Natural gas cogeneration is one of the most energy efficient and environmentally friendly low-carbon energy utilization methods. However, due to factors such as inadequate industrial policies and industry supporting facilities, there are some constraints on the development of the industry, which have recently raised some concerns. The author only analyzes from the aspects of energy security, resource endowment and market price.
■ Doubt 1: Does the development of natural gas cogeneration affect energy security?
1. Diversified natural gas sources
Natural gas combined heat and power sources include domestically produced gas and imported gas, and the imported gas has many directions: Central Asian natural gas, Myanmar natural gas, Russian natural gas, and imported LNG by sea. The diversification of gas sources has promoted the gradual improvement of related industries and supporting facilities, and better protected natural gas supply.
2. The natural gas cogeneration project is an important guarantee for the safe operation of the gas network and the power grid
The natural gas cogeneration project has double peak regulation function, which can guarantee the safe operation of the power grid and gas grid. On the one hand, gas turbines have superior peak shaving performance and are superior to coal power in terms of start-stop rate and low-load operation depth peak shaving. The natural gas cogeneration project can go deep into the load center, meet the peak load regulation needs of the power grid and other distribution, and ensure the security of power grid operation. On the other hand, the combined heat and power project also has a peak regulation effect on the gas network. The characteristic of natural gas is that it is not easy to store. Excessively high or low pressure will affect the safety of the gas network. The natural gas cogeneration project is equivalent to a dynamic gas storage facility. It can respond quickly based on the supply of gas and the safe operating pressure of the pipeline network. , Increase or decrease gas consumption in time to ensure the safe and stable operation of the gas network.
■ Doubt 2: Is the natural gas resource scarce?
1. China has abundant natural gas reserves
According to BP statistics, as of the end of 2018, the world's proven natural gas reserves were 196.9 trillion cubic meters. China's proven natural gas reserves have shown a steady growth trend, with conventional natural gas resources of approximately 56 trillion cubic meters, and as of the end of 2018, the recoverable resources amounted to 6.1 trillion cubic meters. In terms of production, China's natural gas output in 2016 was 161.5 billion cubic meters, ranking sixth in the world. In addition, China has abundant unconventional natural gas reserves, and its shale gas reserves are the largest in the world. At present, the degree of unconventional natural gas development is low, but with the advancement of technology and the deepening of oil and gas reforms, the economy of developing low-quality, difficult-to-use resources in low-permeability, deep, deepwater, volcanic rocks and other fields will gradually emerge. The potential of resources will be continuously released. It is believed that natural gas production will grow explosively in the next few years.
2. Sufficient gas supply in the international market
According to the "Development Report of the Domestic and Foreign Oil and Gas Industry 2018" released by the China Petroleum Institute of Economics and Technology in early 2019, the increase in global LNG exports last year came mainly from Australia and the United States. At present, Qatar, Russia, Canada, Australia, Indonesia and other major gas producing countries are investing in the construction of export-oriented liquefaction plants, and global natural gas supply has shown a loose trend.
■ Doubt 3: Is the price of natural gas high?
At present, the main factor restricting the cogeneration of natural gas is the high price of domestic natural gas.
In recent years, the total global LNG market demand has continued to increase significantly, from 239 million tons in 2014 to 290 million tons in 2017. In 2017, China implemented the "coal to gas" policy, coupled with inadequate domestic natural gas facilities and other reasons, LNG import prices rose sharply in the second half of 2017. However, in the international market, the spot price of LNG has been at a relatively low level. Because the domestic natural gas market has not yet been fully liberalized, and the gas storage facilities are not complete, the price at the user end is much higher than the international spot market price of natural gas. Since 2019, the spot price of LNG in the international market has continued to decline. The recent CIF price is only US $ 4.4 per million British thermals (equivalent to RMB 1.5 per cubic meter), which is far lower than the listing prices of domestic LNG receiving stations and pipeline valve stations. price. The global LNG market will maintain a loose supply situation for some time, and LNG prices will tend to be reasonable.
