WO2007115660A2

WO2007115660A2 - Method and device for the production of nitrogen fertilizer from biogenic materials

Info

Publication number: WO2007115660A2
Application number: PCT/EP2007/002532
Authority: WO
Inventors: Bernhard Krieg; Jörg WARTENBERG; Horst Hennig; Thomas Weidele; Jörg Hofmann; Mike Wecks
Original assignee: Energietechnik Leipzig Gmbh
Priority date: 2006-04-03
Filing date: 2007-03-22
Publication date: 2007-10-18
Also published as: WO2007115660A3; DE102006015496B4; DE102006015496A1

Abstract

The invention relates to a method and a device for producing nitrogen-containing fertilizers by treating biogenic materials. The aim of the invention is to eliminate the two gases ammonia and carbon dioxide, which are produced during the biogas process and are dissolved in the liquid, from the liquid in an elegant technical manner and utilize said gases. Said aim is achieved by applying ultrasound to degassing vessels and absorption vessels and then obtaining fertilizers.

Description

Process and device for the production of nitrogen fertilizers from biogenic substances

The invention relates to methods and apparatus for the production of nitrogen fertilizer from biogenic substances, in particular from residues of biogas plants

It is already known to produce nitrogen fertilizer from agricultural and forestry waste. Often, this procedure is associated with the production of biogas, which is intended to generate energy with the proviso to supply the residues of the process for further use. Among other things, this involves converting the residues resulting from the fermentation process into agriculturally usable compounds, for example mineral fertilizers.

Thus, WO 2005/049495 describes the course of the process of processing animal manure and manure into nitrogen fertilizer. According to this teaching, a method and a device for the recovery of nitrogen fertilizer from organic waste products in the liquid phase (suspension, emulsion, solution) and for the sanitation of the waste or for emission reduction by thermal treatment using mineral or organic additives is proposed. According to the teaching of WO 2005/049495, this is achieved by a method in which the heated to-utilizing waste product in vacuum at temperatures between 40 ⁰ C and 90 ⁰ C, cooling the thereby escaping carbon dioxide and ammonia containing gas and and introduced into an aqueous absorption medium , the nitrogen fertilizer formed thereby discharged and the unabsorbed and carbon dioxide-containing excess gas is pumped back into the drain tank, wherein the negative pressure generated at the beginning of the process by a vacuum pump is maintained autogenous by the course of the process.

It is expedient according to this technical teaching to recirculate the excess gas into the circuit by introducing it either directly above the waste product to be treated or via a gas cooling system above the waste product to be treated or divided and a partial flow through the waste product and another partial stream above the waste product is initiated. Preferably, a gypsum slurry is used as the aqueous absorbent.

In DE 10 2005 047 719.4 it is proposed to bring biomass consisting of biogenic products into a pumpable state, in fermenters to promote the biogas formation process with continuous stirring by mesophilic fermentation at 38 to 42 ⁰ C or thermophilic fermentation at 50 to 60 ⁰ C takes place. The resulting biogas is stored and subsequently recycled. Part of the digestate is heated to 70 to 90 ° C, in a stripping ammonia / ammonium nitrogen is withdrawn, the sanitized low-nitrogen digestate is separated in solid and liquid phase. The stripping process takes place under reduced pressure in a batch process. The discharge of the gas ammonia is not specified.

A disadvantage of the known technical solution of WO 2005/049495 is that the fresh or fermented manure must be heated to 90 ° C.

Another disadvantage of the proposed procedure is that only the batch process is used. In the text of the description of the invention, the possibility of continuous work is mentioned, but neither in the examples nor in the claims is there a concretization.

The disadvantage is the need for a sophisticated temperature / pressure regime, which must ensure that the stripping container for hours constantly 80 ⁰ C and 300 to 500 mbar must be maintained.

Another disadvantage is the complicated stirring of a receiving suspension for the expelled gases carbon dioxide and ammonia. For this purpose, a slurry of mineral flour such as gypsum or the like is generally used, in which the carbon dioxide / ammonia gas mixture is introduced. This gives lime and ammonium sulfate, which are separated from the liquid phase.

