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1、Lesson 22OIL POLLUTION PREVENTION(防止油污染防止油污染)Jimei universityThere are three major sources of oil pollution from the operation of ships:1.the discharge into the sea of tank washings from tankers(油油轮轮);Jimei university2.the ballast carried in oil cargo and bunker tanks and3.the discharge from machine
2、ry space bilges.Jimei universityTo prevent pollution by oil from ships,the IMO has published Regulations(规规 则则,规规章章)for the Prevention of Pollution by OilJimei university(MARPOL 73/78)that came into force(开开始始有有效效,开开始始实实行行)in December 1983.Jimei universityThe first source is reduced by the discharge
3、 of tank washings to a slop tank(污污 水水 舱舱)for settling,Jimei universityand discharge overboard of the water while retaining the load on top for pumping ashore to the refinery(炼油厂炼油厂).Jimei universityCrude Oil Washing(COW)eliminates the use of water and enables cargo residues(残残余余,剩剩余余物物)to be pumped
4、 ashore during cargo discharge because Jimei universitybecause cleaning is carried out simultaneously(同同时时地地)with the discharge.Jimei universityAs well as requiring tankers of certain sizes to have segregated(隔隔 离离)or clean ballast tanks(SBT or CBT)to reduce the ballast contaminated(污染污染)with oil,Ji
5、mei universitynew regulations have strict requirements for control of discharge of oil from a tanker.Jimei universityIn brief,if oil cargo residue is to be discharged from a tanker it must:a)not be in a Special Area;b)be farther than 50 nautical miles(海里海里)from land;Jimei universityc)be on passage.A
6、dditionally;d)the instantaneous(瞬瞬间间的的)rate of discharge must not be more than 30 litres per mile;e)the total amount must be not more than 1/30,000 of the particular cargo,and Jimei universityf)the oil discharge monitoring and control system and slop tank arrangement required must be in operation Ji
7、mei universityEngine room bilge disposal(处处理理)is treated separately in the regulations from discharges related to cargo/ballast operation.Jimei universityIn general,ships over 400 gt are permitted to discharge machinery space bilges into the sea provide:Jimei universitya)the oil in the bilge dischar
8、ge without dilution(稀稀释释)does not amount to more than 15 ppm;Jimei universityb)this is achieved by the operation of an oily water separator and/or filtering system with discharge monitoring and control;Jimei universityc)the ship is moving on passage;d)it is at least 12 nautical miles from land,ande)
9、is not within a Special Area.Jimei universityA tank or tanks of adequate capacity,having regard to(without regard to)the type of machinery and length of voyage,should be provided on board to receive the oil residues(sludge),Jimei universitysuch as those resulting from the purification(purifier/clari
10、fier)of fuel and lubricating oils and oil leakage in the machinery spaces.Jimei universityThe operations related to cargo oil,oil residue,oil and fuel tank ballast and washing,and bilge must be filled in the Oil Record Book.Jimei universityThe Oil Record Book(part one)for machinery space operations
11、is the responsibility of the engine room department.Jimei universityAll constructions and equipment for oil pollution prevention must be proved in accordance with the regulations,Jimei universityand issued with International Oil Pollution Prevention(IOPP)certificates.Jimei universityOILY WATER SEPAR
12、ATORS Oily water separators are used to ensure that ships do not discharge oil when pumping out bilge water,or oily water from oil tanks or any oil contaminated(污染污染)space.Jimei universityAccording to international legislations(国国际际法法规规MARPOL 73/78(International convention for the prevention of poll
13、ution from ships)related to oil pollution,Jimei universitydepending upon the size of a ship a discharge purity of 100 or 15 parts per million(p.p.m)(百百万万分分之之)of oil will be required.Jimei universityOily water separators using the gravity system can only achieve 100 ppm and Jimei universityand must t
14、herefore be used in conjunction with some form of filter to discharge clean water with less than 15 ppm of oil.Jimei university15,9oil collection space22coarse separating compartment23fine separating compartment100ppmCoalescer inserts24catchplate15ppmJimei universityA complete oil/water separator an
15、d filter unit is first filled with clean water;Jimei universitythe oily water mixture is then pumped through the separator inlet pipe into the coarse(粗粗（糙糙）的的)separating compartment.Jimei universityHere some oil,as a result of its lower density,will separate and rise into the oil collection space.Ji
16、mei universityThe remaining oil/water mixture now flows down into the fine separating compartment and moves slowly between the catch plates(捕捕集集板板).Jimei universityMore oil will separate out onto the underside of these plates and travel outwards until it is free to rise into the oil collecting space
17、.Jimei universityThe almost oil-free water passes into the central pipe and leaves the separator unit.The purity at this point will be 100 p.p.m.or less.Jimei universityAn automatically controlled valve release the separated oil to a storage tank.Jimei universityAir is released from the unit by a ve
