Finding and Facing the Root Cause of Haze Outbreak in China (2): Mutation Factors and Unconventional Pollutants
2021/3/3 15:25:00 本站

1. Condensable particles leading to haze outbreak


Even today, the main goal of coal-fired flue gas treatment is to continue the conventional pollutants such as sulfur dioxide, nitrogen oxides, dust (filterable particles) in acid rain treatment in the past. Since 2007, the emissions of nitrogen oxides and sulfur dioxide in the power industry have dropped by 90%, and the whole society has also seen a significant and continuous decline, with the emission index reaching the international advanced level. But for the international standard, condensable particles are missing, which are also the main pollutants leading to haze.


2. Before 2011, some of the coal-fired flue gas treatment facilities had GGH or relatively low operation rate, similar to the dry flue gas emission mode; the frequency of haze in this stage belonged to the conventional change, without a mutation.


3. 2012 is a year of centralized transformation of coal-fired flue gas treatment facilities. Many enterprises have been demolished due to the problems of GGH scaling and flue gas leakage not reaching the standard. A large number of wet flue gas emission facilities have been newly added or started normal operation, and a large number of ammonia denitration facilities have been newly installed. The coal-fired flue gas treatment facilities have a sudden change


The main mutations in this year are as follows:


l Some wet FGD facilities with GGH were canceled, dry stack became wet stack, dry flue gas emission became wet flue gas emission.

l Most of the original and later new wet FGD facilities did not have GGH, which was wet flue gas emission.

l In 2012, large-scale denitration transformation was started, and the wet desulfurization facilities and denitration were operated in series.


To achieve the emission standard of nitrogen oxides which is much more stringent than the international level, the enterprise sprayed excessive ammonia, increased the number of catalyst layers, and increased the ratio of sulfur dioxide to sulfur trioxide; the excess ammonia and sulfur trioxide preferentially carried out acid-base neutralization reaction to produce ammonium bisulfate. This can also be confirmed by the fact that there are a lot of ammonia salts in desulfurized fly ash.


After 2012, the combination of real-time online monitoring, powerful stimulus policies, and punitive measures for illegal emission completely reversed the problem of the low operation rate of flue gas treatment facilities for several consecutive years before 2011, resulting in a sharp increase in wet flue gas emissions.

 

4. From the changes brought by the cancellation of GGH, it can be briefly explained that the defect of coal-fired flue gas treatment is one of the important reasons for the occurrence of haze.


5. Abrupt changes brought about by wet flue gas emission, cancellation of GGH, denitration, and other flue gas treatment around 2013.


6. The technical and management defects of conventional pollutant treatment lead to the emission of unconventional haze pollutants, which is characterized by the concentration of PM2.5 in the atmosphere rising sharply, leading to the outbreak of haze in 2013 and continues to this day.


The use of defective coal-fired flue gas treatment facilities and management measures to control conventional pollutants led to the emission of unconventional haze pollutants which were not monitored and controlled in the atmosphere, which was characterized by the concentration of PM2.5 in the atmosphere, resulting in the outbreak of haze in 2013 and has continued to this day. Haze is a secondary man-made disaster caused by technical and management defects in the process of controlling conventional pollutants. It is a man-made disaster caused by human error and cannot be a meteorological disaster.


7. It is not the change or mutation of PM2.5 mass concentration that leads to the outbreak of haze.


After 2015, the ultra-low emission transformation is the deep reduction of conventional pollutants. There are still enough unconventional pollutants that cause haze into the atmosphere, but the degree is reduced.


1. Ultra-low emission is an enhanced version of the main measures to control acid rain when there was acid rain in the past, not for haze control.

2. After considering the condensable particulate matter, under the strict Beijing ultra-low emission standard, the particulate matter concentration also exceeds the Beijing standard of 5 mg.

3. Authoritative expert evaluation: the ultra-low emission evaluation significantly underestimates the actual emission level of particulate matter.

4. At present, the transformation of ultra-low emission has been completed in key areas. According to the PM2.5 mass concentration, the number of days of haze, fog, and light fog with low visibility has decreased by 50% before the outbreak of haze, which is more than ten times, rather than half. Compared with haze control, ultra-low emission is not the right medicine.


The total coal consumption, bulk coal combustion, motor vehicle emissions, and other conventional variables have no mutation around 2013, which is unlikely to lead to the outbreak of haze.

1. There is no big change in coal consumption before and after the outbreak of haze.

2. Other conventional variables did not change significantly, even though they had a great contribution to the local PM2.5 concentration.

3. In large cities of North China plain or Beijing as a coal forbidden area, motor vehicle emissions may sometimes be the main source of fine particles, but the primary and secondary particles produced by coal-fired flue gas treatment have moved in with the wind before each haze outbreak, and the defects of coal-fired flue gas treatment also have a great impact on it.

4. The total coal consumption and PM2.5 mass concentration began to decouple in 2007, which is not accurate.


The haze outbreak that started in 2013 is due to the secondary pollution or secondary disaster of flue gas treatment link caused by technical defects such as wet desulfurization and denitrification, lack of standards, and lack of supervision. It is not caused by the change of coal consumption or PM2.5 mass concentration, which is the root cause of the haze outbreak. Otherwise, it is very difficult to treat haze. Similar to the haze outbreak in Shenyang in 2013, the coal consumption at that time was much lower than that around 2000. It can be seen that controlling coal to control haze is not the right medicine. Aiming at the secondary pollution caused by the defects of coal-fired flue gas treatment, it is the key to fast, low-cost, and efficient haze treatment.


Translator/Wang Lei


Original Chinese Article

https://mp.weixin.qq.com/s?__biz=MzAxOTExMzM4Mg==&mid=2649661584&idx=4&sn=414741fd0bffa158fcda2f3c53892621&chksm=83d1f459b4a67d4f4af0b0f1646a1a16b0afab38e6a8c9418a9b17fb4c2977e2ae26883043f4&scene=21#wechat_redirect


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