燃煤電廠重金屬流佈分析研究

Study on Heavy Metal Distribution in Coal-fired Power Plant

陳胎雄(CHEN TAI-SHOUNG)

指導教授 ： 王雅玢

中原大學/工學院/環境工程學系/碩士(2021年)

https://doi.org/10.6840/cycu202100867

摘要

摘要
我國能源長期依賴進口，政府積極發展乾淨綠能，使用天然氣及超超臨界燃煤火力發電廠，以改善PM2.5 空氣品質及保障國人身體健康。但對於超超臨界燃煤火力發電廠周界重金屬空品監測數據可參考數據相對較少，因此本研究針對超超臨界燃煤火力發電廠進行重金屬流佈之分析研究。
重金屬具有型態多樣、流布廣泛、毒性累積且無法被完全分解等多重特性；在環境中遵循物質不滅定律、而僅做相的移轉；如持續長期累積將對人體及環境產生危害。而國際間一般常見重金屬管制項目大都以鉛(Pb)、鎘(Cd)、汞(Hg)、砷(As)等四大類為主。鑒於該等重金屬會對人體、環境產生極大危害，對其排放濃度加以立法管制是現行世界各國重要空氣污染管制重點工項。
國外對於燃煤電廠燃燒後之不同金屬元素在廢氣、底灰及飛灰流布探討分析結果顯示，煤炭經高溫燃燒後，多數沸點較高之重金屬將會附著於細小粒狀物上；若透過良好除塵設備，將其有效捕集在飛灰中，可避免排放擴散於大氣。而汞型態則較為特殊，因其沸點低、高溫燃燒後主要以氣態為主，不易被捕捉，處理上也是最為棘手。
研究結果顯示，超超臨界燃煤火力發電廠，非汞重金屬多數附著於飛灰上，因此袋式集塵器對非汞重金屬去除效果顯著，除Se之外，其他非汞重金屬（Sb, As, Be, Cd, Cr, Co, Pb, Mn, Ni）的去除效率皆可達到99%以上，非汞重金屬經由質量平衡計算（輸出/輸入）可達98~149%，而汞在各污染防治設備單元中之質量平衡達100.00%~126.84%，尤是SwFGD質量平衡率最差，可能因汞的濃度極微量，檢測數值極易受干擾，加上海水量體大，在加成效應下易產生大誤差。煙道檢測結果顯示，除了Be之外，超超臨界鍋爐所排放的非汞重金屬的濃度皆小於亞臨界鍋爐，排放係數跟美國MATS既存標準比較，不論是超超臨界鍋爐或亞臨界鍋爐，其非汞重金屬排放濃度皆符合標準，但若和新設標準比較，亞臨界鍋爐所排放的Cr和Mn就略高於MATS新設標準，此結果提供寶貴資訊予以未來訂定管制標準或進行空氣品質模式推估及風險評估之進一步應用。

關鍵詞：超超臨界燃煤機組、非汞重金屬、汞重金屬、PM2.5、MACT、MATS

關鍵字

超超臨界燃煤機組、非汞重金屬、汞重金屬、PM2.5、MACT、MATS

並列摘要

ABSTRACT
Our country energy has long relied on imports. The government is actively developing clean green energy, using natural gas and ultra-supercritical coal-fired thermal power plants to improve PM2.5 air quality and protect people’s health. However, there are relatively few monitoring data for reference of heavy metal air products in the periphery of ultra-supercritical thermal power plants. Therefore, this study focuses on the analysis and research of heavy metal distribution in ultra-supercritical thermal power plants.
Heavy metals have multiple characteristics such as various types, widespread distribution, accumulation of toxicity and inability to be completely decomposed; they follow the law of immortality in the environment and only move in direction; if continue to accumulate for a long time, they will cause harm to the human body and the environment. The common international heavy metal control items are mostly lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As). Given that these heavy metals can cause great harm to the human body and the environment, legislative control of their emission concentration is currently an important item of air pollution control in all countries in the world.
Foreign countries have discussed and analyzed the distribution of different metal elements in exhaust gas, bottom ash and fly ash after combustion in coal-fired power plants. The results show that after coal is burned at high temperatures, most of the heavy metals with higher boiling points will adhere to the fine particles; Through good dust removal equipment, it can be effectively trapped in the fly ash, which can prevent the emission from spreading to the atmosphere. The mercury form is more special, because of its low boiling point and high-temperature combustion, it is mainly gaseous, which is not easy to be captured, and the handling is also the most difficult.
Research results show that in ultra-supercritical coal-fired power plants, most of the non-mercury heavy metals are attached to fly ash. Therefore, the bag dust collector has a significant effect on the removal of non-mercury heavy metals (Sb, As, Be Cd, Cr, Co, Pb, Mn, Ni). Except for Se, other non-mercury heavy metals have a removal efficiency can reach more than 99%. Non-mercury heavy metals can reach 98%-149% through mass balance calculation (output/input). The mass balance of mercury in each pollution prevention equipment unit is100.00%-126.84%, especially SWFGD has the worst mass balance rate. Probably because the concentration of mercury is extremely small, the detection value is very susceptible to interference. Coupled with the large volume of seawater, large errors are prone to occur under the multiplicative effect. The flue test results suggest that, except for Be, the concentration of non-mercury heavy metals emitted by ultra-supercritical boilers is less than subcritical boilers. The emission coefficient is compared with the existing MATS (Mercury and Air Toxics Standards ). Regardless of whether it is an ultra-supercritical boiler or a subcritical boiler, the emission concentration of non-mercury heavy metals meets the standard. But if compared with the new standards, the emission of Cr and Mn from the subcritical boiler is slightly higher than the new MATS. This result provides valuable information to set control standards in the future, carry out further application of air quality model estimation and risk assessment.

Keywords: ultra-supercritical coal-fired units, non-mercury heavy metals, mercury heavy metals, PM2.5, MACT, MATS

並列關鍵字

ultra-supercritical coal-fired units, non-mercury heavy metals, mercury heavy metals, PM2.5, MACT, MATS

參考文獻

第六章 參考文獻

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