CN111007718A - Method for determining optimal circulation ratio of heat exchange network provided with circulating reactor - Google Patents
Method for determining optimal circulation ratio of heat exchange network provided with circulating reactor Download PDFInfo
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Abstract
The invention discloses a method for determining an optimal circulation ratio of a heat exchange network with a circulation reactor, which comprises the following steps: extracting the inlet and outlet temperature and flow of cold heat flow in the heat exchange network to determine the heat quantity emitted by the cold heat flow, recording the heat quantity as heat load, combining all heat sources into a source composite curve, and drawing a trap composite curve in the same way; extracting parameters of the circulating reactor at least comprising inlet flow, component concentration, inlet temperature, outlet temperature and conversion rate, determining the relation between the outlet temperature of the circulating reactor and the circulation ratio according to reaction kinetics, and determining the relation between the inlet temperature of the circulating reactor, the outlet temperature of the circulating reactor and the circulation ratio according to thermodynamics; determining inlet and outlet temperatures corresponding to different circulation ratios, and determining the relationship of the heat exchange network for recovering energy when the temperature of the reactor changes; and constructing a temperature-energy-benefit-circulation ratio graph based on the variation curves of the inlet temperature, the outlet temperature, the recovered energy and the benefit of the reactor along with the circulation ratio, and determining the optimal circulation ratio.
Description
Technical Field
The invention belongs to the technical field of heat exchange integration, and particularly relates to a method for determining an optimal circulation ratio of a heat exchange network with a circulation reactor.
Background
At present, the conventional reactor and heat exchange network integration optimization is to determine the reasonable setting of the reactor based on the relative position of a composite curve of a temperature-enthalpy diagram analysis heat exchange network and a temperature-energy straight line representing the reactor. Because the reaction kinetics and thermodynamics are not considered in the method, the system optimization cannot be carried out by comprehensively considering all parameters of the reactor.
The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
Disclosure of Invention
The invention provides a method for determining the optimal circulation ratio of a heat exchange network with a circulating reactor, which can clearly and visually integrate the circulating reactor and the heat exchange network, show the relation between the energy consumption of a system and key parameters, and determine the minimum energy consumption of the system, the corresponding circulation ratio, the inlet and outlet temperature and other key parameters so as to realize better energy conservation and environmental protection. It is emphasized that the benefits referred to throughout the present invention refer to energy savings and environmental protection to maximize energy savings and environmental benefits.
The invention aims to realize the purpose by the following technical scheme, and the method for determining the optimal circulation ratio of the heat exchange network with the circulation reactor comprises the following steps:
in the first step, the inlet and outlet temperature and flow of cold heat flow in a heat exchange network are extracted to determine the heat quantity released by the cold heat flow, and the heat quantity is recorded as a heat load, wherein the hot flow to be cooled is a heat source; the method comprises the following steps that cold material flow needing to be heated is a hot trap, the initial temperature of the flow is an initial temperature, the target temperature is a final temperature, each heat source is represented by a straight line segment according to the temperature and the heat load of the heat source, the ordinate of the two end points of the heat source respectively represents the inlet temperature and the outlet temperature, the difference of the abscissa represents the heat load of the heat source, all the heat sources are combined into a source composite curve, the abscissa between every two end points of the heat source represents the sum of the heat loads of all the material flows in a temperature interval, and a trap composite curve is drawn in the same way;
in the second step, extracting parameters of the circulating reactor at least comprising inlet flow, composition concentration, inlet temperature, outlet temperature and conversion rate, determining the relation between the outlet temperature and the circulation ratio of the circulating reactor according to reaction kinetics, and determining the relation between the inlet temperature, the outlet temperature and the circulation ratio of the circulating reactor according to thermodynamics;
in the third step, determining inlet and outlet temperatures corresponding to different circulation ratios based on the relationship among the inlet temperature, the outlet temperature and the circulation ratio of the reactor in the second step, and determining the relationship among the heat exchange network recovered energy when the temperature of the reactor changes based on the source composite curve and the trap composite curve in the first step;
in the fourth step, a temperature-energy-benefit-circulation ratio graph is constructed based on the variation curves of the reactor inlet temperature, the reactor outlet temperature, the recovered energy and the benefit along with the circulation ratio, and the minimum circulation ratio when the maximum benefit is achieved, namely the optimal circulation ratio, is determined.
In the method, in the first step, the heat load of the hot stream is in a temperature relationship of Δ H — CP (T)Final temperature-TInitial temperature) Where Δ H is the heat stream heat load, CP is the heat capacity flow rate, T represents the temperature, and the subscripts indicate the final and initial temperatures, respectively.
