Calculation method and system for key parameters of saturated steam power generation using waste heat from steelmaking flue gas from electric furnace

Abstract

The present invention provides a method for calculating the key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation, comprising the following steps: first, obtaining the flue gas enthalpy of the electric furnace steelmaking flue gas, and calculating the flue gas heat at the boiler inlet; second, calculating the boiler efficiency and the effective use of heat by the boiler; third, calculating the evaporation amount of the boiler saturated steam according to the effective use of heat, self-use steam enthalpy, sewage enthalpy, and condensed water enthalpy; finally, taking a production cycle of electric furnace steelmaking as the research object, calculating the necessary heat storage capacity of the heat accumulator and the volume of the heat accumulator. The present invention also provides an electric furnace steelmaking flue gas waste heat saturated steam power generation system based on the above calculation method. By studying the key technologies of steelmaking electric furnace waste heat saturated steam power generation, the key parameters of the waste heat boiler and the heat accumulator are determined more accurately, which can avoid the selection error of the steelmaking electric furnace waste heat saturated steam power generation system, ensure the safe and stable operation of the unit, and improve the boiler operation efficiency and steam supply quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste heat recovery of flue gas from electric furnace steelmaking, and specifically relates to a method for calculating key parameters of saturated steam power generation from waste heat of flue gas from electric furnace steelmaking, and also relates to a saturated steam power generation system from waste heat of flue gas from electric furnace steelmaking. Background Art

[0002] At present, there are two types of steelmaking processes in the world: converter steelmaking and electric furnace steelmaking. Compared with these two steelmaking processes, electric furnace steelmaking has the following advantages: saving iron ore resources, short production cycle, low investment, energy saving, reducing carbon dioxide emissions, saving land and water resources, promoting the sustainable development of the steel industry, and maintaining a virtuous cycle of the economy. Therefore, countries around the world attach great importance to the development of electric furnace steelmaking production processes with scrap steel as the main raw material. In order to achieve carbon peak by 2030 and carbon neutrality by 2060, my country will gradually use electric furnace steelmaking instead of converter steelmaking in the next 3 to 15 years.

[0003] The flue gas treatment and waste heat recovery technology brought by the electric furnace steelmaking process needs to be studied in depth. At present, there are two ways to recover waste heat from electric furnace steelmaking. The flue gas produces saturated steam through convection heat exchange in the waste heat boiler. The first way uses saturated steam as the steam source for the vacuum furnace, and the second way uses saturated steam to generate electricity. Compared with these two methods, the energy utilization rate of saturated steam power generation is relatively high, which further reduces the energy consumption per ton of steel, is conducive to the sustainable development of enterprises, and enhances the market competitiveness of enterprises. The social and economic benefits are very significant and worthy of vigorous promotion.

[0004] However, since the flue gas generated during the electric furnace steelmaking process has the characteristics of large flue gas volatility, high instantaneous flue gas temperature, high dust content and strong viscosity, it can easily have an adverse effect on the stability and safety of the generator set operation, bringing challenges to the electric furnace steelmaking flue gas waste heat saturated steam power generation technology.

[0005] Based on this, how to optimize and improve the electric furnace steelmaking flue gas waste heat saturated steam power generation system, and control the key parameters and conditions, so that the evaporation volume of the waste heat boiler, the heat storage capacity of the heat accumulator, and the volume of the heat accumulator are controlled within a reasonable range, and eliminate equipment selection errors to ensure the safe and stable operation of the generator set, is a technical problem that needs to be solved urgently. Summary of the invention

[0006] One of the purposes of the present invention is to provide a calculation method that can accurately calculate the key parameters of the waste heat boiler and the heat accumulator in the electric furnace steelmaking flue gas waste heat saturated steam power generation system, providing an important basis for equipment selection.

