NL2013979B1 - System for production of biogas and fertilizer. - Google Patents

Abstract

Biogas and fertilizer producing system comprising a manure storage device 1, a plant material storage device such as grass or grass silage storage device 2, at least two fermenters 3, a separator 4, an intermediate storage facility 5 for a recirculating composition, an evaporator 6 a concentration device 7, a pelleting device 8, and a gas processing device 9 for producing biogas and fertilizer in large scale and high quality, and a method for producing biogas and fertilizer in this system.

Description

Title: System for production of biogas and fertilizer

The present invention refers to a system for producing biogas and a fertilizer in large scale as well as a method for large scale production of biogas and fertilizer.

Technical background

Within the recent years numerous systems and methods were developed to gain biogas. Biogas typically refers to a mixture of different gases produced by the breakdown of many organic matter in the absence of some oxygen. Biogas can be produced from regionally available raw materials such as recycled waste. It is a renewable energy source and in many cases exerts a very small carbon footprint.

Biogas is produced by anaerobic digestion with anaerobic bacteria or fermentation of biodegradable materials such as manure, sewage, municipal waste, green waste, plant material, and crops. It is primarily methane (CH4) and may comprise small amounts of hydrogen sulphide (H2S), moisture and siloxanes.

The gases methane, hydrogen, and carbon monoxide (CO) can be combusted or oxidized with oxygen. This energy release allows biogas to be used as a fuel; it can be used for any heating purpose, such as cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat.

Biogas can be compressed, the same way natural gas is compressed to CNG, and used to power motor vehicles. In the UK, for example, biogas is estimated to have the potential to replace around 17% of vehicle fuel. It qualifies for renewable energy subsidies in some parts of the world. Biogas can be cleaned and upgraded to natural gas standards when it becomes biomethane.

The production of biogas is promoted in numerous countries as an alternative source of energy. It is the aim to increase the amount of production as well as the quality of biogas to make efficient use of biological waste.

The quantity of biogas generated depends on factors such as: temperature, residence time and the composition of the substrate in the fermenter. Due to increasing production of biodegradable waste material such as manure, it is desirable to increase the amount of biological waste material, which is highly efficiently degraded into biogas and fertilizer in one system.

The present invention provides a solution to this problem.

Summary of the invention

The system and method of the present invention uses manure comprising at least 5 % by weight dry matter for the production of biogas and fertilizer. The system processes up to 800.000 tons manure per year.

The system comprises a manure storage device 1, a plant material storage device such as grass or grass silage storage device 2, at least two fermenters 3, a separator 4, an intermediate storage facility 5, e.g., for a recirculating composition, an evaporator 6, a concentration device 7, a pelleting device 8, and a gas processing device 9. The fermenter comprises manure and plant material such as grass or grass silage received from the manure storage device and the plant material storage device, wherein the fermenter is connected to the gas processing device and the separator for separating liquid and solid compounds of the mixture of manure and grass silage. The solid compounds form a fertilizer, which is transported to the evaporator, which is connected to a concentration device and a pelleting device for pelleting the dried fertilizer.

In some embodiments, the system according to the present invention comprises up to 10 to 15 fermenters, wherein each fermenter has a volume of 5.000 to 20.000 m3, 8.000 to 18.000 m3, 10.000 to 15.000 m3, or 12.000 to 14.000 m3.

In certain embodiments, the fermenter is a lagoon comprising a gas hood for intermediate storage of the gas, and an agitator for mixing the liquid manure, the plant material such as grass or grass silage and bacteria, and for supporting ascending of the gas in the fermenter. In some embodiments, the lagoon further comprises a foil lining the fermenter.

The manure is transported into the system, i.e., into the fermenter from the manure storage device via a pump, and the plant material storage device such as grass or grass silage storage device is connected to the fermenter via a plug-in module. In some embodiments, the manure and/or the plant material such as grass or grass silage is preheated before adding to the fermenter.

The gas in the fermenter comprising CO2 and biogas is transferred to the gas processing device via high pressure, where the gas is cooled down to separate biogas and CO2. CO21S in high purity, which allows for example its use in greenhouses to grow vegetables, salad, fruits, etc.

Biogas and fertilizer are produced in the system of the present invention following in some embodiments the steps of: a) adding manure and plant material such as grass or grass silage to a fermenter system comprising at least two fermenters 3, and mixing same in the fermenter, b) aspirating the biogas from the fermenter into a gas processing device 9 via high pressure, c) transferring the mixture of manure and grass silage into a separator 4, where sohd and liquid fractions are separated, d) transferring the liquid fraction into an intermediate storage facility 5, and the sohd fraction, which is a fertilizer, into an evaporator 6, e) removing water from the fertilizer in the evaporator and transferring the remaining water into a concentration device 7, f) drying the fertilizer at 100 to 120 °C, and g) pelleting the fertilizer.

