Can anyone tell me about how Heat Stable Salt works?
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01/08/2018
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Berthold Otzisk, Kurita Europe GmbH, Berthold.Otzisk@kurita-water.com
Heat stable salts are undesirable products that are formed in alkanolamine units when acidic components other than H2S or CO2 react with the amine. Unwanted acids are chlorides, organic acids, oxalates, cyanides, thiocyanides, thiosulphates and many other acidic components. These salts are formed as a reaction of the acid and base (alkanolamine). Oxygen can be absorbed into the amine solution, where the oxidation reaction creates oxalates or formates.
Salts from H2S and CO2 reactions with the amine are relatively weak and will be removed at the regenerator (stripper, stabilizer) to get a lean amine again. Heat stable salts stay in the regenerated amine by reducing the absorption capacity of the amine. Fouling and corrosion caused by heat stable salts are severe problems at amine units. Heat stable salts (HSS) are defined as the sum of heat stable anion bound salts (HSAS) and heat stable cation bound salts (HSKS). Some refineries use NaOH, Na2CO3 or KOH to shift the balance from HSAS to HSKS.
HSKS are expected to cause less problems, but the use of sodium or potassium addition will not solve the original problem. As a rule of thumb the total heat stable salt concentration should not exceed 10% of the total alkanolamine concentration.
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01/08/2018
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Krishna Rao Pulugurti, Retired/Consultant, pkrao2012@yahoo.com
Please follow the link given below.
https://www.protreat.com/files/publications/58/Weiland_Vol_3_Issue_1.pdf
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01/08/2018
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Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
Amine treatment of Fuel gases is aimed at removal of H2S, CO2 and other acid gases. Amines absorb the acid gases (become RICH Amines), regenerated (to become LEAN Amines) and are circulated back to the Amine absorbers. The Heat stable salts (Acetates / Formates) are formed in the process adversely affect the regeneration process and will lead to high Amine losses. Removal of Heat Stable salts (HSS) will reduce the Amine losses substantially as Amine life can be extended thru regenerations. There are processes that will allow complete neutralisation of HSS, as well as partial neutralisation. Conventional Lean Amines contain about 400 PPM of acid gases, while the acid gas levels can be brought down to less than 5 PPM levels with HSS neutralised Amines. Google search will also give additional information on HSS in addition to the link provided by Sh. PK RAO.
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01/08/2018
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Lindsay McRae, Pall Corporation, Lindsay_McRae@pall.com
Heat stable salt is a salt that cannot be regenerated at the usual regenerator operating conditions. The bond is too strong. What that means is some of the amine remains bound up and not able to pick up H2S in the absorber so amine absorber efficiency is impaired. Also HSS tend to be corrosive so elevated HSS content in amine systems generally results in higher corrosion rates, increase amine loop filter usage, more fouling of lean- rich exchanger and higher energy/maintenance costs . HSS should be maintained below 1% for stable amine plant operation.
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31/07/2018
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Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Amine forms a weak chemical bond with H2S and CO2, which causes a high % of those contaminants to be absorbed out of the gas or liquid stream they were in. Those bonds are broken by the heat supplied in the amine regenerator tower, which springs the H2S and CO2 free from the amine so it can go to the sulfur plant. The regenerated amine can then be recycled to recover more H2S and CO2.
Other acids such as HCl, acetic acid, formic acid, etc. form a thermally stable reaction product (Heat stable salt). The energy in the regenerator does not break the chemical bond so the amine remains bound to these acids. As a result the amine tied up as a heat stable salt is no longer available to carry out its intended purpose. HSS levels will tend to build up to some sort of equilibrium in the amine system where the HSS salt purge rate via system losses equals the rate of HSS formation. If the HSS level is high enough it will impair amine performance and cause corrosion.
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31/07/2018
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Krishna Rao Pulugurti, Retired/Consultant, pkrao2012@yahoo.com
Please click the following link
https://www.sciencedirect.com/science/article/pii/S1876610211000956#!
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