Pulp and paper integrated energy system planning method in carbon trading and equipment modification scenarios

Abstract

The pulp and papermaking integrated energy system planning method in the carbon trading and equipment modification scene includes establishing a modification equipment model applicable to the pulp and papermaking integrated energy system; selecting the optimal comprehensive energy consumption cost of the pulp and papermaking integrated energy system as the planning target, considering the energy balance and equipment operation constraint conditions, establishing a planning model of the optimal comprehensive energy consumption cost of the pulp and papermaking integrated energy system under the carbon quota mechanism; designing different scenarios from the different factors of the carbon trading and equipment modification scheme combination, determining the known quantities and the to-be-solved quantities in each scenario, solving the optimal planning model to obtain the planning scheme; and analyzing and comparing the parameters such as the equipment planning capacity and the system comprehensive energy consumption cost in different carbon trading and equipment modification scenes. The method can further calculate the comprehensive energy consumption cost of the pulp and papermaking industry by using the pulp and papermaking integrated energy system planning model, and provide theoretical support for the planning and scheduling scheme of the pulp and papermaking industry.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy system planning methods, and specifically to a pulp and paper integrated energy system planning method under the scenarios of carbon trading and equipment modification. BACKGROUND

[0002] As an energy-intensive industry, the pulp and paper industry has the characteristics of high energy consumption and high carbon emission. Carbon emission reduction and energy storage and conversion technology give the pulp and paper industry a certain degree of environmental sustainability. However, in the planning of the pulp and paper industry integrated energy system, due to the problem of oversimplified energy flow and equipment model, there is a gap in the planning method of the pulp and paper industry integrated energy system that comprehensively considers carbon emission reduction and energy storage and conversion technology.

[0003] In addition, under the background of building an energy green low-carbon transformation promotion mechanism led by the energy consumption "double control" and non-fossil energy target system, the carbon quota allocation and trading mechanism is of great significance to reducing the carbon emissions of the pulp and paper industry integrated energy system. The carbon quota mechanism includes a mandatory compliance mechanism and a carbon emission reduction credit mechanism. The carbon quota mechanism is used by the emission control enterprise to offset a certain proportion of carbon quota payment to improve the ecological efficiency of the enterprise while bringing economic benefits to the enterprise. However, the current carbon quota mechanism project focuses on mechanism optimization and market supply and demand structure, etc. There is a gap in the carbon quota allocation and trading mechanism model suitable for the planning of the pulp and paper industry integrated energy system.

[0004] In addition, the traditional planning method of the pulp and paper industry integrated energy system generally considers energy balance, equipment operation and other constraints, analyzes the planning capacity of the pulp and paper industry integrated energy system equipment and the economic efficiency of the system, and ignores the comprehensive influence of the combination of equipment modification schemes and the additionality of the carbon quota mechanism on system planning. SUMMARY

[0005] To solve the above technical problems, the application provides a pulp and paper integrated energy system planning method under the scenarios of carbon trading and equipment modification, which can guide the formulation of the planning scheme of the pulp and paper industry integrated energy system.

[0006] To achieve the above purpose, the technical scheme adopted by the application is:

[0007] The pulp and paper integrated energy system planning method under the scenarios of carbon trading and equipment modification, characterized in that it comprises the following steps:

[0008] S1, establishing a modified equipment model applicable to the pulp and paper industry integrated energy system, including carbon capture equipment, steam accumulator, booster pump and electric boiler;

[0009] S2, taking the comprehensive energy cost optimization of the pulp and paper industry comprehensive energy system as a planning target, considering energy balance, equipment operation constraints, and establishing a carbon quota mechanism for the pulp and paper industry comprehensive energy system, a comprehensive energy cost optimization planning model of the pulp and paper industry comprehensive energy system is established;

[0010] S3, different scenarios are designed from the perspective of carbon trading and equipment modification scheme combination, known quantities and unknown quantities in each scenario are determined, and the optimal planning model is solved to obtain a planning scheme;

[0011] S4, the equipment planning capacity, system comprehensive energy cost, system external energy cost, system carbon trading cost, system operation cost, system carbon capture cost and system equipment investment cost in different carbon trading and equipment modification scenarios are analyzed and compared.

[0012] As a further improvement of the application, the modification equipment model applicable to the pulp and paper industry comprehensive energy system in step S1 is as follows, wherein the carbon capture equipment model is:

[0013]

[0014] In the formula: Wt is the electric power consumed by the carbon capture equipment in the tth hour, and the unit is MW / yr; W C emi is the energy consumption required by the carbon capture equipment to capture one ton of carbon dioxide, and the unit is MWh / t; c t / tce is the carbon dioxide generated by burning one ton of standard coal, and the unit is t / tce; Wt is the coal consumption of the coal-fired combined heat and power unit, the alkali recovery combined heat and power unit and the lime kiln in the tth hour, and the unit is t / h; Wt is the carbon capture coefficient of the coal-fired combined heat and power unit, the alkali recovery combined heat and power unit and the lime kiln in the tth hour; Cap is the maximum value of the carbon capture coefficient of the coal-fired combined heat and power unit, the alkali recovery combined heat and power unit and the lime kiln; CC Wt is the carbon capture equipment planning capacity, and the unit is MW; Wt is the maximum capacity of the carbon capture equipment planning, and the unit is MW;

[0015] The steam accumulator model is as follows:

[0016]

[0017] 0≤m cha,t ≤f cha,t m cha,max

[0018] 0≤m dis,t ≤f dis,t m dis,max

[0019]

[0020] f cha,t ,f dis,t ∈{0,1}

[0021] f cha,t p valve ≤p cha,t

[0022] Where: Cap SA Plan the capacity of the steam accumulator in MW; Plan the maximum capacity of the steam accumulator in MW; m cha,t m dis,t is the mass flow rate of steam charging and discharging in the steam accumulator at hour t, in t / h; f cha,t is the state characterizing quantity of the steam accumulator charging at hour t, with a value of 1 when charging and 0 when not charging; f dis,t is the state characterizing quantity of steam accumulator steam release at hour t, with a value of 1 when steam is released and a value of 0 when steam is not released; is the heat storage of the steam accumulator at the end of hour t, in MWh; cha,t is the steam accumulator charging enthalpy value at hour t, in MJ / t; h LP is the steam accumulator enthalpy value, in MJ / t; Δt is the number of hours in the planning period; p valve is the pressure threshold of the steam accumulator charging valve, in MPa; p cha,t is the charging pressure of the steam accumulator at hour t, in MPa;

[0023] The booster pump model is:

[0024] p cha,min ≤p cha,t ≤p cha,max

[0025] h cha,t =c1p cha,t T cha +c2T cha +c3p cha,t +c4

[0026]

[0027] Where: p cha,min p cha,max The minimum and maximum pressures of the booster pump charging the steam accumulator, in MPa; T cha is the charging temperature of the steam accumulator by the booster pump, in K; c1c2c3c4 are the quasi-linear fitting coefficients of the steam enthalpy; The electric power consumed by the booster pump in hour t, in MW; Cap is the planned capacity of the booster pump, in MW; Capmax is the maximum planned capacity of the booster pump, in MW;

[0028] The electric boiler model is:

[0029]

[0030]

[0031]

[0032] Cap is the planned capacity of the electric boiler, in MW; EB Capmax is the maximum planned capacity of the electric boiler, in MW; P is the electric power consumed by the electric boiler in the tth hour, in MW; Q is the heat power generated by the electric boiler in the tth hour, in MW; Qmax is the maximum heat power generated by the electric boiler, in MW; M is the mass flow rate of steam emitted by the electric boiler in the tth hour, in t / h; Mmax is the maximum mass flow rate of steam emitted by the electric boiler, in t / h; Γ represents the ratio of the maximum uphill and downhill climbing rates of the electric boiler to the maximum planned capacity; η EB η is the electric-thermal conversion efficiency of the electric boiler.

