Since the steam turbine plant has the flexibility of fuel selection [oil only, gas only or dual] so most propulsion plants for Liquid Natural Gas (LNG) Carriers have been up till now, steam turbine. However, what with the rising prices of fuel and the shortage of steam turbine engine room crew, investigation into a higher efficiency propulsion plant has been growing. Actually, a lot of LNG carriers, for European owners, have adopted a dual fuel diesel engine plant with an electric propulsion motor (DFE) . Many large size LNG carriers (200, 000 m3) being built in Korean shipyards have recently adopted a diesel engine plant with a re-liquefaction system (DRL) . Under these circumstances we propose a new high efficiency plant. The Ultra Steam Turbine (UST) plant offers advantages over conventional steam turbines; high reliability, safety, low maintenance cost and easy operation. The restitution of the steam turbine plant contributes to the recovery of market share and the exploitation of new markets. In this paper we introduce the outline, features and key technology about the development of the reheat boiler, that which is one of main components of the UST plant.
The steam turbine plant is well known, good for reliability, but not good for specific fuel consumption to the diesel plant. As the demand for LNG carriers and the requirements for fuel saving are increasing year and year, more efficient steam plant is being required. In response to this requirement, a new steam plant, which adopts the reheat cycle with the steam pressure of 10 MPa, has been developed. The adoption of higher pressure steam would require the more sophisticated water quality control so that its reliability could be maintained at high level as same with the conventional 6MPa plants. This paper considers the appropriate water quality control criteria and phosphate treatment for the new plant, and makes it clear that a quite different boiler water treatment is needed from the treatment of conventional plant.
Modern marine diesel engines, most especially the 2-stroke, large-bore, low-speed models, have already developed their thermal efficiency to a very high level and would seem to have little potential for further improvement. However, this does leave us with approximately 50% of the input energy not being fully utilized on board and consequently is wasted. This paper proposes a more efficient waste energy recovery system, this mainly from the main engine exhaust gases. Using a compact module consisting of a steam turbine and an exhaust gas power turbine, it was found that the total thermal efficiency improvement to a propulsive plant was more than 10%.
Since the steam turbine plant have flexibility of fuel selection (oil only, gas only and dual), most propulsion plants for Liquid Natural Gas Carriers (LNGC) have been the steam turbine plant. However, the rising prices of fuel and shortage of the crew for the steam turbine plant, the movement to investigate higher efficiency propulsion plant has gotten active. Actually, a lot of LNGCs for European owners have adopted dual fuel diesel engine (DFE) with electric propulsion motor, and many large size LNGCs (200, 000 m3) built in Korean shipyard have adopted diesel engine with re-liquefaction plant (DRL) recently. Under such a situation, we propose new high efficiency plant; UST (Ultra Steam Turbine Plant) that has advantages of conventional steam turbines (high reliability, safety, low maintenance cost and easy operation) for the restitution of steam turbine plant, the recovery of the share and the exploitation of the new market. In this paper, we introduce the outline of the UST plant, and present the features and key technology of reheat turbine that is one of main components of UST plant.
We experienced corrosion troubles of some Aluminum Brass cooling tubes of a turbo generator condenser. To clarify those causes, we investigated actual conditions and circumstances on board vessels and as seawater flowed into the cooling tubes. This was during the actual operational conditions of the condenser. We considered the protection film of the iron ion on the internal surface of the cooling tubes, and preventive maintenance conditions by means of anodes and/or injection of chlorine and so on. Through results of these investigations we found that such as the proper feeding of iron ion into the cooling tubes, a lack of protective anodes and the excessive interposition of the chlorine (by means of the anti-fouling device effect) of the said corrosion troubles, before reaching our countermeasures for some of them.
