Produced Water Treatment with Deoiling Hydrocyclones – Misconceptions & Corrections (B-PWT004)
Produced Water Treatment Technology; Selection
Here we present an extended overview of the technologies we have introduced previously. We have defined each of the technologies by general category, separation mechanism, basic internal details, and design basis. These are the main criteria for selecting equipment.
Two main performance variables include:
- Oil in Water Concentration Limits
The maximum amount of oil in water the technology can accept while performing (separating) efficiently within its designed operating envelope. The greater the amount of oil the technology can remove, the greater the flexibility of the technology to operate over a wide range of process conditions.
- Relative Performance Capabilities, Oil Drop Size Removal Range
The minimum (dispersed) oil drop size the technology will separate and remove from the water stream, given a set of similar process conditions including operating temperature and pressure. The smaller the oil drop size the technology can remove the more efficient the separation process.
Directionally these two performance variables are usually opposed to each other, that is, the more effective the separation technology, the narrow the range of inlet oil in water concentrations it can handle. The wider the range of inlet oil in water concentrations the technology can handle, the less effective (relatively) in separating tough applications. This is an important point to remember when equipment vendors try to convince clients that their equipment is appropriate, performance wise, for all applications, under all conditions. Clearly this is not the case, and although some equipment works better than others under certain circumstances, the inlet process conditions will dictate which equipment one should choose as the most appropriate.
Apart from performance considerations, there are also other ‘advantages’ and ‘disadvantages’ of each technology in relation to each other. This is summarised as follows;
One important variable is the size and weight of the various technologies. Smaller technology not only translates into capital cost savings, but also results in lower maintenance and operational costs.
Operational considerations are critical for the ongoing cost of any separation equipment. It is important for the equipment to have the ability / flexibility to operate over a wide range of inlet process conditions, and outlet specification requirements.
Furthermore other ‘desirable’ equipment characteristics might include:
- off-the-shelf designs that provide flexible features at low cost, in a timely fashion, from a vendor that does not need major input and supervision from the client;
- leveraging throughput and flexibility of the upstream and downstream equipment in the existing product facilities;
- minimal impact on existing facilities during retrofit into existing facilities;
- provision of the ability to solve day to day problems that operators might ignore, with a subsequent impact on plant availability and OPEX;
- being compact in nature, minimal size and weight requirements in an offshore environment where this is important;
Some other general features might include:
- The package should be “fit for purpose”;
- The package should be environmentally friendly, with minimal environmental emissions;
- The package will be safe in operation, and equipped with automatic shutdown systems;
- Design and layout will take into consideration the likely impact of hazardous areas;
- Design will be based on appropriate industry and legislative standards;
- Godec, M.L., et. al., ICF Resources Inc., “Economic Impacts of Alternate Produced Water Treatment and Disposal Practices on Oil & Gas Resources in the Gulf of Mexico”, OTC 7404, OTC Houston, May 2-5, 1994.