DE20301645U1 - Assembly for processing farm animal slurry by drying, conversion to pellets, incineration, energy recovery and ammonia stripping - Google Patents

Abstract

An assembly for processing animal slurry using aggregate components which separates solids, converts into pellet form and dries. The pellets are subsequently incinerated. The assembly further strips ammonia from solids which are essentially devoid of liquid residues. Liquid residues are then subjected to biological cleaning processes.

Description

Much &Wieske

European Patent Attorneys * Mandataires agrees pres l'Office europeen des brevets
European Trademark Attorneys * Mandataires en marques europeennes

Patent Attorneys' Office Viel & Wieske · P.O. Box 65 04 03 · D-66143 Saarbrücken

Society for environmentally compatible process technology mbH
In the Stadtwald, Building 47 66123 Saarbrücken

AQUEX Wastewater and Sludge Treatment Systems GmbH Mühlener Str. 42
51674 Wiehl

Patent attorneys

Georg Viel, graduate engineer Christof Viel, engineer diploma EHICS,

Conseil en propriete industrial (France) Thilo Wieske, graduate engineer

PO Box 65 04 03
D-66143 Saarbrücken

Phone: ++49-(0)681-58 59 59
Fax: ++49-(0)681-58 59 81

Feldmannstr. 110 D-66119 Saarbrücken

kanzlei@saarpatent.de http://www.saarpatent.de

02104/03.02.2003

DESCRIPTION Device for processing liquid manure

The invention relates to a device for processing liquid manure.

Over the last two decades, technical developments in the area of livestock farming have generally led to an increase in livestock numbers and a change in livestock farming from manure to liquid manure. Since liquid manure can lead to a variety of environmental impacts during storage or application due to its organic and inorganic ingredients (e.g. nitrate pollution of groundwater, eutrophication of surface waters as a result of the input of nitrogen and phosphorus, release of ammonia, nitrous oxide and methane into the atmosphere), its agricultural use is subject to various environmental regulations.

VAT ID No. DE 81 21 16 997 / Tax No.: 040/166/28609

BanklSaar eG (BLZ 591 900 00) No. 67584007
Deutsche Bank Saar (bank code 590 700 70) No. 0 742 700

Cooperation with / cooperation with / cooperation with:
Cabinet
VITL

Conseils en propriete industrial F-57520 Grosbliederstroff

Patent Attorney's Office Dr. rer. &eegr; at. Dipl.-Biol. Ulrike Rudolph

rrosbliederstroff D-69198 Schriesheim / Heidelberg

DE 203 016^5 Ul

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If the amount of liquid manure generated within the company exceeds the amount that may be spread on the company's existing land in accordance with the applicable environmental regulations, the corresponding surplus quantity must be classified as waste and, if possible, recycled for material or energy purposes.

The requirements for a suitable technology for the sustainable (i.e. environmentally friendly and at the same time economical) disposal of liquid manure from livestock farming (especially from commercial livestock farming) can be summarised as follows:

• Reliability and functional safety with the lowest possible specific operating costs

• minimal specific net consumption of primary energy through maximum exploitation of the energy content of the organic manure ingredients

• Storage capacity, ecological and hygienic safety of the processing products in order to enable them to be returned to the agricultural or operational material cycle without negative effects on the environment or livestock

• minimal transport costs for the disposal of waste

• Minimizing the amount of waste to be disposed of (i.e. saving landfill space)

• minimal odor emissions

• Avoiding/minimising the release of veterinary medicinal products into the environment

• minimal space requirement through the use of compact systems with high efficiency or high space-time yield

The technologies currently available or technically tested for partial or full processing of liquid manure either only partially meet this range of requirements or are associated with high costs.

The object of the invention is therefore to create a device for processing liquid manure which meets the above-mentioned technical requirements while at the same time keeping costs to a minimum.

DE 203 0 i SkS U1

EN

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This object is achieved according to the invention in that means are provided for separating, pelletizing and drying solids in the liquid manure, followed by means for burning the dried liquid manure pellets, in that means are provided for stripping ammonia from the liquid manure which has essentially been freed of solids, and in that means are provided for biologically cleaning the liquid phase which is then present.

The following process steps are carried out in this device:

• Separation, drying and energetic recovery of solids

• Ammonia stripping from the aqueous phase

• Treatment of the aqueous phase to process water quality.

