Method and system for utilizing waste heat from biogas mining

Abstract

The present invention relates to the field of energy utilization technology, and in particular to a method and system for utilizing waste heat from biogas mining and refining. The method comprises: A) mixing livestock and poultry manure and agricultural and forestry waste, crushing them, adjusting the pH value to 7-8, and obtaining a mixed material; the carbon-nitrogen ratio of the mixed material is 25-30:1; B) mixing the mixed material with anaerobic microorganisms, and pre-fermenting them under the conditions of an anaerobic environment, 30-40°C, and a water content of 50%-60% by mass; C) performing anaerobically fermenting the pre-fermented material at 35-55°C; the heat energy in the anaerobic fermentation process comes from the high-temperature flue gas generated in the mining and refining process; D) performing biodesulfurization and biodecarbonization on the biogas after anaerobic fermentation; E) using the biogas treated in step D) in the mining and refining process. The present invention realizes efficient recycling of energy, significantly improves the output and production efficiency of biogas, and reduces energy consumption and environmental pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of energy utilization, and in particular to a method and system for utilizing waste heat from biogas mining and refining. Background Art

[0002] With the increase in global energy demand and the growing pressure on environmental protection, how to use energy efficiently and environmentally friendly has become an important issue at present. Biogas refers to the use of livestock and poultry manure, crop straw and other raw materials to produce biogas through anaerobic fermentation, and further purification to obtain green, low-carbon, clean, environmentally friendly and renewable fuel gas with basically the same composition and calorific value as conventional natural gas. Using biogas to provide heat source for mineral refining can ensure heat while causing less pollution to the environment.

[0003] Mineral refining refers to extracting the useful components of minerals from ores and processing them through a series of processes to make them meet industrial application standards. The existing mineral refining process generates a large amount of waste heat that cannot be recycled and utilized, resulting in a large amount of energy waste and low energy efficiency. At the same time, in the biogas manufacturing process, other heat sources are required to provide heat for anaerobic fermentation, making the entire system investment cost high. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method and system for utilizing waste heat from biogas refining, which can achieve two-way synergistic utilization of biogas and waste heat from refining, realize efficient recycling of energy, significantly improve the output and production efficiency of biogas, reduce the use of fossil fuels, and reduce energy consumption and environmental pollution in the refining process.

[0005] The present invention provides a method for utilizing waste heat from biogas smelting, comprising the following steps:

[0006] A) mixing livestock and poultry manure and agricultural and forestry waste, crushing the mixture, and adjusting the pH value to 7-8 to obtain a mixed material; the carbon-nitrogen ratio of the mixed material is 25-30:1;

[0007] B) mixing the mixed material with anaerobic microorganisms, and pre-fermenting in an anaerobic environment at 30-40° C. and a water content of 50% to 60% by mass;

[0008] C) subjecting the pre-fermented material to anaerobic fermentation at 35-55° C.; the heat energy in the anaerobic fermentation process comes from the high-temperature flue gas generated during the smelting process;

[0009] D) subjecting the biogas after anaerobic fermentation to bio-desulfurization and bio-decarbonization;

[0010] E) using the biogas processed in step D) in a mining and refining process.

[0011] Preferably, in step A), the mass ratio of livestock and poultry manure to agricultural and forestry waste is 0.5-1.5:2.5-3.5.

[0012] Preferably, in step A), the particle size of the crushed material is less than 25 mm;

[0013] After the crushing, the method further comprises: screening.

[0014] Preferably, in step A), the reagent used to adjust the pH value to 7-8 includes lime or sodium carbonate.

[0015] Preferably, in step C), the pH value of the anaerobic fermentation is controlled to be 6.8 to 7.2;

[0016] The anaerobic fermentation is carried out under stirring conditions, and the stirring rate is 30 to 50 rpm;

[0017] The anaerobic fermentation time is 20 to 30 days;

[0018] The temperature of the high-temperature flue gas is 140-160°C.

[0019] Preferably, in step D), the biological desulfurization method comprises:

[0020] Inoculating Thiobacillus in the logarithmic growth phase into the reactor, starting the stirring system of the reactor, and introducing the biogas after anaerobic fermentation into the reactor so that the culture medium inoculated with Thiobacillus and the biogas are fully mixed to perform biological desulfurization;

[0021] The temperature of the biological desulfurization is controlled to be 20-35°C; the pH value is 6-8; and the concentration of dissolved oxygen is 2-8 mg / L.

