Directly rotating gasification process optimization method for regulating the amount of combustion air feed to a box furnace

Abstract

A method for optimizing a direct-to-gasification process for regulating the combustion air feed rate of a square box furnace. In the method, a direct-to-gasification process flow is obtained, current combustion data of the square box furnace is extracted, a current baseline state assessment is performed on the direct-to-gasification process, and based on the current fuel gas feed, the combustion air feed rate of the square box furnace is adjusted to construct a trend graph of flue gas residual oxygen content, air feed rate, fuel gas feed rate, and combustion heat release; trend graphs of flue gas residual oxygen content, air feed rate, fuel gas change, by-product steam change, and annual operating cost savings corresponding to a first strategy and a second strategy are drawn to determine the economically optimal strategy under different flue gas residual oxygen content targets and its corresponding air feed rate, fuel gas change, and by-product steam change.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of direct conversion gasification process, in particular to a direct conversion gasification process optimization method for adjusting the combustion air feed quantity of a square box furnace. BACKGROUND

[0002] In the industrial direct conversion gasification process, the square box furnace is the core equipment of the primary conversion process, and its combustion efficiency directly affects the energy and resource utilization rate of the entire process. For the combustion of natural gas, the ideal residual oxygen content of flue gas should generally be maintained between 3-5%. This range ensures sufficient fuel combustion and improves thermal efficiency. In the current combustion system, the residual oxygen content of flue gas is often higher than the ideal level, and there is an excess of combustion air feed quantity, which will reduce the combustion thermal efficiency and cause unnecessary energy or resource waste.

[0003] The above information disclosed in the background section is only intended to enhance the understanding of the background of the present application, and therefore can contain information that is not prior art known to those of ordinary skill in the art. SUMMARY

[0004] To solve the problems in the prior art, the present application provides a direct conversion gasification process optimization method for adjusting the combustion air feed quantity of a square box furnace, which clearly and intuitively shows the difference between the current residual oxygen content of flue gas and the ideal level, clearly defines the theoretical combustion air feed quantity under different residual oxygen content targets of flue gas, provides two feasible energy-saving optimization paths aimed at improving the energy or resource utilization efficiency of the system by increasing the by-product steam or reducing the fuel gas consumption, determines the optimization strategy with higher annual operating cost saving under a given residual oxygen content target of flue gas, and the corresponding key parameters such as theoretical air feed quantity, fuel gas change quantity, and by-product steam change quantity, thereby achieving better energy saving and environmental protection.

[0005] The present application is realized by the following technical solutions:

[0006] A direct conversion gasification process optimization method for adjusting the combustion air feed quantity of a square box furnace, comprising:

[0007] S100: obtaining a direct conversion gasification process flow, extracting the current combustion data of the square box furnace, evaluating the current baseline state of the direct conversion gasification process, and constructing an Aspen Plus simulation model;

[0008] S200: based on the current fuel gas feed, adjusting the combustion air feed quantity of the square box furnace in the Aspen Plus simulation model, constructing a trend chart of the residual oxygen content of flue gas, the air feed quantity (F air ), the fuel gas feed quantity (F fuel ), and the combustion heat release quantity (Q total );

[0009] S300: Obtain the trend of the current fuel gas feed quantity, the current heat requirement of the box furnace, and the air feed quantity and the boiler feed water preheater heat load under the process gas preheater heat load with the flue gas residual oxygen content, and mark it as the first strategy; Extract the enthalpy of the byproduct steam of the direct conversion process, and obtain the change amount of the byproduct steam under different flue gas residual oxygen contents based on the trend of the boiler feed water preheater heat load with the flue gas residual oxygen content; Obtain the unit price of the byproduct steam, and calculate the trend of the annual operating cost saving amount brought by the change of the byproduct steam with the flue gas residual oxygen content;

[0010] S400: Obtain the fuel natural gas combustion heat value, and obtain the trend of the current boiler feed water preheater heat load, the current heat requirement of the box furnace, and the air feed quantity and the fuel gas feed change amount under the process gas preheater heat load with the flue gas residual oxygen content based on the trend graph, and mark it as the second strategy; Obtain the unit price of the fuel gas, and calculate the trend of the annual operating cost saving amount brought by saving the fuel gas with the flue gas residual oxygen content.

[0011] S500: Draw the flue gas residual oxygen content, air feed quantity, fuel gas change amount, byproduct steam change amount, and annual operating cost saving amount trend graph corresponding to the first strategy and the second strategy, and determine the economically optimal strategy and its corresponding air feed quantity, fuel gas change amount, and byproduct steam change amount under different flue gas residual oxygen content targets.

[0012] In the direct conversion gas process optimization method for adjusting the combustion air feed quantity of the box furnace, in step S100, in the direct conversion gas process, natural gas and steam mixed gas are respectively sent into the box one-stage furnace and the heat exchange type conversion furnace, and the two one-stage conversion gases are combined and then enter the two-stage furnace. The heat source of the box furnace is the combustion fuel gas, and the heat source of the heat exchange type conversion furnace is the high-temperature two-stage conversion gas. The fuel gas is heated in the convection section coil of the one-stage conversion furnace and then used as the fuel of the top burner and auxiliary burner of the box type conversion furnace. The flue gas out of the one-stage conversion furnace enters the convection section to preheat the raw material gas, fuel gas, and air process gas and to preheat the boiler feed water to produce byproduct steam. Finally, it goes to the induced draft fan to be discharged at the design flue gas discharge temperature.

