HPVA II – High Pressure Volumetric Analyzer

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HPVA II - High Pressure Volumetric Analyzer

High Pressure Specialty Applications:

The HPVA II Series of adsorption analyzers from Particulate Systems uses the static volumetric method to obtain high-pressure adsorption and desorption isotherms utilizing gases such as hydrogen, methane, and carbon dioxide.

The volumetric technique consists of introducing (dosing) a known amount of gas (adsorptive) into the chamber containing the sample to be analyzed. When the sample reaches equilibrium with the adsorbate gas, the final equilibrium pressure is recorded. These data are then used to calculate the quantity of gas adsorbed by the sample.

This process is repeated at given pressure intervals until the maximum preselected pressure is reached. Then the pressure can be decreased to provide a desorption isotherm. Each of the resulting equilibrium points (volume adsorbed and equilibrium pressure) is plotted to provide an isotherm.

Excellent reproducibility and accuracy are obtained by using separate transducers for monitoring low and high pressures.

Features:

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    Wide Operating Pressure range: High Vacuum to 100 or 200 bar
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    Broad Temperature Capability: From cryogenic to 500 °C
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    Excellent control of sample temperature by means of a recirculating temperature bath, cryogen dewar, or furnace
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    Manifold temperature controlled with heater for stability and accuracy 
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    Fully automated analysis using interactive software
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    Excellent data reproducibility 
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    Handles typical adsorbates such as nitrogen, hydrogen, methane, argon, oxygen, and carbon dioxide 
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    Comprehensive Data Analysis package using Microsoft Excel macros for data processing and graphing
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    Software includes NIST REFPROP
Also available in a 4-port system

Benefits:

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    Dual free-space measurement for accurate isotherm data
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    Free space can be measured or entered
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    Correction for non-ideality of analysis gas using NIST REFPROP compressibility factors calculated from multiple equations of state
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    Reports provided as interactive spreadsheets
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    Isotherm and weight percentage plots created automatically
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    Real-time charts for Pressure vs. Time and Temperature vs. Time
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    Gas mixtures with up to three components can be used
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    Kinetic data provided for rate of adsorpotion calculations
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    Langmuir equation used to model Type I isotherms
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    High-precision, solid-state design high-pressure transducer provides a reading accuracy of ±0.04% full scale with a stability of ±0.1%
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    System can attain a maximum pressure of 200 bar
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    Hydrogen gas sensor automatically shuts down the system should a hydrogen leak occur
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    BET surface area, Langmuir surface area, and total pore volume calculations included

HPVA II System Overview

Four Methods of Sample Temperature Control:

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    Refrigerated/heated recirculation vessel (customer provides temperature control bath)
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    Four-liter, stainless-steel dewar for liquid cryogen
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    Furnace allows for experiments ranging up to 500 °C
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    Cryostat can precisely control sample temperatures from ambient conditions to 30 K

Manifold:

All the valves in the manifold are pneumatically operated, high-pressure valves with Kel-F® seats. Valve tubing is constructed with heavy wall, 316L stainless steel and is attached via a VCR connection or welded. The temperature of the insulated manifold region is stabilized using a heater controlled by an adjustable PID controller.

Pressure Transducers:

Two transducers are used to precisely measure the system pressure. A 1000- torr transducer is used to accurately monitor pressures below 1 atmosphere and is protected from high pressure with an isolation valve and a cracking valve that relieve to the vent. A high pressure transducer (100 bar or 200 bar) is used to accurately monitor high pressures through the isotherm. As an option, the low pressure transducer range can be selected to better suit the specific application. An optional 15 bar or 20 bar transducer can be configured.

Servo Valves:

The servo valves are used to automatically regulate flow of the gas in the manifold to the vent and vacuum. Servo Valves The servo valves are used to automatically regulate flow of the gas in the manifold to the vent and vacuum.

Vacuum Systems:

Consists of a mechanical pump and internal Pirani vacuum gauge. User can provide their own pump or purchase the high-vacuum turbo pump package.

Typical Applications:

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    Carbon Dioxide Sequestration:

    High pressures obtained with the HPVA II can simulate the underground conditions of sites where CO2 is to be injected. Configuring the HPVA II with a chiller/heater bath allows the user to evaluate the CO2 uptake at a range of stable temperatures, providing data that can be used to calculate heats of adsorption.

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    Shale Gas:

    High-pressure methane can be dosed onto shale samples to generate adsorption and desorption isotherms. This provides the methane capacity of the shale at specific pressures and temperatures. The adsorption isotherm can be used to calculate the Langmuir surface area and volume of the shale.

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    Coal-Bed Methane:

    Porous coal samples from underground beds can be analyzed to determine their methane capacity at high pressures. This allows the user to find the methane adsorption and desorption properties which can be used in determining approximate amounts of hydrocarbons available in coal-bed reserves. Kinetic data can also indicate the rate of methane adsorption and desorption at specific pressures and temperatures.

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    Hydrogen Storage:

    Determining the hydrogen storage capacity of porous carbons and metal organic frameworks (MOFs) is pivotal in the demand for clean energy. Stored adsorbed hydrogen in MOFs has a higher energy density by volume than gaseous hydrogen. The HPVA II provides a weight percentage plot that illustrates the amount of gas adsorbed at a given pressure as a function of the sample mass − the standard method for reviewing a sample’s hydrogen storage capacity.

Application Notes: