WO1993016968A1

WO1993016968A1 - Method of transport and storage of fertilizer compositions

Info

Publication number: WO1993016968A1
Application number: PCT/NO1992/000039
Authority: WO
Inventors: Arne Carlsen; Erik Christopher Nygaard; Erik Syrstad; Tom Consoli
Original assignee: Norsk Hydro A.S
Priority date: 1992-02-28
Filing date: 1992-03-05
Publication date: 1993-09-02
Also published as: NO920787D0

Abstract

The present invention relates to a method for transport and storage of fertilizer compositions. The nutrient component of the fertilizer composition, in the form of a melt, solution or dispersion is mixed with a hydrocarbon component and at least one emulsifying agent under intensive stirring for forming a water-in-oil type emulsion in which the discontinuous phase comprises the nutrient component and the volume phase ratio, discontinuous phase: total volume is in the range of 0.85-0.95. Said composition which may comprise 0-60 weight % solid nutrients and minor amounts of micronutrients are transported by ship, tank, rail cars or pipe line to storage and applied directly on the plants or crops and can be spread on the field or the emulsion is demulsified prior to application. The nutrient component, for instance urea, ammonium nitrate or calcium ammonium nitrate melt may be supplied directly from the fertilizer plant and emulsified with a hydrocarbon.

Description

Method of transport and storage of fertilizer compositions

The present invention relates a method of transporting fertilizer compositions to be applied as liquid fertilizer.

On a worldwide basis, the use of liquid fertilizer systems is increasing. Until now, most fertilizers have been manufactured as dry (crystalline, prilled or granular) material. Afterwards the product has been shipped in bulk or in bags and then dissolved again in order to make liquid fertilizer. These steps all involve wasted energy as energy first is used in order to make the dry material and then again during manufacture of the solution from the solids.

It is known to transport various types of aqueous fertilizer solutions from the manufacturer to the customer, for instance by tank cars. However, such aqueous solutions are not feasible for transport over long distances because substantial amounts of water have to be added in order to avoid salting out of crystals. Some aqueous solutions would have to contain as much as 50% of water in order to avoid salting out at a temperature of 0°C. Thus necessary large amounts of water have to be transported and thereby limits economical application of liquid fertilizer. The main object of the present invention was to arrive at a method of transporting fertilizer compositions as liquids which could be transported or stored for a long period of time and at rather low temperature without risk of salting out or precipita¬ tion or plugging of valves.

Another object was to transport highly concentrated liquids of fertilizer directly from the fertilizer plant without having to first manufacture dry particulated fertilizer which then had to be dissolved before transportation.

A further object was to transport highly concentrated liquids of fertilizer without having to supply extra energy to maintain the liquid at relatively high temperatures to prevent salting out or precipitation.

The inventors found that these objects could not be achieved by using conventional fertilizers and found that a new type of ertilizer^• composition had to be made in order to be able to transport such fertilizers over long distances at low tempera¬ tures. Development of a new type of fertilizer compositions was therefore started. It was then found that high concentrated fertilizer solutions/dispersions of nutrient compounds could be obtained by letting this solution/dispersion constitute the discontinuous phase of water-in-oil type emulsion. Further investigations proved that the amount of the oil component could be extremely low without reducing the stability of the w-i-o emulsion. The discontinuous phase of such an emulsion could either be an aqueous solution/dispersion of nutrient compounds or a concentrated fertilizer melt as both these are not soluble in oil. The new fertilizer composition may also contain solid fertilizers and even minor amounts of water insoluble salts and still be pumpable. This new fertilizer composition is further described in the co-pending application. The nutrient compounds are dissolved or dispersed in water at a temperature of 5-15°C above the crystallization temperature of the mixture and then added while stirring to a mixture of emulsifier and hydrocarbon which may contain elastomeres, the latter mixture having been heated to about the same temperature as the aqueous mixture. The combined mixtures are exposed to intensive stirring whereby stable w-i-o type emulsion is made. Typical range for stirring time will be in the range of 0.3-3 minutes. For industrial application a continuous emulsification process will be preferred.

Such an emulsion can also be made from a fertilizer melt as the discontinuous phase of the emulsion. Further, solid fertilizer compounds can be mixed with the emulsion in amounts of up to 60% in weight of the total composition. Right after forming the above described fertilizer composition it can be transferred to tank cars or ships for further transport to storage tanks or being directly applied on the plants or crops and can be spread on the field by conventional spreaders.

Several different types of fertilizers are applicable for being transported and stored within the concept of the present invention. The following are mentioned as examples of such fertilizers: ammonium-, calcium- and potassium nitrate, urea, NPK, calcium ammonium nitrate and ammonium sulphate.