[0022] Preferably, in step D), the biological decarbonization method comprises:

[0023] Inoculate microalgae in the logarithmic growth phase into a reactor, start the stirring system of the reactor, and introduce bio-desulfurized biogas into the reactor so that the culture medium inoculated with the microalgae and the biogas are fully mixed, and perform photosynthesis under light conditions;

[0024] The temperature of the biological decarbonization is controlled to be 20-35°C; the pH value is 6-8; and the concentration of dissolved oxygen is 2-8 mg / L.

[0025] Preferably, in step D), after biodesulfurization and biodecarbonization, the hydrogen sulfide content in the biogas is reduced to <200 ppm, the moisture content is <1%, and the CO2 content is <500 ppm.

[0026] Preferably, in step E), during the smelting process, the combustion temperature of the biogas is 1000-1500° C., and the thermal efficiency is 70%-80%; the smelting temperature is 1200-1300° C., and the time is 6-8 hours.

[0027] The present invention also provides a system for utilizing waste heat from biogas ore refining, comprising:

[0028] Regulation area;

[0029] An anaerobic fermentation tank connected to the material outlet of the regulating zone; the anaerobic fermentation tank is equipped with a heating device;

[0030] a biogas purification device connected to the gas outlet connected to the anaerobic fermentation tank;

[0031] a biogas storage tank connected to the gas outlet of the biogas purification device;

[0032] a biogas combustion device connected to the gas outlet of the biogas storage tank;

[0033] An ore smelting furnace matched with the biogas combustion device;

[0034] a waste heat recovery boiler connected to the gas outlet of the ore smelting furnace;

[0035] a heat exchange system connected to the gas outlet of the waste heat recovery boiler;

[0036] A hot water storage tank is connected to the hot water outlet of the heat exchange system; the hot water outlet of the hot water storage tank is connected to the heating device of the anaerobic fermentation tank.

[0037] The present invention proposes for the first time the concept of utilizing waste heat from smelting and biogas production to achieve two-way efficiency enhancement, thus realizing efficient recycling of energy. The innovative waste heat recovery design effectively improves the recovery efficiency and utilization value of waste heat. The waste heat is used to accelerate the anaerobic fermentation process, significantly improving the output and production efficiency of biogas. By using biogas to assist smelting, the use of fossil fuels is reduced, and the energy consumption and environmental pollution of the smelting process are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A system diagram for utilizing waste heat from biogas refining provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The present invention provides a method for utilizing waste heat from biogas smelting, comprising the following steps:

[0041] A) mixing livestock and poultry manure and agricultural and forestry waste, crushing the mixture, and adjusting the pH value to 7-8 to obtain a mixed material; the carbon-nitrogen ratio of the mixed material is 25-30:1;

[0042] B) mixing the mixed material with anaerobic microorganisms, and pre-fermenting in an anaerobic environment at 30-40° C. and a water content of 50% to 60% by mass;

[0043] C) subjecting the pre-fermented material to anaerobic fermentation at 35-55° C.; the heat energy in the anaerobic fermentation process comes from the high-temperature flue gas generated during the smelting process;

[0044] D) subjecting the biogas after anaerobic fermentation to bio-desulfurization and bio-decarbonization;

[0045] E) using the biogas processed in step D) in a mining and refining process.

[0046] A large amount of waste heat is generated in the mineral refining process. The present invention supplies the waste heat to the preparation of biogas, ensures the temperature of the anaerobic fermentation process, and realizes two-way efficient utilization of energy.

[0047] In step A):

[0048] The livestock and poultry manure and agricultural and forestry wastes are mixed, crushed, and the pH value is adjusted to 7-8 to obtain a mixed material; the carbon-nitrogen ratio of the mixed material is 25-30:1, for example 25:1.

[0049] In certain embodiments of the present invention, the livestock and poultry manure is the manure of chickens, cows, pigs and other livestock and poultry in the farm; specifically, at least one of chicken manure, cow manure and pig manure.

[0050] In certain embodiments of the present invention, the agricultural and forestry waste is at least one of straw, rice straw and corn stalks.

[0051] The mass ratio of livestock and poultry manure to agricultural and forestry waste is 0.5-1.5:2.5-3.5; for example, 1:3.

