WO2021144495A1

WO2021144495A1 - Purine drying unit

Info

Publication number: WO2021144495A1
Application number: PCT/ES2021/070024
Authority: WO
Inventors: Jaume PUIG LUNA; Claudia ESTADELLA RODRÍGUEZ; Raúl María MIR COLL
Original assignee: Puig Luna Jaume; Estadella Rodriguez Claudia; Mir Coll Raul Maria
Priority date: 2020-01-17
Filing date: 2021-01-18
Publication date: 2021-07-22

Abstract

A purine drying unit for treating liquid purines from pigs, dairy cows and others by drying, with a greenhouse (24), regulated ventilation system, homogenisation tank (14) and purine acidification and natural filter (12) at the outlet of the ventilation air moistened with an acid solution, said greenhouse (24) having a radiant floor (100) with cross-linked polyethylene, multilayer polyethylene, or polybutylene tubing (6), insulated from the floor with expanded polystyrene (4) or other low-conductivity materials, covered with mortar or concrete; with an external energy collection point; one or more regulation tanks (17) in the radiant circuit as storage units for the excess thermal energy not transferred to the purine mass; a heat recovery unit after the natural filter (12) for heating the water of a heating circuit and condensing part of the evaporated water for reuse as cleaning water.

Description

PURINE DRYING UNIT

DESCRIPTION

OBJECT OF THE INVENTION

The invention, as expressed in the wording of the present specification, refers to a slurry drying unit. More specifically, a unit for drying liquid manure from pigs, dairy cattle and other animal species using underfloor heating powered by solar thermal energy and other energy sources.

The object of the invention is a high-performance unit for drying liquid slurry from swine species without ammonia emissions to the environment, equipped with a radiant floor that can be powered by renewable energies such as: thermosolar, photovoltaic, wind, biomass, etc. geothermal energy, or other energy supply systems such as natural gas, propane or LPG.

FIELD OF APPLICATION OF THE INVENTION

The present invention belongs to the livestock sector.

BACKGROUND OF THE INVENTION

The drying units have a long history in the agricultural sector for the dehydration of different products such as vegetables, corn, coffee, etc. These units consist of greenhouses equipped with a wooden or metallic infrastructure closed with a polyethylene sheet, ethylene vinyl acetate copolymer, polyvinyl chloride (PVC), polycarbonate or glass.

To determine the energy exchange, the following are taken into account: the intensity of solar radiation, the speed and temperature of the air, the area of the greenhouse enclosure and the values of the specific heats.

There are numerous publications referring to different models of dryers, both for batch drying such as continuous drying, some of them using electricity, fossil fuels, or even solar energy, but in all of them the element to be heated is the air that circulates over the product and is saturated with the water that is extracted from him.

Existing dryers are classified into active systems, with forced ventilation, and passive systems, with natural ventilation. In all of them the main components are:

- A greenhouse that acts as a solar energy collector.

- Properly insulated ducts.

- A drying surface.

- A chimney for the extraction of humid air.

And, in addition, in active systems:

- Monitored windows.

- Air impellers (fans).

The performance of these facilities is adequate for the dehydration of agricultural products, but it is not sufficient for the extraction of large amounts of water.

There are those that face this problem, such as some facilities that extract salt from seawater, accelerating the evaporation process using photovoltaic energy, following the model of dryers for agricultural products, resulting in an unviable investment.

In the livestock sector, slurry dryers have been set up that follow essentially the same model, with some improvements. It must be taken into account that, in addition to the technical challenge of extracting large amounts of water in a profitable way, in the case of slurry, the emission of ammonia into the atmosphere during the process must be avoided.

The company EMA DEPURACIÓN SL located in Olot, designed in 2014 a greenhouse-dryer for cattle slurry, after concentrating them on the farm (use of drag scrapers). The distinctive elements with respect to the previous greenhouses-dryers are, firstly, the need to acidify the input slurry until it reaches a pH between 5.5 and 6 in order to fix up to 70% of the ammonium present in it, converting it into nitrate, and thus avoid its emission in the form of ammonia. Acidification is a technique used in Denmark by the company INFARM SA since 2006, and in Spain in physical-chemical treatments (company ROTECNA SA), in drying of slurry by hot air with natural gas in companies such as TRACJUSA, in other greenhouses-dryers implemented by INNOVACC (Catalan Association for innovation in the pork meat sector), SOLARPUR etc. Second, use a stirrer, invented by the company itself, to advance the slurry mass through the dryer as it loses moisture and increases its density, until it is collected in an auger that extracts it outside. The steam emitted during the process is transported by the air entering the greenhouse, being directed by interior fans and extracted by a fan that leads it through a duct to a filter made up of tree bark moistened with an acid solution that will act as a final scrubber of the ammonia that may remain in the extracted water vapor. This technique is based on stripping or degassing, which consists of capturing a volatile component of a liquid effluent through the action of an inducing element that can be air, steam, nitrogen, etc. Widely used in leachate degassing by companies such as TECNIUM.

When wanting to transfer the experience of drying concentrated cattle slurry to slurry with a higher liquid component, such as pig slurry or dairy cattle, the poor performance of the facility required that a solid-liquid separation be previously carried out with separators already existing in the market and the solid component was dehydrated, while the liquid fraction had to have a second treatment or be applied to the field, with a content of 80-85% of the N of the fresh slurry. This solution for liquid manure is not very applicable because the most solid fraction of the separation can be removed by composting companies, which mix it with manure from other animal species, or add wood chips to structure it, offering standardized organic fertilizer to the market. Therefore, dehydration of this component is not very useful, and the liquid fraction continues to have the same volume, assuming the same transport and field application problem.

In this line, INNOVACC has set up slurry dryers with dynamic or natural ventilation, using the energy captured by the greenhouse itself through its walls and ceilings, and the thermal energy of the air that enters it, which greatly reduces their functional period, and therefore their performance, to be able to solve the amount of liquid slurry generated. The SOLARPUR company has set up slurry dryers optimizing ventilation, avoiding ammonia emissions by acidifying the slurry and a final air filtering system. Using a software that optimizes the ventilation ratios according to the incident radiation in the greenhouse, it has managed to double the evaporation rate that is achieved in natural solar evaporation, but even with this achievement, its objective is not to obtain total dehydration of the slurry, but, eliminating part of the water, a concentration prior to its transport and application to the field.

Greenhouse drying system references:

1. SOGARI, N et al (2000). "Use of solar energy and biogas in the dehydration of horticultural products" In Scientific and Technological Communications ". National University of the Northeast (Argentina).

2. GONZÁLEZ ZÚNIGA, C.E (2016). "Evolution of the performance of a dryer operated with solar energy and biogas for removal of moisture in coffee beans" Escuela Agrícola Panamericana Zamorano (Honduras). Graduation project. Environmental and Development Engineering.

3. AMEER B.M.A et al (2010). "Design and performance evaluation of a new hybrid solar dryer for banana" In Energy Conversion and Management 51; pp: 813-820.

4. MONTERO, I et al (2010). "Design, construction and performance testing of a solar dryer for agroindustrial by-products" In Energy Conversion and Management 51; pp: 1510-1521.

5. EKECHUKWU OV et al (1999). “Review of solar-energy drying systems: an overview of drying principles and theory” In Energy Conversion and Management 40 (6); pp: 615-655.

6. GONZÁLEZ HALCÓN, C (2018). "Feasibility study of annual production of salt marsh in marsh with renewable energies" Higher Technical School of Engineering (ICAI). Electromechanical Engineering Degree. Madrid.

7. FERNÁNDEZ-LÓPEZ et al (2007). “Integrated system of desalination by renewable energies without emission of brine”. Conference paper. Ibero-American Congress of Mechanical Engineering. 8. INNOVACC. https://www.lavanguardia.com/local/girona/20140630/544114297 14 / olot-trial-pilot-drying-purines-energia-solar.html.

9. EMA DEPURACIÓN S.L https://www.innovacc.cat/2016/11/11/visita-a-un- greenhouse-de-drying-solar-de-purines /? Lang = es.

10. SOLARPUR. https://ecoinventos.com/solarpur/.

EXPLANATION OF THE INVENTION

The inventors of the present application have developed a high-performance slurry drying plant in which, from elements already known, such as the use of solar energy captured through a greenhouse-type structure, the previous acidification with sulfuric acid For the control of ammonia emissions, and the final filtration of the air, a radiant floor is incorporated to increase the capture of energy from the medium and its transfer to the slurry mass.

Drying occurs as a result of the heat balance. The thermal needs are the result of adding the enthalpy of the water so that evaporation takes place, the energy necessary to raise the initial temperature of the slurry to the set temperature, and the energy necessary to heat the temperature of the air entering the greenhouse. to transport the water vapor that is produced during the dehydration process.

The main novelty of the installation, for which registration as a utility model is requested, is the incorporation of underfloor heating and the use of water tanks for storing energy that could not be transferred during the day, using it during the night, or the days that there is less energy contribution.

The fresh, unhomogenized slurry reaches a closed tank with a propeller mixer, where sulfuric acid is incorporated for acidification, and is controlled with a continuous pH meter.

Once it has been homogenized and acidified to pH 5.5-6, it is driven by a pump to the slurry greenhouse, spreading over the surface of the radiant floor until it forms a layer 3-6 c thick. The energy that we will have will be the radiation that affects the greenhouse cover, the energy from the air that we incorporate into the greenhouse, and the energy that we transfer to the slurry mass through the underfloor heating.

The underfloor heating is essentially made up of several serpentine ducts that carry water. The water is driven by pumping motors, whose power and number will depend on the linear meters of coil through which it must circulate. The technology for this system is widely developed in residential heating systems. The circulating water has one or more regulation tanks that allow the storage of excess energy in the form of hot water.

The water from the underfloor heating is part of a tight closed circuit that will incorporate and transfer energy by heat exchange.

Energy capture can be in different ways:

- Solar thermal field: solar thermal collectors can be flat or with vacuum tubes. A number of panels optimized for the volume of slurry to be dehydrated is installed in a conditioned space near the greenhouse, facing South. Solar thermal technology is widely used and proven. The water in the circuit receives the thermal energy by heat exchange, as it passes through the collectors, is collected in the regulation tanks and is pumped into the greenhouse, where it will transfer the energy to the slurry mass.

- Photovoltaic field: the photovoltaic panels will be installed optimizing their number and power to the volume of slurry to be dehydrated in a conditioned space near the greenhouse, facing south. The direct current from the photovoltaic panels is transformed into alternating current with an inverter. The water in the circuit receives the thermal energy by heat exchange with the electrical resistances placed inside the regulation tanks. In the case of photovoltaic energy, energy can also be stored with lead-acid or lithium batteries (depending on the technology currently available).

- Biomass: the biomass boiler is fed with different fuels with a neutral C02 balance: wood pellets, olive pits, dried fruit shells, stone pits. peach etc. The water in the circuit acquires thermal energy as it passes through the boiler and is stored in the regulation tanks, from where it is driven into the greenhouse, where it will transfer the energy to the slurry mass.

- Natural gas, propane or LPG boilers: The water in the circuit acquires thermal energy as it passes through the boiler and is stored in the regulation tanks, from where it is driven into the greenhouse, where it will transfer the energy to the slurry mass. .

- The energy contained in a slurry storage basin as a geothermal circuit. All farms store liquid slurry in reception basins with a minimum capacity of 3 months. Slurry is an unstable element, producing anaerobic reactions inside it with the generation of heat, harmful gases such as ammonia and greenhouse gases such as methane and nitrous oxide. This energy is harnessed for use in the drying plant thanks to the capture carried out by a heat pump, which transfers all the energy to the buffer tank that contains the fluid of the greenhouse's radiant circuit. The collection field is made up of polyethylene tubes inside the basin at mid-height, without allowing them to settle on the bottom to prevent the sediment from solidifying and thus blocking energy collection. The heat pump is programmed to stop working when the slurry temperature drops to 4 ° C, allowing the slurry mass to recover thermal energy from solar irradiation and internal anaerobic reactions. This form of capture has two advantages: the first is the energy use for the drying of slurry in a very efficient way, with an Energy Efficiency Coefficient of 5-6, and the second, by decreasing the temperature of the slurry mass, it slows down the anaerobic microbial activity and the enzymatic reactions responsible for the emissions of ammonia, methane and nitrous oxide, reducing them significantly.

Additionally, to increase the energy production of the slurry basin, an oxygen diffuser tube is used that circulates inside it and an oxygen-producing ozonation equipment is used. Aerobic activation allows the extraction of more internal energy and additionally has a fixing effect on the nitrogen present in the slurry.

- Aerothermal energy thanks to the capture carried out by a heat pump that uses propane gas or the like as a refrigerant in the circuit. This high-performance pump is complementary to the previous heat pump, allowing the energy supply to continue when the energy from the slurry pond is exhausted.

- High-performance heat exchangers that capture solar radiation and transfer it to the air stream that is introduced into the greenhouse by the depression generated by a fan. The size and power of the heat exchanger will depend on the inlet setpoint temperature.

Once homogenized and acidified to pH 5.5-6, it is driven by a pump to the slurry greenhouse, spreading over the radiant floor surface until forming a 3-15 cm thick layer. This thickness will depend on the surface of the greenhouse, the density of the slurry and the desired time interval between drying.

An OH radical diffuser equipment is incorporated to replace or complement the acidification of the slurry. It is an emitter of ultraviolet radiation that excites hydrogen peroxide molecules from an internal tank equipped with a passive diffuser, generating OH radicals- Said OH radicals are very reactive and although their half-life is measured in picoseconds, they produce a chain reaction with water molecules in the form of steam, generating more OH- radicals OH- radicals react with the microorganisms present in the slurry, inactivating them, and breaking the molecules of ammonia, methane and volatile organic compounds, allowing steam extraction low in emissions and odorless.

- Other energy sources: water vapor from industrial processes, thermal energy from industrial process fluids. Any system that allows an energy exchange with our closed water circuit.

The design of the plant is specially oriented to slurry with a high water content. In tests carried out by the inventors in 2017 with a small 2 m2 pilot plant, this type of slurry, as it contains between 3.5 and 16% of dry matter, does not generate the “crust” effect when the thickness of the sheet it does not exceed 6 cm, becoming dehydrated to humidity values of 20%. When it reaches this humidity value, the slurry becomes a manipulable product that can be stacked in a roofed space attached to the greenhouse and can be subsequently removed by composting companies. Dehydration to these levels also allows no additional ammonia emissions to occur.

The slurry, once dehydrated, can be removed from the greenhouse manually or with agricultural machinery and a rubber drag attachment until it is evacuated from one end of the greenhouse.

Automated collection systems can also be implemented by means of a bridge crane that runs along the sides of the greenhouse with a rubber accessory and brooms that introduce it into a channel inside which an endless screw is activated, transporting the dehydrated to a covered outdoor space where it can be stacked.

The automation includes the control of the pumping of slurry from the storage tank to the homogenization tank or directly inside the greenhouse, with a filling sensor that stops the operation of the pump when the desired level has been reached; control of ventilation flow through electronic fans; control of the circulation pump of the hydrothermal circuit in the underfloor heating; control of the level of drying with warning of the end of the process; injected sulfuric acid into the homogenization tank and mixing time; control of the pump for emptying the homogenization tank towards the greenhouse with its filling sensor; control of the photovoltaic installation with battery fill level. All this regulated by a PLC adapted to the needs of each drying unit.

Drying requires a controlled supply of air. The air acts as a transport element for the water vapor that is generated, entering with a relative humidity, determined by the inlet temperature and by the environmental humidity load of the geographical area where the greenhouse is located. Inside the greenhouse, the air will raise its temperature to the setpoint temperature, increasing its ability to saturate with humidity.

The air supply is controlled by two low-consumption forced ventilation systems synchronized with each other, one for the intake and the other for the extraction. The operating regime of both systems is controlled by software that collects outdoor temperature and relative humidity data.

The moisture-laden air outside the greenhouse passes through a filter made of biological material. This filter consists of a cylindrical or polyhedral tank with a grid below which the humid air from the greenhouse is evacuated. On top of the grid, porous material of biological origin accumulates: pine bark, coarse chipboard, wood chips, etc. This biological material is sprayed with a dilution of sulfuric acid and water, in such a way that it acts as an acid trap for the ammonia residue in the air flow. Once saturated, this material can be crushed and added to the dehydrated slurry as a structuring agent.

After the biological filter, the hot steam passes through a heat exchanger which, in the case of farms, can circulate water from the heating system. We will take advantage of this heat to preheat the heating water for maternity wards, suckers, water for the rehydrated milk of suckling pigs in the case of cattle or other uses. The water vapor extracted from the greenhouse will partially condense, and will be collected in a basin from where it will be reused as cleaning water for the facilities.

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, the present specification is accompanied, as an integral part thereof, by a set of drawings in which, for illustrative purposes and non-limiting, the following has been represented:

Figure number 1.- Shows a schematic sectional view of the underfloor heating structure and the arrangement of the different structural elements of the entrance and perimeter of the slurry drying area.

Figure number 2-A.- Shows a schematic plan representation of an embodiment of the invention in which the different radiant floor circuits are shown, the number of which will depend on the size of the greenhouse, and on two lines of panels of thermosolar collection with its pipes to the buffer tank, as an example of the energy system, also appreciating, along the route, the expansion vessels and the impulsion pumps, both for the flow and return circuits, and the collector box in which the hot water from the buffer tank is distributed to the different circuits of the heated floor.

Figure number 2-B.- Shows an enlargement of detail A indicated in figure 2-A that shows the main elements of the installation shed of said example.

