CN1205116C - Method for producing phosphoric acid by adopting steam heating forced circulation concentration wet process and its equipment - Google Patents
Method for producing phosphoric acid by adopting steam heating forced circulation concentration wet process and its equipment Download PDFInfo
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- CN1205116C CN1205116C CN 03131937 CN03131937A CN1205116C CN 1205116 C CN1205116 C CN 1205116C CN 03131937 CN03131937 CN 03131937 CN 03131937 A CN03131937 A CN 03131937A CN 1205116 C CN1205116 C CN 1205116C
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Abstract
The present invention discloses a method for producing phosphoric acid by adopting a steam heating forced circulation concentration wet process, and equipment thereof. The phosphoric acid is circularly heated and concentrated in a circulation loop formed by a flash chamber, a graphite heat exchanger and an axial flow circulating pump; sparse phosphoric acid is added to the circulation loop from an outlet pipe of the graphite heat exchanger, evaporated vapor removes entrained acid foam through a foam remover; then through spray washing of a two stage fluorine absorbing tower, fluorides in gas phases are recovered, and the desired vacuum degree of the flash chamber is provided by an atmosphere condenser. When the present invention is used, the wet process phosphoric acid can be concentrated from 20 to 25% of P2O5 into 48 to 50% of P2O5; the present invention can reduce the P2O5 loss in the concentration process, and can enhance the fluorine recovery efficiency of tail gas, and the fluosilicic acid quality.
Description
Technical Field
The invention relates to a production process of phosphoric acid, in particular to a concentration technology of wet-process phosphoric acid and equipment thereof.
Background
Phosphoric acid concentration has two methods, direct heat transfer and indirect heat transfer. Early wet phosphoric acid concentration used direct heat transfer methods to avoid fouling of dilute acid dissolved impurities on heat transfer surfaces. The concentration method of indirect heat transfer gradually replaces the direct heat transfer method due to the increase of fuel cost and the appearance of new manufacturing materials, and the accumulation of operation experience and engineering experience for reducing the scaling. The most widely used indirect heat transfer concentration process at present is a forced circulation vacuum evaporation process using low-pressure steam as a heat source.
In phosphoric acid production, most of the fluorine escapes during concentration, when phosphoric acid is concentrated to 50% P2O5During the process, the fluosilicic acid therein is decomposed at high temperature and under vacuum in an evaporator, and the fluorine contained therein is about 50-60% by SiF4And HF morphological escape:
escaped HF, SiF4Absorbing the fluosilicic acid with circulating liquid to prepare 12 percent of fluosilicic acid for producing various fluorine salts.
The traditional process has the disadvantages of complicated equipment, high operation and maintenance cost and P in the concentration process2O5Large loss, large steam consumption, low fluorine washing efficiency and the like.
Disclosure of Invention
The invention aims to provide a method and equipment for concentrating wet-process phosphoric acid by heating and forced circulation with steam. The process can make wet-process phosphoric acid from 20-25% of P2O5Concentrating to 48-50% P2O5And can reduce P in the concentration process2O5Loss, and improves the fluorine recovery efficiency of the tail gas and the quality of the fluosilicic acid.
The technical scheme of the invention is as follows:
a method for concentrating wet-process phosphoric acid by adopting steam heating forced circulation is characterized in that phosphoric acid is circularly heated and concentrated in a circulation loop formed by a flash chamber, a graphite heat exchanger and an axial flow circulating pump, dilute phosphoric acid is added into the circulation loop from an outlet pipe of the graphite heat exchanger, evaporated steam is subjected to defoaming by a demister to remove acid foam entrained in the steam, then fluoride in a gas phase is recovered by spraying and washing through a two-stage fluorine absorption tower, and the vacuum degree required by the flash chamber is provided by an atmospheric condenser.
The specific process comprises the following steps: phosphoric acid is circularly heated and concentrated in a circulating loop formed by a flash chamber, a graphite heat exchanger and an axial flow circulating pump, dilute phosphoric acid is added into circulating acid from an outlet pipe of the graphite heat exchanger, the concentrated phosphoric acid overflows from the flash chamber and is discharged, the phosphoric acid separated from the demister enters a circulating loop, fluorine-containing vapor discharged from the demister enters a first fluorine absorption tower for spray washing, and then enters a second fluorine absorption tower for spray washing, fluosilicic acid is discharged from the first fluorine absorption tower, process water is directly added into the second fluorine absorption tower as make-up water for fluorine absorption, the second fluorine absorption tower overflows to the first fluorine absorption tower, gas discharged from the second fluorine absorption tower enters an atmospheric condenser, circulating cooling water is used for cooling water vapor in the gas in the atmospheric condenser, non-condensable gas enters a condensate liquid seal tank along with circulating cooling return water for emptying, and the circulating water overflows to a hot water pool of a circulating water station.
