WO2002083566A2

WO2002083566A2 - Method for preparing copper hydroxide and device used in the method

Info

Publication number: WO2002083566A2
Application number: PCT/EP2002/003000
Authority: WO
Inventors: Giordano Donelli
Original assignee: Isagro Copper SRL
Current assignee: Isagro Copper SRL
Priority date: 2001-03-22
Filing date: 2002-03-19
Publication date: 2002-10-24
Anticipated expiration: 2003-09-22
Also published as: ITMI20010607A0; AU2002242727A1; ITMI20010607A1; WO2002083566A3

Abstract

A method for preparing copper hydroxide by reaction of copper oxychloride or oxysulfate with sodium hydroxide, wherein the reaction is performed continuously, so that the reaction mass advances in piston-like fashion along a path. Agitation of the mass sufficient to keep it fluid is provided. The device includes a reactor formed by a plurality of units, each formed by an agitator and by a non-agitated duct. The invention allows to obtain a highly pure product at low cost.

Description

METHOD FOR PREPARING COPPER HYDROXIDE AND DEVICE USED IN THE METHOD

The present invention relates to a method for preparing copper hydroxide by reaction of copper oxychloride or oxysulfate with sodium hydroxide and to a device used in the method. The produced copper hydroxide can be used, for example, as a pesticide to be sprayed on vines. This is a well-known pesticide, which is produced with well-tested means in a mature industrial sector. Accordingly, achieving significant improvements in this sector is particularly difficult and risky. Methods for preparing copper hydroxide are well-known from US-4404169,

US-4418056, US-4944935, US-4614640, EP-080227 and have been used for almost twenty years. However, all these known methods must use an excess of soda of more than 100% with respect to the stoichiometric value required to complete the reaction. This excess of soda entails an important financial burden for operating the plant and causes environmental problems in disposing of the salt produced after neutralization. Furthermore, known processes, in order to avoid forming unwanted by-products, are unable to produce a pure product without stabilizing agents for cases in which this purity is required. Stabilizing agents based on phosphates, ammonium salts, silicates and dispersants based on lignosulfonate are in fact used during the reaction. Finally, problems in terms of constant quality and limited productivity have been observed.

The aim of the present invention is to overcome the above mentioned drawbacks with a method for preparing copper hydroxide by reaction of copper oxychloride or oxysulfate with sodium hydroxide, characterized in that the reaction is performed continuously, so that the reaction mass advances in piston-like fashion along a path; agitation of the mass sufficient to keep it fluid being provided along the path.

Preferably, the path alternates free advancement steps and agitation steps. More preferably, at least two free advancement steps and two agitation steps are used. This helps to provide a piston-like advancement and to reduce the formation of unwanted by-products.

Preferably, a final part of the reaction is performed without agitation. In particular, this final part of the reaction is preferably performed after reaching a degree of conversion of at least 60% and preferably at least 80%. In this manner it is possible to contain the overall dimensions of the plant and plant costs.

Preferably, the reaction is performed with a copper concentration between 50 and 250 g/l and preferably between 100 and 180 g/l.

Preferably, at least along part of the path, by virtue of the agitation, a power of over 20 watts/liter, preferably over 50 watts/liter, more preferably over 100 watts/liter, is transferred to the mass. This helps to avoid producing unwanted byproducts.

If this agitation is provided by at least one pump, a recirculation fraction of the fluid that passes through the pump is recirculated upstream of the pump, the recirculation fraction preferably having a volume at least 10 times greater than the non-recirculated fraction, more preferably at least 50 times greater than the non- recirculated fraction, even more preferably at least 100 times greater than the non-recirculated fraction. This embodiment allows to provide the plant with means that are easily commercially available.

Preferably, an excess of sodium hydroxide with respect to the stoichiometric value is maintained between 20% and 70%, preferably between

25% and 50%. In this manner, the amount of soda used can be more than halved with respect to known methods. Furthermore, it has been found that beyond the lower limits of the indicated range the reaction is not completed.

