PEFTEC
Petroleum, Refining & Environmental Monitoring Technologies
PP087 - Online and Offline Determination of Arsenic in Wastewater from Oil and Gas Refinery
Authors: Dr Warren T Corns and Dr Bin Chen (PSA)
Arsenic is naturally present in oil and gas at trace levels. During the refining of gas and oil there are number of processes that use water and this can become contaminated with Arsenic because of its affinity to the aqueous phase streams. Waste water streams from the plant are typically combined and then treated prior to discharge to surface water in the vicinity of the plant. The efficiency of the wastewater treatment process has to be monitored to ensure that the agreed permitted discharge levels are not exceeded. In this presentation we describe the use of a newly developed online analyser laboratory method and the results were compared.
The system offers multiple stream analysis so in principle it is possible to monitor the inlet and outlet of water treatment technologies. The sample is injected using FIA with a water carrier. This is then mixed with an acidified oxidant and passed through a UV photolysis unit. This converts all forms of Arsenic in the sample to Arsenate (As V). This is an important step of the analysis as different arsenic species have different hydride generation yields so conversion to one form provides a more accurate determination. The acidified sample is then mixed with sodium tetrahydroborate (III) which reacts with the arsenic to form the gaseous hydride (Arsine, AsH3). This is then separated from the liquid phase using a gas liquid separator and then delivered to the detector using an argon carrier gas. The Arsine is atomized using a miniature hydrogen flame and the arsenic atoms are excited using a boosted discharge hollow cathode lamp. The detector then monitors the atomic fluorescence signal.
Results will be presented showing the analytical performance obtainable.
To request a copy of this poster click here.
PP088 - Mercury Mass Balance Studies on Ethylene Plants
Authors: Dr Warren T Corns (PSA)
Knowledge of the mercury content in petrochemical feed-stocks and refinery products is extremely important. The damage caused to petrochemical plants can be financially crippling especially when unscheduled shutdowns are forced. Mercury has been found to be responsible for many cases of selective hydrogenation catalyst deactivation even at low concentrations. These are typical based on palladium or platinum which form a strong amalgam with Hg. Mercury is also known to be the cause of corrosion problems with aluminum-based heat exchangers which operate at cryogenic temperatures, rotors and condensers at natural gas refinery plants. Heat exchanger replacement is a costly operation due to the capital investment of the exchanger itself and the plant down time incurred for its replacement. Because of these facts many plants install mercury removal systems to ensure that important parts of the plant are protected, this means that periodic measurements of the outlets of these removal systems need to be made to ensure that they are working correctly. Also other parts of the plant require accurate measurements to help provide a better understanding of the fate of mercury.
This presentation will focus on the analytical challenges and techniques to perform a mass balance of Hg on an ethylene plant. Atomic Fluorescence Spectrometry was utilized to determine Hg in various streams including gas, liquid and solid phase samples and the results were applied to the mass flow rates across the plant. A butane feedstock containing 18ppbw of Mercury was responsible for the rapid degradation of an acetylene reactor catalyst which was replaced and later protected by Hg removal beds. Mercury was partly removed during acid gas treatment and gasoline stripping. The majority of mercury was found in the C2 cracked gas as this represented the bulk mass flow. Mass balance data will be presented in addition to emission rates to the environment. The development of a model to predict Hg condensation rates in relation to process conditions will also be presented and discussed.
To request a copy of this poster or oral presentation click here.
PP089 - Online Determination of Mercury in Unstabilised Hydrocarbon Liquid Streams
Authors: Dr Matthew A Dexter and Dr Warren T Corns
Unstabilised hydrocarbon liquid streams such as unstabilised condensate present particular challenges for sampling and determination. If the liquid sample is depressurised, a portion of the sample is vaporised, producing a two phase sample for determination. Mercury can be associated with both the gas and liquid portions of the sample. The most accurate mercury measurement is therefore obtained when the analysis is performed at process conditions.
Conventionally, determination of liquid process streams which are gas-liquid mixtures when depressurised is difficult due to the need to characterise two separate phases and combine the results. This can lead to high measurement uncertainty and complicated procedures.
