JPS61281005A - Production of phosphoric acid for fertilizer - Google Patents

Abstract

PURPOSE:To industrially and advantageously treat a process waste liquor discharged from a process for producing methacrylic acid or methyl methacrylate by the acetone cyanhydrin method, by treating the above-mentioned waste liquor to reduce the COD value, and utilizing the resultant waste liquor as part of an acid for decomposing rock phosphate. CONSTITUTION:Methacrylic acid or methyl methacrylate is produced by the acetone cyanhydrin method. In the process, a waste liquor (1) discharged from an esterification tank or hydrolysis tank is cooled to remove scum. The resultant waste liquor (2) is then subjected to a distillation step. For example, the waste liquor (2) is subjected to steam distillation at about 110-150 deg.C, and the bottoms are cooled to <=100 deg.C to remove floating organic materials and give a treated waste liquor (3) having <=25g/l (measured by the Mn method at 100 deg.C) COD, which is then used as part of an acid for decomposing rock phosphate in the wet process for producing phosphoric acid. The above-mentioned waste liquor (1) contains 44-54% acid ammonium sulfate, 14-20% sulfuric acid, 25-35% water and further several % organic materials and exhibits 30-50g/l COD value.

Description

[Detailed Description of the Invention] [Industrial Application Field] When producing methyl methacrylate or methacrylic acid by the uninvented acetone cyanohydrin method, waste liquid (1) discharged from an esterification tank or a hydrolysis tank is The COD concentration (hereinafter referred to as C
The present invention relates to a method for producing phosphoric acid for gypsum and fertilizer, in which a treated waste liquid (3) whose OD concentration (OD concentration is the Mn method, value at 100° C.) is lowered to 2597 or less is used as part of the decomposition acid.

[Conventional technology]

Methyl methacrylate (methacrylic acid) can be obtained as K by diamidating acetone cyanohydrin with concentrated sulfuric acid and then esterifying (hydrolyzing) it with methanol (water). In this esterification (hydrolysis) tank, crude methyl methacrylate (hereinafter referred to as waste liquid) is converted into amine-P by using an excessive amount of concentrated sulfuric acid. The amount of waste liquid discharged is a large amount, about 2 to 3 tons per 1 ton of methyl methacrylate product.This waste liquid contains large amounts of sulfuric acid and acidic ammonium sulfate, so conventionally this was burned to convert into SOI. Methods have been proposed to recover the sulfuric acid after that, (1) to react with lime and recover it as gypsum, (2) to neutralize it with ammonia and recover it as ammonium sulfate (ammonium sulfate). However, method (2) cannot be effectively recovered, and requires a large amount of operating cost.

In method (2), the organic components contained in the waste liquid cause precipitation of gypsum crystals, poor growth, and the generation of a bad odor. Additionally, there are also difficulties in disposing of by-product ammonia.

Method (2) is the simplest method, but like (2), it has problems in that it produces a bad odor due to organic impurities, degrades the quality of ammonium sulfate, and produces a large amount of ammonium sulfate, which already tends to have little industrial value today. Although an effective method for treating the waste liquid discharged from the methyl methacrylate manufacturing process has been desired, no satisfactory method has yet been established.

On the other hand 1. After producing gypsum hemihydrate from phosphate rock and sulfuric acid,
In a wet phosphoric acid production method for producing gypsum dihydrate and phosphoric acid, a method has been proposed in which sulfuric acid containing ammonium sulfate is used as a decomposition acid and the reaction is carried out in two stages, but this method is industrially advantageous. Atb is not known about. If the waste liquid that is the object of the present invention is used as it is as a part of decomposed sulfuric acid, the organic components in the waste liquid, especially polyester-like substances, will contaminate the phosphoric acid production process and cause blockages, and the gypsum and phosphoric acid produced will It is undesirable because it is contaminated with organic substances.

Furthermore, a large amount of COD-loaded components are discharged into the wastewater from the phosphoric acid production process, which poses a problem from the standpoint of pollution prevention.

[Problem that the invention seeks to solve]

As a result of repeated studies on industrially advantageous treatment methods for the waste liquid discharged from the methyl methacrylate manufacturing process, the present inventors found that the treated waste liquid (3 ) [hereinafter referred to as treated waste liquid],
By using it as part of the decomposition acid in the wet phosphoric acid production method, it is possible to produce high-quality gypsum and ammonium phosphate (ammonium phosphate) without causing any trouble in the phosphoric acid production process due to ammonium sulfate or organic impurities in the waste liquid. ) It was discovered that it is possible to produce phosphoric acid for fertilizer containing the following, leading to the present invention.

