WO2018145964A1

WO2018145964A1 - Method and facility for producing a liquid fertiliser from air loaded with ammonia from animal urine

Info

Publication number: WO2018145964A1
Application number: PCT/EP2018/052324
Authority: WO
Inventors: Franck PORCHER; Corentin VIEL; Brieuc JOSSE
Original assignee: Denitral
Priority date: 2017-02-07
Filing date: 2018-01-31
Publication date: 2018-08-16
Also published as: CN110382447A; FR3062650B1; FR3062650A1

Abstract

The invention relates to a method for producing a fertiliser from air from urine. Said method comprises the following steps: a) an acid solution is circulated through a conduit (1), and an air flow loaded with ammonia is circulated counter-currently in such a way as to at least partially extract the ammonia contained in the air due to the passage of urine over said air flow, one end (11) of said conduit (1) communicating with a storage tank (3) containing said aqueous acid solution and receiving the ammonium salt formed; b) the pH of the liquid in the tank (3) is permanently maintained at a nominal value between two value limits ph1 and pH2 by acid addition; c) once a high level of said tank (3) is reached, the introduction of urine is interrupted in such a way as to circulate a flow that is more and more depleted in ammonia and the circulation of said liquid is continued but without maintaining the pH; d) the circulation of said liquid is interrupted as soon as it reaches a nominal value pH3; and e) said liquid is extracted.

Description

PROCESS AND PLANT FOR PRODUCTION OF LIQUID FERTILIZER FROM AMMONIA AIR CHARGED FROM ANIMAL URINE

FIELD OF THE INVENTION

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

BACKGROUND OF THE INVENTION

A few years ago, the group to which the applicant belongs has developed a system that separates feces (solids) from pig urine (liquid fraction) below the gratings under which they are grown.

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

This system makes it possible 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.

With this system, the volume of urine is significantly reduced compared to a volume of raw liquid manure. The plan for spreading livestock is decreasing thanks to a lower phosphorus and nitrogen content of the urine compared to a raw slurry. However, the amount of nitrogen remaining in the urine is still significant and still causes problems in some areas where application is limited. And some farms have little land so little area where spreading is possible.

The present applicant knows a process with the trade name Balcopure, which aims the purification of manure for adding quicklime and centrifugation.

This process operates in cycles. Thus, manure from livestock buildings is stored in a pit and is homogenized. The slurry is centrifuged at 4000 rpm. The solid portion of manure is recovered in a hopper located below the centrifuge. The liquid part of the manure is sent to the so-called "stripping" storage tank. This tank has a capacity of 10 m ³ . A whitewash is made (mixture of water and lime) and added to the liquid part. The milk of lime makes it possible to raise the pH of the liquid part to 12. The whole is put under agitation and the liquid circulates in a hood provided with nozzles of spray in order to extract the ammoniacal nitrogen. The treatment lasts 10 hours. The air loaded with ammonia is discharged to an air washer and neutralized in a washing column with a solution of sulfuric acid + water. A product is obtained which is ammonium sulphate.

But in order to capture the ammonia in the air, the pH of the solution to be diffused (sulfuric acid + water) is preferably less than 2.5, in order to obtain a satisfactory yield. However, a fertilizer that has a pH of 2.5 can be a brake for its marketing because, once spread on crops, it may burn them.

The present invention therefore aims to overcome this drawback, by improving the above technique so as to obtain a higher pH fertilizer and if possible close to neutrality, this fertilizer may be another salt than ammonium sulfate. SUMMARY OF THE INVENTION

Thus, the present invention relates in the first place to a method for producing a liquid fertilizer from ammonia-laden air from animal urine, characterized in that it consists in implementing, in particular, the successive stages:

a) through a pipe, is circulated in a first direction an aqueous solution of acid and countercurrent, that is to say in a second direction opposite to the first direction, a flow of air loaded with ammonia, so as to extract at least partially the ammonia contained in the air from the passage of urine on this air stream, in the form of an ammonium salt in solution, an end of said pipe communicating with a storage tank in which the said aqueous solution of sulfuric acid 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 acidic set point value between two pH and pH ₂ value terminals by addition of acid;

c) once a high level of said reservoir has been reached, the introduction of urine is interrupted so as to now circulate a stream of air that is increasingly depleted of ammonia and, for a predetermined period, circulation is continued said liquid from the reservoir, but without any maintenance of the pH value;

d) the circulation of said liquid coming from the reservoir is definitively interrupted once the latter has reached a predetermined set point value pH ₃ higher than the values ph 2 and pH ₂ , and

e) extracting said liquid from the reservoir.

