Economic analysis of induced draft fans for large thermal power units
Fourth, economic comparison
Taking a 600MW unit denitrification retrofit project as an example, it is proposed to use the combined fan to overcome the denitrification, induced wind and desulfurization resistance. After the thermal performance test, according to the actual operation of the power plant in 2012, the annual load of the unit is divided into high, medium and low. The section, three load fan parameters represent the fan operating parameters of the three sections. The power consumption difference between the two types of fans in the three load sections is calculated by the difference between the power of the static and dynamic fan shafts.
Analysis of operating costs and input costs
Power saving: a single fan static adjustment + frequency conversion than dynamic adjustment to save about 11.75 million degrees of electricity per year, to the on-grid price of 0.4 yuan / kWh, a single fan to save electricity costs of 470,100 yuan a year.
Input cost: single HA46036-8Z static adjustment fan 120w, inverter 165w; HU16050-02 dynamic adjustment fan 145w, static adjustment + frequency conversion initial investment than the dynamic adjustment of each unit 140w.
Maintenance cost: The average annual maintenance cost of the static fan is about 3w, the average frequency of the inverter is 7w; the average annual maintenance cost of the dynamic fan is 20w.
Taking into account the dynamic theory of the time value of funds, calculate the investment difference recovery period n, the formula is as follows:
ΔC=ΔZ(A/P,i,n)
The meanings of the symbols are as follows:
ΔZ: the amount of investment that the static adjustment + frequency conversion is more than the dynamic adjustment;
ΔC: annual difference income, energy saving costs plus increased operating and maintenance costs;
i: benchmark rate of return, calculated at 8%;
n: The difference recovery period.
Bring the data into the formula calculation, and the recovery period is n=3.1, that is, the static investment + frequency conversion scheme can recover the increased investment cost in about 3 years.
Therefore, from the perspective of long-term economic operation, static adjustment + frequency conversion is undoubtedly the best economy.
Due to its simple structure, small maintenance and low failure rate, the static regulation fan has been the first choice for large-scale thermal power unit induced draft fans since the 1990s. In recent years, with the implementation of national energy conservation and emission reduction, the market share has declined. However, with the continuous decline of the price of the inverter, the static adjustment + speed regulation is called the "golden partner" mode in the industry, and the advantages are more and more obvious.
Simple denitration + induced air large domestic thermal power units, the basic choice is to carry out partial transformation on the basis of the original static adjustment fan, mainly based on static adjustment.
The 300MW grade combined fan is mainly based on the static adjustment selection range, but some power plant development methods have also appeared. For example, the 300MW unit of the Weihe Power Plant adopts a single configuration static adjustment fan. At present, for the 300MW joint fan users to use the market demand for static adjustment, Chengdu Electric Power Machinery Factory and related units and institutions are also studying the over-frequency and motor expansion of the inverter, so that the fan speed will increase from 1000 rpm to 1200-1300 rpm. To meet the needs of the parameters.
The 600MW unit combined fan is the main controversy. The power plant should choose a reasonable fan type according to its actual situation. It can be seen from the data that the static adjustment + frequency conversion has no energy-saving effect on the load above 80%, and even consumes more electricity. However, the energy-saving effect of the load below 75% is gradually obvious, and the lower the load, the more obvious the energy-saving effect. In view of the fact that the domestic unit load rate is generally not high, and the operation and maintenance level of the power plant is limited, the reliability that the static adjustment fan cannot match is absolutely superior.
The combined fan of 1000MW unit mainly adopts static adjustment + speed regulation, and the speed regulation of steam turbine is relatively common. There are also some parts adopting frequency conversion speed regulation and dynamic adjustment. As the capacity of the unit increases, the parameters are more suitable for the selection range of static adjustment, and the speed regulation of the turbine makes the power consumption of the induced draft fan factory almost zero, which brings great economic and political effects. At the same time, as the capacity of the unit increases, the revenue from power saving also makes the input and recovery period of the turbine become shorter and shorter. According to the situation of multiple 1000MW units that have been put into operation, the investment cost can be recovered in 2-3 years.
V. Conclusions and recommendations
In order to continue to be at the forefront of technology, we are currently studying the relevant technology for the reserve 1300MW class combined fan. The static adjustment + speed regulation should be the preferred solution for the 1300MW class combined fan.
In summary, the large-scale thermal power unit induced draft fan adopts the static adjustment + speed regulation scheme with obvious advantages, in line with the national energy conservation and emission reduction guidelines, in line with the vital interests of the power plant, should be the preferred option for all power generation enterprises.