In certain embodiments, it is important to have a continuously homogenous mixture in the fermenter, which is reached by retransferring the liquid fraction from the intermediate storage facility into the fermenter.

In the evaporator, water is removed from the fertilizer, which is for example pelleted.

Thus, the present invention results in a high degree of recycled energy from biological waste, in particular manure and plant material such as grass or grass silage.

Brief description of the figures

Figure 1 depicts the system of the present invention comprising at least a manure storage device 1, a plant material storage device 2, at least two fermenters 3, a separator 4, an intermediate storage facility 5, an evaporator 6, a concentration device 7, a pelleting device 8, and a gas processing device 9.

Detailed description of the invention

The system and method for producing biogas and fertilizer of the present invention differs significantly from all available systems with regard to the combination of the different components of the system and their size. This results in the combined production of biogas and fertilizer in one system and in an unexpected increase in the yield of biogas and fertilizer. Thus, the system and method are highly efficient in the recycling of biological waste.

The system and method are primarily run with manure and plant material such as grass, wherein the plant material is for example in form of a silage such as grass silage. The manure comprises at least 1, 3, 5, 7 or 10 % by weight dry matter, which is of same or different origin, e.g. of pig, cattle, sheep or any other mammalian; it comprises for example about 40 to 80 % manure of pigs and about 20 to 60 % manure of cattle, preferably about 60 % manure of pigs and 40 % manure of cattle.

The dry matter is a measurement of the mass of something when completely dried. The dry matter of plant and animal material would be its solids, i.e. all its constituents excluding water.

In the system of the present invention and according to the method of the present invention about 100.000 to 800.000 tons of manure, 150.000 to 700.000 tons of manure or 200.000 to 600.000 tons of manure are recycled per year. The manure is mixed with 50.000 to 500.000 tons, 100.000 to 400.000, or 150.000 to 300.000 tons of plant material such as grass, e.g., grass silage per year. In certain embodiments, manure and plant silage, e.g. grass silage, are mixed in an amount of 30 to 80 % of manure and 20 to 70 % of planter material, e.g. grass silage, e.g., 70 % manure and 30 % grass silage. In some examples about 420 tons of plant material such as grass silage are inserted. Manure alone does not result in high amount of biogas, but the addition of plant material such as grass silage, in particular in the above mentioned amounts, increases the production of gas significantly. The combination of 70 % manure and 30 % grass silage in the present system and according to the present method, respectively, results for example in an amount of biogas of about 4000 — 6000 m3/h, or 5000 m3/h.

In some embodiments, the grass used in the present system and method is cut next to streets or motorways, which is usually not used in animal feeding for example. The grass is stored in a plant material storage device such as a grass storage device 2, where it is ensiled according to a standard procedure, or ensiled grass is brought into the storage device 2.

The system of the present invention comprises in addition to the grass storage device 2, a manure storage device 1, at least two fermenters 3, a separator 4, an intermediate storage facility 5, an evaporator 6, a concentration device 7, a pelleting device 8, and a gas processing device 9. The system further optionally comprises a CO2 tank 10, a device for hygenising the purified water 11, a storage device for H2SO4 12, a dryer for ammonium sulfate crystals 13, and/or one or more devices for heat recovery 14, 15.

In some embodiment, the different components of the system of the present invention are connected via transporting devices, which is for example a pump, a screw conveyer, a suction device or any other device for transporting liquid or solid material.

In some embodiments, the system comprises 2 to 15, 4 to 12, 6 to 10 fermenters for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 14 fermenters. The fermenters are of the same of different size, wherein a fermenter has for example a volume of about 5.000 to 20.000 m3, 8.000 to 18.000 m3, 10.000 to 15.000 m3, or 12.000 to 14.000 m3, i.e., about 5.000 m3, 6.000 m3, 7.000 m3, 8.000 m3, 9.000 m3, 10.000 m3, 11.000 m3, 12.000 m3, 13.000 m3, 14.000 m3, 15.000 m3, 16.000 m3, 17.000 m3, 18.000 m3, 19.000 m3 or 20.000 m3.

In certain embodiments, the fermenter is a lagoon comprising a gas hood for intermediate storage of the biogas comprising CO2, and optionally an agitator for mixing the manure, the plant material such as a grass silage and bacteria, and for supporting ascending of the gas in the fermenter. In addition, the fermenter optionally comprises nozzles along the side wall to improve the ascending of the biogas comprising CO2 to the surface in direction to the gas hood. In some embodiments, the fermenter has a big surface, which additionally improves the ascending of the biogas comprising CO2 to the surface in direction to the gas hood. In certain embodiments the fermenter comprises a foil lining, e.g., on the inner walls.

