Iron Removal from High-Temperature Fischer鈥揟ropsch-Derived Distillate through Thermal Treatment
详细信息 查看全文
- 作者：Siphamandla W. Hadebe ; Dieter Leckel
- 刊名：Energy & Fuels
- 出版年：2013
- 出版时间：September 19, 2013
- 年：2013
- 卷：27
- 期：9
- 页码：5161-5167
- 全文大小：315K
- 年卷期：v.27,no.9(September 19, 2013)
- ISSN：1520-5029
文摘
Hydrotreating units at the Sasol high-temperature Fischer鈥揟ropsch plant in Secunda, South Africa, experience a number of unplanned shutdowns because of sudden increases in pressure over the reactor beds. This is caused by a solid crust that builds up at the top of the catalyst bed. The crust constituents were studied using inductively coupled plasma (ICP), and it was found that the major constituents of the crust are iron (48 mass %) and sulfur (28 mass %), in the form of iron sulfide (Troilite), as confirmed by X-ray diffraction (XRD) spectroscopic techniques. FeS is believed to originate from dissolved iron carboxylates present in the feed streams. A range of aliphatic iron carboxylates (C5鈥揅11) expected to be present in the distillate hydrotreater feed were subsequently synthesized and characterized using infrared (IR) spectroscopy. The thermal behavior of these carboxylates was studied using high-pressure differential scanning calorimetry (HP-DSC); decomposition temperatures established ranged from 299 to 282 掳C from C5 to C11. It has been shown experimentally that iron carboxylates dissolved in feed streams may be thermally decomposed in situ and removed as iron sulfide or iron oxide in the presence or absence of H2S, respectively. High-pressure hydrogen or nitrogen may not be necessary during thermal decomposition of the iron carboxylates. However, hydrogen gas may be necessary to prevent coking but has no significant role in iron carboxylate decomposition. Therefore, iron carboxylates may still be decomposed and removed effectively from the feed streams using an upstream guard bed even at pressures lower than those used in the hydrotreating reactor.