[Means for solving problems]

The waste liquid used in the present invention is acidic ammonium sulfate = +7A
44-54%, sulfuric acid 14-20%, water 25-35% (
In addition to ammonium sulfate (expressed in sulfuric acid equivalent composition: 25-31% ammonium sulfate, 31-44% sulfuric acid, 25-35% water), it also contains several organic substances, and exhibits a COO value of 30-501/l. These organic substances include acetone, methanol, methacrylic acid, methyl methacrylate, dimethyl ether, α-hydroxyinbutyric acid, methyl α-hydroxyinobutyrate, methyl sulfate, and many other unidentified organic compounds and polymers. include. Among these organic substances, acetone, methanol,
Low-boiling components such as methyl methacrylate and dimethyl ether are discharged into the waste water in the phosphoric acid production process, and therefore cause an increase in the COO value of the waste water. However, the content of the above-mentioned low boiling point components in the waste liquid is only about 1 to 2 inches, and it is very difficult to remove them almost completely by mere distillation. In addition, some dimethyl sulfates and other organic compounds that have been identified as fine powders liberate methanol and acetone when heated and evaporated, resulting in CO in the phosphoric acid manufacturing process.
D negative! It becomes a new source of pollutants and causes contamination of wastewater. The method of evaporating these COD load-causing substances from the waste liquid together with water causes concentration of the bottom liquid, and there is a risk of precipitation of acidic ammonium sulfate crystals, making transportation to the phosphate rock decomposition process complicated.

According to the studies of the present inventors, for example, the waste liquid is
After steam distillation at 50°C, the canned liquid was cooled to below 100°C to remove suspended organic matter, resulting in a COD concentration of 2.
It was found that scum was formed when 51/ was used as the following treated waste liquid.

The method for producing wet phosphoric acid using the treated waste liquid of the present invention as a part of decomposition acid involves reacting phosphate rock and decomposition acid under conditions for producing gypsum hemihydrate, and then producing phosphoric acid and gypsum hemihydrate. This can be carried out by maintaining dihydrate gypsum under stable conditions in a hydration tank and filtering out the generated dihydrate gypsum and phosphoric acid.

In addition to being decomposed into gypsum and phosphoric acid through a normal decomposition reaction with sulfuric acid, phosphate rock undergoes an apparent volumetric decomposition reaction with acidic ammonium sulfate contained in the treated waste liquid, and is decomposed into gypsum and ammonium phosphorus. In this way, all of the ammonium and sulfate radicals in the treated waste liquid can be converted into useful substances.

The amount of treated waste liquid used as part of the decomposition acid is determined by the Durham atomic ratio (N/P) of nitrogen in the treated waste liquid to phosphorus in the phosphate ore.
) is 0.5 or less, preferably 0.3 or less. If N/P is 0.5 or more, the r-permeability of gypsum is inhibited by organic substances, and ammonium phosphoric acid crystals are precipitated in the step of concentrating the produced crude phosphoric acid, which is not preferable. Although the treated waste liquid can be directly supplied to the phosphate rock decomposition tank, it is preferable to mix it with sulfuric acid and/or circulating phosphoric acid before use. The production of hemihydrate gypsum through the decomposition of phosphate rock and the subsequent production of dihydrate gypsum through water utilization reactions can be carried out according to conventional methods.

〔Example〕

Next, the present invention will be specifically explained with reference to examples.〇Example 1 A waste liquid containing sulfuric acid and acidic ammonium sulfate discharged from the manufacturing process of methyl methacrylate and methacrylic acid was cooled for 80 to 100'CK to form a floating ring. The liquid from which the Hg5Oi 19
．． 3% HtO26.5% Organic impurities, other 2
．． 91 COD low boiling point backload 3 P/t
, a high-boiling material load of 13.2 f/t) was obtained.

Powdered sinterite from Morocco (ptos 33.6%)
.

Ca0 49.1%, particle size 100 mesh or less 75
~77ch) was continuously supplied at 3.0 Kf/H to each contents & 12t decomposition tank connected in series, and at the same time,
Processed waste liquid 0.31 odor/H, 98 sulfuric acid 2.54 KJI
/H, and circulating fluid (P, 0.21.5% HtSo.

