown in FIG. Therefore, eight cleaning liquid values can be selected arbitrarily. However, since this liquid contains some solid matter, it is necessary to circulate a large amount of cleaning liquid.

If the filtrate from the second seal tank 32 is used as the washing liquid for the cleaning cloth 3, as shown in FIG. 7, the amount of liquid that can be used as the washing liquid will be determined by the gross conditions. . However, since this washing liquid is a filtrate from the cake f1 filtration zone, there is almost no solid content in the z-liquid. This/(can be cleaned well without using a large amount of cleaning liquid.

・ Nao-Sawafurai [4? Use pipe 21. The cleaning of the rli cloth 3 by the if' cloth cleaning nozzle pipe 22 is not limited to cleaning from both sides as in the embodiment, but may be performed from one side.

Next, the present invention was applied to produce high-concentration phosphoric acid and by-product gypsum using a half-water separation and three-water process. The manufacturing conditions and manufacturing results are shown below.

Manufacturing conditions (1) Phosphate rock brand Morocco B, P, L, 72 Particle size 100 mesh paas 95% or more (Tiller standard sieve) Composition P2O, 32,98% CaO50
,75965o31.63%F 3.82%
S t 02 1.69% Consumption 7.7TOru City (2) Sulfuric acid concentration H2S0490% Temperature 50℃ or less Consumption 4 TON/M (O890% sulfuric acid) (3) Gypsum hemihydrate slurry (supplied to gypsum hemihydrate filter Slurry flow rate: 30T/) I Slurry concentration: 30-35・Temperature: 80-85℃ (4) Semi-water filter operating conditions Effective area: 6 m2 Belt speed: 6-10 m/cloth cleaning pipe Diameter: 50 gates φ tube length
1300mm Tip opening 25mm φ Slit width 5' Slit length 1000ml Cloth cleaning nozzle pipe Tube length 1300FJ mouthpiece 20fin φ Nozzle diameter 2 barrels φ Nozzle spacing 10 Sieve φ Nozzle row spacing (2 rows) 10 φ 1 Cloth washing water amount 0.2 m/) lriP Cloth washing compression 35 kg/cm G air 4415~2
5 rn /) (R iF Fabric washing water%: (・mU, night) 1
5 to 25 m/) (r degree of vacuum -4
00 Hg hemihydrate]゛1 Cake liquid content 40
(5) Type slurry flow-k 240k17/Hr slurry concentration
15% (6) Stone) [slurry (slurry applied to gypsum filter) Flow rate 40T/Hr Slurry concentration 28-32% Temperature 55-60℃ (7) Gypsum filter operating conditions Effective r over area 9m2 Cake washing water amount 9.2 an /1 (r degree of vacuum
-400 Hg As a result, the product acid was P2O540%, H2So4
We were able to produce 60T/day of 2.5% concentration. In this case, the phosphoric acid yield was as high as 98.0-985%.

In addition, T-P2O50.4% or less (
drybase), W-P2O50, 28% or less (d
ry base), moisture content of 25% or less (wet base)
e) and high quality ones at 16,2 TON/Mr (w
et base) could be produced.

In this example, the water flow of the mist-like cleaning water is 02 to 0.3.
A sufficient cleaning effect was obtained at m/Hr. This amount is the amount of cake washing water in the gypsum filter (9 to 9.5
m'/Hr), the water balance of the entire system can be easily maintained by reducing the amount of cake washing water by 02 to 0.3 m, lHr.

Furthermore, by carrying out two-stage washing under the washing conditions as in the example, the life of one cloth was extended by two to three times (compared to the case where only the first stage was washed).