In some embodiments the dry matter in the fermenter is 5 to 10 % or 6 to 8% for example 8 %.

The biological waste material such as a mixture of manure and plant material, e.g. grass silage, remains in the fermenter for example for about 15 to 80 days, 20 to 75 days, 25 to 70 days, or 30 to 65 days. In certain embodiments the temperature in the fermenter is about 18 °C, 20°C, 25°C, 30 °C, 35 °C or 37 °C.

In some embodiments, the manure is transported from the manure storage device to the fermenter via a transporting device 16 such as a pump or suction device, which permanently or only in case of use connects the manure storage device and the fermenter. The plant material such as grass silage is inserted into the fermenter for example via a transporting device such as a plug-in mechanism, a screw conveyer etc., which permanently or only in case of use connects the grass storage device and the fermenter. The mixture of manure and plant material such as grass or grass silage is distributed in the fermenter that each fermenter comprises the same amount or different amounts of the mixture.

Biogas comprising CO2 in the fermenter is sucked from the fermenter into the gas processing device 9 using high pressure, e.g., overpressure of about 0.1 to 1 bar, 0.2 to 0.8 bar or 0.3 to 0.6 bar. In the gas processing device the temperature is lowered to about - 25 °C for example at about 8 bar, when the CO2 becomes liquid, and is removed from the biogas, mainly consisting of methane. CO21S released and for example used in greenhouses to grow plants. The pressure on the biogas is increased to 40 bar and the gas distribution system is for example supplied with methane from the system of the present invention.

Liquid and solid compounds of the mixture of manure and plant material such as grass or grass silage is transferred from the fermenter to the separator for example via a transporting device 17 such as a pump. In the separator, liquid and solid material are separated. In certain embodiments, the separator separates about 50, 60, 70 or 80 tons of liquid and solid compounds / h. Solid material is transported to a drying-hygenising device 25, wherein the solid material is dried for example at about 90 to 120 °C, 100 to 115 °C, for example at 110 °C. In certain embodiments, the solid material, which represents the fertilizer, is distributed on the belt of the dryer and dried via hot air, which is for example heated by a burner operated with biogas, i.e., methane, produced in the gas processing device of the present system before the pressure is increased to 40 bar. The fertilizer, is optionally pelleted in the pelleting device 8.

The liquid material in the separator, comprising about less than 3, 5 or 8 % dry matter, is transferred from the separator to the intermediate storage facility 5 via a transporting device 18 such as a pump. Parts of the liquid, which form a recirculating composition, are re-transferred from the intermediate storage device to the fermenter, e.g., vie a pump 30, to keep the mixture homogenous and at a dry matter content of 5 to 10 % or 6 to 8% for example 8 %. In certain embodiments about 900.000 tons of the recirculating composition are retransferred from the intermediate storage facility to the fermenter per year. Other parts of the liquid material remaining in the intermediate storage facility are transferred to the concentration device 7 via a transporting device 20 such as a pump. In the concentration device the liquid material is evaporated for example under pressure to remove e.g., potassium and phosphate from the remaining water.

In certain embodiments the liquid is evaporated via a stripping method. Air stripping is the transferring of volatile components of a liquid into an air stream. It is a environmental engineering technology used for the purification of groundwaters and wastewaters containing volatile compounds. Volatile compounds have relatively high vapor pressure and low aqueous solubility characterized by the compound’s Henry's law coefficient, which is the ratio of the concentration in air that is in equilibrium with its concentration in water. Pollutants with relatively high Henry’s Law coefficients can be economically stripped from water.

The water evaporated in the concentration device is condensed. In some embodiments the condensed water still comprises N-ammonium. It is transferred to another compartment of the concentration device, where it is further condensed under pressure until it evaporates at 70 °C under vacuum. In this stage H2SO4 is added to remove the N-ammonium, which is separated from the evaporated water.

The N-ammonium free, purified water is transferred to a hygenising device 11, where it is hygenised, cooled down via a heat recovery device 14 and released completely purified in the environment. The recovered heat is re-transferred into the system of the present invention for example to preheat manure and/or plant material or material in the intermediate storage facility, in the evaporator 6, and/or in the concentration device, or the component as such.

The solid material remaining in the concentration device and/or the evaporator, representing the fertilizer, is transferred to the drying-hygenising device 25 via a transporting device and is optionally combined with the fertilizer from the separator, is dried for example as described previously and is optionally pelleted. Heat used for the drying process is recovered and used for example for preheating of the manure and/or plant material, the fermenter and/or any other component of the present system.

The remaining ammonium sulfate produced in the concentration device during the purification of water, comprises 5 to 10 %, 6 to 8 %, e.g., 8 % dry matter. It is transferred to an ammonium sulfate drying-hygenising device 13 via a transporting device and is dried therein for example to crystals, and hygenised before it is released from the system of the present invention. The ammonium sulfate crystals are for example stored in a storage device for ammonium sulfate 28 and released in amounts of 2000 tons.