[0033] As a further improvement of the present application, the comprehensive energy consumption cost of the integrated energy system of the pulp and paper industry in step S2 includes: system purchased energy cost, system carbon trading cost, system operation cost, system carbon capture cost, and system equipment investment cost. The model of the system purchased energy cost is:

[0034]

[0035] E is the purchased energy cost, in $; r sp r e,t r ge,t P is the electricity price and green electricity price in the tth hour, in $ / MWh; P e,t P ge,t P is the electricity price and green electricity purchase quantity in the tth hour, in MWh; r coal r loss r M is the abandoned steam quality, in t;

[0036] The carbon trading mechanism model is:

[0037] ​

[0038]

[0039]

[0040]

[0041] wherein: ε grid,carb is the carbon emission factor of electricity; CA t is the carbon emission of the pulp and paper industry integrated energy system in the tth hour, in t; FCA t is the carbon quota allocated to the pulp and paper industry integrated energy system in the tth hour, in t; is the electricity output of the coal-fired cogeneration unit and the alkali recovery cogeneration unit in the tth hour, in MW; b e,coal is the electricity supply reference of the coal-fired unit; f r,coal is the heat supply correction coefficient of the coal-fired unit; f l,coal is the cooling mode correction coefficient of the coal-fired unit, set to 1; f f,coal is the load output correction coefficient of the coal-fired unit, set to 1; is the heat output of the coal-fired cogeneration unit and the alkali recovery cogeneration unit in the tth hour, in MW; is the black liquor mass flow consumed by the alkali recovery cogeneration unit in the tth hour, in t / h; LHV BL is the low heat value of black liquor, in MJ / t; b h，,coal is the heat supply reference of the coal-fired unit; is the carbon trading cost, in $, which is a cost when the parameter is greater than 0 and a benefit when the parameter is less than 0; c carb,eua c carb,cer is the carbon quota price and the certified voluntary emission reduction price, in $ / t; EUA is the carbon quota trading volume, in t; CER is the certified voluntary emission reduction, in t; λ is the reduction rate of the carbon quota reference value; μ CER is the maximum offset ratio of the certified voluntary emission reduction;

[0042] The system operation cost model is:

[0043]

[0044] wherein: is the unit operation cost of the coal-fired cogeneration unit, the alkali recovery cogeneration unit, the booster pump, the carbon capture device, and the electric boiler in the tth hour, in $ / MW; is the unit operation cost of the steam accumulator in the tth hour, in $ / MWh; is the unit operation cost of the medium-pressure and low-pressure steam busbar waste heat recovery device in the tth hour, in $ / MW; Ctis the unit operation cost of lime kiln in the tth hour, unit is $ / MW; Ctis the medium and low pressure steam mass flow recovered in the tth hour, unit is t / h;h HP h MP Ctis the medium and low pressure steam enthalpy in the tth hour, unit is MJ / t; Ctis the heat generated by lime kiln in the tth hour, unit is MW;

[0045] The system carbon capture cost model is:

[0046]

[0047] E is the carbon capture cost, unit is $; r cc r is the carbon capture unit price, unit is $ / t; CC r is the carbon capture unit price, unit is $ / t;

[0048] The system equipment investment cost model is:

[0049]

[0050]

[0051] E is the system equipment investment cost, unit is $; inv E is the system equipment investment cost, unit is $; E is the carbon capture equipment, electric boiler, steam accumulator, booster pump investment cost, unit is $; h is the annual return on investment of equipment; τ CC τ EB τ SA τ PU τ is the service life of carbon capture equipment, electric boiler, steam accumulator, booster pump, unit is year; I CC I EB I PU I is the carbon capture equipment, electric boiler, booster pump unit investment cost, unit is $ / MW; I SA I is the steam accumulator unit investment cost, unit is $ / MWh;

[0052] The system planning objective function is:

[0053]

[0054] Obj is the system comprehensive cost, unit is $.

[0055] As a further improvement of the present application, in step S2, the pulp and paper industry comprehensive energy system planning is subject to relevant conditions, including energy balance, equipment operation constraints:

[0056] 1) energy balance constraint;

[0057] Energy balance constraints include electrical energy balance constraints, thermal energy balance constraints, and process energy supply constraints:

[0058] P t CHP +P t e +P t ge +P t AR =P t CC +P t EB +P t PU +P t eload

[0059]

[0060] Where: is the electrical load of the process in the tth hour, in MW; H2M χ M2L are the medium-pressure and low-pressure steam bus recovery factors, respectively; are the medium-pressure and low-pressure steam load mass flows, in t / h; δ en , n = 1, 2…, 8 is the electricity demand per unit product of each dispatchable process in hour t; δ hn , n = 1, 2…, 8 is the heat energy demand per unit product of each schedulable process in hour t; are the power load and thermal load demands of other processes except the dispatchable processes in hour t, in MW;

[0061] 2) Equipment operation constraints;

[0062] Equipment operation constraints include coal-fired cogeneration units, alkali recovery cogeneration units, and lime kiln operation constraints:

[0063] Coal-fired cogeneration unit operating constraints:

[0064]

[0065]

[0066]

[0067] Where: and It is the upper and lower limits of the electrical output of the coal-fired cogeneration unit, in MW; and is the upper and lower limits of thermal output of coal-fired cogeneration units, in MW; k CHP,min and kCHP,max η is the electric-thermal conversion coefficient of the coal-fired cogeneration unit corresponding to the minimum and maximum electric output; C m is the slope of the cogeneration supply curve; is the mass flow of high-pressure, medium-pressure, and low-pressure steam supplied by the coal-fired cogeneration unit in the tth hour, in t / h; is the maximum downhill and uphill climbing rate of the coal-fired cogeneration unit, in MW; ζ CHP is the electric-thermal output correction coefficient of the coal-fired cogeneration unit; η CHP is the thermal efficiency of the coal-fired cogeneration unit; LHV coal is the low calorific value of coal, in MJ / t;

[0068] Operation constraints of the alkali recovery cogeneration unit:

[0069]

[0070]

[0071]

[0072]

[0073]