[0013] In the direct conversion gas process optimization method for adjusting the combustion air feed quantity of the box furnace, in step S100, the extraction of the current combustion data of the box furnace includes the fuel gas feed quantity, the air feed quantity, the combustion heat release quantity, and the flue gas residual oxygen content. The current baseline state evaluation of the direct conversion gas process includes the evaluation of the one-stage conversion heat requirement, the heat load of each process gas preheater, the heat load of the boiler feed water preheater, and the design flue gas discharge temperature.

[0014] In the direct conversion gas process optimization method for adjusting the combustion air feed quantity of the box furnace, in step S200, the current fuel gas feed quantity is maintained unchanged, and the combustion air feed quantity of the box furnace is gradually adjusted to obtain the flue gas residual oxygen content and the total combustion heat release quantity change trend under different fuel air feed quantities.

[0015] In the method for optimizing a straight conversion gas-making process by adjusting the air feed quantity of a box furnace combustion, in step S300, the air feed quantity under different flue gas residual oxygen amounts in the first strategy is represented as: air，策略1 air wherein F air，第一策略 represents the air feed quantity in the first strategy, and the boiler feed water preheater heat load under different flue gas residual oxygen amounts is represented as:

[0016]

[0017] wherein Q3 represents the boiler feed water preheater heat load; Qtota l represents the total combustion heat release; Q1 represents the heat requirement of the first conversion stage; Q2 represents the process gas preheater heat load; and the superscript ini represents the current value; and the by-product steam variation under different flue gas residual oxygen amounts is represented as:

[0018]

[0019] wherein ΔF steam represents the by-product steam variation; h steam represents the steam enthalpy; and the annual operating cost saving under different flue gas residual oxygen amounts is represented as:

[0020] ΔCo1=ΔF steam ·c steam

[0021] wherein ΔCo1 represents the annual operating cost saving in the first strategy; C steam represents the steam unit price.

[0022] In the method for optimizing a straight conversion gas-making process by adjusting the air feed quantity of a box furnace combustion, in step S400, the air feed quantity under different flue gas residual oxygen amounts in the second strategy is represented as:

[0023]

[0024] wherein F air，第二策略 represents the air feed quantity in the second strategy.

[0025] In the method for optimizing a straight conversion gas-making process by adjusting the air feed quantity of a box furnace combustion, in step S400, the fuel gas feed variation under different flue gas residual oxygen amounts in the second strategy is represented as:

[0026]

[0027] wherein ΔF fuel represents the fuel gas variation; and q fuel represents the fuel gas combustion heat value.​

[0028] In the method, in the second strategy, the annual operation cost saving amount under different flue gas residual oxygen amounts is represented by:

[0029] ΔCo2 = ΔF fuel ·c fuel Wherein, ΔCo2 represents the annual operation cost saving amount of the second strategy; c fuel represents the unit price of the fuel natural gas.

[0030] In the method, in step S500, the flue gas residual oxygen amount is taken as the horizontal coordinate, and the air feed amount, the fuel gas change amount, the by-product steam change amount and the annual operation cost saving amount are taken as the vertical coordinates, and the flue gas residual oxygen amount, the air feed amount, the fuel gas change amount, the by-product steam change amount and the annual operation cost saving amount change trend graphs corresponding to the first strategy and the second strategy are respectively drawn.

[0031] In the method, for a given target residual oxygen amount, according to the flue gas residual oxygen amount, the air feed amount, the fuel gas change amount, the by-product steam change amount and the annual operation cost saving amount change trend graphs, the annual operation cost saving amounts corresponding to the first strategy and the second strategy are respectively determined: if ΔCo1 > ΔCo2, the first strategy is the more economical energy-saving scheme, the fuel gas consumption amount is unchanged, the by-product steam amount changes, and the air feed amount and the by-product steam change amount under the target residual oxygen amount are obtained from the trend graph; if ΔCo1 < ΔCo2, the second strategy is the more economical energy-saving scheme, the by-product steam amount is unchanged, the fuel gas consumption amount changes, and the air feed amount and the fuel gas change amount under the target residual oxygen amount are obtained from the trend graph.

[0032] Compared with the prior art, the method has the following advantages:

[0033] The present application obtains the parameters such as residual oxygen content of flue gas and combustion heat release under different air feed amounts on the basis of extracting the current direct top gas process parameters, and then determines the change trend of air feed amount, fuel gas change amount, by-product steam change amount and annual operating cost saving amount with the change of residual oxygen content of flue gas respectively by taking increasing by-product steam and saving fuel gas as energy-saving optimization strategies, so as to determine the energy-saving optimization path with larger annual operating cost saving amount under the target residual oxygen content of flue gas as the optimal energy-saving optimization strategy, and the corresponding key parameters such as theoretical air feed amount, fuel gas change amount, by-product steam change amount and annual operating cost saving amount. The optimization of air feed amount and increasing by-product steam / saving fuel gas consumption is of great significance to improve the thermal efficiency of square box furnace and the energy / resource utilization efficiency of direct top gas process. The present disclosure can also be popularized to other fuel type direct top gas systems to build the correlation between residual oxygen content of flue gas and fuel-air ratio, analyze the energy or resource utilization efficiency improvement potential of the system under the target residual oxygen content, and in actual production, the real-time adjustment of air feed amount of square box furnace and the efficient utilization of system energy resources can be realized by combining with automatic monitoring and control system. BRIEF DESCRIPTION OF DRAWINGS

[0034] Various other advantages and benefits of the present application will become apparent to those of ordinary skill in the art, upon reading the following detailed description of the preferred embodiment. The accompanying drawings are included to provide a better understanding of the preferred embodiment and are not to be considered as limitations of the present application. It should be readily understood that the drawings are merely illustrative of the present application and that they, therefore, do not limit the present application, as defined in the appended claims, in any way. Rather the intent is to present embodiments of the application in connection with which the invention can be better understood.

