Dry quenching high-temperature steam energy gradient recovery power generation process

Abstract

A dry quenching high-temperature steam energy gradient recovery power generation process belongs to the technical field of dry quenching energy recovery and power generation, and comprises steam pretreatment, two-stage steam acting, three-stage waste heat utilization and intelligent regulation and control, and the energy utilization rate is remarkably improved through'high pressure-medium pressure-low pressure 'three-stage gradient energy recovery. An intelligent regulation and control system is adopted to deal with load fluctuation, closed-loop water circulation is adopted to reduce water consumption, energy conservation and environmental protection are remarkable, and system stability is good.

Description

Technical Field

[0001] This invention relates to the field of dry quenching coke energy recovery and power generation technology, specifically a dry quenching coke steam energy recovery and power generation process based on high-temperature steam staged work, waste heat closed-loop utilization, and intelligent load regulation. Background Technology

[0002] Dry quenching (CDQ) is an energy-saving and environmentally friendly technology for coke cooling. Its core is to recover the sensible heat of red coke through inert gas in a closed system and generate high-temperature and high-pressure steam through a waste heat boiler. The energy recovery efficiency of this steam directly determines the energy-saving efficiency of the dry quenching system.

[0003] Currently, the technology for utilizing this steam has undergone three generations of development. The first-generation technology is direct power generation using a single-stage condensing steam turbine, which is the most widely used solution. This process involves directly feeding waste heat boiler steam into a single-stage condensing steam turbine, where it performs work and is then condensed into water for reuse. In this process, the high-temperature steam undergoes one expansion to perform work, and then the lower-grade heat energy in the steam is discharged with the condensate, resulting in low energy utilization. The steam temperature remains high after work, and condensation requires a large amount of circulating water for cooling, leading to high resource and energy consumption. Furthermore, when fluctuations in the amount of red coke in dry quenching cause changes in steam flow, the turbine deviates from its design operating conditions, resulting in a sharp drop in power generation efficiency. Pressure fluctuations can even trigger surge, posing significant safety hazards.

[0004] To avoid wasting low-grade heat energy in condensing steam turbines, some companies have improved upon the first-generation technology by adopting single-stage back-pressure steam turbines, using exhaust steam for industrial heat generation within the plant area, such as heating. However, on the one hand, industrial heat load is not correlated with dry quenching steam output. When industrial heat demand is low, or even lower than dry quenching steam output, excess steam still needs to be vented or depressurized for condensation, resulting in continued energy waste. On the other hand, the fixed exhaust pressure of back-pressure steam turbines leads to insufficient work done at the high-pressure end, resulting in lower power generation compared to condensing steam turbines and poor overall economic efficiency.

[0005] To further recover waste heat, the design was improved by adding a low-pressure heat exchanger after the single-stage steam turbine. This heats the condensate using exhaust steam, becoming the third-generation technology. The low-pressure heat exchanger effectively recovers sensible heat and improves energy utilization. However, the heat exchanger and the steam turbine are not coordinated. When steam parameters fluctuate, the heat exchanger is prone to a sharp drop in heat exchange efficiency due to overpressure or insufficient flow, resulting in poor stability.

[0006] Therefore, there is an urgent need for a dry quenching steam power generation process that can maintain system stability and adapt to load fluctuations while ensuring full energy utilization, in order to break through the efficiency and stability bottlenecks of existing technologies. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention proposes a dry quenching coke high-temperature steam energy gradient recovery power generation process, which achieves high system stability and adaptability to load fluctuations, increasing the total energy utilization rate to over 85%.

[0008] The technical problem to be solved by the present invention is achieved through the following technical solution: A dry quenching coke high-temperature steam energy gradient recovery power generation process includes the following steps: S1: High-temperature steam pretreatment: High-temperature and high-pressure steam generated by dry quenching waste heat boiler is introduced into steam purification device to remove impurities and free water to obtain clean high-temperature steam. The parameters of high-temperature and high-pressure steam are 4.0-5.4 MPa and 400-450 ℃. The impurity separation efficiency of steam purification device is ≥99.5%, and the steam moisture content after free water removal is <0.5%.

[0009] The impurity removal method employs a combination of cyclone separation and wire mesh filtration to remove mechanical impurities and free water with a particle size exceeding 5 μm from the steam.

[0010] S2: First-stage work: The clean, high-temperature steam is introduced into a high-pressure condensing steam turbine for expansion and work, driving a matching generator to generate electricity. The discharged medium-pressure steam is transported to the medium-pressure steam pipeline network. The intake pressure of the high-pressure condensing steam turbine is 4.0-5.4 MPa, and the temperature is 400-450 ℃. The exhaust pressure is 1.0-1.4 MPa, and the temperature is 240-260 ℃. The medium-pressure steam pipeline network is equipped with a pressure buffer tank, and the pressure fluctuation is controlled within ±0.05 MPa. The matching generator power is 12-18 MW.

[0011] S3: Secondary power generation: Steam from the medium-pressure steam pipeline is introduced into the medium-pressure back-pressure steam turbine for expansion and power generation, driving the matching generator to generate electricity. The discharged low-pressure saturated steam is transported to the waste heat utilization system. The intake pressure of the medium-pressure back-pressure steam turbine is 1.0-1.4 MPa, and the temperature is 240-260 ℃. The exhaust pressure is 0.2-0.4 MPa, and the temperature is 120-140 ℃. The matching generator has a power of 4-6 MW.

