Direct-drive power generation system for producing steam by using waste heat of medium and low temperature flue gas

Abstract

The invention discloses a medium and low temperature flue gas waste heat direct drive power generation system integrating a high temperature ceramic filter dust remover, a compact steam generator and a steam generator set. The method comprises the following steps: firstly, dust-containing flue gas passes through a high-temperature ceramic filter dust remover combined with a catalytic purification technology to synchronously remove particulate matters and nitrogen oxides; then, the purified flue gas enters a compact steam generator, and clean water is heated into superheated steam through heat exchange; then, the high-temperature and high-pressure steam enters a steam turbine to drive a generator to generate electricity and becomes low-temperature and low-pressure dead steam; and finally, dead steam is liquefied into clean water through a condenser, and the clean water is pressurized by a working medium pump and sent back to the steam generator to form closed circulation. The waste heat utilization efficiency is remarkably improved while deep removal of pollutants is guaranteed, the occupied space and the investment and maintenance cost can be effectively reduced through equipment compactness, and remarkable environmental protection benefits and economic benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas waste heat power generation, and particularly to a medium and low temperature flue gas waste heat steam direct drive power generation system. Background Art

[0002] The iron and steel industry is an important field of energy consumption and carbon emissions. Among them, the energy consumption of rolling heating furnaces accounts for more than 60% of the total energy consumption of the workshop. The heating furnace uses blast furnace gas, coke oven gas, etc. as fuel. The temperature in the high-temperature area inside the furnace can reach 1300°C, and the tail gas exhaust temperature is usually higher than 300°C. The flue gas waste heat accounts for 30% - 40% of the total calorific value of the fuel. Although the existing technology recovers part of the sensible heat through air preheaters or waste heat boilers, there are still severe challenges in the deep utilization of medium and low temperature flue gas, especially flue gas with a temperature lower than 300°C: First, sulfur oxides (SOx) in the flue gas are prone to form acid dew point corrosion during the waste heat recovery process, resulting in a decline in the efficiency of heat exchange equipment and a shortening of its service life; Second, traditional step-by-step treatment processes (such as electrostatic precipitation + SCR denitrification) have problems such as redundant equipment, large floor area, and high investment costs due to the need for co-removal of dust and nitrogen oxides (NOx). Taking a rolling mill as an example, when the external flue gas volume is large, using a conventional waste heat boiler can only recover part of the heat and requires frequent maintenance, making it difficult to coordinate economy and environmental protection.

[0003] Current research mostly focuses on high-temperature flue gas waste heat power generation or single pollutant treatment technologies, lacking a systematic breakthrough in the integrated solution for the efficient recovery of medium and low temperature flue gas waste heat and the integrated treatment of multiple pollutants. For example, the organic Rankine cycle (ORC) power generation technology has been used in the building materials industry, but for the iron and steel industry, due to problems such as complex flue gas composition (containing high concentrations of SOx, NOx, and dust) and high risk of acid dew point corrosion, targeted solutions are urgently needed. In addition, the thermal efficiency of traditional waste heat boilers in medium and low temperature waste heat utilization is generally lower than 15%, and dust deposition aggravates equipment wear, severely restricting its large-scale application.

[0004] Therefore, a medium and low temperature flue gas waste heat steam direct drive power generation system is needed to solve the above problems. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above problems of a medium and low temperature flue gas waste heat steam direct drive power generation system, the present invention is proposed.

[0007] Therefore, the object of the present invention is to provide a direct-drive power generation system for producing steam from the waste heat of medium- and low-temperature flue gas, which is used to solve the problems such as "sulfur oxides (SOx) in the flue gas are prone to form acid dew point corrosion during the waste heat recovery process, resulting in a decrease in the efficiency of heat exchange equipment and a shortening of its service life; and its traditional equipment is redundant, occupies a large area, and has a high investment cost".

