Abstract:

This review summarized the VOCs generation and emission mechanisms, emission characteristics, as well as the progress in VOCs reduction, recovery and thermal oxidation technologies for the petrochemical storage tanks. It proposes opinions and suggestions, aiming to contribute to the deep reduction of VOCs emissions from petrochemical storage tanks in China. Besides the gas generation from the large and small breathing of storage tanks, there are also gas generation phenomena such as high temperature heavy oil thermal cracking. When calculating the combustible gas concentration in tank emissions, components such as hydrogen sulfide, methane, hydrogen and ammonia should not be overlooked. The current VOCs control for storage tanks in China and the United States mainly focuses on source reduction through the use of floating roof tanks, with process control during tank operation and end-of-pipe treatment as supplementary measures. However, it is difficult to meet increasingly strict environmental requirements. It is suggested that China should revise the current standards in a timely manner. According to calculations, the VOCs emissions from organic liquid storage tanks in China in 2019 were estimated to be approximately 392000t to 904000t, mainly from petrochemical enterprises. It is recommended to prioritize control emissions from intermediate product tanks such as crude diesel, crude gasoline, crude aviation kerosene, wax oil, fuel oil, and residual oil, together with tanks containing benzene, toluene, xylene, methanol, and other substances. It is proposed that China should carry out deep reduction of VOCs emissions from petrochemical storage tanks, including source reduction, process control and end-of-pipe treatment. The internal floating roof tanks with built-in gas bag could become another important source reduction technology following floating roofs. It is also emphasized that compared to absorption and condensation, low-temperature diesel absorption have advantages in treating exhaust gases from tanks with high sulfur content, such as crude gasoline, crude diesel, and high-temperature heavy oil. Furthermore, it is noted that overall VOCs control for external emissions from petrochemical storage tanks in China is transitioning from recovery to combined recovery and thermal oxidation (catalytic oxidation, regenerative thermal oxidation, incinerators, process heating furnaces, boilers). The control target for non-methane total hydrocarbons at the outlet of thermal oxidation units is set to be less than 20mg/m³.

Key words: petrochemical storage tank, volatile organic compounds (VOCs), gas production mechanism, emission reduction, recovery, oxidation, safety

摘要：

全面总结了石化储罐VOCs产排机理、排放特征以及VOCs减排、回收和热氧化技术进展，并提出了意见和建议，希望对我国石化储罐VOCs深度减排有所裨益。石化储罐除大小呼吸产气外，还有高温重油储存热裂解等产气现象。在计算储罐排气中可燃物浓度时不应忽视硫化氢、甲烷、氢气、氨等组分。目前，中美储罐VOCs管控都以选择浮顶罐等源头减排为主，以储罐使用过程控制和排放气末端治理为辅，我国应适时修订现行标准，以适应越来越严的环保要求。核算得出2019年我国有机液体储罐VOCs排放量为(39.2~90.4)×10⁴t，主要来自石化企业，建议将粗柴油、粗汽油、粗航煤、蜡油、燃料油、渣油等中间产品罐或重油罐与苯、甲苯、二甲苯、甲醇等储罐一起列为优先管控对象。建议我国开展石化储罐VOCs深度减排，包括源头减排、过程控制和末端治理，内浮顶罐内置气袋有可能成为继浮盘之后又一重要的源头减排技术；低温柴油吸收与吸附、冷凝相比，在处理含硫量较高的粗汽油、粗柴油、高温重油等储罐废气上具有优势。总体上，我国石化储罐外排VOCs治理正在从回收向回收+热氧化（催化氧化、蓄热氧化、焚烧炉、工艺加热炉、锅炉）转变，控制热氧化单元出口非甲烷总烃小于20mg/m³。

关键词: 石化储罐, 挥发性有机物, 产气机理, 减排, 回收, 氧化, 安全