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Enel Green Power is looking for novel solutions to maximize H2S abatement in geothermal power plants and at the same time reducing the OPEX associated with needs of chemicals. Moreover, the present end-cycle effect of the AMIS® (Abatement of Mercury and Hydrogen Sulfide) process is quite good: no materials from the reactions outcomes are handled as solid waste nor sulfur cake are produced to be reprocessed. These condition should not be penalized (or even better improved) by the proposed solutions.


- Submission extended to November 11, 2017 (23:59 CET) according to Section 7 of the Regulations -

Sustainable integration of geothermal power plants and related infrastructures, abatement of the gaseous emission and of the cooling tower drift, reduced noise level, etc., allow the preservation of natural beauties, environmental features and life quality of the people living near the plants.
One of the major problem of the geothermal energy is related to the atmospheric emission of the power plants, mainly hydrogen sulphide and mercury in elemental form.
Hydrogen sulphide is characterized by an odor threshold concentration of few ppb (part per billion), remarkably lower than the reference value of 100 ppb (as 24 hours average) established by the World Health Organization (WHO) for the protection of the population health.
Hydrogen sulphide concentrations in the ambient air, measured both by ENEL and ARPAT (the Environmental Protection Agency of Tuscany) are much lower than WHO reference value, so that this compound doesn’t pose any problem for the population health. However, the bad smell of hydrogensulphide is often perceived in the geothermal areas, depending on the atmospheric conditions and represents a real nuisance.
As for mercury, the emissions of this element are quite low, but there is some concern about possible build-up in the long term operation even at significant distances from the power plants, due to the mobility of this element.
Emission cleaning and in particular the elimination of the bad smell of hydrogen sulphide is a crucial point for the perfect compatibility between geothermal exploitation and valuable use of the territory, fundamental requirement for the consensus of the local communities.
Owing to the particular features of the Italian power plants (small and unattended) and of the geothermal fluids (high content of non condensable gases), the abatement technologies available on the market were not suitable and entailed excessive costs. As a consequence, it became necessary to develop an innovative process. This objective was achieved through the invention of AMIS® technology below outlined.
The invention of a proprietary technology (AMIS® - acronym for “Abatement of Mercury and Hydrogen Sulfide” in Italian language) for the abatement of hydrogen sulphide and mercury emission and its application both to new geothermal plants and to the retrofit of the existing one’s is a cornerstone of the New Geothermal Deal in Italy. Hydrogen sulphide is responsible of the bad smell often perceived in the geothermal areas.
AMIS® is an environmentally friendly process because doesn’t produce sulphur based by-products to be landfilled or recycled.
At present, all power plants are equipped with AMIS® systems. The process consists of three basic steps:
• Removal of mercury by chemical absorption;
• Selective catalytic oxidation of hydrogen sulfide to sulfur dioxide;
• Sulfur dioxide scrubbing by a side stream of cooling water.
According to the ammonia content of the steam, which contributes to neutralize the absorbed SO2, the process may require the addition of chemicals (e.g. sodium hydroxide) to maintain the cooling water within the desired pH range. NaOH is injected in the column feed. Unfortunately, the cost of sodium hydroxide is getting an operative issue.
Therefore, Enel GP is looking for novel solutions to maximize H2S abatement and at the same time reducing the OPEX associated with needs of chemicals.

Enel GP is looking for novel solutions to maximize H2S abatement in geothermal power plants and at the same time reducing the OPEX associated with needs of chemicals. Moreover, the present end-cycle effect of the AMIS® (Abatement of Mercury and Hydrogen Sulfide) process is quite good: no materials from the reactions outcomes are handled as solid waste nor sulfur cake are produced to be reprocessed. These condition should be considered in the proposed solution and should not be penalized (or even better improved) by the new proposed solutions
Any proposed solution should address the following Solution Requirements

  1. The proposed solution must maximize H2S abatement in geothermal fluids, without using or minimizing chemicals
  2. The proposed solution must be economical (including capital, installation and maintenance costs) in order to be amenable to mass deployment in geothermal plants
  3. The solution must be easy to install and require low maintenance
  4. The proposed solution must be adaptable to typical geothermal plants
  5. The solution must use no toxic chemicals or have any negative impact on the environment
  6. The proposed system should offer the Seeker “freedom to practice” or be available for potential licensing. There should be no third party patent art preventing the use of specific equipment and materials for their commercial application.

The submitted proposal should include the following:

  1. Detailed description of the proposed solution that can meet the above Solution Requirements.
  2. Rationale as to why the Solver believes that the proposed solution will work. This rationale should address each of the Solution Requirements described in the Detailed Description and should be supported with any relevant examples.
  3. Data, drawings, case studies, patent and journal references or any additional material that supports the proposed solution.

Details of AMIS® process are available in the attached Regulation,
as annex 1. 
The following links can be used by Solvers as a first introduction to the AMIS® technology:

  1. Baldacci A., 2001. Italian Patent #01305033 dated 10 April 2001 (applied for 16 October 1998).Baldacci A., M. Mannari and F. Sansone, 2005: “Greening of Geothermal Power: An Innovative Technology for Abatement of Hydrogen Sulphide and Mercury Emission.” Proceedings of World Geothermal Congress 2005, Antalya, Turkey, 24-29 April 2005.
  2. Cesare Pertot, Fabio Sabatelli, Massimo Messia, Marco D’aleo, 2013: “Assessment of Geothermal Power Plants Impact on Air Quality – Effect of H2S Abatement with AMIS® in the Larderello-Travale-Radicondoli Geothermal Area (Tuscany)”. Proceedings of European Geothermal Congress 2013, Pisa, Italy, 3-7 June 2013
  3. Fabio Sabatelli, Massimo Mannari, and Roberto Parri, 2009: “Hydrogen Sulfide and Mercury Abatement: Development and Successful Operation of AMIS® Technology”, GRC Transactions, Vol. 33, 2009

Challenge rules

This challenge has a specific Regulations and it is available as attachment at the end of this page. Read the Regulations to see terms and conditions of this challenge and to see if you can take part to the contest. All proposers are invited to read it keeping in mind that submitting a solution they automatically accept the Regulations other than the Terms of Usage of this platform.

What happens next?

An Enel technical panel will evaluate your proposal and might contact you to gather additional information.
- Your innovative proposal will be evaluated based on technical parameters, economic and business impact for Enel. The presentation of the proposal will also be evaluated.
- At the end of the assessment, you will receive feedback.
- In case of success, an Enel contact person will get in touch with you to discuss the next steps.



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