[0035] In the drawings:

[0036] Figure 1 is a flow chart of a direct top gas process energy-saving optimization method for adjusting the combustion air feed amount of a square box furnace provided by one embodiment of the present disclosure;

[0037] Figure 2 is a direct top gas process flow diagram provided by another embodiment of the present disclosure;

[0038] Figure 3 is a residual oxygen content of flue gas-air feed amount / fuel gas feed amount / combustion heat release trend diagram under the current fuel gas feed amount of another embodiment of the present disclosure;

[0039] Figure 4 is a residual oxygen content of flue gas-air feed amount / fuel gas change amount / by-product steam change amount / annual operating cost saving amount change trend diagram corresponding to the first strategy and the second strategy of energy-saving optimization provided by another embodiment of the present disclosure.

[0040] The application will be further explained with reference to the drawings and embodiments. DETAILED DESCRIPTION

[0041] The specific embodiments of the present application will be described in greater detail below with reference to the drawings. Although specific embodiments of the present application are shown in the drawings, it is understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thoroughly and completely understood, and one skilled in the art will be able to fully convey the scope of the present application to others skilled in the art.

[0042] It should be noted that certain terms are used throughout the present specification and claims which have particular meanings as set forth below. Those skilled in the art will understand that not all terms are used as they are defined in common dictionaries, and that terms used by those skilled in the art could differ from the definitions in common dictionaries. The present specification and claims are not to be limited by the terminology used in the description.

[0043] For the purpose of promoting an understanding of the principles of the application, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the application is intended by this specification. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the application as described herein are contemplated with the scope of the application as defined by the following claims.

[0044] As Figures 1 to 4 shown, the present application discloses a method for optimizing a direct conversion gasification process by adjusting the amount of combustion air fed to a box furnace, comprising,

[0045] S100: Obtain the direct conversion gasification process, extract the current combustion data of the box furnace, evaluate the current reference state of the direct conversion gasification process, and build an Aspen Plus simulation model; the Aspen Plus simulation model includes:

[0046] Process flow component input and property method selection;

[0047] Process building interface builds an industrial process, focusing on reflecting key equipment and corresponding stream inputs and outputs, connecting different equipment through streams to form a complete production process. In this method, the key equipment is the box furnace, the process gas preheater, and the boiler feed water preheater, and the key streams are the feed combustion air, the fuel natural gas, the combustion flue gas, the raw material gas, the conversion gas, the process gas, and the boiler feed water, as shown in Figure 2 .

[0048] The temperature, pressure, flow rate and composition of the above-mentioned key streams are obtained and input, and the process simulation is realized, and then the heat data of the key equipment / streams are read.

[0049] S200: Based on the current fuel gas feed, the amount of combustion air feed of the rectangular box furnace is adjusted in the Aspen Plus simulation model, and the trend graphs of the residual oxygen content of the flue gas, the air feed amount (F air ), the fuel gas feed amount (F fuel ) and the combustion heat release (Q total ) are constructed; by adjusting the amount of combustion air feed of the rectangular box furnace in the Aspen Plus simulation model, the data of the residual oxygen content of the flue gas and the combustion heat release under different combustion air feed amounts are read, and then the trend graph construction of the residual oxygen content of the flue gas, the air feed amount (F air ), the fuel gas feed amount (F fuel ) and the combustion heat release (Q total ) is realized. With the help of Aspen Plus simulation, the complexity of calculation is simplified, and the relationship between the residual oxygen content of the flue gas, the air feed amount, the fuel gas feed amount and the combustion heat release is directly obtained through simulation. Further, this relationship can also be obtained by heat and mass balance calculation of the combustion furnace, and further, the accuracy of the relationship can be improved by comparison and correction.

[0050] S300: Based on the trend graph, the current fuel gas feed amount and the current heat requirement of the rectangular box furnace and the air feed amount and the heat load of the boiler feed water preheater under the process gas preheater heat load are obtained, and the trend of the change of the air feed amount and the heat load of the boiler feed water preheater with the residual oxygen content of the flue gas is recorded as the first strategy; the enthalpy of the by-product steam of the direct conversion process is extracted, based on the trend of the change of the heat load of the boiler feed water preheater with the residual oxygen content of the flue gas, the change amount of the by-product steam of the direct conversion process under different residual oxygen contents of the flue gas is obtained; the unit price of the by-product steam is obtained, and the trend of the annual operating cost saving amount brought by the change of the by-product steam with the residual oxygen content of the flue gas is calculated;

[0051] S400, the combustion heat value of fuel natural gas is obtained, based on the trend graph, the current heat load of the boiler feed water preheater and the current heat requirement of the rectangular box furnace and the air feed amount and the change amount of the fuel gas feed under the process gas preheater heat load are obtained, and the trend of the change of the air feed amount and the change amount of the fuel gas feed with the residual oxygen content of the flue gas is recorded as the second strategy; the unit price of the fuel gas is obtained, and the trend of the annual operating cost saving amount brought by saving the fuel gas with the residual oxygen content of the flue gas is calculated;

[0052] S500: The trend graphs of the residual oxygen content of the flue gas, the air feed amount, the change amount of the fuel gas, the change amount of the by-product steam, the annual operating cost saving amount corresponding to the first strategy and the second strategy are drawn, and the economically optimal strategy and its corresponding air feed amount, change amount of the fuel gas and change amount of the by-product steam under different residual oxygen content targets of the flue gas are determined.

