public interface IConverterService
{
    object ConvertData(object sourceData);
}

public class ConverterService : IConverterService
{
    private ISettingsProvider _settingsProvider;

    public ConverterService(ISettingsProvider settingsProvider)
    {
        _settingsProvider = settingsProvider;

        // Do some one-time initialisation using info from settingsProvider
        // and store the results in class variables (not shown), used by ConvertData.
    }

    public object ConvertData(object sourceData)
    {
        // Do the conversion - also uses _settingsProvider,
        // and other variables initialised in the constructor ..
    }
}

container.Register(Component.For<IConverterService>().ImplementedBy<ConverterService>().LifeStyle.Singleton);
container.Register(Component.For<ISettingsProvider>().ImplementedBy<SettingsProvider>().LifeStyle.Singleton);