A method for optimizing the calculation of biogas production using livestock and poultry manure as raw materials

Abstract

The invention discloses a method for optimizing the calculation of biogas production using livestock and poultry manure as raw materials; the method comprises the following steps: step 1, calculating the biogas production by using a solid content calculation method or a breeding amount calculation method according to the manure situation; step 2, calculating the output of organic fertilizer by a manure cleaning method using a water-soaking manure method or a dry manure cleaning method; step 3, calculating the biogas purification amount or the biogas power generation amount; step 4, outputting the calculation result through a computer. The application of the invention can further improve the calculation accuracy of the biogas production using livestock and poultry manure as raw materials, and overcome the defects of the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of computer-aided design, and in particular to a method for optimizing calculation of biogas production using livestock and poultry excrement as raw materials. Background Art

[0002] In terms of technical route, the most widely used resource utilization method is to use livestock and poultry manure, rural straw and wet garbage as raw materials to produce biogas through anaerobic fermentation and then burn it to generate electricity or purify biogas.

[0003] For the entire biogas power generation project, the biogas production is very important for the design, investment and operation of the entire project. The accuracy of the calculation of biogas production during the design process will affect the volume design of the anaerobic fermentation tank, the volume design of the gas storage tank, the design of the treatment scale of the purification equipment, the design of the power generation installed capacity, the investment scale and the project's benefits. Therefore, how to accurately calculate the biogas production through the obtained raw material information is particularly critical.

[0004] The existing calculation method is as follows:

[0005] (1) TS, solid matter calculation method

[0006] TS refers to the total solids in the fermentation raw materials, also known as dry matter, including soluble solids and insoluble solids. The total solid content is generally expressed in %. Using TS content to calculate biogas production is currently the most commonly used method.

[0007] The "Technical Specifications for Biogas Engineering Part 1: Engineering Design" (NY / T1220.1-2019) stipulates that the biogas production of biogas projects is calculated according to the following formula:

[0008] q=WSY p

[0009] Where:

[0010] q is the biogas production, m 3 / d

[0011] W is fermentation raw material, kg / d

[0012] S is the total solid content of fermentation raw materials (TS), %

[0013] Y p is the gas production rate of raw material TS, m 3 / kg, refer to the following table for values

[0014] Table 2-1 Gas production rate m of different biogas fermentation raw materials TS 3 / kg

[0015]

[0016] In addition, the Technical Specifications for Large and Medium-sized Biogas Projects (GB / T51063-2014) also gives some ranges of raw material TS yields in L / kgTS, as shown in the following table:

[0017] Table 2-2 Summary of properties of agricultural organic waste L / kg

[0018]

[0019] The data of the gas production rate comes from the "Biogas Technology Manual" (Sichuan Science and Technology Press, first edition in September 1990). The fermentation temperature used is 35°C, and the fermentation cycle is 90 days for straw and 60 days for feces. Comparing the TS gas production rate of different fermentation raw materials in the "Technical Specifications for Biogas Engineering Part 1: Engineering Design" and the "Technical Specifications for Large and Medium-sized Biogas Engineering", it can be found that the TS gas production rate value ranges given by the two are basically the same. However, it should be pointed out that in actual biogas projects, the fermentation time of raw materials cannot reach 90 days for straw and 60 days for feces. Therefore, this data is only theoretical data and there is a deviation from the actual project.

[0020] (2) VS calculation method

[0021] VS refers to volatile solids, which refers to the organic components in the total solids. The measured total solids are further placed in a muffle furnace and burned. After all the organic matter is decomposed and volatilized, the remaining substance is inorganic matter (ash). The total solid minus the ash is the volatile solid. Volatile solids are usually expressed in %. Compared with calculating biogas production using TS content, calculating biogas production using VS content is more accurate. This is because the TS content includes inorganic matter that does not produce biogas. Since the content of inorganic matter is unclear, it may cause errors in the calculation of biogas production. The VS calculation method is commonly seen in some research literature, but the current specifications do not provide a calculation method for calculating biogas production using VS content and the range of VS production rate values.

[0022] By consulting the literature, the formula for calculating methane production using VS content is as follows:

[0023] q CH4 =WSY VS

[0024] Where:

[0025] q CH4 is the methane production, m 3 / d

[0026] W is fermentation raw material, kg / d

[0027] S is the volatile solid content (VS) of fermentation raw materials, %

[0028] Y VS is the raw material VS gas production rate, m 3 / kg, refer to the following table for values

[0029] Table 2-3 Different biogas fermentation raw materials VS methane production rate 3 / kg

[0030]

[0031] It should be noted that when using VS content to calculate biogas production, what is calculated is actually the methane production. The actual biogas production should be converted according to the content of biogas. Under normal circumstances, the methane content in biogas is 55%-60%, and the rest is mainly carbon dioxide.

[0032] In addition, from the data in the table, it can be found that the empirical data range of VS methane production rate given by various literature materials is relatively wide, such as 0.18-0.36m 3 / kg, cow dung 0.13-0.33m 3 / kg. In large and medium-sized biogas projects, it is difficult to obtain accurate measured values ​​of the project. When the VS calculation method is used, due to the large amount of manure and sewage, once the VS methane production rate is improperly taken, the error caused by the calculation process will be amplified, and the final calculated biogas production will deviate greatly from the actual value.

[0033] (3) COD calculation method

[0034] COD refers to chemical oxygen demand, which is the amount of oxygen consumed when the organic matter in the sample reacts with the strong oxidant potassium dichromate under certain conditions. Under these conditions, the organic matter is almost completely oxidized, and the amount of oxygen consumed at this time is the chemical oxygen demand, which is expressed in mg / L. Chemical oxygen demand can more accurately reflect the content of organic matter in the sample.