In the method, in the first step, the inlet and outlet temperatures of the cold and hot streams in the heat exchange network, the composition and the flow rate of the cold and hot streams are extracted to determine the heat released by the cold and hot streams.
In the method, in the first step, when the temperature intervals of different heat sources overlap, the corresponding heat loads are overlapped.
In the method, in the first step, the slope of the source recombination curve is equal to the inverse of the sum of the heat capacity flow rates of all the thermal streams.
In the method, in the first step, when the minimum vertical temperature difference of the source recombination curve and the trap recombination curve reaches the preset pinch point temperature difference, the superposed part of the curves is the energy recovered by the outlet of the circulating reactor.
In the method, the energy recovered from the outlet of the circulating reactor is,
Qrecovering＝(1+β)CP2(T4-T5) Wherein Q isRecoveringFor recycling reactor outlet energy recovery β is recycle ratio, CP2Product heat capacity flow rate, T, for the output of the circulating reactor4Is the reactor outlet temperature, T5Is the exit temperature of the recycle reactor exit steam generator.
In the method, in the second step, the relationship between the circulating reactor outlet temperature and the circulation ratio is determined according to the reaction kinetics,
wherein W is the catalyst loading of the circulating reactor;
the flux of the reactant A at the inlet 0, the circulation ratio β, the conversion rate X, the pre-factor A, the activation energy E and the conversion rate T4Is the reactor outlet temperature; c is the concentration of reactant A, B and product C at inlet 0,
determining the relation between the inlet temperature and the outlet temperature of the circulating reactor and the circulation ratio according to thermodynamics,
wherein, T3Is the temperature of the recycle stream, β is the recycle ratio, T1Fresh feed at reactor inlet temperature; delta TminIs the minimum heat transfer temperature difference; CP (CP)0Is the heat capacity flow rate of the fresh feed; t is0Is the temperature of the fresh feed; CP (CP)4Is the heat capacity flow rate of the reactor outlet product.
In the third step, the relationship between the recovered energy and the circulation ratio is QRecovering＝(1+β)CP2(T4-T1-ΔTmin) Wherein Q isRecoveringFor recycling reactor outlet energy recovery β is recycle ratio, CP2Product heat capacity flow rate, T, for the output of the circulating reactor4Is the reactor outlet temperature, T1Fresh feed at reactor inlet temperature; delta TminIs the minimum heat transfer temperature difference.
In the method, the fourth step,
Compared with the prior art, the invention has the following advantages:
the invention is different from the composite curve of the matching reactor and the heat exchange network only according to the image temperature constraint and the energy balance of the existing method, the invention researches the relationship between the inlet and outlet temperature of the reactor and the circulation ratio on the basis of thermodynamics and reaction kinetics, analyzes the influence of the temperature change on the public engineering consumption of the heat exchange network on a temperature-enthalpy diagram, and draws a temperature-energy-benefit-circulation ratio image to show the change of the parameters of the axial power of the circulating material flow pump, the energy recovered from the outlet of the reactor, the system benefit and the like along with the circulation ratio; and determining the minimum circulation ratio under the maximum benefit, and the corresponding inlet and outlet temperatures of the reactor and the energy consumption of the system.
Drawings
Various other advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. Also, like parts are designated by like reference numerals throughout the drawings.
In the drawings:
FIG. 1 is a schematic illustration of the steps of a method for determining an optimal circulation ratio for a heat exchange network provided with a circulating reactor according to one embodiment of the present invention;
FIG. 2 is a schematic diagram of a recirculating reactor equipped with a method for determining an optimal circulation ratio for a heat exchange network of the recirculating reactor in accordance with one embodiment of the present invention;
FIG. 3 is a schematic diagram of a complex curve construction method for a method of determining an optimal circulation ratio for a heat exchange network with a recirculating reactor in accordance with one embodiment of the present invention;
FIG. 4 is a composite curve schematic of a method for determining an optimal circulation ratio for a heat exchange network with a recirculating reactor, according to one embodiment of the present invention;
FIG. 5 is a temperature-energy-benefit-recycle ratio schematic and an optimal recycle ratio thereof for a method for determining an optimal recycle ratio for a heat exchange network equipped with a recycle reactor according to an embodiment of the present invention.
