CN203296838U - Heating furnace flue gas and steam waste heat recovery and power generation system - Google Patents

Abstract

The utility model relates to a heating furnace flue gas and steam waste heat recovery power generation system. The system provides a flue gas waste heat boiler system, a heating furnace vaporization cooling system, a steam turbine generator system, a condensate return water supply system and a combined control system. The flue gas waste heat boiler system includes an economizer, an evaporator, and a superheater; the feed water for the vaporization cooling system comes from the economizer of the heating furnace, and the saturated steam generated enters the superheater of the heating furnace for superheating. According to the operation characteristics of the heating furnace, the utility model unifies the development and utilization of the flue gas of the heating furnace and the vaporized cooling steam, and realizes the power generation of the waste heat of the combined evaporation of the flue gas and steam. It not only utilizes the waste heat of the flue gas, but also utilizes the waste heat of the vaporized cooling saturated steam, and at the same time, it ensures the stability of the system and maximizes the use of waste heat.

Description

Heating furnace flue gas and steam waste heat recovery power generation system

technical field

The utility model relates to metallurgical technology, in particular to the waste heat recovery and utilization technology of a steel rolling heating furnace in a steel plant.

Background technique

Heating furnace is a large energy consumer in iron and steel enterprises, with high energy consumption and low energy utilization level. At present, many enterprises are carrying out technical transformation and upgrading of heating furnaces to achieve energy saving and emission reduction. The main method is to arrange a waste heat boiler in the tail flue of the heating furnace, and use the steam generated by the boiler to generate electricity. For example, the patent number ZL201010114344.7, titled "A Heating Furnace Waste Heat Power Generation System and Its Method", is an additional supplementary combustion waste heat boiler, with the supplementary combustion waste heat boiler as the main body of the system to ensure a certain amount of steam and absorb flue gas fluctuations to reach the system of stability. This waste heat recovery method does utilize part of the heat energy, but there are also some problems. For example, only part of the flue gas heat is recovered, and the waste heat recovery and utilization capacity is limited; in the case of unstable output of the heating furnace, the stability of the flue gas volume cannot be guaranteed, so the continuous and stable operation of the waste heat power generation system cannot be guaranteed. When the flue gas waste heat boiler is out of operation, the system is equivalent to a small thermal power plant, which is prohibited by the state. The energy-saving effect generated by the operation of the waste heat boiler is also partially offset by the lower system parameters (compared to large thermal power plants).

Contents of the invention

The purpose of this utility model is to propose a heating furnace flue gas and steam waste heat recovery power generation system, which can not only achieve the maximum recovery and utilization of heat, but also solve the problem of continuous and stable operation of the waste heat power generation system.

In order to realize the purpose of this utility model, the technical scheme proposed is as follows:

A heating furnace flue gas and steam waste heat recovery power generation system, the waste heat recovery power generation system includes a flue gas waste heat boiler system, a heating furnace vaporization cooling system, a turbine generator system, a condensate return water supply system and a combined control system;

The flue gas waste heat boiler system includes a flue gas waste heat boiler 1 composed of a superheater 2, an evaporator 3, and an economizer 4, a flue gas waste heat boiler drum 5, and a flue gas waste heat boiler drum feed water regulating valve 17;

The heating furnace vaporization cooling system includes a vaporization cooling drum 6, a heating furnace water beam vaporization cooling circuit 7, a vaporization cooling forced circulation pump 8 and a vaporization cooling drum feed water regulating valve 16;

The turbogenerator set includes a steam turbine 9 and a generator 10; wherein,

The flue gas from the main flue of the heating furnace passes through the superheater 2, the evaporator 3, and the economizer 4 in turn for heat exchange and then discharges into the atmosphere;

The condensed water return supply system is respectively connected with the steam turbine 9 of the steam turbine generator set and the inlet of the economizer 4, and the condensed water produced by the steam turbine 9 is sent into the economizer 4;

