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Method for recovering waste nitric-hydrofluoric acid from stainless steel annealing-pickling by micro- and negative-pressure evaporation and crystallization processes

A technology of nitric acid hydrofluoric acid and negative pressure evaporation, which is applied in the field of stainless steel pickling waste acid recovery complete set process, can solve the problems of consumption, increase investment in pure water system and waste water treatment system, and reduce investment, simplify operation process, and run The effect of low cost

Inactive Publication Date: 2011-11-16
BEIJING TIANTAIXING ENG TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, its disadvantage is that after the resin adsorption treatment reaches saturation, at least the same amount of pure water will be consumed for the regeneration of the resin
As a result, the investment in the pure water system and the waste water treatment system have increased, and there are still about 20% of metal ions in the recovery acid

Method used

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  • Method for recovering waste nitric-hydrofluoric acid from stainless steel annealing-pickling by micro- and negative-pressure evaporation and crystallization processes

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0028] Example 1 Micro-negative pressure-negative pressure evaporation and crystallization process was used to recycle stainless steel waste acid.

[0029] The waste acid from the stainless steel pickling waste mixed acid storage tank is pumped to the evaporator for heating and vaporization. The vapor-liquid mixture is vaporized, flashed and separated in the vaporizer, so that 50% of the water, nitric acid and hydrofluoric acid in the waste acid are evaporated, and the liquid phase is preliminarily concentrated to make the specific gravity reach 1.3g / cm 3 . The vapor phase is sent to the condenser to be condensed to recover dilute nitric acid and hydrofluoric acid, and sent to the dilute acid storage tank. The metal nitrate-containing concentrated liquid separated from the vaporizer is sent to the secondary evaporator, and under the action of the circulating vacuum pump, it is evaporated and concentrated again at a deep negative pressure of 800 kPa. The evaporated hydrochlor...

example 2

[0030] Example 2 Recover stainless steel waste acid by micro-negative pressure-negative pressure evaporation and crystallization process.

[0031] The waste acid from the stainless steel pickling waste mixed acid storage tank is pumped to the evaporator for heating and vaporization. The vapor-liquid mixture is vaporized, flashed and separated in the vaporizer, so that 60% of the water, nitric acid and hydrofluoric acid in the waste acid are evaporated, and the liquid phase is initially concentrated to make the specific gravity reach 1.45g / cm 3 . The vapor phase is sent to the condenser to be condensed to recover dilute nitric acid and hydrofluoric acid, and sent to the dilute acid storage tank. The metal nitrate-containing concentrated liquid separated from the vaporizer is sent to the secondary evaporator, and under the action of the circulating vacuum pump, it is evaporated and concentrated again at a deep negative pressure of 700 kPa. The evaporated hydrochloric acid vapo...

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Abstract

The invention belongs to stainless steel pickling waste acid recovery technical processes and particularly relates to a method for recovering waste nitric-hydrofluoric acid from stainless steel annealing-pickling by micro- and negative-pressure evaporation and crystallization processes, which comprises the following steps of: under a condition of less than atmospheric pressure, heating the waste acid to the boiling point so as to separate 50 to 60 percent of nitric acid and hydrofluoric acid in the waste acid, condensing obtained vapor containing the nitric acid and hydrofluoric acid for separation and making the total acidity of the recovery acid in form of the nitric acid reach 20 to 30 percent; performing negative pressure evaporation concentration: under a negative pressure of 700 to 800kpa, performing secondary deep evaporation of primary evaporation concentration solution under a negative pressure condition so as to make the condensation rate rise to 65 to 75 percent; performingcondensation of the acid-containing vapor obtained by negative pressure evaporation to obtain a mixture of the recovery nitric acid and hydrofluoric acid; simultaneously, making the secondary negative pressure evaporation concentration solution enter a cooling crystallization reactor to perform cooling crystallization for 4 to 6 hours under an action of circulating cooling water; and discharging the crystallization mixture to a filter for solid-liquid separation. By the process, the aims of recovering and recycling the waste mixed acid are fulfilled.

Description

technical field [0001] The invention belongs to a complete set of technology for recycling waste acid from stainless steel pickling. That is, the use of micro-negative pressure-negative pressure evaporation and crystallization technology to recycle stainless steel pickling waste nitric acid hydrofluoric acid to obtain a mixture of nitric acid hydrofluoric acid mixed acid and metal nitrate and fluoride with a total acid concentration of 20-30%. Adopting this process to recycle waste pickling acid for reuse reduces the consumption of stainless steel pickling nitric acid and hydrofluoric acid, is beneficial to environmental protection, and realizes the goal of recovery and recycling of waste mixed acid. Background technique [0002] At present, there are three main methods for the treatment of stainless steel pickling waste nitric acid and hydrofluoric acid: simple neutralization method, evaporation process, direct incineration and resin adsorption technology. In comparison, t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23G1/36
Inventor 雍兴海雍兴跃赵明
Owner BEIJING TIANTAIXING ENG TECH