US-12623977-B2 - Method for producing a fertilizer

Abstract

A method for producing a fertilizer that comprises urea and/or at least one ammonium compound may involve obtaining ammonia as an impurity in the production process, and photocatalytically decomposing the ammonia by irradiation with UV radiation. Further, an apparatus for producing fertilizer granules that comprise urea and/or at least one ammonium compound may include a plant section having a fertilizer granulator configured to produce the fertilizer granules, a supply line configured to pass a urea melt or a concentrated urea solution to the plant section, a UV lamp arrangement that is proximate the supply line and is configured to irradiate with UV radiation the urea melt or the concentrated urea solution flowing in the supply line.

Inventors

• Harald Franzrahe

Assignees

• THYSSENKRUPP FERTILIZER TECHNOLOGY GMBH
• THYSSENKRUPP AG

Dates

Publication Date

20260512

Application Date

20201221

Priority Date

20200108

Claims (10)

1. 1 . A method for producing a fertilizer that comprises at least one of urea or an ammonium compound, the method comprising: obtaining ammonia as an impurity in the production of the fertilizer; and decomposing the ammonia, as it is bound or dissolved in a urea melt or in a concentrated urea solution, photocatalytically by irradiation with UV radiation; wherein decomposing the ammonia photocatalytically includes irradiating the urea melt or the concentrated urea solution with UV radiation on a transport path to a fertilizer granulator.
2. 2 . The method of claim 1 comprising producing fertilizer granules in a granulation process.
3. 3 . The method of claim 1 comprising producing urea-containing fertilizer granules in a granulation process.
4. 4 . The method of claim 3 comprising producing the urea-containing fertilizer granules by fluidized bed granulation.
5. 5 . The method of claim 1 wherein the urea melt or the concentrated urea solution is irradiated with UV radiation at a low spatial and/or temporal distance or immediately prior to addition to the fertilizer granulator.
6. 6 . The method of claim 1 wherein the UV radiation has a wavelength in a range from 170 nm to 350 nm.
7. 7 . The method of claim 1 wherein the UV radiation has a wavelength in a range from 185 nm to 254 nm.
8. 8 . The method of claim 1 comprising photocatalytically decomposing the ammonia predominantly into nitrogen and water.
9. 9 . The method of claim 1 wherein the irradiation occurs by way of a UV lamp arrangement disposed proximate a supply line via which the urea melt or the concentrated urea solution is passed to a fertilizer granulator.
10. 10 . A method for producing a fertilizer that comprises at least one of urea or an ammonium compound, the method comprising: obtaining ammonia as an impurity in the production of the fertilizer; and decomposing the ammonia, as it is bound or dissolved in a urea melt or in a concentrated urea solution, photocatalytically by irradiation with UV radiation; wherein the irradiation occurs by way of a UV lamp arrangement disposed proximate a supply line via which the urea melt or the concentrated urea solution is passed to a fertilizer granulator.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a U.S. National Stage Entry of International Patent Application Serial Number PCT/EP2020/087545, filed Dec. 21, 2020, which claims priority to European Patent Application No. EP 20 150 740.7, filed Jan. 8, 2020, the entire contents of both of which are incorporated herein by reference. FIELD The present disclosure generally relates fertilizers, including methods for producing a fertilizer that comprises urea and/or an ammonium compound, where ammonia is obtained as an impurity in the production process. BACKGROUND In view of global population growth, the development of flexible and efficient fertilizers is of major and growing significance. What is important here is not just the fertilizer itself, i.e., the chemical composition, but also the processing forms in transportable containers and the application to the land. Of greatest significance here is certainly granulation to form regular particles which are the same in size and characteristics. Important parameters in this context are low dusting, strength, low aggregation tendency, uniform size, storability, and stability. One established granulation technique is fluidized bed granulation, which exhibits improved particle properties compared, for example, to the prilling and pelletizing techniques. Virtually all fertilizers require ammonia in some form in their production. Urea is the diamide of carbonic acid and is produced industrially in a high-pressure process from ammonia and carbon dioxide. Other fertilizers are mixtures of ammonia and nitrates or combinations of ammonia-containing compounds, ammonia salts for example, phosphorus and potassium. A very large share of worldwide fertilizer production is accounted for by urea-containing fertilizers. This water-soluble fertilizer breaks down in the soil to give ammonium salts and/or nitrates, and is an important base fertilizer. This urea-containing fertilizer can be combined with further elements such as potassium, phosphates or sulfur compounds. All of the aforesaid processes for producing fertilizers require ammonia in some form, particularly when solid fertilizer granules are being produced. Ammonia may be released during the production process. With some methods, especially in the production of urea-containing granules, ammonia is absorbed physically in the melt or is formed by polymerization reactions—for example, by the formation of biuret in accordance with the following equation: 2NH2—CO—NH2→H2N—CO—NH—CO—NH2 (biuret)+NH3  (1) Many methods for producing fertilizer granules use large airflows, an example being fluidized bed granulation. If the ammonia enters the airflow, it must be removed, in order to satisfy the present protocols relating to emissions from plants producing large quantities of inorganic compounds. As a raw material, in granulation, particularly in the fluidized bed granulation of fertilizers, a concentrated urea solution is required. This solution generally contains a dissolved ammonia fraction, more particularly of the order of about 500 ppm to 800 ppm. During granulation, this ammonia is released and enters the granulator offgas. In order to comply with ammonia emission limits, therefore, an ammonia offgas scrubber has to be used. This is very complicated in terms of apparatus and energy-consuming and produces an aqueous solution of an ammonia salt. This solution must either be disposed of or processed. In certain cases (in the case of nitrate fertilizers, for example), the ammonium salts obtained from offgas scrubbing can be returned to the process. In the production of urea-containing fertilizer granules, however, this possibility is absent or very limited (see EP 2 362 863 B1). If the fraction of ammonium salts in the product is increased, this leads to unwanted product properties in urea-containing fertilizer granules, for example to an increased hygroscopicity (see EP 2 616 412 B2). A further disadvantage is that the offgas scrubbers lead to a pressure loss and therefore sizeable fans are needed for the plant, which have a relatively high power consumption. The capital costs and the operating costs of a plant for producing fertilizer granules increase accordingly. Methods for reducing the ammonia emissions of a urea granulation plant, where the ammonia is absorbed in an acidic scrubbing solution and is reacted to form ammonium sulfate, are described in WO 2010/060535 A1, for example. Other approaches employed in the prior art provide for ammonia removal by stripping with carbon dioxide (see U.S. Pat. No. 6,084,129 A). A method and an apparatus for granulating urea in a fluidized bed granulator are known from EP 0 900 589 B1, for example. With this method, seeds of urea particles are introduced into a granulator, and these seeds are sprayed via nozzles with a concentrated aqueous urea solution. The granulator has a base plate with a multiplicity of apertures through which fluidizing air is blown in from below, caus