The outlet of the economizer 4 is respectively connected to the flue gas waste heat boiler drum 5 and the vaporization cooling drum 6, and the heated condensed water is sent to the flue gas waste heat boiler drum 5 and the vaporization cooling drum 6 respectively;

The flue gas waste heat boiler drum 5 is connected to the inlet of the evaporator 3 through a downcomer, and the outlet of the evaporator 3 is connected back to the flue gas waste heat boiler drum 5; the steam pipe of the flue gas waste heat boiler drum 5 is connected to the superheater The entrance of 2; the unsaturated water absorbs the flue gas heat of the evaporator 3 and becomes a mixture of steam and water. After the steam and water are separated in the steam drum 5 of the flue gas waste heat boiler, the saturated water enters the next cycle, and the saturated steam enters the superheater 2;

The vaporization cooling steam drum 6 is connected with the vaporization cooling circuit 7 of the heating furnace water beam through the descending pipe and the vaporization cooling forced circulation pump 8 to form a circulation circuit, so that saturated water enters the heating furnace water beam vaporization cooling circuit 7 and becomes a mixture of steam and water After being sent back to the vaporization cooling drum 6 for steam-water separation, the saturated water enters the next cycle, and the saturated steam enters the superheater 2;

The outlet of the superheater 2 is connected to the steam turbine 9 of the turbogenerator, and the superheater 2 supplies superheated steam to the steam turbine 9 .

The condensed water return supply system includes a condenser 11, a condensed water pump 12, a thermal deaerator 13 and a boiler feed water pump 14; the condenser 11 is connected to the steam turbine 9 to condense exhausted steam after doing work into condensed The water is sent to the thermal deaerator 13 via the condensate pump 12, and is pumped and heated by the steam turbine 9 to realize thermal deaeration, then enters the feedwater pump 14 for pressurization, and then is sent to the economizer 4, Complete the thermodynamic cycle.

The combined control system includes a flue gas waste heat boiler feedwater regulating valve 17 installed on the water supply pipeline from the outlet of the economizer 4 to the flue gas waste heat boiler drum 5; a vaporization cooling drum feedwater regulating valve 16 installed on the economizer 4 The outlet is connected to the water supply pipeline of vaporization cooling steam drum 6; the combined control system adjusts and controls the opening of the two regulating valves according to the water level of the two steam drums, the main steam flow rate, and the steam drum feed water flow rate to ensure the stability of the steam drum water level and the stability of the two steam drums. packages run in parallel.

The utility model unifies the development and utilization of the flue gas of the heating furnace and the vaporized cooling steam, and realizes the combined evaporation of the flue gas and the steam to generate electricity with waste heat. It not only utilizes the residual heat of flue gas, but also utilizes the residual heat of vaporized cooling saturated steam, so as to achieve the maximum utilization of residual heat.

The utility model does not affect the original production process of the heating furnace, uses all the steam produced by the flue gas waste heat boiler for power generation, maximizes the use of waste heat, adapts to the changing requirements of the heating furnace, improves the power generation, and recovers these Waste heat and its soft water resources can also reduce power consumption in the factory area, reduce product costs, and have good social and economic benefits.

Description of drawings

Fig. 1 is a schematic diagram of a heating furnace flue gas and steam waste heat recovery power generation system of the utility model.

in

1 Flue gas waste heat boiler 10 Generator

2 Superheater 11 Condenser

3 evaporator 12 condensate pump

4 Economizer 13 Thermal Deaerator

5 Flue gas waste heat boiler steam drum 14 Boiler feed water pump

6 Evaporative cooling steam drum 15 Combined control system

7 Heating furnace water beam vaporization cooling circuit 16 Evaporation cooling steam drum feed water regulating valve

8 Evaporation cooling forced circulation pump 17 Flue gas waste heat boiler steam drum feed water regulating valve

9 steam turbine

T, P and F are temperature sensor, pressure sensor and flow sensor respectively

Detailed ways

In order to make the purpose, technical solutions and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The system of the utility model mainly includes flue gas waste heat boiler 1, superheater 2, evaporator 3, economizer 4, flue gas waste heat boiler steam drum 5, vaporization cooling steam drum 6, heating furnace water beam vaporization cooling circuit 7, vaporization Cooling forced circulation pump 8, steam turbine 9, generator 10, condenser 11, condensed water pump 12, thermal deaerator 13, boiler feed water pump 14, combined control system 15, vaporization cooling drum feed water regulating valve 16, flue gas waste heat Boiler drum feedwater regulating valve 17, etc.

