Chloride removing in method for preparing phosphonomethyliminodiacetic acid

FIELD: chemical technology.

SUBSTANCE: invention relates to a selective method for removing chloride as NaCl from waste in method for preparing N-phosphonomethyliminodiacetic acid. The waste flow is neutralized with NaOH to pH value about 7, water is evaporated from flow of neutralized waste under atmospheric or lower pressure at temperature from 40°C to 130°C until to precipitation of NaCl. The precipitate is filtered off at temperature from 35°C to 110°C to isolate NaCl from filtrate and NaCl is washed out with saturated saline solution. Invention provides effective removal of NaCl from waste in a method for manufacturing N-phoaphonomethyliminodiacetic acid.

EFFECT: improved treatment method.

7 cl, 2 ex

The present invention relates to a method for the effective removal and extraction of chloride from waste method of obtaining N-phosphonomethyliminodiacetic acid. More specifically, the present invention includes the neutralization of the waste stream with sodium hydroxide (NaOH) and the crystallization of sodium chloride (NaCl) by evaporation.

In the industrial production of the herbicide glyphosate iminodiethanol acid (IDK) is transformed into N-phosphonomethyliminodiacetic acid (FMEC) by reaction with hydrochloric acid (HCl), phosphoric acid (H₃RHO₃) and formaldehyde (CH₂O) or by reaction with phosphorus trichloride (PCl₃), NaOH and CH₂O. From waste method at this stage is usually disposed of by loading in a deep vessel. Due to the high content of chloride and a large amount of this waste stream other, more environmentally friendly ways of waste treatment, such as oxidation wet air or thermal incineration, the economically disadvantaged. It would therefore be desirable to have a method of reducing the content causes corrosion of chloride and total hydraulic volume of waste in the waste stream FMIDS to other methods of waste disposal have become economically possible.

At present, it was found that NaCl can be effectively removed and separate from waste retrieval method f is stomatologiczny acid (FMEC) by neutralization of the waste stream NaOH and crystallization by evaporation. The present invention relates to a method for the removal and excretion of NaCl from the waste stream method of obtaining FMEC, which includes the neutralization of the waste stream NaOH to a pH of about 7 by evaporation of water at atmospheric or lower pressure, at a temperature of from 40 to 130°until then, until you fall NaCl precipitate, filtering the precipitate at a temperature of from 35 to 110°and washing the precipitate with a saturated solution of salt. Because it is obvious that the concentration of sodium salts of other compounds in the flow of neutralized waste lowers the solubility of NaCl in the matrix, NaCl can be deleted and select from the waste stream method of obtaining FMEC with a surprisingly high degree of separation and purity.

The flow of waste water in the production FMEC usually can contain phosphorous acid (from 0.3 to 2 mass%), phosphoric acid (0.3 to 3 mass%), HCl (from 9 to 15 mass percent), iminodiethanol acid (IDK; from 0.1 to 0.3 mass%), FMEC (from 0.8 to 4 mass%), N-methyliminodiacetic acid (Novocherkassk Museum; from 0.5 to 8 mass percent), and small quantities of methanol, formaldehyde and formic acid.

In the first stage of the method of removal and excretion of NaCl flow of waste water FMEC neutralize NaOH to a pH of about 7, so that all organic and inorganic acids, including HCl, transformed the into the corresponding sodium salt, NaCl and water. In order to minimize the total hydraulic load, it is preferable to carry out the neutralization of relatively concentrated solutions of NaOH. To neutralize the preferred commercially available 50% NaOH. The heat of neutralization significantly raises the temperature of the neutralized mixture to crystallization by evaporation.

After neutralization of the water removed from the neutralized mixture until then, until you fall precipitate NaCl. The water is evaporated at atmospheric or lower pressure at a temperature of from 40 to 130°C, preferably at a temperature of from 60 to 100°C. the Evaporation continues until, until you precipitate a large part of NaCl, but not to such an extent that when the suspension becomes difficult to handle when the foaming becomes excessive or when the subsequent filtrate becomes too viscous. As a rule, from the neutralized mixture is evaporated amount of water equivalent to from 35 to 70 mass%, preferably from 50 to 65 mass%. Naturally, the number of remote water will vary depending on the initial concentration of the neutralized stream waste concentration used to neutralize the base. The exact amount of water that must be removed can be easily optimized by conventional experimental the tests with specific processed by the waste stream. For evaporation possible a wide range of operating conditions based on thermal stability of the components of the waste stream and limitations on pressure-related equipment. Water vapor this way you can condense for a potential return in the loop.

