Amines Purification - HSAS Removal Unit (RU)

APL SERVICES TO ENGINEERING COMPANIES AND APL AMINE END USERS

Amine solvents are used to remove acidic components like hydrogen sulfide and carbon dioxide from the feed gas of the refineries, natural gas plants and other gas treating processes.

During this operation various contaminants can enter in the amine unit or are produced within the amine` unit. These contaminants are mainly heat stable Amine salts (HSAS), solid particulates, hydrocarbons etc.

HSAS in amine solutions, as amine or stronger base salts, can cause a number of problems. Corrosion and erosion of metal components are accelerated by the increase in ionic strength of the solution, precipitation of salts and corrosion products. Increased foaming and reduced mass transfer rates are caused by changes in the surface-active character and the increased viscosity of the solution. Reduced acid gas carrying capacity is the result of less amine present in a usable absorptive state. All of these problems have been experienced in numerous operations. Removal HSAS ultimately requires reclaiming the amine solution by vacuum distillation, modified electrolysis or ion exchange resin treatment.

Sources of HSAS

Heat stable amine salts are formed with acidic components other than H₂S and CO₂ in the inlet process stream to the amine absorber. Typical acidic components include acids which form salts of chloride, sulfate, formate, acetate, oxalate, cyanide, thiocyanide, and thiosulfate. In addition, oxygen absorbed into the amine solution creates amine oxidation products that include formate. Carbon monoxide reacts in alkaline solutions to form formate. SO₂, commonly occurring in tail gas unit reduces reactor breakthroughs, results in sulfate and thiosulfate contamination.

The APL HSAS-RU is employed to continuously remove the HSAS formed in the amine. Continuous purification of the amine solution will result in a stable operation and an optimum performance of the amine unit. The result will be low operating costs.

Advantages of HSAS-RU

The advantages are: Improved the condition of the amine solution, improved amine solution performance, decreased foaming and corrosion, reduction of operating and maintenance costs.

Other benefits include

1. Lower fouling of heat exchangers and reduced energy consumptions.
2. Reduction in filter replacement frequency.
3. Reduction in the use of chemicals for column cleaning.
4. HSS free amine will be available for gas treating using the HSAS-RU on-line or in operation purifying the contaminated amine stored in a separate tank.
5. Increased life of equipments due to low corrosion rate.
6. Lower amine losses due to bleed and feed.
7. Reduced antifoam and anticorrosion products usage.

HSAS Unit Description

This APL HSAS Removal unit is basically an Ion exchange unit having a compatible specialty, APL’s proprietary AMION resin, which is specially designed to suit the lean amine solvent. APL HSAS Removal Unit is connected to the side stream after the lean amine cooler. The HSAS Removal unit consists of two Ion exchange units pre- assembled with valves, piping, cartridge filters, flow meters, conductivity meter, temperature and pressure indicators and regeneration reservoir. The total system will be in SS 316 construction. The Ion Exchange units (1 working + 1 standby) consist of cylindrical vessels provided with strainer plate at both side of the vessel. The polypropylene strainer will be fitted on the strainer plate to retain the resin. One heat exchanger is provided for cooling the lean amine before passing through the HSAS Removal Unit. The unit is provided with frontal pipework & valves for various operations. The entire unit will be bolted on ISMC channel frame.

A slip stream amine solution taken from lean amine circuit after the lean amine cooler is passed through filter and then Ion exchange resin bed. As the lean amine gets into contact with the resin, HSAS will be removed from amine solution and exchanged on resins and the purified amine solution comes out of the unit and is returned back to the circuit. Once the required quantity is passed through the unit, the lean amine solvent can be switched to the already generated unit. Meanwhile the exhausted unit will go under the regeneration.

Services by APL

APL will depute its Engineer/Chemist for supervision during erection and commissioning of the equipment.
APL will also train customer’s personnel to operate the unit.
Part of analysis of lean amine outlet from HSAS RU will be carried out at the plant site and detailed analysis will be carried out at APL’s lab in India.