Shanghai Waigaoqiao Third Power Generation Co., Ltd. (hereinafter referred to as the third) put into operation the same year, it hit the world's lowest actual operation coal consumption: 287 g / kWh. This is still the case of only 74% of the load factor. Since then, each year, driven by continuous technological innovation, the world's lowest coal consumption record has been significantly refreshed. By 2013, the record set by the three coal companies in the international coal and electricity sector has fallen below 280 g / kWh, reaching 276 g / kWh.
Around the world, the best-known coal-fired power plant outside China is Danish NORDJYLL Power Plant Unit 3. Due to the implementation of the second reheat ultra-supercritical technology and the unique advantages of ultra-low temperature cooling seawater, the actual operation of power supply Coal consumption is 286.08 g / kWh. We found that the "original world record" worse than the third three 10 g / kWh, and 10 g / kWh is the coal industry, the so-called generation of technology gap.
May 25-26, Polaris Power Grid in conjunction with the China Energy Conservation Association, organized by the 2017 Clean Coal-fired Power China International Forum, the third power plant will participate as a full participation in the forum as a base. At 9:00 on the 26th, Shi Min, general manager of the third power plant delivered a speech at 2:30 pm at the three power plant field trips (visitors limit 30). There will be professionals outside the three efficient green coal technology introduced, I believe for each person on-site to bring a zero-distance technology feast, immediately click grab! If you want to understand the Clean Coal Power China International Forum More conference information, welcome to click: The following as a warm-up visit to the field, the external power plant using three energy-saving technologies to make inventory.
First, the main side of the boiler technology
1, exhaust loss and recovery technology
As we all know, the loss of the boiler, the smoke loss accounts for about 80% of the total loss, therefore, how to reduce the loss is an extremely attractive subject. In addition, the induced draft fan and desulfurization booster fan work so that the flue gas enthalpy and temperature rise, the maximum temperature up to 10 ℃, quite impressive. However, the absolute value of the boiler exhaust gas temperature is low, usually about 130 ℃ or even lower, the available useful limited energy. As the flue gas contains SO2, after the installation of SCR denitration device will increase SO3 and ammonium sulfate, waste heat recovery device prone to surface condensation sulfuric acid dew, which will produce strong corrosion of the heat exchanger, fly ash in the flue gas easily at the same time Stick on the surface of the heat exchanger condensation, alkaline soot and cement after the combination of cement-like, very difficult to remove. Continued development of this situation can even seriously degrade the ventilation capacity of the flue. Germany has made a useful exploration in solving such problems, using acid-resistant plastic pipe for making heat exchangers. However, due to the low heat transfer coefficient of the plastic, the resulting heat exchange device is very large and expensive. It is reported that Japan adopted a steel heat exchanger to recover flue gas waste heat, but to prevent condensation, flue gas temperature drop is limited, and the sulfur content of coal to be strictly controlled.
China has a large amount of steam coal reserves, but its sulfur content is high and unstable. In addition, as a developing country, investment should consider the cost-effective, so the above two programs are difficult to learn from.
Through in-depth study, we have solved the problem by changing the perspective of problem solving. The basic idea is through special control measures as far as possible not to heat the surface of the heat exchanger, supplemented by low temperature steel heat exchanger with a certain degree of acid resistance, and placed between booster fan and desulfurization tower Low dust areas, both to prevent wear and tear, but also reduce the risk of fouling and clogging, but also take into account the induced draft fan, booster fan to do the recovery of enthalpy smoke. Heat exchanger using fin tube to improve heat transfer efficiency. Waste heat recovery refrigerant is condensed water between low-pressure heaters, heated condensate reduces low-pressure cylinder extraction, reducing the heat consumption of the steam turbine.
The desulfurization and flue gas waste heat recovery systems of the two units were put into operation in June and October of 2009 respectively and have operated well so far. After repeated inspections, corrosion is minimal, the impact of life can be ignored. The performance test shows that the commissioning of this set of equipment increased the unit efficiency by 0.4% and the desulfurization tower water jet decreased by 45t / h.
