Design And Simulation Of Saving Energy System For Dry Process Of Dyeing Fabric

As an essential part of the dyeing and printing process, drying contributesto30%~40%of the total energy waste throughout the whole production line, mainlybecause: a lack of a recovery system for energy in waste gas which goes directly intothe air; a lack of devices for real time measurement and control of water content infabrics, which leads to energy waste as the water content in dried fabrics is lowerthan required. Therefore, based on the original drying system, this topic designs theexhausting heat recovery process and proposes the strategy of online control of fabricmoisture content which is good for deying and priting industry to reduce the energyconsumption and save the cost. Main contents of this research：(1) Proposed the method of recycling the heat included in the exhaust gas withheat exchanger, and analyzes its feasibility; to make the realationship between theprocess parameters in the fabric drying process clear, ralated mathematical model isestablished, and then we put forword the control method of fabric’s moisture content.(2) Combining with the advantages of plate heat exchanger in gas-gas heattransfer, it determines the type of heat exchanger designed and makes the choice ofsheet bar, technological process and flow direction according to the design principleof plate heat exchanger. Besides, it utilizes CFD software to conduct the simulationon the V-shape corrugated plate in the flow fields with different flow velocitiesbetween plates, to provide the reference for the choice of the flow velocity betweenplates and quantity of flow channel. The result shows that, the higher the flowvelocity between plates is, the more obvious the vortex phenomenon in the channel is.Hence, it will be better for the heat transfer. That is, with the allowance of the voltagedrop, it is better to choose quite higher flow velocity between plates. Through themethod of LMTD, it calculates the heat exchange area and the quantity of the sheetbar needed when the energy conservation index of the heat exchanger is6%.Meanwhile, under the helpf of HTRI Xchanger Suite, it is checked. Compared withthe theoretical design, the data result shows that the error is small. It satisfies thedesign needs. (3) Aiming to quite serious time lag and inertia existing in the drying systemand different sizes of dried fabric, the tuning method of regular PID controlparameter is hard to achieve the better control effect. On this basis, it presents thevague PID control strategy and applies STEP7to accomplish the compilation of thevague control algorithm program. The result of the application on the original systemshows that the moisture content after drying of the printing and dyeing fabric can bemaintained at the setting value, with quite good control effect. Hence, it is good forreduce the energy consumption.(4) It applies the kingview software to make the simulation on the drying systemafter the adding of heat exchanger. Additionally, depending on the energyconservation model and moisture content control model, it finishes the program ofthe system parameter input and output and finally makes the simulation computationon the energy consumption of the drying system after the increase of the heatexchanger. The result indicates that the energy conservation rate of the drying systemafter the increase of the heat exchanger can reach7.7%. Meanwhile, it effectivelyenhances the drying rate of the system on the fabric.