[0052] In certain embodiments of the invention, the mixing is performed in a conditioning zone.

[0053] In certain embodiments of the present invention, the crushing is performed by a crusher, and the particle size of the crushed material is less than 25 mm.

[0054] In some embodiments of the present invention, after the crushing, the process further comprises: screening, which is used to remove large non-biodegradable materials, such as stones, plastics and other impurities.

[0055] In certain embodiments of the present invention, the reagent used to adjust the pH value to 7-8 is an alkaline substance, such as lime or sodium carbonate.

[0056] The ideal carbon-nitrogen ratio (C / N ratio) is critical for anaerobic fermentation. The nitrogen content of livestock and poultry manure is high, while the carbon content of straw is high. Through reasonable proportioning, the C / N ratio is adjusted to 25-30:1 to optimize the biodegradation process. In some embodiments, the C / N ratio is 25:1.

[0057] In step B):

[0058] The mixed material is mixed with anaerobic microorganisms, and pre-fermented in an anaerobic environment at 30-40° C. and with a water content of 50%-60%.

[0059] In certain embodiments of the present invention, the anaerobic microorganism is at least one of methanogens, anaerobic bacteria, fermentative bacteria and cellulolytic bacteria. 8 ~10 10 CFU / g, for example 10 9 CFU / g.

[0060] The mixing is stirring and mixing. After the mixing, the process further comprises: preheating to a pre-fermentation temperature.

[0061] In certain embodiments of the present invention, the temperature of the pre-fermentation is 35-37°C; the moisture content is 55%. The time of the pre-fermentation is 3-5 days, such as 4 days. The pH value of the pre-fermentation is controlled to be 6.5-7.5. The reagent used to adjust the pH value is sodium carbonate, acetic acid or phosphate buffer (such as sodium dihydrogen phosphate (NaH2PO4) and disodium hydrogen phosphate (Na2HPO4).

[0062] The pre-fermentation is carried out in an anaerobic fermentation tank, specifically a continuous stirred tank reactor (CSTR). Before the mixed material enters the anaerobic fermentation tank, it can be preheated to the pre-fermentation temperature to reduce the energy consumption of temperature regulation in the anaerobic fermentation tank and accelerate the stable operation of the fermentation process.

[0063] In the present invention, the pre-fermentation helps to degrade a portion of complex organic matter that is difficult to directly utilize, and prepares substrates that are easier for microorganisms to utilize for the main fermentation stage.

[0064] In step C):

[0065] The pre-fermented material is subjected to anaerobic fermentation at 35-55°C.

[0066] In certain embodiments of the present invention, the temperature of the anaerobic fermentation is 40-42° C., and the pH value is 6.8-7.2. The pH value is maintained by adding alkaline substances (such as sodium carbonate) or adjusting the C / N ratio of the feed.

[0067] In certain embodiments of the present invention, the anaerobic fermentation is carried out under stirring conditions. The stirring rate is 30 to 50 rpm, such as 40 rpm. The anaerobic fermentation time is 20 to 30 days, such as 30 days.

[0068] In certain embodiments of the present invention, the anaerobic fermentation reactor is an anaerobic fermentation tank, specifically a continuous stirred tank reactor (CSTR).

[0069] The anaerobic fermentation produces biogas.

[0070] In the present invention, the heat energy in the anaerobic fermentation process comes from the high-temperature flue gas generated in the smelting process. The heat energy in the high-temperature flue gas can be recovered by a waste heat recovery boiler and used as heat energy for anaerobic fermentation.

[0071] In some embodiments of the present invention, the temperature of the high-temperature flue gas is 140-160°C, such as 150°C.

[0072] The residue after the anaerobic fermentation is used for fertilizing farmland.

[0073] In step D):

[0074] The biogas after anaerobic fermentation is subjected to bio-desulfurization and bio-decarbonization.

[0075] The biogas after anaerobic fermentation mainly includes methane (CH4) and carbon dioxide (CO2); in addition, it also includes: hydrogen (H2), nitrogen (N2), oxygen (O2) and a small amount of hydrogen sulfide (H2S) and the like.

