CN1603230A

CN1603230A - Method for preparing phosphoric acid and by-product cement by thermal decomposition

Info

Publication number: CN1603230A
Application number: CNA2004100854408A
Authority: CN
Inventors: 李兴德
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-10-07
Filing date: 2004-10-07
Publication date: 2005-04-06

Abstract

The invention relates to a more than 85% industry phosphoric acid product that is made from cooling and absorbing decomposing furnace gas, which is from the thermal decomposition of compound of the reaction of phosphate rock powder and concentrated sulfuric acid. And the dregs after thermal decomposition is added with kaolin and carbon powder, then, calcinating and reacting, thus Sulfur-Aluminum-Ballit concrete would be available. The quality of phosphoric acid the invention used is conformed to the index of GB2091-92. The quality of concrete reaches to 400 grade. It has the advantages of low cost, great output, high quality, low energy consumption, no pollution and the utilization rate of mine resource could reach to 99%. The profit margin of phosphoric acid product is about 38%, and the profit margin of concrete product could reach to 35%. It is suited both new phosphoric acid factory and concrete factory.

Description

Method for preparing phosphoric acid and by-product cement by thermal decomposition method

The technical field is as follows: the invention relates to a novel chemical process method for preparing industrial phosphoric acid and by-producing cement by taking powdered rock phosphate and concentrated sulfuric acid as raw materials.

Secondly, background art: the prior process for preparing phosphoric acid at home and abroad comprises the following steps: A. preparing phosphoric acid by an electric furnace yellow phosphorus thermal method: the phosphoric acid is prepared by burning and oxidizing yellow phosphorus and air and combining the yellow phosphorus and the air with water. B. Wet-process phosphoric acid preparation: the phosphate rock powder is reacted with dilute inorganic acid (such as sulfuric acid and hydrochloric acid) to generate a mixed slurry of phosphoric acid aqueous solution and phosphogypsum, the slurry is washed and filtered, the filtrate is 30-40% of dilute phosphoric acid, and the filter cake is waste residue phosphogypsum. C. The patent No. 931114470 of research institute of Long Sand mining and metallurgy in the department of metallurgy industry discloses a method for producing phosphoric acid by directly reducing phosphate ore. The method is that phosphate rock powder, silica powder and carbon powder are mixed in a certain proportion and pelletized twice, and reacted at high temperature, and the reaction furnace gas is hydrated to form phosphoric acid.

The invention aims to overcome the defects of the existing phosphoric acid production method, utilizes the exothermic reaction of concentrated sulfuric acid and powdered rock phosphate to remove fluoride impurities in the phosphoric acid and thermally decompose the reaction materials into pure P₂O₅Separating gas from solid residue; cooling with dilute phosphoric acid solutionI.e. absorption of P after decomposition₂O₅And (5) gas, so as to obtain a high-purity phosphoric acid product. Adding kaolin (or mixed mineral of aluminum, silicon and iron) and carbon powder into the decomposed solid residue, and performing reduction reaction in a calcining kiln to obtain the sulpho-aluminosilicate cement clinker. The calcining furnace gas is washed and absorbed by soda water solution to obtain sodium sulfite water solution for reacting the fluorine waste gasWashing and absorbing to obtain sodium fluosilicate by-product. The waste liquid after recovering the sodium fluosilicate product is mixed with part of dilute phosphoric acid solution and then is used for diluting concentrated sulfuric acid.

