Solutions for Oil and Gas
Carus advanced technologies are successfully applied in crude oil refining during plant turnarounds to remove pyrophoric iron sulfide scale, reducing the threat of exothermic reactions, and toxic sulfide odor production. Carus products for chemical oxidation are an effective solution in produced water treatment.
Produced Water Treatment
Produced water management and disposal challenges are growing, along with the increased production of oil and gas wells. It is estimated that for every 1 barrel of oil produced there is 8 to 10 barrels of produced water recovered. To decrease costs associated with produced water management, water reuse and recycle technologies are implemented.
Selecting the right water treatment can be difficult as the physical and chemical characteristics of produce water change from location to location. Water treatment options differ according to the intended final use. Collected produced water can have various contaminants of concern, including high levels of iron and sulfur containing compounds such as hydrogen sulfide (H2S). These compounds can cause difficulties in water treatment, site safety issues due to odors, and corrosion problems within the treatment system.
Chemical oxidation via permanganate can be an effective option for produced water treatment, especially if lab tests point to issues with iron or sulfur. Permanganate effectively oxidizes soluble iron and manganese to insoluble precipitates which can then be removed from the water via clarification and filtration. Permanganate can also oxidize (destroy) odorous and corrosive sulfur containing compounds such as hydrogen sulfide and mercaptans.
Pyrophoric Iron Removal
During the refining of crude petroleum, the sulfur component of the crude oil reacts with the specialty alloy steel processing equipment producing iron sulfide scale. Pyrophoric iron sulfide scale, when exposed to air, reacts exothermically and can result in a fire. Toxic sulfide odors can also be formed during these turnarounds.
Permanganate oxidizes pyrophoric iron sulfide to iron sulfate eliminating the potential for exothermic reactions and fires or explosions during shut downs for maintenance of refinery process equipment. Permanganate treatment also controls toxic odors by oxidizing the sulfides to odorless sulfates.
Benefits of Permanganate
- Complete, effective control of pyrophoric iron sulfide
- Lower overall costs of vessel cleaning
- Reduced danger of toxic gas release
- Reduced danger of fire or explosion
- Visual indication when reaction is complete
- Safer employee working conditions
- No pH adjustment necessary
- Spent solution can be discharged safely
- No special materials of construction needed
Application
Permanganate (NaMnO4 or KMnO4 ) is added to the process equipment as a 0.1% to 1.0% aqueous solution. The units are filled with the permanganate solution and the solution is recirculated, or agitated depending on the design of the process. Control is visual. As the solution turns from purple to brown in color, the permanganate is being used up. The spent permanaganate solution can be discharged directly to the sanitary sewer.
Dosage
Due to the variability of the amount of iron sulfide present on the equipment, an exact dose of permanganate cannot be calculated. It is recommended that the permanganate solution be fed until a faint purple to pink color is observed in the finished water.
Facility Requirements
Proper mixing tanks and feed pumps compatible with a permanganate solution are required. Operators should be trained in making up the permanganate solution and in monitoring permanganate residuals. Operators should be given appropriate safety and emergency training.