2, air preheater sealing technology
Rotary air preheater is the common configuration of today's large boilers, the third power plant is the rotor rotary type, the rotor diameter of 17m × 2.5m high. Design leakage rate <5%, after a year <6%.
Rotor air preheater although there are many advantages, but the rotor will appear in the operation of "mushroom-type" nonlinear deformation, dynamic and static clearance more difficult to control, which led to greater leakage rate. Air leakage will lead to two consequences. One is the increase of the total air volume of each relevant fan and the corresponding increase of power consumption. The increase of its power is approximately related to the third power of air leakage rate. Second, the heat exchange efficiency of the air preheater is reduced, Losses increase and boiler efficiency decreases.
In order to reduce the air leakage rate of the air preheater, we have researched and developed "Omnidirectional Flexible Sealing Technology". This kind of sealing device is based on the premise of not changing the original equipment structure, and is installed in the radial, axial and circumferential directions The wear rate of contact controllable flexible seal, the use of its flexible features to compensate for the dynamic and static gap of non-linear changes, so that the air leakage rate significantly reduced. After the application of this technology, the rated power consumption rate of the factory will be reduced below 3.5% (including desulfurization and denitrification). At the same time, the boiler hot air temperature is also significantly increased, corresponding to increased boiler thermal efficiency. This innovation has increased unit efficiency by about 0.29%.
3, the boiler energy-saving start series of technologies
Large-scale super (super) critical unit start-up, need to consume a large amount of water, electricity, oil, coal, steam and other resources, a long time, and the risk of this stage is much higher than the unit during normal operation. In order to prevent sticky soot pollution on the dust removal device, pure fuel and kerosene should not be mixed firing phase dust collector, which in turn significantly increased this stage of pollutant emissions.
Through in-depth study on different ways to start the domestic and foreign DC boilers and corresponding advantages, disadvantages and existing problems, we have made a series of major breakthroughs in theory. On this basis, the traditional method of unit startup was completely subversed and innovated, a whole new set of startup technology was researched and designed, and fruitful results were achieved. Such as:
(1) Do not start the feed pump, the boiler under hydrostatic pressure and hot water without ignition to rinse. This water washing technology does not start the feed pump, nor ignition heating, saving a lot of fuel and power plants, and the operation is simple, good controllability. Since the flushing water temperature is high and the flushing medium in the heated face being washed is in a soda-water two-phase flow, the flushing effect is greatly improved.
(2) DC boiler steam heating start and steady combustion technology. With this start-up technology, fuel consumption has dropped by more than an order of magnitude. The method not only switches the boiler from a cold start to a hot start, but also enables the operating condition of the flue gas system to be better than that of the hot start, thereby greatly improving the ignition and steady-state conditions of the boiler and creating a minimum oil breakage Burning load <20% BMCR record, significantly improved the startup safety of the boiler.
(3) to cancel the water circulation pump low water flow hydrophobic start. This technology greatly simplifies startup and operation control, improves safety and reliability, reduces start-up losses, and still has the advantages of short start-up time and low losses in the very hot state of conventional boiler with water circulation pump.
After the successful application of the new start-up technology, the entire start-up operation is obviously simplified, the time is greatly shortened, and the start-up energy consumption is greatly reduced. In particular, the power consumption of the plant and the ignition and combustion aids are decreased by an order of magnitude, while the safety is remarkably improved. At present, the time can be controlled within 120 minutes from the ignition of the boiler to the grid connection of the generator, regardless of the state of the unit, including cold start. Less than 10 to 20 tons of fuel consumption, power consumption of 80,000 degrees, 200 tons of coal consumption (including heating steam).
Second, the main steam turbine side technology
1, the main steam parameters and operation of the adjustment of the optimization
Siemens super (super) critical turbine are used without regulation level design, the basic mode of operation for the sliding pressure operation. In order to further improve the economy of FM operation, the ultra-supercritical model introduced for the Chinese market adopts the FM and over-load regulation technologies of the "steam-trap valve". The high-pressure cylinder adds a fifth stage after the move into (fill) steam mouth. After the main steam valve and the fill port between the even a steam valve. In the normal load range, the main tune valve and steam valve are involved in FM. Increase (minus) load by opening the check valve or closing the main door. Obviously, turbine efficiency drops significantly when the makeup valve is opened. If frequently open the steam valve and run in a small opening, can easily lead to erosion and leakage.
