Plant for the production of a biogas mixture. A biogas mixture and biogas production.

Abstract

Plant for the production of a biogas mixture from soy whey, with a bioreactor with anaerobic bacteria, in particular a UASB or EGSB.

Description

[0001] The invention relates to a plant for producing a biogas mixture according to the preamble of claim 1, a biogas mixture according to the preamble of claim 4 and a biogas production according to the preamble of claim 9.

[0002] Soy whey is produced during the production of tofu. In the first step, the soybeans are soaked, cooked, and ground. A coagulant, typically magnesium chloride or—as in this case—calcium sulfate, is then added to the soybean-water mixture.

[0003] It is known that soy whey from tofu production is used as animal feed or has to be disposed of in other costly ways due to its high COD content. COD is a measure of the sum of all inorganic and organic compounds in water, including those that are difficult to degrade, which creates a chemical oxygen demand (COD), which, as a sum parameter, is a measure of the sum of all substances present in water that are oxidizable under certain conditions.

[0004] The object of the present invention is to provide a simple and safe subsequent use of soy whey.

[0005] The task is solved by a plant for producing a biogas mixture from soy whey, with a bioreactor with anaerobic bacteria, in particular a UASB or EGSB, in particular characterized by a COD volume load of about 3 - 5 kg COD / m 3 · d.

[0006] Anaerobic degradation refers to the microbial conversion of high-molecular-weight compounds by microorganisms in the absence of dissolved and undissolved oxygen. Long-chain polymers are degraded into methane and carbon dioxide in four steps. This process involves a variety of different microorganism strains, which are best carried out in a bioreactor.

[0007] EGSB (Expanded Granular Sludge Bed) and UASB (Upflow Anaerobic Sludge Blanket) reactors are similar in terms of process technology, using different embedding or bacterial arrangements.

[0008] In the fermentations according to the invention, a biogas mixture from soy whey is unexpectedly successfully obtained in a UASB reactor under mesophilic and a neutral pH range conditions, without the need for complex additional processes.

[0009] Soy whey, for example, has a COD concentration of about 31.1 to 52.1 kg / m 3 The tests have shown that fermentation is possible. Up to a COD volume load of approximately 3 - 5 kg COD / m 3 · d, ie about 3-5 kg ​​COD per m 3 bioreactor volume per day, a proportional increase in biogas production to a maximum of about 18 l / h was measured in the pilot plant with a volume of about 250 l. The biogas yield was about 0.62 m 3 / kg COD. The methane content was between approximately 54.0 and 56.2 vol%.

[0010] To prevent excessive microorganism removal from the process, a separation process is implemented downstream of the anaerobic bioreactor. The separator (solid-liquid separation) allows the settled biomass to be returned to the anaerobic bioreactor.

[0011] It is advantageous to provide a feeder for adding an iron(III) compound to the soy whey before entering the bioreactor, particularly for use with soy whey resulting from treatment with a coagulant such as calcium sulfate during tofu production. The use of calcium sulfate as a coagulant in tofu production results in hydrogen sulfide formation during anaerobic digestion. Hydrogen sulfide concentrations of over 4,000 ppm have been measured. Hydrogen sulfide production was unexpectedly successfully and permanently reduced by over 97% through the continuous addition of iron(III) compounds in the in-situ process. A stoichiometric dosage was advantageously used.

[0012] It is advantageous if a biosludge return is provided after the bioreactor in front of the inlet of the bioreactor.

[0013] The problem is solved by a biogas mixture, mainly comprising methane, obtainable by a plant with an anaerobic bioreactor, in particular UASB or EGSB, which is to be fed with soy whey.

[0014] It is advantageous if the bioreactor contains anaerobic bacteria, especially predominantly methane-producing bacteria.

[0015] It is advantageous if an iron (III) compound is added to the soy whey before feeding the bioreactor

[0016] It is advantageous if a biogas yield of about 0.6-0.7 m 3 / kg COD removed is available.

[0017] It is advantageous if the resulting biogas mixture is passed through a conventional biogas processing plant, in particular a desulfurizer.