[0007] The second purpose of the present invention is to provide an electric furnace steelmaking flue gas waste heat saturated steam power generation system in which the selection of waste heat boilers and heat accumulators is more reasonable, the boiler operating efficiency and gas supply quality are improved, and the safe and stable operation of the generator set is ensured.

[0008] The technical solution adopted by the present invention to achieve one of the purposes is to provide a method for calculating key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation, comprising the following steps:

[0009] S1. Obtain the flue gas enthalpy of the electric furnace steelmaking flue gas and calculate the flue gas heat at the boiler inlet;

[0010] S2. Calculate the flue gas loss and the ash physical heat loss according to the flue gas heat at the boiler inlet, and then obtain the boiler efficiency according to the flue gas loss, the ash physical heat loss and the heat dissipation loss;

[0011] S3, obtaining the effective utilization heat of the boiler according to the boiler efficiency and the heat of the flue gas at the boiler inlet;

[0012] S4. Obtain the evaporation amount of boiler saturated steam according to the effectively utilized heat, self-used steam enthalpy, sewage enthalpy, and condensed water enthalpy;

[0013] S5. Taking a production cycle of electric furnace steelmaking as the research object, the average gas production and heating time of the intermittent steam source are obtained, and the required heat storage of the heat accumulator is calculated;

[0014] S6. Obtain the volume of the heat accumulator according to the required heat storage amount, the thermal efficiency of the heat accumulator and the water filling coefficient.

[0015] Based on the above technical solution, in step S1, the calculation formula of flue gas enthalpy is: y =I q +I k +I h ;

[0016] In the formula, I y is the flue gas enthalpy; I q is the enthalpy of the mixed gas; I k is the air enthalpy; I h is the fly ash enthalpy in the flue gas.

[0017] On the basis of the above technical solution, the calculation formula of the enthalpy of the mixed gas is:

[0018] In the formula, They represent the enthalpy values ​​of CO2, N2, H2O, and O2 at θ℃ respectively; Respectively represent the volume fractions of CO2, N2, H2O, and O2 in the flue gas; V y is the flue gas volume at the boiler inlet;

[0019] The calculation formula of the air enthalpy is: k =ΔV k (cθ) k ; In the formula, ΔV k is the air leakage; (cθ) k is the enthalpy of air at θ℃;

[0020] The calculation formula of the fly ash enthalpy is: h =α h V y (cθ) h ; In the formula, α h is the dust concentration in the flue gas; (cθ) h is the enthalpy value of 1kg ash at θ℃.

[0021] On the basis of the above technical solution, in step S2, the calculation formula of boiler efficiency is:

[0022] η=100-q2-q5-q6;

[0023] In the formula, η is the boiler efficiency, unit is %; q2 is the flue gas loss; q5 is the heat dissipation loss; q6 is the ash physical heat loss.

[0024] Based on the above technical solution, the calculation formula of the exhaust heat loss q2 is:

[0025]

[0026] In the formula, is the heat removed by the dry flue gas, Q r is the heat of flue gas at boiler inlet; is the sensible heat of water vapor contained in the flue gas; C p·gy For dry flue gas from t0 to t py The average specific heat capacity at constant pressure; is the water vapor from t0 to t py The average specific heat capacity at constant pressure; t0 is the reference temperature; t py is the exhaust gas temperature; V gy V is the volume of dry flue gas generated by incomplete combustion of each kg of base fuel received; H2O is the volume of water vapor contained in the flue gas;

[0027] The calculation formula of the ash physical heat loss q6 is:

[0028]

[0029] Where, (cθ) ph is the enthalpy value of 1kg ash at the ash discharge temperature; α phis the proportion of the ash discharge amount of a certain ash discharge point to the total ash discharge amount; α h is the dust concentration in the flue gas; Vy is the flue gas volume at the boiler inlet; Q r is the flue gas heat at the boiler inlet.

