Product recovery (Example)
O -gas from re nery or multiple sources O -gas is delivered to the battery limits at low pressure
Sulphur removal & drying
ActiSorb Series Impurities removal (optional)
OleMax 100 Series Ni-based catalysts
Compression
Methane / fuel gas H
Compression raises pressure, typically in multiple stages. Many designs do not have compression
Impurities such as AsH , PH , Hg are removed. Removal level depends
Conversion of NOx, O , Ac takes
place over the catalyst that is sulphur tolerant . Conversions depend on objectives
Ethylene Ethane Propylene
Cold recovery
on catalysts and adsorbents used
Bene ts and considerations
Excellent conversions with low ethylene loss High reliability and long cycles achieved Feed composition and operating pressure are important factors for performance
Propane C +
Figure 3 Category #2: Raw refinery gas clean-up of NOx, O₂, and Ac at high and low pressures to recover valuable products
be used as chemical building blocks (light olefins) or feed - stock (saturated hydrocarbons) for other downstream or integrated processes such as ethylene plants.1 With refineries producing lesser amounts of transportation fuels today, on-site technologies like FCC or deep catalytic cracking (DCC) units can be updated to produce more olefins. Those streams also require purification before processing and separation. In addition, some technologies can accept heavier streams, specifically converting low-value olefinic, paraffinic, or mixed streams into high-value propylene and ethylene with subsequent purification and separation.2 Although each project is unique in its feed rate, compo - sition, pressure, and integration with other processes, the application can be clustered into three major categories, with the successful implementation of solutions to individ - ual purification challenges in more than 25 projects served, as will be discussed in more detail. Complete conversion The first category is the most severe operation with hydro - genating acetylene, propyne (MA), and propadiene (PD) in olefinic streams that contain sulphur and high levels of CO (see Figure 2 ). The feed source application, in this case, is processing refinery hydrocarbon feed through cracking furnaces to pro - duce olefinic cracked gas. Cracking mixed hydrocarbons at high temperatures inevitably leads to the generation of C₂ and C₃ acetylenes as byproducts. Therefore, besides removing nitric oxide and oxygen, acet - ylene needs to be quantitatively converted to meet stringent ethylene specifications and as much MA/PD conversion as possible to off-load downstream MA/PD converters (if appli - cable). This configuration typically does not contain a caustic system to remove sulphur species such as hydrogen sulphide (H₂S) and carbonyl sulphide (COS). As a consequence, a sul - phur-tolerant catalyst for the clean-up task is required. For this application, the OleMax 100 series nickel-based catalyst exhibits high selectivity for oxygen and nitric oxide (NOx) conversion while minimising ethylene losses through hydro - genation. It is available in several nickel loadings to cover a wide range of process conditions and feed compositions. Category #1’s primary advantage lies in its streamlined single-reactor system for comprehensive impurity removal. The process requires precise optimisation between meeting
outlet specifications and ethylene retention efficiency. The upstream nickel converter’s absorption of heavy metals and phosphorus compounds may accelerate the deactivation kinetics of OleMax 100, resulting in progressive, moderate elevation of ethylene losses throughout the operational cycle. Refinery raw gas clean-up The most common application is the clean-up treatment of highly contaminated ROGs. In this category, the primary objective is to prepare the gas mixture for further separation in an ethylene plant, specifically integrating it into the prod - uct recovery section, including the cold box (see Figure 3 ). The gas streams are typically produced from FCC and DCC units in the refinery complex. Light off-gases from the DCU may be combined. The primary objective is to remove oxygen, nitric oxides, and often acetylene to various levels. In addition, contaminants such as heavy metals and phos - phorus compounds may be associated, with the specific contaminants differing for each project. Category #2 differentiates from Category #1 as the non-catalytic removal of highly critical contaminants (poi - sons) is separated from the catalytic conversion of compo - nents that are safety-relevant to further processing in the cold recovery section. The benefits of this separation are the contamination avoidance of the nickel converter (OleMax 100). This results not only in longer life and cycle times but, more importantly, maintains a well-defined operation win - dow for the catalytic conversion process, leading to more stable selectivities. The primary treatment objectives typically focus on NOx reduction, oxygen removal, and selective acetylene hydro - genation. When more extensive purification is required, the process can be modified to achieve deeper conversion lev - els, including the reduction of methyl acetylene, propadiene, and butadiene components from the hydrocarbon or off-gas stream. Refinery as source The off-gases from the refinery or other sources are usually delivered to the battery limits of the ROG/ERU/PRU at low pressures (50-250 psig). The gas may be compressed to the required pressure using a two-, three-, or four-stage com - pression, depending on plant requirements. In any case, feed gas pressure needs to align with the pressure of the targeted
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Gas 2025
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