By – David Graubard
Refinery Purification
Today’s refinery operations process more difficult crude types than ever before. Crude supplies coming from oil sands and heavy oil reservoirs are more sour and have many contaminants that need to be removed throughout the refining process. Global business demands that crudes from across the world may be bought and processed in a region where the refineries are not conditioned to handle some of the contaminants inherent in some exotic crudes. These crude changes impact refinery costs and operations by introducing contaminants as Mercury, Carbonyl Sulfide, Hydrogen Sulfide, Arsine, Chlorides and Fluorides). Following is a simplified process flow diagram of a typical refinery; color-coded dots represent where you can find these contaminants, their process impacts, and the UOP adsorbents to remove them.
Chloride
Found in isomerization operations; activating agent for reforming catalysts. Process strips away HCl, requiring further, continuous or discrete addition of Cl. Lost Cl leaves the reformer loop in the make-up gas and off-gas streams. Cl causes fouling and corrosion, reduces adsorbent life and deactivates catalysts. UOP CLR-204, UOP CLR-454
Sulfur
Naturally occurs in most hydrocarbons. Modern high-activity catalysts are extremely sensitive to sulfur poisoning. Emission standards are tightened as are refined product quality requirements. In wet environments, sulfur can cause corrosive damage to equipment and piping. Sufficiently high sulfur levels in refinery streams can (1) deactivate the catalysts that promote desired chemical reactions in certain refining processes, (2) cause corrosion in refinery equipment, and (3) lead to air emissions of sulfur compounds, which are undesirable and may be subject to stringent regulatory controls. UOP ADS-120, UOP SG-731,
Oxygenates/Water
Vary from ketones, aldehydes, alcohols and ethers. Polymerization and isomerization catalysts are extremely sensitive to poisoning by these compounds. UOP AZ-300, UOP GB-620, UOP A-201, ADG-401, HPG-250
Mercury
Found in most crudes and common to naphtha, diesel and C3 fractions. Proven catalyst poison and a danger to process equipment. Mobile and capable of adsorbing/desorbing to-and-from pipework and other assets. Reduces the value of export naphtha. Elemental mercury has a high vapor pressure. Unlike other “heavy” metals, mercury will distribute into lighter products and gaseous streams. Operational-wise: mercury causes cracking of copper-based trays or valve components, corrosion of Al surfaces, and troublesome contamination, maintenance or cutting of mercury contaminated steel surfaces. UOP GB-346, UOP GB-346S
Arsine
Present in most crudes and mostly evident in C3 fractions. Reduces value of C3 product to downstream petrochemical processors. Polymerization catalysts are sensitive to poisoning by Arsine. Arsine is generally present in the refinery gases in the concentration of less than 1ppm. This small quantity is enough to poison the selective hydrogenation catalyst. UOP GB-238
Fluoride
Present in HF alkylation units. HF alkylation catalyst forms organic fluoride via reaction with olefins. Corrosive by nature. Defluorination of butane, propane and alkylate streams is very common. UOP P-188
UOP is at the forefront of investigating new and improved adsorbent technologies that more safely, efficiently and cost-effectively remove contaminants from refinery operations. The adsorbents’ team is committed to answering your questions, helping you discover new opportunities and working to resolve the challenges that face your operation every day.
For more information regarding UOP adsorbents, visit uop.com or contact your local sales representative.
Case Studies
1. Asia-Pacific Refinery
A plant in Asia Pacific running a net gas treater reported chloride slip in their hydrogen stream, causing equipment corrosion. The existing adsorbent was more than 10 years old and required changeouts several times a year. UOP’s high-capacity CLR-204 adsorbent increased the life of the adsorbent by more than 45%, reporting no chloride slip or equipment failures due to corrosion.
2. Americas Refinery
An HF Alkylation unit in the Americas was experiencing excessive hydrocarbon coking resulting in a shortened adsorbent life cycle. UOP’s P-188 adsorbent increased the unit’s capacity by 34%. Coking has also been significantly reduced, increasing the time between required change-outs.
3. European Refinery
A plant in Europe was concerned with the significant cost of handling, disposing and replacing a nickel-based adsorbent. If handled improperly, nickel carbonyl, a highly poisonous gas, may form when a Ni-type compound is exposed to air. UOP’s ADS-120 copper/alumina mixed metal oxide adsorbent increased the life of the adsorbent by 18%.
4. Pacific Rim Refinery
A plant in the Pacific Rim suffered from a precious metal catalyst deactivation and required periodic heat treatment to desorb the contaminants. This resulted in a steady sintering of the active phase of the catalyst. A bed of UOP’s GB-346 and GB-238 was installed, successfully removing the contaminants and increasing catalyst life. The requirements for catalyst heat treatment have been eliminated, and the catalyst has maintained its expected conversion.