According to other nonlimiting and advantageous features of this method, taken alone or in a combination of at least two of them:

the values ph 2 and pH ₂ are less than 3, preferably less than 2.5;

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

said pipe is a vertical tower and that said aqueous solution is projected from the top to the bottom of this tower, in the direction of a lining, which is traversed countercurrently by said flow of air charged with ammonia;

said storage tank is located vertically 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 operated automatically taking into account a regular reading of the pH value of said liquid;

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

said stream of ammonia-laden air is recycled in 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 sulphate or ammonium nitrate are produced respectively; at least once said steps a) to e) are repeated. Furthermore, the invention relates to an installation for implementing the method as described above. Thus, thanks to the method according to the invention, a fertilizer is recovered having a higher pH than in accordance with the prior art, which facilitates its handling and allows a safe spreading on crops.

In addition, as long as 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 pollutants and thus recycling the ammonia in the form of a fertilizer.

If the animals are those raised on a farm, the implementation of the process on this same farm not only makes it possible to manufacture the fertilizer on site, but also to use it 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 Figure 1 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 process according to the invention consists in circulating through a pipe, in a first direction, an aqueous solution of sulfuric acid and, against the current, that is to say in a second direction opposite to the first direction. a stream of air charged with ammonia, so as to extract at least partially the ammonia contained in the air, in the form of ammonium sulfate in solution. In addition, an end of said pipe communicates with a storage tank in which the said aqueous solution of sulfuric acid is contained and in which the ammonium sulphate solution thus formed is received. In the embodiment which is described below, said pipe advantageously but non-compulsorily has the shape of a vertical tower 1. It can measure up to 10 meters high and have a diameter of between 0.40 and 1.50 meters.

At its upper end 10 is connected a pipe 2 which serves, as will be seen later, to extract air that was introduced into the tower 1 by another place.

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

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

Furthermore, another line 310 of water inlet opens into the tank 3. It is equipped with a solenoid valve 31 1.

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 channel 32 equips the tank 3. Its lower end 320 dips inside the tank 3, while its upper end 321 opens into the interior of 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 to spread, on a lining (also not shown) for example consisting of Pall rings and / or Raschig, a liquid that will be identified further in the description.

A pump 322 is provided on the pipe 32 for the delivery of liquid to the end 321. A bifurcation 323 is provided downstream of the pump 322, access to which is made possible by a pinch valve 324. Downstream of this bifurcation is provided another valve 325 with a sleeve, a manual valve 326 and a flowmeter 327.

As mentioned above, at the upper end 10 of the tower 1 is connected a pipe 2 which serves to extract the air introduced into the tower 1, called "washing", at another location.

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

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 comes preferentially directly from an animal farm such as pigs in which the urine has been previously collected and treated.

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

This end 501 is configured in a manner similar 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 flowmeter 52.

The top of the tower 4 is provided with an extension 40 whose distal end 400 is connected to the tower 1, substantially at the 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 connection with 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, the tower 4 has been started, so that the pump 51 extracts treated urine from the decanter 5. This urine is injected into the tower 4 is distributed on the lining it contains.

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

In doing so, the air is charged with ammonia, which escapes from the tower 4 by its extension 40 to be reinjected into the tower 1. At the same time, the urine at least partially freed of its ammonia flows gravitarily down the tower 4 where it can be collected for storage.

The preparation cycle can be implemented as follows.

The stripping tower 4 is stopped. The valve 325 is in the open position to the tower 1 and the valve 324 is closed. The opening of the solenoid valve 311 is effective. Thus, the reservoir 3 fills with water to a first predetermined high level detected by the aforementioned sensor. Once this first high level reached, the solenoid valve 311 closes, so that the water supply is stopped.

The pump 322 and the pump 301 for dosing the acid start. Note that the injection of water and acid into the tank 3 is not simultaneous.

The acid injection is stopped automatically as soon as the above-mentioned pH meter indicates a low pH value. This low value ph ^ is for example equal to 0.5.