Compared with the hot phosphoric acid, the method can save about 80 percent of electric energy, can reduce about 40 percent of the production cost of the phosphoric acid, and does not generate three wastes (8-10 tons of waste residues and 60m of waste water are generated by each ton of yellow phosphorus)³). Compared with wet phosphoric acid, the method overcomes the defects of difficult filtration, more impurities and low concentration of the wet method, and can reduce the production cost by 30 percent (the production cost is converted into H content₃PO₄85 percent) of the total phosphorus content in the phosphorus ore, can improve the P content in the phosphorus ore₂O₅The utilization rate of the method is about 6%, the production efficiency is improved by 3 times, the labor intensity is reduced by 2 times, the amount of waste residues can be reduced by 3-4 tons, the amount of waste water is reduced by 2-3 tons, and the method has the characteristics that the concentration of phosphoric acid can reach more than 85% (the concentration of a wet method is 30-45%), the quality is excellent (the acid of the wet method contains a large amount of chemical and physical impurities, and the quality of the phosphoric acid meets the national standard GB 2091-92), the investment is saved, the process is simple, and the yield is high. Compared with the method of the 931114470 patent: the method has the advantages of low decomposition reaction temperature, high reaction speed, production efficiency improved by more than 3 times, great reduction of industrial implementation difficulty, and improvement of the utilization rate of P2O5 in the phosphorite by about 20% (the reduction rate of the 931114470 method is about 80%). The generation of solid waste residues is avoided (about 3 tons of waste residues are generated per ton of standard acid in the 931114470 method). In conclusion, the method disclosed by the invention has strong advantages in the aspects of energy conservation, environmental protection, investment, cost and benefit, and full and effective utilization of mineral resources.

Thirdly, the invention content: the method comprises the steps of adding sulfuric acid with the content of 70-95% and ground phosphate rock into a stirring reactor according to a certain proportion for reaction, and controlling the content of free sulfuric acid in the reacted material to be 0.5-3%. The reaction releases heat to raise the temperature of the material to 100-200 ℃, and the reaction is carried outThe generated fluorine-containing waste gas is pumped into a washing absorption tower by a waste gas suction pump and is absorbed by sodium sulfite aqueous solution to obtain a byproduct sodium fluosilicate. And mixing the waste liquid after recovering the sodium fluosilicate with a part of dilute phosphoric acid liquid for preparing concentrated sulfuric acid for recycling. Adding residues after thermal decomposition into the materials after reaction, wherein the residues are 2-4 times of the materials, returning, stirring and mixing, so that the viscosity of the mixed materials is reduced, and the materials are favorable for thermal decomposition reaction and do not stick to walls. Feeding the mixed materials into a rotary kiln for thermal decomposition reaction at 300-1000 ℃, controlling the retention time of the materials in the decomposition kiln to be 20-60 minutes, and performing thermal decomposition on the materials to obtain P in decomposed residues₂O₅The content is preferably less than or equal to 0.5 percent, the decomposing furnace gas is sent to a hydration absorption tower after cyclone dust removal, diluted phosphoric acid solution is used for circulating cooling absorption, when the circulating phosphoric acid content reaches more than 87 percent, the circulating phosphoric acid solution is pumped into a finished product phosphoric acid storage pool for static sedimentation, and the finished product phosphoric acid product is obtained after inspection and packaging. Part of the residue after the thermal decomposition reaction is used as a returning material and a material-feeding mixing process as a viscosity reducing material, and the rest is used as a cement ingredient. The cement ingredient ratio is (all calculated by dry basis weight ratio), residue after decomposition: 70-80% of kaolin (or a mixed mineral of aluminum, silicon and iron): 15-25%; carbon powder: 2.5 to 4 percent. Grinding the well-mixed cement materials into powder of 100-200 meshes, and carrying out reduction calcination in a rotary calcining kiln at 1250-1350 ℃, wherein the retention time of the materials in the kiln is controlled to be 60-120 minutes. The calcined material is cooled and ground to a pass rate of 80% of 320 meshes, and the by-product cement is obtained after weighing, packaging and curing. The furnace gas of the calcination reaction contains SO₂4-10% of raw material gas for sulfuric acid production, or sodium sulfite liquid obtained by washing and absorbing with soda ash aqueous solution for washing and absorbing waste fluorine gas.

The chemical reaction equation is as follows:

1. reaction of powdered rock phosphate with concentrated sulfuric acid:

2. hydrogen fluoride and SiO in phosphate ore₂Reaction:

3. reaction of silicon tetrafluoride with aqueous sodium sulfite solution:

4. thermal decomposition reaction of phosphoric acid:

5. decomposition of P in gas₂O₅Reaction in a cooled absorber:

6. the main chemical components of the byproduct cement are as follows:

SiO₂：11.5～21.5％；Al₂O₃：5～10.5％；Fe₂O₃：0.8～2.5％

and CaO total: 30-50%; SO (SO)₃：6.5～40％；P₂O₅≤0.5％。

7. The strength of the cement can reach 35-39 MPa, which is equivalent to the strength of No. 400 quick-hardening cement.