[0012] S4: Three-stage waste heat utilization: The low-pressure saturated steam enters a low-pressure steam heat exchanger, where it exchanges heat with the low-temperature condensate in the condensate tank. The heated condensate is then transported to the deaerator. Of the low-pressure steam generated after the heat exchange, 60%-80% is used for deaeration in the deaerator, and the remaining portion is condensed and returned to the condensate tank, forming a closed-loop water circulation. The heat exchange area of ​​the low-pressure steam heat exchanger is 800-1200 m². 2The pressure is 0.5-0.8 MPa, the initial temperature of the low-temperature condensate is 40-50 ℃, and the temperature rises to 100-110 ℃ after heat exchange. The working pressure of the deaerator is 0.02-0.05 MPa, the working temperature is 104-108 ℃, and the low-pressure steam generated after heat exchange has a pressure of 0.08-0.12 MPa and a temperature of 95-100 ℃.

[0013] In this invention, the process includes intelligent control, employing a PLC control system. The PLC control system has a sampling frequency of 1-2 seconds / time, with sampling accuracies of ±2℃ for temperature and ±0.05 MPa for pressure, and executes the following control logic in real time: (1) Data acquisition: Collect the steam pressure / temperature / flow rate at the outlet of the waste heat boiler, collect the pressure, temperature and flow rate of the steam inlet / outlet of the high-pressure / medium-pressure steam turbine, collect the steam turbine speed, engine power, inlet and outlet temperatures of the low-pressure heat exchanger and the liquid level of the condensate tank; (2) Overpressure regulation: When the steam inlet pressure of the high-pressure steam turbine exceeds the rated value by 0.2 MPa, open the high-pressure steam turbine bypass valve with an opening degree of 5%-20% to directly introduce some steam into the medium-pressure steam pipeline network to avoid overpressure of the steam turbine; (3) Low flow rate regulation: When the total steam flow rate is less than 80% of the rated value, the load of the medium-pressure steam turbine is automatically reduced to 50%-70% of the rated load, giving priority to ensuring that the high-pressure steam turbine operates under the design conditions; (4) Pump frequency conversion regulation: The speed of condensate pump and cooling water pump is adjusted by frequency converter, with a frequency of 25-50 Hz, so that the pump flow rate matches the system load and the pump energy consumption is reduced.

[0014] In this invention, a three-stage gradient energy utilization approach—high pressure, medium pressure, and low pressure—is employed to minimize irreversible losses and approach the efficiency of an ideal Carnot cycle. Traditional single-stage steam turbines directly expand steam from 5.0 MPa / 430℃ to 0.08 MPa / 45℃, resulting in a single enthalpy drop of 800 kJ / kg. According to thermodynamic theory, this large pressure difference and irreversible throttling expansion lead to a significant increase in entropy, causing substantial loss of work capacity. Furthermore, the large potential temperature difference and single-stage expansion make the expansion process line easily penetrate into the gas-liquid two-phase region, generating wet steam, leading to kinetic energy loss and equipment corrosion. This scheme decomposes the total enthalpy drop into two stages. The first stage, a high-pressure steam turbine, expands steam from 5.0 MPa / 430℃ to 1.2 MPa / 250℃, resulting in an enthalpy drop of approximately 500 kJ / kg. During this stage, the steam is in a superheated state, with no wet steam loss, and the intermediate-pressure exhaust steam still maintains a high enthalpy value (approximately 2800 kJ / kg). The second stage, an intermediate-pressure steam turbine, expands steam from 1.2 MPa / 250℃ to 0.3 MPa / 133℃, resulting in an enthalpy drop of approximately 300 kJ / kg. The intermediate-pressure steam remains in a superheated state, avoiding the wet steam problem in the low-pressure section. The combined loss from both stages is reduced to 5%-8%, and the total entropy increase ΔS ≤ 0.1 kJ / (kg·K). Therefore, theoretically, gradient expansion can reduce irreversible losses within the steam turbine by more than 60%, laying the foundation for increasing energy utilization efficiency to over 85%.

[0015] Throughout the entire process of this invention, high-temperature steam pretreatment ensures the cleanliness of the steam. The two-stage steam turbines perform work according to the graded matching principle of pressure energy to mechanical energy conversion, achieving precise energy conversion. The three-stage waste heat utilization follows the principle of minimizing heat transfer temperature difference and matching energy quality. Sensible heat recovery adopts countercurrent heat exchange in a low-pressure steam heat exchanger, where high-temperature steam and low-temperature condensate exchange heat, with the steam releasing heat and cooling down, and the condensate absorbing heat and heating up. Latent heat reuse involves using the low-pressure steam after heat exchange in a deaerator, utilizing its saturation temperature to achieve isothermal deaeration, replacing the traditional superheated deaeration that requires the consumption of new steam, and reducing heat energy waste caused by excessive temperature difference. Closed-loop water circulation involves recycling all condensate back to the boiler, avoiding evaporation losses in an open-loop system, while reducing industrial water consumption, with a recycling rate of over 95%.