This system introduces the 400-500°C flue gas at the tail of the main exhaust flue of the heating furnace into the flue gas waste heat boiler 1, and the flue gas system of the waste heat boiler 1 is connected from the main exhaust flue of the heating furnace, and the flue gas passes through the superheater 2, After the evaporator 3 and the economizer 4 perform heat exchange, the temperature drops to about 150°C. It enters the chimney through the induced draft fan and is discharged into the atmosphere.

The thermal circulation system flow of the heating furnace flue gas and steam waste heat recovery power generation system of this system is as follows: the deoxygenated water generated by the thermal deaerator 13 is pressurized by the boiler feed water pump 14, and then sent to the economizer 4 of the flue gas waste heat boiler 1 , absorb the waste heat of the flue gas in the low-temperature area, and send it to the flue gas waste heat boiler drum 5 and the vaporization cooling drum 6 after being heated to a certain temperature. The unsaturated water in the flue gas waste heat boiler drum 5 enters the evaporator 3 through the downcomer , absorb the flue gas heat in the evaporator 3, turn it into a steam-water mixture and send it to the steam drum 5, after the steam-water separation in the steam drum 5, the saturated water enters the next cycle, and the saturated steam enters the superheater 2. The saturated water in the vaporization cooling drum 6 enters the heating furnace water beam vaporization cooling loop 7 through the vaporization cooling forced circulation pump 8, absorbs heat and turns into a mixture of steam and water, and then sends it back to the vaporization cooling drum 6, where the steam and water are separated , the saturated water enters the next cycle, and the saturated steam and the saturated steam generated by the steam drum 5 of the flue gas waste heat boiler enter the superheater 2 together. It is uniformly heated by the superheater 2 of the flue gas waste heat boiler 1 to become superheated steam. The superheated steam enters the steam turbine 9 to do work, and drives the generator 10 to generate electricity. The exhausted steam after work enters the condenser 11 to condense into condensed water, which is sent to the thermal deaerator 13 through the condensed water pump 12, and is heated by steam turbine extraction to realize thermal deoxygenation. Qualified deoxygenated water enters the boiler feed water pump 14 to complete the thermodynamic cycle.

The demineralized water required by the waste heat power generation system is supplied by the condensate return water of the system. System make-up water is supplied by the chemical water treatment system.

The combined control system 15 includes a flue gas boiler waste heat boiler steam drum water supply regulating valve 17, which is installed on the water supply pipeline from the outlet of the economizer 4 to the flue gas waste heat boiler steam drum 5; the vaporization cooling steam drum water supply regulating valve 16 is installed on the coal saving On the water supply pipeline from the device 4 to the vaporization cooling steam drum 6; the combined control system 15 adjusts and controls the opening of the water supply regulating valves 16 and 17 according to the steam drum water level, the steam drum outlet steam flow rate, and the steam drum feed water flow rate, so as to ensure the stability of the steam drum water level. Solve the problem of parallel operation of two steam drums.

The utility model unifies the development and utilization of the flue gas of the heating furnace and the vaporized cooling steam, and realizes the combined evaporation of the flue gas and the steam to generate electricity with waste heat. It not only utilizes the residual heat of flue gas, but also utilizes the residual heat of vaporized cooling saturated steam, so as to achieve the maximum utilization of residual heat.

When the heating furnace is operating at full load, the flue gas volume of the heating furnace and the vaporization cooling evaporation increase less, so the design of the flue gas waste heat boiler and turbogenerator set has a margin to meet the requirements of the changing working conditions of the heating furnace.

