1 fast cut function
The quick cut-off function is mainly for safety reasons. When a fire hazard occurs in a gas turbine power plant, it is necessary to quickly cut off the natural gas source. At present, the most popular configuration of each gas turbine power plant is to install a fire alarm shut-off valve at the entrance of natural gas into the plant area. The valve is generally driven by pneumatic or electric drive to achieve remote control, and the cut-off time of the valve can not be too long. The requirement is less than 10s. Now the general power plant is driven by compressed air, which can use the original compressed air source of the power plant.
2 filtering function
The large solid particles in the natural gas enter the gas turbine turbine, which will directly damage the turbine blades. The small particles will also cause wear to the flow passage of the gas turbine and scratch the sealing surface of the valve equipment along the way, resulting in a decrease in the sealing performance of the equipment. Doped droplets in natural gas can cause instability in the combustion of the gas turbine and damage the equipment. Therefore, natural gas must be filtered before entering the gas turbine combustor to remove all large particles (>10 m), droplets and most of the small solid particles (<10 m) and small droplets. There are currently three main types of filtration equipment to choose from.
2.1 cyclone separator
The cyclone separator adopts the gravity separation principle. When the airflow enters the filter cylinder from the inlet duct, the impact force on the shell surface or the filter cartridge bracket causes the gas to decelerate, and the solid particles affected by gravity are separated.
The cyclone separator has a low filtration accuracy. It is necessary to configure the cyclone on the natural gas system, depending on the cleanliness of the natural gas and the length of the upstream pipe of the cyclone.
For relatively clean natural gas, such as liquefied natural gas (LNG), the large particulate matter contained in it is almost negligible, and it is considered that no cyclone separator is provided. For relatively unclean natural gas associated with offshore oil fields, and where natural gas is not treated before it is supplied to the power plant, it is necessary to provide a cyclone separator.
There are two ways to configure the cyclone separator: one is to set two, each one is equipped with an isolation valve, one for each device, so that the reliability of the setting is high. When one cyclone fails, it can be online. Switching to another cyclone separator, but the cost is higher and the economy is poor; the other is the current mainstream configuration, that is, a single cyclone separator is installed, and then a bypass system is added. When the cyclone separator fails, Choose to let natural gas flow directly from the bypass.
From the current operation of most gas turbine power plants, it is more reasonable to set up a cyclone separator plus a bypass. This is because most natural gas plants are dirty at the initial stage of operation, and the cyclone filter runs for a period of time. The cleanliness of natural gas is improved, and the bypass is selected. This can reduce the pressure loss caused by the natural gas passing through the cyclone separator, and can also reduce the loss to the cyclone separator. The operation mode is more flexible and can be adapted to different gases. Source condition.
Cyclone separators are generally located at the most upstream of all filters. Their function is to filter out large particles, but the natural gas treated by the cyclone separator cannot meet the gas turbine requirements.
2.2 coarse filter separator
The filtration accuracy of the coarse filter separator is much higher than that of the cyclone separator.
The coarse filter separator consists of two stages: the first stage consists of several replaceable and washable filter elements whose type and precision need to be selected according to the working conditions in order to remove the smallest solid particles and to agglomerate the mist. The material is removed to the utmost extent in the second stage vane separator; the second stage utilizes the principle of vane separation to remove liquid particles from the natural gas. At present, a general coarse filter separator can filter out 99.99% of solid particles and droplets larger than 5 m in the system.
The coarse filter separator is an important processing step in the entire natural gas processing system. It will filter out most of the tiny solid particles and droplets in the natural gas, greatly reducing the burden on the downstream filtration equipment. In many gas turbine power plants, coarse filtration Most of the splitters are available in one-off configuration.
2.3 fine filter
The filtration process can also be divided into two stages: natural gas is first separated by the first stage cyclone to remove larger particles; after the natural gas enters the second stage, the accumulation filter with a filtration accuracy of 0.3 m can put more than 0.3 m of solid in the gas. The particles are removed by 99.99%, and the liquid particles larger than 0.3m are removed by 99.5%. The natural gas filtered by the fine filter is basically in line with the current gas turbine filtration standards for all gas turbines.
