OCETA ENVIRONMENTAL TECHNOLOGY PROFILES
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BgPur™- Biogas Purification System for Hydrogen Sulphide Removal CAT. #05-003-U #08-028 |
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PROCESS/ PRODUCT DESCRIPTION:
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Eco-Tec offers the BgPur™ biogas scrubber for removal of hydrogen sulphide
gas and particulate matter from biogas as it is produced. Hydrogen
sulphide (H2S) itself has an offensive odour of "rotten eggs"
at concentrations as low as 50 parts per billion by volume (ppbv)
and is toxic at concentrations above 1000 parts per million by volume
(ppmv). H2S is a health and safety hazard, and when combined with
carbon dioxide (CO2) and water vapour (H2O), corrodes plant equipment
such as boilers and piping, and can ruin power-generating equipment.
Energy recovery from biogas and other waste streams, a common practice
today, is hampered if H2S gas is present. High levels of H2S can also
interfere with other processes such as killing useful bacteria in
anaerobic digesters. Reducing H2S offers cost savings associated with
less maintenance, increased process and energy efficiency, and reduced
toxic emissions. First installed and tested at the Metropolitan Toronto Works Department's Main Treatment Plant at Ashbridges Bay in 1993/4, the Eco-Tec scrubber was found to be up to 99 percent efficient in the removal of hydrogen sulphide. |
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| This resulted in greater energy recovery; lower sulphur dioxide (SO2) emissions, reduced equipment corrosion, and a solution to other process problems associated with H2S. A commercial unit is shown in Figure 1. The key innovation, from which other advantages arise, is the extremely high mass transfer rate generated by the proprietary gas-liquid contacting system. Chemical costs are reduced through the combination of reduced catalyst inventories | and concentration, a result of the increased mass transfer rates. The unit is not affected by fluctuations in biogas feed rates and hydrogen sulphide concentration within the feed, and may be scaled up or down very efficiently. The scrubber also includes self-induced gas flow, which may reduce or eliminate the need for a fan, blower or compressor, and low pressure drop across the system as illustrated in Figure 2, Eco-Tec's Biogas Schematic. | ||
PROCESS/ PRODUCT APPLICATION:
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A growing percent of wastewater treatment plants use anaerobic digestion
to reduce the volume of sludge requiring disposal. That process produces
a biogas, which is composed mostly of methane and carbon dioxide and
is generally contaminated with small quantities of other gases such
as H2S. Hydrogen sulphide and other sulphur compounds must be removed
from anaerobic digester gas streams before they can be used as fuel
for stationary engines and cogeneration units. The Eco-Tec scrubber is also used in other places such as landfill sites and industrial anaerobic digesters. |
Industrial digesters are used on wastewater streams produced by industries
such as large-scale cattle farms, food processing, beverage manufacturers,
and the pulp and paper industry. The level of hydrogen sulphide in
the biogas from these industrial sources is often higher than that
from anaerobic digesters in municipal waste treatment plants. Eco-Tec's BgPur™ Series process has a powerful mixing unit that transfers gas into the scrubbing medium up to twenty times faster than conventional liquid contactors, thus enabling this compact unit to handle gas flows |
as effectively as competitor units several times its size. Upgraded biogas, free of H2S, may be used as a low-energy content fuel for boilers as well as for stationary engines and cogeneration plants to produce heat for plant digestion tanks and control buildings. Due to the compact size of the unit, it has fewer components, thus lowering the cost to build, own, and operate. Eco-Tec gas scrubbers eliminate noxious odors and sulphur dioxide emissions, and save money by reducing corrosion and downtime, and extending equipment lifespan. |
PROCESS / PRODUCT OPERATION:
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The Eco-Tec process is based on a patented, high efficiency, gas-liquid contactor that has as its basis an impeller-shroud mixing device. The scrubber removes H2S from a gas stream using a regenerating scrubbing solution in a dual-tank system. Gases, up to 20,000ppmv H2S and at a flow rate of 100 to 5000 SCFM, are routed through a scrubbing vessel where up to 99% of the H2S is extracted with an aqueous scrubbing solution which uses well known iron redox chemistry. The regeneration vessel uses atmospheric oxygen to convert H2S from the scrubbing solution to elemental sulphur that is non-hazardous and can be disposed of safely with biosolids or in a landfill. The scrubbing solution now free of H2S is | ||
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returned to the scrubbing vessel. A process flow diagram is illustrated
in Figure 3. Removal efficiencies are maintained even when there are fluctuations in both flow rates and concentrations, provided the scrubber has an adequate catalyst concentration and recirculation rate. Maintenance requirements are less than those of competitor units |
as the heavy-duty bearings need servicing less than once a year, shaft seals are water flushed for a long life, and chemicals are automatically metered while a simple mechanical unit removes sulphur without plugging. The catalyst, reaction products, and buffer additive are all environmentally acceptable (according to the Ontario Ministry of the Environment). | ||
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VENDOR INFORMATION: Eco-Tec
Inc. |
Eco-Tec is a globally recognized, manufacturer of economical industrial systems with over 1500 installations in 52 countries. Eco-Tec specializes | in products and services that address customer needs in industrial water treatment, gas processing, and chemical recovery. Using proprietary, advanced | technology, Eco-Tec engineers, designs and manufactures a large selection of systems that offer superior efficiency with economical and proven environmental benefits. |
This document was originally published June 1996 and Updated Sept, 2002. It is best viewed with the font Times, size 12. While OCETA has reviewed this product/process with the Vendor and conducted limited independent investigation, OCETA assumes no responsibility for the accuracy and completeness of the information. |
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