Figure number 3.- Shows a representation of the example of the drying unit shown in the preceding figures, in which the distribution of the slurry homogenization tanks and the sulfuric acid storage tank, as well as the natural filter, can be seen. connected to the greenhouse air extraction tube.

Figure number 4 shows a schematic plan representation of another embodiment of the slurry drying unit, according to the invention, specifically an example with an external energy collection point based on heat pumps connected to a geothermal circuit that extracts energy from a slurry storage basin.

And figure number 5.- Shows an enlargement of a portion of the plant shown in figure 4 that shows the elements of the equipment shed in greater detail.

PREFERRED EMBODIMENT OF THE INVENTION

In view of the aforementioned figures, and in accordance with the numbering adopted, it can be seen in them respective examples of non-limiting embodiment of the drying unit of the invention, which comprises what is indicated and described in detail below.

Thus, taking into account Figures 1 to 3, in a preferred embodiment, the unit object of the invention, which is applicable to a plant for the treatment of liquid slurry from pigs, dairy cattle and other animal species by drying, is It is made up of a greenhouse (24), a regulated ventilation system (12), a tank for homogenization (14) and acidification of the slurry and a natural filter moistened with an acid solution (13), distinguished by comprising the following elements: - Underfloor heating (100) for the treatment of slurry (figure 1) which, in turn, comprises:

- Base formed by a casing of bowling pins (1) between 15 and 20 cm thick.

- Geotextile sheet (2) for the protection of possible leaks or slurry leaks.

- Concrete base (3) "poor" for leveling the treatment room.

- Expanded polystyrene plate (4) of 2.00 x 1.00 x 0.10 meters, for thermal insulation that prevents the diffusion of heat downwards. In the same way, the perimeter of the space destined to the treatment of slurry will be isolated, in the base type.

- Placement of mesh (5) # 20 cm, of 10 mm rod, raised 5 cm above the insulation base.

- Installation of 5-layer Evhofelex pipe (6) with oxygen barrier for the formation of the underfloor heating circuits (21). It will be attached to the mesh (5) for its fixation, raised with supports (11).

- 15 cm layer of concrete type HAF-30 / F / 20 / lia + Qc with SR (sulfo-resistant) cement poured with a pump and vibrated, to be reinforced with the previous mesh.

- Perimeter concrete wall (8), in the formation of closure of the space for slurry treatment, 30 cm thick, reinforced with double mesh type HAF-30 / F / 20 / lia + Qc with poured SR (sulfo-resistant) cement with pump and vibrated.

- Helicopter trowel the concrete slab.

- Completion of the base of the treatment slab with a protective layer of Expoxi bicomponent resin (7), such as Basf, Sika, or similar.

- An access ramp (9) on one side, visible in figures 1 and 3.

The underfloor heating (100) also consists of a floor with two possible forms of construction:

- Radiant floor built in situ.

- Prefabricated underfloor heating built in nestable pieces of different sizes, according to the final dimensions of the greenhouse.

- Greenhouse (24), consisting, in a first option of realization, in:

- Greenhouse (24) tunnel type, without straight walls, the structure being totally curved from the fixing point on the ground to the ridge. The shape of the arches is curve.

- It is composed of modules, with a series of arches made of hot-dip galvanized cylindrical tubes protected with a layer of zinc to prevent corrosion. The tubes will be inserted into concrete footings that will form part of the underfloor heating structure. Its shape allows it to accommodate a greater volume of air and provides resistance to rain.

This type of greenhouse has a greater sealing capacity than the flat greenhouse, and facilitates operations with agricultural machinery.

And, in another option of realization, in:

- Flat greenhouse with straight walls for surfaces smaller than 16 square meters in a single module, with a hot-dip galvanized metal structure protected with a layer of zinc to prevent corrosion. The structure is inserted in concrete footings that will be part of the radiant floor structure.

This type of greenhouse is designed for the manual removal of the dry residue resulting from the dehydration process

- Energy capture:

- Solar thermal capture (figures 2 and 3) which, in turn, comprises:

- Thermal panels (22) of 24 vacuum tubes per unit with heatsinks (23)

- Panel support structure at 45 ° inclination

- 5-layer tubing with oxygen barrier

- Collector (20) for various circuits (6)

- Buffer tank (17)

- Impulse pumps (18, 19) for each of the flow and return circuits

- Solar expansion vessel (16)

- Heat transfer fluid

- Insulated tube from the thermal panels (22) to the buffer tank (17)

- Insulated tube from the buffer tank (17) to the ground circuits (21) - greenhouse radiant (24)

