Huanbin Liu

A Static Energy Model of Conventional Paper Drying for Multicylinder Paper Machines

A static energy model was developed to describe the conventional paper drying process for a multicylinder paper machine. The model is based on the mass and energy balance relationships written for fiber, steam, air, and water. With the purpose of developing a clear understanding of the paper drying process and evaluating its drying performance, the model developed was made up of seven basic blocks according to the technical art of paper drying. In this work, a multicylinder newsprint machine was chosen to illustrate the energy model. The module schematic and instructions are presented first, followed by mathematical descriptions for each block. In addition, paper drying models are reviewed. The specific drying rate, specific heat consumption, and energy efficiency are introduced to evaluate the drying performance. Experiments were conducted to measure the operating parameters and the newsprint drying process was simulated based on the model. A Sankey diagram is also presented. The results are compared with a typical newsprint machine to identify more energy-saving opportunities. The calculations indicate that the consistency of the energy model with experimental results and experience is reasonable. A series of simulations was performed to examine the effects of supply air temperature and exhaust air humidity on specific heat consumption. The results show that the specific heat consumption was decreased by 3.3% when the supply air temperature decreased from 112 to 100°C by adjusting the steam flow into the air heaters. Correspondingly, increasing the exhaust air humidity to 0.14 kg water/kg dry air from 0.10 kg water/kg dry air by adjusting the fan speed led to a 4.6% reduction in specific heat consumption and a 32% power savings for the fans.

Waste Heat Integration of Coating Paper Machine Drying Process

The paper sheet drying process consumes about 70% of the total energy required in coated papermaking, and almost all the thermal energy used in the process can be found in the exhaust air; thus, it has significant potential to recover the heat. With the aim of saving energy, the recovered energy is usually used to heat different process streams instead of steam. This article examines the drying process of an operating coating paper machine to demonstrate an optimization method. To study the possibility of improving energy efficiency, thermodynamic analysis was conducted. The reasons why there is so much heat lost during drying were investigated. Based on the results of the energy and exergy analysis, a new waste heat integration scheme is presented. Furthermore, the performance of the proposed scheme has been evaluated. The results of the case study show an energy efficiency improvement of 7.3% and a specific energy consumption reduction of 4.6% with profitable investments.

Process Parameters Optimization for Energy Saving in Paper Machine Dryer Section

Due to high energy consumption in the Chinese paper industry, this study considers higher-energy efficiency for the multicylinder dryer section of paper machines. A common situation in the Chinese paper industry is that energy is consumed in extensive mode. In order to improve the energy efficiency of the paper machine dryer section, deeper analysis and optimization of process parameters are necessary. A NLP optimization method is developed for integration of steam system and air system to reduce the steam consumption and decrease the loads of centrifugal blowers in the multicylinder dryer section of a paper machine. Equality constraints of the optimization model are extracted from different process modules based on material and energy balance. Inequality constraints are from the production capacity, operating condition, etc. Two illustrative examples are presented in this paper. The results show that the optimization model is adaptive and convenient for application. For a newsprint machine, less dry air and steam are used and the energy consumption can be reduced by about 8% in the dryer section. Applied on a linerboard machine which has surface sizing, the method can reduce the energy consumption by 5.6%.

Energy system diagnosis of paper-drying process, Part 1: Energy performance assessment

ABSTRACT Paper drying is a highly energy-intensive and complicated multivariate process. The dryer section plays an important role in the energy consumption of a paper machine, especially of thermal energy. A comprehensive method for assessing the energy performance of the dryer section was investigated in this study to improve energy efficiency. This method was divided into three component processes: energy and evaporation load audit, field test and observation, and energy flow analysis and energy efficiency estimation. In a case study, we found that the method could, in addition to analyzing the key factors that restrict drying efficiency, also depict the details of energy consumption clearly. At the same time, several significant energy-saving measures were suggested to improve the energy efficiency of the paper-drying process.

Energy system diagnosis of paper-drying process, Part 2: A model-based estimation of energy-saving potentials

ABSTRACT The pulp and paper sector is the fourth largest industrial sector in terms of energy use in the world. Of the numerous processes involved in paper-making by a paper machine, the dryer section is the process that consumes the largest amount of energy. A model-based method for estimating energy-saving potentials of the dryer section was put forward in the present study. It was done by four steps: establishing a mathematical model about energy consumption, determining the model parameters, benchmarking the drying performance to obtain the corresponding energy-saving measures, and estimating the energy-saving potentials by using the mathematical model. In a case study, a multi-cylinder dryer section was selected to illustrate the method. After a fundamental field test and observation, several operating problems that restricted the energy performance of paper drying were found. And then several reasonable energy-saving measures were suggested to the operators. Finally, applying the mathematic model, it was found that 0.32 ton of steam will be saved when producing 1 ton of paper in recommended operating conditions. With the designed capacity of 200,000 tons/year, the annual steam-savings will be 64,000 tons. Generally, the price of steam is 130–150 Chinese Yuan (about US

Effect of operating parameters on the drying performance of multicylinder paper machine dryer section

21–24) in China, and the annual economic benefits will be 8.32–9.60 million Chinese Yuan (about US

Dryer Section Energy System Measurement and Energy-Saving Potential Analysis for a Paper Machine:

1.344–1.536 million).

Data-based analysis of energy system in papermaking process

ABSTRACT The drying performance of multicylinder dryer section in a paper machine was investigated under various operating parameters: Inlet paper solid content (48–50%), inlet paper temperature (45–50°C), supply air temperature (100–90°C), and exhaust air humidity (75–85 g H2O/kg dry air). The variation in environmental conditions was also considered. In this study, an improved static model was utilized to study the influence of these operating parameters on paper drying. The model was constructed using sequential modeling approach based on the drying techniques of multicylinder dryer section of a paper machine. The calculated paper solid content leaving each paper drying module and energy use is in agreement with the measured results. The simulation results showed that higher paper solid content and temperature entering the dryer section, lower supply air temperature, and higher exhaust air humidity were favorable for drying performance within the studied range of these parameters.

An energy-saving assessment approach for hood retrofitting in multi-cylinder dryer sections

In this paper, a detailed dryer section audit was conducted on a paper machine to evaluate its energy performance. The methodology and instruments used for field measurements are introduced as an important part of dryer audit. The deficiency points which limit drying performance of the paper machine are identified based on the tested data. It was found that significant energy savings can be achieved in the studied paper machine.

Notice of Retraction Modelling sheet relative bonded area with fiber flexibility

ABSTRACT Papermaking process is highly energy-intensive, complicated, and influenced by multiple unit processes, which plays an important role in the energy consumption, especially of thermal energy and electricity energy. An energy management system (EMS) was built to acquire the systematic, consistent, and accurate online information of the production process in a typical coated paperboard mill. The EMS first fulfilled the online energy information calculation from the process data acquisition and integration, second provided the massive historical data to find out the internal variation of production process for inferring decisions. In a case study, the online energy flow analysis and the estimation of specific energy consumption (SEC) were carried out. Based on data-driven techniques, three different operation conditions were recognized by adopting the kernel principal component analysis and DBSCAN (Density-Based Spatial Clustering of Applications with Noise) when the basis weight was 220 g/m2. The energy consumption was described in each cluster. Particular attention needed to be paid to LP steam in the high-speed production process with the change in environmental temperature and humidity in cluster 3. A novel indicator was proposed to appraise the level of energy consumption in different paper machine speeds. The benchmarking SEC was extracted from the massive historical data for the estimation of energy-saving potential. With the designed capacity of 300,000 ton/year, the potential economic benefits will be 20127 thousand RMB/year.