Patent Application
20220204419
Currently there are national and international discussions about the emission of too many Nitrogen (N) and in specific Ammonia (NH3) by farmers in the Netherlands Ammonium (NH4+) is formed when urea from the urine of cows and pigs is degraded by the enzyme urease. This enzyme exists in the feces from the animals. In the liquid manure the amount of ammonium and the amount of ammonia are in equilibrium and this equilibrium shifts dependent on the pH value and the temperature. The ammonia vaporizes from the liquid manure, depending on the amount of ammonia in the air directly above the liquid manure.
Ammonia is a base and a natural component in the atmosphere. In the atmosphere, ammonia will neutralize acids, like nitric acid (HNO3), hydrochloric acid (HCl) and sulfuric acid (H2SO4), and form ammonium salt particles. Once ammonia enters the soil, it will contribute to the acidification of the soil and to the nitrogen fortification of the environment. Through nitrification in the soil, ammonium will form nitric acid. In this way, ammonia will contribute to the eutrophication, but also to the soil acidification.
To neutralize these negative effects, systems are known to manipulate the liquid manure in such a way, that usable environmental neutral products will remain. However, these existing systems do not have a high efficiency and a relatively low capacity.
It is an object of the present invention to design a liquid manure processor, which is capable of manipulating the liquid manure in such a way, that all negative effects from ammonia will be neutralized and phosphate (PO43−), Nitrogen salts and Potash will be recovered. The method according to the invention is characterized by:
In a continuous process it is preferred to increase the pH level in the liquid Struvite to convert the Ammonium into Ammonia before adding Hydrochloric acid to convert Ammonia into Ammonium Chloride.
During the treatment of the liquid part by adding Magnesium Chloride preferably air is inserted in the liquid to promote the process.
The liquid remaining from the reverse Osmose process is preferably neutralized to get clean water.
The pH level in the liquid Struvite is preferably increased by Lime injection.
The invention also relates to a device for processing liquid manure, in particular cattle manure, comprising:
The device preferable further comprises a neutralizing filter to neutralize the remaining liquid to get clean water.
The invention will be further elucidated below on the basis of drawings. These drawings show an embodiment of the method according to the present invention. In the drawings:
A reactive process has been designed to treat the liquid manure. This process converts components in the manure with negative impact on the environment, to useable components that can be used as fertilizer. The aim for removing the amount of harmful ingredients is more than 90%.
This process is used to treat slurry cattle manure by reducing nitrogen and phosphate components as polluting components. Reactive treatment will convert polluting nitrogen and phosphate components to a “slow-releasing” fertilizer: Struvite. Excess Nitrogen components are converted to the known and widely used fertilizer; Ammonium Chloride. Furthermore, excess water from the slurry will go through a water purification process which produces clean drinking water. Furthermore, excess water from the slurry will go through a water purification process which produces clean drinking water.
The process will be designed to handle (up-to) a preset capacity corresponding to the manure produced. This preset amount take small and big cattle owning clients into account. Operation of the process is mainly automated and requires low manual input.
The process steps are schematically shown in
Liquid manure is caught in a slurry pit which is located at slope (below grade) from the cattle housing. Next to the slurry pit is a slurry silo; a vertical drum for storage of manure that functions as the starting location for the treatment process. The slurry is transported from the pit to the slurry silo by a vacuum system. A schematic representation can be seen in
The manure in the silo is further used for the manure treatment process. During emptying of the slurry pit, the downstream processing of the manure will be stopped.
Solid/Liquid separation is done by means of a screw press or a vertical leaf filter. The screw press functions by pushing the slurry through a small mesh membrane pipe, with the driving force being a screw inside the meshed pipe. Water is pushed through the membrane and the solid part of the manure is pushed to the end of the screwed line, where it is collected in a collection box. A schematic drawing of a screw press can be seen below in
A screw press performance is selection based; high content of liquid without solid particle carryover means that the separated solid content will have a higher liquid content. Vice versa, a very dry solid after separation will have the liquid contain an amount of solid carryover. Separation favours a dry solid composition as the later reverse osmosis step separates the remaining solid particles from the liquid.
Alternatively, solid liquid separation can be done by means of vertical leaf filters. A vertical leaf filter can separate the solid content from the liquid with a high separation rate.
Hanging clothed filters are installed in a pressure vessel. The slurry is pushed through the filters, with the filters catching the solids which will stick to the filters. The liquid is collected and transported for further treatment. Intermittently, the filters need to be cleaned by vibrating the filters and pressurizing them with air. The solid substrate is collected at the bottom of the pressurized vessel.
With most of the nitrogen and phosphate present in the liquid manure, the liquid treatment is where most gains in term of converting said components to useful fertilizing components can be made. The present components in the liquid which will be treated are:
Ammonium and ammonia in a solution (water) are in equilibrium in the following reaction:
H2O+NH3↔OH−+NH4+
To produce the slow releasing fertilizer Struvite, the liquid manure must contain ammonium and phosphates. To shift the reaction to the favoured ammonium and subsequently convert said ammonium and phosphorous components present in the liquid manure, the following process steps are included in the liquid treatment and are elaborated on.
