Wednesday, 26 September 2012 09:33

Sophisticated innovations support green energy production in pulp mills Featured

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Historically, the standard of living has followed the consumption of fossil fuels. Concern over the environment, global warming, and the predicted shortages in fuel reserves are gradually shifting the focus to energy saving, developing new processes and the search for new fuels. Metso acknowledged the challenge in its annual report in 2009: “The greenhouse effect necessitates significant changes in energy use and production. Technology development is one of the key solutions to these challenges.”

Pls feel free to ask for more information. We also appreciate your feedback in all automation related issues.

Automation is often overlooked, but it is a great potential performance booster when the process has to be pushed to the limit. In addition, the more challenging fuels and mixtures of them, modern combustion technology, and the continuous monitoring of the environmental impacts of the new, state-of-the-art plants call for advanced measurement and control applications.

R&D shows the way to energy savings

Fuel chemistry together with burning process know-how is the specialty of the Process Chemistry Center at Åbo Akademi University, where Professor Mikko Hupa is in charge of a team of over 50 international scientists. Cooperation with the university complements Metso’s knowledge and experience. For example, the rapid development of the furnace flow modeling technique known as Computational Fluid Dynamics (CFD) has become a crucial tool in the design of new furnaces. It is partly due to advanced CDF that Metso has been able to develop the huge, recovery boilers, with black liquor capacity of over 7000 tds/d, which fully comply with the tightest environmental regulations. Metso has also made use of the groundbreaking detailed descriptions of the black liquor droplet combustion process in its development of boiler operation control systems and advanced automation solutions. Accurate control is essential when pushing the performance of these complex units to the limit. 

Professor Mikko Hupa, Process Chemistry Center at Åbo Akademi University

 

The Metso Recovery Boiler Optimizer has been used successfully for recovery boiler burning and sootblowing controls in several applications. It carefully controls the black liquor flow to the furnace, maintains a stable spraying pattern and adjusts the liquor droplet size according to quality variations. Air distribution controls guarantee the supply of the necessary combustion air for the burning process. Maintaining the optimum combustion conditions in the boiler furnace practically eliminates SO2 and TRS emissions. 

 

Recovery boiler

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The Intelligent sootblowing controls enhance the availability of the recovery boiler by cleaning the heat transfer surfaces only when and where needed. This results in sootblowing steam savings and increased thermal efficiency. Typical energy savings include an approximate 5% increase in burning capacity, a 5% increase in steam production, and extending the uninterrupted operating period beyond one year.

“It is impossible to maintain the optimum combustion conditions in the furnace continuously using manual controls. Also, systems based on what is called adaptive control will often face difficulties in the practical solutions of the process industry,” states Professor Hupa.


Renewable fuels as profitable business

The search for new potential fuels is ongoing, and it is becoming more and more important to understand the whole value chain from feedstock to end product. Biomass like agro residue, wood waste, and other waste materials require fuel handling and preprocessing before the proper conversion process can be applied.

Biomass power_plant_1300px

click on the picture to enlarge

Maintaining a high and stable combustion temperature in the furnace simultaneously with a moderate boiler equipment corrosion/erosion rate is challenging because of the extensive quality variation of some bio fuels. In addition, recycled wood often contains variable amounts of zinc and lead, which lead to superheater corrosion in the boiler.

Fluidized bed boilers like CYMIC and HYBEXprovide a state-of-the-art and environmentally suitable solution for the demanding new bio fuels. As with the recovery boilers, the operation of these plants benefits from sophisticated automation. The Combustion Management Solution calculates the heat value of the fuel mixture used continuously. The fuel power computed from the fuel heat value and fuel flow is used as the basis for combustion air calculation and fuel feed control. The fuel flow disturbance control compensates variations in fuel quality and flow by modulating the fuel feed to the furnace. The air-to-fuel ratio control allows for the correct air fuel mixture for the complete oxidization of the fuel at the desired excess oxygen level. At the same time, steam production is monitored and the necessary adjustments are carried out in the feed water flow and fuel feed. The furnace temperature is maintained between acceptable limits to prevent melting of the fluidized bed and the formation of thermal NOx. SO2 emissions can be controlled by means of the limestone feed to the furnace and by the combustion temperature control.

The plant’s thermal efficiency is continuously monitored and reported to the operators for immediate actions. The performance follow-up is beneficial especially during process disturbances and in load change situations. Several installations of the Combustion Management Solution have proven that a stable steaming rate from the boiler can be achieved regardless of quality variations in the feedstock.

Professor Hupa reflects: “Deeper understanding and a reliable prediction of the behavior of several fuels burned together is one of the future development targets.”


Environmental solutions manage plant performance

Power plants have to comply with environmental requirements in order to receive an operating permit. Running old inefficient equipment means plants face the threat of closure. Deviations have to be reported to the authorities and the necessary actions have to be initiated immediately. The consequences can be fatal if disturbances remain unnoticed. 

The emission monitoring and reporting solutions are built on the Metso DNA Information system platform to comply with the LCP Directive and the plant’s environmental permit. The process operators have online access to the emission measurements and the condition of the automated measurement systems. Alarm reporting complements the process information for fast and efficient management in disturbance situations. In addition, the accumulated information can be used for operation improvement and the development of new processes. 


Large Combustion Plants (LCP) emissions can be effectively managed by dedicated monitoring application

The system compares the accumulated averages of the measured data with the previous two-day averages and the permitted limits. The forecasts for the coming two days are calculated based on the present operating parameters and the collected process data. The analyzer display monitors the current status, last maintenance, and calibration of the equipment so that the quality assurance of AMS according to EN 14181- standard can be realized.

Daily, monthly, and annual reports can be used for self-assessment of the mill’s emissions and in reports to the authorities. A summary display collects the real-time and cumulative emission measurements and their averages in an easy-to-use information window. The data and related forecasts are compared with the operational permits. The summary display provides an effective tool for evaluating the environmental performance of the mill because it contains complementary information of the process and equipment status. This knowledge can also be utilized in communications with the authorities.


Total emission reporting with corresponding trends complies with regulations applied on LCP


Metso DNA Eco Diary is an efficient environmental data analysis and knowledge distribution tool for all relevant users. It contains the process measurements and the event-based manual entries regarding the disturbance, production loss, and shift operation. The operators’ descriptions in the diary of the time and place of the disturbances build up experience. They also list the actions taken and the consequences of the incident. Recommendations on how the situation could be prevented in the future complement the analysis.

Kari Kerkelä, automation manager at UPM Kaukas Mill, summarizes the benefits that can be achieved with the environmental automation solutions: “With Metso’s applications, we can prove that we comply with the requirements of the new environmental permit. We are continuously aware of the plant emissions and can react to potential problems in time.”


Sustainability is achievable

Our welfare continues to be based on the use of fossil fuels. The coal consumption in 2010 was 10% higher than the average during the 2000s, and the total electricity consumption increased by 7.6% during 2010. Yet Professor Hupa is optimistic about the future: “It is possible to get rid of fossil fuels in the long run. Sustainable energy is achievable, but lots of innovative engineering supported by genuine scientific research is needed to reach the goal.”


Pls feel free to ask for more information. We also appreciate your feedback in all automation related issues


More information:

Jukka Puhakka, Manager, Pulp & Paper Applications 
jukka.puhakka(at)metso.com

 

 

Read 9586 times Last modified on Wednesday, 26 September 2012 10:08