[0074] In the formula: and are the upper and lower limits of the electric output of the alkali recovery cogeneration unit, in MW; and are the upper and lower limits of the thermal output of the alkali recovery cogeneration unit, in MW; k AR,min and k AR,max are the electric-thermal conversion coefficients of the alkali recovery cogeneration unit corresponding to the minimum and maximum electric output; is the mass flow of high-pressure steam supplied by the alkali recovery cogeneration unit in the tth hour, in t / h; is the maximum downhill and uphill climbing rate of the alkali recovery cogeneration unit, in MW; ζ AR is the electric-thermal output correction coefficient of the alkali recovery cogeneration unit; η AR is the thermal efficiency of the alkali recovery cogeneration unit;

[0075] Operation constraints of the lime kiln:

[0076]

[0077]

[0078] In the formula: m m,t is the amount of lime mud consumed by the lime kiln in the tth hour, in t; M mis the total amount of lime mud consumed by the lime kiln per day, in t; η LK is the efficiency of the lime kiln; ΔH m is the enthalpy change of the lime mud to limestone conversion process, in MW / t; is the mass flow of medium-pressure steam generated by the lime kiln in the tth hour, in t / h; is the coal consumption of the lime kiln in the tth hour, in t / h; is the thermal output of the lime kiln in the tth hour, in MW.

[0079] As a further improvement of the present application, in step S3, the method of designing differentiated scenarios from the perspective of different factors of carbon trading and equipment modification scheme combination includes:

[0080] S31, the carbon capture equipment, steam accumulator, booster pump, and electric boiler model are set as four equipment modification scheme combinations;

[0081] S32, based on the carbon quota allocation and trading mechanism in the same period, a cost optimization model of the pulp and paper industry comprehensive energy storage system is solved; the four equipment modification scheme combinations in S31 are sequentially added, and a cost optimization model of the pulp and paper industry comprehensive energy system considering equipment modification scheme combination is solved;

[0082] S33, according to the carbon quota allocation and trading mechanism, four carbon trading periods are divided and set;

[0083] S34, the cost optimization model of the pulp and paper industry comprehensive energy system after equipment modification is selected, the parameters of the carbon quota allocation and trading mechanism in different periods are substituted, the carbon trading related information of the objective function of the optimization model in S32 is corrected, and the cost optimization models of the pulp and paper industry comprehensive energy system considering carbon trading are respectively solved.

[0084] Beneficial effects:

[0085] This invention establishes a carbon quota allocation and trading mechanism model and a system transformation equipment model applicable to the integrated energy system planning of the pulp and paper industry. Through baseline emissions, carbon quota allocation, and carbon quota trading settlement, the methodological foundation and top-level design of the carbon quota mechanism are concretized into a carbon quota subsidy mechanism model applicable to the integrated energy system planning of the pulp and paper industry, providing the conditions for establishing a mathematical model for the integrated energy system planning of the pulp and paper industry based on the carbon quota mechanism. The equipment combination of carbon capture equipment, steam accumulators, booster pumps, and electric boilers is then comprehensively considered to establish an integrated energy system planning model for the pulp and paper industry for carbon trading and equipment transformation scenarios. By solving the planning model, the planned equipment capacity and system comprehensive energy cost parameters in different scenarios can be further analyzed and compared. Specifically, the planned equipment capacity, system comprehensive energy cost, system purchased energy cost, system carbon trading cost, system operating cost, system carbon capture cost, and system equipment investment cost of the pulp and paper mill in each scenario can be calculated and compared. This allows for a quantitative comparison of the impact of the system transformation equipment combination and the carbon quota mechanism on the comprehensive economic performance of the pulp and paper mill. This can guide the formulation of comprehensive energy system planning schemes for the pulp and paper industry, clarify the importance of the carbon quota mechanism and system transformation equipment combination to the comprehensive energy economy of the pulp and paper industry, and improve the comprehensive economic benefits of the comprehensive energy system of the pulp and paper industry through carbon quota mechanism scenarios and diversified equipment transformation scenarios in different periods. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 is a flow chart of the steps of the method of the present invention;

[0087] Figure 2 Schematic diagram of the comprehensive energy system for the pulp and paper industry taking into account all system transformation equipment in an embodiment of the present invention;

[0088] Figure 3 This is a schematic diagram of the energy flow balance of the pulp and paper industry integrated energy system modified in an embodiment of the present invention;

[0089] Figure 3 (a) is the electric busbar balance diagram, (b) is the high-pressure steam busbar mass flow balance diagram, (c) is the medium-pressure steam busbar mass flow balance diagram, and (d) is the low-pressure steam busbar mass flow balance diagram; Figure 3 The horizontal axis is the typical day hour number.

[0090] Figure 4 is a diagram comparing the comprehensive costs of the systems in the embodiments of the present invention;

[0091] Figure 4 (a) is a cost comparison chart under different system transformation scenarios, and (b) is a cost comparison chart under different carbon trading periods. DETAILED DESCRIPTION

[0092] The technical solutions of the application will be further described in detail below with reference to the drawings. The described embodiments are only a part of the embodiments involved in the patent. All non-innovative embodiments of other researchers in this field on the embodiments belong to the protection scope of the patent.

[0093] Embodiment 1

[0094] A pulp and paper industry comprehensive energy system planning method for carbon trading and equipment modification scenarios, a step flowchart of the method is shown in Figure 1 A pulp and paper industry comprehensive energy system schematic diagram considering all system modification equipment is shown in Figure 2 The method comprises the following steps:

[0095] S1, establishing a modification equipment model applicable to the pulp and paper industry comprehensive energy system, including carbon capture equipment, steam accumulator, booster pump and electric boiler;

[0096] S2, selecting the optimal comprehensive energy consumption cost of the pulp and paper industry comprehensive energy system as the planning target, considering energy balance, equipment operation constraints, and establishing a comprehensive energy consumption cost optimal planning model of the pulp and paper industry comprehensive energy system under the carbon quota mechanism;

[0097] S3, designing different scenarios from the perspective of carbon trading and equipment modification scheme combination, determining the known quantities and unknown quantities in each scenario, and solving the optimal planning model to obtain the planning scheme;

[0098] S4, analyzing and comparing the parameters such as equipment planning capacity and system comprehensive energy consumption cost in different carbon trading and equipment modification scenarios.