8. Quality of phosphoric acid product: containing H₃PO₄Not less than 85 percent, and the impurity index accords with the national standard.

The process flow diagram of the method of the invention is shown in the attached drawing of the specification.

Fourth, the embodiment: the main equipment used for implementing the method of the invention is as follows:

1. ground phosphate rock feeder: 3-10 kg/min (adjustable); one, carrying out the following steps;

2. one sulfuric acid storage tank; 8m³。

3. A sulfuric acid blending tank: one, 5m³。

4. A sulfuric acid metering pump: and 5-20 kg/min (adjustable).

5. Sealing the double-helix stirrer: the length is 1.5m, the width is 0.46m, and one set of reaction and one set of mixing materials are adopted.

6. A rotary calcining kiln: phi inner diameter is 0.8m multiplied by 15m long; two sets, one set is decomposed and the other set is calcined.

7. Exhaust gas suction treatment device: two sets of reaction waste gas and calcination waste gas are used respectively.

8. Phosphoric acid cooling absorption tower: phi 0.4m by 5m high, two are used in series.

9. One set of decomposed gas suction device.

10. Storage tanks, valves, pipelines, temperature testing, displaying, electrical appliances and the like.

B. Preparing materials:

1. phosphate rock: the ore of Kunyang phosphorite in Yunnan province is adopted, and the main component content is as follows: p₂O₅：33.41％；CaO：46.65％；SiO₂: 10.48 percent, and grinding the ore by Raymond mill until the passing rate of the ore with 150 meshes reaches 80 percent for later use.

2. Sulfuric acid: purchasing 98% concentrated sulfuric acid, diluting with diluted phosphoric acid and waste liquid after recovering sodium fluosilicate until it contains H₂SO₄80% later for standby.

3. Soda ash: purchased Na-containing₂CO₃98 percent of the waste gas is dissolved into 25 percent of the waste gas by water and used for washing and absorbing the waste gas.

4. Kaolin: drying until the water content is less than or equal to 1 percent, and then crushing until the passing rate of 100 meshes is more than or equalto 80 percent.

