CN116777141A - Optimization method of waste heat recovery system of steel plant - Google Patents

Abstract

The invention discloses an optimization method of a waste heat recovery system of a steel plant, which optimizes a system structure model of the waste heat recovery system of the steel plant by establishing an equipment planning optimization model and an equipment operation control optimization model to obtain an optimization result, and controls the operation of the waste heat recovery system of the steel plant so as to obtain the maximum economic benefit of low-temperature waste heat recovery of the steel plant. According to the embodiment of the invention, the economic benefit influence of peak-valley electricity price and natural gas price on waste heat recovery can be simultaneously considered, the models of system components such as an organic Rankine cycle unit, an electric heat pump unit, a heat exchanger direct heat supply unit, an absorption refrigeration unit, an electric refrigeration unit, a gas boiler and the like in the waste heat recovery system of the steel plant are constructed, the optimal planning and operation control optimization model of the equipment is established, the constant volume of the equipment in the waste heat recovery system is completed and the operation state of the waste heat recovery equipment is controlled according to the optimization result of the model, so that the maximum economic benefit is obtained for the low-temperature waste heat recovery of the steel plant.

Description

Optimization method of waste heat recovery system of steel plant

Technical Field

The invention relates to the technical field of waste heat recovery, in particular to an optimization method of a waste heat recovery system of a steel plant.

Background

Carbon emission reduction and energy utilization efficiency improvement work of various industries in China are being accelerated, and energy recycling is one of the most effective and economic modes. In the current energy structure of China, the energy consumed by the industrial industry is huge and accounts for about 70% of the total energy consumption, and more than 60% of the energy is dissipated into the environment in various forms of waste heat, so that the extremely waste of resources is caused, and obvious environmental problems are also caused. However, the recycling rate of waste heat, especially low-temperature waste heat, in the industrial industry is still low at present due to the problems of economic benefit and the like, and huge lifting space and waste heat recycling system planning requirements still exist in the future.

Among technologies for low-temperature waste heat recovery, technologies which are widely applied in commercialization at present mainly comprise Rankine cycle, organic Rankine cycle, kalina cycle, heat pump, absorption refrigeration, heat exchange utilization, boiler, heat storage and the like. The conditions and effects of different recovery techniques are greatly different, and the techniques are mainly applicable to recovery of waste heat in the form of fluid and have certain requirements on temperature. A great deal of waste heat resources in steel plants mainly exist in flue gas, circulating cooling water and products, the former two can be recovered by utilizing the waste heat recovery technology according to actual conditions, and the recovery of solid sensible heat can influence the performance of the products and is difficult to find an effective and economic recovery technology.

Disclosure of Invention

The invention provides an optimization method of a waste heat recovery system of a steel plant, which can simultaneously consider the influence of peak-valley electricity price and natural gas price on the economic benefit of waste heat recovery, establishes an equipment optimal planning and operation control nested optimization model of the waste heat recovery system of the steel plant, completes the constant volume of equipment in the waste heat recovery system and controls the operation state of the waste heat recovery equipment according to the optimization result of the model, so that the low-temperature waste heat recovery of the steel plant obtains the maximum economic benefit.

In order to achieve the above object, in a first aspect, an embodiment of the present invention provides a method for optimizing a waste heat recovery system of a steel plant, including:

establishing an equipment planning optimization model and an equipment operation control optimization model;

optimizing a system structure model of the waste heat recovery system of the steel plant according to the equipment planning optimization model and the equipment operation control optimization model to obtain an optimization result;

controlling the operation of the waste heat recovery system of the steel plant based on the optimization result so as to obtain the maximum economic benefit of low-temperature waste heat recovery of the steel plant;

the system structure model comprises a waste heat recovery equipment unit, an electric refrigeration unit, a gas boiler unit, a fan and pump unit and a bus; the waste heat recovery equipment unit comprises one or more of an organic Rankine cycle power generation unit, an electric heating pump unit, a heat exchanger direct heat supply unit and an absorption refrigeration unit; the bus bars comprise an electric bus bar, a hot bus bar and a cold bus bar;

The objective function of the equipment planning optimization model is the difference between the total positive benefit and the total negative benefit of the system structure model, wherein the total positive benefit is the economic value of all energy sources produced by the waste heat recovery equipment, and the total negative benefit comprises the depreciation cost and all energy utilization cost of the waste heat recovery equipment unit; the independent variable of the equipment planning optimization model is the construction quantity of the waste heat recovery equipment units; the constraint condition of the equipment planning optimization model is the construction quantity constraint of the waste heat recovery equipment units;

the objective function of the equipment operation control optimization model is the difference between positive gain and negative gain of the system structure model, wherein the positive gain is the economic value of energy produced by the waste heat recovery equipment in one working day, and the negative gain is the energy cost of the waste heat recovery equipment unit in the one working day; the independent variables of the equipment operation control optimization model are the electric power output by the organic Rankine cycle power generation unit in each period, the thermal power output by the electric heating pump unit in each period, the thermal power output by the heat exchanger direct heat supply unit in each period and the cold power output by the absorption refrigeration unit in each period; the constraint condition of the equipment operation control optimization model is the output power constraint of the waste heat recovery equipment unit and the thermal power constraint of the waste heat source.

Preferably, the expression of the equipment planning optimization model is:

Benefit _opt ＝Of(b _i,j ,Φ)，

where obj_1 (b) _i,j ) Representing an objective function of the equipment planning optimization model, wherein i is the number of the waste heat source; j is the number of the waste heat recovery equipment; b _i,j 、Λ _i,j And lambda (lambda) _i,j Respectively representing the planning quantity of waste heat recovery equipment with the number j in the ith waste heat source, the capacity of a single waste heat recovery equipment and the unit construction cost; benefit _opt And Cost _con Respectively representing the maximum net economic benefit and the one-time construction cost of the operation of the waste heat recovery system under the given planning condition of the waste heat recovery equipment; alpha represents a depreciation coefficient; n represents the quantity of low-temperature waste heat sources with recovery potential in the steel plant; of () represents an operation control optimization function whose output is the maximum economic benefit Of the operation Of the waste heat recovery system;Φ represents other operating parameters; b _i,j,max Representing the upper limit of the allowable construction quantity of 4 kinds of waste heat recovery equipment, if the (r) waste heat source cannot perform waste heat recovery through the (m) waste heat recovery equipment, b is present _r,m,max ＝0。