[0016] In this invention, fluctuations in dry quenching steam parameters, such as changes in the amount of red coke leading to changes in steam flow and steam pressure, are the main sources of disturbance to the stable operation of the system. This invention achieves adaptive adjustment based on a PID control algorithm. First, pressure closed-loop control is implemented, targeting the high-pressure turbine inlet steam pressure. When the pressure exceeds the limit, the PLC system calculates the deviation value and proportionally opens the bypass valve. Simultaneously, the integral term eliminates steady-state error to avoid continuous overpressure, and the derivative term predicts pressure change trends for early adjustment. Second, load-coordinated regulation is adopted. When the steam flow rate drops to 80% of the rated value, the system prioritizes the high-pressure turbine to operate under design conditions and ensures the highest efficiency range by coupling the power feedback of the high-pressure and medium-pressure turbines. This reduces the load on the medium-pressure turbine, minimizing its deviation from design conditions. By sacrificing secondary loads to ensure core efficiency, the overall efficiency fluctuation is controlled. Finally, variable frequency drive (VFD) regulation of the water pump is used. Based on the condensate tank level and heat exchanger outlet temperature, the VFD changes the water pump speed, dynamically matching the water circulation flow rate with the steam heat input. This avoids ineffective energy consumption due to large flow rates and small temperature differences, effectively saving power for the water pump.

[0017] In this invention, each stage achieves overall optimization through the three-dimensional coupling of energy flow, material flow, and information flow. Regarding energy flow, the energy transfer chain—high-pressure work, medium-pressure supplementary energy, and low-pressure waste heat—enables steam to be utilized step-by-step from high-grade to medium-grade and then to low-grade. Each stage's energy output is precisely connected to the next stage's input, avoiding quality gaps in energy transfer. Regarding material flow, the closed-loop flow of condensate from the condenser to the condensate tank, low-pressure heat exchanger, deaerator, and waste heat boiler is reverse-matched with the steam's expansion-heat release-condensation process, achieving simultaneous recovery of water resources and thermal energy. Regarding information flow, the PLC system collects multiple key parameters in real time. By establishing parameter correlation models, such as the mathematical relationship between steam flow and turbine load, control commands can be applied simultaneously to multiple stages. For example, adjusting the bypass valve can be done while simultaneously adjusting the water pump speed, effectively avoiding system oscillations caused by localized adjustments and further improving control speed and accuracy.

[0018] Compared with the prior art, the present invention has the following advantages: (1) This application improves the total energy utilization rate of steam from 65%-70% in traditional processes to 85%-90% through three-stage energy recovery, resulting in a significant improvement in energy utilization. (2) The application adopts an intelligent control system to reduce the frequency of the steam turbine deviating from the design operating conditions by more than 80%, stabilize the power generation efficiency, and control the fluctuation range within ±3%, which effectively solves the problem that traditional processes cannot effectively cope with load fluctuations; (3) This application adopts a closed-loop water circulation to reduce industrial water consumption by 30%-40%, and the waste heat boiler is used for deoxygenation to reduce external steam consumption by 15%-20%. Wastewater discharge is reduced by more than 50%, while standard coal consumption is reduced, resulting in outstanding energy-saving and environmental protection benefits. (4) This application adopts staged work to reduce the load pressure of a single steam turbine, reducing the equipment failure rate from 8% to below 1%. The pressure buffer tank and intelligent control avoid surge, greatly improving system stability, effectively extending the operating cycle and reducing downtime maintenance costs. Attached Figure Description

[0019] Figure 1 This is a process flow diagram for this application. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0021] Example 1 A dry quenching coke high-temperature steam energy gradient recovery power generation process, such as Figure 1 As shown, it includes the following steps: 1. High-temperature steam pretreatment The high-temperature and high-pressure steam generated by the dry quenching coke waste heat boiler, with a pressure of 4.0-5.4 MPa and a temperature of 400-450 ℃, first enters the steam purification device. Through cyclone separation and wire mesh filtration, mechanical impurities with a particle size greater than 5 μm and free water in the steam are removed, so that the steam moisture content is less than 0.5%, resulting in clean high-temperature steam.

[0022] 2. First stage of work: High-pressure steam turbine generates electricity. Clean, high-temperature steam is introduced into a high-pressure condensing steam turbine. The inlet parameters are 4.0-5.4 MPa and 400-450 ℃, while the exhaust parameters are 1.0-1.4 MPa and 240-260 ℃. This steam drives a matching generator with a power output of 12-18 MW. The discharged medium-pressure steam is then transported to a medium-pressure steam pipeline network with a volume of 5-10 m³. 3 The pressure buffer tank stabilizes the fluctuations in medium-pressure steam pressure, controlling it within ±0.05 MPa.

[0023] 3. Secondary power generation: Medium-pressure back-pressure steam turbine generates electricity. Steam from the medium-pressure steam pipeline is introduced into a medium-pressure back-pressure steam turbine with inlet parameters of 1.0-1.4 MPa and 240-260℃, and exhaust parameters of 0.2-0.4 MPa and 120-140℃. The turbine drives a matching generator to generate electricity, with a generator power of 4-6 MW. The low-pressure saturated steam discharged after power generation is transported to the waste heat utilization system.