The cause of the disadvantage of the necessary heating is due to the process principle. The heat supply causes the expulsion of the gases ammonia and carbon dioxide from the suspension of manure, animal manure or the like Method and apparatus are aligned to the batch process. There are no studies on a continuous procedure.

The temperature / pressure regime must be observed because the heat causes the degassing and the resulting gas must be sucked with vacuum to influence the balance between dissolved and free gas. Despite all this, noticeable amounts of water vapor are extracted, another cause of energy loss.

Mineral flour such as gypsum or the like must be kept in suspension by stirring, so that a reaction of the solids with the gases can take place.

The invention has the goal of a cost-effective, energetically much less expensive process step of degassing of biogenic substances, such. As liquid manure or an animal kot suspension or digestate of a biogas plant to effect.

The process should be designed continuously.

The escaping gases should be removed without energy loss.

The tedious energetic disadvantageous stirring of mineral suspensions is to be replaced by an efficient method of mixing.

The invention has the object of removing the two essential gases ammonia and carbon dioxide in a technically simple manner from the liquid and convert to fertilizers.

The method should be applicable to almost all fermentable biogenic substances and define manure and animal excrement as a special case.

The technical system should be able to be operated continuously by a special design and arrangement of degassing. It is to be avoided that the gases to be discharged away heat energy, whereby water vapor escapes in appreciable amounts with.

The required for the reaction between solids and gases surface contact should be reliably secured.

The object is achieved according to the invention by subjecting biogenic substances, in particular manure or animal kot suspension, to ultrasound in two essential process steps during the process of biogas production with subsequent production of nitrogen fertilizer. The use of ultrasound is based on the scientific knowledge that under special conditions it is possible to create a cavitation zone in a liquid, but also in a suspension, within which the liquid is degassed.

Prerequisites for this are, according to the invention, that the suspensions to be degassed are passed through a cavitation zone, the cavitation space is not higher than 200 cm, that powerful sonotrodes are used and interference of the ultrasonic waves is avoided by using a plurality of ultrasound transmitters.

The ultrasound sensors used according to the invention are flanged laterally in the inlet or on the underside of the degassing container. It is possible to design sonotrodes as cylinders and to arrange them centrally in the degassing tanks. It is also possible to design the sonotrodes as discs and to flanging on the bottom of the degassing. They may be rod-shaped and attached laterally. Finally, it can be used on any sonotrode forms that are available.

The frequency is preferably between 20 kHz and 1.7 MHz and can be regulated.

According to the invention, several, preferably three to ten degassing tanks with a height of 200 cm are connected in parallel or in series.

In a preferred embodiment, the degassing tanks have a diameter of 10 to 20 cm. Particularly favorable is a diameter of 15 cm. The liquid to be degassed is kept above room temperature, with a range up to 40 ⁰ C is preferred, so that energy losses largely excreted.

The escaping gas, a mixture of carbon dioxide and ammonia, is rinsed out of the degassing vessel by a carrier gas or sucked off by a slight negative pressure and passed through a compressor in an adsorption vessel.

The second process step, in which the ultrasonic application is used, is the process of the reaction of ammonia gas with CaSO ₄ in aqueous solution or suspension. Ultrasound causes an exceptionally efficient mixing of the reactants and a surface activation of the solids and thus a sufficient contact surface between solid and gas and thus a faster and more advantageous reaction sequence.

The surface contact between the gases carbon dioxide and ammonia and reactants such as mineral flour, for example gypsum or the like, is achieved by ultrasonically impinging an absorption vessel, which ensures the distribution of the initial solid mineral flour in a liquid such as water or the like, and thus a sufficient Ensured contact surface between solid and gas.

The ultrasound transmitters to be used for mixing the reaction liquid are of any desired design. At least one sonotrode is used per reactor, but it is possible to attach several sonotrodes whose frequencies are coordinated to avoid interference. As in the first step of applying the solution or suspension with ultrasound, the formation of the sonotrodes is arbitrary. Preference is given to the use of circular discs with a diameter of 10 to 20 cm, with 15 cm are favored. The form of the sonotrodes is by no means limited to this.

