The Invention Relates to a Method for Producing an Organic Fertilizer with Humic Properties

Abstract

The present invention relates to a method for producing an organic fertilizer with humic substance properties by oxidizing and ammonifying lignite, wherein the organic fertilizer has a nitrogen content of up to 8 wt. %, based on the dry weight of the fertilizer, and a C/N ratio of 7 to 15, which is characterized in that the method is carried out as a continuous method and comprises the following steps: a) dispersing the lignite and aqueous ammonia solution in a dispersing circuit having a dispersing device, a recirculation container, and a recirculation pump; b) oxidizing the suspension from step a) with an oxygen-containing oxidizing agent at a temperature of <100 C. in an oxidation reactor; c) drying the product suspension obtained in step b) at a temperature of >50 C.; and d) cooling the dried product obtained in step c).

Claims

1. A method for producing an organic fertilizers with humic substance properties by oxidizing and ammonifying lignite, wherein the organic fertilizer has a nitrogen content of up to 8 wt. %, based on the dry weight of the fertilizer, and a C/N ratio of 7 to 15, wherein the method is carried out as a continuous method and comprises the following steps: a) feeding lignite particles, an aqueous ammonia solution, and optionally recovered product of step b) as starting materials into a dispersing circuit comprising a dispersing device, a recirculation container, and a recirculation pump; dispersing the starting materials while simultaneously reducing the lignite particles in size until a suspension of lignite particles and aqueous ammonia solution is formed; and taking the suspension out of the dispersing circuit and transferring it to step b); b) oxidizing the suspension obtained in step a) in an oxidation reactor with an oxygen-containing oxidizing agent at a temperature of <100 C., thereby forming a product suspension that is completely transferred to step c), or partially transferred to step c) and partially transferred to step a) as the starting material; c) drying the product suspension obtained in step b) at a temperature of >50 C. up to a residual moisture content of at most 30 wt. %, based on the total weight of the dried product; and d) cooling the dried product obtained in step c).

2. The method according to claim 1, wherein in step a) lignite particles with particle sizes >10 m are employed, which are reduced in size in the dispersing device to particle sizes of 10 m.

3. The method according to claim 1, wherein the concentration of the aqueous ammonia solution used in step a) is up to 10 wt. %, based on the total weight of the aqueous ammonia solution.

4. The method according to claim 1, wherein in step a) up to 30 wt. % of lignite particles and at least 70 wt. % of the aqueous ammonia solution are employed, each based on the total weight of the mixture of lignite particles and aqueous ammonia solution.

5. The method according to claim 1, wherein the mean retention time of the mixture of lignite particles and aqueous ammonia solution in the dispersing device of step a) is 30 to 300 min.

6. The method according to claim 1, wherein in step a) additionally an oxygen-containing oxidizing agent is fed to the suspension of lignite particles and aqueous ammonia solution that is selected from oxygen, oxygen-enriched air, air, ozone, or hydrogen peroxide.

7. The method according to claim 1, wherein the oxygen-containing oxidizing agent used in step b) is an oxygen(O.sub.2)-containing gas that is selected from oxygen, oxygen-enriched air or air or ozone or hydrogen peroxide.

8. The method according to claim 7, wherein the oxygen-containing oxidizing agent used in step b) is an oxygen(O.sub.2)-containing gas or ozone that is fed to the suspension at an excess pressure of up to 0.8 MPa by means of a gas metering device.

9. The method according to claim 1, wherein the mean retention time of the suspension obtained in step a) in the oxidation reactor is 15 to 300 min.

10. The method according to claim 1, wherein the oxidation reactor is connected to a further dispersing device.

11. The method according to claim 1, wherein the oxidation reactor runs at an excess pressure of up to 0.7 MPa.

12. The method according to claim 1, wherein the product suspension obtained in step b) is completely fed to step c).

13. The method according to claim 1, wherein the exhaust steam of ammonia and water vapor formed in step c) is purified by means of distillation.

14. The method according to claim 1, wherein an agglomerating agent is added in step c) and/or in step d).

15. The method according to claim 1, wherein the product suspension is doped with macro- and micronutrients, bacteria, fungi, or water reservoirs during drying in step c) and/or in step d).

16. The method according to claim 1, wherein drying of the product suspension in step c) is performed in a combined fluid dryer and/or cooling of the dried product in step d) is performed in rotary drum.

17. An organic fertilizer with humic substance properties having a nitrogen content of up to 8 wt. %, based on the dry weight of the fertilizer, and a C/N ratio of 7 to 15.

Description

EXAMPLE

[0083] 100 kg/hr of lignite dust are continuously withdrawn from a receiving vessel and fed into a dispersing device (Modell Ytron ZC) that is part of a circulation system that is additionally consisting of a recirculation container as well as a recirculation pump.

[0084] An aqueous 5% ammonia solution is continuously charged into the circulation system via the recirculation container, so that a mixture of 20 wt. % of lignite dust and 80 wt. % of ammonia solution, based on the total weight of the mixture, is formed. The mixture is pumped through the circulation system for a mean retention time of 180 min, wherein an intensive thoroughly mixing and size reduction of the lignite particles takes place.

[0085] The resulting lignite suspension is continuously withdrawn from the recirculation container and fed to the oxidation reactor.

[0086] The oxidation reactor is composed of a vessel with a usable volume of 2.5 m.sup.3 and further comprises a gassing agitator. In this arrangement the lignite suspension is gassed with pressurized air for a mean retention time of 120 min at 0.3 MPa (3 bar) and a temperature of 70 C. while stirring. The oxidized product suspension is continuously withdrawn via a receiving vessel, wherein the receiving vessel is under standard pressure.

[0087] The product suspension is continuously fed from the receiving vessel into a combined fluid dryer and dried at a mean temperature of 100 C. over a mean retention time of 10 hrs to a residual moisture of 25 wt. %, based on the total weight of the dried product. The mean retention time results from the volume of the dryer (3000 L) and the withdrawal quantity of the dried product (300 L/hr). The thus formed exhaust steam is purified by means of washing and distillation. The resulting aqueous ammonia solution is recycled into the process. An agglomeration agent is added to the product during drying to generate an agglomerate.

[0088] After drying, the agglomerated product is cooled in a slowly running drum and thereby can further be agglomerated as needed by adding further agglomerating agent. Then, the product temperature is at room temperature (20 to 30 C.).

[0089] Nitrogen yield of the thus obtained product was analytically determined.

[0090] Elemental Analysis:

[0091] C: 58.8%,

[0092] H: 5.1%,

[0093] N: 5.5%,

[0094] S: 0.7%.

[0095] Binding forms of the nitrogen (in wt. %, based on the total nitrogen content):

[0096] ammonium-N: 32.7 wt. %, organically bonded: 54.5 wt. %, amide-N: 12.7 wt. %.