Below, let's give a few examples.
The first example is wet desulfurization of coal-fired flue gas.
There is a few thousandths to a few percent sulfur in coal. When coal is burned, sulfur also participates in the combustion to generate sulfur dioxide. If there are alkaline substances in the atmosphere, such as ammonia, sulfur dioxide discharged into the atmosphere will combine with the alkaline substances to form sulfate and sulfite, forming tiny particles-PM2.5, and its synthesis speed is closely related to atmospheric humidity.
If there is a lack of alkaline substances and heavy rainfall, it will combine with rain to form acid rain, which often happens in southern China.
Therefore, the purification treatment of coal-fired flue gas is to remove particulate matter and desulfurization. In the past few years, wet desulfurization technology has been widely used in domestic coal-fired flue gas desulfurization, including calcium desulfurization, double alkali desulfurization, ammonia desulfurization, magnesium desulfurization and so on.
The basic principle is that the flue gas enters the wet desulfurization tower after dust removal, so that the sulfur dioxide gas in the flue gas is dissolved in water, and then reacts with alkaline substances to remove sulfur dioxide from the flue gas.
However, the smoke carries some water mist containing sulfate or fine particles out of the chimney. On a clear day, if you see that the water mist from the chimney of a coal-fired boiler dissipates, there is still a long light blue smoke-commonly known as tailing or smoking, which is the particulate matter left by the evaporation of the water mist in the smoke.
This means that a large amount of sulfur dioxide directly generates particles during desulfurization. At present, the content of secondary particles in flue gas after various wet desulfurization is still a mystery.
On the basis of wet desulfurization, there are two ways to remove this part of particles.
First, the expensive corrosion-resistant wet electrostatic precipitator is used for secondary dust removal, which will increase the wind resistance and thus increase the power consumption of the fan; At present, only some large coal-fired power plants in China use wet electrostatic precipitator for secondary dust removal of flue gas after wet desulfurization.
The second is to heat the flue gas with a heat exchanger to evaporate the water mist, and then remove the particles separated from the water mist with an electrostatic precipitator or a bag filter. Although the investment of this process is less than that of wet electrostatic precipitator, it will consume a lot of heat energy and increase the power consumption of fans. Needless to say, wet desulfurization also has the problems of wastewater and waste residue treatment, as well as serious equipment corrosion.
Serious corrosion of wet desulfurization tower
However, western developed countries adopted semi-dry comprehensive desulfurization (even denitration and removal of harmful substances such as heavy metals) and dust removal technology more than ten years ago, with relatively low construction and operation costs and no secondary particulate matter.
The process route is: firstly, coarse dust removal is carried out by a low-cost cyclone separator, and then sulfur, denitration, heavy metals and dioxins (if there are dioxins in the flue gas) are comprehensively removed by a semi-dry method in the reaction tank.
In recent years, Beijing-Tianjin-Hebei region has spent tens of billions of yuan to install thousands of wet desulfurization devices that will produce secondary particles. In order to improve the atmospheric environment in Beijing-Tianjin-Hebei region, it is necessary to carry out large-scale secondary transformation in the future.
It takes tens of billions of yuan to carry out large-scale secondary transformation. Who should bear this huge economic loss? Who should bear the responsibility? Will it be unfair to let those enterprises that have installed wet desulfurization devices bear this economic loss?
The second example is the large-scale promotion of coal to gas.
The most common way to change coal into gas is to change coal-fired boilers into natural gas boilers. In Beijing, Tianjin and Hebei, the market price of natural gas is about three times that of coal according to the unit calorific value price.
With the current coal price and gas price, the cost of producing 1 ton steam by ordinary coal-fired boilers is about 180 yuan; Using gas-fired boilers to produce steam, the cost rises to about 300 yuan/ton. For an enterprise whose steam cost accounts for a few percent of the total production cost, it is very difficult to substantially double the steam cost if the profit of the enterprise is not high.
However, if ultra-clean coal-fired boiler technology is used to produce steam, the cost is only about 200 yuan/ton.
In today's Germany, there are still quite a few enterprises (such as edible oil processing and paper making) and small cogeneration stations (such as Kaiserslautern) that use coal-fired boilers-generally cogeneration, to improve economic benefits.
The most unfair example of changing coal to gas is in a glass enterprise. Many glass enterprises in Beijing, Tianjin and Hebei use coal to make gas, and then burn the gas in a glass kiln to melt the glass liquid. There are particles in gas, sulfur in coal, and sulfur (mirabilite) in glass raw materials. The gas in glass kiln burns at high temperature, so there are a lot of particles, sulfur dioxide and nitrogen oxides in combustion flue gas.
Driven by the policy of changing coal into gas to control air pollution, some glass enterprises no longer burn gas in glass kilns, but burn natural gas.
The problem is that after burning natural gas, the pollution problem has basically not been solved. The emission of particulate matter in flue gas is very small, reaching the standard; There is no sulfur in natural gas, but there is sulfur in glass raw materials, so desulfurization is needed; Nitrogen oxides have not decreased at all, so the amount of denitration is not small.
As far as the purification cost of flue gas from glass kiln combustion is concerned, the cost of removing particles (dust) is the lowest, the cost of desulfurization is higher and the cost of denitrification is the highest. Therefore, the cost of flue gas treatment has not decreased much after coal is changed to gas.
However, the price of natural gas is much more expensive than that of coal-based gas. A square meter of 4mm glass, the market price is about 12 yuan/square meter, the original coal-fired gas, and the energy cost is more than 2 yuan/square meter; After burning natural gas, it becomes about 5 yuan/m2. How to open this glass kiln? close the door
The third example is that some experts have suggested that air pollution should be controlled through the adjustment of energy structure and industrial structure.
How long will it take to transform the energy structure? Germany's energy transformation schedule is that from 2000 to 2050, the amount of carbon dioxide emitted by fossil energy combustion will be reduced by 80%.
China's version of energy transformation-China's Long March known as the energy revolution has just begun. The goal put forward by the China administration is that China's carbon dioxide emissions will peak in 2030-almost in sync with the peak of fossil energy consumption.
In other words, in the worst case, the consumption of fossil energy will increase in the next 15 years, so how to adjust the energy structure?
Even if the Beijing-Tianjin-Hebei region is special, the use of coal energy has reached its peak. How many years will it take to reduce the use of coal by half? It's estimated to take 20 years? How many years will it take for Beijing, Tianjin and Hebei to reduce coal use by 80%? 35 years, I guess? I'm afraid neither the government nor the people can afford to wait for such a long time.
The adjustment of industrial structure takes longer than the adjustment of energy structure. Ruhr-gebiet is a typical example.
Since the 1970s, Ruhr-gebiet has been adjusting its industrial structure, and it took 40 years to basically put it in place. But the so-called "in place" is not to completely cut off the heavy chemical industry, but to reduce the steel output by about half. However, in order to control air pollution, how can related industries reduce emissions by half? Generally, it needs to be reduced by an order of magnitude.
In fact, Ruhr-gebiet's industrial structure adjustment is not to control air pollution, but because some industries lack international competitiveness. For example, underground coal mining, because the cost is too high, most mines are closed now, and only two pairs of mines are still mining.
China's de-capacity should be linked to overcapacity, not environmental protection. To control air pollution through capacity reduction, which ratio of 10% to 50% is enough for capacity reduction? How can the production capacity be around 80%? But such a de-capacity ratio is not to de-capacity, but to eliminate an industry.
Control air pollution by adjusting energy structure and industrial structure? Thank god it hasn't happened yet. I sincerely hope not to take this detour.
To control air pollution, the first thing that is lacking is not the iron fist of the government, but the correct control method. Wrong method, detour, wrist is iron, and the opposite is also true. If experts from the government and professional departments can't provide enterprises with the correct methods to control smog, how can enterprises control pollution?
Of course, we can't be too responsible for these experts. After all, it is the first time for a big girl to control air pollution on a large scale in a Chinese sedan chair. Many experts are knowledgeable in air pollution control, but lack experience. The above detours are tuition fees! Although the tuition is a bit high.