[0053] In the preferred embodiment of the method for optimizing a straight conversion gas production process with a regulating amount of combustion air fed into a box furnace, in step S100, in the straight conversion gas production process, natural gas and steam mixed gas are fed into a box furnace and a heat exchange reformer respectively, two streams of primary conversion gas are combined and then fed into a secondary reformer, the heat source of the box furnace is fuel gas, and the heat source of the heat exchange reformer is high-temperature secondary conversion gas; the fuel gas is heated in the coil of the convection section of the primary reformer and then used as fuel for the top burner and auxiliary burner of the box furnace, the flue gas discharged from the primary reformer is used to preheat raw material gas, fuel gas, air process gas and boiler feed water to produce steam, and finally goes to an induced draft fan to be discharged at a design flue gas temperature.

[0054] In the preferred embodiment of the method for optimizing a straight conversion gas production process with a regulating amount of combustion air fed into a box furnace, in step S100, the extraction of current combustion data of the box furnace includes the amount of fuel gas fed, the amount of air fed, the amount of heat released by combustion, and the residual oxygen content of flue gas; and the assessment of the current baseline state of the straight conversion gas production process includes the assessment of the heat required for primary conversion, the heat load of each process gas preheater, the heat load of the boiler feed water preheater, and the design flue gas temperature.

[0055] In the preferred embodiment of the method for optimizing a straight conversion gas production process with a regulating amount of combustion air fed into a box furnace, in step S200, the amount of combustion air fed into the box furnace is adjusted step by step while the amount of fuel gas fed is kept unchanged, and the change trend of the residual oxygen content of flue gas and the total heat released by combustion under different amounts of fuel air fed is obtained.

[0056] In the preferred embodiment of the method for optimizing a straight conversion gas production process with a regulating amount of combustion air fed into a box furnace, in step S300, in the first strategy, the amount of air fed under different residual oxygen contents of flue gas is represented as: air，策略1 F air , wherein F air，第一策略 represents the amount of air fed in the first strategy, the heat load of the boiler feed water preheater under different residual oxygen contents of flue gas is represented as:

[0057]

[0058] , wherein Q3 represents the heat load of the boiler feed water preheater; Qtota l represents the total heat released by combustion; Q1 represents the heat required for primary conversion; Q2 represents the heat load of the process gas preheater; the superscript ini represents the current value; and the change amount of steam produced under different residual oxygen contents of flue gas is represented as:

[0059]

[0060] , wherein ΔF steam represents the change amount of steam produced; and h steamrepresents the steam enthalpy; the annual operating cost saving amount under different flue gas residual oxygen amounts is represented as:

[0061] ΔCo1= ΔF steam · c steam

[0062] wherein ΔCo1 represents the annual operating cost saving amount of the first strategy; c steam represents the steam unit price.

[0063] In the preferred embodiment of the method for optimizing the direct conversion gas-making process by adjusting the air feed amount of the square box furnace combustion air, in step S400, in the second strategy, the air feed amount under different flue gas residual oxygen amounts is represented as:

[0064]

[0065] wherein F air，第二策略 represents the air feed amount in the second strategy.

[0066] In the preferred embodiment of the method for optimizing the direct conversion gas-making process by adjusting the air feed amount of the square box furnace combustion air, in step S400, in the second strategy, the fuel gas feed variation amount under different flue gas residual oxygen amounts is represented as:

[0067]

[0068] wherein ΔF fuel represents the fuel gas variation amount; q fuel represents the fuel gas combustion heat value.

[0069] In the preferred embodiment of the method for optimizing the direct conversion gas-making process by adjusting the air feed amount of the square box furnace combustion air, in step S400, in the second strategy, the annual operating cost saving amount under different flue gas residual oxygen amounts is represented as:

[0070] ΔCo2= ΔF fuel · c fuel wherein ΔCo2 represents the annual operating cost saving amount of the second strategy; c fuel represents the fuel natural gas unit price.

[0071] In the preferred embodiment of the method for optimizing the direct conversion gas-making process by adjusting the air feed amount of the square box furnace combustion air, in step S500, the flue gas residual oxygen amount is taken as the horizontal coordinate, and the air feed amount, the fuel gas variation amount, the byproduct steam variation amount, and the annual operating cost saving amount are taken as the vertical coordinates, and the flue gas residual oxygen amount, the air feed amount, the fuel gas variation amount, the byproduct steam variation amount, and the annual operating cost saving amount change trend graphs corresponding to the first strategy and the second strategy are respectively drawn.

[0072] In a preferred embodiment of the direct-conversion gasification process optimization method for adjusting the combustion air feed rate of a square box furnace, for a given target residual oxygen content, the annual operating cost savings corresponding to the first strategy and the second strategy are determined respectively based on the flue gas residual oxygen content, air feed rate, fuel gas change, by-product steam change, and annual operating cost savings trend chart: if ΔCo1>ΔCo2, the first strategy is an economically more optimal energy-saving scheme, the fuel gas consumption remains unchanged, the by-product steam consumption changes, and the air feed rate and by-product steam change at the target residual oxygen content are obtained from the trend chart; if ΔCo1<ΔCo2, the second strategy is an economically more optimal energy-saving scheme, the by-product steam consumption remains unchanged, the fuel gas consumption changes, and the air feed rate and fuel gas change at the target residual oxygen content are obtained from the trend chart.

