选择热泵多效蒸发系统最佳流程的新方法

A new method of selection of optimal feed flow sequence for multiple effect evaporator systems combined with thermal vapor compression

为了能从众多多效蒸发流程中快速准确地筛选出能耗最低的最佳流程,建立了筛选多效蒸发最佳流程的新方法——矩阵法。新方法将多效蒸发系统中的物料衡算和热量衡算非线性方程组描述成矩阵方程,当流程或节能措施改变时,无需重新推导数学模型,只需将矩阵方程中的若干参数重新赋值,模型就能模拟并流、逆流、各种形式的错流、平流和平错流,还能模拟上述流程有或无蒸汽喷射式热泵技术、引出额外蒸汽预热原料液、冷凝水闪蒸和溶液闪蒸的各种情况,从而快速准确地筛选出最佳流程。浓缩菠萝汁的三效蒸发系统的模拟筛选结果表明:不采用任何节能措施或仅采用冷凝水闪蒸或仅采用蒸汽喷射式热泵技术时,最佳流程是逆流;同时采用蒸汽喷射式热泵技术、引出额外蒸汽预热原料液和冷凝水闪蒸的并流流程最佳,其节省的生蒸汽消耗量高达42.77%。矩阵法是筛选多效蒸发最佳流程的新方法,具有通用性强、效率高、速度快且准确等突出优点。

In order to rapidly and accurately select optimal feed flow sequence in the multiple effect evaporator system, a new method is developed, called matrix method. Nonlinear material balance equations and heat balance equations are described as a matrix equation in this method. The model can simulate the co-current, countercurrent, mixed and parallel feed flow sequences by changing several parameters rather than re-deriving all equations. In addition, the model can simulate the multiple effect evaporator system with various energy reduction schemes such as thermal vapor compression, vapor bleeding to the feed, solution flashing and condensate flashing by changing the matrix equation. The model can be used to select optimal feed flow sequence. An example of the triple effect evaporator system is considered. The simulation results show that the optimal feed flow sequence is backward feed flow sequence when none of energy reduction schemes or only condensate flashing or only thermal vapor compression is included in the system. The simulation results also show that the optimal feed flow sequence is forward flow sequence when thermal vapor compression, vapor bleeding to the feed and condensate flashing are used in the system and these schemes can reduce the steam consumption up to 42.77%. Matrix method is a new method to screen multi-effect evaporation processes and this method has many outstanding advantages such as strong versatility, highly efficiency, highly speed and accurate.