[0008] To solve the above technical problems, on the one hand, the present invention provides the following technical solution: A direct-drive power generation system for producing steam from the waste heat of medium- and low-temperature flue gas, comprising:

[0009] A high-temperature ceramic filter dust collector, which is used to efficiently purify particulate matter and nitrogen oxides in the dust-containing flue gas and provide clean flue gas for subsequent waste heat recovery;

[0010] A compact steam generator, which is used to heat clean water into superheated steam by the waste heat of clean flue gas;

[0011] A steam generator set, which is used to convert the thermal energy of the high-temperature and high-pressure steam generated by the compact steam generator into electrical energy and form a closed cycle at the same time.

[0012] As a preferred scheme of the direct-drive power generation system for producing steam from the waste heat of medium- and low-temperature flue gas of the present invention, wherein: the high-temperature ceramic filter dust collector uses a silicon carbide-based porous ceramic material as a filter carrier, its porosity ≥ 60%, the average pore diameter is 10 - 20 μm, and the surface is loaded with V 2 O 5 -WO 3 / TiO 2 catalyst (loading amount 3 - 5 wt%), the filter element structure of the filter carrier is honeycomb-shaped, the size is Φ150mm × 1000mm, the wall thickness of the filter element is 20mm, and the honeycomb hole density is 200 CPSI (holes / square inch).

[0013] As a preferred scheme of the direct-drive power generation system for producing steam from the waste heat of medium- and low-temperature flue gas of the present invention, wherein: the compact steam generator adopts a vertical compact structure, and its internal integrates a feed water inlet, a flue gas channel, a steam outlet and a discharge system; there is a shell outside it, the shell adopts a carbon steel lined 316L composite structure of Φ3200 × 15000mm, a deflector and a shock-proof grille (spacing 800mm) are arranged inside the shell, and a vane separator is arranged at the upper part of the flue gas channel of the compact steam generator to the steam outlet.

[0014] As a preferred embodiment of the medium and low temperature flue gas waste heat steam direct drive power generation system of the present invention, the following is provided: The compact steam generator further includes a tube bundle, which adopts a spiral finned tube bundle structure and is composed of a base tube and fins. The base tube is made of a stainless steel heat exchange tube with an outer diameter of 25 mm and a wall thickness of 3 mm, and its material is ASTM A213 TP316L. The fins are made of sulfuric acid dew point corrosion resistant steel fins with a height of 12 mm and a pitch of 4 mm, and its material is 09CrCuSb.

[0015] As a preferred embodiment of the medium and low temperature flue gas waste heat steam direct drive power generation system of the present invention, the following is provided: The steam generator set includes a back pressure steam turbine, a condenser and a working fluid pump.

[0016] As a preferred embodiment of the medium and low temperature flue gas waste heat steam direct drive power generation system of the present invention, the following is provided: The power of the back pressure steam turbine is 715 kilowatts.

[0017] As a preferred embodiment of the medium and low temperature flue gas waste heat steam direct drive power generation system of the present invention, the following is provided: The condenser is of a shell and tube structure, and the cooling water flow rate of the condenser is 700 m 3 / h.

[0018] As a preferred embodiment of the medium and low temperature flue gas waste heat steam direct drive power generation system of the present invention, the following is provided: The working fluid pump adopts a multi-stage centrifugal pump, and the head of the multi-stage centrifugal pump is 160 m, forming a closed cycle.

[0019] On the other hand, the present invention provides a medium and low temperature flue gas waste heat steam direct drive power generation control system, which includes,

[0020] A monitoring and feedback module, which includes flue gas parameter monitoring and steam system monitoring;

[0021] A safety and fault diagnosis module, which includes acid dew point warning and dust deposition warning.

[0022] As a preferred embodiment of the medium and low temperature flue gas waste heat steam direct drive power generation control system of the present invention, the following is provided: The flue gas parameter monitoring includes a high temperature thermocouple, a differential pressure sensor and an on-line gas analyzer, and the steam system monitoring system includes a pressure transmitter and a vortex flowmeter.

