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A kind of method for preparing polyphosphoric acid

A technology of polyphosphoric acid and dilute phosphoric acid, which is applied in the field of phosphorus chemical industry, can solve the problems of high production energy consumption, easy fluctuation of pressure, small mass transfer and heat transfer, etc., so as to improve the utilization rate of heat energy, avoid production accidents, and improve heat transfer. uniform effect

Active Publication Date: 2015-09-09
绵阳启明星磷化工有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The above-mentioned method for preparing polyphosphoric acid has the following disadvantages: 1, the mixed acid solution of phosphoric acid and phosphorus pentoxide has a high viscosity, which easily causes blockage in the graphite tube, further causing production accidents; 2, the acid solution is heated in the heat exchange tube , the heat is transferred from the wall of the heat exchange tube to the center of the heat exchange tube. Due to the high viscosity of the hot acid liquid, the mass transfer and heat transfer inside the acid liquid are particularly small, so that part of the acid liquid close to the heat exchange tube wall is prone to polymerization, and the obtained Polyphosphoric acid, and part of the acid liquid close to the center of the heat exchange tube has a low temperature and is difficult to polymerize, which leads to uneven distribution of components in the prepared polyphosphoric acid product; 3. Using high-temperature steam (above 200°C Steam) heats the graphite tube, the pressure of the steam is high and the pressure is easy to fluctuate, the graphite heat exchange tube is prone to rupture, and the strength of the heat exchanger material is high; at the same time, the use of steam to heat the graphite tube results in high energy consumption and high production cost ; 4, utilizing phosphorus pentoxide to produce polyphosphoric acid, the production cost is high and the production process is complicated

Method used

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  • A kind of method for preparing polyphosphoric acid
  • A kind of method for preparing polyphosphoric acid
  • A kind of method for preparing polyphosphoric acid

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0041] Such as figure 1 As shown, the device for implementing the method for preparing polyphosphoric acid in this embodiment includes a heater 2, a separator 3, and a concentrated acid tank 6, and the inside of the separator 3 is in communication with a vacuum barostat 4; figure 2 As shown, the heater 2 includes a heat exchange tube 21 and a heat ventilation zone. The heat exchange tube 21 is a graphite tube. The outer wall of the graphite tube is provided with an anti-oxidation coating which does not react with high-temperature flue gas; The ventilation area is surrounded by an insulation layer 22, and the heat exchange pipe 21 is located in the heat ventilation area; the heat exchange pipe 21 is coiled in an S shape in the heat ventilation area. image 3 Is a top view of the upper part of the heat exchange tube 21, Figure 4 It is a bottom view of the lower part of the heat exchange tube 21, the upper outlet 2103 of the heat exchange tube is connected with the lower inlet 2104...

Embodiment 2

[0046] The method for preparing polyphosphoric acid by using the device for preparing polyphosphoric acid in Example 1, wherein the heat exchange tube 21 is inclined downward at an angle of 1° from the acid inlet 2101 of the heat exchange tube to the acid outlet 2102 of the heat exchange tube:

[0047] The dilute phosphoric acid with a mass concentration of 45% from the dilute acid tank 1 enters the heat exchange tube 21 through the acid inlet 2101 of the heat exchange tube. The pressure at the acid inlet 2101 of the heat exchange tube is -594mmHg, and the dilute phosphoric acid passes through the hot ventilation zone. , That is, inside the insulation layer 22, heat exchange with the yellow phosphorous waste gas (220°C) in the shell of the heat exchange tube 21 to heat up to 210°C. At this time, the insulation layer 22 is under normal pressure, and at the same time, phosphoric acid polymerizes to form Polyphosphoric acid, the acid liquid exits the heat exchanger 2 from the acid ou...

Embodiment 3

[0050] Using the method for preparing polyphosphoric acid using the device for preparing polyphosphoric acid in Example 1, the heat exchange tube 21 is inclined downward at an angle of 3° from the acid inlet 2101 of the heat exchange tube to the acid outlet 2102 of the heat exchange tube:

[0051] The dilute phosphoric acid with a mass concentration of 70% from the dilute acid tank 1 enters the heat exchange tube 21 through the acid inlet 2101 of the heat exchange tube. The pressure at the acid inlet 2101 of the heat exchange tube is -450mmHg, and the dilute phosphoric acid passes through the hot ventilation zone. , That is, inside the insulation layer 22, heat exchange with the yellow phosphorus tail gas (200°C) in the shell of the heat exchange tube 21 to increase the temperature to 195°C. At this time, the insulation layer 22 is at normal pressure, and under high temperature conditions, phosphoric acid polymerizes Polyphosphoric acid, the acid liquid exits the heat exchanger 2 ...

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Abstract

The invention relates to the field of phosphorus chemical industry, in particular to a preparation method for polyphosphoric acid. The method for preparing polyphosphoric acid includes: letting dilute phosphoric acid enter a heater through a heat exchange tube acid inlet to be heated to 185DEG C-230DEG C, then discharging the dilute phosphoric acid out of the heater from a heat exchange tube acid outlet, and making the dilute phosphoric acid enter a separator to undergo flash concentration, keeping the vacuum degree in the separator ranging from -500 to -700mmHg, discharging the concentrated acid liquor out of the separator through an acid outlet tube at the lower end of the separator, and leading the concentrated acid liquor into a concentrated acid tank through a concentrated acid tank acid inlet to undergo cooling and storage. The heat exchange tube is coiled in an S shape in the heater, from the heat exchange tube acid inlet to the heat exchange tube acid outlet, the heat exchange tube tilts downward at an angle of 1-3 degrees. The preparation method for polyphosphoric acid provided by the invention has a simple process, can prepare high concentration polyphosphoric acid from dilute phosphoric acid by one-step polymerization. By taking dilute phosphoric acid as the raw material, the acid liquor cannot adhere to the heat exchange tube wall, thus avoiding blocking of the heat exchange tube. Further, the prepared polyphosphoric acid product has uniformly distributed components.

Description

Technical field [0001] The present invention relates to the field of phosphorus chemical industry, in particular to a method for preparing polyphosphoric acid. Background technique [0002] In the 1930s, the Tennessee River Basin Administration Institute of the United States found that orthophosphoric acid (H 3 PO 4 ) And pyrophosphate (H 4 P 2 O 7 ) There is a eutectic composition of liquid phosphoric acid in between. Its ωP 2 O 5 Is 76%[Equivalent to ω(H 3 PO 4 ) Is 105%], of which about 49% P 2 O 5 Exist in the form of orthophosphoric acid, 42% is pyrophosphoric acid, 8% is tripolyphosphoric acid (H 5 P 3 O 10 ), 1% is tetrapolyphosphoric acid (H 6 P 4 O 13 )exist. This mixture of orthophosphoric acid and polyphosphoric acid is called poly phosphoric acid. [0003] Polyphosphoric acid, also known as tetrapolyphosphoric acid, polyphosphoric acid or polyphosphoric acid, is a colorless, transparent, viscous liquid, easily deliquescent, non-crystalline, corrosive, and can be miscib...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B25/24
Inventor 唐希勇彭永
Owner 绵阳启明星磷化工有限公司
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