[0035] The theoretical chemical oxygen demand can be obtained according to the chemical equation. For example, the theoretical oxygen demand of glucose can be calculated as follows (the molecular weight in the following formula is the relative molecular weight):

[0036] C6H 12 O6+6O2→6CO2+6H2O

[0037]

[0038] That is, the theoretical chemical oxygen demand of 1g of glucose is 1.067g. Similarly, the corresponding methane production can be calculated by the following formula:

[0039] C6H 12 O6→3CO2+3CH4

[0040]

[0041] That is, the theoretical methane production of 1gCOD is 0.35L, and the theoretical methane production of 1kgCOD is 0.35m 3 The result is calculated under standard conditions. Under medium-temperature anaerobic fermentation conditions (35°C, 1 atmosphere), the theoretical methane production of 1kgCOD is 0.395m 3 The COD content of different types of livestock and poultry manure can be determined by referring to the COD content range given in the "Technical Specifications for Pollution Control Engineering in Livestock and Poultry Breeding Industry" (HJ497-2009), as shown in the following table:

[0042] Table 2-4 COD content of different biogas fermentation raw materials (mg / L)

[0043]

[0044] Using COD to calculate biogas production is a relatively accurate calculation method, but this method also has two problems. First, due to various restrictions, it is difficult to obtain actual COD parameters in actual large and medium-sized biogas projects, and reference values ​​need to be used. The "Technical Specifications for Large and Medium-sized Biogas Projects" gives a wide range of COD values ​​for different types of livestock and poultry manure. For example, the COD content of pig manure (water-flushed manure) is 15600-46800 mg / L, and the maximum value is 3 times the minimum value. When calculating the biogas production of large-scale biogas projects, since the total amount of manure is very large, once the value is improperly selected, the error caused by the calculation process will be amplified, and the final calculated biogas production will deviate greatly from the actual value. Second, the calculation of biogas production by COD is a purely theoretical calculation. For actual projects, due to various influencing factors, there is a large gap between the biogas production and the calculated value. For example, the theoretical biogas production of 1kgCOD is 0.583m 3 However, according to the actual project operation data, the biogas production of 1kgCOD is only 0.45-0.50m 3 .

[0045] However, through the analysis of the above three biogas production calculation methods and combined with actual projects, the above calculation methods all have the following problems in practical application:

[0046] 1. When using the TS calculation method, the TS gas production rate data given in the "Technical Specifications for Large and Medium-sized Biogas Projects" comes from the "Biogas Technical Manual". The data in this document is obtained by using a fermentation temperature of 35°C and a fermentation period of 90 days for straw and 60 days for feces. However, in actual biogas projects, the fermentation time of raw materials cannot reach 90 days for straw and 60 days for feces, and is generally only about 20 days. Therefore, the results of biogas production calculated by this method are often larger than the actual results.

[0047] 2. The VS calculation method and COD calculation method give a wide range of VS methane production rate and COD content of different types of livestock and poultry manure. For example, the Technical Specifications for Pollution Control Engineering in Livestock and Poultry Breeding (HJ497-2009) gives the COD range of pig manure (water-flushed manure) as 15600-46800 mg / L, and the upper limit is about 3 times the lower limit. When calculating the biogas production of large-scale biogas projects, since the total amount of manure is very large, once the value is improperly selected, the error caused by the calculation process will be amplified, and the final calculated biogas production will deviate greatly from the actual amount.

[0048] 3. The calculation of biogas production by COD is purely theoretical. For actual projects, there is a large gap between biogas production and the calculated value due to various influencing factors. The actual biogas production often does not reach the theoretical calculated value of COD.

[0049] 4. When calculating biogas production, in addition to TS production rate, VS production rate and COD content, the amount of manure is also an important factor affecting the accuracy of biogas production calculation. In the several calculation methods given, the amount of manure is generally assumed to be a known value. In reality, the amount of manure is often not obtained through test measurement, but is estimated based on the scale of breeding. The total amount of manure for the entire project is estimated by the amount of manure of one pig, one chicken, and one cow. The amount of manure and TS, VS and COD contents of livestock and poultry in different regions and different breeding methods are different. Therefore, only by using a more accurate method to estimate the manure emissions of a single livestock and poultry can we avoid the error being amplified when calculating the total amount of manure of hundreds of thousands of livestock and poultry.

[0050] 5. The impact of the manure cleaning cycle on biogas production should be fully considered. The biogas released by the fermentation of manure at ambient temperature before entering the anaerobic tank for anaerobic fermentation should be deducted when calculating the biogas production. In addition, the relationship between the fermentation time and gas production of livestock and poultry manure in the anaerobic fermentation tank should also be fully considered. Different from theoretical calculations, in actual engineering, the entire fermentation process is limited by the fermentation time, resulting in the presence of incompletely fermented substances in the discharged biogas slurry and sludge. The biogas production corresponding to this part of the substance should also be deducted when calculating the biogas production.

[0051] 6. When calculating the gas production, the methane content in the biogas should be clearly stated. Since both the VS gas production calculation method and the COD gas production calculation method are for methane production, and the two main components of actual biogas are methane and carbon dioxide, the final biogas production needs to be converted by the methane content.

[0052] 7. When using the TS, VS or COD calculation method, you will find that you need to collect two important data: the total amount of manure and the TS content (or VS content or COD content). The total amount of manure needs to be obtained by installing a metering device in the pig farm, and the TS content (or VS content or COD content) needs to be obtained by sampling and testing. However, the total amount of livestock and poultry manure and the TS content (or VS content or COD content) produced in different seasons during livestock and poultry breeding will vary. For example, the amount of pig food and flushing water in different seasons will cause differences in the total amount of livestock and poultry manure and the TS content (or VS content or COD content). If only the sampling data of a certain time and time is used as the basis for calculation, it will affect the calculation of biogas production.

[0053] Therefore, how to improve the calculation accuracy of biogas production using livestock and poultry manure as raw materials has become a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0054] In view of the above-mentioned defects of the prior art, the present invention provides a method for optimizing the calculation of biogas production using livestock and poultry manure as raw materials, the purpose of which is to improve the calculation accuracy of biogas production using livestock and poultry manure as raw materials.