[0023] The beneficial effects of the present invention:

[0024] 1. The present invention adopts a high temperature ceramic filter dust collector, which combines a silicon carbide-based porous ceramic filter element with V 2 O 5 -WO 3 / TiO 2The catalyst can achieve a particulate matter (PM) removal rate > 99.9% and a denitration efficiency of nitrogen oxides (NOx) > 85%, synchronously solve the problem of the synergistic removal of dust and NOx, and reduce the equipment redundancy and floor area of traditional step-by-step treatment processes;

[0025] 2. In the present invention, the filter carrier and the steam generator tube bundle adopt corrosion-resistant materials (such as silicon carbide, 09CrCuSb steel), combined with an acid dew point warning system, which can effectively resist the acid dew point corrosion caused by sulfur oxides (SOx), extend the service life of the equipment (the filter element life > 3 years), and reduce the maintenance frequency and cost;

[0026] 3. In the present invention, the steam generator adopts a vertical compact structure, integrating a deflector, a shock-proof grille and a spiral fin tube bundle, which significantly improves the heat transfer efficiency (the thermal efficiency reaches 85%), and at the same time reduces the equipment floor area to meet the requirements of limited space in industrial sites;

[0027] 4. In the present invention, power generation is driven by a back-pressure steam turbine (rated power 715 kW). The exhausted steam is recycled by a working fluid pump after being recovered by a condenser, forming a closed cycle. The net power generation efficiency of the system reaches 18% - 22%, and the annual power generation can reach 5.76 GWh (operating 8000 hours a year), greatly improving the utilization rate of low- and medium-temperature flue gas waste heat;

[0028] 5. The present invention is equipped with a monitoring and feedback module (such as high-temperature thermocouples, on-line gas analyzers) and a safety warning system (acid dew point warning, dust deposition warning), which can realize real-time monitoring and dynamic adjustment of flue gas parameters and steam status, ensure the stable operation of the system, and reduce the risk of failure;

[0029] 6. The present invention integrates the functions of pollutant treatment and waste heat power generation, reduces the total amount of pollutants discharged, and at the same time reduces the energy cost of enterprises through waste heat power generation. It is applicable to the treatment scenarios of low- and medium-temperature flue gas in industrial fields such as metallurgy, building materials, and chemical engineering, and has significant environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0031] Figure 1 It is a schematic diagram of the solution of a low- and medium-temperature flue gas waste heat steam direct drive power generation system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the accompanying drawings of the specification.

[0033] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0034] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an individual or alternative embodiment that is mutually exclusive with other embodiments.

[0035] Thirdly, the present invention will be described in detail in conjunction with the schematic diagrams. When describing the embodiments of the present invention in detail, for the convenience of explanation, the cross-sectional views showing the device structure will be enlarged locally not in accordance with the general ratio, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0036] Embodiment 1

[0037] Referring to Figure 1 , for an embodiment of the present invention, a specific process of a medium and low temperature flue gas waste heat steam direct drive power generation system is provided, which includes:

[0038] Flue gas purification stage: The medium and low temperature flue gas discharged from the steel rolling heating furnace first enters the high-temperature ceramic filter dust collector. When the flue gas passes through the silicon carbide-based porous filter element, particulate matter (PM) is intercepted on the surface of the filter membrane. At the same time, the loaded V 2 O 5 -WO 3 / TiO 2 catalyst reacts with the injected NH 3 to carry out selective catalytic reduction (SCR) reaction, converting NOx into N 2 and H 2 O, achieving a PM removal rate > 99.9% and a NOx denitrification efficiency > 85%;

[0039] Specifically, the high-temperature ceramic filter dust collector uses silicon carbide-based porous ceramic material as the filter carrier, with a porosity ≥ 60%, an average pore diameter of 10 - 20 μm, and the surface is loaded with V 2 O 5 -WO 3 / TiO 2Catalyst (loading 3 - 5 wt%). The filter element structure is honeycomb-shaped, with dimensions of Φ150mm × 1000mm, a designed filtration air velocity of 1.2 - 1.5 m / min, and an operating temperature of 200 - 300°C. When the flue gas passes through, PM is intercepted on the surface of the filter membrane, and NOx is converted into N 3 under the action of the catalyst into N 2 and H 2 O, achieving a PM removal rate > 99.9% and a NOx denitration efficiency > 85%. The compressive strength of the filter element is ≥12 MPa, equipped with a pulse back-blowing dust cleaning system, a pressure drop ≤400 Pa, and a service life > 3 years.