18、nt valve.Jimei universitySteam or electric heating coil are provided in the upper and and sometimes the lower parts of the separator,depending upon the type of oil to be separated.Jimei universityWhere greater purity is required,the almost oil-free water passes to a filter unit.Jimei universityThe w
19、ater flows in turn through two filter stages and the oil removed passes to oil collecting spaces.Jimei universityThe first stage filter removes physical impurities present and promote some fine separation.Jimei universityThe second stage filter uses coalescer(聚聚合合器器、聚聚合合元元件件)inserts to achieve the f
20、inal de-oiling(脱油脱油).Jimei universityCoalescence(聚聚 合合)is the breakdown(破破 坏坏)of surface tension(表表面面张张力力)between oil droplets(液液滴滴)in an oil/water mixture which causes them to join and increase in size.Jimei universityThe oil from the collecting spaces is drained away manually,as required,usually a
21、bout once a week.Jimei universityThe filter inserts will require changing,the period of useful life depending upon the operating conditions.Jimei universityDrawing for oil/water separator&filter unit Catch platesFine separatingcompartmentCoarse separating compartmentOil collecting spaceOily water mi
22、xtureSeparator unitFilter unitDischarge purity are 15 p.p.m.or less.100 p.p.mor lessJimei universityThe latest legislative requirements are,where 100 p.p.m.purity is required,a monitoring unit which continuously records,Jimei universityand where 15 p.p.m.purity is necessary,an alarm unit to provide
23、warning when levels of discharge is in excess of 15 p.p.m.Jimei universityCrude Oil Washing(COW)Crude oil washing of cargo tanks,although relatively new,has been installed on board a number of existing tankers.Jimei universityThe principle itself is simple,the tanks are washed by the cargo during di
24、scharge and only a water rinse(用用清清水水刷刷,冲冲洗洗,漂漂洗洗)is necessary to enable the tanks to carry clean ballast.Jimei universityWith this system all crude oil washing must be completed before the ship leaves its final port of discharge.Jimei universityThe advantages are that the volume of oily water mixtu
25、res to be separated is considerably reduced compared with the conventional water washing.Jimei universityAlso constituents(组组成成部部分分)of the crude oil which have settled out on the tank surfaces during the voyage are discharged along with the cargoJimei universitythereby increasing the total quantity
26、of oil discharged.Jimei universityWhilst COW may have the disadvantage that the discharged time is increased this is,one would imagine,Jimei universityoutweighed(比比 更更 重重 要要)by the fact that tank washing during the ballast voyage,usually a tedious(单单调调乏乏味味的的)and time consuming exercise is eliminated
27、.Jimei universityThe system is to consist of permanent steel piping and is to be independent of the fire main or any system other than Jimei universityother than for tank washing except that sections of the ships cargo system may be incorporated in the crude oil washing system.Jimei universityThe ta
28、nk washing machines for COW are to be permanently mounted and are to be of approved design.Jimei universityEach machine is to be capable of being isolated by means of stop valves in the supply line.Jimei universityThe number and location of the tank washing machines is to be such that all horizontal
29、 and Jimei universityand vertical areas are washed by direct impingement(冲冲击击,撞撞 击击)or effectively by deflection or splashing of the impinging jet.Jimei universityThe three stages washing pattern is called a programmable machine,that is one where the single nozzle can be controlled to give pre-set a
30、rcs.Jimei universityA dual nozzle machine is not considered to be programmable since the nozzle is constantly rotating through 360o.Jimei universitySubmerged(浸浸沉沉,淹淹没没的的,水水下下的的)machines are usually dual nozzle machines and therefore non-programmable but Jimei universitybut single nozzle machines are
31、 being developed which could be made programmable either by means of cams or possibly intrinsically(本本质质地地，固固有有地地)safe electronic controls.Jimei universityThe pumps supplying crude oil to the machines should be either the existing cargo pumps or pumps specially provided for the purpose.Jimei univers
32、ityThe pumping and piping arrangements are to be such that the COW system can be effectively operated with any one pump out of use.Jimei universityThe design and capacity of the cargo tank stripping(清清舱舱，扫扫线线)system should ensure that Jimei universitythat the bottom of the tank being cleaned is kept
33、 free of accumulations of oil and sediment towards completion of the tank washing process.Jimei universityREADING MATERIAL A.TURBULO SEPARATORS Jimei universityTurbulo separators with the Turbulo filter are used for the separation of oil from bilge and ballast water.Jimei universityThe complete plan