[0055] To achieve the above purpose, the present invention discloses a method for optimizing the calculation of biogas production using livestock and poultry manure as raw materials; the method comprises the following steps:

[0056] Step 1: Calculate the biogas production by solid content calculation method or livestock volume calculation method according to the manure situation; the solid content calculation method is calculated by the following formula:

[0057]

[0058] Among them, Q is the biogas production, unit is m 3 / d; q is the theoretical biogas production corresponding to the total amount of manure, unit is m 3 / day;q s The amount of biogas naturally emitted during storage and transportation before entering the fermentation tank corresponding to the total amount of manure, unit: m 3 ; y is the correction factor for the number of days of residence in the fermentation tank; W is the fermentation raw material, in kg / day; S is the total solid content of the fermentation raw material; Y p is the gas production rate of raw solid matter, in m 3 / kg; k is the room temperature, that is, the dry matter gas production rate at an average temperature of 15°C, in m 3 / kg, take 4.16×10 -3 ; d is the manure cleaning cycle, in days;

[0059] The calculation formula for breeding quantity is as follows:

[0060]

[0061] Among them, M is the breeding scale, the unit is head; S0 is the total solid content of manure of a single livestock and poultry, the unit is kg / d·head;

[0062] Step 2: Calculate the output of organic fertilizer by using the water-soaked manure cleaning method or the dry manure cleaning method;

[0063] The relationship between the output of organic fertilizer by the water-soaked manure cleaning method is as follows:

[0064]

[0065] W c =W f ×σ1×θ+(WW f );

[0066] S y =WQ×ρ-S S ;

[0067]

[0068] Among them, W f is the amount of manure separated by solid-liquid separation, in t / day, W is the total amount of manure, in t / day; σ1 is the rated solid matter concentration of the CSTR fermenter; σ2 is the TS concentration of manure; W c is the amount of manure entering the CSTR fermentation tank, in t / day; θ is the solid-liquid separation efficiency; S y is the biogas production, in t / day; ρ is the biogas density, in t / m 3 ; S S is the biogas residue production, in t / day; S b is the output of organic fertilizer, in t / day; σ3 is the solid content of biogas residue; σ4 is the solid content of organic fertilizer;

[0069] The relationship between the output of organic fertilizer by dry manure removal is as follows:

[0070]

[0071]

[0072]

[0073] Among them, Q water is water consumption, in t / day; is the biogas slurry return ratio; S y is the biogas slurry production, in t / day; S S is the biogas residue production, in t / day; W is the total amount of manure, in t / day;

[0074] Step 3, calculating the biogas purification amount or biogas power generation;

[0075] The calculation formula of the biogas purification amount is as follows:

[0076]

[0077] Among them, Q S is the biogas production, in m 3 / day; α is the methane content of biogas; β is the biogas content of biogas; ε is the proportion of the fermentation tank insulation heat load to the biogas heat load;

[0078] The calculation formula of biogas power generation is as follows:

[0079] W S =Q×q1÷24÷3600;

[0080] Y=W S ÷δ;

[0081] W1=Y×τ;

[0082] Among them, W S is the biogas heat load, in MW; q1 is the biogas calorific value, in MJ / m 3 ; Y is the installed capacity of the biogas internal combustion engine, in MW; δ is the thermal efficiency of the biogas internal combustion engine; W1 is the annual power generation, in MWh; τ is the annual operating hours, in hours;

[0083] Step 4: Output the calculation results through a computer.

[0084] Preferably, when the livestock and poultry are fattening pigs, the total solid content of manure of a single livestock and poultry is S0=0.39.

[0085] Preferably, at an average temperature of 15°C, the dry matter gas production rate k = 4.16 × 10 -3 .

[0086] Preferably, the raw material gas production rate Y p The values ​​of are as follows:

[0087] When the raw material is pig manure, Y p =0.325;

[0088] When the raw material is chicken manure, Y p =0.36;

[0089] When the raw material is dairy cow dung, Y p =0.22.

[0090] Preferably, the calculation method of the correction factor y for the number of days of residence in the fermentation tank is as follows:

[0091] When the raw material is pig manure, y=0.0003x 3 -0.0492x 2 +2.6643x+51.774;

[0092] When the raw material is human feces, y = 0.0017x 3 -0.2210x 2 +9.3775x-32.358;

[0093] When the raw material is horse manure, y = 0.0004x 3 -0.0565x 2 +3.0457x+38.587;

[0094] When the raw material is cow dung, y = 0.0017x 3 -0.2119x 2 +8.9993x-35.606;

[0095] Here, x is the number of days.

[0096] Beneficial effects of the present invention:

[0097] The application of the present invention can further improve the calculation accuracy of the biogas production using livestock and poultry manure as raw materials, and overcome the defects of the prior art.

[0098] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] Figure 1 A calculation flow chart of an embodiment of the present invention is shown.

[0100] Figure 2 The fitting curve of pig manure fermentation time and conversion rate and the corresponding functional relationship diagram in one embodiment of the present invention are shown.

[0101] Figure 3 A graph showing the relationship between the cumulative gas production of anaerobic fermentation of pig manure at different reaction temperatures in one embodiment of the present invention is shown.

[0102] Figure 4 A cross section of a window after programming in VB programming language in one embodiment of the present invention is shown.

[0103] Figure 5 A schematic diagram showing the calculation output results of a plan to build a dairy farm in a certain animal husbandry park in one embodiment of the present invention.

[0104] Figure 6 The calculation result of biogas production in a healthy breeding ecological park in Beijing with a fermentation period of 15 days in one embodiment of the present invention is shown.

[0105] Figure 7 The calculation result of biogas production in a healthy breeding ecological park in Beijing with a fermentation period of 18 days in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0106] Example

[0107] like Figure 1 As shown, a method for optimizing the calculation of biogas production using livestock and poultry manure as raw materials comprises the following steps:

[0108] Step 1: Calculate the biogas production by solid content calculation method or livestock volume calculation method according to the manure situation; the solid content calculation method is calculated by the following formula:

[0109]

[0110] Among them, Q is the biogas production, unit is m 3 / d; q is the theoretical biogas production corresponding to the total amount of manure, unit is m 3 / day;q s The amount of biogas naturally emitted during storage and transportation before entering the fermentation tank corresponding to the total amount of manure, unit: m 3 ; y is the correction factor for the number of days of residence in the fermentation tank; W is the fermentation raw material, in kg / day; S is the total solid content of the fermentation raw material; Y p is the gas production rate of raw solid matter, in m 3 / kg; k is the room temperature, that is, the dry matter gas production rate at an average temperature of 15°C, in m 3 / kg, take 4.16×10 -3 ; d is the manure cleaning cycle, in days;

[0111] The calculation formula for breeding quantity is as follows:

[0112]