The invention is further explained below with reference to the figures and examples.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to fig. 1 to 5. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
It should be noted that certain terms are used throughout the description and claims to refer to particular components. As one skilled in the art will appreciate, various names may be used to refer to a component. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description which follows is a preferred embodiment of the invention, but is made for the purpose of illustrating the general principles of the invention and not for the purpose of limiting the scope of the invention. The scope of the present invention is defined by the appended claims.
For the purpose of facilitating understanding of the embodiments of the present invention, the following description will be made by taking specific embodiments as examples with reference to the accompanying drawings, and the drawings are not to be construed as limiting the embodiments of the present invention.
For a better understanding, fig. 1 is a schematic representation of the steps of a method according to one embodiment of the invention, as shown in fig. 1, a method for determining an optimal circulation ratio of a heat exchange network provided with a circulating reactor comprising the steps of:
in a first step S1, the inlet and outlet temperatures and flow rates of the cold and hot flows in the heat exchange network are extracted to determine the heat quantity released by the cold and hot flows, and the heat quantity is recorded as a heat load, wherein the hot flows to be cooled are heat sources; the method comprises the following steps that cold material flow needing to be heated is a hot trap, the initial temperature of the flow is an initial temperature, the target temperature is a final temperature, each heat source is represented by a straight line segment according to the temperature and the heat load of the heat source, the ordinate of the two end points of the heat source respectively represents the inlet temperature and the outlet temperature, the difference of the abscissa represents the heat load of the heat source, all the heat sources are combined into a source composite curve, the abscissa between every two end points of the heat source represents the sum of the heat loads of all the material flows in a temperature interval, and a trap composite curve is drawn in the same way;
in a second step S2, extracting parameters of the circulating reactor at least including inlet flow, composition concentration, inlet temperature, outlet temperature and conversion rate, determining the relationship between the outlet temperature and the circulation ratio of the circulating reactor according to reaction kinetics, and determining the relationship between the inlet temperature, the outlet temperature and the circulation ratio of the circulating reactor according to thermodynamics;
in a third step S3, determining inlet and outlet temperatures corresponding to different circulation ratios based on the relationship among the inlet temperature, the outlet temperature and the circulation ratio of the reactor in the second step, and determining the relationship among the heat exchange network recovered energy when the temperature of the reactor changes based on the source composite curve and the trap composite curve in the first step;
in the fourth step S4, a temperature-energy-benefit-recycle ratio map is constructed based on the reactor inlet temperature, outlet temperature, recovered energy and benefit versus recycle ratio curves, and the minimum recycle ratio at which the maximum benefit is achieved, i.e., the optimum recycle ratio, is determined.
In a preferred embodiment of the process, in the first step S1, the heat load of the hot stream has a temperature relationship Δ H ═ CP (T) ofFinal temperature-TInitial temperature) Where Δ H is the heat stream heat load, CP is the heat capacity flow rate, T represents the temperature, and the subscripts indicate the final and initial temperatures, respectively.
In a preferred embodiment of the method, in the first step S1, the inlet and outlet temperatures of the cold and hot streams in the heat exchange network, the composition and flow rate of the cold and hot streams are extracted to determine the amount of heat they give off.
In a preferred embodiment of the method, in the first step S1, when the temperature ranges of the different heat sources overlap, the heat loads corresponding to the overlap are superimposed.
In a preferred embodiment of the method, in a first step S1, the slope of the source recombination curve is equal to the inverse of the sum of the heat capacity flow rates of all the hot streams.
In a preferred embodiment of the method, in the first step S1, when the minimum vertical temperature difference between the source recombination curve and the trap recombination curve reaches the predetermined pinch point temperature difference, the overlapping portion of the curves is the energy recovered from the outlet of the circulating reactor.
In a preferred embodiment of said process, the energy recovery at the outlet of the circulating reactor is,
Qrecovering＝(1+β)CP2(T4-T5) Wherein Q isRecoveringFor recycling reactor outlet energy recovery β is recycle ratio, CP2Product heat capacity flow rate, T, for the output of the circulating reactor4Is the reactor outlet temperature, T5Is the exit temperature of the recycle reactor exit steam generator.
In a preferred embodiment of the process, in a second step S2, the relationship between the circulating reactor outlet temperature and the circulation ratio is determined on the basis of the reaction kinetics,
determining the relation between the inlet temperature and the outlet temperature of the circulating reactor and the circulation ratio according to thermodynamics,
wherein, T3Is the temperature of the recycle stream, β is the recycle ratio, T1Fresh feed at reactor inlet temperature; delta TminIs the minimum heat transfer temperature difference; CP (CP)0Is the heat capacity flow rate of the fresh feed; t is0Is the temperature of the fresh feed; CP (CP)4Is the heat capacity flow rate of the reactor outlet product.
In a preferred embodiment of said process, in a third step, the recovered energy is related to the recycle ratio QRecovering＝(1+β)CP2(T4-T1-ΔTmin) Wherein Q isRecoveringFor recycling reactor outlet energy recovery β is recycle ratio, CP2Product heat capacity flow rate, T, for the output of the circulating reactor4Is the reactor outlet temperature, T1Fresh feed at reactor inlet temperature; delta TminIs the minimum heat transfer temperature difference.
In a preferred embodiment of the method described herein,
in the fourth step, the first step is carried out,
wherein R is annual income; qRecoveringRecovering energy for the outlet of the circulating reactor; m1Annual price for steam recovery; j. the design is a square1For recovering the energy consumed per unit of steam; | QCooling downI is the cooling utility usage; m2Annual price for cooling utilities; j. the design is a square2Energy consumed per unit cooling utility β*Initial circulation ratio, β circulation ratio, N*The axial work of an initial circulating material flow pump is obtained; w is annual operating time; and D is the unit electric energy price.
To further understand the present invention, in one embodiment, the inlet and outlet temperature and heat load data of all heat sources and heat traps are extracted and calculated according to the inlet and outlet temperature, flow rate and composition of each heat exchange stream in the heat exchange network. As shown in FIG. 2, with a cyclic reverseThe reactor system and the inlet and outlet materials of the reactor exchange heat with each other, and the material flow influencing the utility consumption of the heat exchange network is the initial temperature of the heat source at the outlet of the reactor R1 and the inlet temperature of the hot material flow of the heat exchanger E3. In order to achieve the best heat exchange effect, the minimum heat transfer temperature difference of the inlet and outlet material flow heat exchangers is delta TminThat is, the temperature difference between the ⑤ stream and the ① stream is Δ Tmin。
1, making a composite curve of the existing heat exchange network on a temperature-enthalpy diagram, and determining the relation between energy consumption and temperature:
inlet and outlet temperature and heat load data are extracted for all hot streams, each of which can be represented in a temperature-enthalpy diagram as a straight line segment with the ordinate pointing from the initial temperature to the target temperature and the difference between the abscissas being the heat load of the stream. When the heat capacity flow rate of the material flow is a fixed value, the relationship between the heat and the temperature can be expressed as:
ΔH＝CP(Tfinal temperature-TInitial temperature) (1)
In the formula,. DELTA.H-stream heat load
CP-Heat flow Rate
T-temperature
For multiple heat flows, they can be combined into one thermal recombination curve in a temperature-enthalpy diagram, as shown in fig. 3. When there are three hot streams, the heat capacity flow rates are A, B and C, respectively, and the temperature ranges from high to low are T4，T1]、[T5，T3]And [ T4，T2]. In the overlap temperature interval [ T4，T3]And [ T3，T2]The heat capacity flow rate is the sum of all streams in the interval, i.e. a + B + C and a + C.
Based on the method, cold and hot compound curves of the heat exchange network are respectively constructed in a temperature-enthalpy diagram. When the minimum vertical temperature difference of the cold and hot compound curves reaches delta TminWhen the utility usage of the heat exchange network is minimal, as shown in fig. 4.
The section AB on the thermal compounding curve represents the energy recovered by the reactor outlet stream flowing through heat exchanger F1, the section BC is the heat stream of heat exchanger E2 and the section CD is the heat stream of heat exchanger E3. The AB stage recovered energy is related to the reactor outlet temperature and the recycle ratio and can be calculated from equation 2:
Qrecovering＝(1+β)CP2(T4-T5) In the formula (2), QRecoveringRecovery of energy at the reactor outlet
β -circulation ratio
CP2The product heat capacity flow rate at the output of the reactor system is constant at a given conversion
The BC section is a heat exchanger E2 hot material flow, the heat exchanger exchanges heat for an inlet material flow and an outlet material flow, the external energy consumption is avoided, and the E2 position is a heat exchange pinch point of the system. E3 is a final product cooler, located below the pinch point, whose initial temperature point, C, changes in temperature, will affect cooling utility usage, the higher the temperature at point C, the cooling utility usage QCooling downThe larger the expression, the more its expression is shown in equation 3.
In the formula, QCooling down *Cooling utility usage at current operating parameters
T*Temperature at the current operating parameter
2) Determining a relationship between circulating reactor temperature and circulation ratio based on reaction kinetics and thermodynamics
The reaction in the reactor is represented as follows:
A+B→C
wherein A and B are reactants and C is a product.
The relationship between the reaction temperature and the circulation ratio is constructed based on the design equation and the reaction rate equation of the reactor, as shown in formula 4.
The method comprises the following steps: w-catalyst loading;
c-concentration;
a-denotes a pre-factor;
(ii) X-conversion;
T4-a reaction temperature;
β -circulation ratio;
e-activation energy;
the energy conservation is used for analyzing a circulating reactor, and the energy consumption of the reactor consists of reaction heat, energy difference of inlet and outlet material flows and external heat exchange. Wherein, import and export commodity circulation includes two parts: fresh feed b and recycle stream a of the reaction take place as shown in figure 2. For fresh feed b, the stream reacts in the reactor, generating heat of reaction; in the case of the recycle stream a, this part of the stream corresponds to the fact that no reaction takes place in the reactor, and a part of the heat is removed. The energy balance of the circulating reactor is shown by formula 5.
In the formula: Δ HR-the heat of reaction;
delta CP-inlet-outlet stream heat capacity difference;
CP-Heat Capacity flow Rate;
QR-reactor heat exchange capacity;
the energy conservation of heat exchanger E1 is as shown in equation 3.
(1+β)CP4(T5-T3)＝CP0(T1-T0) (6)
Due to the fact that
T5＝T1+ΔTmin(7)
T is obtained from formula 63The expression, as follows:
equation 8, equation 5 and equation 4 are solved simultaneously to obtain corresponding reaction inlets T under different circulation ratios of β1And the outlet temperature T4And plotting the temperature-to-cycle ratioCurves, as shown by the red and blue curves in fig. 4.
3) Determining the relation between the energy consumed and recovered by the heat exchange network in the step 1 and the circulation ratio based on the relation between the temperature and the circulation ratio in the step 2
The reactor inlet temperature T is calculated from 21The relationship between the outlet temperature of the heat exchanger E2 and the circulation ratio is obtained by substituting the relationship with the circulation ratio in equation 7. The relationship between the recovered energy and the circulation ratio is obtained by substituting in equation 2, as shown in equation 9. The determined recovered energy versus recycle ratio curve is the curve in fig. 5.
QRecovering＝(1+β)CP2(T4-T1-ΔTmin) (9)
Determining T according to equation 83Substituting the relationship with the recycle ratio into equation 3 results in equation 10 for determining the amount of cooling utility change at different recycle ratios. The determined utility usage versus recycle ratio curve is shown in the graph of fig. 5.
Changes in recycle reactor recycle ratio will also affect changes in reactor recycle pump P1 shaft power. Since the shaft power of the circulation pump is determined by its flow rate, its changed power is shown in equation 11 and the curve in fig. 5.
In the formula, N-axis power
N*Shaft power at the current operating parameters
β*Current circulation ratio
3) Determining revenue for a circulating reactor and heat exchange network integrated system
The calculation of the annual income R of the heat exchange network integrated system mainly comprises three parts of reactor outlet recovery energy, heat exchange network cooling utility consumption and shaft work, as shown in a formula 12.
In the formula, M-annual price
J-unit recovery of steam or energy consumed by utilities
W-year operating time
D-price per unit of electric energy
4) Determination of optimal cyclic ratio
The plotting of equation 12 as a curve is shown in fig. 5. The curve represents the variation of the integrated system gains for different recycle ratios, the recycle ratio that achieves the maximum gain being the optimal point for this system. If the current operation circulation ratio is too large, energy waste is caused, and the circulation ratio is required to be reduced; if the recycle ratio is too small, the optimum point should be adjusted to increase the system gain.
Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments and application fields, and the above-described embodiments are illustrative, instructive, and not restrictive. Those skilled in the art, having the benefit of this disclosure, may effect numerous modifications thereto without departing from the scope of the invention as defined by the appended claims.
