Oily Water Separator SKIT/S-DEB

Transcription

1 Oily Water Separator SKIT/S-DEB A. IMO Resolution MEPC.107(49) The IMO Resolution MEPC.107 (49) has been adopted on 18 th July 2004 and applies to all oily water separators and 15-ppm alarm devices to be installed onboard ships on or after 1 st January The IMO Resolution MEPC.107(49) describes in detail the type approval procedures for oily water separators and 15-ppm oil content alarm devices. The main difference between the former MEPC.60 (33) rule and the new MEPC.107(49) one, is the required performance compliance involving an oilin-water emulsion. The emulsion is created by mixing the different test oils with a specified emulsifying chemical and a powder of iron oxide under controlled conditions for one hour by means of a high speed centrifugal pump. The oily water separator must then be able to breakdown the emulsion and extract the oily residues. An emulsion is a mixture of two or more components. In this application it involves oil and water. In this mixture the oil particle is still present, but does not form droplets and larger concentrations. It requires mechanical energy to make an emulsion i.e. a high pressure water jet, high speed centrifugal pumps, all of which are transforming the oil droplets into very small particles. This type of mechanical emulsion can easily be handled by an efficient coalescer, but in the presence of an emulsifying chemical the oil particle becomes hydrophob by ionic and anionic tensides on the oil particle surface. The same micro electric load of all particles in a stable chemical emulsion makes the agglomeration impossible. B. Emulsion Separation Mechanical emulsions can normally be separated by mechanical coalescers, however stable chemical emulsions can not be handled by a coalescer because the active compounds on the surface prevent the coalescing effects of the coalescer material. Stable chemical emulsions can be split by means of: heat treatment i.e. evaporation chemically, by using adequate flocculents

2 membrane ultrafiltration, which retains the oil molecules Absorption by suitable materials C. Comparison of emulsion splitting processes Heat treatment consumes much energy. In steam heated evaporators incrustation can occur. Gas emissions are considerable and also difficult to handle. Splitting of emulsions by chemical means requires knowledge of the type of emulsion. It is difficult to have always the correct chemical available, right dosing quantity, suitable reaction time for the process and the required input energy. An oily flocculent sludge, consisting mainly of water, has to be kept in a sludge tank and disposed off. Membrane ultrafiltration is a very sensitive method of treatment. Free floating oil particles are causing surface fouling of the membrane which is reducing the capacity down to a minimum permeate flow. Chemical or physical influences can easily lead to a permanent clogging and even a chemical cleaning process cannot restore the permeate flow. Such effects occur often without the possibility of tracing the real reasons. Maintenance and exchange of membranes requires skills and is expensive. The absorption process, using suitable material able to cope with all types of hydrocarbons and with a high absorption capability, is a safe and simple way of cleaning polluted bilge water perfectly, easy to install, easy to handle, no special training or skills required, always ready for safe operation and resulting in clean discharges. D. Description of the process of the RWO oily water separator SKIT/S-DEB The RWO oil/ water separation system type SKIT/S-DEB complies with the recent IMO Resolution MEPC 107 (49), using the combination of a highly effective open porous coalescer, the well known RWO oily water separator SKIT/S, together with a second stage newly developed emulsion breaking oil and hydrocarbon absorber.

3 The excellent and long experience with the RWO "SKIT/S" coalescing type oily water separator guarantees performance. More than 6000 (six thousand) ships have already been equipped with this efficient oily water separator. The periodical backflushing keeps the coalescer surface clean and guarantees longlasting operation without requiring constant attendance and maintenance. During the IMO type test it was found, that the oil content after the first stage SKIT/S coalescer is below 2 ppm. Only when using the emulsified test fluid "C" the oil content rose to approximately 15 ppm. Absorber bypass The demulsifier has a certain absorption capacity. To extend the operating life of the absorber an automatic bypass is fitted to the separating system. The 15ppm oil content measuring device periodically checks the water quality of the SKIT/S separator and if below 15ppm, the demulsifier is bypassed until the 15ppm alarm is activated. This process control guarantees a considerable prolonged life cycle of the absorber elements. 15 ppm oil content monitor OMD-2005 The oily water separating system is equipped with the 15 ppm oil content alarm device OMD 2005, type tested and approved in accordance with IMO Resolution MEPC.107 (49). The new resolution requires: The 15ppm Bilge Alarm should record date, time alarm status and operating status of the 15ppm Bilge Separator. The recording device should also store data for at least eighteen months and should be able to display or print a protocol for official inspections as required. In the event that the 15ppm Bilge Alarm is replaced, procedures should be put in place to ensure the recorded data remain accessible on board for 18 months. To prevent tempering with the 15ppm Bilge Alarms, the following precautions should be taken: Every access of the 15ppm Bilge Alarm beyond the essential requirements of paragraph requires the breaking of a seal. The 15ppm Bilge Alarm should be so constructed that the alarm is always activated whenever clean water is used for cleaning or zeroing purposes. The RWO OMD 2005 complies with the above rules. The measuring cell can be removed for calibration while the control device remains on the oily water separator to keep the recorded data on board for at least 18 months.

4 The 3-way cock for flushing is fitted with a contact to ensure that during flushing of the alarm device, the alarm is activated and the 3-way diverting valve is in recirculation mode (automatic stopping device). According to IMO Resolution MEPC.107 (49) a 3-way valve must be installed downstream of the oily water separator in the overboard line to recirculate the water to the bilge during port mode. E. Advantages of the new RWO oily water separator SKIT/S-DEB The system comes as a complete package, skid mounted with all necessary accessories and controls and providing the following benefits: For the Shipyard + There are no major differences compared to original RWO SKIT/S A small and compact second stage absorber is added Location of the second stage unit is not necessarily at the same location + All pipe connection points are the same as before Only the clean water discharge is slightly different Power supply remains the same Compressed air supply remains the same Alarm to control room remains the same + Easy to install + Easy to handle + No additional requests for installation + No requirement for RWO commissioning engineer + No extra chemicals for commissioning + No additional request for maker s start-up procedure + No training required for shipyard staff + No guarantee problems expected For the Shipowner + Exceptionally high purity levels i.e. less than 1 ppm oil content in the effluent water under IMO conditions. + All special rules of restricted areas are fully met (USGC; Alaska requirements, Great Lakes, St Laurence Seaway requirement

5 + All special rules and requirements of classification societies are fully met (5ppm-Criterion, DNV-Green Ship, Environmental Sound Ship, GL Environmental Passport, Blue Angel + Easy to handle: + No chemicals involved + No limitation for bilgewater pollutents + No extra intermediate tank required + No extra tank for residues required + No special skills needed + No training required + Retrofit to existing RWO Oily Water Separators type SKIT/S is possible so that they can receive the IMO Certificate MEPC.107 (49) as well + Worldwide Service & Support