Optionally the system of the present invention comprises an air filter in one or more components of the system for example in the manure storage device and/or in the intermediate storage facility.

The main steps for producing biogas and a fertilizer according to the present invention are the following a) adding manure and grass silage to a fermenter system comprising at least two fermenters 3, and mixing same in the fermenter, b) aspirating the biogas from the fermenter into a gas processing device 9 via high pressure, c) transferring the mixture of manure and grass silage into a separator 4, where solid and liquid fractions are separated, d) transferring the liquid fraction into an intermediate storage facility 5, and the solid fraction, which is a fertilizer, into an evaporator 6, e) removing water from the fertilizer in the evaporator and transferring the remaining water into a concentration device 7, f) drying the fertilizer at 100 to 120 °C, and g) pelleting the fertilizer.

The liquid fraction of step c) is a recirculating composition as described previously.

The system and the method, respectively, as shown in Fig. 1 is run continuously or discontinuously. Fig. 1 provides an example for the system and the method steps of the present invention.

Claims (17)

A biogas and fertilizer-producing system, comprising a manure storage device (1), a grass storage device (2), at least two digesters (3), wherein each digester has a volume of 5,000 to 20,000 m3, a separator (4), a separator (4), a intermediate storage facility (5) for a recirculating composition, an evaporator (6), a concentration device (7), a pelletizer (8) and a gas processing device (9), wherein each digester comprises manure and ensilaged grass received from the manure storage device and the grass storage device, the digester is connected to the gas processing device and the separator for separating liquid and solid compounds from the mixture of manure and grass, the solid compounds forming a fertilizer, which is transported to the evaporator, which is connected to a concentration device and a pelletizing device for pelletizing the dried fertilizer. The biogas and fertilizer producing system of claim 1, wherein the system comprises 2 to 15, 4 to 12, 6 to 10, or 8 digesters. The biogas and fertilizer producing system of claim 1 or 2, wherein each digester has a volume of 8,000 to 18,000 m3, 10,000 to 15,000 m3, or 12,000 to 14,000 m3. A biogas and fertilizer-producing system according to any one of claims 1 to 3, wherein the digester is a lagoon, comprising a gas cover for intermediate storage of the gas, and a stirrer for mixing the manure, the grass and bacteria, and for supporting the ascent of the gas in the digester. The biogas and fertilizer-producing system according to claim 4, wherein the lagoon further comprises a foil that liner the fermenter. A biogas and fertilizer-producing system according to any one of claims 1 to 5, wherein the manure storage device is connected to the fermenters via a pump, and the storage of ensilaged grass is connected to the fermenters via a connection module. The biogas and fertilizer producing system according to any of claims 1 to 6, wherein the biogas in the digester is transferred via high pressure to the gas processing device. A method for producing biogas and fertilizer, which comprises the following steps: a) adding manure and ensilaged grass to a digester system comprising at least two digesters (3), each digester having a volume of 5,000 to Has 20,000 m3 and mixing thereof in the digester, b) suctioning the biogas from the digester under high pressure into a gas processing plant (9), c) transferring the mixture of manure and ensilaged grass into a separator (4) , where solid and liquid material are separated, d) transferring the liquid material into an intermediate storage facility (5), and the solid material, which is a fertilizer, into an evaporator (6), e) removing water from the fertilizer in the evaporator and transferring the remaining water into a concentration device (7), f) drying the fertilizer at 100 to 120 ° C, and g) pelletizing the fertilizer. The method of claim 8, wherein the liquid fraction of step c) is a recirculating composition. The method according to claim 8 or 9, wherein the manure and / or the grass is preheated prior to its addition to the digester. The method of any one of claims 8 to 10, wherein the liquid fraction is re-transferred from the intermediate storage facility to the digester to have a continuously homogeneous mixture in the digester. A method according to any of claims 8 to 11, wherein the water is removed from the digester via a stripping process in the evaporator in step e). The method of claim 12, wherein H 2 SO 4 is added to the removed water containing N-ammonium to remove the N-ammonium from the water, and to reduce the remaining water at 70 to 100 ° C with or without vacuum . A method according to any of claims 8 to 13, wherein the dry substance in the digester is 5 to 10% by weight or 6 to 9% by weight or 8% by weight. The method of any one of claims 8 to 13, wherein the liquid fraction of step d) comprises less than 5% by weight of dry matter. A method according to any of claims 8 to 15, wherein the gas sucked away in step b) is cooled to -25 ° C in the gas processing plant to separate the biogas and the CO2. A method for producing biogas and fertilizer according to any of claims 8 to 16 in a biogas and fertilizer producing system according to any of claims 1 to 7.