A disaster happened in a nuclear power plant in Japan in August 2004, which was caused by failure of condensation water pipe in the secondary line. Shipping industries are concerned for possibility of occurrence of such a disaster in ships due to its construction similarity to marine boiler plant in steam, feed water, and condensation piping for main or auxiliary boilers. Nippon Kaiji Kyokai has therefore investigated and gathered data of piping lines corrosion in ships collaborated with major Japanese shipowners right after the disaster. The results show that similar corrosion failure as in the nuclear power plant has occurred in shipboard steam/feed water/condensation water pipes for main and auxiliary boiler plants without causing severe consequences. It is also found that this kind of failure, named“Flow Accelerated Corrosion”and referred to as“FAC”, is caused by erosion-corrosion at a place where the flow is extremely turbulent, such as a location right downstream side of an orifice or a control valve, or at bend parts including elbows, etc., under strong influence of temperature, flow velocity or pH of the fluid. The wall thickness measurements on actual pipe lines of steam, condensation water and feed water at bend parts, at T-junctions, behind orifices, behind valves and at diffusers/reducers with a ultrasonic thickness gauge show a very definite evidence of a reduction in wall thickness of carbon steel piping. It was confirmed that the amount of actual reduction in wall thickness could be well predicted by Kastner Equation.
This report is a summary of our technical seminars and our inhouse training sessions for marine engineers over the last seven years. Our focus here is corrosion and fouling control in the cooling water system of diesel engine. We are pleased to provide here our basic understanding of corrosion control and in an engine cooling water system. Also, a new cleaning method for air-cooler, those at use not only in marine industries, but also for factory generators in general.
Marine heavy fuel oil is usually supplied to diesel engines after some purifications on board . The purification systems are generally settling system, filtering system, centrifuging system, etc. The centrifuging system has a good performance for the purification. It is identified by using various apparatus and complicated procedures at a laboratory. To examine a property of heavy oil precisely and easily, the analysis and evaluation methods were examined. Three analysis methods before and after centrifuging were compared with each fuel oil sampled : 1) general oil analysis 2) combustion test 3) ferrography. Next other effectiveness were checked on some published indexes. The result shows the conclusion that the centrifuging effectiveness and the delicate characteristic difference to dirty of recent marine heavy fuel oil can be clearly confirmed by the ferrography analysis. The fuel properties after centrifuging are improved to the combustion test in some cases.
A steam-water separator with the help of the Coulomb force generated by the Corona discharge, has the merits of being a simple structure, one capable of separating very small quantities of water droplets while decreasing the flow pressure resistance in the system under development. while the principle behind this separator is the same as that of the electrostatic precipitator, used for the separation of particulate pollutants, the characteristics of an electric field in a mist flow, the water droplet is different from that of the air flow, which is without the water droplets. A calculating method to predict the water droplet collecting efficiency of this separator has been developed on the basis of this experimental data. This was conducted using water-air under conditions of room temperature and atmospheric pressure.
The NOx Technical Code under the MARPOL 73/78 Convention ANNEX 6 specifies the NOx emission limits and has determined the direct measurement and monitoring method for the on-board NOx verification procedure. But the monitoring method might not have been established yet, since it is reported that some results of NOx emission values measured on board exceed the 15% allowance even in the case of engines with certification. Since there are several constraints in the measurements on board, the uncertainty is enhanced comparing to the measurements at a shop-test. In this report an alternative index is proposed to reduce the uncertainty and simplify the on-board measurement. The index is named as NOx 13 that is normalized with oxygen concentrations and contains the correction factor for humidity and temperature. The NOx emission value, NOx [g/kWh], is theoretically correlated to the NOx13 as in the following expression and the correlation is experimentally confirmed. NOx [g/kWh] = α1×α2× be [g/kWh] × N0x13 [ppm] α1, α2; constant, be [g/kWh] ; specific fuel consumption
The on-board NOx monitoring method is one of the three ways for the periodical survey, which demonstrates compliance by means of the measurement of the NOx emission value on in-service conditions. In this study of the NOx emission measurement, made on the same two-stroke engine, and with the same gas analyzer, was carried out on three occasions. That is a shop test, an at sea trial and during in-service. The effects on the NOx emission value are discussed with regard to the derivation methods of the exhaust gas flow rate. They are gas concentrations in UOB (universal oxygen balance) and UCB (universal carbon balance) method, compositions of the sampled fuel, stability of engine output power in operation, and the temperature & humidity correction factor KHdies. The coefficient of humidity term, for the factor KHajes, should be larger than that of KHdiesas specified in the NOx technical code. This correlates the NOx emission values measured at sea trial and during in-service. The temperature and humidity should be measured in the engine room rather than in the steering house. The stability of the engine power can be evaluated alternatively by using the C.O.V. of the oxygen concentrations. The NOx emission values on an actual vessel do not agree to those at a test-bed due to the effect of the derived exhaust gas flow rate and the temperature of the intercooler outlet air.