[0113] Among them, M is the breeding scale, the unit is head; S0 is the total solid content of manure of a single livestock and poultry, the unit is kg / d·head;

[0114] Step 2: Calculate the output of organic fertilizer by using the water-soaked manure cleaning method or the dry manure cleaning method;

[0115] The relationship between the output of organic fertilizer by the water-soaked manure cleaning method is as follows:

[0116]

[0117] W c =W f ×σ1×θ+(WW f );

[0118] S y =WQ×ρ-S S ;

[0119]

[0120] Among them, W f is the amount of manure separated by solid-liquid separation, in t / day, W is the total amount of manure, in t / day; σ1 is the rated solid matter concentration of the CSTR fermenter; σ2 is the TS concentration of manure; W c is the amount of manure entering the CSTR fermentation tank, in t / day; θ is the solid-liquid separation efficiency; S y is the biogas production, in t / day; ρ is the biogas density, in t / m 3 ; S S is the biogas residue production, in t / day; S b is the output of organic fertilizer, in t / day; σ3 is the solid content of biogas residue; σ4 is the solid content of organic fertilizer;

[0121] The relationship between the output of organic fertilizer by dry manure cleaning is as follows:

[0122]

[0123]

[0124]

[0125] Among them, Q water is water consumption, in t / day; is the biogas slurry return ratio; S y is the biogas slurry production, in t / day; S S is the biogas residue production, in t / day; W is the total amount of manure, in t / day;

[0126] Step 3, calculating the biogas purification amount or biogas power generation;

[0127] The calculation formula of biogas purification amount is as follows:

[0128]

[0129] Among them, Q S is the biogas production, in m 3 / day; α is the methane content of biogas; β is the biogas content of biogas; ε is the proportion of the fermentation tank insulation heat load to the biogas heat load;

[0130] The calculation formula of biogas power generation is as follows:

[0131] W S=Q×q1÷24÷3600;

[0132] Y=W S ÷δ;

[0133] W1=Y×τ;

[0134] Among them, W S is the biogas heat load, in MW; q1 is the biogas calorific value, in MJ / m 3 ; Y is the installed capacity of the biogas internal combustion engine, in MW; δ is the thermal efficiency of the biogas internal combustion engine; W1 is the annual power generation, in MWh; τ is the annual operating hours, in hours;

[0135] Step 4: Output the calculation results through a computer.

[0136] The present invention uses the calculated biogas production to further calculate the biogas slurry production, biogas residue production, organic fertilizer production, power generation capacity, water consumption, power generation, biogas production, total investment, static payback period and other parameters of the entire biogas project. Based on this, a calculation program is edited using the VB programming language and can be used for related calculations of biogas projects. The interface of the calculation program is shown in the attached figure. Figure 1 As shown, it is divided into two parts: parameter input and calculation results. The parameter input part includes five parts: capital collection, solid content and manure, breeding scale (stock), other raw materials and design parameters. According to the project situation, the manure situation, manure cleaning method and biogas utilization are selected, and the relevant data required for the operation of the calculation program are input. The calculation results include two parts: basic situation and product situation. The basic situation includes 13 results, including daily biogas production, annual biogas production, daily biogas production, annual biogas production, daily biogas residue production, annual biogas residue production, daily water consumption, annual water consumption, installed power generation capacity, total project investment, static payback period, number of CSTR fermentation tanks, number of USR fermentation tanks, etc. The gas production situation includes 8 results, including daily biogas production, annual biogas production, daily power generation, annual power generation, daily grid-connected electricity, annual grid-connected electricity, daily organic fertilizer production, and annual organic fertilizer production.

[0137] The calculation process of the calculation program is as follows:

[0138] 1. Determine whether the manure situation is known solid content or known breeding scale. If the solid content is known, load the corresponding solid content calculation module and enter the solid content and total manure. If the breeding scale is known, load the corresponding breeding scale calculation module and enter the breeding volume in the corresponding livestock and poultry type.

[0139] 2. Determine whether the manure cleaning method is water-soaked manure or dry manure cleaning. If water-soaked manure is selected, the water-soaked manure calculation module is loaded; if dry manure cleaning is selected, the dry manure cleaning calculation module is loaded.

[0140] 3. Determine whether the biogas utilization method is to purify biogas or to generate electricity through a biogas internal combustion engine. If you choose to purify biogas, load the purification calculation module; if you choose to generate electricity through a biogas internal combustion engine, load the power generation calculation module.

[0141] 4. Input the boundary conditions required for calculation, including: pre-fermentation retention time, biogas slurry sales price, organic fertilizer sales price, manure treatment fee, grid-connected electricity price (if biogas internal combustion engine power generation is selected in step 3), and natural gas sales price (if purified biogas is selected in step 3).

[0142] 5. Input the design parameters required for calculation, including CSTR fermentation days, solid content entering CSTR, annual operation time, methane content of biogas, plant electricity consumption ratio, biogas slurry return ratio (if dry manure is selected in step 2), USR fermentation days (if water-soaked manure is selected in step 2), and USR volumetric gas production rate (if water-soaked manure is selected in step 2).

[0143] 6. Run the calculation program according to the loaded program module.

[0144] 7. Output the calculation results. The calculation process is as follows Figure 1 shown.

[0145] In certain embodiments, when the livestock and poultry are fattening pigs, the total solid content of manure of a single livestock and poultry is S0=0.39.

[0146] In some embodiments, at an average temperature of 15°C, the dry matter gas production rate k = 4.16 × 10 -3 .

[0147] In certain embodiments, the raw material gas production rate Y p The values ​​of are as follows:

[0148] When the raw material is pig manure, Y p =0.325;

[0149] When the raw material is chicken manure, Y p =0.36;

[0150] When the raw material is dairy cow dung, Y p =0.22.

[0151] In certain embodiments, the fermentation tank residence days correction factor y is calculated as follows:

[0152] When the raw material is pig manure, y=0.0003x 3 -0.0492x 2 +2.6643x+51.774;

[0153] When the raw material is human feces, y = 0.0017x 3 -0.2210x2 +9.3775x-32.358;

[0154] When the raw material is horse manure, y = 0.0004x 3 -0.0565x 2 +3.0457x+38.587;

[0155] When the raw material is cow dung, y = 0.0017x 3 -0.2119x 2 +8.9993x-35.606;

[0156] Here, x is the number of days.

[0157] The principle of the present invention is as follows:

[0158] In view of the problems existing in several existing biogas production calculation methods, this method intends to further optimize the existing biogas production calculation methods through the following methods. The specific principles are as follows:

[0159] 1. Considering that the VS calculation method and COD calculation method give a wide range of VS methane production rate and COD content of different types of livestock and poultry manure, it is easy to cause the calculation error to be amplified. Therefore, it is planned to use the TS calculation method as the main calculation method and optimize this calculation method.

[0160] 2. Determine the biogas production within the designed fermentation cycle through the correspondence between biogas production and fermentation time during medium-temperature fermentation.

[0161] 3. The corresponding relationship between the biogas production at ambient temperature and the number of fermentation days is used to determine the biogas released by the fermentation of the raw materials at ambient temperature before they enter the fermentation tank.

[0162] 4. Determine the manure production of each livestock and poultry by collecting literature data and conducting statistical analysis.

[0163] 5. Data that cannot be collected will be converted based on pig manure. The specific conversion method is referred to in literature and normative materials.

[0164] 6. Determine the methane content in biogas by collecting experimental data.

[0165] Based on the above principles, the calculation process is constructed according to the following requirements:

[0166] 1. Establish a method to calculate the theoretical total gas production of medium-temperature anaerobic fermentation per unit solid content of raw materials;

[0167] 2. Establish the functional relationship between the medium-temperature anaerobic fermentation time of raw materials per unit solid content and the theoretical total gas production;

[0168] 3. Establish the functional relationship between natural fermentation time and gas production at the ambient temperature of raw materials per unit solid content;

[0169] 4. Establish a functional relationship between the scale of breeding and the total solid content of manure;

[0170] 5. Determine the parameter conversion method for which no relevant data is available;

[0171] 6. Determine the methane content in biogas;

[0172] 7. The above calculation method and functional relationship are coupled to form a method for calculating biogas production.

[0173] Considering that the data of "Technical Specifications for Large and Medium-sized Biogas Projects" (GB / T51063-2014) is derived from the "Biogas Technical Manual", the fermentation temperature used is 35℃, and the fermentation period is 90 days for straw and 60 days for feces. After comparison, the following conclusions are drawn: 1) The fermentation temperature used in this specification is in the temperature range of medium-temperature anaerobic fermentation; 2) The fermentation period used in the data in this specification is long (the fermentation period of actual projects is generally about 20 days), and it can be considered that the raw materials have been fully fermented; 3) The range of TS gas production rate given in this specification is relatively narrow, and the error caused by value deviation is small.

[0174] In summary, in the gas production prediction model, the TS gas production rate of medium-temperature anaerobic fermentation of various raw materials is taken as the average of the TS yield value range given in the "Technical Specifications for Large and Medium-sized Biogas Projects" (GB / T51063-2014), as shown in the following table:

[0175] Table 3-1 Theoretical gas production rate m of medium-temperature anaerobic fermentation unit TS of various raw materials 3 / kg

[0176]

[0177] Functional relationship between warm anaerobic fermentation time and theoretical total gas production

[0178] For fermentation raw materials, the longer the fermentation time, the more gas is produced. However, the later the fermentation time, the lower the biogas production. In actual projects, considering the economic efficiency of the project, the scale and investment of the anaerobic tank will be comprehensively considered to select the appropriate fermentation days. While ensuring a certain biogas production, the scale of the fermentation tank is controlled to reduce the total investment of the project.

[0179] First, the biogas production rate is defined as follows:

[0180]

[0181] Where n is the biogas production rate, %

[0182] q1 is the actual biogas production, m3

[0183] q0 is the theoretical biogas production, m 3

[0184] The book "Technical Guide for Biogas in China's Livestock and Poultry Farms and Light Industry" and the book "Biogas Engineering Construction Manual" both give the relationship between the fermentation time of different raw materials and the gas production rate. The data given in the two books are the same, as shown in the table below.

[0185] Taking pig manure as an example, it takes 60 days of fermentation for pig manure to produce gas completely. However, after 20 days of fermentation, the biogas conversion rate can reach 86.3%. At this time, the scale of the fermentation tank only needs 1 / 3 of the complete fermentation. Although the fermentation is not complete at this time, 2 / 3 of the investment in the fermentation tank can be saved. From an economic point of view, fermentation for 20 days is better than fermentation for 60 days.

[0186] Table 3-2 Relationship between fermentation time and gas production rate of various raw materials

[0187]

[0188] After polynomial fitting based on the data given in the table, the fitting curves of fermentation time and biogas conversion rate of various raw materials are obtained and converted into corresponding functional relationships. Taking pig manure as an example, after polynomial fitting based on the data in the table, the fitting curves of pig manure fermentation time and conversion rate and the corresponding functional relationship are obtained, as shown in the figure. Figure 2 In the fitting formula, y represents the gas production rate and x represents the fermentation time.

[0189] After polynomial fitting of the above raw materials, the functional relationship between the fermentation time and gas production rate of various raw materials was obtained as shown in the following table.

[0190] Table 3-3 Optimal polynomial regression equations for fermentation time and gas production rate of various raw materials

[0191]

[0192] Use the formula in the above table to correct the gas production in the TS gas production calculation method. The correction formula is as follows:

[0193] q=WSY p ×y

[0194] Where:

[0195] q is the biogas production, m 3 / d

[0196] W is fermentation raw material, kg / d

[0197] S is the total solid content of fermentation raw materials (TS), %

[0198] Yp is the gas production rate of raw material TS, m 3 / kg

[0199] y is the correction factor for the number of days of residence in the fermentation tank, %, calculated through Table 3-3.

[0200] Functional relationship between natural fermentation time and gas production at ambient temperature

[0201] In actual projects, for livestock and poultry manure, it is necessary to fully consider the biogas released by the fermentation of raw materials at ambient temperature before entering the anaerobic tank for anaerobic fermentation, and deduct this part when calculating the biogas production. The fermentation time at ambient temperature includes the sum of the storage time of livestock and poultry manure in the farm and the time consumed in transportation.