[0030] Based on the above technical solution, in step S3, the boiler effectively utilizes the heat Q yx The calculation formula is:

[0031] Q yx =ηQ r ;

[0032] In the formula, Q yx is the effective utilization heat of the boiler; η is the boiler efficiency; Q r is the flue gas heat at the boiler inlet.

[0033] On the basis of the above technical solution, in step S4, the calculation formula of the evaporation amount of saturated steam from the boiler is:

[0034]

[0035] Where D gr is the saturated steam evaporation of the boiler, D zy is the steam flow rate for self-use, D pw is the sewage flow rate, D ns is the condensate flow rate; h” gr 、h gs 、h ns are saturated steam enthalpy, feed water enthalpy, and condensed water enthalpy after heat exchange; h zy 、h gs and h' are the self-use steam enthalpy, feed water enthalpy and saturated water enthalpy respectively.

[0036] On the basis of the above technical solution, in step S5, a production cycle of electric furnace steelmaking includes: waiting mode, shaft charging I, shaft charging II, shaft discharging I, shaft discharging II, smelting-shaft full, smelting-shaft empty, steel tapping-power on, steel tapping-power off.

[0037] On the basis of the above technical solution, in step S5, the calculation formula of the volume of the heat accumulator is:

[0038]

[0039] Where: V is the volume of the heat accumulator; G is the required heat storage capacity of the heat accumulator; η xr is the thermal efficiency of the heat storage device; is the water filling coefficient; g1 is the unit saturated water heat storage capacity;

[0040] The calculation formula for the required heat storage capacity G of the heat accumulator is:

[0041]

[0042] Where Q is the average steam production of the intermittent steam source in one production cycle of electric furnace steelmaking; t is the heating time of one production cycle of electric furnace steelmaking.

[0043] The technical solution adopted by the present invention to achieve the second purpose is: to provide an electric furnace steelmaking flue gas waste heat saturated steam power generation system based on the electric furnace steelmaking flue gas waste heat saturated steam power generation key parameter calculation method according to one of the purposes of the present invention, which comprises a flue gas subsystem and a power generation thermal subsystem;

[0044] The flue gas subsystem includes: a settling chamber, a quenching tower, a waste heat boiler, a bag filter, a chimney and an induced draft fan;

[0045] The power generation thermal subsystem includes: a supplementary steam-water separator, a main steam-water separator, a saturated steam turbine, a generator, a condenser, a cooling tower, a condensate pump, a deaerator, a waste heat boiler, a condensate heat exchanger and a heat accumulator;

[0046] The condensate heat exchanger is arranged inside the waste heat boiler.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention provides a method for calculating the key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation, studies the key parameters of the waste heat boiler and heat accumulator, which are key equipment of the steelmaking electric furnace waste heat saturated steam power generation system, and provides an important reference for selecting suitable waste heat boilers and heat accumulators. The electric furnace steelmaking flue gas waste heat saturated steam power generation system based on the calculation method can significantly improve the boiler operation efficiency and steam supply quality, which is conducive to the accurate thermal design of the steelmaking electric furnace waste heat saturated steam power generation technology and ensures the safe and stable operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic flow chart of a method for calculating key parameters of an electric furnace steelmaking flue gas waste heat saturated steam power generation system provided by the present invention;

[0050] Figure 2 A schematic diagram of the structure of a flue gas subsystem of an electric furnace steelmaking flue gas waste heat saturated steam power generation system provided by an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of the structure of a thermal power generation subsystem of an electric furnace steelmaking flue gas waste heat saturated steam power generation system provided in an embodiment of the present invention.