The fine filter is equipped with a liquid level gauge, a differential pressure gauge and other instruments. The signals are generally directly connected to the gas turbine control system, and the liquid concentration in the filter and the pressure difference on both sides of the filter can be monitored online.
Fine filters are generally used in two sets, one open and one ready configuration.
The above three types of filters are common in current gas turbine power plants. The cyclone separators may not be provided, and one or two units may be provided. The coarse filter separators are generally set in two sets, but they can be discarded in order to reduce the cost in the case of high cleanliness of the gas supply; the fine filter must be set because it is the ultimate guarantee of natural gas quality. The signals of the general filter are directly connected to the control system of the gas turbine body.
3 pressure adjustment function
Different gas turbines have very different requirements for natural gas pressure, but one thing in common is that all gas turbines need to have a stable pressure, and the pressure fluctuation range cannot be too large. Taking the 9E gas turbine produced by GE as an example, the pressure requirement for natural gas is 1.86~2.64MPa, the pressure variation range is 1%, the change rate is 0.25%/s, and the instantaneous maximum change value is 1%/s. If the pressure of the gas source is high For the intake pressure required by the gas turbine, it is necessary to provide a pressure reducing device on the natural gas processing system, and vice versa.
3.1 decompression station
The function of the decompression station is to reduce the pressure supplied to the natural gas to the intake pressure required by the gas turbine. There are three main design schemes for decompression stations: unit design, master control design and hybrid design.
3.1.1 unit system
Unit system pressure regulating system. Each gas turbine adopts two-way pressure regulation, divided into main road and auxiliary road, one open and one standby. Each pressure regulating pipeline process is controlled by an emergency shut-off valve, and the pressure regulator is from upstream to downstream. The sequence, in series, constitutes a safe, monitored pressure regulating system. Under normal conditions, the emergency cut-off and monitor are in the fully open position, and the downstream pressure is controlled by the regulator. When the regulator fails and the downstream pressure cannot be controlled, the monitor begins to operate to maintain a safe range of downstream pressure; or at least remain in the current position or fully open.
The monitor and emergency shut-off valve are of the fail-close type and are in the fully closed position in the event of a fault. If the monitor also fails and cannot control the downstream pressure, the emergency shut-off valve automatically cuts off the air supply to ensure the safety of the downstream pipeline and equipment. When the working pressure regulating pipeline is cut off, it should be able to automatically switch to the standby road, and the standby road regulator is automatically put into operation. During pipeline switching, the regulator outlet pressure fluctuations must not exceed the gas turbine inlet demarcation point requirements for natural gas pressure fluctuations.
3.1.2 Parental Control
The mother control pressure regulating system. Two or more gas turbines share two-way voltage regulation, divided into main road and alternate road, and the other is similar to the unit system.
3.1.3 mixed system
Each gas turbine has a common alternate road, and the other units are similar to the unit system.
Each of the three schemes has its advantages and disadvantages. The advantages of the unit system are high redundancy and reliable operation. The disadvantage is high cost; the parent regulation is just the opposite; the reliability and economy of the hybrid system are somewhere in between.
3.2 booster station
The function of the booster station is to increase the supply pressure to the intake pressure required by the gas turbine. Natural gas compressors are available in centrifugal and piston versions.
The advantages of centrifugal compressor are stable output pressure, reliable operation, low noise compared with piston compressor, advanced technology and convenient maintenance. The disadvantage is expensive. For a specific centrifugal compressor, the pressure adjustment range It is strictly limited by the pressure ratio and has a small adjustable range. For example, in engineering, it is sometimes necessary to add a decompression device to the centrifugal compressor to reduce the inlet pressure to a certain value, and then compress it through the compressor to meet the gas turbine intake requirements.