In addition, we cannot compare the economics of coal and natural gas based on price alone. Although the price of coal is lower, there are more waste, greater pressure on environmental protection, and the subsequent cost of environmental protection needs to be greater. As a high-quality, efficient, green and clean low-carbon energy source, natural gas has great value and advantages in reducing environmental pollution and social costs caused by coal combustion.
■ Developing natural gas cogeneration projects should become an important direction for natural gas utilization
China's energy industry is undergoing an unprecedented transformation, transforming towards diversification, cleanliness, digitalization and marketization. Natural gas cogeneration should be an important form of natural gas utilization. Compared with coal-fired units, natural gas cogeneration has the following significant advantages:
1. Natural gas power generation is an important component of power generation in developed countries
China's natural gas power generation is still in its infancy, but at present, developed countries such as the United States, Japan, South Korea, and Europe have taken natural gas power generation as one of the main energy sources, and their installed capacity accounts for an increasing proportion, of which the United States 42%, the United Kingdom 42%, South Korea 27%.
According to US Energy Information Administration (EIA) statistics, as of January 2019, the installed capacity of US natural gas combined cycle power plants was 264 million kilowatts, while the installed capacity of coal-fired power plants was 243 million kilowatts. In May 2019, the United States' net electricity generation fell 2.4% year-on-year. Among them, coal power generation amounted to 73.7 billion kWh, a year-on-year decrease of 13.6%, which has maintained a downward trend for six consecutive months since December 2018; natural gas power generation amounted to 117.4 billion kWh, an increase of 1.1% year-on-year. It is foreseeable that natural gas power generation is still the most basic form of energy supply in the United States.
2.Cogeneration of natural gas has greatly improved energy efficiency
In coal-fired generating units, the cycle efficiency of ultra-supercritical parameter units is about 45%; the cycle efficiency of ultra-supercritical secondary reheat units is about 48%. If it is operated in a combined cycle + heating mode, the integrated energy utilization mode is more efficient: a pharmaceutical energy station in Zhejiang has designed two 12.9 MW + 7.95 MW gas-fired generating units, with a heat supply of 61.22 tons / hour and plant power The rate is 4%, the single-cycle gas turbine efficiency is 34.5% (equivalent to the cycle efficiency of coal-fired power units with ultra-high voltage parameters), the heat (cold) electricity ratio is 146.91%, and the overall energy utilization thermal efficiency is as high as 82%.
Comparing the 9HA.01 gas-fired combined cycle unit with the 660MW ultra-supercritical coal-fired power unit, and considering the extraction of heating to maximize the overall efficiency, the power generation and heating of the two technologies are as follows (converted by equal capacity):
As can be seen from the figure above, the efficiency of gas-fired combined cycle cogeneration is much better than coal power. In the case of burning the same calorific value fuel, the loss is only less than half of coal power. The production of high-quality energy "electricity" is The output rate is 157% of coal power, and the heat supply is 83% of coal power (the above data is calculated based on the heat balance of the maximum extraction heating capacity of 9HA.01 and 660,000 ultra-supercritical coal power).
3. Natural gas cogeneration is more suitable as a city center energy point
At present, domestic cogeneration units are mainly divided into coal-fired cogeneration units, natural gas cogeneration units and biomass cogeneration units. Among them, biomass thermal power units are not suitable for widespread promotion due to unstable fuel sources and fuel quality; coal-fired units are currently the mainstream of combined heat and power units, but coal-fired units have greater environmental pollution and poor load regulation performance, and The system structure is complicated. Today, when more attention is paid to energy conservation, emission reduction and energy supply security, it can no longer meet the development needs of society and should not be used as the only cogeneration option.
The natural gas combined heat and power unit consumes only one-third of the water used by coal-fired generating units and occupies more than half of the area than coal-fired units. There is no need to set up auxiliary facilities such as coal yards and ash yards that have large dust pollution. High degree of automation, greatly improving the stability and safety of operation. Obviously, natural gas cogeneration units are more suitable as urban energy sources.