[0052] Among them, 1-sedimentation chamber; 2-quenching tower; 3-waste heat boiler; 4-bag dust collector; 5-chimney; 6-induced draft fan; 7-steam steam-water separator; 8-main steam steam-water separator; 9-saturated steam turbine; 10-generator; 11-condenser; 12-cooling tower; 13-condensate pump; 14-deaerator; 15-condensate heat exchanger; 16-heat accumulator. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0055] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0056] Example

[0057] The flue gas generated during the electric furnace steelmaking process can reach a temperature of more than 1500°C at its highest, but only 100°C at its lowest. The flue gas temperature fluctuates greatly and the flue gas is discontinuous. In addition, the flue gas from electric furnace steelmaking also has the characteristics of high dust content and strong viscosity, which can easily have an adverse effect on the stability and safety of the generator set operation, and bring challenges to the technology of saturated steam power generation from waste heat of flue gas from electric furnace steelmaking. In view of the above situation, the present invention provides a system that uses saturated steam generated by convection heat exchange between the flue gas from electric furnace steelmaking and the water-cooled wall of the waste heat boiler to generate electricity.

[0058] See also Figure 2 and Figure 3 , Figure 2 and Figure 3 They are respectively structural schematic diagrams of a flue gas subsystem and a power generation thermal subsystem of a saturated steam power generation system for electric furnace steelmaking flue gas waste heat provided by the present invention.

[0059] The flue gas subsystem includes: a settling chamber 1, a quenching tower 2, a waste heat boiler 3, a bag filter 4, a chimney 5 and an induced draft fan 6;

[0060] The power generation thermal subsystem includes: a supplementary steam water separator 7, a main steam water separator 8, a saturated steam turbine 9, a generator 10, a condenser 11, a cooling tower 12, a condensate pump 13, a deaerator 14, a waste heat boiler 3, a condensate heat exchanger 15 and a heat accumulator 16.

[0061] In the present invention, the condensate heat exchanger 16 is arranged inside the waste heat boiler 3. By arranging the condensate heat exchanger in the furnace, energy saving effect can be achieved.

[0062] During the design phase of the above system, it is necessary to calculate whether the key equipment waste heat boiler and heat accumulator are reasonable, verify the boiler saturated steam evaporation capacity and heat accumulator related parameters, and then select equipment based on the relevant parameters to ensure safe and stable operation of the unit and improve boiler operation efficiency and steam supply quality.

[0063] This embodiment provides a method for calculating key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation. The flow chart of the calculation method is as follows: Figure 1 As shown, it includes the following steps:

[0064] S1. Obtain the flue gas enthalpy of the electric furnace steelmaking flue gas and calculate the flue gas heat at the boiler inlet;

[0065] S2. Calculate the flue gas loss and the ash physical heat loss according to the flue gas heat at the boiler inlet, and then obtain the boiler efficiency according to the flue gas loss, the ash physical heat loss and the heat dissipation loss;

[0066] S3, obtaining the effective utilization heat of the boiler according to the boiler efficiency and the heat of the flue gas at the boiler inlet;

[0067] S4. Obtain the evaporation amount of boiler saturated steam according to the effectively utilized heat, self-used steam enthalpy, sewage enthalpy, and condensed water enthalpy;

[0068] S5. Taking a production cycle of electric furnace steelmaking as the research object, the average gas production and heating time of the intermittent steam source are obtained, and the required heat storage of the heat accumulator is calculated;

[0069] S6. Obtain the volume of the heat accumulator according to the required heat storage amount, the thermal efficiency of the heat accumulator and the water filling coefficient.

[0070] In the present invention, on the one hand, the relevant parameters of the flue gas from electric furnace steelmaking are used as an important reference for the selection of waste heat boilers. First, the flue gas enthalpy is calculated to obtain the flue gas heat at the boiler inlet; then, various heat losses are calculated based on the flue gas heat at the boiler inlet to obtain accurate boiler efficiency and the effective utilization heat of the boiler. Then, based on the effective utilization heat, self-use steam enthalpy, sewage enthalpy, and condensate enthalpy of the condensate heat exchanger inside the boiler, the saturated steam evaporation amount of the boiler is calculated to obtain an important reference for the selection of waste heat boilers. On the other hand, in the selection of the heat accumulator, the required heat storage amount of the heat accumulator is based on a complete production cycle of electric furnace steelmaking, and the average gas production and heating time are obtained to obtain a more accurate required heat storage amount; on this basis, the volume of the heat accumulator is calculated, and the above parameters are used as an important reference for the selection of the heat accumulator in the saturated steam power generation system.