[0073] In one embodiment, Figure 1 As shown, a method for energy-saving optimization of a direct-conversion gasification process for adjusting the combustion air feed amount of a square box furnace includes the following steps:

[0074] S100: Obtain key equipment for the direct-flow gasification process, including the box furnace, process gas preheater, and boiler feed water preheater, as well as key process flows for the direct-flow gasification process, including combustion air, natural gas fuel, combustion flue gas, process gas, and boiler feed water. Extract parameters such as the heat load of key equipment, inlet and outlet temperatures, flow rates, and composition of key process flows, the total heat release of fuel gas combustion, residual oxygen content in flue gas, and exhaust temperature.

[0075] In this step, key equipment such as the box furnace, process gas preheater, boiler feed water preheater, etc. are interconnected through key process flows such as combustion air, fuel natural gas, combustion flue gas, process gas, boiler feed water, etc. Figure 2 An exemplary display was performed.

[0076] Under a given exhaust gas temperature, the relationship between the total heat released by fuel gas combustion, the heat required for the first stage conversion, the heat load of the process gas preheater, and the heat load of the boiler feed water preheater can be expressed as follows:

[0077] Q total =Q1+Q2+Q3 (1)

[0078] Among them, Q total It represents the total heat released by combustion; Q1 represents the heat required for the first stage conversion; Q2 represents the heat load of the process gas preheater; Q3 represents the heat load of the boiler feed water preheater.

[0079] Based on the acquired parameters such as the heat load of key equipment, inlet and outlet temperatures, flow rates and composition of key process flows, total heat release of fuel gas combustion, residual oxygen content of flue gas and exhaust temperature, the Peng-Robinson physical property method was used to construct an Aspen Plus simulation model.

[0080] S200: On the basis of the current fuel gas feed quantity, a flue gas residual oxygen quantity-air feed quantity (F air ) / fuel gas feed quantity (F fuel ) / combustion heat release quantity (Q total ) diagram is constructed;

[0081] In this step, the current fuel gas feed quantity is maintained unchanged, the combustion air feed quantity is adjusted gradually, the outlet flue gas residual oxygen quantity and the total combustion heat release quantity under different combustion air feed quantities are obtained, and a flue gas residual oxygen quantity-air feed quantity / fuel gas feed quantity / combustion heat release quantity diagram is constructed, Figure 3 An exemplary display is performed.

[0082] S300: Based on the flue gas residual oxygen quantity-air feed quantity / fuel gas feed quantity / combustion heat release quantity diagram of S200, the air feed quantity and the boiler feed water preheater heat load change trend with the flue gas residual oxygen quantity under the current fuel gas feed quantity, the current square box furnace heat requirement and the process gas preheater heat load (denoted as a first strategy) are obtained; the enthalpy of the by-product steam of the direct conversion process is extracted, the by-product steam change quantity under different flue gas residual oxygen quantities is obtained based on the boiler feed water preheater heat load change trend with the flue gas residual oxygen quantity, and the by-product steam unit price is obtained to calculate the annual operating cost saving quantity change trend with the flue gas residual oxygen quantity brought by the by-product steam change;

[0083] In this step, the fuel gas feed quantity is unchanged, and the air feed quantity change trend with the flue gas residual oxygen quantity is as shown in step S200 Figure 3 , which can be expressed as:

[0084] F air，策略1 =F air (2)

[0085] Wherein, F air，第一策略 is the air feed quantity in the first strategy.

[0086] If the current square box furnace heat requirement and the process gas preheater heat load are unchanged, the boiler water preheater heat load under different flue gas residual oxygen quantities in the first strategy can be expressed as:

[0087]

[0088] Wherein, the superscript ini represents the current value.

[0089] The enthalpy h steam of the steam in the direct conversion gasification process is obtained, and the by-product steam change quantity under different flue gas residual oxygen quantities in the first strategy can be expressed as:

[0090]

[0091] Wherein, ΔF steam represents the by-product steam change quantity.

[0092] The unit price c of steam in the direct conversion gas process is obtained steam The annual operating cost saving amount in the first strategy under different flue gas residual oxygen amounts can be represented as:

[0093] ΔCo1=ΔF steam ·c steam (5)

[0094] Wherein, ΔCo1 represents the annual operating cost saving amount in the first strategy.

[0095] S400, the fuel natural gas combustion heat value is extracted, based on the flue gas residual oxygen amount-air feed amount / fuel gas feed amount / combustion heat release amount diagram of S200, the air feed amount and the fuel gas feed change amount change trend with the flue gas residual oxygen amount under the current boiler feed water preheater heat load and the current box furnace heat demand and the process gas preheater heat load (denoted as the second strategy) are obtained; the unit price of the fuel gas is obtained, and the annual operating cost saving amount saved by the fuel gas change trend with the flue gas residual oxygen amount is calculated;

[0096] In this step, the current boiler feed water preheater heat load and the current box furnace heat demand and the process gas preheater heat load are unchanged, that is, the total heat demand of the system is unchanged, which can be represented as:

[0097]

[0098] Under the current total heat demand of the system, the combustion air feed amount in the second strategy under different flue gas residual oxygen amounts can be represented as:

[0099]

[0100] Wherein, F air,第二策略 is the air feed amount in the second strategy;

[0101] The fuel gas combustion heat value q fuel is obtained, and the fuel gas feed change amount in the second strategy under different flue gas residual oxygen amounts can be represented as:

[0102]

[0103] Wherein, ΔF fuel represents the fuel gas change amount.

[0104] The unit price c of fuel natural gas in the direct conversion gas process is obtained fuel The annual operating cost saving amount in the second strategy under different flue gas residual oxygen amounts can be represented as:

[0105] ΔCo2=ΔF fuel ·c fuel (9)

[0106] Wherein, ΔCo2 represents the second strategy annual operation cost saving amount.

