Breaking the bottleneck of green development in the steel industry and changing the destination of gas from "lighting the sky lantern" to "turning on the electric light"
Our reporter Wu Chunxin correspondent Ma Lan Shu Jun
In 2021, the crude steel output of my country's iron and steel industry will be 1.033 billion tons, and the excess gas in the steel mill will be about 0.77 standard cubic meters per hour. If supercritical gas power generation technology is used, nearly 31,000 megawatts can be installed.
Compared with the ultra-high pressure technology currently commonly used in the iron and steel metallurgy industry, it can install nearly 5,000 megawatts more, generate 40 billion kWh of new electricity annually, and reduce carbon dioxide emissions by 32 million tons.
Recently, the world's first supercritical gas generating unit was put into operation in Guangxi.
The unit was independently developed by MCC Southern Metropolis Environmental Protection Engineering Technology Co., Ltd. (hereinafter referred to as MCC Southern Urban Environmental Protection). Reduce carbon dioxide emissions by 854,000 tons.
my country's gas power generation technology has developed from medium temperature to medium pressure, high temperature and high pressure, and high temperature and ultra-high pressure to subcritical and supercritical, constantly consolidating my country's right to speak in the field of international gas utilization, and increasing China's confidence in the practice of global carbon reduction and emission reduction.
At present, a number of innovative technologies for gas power generation in my country have been extended to Indonesia, Malaysia and other countries.
Turn waste into treasure and increase the efficiency of gas power generation from 25% to 43.5%
my country's iron and steel production capacity ranks first in the world, but in the process of iron and steel smelting, a large amount of toxic gas is emitted, and the calorific value is low and difficult to store.
1 cubic meter of steel smelting blast furnace will produce about 1 kilogram of gas, and the calorific value of gas is about 800 kcal, only one-third of inferior coal and one-tenth of household natural gas.
In the past, except a small amount of this gas was used for power generation in small-capacity and low-parameter gas boilers, most of it was burned and discharged in the way of "lighting lanterns", which not only caused a lot of energy waste, but also seriously polluted the environment.
In fact, the gas emitted during the iron and steel smelting process can be reused, that is, the gas is collected and burned to generate electricity.
Gas power generation is also a "magic weapon" for iron and steel enterprises to achieve energy saving, emission reduction and efficiency enhancement, and the efficiency of gas power generation is the key to measuring its "magic power".
In the past, the use of coal gas in small-capacity and low-parameter gas boilers for power generation had low secondary energy utilization efficiency, only less than 37%.
The existing high-efficiency low-calorific value exhaust gas turbine combined cycle power generation technology has been monopolized by foreign countries for a long time, the equipment is expensive, the operating cost is high, and the quality of the gas used for power generation is high, so it is difficult to popularize and apply in my country on a large scale.
MCC Southern Urban Environmental Protection, who was "born" in Wuhan Iron and Steel Design and Research Institute, is well aware of this pain point for steel companies. generate electricity.
"It is difficult to improve power generation efficiency in technical system research and development, parameter design and equipment integration control. Every small step forward will bring about a substantial increase in benefits." Song Zixin, chief engineer of MCC Southern Urban Environmental Protection, introduced that the company has gradually upgraded its technology for nearly 20 years. , the gas consumption for 1 kWh of electricity will be reduced from 4.3 cubic meters to 2.5 cubic meters, and each 1 kWh of electricity will save 200 grams of standard coal.
Song Zixin said that the gas power generation technology has developed from medium temperature and medium pressure, high temperature and high pressure, and high temperature and ultra-high pressure to subcritical and supercritical.
After five generations of products, MCC Southern Urban Environmental has increased the power generation efficiency of gas power generation from 25% to 43.5%.
Behind every 1% is a new technological breakthrough, which also means that more steel waste gas can be turned into clean electricity, reducing more coal consumption.
Taking a set of 135 megawatt (MW) units as an example, using the same fuel, the annual power generation of the unit using subcritical technology can increase by about 80 million kWh compared with the previous generation technology, and the annual economic benefit is about 40 million yuan.