The introduction of vaporized cooling steam, using the relatively stable characteristics of vaporized cooling steam, can effectively alleviate the impact of flue gas waste heat fluctuations on the stable operation of the waste heat power generation system, and ensure the long-term safe and stable operation of the waste heat power generation system.

This heating furnace flue gas and steam waste heat recovery power generation system has carried out long-term tracking and research on the operating parameters of flue gas and vaporization cooling devices, and conducted small-scale experiments, and developed a set of effective adjustment waste heat power generation systems and control methods and applied them to waste heat power generation The automatic control system ensures the stability of the system operation reliably.

The main innovations of the utility model are:

1. When the heating furnace is waiting for rolling, the fuel consumption and flue gas volume are only about 15% of the normal amount, which are only used to maintain the furnace temperature. At this time, the steam volume of the flue gas waste heat boiler is greatly reduced, and the power generation system cannot normal operation. The utility model combines the vaporization cooling of the heating furnace with the flue gas waste heat boiler, and uses the cooling steam volume (20t/h-30t/h) necessary for the heating furnace to keep warm as the stable basic steam volume of the system, and the flue gas waste heat boiler is mainly used for The steam is superheated, which solves the problem that the amount of flue gas is less and the amount of steam is not continuous when the heating furnace is waiting for rolling. No additional supplementary combustion waste heat boiler is required.

For example, the flue gas volume of a heating furnace in a steel plant is 74500Nm ³ /h, the inlet temperature of waste heat boiler flue gas is 440°C, and the outlet temperature is 150°C. In the case of not using vaporization to cool saturated steam and only using flue gas from heating furnace to generate electricity, the data are as follows:

When the heating furnace is working normally, the steam flow rate of the flue gas waste heat boiler is 13.5t/h;

When the heating furnace is waiting for rolling, the flue gas volume is 11200Nm ³ /h, and the steam flow rate of the flue gas waste heat boiler is 2t/h.

In the above two cases, the minimum steam flow rate is 2t/h, the maximum value is 13.5t/h, and the minimum steam flow rate is only 15% of the maximum value. Such a huge flow difference is the biggest difference for any steam turbine generator set. are unbearable.

After using the heating furnace to vaporize and cool the saturated steam and the flue gas waste heat boiler, the data is as follows:

When the heating furnace is working normally, the steam flow rate of the flue gas waste heat boiler is 13.5t/h, the vaporization cooling saturated steam flow rate is 20t/h-30t/h, and the total steam flow rate is 33.5t/h-43.5t/h;

When the heating furnace is waiting for rolling, the steam flow rate of the flue gas waste heat boiler is 2t/h, the vaporization cooling saturated steam flow rate is 20t/h-30t/h, and the total steam flow rate is 22t/h-32t/h;

In the above two cases, the minimum value of the total steam flow is 22t/h, the maximum value is 43.5t/h, and the minimum steam flow rate is 51% of the maximum value. Within this range, the steam turbine can guarantee normal and stable operation.

2. Since the flue gas waste heat boiler is a natural circulation boiler, and the vaporization cooling system of the heating furnace is a forced circulation evaporation system, the parallel operation of the two has relatively high technical difficulty. Based on years of experience in the development and operation of systems in the field of cement waste heat power generation, a solution is proposed for the fluctuation characteristics of the thermal conditions of the heating furnace, so that the water level of the vaporization cooling drum and the steam drum of the flue gas waste heat boiler can be well controlled to ensure the continuous operation of the power generation system. Stable operation.

①Because the water level on the left and right sides of the steam drum is inconsistent during the actual operation, two water level monitoring devices are installed at the symmetrical positions on the left and right sides of the steam drum, and the program setting uses the average value of the two monitoring values as the calculation input of the steam drum water level value to ensure the accuracy of the value.

