FR3062650A1 - PROCESS AND PLANT FOR PRODUCTION OF LIQUID FERTILIZER FROM AMMONIA AIR CHARGED FROM ANIMAL URINE - Google Patents

Abstract

The invention relates in particular to a method of producing a fertilizer from air from urine. It comprises the following steps: a) through a pipe (1), an acid solution is circulated and, against the current, a stream of air charged with ammonia, so as to extract at least partially the ammonia contained in the air coming from the passage of urine on this flow of air, an end (11) of said pipe (1) communicating with a storage tank (3) in which is contained said aqueous solution of acid and wherein the ammonium salt formed is received; b) the pH of the liquid of the reservoir (3) is permanently maintained at a set value between two pH1 and pH2 value terminals by addition of acid; c) once a high level of said reservoir (3) reached, the introduction of urine is interrupted so as to circulate an increasingly depleted stream of ammonia and continue to circulate said liquid, but without proceeding to a maintenance of the pH; d) the flow of said liquid is interrupted as soon as the latter has reached a set value pH3, and e) the said liquid is extracted.

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number: 3,062,650 (to be used only for reproduction orders)

©) National registration number: 17 50988

COURBEVOIE © Int Cl ⁸ : C 05 F 3/00 (2017.01), C 05 C 3/00

A1 PATENT APPLICATION

©) Date of filing: 07.02.17. © Applicant (s): DENITRAL - FR. (30) Priority: @ Inventor (s): PORCHER FRANCK, VIEL COREN- TIN and JOSSE BRIEUC. (43) Date of public availability of the request: 10.08.18 Bulletin 18/32. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ® Holder (s): DENITRAL. related: ©) Extension request (s): ©) Agent (s): REGIMBEAU.

IN

FR 3 062 650 - A1

PROCESS AND INSTALLATION FOR PRODUCING A LIQUID FERTILIZER FROM AMMONIA FILLED AIR FROM ANIMAL URINE.

_ The invention relates in particular to a process for producing a fertilizer from air from urine. It includes the following steps:

a) through a pipe (1), an acid solution is circulated and, against the current, an air flow loaded with ammonia, so as to at least partially extract the ammonia contained in the air coming from the passage of urine on this air flow, one end (11) of said pipe (1) communicating with a storage tank (3) in which the said aqueous acid solution is contained and in which the salt is received ammonium formed;

b) the pH of the reservoir liquid (3) is permanently maintained at a set value between two limits of pH-ι and pH ₂ values by adding acid;

c) once a high level of said reservoir (3) has been reached, the introduction of urine is interrupted so as to circulate a flow which is increasingly depleted in ammonia and one continues to circulate said liquid, but without proceeding to maintaining the pH;

d) the circulation of said liquid is interrupted as soon as the latter has reached a set value pH ₃ , and

e) extracting said liquid.

i

DOAAAINE OF THE INVENTION

The present invention relates to a method and an installation for producing a liquid fertilizer from air loaded with ammonia coming from animal urine.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

A few years ago, the group to which the present applicant belongs developed a system which makes it possible to separate faeces (solid matter) from pig urine (liquid fraction) below the gratings under which they are reared.

The urine is then stored and then spread in the fields. The solid fraction is dried and recovered in the form of fertilizers.

This system allows to concentrate more than 90% of the phosphorus present, more than 50% of the total nitrogen and more than 40% of total potassium in the solid phase. The liquid phase (urine) contains about 9% phosphorus, 45% nitrogen and 55% potassium.

Thanks to this system, the volume of urine is significantly reduced compared to an initial volume of raw manure. The spreading plan of the farm decreases thanks to a lower phosphorus and nitrogen content of the urine compared to a raw manure. However, the amount of nitrogen remaining in the urine is still significant and still poses problems in some areas where spreading is limited. And some farms have little land so little surface where spreading is possible.

The present applicant knows of a process having the trade name Balcopure, which aims to purify the slurry for adding quicklime and centrifugation.

This process works in cycles. Thus, the slurry from the livestock buildings is stored in a pit and is homogenized. The slurry is centrifuged at 4,000 rpm. The solid part of slurry is collected in a hopper located below the centrifuge.

The liquid part of the slurry is sent to the so-called “stripping” storage tank. This tank has a capacity of 10 m ³ . Lime milk is made (mixture of water and lime) and added to the liquid part. The whitewash makes it possible to raise the pH of the liquid part to 12. The whole is stirred and the liquid circulates in a hood provided with spray nozzles in order to extract the ammoniacal nitrogen therefrom. The treatment lasts 10 hours. The air loaded with ammonia is discharged to an air washer and is neutralized in a washing column with a solution of sulfuric acid + water. We then obtain a product which is ammonium sulfate.

But in order to capture the ammonia in the air, the pH of the solution to diffuse (sulfuric acid + water) must be below 2.5. However, a fertilizer that has a pH of 2.5 can be an obstacle to its marketing because, once applied to crops, it risks burning them.

The present invention therefore aims to overcome this drawback, by improving the above technique so as to obtain a fertilizer with a higher pH and if possible close to neutral, this fertilizer possibly being a salt other than ammonium sulphate.

SUMMARY OF THE INVENTION

Thus, the present invention relates firstly to a process for producing a liquid fertilizer from air loaded with ammonia from animal urine, characterized in that it consists in implementing in particular the following successive steps:

- a) through a pipe, an aqueous solution of acid is circulated in a first direction and, against the current, that is to say in a second direction opposite to the first direction, a flow of air charged with ammonia, so as to at least partially extract the ammonia contained in the air coming from the passage of urine on this air flow, in the form of an ammonium salt in solution, one end of said pipe communicating with a storage tank in which the said aqueous sulfuric acid solution is contained and in which the ammonium salt in solution thus formed is received;

b) the pH of the liquid contained in said reservoir is permanently maintained at an acid reference value between two limits of phL and pH ₂ values by addition of acid;

-c) once a high level of said reservoir is reached, the introduction of urine is interrupted so as to circulate henceforth a flow of air increasingly depleted in ammonia and one continues, for a predetermined period, to circulate said liquid coming from the reservoir, but without any maintenance of the pH value;

d) the circulation of said liquid coming from the reservoir is definitively interrupted as soon as the latter has reached a predetermined set value pH ₃ greater than the values pl-h and pH ₂ , and

e) extracting said liquid from the reservoir.

According to other non-limiting and advantageous characteristics of this process, taken alone or according to a combination of at least two of them:

- the values pl-h and pH ₂ are less than 3;

- said pH ₃ value is greater than 3 and less than 7;

- Said pipe is a vertical tower and that said aqueous solution is sprayed from the top to the bottom of this tower, in the direction of a packing, which is crossed against the current by said flow of air charged with ammonia;

- Said storage tank is located directly above the lower end of said tower, so that it receives by gravity the ammonium salt in solution;

- in step b), the addition of acid is carried out automatically, taking into account a regular reading of the pH value of said liquid;

in step c), said high level of reservoir is measured while a circulation pump of said liquid contained in said reservoir is in operation;

- Said air flow loaded with ammonia is recycled in a closed circuit, so that it is extracted from said pipe to proceed with the treatment of said urine;

- Said acid is sulfuric acid or nitric acid, so that ammonium sulfate or ammonium nitrate are produced respectively;

- We repeat at least once said steps a) to ej. Furthermore, the invention relates to an installation for implementing the method as described above.

Thus, thanks to the process according to the invention, a fertilizer having a higher pH is recovered than in accordance with the prior art, which facilitates its handling and allows spreading without risk on the crops.

In addition, provided that the air loaded with NH ₃ comes from a stripping cycle during which a large part of the ammonia extracted from the urine produced by animals has been recovered, then the pollutant releases are reduced accordingly and the ammonia is thus recycled in the form of a fertilizer.

If the animals are those raised on a farm, the implementation of the process on this same farm allows not only to manufacture the fertilizer on site, but also to use the latter on crops attached to the farm, which contributes sustainable agriculture.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention. This description is made with reference to the accompanying drawing in which FIG. 1 is which is an illustrative diagram of an installation for implementing the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

A first step of the method according to the invention consists in circulating through a pipe, in a first direction an aqueous solution of sulfuric acid and in countercurrent, that is to say in a second direction opposite to the first direction , a flow of air charged with ammonia, so as to at least partially extract the ammonia contained in the air, in the form of ammonium sulfate in solution. In addition, one end of said pipe communicates with a storage tank in which the said aqueous sulfuric acid solution is contained and in which the ammonium sulfate in solution thus formed is received.

In the embodiment which is described below, said pipe advantageously but not necessarily has the shape of a vertical tower 1. It can measure up to 10 meters high and have a diameter between 0.40 and 1.50 metre.

At its upper end 10 is connected a pipe 2 which serves, as will be seen later, to extract air which has been introduced into the tower 1 from another location.

The lower end 11 of the tower 1 opens directly into a storage tank 3.

This reservoir 3 is coupled with a reserve 30 of pure or practically pure sulfuric acid. This reserve is preferably replenished automatically when it is practically empty. It is connected to the reservoir 3 by a pipe 300 on which a metering pump 301 is installed.

Furthermore, another pipe 310 for the water inlet opens into the tank 3. It is equipped with a solenoid valve 311.