[0071] In the present invention, the flue gas volume at the boiler heating surface outlet is first calculated using the following formula:

[0072] V' y =(1+Δα)×V y (1)

[0073] Where V y 、V' y is the flue gas volume at the inlet and outlet of the heating surface, Nm 3 / h; Δα is the air leakage coefficient of the heating surface, which can be checked and is defined as the ratio of the air leakage volume of the heating surface to the smoke volume at the heating surface inlet.

[0074] In step S1, the flue gas enthalpy includes the enthalpy of the mixed gas, the air enthalpy and the fly ash enthalpy in the flue gas, and the calculation formula is:

[0075] I y =I q +I k +I h (2);

[0076] In the formula, I y is the flue gas enthalpy, kJ / h; I q is the enthalpy of the mixed gas, kJ / h; I k is the air enthalpy, kJ / h; I h is the enthalpy of fly ash in flue gas, kJ / h.

[0077] Wherein, the calculation formula of the enthalpy of the mixed gas is:

[0078]

[0079] In the formula, Respectively represent the enthalpy values ​​of CO2, N2, H2O, and O2 at θ℃, kJ / Nm 3 ; Respectively represent the volume fractions of CO2, N2, H2O, and O2 in the flue gas; V y is the flue gas volume at the inlet of the waste heat boiler, Nm 3 / h.

[0080] The calculation formula of the air enthalpy is: k =ΔV k (cθ) k (4);

[0081] Where, (cθ) k is the enthalpy of air at θ℃, kJ / Nm 3 ; ΔV k is the air leakage, Nm 3 / h, calculated based on the air leakage coefficient and the flue gas volume at the boiler inlet;

[0082] The calculation formula of fly ash enthalpy is: h =α h V y (cθ) h I h =α h V y (cθ) h (5);

[0083] Where, (cθ) h is the enthalpy value of 1kg ash at θ℃, kJ / kg; α h is the dust concentration in the flue gas, g / Nm 3 .

[0084] The flue gas enthalpy I calculated according to the above method is y , the heat of flue gas at the boiler inlet Q can be calculated r .

[0085] Furthermore, in step S2, the method for obtaining the boiler efficiency is as follows:

[0086] For waste heat boilers, the chemical incomplete combustion heat loss (q3) and mechanical incomplete heat loss (q4) are 0. Therefore, in the present invention, only the exhaust loss (q2), heat dissipation loss (q5) and ash physical heat loss (q6) are considered in the calculation of boiler efficiency. The calculation formula of the exhaust heat loss q2 of the waste heat boiler is:

[0087]

[0088] In the formula, is the heat removed by the dry flue gas, Q r is the heat of flue gas at boiler inlet; is the sensible heat of water vapor contained in the flue gas; C p·gy For dry flue gas from t0 to t py The average specific heat capacity at constant pressure; is the water vapor from t0 to t py The average constant pressure specific heat capacity of

[0089]

[0090]

[0091] In the formula, is the heat removed by the dry flue gas, Q r is the heat of flue gas at boiler inlet; is the sensible heat of water vapor contained in the flue gas; C p·gy For dry flue gas from t0 to tpy The average specific heat capacity at constant pressure; is the water vapor from t0 to t py The average constant pressure specific heat capacity; t0 is the reference temperature, which is generally the air temperature at the inlet of the blower; t py is the exhaust gas temperature; V gy The volume of dry flue gas generated by incomplete combustion of each kg of base fuel received, in Nm 3 / kg; V H2O The volume of water vapor contained in the flue gas, in Nm 3 / kg.