Preferably, the operation variable expression of the organic rankine cycle power generation unit is:

wherein P is _i,ORC,t And Q _i,ORC,t Respectively representing the output electric power of the organic Rankine cycle power generation unit in the ith waste heat source in the t period and the waste heat power absorbed from the waste heat source; epsilon _i,ORC 、P _i,ORC,min 、P _i,ORC,max And DeltaP _i,ORC,max Respectively representing the efficiency coefficient of the organic Rankine cycle power generation unit, the minimum value and the maximum value of the output electric power and the maximum climbing rate in the ith waste heat source; p (P) _i,ORC,t+1 Representing the output electric power of the organic Rankine cycle power generation unit in the ith waste heat source at the (t+1) th period;

the operation variable expression of the electric heating pump unit is as follows:

wherein H is _i,EHP,t 、P _i,EHP,t And Q _i,EHP,t Respectively representing the output thermal power, the input electrical power and the waste heat power absorbed from the waste heat source of the electric heating pump unit in the ith waste heat source in the t period; COP of _i,EHP 、H _i,EHP,min And H _i,EHP,max Respectively representing the energy efficiency coefficient of the electric heating pump unit, the minimum value and the maximum value of the output heat power in the ith waste heat source;

the operation variable expression of the direct heat supply unit of the heat exchanger is as follows:

wherein H is _i,HE,t And Q _i,HE,t Respectively representing the output heat power of the heat exchanger direct heating unit in the ith waste heat source in the t period and the waste heat power absorbed from the waste heat source; η (eta) _i,HE 、H _i,HE,min And H _i,HE,max Respectively representing the efficiency coefficient, the minimum value and the maximum value of the output heat power of the direct heat supply unit of the heat exchanger in the ith waste heat source;

the operation variable expression of the absorption refrigeration unit is as follows:

Wherein C is _i,AC,t 、Q _i,AC,t And P _i,AC,t Respectively representing the output cold power of the absorption refrigeration unit in the ith waste heat source in the t period, the waste heat power absorbed from the waste heat source and the electric power consumed by the working medium pump in operation; COP of _i,AC 、ε _i,AC 、C _i,AC,min And C _i,AC,max Respectively representing the energy efficiency coefficient, the electricity consumption coefficient and the minimum value and the maximum value of the output cold power of the absorption refrigeration unit in the ith waste heat source;

the operation variable expression of the electric refrigeration unit is as follows:

C _EC ＝COP _EC ·P _EC ，

wherein C is _EC And COP _EC The output cold power and the energy efficiency coefficient of the electric refrigerating unit are respectively; p (P) _EC Indicating that when the output cold power of the electric refrigeration unit is C _EC The electrical power consumed by the unit at that time;

the operation variable expression of the gas boiler unit is as follows:

H _GB ＝η _GB ·V _gas ·J，

wherein H is _GB And eta _GB Respectively outputting heat power and efficiency coefficient of the gas boiler unit; v (V) _GB Indicating that when the output heat power of the gas boiler unit is H _GB The volume of natural gas consumed by the unit; j represents the heating value per unit volume of the natural gas.

As a preferred solution, inputting the argument of the plant planning optimization model as a boundary condition into the operation control optimization model may be specifically expressed as:

wherein k is _i,ORC 、k _i,EHP 、k _i,HE And k _i,AC For the lower limit coefficient of operation, the lower limit coefficient of operation power and the equipment planning capacity of the organic Rankine cycle power generation unit, the electric heating pump unit, the direct heat supply unit of the heat exchanger and the absorption refrigeration unit are respectively represented; mu (mu) _i,ORC And (3) a climbing rate coefficient of the organic Rankine cycle power generation unit is represented as a proportionality coefficient between equipment planning capacity and a maximum climbing rate of the organic Rankine cycle power generation unit.

Preferably, the objective function expression of the equipment operation control optimization model is:

in PrE _t Representing the electricity price of electricity purchased from a power grid by the steel plant in the t-th period; prH _t The heat energy representing the t time period is the economic benefit brought by the steel plant, namely equivalent to the natural gas cost saved by waste heat recovery for the gas boiler unit; prC (PrC) _t The economic benefit brought by the cold energy of one unit in the t-th period for the steel plant is equivalent to the electricity cost saved by waste heat recovery for the electric refrigerating unit; t represents an optimization period; Δt represents a unit scheduling time.

As a preferred scheme, the objective function expression of the equipment operation control optimization model is simplified and arranged based on the operation variable expressions of the organic rankine cycle power generation unit, the electric heat pump unit, the heat exchanger direct heat supply unit, the absorption refrigeration unit, the electric refrigeration unit and the gas boiler unit, and the objective function expression after the simplified and arranged is as follows:

Wherein PrG _t Representing the price of the iron and steel plant purchasing a unit volume of natural gas from a natural gas network during the t-th time period.

Preferably, the constraint conditions in the operation control optimization model further include:

climbing power constraint of the organic Rankine cycle power generation unit;

the thermal power constraint of the waste heat source can be expressed as:

0≤Q _i,1,t +Q _i,2,t +Q _i,3,t +Q _i,4,t ≤Q _i,max,t ，

in which Q _i,max,t Representing the maximum waste heat power available in the ith waste heat source;

the output power constraint of the waste heat recovery device unit may be expressed as:

the climbing power constraint of the organic Rankine cycle power generation unit can be expressed as:

as a preferred solution, the controllable quantity in the equipment planning optimization model includes the number of equipment planned for the waste heat recovery equipment unit; the uncontrollable quantity in the equipment planning optimization model comprises: the construction cost of the waste heat recovery equipment unit, the upper limit of the number of allowable construction of the waste heat recovery equipment unit and the depreciation coefficient; and the optimal operation condition of the waste heat recovery system is determined by the equipment operation control optimization model.

As a preferable scheme, the controllable operation parameters of the equipment in the waste heat recovery system are independent variables of the equipment operation control optimization model; the uncontrollable quantity of the waste heat recovery system comprises: the inherent parameters of the efficiency coefficient, the energy efficiency coefficient, the electricity consumption coefficient and the local resistance coefficient of the waste heat recovery equipment unit, the flow velocity, the density and the volume flow of the fluid in the pipeline, the capacity of a single waste heat recovery equipment unit and the planned equipment quantity, and the maximum waste heat power available for each waste heat source; the operation condition of the electric power additionally consumed by the fan and the pump unit is jointly determined by controllable operation parameters of the equipment and uncontrollable quantity of the waste heat recovery system, and the controllable operation parameters of each group of equipment determine the operation condition of the waste heat recovery system.

As a preferred scheme, the optimizing the system structure model of the waste heat recovery system of the steel plant according to the equipment planning optimizing model and the equipment operation control optimizing model to obtain an optimizing result, specifically comprises the following steps:

and the equipment planning optimization model optimizes the waste heat recovery equipment unit of the system structure model to obtain an optimal capacity plan of the waste heat recovery equipment unit, and controls the waste heat recovery equipment unit according to the equipment operation control optimization model to obtain the maximum economic benefit of equipment operation of the waste heat recovery equipment unit.

Compared with the prior art, the optimizing method of the waste heat recovery system of the steel plant disclosed by the embodiment of the invention optimizes the system structure model of the waste heat recovery system of the steel plant according to the equipment planning optimizing model and the equipment operation control optimizing model by establishing the equipment planning optimizing model and the equipment operation control optimizing model, and obtains an optimizing result to control the operation of the waste heat recovery system of the steel plant so as to obtain the maximum economic benefit of low-temperature waste heat recovery of the steel plant. Therefore, the embodiment of the invention can simultaneously consider the economic benefit influence of peak-valley electricity price and natural gas price on waste heat recovery, build the models of system components such as an organic Rankine cycle unit, an electric heat pump unit, a heat exchanger direct heat supply unit, an absorption refrigeration unit, an electric refrigeration unit, a gas boiler and the like in the waste heat recovery system of the steel plant, build the equipment optimal planning and operation control nested optimization model of the waste heat recovery system of the steel plant, finish the constant volume of equipment in the waste heat recovery system and control the operation state of the waste heat recovery equipment according to the optimization result of the model, so that the low-temperature waste heat recovery of the steel plant obtains the maximum economic benefit.

Drawings

Fig. 1 is a schematic flow chart of an optimization method of a waste heat recovery system of a steel plant according to an embodiment of the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that the terms "comprises" and "comprising," along with any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed or inherent to such process, method, article, or apparatus, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Referring to fig. 1, fig. 1 is a flow chart of an optimization method of a waste heat recovery system of a steel plant according to an embodiment of the present invention, where the optimization method of the waste heat recovery system of the steel plant includes steps S11 to S13:

S11: establishing an equipment planning optimization model and an equipment operation control optimization model;

s, 2: optimizing a system structure model of the waste heat recovery system of the steel plant according to the equipment planning optimization model and the equipment operation control optimization model to obtain an optimization result;

s13: controlling the operation of the waste heat recovery system of the steel plant based on the optimization result so as to obtain the maximum economic benefit of low-temperature waste heat recovery of the steel plant;

the system structure model comprises a waste heat recovery equipment unit, an electric refrigeration unit, a gas boiler unit, a fan and pump unit and a bus; the waste heat recovery equipment unit comprises one or more of an organic Rankine cycle power generation unit, an electric heating pump unit, a heat exchanger direct heat supply unit and an absorption refrigeration unit; the bus bars comprise an electric bus bar, a hot bus bar and a cold bus bar;

the objective function of the equipment planning optimization model is the difference between the total positive benefit and the total negative benefit of the system structure model, wherein the total positive benefit is the economic value of all energy sources produced by the waste heat recovery equipment, and the total negative benefit comprises the depreciation cost and all energy utilization cost of the waste heat recovery equipment unit; the independent variable of the equipment planning optimization model is the construction quantity of the waste heat recovery equipment units; the constraint condition of the equipment planning optimization model is the construction quantity constraint of the waste heat recovery equipment units;

The objective function of the equipment operation control optimization model is the difference between positive gain and negative gain of the system structure model, wherein the positive gain is the economic value of energy produced by the waste heat recovery equipment in one working day, and the negative gain is the energy cost of the waste heat recovery equipment unit in the one working day; the independent variables of the equipment operation control optimization model are the electric power output by the organic Rankine cycle power generation unit in each period, the thermal power output by the electric heating pump unit in each period, the thermal power output by the heat exchanger direct heat supply unit in each period and the cold power output by the absorption refrigeration unit in each period; the constraint condition of the equipment operation control optimization model is the output power constraint of the waste heat recovery equipment unit and the thermal power constraint of the waste heat source.

The system structure model comprises a waste heat recovery device unit, an electric refrigeration unit, a gas boiler unit, a fan and pump unit, an electric load, a heat load, a cold load, an electric bus, a heat bus and a cold bus. The waste heat energy of the system is derived from a waste heat source, and the natural gas is derived from a natural gas pipeline. The number of waste heat sources may be one or more. The number of the waste heat recovery equipment units is equal to that of the waste heat sources. Each waste heat recovery equipment unit can contain one or more of an organic Rankine cycle power generation unit, an electric heating pump unit, a heat exchanger direct heat supply unit and an absorption refrigeration unit, and can also not contain any equipment.

The waste heat source is connected with the waste heat recovery equipment unit; if an organic Rankine cycle power generation unit exists, the device is connected with the waste heat source and the electric bus; if an electric heating pump unit exists, the equipment is connected with the waste heat source, the electric bus and the heat bus; if a heat exchanger direct heating unit exists, the equipment is connected with the waste heat source and the thermal bus; if an absorption refrigeration unit exists, the equipment is connected with the waste heat source, the electric bus and the cold bus; the electric refrigerating unit is connected with the electric bus and the cold bus; the natural gas pipeline is connected with the gas boiler unit; the gas boiler unit is connected with the thermal bus; the fan and the pump unit are connected with the electric bus; the electric load is connected with the electric bus; the thermal load is connected with the thermal bus; the cold load is connected with the cold bus.

For example, the objective function of the equipment planning optimization model is to maximize the economic benefit brought by waste heat recovery within the service life of the equipment. The economic benefit is determined by three parts, wherein the depreciation cost of the equipment is negative benefit, the additionally increased energy consumption cost of the waste heat recovery equipment is negative benefit, and the economic value contained in the energy produced by the waste heat recovery equipment is positive benefit. The independent variables are the number of organic Rankine cycle power generation units, the number of electric heating pump units, the number of direct heat supply units of the heat exchanger and the number of absorption refrigeration units; the constraint conditions are as follows: the method comprises the following steps of restraining the number of the organic Rankine cycle power generation units, restraining the number of the electric heating pump units, restraining the number of the direct heat supply units of the heat exchanger and restraining the number of the absorption refrigeration units.