[0107] S500: draw the flue gas residual oxygen content-air feed amount / fuel gas change amount / steam change amount / year operation cost saving trend chart corresponding to the first strategy and the second strategy, and determine the economic optimal energy saving optimization strategy and the corresponding air feed amount, fuel gas change amount and steam change amount under different flue gas residual oxygen content targets.

[0108] In this step, the flue gas residual oxygen content-air feed amount / fuel gas change amount / steam change amount / year operation cost saving trend chart corresponding to the first strategy and the second strategy is drawn respectively, taking the flue gas residual oxygen content as the abscissa and the air feed amount, fuel gas change amount, steam change amount and annual operation cost saving amount as the ordinate, as shown in Figure 4 .

[0109] From the chart, the difference between the current flue gas residual oxygen content and the target residual oxygen content can be obtained, and from the flue gas residual oxygen content-year operation cost saving curve, the highest saving potential of the year operation cost of the direct conversion gasification system under different residual oxygen contents and the corresponding energy saving optimization strategy can be obtained. Combining the flue gas residual oxygen content-combustion air feed amount, flue gas residual oxygen content-fuel gas change amount, flue gas residual oxygen content-steam change amount curves, the combustion air feed amount required to achieve the target residual oxygen content and the corresponding fuel gas feed change amount / steam change amount in the energy saving optimization strategy can be obtained.

[0110] Next, the existing method and the scheme described in the present disclosure are used to optimize a certain direct conversion gasification process to further illustrate the technical effects of the present scheme.

[0111] The optimal level of flue gas residual oxygen content of the existing direct conversion gasification process is usually determined by referring to industry standards and considering the combustion efficiency and combining actual operation experience, and the ideal value of the flue gas residual oxygen content of the natural gas box furnace is 3-5%. In the actual production process, due to improper feed amount, the flue gas residual oxygen content may be higher than the ideal value. During the design stage, a process gas preheater and a boiler feed water preheater are usually used to recover the high-temperature flue gas waste heat.

[0112] The scheme described in the present disclosure is used to optimize the combustion air feed amount of the direct conversion gasification process box furnace and the energy / resource utilization efficiency, and the calculation data of each step is as follows:

[0113] In step S100, the key equipment of the direct conversion gasification process including the box furnace, the process gas preheater and the boiler feed water preheater, and the key process flow of the direct conversion gasification process including the combustion air, the fuel natural gas, the combustion flue gas, the process gas and the boiler feed water are obtained; the key equipment heat load, the key process flow inlet and outlet temperature, flow and composition, fuel gas combustion heat release amount, flue gas residual oxygen content and exhaust gas temperature and other parameters are extracted. Some parameters are shown in Table 1.

[0114] Table 1: Some parameters of a direct gas conversion process

[0115]

[0116] In step S200, the combustion air feed quantity is gradually adjusted on the basis of the current fuel gas feed quantity, and the outlet flue gas residual oxygen quantity and the total combustion heat release under different combustion air feed quantities are obtained, as shown in Table 2.

[0117] Table 2: Current fuel gas feed quantity and outlet flue gas residual oxygen quantity and total combustion heat release under different combustion air feed quantities

[0118] Combustion air feed quantity F air t / h 20.99 19.17 17.89 17.42 16.97 16.55 16.14 15.75 Fuel gas feed amount F fuel / Nm 3 / h]]> 1100 1100 1100 1100 1100 1100 1100 1100 Residual oxygen content of flue gas / % 7.2 6 5 4.6 4.2 3.8 3.4 3 Total heat release Q total / kW 10091 10149 10190 10205 10220 10234 10247 10259

[0119] In step S300, the current fuel gas feed quantity and the air feed quantity under the current heat requirement of the square box furnace and the heat load of the process gas preheater, the fuel gas feed variation quantity, the boiler feed water preheater heat load, the variation quantity of the by-product 1.45 MPa steam, and the annual operating cost saving amount due to the variation of the by-product steam are obtained, as shown in Table 3.

[0120] Table 3: Air feed quantity, boiler feed water preheater heat load, variation quantity of by-product steam, and annual operating cost saving amount corresponding to different flue gas residual oxygen quantities in the first strategy

[0121] Residual oxygen content of flue gas / % 7.2 6 5 4.6 4.2 3.8 3.4 3 Combustion air feed quantity / t / h 20.99 19.17 17.89 17.42 16.97 16.55 16.14 15.75 Fuel gas feed change amount / Nm 3 / h]] 0 0 0 0 0 0 0 0 Boiler feed water preheater heat duty / kW 861 920 961 976 990 1004 1017 1030 By-product steam change quantity / t / h 0.00 0.11 0.18 0.21 0.24 0.26 0.29 0.31 Annual operating cost saving / ten thousand yuan / year 0.00 14.65 24.97 28.76 32.38 35.83 39.12 42.27

[0122] In step S400, the current boiler feed water preheater heat load and the air feed quantity under the current heat requirement of the square box furnace and the heat load of the process gas preheater, the variation quantity of the by-product 1.45 MPa steam, and the annual operating cost saving amount due to the variation of the fuel gas feed quantity are obtained, as shown in Table 4.