[0202] Before entering the anaerobic fermentation tank, livestock and poultry manure is usually in a manure collection tank, a manure tank of a manure truck, and a manure pipe. The temperature conditions of these facilities and equipment are room temperature, the manure collection tank is a limited oxygen environment, and the manure tank of a manure truck and the manure pipe are basically anaerobic environments. Since no experimental data that is completely consistent with this condition has been obtained, the biogas released by livestock and poultry manure during storage and transportation is temporarily based on the gas production characteristics under room temperature (average 15°C) in the literature "Experiment on Methane Production and Capacity of Anaerobic Fermentation of Pig Manure at Different Temperatures", and will be revised after further research data is available. Compared with the actual situation, the temperature conditions of this experimental condition are consistent, but the oxygen conditions are slightly different. Oxygen conditions mainly affect the growth of methanogens. The main function of methanogens is to decompose raw materials and produce methane. They are sensitive to oxygen and need to reproduce in an anaerobic environment. They mainly exist in bottom sediments. During the storage and transportation of livestock and poultry manure, the only place that can be exposed to oxygen is at the liquid surface, which is an overall limited oxygen environment. However, methanogens have certain growth conditions at the bottom of the manure collection pool, the bottom of the manure tank of the manure transport truck, and in the pipeline.

[0203] In the literature "Experiment on Methane Production and Capacity of Anaerobic Fermentation of Pig Manure at Different Temperatures", Figure 3 As shown in the figure, the gas production characteristics of pig manure under four different temperature conditions were experimentally studied, including room temperature (average 15°C), 20°C, 35°C and 55°C, the TS concentration of the reactant was 6.6%, the total amount of the reactant was 25.5kg, Figure 3 The cumulative gas production for 41 days under each operating condition is given.

[0204] from Figure 3It can be seen that the cumulative gas production curve of anaerobic fermentation of pig manure at room temperature (average 15°C) is close to a straight line. The curve was fitted by univariate regression method, and the positive proportional function relationship between the anaerobic fermentation time of pig manure and the cumulative gas production under room temperature (average 15°C) was obtained. On this basis, the dry matter gas production rate under room temperature (average 15°C) was converted to 4.16×10 -3 m 3 / kg. In addition, the influence of the actual manure cleaning cycle is taken into account according to the average value (for example, if the manure cleaning cycle is 7 days, the manure on the first day is naturally fermented at room temperature for 7 days, and the manure on the 7th day is naturally fermented at room temperature for 0 days), and finally the calculation formula for biogas production under room temperature (average 15°C) is obtained as follows:

[0205]

[0206] Where:

[0207] q s The amount of biogas naturally emitted during storage and transportation before entering the fermentation tank corresponding to the total amount of manure, m 3

[0208] k is the gas production rate of dry matter under room temperature (average 15°C), m 3 / kg, take 4.16×10 -3

[0209] W is fermentation raw material, kg / d

[0210] S is the total solid content of fermentation raw materials (TS), %

[0211] d is the feces cleaning cycle,

[0212] At present, only relevant data on biogas production from anaerobic fermentation of pig manure at room temperature have been collected, and relevant data on biogas production from other types of livestock and poultry manure at room temperature have not been collected. Therefore, at present, the gas production from natural fermentation of other types of livestock and poultry manure before entering the anaerobic fermentation tank is temporarily converted according to pig equivalent, and will be refined after further data is available.

[0213] Functional relationship between farm size and total solids content of manure

[0214] During the project funding process, if the total amount of manure and TS content can be obtained, the biogas production can be directly calculated using the TS calculation method. However, in the actual funding process, only the accurate breeding scale can be obtained, and it is difficult to obtain the accurate total amount of manure and TS content. Therefore, a more accurate method is needed to calculate the biogas production based on the breeding scale.

[0215] Pig farm size and pig manure volume

[0216] The book "Technical Guide for Biogas in Livestock and Poultry Farms and Light Industry in China" gives a rough correspondence between the size of pig farms and the amount of pig manure, which is summarized in the following table.

[0217] Table 3-4 Pig farm scale and pig manure volume

[0218]

[0219] Amount of manure discharged from a single livestock or poultry

[0220] 1. The book "Biogas Engineering Construction Manual" gives the manure emissions of various livestock and poultry, which are sorted out as shown in the following table.

[0221] Table 3-5 Manure discharge of a single livestock and poultry

[0222]

[0223] 2. The book "Technical Guide for Biogas in Livestock and Poultry Farms and Light Industry in China" gives the manure emission characteristics of different types of pigs, which are organized as shown in the following table.

[0224] Table 3-6 Manure discharge characteristics of different types of pigs

[0225]

[0226]

[0227] 3. The National Pollution Source Census Livestock and Poultry Breeding Industry Source Production and Emission Coefficient Manual gives the amount of feces and urine of individual livestock and poultry in different regions, but fails to give the specific solid content, including nursery pigs, fattening pigs, sows, growing cattle, dairy cows, beef cattle, laying hens, broilers, etc. Here, fattening pigs are taken as an example, as shown in the following table:

[0228] Table 3-7 The amount of feces and urine of fattening pigs in different regions

[0229]

[0230] Method for calculating total solid content of manure from a single fattening pig

[0231] Since the accurate breeding scale can be obtained in the actual collection process, but the accurate total amount of manure and TS content are difficult to obtain, the research team intends to use the total solid amount of manure S0 of a single livestock and poultry and the breeding scale to estimate the total solid amount of manure in large-scale farms. This method can calculate the total solid amount in manure through the breeding scale M (that is, when both W and S in the TS calculation method are unknown) when the total amount of manure and TS content of livestock and poultry farms are unknown, and calculate the biogas production.