[0018] The problem is also solved by producing biogas from soy whey using an anaerobic bioreactor, which produces a biogas mixture essentially comprising methane from introduced soy whey by means of a fermentation process with anaerobic bacteria.

[0019] It is advantageous if, using a bioreactor, a COD volume load of approximately 3 - 5 kg COD / m 3 · d is accessible.

[0020] Further features and advantages of the invention emerge from the claims and the following description, in which embodiments of the subject matter of the invention are explained in more detail in conjunction with the drawing.

[0021] It shows: Fig. 1 a schematic system according to the invention.

[0022] Fig.1 shows a plant 1 for producing a biogas mixture 6 from soy whey, with a bioreactor 2 with anaerobic bacteria, in particular a UASB or EGSB, in particular characterized by a COD volume load of about 3 - 5 kg COD / m 3· d. In particular, a feed means 3 for feeding an iron(III) compound into the soy whey is provided upstream of an inlet 4 into the bioreactor 2, particularly for use with soy whey resulting from treatment with a coagulant, calcium sulfate, during tofu production. Furthermore, if required, sodium hydroxide solution, acid, and trace substances can be added to the soy whey in a feed means 8. The soy whey can be conveyed into a recirculation 9 via a feed pump and then advantageously fed close to the bottom into the anaerobic bioreactor 2, in particular a UASB bioreactor. The anaerobic bioreactor 2 can be equipped with a 3-phase separator in the head region. The recirculation 9 can be controlled by a compressed air diaphragm pump. The flow rate and discharge pressure of the compressed air diaphragm pump are controlled by a needle valve and the compressed air maintenance unit.For example, a pH probe can be installed in recirculation 9 to continuously monitor the pH value. If necessary, the recirculated water can be passed through a heating module. The heating module can be controlled via the temperature measurement in anaerobic bioreactor 2. The target temperature is preferably 37 °C. Clear water from anaerobic bioreactor 2 flows via an overflow pipe into a sludge separator 10. The sludge separator can be degassed via a vent valve. The separated sludge is collected, for example, in a sludge tank. LIST OF REFERENCE SYMBOLS 1 system 2 bioreactor 3 Feeding means 4 Entrance 5 Biosludge recirculation 6 Biogas mixture 7 Biogas upgrading 8 Feeding means 9 Recirculation 10 sludge separators

Claims

[1] Plant (1) for producing a biogas mixture (6) from soy whey, with a bioreactor (2) with anaerobic bacteria, in particular a UASB or EGSB, in particular characterized by a COD volume load of 3 - 5 kg COD / m 3 · d. [2] Plant according to claim 1, characterized by that a feeding means (3) for feeding an iron(III) compound into the soy whey is provided upstream of an inlet (4) into the bioreactor (2), in particular for use for soy whey resulting from a treatment with a coagulant calcium sulfate in tofu production. [3] Plant according to claim 1 or 2, characterized by that after the bioreactor (2) a biosludge return (5) is provided in front of the inlet (4) of the bioreactor (2). [4] Biogas mixture (6), mainly comprising methane, obtainable by a plant (1) with an anaerobic bioreactor (2), in particular according to one of claims 1 to 3, in particular UASB or EGSB, which is to be fed with soy whey. [5] Biogas mixture (6) according to claim 4, characterized by that the bioreactor (2) contains anaerobic bacteria, in particular predominantly methane-producing bacteria. [6] Biogas mixture (6) according to claim 4 or 5, characterized by that an iron (III) compound must be added to the soy whey before feeding the bioreactor (2) [7] Biogas mixture (6) according to one of claims 4 to 6, characterized by that a biogas yield of about 0.6-0.7 m 3 / kg COD removed is available. [8] Biogas mixture (6) according to one of claims 4 to 7, characterized by that the resulting biogas mixture must be passed through a conventional biogas processing plant (7), in particular a desulfurizer. [9] Biogas production from soy whey by means of an anaerobic bioreactor (2) which produces a biogas mixture (6) essentially comprising methane from introduced soy whey by means of a fermentation process with anaerobic bacteria. [10] Biogas production according to claim 9 using a bioreactor (2), in particular with a COD volume load of 3 - 5 kg COD / m 3 · d.

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