[0092] The heat dissipation loss q5 can be determined based on experience or selected with reference to the boiler.

[0093] The ash physical heat loss q6 is the percentage of the heat brought out by the ash at each ash discharge point to the flue gas enthalpy at the inlet of the waste heat boiler. The calculation formula is:

[0094]

[0095] Where, (cθ) ph is the enthalpy value of 1kg ash at the ash discharge temperature, kJ / kg; α ph The proportion of the ash discharge amount of a certain ash discharge point to the total ash amount;

[0096] Finally, the boiler efficiency η (%) is calculated based on the exhaust loss (q2), heat dissipation loss (q5) and ash physical heat loss (q6). The calculation formula is as follows:

[0097] η=100-q2-q5-q6 (9);

[0098] Further, in step S3, the effective utilization heat Q of the boiler yx The calculation formula is:

[0099] Q yx =ηQ r (10);

[0100] In the formula, Q yx is the effective utilization heat of the boiler, KJ / s; Q r is the boiler inlet heat, KJ / s; η is the boiler efficiency.

[0101] Furthermore, in step S4, the method for obtaining the evaporation amount of saturated steam from the boiler is as follows:

[0102] First, according to the effective utilization of heat Q yx The calculation formula (11) is used to obtain the boiler saturated steam evaporation capacity D gr The calculation formula (12)

[0103] For saturated steam boilers, the calculation formula for boiler evaporation is:

[0104] Q yx =D gr (h” gr -h gs )+D zy (h zy -h gs )+D pw (h'-h gs )+D ns (h ns -h gs ) (11);

[0105] Right now

[0106] Where D gr is the saturated steam evaporation of the boiler, D zy is the steam flow rate for self-use, D pw is the sewage flow rate, D ns is the condensate flow rate, the unit is kg / s; h" gr 、h gs 、h ns They are saturated steam enthalpy, feed water enthalpy, and condensed water enthalpy after heat exchange, kJ / kg; h zy 、h gs and h' are the self-use steam enthalpy, feed water enthalpy and saturated water enthalpy, respectively, in kJ / kg.

[0107] Since the steam power generation system of the present invention sets the condensate heat exchanger inside the waste heat boiler, the present invention also adjusts and supplements the calculation formula of the boiler evaporation amount accordingly. In the above calculation method, the self-use steam enthalpy of the boiler drum is used as a calculation parameter, and the change of the condensate enthalpy value is also fully considered when calculating the boiler evaporation amount. This calculation method takes into account a variety of influencing factors more comprehensively and designs a more accurate calculation formula to achieve accurate calculation of key parameters, provide necessary conditions for the selection of appropriate equipment, and ensure the safe, stable and environmentally friendly operation of the steam power generation system.

[0108] The rated evaporation capacity of a boiler refers to the evaporation capacity of a boiler specified when the designed fuel is used and the efficiency is guaranteed under the rated steam parameters and rated feed water temperature. The maximum continuous evaporation capacity is usually 1.03 to 1.2 times the rated evaporation capacity. The selection of the waste heat boiler can be realized based on the above calculation results.

[0109] Furthermore, in step S5, the method for obtaining the required heat storage capacity of the heat storage device is as follows:

[0110] The amount of steam that must be stored in the accumulator is referred to as the required heat storage, generally represented by G. The flue gas of the steelmaking electric furnace flows through the waste heat boiler to generate saturated steam to drive the steam turbine to generate electricity. The calculation formula for the required heat storage is:

[0111]

[0112] Where, Q is the average steam production of the intermittent steam source in a steam production cycle, kg / h; t is the charging time (i.e., the steam production time in the steam production cycle), min;

[0113] Among them, Q and t are calculated according to a production cycle of electric furnace steelmaking. In the present invention, a production cycle of electric furnace steelmaking includes: waiting mode, shaft charging I, shaft charging II, shaft discharging I, shaft discharging II, smelting-shaft full, smelting-shaft empty, steel tapping-power on, steel tapping-power off and other links. Since the steam production fluctuates greatly at different stages of the same production cycle of electric furnace steelmaking, the present invention calculates the necessary heat storage according to a complete production cycle of electric furnace steelmaking, so that steam can be continuously and stably input to users after passing through the heat accumulator, avoiding overpressure of the waste heat boiler and tripping the safety valve to discharge steam.