[0232] q=WSY p

[0233] q=MS0Y p

[0234] Where:

[0235] q is the biogas production, m 3 / d

[0236] W is fermentation raw material, kg / d

[0237] S is the total solid content of fermentation raw materials (TS), %

[0238] Y p is the gas production rate of raw material TS, m 3 / kg

[0239] M is the breeding scale, only

[0240] S0 is the total solid content of feces of a single livestock and poultry, kg / d·head

[0241] This method replaces the two unknowns W and S in the TS calculation method with one unknown S0, which can improve the calculation accuracy. The accuracy of the S0 value will directly determine the accuracy of the gas production rate calculation. Here, taking fattening pigs as an example, according to the summary of 3.5.1 and 3.5.2, the total solid content of manure of a single fattening pig is summarized in the following table:

[0242] Table 3-8 Total solids in manure from a single fattening pig

[0243]

[0244] Finishing Pig Data

[0245] It can be found from the above table that the total solid content of manure from a single fattening pig is between 0.36-0.42kg / d. Among them, the 0.36kg / d calculated according to the Manual of Biogas Engineering Construction only considers the solid content in feces, but not the solid content in urine, so the value is too small; the 0.42kg / d given in the Technical Guidelines for Biogas in China's Livestock and Poultry Farms and Light Industry takes into account the solid content in urine, but compared with the feces volume in the Manual of Source Production and Emission Coefficients of Livestock and Poultry Breeding in the National Pollution Source Census (1.41kg / d), the feces volume of a single fattening pig in the Guidelines is too large (1.75kg / d). The possible reason is that the Guidelines use the feces volume of fattening pigs at an age of 135 days. The growth cycle of a fattening pig given in the Construction of Large-Scale Pig Farms (GB / T 17824.1-2008) is 168-175 days. The weight of a fattening pig at 135 days old is heavier than the average weight of all fattening pigs in the pig farm (0-175 days), and the amount of feces produced is also larger than the average. Taking all the above factors into consideration, the research team intends to use 0.39kg / d as the total solid content of manure for a single fattening pig in the calculation.

[0246] Conversion method for livestock and poultry species

[0247] In the absence of detailed data, different types of livestock and poultry are converted to pig equivalents in accordance with the Pollutant Emission Standards for Livestock and Poultry Industry (GB18596-2001). The specific conversion method is as follows: 1 dairy cow is converted to 10 pigs, 1 beef cattle is converted to 5 pigs, 3 sheep are converted to 1 pig, 30 laying hens are converted to 1 pig, 60 broilers are converted to 1 pig, and 20 ducks and geese are converted to 1 pig.

[0248] Taking dairy cows as an example, according to the single manure emission in Table 3-5 and combined with the average TS gas production rate given in the "Technical Specifications for Biogas Engineering Part 1: Engineering Design", the results show that the gas production of one dairy cow's manure is equal to that of 10.15 pigs, which is basically consistent with the "Pollutant Emission Standards for Livestock and Poultry Breeding Industry" that one dairy cow is converted to 10 pigs. The specific analysis is shown in Table 3-9. Therefore, in the absence of detailed data, other livestock and poultry can be temporarily converted to pig equivalents according to the conversion method in the "Pollutant Emission Standards for Livestock and Poultry Breeding Industry".

[0249] Table 3-9 Comparison of gas production of a single pig and dairy cow

[0250]

[0251] Methane content in biogas

[0252] According to the above calculation method, only the biogas production can be obtained, but the methane content in the biogas cannot be known. The methane content in the biogas is very important for the subsequent calculation of biogas calorific value, biogas internal combustion engine installed capacity, and biogas production. In addition, when the VS calculation method and the COD calculation method are used for horizontal comparison and verification of biogas production, they also need to be converted according to the methane content in the biogas.

[0253] The document "Experiment on Methane Production and Capacity of Anaerobic Fermentation of Pig Manure at Different Temperatures" gives the changes in methane content in biogas under medium-temperature anaerobic fermentation conditions of pig manure during different fermentation time periods. The experimental results are summarized in the following table:

[0254] Table 3-10 Changes in methane content in medium-temperature anaerobic fermentation

[0255]

[0256] The researchers pointed out that since there was air during the start-up process of the experiment, the methane content data from the 9th day was valid data. Considering that the fermentation time in actual projects generally does not exceed 30 days, the average methane content from 9 to 27 days was taken as the methane content value of the mesophilic anaerobic fermentation of pig manure in this calculation method. After calculation, the methane content was 54.32%, which is close to the reference value of 55% for methane content in biogas given by some manufacturers.

[0257] Computational method coupling

[0258] According to the optimization of the above chapters, the final biogas production calculation formula is formed. When the total amount of manure and TS content are known, formula (1-1) is used, and when the breeding scale is known, formula (1-2) is used:

[0259]

[0260]

[0261] Where:

[0262] Q is the biogas production, m 3 / d

[0263] q is the theoretical biogas production corresponding to the total amount of manure, m 3 / d

[0264] q s The amount of biogas naturally emitted during storage and transportation before entering the fermentation tank corresponding to the total amount of manure, m 3

[0265] y is the correction factor for the number of days of residence in the fermentation tank, %, and different raw materials need to be calculated according to Table 3-11

[0266] W is fermentation raw material, kg / d

[0267] S is the total solid content of fermentation raw materials (TS), %

[0268] Y p is the gas production rate of raw material TS, m 3 / kg, refer to Table 3-12 for the value

[0269] k is the gas production rate of dry matter under room temperature (average 15°C), m 3 / kg, take 4.16×10 -3

[0270] M is the breeding scale, only

[0271] S0 is the total solid content of manure of a single livestock and poultry, kg / day·head, and 0.39 for fattening pigs;

[0272] d is the feces cleaning cycle,

[0273] Table 3-11 Optimal polynomial regression equations for fermentation time and gas production rate of various raw materials

[0274]

[0275]

[0276] Table 3-12 Gas production rate m of different biogas fermentation raw materials TS 3 / kg

[0277]

[0278] Finally, the calculation program for the biogas project plan stage was edited using the VB programming language, in which the biogas production calculation part adopted the biogas production calculation formula in this method. The interface is as follows: Figure 4 shown.

[0279] A local animal husbandry park plans to build a dairy farm with 30,000 dairy cows. The construction is divided into two phases. The first phase of the cowshed with 15,000 dairy cows was completed and put into use in June 2015, and the biogas project was put into operation in the same month. The project uses a medium-temperature anaerobic CSTR reactor with a single tank volume of 4200m 3 , 3 reaction tanks in total. The fermentation concentration is 5%, and the hydraulic retention time is 12.5 days. The operation data of the project in May 2017 is shown in the following table.

[0280] According to calculations, the average biogas production of the biogas project in the animal husbandry park in May 2017 was 16709m 3 / d. In large and medium-sized biogas projects, the biogas production fluctuates at the start of the project and in summer and winter. The project has been in operation for 2 years by May 2017, and the data in May can be used as the annual average.