[0076] In certain embodiments of the present invention, the microorganism used in the biodesulfurization is Thiobacillus. Thiobacillus is used to oxidize H2S in biogas into sulfate or elemental sulfur. For example, Thiobacillus oxidizes H2S into sulfuric acid (H2SO4) under aerobic conditions. The Thiobacillus may be of the genus Thiobacillus, such as Thiobacillus thioparus or Thiobacillus denitrificans.

[0077] The reactor used in the biological desulfurization is a completely mixed fixed bed reactor.

[0078] In certain embodiments of the present invention, the method of biological desulfurization comprises:

[0079] Thiobacillus in the logarithmic growth phase is inoculated into the reactor, the stirring system of the reactor is turned on, and the biogas after anaerobic fermentation is introduced into the reactor, so that the culture medium inoculated with Thiobacillus and the biogas are fully mixed, and hydrogen sulfide is oxidized into sulfuric acid under aerobic conditions.

[0080] The inoculation amount of Thiobacillus is 5% to 10%, for example 8%, of the total liquid volume of the reactor.

[0081] The inlet flow rate of biogas is 5 to 10 L / min, for example 8 L / min.

[0082] The temperature of the biological desulfurization is controlled to be 20-35°C, the pH value is 6-8, and the concentration of dissolved oxygen is 2-8 mg / L. The reagent used to adjust the pH value is dilute hydrochloric acid or sodium hydroxide solution.

[0083] When the concentration of H2S in biogas is less than 10ppm, biological desulfurization ends.

[0084] In certain embodiments of the present invention, the microorganisms used in the biological decarbonization are microalgae, such as Spirulina. The photosynthesis of microalgae is used to absorb CO2. For example, Spirulina can efficiently absorb CO2 and convert it into biomass under light and appropriate temperature conditions.

[0085] The reactor used in the biological decarbonization is a completely mixed fixed bed reactor.

[0086] In certain embodiments of the present invention, the method of biological decarbonization comprises:

[0087] The microalgae in the logarithmic growth phase are inoculated into the reactor, the stirring system of the reactor is turned on, and the bio-desulfurized bio-natural gas is introduced into the reactor so that the culture medium inoculated with the microalgae and the bio-natural gas are fully mixed, and photosynthesis is carried out under light conditions.

[0088] The temperature of the biological decarbonization is controlled to be 20-35°C, the pH value is 6-8, and the concentration of dissolved oxygen is 2-8 mg / L. The reagent used to adjust the pH value is dilute hydrochloric acid or sodium hydroxide solution.

[0089] The biological decarbonation and biological desulfurization are carried out separately using respective completely mixed fixed bed reactors.

[0090] After biodesulfurization and biodecarbonization, the hydrogen sulfide content in biogas is less than 10ppm, the moisture content is <1%, and the CO2 content is <500ppm.

[0091] In step E):

[0092] The biogas processed in step D) is used in the ore-refining process.

[0093] The ore smelting process is the ore smelting process, and the ore is iron ore.

[0094] The smelting process produces high-temperature flue gas, which is used as heat energy in the anaerobic fermentation process and is used for heating the anaerobic fermentation process.

[0095] In certain embodiments of the present invention, during the smelting process, the combustion temperature of the biogas is 1000-1500°C, and the thermal efficiency is 70%-80%; the smelting temperature is 1200-1300°C, and the time is 6-8h.

[0096] In certain embodiments of the present invention, waste heat in high-temperature flue gas can be recovered by a waste heat recovery boiler, and the recovered waste heat is transferred to hot water through a heat exchange system, and the hot water is transported to the anaerobic fermentation tank to provide the heat source required for fermentation.

[0097] The waste generated during the ore smelting process is treated harmlessly.

[0098] The present invention also provides a system for utilizing waste heat from biogas ore refining, comprising:

[0099] Regulation area;

[0100] An anaerobic fermentation tank connected to the material outlet of the regulating zone; the anaerobic fermentation tank is equipped with a heating device;

[0101] a biogas purification device connected to the gas outlet connected to the anaerobic fermentation tank;

[0102] a biogas storage tank connected to the gas outlet of the biogas purification device;

[0103] a biogas combustion device connected to the gas outlet of the biogas storage tank;

[0104] An ore smelting furnace matched with the biogas combustion device;

[0105] a waste heat recovery boiler connected to the gas outlet of the ore smelting furnace;

[0106] a heat exchange system connected to the gas outlet of the waste heat recovery boiler;

[0107] A hot water storage tank is connected to the hot water outlet of the heat exchange system; the hot water outlet of the hot water storage tank is connected to the heating device of the anaerobic fermentation tank.

