API separator

A eoaleseer aehieves separation of an oily phase from water on the basis of density differences between the two fluids. These systems obviously work best with non-emulsified oils. Applications historically have been in the oil and gas industry, and hence the most famous oil/water separator is the API separator (API being the abbreviation for the American Petroleum Institute). 

API separator A facility developed by the Committee on Disposal or Refinery Wastes of the American Petroleum Institute for separation of oil from wastewater in a gravity differential and equipped with means for recovering the separated oil and removing sludge. 

The American Petroleum Institute Manual on Disposal of Refinery Wastes provides specific design and construction standards for API-separators that are often used in oilfield waste disposal [24],... 

Feed rates for fuel oil emulsion breakers vary significantly, but a starting point is perhaps 3,000 ppm. Where used to treat oily sludges (by adding to an API separator), the POE-POP ether component in the formulation aids the rejection of greasy soils from the oil and enables the separated oil to be reused as a fuel. 

In Instone s data (1989) the OSBL equipment most often involved in large losses seems to be storage tanks (14%). Heaters and furnaces are mentioned in 15% of incidents. Pumps, compressors and boilers are involved equally (5% each) in large losses, whereas flares, cooling towers and API separators happen to be quite rarely involved (<1% each). 

APILIT database, 18 231 APIPAT database, 18 231, 243 APIPAT fragmentation system, 18 242 API separators, 22 60... 

The separation of immiscible liquids and solids is performed by gravity separation in API Separators (or equivalent) or even the wastewater stripper feed drum. The purpose is to remove as much of the nondissolved organics from the wastewater as possible prior to biological treatment. Settleable solids are also removed by air flotation after stripping to further reduce the load on the biological treatment unit. 

In addition, oily sludge from a wastewater treatment facility that results from treating sour wastewaters may be a hazardous waste (unless recycled in the refining process). These include API separator sludge, primary treatment sludge, sludge from various gravitational separation units, and float from dissolved air flotation units. 

As an example of the problems such mixing can cause, consider the case with API separator sludge that is a listed hazardous waste (K051). The wastewater from a properly operating API separator is not hazardous unless it exhibits one of the characteristics of a hazardous waste. That is, the derived-from rule does not apply to the wastewater. However, if the API separator is not functioning... 

This wastewater is often cleaned further by other treatment systems (filters, impoundments, etc.). The solids separating in these systems continue to be API separator sludge, a listed hazardous waste. Therefore, all downstream wastewater treatment systems are receiving and treating a hazardous waste and are considered hazardous waste mauagement units subject to regulation. 

Oily wastewater is often treated or stored in unlined wastewater treatment ponds in refineries. These wasfes appear to be similar to API separator waste. 

Table 8 Topping Subcategory Raw Waste Load Effluent from Refinery API Separator ...

The API separator is a widely used gravity separator for removal of free oil from refinery wastewater. It can be installed either in the central wastewater treatment plant or as an upstream pretreatment process to remove gross quantities of free oil and solids. 

The process involves removal of materials less dense than water (such as oil) and suspended materials that are more dense than water by settling. The API separator does not separate substances in solution, nor does it break emulsions. The effectiveness of a separator depends on the temperature of the water, the density and size of the oil globules, and the amounts and characteristics of the suspended materials. The susceptibility to separation (STS) test is normally used as a guide to determine what portion of the influent to a separator is amenable to gravity separation [38]. In terms of globule size, an API separator is effective down to globule diameters of 0.015 cm (15 microns). 

Because of the limitations in gravity separator design, the lower limit of free oil in API separator effluent is usually around 50 mg/L. Removal of other contaminants in an API separator is highly variable. Table 16 shows typical removal efficiencies of oil separator units for several contaminants [17]. Chemical oxygen demand removal efficiencies range from 16 to 45%, and suspended solids removal ranges from 33 to 68%. 

Because of the coalescing action, these separators can separate oil droplets as small as 0.006 mm (6 microns) in diameter and produce effluent-free oil concentrations as low as 10 mg/L [27], There is a broad range of applications for tilted-plate separators. As little space is required, they can be installed to polish the effluent from existing API separators that are either overloaded or improperly designed, or they can be installed parallel with existing separators, reducing the hydraulic load and enhancing the oil removal capacity of the system. 

The BP rebnery used a bltration/GAC system to treat API separator effluent before discharge. It consisted of three parallel adsorbers each containing 42,000 kg of carbon in beds 14 m (45 ft) deep. The design contact time was 40 minutes and theorebcal carbon capacity was 0.3 kg TOC /kg carbon. The regeneration facility was a 1.5 m diameter, mulbple-hearth furnace. After several years of operabon, BP abandoned the GAC system and installed a biological... 

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