The advantage of the piston compressor is that the pressure adjustment range is large and the cost is low; the disadvantage is that the noise is large, and the pressure output is unstable compared with the centrifugal compressor, but generally it can also meet the gas turbine inlet pressure fluctuation requirement.
These two compressors are currently widely used in gas turbine power plants. For power plants with strict cost control, piston compressors may be selected, and for gas turbine power plants with higher pursuit of operational reliability and stability, centrifugal The compressor is the best choice.
Natural gas compressors are generally not used because of their high price.
4 temperature adjustment function
4.1 Heating If the pressure of the gas source is relatively high, the temperature of the natural gas after decompression by the pressure regulating station is generally low, which cannot meet the requirements of the gas turbine specification for natural gas (generally, the gas turbine requires more than 28 °C for the dew point temperature. The temperature of the natural gas after the pressure regulating station is out may be lower than 0 ° C), so the natural gas must be heated.
The more commonly used heaters are hot water heaters, steam heaters and electric heaters.
The advantage of the hot water heater is that the heating is stable and the adjustability is good.
There are many types of hot water heaters, and the shell type is generally used. The water source of the hot water can be taken from the return water of the circulating cooling water outside the gas turbine, which can improve the efficiency of the entire power plant. Hot water heaters can only heat natural gas to below 30 °C due to the temperature limit of the return water of the gas turbine circulating cooling water.
The heating medium of the steam heater can be from a small boiler provided by the power plant, or from a waste heat boiler, and generally adopts a shell-and-tube type.
Steam heaters can heat natural gas to relatively high temperatures, such as 50 °C.
Electric heaters are used less in engineering, mainly because of the relatively low operational safety, and the commissioning of electric heaters will increase the plant's power consumption rate.
The more reasonable configurations in the current project are:
(1) Option A, one steam heater and one hot water heater are connected in series, and each heater is provided with a bypass. In actual operation, generally only the hot water heater is put in, but when the ambient temperature is low in winter At the beginning of the gas turbine, the temperature of the circulating cooling water has not risen enough to heat the natural gas to the required temperature, or when the hot water heater fails, the steam heater needs to be put into operation.
(2) Option B, 2 sets of hot water heaters are connected in parallel, one is opened, and one steam heater is installed on the hot water pipe. When the hot water temperature is not enough, it is used to heat the hot water and heat it in the steam boiler. The device module is relatively far away, and this scheme can be adopted when the steam pipe arrangement is inconvenient.
The choice of the plan depends on the equipment layout of the entire power plant. Relatively speaking, the plan A is more economical and reasonable, the plan B is more reliable, and the investment cost is relatively high.
4.2 cooling
If the pressure of the gas source is relatively low, the natural gas is generally compressed after being compressed by the compressor and needs to be cooled. Generally, the compressor body is equipped with a cooler, but it can only be cooled to about 100 ° C. It is also necessary to cool the natural gas to about 50 ° C with a special cooler.
The chillers are typically water cooled and are placed in an open and ready arrangement.
5 Conclusion
The gas turbine's natural gas system configuration needs to be based on the gas source conditions and the specific conditions of the entire gas turbine power plant in order to make the most reasonable choice.
Special vehicles for railway transportation in mines.In order to adapt to the narrow conditions of underground roadway, the external dimension is compact.There are trucks, rickshaws, carts and so on
A mining vehicle is a narrow track railway transport vehicle for transporting loose materials such as coal, ore and waste rock in a mine.Harvesters according to the structure and unload in a different way is divided into: stationary harvesters (material car, flat car), tilting harvesters, unilateral bend side dump car, bottom (side) dump car and shuttle car a total of 5 categories.
A vehicle that carries coal, gangue, equipment, equipment and personnel, drawn by a locomotive or winch.The mining vehicle is mainly used for the underground roadway, wellbore and ground rail transportation in the mine. It is the largest and most widely used transportation equipment in the coal mine
Mine Car,Rail Mine Car,Mining Ore Car,Mining Transportation Car
Jining Dongda Electromechanical Co.,Ltd. , http://www.coal-mine-equipment.com