[0024] 4. Three-stage waste heat utilization: low-pressure steam heat energy recovery and closed-loop water circulation (1) Low-pressure saturated steam enters the low-pressure steam heat exchanger, with a heat exchange area of ​​800-1200 m². 2The working pressure is 0.5-0.8MPa. It exchanges heat with the 40-50℃ low temperature condensate from the condensate tank in a countercurrent manner to heat the condensate to 100-110℃. (2) The heated condensate is transported to the deaerator with a working pressure of 0.02-0.05 MPa and a working temperature of 104-108℃, and is used as makeup water for the waste heat boiler; (3) The low-pressure steam generated after heat exchange has a pressure of 0.08-0.12 MPa and a temperature of 95-100 ℃. This low-pressure steam is divided into two streams. One stream, accounting for 60%-80%, is introduced into the deaerator for deoxygenation of feedwater, replacing the traditional external steam. The other stream, accounting for 20%-40%, enters the condenser and is condensed into water, which is then returned to the condensate tank to form a closed-loop water circulation. The condenser has a cooling area of ​​500-800 m². 2 ; 5. Adaptive load adjustment of intelligent control system A PLC control system is adopted, with a sampling frequency of 1-2 seconds / time and sampling accuracies of ±2℃ for temperature and ±0.05MPa for pressure. The following control logic is executed in real time: (1) Data acquisition: Collect the steam pressure / temperature / flow rate at the outlet of the waste heat boiler, collect the pressure, temperature and flow rate of the steam inlet / outlet of the high-pressure / medium-pressure steam turbine, collect the steam turbine speed, engine power, inlet and outlet temperatures of the low-pressure heat exchanger and the liquid level of the condensate tank; (2) Overpressure regulation: When the steam inlet pressure of the high-pressure steam turbine exceeds the rated value by 0.2 MPa, open the high-pressure steam turbine bypass valve with an opening degree of 5%-20% to directly introduce some steam into the medium-pressure steam pipeline network to avoid overpressure of the steam turbine; (3) Low flow rate regulation: When the total steam flow rate is less than 80% of the rated value, the load of the medium-pressure steam turbine is automatically reduced to 50%-70% of the rated load, giving priority to ensuring that the high-pressure steam turbine operates under the design conditions; (4) Pump frequency conversion regulation: The speed of condensate pump and cooling water pump is adjusted by frequency converter, with a frequency of 25-50 Hz, so that the pump flow rate matches the system load and the pump energy consumption is reduced.

[0025] Example 2 This embodiment takes a dry quenching project of a steel company with an annual output of 1.2 million tons of coke as an example, and conducts the experiment by implementing this process according to the steps of Example 1.

[0026] 1. Equipment Selection Steam purification unit: ASF-H4 (Armstrong), with a processing capacity of 500 5 / h and a separation efficiency of ≥99.5%, installed between the waste heat boiler outlet pipe and the high-pressure steam turbine; High-pressure condensing steam turbine: N15-5.0 / 430 (Qingdao Jieneng Steam Turbine), inlet pressure 5.0 MPa / 430℃, exhaust pressure 1.2 MPa / 250℃, installed downstream of the steam purification device; High-voltage generator: QF-15-2 (Sichuan Dongfeng generator), power 15 MW, voltage 10.5 kV, coaxially connected to the high-voltage steam turbine; Medium-pressure back-pressure steam turbine: B5-1.2 / 250 (Hangzhou Steam Turbine), inlet pressure 1.2 MPa / 250℃, exhaust pressure 0.3 MPa / 133℃, installed downstream of medium-pressure steam pipeline network; Medium-voltage generator: QF-5-2 (Shanghai generator), power 5 MW, voltage 10.5 kV, coaxially connected to the medium-voltage steam turbine; Low-pressure steam heat exchanger: Type F shell-and-tube heat exchanger (F=1000 m³) 2 (Wuxi Heat Transfer Equipment), heat exchange area 1000m² 2 The working pressure is 0.6 MPa, and it is installed at the exhaust end of the medium-pressure steam turbine. Deaerator: Rotary film deaerator (Q=100 t / h) (Shanghai Electric Auxiliary Machinery), working pressure 0.03 MPa, working temperature 104℃, water treatment capacity 80-120 t / h, installed downstream of low-pressure steam heat exchanger and upstream of waste heat boiler feed water pump; Condenser: Surface condenser (F=600 m 2 (Zhejiang Hangzhou Oxygen Plant), cooling area 600 m² 2 It is installed downstream of the low-pressure steam heat exchanger and upstream of the condensate tank; Condensate pump / cooling water pump: Multistage centrifugal pump (Q=250 m³) 3 / h, H=120 m (Shanghai Kaiquan Pump Industry); PLC control system: S7-400 (Siemens), sampling frequency 1-2 s / time, sampling accuracy ±0.05 MPa / ±2℃; Inverter: ATV610 (Schneider Electric), compatible with S7-400 PLC communication, frequency adjustment range 25-50 Hz, designed for use with water pumps; Medium-pressure steam pipeline pressure buffer tank: 8m³ 3 The working pressure is 2.0 MPa. Its shell is made of Q345R steel plate with a wall thickness of 16 mm. It adopts a horizontal cylindrical structure with elliptical end caps at both ends. The bottom of the tank is equipped with a drain port and anti-impact plate, and the top is equipped with a pressure safety valve and pressure gauge interface. The inlet and outlet are connected by DN200 flanges. It is equipped with valve group and pressure transmitter interface. It is covered with a 50 mm aluminum silicate insulation layer and is equipped with supports and ladders.