②According to the current pressure of the steam drum, make pressure compensation for the water level signal of the steam drum according to the compensation formula to eliminate the influence of pressure changes on the accuracy of the water level signal. The pressure compensation formula is as follows:

h=[L(ρ ₁ -ρ ₃ )g-ΔP]/(ρ ₂ -ρ ₃ )gh ₀

Where: h: drum water level after pressure compensation, m;

L: height difference between two sampling tubes in the balance container, m;

ρ ₁ : Density of condensed water, kg/m ³ ;

ρ ₂ : saturated water density, kg/m ³ ;

ρ ₃ : saturated steam density, kg/m ³ ;

g: gravitational acceleration, m/s ² ;

ΔP: differential pressure, Pa;

h ₀ : the height from the zero point of the steam drum water level to the lower sampling pipe, m;

③The combined control system calculates and analyzes the three impulse signals based on the steam drum water level signal, steam drum outlet steam flow, and steam drum feedwater flow, and then gives a control signal to control the opening of the water supply valve to ensure the accuracy of the command and the normal water level of the steam drum.

Set the high and low fixed values of the steam drum water level in the system. When the steam drum water level is higher than the high fixed value, the system reads the steam drum outlet steam flow and the steam drum feed water flow value. If the steam drum outlet steam flow is greater than the feed water flow at this time , then no action; if the steam drum outlet steam flow rate is less than or equal to the steam drum feed water flow, the system will give an action signal to reduce the opening of the feed water regulating valve, and the steam drum water level will gradually decrease; when the water level drops to a low set value, the system will Read the steam drum outlet steam flow and steam drum feed water flow value, if the steam drum outlet steam flow is less than the feed water flow at this time, no action; if the steam drum outlet steam flow is greater than or equal to the steam drum feed water flow, the system will give an action signal, Increase the opening of the feed water regulating valve, and the water level of the steam drum will gradually rise. When the drum water level is between the high and low set values, the system is in a stable and balanced state.

④ Make pressure compensation and temperature compensation for the steam flow signal at the outlet of the steam drum to eliminate the influence of pressure changes on the accuracy of the flow signal.

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&times;</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}}{\frac{\mathrm{<span\; class="notranslate">\; 0.00471</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1.268</span>}}{\mathrm{<span\; class="notranslate">\; 10.149</span>}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0.0097</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.0000132</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}}$

Where: M: steam pressure after pressure compensation and temperature compensation, Pa;

K: constant;

ΔP: differential pressure, Pa;

T: steam drum outlet steam temperature, °C;

P: steam drum outlet steam pressure, Pa;

3. Since the heating furnace vaporization cooling is used as the basic heat source of the system, there is no need to add a supplementary combustion boiler. The selection of system parameters needs to be optimized according to the test and operation experience, and because the thermal conditions of each heating furnace are different, it is necessary to Optimize parameters in a targeted manner. According to theoretical calculation and experience correction, optimize the host parameters such as waste heat boilers and steam turbines and optimize the target parameters of the automatic control system to ensure the safe, stable and efficient operation of the system.

For example, the flue gas volume of heating furnace in a steel plant is 74500Nm ³ /h, the inlet temperature of waste heat boiler flue gas is 440℃, the outlet temperature is 150℃, and the flow rate of vaporized cooling saturated steam is 20t/h-30t/h. From the table below, it can be clearly seen that when the main steam pressure is optimized to 1.25MPa, the waste heat will be more fully utilized, and the output power of the generator will be the largest.

main steam pressure MPa 1.0 1.25 1.35 main steam temperature ℃ 325 325 325 main steam flow t/h 34.2 33.5 32.3

Feed water temperature ℃ 104 104 104 Evaporation saturated steam flow t/h 20.4 20 19.5 Flue gas waste heat boiler steam flow t/h 13.8 13.5 12.8 Generator output power kW 8190 8300 8210

4. On the premise of ensuring the safe, stable and efficient operation of the system, the system can be simplified because there is no need to set up a supplementary combustion boiler, which not only reduces equipment investment, but also makes full use of the original waste heat resources of the heating furnace system. The economic benefit and social benefit are very remarkable.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present utility model in detail. It should be understood that the above descriptions are only specific embodiments of the present utility model and are not intended to limit In the present utility model, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims (3)