- Battery kit for heat sinks

- Distribution panel

- Control unit

- In facilities booth (15)

Figure 4 shows another example of a solar thermal energy collection system that comprises:

- Thermal panels (22) of 24 vacuum tubes per unit

- Panel support structure at 45 ° inclination

- 5-layer tubing with oxygen barrier

- Manifold for various circuits leading to the equipment shed (29)

- Buffer tank (17)

- Impulse pumps for each of the flow and return circuits (18, 19)

- Solar expansion vessel (16)

- Heat transfer fluid

- Insulated tube from the thermal panels to the buffer tank

- Insulated pipe from the buffer tank to the greenhouse underfloor heating circuits

- Battery (39) for the heat sinks and the corresponding regulator (45)

- Distribution panel

- Control unit.

- Purothermic catchment (figures 4 and 5) which, considering the inclusion of a pond (28) of slurry, comprises, housed in an equipment shed (29) located next to the greenhouse (24) and said pond (28):

- Heat pump (30) or puritermia machine, dimensioned based on the energy potential of the plant's slurry basin (28).

- Evaporator

- Compressor

- Condenser

- Expansion valve

- U-shaped polyethylene water circulation tubes, constituting a circuit geothermal (31), which circulate inside the pond (28) of slurry subject to an upper structure that keeps them at half height of the accumulated liquid slurry

- Distribution panel

- Control unit

- Aerothermal capture (figures 4 and 5), which extracts energy from the ambient air by taking advantage of the gases produced in the reservoir (28) and which, in this case, comprises:

- A second heat pump (32) or aerothermal machine, sized to the energy needs of the slurry drying unit with the following elements:

- Evaporator

- Compressor

- Condenser

- Expansion valve

- Distribution panel

- Control unit

- Capture of photovoltaic energy that includes:

- Photovoltaic panels (33)

- Structure (34) on a gravel pavement (35)

- box of stings or splices (36) that connect to an inverter (37) of the equipment shed (29).

- Heat exchanger (40) of the air entering the greenhouse (24), comprising:

- System of thermal glass plates or transparent thermal plastic films with internal titanium dioxide spacers. They are placed in series and in parallel and their number depends on the thermal needs required by the slurry drying unit in each case.

- Aerobic slurry activation system (41) comprising:

- Ozonization equipment - Tubes with microperforations for the diffusion of oxygen inside the liquid mass of slurry.

- Deposits:

- Slurry accumulation tank (14), with inlet, outlet, connection with sulfuric acid tank (13), register for cleaning and discharge, and mixer for homogenization of slurry and sulfuric acid.

- Tank for sulfuric acid (13)

- Sulfuric acid dilution tank for spraying the natural filter (12)

- Tank for the formation of a natural filter (25), with a stainless steel grill in the lower part and a watering system with sprinkler nozzles in the upper part. It is connected (26) with the greenhouse air extractor (27) and with the heat exchanger.

- Air extraction system comprising:

- Air inlet fans to the greenhouse at the end opposite the extraction system. They are low consumption fans synchronized with the extraction fans, in such a way that the inlet and outlet flow is controlled and quantified.

- Impulse fans inside the greenhouse. They are low consumption fans that help drive the air inside the greenhouse, avoiding the formation of turbulence.

- Extraction fans. They are low consumption fans, synchronized with the inlet fans, that extract the air from the greenhouse and blow it through a flexible corrugated polyethylene duct to the natural filter.

- Fan synchronization and regulation unit.

- Water / air heat exchanger, at the outlet of the internal steam jet to connect it with the inlet heat exchanger and collect the condensed water for use as cleaning water for the farm.

- Control elements, which include: - Continuous pH measurement equipment in the homogenization tank and in the dilution tank for spraying the natural filter.

- Outdoor weather station that measures: temperature, relative humidity, atmospheric pressure, wind speed and direction.

Indoor thermometers that measure: temperature of the slurry mass and air temperature in the greenhouse.

- Continuous ammonia measurement probe, with datalogger, in the air collection duct after the natural filter.

- PLC control for:

Automatic filling of the homogenization tank.

Ventilation flow control.

Control of the impulsion pump of the hydrothermal circuit.

Drying control.

- Computer application for comprehensive control of the entire process.

Furthermore, the drying unit has one or more regulation tanks in the radiant circuit (100) that act as storage units for the excess thermal energy not transferred to the slurry mass. And, in addition, a heat recovery unit behind the natural filter to heat the water in a heating circuit of the farm attached to the installation and to condense part of the evaporated water to be reused as cleaning water.