[0027] 2. Debugging and Operation Process (1) No-load commissioning (lasting 72 hours) Start the PLC control system and test the data acquisition module: ensure that signals such as steam pressure, temperature and flow rate at the waste heat boiler outlet, turbine speed and steam inlet and outlet parameters are accurately acquired; Test execution module: Open the high-pressure turbine bypass valve by 10% and the medium-pressure turbine load regulating valve by 20%. The valve action response time is ≤1 second, and there is no jamming. Test the water circulation system: Start the condensate pump and cooling water pump, and adjust their speeds to 30-50 Hz using a frequency converter. Maintain a stable water circulation flow rate of 200-300 m³ / h. 3 / h, the condensate tank level is controlled at 40%-60%.

[0028] (2) Load testing (lasting 168 hours) Phase 1 (0-48 h): Gradually increase the steam output of the waste heat boiler to 50 t / h, which is 50% of the rated value. The high-pressure steam turbine inlet pressure is 3.0 MPa and the temperature is 400℃, with a power generation of 8 MW. The medium-pressure steam turbine is not started, and the pressure of the medium-pressure steam pipeline network is stabilized at 1.0 MPa. Phase 2 (48-120 h): Increase steam production to 80 t / h, i.e., 80% of the rated value; high-pressure turbine inlet steam pressure 4.0 MPa, temperature 420℃, power generation 12 MW; start medium-pressure turbine, inlet steam pressure 1.1 MPa, temperature 245℃, power generation 4 MW; low-pressure heat exchanger outlet condensate temperature 95℃, deaerator steam consumption reduced by 15%; Phase 3 (120-168 h): Steam production is increased to 100 t / h, which is 100% of the rated value. The high-pressure steam turbine has an inlet steam pressure of 5.0 MPa and a temperature of 430℃, with a power generation of 15 MW. The medium-pressure steam turbine has an inlet steam pressure of 1.2 MPa and a temperature of 250℃, with a power generation of 5 MW. The condensate temperature at the outlet of the low-pressure heat exchanger is 105℃. The deaerator uses low-pressure steam after heat exchange for deaeration, with no external steam consumption.

[0029] (3) Full-load operation and testing (for 90 consecutive days) Operating parameters: Total steam flow rate is stable at 100±5 t / h, high-pressure steam turbine power generation is 15±0.3 MW, medium-pressure steam turbine power generation is 5±0.2 MW, and total system power generation is 18-19 MW; Energy consumption indicators: energy utilization rate 88%, condensate reuse rate 95%, industrial water consumption reduced by 35% compared with traditional processes, and standard coal consumption reduced by about 1000 t; Stability indicators: Equipment failure rate 0.5%, only one minor failure of cooling water pump frequency converter, which was repaired within 30 minutes, continuous operation for 90 days without downtime, and no surge phenomenon in steam turbine.

[0030] 3. Comparison with traditional techniques The experimental examples of the new process of this invention are compared with the original traditional single-stage steam turbine process. The comparison data are shown in Table 1: Table 1 shows the comparison data between the process of this invention and the traditional process. index The process of this invention Traditional single-stage steam turbine technology Increase / Decrease Amount Energy utilization rate 88% 68% +20% Annual power generation (1.2 million tons of coke) <![CDATA[1.8×10 8 kWh]]> <![CDATA[1.5×10 8 kWh]]> +20% Range of power generation efficiency ±2.5% ±12% Reduced by 87.5% Equipment failure rate 0.5% 8% Reduced by 93.75% Industrial water consumption <![CDATA[150 m 3 / h]]> <![CDATA[230 m 3 / h]]> -34.8% In the table, the improved energy utilization rate demonstrates that the three-stage gradient recovery of this invention solves the problem of low-grade heat energy waste in traditional single-stage processes, significantly improving energy utilization efficiency; annual power generation is a direct economic manifestation of the improved energy utilization rate, resulting in significant annual revenue growth while reducing the consumption of purchased electricity and fossil fuels; reduced power generation efficiency fluctuations prove that intelligent control solves the problem of sudden efficiency drops caused by steam parameter fluctuations in traditional processes, leading to more stable operation; reduced equipment failure rate indicates that the load pressure on individual equipment is reduced through graded load reduction and pressure buffering, reducing losses and improving equipment reliability; reduced industrial water consumption shows that the closed-loop water circulation design reduces the waste of open-loop water replenishment in traditional processes, resulting in outstanding energy-saving and environmental protection benefits.

[0031] Example 3 This embodiment targets small, independent coking plants with an annual coke production of 500,000 to 800,000 tons, and uses the process described in Example 1 for testing. Because these plants are small in scale, have limited investment budgets, limited plant space, and intermittent industrial steam demand, this embodiment attempts to provide a lightweight, low-cost high-temperature steam energy recovery power generation solution.

[0032] In this experiment, the original project had a low red coke processing capacity of about 90 t / h, and the dry quenching waste heat boiler produced only 50-60 t / h of gas. If the configuration of Example 1 were directly implemented, the equipment load rate would be less than 60%, and the investment cost would account for more than 40% of the total project investment. At the same time, the enterprise needs a small amount of industrial steam for winter heating and coke oven auxiliary heating, about 5-10 t / h. The traditional single-stage process cannot take into account the synergy of both.

