Development of Polyurethane Foam Insulator with High Thermal Insulation Performance for KC-1 LNG Carrier

摘要

Nowadays the price of natural gas has become high and the efficiencyof propulsion systems of LNG (Liquefied Natural Gas) carriers hasincreased. Due to these trends, a lot of effort has been made to developan insulator for a LNG carrier with high thermal insulatingperformance and a low boil-off rate (BOR). A typical BORspecification for a 170K LNG carrier has been 0.15 vol.%/day. But theabove mentioned reasons have resulted in pressure to lower this BORspecification to 0.12~0.10 vol.%/day.Polyurethane foam (PUF) blown by trichlorofluoromethane (CFC-11)has been widely used as an insulator in various industries. PUF consistsof polymer skeleton and closed cells filled with blowing gas. But sinceCFC-11 depletes the ozone layer, many attempts have been made todevelop new alternatives. Due to its low Ozone Depletion Potential(ODP), 1,1-dichloro-1-fluoroethane (HCFC-141b) has replaced CFC-11.Polyurethane foam has been used as the main insulator for LNG carrierswith corrugated membrane type cargo containment systems. 270 mmthickness of insulation panel with PUF as the main insulator has typicallybeen used to meet the 0.15 vol.%/day BOR specification. But HCFC-141b also depletes the ozone layer although its effect is small comparedto CFC-11 (a tenth of CFC-11). Nowadays the third generation blowingagents, hydroflurocarbons (HFCs) have begun to replace HCFC-141b.Since the thermal conductivity of HFCs is higher than that of HCFC-141b, thicker insulation panels should be used to show the sameinsulation performance when adopting HFCs as a blowing agent.Because of a requirement for LNG carrier with a lower BORspecification, thicker insulation panels should be used. This solutioncould cause two problems. One is the increase in insulation panel price.The other one is the increase in the LNG ship size.In this study, many attempts have been tried to increase the insulatingperformance of polyurethane foam blown by HFCs. These attemptsinclude the use of new raw materials, and blending of well knownpolyether polyols, polyester polyols and various additives such assurfactants, catalysts, and so on. As a result, the same thickness of thenew insulation panel using PUF blown by HFCs as a main insulatormeets lower BOR specification for a LNG carrier.