[0099] Further, in step S1, the modification equipment model applicable to the pulp and paper industry comprehensive energy system includes carbon capture equipment, steam accumulator, booster pump and electric boiler, wherein the carbon capture equipment model is:

[0100]

[0101] In the formula: Wt is the electric power consumed by the carbon capture equipment in the tth hour, in units of MW / yr; W C emi is the energy consumption required by the carbon capture equipment to capture one ton of carbon dioxide, in units of MWh / t; c emi is the carbon dioxide generated by the combustion of one ton of standard coal, in units of t / tce; Wt is the coal consumption of the coal-fired cogeneration unit, alkali recovery cogeneration unit and lime kiln in the tth hour, in units of t / h; Wt is the carbon capture coefficient of the coal-fired cogeneration unit, alkali recovery cogeneration unit and lime kiln in the tth hour; The maximum carbon capture coefficient of a coal-fired cogeneration unit, an alkali recovery cogeneration unit, and a lime kiln CC Cap is the planned capacity of the carbon capture equipment, in MW; Capmax is the planned maximum capacity of the carbon capture equipment, in MW;

[0102] The steam accumulator model is:

[0103]

[0104] 0≤m cha,t ≤f cha,t m cha,max (7)

[0105] 0≤m dis,t ≤f dis,t m dis,max (8)

[0106]

[0107] f cha,t ,f dis,t ∈{0,1} (12)

[0108] f cha,t p valve ≤p cha,t (13)

[0109] In the formula, Cap SA is the planned capacity of the steam accumulator, in MW; Capmax is the planned maximum capacity of the steam accumulator, in MW; m cha,t m dis,t is the mass flow of steam charging and discharging of the steam accumulator in the tth hour, in t / h; f cha,t is a state characteristic quantity of steam charging of the steam accumulator in the tth hour, with a value of 1 when charging and a value of 0 when not charging; f dis,t is a state characteristic quantity of steam discharging of the steam accumulator in the tth hour, with a value of 1 when discharging and a value of 0 when not discharging; is the heat storage amount of the steam accumulator at the end of the tth hour, in MWh; h cha,t is the enthalpy value of steam charging of the steam accumulator in the tth hour, in MJ / t; h LP is the enthalpy value of steam discharging of the steam accumulator, in MJ / t; Δt is the number of hours in the planning period; p valve is the pressure threshold of the steam accumulator charging valve, in MPa; p cha,t is the charging pressure of the steam accumulator in the tth hour, in MPa;

[0110] The booster pump model is:

[0111] pcha,min ≤p cha,t ≤p cha,max (14)

[0112] h cha,t =c1p cha,t T cha +c2T cha +c3p cha,t +c4 (15)

[0113]

[0114] wherein: p cha，min p cha，max are the minimum and maximum values of the charging pressure of the booster pump to the steam accumulator, in MPa; T cha is the charging temperature of the booster pump to the steam accumulator, in K; c1c2c3c4are the linear fitting coefficients of the steam enthalpy; is the electric power consumed by the booster pump in the tth hour, in MW; is the planned capacity of the booster pump, in MW; is the maximum planned capacity of the booster pump, in MW;

[0115] The electric boiler model is:

[0116]

[0117] 0≤P t EB ≤Cap EB (20)

[0118]

[0119]

[0120] wherein: Cap EB represents the planned capacity of the electric boiler, in MW; represents the maximum planned capacity of the electric boiler, in MW; is the electric power consumed by the electric boiler in the tth hour, in MW; is the heating power of the electric boiler in the tth hour, in MW; is the maximum heating power of the electric boiler, in MW; is the mass flow rate of steam emitted by the electric boiler in the tth hour, in t / h; is the maximum mass flow rate of steam emitted by the electric boiler, in t / h; Γrepresents the ratio between the maximum uphill and downhill ramp rates of the electric boiler and the maximum planned capacity; η EB is the electric-thermal conversion efficiency of the electric boiler.

[0121] Further: the comprehensive energy cost of the pulp and paper industry comprehensive energy system in step S2 includes: system purchased energy cost, system carbon trading cost, system operation cost, system carbon capture cost, and system equipment investment cost. The system purchased energy cost model is:

[0122]

[0123] wherein: E sp is the purchased energy cost, with a unit of $; r e，trge，t is the electricity price and green electricity price in the tth hour, with a unit of $ / MWh; P e，t P ge,t is the electricity price and green electricity purchase amount in the tth hour, with a unit of MWh; r coal is the unit price of coal, with a unit of $ / t; r loss is the abandoned steam penalty unit price, with a unit of $ / t; is the abandoned steam quality, with a unit of t;

[0124] The carbon trading mechanism model is:

[0125]

[0126] wherein: ε grid，carb is the carbon emission factor of electricity; CA t is the carbon emission of the pulp and paper industry comprehensive energy system in the tth hour, with a unit of t; FCA t is the carbon quota allocated to the pulp and paper industry comprehensive energy system in the tth hour, with a unit of t; is the electricity output of the coal-fired cogeneration unit and the alkali recovery cogeneration unit in the tth hour, with a unit of MW; b e，coal is the power supply benchmark of the coal-fired unit; f r，coal is the heat supply correction coefficient of the coal-fired unit; f l，coal is the cooling mode correction coefficient of the coal-fired unit (set as 1); f f，coal is the load output correction coefficient of the coal-fired unit (set as 1); is the heat output of the coal-fired cogeneration unit and the alkali recovery cogeneration unit in the tth hour, with a unit of MW; is the black liquor mass flow rate consumed by the alkali recovery cogeneration unit in the tth hour, with a unit of t / h; LHV BL is the low heat value of black liquor, with a unit of MJ / t; b h，coal is the heat supply benchmark of the coal-fired unit; is the carbon trading cost, with a unit of $, and the parameter is greater than 0 as cost, and the parameter is less than 0 as income; c carb，eua c carb，ceris the carbon quota unit price and the voluntary carbon offset unit price, unit: $ / t; EUA is the carbon quota trading volume, unit: t; CER is the voluntary carbon offset, unit: t; λ is the reduction rate of the carbon quota benchmark value; μ CER is the maximum offset ratio of the voluntary carbon offset;

[0127] The system operation cost model is:

[0128]

[0129] In the formula: is the unit operation cost of the coal-fired combined heat and power unit, the alkali recovery combined heat and power unit, the booster pump, the carbon capture device and the electric boiler in the tth hour, unit: $ / MW; is the unit operation cost of the steam accumulator in the tth hour, unit: $ / MWh; is the unit operation cost of the medium-pressure and low-pressure steam busbar waste heat recovery device in the tth hour, unit: $ / MW; is the unit operation cost of the lime kiln in the tth hour, unit: $ / MW; is the recovered steam mass flow of the medium-pressure and low-pressure steam busbar in the tth hour, unit: t / h; h HP h MP is the enthalpy of the medium-pressure and low-pressure steam in the tth hour, unit: MJ / t; is the heat generated by the lime kiln in the tth hour, unit: MW;

[0130] The system carbon capture cost model is:

[0131]

[0132] In the formula: E cc is the carbon capture cost, unit: $; r CC is the carbon capture unit price, unit: $ / t;

[0133] The system device investment cost model is:

[0134]

[0135]

[0136] In the formula: E inv is the system device investment cost, unit: $; is the investment cost of the carbon capture device, the electric boiler, the steam accumulator and the booster pump, unit: $; h is the annual return on investment of the device; τ CC τ EB τ SA τ PU is the service life of the carbon capture device, the electric boiler, the steam accumulator and the booster pump, unit: year; ICC I EB I PU is the unit investment cost of carbon capture equipment, electric boiler, and booster pump, in $ / MW; I SA is the unit investment cost of steam thermal accumulator, in $ / MWh;

[0137] The system planning objective function is:

[0138]

[0139] Where: Obj is the comprehensive cost of the system, in $;

[0140] Further: In step S2, the integrated energy system planning of the pulp and paper industry is subject to relevant conditions, including energy balance and equipment operation constraints:

[0141] 1) Energy balance constraints;

[0142] Energy balance constraints include electrical energy balance constraints, thermal energy balance constraints, and process energy supply constraints:

[0143]

[0144]

[0145]

[0146] Where: is the electrical load of the process in the tth hour, in MW; H2M χ M2L are the medium-pressure and low-pressure steam bus recovery factors, respectively; are the medium-pressure and low-pressure steam load mass flows, in t / h; δ en (n=1, 2…, 8) is the power demand per unit product of each dispatchable process at hour t; δ hn (n=1, 2…, 8) is the heat energy demand per unit product of each schedulable process in hour t; are the power load and thermal load demands of other processes except the dispatchable processes in hour t, in MW;

[0147] 2) Equipment operation constraints;

[0148] Equipment operation constraints include coal-fired cogeneration units, alkali recovery cogeneration units, and lime kiln operation constraints:

[0149] Coal-fired cogeneration unit operating constraints:

[0150]

[0151]

[0152]

[0153]

[0154] wherein: and are the upper and lower limits of the electric output of the coal-fired cogeneration unit, in MW; and are the upper and lower limits of the thermal output of the coal-fired cogeneration unit, in MW; k CHP,min and k CHP,max are the electric-thermal conversion coefficients of the coal-fired cogeneration unit corresponding to the minimum and maximum electric output; C m is the slope of the cogeneration supply curve; is the mass flow rate of high-pressure, medium-pressure, and low-pressure steam supplied by the coal-fired cogeneration unit in the tth hour, in t / h; is the maximum downhill and uphill ramp rate of the coal-fired cogeneration unit, in MW; ζ CHP is the electric-thermal output correction coefficient of the coal-fired cogeneration unit; η CHP is the thermal efficiency of the coal-fired cogeneration unit; LHV coal is the low calorific value of coal, in MJ / t;

[0155] Operation constraints of the alkali recovery cogeneration unit:

[0156]

[0157] wherein: and are the upper and lower limits of the electric output of the alkali recovery cogeneration unit, in MW; and are the upper and lower limits of the thermal output of the alkali recovery cogeneration unit, in MW; k AR，min and k AR，max are the electric-thermal conversion coefficients of the alkali recovery cogeneration unit corresponding to the minimum and maximum electric output; is the mass flow rate of high-pressure steam supplied by the alkali recovery cogeneration unit in the tth hour, in t / h; is the maximum downhill and uphill ramp rate of the alkali recovery cogeneration unit, in MW; ζ AR is the electric-thermal output correction coefficient of the alkali recovery cogeneration unit; η AR is the thermal efficiency of the alkali recovery cogeneration unit;

[0158] Operation constraints of the lime kiln:

[0159]

[0160] wherein: mm，t M is the amount of lime mud consumed by the lime kiln in the tth hour, in t; M m M is the total amount of lime mud consumed by the lime kiln per day, in t; η LK η is the efficiency of the lime kiln; ΔH m ΔH is the enthalpy change of the lime mud to limestone conversion process, in MW / t; M is the mass flow of medium-pressure steam generated by the lime kiln in the tth hour, in t / h; M is the coal consumption of the lime kiln in the tth hour, in t / h; M is the thermal output of the lime kiln in the tth hour, in MW;

[0161] In the example, the data of a comprehensive energy system of a pulp and paper mill in Jiangsu Province is substituted into the model for calculation and solution. The specific data of the operating parameters of the equipment involved are shown in Table 1. The conventional electricity price and green electricity price data in the area where the pulp and paper mill is located are shown in Table 2.

[0162] Table 1 Data of operating parameters of equipment of pulp and paper mill in example

[0163]

[0164] Table 2 Conventional electricity price and green electricity price data in the area where the pulp and paper mill in example is located

[0165]

[0166] Further, in step S3, the method of designing differentiated scenarios from the perspectives of carbon trading and different combinations of equipment modification schemes includes:

[0167] S31, set the carbon capture equipment, steam accumulator, booster pump, and electric boiler model as four combinations of equipment modification schemes, and generate scenarios A, B, C, and D in sequence according to specific combination strategies. Scenario A represents no added equipment, scenario B represents only added carbon capture equipment, scenario C represents added carbon capture equipment and electric boiler, and scenario D represents added carbon capture equipment, steam accumulator, booster pump, and electric boiler. The specific scenario classification is shown in Table 3.

[0168] Table 3 Classification table of comprehensive energy system modification scenarios of pulp and paper mill in example

[0169] Note: indicates that the technology / equipment is applied, and indicates that the technology / equipment is not applied.

[0170] S32, based on the carbon quota allocation and trading mechanism in the same period, solve the cost optimization model of the comprehensive energy storage system of the pulp and paper industry; add the four combinations of equipment modification schemes in S31 in sequence, and solve the cost optimization model of the comprehensive energy storage system of the pulp and paper industry considering the combinations of equipment modification schemes;

[0171] S33, four carbon trading periods are divided according to the carbon quota allocation and trading mechanism, based on the prediction of carbon market situation from 2025 to 2040 every five years, A, B, C and D carbon trading periods are divided, and the maximum offset ratio of certified voluntary emission reduction and the change of the decline rate of carbon quota benchmark value are included in the scenario evolution, and different carbon quota unit price and certified voluntary emission reduction unit price are substituted in different carbon trading periods. The specific carbon trading period classification is shown in Table 4;

[0172] Table 4 Carbon trading period division table in the embodiment

[0173]

[0174] S34, the cost optimization model of the pulp and paper industry comprehensive energy system after equipment modification is selected, the parameters of the carbon quota allocation and trading mechanism in different periods are substituted, the carbon trading related information of the objective function of the optimization model in S32 is corrected, and the cost optimization model of the pulp and paper industry comprehensive energy system considering carbon trading is calculated respectively;

[0175] Further, in step S4, the equipment planning capacity, system comprehensive energy cost, system purchased energy cost, system carbon trading cost, system operation cost, system carbon capture cost, and system equipment investment cost in different carbon trading and equipment modification scenarios are analyzed and compared.

[0176] Table 5 compares and analyzes the equipment planning capacity, system comprehensive energy cost, system purchased energy cost, system carbon trading cost, system operation cost, system carbon capture cost, and system equipment investment cost of four equipment modification scenarios. The purchased energy cost is divided into fossil energy consumption cost, conventional electricity consumption cost and green electricity consumption cost, so as to refine the analysis of the influence of equipment modification on system economy. In addition, the cost comparison of equipment technology application change scheme is shown in Table 6. Figure 4 (a). The planning results specifically include carbon quota trading volume, certified voluntary emission reduction trading volume and equipment planning capacity. The positive value of the trading volume indicates the purchase of quota, and the negative value indicates the sale of quota.