[0114] Then, the required heat storage G is used to calculate the volume V of the heat storage tank. The calculation formula for the volume V of the heat storage tank is:

[0115]

[0116] Where: V is the volume of the heat accumulator, m 3 ; G is the required heat storage capacity of the heat accumulator, kg; η xr is the thermal efficiency of the heat storage device; is the water filling coefficient; g1 is the heat required per unit of saturated water.

[0117] Preferably, the thermal efficiency η of the heat accumulator is 0.98-0.99, and the water filling coefficient The value of is 0.9.

[0118] Furthermore, the present invention also determines the working pressure of the heat accumulator. The charging pressure is the highest pressure at the end of the heat charging process of the heat accumulator, which is represented by P1. The heat release pressure is the lowest pressure at the end of the heat release process of the heat accumulator, which is represented by P2. The highest charging pressure is the rated pressure of the boiler minus the pressure drop loss of the pipeline from the boiler to the steam heat accumulator, and the lowest heat release pressure is the lowest pressure at the heat user plus the pressure drop loss of the pipeline from the heat accumulator outlet to the heat user.

[0119] Finally, the type of heat accumulator for the electric furnace steelmaking flue gas waste heat saturated steam power generation system can be selected based on the volume of the heat accumulator, the required heat storage capacity of the heat accumulator and the working pressure of the heat accumulator.

[0120] In summary, the method for calculating the key parameters of an electric furnace steelmaking flue gas waste heat saturated steam power generation system provided by the present invention is suitable for selecting equipment that has not yet been installed during the system design stage. The present invention combines the layout of the process equipment with the characteristics of the electric furnace steelmaking flue gas itself, takes into account a variety of influencing factors more comprehensively, and designs a more accurate calculation formula to achieve accurate calculation of key parameters, and then selects appropriate waste heat boilers and heat accumulators based on the relevant parameters. This calculation method can improve the operating efficiency of the boiler and the quality of steam supply, is conducive to the accurate thermal design of the steelmaking electric furnace waste heat saturated steam power generation technology, ensures the safe and stable operation of the unit, and has important guiding significance for safe production.

[0121] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation, comprising the following steps: S1. Obtain the flue gas enthalpy of the electric furnace steelmaking flue gas and calculate the flue gas heat at the boiler inlet; S2. Calculate the flue gas loss and the ash physical heat loss according to the flue gas heat at the boiler inlet, and then obtain the boiler efficiency according to the flue gas loss, the ash physical heat loss and the heat dissipation loss; S3, obtaining the effective utilization heat of the boiler according to the boiler efficiency and the heat of the flue gas at the boiler inlet; Effective use of heat The calculation formula is: ; In the formula, For efficient use of heat by boilers; is the boiler efficiency; is the heat of flue gas at boiler inlet; S4. Obtain the evaporation amount of boiler saturated steam according to the effectively utilized heat, self-use steam enthalpy, sewage enthalpy, and condensed water enthalpy; the calculation formula of the evaporation amount of boiler saturated steam is: ； In the formula, is the saturated steam evaporation of the boiler, The steam flow rate for self-use, The sewage flow rate, is the condensate flow rate; , , They are saturated steam enthalpy, feed water enthalpy, and condensed water enthalpy after heat exchange; , , They are self-use steam enthalpy, feed water enthalpy, and saturated water enthalpy respectively; S5. Taking a production cycle of electric furnace steelmaking as the research object, the average gas production and heating time of the intermittent steam source are obtained, and the required heat storage of the heat accumulator is calculated; A production cycle of electric furnace steelmaking includes: waiting mode, shaft charging I, shaft charging II, shaft discharging I, shaft discharging II, smelting-shaft full, smelting-shaft empty, steel tapping-power on, steel tapping-power off; Heat storage is required G The calculation formula is: ; In the formula, Q It is the average steam production of intermittent steam source in one production cycle of electric furnace steelmaking; t It is the heating time of one production cycle of electric furnace steelmaking; S6. Obtaining the volume of the heat accumulator according to the required heat storage, the thermal efficiency of the heat accumulator and the water filling coefficient; The volume of the heat accumulator is calculated as: ; Where: V is the volume of the heat accumulator; G The required heat storage capacity of the heat storage device; is the thermal efficiency of the heat storage device; is the water filling coefficient; g1 is the unit saturated water heat storage capacity.