[0108] Figure 1 A system diagram for utilizing waste heat from biogas refining provided in accordance with an embodiment of the present invention.

[0109] In certain embodiments of the present invention, the biogas mining waste heat utilization system further comprises: a raw material storage area. Livestock and poultry manure and agricultural and forestry waste in the raw material storage area enter the conditioning area through a conveyor belt.

[0110] The present invention has no special restrictions on the structure and type of the raw material storage area, which can be used to store raw materials. The present invention has no special restrictions on the structure and type of the adjustment area, which can achieve the operation of step A).

[0111] In certain embodiments of the present invention, the anaerobic fermenter is a continuous stirred tank reactor (CSTR).

[0112] The present invention has no particular limitation on the structure and type of the heating device, and the heating device can be used to heat an anaerobic fermentation tank.

[0113] In certain embodiments of the present invention, the biogas purification device is a completely mixed fixed bed reactor.

[0114] The present invention has no special restrictions on the structure and type of the biogas storage tank, and any biogas storage tank can be used to store biogas.

[0115] In certain embodiments of the present invention, the biogas combustion device is a nozzle-type biogas burner.

[0116] In certain embodiments of the present invention, the heat exchange system is a condensing multi-tube flue gas heat exchanger.

[0117] The present invention has no particular limitation on the structure and type of the hot water storage tank, and any hot water storage tank can be used to store hot water.

[0118] In certain embodiments of the present invention, the biogas mining waste heat utilization system further comprises: a hot water circulation pump. The hot water circulation pump is used to transport hot water in the hot water storage tank to the heating device of the anaerobic fermentation tank.

[0119] The regulated raw materials enter the anaerobic fermentation tank, where they are pre-fermented and fermented under suitable temperature and pH conditions to produce biogas (biogas). The produced biogas enters the biogas purification device through a pipeline, and enters the biogas storage tank after removing impurities. The pure biogas enters the biogas combustion device from the biogas storage tank, where it burns to produce high-temperature heat energy. The high-temperature heat energy is used for ore smelting in the ore smelting furnace, and the waste heat generated during the smelting process is recovered by the waste heat recovery boiler. The recovered waste heat is transferred to hot water through a heat exchange system, and the hot water is stored in a hot water storage tank. The hot water circulation pump transports the hot water to the anaerobic fermentation tank through a hot water delivery pipeline to provide the heat source required for fermentation.

[0120] This cycle ensures the efficient operation of the system and the maximum utilization of energy. The various devices work closely together to achieve two-way efficient utilization of waste heat from biogas mining and refining, which not only improves energy utilization efficiency but also reduces environmental pollution.

[0121] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0122] In order to further illustrate the present invention, a method and system for utilizing waste heat from biogas smelting provided by the present invention are described in detail below in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0123] Comparative Example 1

[0124] 1) livestock and poultry manure (pig manure) and agricultural and forestry waste (straw) are mixed in a conditioning area at a mass ratio of 1:3, crushed (the particle size of the crushed material is below 25 mm), sieved, and the pH value is adjusted to 7-8 with lime to obtain a mixed material; the carbon-nitrogen ratio of the mixed material is 25:1;

[0125] 2) The mixed material and anaerobic microorganisms (methanogens, from the Institute of Microbiology, Chinese Academy of Sciences) were stirred and mixed in a continuous stirred tank reactor (CSTR); the amount of anaerobic microorganisms added to the mixed material was 10 9 CFU / g; pre-fermented for 4 days in an anaerobic environment at 35-37°C, pH 6.5-7.5, and a water content of 55%;

[0126] 3) continuing to anaerobically ferment the pre-fermented material in a continuous stirred tank reactor (CSTR) at 35-37° C., pH 6.8-7.2, and stirring (stirring rate of 40 rpm) for 30 days;

[0127] 4) subjecting the biogas after the anaerobic fermentation to bio-desulfurization and bio-decarbonization;

[0128] The method of biological desulfurization comprises:

[0129] Inoculating Thiobacillus thioparus (State Key Laboratory of Microbial Technology (Shandong University)) in a logarithmic growth phase into a first completely mixed fixed-bed reactor, starting a stirring system of the reactor, and introducing biogas after anaerobic fermentation into the reactor, so that the culture medium inoculated with Thiobacillus thioparus and the biogas are fully mixed, and hydrogen sulfide is oxidized into sulfuric acid under aerobic conditions;

[0130] The inoculum amount of Thiobacillus was 8% of the total liquid volume of the reactor; the inlet gas flow rate of biogas was 8 L / min;

[0131] The biological desulfurization temperature is controlled to be 25°C; the pH value is 7; and the concentration of dissolved oxygen is 5 mg / L;

[0132] When the concentration of hydrogen sulfide in biogas is less than 10 ppm, biological desulfurization ends.

[0133] The method for biological decarbonization comprises:

[0134] Inoculate Spirulina (Shandong Boran Spirulina Biological Co., Ltd.) in the logarithmic growth phase into a second completely mixed fixed bed reactor, start the stirring system of the reactor, and introduce bio-desulfurized bio-natural gas into the reactor so that the culture medium inoculated with microalgae and the bio-natural gas are fully mixed, and perform photosynthesis under light conditions;

[0135] The temperature of the biological decarbonization is 25°C; the pH value is 7; the concentration of dissolved oxygen is 5 mg / L; the biological decarbonization is carried out in a completely mixed fixed bed reactor;

[0136] After biodesulfurization and biodecarbonization, the hydrogen sulfide content in biogas is less than 10ppm, the moisture content is <1%, and the CO2 content is <500ppm.

[0137] 5) using the biogas processed in step 4) in an ore smelting process (ore smelting, the ore being iron ore);

[0138] In the smelting process, the combustion temperature of biogas is 1300°C; the smelting temperature is 1250°C.

[0139] In this comparative example, the biogas produced by anaerobic fermentation of manure was directly used for smelting without waste heat recovery and utilization. The corresponding data are as follows:

[0140] Biogas production:

[0141] Raw material processing capacity: 1,000 tons of manure.

[0142] Biogas production: about 20000m 3 .

[0143] Mining and refining efficiency:

[0144] Ore processing capacity: 100 tons of iron ore.

[0145] Mineral refining time: 8h.

[0146] Fuel consumption: 20000m 3 Biogas.

[0147] Energy efficiency:

[0148] Biogas calorific value: 20MJ / m 3 .

[0149] Total energy input: 400GJ.

[0150] Ore refining thermal efficiency: 70%.

[0151] Economic benefits:

[0152] Biogas cost: 0.5 yuan / m 3 .

[0153] Total cost: 10,000 yuan.

[0154] Ore output: 80 tons of iron.

[0155] Market value: 320,000 yuan (calculated at 4,000 yuan / ton).

[0156] Environmental benefits:

[0157] Greenhouse gas emissions reduction: equivalent to reducing 200 tons of carbon dioxide emissions.

[0158] From the above data, it can be seen that the above technical scheme has certain limitations in terms of biogas production and mining efficiency. It fails to fully utilize the waste heat in the mining process, resulting in low energy utilization efficiency, and the economic and environmental benefits need to be improved.

[0159] Example 1

[0160] use Figure 1 The system shown is used to utilize the waste heat from biogas smelting:

[0161] 1) livestock and poultry manure (pig manure) and agricultural and forestry waste (straw) are mixed in a conditioning area at a mass ratio of 1:3, crushed (the particle size of the crushed material is below 25 mm), sieved, and the pH value is adjusted to 7-8 with lime to obtain a mixed material; the carbon-nitrogen ratio of the mixed material is 25:1;

[0162] 2) The mixed material and anaerobic microorganisms (methanogens, from the Institute of Microbiology, Chinese Academy of Sciences) were stirred and mixed in a continuous stirred tank reactor (CSTR); the amount of anaerobic microorganisms added to the mixed material was 10 9 CFU / g; in anaerobic environment, 35~37℃ (Temperature increased to 40-42°C through waste heat recovery) , pre-fermentation for 4 days under the condition of water content of 55%;

[0163] 3) The pre-fermented material is continued to be heated in a continuous stirred tank reactor (CSTR) at 35-37°C. (Through Yu Heat recovery to increase temperature to 40-42℃) , anaerobic fermentation for 25 days at a pH value of 6.8 to 7.2 and stirring (stirring rate of 40 rpm); The heat energy in the anaerobic fermentation process comes from the high-temperature flue gas (150°C) generated during the smelting process;