For example, the objective function of the plant operation control optimization model is to maximize the economic benefit of operating the waste heat recovery plant during a typical workday. The economic benefit is determined by the two parts together, the additional energy consumption cost of the waste heat recovery equipment is negative benefit, and the economic value contained in the energy produced by the waste heat recovery equipment is positive benefit. The independent variables of the operation control optimization model are the electric power output by the organic Rankine cycle power generation unit in each period, the thermal power output by the electric heat pump unit in each period, the thermal power output by the heat exchanger in each period and the cold power output by the absorption refrigeration unit in each period; constraint conditions of the optimization model are as follows: the system comprises an organic Rankine cycle power generation unit, an electric heating pump unit, a heat exchanger direct heat supply unit, an absorption refrigeration unit and a waste heat source.

The electric energy between the organic rankine cycle power generation unit and the electric bus can flow in both directions, namely when the electric power output by the organic rankine cycle power generation unit is greater than the electric power consumed by the operation of the organic rankine cycle power generation unit, the electric energy flows from the organic rankine cycle power generation unit to the electric bus, and when the electric power output by the organic rankine cycle power generation unit is less than the electric power consumed by the operation of the organic rankine cycle power generation unit, the electric energy flows from the electric bus to the organic rankine cycle power generation unit; the electric energy between the electric heating pump unit and the electric bus can only flow unidirectionally, namely, the electric energy flows from the electric bus to the electric heating pump unit; the electric energy between the absorption refrigeration unit and the electric bus can only flow unidirectionally, namely, the electric energy flows from the electric bus to the absorption refrigeration unit; the electric energy between the fan and the pump unit and the electric bus can only flow unidirectionally, namely, the electric energy flows from the electric bus to the fan and the pump unit; the electrical energy between the electrical load and the electrical bus can only flow in one direction, i.e. from the electrical bus to the electrical load.

The heat energy between the gas boiler unit and the thermal bus can only flow unidirectionally, namely, flows from the gas boiler unit to the thermal bus; the heat energy between the electric heating pump unit and the thermal bus can only flow unidirectionally, namely, flows from the electric heating pump unit to the thermal bus; the heat energy between the direct heat supply unit of the heat exchanger and the thermal bus can only flow unidirectionally, namely flows from the direct heat supply unit of the heat exchanger to the thermal bus; the heat energy between the heat load and the heat bus can only flow unidirectionally, namely, the heat energy flows from the heat bus to the heat load.

The cold energy between the absorption refrigeration unit and the cold bus can only flow unidirectionally, namely flows from the absorption refrigeration unit to the cold bus; the cold energy between the electric refrigerating unit and the cold bus can only flow unidirectionally, namely flows from the electric refrigerating unit to the cold bus; the cold energy between the cold load and the cold bus can only flow unidirectionally, namely, the cold energy flows from the cold bus to the cold load.

The input of the organic Rankine cycle power generation unit is waste heat energy and electric energy, and the output is electric energy; the input of the electric heat pump unit is waste heat energy and electric energy, and the output is heat energy; the heat exchanger directly supplies heat to the heat supply unit, and the heat exchanger directly supplies heat to the heat supply unit; the input of the absorption refrigeration unit is waste heat energy and electric energy, and the output is cold energy; the input of the electric refrigerating unit is electric energy, and the output is cold energy; the input of the gas boiler unit is natural gas, and the output is heat energy.

The energy requirement of the self electric load of the steel plant can only be met by the organic Rankine cycle power generation unit and the power grid; the energy requirement of the heat load can only be met by the gas boiler unit, the electric heating pump unit and the heat exchanger direct heat supply unit; the energy requirement of the cold load can only be met by absorption refrigeration units and electric refrigeration units. The energy requirements of the electric load, the heat load and the cold load of the steel plant are great, namely, the energy generated by waste heat recovery can be completely absorbed by the steel plant. The net output energy of the waste heat recovery device can reduce the natural gas and electrical energy required for the operation of the steel plant.

The waste heat energy is contained in the fluid such as flue gas or circulating cooling water, the fluid is provided with pressure by the fan and the pump unit and flows in the pipeline, and the waste heat recovery equipment unit acquires the waste heat energy by adding the heat exchange component in the pipeline. The addition of the heat exchange component increases the pressure loss of the pipeline, so that the fan and the pump unit consume more electric energy to provide larger pressure for the fluid in order to ensure that the flow rate of the fluid is kept unchanged, namely the waste heat recovery equipment unit additionally increases the energy consumption cost of the fan and the pump unit. The quantity of the devices in the waste heat recovery device unit is determined by the independent variable of the device planning optimization model, and when a certain value of the independent variable is 0, the waste heat recovery device unit does not contain corresponding devices.

Specifically, the expression of the equipment planning optimization model is:

Benefit _opt ＝Of(b _i,j ,Φ)，

where obj_1 (b) _i,j ) Representing an objective function of the equipment planning optimization model, wherein i is the number of the waste heat source; j is the number of the waste heat recovery equipment; b _i,j 、Λ _i,j And lambda (lambda) _i,j Respectively representing the planning quantity of waste heat recovery equipment with the number j in the ith waste heat source, the capacity of a single waste heat recovery equipment and the unit construction cost; benefit _opt And Cost _con Respectively representing the maximum net economic benefit and the one-time construction cost of the operation of the waste heat recovery system under the given planning condition of the waste heat recovery equipment; alpha represents a depreciation coefficient; n represents the quantity of low-temperature waste heat sources with recovery potential in the steel plant; of () represents an operation control optimization function whose output is the maximum economic benefit Of the operation Of the waste heat recovery system; Φ represents other operating parameters; b _i,j,max Representing the upper limit of the allowable construction quantity of 4 kinds of waste heat recovery equipment, if the (r) waste heat source cannot perform waste heat recovery through the (m) waste heat recovery equipment, b is present _r,m,max ＝0。

Specifically, when calculating the electric power additionally consumed by the fan and the pump unit in a certain waste heat source, firstly, pressure loss caused by various devices needs to be calculated, then, the influence of the addition of the devices on the electric power of the fan and the pump unit is calculated, and finally, the electric power influence effects caused by all the devices are overlapped, wherein the specific mathematical deduction process is as follows:

Wherein Δp _i,j,t And P _i,j,t,add Respectively representing the pressure loss caused by the equipment numbered j in the ith waste heat source in the t time period and the electric power which is additionally consumed by the fan and pump unit for compensating the pressure loss; zeta type _i,t Representing the local resistance coefficient of a j-numbered device in the ith waste heat source; v _i,t 、ρ _i,t And q _i,t Respectively representing the flow rate, density and volume flow rate of the fluid in the ith waste heat source at the t-th period; p (P) _i,t,add Representing the electric power additionally consumed by the fan and the pump unit for compensating the pressure loss caused by all waste heat recovery devices in the ith waste heat source in the t-th period; η (eta) _i,dy Representing the efficiency of the fan and pump unit in the ith waste heat source.