Fertilizer conversion to struvite requires the presence of Ammonium, Phosphate, Magnesium and water. Since Ammonium and phosphate are present, a reaction with magnesium is required to form Struvite. In case of a continuous process the process of Struvite creation can be done by treating the liquid manure in a continuous flow Struvite reactor where Magnesium Chloride (MgCl) is added with a dosing unit. In the Struvite reactor, air will be inserted to start the Struvite creating reaction. The Struvite will form as precipitate and separate from the liquid. The reaction of individual components to Struvite in the can be seen below:
Mg2++NH4++PO43−+6H2O→MgNH4PO4.6H2O↓
The reaction between the free ions occurs in a 1:1:1 molar ratio of respectively Magnesium, Ammonium and a Phosphate ions in the presence of water. Aeration will happen during the reaction to properly mix the Magnesium Chloride to the influent and increase reaction potential.
Precipitate Struvite formed in the Struvite reactor is collected from the reactor collection pipe. When removed, the Struvite is inserted into a mixer for final step fertilizer mixing.
Phosphates present in the liquid manure are converted with an equal number of moles of Ammonium to Struvite. Excess Ammonium is still present in the liquid manure stream. To convert leftover nitrogen to usable fertilizer, the ammonium needs to be shifted to Ammonia, and subsequently converted in a Ammonium Chloride reactor to Ammonium Chloride (NH4Cl) by adding Hydrochloric acid (HCl).
For a continuous flow process the steps of Ammonia shift, pH injection, ion exchange by other means or influencing ammonium ammonia equilibrium by other means as described hereafter are preferred. These steps can be omitted in case a batch process is performed.
The desired nitrogen components for conversive treatment to Ammonium Chloride is Ammonia (NH3). Since Ammonium and Ammonia exist in equilibrium, and a composition with only Ammonium is desired, the equilibrium reaction must be switched to Ammonium. The equilibrium reaction between Ammonium and Ammonia can be switched with a change in alkalinity, with a lower pH switching the reaction to Ammonium and a higher pH switching the reaction to Ammonia.
There are several possibilities to increase the pH level. In below two sections two common possibilities are discussed. In a later stage, the most effective method will be chosen.
To attain a mostly ammonia containing solution, pH dosing will be added. A separate dosing tank, pump and flow control system is installed that injects Lime into the liquid manure. Lime has no reactive properties with components present in the liquid and will not affect further liquid treatment steps negatively. Excess dosing is removed in a later process step. A schematic representation of the dosing and injection can be seen in
A small dosing installation is installed, dosing the influent by means of a pump with flow control. The injection is regulated by means of a pH indicating transmitter installed in the influent line downstream the pH injection point. The pH control is automated and provides the proper alkalinity for Ammonium to Ammonia conversion in the liquid manure.
As alternative to pH injection, more options where ion exchange takes place, such as applying the “common ion” effect or usage of resin to switch the Ammonium content to Ammonia can be used in the process.
With all Ammonium converted to Ammonia, the Ammonia can be converted to Ammonium Chloride with the addition of Hydrochloric acid.
A separate dosing tank, pump and flow control system is installed that injects Hydrochloric acid into the waste water and the liquid stream will pass through a Ammonium Chloride reactor. From this reactor the liquid will continue to the Reverse Osmose System.
The reaction between Ammonia and Hydrochloric acid is:
HCl+NH3↔NH4Cl
The Phosphor, and Nitrogen containing components are converted and can be separated from the liquid waste stream by means of reverse osmosis. Reverse Osmose (RO) is a liquid-driven membrane process, with the reverse Osmose membranes being capable of allowing water to pass through while rejecting solutes, such as salts or low molecular weight organic materials. This means that after the RO process, the ammonium chloride and potash present in the waste water stream are separated from the water present. The water from the reverse osmosis will have very low contamination components left.
The Reverse Osmose depends on acceptance of contamination in either the water stream, or the “fertilizer” stream. When the contamination of components in the water stream is very low, more water will carry over into the “fertilizer” stream during the reverse osmosis. Opposite, when the “fertilizer” is desired as having low water content, more “fertilizer” will go in the water stream.
The desired mode of operation for the reverse osmosis step is focused towards clean water, having water carry over into the “fertilizer” stream. The fertilizer stream can optionally be passed through another reverse osmose membrane for extra water retrieval.
The last step for cleaning the water is done by processing the clean water stream through a neutralizing filter.
The “fertilizer” stream will be directed to the mixer for final step fertilizer mixing.
Vacuum will be created by a compressor driving compressed air through an ejector, creating a lower pressure environment in the slurry silo.
The magnesium chloride will be added to the liquid manure as a dissolved mixture; MgCl2.6H2O. The solution will intermittently be prepared by mixing clean water from the downstream reverse Osmose to MgCl2.
In
Although the present invention is elucidated above on the basis of the given drawings, it should be noted that this invention is not limited whatsoever to the embodiments shown in the drawings. The invention also extends to all embodiments deviating from the embodiments shown in the drawings within the scope of the invention defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2027252 | Dec 2020 | NL | national |