[0033] 1. Equipment selection and installation Dry quenching coke waste heat boiler: QX-60, gas production capacity 60 t / h, outlet steam 3.82 MPa / 420℃, installed next to the dry quenching furnace, with a distance of ≤8 m from the steam purification device; Steam purification unit: ASF-H3, with a processing capacity of 60 t / h and a separation efficiency of ≥99.5%, is installed between the waste heat boiler outlet and the steam turbine; Medium-pressure condensing steam turbine: C10-3.82 / 420 / 0.9, inlet steam pressure 3.82 MPa / 420℃, exhaust steam pressure 0.08 MPa / 45℃; extraction steam pressure 0.9 MPa, extraction capacity 0-10 t / h, installed downstream of the steam purification device and coaxially connected to the generator; Generator: QF-10-2, power 10 MW, voltage 10.5 kV, installed on one side of the steam turbine; Integrated heat exchanger-condenser unit: BR-L500 (integrated heat exchanger and condenser), heat exchange area 500 m² 2 condensation area 300 m² 2 The working pressure is 0.8 MPa, and it is installed at the exhaust end of the steam turbine, adjacent to the condensate tank. Deaerator: CY-60, water treatment capacity 60 t / h, working pressure 0.03 MPa / 105℃, installed upstream of the integrated equipment, high-level installation; PLC control system: S7-1200, sampling frequency 2 s / time, collecting 8 core parameters; Condensate pump: KQL150 / 200-37 / 2, flow rate 80 m³ / h 3 / h, head 80 m, frequency conversion 25-50 Hz, installed next to the outlet of the condensate tank.

[0034] 2. Process Steps 2.1 Steam pretreatment: The 3.82 MPa / 420℃ steam generated by the waste heat boiler enters the steam purification device to remove impurities with a particle size greater than 5 μm and free water, and obtain clean steam with a moisture content of <0.5%; 2.2 Work done by extraction steam turbine: Clean steam enters the steam turbine, expands and does work to drive the generator to generate electricity. When the enterprise needs industrial steam, the steam turbine extraction port is opened to extract 5-10 t / h of steam to the steam pipeline network in the plant area. The extraction amount is automatically adjusted by PLC. 2.3 Waste heat recovery: Steam exhaust from the turbine at 0.08 MPa / 45℃ enters the integrated equipment. It first heats the condensate from 40℃ to 95℃ through a heat exchanger, and then condenses it into 40℃ water through the built-in condenser. The condensate flows back to the condensate tank. 2.4 Closed-loop water circulation and deoxygenation: The condensate pump pressurizes the water in the tank to the heat exchanger, and after heating, it is sent to the deaerator. The low-pressure steam (0.1 MPa / 99℃) at the outlet of the integrated equipment is used for deoxygenation. The deoxygenated water (105℃, oxygen content ≤0.01mg / L) is reused in the waste heat boiler. 2.5 Intelligent Control: The PLC system collects eight parameters: steam pressure / flow rate, turbine speed, steam extraction rate, and deaerator liquid level. When the steam flow rate is less than 48 t / h, i.e. 80% of the rated value, the steam extraction rate is automatically reduced to a minimum of 0 to prioritize power generation efficiency. When the steam demand suddenly increases, the power generation capacity is temporarily reduced (not exceeding 10%) to meet the steam demand.

[0035] 3. Debugging and operational monitoring (continuous for 60 days) 3.1 No-load commissioning (48 h): Test the steam turbine extraction valve action response time, the heat exchange efficiency of the integrated equipment, and the PLC parameter acquisition; 3.2 Load commissioning (72 h): When the steam output increases from 30 t / h to 60 t / h and the steam extraction rate is 5 t / h, the power generation is 8.5 MW; when there is no steam extraction, the power generation is 10 MW, and the deaerator is completely self-sufficient in steam. 3.3 Full load operation: Energy utilization rate 83%, power generation efficiency fluctuation ±2.8%, industrial steam supply satisfaction rate 100%, equipment failure rate 0.8%.

[0036] 4. Implementation Results Table 2 compares the large-scale solution of this embodiment with that of Embodiment 2 and the traditional single-stage process. index This embodiment (small-scale solution) Example 2 (Large-scale solution) Traditional single-stage process Equipment investment ratio 30% 25% 35% Energy utilization rate 83% 88% 68% Industrial steam demand satisfaction rate 100% Additional steam piping network needs to be configured. 50% (severe emissions) Factory area space occupancy 40% reduction compared to Example 2 100% (benchmark) 80% The comparison reveals that this embodiment offers cost adaptation, with equipment investment accounting for a lower percentage than traditional single-stage processes, avoiding the waste of large investments and low loads for small enterprises, and matching the budget; while maintaining functionality, with 100% industrial steam demand satisfaction, breaking through the limitations of traditional power generation processes; and in terms of space adaptation, the plant space required is 40% less than that of large-scale solutions, fitting the actual conditions of small enterprises, while the energy utilization rate is still much higher than that of traditional processes, achieving both high efficiency and practicality.

[0037] Example 4 This embodiment addresses the problem of ineffective utilization of waste heat from the coke oven riser pipe and the release of low-grade steam in coking enterprises. Based on Embodiment 1, it attempts to couple dry quenching steam with waste heat from the riser pipe to improve the overall energy utilization rate.