[0177] Table 5 Comparison table of equipment modification scenario planning results in the embodiment

[0178]

[0179]

[0180] The comparison of Scenario A and Scenario B shows the benefit of carbon capture equipment, which reduces the system integrated cost by about 9.3%. The planning of additional 13.5 MW carbon capture equipment directly increases the equipment investment by 0.024*105$ and the carbon capture cost by 17.35*105$, and causes the system to increase the clean energy consumption by 17.35*105$ and the fossil energy consumption by 11.9*105$, but at the same time, it generates the carbon trading benefit of 111.24*105$. Overall, the carbon emission reduction benefit of carbon capture equipment offsets the increase of other costs.

[0181] The comparison of Scenario B and Scenario C aims to evaluate the economic benefit of electric boiler, which can reduce the system integrated cost by about 2.3%. The planning of additional 50 MW electric boiler capacity, although reduces the carbon capture equipment capacity by 1.28 MW, but increases the equipment investment by 0.475*105$. Among them, the reduction of carbon capture equipment capacity is because the electric boiler supplements the energy supply of the low-pressure steam busbar, reduces the output of the low-pressure steam busbar waste heat recovery device, and thus reduces the output of the lime kiln that supplies energy to the medium-pressure steam busbar, resulting in a reduction in the planned capacity of the carbon capture equipment. This reduces the system operating cost by 64.56*105$ and the carbon capture cost by 12.11*105$. However, the reduction of carbon capture equipment capacity results in a loss of carbon trading benefit of 57.68*105$. In addition, the planning of additional electric boiler capacity increases the system clean energy consumption, but reduces the fossil energy consumption by 28.22*105$ due to the reduction of lime kiln output.

[0182] The comparison of Scenario C and Scenario D shows the benefit of using steam accumulators and booster pumps, which can reduce the system integrated cost by about 1.88% and increase the equipment investment by 1.627*105$. However, due to the charging and discharging process of steam accumulators, the system's thermal and electrical energy demand is reduced, which results in a decrease in system clean energy consumption by 9.93*105$. At the same time, the planned capacity of the system's carbon capture equipment is reduced by 1.04 MW, and the carbon capture cost is reduced by 0.45*105$ and the carbon trading income is reduced by 1.58*105$.

[0183] In summary, the integration of carbon capture equipment, steam accumulators, booster pumps, and electric boilers reduces the system integrated cost by 5.19*106$. In addition, the daily carbon emissions of the pulp and paper integrated energy system are significantly reduced from 1,251.2 tce to 799 tce, a total of 452.2 tce.

[0184] In order to further analyze the reasons for the reduction of system carbon emissions and integrated cost after technical transformation, the coordinated operation of the planned equipment in a typical day is analyzed.

[0185] Figure 3(a) shows the power balance of the pulp and paper integrated energy system with the addition of carbon capture equipment, steam accumulator, booster pump, and electric boiler in scenario D. During the off-peak and night valley electricity price periods, the system increases the power demand, purchases conventional and green electricity from the grid, and increases the output of the electric boiler (especially during 1 :00-8:00). During the typical day, the electric load is mainly met by the coal-fired cogeneration unit and the alkali recovery cogeneration unit. Among them, the coal-fired cogeneration unit provides relatively stable output, while the alkali recovery cogeneration unit meets the demand fluctuations caused by conventional and green electricity consumption.

[0186] Figure 3 (b)-(d) show the mass flow balance of the high, medium, and low pressure steam buses. The high pressure steam bus is mainly supplied by the alkali recovery cogeneration unit, and the steam supply flow remains stable at 36.83 t / h during the valley electricity price period. During the valley electricity price period (9:00-11 :00, 18:00-22:00), the heat output of the ARCHP is reduced.

[0187] There is a stable heat demand in the medium pressure steam bus. However, during the low valley electricity price period, the heat transferred from the high pressure to the medium pressure steam bus is reduced, prompting the lime kiln to increase its heat output to meet the demand. The medium pressure steam demand peaks at 9.23 t / h in the morning (4:00-8:00) and 8.52 t / h in the afternoon (12:00-17:00).

[0188] The low pressure steam bus demand is mainly determined by the production process and the steam accumulator charging amount, and is mainly supplied by the low pressure steam bus waste heat recovery device, coal-fired cogeneration unit, electric boiler, and steam accumulator steam release process. During the peak electricity price period (9:00-11 :00, 18:00-22:00), the low-grade heat demand is minimal, while during the non-peak electricity price period, the low pressure steam demand increases to 154.9 t / h to 184.5 t / h. During the valley electricity price period, the system increases the output of the electric boiler and the steam release amount of the steam accumulator to meet the increased demand. Conversely, during the peak electricity price period, the electric boiler output is reduced, and the system charges steam into the steam accumulator, thereby ensuring a constant heat storage amount at the beginning and end of the planning period.

[0189] Table 6 compares and analyzes the equipment planning capacity, system integrated energy cost, system purchased energy cost, system carbon trading cost, system operation cost, system carbon capture cost, and system equipment investment cost during the four carbon trading periods. The purchased energy cost is divided into fossil energy consumption cost, conventional and green electricity consumption cost, in order to refine the analysis of the impact of carbon trading period on system economy. In addition, the comparison of each cost parameter of the system during the carbon trading period is shown in Table 7. Figure 4(b). The planning results include carbon quota trading volume, voluntary carbon credit trading volume and equipment planning capacity. The positive value of the trading volume means buying quota, and the negative value means selling quota.

[0190] Table 6 Comparison of carbon trading period planning results in the example

[0191]

[0192]

[0193] In periods A to D, as the carbon quota price, voluntary carbon credit price, maximum offset ratio of voluntary carbon credit and the decline rate of carbon quota benchmark value gradually increase, the pulp and paper integrated energy system reduces carbon emissions by adding carbon capture equipment, steam accumulators, booster pumps and electric boilers. Therefore, the system's carbon trading income increases and the system's comprehensive cost decreases.

[0194] Specifically, from period A to C, the planning capacity of carbon capture equipment, steam accumulators and booster pumps all increase, resulting in a continuous increase in carbon quota sales. Considering the carbon capture equipment investment and operation and maintenance costs in period A, the carbon quota price has limited incentive for carbon capture equipment. Therefore, the actual carbon emissions are still greater than the free allocation of quotas, and the system needs to buy about 7 tons of carbon quotas to offset carbon emissions. Therefore, the system buys 50.22 tons of low-cost voluntary carbon credits to offset carbon quotas, and sells 43.24 tons of carbon quotas at a high price to obtain high carbon trading income. In periods B and C, the prices of carbon quotas and voluntary carbon credits fully stimulate carbon capture by carbon capture equipment, so the system can sell about 834 tons and 785 tons of carbon quotas to offset carbon emissions. In period D, although the total amount of carbon quotas sold by the system is reduced to about 756 tons, due to the high prices of carbon quotas and voluntary carbon credits, the system's carbon trading income still increases. The system's high carbon trading income exceeds the cost reduction through flexible use of heat energy by steam accumulators, which makes the system reduce the planning capacity of steam accumulators and booster pumps, and tend to increase green electricity purchases. Therefore, the system's carbon trading income is 65.31*105$ more than that in period C, and the system's comprehensive cost is reduced by 54.86*105$.