The tank 3 is also equipped with a pH meter and high and low level sensors, which are not shown in the figures.

Finally, a last pipe 32 equips the reservoir 3. Its lower end 320 plunges inside the reservoir 3, while its upper end 321 opens out inside the tower 1, not far from its upper end 10.

Although this is not visible in the figure, this upper end 321 is configured to allow a liquid to be identified, for example made up of Pall and / or Raschig rings, on a lining (also not shown). later in the description.

A pump 322 is provided on the pipe 32 for conveying liquid towards the end 321. A bifurcation 323 is provided downstream of the pump 322 whose access is made possible by a pinch valve 324. Downstream of this another branch valve 325, a manual valve 326 and a flow meter 327 are provided.

As was specified above, at the upper end 10 of tower 1 is connected a pipe 2 which is used to extract the air introduced into this tower 1, called washing, at another location.

In the example illustrated here, the air extracted from tower 1 is blown into a second tower 4 which has, for example, a structure similar to tower 1. It can be qualified as a stripping tower according to the English terminology used.

This tower 4 is coupled to a decanter 5 (which constitutes a storage tank) in which is contained a certain volume of urine which has been treated with lime. This urine preferably comes directly from a farm of animals such as pigs in which the urine has been previously collected and processed.

A first end 500 of a pipe 50 is connected to the decanter 5, while the opposite end 501 opens out inside the tower 4, not far from its top.

This end 501 is configured in a similar manner to that of the end 321 of the pipe 32 described above. It will be noted that the pipe 50 is provided with a pump 51 and a flow meter 52.

The top of the tower 4 is provided with an extension 40, the distal end 400 of which is connected to the tower 1, substantially at the level of the first lower third of its height.

Similarly and as indicated above, the pipe 2 which originates at the top of the tower 1 is connected to the tower 4, via a flange 20 which extends substantially at the level of the first lower third of the height of the tower

4.

An example of implementation of the method is described below, in relation to the installation which has just been detailed.

This process can be divided into three cycles, respectively of preparation, treatment and finishing.

Prior to the preparation cycle, tower 4 was started, so that the pump 51 extracts treated urine from the decanter

5. This urine is injected in tower 4 is distributed over the lining which it contains.

Furthermore, by starting the fan 6, air is blown against the current, that is to say in an upward direction, opposite to that of the urine which moves by gravity. Preferably, the air is blown in slight overpressure relative to atmospheric pressure.

In doing so, the air is charged with ammonia, which escapes from tower 4 through its extension 40 to be reinjected into tower 1.

At the same time, the urine at least partially freed of its ammonia flows by gravity at the bottom of tower 4 where it can be collected to be stored.

The preparation cycle can be implemented as follows.

The stripping tower 4 is stopped. The valve 325 is in the open position towards the tower 1 and the valve 324 is closed. Opening the solenoid valve

311 is effective. Thus, the reservoir 3 fills with water up to a first predetermined high level detected by the aforementioned sensor. When this first high level is reached, the solenoid valve 311 closes, so that the water supply is stopped.

The pump 322 and the pump 301 used to dose the acid start up. It should be noted that the injection of water and acid into the reservoir 3 is not done simultaneously.

The acid injection is automatically stopped as soon as the aforementioned pH meter indicates a low pH value. This low phL value is for example equal to 0.5.

The processing cycle can be implemented as follows.

The pump 51 at the decanter outlet is started with a flow regulation (made possible by the flow meter 52 which operates according to a flow set point value). The stripping tower 4 assembly is started.

The air charged with ammonia which enters the tower 1 flows upwards against the acid / water mixture which is distributed in the tower via the end 321 of the pipe 32.

In doing so, the acid captures the ammonia, so that water-soluble ammonium sulfate is formed, while the air is at least partially freed from the ammonia it contained. This purified air is then sucked in by fan 6 and is reinjected into tower 4, via line 2. Air recycling is thus carried out, so that no pollution, particularly olfactory pollution (due to ammonia) n takes place.

During the treatment, that is to say during this operation for manufacturing liquid ammonium sulfate which flows by gravity into the tank 3, the pH of the acid / water mixture present in this tank increases.

However and in accordance with a second step of the process according to the invention, as soon as the aforementioned pH meter measures a high pH value, for example consisting of a pH value ₂ equal to 1, the pH of this liquid is permanently maintained at a value between phL and pH ₂ by adding sulfuric acid. It is indeed necessary to maintain a pH as acidic as possible to obtain a good yield for manufacturing ammonium sulfate.

Under these conditions, the dosing pump is started in order to reach the set point phL. During this pH regulation, the two towers 1 and 4 are in operation.

This is continued until a second high level of the reservoir 3 is reached and detected by the aforementioned sensor.