2. The method for calculating key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation according to claim 1, characterized in that: In step S1, the calculation formula of flue gas enthalpy is: ; In the formula, is the flue gas enthalpy; is the enthalpy of the mixed gas; is the enthalpy of air; is the fly ash enthalpy in the flue gas.

3. The method for calculating key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation according to claim 2, characterized in that: The calculation formula of the enthalpy of the mixed gas is: ； In the formula, , , , Respectively represent CO2, N2, H2O, O2 in Enthalpy at ℃; , , , They represent the volume fractions of CO2, N2, H2O and O2 in the flue gas respectively; is the flue gas volume at the boiler inlet; The calculation formula of the air enthalpy is: ; In the formula, is the air leakage; For air Enthalpy at ℃; The calculation formula of the fly ash enthalpy is: ; In the formula, is the dust concentration in the flue gas; For 1kg ash Enthalpy value at ℃.

4. The method for calculating key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation according to claim 1, characterized in that: In step S2, the calculation formula of boiler efficiency is: ； In the formula, is the boiler efficiency; q2 is the exhaust loss; q5 is the heat loss; q6 is the ash physical heat loss.

5. The method for calculating key parameters of electric furnace steelmaking flue gas waste heat saturated steam power generation according to claim 4, characterized in that: The calculation formula of the exhaust loss q2 is: ； In the formula, The heat carried away by the dry flue gas, is the heat of flue gas at boiler inlet; is the sensible heat of water vapor contained in the flue gas; For dry flue gas arrive The average specific heat capacity at constant pressure; For water vapor from arrive The average specific heat capacity at constant pressure; is the reference temperature; is the exhaust temperature; Vy The volume of dry flue gas generated by incomplete combustion of each kg of base fuel received; VH2O is the volume of water vapor contained in the flue gas; The calculation formula of the ash physical heat loss q6 is: ； In the formula, is the enthalpy value of 1kg ash at the ash discharge temperature; The proportion of the ash discharge amount of a certain ash discharge point to the total ash amount; is the dust concentration in the flue gas; Vy is the flue gas volume at the boiler inlet; is the flue gas heat at the boiler inlet.

6. An electric furnace steelmaking flue gas waste heat saturated steam power generation system based on the electric furnace steelmaking flue gas waste heat saturated steam power generation key parameter calculation method according to any one of claims 1 to 5, characterized in that: Includes flue gas subsystem and power generation thermal subsystem; The flue gas subsystem comprises: a settling chamber (1), a quenching tower (2), a waste heat boiler (3), a bag filter (4), a chimney (5) and an induced draft fan (6); The power generation thermal subsystem comprises: a supplementary steam-water separator (7), a main steam-water separator (8), a saturated steam turbine (9), a generator (10), a condenser (11), a cooling tower (12), a condensate pump (13), a deaerator (14), a waste heat boiler (3), a condensate heat exchanger (15) and a heat accumulator (16); The condensate heat exchanger (15) is arranged inside the waste heat boiler (3).

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