As explained above, according to the present invention, the shape of the fabric cleaning pipe is devised to prevent the accumulation of sludge, and the cleaning liquid, which is a phosphoric acid solution, can be constantly spouted uniformly. Since it squirts out water, continuous and efficient washing can be performed with a small amount of washing water, and it is also possible to easily maintain the water balance of the entire system and extend the life of one cloth.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the cleaning device for the hemihydrate gypsum filter proposed earlier, Fig. 2 is the front side of the filter cloth cleaning gutter of the same device, and Fig. 3 is a hemihydrate gypsum filter showing an embodiment of the present invention. An explanatory diagram of cleaning the filter, Figure 4 is the filter 1 of the same device! Ii is a front view of the cleaning tube, FIG. 5 is a front view of the cloth cleaning spray nozzle tube, and FIGS. , explanation showing the supply method for each different wash'<'jr F2! It is l. 1... Belt filter, 2... Belt, 3... f'' cloth, 4.5... f cloth cleaning gutter, 6 + 7... r spray nozzle for cloth cleaning, 8, 9, 11. 12... Drinopunokun, 10... Striped nozzle pipe for belt cleaning, 2
1...1 cloth cleaning pipe, 22...r spray nozzle pipe for cloth cleaning, 23...slit J-124...spout port,
25... Compressed gas supply pipe, 26... Washing water supply pipe,
27.l112 fog nozzle, 3...1st seal tank, 32...2nd seal tank, 33..., I? Pump 34...Cleaning liquid, 35...Pump, 36...Circulating acid, 37...? 38...Product acid, 4...Slurry, 42...Hemihydrate ↑r cake. Applicant/Agent Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 6 Figure 7

Claims (6)

[Claims] (1) Wet phosphoric acid method in which phosphate rock is decomposed with sulfuric acid or a mixed acid of sulfuric acid and phosphoric acid to obtain a slurry of gypsum hemihydrate and phosphoric acid, and then gypsum hemihydrate and phosphoric acid in the slurry are filtered out using a gypsum hemihydrate filter. In the manufacturing method, a belt filter is used for the above-mentioned gypsum hemihydrate filter, and at the time of filtration, the filter cloth of the belt filter is continuously washed with a phosphoric acid solution, and the filter cloth of the belt filter is continuously washed with a mist of washing water. A method for cleaning a hemihydrate gypsum filter in a wet phosphoric acid manufacturing method characterized by cleaning. (2) Gypsum hemihydrate in the wet phosphoric acid manufacturing method according to claim 1, characterized in that the phosphoric acid solution filtered in the filter medium filtration zone of the belt filter is used as the phosphoric acid solution for cleaning the filter cloth of the belt filter. How to clean the filter. (3) Gypsum hemihydrate in the wet phosphoric acid manufacturing method according to claim 1, characterized in that the phosphoric acid solution filtered in the cake filtration zone of the belt filter is used as the phosphoric acid solution for cleaning the filter cloth of the belt filter. How to clean the filter. (4) A belt filter that includes a filter cloth and a belt, in which the filter cloth moves on the belt at the top, and the filter cloth is separated from the belt at the bottom and circulates, and a filter cloth cleaning pipe that sprays a phosphoric acid solution onto the filter cloth at the bottom. and a filter cloth cleaning spray nozzle tube that sprays a mist-like cleaning liquid onto the filter cloth at the bottom, and a tank containing phosphoric acid connected to the filter cloth cleaning tube, and the filter cloth cleaning tube has a slit in its longitudinal direction. The filter cloth cleaning spray nozzle tube has a plurality of mist spray nozzles arranged in parallel toward the filter cloth in the longitudinal direction, and both ends are opened in the spouting direction of the slit. When gypsum and phosphoric acid are separated by filtration, phosphoric acid is continuously spouted from the filter cloth cleaning tube, and a mist of cleaning water is spouted from the cloth cleaning spray nozzle tube after the first stage of filter cloth cleaning. A cleaning device for a gypsum hemihydrate filter in a wet phosphoric acid production method, which performs a second stage of filter cloth cleaning. (5) As tanks containing phosphoric acid, a first tank containing phosphoric acid filtered in the filter media filtration zone of the belt filter and a second tank containing phosphoric acid filtered in the cake filtration zone of the belt filter are provided, and the phosphoric acid in the first tank is 5. A cleaning device for a gypsum hemihydrate filter in a wet phosphoric acid manufacturing method according to claim 4, wherein the solution is jetted out from a filter cloth cleaning pipe and returned to the first tank. (6) As tanks containing phosphoric acid, a first tank containing phosphoric acid filtered in the filter medium filtration zone of the belt filter and a second tank containing phosphoric acid filtered in the cake filtration zone of the belt filter are provided, and the phosphoric acid in the second tank is provided. 5. A cleaning device for a gypsum hemihydrate filter in a wet phosphoric acid manufacturing method according to claim 4, wherein the solution is jetted out from a filter cloth cleaning pipe and returned to the first tank.