[0164] 4) subjecting the biogas after the anaerobic fermentation to bio-desulfurization and bio-decarbonization;

[0165] The method of biological desulfurization comprises:

[0166] Thiobacillus thioparus (State Key Laboratory of Microbial Technology (Shandong University)) in the logarithmic growth phase is inoculated into a completely mixed fixed-bed reactor, the stirring system of the reactor is turned on, and the biogas after anaerobic fermentation is introduced into the reactor so that the culture medium inoculated with Thiobacillus thioparus and the biogas are fully mixed, and hydrogen sulfide is oxidized into sulfuric acid under aerobic conditions.

[0167] The inoculum amount of Thiobacillus was 8% of the total liquid volume of the reactor; the inlet gas flow rate of biogas was 8 L / min;

[0168] The biological desulfurization temperature is controlled to be 25°C; the pH value is 7; and the concentration of dissolved oxygen is 5 mg / L;

[0169] When the concentration of hydrogen sulfide in biogas is less than 10 ppm, biological desulfurization ends.

[0170] The method for biological decarbonization comprises:

[0171] Inoculate Spirulina in the logarithmic growth phase into a second completely mixed fixed bed reactor, start the stirring system of the reactor, and introduce bio-desulfurized bio-natural gas into the reactor so that the culture medium inoculated with microalgae and the bio-natural gas are fully mixed, and perform photosynthesis under light conditions;

[0172] The temperature of the biological decarbonization is 25°C; the pH value is 7; the concentration of dissolved oxygen is 5 mg / L; the biological decarbonization is carried out in a completely mixed fixed bed reactor;

[0173] After biodesulfurization and biodecarbonization, the hydrogen sulfide content in biogas is less than 10ppm, the moisture content is <1%, and the CO2 content is <500ppm.

[0174] 5) using the biogas processed in step 4) in an ore smelting process (ore smelting, the ore being iron ore);

[0175] During the smelting process, the combustion temperature of biogas is 1300°C; the smelting temperature is 1250°C; the smelting process generates high-temperature flue gas; the waste heat in the high-temperature flue gas is recovered by a waste heat recovery boiler, and the recovered waste heat is transferred to hot water through a heat exchange system, and the hot water is stored in a hot water storage tank; the hot water circulation pump transports the hot water to the anaerobic fermentation tank through a hot water delivery pipeline to provide the heat source required for fermentation.

[0176] Compared with Comparative Example 1, Example 1 achieves efficiency improvement through the waste heat recovery system. The following are specific data:

[0177] Biogas production:

[0178] Raw material processing capacity: 1,000 tons of manure.

[0179] Biogas production: about 25000m 3 (Increased by 25%).

[0180] Mining and refining efficiency:

[0181] Ore processing capacity: 100 tons of iron ore.

[0182] Mineral refining time: 6h (reduced by 25%).

[0183] Fuel consumption: 20000m 3 Biogas.

[0184] Energy efficiency:

[0185] Biogas calorific value: 20MJ / m 3 .

[0186] Total energy input: 400GJ.

[0187] Ore refining thermal efficiency: 75% (increased by 5%).

[0188] Waste heat recovery efficiency: 30%.

[0189] Economic benefits:

[0190] Biogas cost: 0.5 yuan / m 3 .

[0191] Ore output: 85 tons of iron (increased by 6.25%).

[0192] Market value: 340,000 yuan (calculated at 4,000 yuan / ton).

[0193] Environmental benefits:

[0194] Greenhouse gas emissions reduction: equivalent to 250 tons of carbon dioxide emissions reduction (25% reduction).

[0195] From the above data, it can be seen that the two-way efficiency enhancement process of the present invention has significantly improved biogas production, mining efficiency, energy utilization efficiency, economic benefits and environmental benefits. The specific performance is as follows:

[0196] Increased biogas production: Through waste heat recovery and temperature increase, the anaerobic fermentation process is more efficient and biogas production is increased by 25%.

[0197] Improved smelting efficiency: smelting time has been reduced by 25%, ore output has increased by 6.25%, and the smelting process is more efficient.