34、t consists of a separator for the preliminary separation,and for the remaining separation a filter with inserts for stopping dirt and for coalescence Jimei universityand an HDW eccentric helical rotor pump with an output precisely suited to the plant.Jimei universityDesigned in accordance with the I
35、nternational Convention for the Prevention of Pollution from Ships,1973,Jimei universityand with the IMCO(Intergovernmental Maritime Consultative Organization 政政府府间间海海事事协协商商组组织织)Test Rules for separators and filtering equipment,Jimei universitythe plant enables a degree of purity better than 15 ppm
36、to be attained.Jimei universityAfter the plant has been filled with clean water the oil/water mixture is pumped into the separator by the eccentric helical rotor pump.Jimei universityThe preliminary separation then takes place in the separator according to the gravity principle.Jimei universityThe p
37、rincipal feature of the internal construction of the separator consists of the coarse separating compartment in the upper part and the fine separating compartment arranged below it.Jimei universityAfter the separation of relatively large quantities of oil in the upper part,the fine separation takes
38、place in the fine separating compartment,which Jimei universitywhich is fitted with a number of chambers with catch-plates with equal flow-through.Jimei universityThe oil to be separated collects on the undersides of the catch-plates.Jimei universityAfter the oil has formed larger drops it detaches(
39、分分开开,分分离离)itself from the edges of the catch-plates and rises into the oil collecting space in the upper part of the separator.Jimei universityFrom there it is automatically drained into the used oil tank.Jimei universityThe air brought along with the oil/water mixture when pumping the bilge is cons
40、tantly let out of the separator through an air-vent valve.Jimei universityThe de-oiled water leaves the separator downwards through a central pipe provided with nozzle holes and flows to the filter for the remaining separation.Jimei universityThe filter is a two-stage filter.In the first stage mecha
41、nical impurities are filtered out simultaneously with some fine oil separation.Jimei universityThe second stage,which is fitted with coalescing inserts,takes over the remaining separation.Jimei universityAs the oily water flows through the coalescing inserts the tiny remaining oil droplets coalesce
42、to large drops of oil and which,Jimei universitywhich,owing to their lower-specific gravity,rise up into the oil collecting space provided for this purpose.From here the oil is drained manually.Jimei universityA pressure control which may be supplied along with the unit indicates the rise in pressur
43、e in the filter and gives signal when the time has come to change the filter inserts.Jimei university At the same time,pressure switches set on(开开始始)an alarm and serve for switching off the bilge pump before the permissible pressure is exceeded.Jimei universityIn addition to the separator and filter
44、 an oil content meter can be supplied as an attachment which Jimei universitywhich sets on a visual alarm as soon as the limit value of 15 ppm oil content,fixed by IMO,is exceeded.Jimei universityA connection enables transmission of the signal for change-over valve or separator pump control.Jimei un
45、iversityB.INCINERATION(焚烧焚烧)OF SOLID WASTE Jimei universityTo incinerate solid waste,stop the auxiliary and waste oil burners and then charge it through the solid waste dump(倾倾倒倒(垃垃圾圾),倾倾卸卸)chute(斜斜槽槽;滑槽滑槽).Jimei universityTo incinerate water cloths,charge 1 to 2 kg at a time as a standard and avoid
46、 charging them excessively Jimei university(When the dump chute is opened during burner combustion,the burner interlock functions to make the burners off).Jimei universityAfter charging solid waste,close the dump chute,and ignite it with the auxiliary burner.Jimei universityBurn solid waste with the
47、 auxiliary burner only without using the waste oil burner.Jimei universityThis is because,when solid waste is charged during waste oil burning,the waste oil burner may be turned off owing to the pressure charge in the combustion chamber.Jimei universityEven if things go well for a moment,the inciner
48、ator is bound to be shut down by the flue gas temperature indicator/regulator as the flue gas temperature will rise excessively.Jimei universityDuring disposal of solid waste,pay utmost attention to the temperature rise of flue gas,and also watch out for the abnormalities(异常异常).Jimei universityRemov
49、e ashes and so on sometimes from inside the combustion chamber through the solid waste dump chute.Jimei universityC.BIOLOGICAL(生物学的生物学的)SEWAGE TREATMENT Jimei universityA number of biological sewage treatment plant types are in use at sea but nearly all work on what is called the extended aeration p
50、rocess(延延时时曝曝气气过过程程).Jimei universityBasically this consists of oxygenating(氧氧化化，充充氧氧)the liquor either by bubbling air through it or by agitating(搅搅动动)the surface.Jimei universityBy so doing a family of bacteria(细细菌菌)is propagated(繁繁殖殖 which thrives(兴兴旺旺,繁繁荣荣,茁茁壮壮成成长长,旺旺盛盛)on the oxygen content and