[0038] In this experiment, the original project, as a traditional coking enterprise, had a raw gas temperature of about 650-750 ℃ ​​in the coke oven riser pipe. The water cooling method resulted in complete heat waste. A few enterprises installed riser pipe heat exchangers, but the by-product 0.8-1.0 MPa low-pressure steam (about 15 t / h) had a release rate of more than 20% due to the lack of matching users. At the same time, the dry quenching coke steam power generation system required external steam for deoxygenation. Therefore, this embodiment attempted to couple the dry quenching coke steam reheating with the riser pipe steam energy supplementation design to achieve full utilization of dual waste heat.

[0039] 1. Equipment selection and installation Dry quenching coke waste heat boiler: QX-100, steam production capacity 100 t / h, outlet steam 5.0 MPa / 430℃, installed next to the dry quenching furnace; Rising tube high-temperature heat exchanger: SRG-200, processing raw coal gas volume of 100,000 m³ 3 / h, outlet steam 4.8 MPa / 450℃, installed at the top of the coke oven riser pipe, 2 sets in parallel; Rising tube cryogenic heat exchanger: SRD-150, processing 100,000 m³ of raw coal gas. 3 / h, outlet steam 0.1 MPa / 99℃, installed downstream of the high temperature heat exchanger, raw coal gas is cooled to 220℃; High-pressure steam turbine: N15-5.0 / 450, inlet steam 5.0 MPa / 430℃, reheat 4.8 MPa / 450℃, exhaust steam 1.2MPa / 250℃, installed downstream of the steam purification device; Medium-pressure steam turbine: B5-1.2 / 250, inlet steam 1.2 MPa / 250℃, exhaust steam 0.3 MPa / 133℃, installed at the exhaust end of the high-pressure steam turbine; Deaerator: CY-100, water treatment capacity 100 t / h, working pressure 0.03 MPa / 105℃, installed upstream of the low-pressure heat exchanger, high-level installation; PLC control system: S7-400, sampling frequency 1 s / time, collecting 18 parameters.

[0040] 2. Process Steps 2.1 Dual Waste Heat Steam Generation: Dry quenching coke side: The waste heat boiler generates 5.0 MPa / 430℃ steam, which enters the high-pressure steam turbine after impurities are removed by the purification device; Coke oven side: Raw coal gas at 650-750℃ first enters the high-temperature heat exchanger of the riser pipe, producing 4.8 MPa / 450℃ reheat steam as a byproduct. Raw coal gas cooled to 350℃ then enters the low-temperature heat exchanger, producing 0.1 MPa / 99℃ low-pressure steam as a byproduct for deoxygenation. 2.2 Steam Reheating and Power Generation: The high-pressure turbine's high-pressure cylinder receives steam at 5.0 MPa / 430℃. After the steam performs power generation, it exhausts at 3.0 MPa / 300℃. The exhaust steam is introduced into the riser tube high-temperature heat exchanger, where it is heated to 450℃ to become reheated steam. It then returns to the turbine's intermediate-pressure cylinder, where it needs to perform power generation. The exhaust steam is at 1.2 MPa / 250℃. The intermediate-pressure steam enters the intermediate-pressure turbine to perform power generation, producing 5 MW of electricity. The exhaust steam is at 0.3 MPa / 133℃ and enters the low-pressure heat exchanger. 2.3 Waste heat coupling utilization: The low-pressure heat exchanger uses the exhaust steam from the medium-pressure steam turbine to heat the condensate from 40℃ to 105℃. The 0.1 MPa / 99℃ steam generated after heat exchange is combined with the by-product steam from the riser tube low-temperature heat exchanger and sent to the deaerator together, completely replacing the external steam source. 2.4 Closed-loop water circulation: 105℃ deoxygenated water is reused in the dry quenching waste heat boiler, and the condensate in the condensate tank is pressurized by the condensate pump and then sent to the low-pressure heat exchanger to form a closed loop. 2.5 Coordinated Control: The PLC system links the amount of red coke in the dry quenching furnace with the amount of coal charged into the coke oven. When the temperature of the raw coke oven gas fluctuates by ±50℃, the circulating water volume of the riser heat exchanger is automatically adjusted to ensure that the reheat steam temperature is stable at 450±5℃. When the amount of steam in the dry quenching furnace decreases, the steam output of the high-temperature heat exchanger in the riser is increased to supplement the steam intake of the turbine.

[0041] 3. Debugging and operational monitoring (80 consecutive days) 3.1 Coupling commissioning (120 h): Dry quenching steam flow rate 100 t / h, riser high-temperature steam flow rate 15 t / h, turbine reheat temperature 450℃, total power generation 21 MW (high pressure 16 MW, medium pressure 5 MW). 3.2 Fluctuation Test (48 h): The temperature of the coke oven raw gas dropped to 600℃, the high-temperature steam output dropped to 10 t / h, and after the PLC adjusted the circulating water flow, the reheat temperature stabilized at 445℃, and the power generation dropped to 19.5 MW, with a fluctuation of 7.1%; 3.3 Long-term operation: Total energy utilization rate 92%, riser steam emissivity 0, deaerator external steam consumption 0, estimated annual power generation increase 2.1×10 7 kWh.