C. The production operation control method comprises the following steps:

firstly, the powdered rock phosphate and sulfuric acid (containing H) are regulated₂SO₄80 percent) is as follows: 1: 1.16, (after a small test, the free sulfuric acid content in the material after completion of the reaction was 1.2%). The charging speed of the phosphate rock powder is adjusted as follows: 5 kg/min, and adjusting the feeding speed of the sulfuric acid as follows: 5.8 kg/min, so that the ground phosphate rock charging switch is linked with the sulfuric acid charging switch. And after checking that other equipment can normally operate, the production can be carried out. Starting the waste gas suction device, starting the stirring reactor, starting the mineral powder and the sulfuric acid feeding device, and simultaneously adding the mineral powder and the sulfuric acid into the double-helix stirring reactor at constant amount. Then theStarting the double-helix mixer, and simultaneously feeding reaction materials and residue returning materials with the material amount being 3 times of that of the reaction materials into the mixer. The mixed material is semi-dry and has low viscosity. And continuously feeding the mixed materials into a thermal decomposition rotary kiln for thermal decomposition reaction. The decomposition kiln uses pulverized bituminous coal and hot air as fuel to heat up, and the temperature of a combustion section of the thermal decomposition kiln is controlled in advance as follows: 800-1000 ℃, and the temperature of the kiln tail is as follows: the material can be added at the temperature of 300-600 ℃. The material is added from the end of the kiln tail, the residue is discharged from the heating end of the kiln, and the decomposed gas is discharged from the feeding end (the kiln tail). And (3) treating the gas after the decomposition reaction by a cyclone dust collector, introducing the gas into cooling absorption towers connected in series, and circularly cooling and absorbing the gas by using a dilute phosphoric acid solution. The absorbed residual gas is pumped and exhausted by a suction pump. About one third of the residue discharged from the front end of the decomposing kiln is used as a return material and sent to a mixer to be used as a viscosity reducing material for recycling, and the rest residue is used as a cement ingredient. The cement mixing ratio is as follows: residue amount: 78%, kaolin: 18 percent; coke powder: 4 percent, calculated according to the dry basis weight ratio, the prepared cement material is crushed to pass rate of 150 meshes which is more than or equal to 80 percent by a Raymond mill, and then is sent into a calcining rotary kiln for calcining reduction reaction. Spraying bituminous coal powder and hot air into the calcining kiln for heating, and controlling the temperature of the heating section of the calcining kilnComprises the following steps: 1250-1350 ℃, and the temperature of the kiln tail is as follows: adding cement materials from the tail part of the kiln at 500-800 ℃, keeping the materials in the kiln for 80 minutes, and discharging clinker from the front end of the kiln. And introducing the calcining furnace gas into a cyclone dust collector from the tail end of the kiln for dust removal treatment, introducing the calcining furnace gas into a furnace gas absorption washing tower, performing absorption washing treatment by using a sodium carbonate aqueous solution, and then emptying the calcining furnace gas by using a suction device. The calcined cement clinker is cooled to below 100 ℃, then is ground by Raymond mill until the passing rate of 320 meshes is more than or equal to 80 percent, and is a cement product, and the cement product can leave a factory after weighing, packaging and curing. When the pH value of the circulating solution for washing the calcining furnace gas reaches 5-6, pumping the circulating solution to the absorption washing process of the reaction waste fluorine gas, replacing the soda water solution and washing the calcining furnace gas again. When the sodium fluosilicate precipitate reaches about 250 g/L in the circulation liquid for washing and absorbing the waste fluorine gas, the circulation liquid is pumped into a centrifuge to separate out a sodium fluosilicate byproduct, the waste liquid is added into a dilute phosphoric acid solution and then sent to a concentrated sulfuric acid blending place for storage and standby applicationThe new sodium sulfite solution absorbs and washes the reaction waste fluorine gas. The pilot plant production device can be used for continuous production, and the amount of the qualified phosphoric acid with 85% of daily yield is 3000-3500 kg; the daily cement yield is: 6000-7000 kg, the quality of the phosphoric acid product meets the indexes of GB2091-92 national standard, and the quality of cement can reach the indexes of 32.5MPa grade of the national standard. The profit rate of phosphoric acid product is more than 38%, the profit rate of cement product is more than 35%, and P in cement₂O₅The content is less than or equal to 0.5 percent, the discharge of solid waste residue and waste water can be thoroughly avoided in the whole process, and the discharged residual gas meets the discharge requirement of environmental protection regulations.

Claims

1. A process for preparing phosphoric acid and by-product cement by thermal decomposition method includes such steps as reaction between powdered phosphorus ore and sulfuric acid, adding the resultant to the dregs of decomposition reaction, stirring, mixing, thermal decomposition at 300-1000 deg.C in decomposing kiln, removing dust, introducing the gas to absorption-hydration tower, and cyclically absorbing and cooling P in it by diluted phosphoricacid solution₂O₅Gas is used to obtain phosphoric acid product, part of the residue after thermal decomposition is used as return material for circulation, the rest residue is added with kaolin (or aluminum, silicon and iron mixed mineral) and carbon powder, the cement clinker of sulpho-alumino silicate is obtained after calcination reduction reaction, and the cement product is obtained after the fine grinding.

2. The method of claim 1, wherein: the adding amount of the sulfuric acid is preferably controlled to be 0.5-3% of the free sulfuric acid content in the reacted materials, and the using concentration of the sulfuric acid is 70-95%; the reaction temperature of the sulfuric acid and the phosphorite is controlled to be 100-200 ℃.

3. The method according to claim 1, characterized in that after the sulfuric acid is reacted with the ground phosphate rock, residues after thermal decomposition reaction with 2-4 times of the amount of the reaction materials are added for stirring and mixing, the mixed materials are thermally decomposed at 300-1000 ℃, the thermal decomposition time of the materials is 20-60 minutes, and P in the decomposed residues is controlled₂O₅The content is less than or equal to 0.5 percent.

4. The method of claim 1, wherein the cement formulation ratio is: 70-80% of residues after thermal decomposition and 15-25% of kaolin (or aluminum, silicon and iron mixed minerals); 2.5-4% of carbon powder in dry weight ratio. And carrying out reduction calcination reaction on the uniformly mixed materials at 1250-1350 ℃, and controlling the retention time of the materials in the calcining kiln to be 60-120 minutes.