The excess gas, which once made iron and steel companies do nothing, has become a "sweet pastry" to make money in technological innovation.
Keep improving, my country has become a leader in gas power generation technology in the metallurgical industry
Six years after the promotion of high temperature and ultra-high pressure gas power generation technology in my country, in January 2019, subcritical technology came head-on, and this year, supercritical gas power generation technology was born in my country.
Supercritical gas power generation refers to the combustion of low calorific value gas in a gas boiler, and the main steam parameters produced reach a supercritical state, that is, the steam pressure is 25.4 megapascals (MPa) and the temperature is 605 °C. generate electricity.
"The innovation of supercritical gas power generation technology subverts the traditional concept, breaks through the 'conclusion' of high parameters, large capacity and high efficiency, and realizes the scientific practice of high parameters, small capacity and high efficiency." Song Zixin said that the high-quality fuel conversion rate high, but with supercritical gas power generation technology, low-quality fuels can also achieve high conversion rates.
At present, the world's first supercritical gas generator set independently developed by MCC Southern Metropolis Environmental Protection has been operating in Guangxi Shenglong Metallurgy.
The facility has set a number of world records for the operating pressure, temperature and power generation efficiency of gas generating units, which also means that my country has become a leader in low-calorific gas power generation technology in the world's metallurgical industry, and strongly supports the low-carbon transformation of iron and steel metallurgical enterprises.
At present, the first set of supercritical gas generating units is 145 megawatts, the power generation efficiency can reach 43.5%, and the annual power generation capacity is 1.06 billion kWh.
"This technology will greatly enhance the ability of iron and steel enterprises to reduce carbon and pollution, and take a big step towards low-carbon smelting." Gao Huai, deputy secretary-general of the China Society for Metals, believes that the efficient use of gas has always been the core of the low-carbon transformation of the iron and steel industry. technology, supercritical gas power generation consumes less energy and is more profitable.
According to reports, as the fifth-generation gas generator set, the steam parameters and power generation efficiency have been greatly improved, which also brings higher safety requirements.
To this end, the new unit has developed and applied intelligent technologies such as "one-key start-stop of APS in the whole plant" and "automatic combustion of gas boiler", which can realize "one-key operation" and automatic control of combustion in the start-stop phase of the unit, and improve the intelligent operation. and security.
It is understood that MCC Southern Metropolis Environmental Protection has a market share of more than 70% in the national gas power generation field. In recent years, the total installed capacity of gas power generation undertaken by the company is equivalent to the Three Gorges Project, with an annual power generation capacity of 130 billion kWh, reducing carbon dioxide emissions by more than 10%. billion tons.
In addition to the steel industry, it can also serve more industries
According to industry experts, gas has low calorific value and unstable pressure. Compared with coal-fired power generation, gas-fired power generation has many difficulties.
However, gas power generation is a clean power generation method with good economic benefits, which is in line with the trend of low-carbon and environmental protection, and is attracting attention.
It is reported that in 2021, the crude steel output of my country's iron and steel industry will be 1.033 billion tons, and the excess gas in the steel plant will be about 0.77 standard cubic meters per hour. If supercritical gas power generation technology is used, nearly 31,000 megawatts can be installed.
Compared with the ultra-high pressure technology currently commonly used in the iron and steel metallurgy industry, it can install nearly 5,000 megawatts more, generate 40 billion kWh of new electricity annually, and reduce carbon dioxide emissions by 32 million tons.
In addition, experts also said that although the supercritical gas power generation technology was born from the steel industry, the prospect of "breaking the circle" to serve more industries is promising.
Song Zixin believes that my country's coal-based energy use industries, such as petrochemical, coal chemical and other energy systems, can also use supercritical gas generator sets, and the application potential is huge.
By using supercritical gas power generation technology, these industries do not burn standard coal, use sufficient industrial waste gas or even use low-quality coal to achieve power generation, and achieve ultra-low emissions, which greatly reduces power generation costs.
In the future, supercritical gas power generation technology will undoubtedly be a sharp sword, galloping across the blue ocean of energy, and overcoming obstacles in order to achieve carbon neutrality and carbon peaking.