[0195] In summary, the embodiment of the present application establishes a pulp and paper industry comprehensive energy system planning model in the carbon trading and equipment modification scenario. The modification equipment model applicable to the pulp and paper industry comprehensive energy system is established, including carbon capture equipment, steam accumulator, booster pump and electric boiler. The methodology basis and top-level design of carbon quota and certified voluntary emission reduction mechanism are visualized into carbon quota mechanism model and certified voluntary emission reduction mechanism model applicable to the pulp and paper industry comprehensive energy system planning, providing conditions for establishing the pulp and paper industry comprehensive energy system planning based on carbon trading. Then, the carbon trading and equipment modification scheme combination parameter requirements are comprehensively considered, and the pulp and paper industry comprehensive energy system planning model applicable to the carbon trading and equipment modification scenario is established. In the embodiment, the carbon quota and certified voluntary emission reduction mechanism are mainly converted into carbon quota price and certified voluntary emission reduction mechanism price parameters. The maximum offset ratio of certified voluntary emission reduction and the decline rate of carbon quota benchmark value are comprehensively considered, and the planning model in four equipment modification scenarios and the planning model in four carbon trading periods are sequentially solved, which can further analyze and compare the equipment planning capacity and system economic parameters in different scenarios, i.e. calculating and comparing the pulp and paper industry comprehensive energy system equipment planning capacity, system comprehensive energy cost, system purchased energy cost, system carbon trading cost, system operation cost, system carbon capture cost, and system equipment investment cost in each scenario. Thus, the influence of the carbon trading and equipment modification scenario on the planning result of the pulp and paper industry comprehensive energy system can be quantitatively compared. The embodiment verifies the reliability and scientificity of the modification equipment model, carbon quota mechanism model and certified voluntary emission reduction mechanism model applicable to the pulp and paper industry comprehensive energy system planning through the model solving result. The modification equipment model, carbon quota mechanism model and certified voluntary emission reduction mechanism model can guide the formulation of the pulp and paper industry comprehensive energy system planning scheme, and clarify the important significance of system modification equipment, carbon quota mechanism and certified voluntary emission reduction mechanism to the comprehensive cost of pulp and paper energy supply system and equipment planning capacity. Furthermore, the pulp and paper industry comprehensive energy system planning model based on the modification equipment model, carbon quota mechanism model and certified voluntary emission reduction mechanism model can reduce the comprehensive cost of the pulp and paper industry comprehensive energy system in different carbon trading periods and diversified equipment modification scenarios.

[0196] The present application verifies the scenario adaptability and planning potential of the pulp and paper industry comprehensive energy system planning model in the carbon trading and equipment modification scenario, and has engineering application value.

[0197] The above is only a preferred embodiment of the present application, and does not limit the present application in any other form. Any modification or equivalent change made according to the technical essence of the present application still falls within the scope of the present application.

Claims

1. A comprehensive energy system planning method for pulp and papermaking in carbon trading and equipment transformation scenarios, characterized by: The steps include: S1, establish a transformation equipment model that can be applied to the integrated energy system of the pulp and paper industry, including carbon capture equipment, steam accumulator, booster pump, and electric boiler; S2: Select the optimal comprehensive energy cost of the pulp and paper industry integrated energy system as the planning target, consider the energy balance and equipment operation constraints, and establish the optimal planning model for the comprehensive energy cost of the pulp and paper industry integrated energy system with a carbon quota mechanism; The comprehensive energy cost of the integrated energy system of the pulp and paper industry in step S2 includes: the system's external energy cost, the system's carbon trading cost, the system's operating cost, the system's carbon capture cost, and the system's equipment investment cost. The system's external energy cost model is: ； Where: is the cost of purchased energy, in $; is the electricity price and green power price at hour t, in $ / MWh; is the electricity price and green electricity purchase amount at hour t, in MWh; is the unit price of coal, in $ / t; The penalty unit price for abandoning steam is $ / t; is the quality of discarded steam, in t; The carbon trading mechanism model is: ； ； ； ； Where: is the electricity carbon emission factor; is the carbon emission of the comprehensive energy system of the pulp and paper industry in hour t, unit is t; The number of carbon quotas allocated to the comprehensive energy system of the pulp and paper industry at hour t, in units of t; The power output of the coal-fired cogeneration unit and the alkali recovery cogeneration unit in hour t, in MW; power supply benchmarks for coal-fired units; Correction factor for heat supply of coal-fired units; The correction factor for the cooling mode of the coal-fired unit is set to 1; The load output factor correction factor for coal-fired units is set to 1; is the thermal output of the coal-fired cogeneration unit and the alkali recovery cogeneration unit in hour t, in MW; is the mass flow rate of black liquor consumed by the alkali recovery cogeneration unit in hour t, in t / h; is the lower calorific value of black liquor, in MJ / t; It is the heating benchmark for coal-fired units; is the carbon trading cost, in $, when the parameter is greater than 0, it is cost, and when the parameter is less than 0, it is benefit; The unit price of carbon quota and certified voluntary emission reduction is $ / t; is the carbon quota trading volume, unit is t; Certified voluntary emission reductions, in tons; is the rate of decrease of the carbon quota baseline value; The maximum offset ratio for certified voluntary emission reductions; The system planning objective function is: ； Where: is the system comprehensive cost, in $, For the cost of carbon capture, Investment cost for system equipment; S3: Design differentiated scenarios from the perspective of different factors in the combination of carbon trading and equipment transformation solutions, determine the known and unknown quantities in each scenario, and solve the optimal planning model to obtain the planning solution; S4. Analyze and compare the equipment planning capacity, system comprehensive energy cost, system purchased energy cost, system carbon trading cost, system operating cost, system carbon capture cost, and system equipment investment cost in different carbon trading and equipment transformation scenarios.

