An optimization method for power generation from biogas of urban household garbage and crop straw

Abstract

The present invention discloses an optimization method for power generation of biogas from urban household garbage and crop straw, which allocates the anaerobic digestion capacity of single or mixed raw materials according to a multi-objective dynamic programming model; the raw materials include urban household garbage and crop straw; the multi-objective dynamic programming model #imgabs0#R is income, C is cost, G2 is carbon emission of biogas power generation, and G1 is carbon emission of garbage treatment. The present invention obtains the project optimization result strategy by setting economic maximization and carbon emission minimization; uses the multi-objective dynamic programming model to execute the best raw material procurement and production configuration plan, dynamically manages the biogas power generation project process, and achieves a balance between the economic and ecological benefits of the project. It significantly reduces carbon emissions and provides good economic benefits, so as to standardize the treatment of urban household waste and crop straw and recover biomass energy.

Description

Technical Field

[0001] The invention belongs to the technical field of biogas power generation, and in particular relates to an optimization method for power generation using biogas from urban household garbage and crop straw. Background Art

[0002] With the shortage of fossil fuels and environmental degradation, more and more attention has been paid to the development of renewable, clean and alternative energy sources; compared with other renewable energy sources, biomass energy has the advantages of wide distribution and easy availability.

[0003] More than 4 billion tons of solid waste are generated worldwide each year, half of which is municipal solid waste composed of organic matter. In addition, the theoretical energy potential of major crop residues worldwide is about 65 EJ per year, accounting for 15% of global primary energy. Therefore, recycling these wastes is crucial to alleviating global energy and environmental pressures.

[0004] In the 1960s, Golueke et al. first conducted research on obtaining biogas from municipal solid waste using anaerobic digestion. Since then, various anaerobic digestion processes have been developed to treat different types of organic waste. Biogas power generation can effectively reduce emissions caused by straw burning or landfills and avoid erosion of soil and groundwater by landfills. The use of anaerobic digestion technology to treat urban household garbage and straw has received increasing research attention.

[0005] Since crop straw has a high carbon-nitrogen ratio (C / N), it requires a long anaerobic digestion time and has a low cellulose conversion rate; therefore, digesting straw alone has obvious defects. Urban household food waste has a relatively low C / N ratio, unstable organic components, and a low rate of anaerobic gas generation. Therefore, it is feasible to co-digest urban household food waste and straw in a single digester because this can adjust the C / N ratio, increase methane production, and improve biomass energy utilization. However, biogasification power generation still has the following problems: (1) Low energy conversion efficiency: This is mainly due to factors such as the low energy density and mass density of biomass raw materials and losses during the conversion process; unstable raw material supply. Biomass raw materials include crop straw, wood waste, etc., and their supply is affected by factors such as season and climate, which may lead to insufficient or unstable supply; (2) Unfriendly to the environment: The waste and emissions generated during biomass power generation may have a certain impact on the environment. For example, when biomass is burned, atmospheric pollutants such as carbon dioxide, nitrogen oxides, and particulate matter are generated. During the anaerobic digestion process, foul-smelling and harmful gases such as hydrogen sulfide are produced, which have certain impacts on the environment and human health. (3) Slow growth rate: The growth rate of anaerobic microorganisms is relatively slow, requiring a longer cultivation process; the treatment efficiency is low. Conventional anaerobic digestion methods have relatively low treatment efficiency and require longer treatment time and larger equipment volume. Summary of the invention

[0006] The purpose of the present invention is to provide an optimization method for power generation from urban household garbage and crop straw biogas, which adopts two anaerobic digestion methods: a continuous feeding method to treat urban household garbage as a single raw material input and a semi-continuous feeding method to treat urban household kitchen waste and straw as a mixed raw material input, so as to reduce carbon emissions and avoid sudden landfill and groundwater erosion.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] An optimization method for power generation from biogas of urban household garbage and crop straw, allocating anaerobic digestion capacity of single or mixed raw materials according to a multi-objective dynamic programming model; the raw materials include urban household garbage and crop straw;

[0009] The multi-objective dynamic programming model R is income, C is cost, G2 is carbon emission from biogas power generation, and G1 is carbon emission from waste treatment.

[0010] Furthermore, the biogas production V T It can be determined by the anaerobic digestion gas production (γ1, γ2);

[0011]

[0012] Where V_T is the biogas production, V T is the biogas production, DOC refers to the content of degradable organic carbon in urban household garbage, γ1 is the biogas output produced by anaerobic digestion of unit raw materials; γ2 is the gas volume produced by anaerobic digestion of unit mixed raw materials; b% is the proportion of digestate converted into fertilizer; is the decision variable, which is the amount of urban household garbage recycled by the biogas power station every day; θ is the heat capture rate in the biogas power generation process; η1 and η2 are the efficiencies of biogas power generation and thermal power generation; φ is the ratio of digestion products produced by anaerobic digestion to unit raw materials; p1 and p2 are the maximum daily processing capacity of a single anaerobic digester and the maximum daily processing capacity of a mixed anaerobic digester.

[0013] Furthermore, the cost C includes raw material cost, shared construction cost and maintenance cost;

[0014] Raw material cost

[0015] In the formula, C1 is the raw material cost, x i,tis the amount of straw from area i during the feeding period t; ω is the ratio of urban household garbage and crop straw in the mixed anaerobic digestion feedstock; y i is the distance from region i to the biogas power station; c1 is the unit transportation cost of crop straw per kilometer; c2 is the collection cost of crop straw per unit; c i is the monthly cost of straw transport vehicles in each region; is the decision variable, the amount of urban household garbage collected by the biogas power plant every day; y0 is the distance from the city to the biogas power plant; c0 is the transportation cost per kilometer of each unit of urban household garbage; x t is the decision variable, i.e. the amount of straw used in the tth feeding in the mixed anaerobic digestion; c j is the monthly salary of the transportation personnel; T / t0 is the working time divided by the interval between each mixing anaerobic digestion feeding;

[0016] Sharing construction costs

[0017] In the formula, C2 is the amortized construction cost, N is the number of periods in the entire life cycle, P is the total income, and r is the interest rate;

[0018] The maintenance cost

[0019] In the formula, is the decision variable, the amount of urban household garbage recycled by the biogas power plant every day; ω is the ratio of urban household garbage and crop straw in the mixed anaerobic digestion raw materials; x t V is the decision variable, which is the amount of straw used in the tth feeding in the mixed anaerobic digestion; T is the biogas production, qc is the cost of treating a unit of waste using anaerobic digestion, dc is the cost of producing a unit of electricity; η l is the conversion rate of biomass electricity.

[0020] Furthermore, the carbon emissions from waste treatment x t is the decision variable, which is the amount of straw used in the tth feeding in the mixed anaerobic digestion; ε1, ε2, ε3 are the proportions of wheat, corn and rice straw in the straw set; α1, α2, α3 are the mass of CO2 produced by burning unit mass of wheat, corn and rice straw, respectively; λ2 is the conversion factor of gas mass units from CH4 to CO2; π1 and π2 are the contents of CH4 and CO2, respectively; δ2 is the utilization conversion coefficient.

[0021] Furthermore, the carbon emissions from biogas power generation G2 = V T ×{π1λ1+π2λ2}, π1 and π2 are the contents of CH4 and CO2 respectively; V Tis the biogas production; λ1 is the conversion factor of CO2 into CO2 gas mass units; λ2 is the conversion factor of CH4 into CO2 gas mass units.

[0022] The present invention has the following beneficial effects:

[0023] (1) A multi-objective dynamic programming model was used to compare the biomass energy utilization methods, demonstrating the benefits of single-feedstock anaerobic digestion in generating economic benefits and mixed-feedstock anaerobic digestion in reducing carbon emissions.

[0024] (2) The method is highly efficient in waste treatment, reducing carbon emissions by 30%.

[0025] (3) Highlights the challenges and opportunities in biomass power generation and emphasizes the importance of providing optimal raw material procurement and production allocation solutions for sustainable project operations.

[0026] (4) Through model transformation and solution, the solution process of multi-objective optimization problems is simplified, and the balance between economic and environmental benefits is effectively achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the processing process of the present invention. DETAILED DESCRIPTION

[0028] like Figure 1 As shown, this embodiment provides an optimization method for power generation from urban household garbage and crop straw biogas, including allocating anaerobic digestion capacity of single or mixed raw materials according to a multi-objective dynamic programming model; the raw materials include urban household garbage and crop straw.

[0029] The anaerobic digestion capacity of single / mixed feedstocks will affect carbon emissions and revenues, as anaerobic digestion technology has clean production characteristics and economic benefits can be achieved through the biomass energy it recovers; while production adjustments will affect revenues and costs.

[0030] In order to ensure the sustainable development of the project, the multi-objective dynamic programming model should take into account both economic and ecological benefits and determine the balance between them. In addition, the instability of production caused by factors such as the seasonal impact of raw material straw inventory should also be considered, which needs to be simulated using dynamic programming.

[0031] Since different time nodes correspond to different situations, various conditions should be taken into account dynamically. First, the production time of crop straw is inconsistent. Different types of crop straw can be used for anaerobic digestion in a year, causing carbon emissions and income to change at the same time; therefore, the balance between economic and ecological benefits should be re-determined through updated decisions, and managers should adjust project decisions to ensure stable operation to cope with complex and changing realities. Therefore, it is necessary to conduct time series analysis based on several different raw material supply scenarios to more accurately determine the carbon emissions and income associated with project execution, thereby providing scientific guidance for managers to determine raw material procurement and production allocation plans.

[0032] The main purpose of this embodiment is to utilize biogas generated from urban domestic waste and crop straw to achieve cogeneration of heat and power, so as to save energy, reduce emissions, and generate income and profits.

[0033] The multi-objective dynamic programming model is: R is income, C is cost, G2 is carbon emission from biogas power generation, and G1 is carbon emission from garbage disposal. The multi-objective dynamic programming model described in this embodiment aims to maximize economic benefits and minimize carbon emissions.

[0034] Biogas production V T It can be determined by the anaerobic digestion gas production (γ1, γ2).

[0035]

[0036] Where V T is the biogas production, V T is the biogas production, DOC refers to the content of degradable organic carbon in urban household garbage, γ1 is the biogas output produced by anaerobic digestion of unit raw materials; γ2 is the gas volume produced by anaerobic digestion of unit mixed raw materials; b% is the proportion of digestate converted into fertilizer; is the decision variable, which is the amount of urban household garbage recycled by the biogas power station every day; θ is the heat capture rate in the biogas power generation process; η1 and η2 are the efficiencies of biogas power generation and thermal power generation; φ is the ratio of digestion products produced by anaerobic digestion to unit raw materials; p1 and p2 are the maximum daily processing capacity of a single anaerobic digester and the maximum daily processing capacity of a mixed anaerobic digester.

[0037] The cost C includes raw material cost, shared construction cost and maintenance cost.

[0038] Raw material costs include transportation costs, related transportation personnel salary costs, and the purchase cost of crop straw owned by farmers themselves.

[0039]

[0040] In the formula, C1 is the raw material cost, x i,t is the amount of straw from area i during the feeding period t; ω is the ratio of urban household garbage and crop straw in the mixed anaerobic digestion feedstock; y i is the distance from region i to the biogas power station; c1 is the unit transportation cost of crop straw per kilometer; c2 is the collection cost of crop straw per unit; c i is the monthly cost of straw transport vehicles in each region; is the decision variable, the amount of urban household garbage collected by the biogas power plant every day; y0 is the distance from the city to the biogas power plant; c0 is the transportation cost per kilometer of each unit of urban household garbage; x t is the decision variable, i.e. the amount of straw used in the tth feeding in the mixed anaerobic digestion; c j Monthly salary for transportation personnel.

[0041] The amortized construction cost refers to the total investment cost during the entire life cycle being amortized into the cost of each month.

[0042]

[0043] Where C2 is the amortized construction cost, N is the number of periods in the entire life cycle, P is the total income, and r is the interest rate.

[0044] The maintenance cost refers to the cost required to maintain the equipment during its life cycle.

[0045]

[0046] In the formula, is the decision variable, the amount of urban household garbage recycled by the biogas power plant every day; ω is the ratio of urban household garbage and crop straw in the mixed anaerobic digestion raw materials; x t is the decision variable, i.e. the amount of straw used in the tth feeding in the mixed anaerobic digestion; V T is the biogas production, qc is the cost of treating a unit of waste using anaerobic digestion, dc is the cost of producing a unit of electricity; η l is the conversion rate of biomass electricity.

[0047] Economic goals

[0048] To determine the environmental benefits of the biogas power generation project, the greenhouse gas emissions from biogas power generation, landfill and incineration were compared. In order to compare the emissions fairly, conversion factors were used to convert other greenhouse gases to carbon dioxide emissions.

[0049] The main gas emitted by burning crop straw is CO2. Since rice, wheat and corn are the three major high-yield cereal crops in the world, this embodiment uses rice, wheat and corn straw as raw materials; crop straw yield (W s ) is based on the economic yield of the crop (W p ) and crop yield to straw ratio (S G ) to determine, W s =W p ×S G .

[0050] CO2 emissions from straw burning: ε1, ε2, ε3 are the proportions of wheat, corn and rice straw in the straw set, α1, α2, α3 are; x t is the decision variable, which is the amount of straw used in the tth feeding in the mixed anaerobic digestion.

[0051] The biogas emitted from the landfill station contains about 55% CH4 and 45% CO2. The CH4 and CO2 contents in the landfill gas are π1 (55%) and π2 (45%) respectively. The total amount of CH4 generated by the landfill is is the emission of CH4; MSW is the municipal solid waste during the period T, η is the landfill rate, DOC is the degradable organic carbon content in the waste 15%; R is the decomposition rate of degradable organic carbon in the waste 17%;

[0052] The amount of CO2 released from landfills is δ2 is the conversion coefficient,

[0053] Total CH4 and CO2 emissions from landfills: λ2 is the conversion factor of gas mass units from CH4 to CO2.

[0054] Biogas power generation emissions: G2 = V T ×{π1λ1+π2λ2}, π1 and π2 are the contents of CH4 and CO2 respectively; V T is the biogas production; λ1 is the conversion factor of CO2 into CO2 gas mass units; λ2 is the conversion factor of CH4 into CO2 gas mass units.

[0055] but

[0056] The above description is only a preferred implementation manner of the present invention, but the protection scope of the present invention is not limited thereto, and any modification and replacement based on the technical solution and inventive concept provided by the present invention should be included in the protection scope of the present invention.

Claims

1. An optimization method for power generation from urban household garbage and crop straw biogas, characterized in that: Allocating anaerobic digestion capacity of single or mixed feedstocks according to a multi-objective dynamic programming model; the feedstocks include urban household waste and crop straw; The multi-objective dynamic programming model R is revenue, C is cost, G2 is carbon emission from biogas power generation, and G1 is carbon emission from waste treatment; Biogas production V T Determined by anaerobic digestion gas production (γ1, γ2); In the formula, DOC refers to the content of degradable organic carbon in urban household garbage, γ1 is the biogas output produced by anaerobic digestion of unit raw materials; γ2 is the gas volume produced by anaerobic digestion of unit mixed raw materials; b% is the proportion of digestate converted into fertilizer; is the decision variable, the amount of urban household garbage recycled by the biogas power plant every day; θ is the heat capture rate in the biogas power generation process; η1 and η2 are the efficiencies of biogas power generation and thermal power generation; φ is the ratio of digestion products produced by anaerobic digestion to unit raw materials; p1 and p2 are the maximum daily processing capacity of a single anaerobic digester and the maximum daily processing capacity of a mixed anaerobic digester; The cost C includes raw material cost, shared construction cost and maintenance cost; Raw material cost In the formula, C1 is the raw material cost, x i,t is the amount of straw from area i during the feeding period t; ω is the ratio of urban household garbage and crop straw in the mixed anaerobic digestion feedstock; y i is the distance from region i to the biogas power station; c1 is the unit transportation cost of crop straw per kilometer; c2 The collection cost of each unit of crop straw; c i is the monthly cost of straw transportation tools in each region; y0 is the distance from the city to the biogas power plant; c0 is the transportation cost per kilometer of each unit of urban household waste; x t is the decision variable, i.e. the amount of straw used in the tth feeding in the mixed anaerobic digestion; c j is the monthly salary of the transportation personnel; T / t0 is the working time divided by the interval between each mixing anaerobic digestion feeding; Sharing construction costs In the formula, C2 is the amortized construction cost, N is the number of periods in the entire life cycle, P is the total income, and r is the interest rate; The maintenance cost Where qc is the cost of treating a unit of waste using anaerobic digestion, and dc is the cost of producing a unit of electricity; η l The conversion rate of biomass electricity generation; Carbon emissions from waste management ε1, ε2, ε3 are the proportions of wheat, corn and rice straw in the straw set; α1, α2, α3 are the CO2 masses produced by burning a unit mass of wheat, corn and rice straw; λ2 is the conversion factor of the gas mass unit from CH4 to CO2; π1 and π2 are the CH4 and CO2 contents, respectively; δ2 is the utilization conversion coefficient; Carbon emissions from biogas power generation G2 = V T ×{π1λ1+π2λ2}, λ1 is the conversion factor of CO2 into CO2 gas mass unit.

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