After crystallization by evaporation of NaCl are filtering. Due to the viscosity of the filtrate filtration is carried out at a temperature of from 35 to 110°preferably at a temperature of from 60 to 90°C. the Driving force for filtration can be gravity, pressure from above is applied from below the vacuum or centrifugal force. NaCl is isolated in the form of cakes on the filter. Volume flow of waste water, now presents the filtrate, substantially less and deleting the most part contained chlorides easier for other waste treatment options, in addition to the load in a deep reservoir, such as oxidation wet air or burning.

At the last stage of the way the cake NaCl on the filter is washed with saturated salt solution to remove residual filtrate. Despite the fact that the concentration of the salt solution is not critical, because the salt flush, you can re-return into the cycle in the flow of neutralized waste, the use of dilute salt solution leads to the dissolution of the precipitate salts, and the use of nasusunog the solution of salt leads to discarding additional NaCl from the salt solution by means of vysalivaniya", due to components containing sodium salt, replaced with a wash solution to the filtrate. Preferably, the concentration of NaCl in the wash solution of salt was the same as in the filtrate. Despite the fact that the temperature at the stage of washing is not critical, viscous residual filtrate in the cake on the filter can be removed more effectively by washing at elevated temperatures, for example from about 35 to 60°C.

The invention is illustrated by the following examples.

Examples

1. A 3-necked 250-millilitre (ml) flask equipped with a lateral throat, water cooled refrigerator and sink, a blade stirrer with adjustable speed and thermoproteales with a heating jacket with temperature control and is equipped with a controlled source of vacuum, 100 grams (g) of the brine process of obtaining FMEC, comprising 0.3% of IDK, 6.7% of the Novocherkassk Museum, 3.8% OF FMEC, 10.1% of HCl, 1.8% Of N₃RHO₃and 2.2% N₃PO₄neutralized to pH 6,97 action 41,2 g 50% NaOH. After sampling 135,3 g neutralized brine was evaporated at atmospheric pressure prior to the removal of 74.5 g of water and the precipitated NaCl. The suspension was filtered under vacuum through a large filter of melted glass and washed the cake on the filter 20 g of saturated salt solution, getting 13.5 g wet white precipitate weighing after drying of 12.0 g of Dry residue definition is ranged as containing 99.8% of NaCl. Viscous filtrate contained 15.0% Novocherkassk Museum, 8,9% FMIDS and 6.5% NaCl, which is estimated corresponds to 9.2% of the chloride in the original solution.

2. In the apparatus, similar to, but larger in size than the one described in example 1, 466 grams (g) of the brine process of obtaining FMEC, including 0,15% IDK 0.8% of the Novocherkassk Museum, 3,0% FMEC, 15,9% HCl and an indefinite number of N₃RHO₃and H₃PO₄neutralized to pH 6.8 by the action of 217 g of 50% NaOH. A portion of this neutralized brine in the amount of 450 g was evaporated at 210 mm RT. Art. (27 kPa) and the final temperature of the tank 96°to delete 273 g of water and the precipitated NaCl. Suspension (177 g) was filtered under vacuum through a large filter of melted glass and washed the cake on the filter 56 g of 25.7% NaCl, getting after drying 81 g of off-white precipitate salt. In dry sediment was determined to 98.5% NaCl, and it still contained 1.1% of FMIDS. Viscous filtrate contained 9.1% of FMIDS and 3.0% NaCl, which is estimated corresponds to 1.9% of the chloride in the original solution.

1. The method of removal and excretion of NaCl from the waste stream method of obtaining N-phosphonomethyliminodiacetic acid (FMEC), characterized in that the waste stream is neutralized with NaOH to a pH of about 7, is evaporated from the stream neutralized waste water at atmospheric or lower pressure, at a temperature of from 40 to 130°until then, until precipitation of NaCl, filtered precipitate pace is the atur from 35 to 110° For the allocation of NaCl from the filtrate and washed with NaCl saturated solution of salt.

2. The method according to claim 1, in which the water is evaporated at a temperature of from 60 to 100°C.

3. The method according to claim 1 or 2, in which the NaCl is filtered at a temperature of from 60 to 90°C.

4. The method according to any of the preceding paragraphs, in which NaCl was washed with saturated salt solution at a temperature of from about 35 to about 60°C.

5. The method according to any of the preceding paragraphs, in which the NaCl concentration in the washing solution of salt is approximately the same as in the filtrate.

6. The method according to any of the preceding paragraphs, in which the wash a saturated solution of salt in return loop in the flow of neutralized waste.

7. The method according to any of the preceding paragraphs, in which the filtrate is further treated by air oxidation or burning.