2. The method for planning an integrated energy system for pulping and papermaking in a carbon trading and equipment transformation scenario according to claim 1 is characterized by: The transformation equipment model that can be applied to the integrated energy system of the pulp and paper industry in step S1, wherein the carbon capture equipment model is: ； ； ； ； ； Where: is the electric power consumed by the carbon capture equipment in hour t, in units of ; The energy consumption required to capture one ton of carbon dioxide by the carbon capture equipment, in ; The carbon dioxide produced by burning one ton of standard coal, in units of ; is the coal consumption of the combined heat and power unit, alkali recovery combined heat and power unit and lime kiln in hour t, in units of ; is the carbon capture coefficient of the coal-fired cogeneration unit, alkali recovery cogeneration unit and lime kiln at hour t; Maximum carbon capture coefficients for coal-fired cogeneration units, alkali recovery cogeneration units, and lime kilns; Plan the capacity of the carbon capture equipment in MW; Plan the maximum capacity of the carbon capture equipment in MW; The steam accumulator model is: ； ； ； ； ； ； ； ； Where: Plan the capacity of the steam accumulator in MW; Plan the maximum capacity of the steam accumulator in MW; is the mass flow rate of steam charging and discharging in the steam accumulator at hour t, in units of ; is the state characterizing quantity of the steam accumulator charging at hour t, with a value of 1 when charging and 0 when not charging; is the state characterizing quantity of steam accumulator steam release at hour t, with a value of 1 when steam is released and a value of 0 when steam is not released; is the heat storage of the steam accumulator at the end of hour t, in units of ; is the steam accumulator charging enthalpy at hour t, in units of ; is the steam enthalpy of the steam accumulator, in units of ; is the number of hours for the planning period; is the steam accumulator charging valve pressure threshold, in units of ; is the steam accumulator charging pressure at hour t, in units of ; The booster pump model is: ； ； ； ； ； Where: The minimum and maximum pressures of the booster pump charging the steam accumulator, in units of ; The temperature of the gas charged to the steam accumulator by the booster pump, in K; is the quasi-linear fitting coefficient of steam enthalpy; The electric power consumed by the booster pump in hour t, in MW; Plan the capacity of the booster pump in MW; The maximum planned capacity of the booster pump, in MW; The electric boiler model is: ； ； ； ； ； ； ； Where: Indicates the planned capacity of the electric boiler, in MW; Indicates the maximum planned capacity of the electric boiler, in MW; is the electric power consumed by the electric boiler in hour t, in MW; is the heating power of the electric boiler in hour t, in MW; The maximum heating power of the electric boiler, in MW; The mass flow rate of steam emitted by the electric boiler in hour t, in t / h; The maximum mass flow rate of steam emitted by the electric boiler, in t / h; Indicates the ratio of the maximum uphill and downhill climbing rate of the electric boiler to the maximum planned capacity; is the electric-to-heat conversion efficiency of the electric boiler.

3. The method for planning an integrated energy system for pulping and papermaking in a carbon trading and equipment transformation scenario according to claim 1 is characterized by: In step 2: The system operation cost model is: ； Where: is the unit operating cost of the coal-fired cogeneration unit, alkali recovery cogeneration unit, booster pump, carbon capture equipment, and electric boiler at hour t, in $ / MW; is the unit operating cost of the steam accumulator at hour t, in $ / MWh; is the unit operating cost of the medium-pressure and low-pressure steam bus waste heat recovery devices at hour t, in $ / MW; is the unit operating cost of the lime kiln at hour t, in $ / MW; The mass flow rate of steam recovered from the medium-pressure and low-pressure steam busbars at hour t, in t / h; is the enthalpy of medium-pressure and low-pressure steam at hour t, in MJ / t; is the heat generated by the lime kiln in hour t, in MW; The system carbon capture cost model is: ； Where: is the cost of carbon capture, in $; is the carbon capture unit price, in $ / t; The system equipment investment cost model is: ； ； Where: is the system equipment investment cost, in $; is the investment cost of carbon capture equipment, electric boiler, steam accumulator, and booster pump, in $; is the annual return on investment of the equipment; The service life of carbon capture equipment, electric boiler, steam accumulator and booster pump is in years; is the unit investment cost of carbon capture equipment, electric boiler, and booster pump, in $ / MW; is the unit investment cost of steam thermal accumulator, in $ / MWh.

4. The method for planning an integrated energy system for pulping and papermaking in a carbon trading and equipment transformation scenario according to claim 1 is characterized by: In step S2, the integrated energy system planning for the pulp and paper industry is subject to relevant constraints, including energy balance and equipment operation constraints: 1) Energy balance constraints; Energy balance constraints include electrical energy balance constraints, thermal energy balance constraints, and process energy supply constraints: ； ； ； ； Where: is the electrical load of the process in hour t, in MW; are the medium-pressure and low-pressure steam bus recovery factors, respectively; are the medium-pressure and low-pressure steam load mass flows, respectively, in t / h; is the electricity demand per unit product of each dispatchable process at hour t; is the heat energy demand per unit product of each dispatchable process in hour t; are the power load and thermal load demands of other processes except the dispatchable processes in hour t, in MW; 2) Equipment operation constraints; Equipment operation constraints include coal-fired cogeneration units, alkali recovery cogeneration units, and lime kiln operation constraints: Coal-fired cogeneration unit operating constraints: ； ； ； ； ； ； Where: and It is the upper and lower limits of the electrical output of the coal-fired cogeneration unit, in MW; and It is the upper and lower limits of thermal output of coal-fired cogeneration units, in MW; and is the electricity-to-heat conversion coefficient of the coal-fired cogeneration unit corresponding to the minimum and maximum electrical output; is the slope of the CHP supply curve; The mass flow rates of high-pressure, medium-pressure, and low-pressure steam supplied by the coal-fired cogeneration unit at hour t, in t / h; is the maximum down-slope and up-slope ramp rate of the coal-fired cogeneration unit, in MW; is the correction factor for the electric and thermal output of the coal-fired cogeneration unit; is the thermal efficiency of the coal-fired cogeneration unit; is the lower calorific value of coal, in MJ / t; Operation constraints of alkali recovery cogeneration units: ； ； ； ； ； ； Where: and It is the upper and lower limits of the electric output of the alkali recovery cogeneration unit, in MW; and It is the upper and lower limits of the thermal output of the alkali recovery cogeneration unit, in MW; and is the electric-to-heat conversion coefficient of the alkali recovery cogeneration unit corresponding to the minimum and maximum electrical output; The mass flow rate of high-pressure steam supplied by the alkali recovery cogeneration unit at hour t, in t / h; is the maximum downhill and uphill ramp rate of the alkali recovery cogeneration unit, in MW; is the correction coefficient of the electric and thermal output of the alkali recovery cogeneration unit; is the thermal efficiency of the alkali recovery cogeneration unit; Lime kiln operation constraints: ； ； ； Where: is the amount of lime mud consumed by the lime kiln in hour t, in t; is the total amount of lime mud consumed daily by the lime kiln, in tons; is the efficiency of the lime kiln; is the enthalpy change of lime mud to limestone conversion process, in MW / t; is the mass flow rate of medium-pressure steam generated by the lime kiln in hour t, in t / h; is the coal consumption of the lime kiln in hour t, in t / h; It is the thermal output of the lime kiln in hour t, in MW.

5. The method for planning an integrated energy system for pulping and papermaking in a carbon trading and equipment transformation scenario according to claim 2 is characterized by: In step S3, the differentiated scenario methods are designed from the perspective of different factors of carbon trading and equipment transformation scheme combination, including: S31, the carbon capture equipment, steam accumulator, booster pump, and electric boiler models are set as a combination of four equipment transformation schemes; S32: Based on the carbon quota allocation and trading mechanism for the same period, solve the optimal cost model of the comprehensive energy stock system of the pulp and paper industry; add the four equipment transformation scheme combinations in S31 in sequence, and solve the optimal cost model of the comprehensive energy system of the pulp and paper industry considering the equipment transformation scheme combinations; S33, set up four carbon trading periods according to the carbon quota allocation and trading mechanism; S34, select the optimal cost model of the comprehensive energy system of the pulp and paper industry after equipment transformation, substitute the parameters of the carbon quota allocation and trading mechanism in different periods, correct the carbon trading related information of the objective function of the S32 optimization model, and solve the optimal cost model of the comprehensive energy system of the pulp and paper industry considering carbon trading.

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