The idea behind the device is to make maximum use of the high energy content (calorific value) of the organic liquid manure ingredients, to largely recover the inorganic nutrients (N, P) for fertilization purposes and to treat the organically contaminated aqueous phase to such an extent that it has service water quality and can be reused internally as process water (e.g. for cleaning the floor in the stables or for irrigating outdoor crops).

The solids contained in the raw liquid manure (50 to 120 kg/m ³ ) have an oTS content of approx. 75%. They should be separated from the aqueous phase in an economical manner and dried to a residual moisture content of approx. 5%. In this form they have a calorific value of 22,000 to 25,000 kJ/kg, which is roughly equivalent to that of brown coal.

As is well known, the liquid manure, which is free of solids, still contains large amounts of ammonium/ammonia (up to 5,000 mg/l). These are to be converted into the gas phase by air stripping and then bound in a sulphuric acid washing solution in the form of ammonium sulphate. The ammonium sulphate solution obtained in this way can then be used as a liquid nitrogen fertilizer (return to the agricultural material cycle).

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The aqueous phase pretreated in this way is biologically cleaned in an activated sludge plant with submerged microfiltration membranes (membrane biology) to direct discharge quality and finally treated in a nanofiltration stage to such an extent that it can subsequently be reused as process water in-house.

It is therefore possible to process raw manure to such an extent that no other residues need to be removed from the respective breeding operation apart from nutrient-rich ash and an ammonium sulphate solution (complete processing).

According to the invention, the means for separating solids from the liquid manure comprise a pre-dewatering cylinder, a thickening cylinder and a press, in particular a belt press, as well as a rapid settling cylinder.

One embodiment of the invention consists in that the means for drying solids from the liquid manure comprise a shaft trickle dryer.

It is also expedient that the means for burning the dried liquid manure pellets comprise a pulsation reactor and means for generating electrical current, in particular a steam turbine.

A further development of the invention consists in the provision of means for returning the waste heat from the combustion to the means for drying the solids.

The invention also includes the fact that the means for stripping ammonia comprise means for alkalizing the liquid manure and a stripping column which can be operated with air in countercurrent and which is followed by a washer with sulphuric acid solution.

It is also advantageous that means for biological purification include a membrane bioreactor.

As part of a further development of the invention, it is provided that a nanofiltration system is connected to the membrane bioreactor.

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Finally, it is according to the invention that means are provided for guiding the exhaust air from the drying means into the biological cleaning means.

The advantages of the invention are essentially that the device is basically suitable for the processing of pig manure as well as cattle manure and poultry manure and that the processing process is at least energy self-sufficient since the calorific value of the manure solids is largely exploited. The internal recycling of the processed aqueous phase as process water enables users to drastically reduce fresh water consumption (annually by up to 3.5 m ³ per livestock unit) and thus makes a significant contribution to conserving the natural resource of water and reducing operating costs. In addition, the specific processing costs for a minimum throughput of 10 m ³ /h of raw manure are well under € 5/m ³ , so that even when the process is used on a single company (i.e. decentralized), significant savings are achieved compared to the currently usual disposal costs or the costs for the known technical solutions. Due to the complete collection and treatment of the exhaust air (use of stripping stage as exhaust air scrubber), it is guaranteed that the harmful gas emissions (ammonia, methane, nitrous oxide) are kept to a minimum.

The invention is explained in more detail below using an embodiment based on a diagram of the device.

It shows

Fig. 1 is a flow diagram schematically showing the device according to the invention.

Processing step 1 (separation, drying and energetic recovery of solids)

To separate the high calorific value coarse solids from the raw slurry, the latter is mixed with an organic flocculant, gravitationally dewatered in a pre-dewatering cylinder and a thickening cylinder and finally passed through a compact belt press

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(screen belt width 1 m). With this "dewatering" section, the solids can be concentrated to a total dry matter content of approx. 25%.

The pressed aqueous phase is led through a rapid settling tank, in which the majority of the remaining organic suspended and settling matter is separated by sedimentation. The liquid slurry produced in this way only has a dry matter content of < 10 mg/l. The suspended and settling matter separated through the rapid settling tank is returned to the belt press.

The press cake from the belt press is formed into short round "noodles" (diameter 6-8 mm) in a pelletizing machine.