More specifically, the operational variable expression of the organic rankine cycle power generation unit is:

wherein P is _i,ORC,t And Q _i,ORC,t Respectively representing the output electric power of the organic Rankine cycle power generation unit in the ith waste heat source in the t period and the waste heat power absorbed from the waste heat source; epsilon _i,ORC 、P _i,ORC,min 、P _i,ORC,max And DeltaP _i,ORC,max Respectively represent the organic light source in the ith waste heat sourceAn efficiency coefficient of the Kenside cycle power generation unit, a minimum value and a maximum value of the output electric power, and a maximum climbing rate; p (P) _i,ORC,t+1 Representing the output electric power of the organic Rankine cycle power generation unit in the ith waste heat source at the (t+1) th period;

The operation variable expression of the electric heating pump unit is as follows:

wherein H is _i,EHP,t 、P _i,EHP,t And Q _i,EHP,t Respectively representing the output thermal power, the input electrical power and the waste heat power absorbed from the waste heat source of the electric heating pump unit in the ith waste heat source in the t period; COP of _i,EHP 、H _i,EHP,min And H _i,EHP,max Respectively representing the energy efficiency coefficient of the electric heating pump unit, the minimum value and the maximum value of the output heat power in the ith waste heat source;

the operation variable expression of the direct heat supply unit of the heat exchanger is as follows:

wherein H is _i,HE,t And Q _i,HE,t Respectively representing the output heat power of the heat exchanger direct heating unit in the ith waste heat source in the t period and the waste heat power absorbed from the waste heat source; η (eta) _i,HE 、H _i,HE,min And H _i,HE,max Respectively representing the efficiency coefficient, the minimum value and the maximum value of the output heat power of the direct heat supply unit of the heat exchanger in the ith waste heat source;

the operation variable expression of the absorption refrigeration unit is as follows:

wherein C is _i,AC,t 、Q _i,AC,t And P _i,AC,t Respectively represent the ith remainderThe absorption refrigeration unit in the heat source outputs cold power in the t time period, waste heat power absorbed from the waste heat source and electric power consumed by the working medium pump in operation; COP of _i,AC 、ε _i,AC 、C _i,AC,min And C _i,AC,max Respectively representing the energy efficiency coefficient, the electricity consumption coefficient and the minimum value and the maximum value of the output cold power of the absorption refrigeration unit in the ith waste heat source;

The operation variable expression of the electric refrigeration unit is as follows:

C _EC ＝COP _EC ·P _EC ，

wherein C is _EC And COP _EC The output cold power and the energy efficiency coefficient of the electric refrigerating unit are respectively; p (P) _EC Indicating that when the output cold power of the electric refrigeration unit is C _EC The electrical power consumed by the unit at that time;

the operation variable expression of the gas boiler unit is as follows:

H _GB ＝η _GB ·V _gas ·J，

wherein H is _GB And eta _GB Respectively outputting heat power and efficiency coefficient of the gas boiler unit; v (V) _GB Indicating that when the output heat power of the gas boiler unit is H _GB The volume of natural gas consumed by the unit; j represents the heating value per unit volume of the natural gas.

It should be noted that two parts of the objective function of the equipment planning optimization model need to be determined by the operation condition of the equipment, and the two parts are: the additional energy cost of the waste heat recovery device and the economic value contained in the energy produced by the waste heat recovery device. In the process of optimizing the planning of solving equipment, each time the value of the objective function obj_1 is calculated, the control optimization of the operation of the primary equipment is required to be solved so as to obtain the maximum economic Benefit Benefit of the operation of the waste heat recovery system _opt This relationship is referred to mathematically as nested optimization, i.e., the plant planning optimization model and the operation control optimization model together form a nested optimization model.

As a preferred embodiment, inputting the argument of the plant planning optimization model as a boundary condition into the operation control optimization model may be expressed as:

wherein k is _i,ORC 、k _i,EHP 、k _i,HE And k _i,AC For the lower limit coefficient of operation, the lower limit coefficient of operation power and the equipment planning capacity of the organic Rankine cycle power generation unit, the electric heating pump unit, the direct heat supply unit of the heat exchanger and the absorption refrigeration unit are respectively represented; mu (mu) _i,ORC And (3) a climbing rate coefficient of the organic Rankine cycle power generation unit is represented as a proportionality coefficient between equipment planning capacity and a maximum climbing rate of the organic Rankine cycle power generation unit.

Specifically, the objective function expression of the equipment operation control optimization model is as follows:

in PrE _t Representing the electricity price of electricity purchased from a power grid by the steel plant in the t-th period; prH _t The heat energy representing the t time period is the economic benefit brought by the steel plant, namely equivalent to the natural gas cost saved by waste heat recovery for the gas boiler unit; prC (PrC) _t The economic benefit brought by the cold energy of one unit in the t-th period for the steel plant is equivalent to the electricity cost saved by waste heat recovery for the electric refrigerating unit; t represents an optimization period; Δt represents a unit scheduling time.

Further, based on the operation variable expressions of the organic Rankine cycle power generation unit, the electric heat pump unit, the heat exchanger direct heat supply unit, the absorption refrigeration unit, the electric refrigeration unit and the gas boiler unit, the objective function expression of the equipment operation control optimization model is simplified and tidied, and the objective function expression after the simplification and tidying is as follows:

wherein PrG _t Representing the price of the iron and steel plant purchasing a unit volume of natural gas from a natural gas network during the t-th time period.

As a preferred embodiment, the constraint conditions in the operation control optimization model further include:

climbing power constraint of the organic Rankine cycle power generation unit;

the thermal power constraint of the waste heat source can be expressed as:

0≤Q _i,1,t +Q _i,2,t +Q _i,3,t +Q _i,4,t ≤Q _i,max,t ，

in which Q _i,max,t Representing the maximum waste heat power available in the ith waste heat source;

the output power constraint of the waste heat recovery device unit may be expressed as:

the climbing power constraint of the organic Rankine cycle power generation unit can be expressed as:

the heat power constraint of the waste heat source ensures that the heat power absorbed by the waste heat recovery equipment from the waste heat source does not exceed the maximum upper limit, and the conditions that the flue gas temperature is lower than the acid dew point, the service life of the equipment is reduced and the like are avoided; the output power constraint of various waste heat recovery devices ensures that the waste heat recovery devices operate in safe upper and lower boundaries; the climbing power constraint of the organic Rankine cycle power generation unit ensures that the safe upper and lower boundaries of the organic Rankine cycle power generation unit are not exceeded when the output power of the organic Rankine cycle power generation unit is increased or reduced.