[0123] Table 4: Air feed quantity, fuel gas feed variation quantity, and annual operating cost saving amount corresponding to different flue gas residual oxygen quantities in the second strategy

[0124] Residual oxygen content of flue gas / % 7.2 6 5 4.6 4.2 3.8 3.4 3 Combustion air feed quantity / t / h 20.99 19.06 17.72 17.23 16.76 16.31 15.89 15.49 Fuel gas feed change amount / Nm 3 / h]] 0.00 6.28 10.70 12.33 13.88 15.36 16.77 18.12 By-product steam change quantity / t / h 0 0 0 0 0 0 0 0 Annual operating cost saving / ten thousand yuan / year 0.00 15.07 25.68 29.59 33.31 36.86 40.24 43.48

[0125] In step S400, the first strategy and the second strategy corresponding flue gas residual oxygen quantity-air feed quantity / fuel gas variation quantity / by-product steam variation quantity / annual operating cost saving amount change trend graphs can be drawn by combining Table 3 and Table 4.

[0126] From Table 1, it can be seen that the current flue gas residual oxygen quantity is 7.2%, which is higher than the ideal value. If the flue gas residual oxygen quantity is reduced to 5%, the maximum annual operating cost saving amount can reach 256,800 yuan / year, and the corresponding energy-saving optimization scheme is the second strategy. At this time, the by-product steam quantity should be maintained unchanged, and from Table 4, it can be seen that the fuel gas consumption can be reduced by 10.70 Nm 3The combustion air feed quantity should be adjusted from the current value of 20.99 t / h to 17.72 t / h.

[0127] Therefore, by using the scheme of the present disclosure to optimize the combustion air feed quantity of the direct conversion gasification process, while determining the optimal energy-saving optimization strategy of the system, the residual oxygen content of the flue gas is reduced to 5%, the optimized combustion air feed quantity is 17.72 t / h, and the corresponding energy-saving optimization strategy is the second strategy, i.e., the amount of by-product steam remains unchanged, the amount of fuel gas changes, and the annual operating cost can be saved by 256,800 yuan.

[0128] Currently, the residual oxygen content of the flue gas of the direct conversion gasification process is 7.2%, as shown in Table 1, at this time, the fuel air feed quantity is 20.99 t / h, and the fuel gas feed quantity is 1100 Nm 3 / h. Therefore, by using the scheme of the present disclosure to optimize the combustion air feed quantity of the direct conversion gasification process, the air feed quantity per unit time can be reduced by about 15.59%, the fuel gas feed quantity per unit time can be saved by 0.97%, and the annual operating cost can be saved by 256,800 yuan.

[0129] In the current direct conversion gasification combustion system, the residual oxygen content of the flue gas is often higher than the ideal level (3-5%), and there is a situation of excessive combustion air feed quantity, which will reduce the combustion thermal efficiency and cause unnecessary waste of energy or resources; the method and optimization strategy for adjusting the air feed quantity of the direct conversion gasification process according to the present disclosure are based on the extraction of current production data and strict simulation calculation, the correlation between the residual oxygen content of the flue gas and the air feed quantity is determined, the increase of by-product steam and the saving of fuel gas are used as the energy-saving optimization strategies, the potential of saving the annual operating cost of the system under different residual oxygen content targets of the flue gas is explored, the maximum annual operating cost saving amount is used as the economic evaluation index to determine the optimal energy-saving optimization strategy, and the obtained energy-saving optimization scheme, air feed quantity theoretical value and annual operating cost saving amount are accurate and effective, which has important significance for guiding the adjustment of industrial parameters and energy-saving optimization.

[0130] In one embodiment, a straight conversion gasification process is acquired, current combustion data of a square box furnace is extracted, a current benchmark state of the straight conversion gasification process is evaluated, and an Aspen Plus simulation model is constructed; based on current fuel gas feed, a flue gas residual oxygen amount-air feed amount / fuel gas feed amount / combustion heat release amount graph is constructed; based on the graph and steam enthalpy, air feed amounts corresponding to different flue gas residual oxygen amounts in the first strategy and change amounts of by-product steam are acquired, and based on a steam unit price, an annual operating cost saving amount is acquired; based on the graph and a fuel gas combustion heat value, air feed amounts corresponding to different flue gas residual oxygen amounts in the second strategy and change amounts of fuel gas feed are acquired, and based on a fuel gas unit price, an annual operating cost saving amount is acquired; a flue gas residual oxygen amount-air feed amount / fuel gas change amount / by-product steam change amount / annual operating cost saving amount change trend graph corresponding to the first strategy and the second strategy is drawn, and an economic optimal energy saving optimization strategy under different flue gas residual oxygen amount targets and air feed amounts, fuel gas change amounts and by-product steam change amounts corresponding to the economic optimal energy saving optimization strategy are determined.

[0131] Although the embodiments of the present application are described above with reference to the drawings, the present application is not limited to the above-described specific embodiments and application fields, and the above-described specific embodiments are merely illustrative and instructive, but not restrictive. Those skilled in the art can make many forms under the guidance of the present specification and without departing from the scope protected by the claims of the present application, and all of these belong to the protection of the present application.