The flash evaporation chamber adopts bottom feeding, and heated circulatingacid is distributed through feedingThe long grid holes on the side surface of the pipe are added into the flash evaporation chamber, so that the turbulence of feeding is reduced, the stability of the liquid level in the flash evaporation chamber can be effectively controlled, water vapor is evaporated on a relatively stable interface, the air velocity at the upper part of the flash evaporation chamber is controlled to be 4-5 m/s, and the evaporation intensity of the flash evaporation chamber is 950kgH2O/m2H, a gas-liquid separation pipe is arranged at the top of the flash chamber, so that liquid foam entrainment in a gas phase is further reduced.
The fluorine absorption tower adopts two cyclone fluorine absorption towers which are connected in series, the airflow speed in the spraying cyclone fluorine absorption tower is 15-18 m/s, and the liquid spraying density is 30-35 m3/m2H, the absorption height is 7-8 m, and the amount of process water supplemented into the circulating washing liquid is controlled by the specific gravity of the washing liquid in the first fluorine absorption tower.
The vacuum degree required by the flash chamber is completely obtained by an atmospheric condenser arranged at a high position, a plurality of layers of spray heads are arranged in the atmospheric condenser, and the liquid spraying amount is 25m3Liquid/m2The flow area h, the height of the atmospheric leg of the atmospheric condenser is more than 16 meters, the flow rate of liquid in the atmospheric leg is controlled to be 1.4-1.6 m/s, and the absolute pressure in the flash chamber can reach 10kPa by the atmospheric condenser.
The equipment for concentrating wet-process phosphoric acid by adopting steam heating forced circulation comprises a circulation loop formed by a flash chamber, a graphite heat exchanger and an axial flow circulating pump, a fluorine absorption tower, an atmospheric condenser and a condensate liquid seal tank.
The graphite heat exchanger is a tube type graphite heat exchanger.
A special anti-blocking nozzle is arranged in the fluorine absorption tower, and the fluosilicic acid is circularly sprayed by a fluosilicic acid circulating pump until the density of the fluosilicic acid reaches H of 12 percent2SiF6When the solution is used, the discharge valve is opened, and the fluosilicic acid is sent to a fluosilicic acid storage tank.
The invention has the advantages that:
1. the production device constructed by the invention has the advantages of less process equipment, compact device arrangement and low floor. The operation and maintenance cost is low.
2. The shell and tube graphite heat exchanger is adopted, low-pressure steam of 0.3MPa is used for heating, and the heat exchange area and the flow of the circulating pump are small. The optimized equipment structure and arrangement of the concentration system ensure that the boiling phenomenon is not generated in the graphite heat exchanger, so that the graphite heat exchanger has long service life and the cleaning period is more than 2 weeks. The lower axial-flow pump lift makes the pump impeller have long service life and high driving rate.
3. The special atmospheric condenser design cancels a steam jet pump, and reduces the steam consumption.
4. The liquid foam in the flash chamber is less entrained, and the P is reduced2O5Loss, and improves the quality of the by-product fluosilicic acid, P in the fluosilicic acid2O5The content is less than 2000 ppm.
5. Two-stage series connection efficient tower type fluorine absorption is adopted, andthe fluorine washing efficiency is high.
Drawings
The attached drawing is a process flow schematic diagram of the invention.
Detailed Description
Example 1
6 million tons/year P using the invention2O5Phosphoric acid concentration device
See the drawings. The equipment for concentrating wet-process phosphoric acid by adopting steam heating forced circulation comprises a circulation loop formed by a flash evaporator 1, a graphite heat exchanger 2 and an axial flow circulating pump 3, wherein a fluorine absorption tower is provided with a first fluorine absorption tower 6 and a second fluorine absorption tower 7, and the outside of the fluorine absorption towers 6 and 7 are respectively provided with a spraying circulating pump 8 and a spraying circulating pump 9. The second fluorine absorption tower 7 is communicated with an atmospheric condenser 10, and the atmospheric condenser 10 is communicated with a condensate liquid seal tank 11.