Preferably, after completion of the reaction, only when necessary, a stabilizing agent is added, the agent being preferably based on phosphoric acid and/or sodium phosphate. In this manner it is possible to avoid adding a stabilizing agent when a pure product is required.

The invention further relates to a device for preparing copper hydroxide by reaction of copper oxychloride or oxysulfate with sodium hydroxide, which includes a reactor formed by a plurality of units, each formed by an agitator and by a non-agitated duct.

The invention will become better apparent with reference to the following description of some embodiments thereof, detailed in the examples that follow and illustrated in the accompanying figures, which are provided merely by way of non-limitative example of the invention and wherein:

Figure 1 is a partially sectional side view of a first embodiment of a reactor according to the invention;

Figure 2 is a partially sectional side view of a second embodiment of a reactor according to the invention; and Figure 3 is a schematic view of a third embodiment of a reactor according to the invention.

With reference to Figures 1 to 3, the device for preparing copper hydroxide by reaction of copper oxychloride or oxysulfate with sodium hydroxide includes a reactor 10 formed by a plurality of units 1 1 , 12, each formed by an agitator 1 1 and by a non-agitated duct 12.

With particular reference to Figures 1 and 2, the non-agitated duct 12 is arranged at a separation diaphragm 13. With particular reference to the embodiment of Figure 1 , the agitator 11 is formed by a rod. With particular reference to the embodiment of Figure 2, the agitator 11 is formed by an impeller. The diaphragms 13 cooperate to provide a piston-like flow, preventing returns of fluid from a unit 11 , 12 to the preceding unit. The rotating shaft 9 provides the agitation energy. These embodiments can be produced with simple and reliable means.

With particular reference to the embodiment of Figure 3, the agitator is formed by a pump 1 1 , preferably a centrifugal pump. By means of the duct 14, the recirculation flow is provided which allows to recirculate the above cited recirculation fraction of the fluid. This embodiment is particularly simple and allows to use currently commercially available equipment. Example 1 The reactor, with a capacity of 3.7 liters, is cylindrical with a horizontal axis, and is provided with a high-shear agitation system; the geometry of the reactor and the agitation system are such as to ensure perfect piston-like advancement of the mass. The reactor is of the type with rods and provides an agitation power of 150-200 watts/liter. 52.7 l/h of copper oxychloride suspension and 10.7 l/h of sodium hydrate are fed continuously into the reactor.

The excess of sodium hydrate is 30% with respect to the stoichiometric value referred to the copper oxychloride. The oxychloride suspension contains 175 g/l of copper from oxychloride and 9 g/l of copper from cupric chloride. The soda solution has a concentration of 409 g/l.

The contact time inside the reactor is 3.5 minutes and the temperature at the output of the reactor is 22÷24 °C.

The temperature at the output of the reactor is controlled by cooling appropriately the two reagents at the input of the reactor. At the output of the reactor, the conversion of cupric chloride to hydroxide is 100%, while the oxychloride conversion is at least 90%.

Copper concentration in the reaction mass is a 153 g/l.

In order to fluidize it, the reaction mass is diluted with a volume of 24.8 l/h of recycled water, so that the suspended copper concentration becomes 1 10 g/l. The reaction mass then passes to the step for completion of the reaction, which occurs in a 75-liter reactor with a vertical axis; the geometry of the reactor and the agitation system are such as to ensure perfect piston-like advancement of the mass.

The completion temperature of the reaction is 20÷24 °C. After a contact time of approximately 50 minutes, reaction conversion is at least 99%.

The reaction mass then receives the addition of 620 g/h of orthophosphoric acid, diluted beforehand with 50.4 l/h of recycled water; suspended copper concentration becomes 70 g/l. In a strongly agitated reactor with a useful volume of 40 liters, the mass is neutralized continuously with a solution of cupric chloride in an amount that brings the pH to a value of 8÷8.2.

Consumption of cupric chloride is approximately 6 l/h of solution at approximately 100 g/l, which is introduced by diluting it in line with 98 l/h of recycled water.

During this step the excess soda is neutralized, with consequent precipitation of the copper phosphate.

