Processes 2021 , 9 , 1707
17of 20
Figure 6a shows that the energy consumption and emissions in the coldest months of the year (M1, M2, M11, and M12) are higher than those in the warmer months (M7 and M8). This fact is due to the strong initial influence with respect to the outside temperature (Ot), due to the poor conditions of the exchangers. As the monitoring and continuous improvement techniques are applied, in Figure 6b, it is observed that in years 5, 6, and 7 there is a significant decrease in the global energy consumption and consequently the CO 2 emissions, decreasing the initial difference between the cold and hot months. Figure 6c shows that the overall level decreases, making the difference between all months very small; the losses decrease, and the exchangers work properly, making the system almost independent of the Ot at the end of year 10. 4. Conclusions As seen in the methodology, the emissions in this case are calculated as an emission balance depending on the primary energy consumed, which in this study is natural gas. The improvement in the energy efficiency due to the reduction in energy process losses and/or the better use of available energy results in a significant reduction in the ratio of the associated CO 2 emissions. The greater availability of energy in the process bottleneck, the drying section, allows an increase in production (Figure 3) so that the energy and CO 2 emissions ratio is reduced. The reduction in CO 2 emissions indicates that it is feasible to achieve significant emissions reduction through the control and maintenance of installations, as well as daily rules and processes. Establishing maintenance guidelines and minor renovations helps facilities meet their emissions reduction targets without first having to make costly investments. This study revealed that the involvement of TPM techniques such as TEI and CPI in production and maintenance workers in controlling the process variables is critical. Moreover, it shows how introducing CO 2 emissions as a principal indicator and identifying subindicators led to a significant emissions reduction in the last six years. This method can also identify the parts of the installation in which it is possible or necessary to take urgent action to reduce emissions and predict the reduction potential, which may allow new investments in the facilities to be planned more effectively. There is a direct relationship between the defined indicator, ‘t CO 2 /t Paper’, and the facility efficiency. An increase in this ratio due to the deterioration of the facilities can be considered to assess the capacity of papermaking and find the causes of a decline in output paper due to process inefficiencies. This manuscript identifies the effect of industrial variables involved in the drying process on CO 2 emissions, such as the amount of cold water added to the boiler circuit and the temperature of the blown air into the drying section (enclosure hood). Author Contributions: Conceptualization, L.M.C. and R.D.; methodology, L.M.C.; formal analysis, L.M.C., R.D.; investigation, L.M.C.; resources, L.M.C., R.D.; writing—original draft preparation, L.M.C.; writing—review and editing, L.M.C., R.D.; supervision, R.D.; funding acquisition, R.D. All authors have read and agreed to the published version of the manuscript. Funding: The authors thank the Spanish Ministry of Science, Innovation and Universities for sup- porting through RTI2018-102215-B-I00 project. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable.
Acknowledgments: The author thanks ASPAPEL for its support. Conflicts of Interest: The authors declare no conflict of interest.
Made with FlippingBook Online document maker