25% P pumped from dilute phosphoric acid2O5Filtering the acid, metering the acid into the heat exchange area of 315m2The outlet pipe of the graphite heat exchanger 2 and the heated circulating acid enter the bottom of the flash evaporator 1 together for vacuum concentration, the diameter of the flash evaporator 1 is phi 5000mm, the height is 8358mm, and the effective volume is 123m3The dilute phosphoric acid is continuously concentrated to reach 48 percent P by continuous conveying and evaporation of a continuous circulating pump 32O5And the overflow is pumped out from the flash evaporator 1 bya concentrated phosphoric acid pump 4 and is sent to a phosphoric acid tank area. The top of the flash chamber is also provided with a gas-liquid separation pipe. HF and SiF contained in the gas discharged from flash evaporator 14Water vapor and a small amount of phosphoric acid mist, and phosphoric acid droplets separated by the demister 5 returnAcid is recycled, acid mist carried in the gas is separated by a demister 5, the gas enters cyclone fluorine absorption towers 6 and 7 for washing and absorption, a large amount of fluorine is absorbed after the gas is subjected to secondary counter-current washing, and 12 percent of H is obtained in the first fluorine absorption tower 62SiF6The solution is sent to the tank area, the diameter of the fluorine absorption tower is phi 2600mm, and the effective height of the tower is 13 m. The washed gas enters an atmospheric condenser 10 with the size of phi 2400 multiplied by 11489; condensed by circulating cooling water with the circulating water flow of 1280m3And h, enabling the non-condensable gas to enter a condensate liquid seal tank 11 along with the circulating cooling return water, and then overflowing to a hot water pool of a circulating water station to serve as process water. The process water is added to the second fluorine absorption tower 7, and the second fluorine absorption tower 7 overflows to the first fluorine absorption tower 6.
The air flow speed at the upper part of the flash chamber is controlled to be 4-5 m/s, and the evaporation intensity of the flash chamber is 950kgH2O/m2H, the airflow speed in the cyclone fluorine absorption tower is 15-18 m/s, and the liquid spraying density is 30-35 m3/m2H, the absorption height is 7-8 m, a plurality of layers of spray heads are arranged in the atmospheric condenser 10, and the liquid spraying amount is 25m3Liquid/m2The flow area h, the height ofthe atmospheric leg of the atmospheric condenser 10 should be larger than 16 meters, the flow rate of the liquid in the atmospheric leg is controlled to be 1.4-1.6 m/s, and the absolute pressure in the flash chamber can reach 10kPa by the atmospheric condenser.
Example 2
8 million tons/year P adopting the invention2O5Phosphoric acid concentration device
See the drawings. 25% P pumped from dilute phosphoric acid2O5Filtering the acid, metering to a heat exchange area of 430m2The outlet pipe of the shell and tube graphite heat exchanger and heated circulating acid enter a flash evaporator together for vacuum concentration, the diameter of the flash evaporator is phi 5800mm, the height is 8358mm, and the effective volume is 160m3Through continuous circulation evaporation, dilute phosphoric acid is continuously concentrated to reach 48-50% of P2O5And the concentrated phosphoric acid is pumped out from the flash evaporator by a concentrated phosphoric acid pump and is sent to a phosphoric acid tank area. HF and SiF contained in the gas discharged from the flash evaporator4Gas such as water vapor and a small amount of phosphoric acid mist is separated by a demister to obtain acid mist carried in the gas, the acid mist enters a fluorine absorption tower for washing and absorption, a large amount of fluorine is absorbed after the gas is subjected to secondary countercurrent washing, and 12% H is obtained in a first fluorine absorption tower2SiF6The solution is sent to a tank area, the diameter of the fluorine absorption tower is phi 3000mm, and the effective height of the tower is 13 m. The washed gas enters an atmospheric condenser with the size of phi 2600 multiplied by 11938; condensed by circulating cooling water with the circulating water flow of 1400m3And h, enabling the non-condensablegas to enter a condensate liquid seal tank along with the circulating cooling return water, and then overflowing to a hot water tank of a circulating water station.
The rest is the same as example 1.