After neutralization, suspended copper concentration is 40 g/l. The mass is then filtered continuously with a vacuum filter and the cake is washed with a volume of softened water equal to the volume of the stock suspension.

The mother liquors are treated in the treatment plant before being sent to discharge, while the wash water is almost entirely recycled to process. A product dried in a spray drier has the following characteristics: Appearance fine powder

Color Pale blue

Copper titer 60% min.

Average particle size 1.2 microns

H3PO4 3.5 ÷ 4% NaCI 2% max

Humidity 2% max

Example 2

75 liters/hour of solution of tetracupric oxychloride containing 130 g/liters of Cu are reacted with 10.5 liters/hour of solution of NaOH at 30% in a continuous reactor, with a volume of 5 liters, with piston-like flow and agitation of the impeller type. The excess sodium hydrate is 30% with respect to the stoichiometric value. Agitation provides the mass with a power of 150 watts/liter. The reaction is performed at a temperature of 25 °C. The fluid exits the reactor after reacting for 90%. To complete the reaction, the fluid is sent to a non-agitated reactor with piston-like flow, where the product is matured in order to complete the reaction. The reaction is 99% complete. The resulting color is pale blue. Example 3

Example 2 is repeated, the difference being that the reactor is formed by a centrifugal pump and by a duct connected to the pump. Example 4

Example 2 is repeated, the difference being that the reactor is formed by two centrifugal pumps and by two ducts, each connected to a pump.

The invention allows to achieve the intended aim and objects. In particular, it is possible to obtain the intended product in pure form, with a considerable saving of soda, with high productivity and with particularly simple and reliable means.

The invention is susceptible of numerous modifications and advantages; in particular, the agitation means, as well as the ducts, may be replaced with other equivalent ones as long as a piston-like flow is provided.

Claims

1. A method for preparing copper hydroxide by reaction of copper oxychloride or oxysulfate with sodium hydroxide, characterized in that said reaction is performed continuously, so that the reaction mass advances in piston- like fashion along a path; agitation of said mass sufficient to keep it fluid being provided along said path.

2. The method according to claim 1 , wherein said path alternates free advancement steps with agitation steps.

3. The method according to claim 2, comprising at least two free advancement steps and two agitation steps.

4. The method according to at least one of the preceding claims, wherein a final part of the reaction is performed without agitation.

5. The method according to claim 4, wherein said final part of the reaction is performed after reaching a degree of conversion of at least 60% and preferably at least 80%.

6. The method according to at least one of the preceding claims, wherein the reaction is performed with a copper concentration between 50 and 250 g/l, preferably between 100 and 180 g/l.

7. The method wherein at least along part of said path, by virtue of said agitation, a power of more than 20 watts/liter, preferably more than 50 watts/liter, more preferably more than 100 watts/liter, is transferred to said mass.

8. The method according to at least one of the preceding claims, wherein said agitation is provided by at least one pump, a recirculation fraction of the fluid that passes through said pump being recirculated upstream of said pump, said recirculation fraction preferably having a volume at least 10 times greater than the non-recirculated fraction, more preferably at least 50 times greater than the non- recirculated fraction, even more preferably at least 100 times greater than the non-recirculated fraction.

9. The method wherein an excess of sodium hydroxide with respect to the stoichiometric is kept between 20% and 70%, preferably between 25% and 50%.

10. The method according to at least one of the preceding claims, comprising, after completion of the reaction, the addition of a stabilizing agent preferably based on phosphoric acid and/or sodium phosphate.

11. A device for preparing copper hydroxide by reaction of copper oxychloride or oxysulfate with sodium hydroxide, comprising a reactor formed by a plurality of units, each unit being formed by an agitator and by a non-agitated duct.

12. The device according to claim 11, wherein said non-agitated duct is arranged at a separation diaphragm.

13. The device according to at least one of the preceding claims, wherein said agitator is formed by an impeller.

14. The device according to at least one of the preceding claims, wherein said agitator is formed by at least one rod.

15. The device according to at least one of the preceding claims, wherein said agitator is formed by a pump, preferably a centrifugal pump.

16. Every new characteristic or new combination of characteristics described or illustrated.