Specifically, the controllable quantity in the equipment planning optimization model includes the number of the equipment planned for the waste heat recovery equipment unit; the uncontrollable quantity in the equipment planning optimization model comprises: the construction cost of the waste heat recovery equipment unit, the upper limit of the number of allowable construction of the waste heat recovery equipment unit and the depreciation coefficient; and the optimal operation condition of the waste heat recovery system is determined by the equipment operation control optimization model.

By way of example, the controllable quantities in the planning optimization include the number of devices for the organic Rankine cycle power generation unit planning, the number of devices for the electric heat pump unit planning, the number of devices for the heat exchanger direct heating unit planning, and the number of devices for the absorption refrigeration unit planning. Other uncontrollable quantities include: the construction cost of various devices, the upper limit of the number of the allowable construction of various devices and the depreciation coefficient. The optimal operation condition of the waste heat recovery system needs to be determined by the equipment operation control optimization model described in the point 3. After the planning condition of the waste heat recovery equipment is determined, the depreciation cost of the equipment can be uniquely determined, and then the operation control optimization is performed on the waste heat recovery system, the additionally increased energy cost of the waste heat recovery equipment and the economic value contained in the produced energy source can be uniquely determined, and the three factors determine the economic benefit of waste heat recovery of the iron and steel plant. The number of the devices of the organic Rankine cycle power generation unit, the electric heating pump unit, the heat exchanger direct heating unit and the absorption refrigeration unit in the factory is planned, so that the net economic benefit which can be obtained in the waste heat recovery system of the steel plant can be changed.

Specifically, the controllable operation parameters of the equipment in the waste heat recovery system are independent variables of the equipment operation control optimization model; the uncontrollable quantity of the waste heat recovery system comprises: the inherent parameters of the efficiency coefficient, the energy efficiency coefficient, the electricity consumption coefficient and the local resistance coefficient of the waste heat recovery equipment unit, the flow velocity, the density and the volume flow of the fluid in the pipeline, the capacity of a single waste heat recovery equipment unit and the planned equipment quantity, and the maximum waste heat power available for each waste heat source; the operation condition of the electric power additionally consumed by the fan and the pump unit is jointly determined by controllable operation parameters of the equipment and uncontrollable quantity of the waste heat recovery system, and the controllable operation parameters of each group of equipment determine the operation condition of the waste heat recovery system.

It should be noted that the objective function value of the net economic benefit obtained by the iron and steel plant when the waste heat recovery system is operated, and the controllable operation parameter of the equipment corresponds to the independent variable. Before optimizing the planning and optimizing model of the waste heat recovery equipment, the construction price of the single waste heat recovery equipment, the upper limit of the planning quantity of the waste heat recovery equipment and the like are required to be acquired. Then, in order to maximize the net economic benefit obtained in the waste heat recovery system of the steel plant, each optimizing needs to optimize the operation control model of the waste heat recovery equipment to obtain at least one group of independent variables which can make the objective function obtain the maximum value. And finally, respectively determining the capacities of the mechanical Rankine cycle power generation unit, the electric heating pump unit, the heat exchanger direct heating unit and the absorption refrigeration unit equipment in each waste heat source according to the obtained independent variables, wherein the net economic benefit of the iron and steel plant in the waste heat recovery system reaches the maximum value under the equipment planning method.

Exemplary, device-controllable operating parameters in the system include: the electric power output by the organic Rankine cycle power generation unit in each period, the thermal power output by the electric heating pump unit in each period, the thermal power output by the heat exchanger direct heat supply unit in each period and the cold power output by the absorption refrigeration unit in each period. Other uncontrollable quantities include: the system comprises the inherent parameters of the equipment such as efficiency coefficient, energy efficiency coefficient, electricity consumption coefficient, local resistance coefficient and the like, the flow rate, density and volume flow of fluid in a pipeline, the capacity of a single waste heat recovery device, the number of device plans and the maximum waste heat power available for each waste heat source. The net output power of the waste heat system to the electric bus, the hot bus and the cold bus in each period, the additional consumed electric power of the fan and the pump unit and other operation conditions are determined by the controllable operation parameters of the equipment and other uncontrollable variables, and the controllable operation parameters of each group of equipment determine the operation condition of the system. The output power of the organic Rankine cycle power generation unit, the electric heating pump unit, the direct heat supply unit of the heat exchanger and the absorption refrigeration unit in the factory is reasonably controlled, so that the net economic benefit obtained when the waste heat recovery system of the steel factory is operated can be changed.

Specifically, the step S12 specifically includes:

and the equipment planning optimization model optimizes the waste heat recovery equipment unit of the system structure model to obtain an optimal capacity plan of the waste heat recovery equipment unit, and controls the waste heat recovery equipment unit according to the equipment operation control optimization model to obtain the maximum economic benefit of equipment operation of the waste heat recovery equipment unit.

It should be noted that the objective function value of the net economic benefit obtained by the iron and steel plant when the waste heat recovery system is operated, and the controllable operation parameter of the equipment corresponds to the independent variable. Before optimizing the operation control optimization model of the waste heat recovery device, the capacity of a single waste heat recovery device, the planned number of the waste heat recovery devices, the power grid electricity price, the natural gas price, the related parameters of various devices, the physical properties of the fluid in the waste heat source and the like need to be acquired. In order to maximize the net economic benefit obtained by the iron and steel plant when the waste heat recovery system is in operation, the objective function needs to be optimally solved to obtain at least one set of independent variables which can enable the objective function to be maximized. And finally, respectively controlling the operation states of the organic Rankine cycle power generation unit, the electric heating pump unit, the heat exchanger direct heat supply unit and the absorption refrigeration unit in each period according to the obtained independent variables, and under the control method, the net economic benefit obtained when the waste heat recovery system of the steel plant is operated can be maximized.

Taking a steel plant containing two flue gas waste heat sources and one circulating cooling water waste heat source as an example, the following gives example data information required in the optimization process of the invention:

examples of the plant include organic Rankine cycle power generation equipment, electric heating pump equipment, heat exchanger direct heating equipment, absorption refrigeration equipment, electric refrigeration equipment, gas boilers, fans, pumps, buses of three energy sources, loads and other facilities; excellent (excellent)The period t=24 h; unit scheduling timePeak Gu Dianjia is set as the business peak-to-valley electricity price of a certain large city in China, and the peak-to-valley electricity price curve is shown in fig. 1; the price of natural gas is 3 yuan/Nm ³ . Wherein, the basic parameters of various waste heat recovery devices are shown in table 1; basic parameters of the electric refrigeration equipment and the gas boiler are shown in table 2; the basic parameters of the fluid in each waste heat source are shown in table 3; the upper limit of the number of allowable construction of various waste heat recovery devices in each waste heat source is shown in table 4.