Considering Figures 4 and 5, the indication of the slurry accumulator tank (14) can also be seen, which includes a mixer, the sulfuric acid tank (13), and impulse pumps (42) installed in a slurry circuit. (43), to drive the slurry from the basin (28), as well as a supply fan (44) installed on the opposite side of the greenhouse (28).

Example 1.

A first concrete example of an embodiment is set out below, based on the example shown in Figures 2 and 3, consisting of an installation with solar thermal collection.

The example would be a pig farm located in Lleida that wants to be able to treat 1000 cubic meters per year of slurry, which would be the equivalent of half of the slurry production from a 1000-place fattening farm.

Each geographical area has its characteristics. To know the available radiation contribution we will use the PV-GIS (Photovoltaic Geographical Informatic System) software, which provides open data on solar radiation and temperature.

For the thermal balance calculations we will take into account the contributions of solar radiation per m2 of greenhouse roof surface, the temperature and relative humidity of the inlet air and the efficiency of the vacuum tube collectors; On the energy consumption side, we will take into account the enthalpy of the water, the energy required for the temperature jump of the slurry mass from the inlet temperature to the set point temperature, the energy losses along the thermal circuit and the inlet air temperature when it is lower than the setpoint temperature.

The drying surface of the greenhouse must be sufficient to effect a total drying of a 3-6 cm thick sheet every 48 hours in winter. In this case, the greenhouse area will be 100 m2, with a roof area of 155.5 m2.

The solar thermal capture will be 222 m2 of vacuum tubes, equivalent to 74 panels of 3 m2.

There will be five circuits that will be fed from several regulation tanks that will accumulate 3000 liters of water (the equivalent of a greenhouse filling).

The installation will operate continuously: filling the homogenization tank; shake with the sulfuric acid that will be incorporated until the pH drops to 5.5 - 6; pumping to the surface of the greenhouse; adaptation of the ventilation flow to the external environmental conditions; pass through the natural filter; passage through the heat exchanger; collection of condensation water in an adjacent basin or tank.

During the night, the installation will continue to operate, taking advantage of the thermal energy accumulated in the regulation tanks.

After the drying period, which will vary depending on the month of the year, the dehydrated fraction will be collected (22.5 kg for each drying in this example), and will be filled again with a new supply of fresh acidified slurry.

The whole process will be controlled by:

- Continuous pH meter

- Ventilation regulators according to outside temperature and relative humidity

- Ammonia probes at the outlet of the natural filter

- Indoor temperature and relative humidity datalogger thermometers.

Example 2

A second concrete example of embodiment is set out below, based on the example shown in Figures 4 and 5, consisting of an installation with an autonomous modular greenhouse with underfloor heating built in situ or with prefabricated nestable pieces, with thermosolar, aerothermal, capture. purothermic, and with heat exchangers.

The example would be a pig farm located in Lleida that wants to be able to treat 1000 cubic meters per year of slurry, which would be the equivalent of 75% of the slurry production of a 1000-bed fattening farm.

For the thermal balance calculations, we will take into account the contributions of solar radiation per m2 of greenhouse roof surface, the temperature and relative humidity of the inlet air, the energy provided by puritermia, aerothermal energy and the efficiency of the collectors. of vacuum tubes; On the energy consumption side, we will take into account the enthalpy of the water, the energy required for the temperature jump of the slurry mass from the inlet temperature to the set point temperature, the energy losses along the thermal circuit and the inlet air temperature when it is lower than the setpoint temperature.

The drying surface of the greenhouse must be sufficient to effect a total drying of a 3-15 cm thick sheet every 12 hours in winter. In this case, the greenhouse area will be 16 m2, with a roof area of 50.3 m2.

The solar thermal capture will be 51 m2 of vacuum tubes, equivalent to 17 panels of 3 m2.

The puritermia equipment will be a 22 kW heat pump.

The aerothermal equipment will be an 18 kW heat pump.

The air inlet heat exchanger to the greenhouse will have a power of 20 kW.

There will be two circuits that will be fed from a regulation tank that will accumulate 200 liters of water (the equivalent of filling the greenhouse).

The photovoltaic installation will have a 45 kW solar field, a 40 kW inverter, regulators-chargers and a battery bank with a capacity of 140 kWh.

The installation will operate continuously: filling the homogenization tank; shake with the sulfuric acid that will be incorporated until the pH drops to 5.5 - 6; pumping to the surface of the greenhouse; adaptation of the ventilation flow to the external environmental conditions; activation of the OH radical team; pass through the natural filter; passage through the heat exchanger; collection of condensation water in an adjacent basin or tank.

