In this issue, our leading article is about Thermocompressors. Thermocompressors are key to optimnizing energy consumption, maximizing production and realizing energy savings when drying paper or paperboard on the machine.

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The Application: Steam in Paper Drying

Paper machines rely on steam-heated dryer cylinders to remove moisture from the paper sheet. The quality of the steam used and available enthalpic energy directly affect the drying rate, sheet quality and energy used. Condensate removal from the dryer is the second leg of the drying process and equally important as poor condensate removal inhibits the energy transfer from the steam to the dryer can surface. Syphons are used to channel the condensate out of the dryer in this closed loop system assisted by low pressure blow through steam to move the condensate out of the dryer. This two-phase condensate and steam flow is collected in a separator tank before being moved to the condensate collection system. To optimize the energy recovery for this low-pressure steam, a thermocompressor is used to recover that free energy and re-introduce it into the drying process. Thermocompressors recover this low-pressure steam, recompressing it for reuse, thereby enhancing steam economy and reducing waste.  

Thermodynamic Principles at Work

Thermocompressors operate on a simple yet effective principle where high-pressure motive steam is accelerated through a nozzle, creating a low-pressure zone that entrains the blow through steam. This mixture then passes through a diffuser, where velocity is converted back into pressure. The result is reusable steam energy at an intermediate pressure, ready to re-enter the drying process. This process not only conserves energy but also stabilizes dryer operation by maintaining consistent pressure and temperature profiles across dryer groups. A typical thermocompressor system includes a nozzle that accelerates the motive steam to create suction for entraining the blow through steam. A throat area that mixes the motive and blow through steam. A diffuser that converts the available kinetic energy into pressure. Finally, an actuated control system is used to modulate the thermocompressor percent opening based on the required set point and measured process variable.

The sizing of the thermocompressor based on specific application requirements is paramount to the system performance and energy optimization. The parameters required include the source steam, syphon sizing, condensate return flow and flash steam formed in the separator. Performance curves guide the selection and tuning of thermocompressors, ensuring optimal pressure and flow conditions.

The Bottom Line

Efficient steam delivery isn’t just about heat. It’s about the control, recovery, and smart design of the complete closed loop system. With the right thermocompressor system, mills can achieve superior drying performance, lower energy bills, and a more sustainable operation. Fulton Systems Inc. delivers the expertise and equipment to make that possible.

Errors in the sizing and design such as incorrect piping or control scheme errors can lead to overloaded systems, energy losses, and unstable operation.

Why Choose Fulton Systems Inc.?

Fulton Systems Inc., with over 100 years in servicing the pulp and paper industry, is a demonstrated leader in the steam delivery and condensate system recovery arenas. Their offerings include complete system design engineering, control scheme generation, desuperheaters, thermocompressors, syphons, modularized collection systems, accessories, and machine performance audits. Their commitment to performance and sustainability makes them a trusted partner in the paper industry.  www.fultonsystems.com

Clean steam starts in the boiler, of course. But there is a lot of piping and valving between the boiler and the dryer section of your paper machine. A clean boiler does not necessarily mean a clean steam system. And this may mean accumulated rust and other debris that may be affecting your dryer performance.

Customerservice@FultonSystems.com

(PART 1)

Revolutionizing Condensate Removal: The Super Syphon

In the demanding environment of paper machine dryers, efficient condensate removal is critical to maintaining drying performance and energy efficiency. The Super Syphon is a rugged, one-piece rotating syphon engineered for superior performance and reliability.

Innovative Design for Maximum Efficiency

The Super Syphon integrates the journal flange, syphon, and horizontal pipe into a single welded carbon steel unit, eliminating the need for multiple components. This streamlined design simplifies installation and enhances durability under high-speed conditions for rotational speeds of 700-2500 FPM. With no internal dryer access required, the Super Syphon can be installed externally through the dryer journal, significantly reducing downtime and maintenance complexity.

(PART 1)

Understanding the Fundamentals

Dryer drainage relies on creating a pressure differential between the steam supply and the condensate header. This differential drives condensate and blow through steam out of the dryer cylinders. Blow through steam is non-condensed steam that exits with the condensate not only assists in condensate removal but also purges non-condensable gases from the system.

Syphon Selection and System Design

The type and size of syphons rotary, low-speed stationary, or high-speed stationary play a critical role in determining the required differential pressure and the volume of blow through steam. Larger syphons allow more blow through at a given pressure, while higher dryer speeds increase centrifugal pressure losses in rotary syphons.

Key Concepts Review

Paper Machine Dryer Drainage: Understand why proper drainage is crucial in paper production.

Differential Pressure: Define differential pressure in the context of dryer drainage and explain its role in condensate removal.

Blow Through Steam Flow: Define blow through steam flow and explain its role in condensate and non-condensable gas removal.

Syphons: Describe the function of syphons in dryer cylinders and the different types discussed (low speed stationary, high speed stationary, rotary).

Pressure Loss: Understand the different factors contributing to pressure loss within the syphon (accelerational, gravitational, centrifugal).

Playing Field: Explain the concept of the "playing field" in relation to operating conditions and its impact on drainage.

Control Strategies: Describe the two main control strategies discussed: differential pressure control and blow through flow control.

Dual Monitoring with Selective Controls: Understand the benefits of monitoring both differential pressure and blow through flow.