Claims (1)
1. A method for concentrating wet-process phosphoric acid by adopting steam heating forced circulation is characterized in that phosphoric acid is circularly heated and concentrated in a circulation loop formed by a flash chamber, a graphite heat exchanger and an axial flow circulating pump, dilute phosphoric acid is added into the circulation loop from an outlet pipe of the graphite heat exchanger and enters the flash chamber together with circulating acid for vacuum concentration, concentrated phosphoric acid overflows and discharges from the flash chamber, steam evaporated from the flash chamber removes entrained acid foam through a foam remover, phosphoric acid separated from the foam remover enters the circulation loop, and the vacuum degree required by the flash chamber is provided by an atmospheric condenser;
fluorine-containing vapor discharged from the demister enters a first fluorine absorption tower for spray washing and then enters a second fluorine absorption tower for spray washing, fluosilicic acid is discharged from the first fluorine absorption tower, process water serving as fluorine-absorbed make-up water is directly added into the second fluorine absorption tower, the second fluorine absorption tower overflows to the first fluorine absorption tower, gas discharged from the second fluorine absorption tower enters an atmospheric condenser, circulating cooling water is used for cooling vapor in the gas in the atmospheric condenser, non-condensable gas enters a condensate liquid seal tank along with the circulating cooling return water and then overflows to a hot water tank of a circulating water station;
the flash evaporation chamber adopts bottom feeding, heated circulating acid is added into the flash evaporation chamber through long grid holes in the side surface of the feeding distribution pipe, the turbulence of the feeding is reduced, the air flow speed at the upper part of the flash evaporation chamber is controlled to be 4-5 m/s, and the evaporation intensity of the flash evaporation chamber is 950kgH2O/m2H, a gas-liquid separation pipe is also arranged at the top of the flash chamber;
the fluorine absorption tower adopts two cyclone fluorine absorption towers which are connected in series, the airflow speed in the spraying cyclone fluorine absorption tower is 15-18 m/s, and the liquid spraying density is 30-35 m3/m2H, the absorption height is 7-8 m, and the amount of process water supplemented into the circulating washing liquid is controlled by the specific gravity of the washing liquid in the first fluorine absorption tower;
the vacuum degree required by the flash chamber is completely obtained by an atmospheric condenser arranged at a high position, a plurality of layers of spray heads are arranged in the atmospheric condenser, and the liquid spraying amount is 25m3Liquid/m2The flow area, the height of the atmospheric leg of the atmospheric condenser is larger than 16 meters, the flow rate of liquid in the atmospheric leg is controlled to be 1.4-1.6 m/s, and the absolute pressure in the flash chamber can reach 10kPa by the atmospheric condenser.
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| CN 03131937 CN1205116C (en) | 2003-06-17 | 2003-06-17 | Method for producing phosphoric acid by adopting steam heating forced circulation concentration wet process and its equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102631800A (en) * | 2012-03-31 | 2012-08-15 | 中昊晨光化工研究院 | System and method for purifying mother liquor steam of polytetrafluoroethylene dispersing liquid |
| CN106829899A (en) * | 2017-01-10 | 2017-06-13 | 四川大学 | Wet Processes of Phosphoric Acid and fluosilicic acid processing method without fluorinated tail gas discharge |
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| CN101774558B (en) * | 2009-12-25 | 2011-10-19 | 中国海洋石油总公司 | Method for improving yield of concentrated phosphoric acid |
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- 2003-06-17 CN CN 03131937 patent/CN1205116C/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102631800A (en) * | 2012-03-31 | 2012-08-15 | 中昊晨光化工研究院 | System and method for purifying mother liquor steam of polytetrafluoroethylene dispersing liquid |
| WO2013143246A1 (en) * | 2012-03-31 | 2013-10-03 | 中昊晨光化工研究院有限公司 | System and method for purifying mother liquid steam of polytetrafluoroethylene dispersion liquid |
| CN102631800B (en) * | 2012-03-31 | 2013-11-06 | 中昊晨光化工研究院 | System and method for purifying mother liquor steam of polytetrafluoroethylene dispersing liquid |
| US9776123B2 (en) | 2012-03-31 | 2017-10-03 | Zhonghao Chenguang Research Institute of Chemiccal Industry Company Limited | System and method for purifying mother liquid steam of polytetrafluoroethylene dispersion liquid |
| CN106829899A (en) * | 2017-01-10 | 2017-06-13 | 四川大学 | Wet Processes of Phosphoric Acid and fluosilicic acid processing method without fluorinated tail gas discharge |
| CN106829899B (en) * | 2017-01-10 | 2019-03-05 | 四川大学 | The Wet Processes of Phosphoric Acid and fluosilicic acid processing method of no fluorinated tail gas discharge |
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