In order to avoid the general situation to open the steam valve, valve for the role of steam valve in two cases, the design parameters and control methods made the following optimization and innovation:
(1) Properly increase the design pressure of the main steam and set the overload valve opening point to the rated load at the maximum cooling water temperature in summer, thus ensuring that the steam trap valve will not be opened at rated load and below for the whole year.
(2) For the frequency regulation operation of steam turbine in normal load section, the successful research and development of energy-saving steam extraction FM technology. The focus of this approach is to change the turbine's FM principle. By adjusting the flow rate of condensate, indirectly change the relevant level of back-air extraction, combined with high extraction steam adjustment to achieve the purpose of turbine transient power regulation (followed by the boiler combustion control system to follow up). With this method, the main tune door can be fully open, fill the valve closed, to eliminate the steam turbine throttling loss.
Frequency response method using this fast, relatively large power adjustment range. From the Waigaoqiao three two units of practice point of view, the new FM mode has been successful. At present, the rate of plus (minus) load of the unit can reach and exceed 1.5MW / min. It is estimated that the above two optimization and innovation measures can increase unit efficiency by about 0.22%. However, in the performance test, these benefits will not be reflected.
2, to the pump and system optimization and energy saving
Based on the analysis of the configuration, commissioning and operation of the water supply system in the past projects and referring to the design and operation experience of the water supply system of the large super (ultra) supercritical units in the United States and Germany, the Third Power Plant in China used the first 100% Self-contained independent condenser, can be activated alone, to cancel the electric water pump. The starting steam source is taken from the cold reheated steam of the adjacent unit.
In the start-up phase of the unit, once the steam is generated by the boiler, the steam supply to the pump turbine can be switched back to the machine (cold reheat steam) in due course, equivalent to the recovery and utilization of some of the steam originally discharged to the condenser through the low pressure bypass. This greatly reduces the energy consumption during the start-up phase of the unit.
The third power plant selected Germany's Alstom special pumps for water supply pumps, the turbine's efficiency as high as 86.7%. In addition, the steam turbine also added a steam source for the cold reheat steam door and adjust the corresponding level.
In the rated working condition of the unit, the first two adjustable doors can be set to be fully open, while the third adjustable door can be used to supplement the steam when the rated load is exceeded, and bear the full power when the FCB and other conditions of the unit (turbine extraction disappears). Therefore, the unit in the rated conditions of the operating efficiency can be maximized.
In addition, researching and experimenting on the successful low-speed start-up and full-speed operation of steam-driven feedwater pumps has not only greatly reduced energy loss during boiler startup, but also improved unit efficiency, greatly simplifying the system control strategy and eliminating the minimum flow Recirculation valve erosion risk of leakage, improve equipment operation safety. Compared with other similar units, the pump is equivalent to raising the efficiency of the unit about 0.117%.
3, generalized heat recovery theory and series of technologies
The generalized regenerative theory is a breakthrough of the classical thermodynamic theory. Its main point is that it can be extended from the traditional heat recovery cycle with boiler feed water as the regenerative medium, and the water, wind and coal as the heat input medium The generalized regenerative cycle. As the heat recovery medium can be expanded to increase the extraction steam turbine applications and extraction volume, which can reduce steam turbine exhaust loss.
According to this theory, Waisanhua Power Plant has developed a series of corresponding technologies and achieved overall success. Taking the technology of air-inlet heat recovery in boiler as an example, this technology utilizes steam turbine extraction to cooperate with boiler air preheater to heat the inlet air of the boiler to improve the combustion efficiency of the boiler while recovering the steam extraction heat of the steam turbine.
This technology does not like the traditional heater will increase unit coal consumption, while improving the safety of the air preheater, but also improve the operating efficiency of the unit. The comprehensive application of this technology can improve the unit operating efficiency by 0.42% or more.