This second level having been reached, the treatment cycle is completed and the introduction of urine to the tower 1 is stopped, while keeping the fan 6 and the pump 322 running so as to now circulate air which s '' gradually depleted in ammonia.

The product thus produced must be as homogeneous as possible. Under these conditions, the second high level mentioned above must be identical at the end of each treatment cycle.

However, this second high level varies a lot during manufacturing. Indeed, during the operation of tower 1, part of the liquid is in the aforementioned packing. When all two towers 1 and 4 are stopped, this residual liquid continues to flow by gravity, so that the level of liquid in the reservoir 3 increases suddenly. Thus, when the assembly is restarted, this reservoir can be more or less filled (for example from 76 to 85%).

To remedy this problem, the tank level is measured and validated a few minutes after the start of all two towers. An instruction allows this time to be defined. The lining is then loaded with liquid. And the liquid level is always the same to enter the finishing cycle.

By doing this, by adding acid to the tank 3 by measuring the set value only during the tower operation period, this achieves the desired final fertilizer concentration.

The finishing cycle can be carried out as follows.

Both towers are still in operation. The pump 51 operates with the regulation setpoint indicated by the flow meter 52.

Air washing increases the pH. A desired high pH setpoint to be reached is indicated. When this setpoint is reached, the pump 51 stops, the pump 301 and the fan 6 stop a few moments after the pump 51. The valve 325 is closed and the valve 324 open to extract the liquid fertilizer which has been manufactured. Pump 322 is started and extracts the product up to a low level setpoint.

This low level being reached, the finishing cycle is finished and the pump 322 stops. Following this stop, a new preparation cycle can be carried out.

Although the present process has been described while the air charged with ammonia comes from a stripping tower which operates in parallel, it could be envisaged that the washing and stripping operations are carried out one independently of the other. .

Furthermore, in the above description, the acid used is sulfuric acid, so that ammonium sulfate is recovered. However, one can make use of another acid such as nitric acid so that the recovered fertilizer is then ammonium nitrate.

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Claims (11)

1. Method for producing a liquid fertilizer from air loaded with ammonia from animal urine, characterized in that it consists in implementing in particular the following successive steps: -a) through a pipe (1), an aqueous acid solution is circulated in a first direction and, against the current, that is to say in a second direction opposite to the first direction, a flow of air charged with ammonia, so as to at least partially extract the ammonia contained in the air coming from the passage of urine on this air flow, in the form of an ammonium salt in solution, one end (11 ) of said pipe (1) communicating with a storage tank (3) in which said aqueous acid solution is contained and in which the ammonium salt in solution thus formed is received; - b) the pH of the liquid contained in said reservoir (3) is permanently maintained at an acid setpoint between two limits of pIT and pH ₂ values by addition of acid; -c) once a high level of said reservoir (3) has been reached, the introduction of urine is interrupted so as to circulate henceforth a flow of air increasingly depleted in ammonia and one continues, for a predetermined period, circulating said liquid from the reservoir (3), but without maintaining the pH value in any way; d) the circulation of said liquid coming from the reservoir 3 is definitively interrupted as soon as the latter has reached a predetermined set value pH ₃ greater than the values pIT and pH ₂ , and - e) extracting said liquid from the reservoir (3). 2. Method according to claim 1, characterized in that the pIT and pH ₂ values are less than 3. 3. Method according to one of claims 1 or 2, characterized in that said pH value ₃ is greater than 3 and less than 7. 4. Method according to one of claims 1 to 3, characterized in that said pipe is a vertical tower (1) and that said aqueous solution is sprayed from the top to the bottom of this tower, on a packing, which is crossed against the current by said air stream charged with ammonia. 5. Method according to claim 4, characterized in that said storage tank (5) is located directly below the lower end (11) of said tower (1), so that it receives by gravity the ammonium salt in solution. 6. Method according to claim 5, characterized in that, in step 5), the addition of acid is carried out automatically taking into account a regular reading of the pH value of said liquid. 7. Method according to one of the preceding claims, characterized in that in step c), said high reservoir level is measured while a pump (322) for circulating said liquid contained in said reservoir (3) 10 is in operation. 8. Method according to one of the preceding claims, characterized in that the said flow of air charged with ammonia is recycled in a closed circuit, so that it is extracted from the said pipe (1) in order to treat the said urine . 15 9. Method according to one of the preceding claims, characterized in that the said acid is sulfuric acid or nitric acid, so that ammonium sulfate or ammonium nitrate are produced respectively. 10. Method according to one of the preceding claims, characterized in that said steps a) to e) are repeated at least once. 20 11. Installation for producing a liquid fertilizer for implementing the method according to one of the preceding claims.