[0040] Waste heat recovery stage: The purified flue gas (temperature 180 - 300°C) enters a compact steam generator. The flue gas flows through the U-shaped tubes, heating the softened water to superheated steam (1.3 MPa, 260°C), with a steam output of 3.0 t / h;

[0041] Specifically, the steam generator adopts a vertical compact structure, internally integrating a feed water inlet, a flue gas passage, a steam outlet, and a discharge system. The blade separator at the top ensures the steam dryness, and the bypass can adjust the feed water temperature to control the tube wall temperature. Based on the inlet flue gas at 300°C and the outlet steam pressure of 1.1 MPa, the total heat transfer area is initially estimated to be approximately 3000 m 2 (including safety margin). ND steel or 15CrMoG is recommended for the high-temperature section to resist acid dew point corrosion, and the steam output is approximately 14 tons per hour (thermal efficiency 85%). The design needs to be optimized in combination with the actual measurement of the flue gas composition, wall temperature monitoring, and ASME specifications to avoid the risk of dew point corrosion in the low-temperature area;

[0042] It should be noted that there is a shell outside the steam generator. The shell adopts a carbon steel lined 316L composite structure of Φ3200×15000mm, and a deflector plate and a shock-proof grille (spacing 800mm) are arranged inside the shell; The steam generator also includes a tube bundle. The tube bundle adopts a spiral finned tube bundle structure, consisting of a base tube and fins. The base tube uses a stainless steel heat exchange tube (outer diameter 25mm, wall thickness 3mm), with a material of ASTMA213TP316L, and the fins are made of 09CrCuSb steel resistant to sulfuric acid dew point corrosion (height 12mm, spacing 4mm).

[0043] Steam power generation stage: The superheated steam drives a back-pressure steam turbine to do work, driving a generator to output electric energy (rated power 715 kW). The exhaust steam of the steam turbine (0.15 MPa, 120°C) enters a shell-and-tube condenser and is condensed into liquid water by cooling water (flow rate 700 m 3 / h), with a condensation rate > 95%;

[0044] Specifically, a steam power generation unit is used in this stage, which includes a back-pressure steam turbine (rated power 715 kW), a condenser, and a working fluid pump. The inlet steam parameters of the back-pressure steam turbine are 1.1 MPa / 260 °C, the exhaust steam pressure is 0.15 MPa, and the isentropic efficiency is 82%; the condenser is of a shell-and-tube structure, with a cooling water flow rate of 700 m 3 / h, and the exhaust steam condensation rate > 95%.

[0045] Working fluid circulation stage: The condensate water is pressurized to 1.5 MPa by a multi-stage centrifugal pump and reinjected into the steam generator to form a closed cycle. The system maintains the stability of the thermal cycle by dynamically adjusting the rotational speed of the working fluid pump and the steam pressure;

[0046] Specifically, the working fluid pump of the steam power generation unit is used in this stage. The working fluid pump adopts a multi-stage centrifugal pump (head 160 m, efficiency 75%) to form a closed cycle. The net power generation efficiency of the system is 18% - 22%, and the annual power generation is 5.76 GWh (operating 8000 h per year).

[0047] Example 2

[0048] Example 2 is the second example of the present invention. The difference between this example and the first example is that a control system for directly driving power generation by producing steam from medium and low temperature flue gas waste heat is provided, including:

[0049] Monitoring and feedback module:

[0050] Flue gas parameter monitoring: Install high-temperature thermocouples, differential pressure sensors, and on-line gas analyzers to collect flue gas temperature (±1 °C), flow rate (±2%), PM concentration (±1 mg / m 3 ) and NOx concentration (±5 ppm) in real time;

[0051] Steam system monitoring: Monitor steam pressure (1.3 ± 0.05 MPa), temperature (300 ± 5 °C), and flow rate (3.0 ± 0.1 t / h) through a pressure transmitter (accuracy class 0.5) and a vortex flowmeter.

