Web API/WCF如何保持对象活动

我有一个引擎（ABBYY FlexiCapture engine），我想将它与REST服务（WebAPI或WCF）一起使用。发动机启动初始化需要30秒。每个请求都太长了。我希望发动机加载服务启动并保持在"预热"状态。如何使用WebAPI或WCF？（最好的方法是保持线程和引擎的活力）。附言：很抱歉我英语不好。

--来自ABBYY示例库

private void ProcessImages()
        {
            trace("Loading FlexiCapture Engine...");
            IEngine engine = LoadEngine();
            try
            {
                string samplesFolder = FceConfig.GetSamplesFolder();
                trace("Creating and configuring the FlexiCapture Processor...");
                IFlexiCaptureProcessor processor = engine.CreateFlexiCaptureProcessor();
                processor.AddDocumentDefinitionFile(samplesFolder + "''SampleProject''Templates''Invoice_eng.fcdot");
                // ....
                trace("Adding images to process...");
                processor.AddImageFile(samplesFolder + "''SampleImages''Invoices_1.tif");
                // ....
                trace("Recognizing the images and exporting the results...");
                while (true)
                {
                    // Recognize next document
                    IDocument document = processor.RecognizeNextDocument();
                    // processing recognized document...
                }
            }
            finally
            {
                UnloadEngine(ref engine);
            }
        }
        private IEngine LoadEngine()
        {
            // FlexiCapture Engine can be loaded in three diffrent ways:
            // 1) Directly, as in this sample
            // 2) As an inproc server (using COM infrastructure)
            // 3) As an out-of-proc server in a worker process (using COM infrastructure)
            IEngine engine;
            int hResult = InitializeEngine(FceConfig.GetDeveloperSN(), null, null, out engine);
            Marshal.ThrowExceptionForHR(hResult);
            return engine;
        }

我想要创建引擎。之后，我将创建并配置几个FlexiCapture处理器。（这需要很长时间，我想在服务启动时完成）然后，当用户添加图像时，我将使用其中一个处理器来识别它们。

启动时：创建引擎->创建多个处理器（+配置它们）；在方法invoke上：使用一个免费的处理器->识别用户图像。

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.Single)]
public static class EngineContainer
{
    private static Engine _engine { get; set; }
    public static Engine GetEngine 
    {
        get { if (_engine == null) Init(); return _engine; }
    }
}