The process according to the invention proceeds as follows. The fermented by microorganisms biogenic substances such as manure, Tierkotsuspension or the like arrive at a temperature of about 40 ° C in degassing, which are connected in parallel or in series. The containers are continuously subjected to ultrasound. Cavitation bubbles form in the liquid, which expel the gases. First, carbon dioxide escapes, then ammonia. The escaping gases are removed by rinsing or suction before they can dissolve again according to the chemical equilibrium. The degassed residue is removed from the container and further treated.

The gases are passed through a compressor in a suspension of mineral flour in water, wherein the suspension is kept stable according to the invention by ultrasound. After the chemical reaction between the gypsum and the gases carbon dioxide and ammonia, in which ammonium sulfate and lime are formed, the solids are separated from the liquid and further processed in a manner known per se.

The ammonia content of the incoming gas mixture is completely converted chemically, resulting in lime and ammonium sulfate. Any excess carbon dioxide content is recycled to the reaction process.

In order to ensure a throughput of 10 m ^{3 of} liquid manure per hour, three ultrasonic degassing tanks are required.

The degassing tanks are preferably made of VA steel, have an inlet and an outlet opening for the liquid and at the upper lid an outlet opening for the escaping gas.

The flow rate of the residual slurry or animal kote suspension is 0.05 to 0.5 m / s, preferably 0.1 m / s.

An apparatus for carrying out the method has the following essential parameters.

The degassing used in the known per se process for the production of biogas for expelling the gases ammonia and carbon dioxide are so designed so that they each carry a liquid inlet and outlet nozzle at a height of up to 200 cm, also a gas outlet opening and at least one ultrasonic generator, while eliminating a stirrer. Several, preferably three to ten, reactors are connected in parallel or in series and the degasification process is continuously controlled.

Absorption vessels for absorbing carbon dioxide and ammonia are designed such that they have an inlet nozzle for a mixture of neutral or sulfuric acid gypsum slurry, a gas inlet nozzle and at least one ultrasonic generator and a discharge for solids.

The ultrasound transmitters can be designed both for the generation of low-frequency and high-frequency ultrasound.

The degassing of the liquid and the mixing of the absorption suspension with ultrasound brings surprisingly significant technical and economic progress. It is astonishing that the researchers and technicians have hitherto disregarded this possibility and the literature on the state of the art does not comment on this possible double function of the ultrasound in a process.

The invention will be explained in more detail by way of examples. Example 1 is shown in Figure 1.

example 1

According to Figure 1, biogenic residues 1 are passed as a pumpable suspension according to the taking place in a conventional manner exposure to microorganisms in a fermenter in the degassing tank 2. Here, the degassing of the liquid takes place by the degassing vessel is subjected to ultrasound. The gases - preferably CO ₂ and NH ₃ - escape rapidly and almost completely under the action of ultrasound. They are derived via 4, pass through the compressor 5 and are passed into the absorption vessel 6, which contains an absorber suspension. This is a gypsum suspension, which may also contain a small amount of H ₂ SO ₄ . From the absorption vessel 6 liquid is withdrawn continuously, which up to 40% Contains ammonium sulfate. The escaping gas is compressed in the compressor 9 and returned to the circulation or energetically utilized. The absorption vessel is subjected to ultrasound, whereby a continuous mixing and close contact of the gas phase with the liquid and solid components is ensured.