During the night, the installation will continue to operate, taking advantage of the thermal energy of the heat pumps.

The electrical energy necessary for the operation of the greenhouse with all its equipment will be supplied by a 50 kW photovoltaic installation with enough batteries for 140 kWh of accumulation.

After the drying period, the dehydrated fraction will be collected (70 kg for each drying in this example), and it will be refilled with a new supply of fresh acidified slurry.

The whole process will be controlled by: - Continuous pH meter

- Ventilation regulators according to outside temperature and relative humidity

- Ammonia probes at the outlet of the natural filter - Indoor temperature and relative humidity datalogger thermometers

- PLC

Having sufficiently described the nature of the present invention, as well as the way of putting it into practice, it is not considered necessary to make its explanation more extensive so that any expert in the field understands its scope and the advantages derived from it, stating that, Within its essentiality, it may be put into practice in other forms of implementation that differ in detail from the one indicated by way of example, and to which it will also achieve the protection that is sought provided that its fundamental principle is not altered, changed or modified. .

Claims

1.- PURINE DRYING UNIT, for a plant for the treatment of liquid slurry from pigs, dairy cattle and other animal species by drying formed by a greenhouse (24), a regulated ventilation system, a homogenization tank (14) and acidification of the slurry and a natural filter (12) at the outlet of the ventilation air moistened with an acid solution, characterized in that the greenhouse (24) has a radiant floor (100) with a tube (6) made of cross-linked polyethylene, multilayer polyethylene or polybutylene, insulated from the ground with expanded polystyrene (4) or other low conductivity materials, covered with mortar or concrete; for having an external energy capture point; by having one or more regulation tanks (17) in the radiant circuit that act as storage units for the excess thermal energy not transferred to the slurry mass; and because it has a heat recovery unit behind the natural filter (12) to heat the water in a heating circuit and to condense part of the evaporated water to be reused as cleaning water.

2.- PURINES DRYING UNIT, according to claim 1, characterized in that the external energy capture point consists of a field of thermosolar plates (22).

3.- PURINES DRYING UNIT, according to claim 1, characterized in that the external energy capture point consists of a field of photovoltaic panels.

4 PURINE DRYING UNIT, according to claim 1, characterized in that the external energy capture point consists of one or more biomass boilers.

5. PURINE DRYING UNIT, according to claim 1, characterized in that the external energy capture point consists of one or more natural gas, propane or liquefied petroleum gas boilers.

6.- PURINE DRYING UNIT, according to claim 1, characterized in that the external energy capture point consists of one or more heat pumps connected to a geothermal circuit that extracts energy from the air, water currents or the Earth.

7.- PURINES DRYING UNIT, according to claim 1, characterized by comprise, as an external energy capture element, at least one heat pump (30) connected to a geothermal circuit (31) that extracts energy from a slurry storage pool (28).

8.- PURINES DRYING UNIT, according to claim 7, characterized in that it comprises a purothermic capture system that, in turn, comprises a heat pump (30), or purothermy machine, with evaporator, compressor, condenser, expansion valve, U-shaped polyethylene water circulation tubes, constituting a geothermal circuit (31), which circulate inside the slurry basin (28) subject to an upper structure that keeps them at the middle of the liquid slurry accumulated, electrical panel, control unit.

9.- PURINES DRYING UNIT, according to claim 7 or 8, characterized in that it also comprises an aerothermal capture system that extracts energy from the ambient air by taking advantage of the gases that are produced in the pond (28) and that, in turn In turn, it comprises a second heat pump (32), or aerothermal machine, with an evaporator, compressor, condenser, expansion valve, electrical panel, and control unit.

10.- PURINE DRYING UNIT, according to any of claims 7 to 9, characterized in that it also comprises a heat exchanger system (40) of the air entering the greenhouse (24) consisting of a system of glass plates Thermal or transparent thermal plastic films with internal titanium dioxide spacers.

11.- PURINES DRYING UNIT, according to any of claims 7 to 10, characterized in that it also comprises an aerobic activation system for the slurry (41) that comprises ozonation equipment, tubes with micro-perforations for the diffusion of oxygen in the interior of the liquid mass of slurry.

12. PURINES DRYING UNIT, according to any of claims 7 to 11, characterized in that the underfloor heating (100) of the greenhouse (24) is a soil built in situ.

13. PURINE DRYING UNIT, according to any of claims 7 to 10, characterized in that the underfloor heating (100) of the greenhouse (24) is a prefabricated floor built in nestable pieces of different sizes.