The treatment cycle can be implemented as follows.

The pump 51 at the outlet of the settling tank starts with flow control (made possible by the flowmeter 52 which operates according to a flow setpoint value). The stripping tower assembly 4 is started.

The ammonia-laden air entering the tower 1 flows upwardly from the acid / water mixture which is distributed in the tower via the end 321 of the pipe 32.

In doing so, the acid "picks up" ammonia, so that water-soluble ammonium sulfate is formed, while the air is at least partially free of the ammonia it contains. . This "purified" air is then sucked by the fan 6 and is "reinjected" into the tower 4, via the pipe 2. There is thus a recycling of air, so that no pollution including olfactory (due to ammonia) does not take place.

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

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

Under these conditions, the dosing pump starts to reach the set point ph ^. During this pH control, both turns 1 and 4 are in operation.

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

This second level being reached, the treatment cycle is completed and the introduction of urine into the tower 1 is stopped, while keeping the fan 6 and the pump 322 running so as to now circulate air which is Gradually depletes ammonia.

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

Out, this second high level varies a lot during manufacturing. Indeed, during operation of the tower 1, a portion of the liquid is in the aforementioned lining. When stopping all of the two turns 1 and 4, this residual liquid continues to flow gravitarily, so that the liquid level in the tank 3 increases sharply. Thus, when restarting the assembly, 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 both sets of laps. An instruction allows to define this time. The packing is then loaded with liquid. And the liquid level is always the same to go into the finishing cycle.

By doing this, by adding acid to the tank 3 by measuring the setpoint only during the period of operation of the towers, this makes it possible to reach the desired final concentration of fertilizer.

The finishing cycle can be implemented as follows.

Both towers are still running. The pump 51 operates with the regulation setpoint indicated by the flowmeter 52.

The washing of air causes an increase of the pH. A desired high pH target to be reached is indicated. This instruction 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 that has been manufactured. The pump 322 is turned on and extracts the product to a low level setpoint.

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

Although the present process has been described while the ammonia-laden air comes from a parallel stripping tower, it could be envisaged that the washing and stripping operations be carried out independently of one another. .

Furthermore, in the foregoing description, the acid used is sulfuric acid, so that ammonium sulfate is recovered. However, it is possible to use another acid such as nitric acid so that the recovered fertilizer is then ammonium nitrate.

Claims

1. A 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 conduit (1), an aqueous solution of acid is circulated in a first direction and, in countercurrent, ie in a second direction opposite to the first direction, a flow of ammonia-laden air, so as to at least partially extract the ammonia contained in the air from the passage of urine on this air flow, in the form of an ammonium salt in solution, an end (1 1) of said pipe (1) communicating with a storage tank (3) in which is contained said aqueous acid solution and in which is received the ammonium salt in solution thus formed;

b) the pH of the liquid contained in said reservoir (3) is permanently maintained at an acidic set point value between two pH and pH ₂ value terminals by addition of acid;

- c) once a high level of said tank (3) reached, the introduction of urine is interrupted so as to now circulate an air stream increasingly depleted of ammonia and is continued, for a predetermined period, circulating said liquid from the reservoir (3), but without any maintenance of the pH value;

d) the circulation of said liquid coming from the tank (3) is definitively interrupted once the latter has reached a predetermined set point value pH ₃ higher than the values pH and pH ₂ , and

e) extracting said liquid from the reservoir (3).

2. Method according to claim 1, characterized in that the pH values and pH ₂ are less than 3, preferably less than 2.5.

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 projected from the top to the bottom of this tower, on a lining, which is traversed countercurrently by said air flow loaded with ammonia.

5. Method according to claim 4, characterized in that said storage tank (5) is in line with the lower end (1 1) 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 b), the addition of acid is operated 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) is in operation.

8. Method according to one of the preceding claims, characterized in that said air stream charged with ammonia is recycled in a closed circuit, so that it is extracted from said pipe (1) to proceed with the treatment of said urine .

9. Method according to one of the preceding claims, characterized in that said acid is sulfuric acid or nitric acid, so that ammonium sulfate or ammonium nitrate is produced respectively.

10. Method according to one of the preceding claims, characterized in that it repeats at least once said steps a) to e).

1 1. Installation for producing a liquid fertilizer for implementing the method according to one of the preceding claims.