Example 2

After extensive decomposition of biogenic residues by microorganisms, a liquid stream is passed into the degassing tank. Of these, 6 pieces are connected in series in this example, they have a height of 2 m with a diameter of 20 cm. They are filled with the liquid to be degassed so far that 0.375 m ^{3 of} available volume remain. The flow rate of the liquid stream is 0.09 m / s. The degassing is carried out by continuous ultrasound. As an ultrasound transducer in this example circular membrane oscillators are used, which are flanged to the bottom of the degassing and emit high-frequency ultrasound, in the example of the frequency 1700 kHz. The expelled gas mixture, predominantly consisting of ammonia and carbon dioxide, is compressed and passed into the absorption vessel, which contains a gypsum suspension. Here, with mixing with ultrasound, the reaction of carbon dioxide, ammonia, gypsum and water to ammonium sulfate, which is withdrawn as the desired end product in solution. Excess gas, containing essentially carbon dioxide, is discharged and used in a conventional manner. Disk-shaped membrane oscillators, which emit frequencies of 1700 KHz, are used as ultrasound transmitters.

Example 3

The procedure is essentially the same as in Example 1, but six degassing tanks, with otherwise identical dimensions and consisting of VA steel, are connected in parallel. Six low-frequency ultrasound transmitters are placed in the inlet of the degassing tank. The sonotrodes operate at a frequency of 20 - 40 kHz. Legend to the picture

1 residues

2 degassing tank

3 residues

4 CO ₂ and NH ₃

5 compressors

6 absorption containers with gypsum suspension

7 lime and ammonium sulfate

8 exhaust

9 compressors

10 CHP

The hatched areas show the ultrasound-loaded suspensions.

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Claims

claims

1. A process for the preparation of nitrogen fertilizer from biogenic substances by introducing a flowable suspension of biogenic substances in fermentation fermentors, treatment of the suspension with microorganisms in the heat with mixing, deriving the resulting gas mixture and its energetic utilization, heating the remaining suspension and expelling the gases CO ₂ and NH ₃ , introducing the gas mixture into a mineral flour suspension with subsequent separation of resulting substances from this suspension, characterized in that the withdrawn from the fermentation fermenter liquid stream for expelling gases produced is subjected to ultrasound and that containing the mineral flour suspension reactor with ultrasound for the purpose of mixing and for the surface activation of the solids is applied.

2. The method according to claim 1, characterized in that biogenic residues in fermentation fermentation by microorganisms fermented manure or animal excrement.

3. Process according to claims 1 and 2, characterized in that the liquid to be degassed with biogenic substances contained is only slightly heated.

4. The method according to claim 3, characterized in that the biogenic substances containing liquid is heated to expelling the gases to 40 degrees.

5. Process according to Claims 1 to 4, characterized in that the substances formed in the mineral flour suspension when the gas mixture is introduced are separated from the suspension.

6. The method according to claims 1 to 5, characterized in that the flow rate of the liquid containing biogenic substances is 0.05 to 0.5 m / s, their residence time in the degassing tanks 100 to 500 s.

7. The method according to claim 6, characterized in that the flow rate of the liquid containing biogenic substances is 0.1 m / s, the residence time 120 to 300 s.

8. Process according to claims 1 to 7, characterized in that the gas transport takes place at a flow rate of 0.01 to 1, 0 m / s.

9. Apparatus for carrying out the method according to claims 1 to 8, consisting of pipelines for the transport of suspensions, one or more degassing tanks, which may be connected in parallel or in series, a compressor, one or more absorption tanks with gypsum suspension, characterized in that the Degassing tank as well as the absorption tanks are equipped with low and high frequency ultrasonic generators.

10. The device according to claim 9, characterized in that the degassing tanks are made of V-A steel, three to ten degassing tanks are connected in parallel, each having a diameter of 10 to 30 cm are up to 200 cm high,

Connecting pipes are made of V-A steel, the absorption vessels are made of V-A steel,

Degassing and absorption vessels are equipped with ultrasonic generators.

11. Device according to claims 9 and 10, characterized in that the ultrasound transmitters operate in the degassing containers with variable frequencies between 20 kHz and 1.7 MHz, the ultrasound transmitters are mounted on the bottom of the degassing container or in the inlet.

12. Device according to claims 9 to 11, characterized in that several ultrasonic transmitters work with tuned frequencies, wherein the tuning only serves to avoid interference.

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3. Device according to claims 10 to 13, characterized in that for gas transport, a fan or compressor is arranged in the gas line.

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