[0281] Table 4-1 Operation data of Jialihe Shandong Leling Animal Husbandry Park in May 2017

[0282]

[0283] Using this calculation method and according to the project data, the results show that the biogas production is 16274m 3 / d, compared with the average daily gas production of 16709m3 of Jialihe Shandong Leling Animal Husbandry Park Biogas Project in May 2017 3 / d, the calculation result error is about 2.60%. The calculation results obtained by this calculation method are as follows Figure 5 shown.

[0284] Example 2

[0285] Taking the county-wide promotion project of livestock and poultry manure resource utilization (energy and fertilizer) in a certain county, the feasibility study report and preliminary design work have been completed. In the design process of the project, the design and selection of biogas pipelines, gas storage tanks, desulfurization and dehydration, flares and biogas internal combustion engines are all based on the biogas production calculated by this calculation method.

[0286] Example 3

[0287] like Figure 6 and Figure 7 As shown in the figure, a healthy breeding ecological park in Beijing produces 212 tons of chicken manure and 318 tons of sewage every day, and produces about 20,000 m3 of biogas per day. 3 .

[0288] Using the calculation method of the present invention, chicken manure is generally cleaned by dry manure cleaning process, and the manure is cleaned every day, considering that the manure stays outdoors for 1 day before fermentation.

[0289] According to the Manual of Biogas Engineering Construction, the solid content of chicken manure is 30%. The total raw material is 530 tons, and the solid content is 12%. Since the article does not provide the number of days for CSTR fermentation, the biogas production is calculated based on the more common fermentation days of 15 days and 18 days. The results are as follows Figure 6 and Figure 7 As shown (the settings of other parameters in the calculation program to the initial default values ​​do not affect the calculation of biogas production).

[0290] The above calculation results show that when the fermentation days are 15 days, the biogas production is 20042m3 / d; when the fermentation days are 18 days, the biogas production is 20433m3 / d. The calculation results under the two conditions are very close to the biogas production of 20000m3 / d given in the literature. The errors of the calculation results are 0.21% and 2.17% respectively.

[0291] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for optimizing the calculation of biogas production using livestock and poultry manure as raw materials; characterized in that: The steps include: Step 1: Calculate the biogas production by solid content calculation method or livestock volume calculation method according to the manure situation; the solid content calculation method is calculated by the following formula: Among them, Q is the biogas production, unit is m 3 / d; q is the theoretical biogas production corresponding to the total amount of manure, unit is m 3 / day;q s The amount of biogas naturally emitted during storage and transportation before entering the fermentation tank corresponding to the total amount of manure, unit: m 3 ; y is the correction factor for the number of days of residence in the fermentation tank; W is the fermentation raw material, in kg / day; S is the total solid content of the fermentation raw material; Y p is the gas production rate of raw solid matter, in m 3 / kg; k is the room temperature, that is, the dry matter gas production rate at an average temperature of 15°C, in m 3 / kg, take 4.16×10 -3 ; d is the manure cleaning cycle, in days; The calculation method of the correction factor y for the number of days of residence in the fermentation tank is as follows: When the raw material is pig manure, y=0.0003x 3 -0.0492x 2 +2.6643x+51.774; When the raw material is human feces, y = 0.0017x 3 -0.2210x 2 +9.3775x-32.358; When the raw material is horse manure, y = 0.0004x 3 -0.0565x 2 +3.0457x+38.587; When the raw material is cow dung, y = 0.0017x 3 -0.2119x 2 +8.9993x-35.606; Where x is the number of days; The calculation formula for breeding quantity is as follows: Among them, M is the breeding scale, the unit is head; S0 is the total solid content of manure of a single livestock and poultry, the unit is kg / d·head; Step 2: Calculate the output of organic fertilizer by using the water-soaked manure cleaning method or the dry manure cleaning method; The relationship between the output of organic fertilizer by the water-soaked manure cleaning method is as follows: IN c =In f ×σ1×θ+(WW f ); S y =W-Q×ρ-S S ; Among them, W f is the amount of manure separated by solid-liquid separation, in t / day, W is the total amount of manure, in t / day; σ1 is the rated solid matter concentration of the CSTR fermenter; σ2 is the TS concentration of manure; W c is the amount of manure entering the CSTR fermentation tank, in t / day; θ is the solid-liquid separation efficiency; S y is the biogas production, in t / day; ρ is the biogas density, in t / m 3 ; S S is the biogas residue production, in t / day; S b is the output of organic fertilizer, in t / day; σ3 is the solid content of biogas residue; σ4 is the solid content of organic fertilizer; The relationship between the output of organic fertilizer by dry manure removal is as follows: Among them, Q water is water consumption, in t / day; is the biogas slurry return ratio; S y is the biogas slurry production, in t / day; S S is the biogas residue production, in t / day; W is the total amount of manure, in t / day; Step 3, calculating the biogas purification amount or biogas power generation; The calculation formula of the biogas purification amount is as follows: Among them, Q S is the biogas production, in m 3 / day; α is the methane content of biogas; β is the biogas content of biogas; ε is the proportion of the fermentation tank insulation heat load to the biogas heat load; The calculation formula of biogas power generation is as follows: IN S =Q×q1÷24÷3600; Y=W S ÷δ; W1=Y×τ; Among them, W S is the biogas heat load, in MW; q1 is the biogas calorific value, in MJ / m 3 ; Y is the installed capacity of the biogas internal combustion engine, in MW; δ is the thermal efficiency of the biogas internal combustion engine; W1 is the annual power generation, in MWh; τ is the annual operating hours, in hours; Step 4: Output the calculation results through a computer.

2. The method for optimizing the calculation of biogas production using livestock and poultry manure as raw materials according to claim 1 is characterized in that: When the livestock and poultry are fattening pigs, the total solid content of the manure of a single livestock and poultry is S0=0.

39.

3. The method for optimizing the calculation of biogas production using livestock and poultry manure as raw materials according to claim 1 is characterized in that: The raw material gas production rate Y p The values ​​of are as follows: When the raw material is pig manure, Y p =0.325; When the raw material is chicken manure, Y p =0.36; When the raw material is dairy cow dung, Y p =0.22.

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