Claims (10)
1. A method for determining an optimal circulation ratio of a heat exchange network provided with a circulating reactor, the method comprising the steps of:
in the first step (S1), the inlet and outlet temperature and flow of the cold heat flow in the heat exchange network are extracted to determine the heat released by the cold heat flow, and the heat released is recorded as heat load, wherein the hot flow to be cooled is a heat source; the method comprises the following steps that cold material flow needing to be heated is a hot trap, the initial temperature of the flow is an initial temperature, the target temperature is a final temperature, each heat source is represented by a straight line segment according to the temperature and the heat load of the heat source, the ordinate of the two end points of the heat source respectively represents the inlet temperature and the outlet temperature, the difference of the abscissa represents the heat load of the heat source, all the heat sources are combined into a source composite curve, the abscissa between every two end points of the heat source represents the sum of the heat loads of all the material flows in a temperature interval, and a trap composite curve is drawn in the same way;
in the second step (S2), extracting circulating reactor parameters including at least inlet flow, constituent concentration, inlet temperature, outlet temperature, and conversion rate, determining a relationship between circulating reactor outlet temperature and circulation ratio according to reaction kinetics, and determining a relationship between circulating reactor inlet temperature, outlet temperature, and circulation ratio according to thermodynamics;
in the third step (S3), determining inlet and outlet temperatures corresponding to different circulation ratios based on the relationship among the inlet temperature, the outlet temperature and the circulation ratio of the reactor in the second step, and determining the relationship among the heat exchange network recovered energy when the temperature of the reactor changes based on the source compound curve and the trap compound curve in the first step;
in the fourth step (S4), a temperature-energy-benefit-recycle ratio map is constructed based on the reactor inlet temperature, outlet temperature, recovered energy and benefit versus recycle ratio curves, and the minimum recycle ratio at which the maximum benefit is achieved, i.e., the optimum recycle ratio, is determined.
2. The method according to claim 1, wherein, preferably, in the first step (S1), the heat load of the hot stream has a temperature relationship Δ H ═ CP (T) ofFinal temperature-TInitial temperature) Where Δ H is the heat stream heat load, CP is the heat capacity flow rate, T represents the temperature, and the subscripts indicate the final and initial temperatures, respectively.
3. The method of claim 1, wherein in the first step (S1), the inlet and outlet temperatures of the cold and hot streams, the composition and flow rate of the cold and hot streams in the heat exchange network are extracted to determine the amount of heat they give off.
4. The method according to claim 1, wherein in the first step (S1), when the temperature intervals of different heat sources overlap, the corresponding heat loads are superimposed.
5. The method of claim 1, wherein in the first step (S1), the slope of the source recombination curve is equal to the inverse of the sum of all thermal mass flow heat capacity rates.
6. The method according to claim 1, wherein in the first step (S1), when the minimum vertical temperature difference between the source recombination curve and the trap recombination curve reaches a predetermined pinch point temperature difference, the curve overlapping part is the energy recovered from the outlet of the circulating reactor.
7. The process of claim 6, wherein the circulating reactor outlet recovers energy by,
Qrecovering＝(1+β)CP2(T4-T5) Wherein Q isRecoveringFor recycling reactor outlet energy recovery β is recycle ratio, CP2Product heat capacity flow rate, T, for the output of the circulating reactor4Is the reactor outlet temperature, T5Is the exit temperature of the recycle reactor exit steam generator.
8. The method according to claim 1, wherein in the second step (S2), the relation between the circulating reactor outlet temperature and the circulation ratio is determined on the basis of reaction kinetics,
determining the relation between the inlet temperature and the outlet temperature of the circulating reactor and the circulation ratio according to thermodynamics,
wherein, T3Is the temperature of the recycle stream, β is the recycle ratio, T1For fresh feed in the reactorAn inlet temperature; delta TminIs the minimum heat transfer temperature difference; CP (CP)0Is the heat capacity flow rate of the fresh feed; t is0Is the temperature of the fresh feed; CP (CP)4Is the heat capacity flow rate of the reactor outlet product.
9. The method of claim 1, wherein in the third step, the recovered energy is related to the recycle ratio by QRecovering＝(1+β)CP2(T4-T1-ΔTmin) Wherein Q isRecoveringFor recycling reactor outlet energy recovery β is recycle ratio, CP2Product heat capacity flow rate, T, for the output of the circulating reactor4Is the reactor outlet temperature, T1Fresh feed at reactor inlet temperature; delta TminIs the minimum heat transfer temperature difference.
10. The method according to claim 1, wherein the fourth step,
wherein R is annual income; qRecoveringRecovering energy for the outlet of the circulating reactor; m1Annual price for steam recovery; j. the design is a square1For recovering the energy consumed per unit of steam; | QCooling downI is the cooling utility usage; m2Annual price for cooling utilities; j. the design is a square2Energy consumed per unit cooling utility β*Initial circulation ratio, β circulation ratio, N*The axial work of an initial circulating material flow pump is obtained; w is annual operating time; and D is the unit electric energy price.
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