3.4chi Ammonia nitrogen 0.4 1(,Q 68
．． 6%)tx, 65Kf/H was supplied, and phosphate rock fractionation was carried out at 97-99°C.

The slurry-containing decomposition liquid discharged from the decomposition tank is led to two hydration tanks connected in series, each with an internal volume of 150 tons, and heated to 67 to 71'C.
hydrated with The generated gypsum is passed through and washed with water to obtain dihydrate gypsum (moisture 13.5%, degree of hydration 1, s 2 ) 5.4
Kg/Ht obtained 4bK, phosphoric acid solution (Pt
Os2s, s%, H, 5o44.6%, ammonia nitrogen 0.6%, Hg057.8%) were obtained. Of the obtained phosphoric acid solution, 3.45 kg/H was extracted as a crude phosphoric acid solution, and the remaining phosphoric acid solution was mixed with gypsum washing water and recycled to the decomposition tank.

Here, the decomposition rate of phosphate rock was calculated to be 98.5%.

Example 2 Processed waste liquid (NH4HS 04
46.8tsSH2SO416.8%, H,033.8
%, other organic impurities 2.6%, COD low boiling point material load 4.2 t/l, high boiling point material load 12.0 f/l
t) was obtained. Next, salt ore 3.0Kq/H, treated waste liquid 1.00% 4/H, 98thiosulfuric acid 2.16Ky/H and circulating fluid (P, 0.23.2CH, H, So, 3.6
%, ammonia nitrogen 1.4 t, H, 064, 6 t) 1
4.53Ky/H, gypsum (moisture 13.0%, degree of hydration 1.85), 5.3Ky/H and crude phosphoric acid solution (Pt
Os 28.4 Chi, H, So.

The decomposition rate of phosphate rock was 98.2chi.

Example 3 In the same manner as in Example 1, treated waste liquid (Nl(, H80°4
9.4chi, HzSOa 18.6%, H,029.2%
, organic impurities, other 2.8%, COD low-boiling material loading 4.5 f/t, high-boiling material loading 12.9 r
/t) was obtained. Next VC#) ore 3.0Kf/)
I, treated waste liquid 1.59 odor/H, 98 sulfuric acid 1.75 odor/
H and circulating fluid (P, 0 @ 22.8 t, l(t S
Oa 3.2 h, ammonia nitrogen 2.3 h, H,0
64,0%) t 2.63Kg/H, gypsum (moisture 13.4%, degree of hydration 1.84) 5.4Kf/
H and crude cynic acid solution (PtOs 28.6H, HtS
o, 4. o%, ammonia nitrogen 2.8%, H,0
55.0chi) 3.49Kf/H was obtained.

The decomposition rate of phosphate rock was 98.7%.

Comparative Example 1 An untreated waste solution (NH, H80, 49°8% , HJO417, 2chi,
H, 028,9%, organic impurities, other 4.1%, CO
D Low boiling point backload 1.2 r/1. In the same manner as in Example 1, using a high-boiling point backload of 19°4r7z), the salt ore 3. OK4/I(.

Untreated waste liquid 0.95 odors/H, 98% sulfuric acid 2.17 odors/H and circulating fluid (Pto@21.7 H, So.

3.3%, ammonia nitrogen 1.3%, H,Q 66.
7%) t4.04 to supply 9/H, plaster (moisture 20.
8%, degree of hydration 1.85) 5.9 disorders/H and crude citric acid solution (P*0s28.3%, H*5O44°3, ammonia nitrogen 1.7h, H,056°5 %) 3゜51Kg
/H was obtained.

Although the decomposition rate of sinterite was 98.3%, organic impurities were mixed into the gypsum, resulting in poor filterability and an increase in the COD value of process wastewater.

〔effect〕

Claims (1)

[Claims] 1) After reacting phosphate rock with a decomposing acid, mainly sulfuric acid, under the conditions for producing gypsum hemihydrate to produce phosphoric acid and gypsum hemihydrate, react in a hydration tank under conditions where gypsum dihydrate is stable. In this method, waste liquid discharged from an esterification tank or a hydrolysis tank (1 ) is cooled and the dregs removed (2), which is then subjected to a distillation process to remove floating organic substances from the bottom liquid again and reduce the COD concentration (Mn method, 100°C) to 2.
A method for producing phosphoric acid for gypsum and fertilizer, characterized in that treated waste liquid (3) whose concentration has been reduced to 5 g/l or less is used as part of the decomposition acid.