[0042] 4. Implementation Results Table 3 compares the solutions in this embodiment with those in Embodiment 2 and the traditional dry quenching single waste heat process. Indicators for this embodiment (dual waste heat coupling): Example 2: Traditional total energy utilization rate 92% 88% 68%; Riser steam venting rate 0% - (without riser utilization) 20%-25%; Deaerator external steam consumption 0 t / h 5-8 t / h 8-12 t / h Expected annual increase in power generation (1.2 million tons of coke) 2.1×10 7 kWh 1.2×10 7 kWh- A comparison reveals that the energy utilization of this embodiment is 4 percentage points higher than that of the waste heat scheme in Embodiment 2, breaking through the limitation of using only dry quenching waste heat and converting the heat wasted in the coke oven riser into benefits; the steam release rate of the riser is reduced from the traditional 20%-25% to 0, and the external steam consumption of the deaerator is reduced from 5-8 t / h to 0, achieving zero resource waste; the expected annual increase in power generation is 9 × 10⁻⁶ more than that of the waste heat scheme. 7 kWh directly demonstrates the value of the coupling, providing a feasible path for coking enterprises to synergistically recover excess heat.

Claims

1. A dry quenching high temperature steam energy gradient recovery power generation process, characterized in that, The method comprises the following steps: S1: high-temperature steam pretreatment: high-temperature and high-pressure steam generated by a dry quenching waste heat boiler is introduced into a steam purification device to remove impurities and free water, and clean high-temperature steam is obtained; S2: primary work: the clean high-temperature steam is introduced into a high-pressure condensing steam turbine to expand and work, a matching generator is driven to generate power, and the discharged medium-pressure steam is transported to a medium-pressure steam pipe network; S3: secondary work: the steam in the medium-pressure steam pipe network is introduced into a medium-pressure back pressure steam turbine to expand and work, a matching generator is driven to supplement power generation, and the discharged low-pressure saturated steam is transported to a waste heat utilization system; S4: tertiary waste heat utilization: the low-pressure saturated steam enters a low-pressure steam heat exchanger, exchanges heat with low-temperature condensed water of a condensed water tank, the heated condensed water is transported to a deaerator, and among the low-pressure steam generated after heat exchange, 60%-80% is used for deaeration of the deaerator, and the remaining part is condensed and returned to the condensed water tank to form a closed loop water circulation.

2. The process according to claim 1, characterized in that, In the S1, the parameters of the high-temperature and high-pressure steam are 4.0-5.4 MPa and 400-450 DEG C, the impurity separation efficiency of the steam purification device is greater than or equal to 99.5%, and the water content of the steam after removal of free water is less than 0.5%.

3. The process of claim 1, wherein, In the S1, the impurities are removed by a method combining cyclone separation and silk screen filtration to remove mechanical impurities and free water with a particle size greater than 5 μm in the steam.

4. The process of claim 1, wherein, In the S2, the inlet gas of the high-pressure condensing steam turbine is 4.0-5.4 MPa and 400-450 DEG C, the exhaust steam is 1.0-1.4 MPa and 240-260 DEG C, a pressure buffer tank is arranged in the medium-pressure steam pipe network, the pressure fluctuation is controlled to be ±0.05 MPa, and the power of the matching generator is 12-18 MW.

5. The process of claim 1, wherein: In the S3, the inlet gas of the medium-pressure back pressure steam turbine is 1.0-1.4 MPa and 240-260 DEG C, the exhaust steam is 0.2-0.4 MPa and 120-140 DEG C, and the power of the matching generator is 4-6 MW.

6. The process of claim 1, wherein: The heat exchange area of the low-pressure steam heat exchanger in the S4 is 800-1200 m 2 , the pressure is 0.5-0.8 MPa, the initial temperature of the low-temperature condensate water is 40-50 ℃, the temperature is raised to 100-110 ℃ after heat exchange, the working pressure of the deaerator is 0.02-0.05 MPa, the working temperature is 104-108 ℃, and the low-pressure steam generated after heat exchange has a pressure of 0.08-0.12 MPa and a temperature of 95-100 ℃.

7. The process of claim 1, wherein, The intelligent control comprises a PLC control system, the sampling frequency of the PLC control system is 1-2 s / time, the sampling accuracy is ±2 DEG C for temperature and ±0.05 MPa for pressure, and the following control logic is executed in real time: (1) data acquisition: the steam pressure / temperature / flow rate at the outlet of the waste heat boiler, the pressure, temperature and flow rate of the inlet and exhaust steam of the high-pressure / medium-pressure steam turbine, the rotating speed of the steam turbine, the power of the engine, the inlet and outlet temperatures of the low-pressure heat exchanger and the liquid level of the condensed water tank are collected; (2) overpressure regulation: when the inlet steam pressure of the high-pressure steam turbine exceeds the rated value by 0.2 MPa, the high-pressure steam turbine bypass valve is opened, the opening degree is 5%-20%, part of the steam is directly introduced into the medium-pressure steam pipe network, and the overpressure of the steam turbine is avoided; (3) low flow regulation: when the total steam flow rate is less than 80% of the rated value, the medium-pressure steam turbine load is automatically reduced to 50%-70% of the rated load, and the high-pressure steam turbine is preferentially ensured to operate at the design condition; (4) water pump frequency conversion regulation: the rotating speed of the condensed water pump and the cooling water pump is adjusted by a frequency converter, the frequency is 25-50 Hz, the water pump flow rate is matched with the system load, and the energy consumption of the water pump is reduced.

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