This paper describes a newly developed fast loop sampling system with self-cleaning filtration, a novel auto-injection system designed to introduce the sample to the analyser at process pressure to avoid the issues associated with depressurisation. Sample is collected in a flow injection sample loop at process conditions. A pressurised sample flows through an injection valve, where aliquots of sample are introduced to the vaporisation chamber which allows the volatilization of the sample so that Hg is collected using high temperature amalgamation. After the pre-concentration step and selective separation of the sample matrix the mercury is thermally desorbed to the Hg analyser which is based on atomic fluorescence spectrometry.
This paper will describe a fully developed ATEX/IECEx zone 1, certified equipment. The system can be configured for up to eight sample streams. Examples and results will be provided from instruments installed in the field.
To request a copy of this poster or oral presentation click here.
ORAL - Mercury Mass Balance Studies on Ethylene Plants
Authors: Dr Warren T Corns (PSA)
Knowledge of the mercury content in petrochemical feed-stocks and refinery products is extremely important. The damage caused to petrochemical plants can be financially crippling especially when unscheduled shutdowns are forced. Mercury has been found to be responsible for many cases of selective hydrogenation catalyst deactivation even at low concentrations. These are typical based on palladium or platinum which form a strong amalgam with Hg. Mercury is also known to be the cause of corrosion problems with aluminum-based heat exchangers which operate at cryogenic temperatures, rotors and condensers at natural gas refinery plants. Heat exchanger replacement is a costly operation due to the capital investment of the exchanger itself and the plant down time incurred for its replacement. Because of these facts many plants install mercury removal systems to ensure that important parts of the plant are protected, this means that periodic measurements of the outlets of these removal systems need to be made to ensure that they are working correctly. Also other parts of the plant require accurate measurements to help provide a better understanding of the fate of mercury.
This presentation will focus on the analytical challenges and techniques to perform a mass balance of Hg on an ethylene plant. Atomic Fluorescence Spectrometry was utilized to determine Hg in various streams including gas, liquid and solid phase samples and the results were applied to the mass flow rates across the plant. A butane feedstock containing 18ppbw of Mercury was responsible for the rapid degradation of an acetylene reactor catalyst which was replaced and later protected by Hg removal beds. Mercury was partly removed during acid gas treatment and gasoline stripping. The majority of mercury was found in the C2 cracked gas as this represented the bulk mass flow. Mass balance data will be presented in addition to emission rates to the environment. The development of a model to predict Hg condensation rates in relation to process conditions will also be presented and discussed.
To request a copy of this poster or oral presentation click here.
ORAL - Online Determination of Mercury in Unstabilised Hydrocarbon Liquid Streams
Authors: Dr Matthew A Dexter and Dr Warren T Corns
Unstabilised hydrocarbon liquid streams such as unstabilised condensate present particular challenges for sampling and determination. If the liquid sample is depressurised, a portion of the sample is vaporised, producing a two phase sample for determination. Mercury can be associated with both the gas and liquid portions of the sample. The most accurate mercury measurement is therefore obtained when the analysis is performed at process conditions.
Conventionally, determination of liquid process streams which are gas-liquid mixtures when depressurised is difficult due to the need to characterise two separate phases and combine the results. This can lead to high measurement uncertainty and complicated procedures.
This paper describes a newly developed fast loop sampling system with self-cleaning filtration, a novel auto-injection system designed to introduce the sample to the analyser at process pressure to avoid the issues associated with depressurisation. Sample is collected in a flow injection sample loop at process conditions. A pressurised sample flows through an injection valve, where aliquots of sample are introduced to the vaporisation chamber which allows the volatilization of the sample so that Hg is collected using high temperature amalgamation. After the pre-concentration step and selective separation of the sample matrix the mercury is thermally desorbed to the Hg analyser which is based on atomic fluorescence spectrometry.
This paper will describe a fully developed ATEX/IECEx zone 1, certified equipment. The system can be configured for up to eight sample streams. Examples and results will be provided from instruments installed in the field.
To request a copy of this poster or oral presentation click here.