[0198] Improved energy efficiency: Through waste heat recovery, the thermal efficiency of ore refining has increased by 5%, the waste heat recovery efficiency has reached 30%, and the overall energy efficiency has been significantly improved.

[0199] Significant economic benefits: Ore output increased, market value improved, and economic benefits significantly improved.

[0200] Enhanced environmental benefits: Greenhouse gas emissions reduction increased by 25%, with significant environmental benefits.

[0201] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for utilizing waste heat from biogas mining, comprising the following steps: A) mixing livestock and poultry manure and agricultural and forestry waste, crushing the mixture, and adjusting the pH value to 7-8 to obtain a mixed material; the carbon-nitrogen ratio of the mixed material is 25-30:1; B) mixing the mixed material with anaerobic microorganisms, and pre-fermenting in an anaerobic environment at 30-40° C. and a water content of 50% to 60% by mass; C) subjecting the pre-fermented material to anaerobic fermentation at 35-55° C.; the heat energy in the anaerobic fermentation process comes from the high-temperature flue gas generated during the smelting process; D) subjecting the biogas after anaerobic fermentation to bio-desulfurization and bio-decarbonization; E) using the biogas processed in step D) in a mining and refining process.

2. The utilization method according to claim 1, characterized in that: In step A), the mass ratio of livestock and poultry manure to agricultural and forestry waste is 0.5-1.5:2.5-3.

5.

3. The utilization method according to claim 1, characterized in that: In step A), the particle size of the crushed material is less than 25 mm; After the crushing, the method further comprises: screening.

4. The utilization method according to claim 1, characterized in that: In step A), the reagent used to adjust the pH value to 7-8 includes lime or sodium carbonate.

5. The utilization method according to claim 1, characterized in that: In step C), the pH value of the anaerobic fermentation is controlled to be 6.8 to 7.2; The anaerobic fermentation is carried out under stirring conditions, and the stirring rate is 30 to 50 rpm; The anaerobic fermentation time is 20 to 30 days; The temperature of the high-temperature flue gas is 140-160°C.

6. The utilization method according to claim 1, characterized in that: In step D), the biological desulfurization method comprises: Inoculating Thiobacillus in a logarithmic growth phase into a reactor, starting a stirring system of the reactor, and introducing biogas after anaerobic fermentation into the reactor so that the culture medium inoculated with Thiobacillus and the biogas are fully mixed to perform biological desulfurization; The temperature of the biological desulfurization is controlled to be 20-35°C; the pH value is 6-8; and the concentration of dissolved oxygen is 2-8 mg / L.

7. The utilization method according to claim 1, characterized in that: In step D), the biological decarbonization method comprises: Inoculate microalgae in the logarithmic growth phase into a reactor, start the stirring system of the reactor, and introduce bio-desulfurized bio-natural gas into the reactor so that the culture medium inoculated with the microalgae and the bio-natural gas are fully mixed, and perform photosynthesis under light conditions; The temperature of the biological decarbonization is controlled to be 20-35°C; the pH value is 6-8; and the concentration of dissolved oxygen is 2-8 mg / L.

8. The utilization method according to claim 1, characterized in that: In step D), after biodesulfurization and biodecarbonization, the hydrogen sulfide content in the biogas is reduced to <200 ppm, the moisture content is <1%, and the CO2 content is <500 ppm.

9. The utilization method according to claim 1, characterized in that: In step E), during the smelting process, the combustion temperature of the biogas is 1000-1500° C., and the thermal efficiency is 70%-80%; the smelting temperature is 1200-1300° C., and the time is 6-8 hours.

10. A system for utilizing waste heat from biogas mining and refining, comprising: Regulation area; an anaerobic fermentation tank connected to the material outlet of the regulating zone; The anaerobic fermentation tank is equipped with a heating device; a biogas purification device connected to the gas outlet connected to the anaerobic fermentation tank; a biogas storage tank connected to the gas outlet of the biogas purification device; a biogas combustion device connected to the gas outlet of the biogas storage tank; An ore smelting furnace matched with the biogas combustion device; a waste heat recovery boiler connected to the gas outlet of the ore smelting furnace; a heat exchange system connected to the gas outlet of the waste heat recovery boiler; A hot water storage tank is connected to the hot water outlet of the heat exchange system; the hot water outlet of the hot water storage tank is connected to the heating device of the anaerobic fermentation tank.

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