| Drying is the most energy-consuming process in the production of tissue paper.Besides,it is also one of the key processes to control the quality of the products.How to reduce the energy consumption of drying section and ensure the quality is a hot issue in the industry.Establishing a mathematical model of energy system in drying section of paper machine for daily use,so as to optimize the drying section process,is of great significance for reducing energy consumption in production.In the drying process of tissue paper,the temperature and moisture of the paper are coupled,which is affected by ventilation system and determines the energy consumption of the drying section.Aiming at the characteristics of drying section of tissue paper machine,the energy system model of drying section of tissue paper machine was established by taking BF-12 paper machine as an example.The drying part model is divided into three modules: ventilation system module,paper drying module and energy consumption module.Firstly,aiming at the ventilation module,the interdependence of temperature and humidity in the ventilation duct is solved by using the iterative method,and the soft measurement of temperature,humidity and air volume in all parts of the ventilation system is realized.Then based on the basic mass transfer equation and Newton cooling,the paper sheet static equation is established quantitatively.Finally,according to the results of soft measurement of ventilation system and the simulation of paper drying process,the steam consumption and fan power consumption in the drying section are solved.In the process of solving the model,the paper machine historical operation data in the enterprise energy management system are used to determine the unknown parameters which are difficult to solve directly.In the process of validating the accuracy of the model,manual measurement data are used to validate the rheumatism degree.The exhaust air temperature,drying energy consumption and drying rate were validated by historical operation data.The validation results show that the average relative error of the model in simulating exhaust air temperature,humidity,steam flow and drying rate is in the range of 3%~5%.The simulation accuracy of the model is high,and the average relative error is 1.6%.The model was used to simulate different operation parameters under the same output.According to the simulation results,it is found that the thermal efficiency of the Yangke dryer is stable and higher than that of the ventilation system.The thermal efficiency of the ventilation system is negatively correlated with the air supply temperature of the hood,and positively correlated with the degree of rheumatism exhaust at the same air supply temperature.According to the energy efficiency analysis,the logic of optimizing the parameters of drying unit was formulated.After optimizing the historical data,it is found that there is an energy-saving potential of about 0.15 t steam/t paper through parameter optimization.A set of parameter optimization system for drying department was developed,and the parameter optimization program was integrated into the energy management system of the enterprise to provide guidance for the operation of the producers.Aiming at the problem of inappropriate hot air return in ventilation system,the model was used to simulate the situation after modifying the pipeline.The results show that the wet side recycling of the dry side hood exhaust air can significantly reduce the humidity of the hood air supply and reduce the steam flow rate of the dryer by about 0.1 t/h.Therefore,the model and optimization method of drying energy system of tissue paper machine established in this study,through optimizing the parameters and process of drying section,have important reference value for improving energy utilization efficiency of drying section and reducing energy consumption of enterprises. |