The pellets are then dried in a shaft dryer for 2 hours by supplying hot air in countercurrent. The small diameter, the round surface and the uniform size of the pellets provide ideal conditions for their economical air drying. To prevent the protein and fat components in the pellets from "burning", the drying temperature is kept constant at 100 ⁰ C by supplying flue gases (ratio of outside air to flue gas approx. 15:1) using a thermostat.

The odorous drying air (vapors) is passed through the membrane biology (see treatment step 3), which also functions as an exhaust air scrubber.

The pellets, which are dried to a residual moisture content of a maximum of 5%, can be stored, are completely hygienic and almost odorless. They are then burned in a pulsation reactor with air supply at around 1,200 ^° C. The resulting ash is enriched with phosphates and other mineral plant nutrients and can be used for fertilization purposes (return to the agricultural material cycle).

Since the pelletized solids are excretion products of secondary consumers, the combustion process can be considered CO2-neutral.

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The combustion heat released is used to generate electricity using a steam turbine. This powers the entire processing plant. Excess electricity is fed into the public grid and the waste heat is used to dry the wet pellets (see processing step 1).

Treatment step 2 (ammonia stripping from the aqueous phase)

The liquid slurry produced by separating the solids is alkalized with technical sodium hydroxide solution (raising the pH value to 11) so that the inorganic nitrogen is mostly in the form of volatile ammonia. The latter is expelled into the gas phase in a stripping column operated with air in countercurrent.

The stripping air is passed through a scrubber with sulfuric acid solution, where the stripped ammonia is bound in the form of ammonium sulfate.

The ammonium sulphate solution obtained in this way can be stored and used as liquid nitrogen fertiliser (return to the agricultural material cycle).

Treatment step 3 (treatment of the aqueous phase to process water quality)

Following the extensive removal of the ammonia from the liquid phase, the latter is biologically purified in a membrane bioreactor after neutralization with technical acid and then removed via microfiltration membranes by applying a slight negative pressure (approx. 0.15 bar).

The membrane bioreactor should preferably be operated as a high-load stage. Under these conditions, a large amount of excess sludge (up to 1.5 TS/kg BOD5) is formed, which experience shows has an oTS content of between 70 and 85%. In order to exploit its calorific value, it should be returned to treatment step 1.

Membranes with small pore size (< 0.2 μηη) should be used, which experience has shown to be a very effective barrier for solids of all kinds as well as for

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germs and viruses. It can therefore be expected that the effluent water from the membrane biology is not only suitable for receiving water (direct discharge quality), but also has the quality of industrial water in terms of its chemical and bacteriological parameters and can therefore be fully reused within the company (e.g. for cleaning the floor in the stables or for watering outdoor crops).

In order to prevent the aqueous phase from becoming too salty during constant circulation and thus reducing the efficiency of the individual process stages, the effluent water from the membrane biology should finally be passed through a nanofiltration system (NF) for partial demineralization.

Claims (9)

1. Apparatus for processing liquid manure, characterized in that means are provided for separating, pelletizing and drying solids in the manure, followed by means for burning the dried manure pellets, that means are provided for stripping ammonia from the liquid manure substantially freed from solids, and that means are provided for biologically cleaning the liquid phase subsequently present. 2. Device according to claim 1, characterized in that the means for separating solids from the liquid manure comprise a pre-dewatering cylinder, a thickening cylinder and a press, in particular a belt press, as well as a rapid settling cylinder. 3. Device according to claim 1, characterized in that the means for drying solids from the liquid manure comprise a shaft trickle dryer. 4. Device according to claim 1, characterized in that the means for burning the dried manure pellets comprise a pulsation reactor and means for generating electrical current, in particular a steam turbine. 5. Device according to claim 4, characterized in that means are provided for returning the waste heat from the combustion to the means for drying the solids. 6. Device according to claim 1, characterized in that the means for stripping ammonia comprise means for alkalizing the liquid manure and a stripping column operable with air in countercurrent, to which a washer with sulphuric acid solution is connected. 7. Device according to claim 1, characterized in that the means for biologically purifying the liquid phase comprise a membrane aeration system. 8. Device according to claim 7, characterized in that a nanofiltration system is connected to the membrane bioreactor. 9. Device according to claim 7, characterized in that means are provided for guiding the exhaust air from the drying means into the biological cleaning means.