The generalized regenerative theory is applicable to all coal-fired units and can break through the bottleneck of thermal efficiency of thermal power units and can solve a series of environmental problems.
4, flexible heat recovery technology
The technology is to expand the traditional technology of feed water recuperation, by increasing the regulation of high-pressure extraction to maintain the water temperature under low load as much as possible without reducing or reducing the decline, but also greatly reduce the low load boiler economizer exports This can completely solve the inherent problems of the denitrification system that it must quit its operation under low load and significantly improve the environmental protection level of the unit. The use of the extraction regulating valve has the capability of rapidly changing the high-pressure extraction steam and can also remarkably improve the efficiency of the unit Frequency response characteristics; meanwhile, the increase of steam turbine extraction under low load can improve the operation efficiency of the unit; in addition, the increase of hot air temperature and the inlet temperature of water wall under low load can obviously improve the combustion of low load boiler Stability, combustion efficiency and hydrodynamic issues. At 75% load, this technology can increase unit operating efficiency by about 0.2%.
5, super-critical unit of the efficiency of protection
As an ultra-supercritical unit, with the improvement of steam parameters, especially the increase of temperature, new technical problems and contradictions are also accompanied. One of the salient issues is the steam-side oxidation of pipes and the resulting solid particle erosion (SPE), posing a serious threat to the safety and economic performance of the unit. This problem occurs more often in the start-up phase of the unit. The peel oxide is peeled off from the steam side of the pipe due to the thermal shock of the boiler. Exfoliated oxides are deposited on the pipe or inside the pipe, or with the steam and form solid particles. In the furnace tube deposition will occur serious burst tube. The solid particles with the steam will cause the steam turbine blade erosion, the efficiency of the irreversible permanent decline. In addition, the solid particles in the startup process will also erode the sealing surface of the bypass valve, causing it to leak and short-circuit some of the steam directly, thus reducing power plant efficiency. The super (super) supercritical unit gradually put into operation in China also appeared Some serious problems in this area, some units only run more than two years, steam turbine efficiency fell by 4% or more.
Prevention of steam-side pipe oxidation and the resulting erosion of solid particles to prevent the decline in efficiency, but also an important way to save energy. However, this involves many aspects such as the selection of main equipment, system design, installation and commissioning, operation mode and control concept, and requires comprehensive and comprehensive prevention and control of the whole process. After more than 10 years of follow-up and research, we have made a series of breakthrough achievements and formulated a complete set of comprehensive prevention and control technologies, which have been strictly implemented in the construction of the Third Power Plant.
For example, the high superheat dry blowing pipe in the construction phase solves the problem of insufflation of the conventional blowing pipe in the outlet area of ​​the water wall, and effectively improves the blowing performance. The large-capacity bypass system is configured and the "high Moisture rinse technology "to perform variable-load, variable-parameter and high-momentum flushing of variable circuits before steam turbine revolution with a special by-pass system and control method to maximize oxide stripping before each turbine starts and The exfoliated scale in the system, including the particles in the zero flow velocity area, etc., are sent directly to the condenser to completely remove the oxide that has shed in the system and completely eliminate the oxidation of the system in the system under high temperature and high load And the re-precipitation of particulate matter to ensure the safety and economy of the generating unit. A new bypass system configuration design and control method has been developed to effectively solve the problem of bypass erosion while shortening the startup of the unit and bypassing working process. In addition, steam heating start and steady load low-load combustion technology is the use of steam instead of oil and coal to the boiler as a whole pre-heating, the boiler has been in a "hot stove, hot air" hot environment. Put an end to the boiler after the fire is usually not saturated furnace heat convection led to the first "dry burning" and accelerate the high temperature oxidation and steam production after the steam into the convection heating surface lead to "quenching" so that the oxide skin loose and spalling phenomenon.
After 30 months in operation, the Third Power Plant conducted pipe inspection of the boiler's tertiary superheater and secondary reheater pipes. The superheater and reheater pipes were as smooth as ever without any scale loss and oxidation Material accumulation phenomenon.
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