1. A heating furnace flue gas and steam waste heat recovery power generation system, characterized in that the waste heat recovery power generation system includes a flue gas waste heat boiler system, a heating furnace vaporization cooling system, a turbogenerator system, and a condensate return water supply system and combined control systems; The flue gas waste heat boiler system includes a flue gas waste heat boiler (1) composed of a superheater (2), an evaporator (3), and an economizer (4), a flue gas waste heat boiler drum (5) and a flue gas waste heat Boiler drum feed water regulating valve (17); The heating furnace vaporization cooling system comprises a vaporization cooling steam drum (6), a heating furnace water beam vaporization cooling loop (7), a vaporization cooling forced circulation pump (8) and a vaporization cooling steam drum feed water regulating valve (16); The turbogenerator set includes a steam turbine (9) and a generator (10); wherein, The flue gas from the main exhaust flue of the heating furnace passes through the superheater (2), evaporator (3) and economizer (4) in turn for heat exchange and then discharges into the atmosphere; The condensed water return water supply system is respectively connected with the steam turbine (9) of the steam turbine generator set and the inlet of the economizer (4), and the condensed water produced by the steam turbine (9) is sent into the economizer (4); The outlet of the economizer (4) is respectively connected to the flue gas waste heat boiler drum (5) and the vaporization cooling drum (6), and the heated condensed water is respectively sent to the flue gas waste heat boiler drum (5) and the vaporization cooling drum (6). Cooling steam drum (6); The flue gas waste heat boiler drum (5) is connected to the inlet of the evaporator (3) through a downcomer, and the outlet of the evaporator (3) is connected back to the flue gas waste heat boiler drum (5); The steam pipe of the drum (5) is connected to the inlet of the superheater (2); the unsaturated water absorbs the heat of the flue gas of the evaporator (3) and becomes a mixture of steam and water, and after steam-water separation in the steam drum (5) of the flue gas waste heat boiler, the saturated Water enters the next cycle, and saturated steam enters the superheater (2); The vaporization cooling steam drum (6) is connected with the heating furnace water beam vaporization cooling circuit (7) through the descending pipe and the vaporization cooling forced circulation pump (8) to form a circulation circuit, so that saturated water enters the heating furnace water beam vaporization cooling circuit ( 7), after turning into a steam-water mixture, send it back to the vaporization cooling drum (6) for steam-water separation, the saturated water enters the next cycle, and the saturated steam enters the superheater (2); The outlet of the superheater (2) is connected to the steam turbine (9) of the turbogenerator set, and the superheater (2) provides superheated steam to the steam turbine (9). 2. The waste heat recovery power generation system according to claim 1, characterized in that, the condensate return water supply system includes a condenser (11), a condensate pump (12), a thermal deaerator (13) and a boiler feeder water pump (14); the condenser (11) is connected to the steam turbine (9), condenses exhaust steam after doing work into condensed water, and sends it to the thermal deaerator (13) via the condensed water pump (12) ), after being pumped and heated by the steam turbine (9) to realize thermal deoxygenation, enter the feed water pump (14) for pressurization, and then send it into the economizer (4) to complete the thermodynamic cycle. 3. The waste heat recovery power generation system according to claim 2, characterized in that the combined control system includes a flue gas waste heat boiler feed water regulating valve (17), installed at the outlet of the economizer (4) to the flue gas waste heat boiler steam on the water supply pipeline of the vaporization cooling drum (5); the vaporization cooling steam drum feedwater regulating valve (16) is installed on the water supply pipeline from the outlet of the economizer (4) to the vaporization cooling steam drum (6); the combined control system is based on two steam drums The water level, main steam flow, and steam drum feed water flow are adjusted to control the opening of the two regulating valves to ensure the stability of the steam drum water level and the parallel operation of the two steam drums.

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