Claims

1. A method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace, characterized in that: include: S100: Obtain the direct-to-gasification process flow, extract current combustion data of the box furnace, conduct a current baseline assessment of the direct-to-gasification process, and construct an Aspen Plus simulation model; S2 00: Based on the current fuel gas feed, adjust the air feed rate of the square box furnace in the Aspen Plus simulation model to build the flue gas residual oxygen content and air feed rate (F air ), fuel gas feed rate (F fuel ) and total heat release from combustion (Q total ) trend chart; S300: Based on the trend graph, obtain the current fuel gas feed rate, the current box furnace heat demand, and the air feed rate and boiler feed water preheater heat load under the process gas preheater heat load as the flue gas residual oxygen content change trend, which is recorded as the first strategy; Extract the thermal enthalpy of the by-product steam in the direct-conversion process. Based on the variation trend of the boiler feedwater preheater heat load with the residual oxygen content in the flue gas, obtain the variation of the by-product steam in the direct-conversion gasification process under different residual oxygen contents in the flue gas. Obtain the unit price of by-product steam and calculate the annual operating cost savings brought about by the change of by-product steam as the trend of the change of flue gas residual oxygen content; S400: Obtain the combustion calorific value of the natural gas fuel. Based on the trend graph, obtain the trend of the change in the air feed rate and the fuel gas feed rate as a function of the residual oxygen content in the flue gas under the current boiler feed water preheater heat load, the current box furnace heat demand, and the process gas preheater heat load, to be recorded as the second strategy. Obtain the unit price of the fuel gas and calculate the annual operating cost savings resulting from fuel gas savings as a function of the residual oxygen content in the flue gas. S500: Draw trend charts of flue gas residual oxygen content, air feed rate, fuel gas change, by-product steam change, and annual operating cost savings corresponding to the first strategy and the second strategy, and determine the economically optimal strategy under different flue gas residual oxygen content targets and its corresponding air feed rate, fuel gas change, and by-product steam change.

2. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 1, characterized in that: In step S100, in the direct conversion gasification process, the natural gas and steam mixture are respectively sent to the square box first stage furnace and the heat exchange reformer. The two first stage reformed gases are merged and then enter the second stage furnace. The heat source of the square box furnace is the burning fuel gas, and the heat source of the heat exchange reformer is the high-temperature second stage reformed gas; the fuel gas is sent to the convection section coil of the first stage reformer for heating and then used as fuel for the top burner and auxiliary burner of the square box reformer. The flue gas from the first stage reformer enters the convection section to preheat the raw gas, fuel gas and air process gas and preheat the boiler feed water to produce by-product steam, and finally goes to the induced draft fan for discharge at the designed flue gas temperature.

3. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 1, characterized in that: In step S100, the extracted current combustion data of the square box furnace includes the fuel gas feed rate, the air feed rate, the total heat release of combustion and the residual oxygen content of the flue gas; the current baseline state assessment of the direct conversion gasification process includes assessing the heat requirement of the first stage conversion, the heat load of each process gas preheater, the heat load of the boiler feed water preheater and the designed flue gas temperature.

4. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 1, characterized in that: In step S200, the current fuel gas feed is maintained unchanged, and the combustion air feed rate of the square box furnace is gradually adjusted to obtain the trend of the flue gas residual oxygen content and the total combustion heat release under different fuel and air feed rates.

5. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 1, characterized in that: In step S300, in the first strategy, the air feed rate under different flue gas residual oxygen contents is expressed as: ， Among them, F air,策略1 represents the air feed rate in the first strategy. The heat load of the boiler feed water preheater under different flue gas residual oxygen contents is expressed as: ， Among them, Q3 represents the heat load of boiler feed water preheater; Q total represents the total heat released by combustion; Q1 represents the heat required for the first stage conversion; Q2 represents the heat load of the process gas preheater; the superscript ini represents the current value; the change in the by-product steam under different flue gas residual oxygen contents is expressed as: ， in, F steam Indicates the change in by-product steam; h steam represents the steam enthalpy; the annual operating cost savings under different flue gas residual oxygen contents are expressed as: ， in, Co1 represents the annual operating cost savings of the first strategy; c steam Indicates the unit price of steam.

6. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 1, characterized in that: In step S400, in the second strategy, the air feed rate under different flue gas residual oxygen contents is expressed as: ， Among them, F air,策略2 is the air feed amount in the second strategy; Q total Indicates the total heat released by combustion; the superscript ini indicates the current value.

7. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 1, characterized in that: In step S400, in the second strategy, the change in fuel gas feed under different flue gas residual oxygen contents is expressed as: ， in, F fuel Indicates the change in fuel gas; q fuel Indicates the combustion calorific value of fuel gas; Q total Indicates the total heat released by combustion; the superscript ini indicates the current value.

8. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 1, characterized in that: In step S400, in the second strategy, the annual operating cost savings under different flue gas residual oxygen contents are expressed as: ， in, Co2 represents the annual operating cost savings of the second strategy; c fuel Indicates the unit price of natural gas fuel; F fuel Indicates the change in fuel gas.

9. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 1, characterized in that: In step S500, with the flue gas residual oxygen content as the horizontal axis and the air feed rate, fuel gas change, by-product steam change and annual operating cost savings as the vertical axis, trend graphs of the flue gas residual oxygen content, air feed rate, fuel gas change, by-product steam change and annual operating cost savings corresponding to the first strategy and the second strategy are drawn respectively.

10. The method for optimizing a direct-conversion gasification process for adjusting the combustion air feed rate of a square box furnace according to claim 9, characterized in that: For a given target residual oxygen content, the annual operating cost savings corresponding to the first strategy and the second strategy are determined based on the trend chart of flue gas residual oxygen content, air feed rate, fuel gas change, by-product steam change, and annual operating cost savings: Co1> Co2, then the first strategy is the most economical and energy-saving solution, the fuel gas consumption remains unchanged, the by-product steam volume changes, and the air feed volume and by-product steam volume changes under the target residual oxygen volume are obtained from the trend chart; if Co1< Co2, the second strategy is the most economical and energy-saving solution. The amount of by-product steam remains unchanged, the amount of fuel gas changes, and the change in air feed amount and fuel gas under the target residual oxygen content is obtained from the trend chart; Co1 represents the annual operating cost savings of the first strategy; Co2 represents the annual operating cost savings of the second strategy.

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