Table 1 basic parameters of various waste heat recovery apparatus

Table 2 basic parameters of electric refrigeration apparatus and gas boiler

Coefficient of energy efficiency COP of electric refrigerating equipment EC	3
		Efficiency coefficient eta of gas boiler GB	0.8

TABLE 3 basic parameters of fluids in waste heat sources

TABLE 4 upper limit on the number of allowable constructions of various waste heat recovery devices in various waste heat sources

In summary, according to the optimization method for the waste heat recovery system of the steel plant disclosed by the embodiment of the invention, the equipment planning optimization model and the equipment operation control optimization model are established, and the system structure model of the waste heat recovery system of the steel plant is optimized according to the equipment planning optimization model and the equipment operation control optimization model, so that the operation of the waste heat recovery system of the steel plant is controlled by the optimized result, and the maximum economic benefit is obtained for the low-temperature waste heat recovery of the steel plant. Therefore, the embodiment of the invention can simultaneously consider the economic benefit influence of peak-valley electricity price and natural gas price on waste heat recovery, build the models of system components such as an organic Rankine cycle unit, an electric heat pump unit, a heat exchanger direct heat supply unit, an absorption refrigeration unit, an electric refrigeration unit, a gas boiler and the like in the waste heat recovery system of the steel plant, build the equipment optimal planning and operation control nested optimization model of the waste heat recovery system of the steel plant, finish the constant volume of equipment in the waste heat recovery system and control the operation state of the waste heat recovery equipment according to the optimization result of the model, so that the low-temperature waste heat recovery of the steel plant obtains the maximum economic benefit.

While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles of the invention, such changes and modifications are also intended to be within the scope of the invention.

Claims (10)

1. An optimization method of a waste heat recovery system of a steel plant is characterized by comprising the following steps:

establishing an equipment planning optimization model and an equipment operation control optimization model;

optimizing a system structure model of the waste heat recovery system of the steel plant according to the equipment planning optimization model and the equipment operation control optimization model to obtain an optimization result;

controlling the operation of the waste heat recovery system of the steel plant based on the optimization result so as to obtain the maximum economic benefit of low-temperature waste heat recovery of the steel plant;

the system structure model comprises a waste heat recovery equipment unit, an electric refrigeration unit, a gas boiler unit, a fan and pump unit and a bus; the waste heat recovery equipment unit comprises one or more of an organic Rankine cycle power generation unit, an electric heating pump unit, a heat exchanger direct heat supply unit and an absorption refrigeration unit; the bus bars comprise an electric bus bar, a hot bus bar and a cold bus bar;

The objective function of the equipment planning optimization model is the difference between the total positive benefit and the total negative benefit of the system structure model, wherein the total positive benefit is the economic value of all energy sources produced by the waste heat recovery equipment, and the total negative benefit comprises the depreciation cost and all energy utilization cost of the waste heat recovery equipment unit; the independent variable of the equipment planning optimization model is the construction quantity of the waste heat recovery equipment units; the constraint condition of the equipment planning optimization model is the construction quantity constraint of the waste heat recovery equipment units;

the objective function of the equipment operation control optimization model is the difference between positive gain and negative gain of the system structure model, wherein the positive gain is the economic value of energy produced by the waste heat recovery equipment in one working day, and the negative gain is the energy cost of the waste heat recovery equipment unit in the one working day; the independent variables of the equipment operation control optimization model are the electric power output by the organic Rankine cycle power generation unit in each period, the thermal power output by the electric heating pump unit in each period, the thermal power output by the heat exchanger direct heat supply unit in each period and the cold power output by the absorption refrigeration unit in each period; the constraint condition of the equipment operation control optimization model is the output power constraint of the waste heat recovery equipment unit and the thermal power constraint of the waste heat source.

2. The optimizing method of the waste heat recovery system of steel plant according to claim 1, wherein the expression of the equipment planning optimizing model is:

Benefit _opt ＝Of(b _i,j ,Φ)，

where obj_1 (b) _i,j ) Representing an objective function of the equipment planning optimization model, wherein i is the number of the waste heat source; j is the number of the waste heat recovery equipment; b _i,j 、Λ _i,j And lambda (lambda) _i,j Respectively representing the planning quantity of waste heat recovery equipment with the number j in the ith waste heat source, the capacity of a single waste heat recovery equipment and the unit construction cost; benefit _opt And Cost _con Respectively representing the maximum net economic benefit and the one-time construction cost of the operation of the waste heat recovery system under the given planning condition of the waste heat recovery equipment; alpha represents a depreciation coefficient; n represents the quantity of low-temperature waste heat sources with recovery potential in the steel plant; of () represents an operation control optimization function whose output is the maximum economic benefit Of the operation Of the waste heat recovery system; Φ represents other operating parameters; b _i,j,max Representing the upper limit of the allowable construction quantity of 4 kinds of waste heat recovery equipment, if the (r) waste heat source cannot perform waste heat recovery through the (m) waste heat recovery equipment, b is present _r,m,max ＝0。

3. The optimizing method of the waste heat recovery system of steel plant according to claim 1, wherein the operation variable expression of the organic rankine cycle power generation unit is:

Wherein P is _i,ORC,t And Q _i,ORC,t Respectively representing the output electric power of the organic Rankine cycle power generation unit in the ith waste heat source in the t period and the waste heat power absorbed from the waste heat source; epsilon _i,ORC 、P _i,ORC,min 、P _i,ORC,max And DeltaP _i,ORC,max Respectively representing the efficiency coefficient of the organic Rankine cycle power generation unit, the minimum value and the maximum value of the output electric power and the maximum climbing rate in the ith waste heat source; p (P) _i,ORC,t+1 Representing the output electric power of the organic Rankine cycle power generation unit in the ith waste heat source at the (t+1) th period;

the operation variable expression of the electric heating pump unit is as follows:

wherein H is _i,EHP,t 、P _i,EHP,t And Q _i,EHP,t Respectively representing the output thermal power, the input electrical power and the waste heat power absorbed from the waste heat source of the electric heating pump unit in the ith waste heat source in the t period; COP of _i,EHP 、H _i,EHP,min And H _i,EHP,max Respectively representing the energy efficiency coefficient of the electric heating pump unit, the minimum value and the maximum value of the output heat power in the ith waste heat source;

the operation variable expression of the direct heat supply unit of the heat exchanger is as follows:

wherein H is _i,HE,t And Q _i,HE,t Respectively representing the output heat power of the heat exchanger direct heating unit in the ith waste heat source in the t period and the waste heat power absorbed from the waste heat source; η (eta) _i,HE 、H _i,HE,min And H _i,HE,max Respectively representing the efficiency coefficient, the minimum value and the maximum value of the output heat power of the direct heat supply unit of the heat exchanger in the ith waste heat source;

the operation variable expression of the absorption refrigeration unit is as follows:

wherein C is _i,AC,t 、Q _i,AC,t And P _i,AC,t Respectively representing the output cold power of the absorption refrigeration unit in the ith waste heat source in the t period, the waste heat power absorbed from the waste heat source and the electric power consumed by the working medium pump in operation; COP of _i,AC 、ε _i,AC 、C _i,AC,min And C _i,AC,max Respectively representing the energy efficiency coefficient, the electricity consumption coefficient and the minimum value and the maximum value of the output cold power of the absorption refrigeration unit in the ith waste heat source;

the operation variable expression of the electric refrigeration unit is as follows:

C _EC ＝COP _EC ·P _EC ，

wherein C is _EC And COP _EC The output cold power and the energy efficiency coefficient of the electric refrigerating unit are respectively; p (P) _EC Indicating that when the output cold power of the electric refrigeration unit is C _EC The electrical power consumed by the unit at that time;

the operation variable expression of the gas boiler unit is as follows:

H _GB ＝η _GB ·V _gas ·J，

wherein H is _GB And eta _GB Respectively outputting heat power and efficiency coefficient of the gas boiler unit; v (V) _GB Indicating that when the output heat power of the gas boiler unit is H _GB The volume of natural gas consumed by the unit; j represents the heating value per unit volume of the natural gas.

4. The optimizing method of the waste heat recovery system of steel plant according to claim 1, wherein inputting the argument of the plant planning optimizing model as a boundary condition into the operation control optimizing model can be expressed as:

wherein k is _i,ORC 、k _i,EHP 、k _i,HE And k _i,AC For the lower limit coefficient of operation, the lower limit coefficient of operation power and the equipment planning capacity of the organic Rankine cycle power generation unit, the electric heating pump unit, the direct heat supply unit of the heat exchanger and the absorption refrigeration unit are respectively represented; mu (mu) _i,ORC And (3) a climbing rate coefficient of the organic Rankine cycle power generation unit is represented as a proportionality coefficient between equipment planning capacity and a maximum climbing rate of the organic Rankine cycle power generation unit.

5. The optimizing method of waste heat recovery system of steel plant according to claim 1, wherein the objective function expression of the plant operation control optimizing model is:

in PrE _t Representing the electricity price of electricity purchased from a power grid by the steel plant in the t-th period; prH _t The heat energy representing the t time period is the economic benefit brought by the steel plant, namely equivalent to the natural gas cost saved by waste heat recovery for the gas boiler unit; prC (PrC) _t The economic benefit brought by the cold energy of one unit in the t-th period for the steel plant is equivalent to the electricity cost saved by waste heat recovery for the electric refrigerating unit; t represents an optimization period; Δt represents a unit scheduling time.

6. The optimizing method of the waste heat recovery system of the steel plant according to claim 1, wherein the objective function expression of the plant operation control optimizing model is simplified and arranged based on the operation variable expressions of the organic rankine cycle power generation unit, the electric heat pump unit, the heat exchanger direct heat supply unit, the absorption refrigeration unit, the electric refrigeration unit and the gas boiler unit, and the simplified and arranged objective function expression is:

wherein PrG _t Representing the price of the iron and steel plant purchasing a unit volume of natural gas from a natural gas network during the t-th time period.

7. The optimizing method of the waste heat recovery system of steel plant according to claim 3, wherein the constraint conditions in the operation control optimizing model further include:

climbing power constraint of the organic Rankine cycle power generation unit;

the thermal power constraint of the waste heat source can be expressed as:

0≤Q _i,1,t +Q _i,2,t +Q _i,3,t +Q _i,4,t ≤Q _i,max,t ，

in which Q _i,max,t Representing the maximum waste heat power available in the ith waste heat source;

The output power constraint of the waste heat recovery device unit may be expressed as:

the climbing power constraint of the organic Rankine cycle power generation unit can be expressed as:

8. the optimizing method of a waste heat recovery system of a steel plant according to claim 1, wherein the controllable quantity in the equipment planning optimizing model includes the number of equipment planned for the waste heat recovery equipment unit; the uncontrollable quantity in the equipment planning optimization model comprises: the construction cost of the waste heat recovery equipment unit, the upper limit of the number of allowable construction of the waste heat recovery equipment unit and the depreciation coefficient; and the optimal operation condition of the waste heat recovery system is determined by the equipment operation control optimization model.

9. The optimizing method of the waste heat recovery system of the steel plant according to claim 3, wherein the controllable operation parameters of the equipment in the waste heat recovery system are independent variables of an equipment operation control optimizing model; the uncontrollable quantity of the waste heat recovery system comprises: the inherent parameters of the efficiency coefficient, the energy efficiency coefficient, the electricity consumption coefficient and the local resistance coefficient of the waste heat recovery equipment unit, the flow velocity, the density and the volume flow of the fluid in the pipeline, the capacity of a single waste heat recovery equipment unit and the planned equipment quantity, and the maximum waste heat power available for each waste heat source; the operation condition of the electric power additionally consumed by the fan and the pump unit is jointly determined by controllable operation parameters of the equipment and uncontrollable quantity of the waste heat recovery system, and the controllable operation parameters of each group of equipment determine the operation condition of the waste heat recovery system.

10. The optimizing method of the waste heat recovery system of the steel plant according to claim 1, wherein the optimizing method optimizes a system structure model of the waste heat recovery system of the steel plant according to the equipment planning optimizing model and the equipment operation control optimizing model to obtain an optimizing result, specifically:

and the equipment planning optimization model optimizes the waste heat recovery equipment unit of the system structure model to obtain an optimal capacity plan of the waste heat recovery equipment unit, and controls the waste heat recovery equipment unit according to the equipment operation control optimization model to obtain the maximum economic benefit of equipment operation of the waste heat recovery equipment unit.