[0052] Safety and fault diagnosis:

[0053] Acid dew point warning: Calculate the real-time acid dew point temperature based on the SOx concentration and flue gas humidity. When the wall temperature is lower than the acid dew point + 10 °C, trigger an alarm and adjust the water flow rate of the heat exchanger;

[0054] Dust deposition warning: Judge the risk of filter element blockage based on the pressure difference growth rate (ΔP / Δt > 50 Pa / h), and start the adaptive adjustment program of the backwashing frequency.

[0055] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A steam direct-driven power generation system using waste heat from medium and low temperature flue gas, characterized in that: include: High-temperature ceramic filter dust collector is used to efficiently purify particulate matter and nitrogen oxides in dusty flue gas, providing clean flue gas for subsequent waste heat recovery; Compact steam generator for heating clean water into superheated steam using waste heat from clean flue gas; The steam generator set is used to convert the thermal energy of high-temperature and high-pressure steam generated by the compact steam generator into electrical energy while forming a closed cycle.

2. The medium and low temperature flue gas waste heat steam direct drive power generation system according to claim 1 is characterized by: The high-temperature ceramic filter dust collector uses silicon carbide-based porous ceramic material as a filter carrier, with a porosity of ≥60% and an average pore size of 10 to 20 μm. A catalyst is loaded on its surface, and the catalyst is V2O5-WO3 / TiO2 with a loading amount of 3 to 5 wt%. The filter element structure of the filter carrier is honeycomb-shaped with a size of Φ150 mm×1000 mm. The filter element wall thickness is 20 mm, and the honeycomb hole density is 200 CPSI (pores per square inch).

3. The medium and low temperature flue gas waste heat steam direct drive power generation system according to claim 1 is characterized by: The compact steam generator adopts a vertical compact structure, with a water inlet, a flue gas channel, a steam outlet and an exhaust system integrated inside; there is a cylindrical shell on the outside, and the shell adopts a carbon steel lining 316L composite structure. A guide plate and a shockproof grille (spacing 800mm) are arranged inside the shell, and a blade separator is arranged from the upper part of the flue gas channel of the compact steam generator to the steam outlet.

4. The medium and low temperature flue gas waste heat steam direct drive power generation system according to claim 3 is characterized by: The compact steam generator also includes a tube bundle, which adopts a spiral fin tube bundle structure and consists of a base tube and fins. The base tube is a stainless steel heat exchange tube with an outer diameter of 25 mm and a wall thickness of 3 mm. The material is ASTMA213TP316L. The fin is made of sulfuric acid dew point corrosion resistant steel fin with a height of 12 mm and a spacing of 4 mm. The material is 09CrCuSb.

5. The medium and low temperature flue gas waste heat steam direct drive power generation system according to claim 1 is characterized by: The steam generator set comprises a back-pressure steam turbine, a condenser and a working fluid pump.

6. The medium and low temperature flue gas waste heat steam direct drive power generation system according to claim 5 is characterized by: The back-pressure steam turbine has a power of 715 kilowatts.

7. The medium and low temperature flue gas waste heat steam direct drive power generation system according to claim 6 is characterized by: The condenser is a shell and tube structure, and the cooling water flow rate of the condenser is 700m 3 / h.

8. The medium and low temperature flue gas waste heat steam direct drive power generation system according to claim 7 is characterized by: The working fluid pump adopts a multi-stage centrifugal pump, and the head of the multi-stage centrifugal pump is 160m, forming a closed cycle.

9. A medium-low temperature flue gas waste heat steam direct-driven power generation control system, based on the medium-low temperature flue gas waste heat steam direct-driven power generation system according to any one of claims 1 to 8, characterized in that: include, Monitoring and feedback module, the monitoring and feedback module includes flue gas parameter monitoring and steam system monitoring; A safety and fault diagnosis module, wherein the safety and fault diagnosis module includes an acid dew point warning and a dust deposition warning.

10. The control system for producing steam directly driven power generation by using waste heat from medium and low temperature flue gas according to claim 9 is characterized in that: The flue gas parameter monitoring includes a high-temperature thermocouple, a differential pressure sensor and an online gas analyzer, and the steam system monitoring system includes a pressure transmitter and a vortex flowmeter.

Images