The new fertilizer composition can be stored at ambient tempera¬ tures as low as -20°C without formation of crystals and for a prolonged period of time. Instead of applying the fertilizer composition directly as a fertilizer the emulsion can be broken (de-emulsified) and the oil and the aqueous component can be separated. However, in most cases this is an extra step involving additional cost and as the amount of oil the fertilizer composi¬ tion is within acceptable agronomical and environmental limits, direct application of the fertilizer is most preferred. For de-emulsification, several methods can be used. The simplest is to add water during agitation and separate the components by settling. Another method involves addition of surfactant capable of breaking the w-i-o emulsion and then separate the components afterwards.

The scope of the invention is as defined in the attached claims.

The invention will now further be explained in connection with the following example.

Example 1

In this example, several emulsions and fertilizer solutions are compared in order to evaluate the flowability at various storage temperatures where result of the tests are shown in the following table.

The UAN- and CAN-solutions represent conventional liquid fertilizers. As shown in the table such solutions will already at 0°C contain some crystals. The UAN- and CAN-emulsions according to the invention described in the co-pending application will not contain crystals and be pumpable even at such low storage temperatures as -20°C. The discontinuous phase of these emulsions is made from UAN/CAN-melt containing virtually no water, but as these melts are not soluable in the hydrocarbon component of the emulsion, they can be emulsified using standard w-i-o e ulsi- fiers. Accordingly, such emulsions can be transported according to the invention and it is emphasized that in this case there is no unnecessary water to be transported and still the fertilizer can be classified as liquid fertilizer and handled according to that. Using a fertilizer composition comprising w-i-o emulsions containing minor amounts of water has been found to possess the same properties as those shown in the table with regard to pumpability and lack of salted out crystals during storage or transport at low temperatures.

Application of this new transportation concept results in substantial reduction of energy requirements. The reason for this is that it is not necessary to first granulate or prill the fertilizer melt or solution from the fertilizer plant and then dissolve these fertilizer solids before being transported as liquids. Further, it is obtained reduced freight costs as only minor amounts of water have to be transported compared to up to 50% water of conventional fertilizer solutions. Also the storage cost will be reduced because in the present case it is highly concentrated nutrient solutions/dispersions which are stored and not liquid comprising about 50% water. Another advantage using this transport concept is that it is possible to transport pure quality fertilizer products easily by bulk. Formerly such products which were difficult to granulate and particulate and having poor caking properties had to be dissolved in large amounts of water and thereby making the transport very expensive.

One inherent effect of the excellent storage properties at low temperatures of the new fertilizer compositions is that there will be no need to heat tanks and pipes etc. in very cold climates to avoid salting out of the nutrient compounds. A further advantage will be that handling of the fertilizer as a liquid is less expensive than handling of particulated fertil¬ izer, especially compared to the conventional method of dis¬ solving solid fertilizers before being spread out as liquid solutions.

Claims

1. Method for transport and storage of fertilizer compositions, c h a r a c t e r i z e d i n t h a t the nutirent component of the fertilizer composi¬ tion, in the form of a melt, solution or disper¬ sion is mixed with a hydrocarbon component and at least one emulsifying agent under intensive stirr¬ ing for forming a water-in-oil type emulsion in which the discontinuous phase comprises the nutrient component and the volume phase ratio, discontinuous phase : total volume is in the range of 0.85-0.95, and that said composition which may comprise 0-60 weight% solid nutrients and minor amounts of micronutrients are transported by ship, tank, rail cars or pipe line to storage and applied directly on the plants or crops and can be spread on the field or that the emulsion is de- emulsified prior to application.

2. Method according to claim 1, c h a r a c t e r i z e d i n t h a t the nutrient component is a urea, ammonium nitrate or calcium ammonium nitrate melt supplied directly from the fertilizer plant and emulsified with a hydrocarbon, preferably white oil, and transported to storage and de-emulsified by addition of water and that the hydrocarbon components are separated from the aqueous nutrient solution prior to its application.

3. Method according to claim 1, c h a r a c t e r i z e d i n t h a t aqueous fertilizer solutions or dispersions com¬ prising complex fertilizer (NPK) , ammonium nitrate, calcium nitrate, ammonium phosphate or mixture of at least two of these prior to granula¬ tion, prilling or crystallization are emulsified and transported and stored as a w-i-o emulsion and applied on the plants or crops directly or sub¬ sequently to de-emulsification.

4. Method according to claim 1, c h a r a c t e r i z e d i n t h a t aqueous fertilizer solutions or dispersions com¬ prising ammonium sulphate are emulsified and transported as a w-i-o emulsion.