Quiz

1. Explain the primary purpose of controlling dryer drainage in a paper machine. Why is this process important for efficient paper production?
2. Define differential pressure as it relates to steam dryer cylinders. How does maintaining a sufficient differential pressure contribute to effective condensate removal?
3. What is blow through steam flow, and what are the two main substances it helps to remove from the dryer cylinders?
4. Describe the key difference between low speed stationary syphons and high speed stationary syphons in terms of their design and typical application.
5. Briefly explain how an increase in blow through rate typically affects the pressure loss within the syphon. What is the underlying reason for this change?
6. What does the term "playing field" refer to in the context of dryer operation? Explain how different operating conditions can influence this "playing field."
7. Describe how differential pressure control is typically implemented to manage dryer drainage. What parameters are usually monitored and adjusted?
8. Explain how blow through flow control works to manage drainage. What is the primary mechanism used to regulate the blow through rate?
9. What are the advantages of implementing dual monitoring of both differential pressure and blow through steam flow with selective controls?
10. In situations where high condensing loads and typically lower blow through rates are common, which of the two main control strategies (differential pressure or blow through flow) might be considered a less attractive primary control strategy, according to the text? Briefly explain why.

Answer Key

1. The primary purpose of controlling dryer drainage is to efficiently remove condensate and non-condensable gases from the dryer cylinders. This is important for maximizing heat transfer efficiency, ensuring uniform drying, and preventing operational issues like flooding.
2. Differential pressure in steam dryer cylinders is the pressure difference between the steam supply header and the condensate header. Maintaining sufficient differential pressure provides the driving force needed to push condensate out of the cylinders through the syphons.
3. Blow through steam flow is a continuous flow of steam through the dryer cylinders, beyond what condenses into water. It helps to remove both the liquid condensate and non-condensable gases (like air) that can hinder heat transfer.
4. Low speed stationary syphons are lightweight devices supported by a pipe connected to the steam joint and are oriented vertically downward in the six o'clock position. High speed stationary syphons are heavier, rigidly supported devices that require cylinder support for installation and are also oriented down in the six o'clock position.
5. An increase in blow through rate generally leads to an increase in frictional pressure loss within the syphon. This is because a higher flow rate results in greater friction between the moving fluid (steam and condensate) and the inner walls of the syphon.
6. The "playing field" refers to the range of acceptable operating conditions for the dryer section, characterized by combinations of differential pressure and blow through rate that ensure effective drainage. Different operating conditions, such as machine speed and steam supply pressure, can shift this optimal operating range.
7. Differential pressure control typically involves maintaining a set pressure difference between the steam supply and condensate headers using control valves. This ensures sufficient driving force for condensate removal, often adjusting based on the pressure in the condensate header.
8. Blow through flow control manages drainage by regulating the amount of steam allowed to pass through the dryer cylinders without condensing. This is typically achieved using a control valve in the blow through line, often adjusted based on measurements of the blow through rate or related parameters.
9. The advantages of dual monitoring with selective controls include additional operating information for improved troubleshooting and maintenance, additional comparative data for various grades and speeds, maximum flexibility to suit operational speeds, and operational back-up control system for increased reliability.
10. Blow through flow control might be a less attractive primary control strategy in situations with high condensing loads and typically lower blow through rates. This is because a low blow through rate may not be sufficient to effectively remove condensate under high condensing conditions, potentially leading to inadequate drainage.

Essay Format Questions

1. Discuss the interplay between differential pressure and blow through steam flow in achieving optimal dryer drainage. Analyze how manipulating one parameter can impact the effectiveness of the other and under what conditions one might be prioritized over the other in a paper machine drying section.
2. Compare and contrast the different types of syphons discussed in the text (low speed stationary, high speed stationary, and rotary), focusing on their design characteristics, typical operating speed ranges, and the factors influencing their selection for a particular dryer application.
3. Explain the concept of the "playing field" in dryer operation and analyze the factors that can cause shifts or changes in this optimal operating range. Discuss how understanding the "playing field" can help optimize dryer performance and troubleshoot drainage issues.
4. Evaluate the two primary control strategies for dryer drainage discussed in the text: differential pressure control and blow through flow control. Discuss the advantages and potential limitations of each strategy and under what specific operating conditions each approach might be most effective.
5. The text highlights the benefits of dual monitoring of differential pressure and blow through steam flow. Elaborate on these advantages, explaining how having data on both parameters can lead to improved control, troubleshooting, and overall efficiency in the paper drying process.

Glossary of Key Terms

Condensate: Water formed by the condensation of steam within the dryer cylinders.

Differential Pressure: The pressure difference between two points in a system, in this context, typically between the steam supply header and the condensate header of the dryer section.

Blow Through Steam Flow: The portion of steam that enters the dryer cylinder and passes through without condensing, carrying away condensate and non-condensable gases.

Syphon: A device located inside the dryer cylinder used to remove condensate.

Stationary Syphon: A type of syphon that remains in a fixed angular position within the rotating dryer cylinder.

Rotary Syphon: A type of syphon that can adjust its internal position relative to the rotating dryer cylinder.

Pressure Loss: The reduction in pressure as a fluid (steam or condensate) flows through a system component, such as a syphon.

Playing Field: The range of acceptable operating conditions (combinations of differential pressure and blow through rate) that result in effective dryer drainage.

Steam Supply Header: The main pipe that delivers steam to the dryer cylinders.

Condensate Header: The main pipe that collects the condensate removed from the dryer cylinders.

Non-Condensable Gases: Gases (such as air) present in the steam system that do not condense into liquid water and can impede heat transfer.

Thermocompressor: A device that uses high-pressure steam to entrain and compress lower-pressure steam, often used in blow through systems.

Orifice Plate: A thin plate with a hole in it, used to restrict flow and create a pressure difference for measurement or control.

Control Valve: A valve used to regulate the flow rate or pressure of a fluid in a system.