Steam System Optimization

The ability to achieve an optimal steam balance is a crucial aspect of Steam System Optimization, helping to improve the overall thermal cycle efficiency of any steam-production system. In any process plant that produces steam, carrying out a steam balance is the most effective way to enhance knowledge of the entire system, including steam generation, distribution, end users, and condensate-recovery systems. This foundational step is essential for optimizing and managing overall steam generation efficiently.

For instance, the valuable knowledge gained from developing or updating a steam balance can help process engineers to develop a road map that will allow the steam system to be used in the most efficient way. Such an effort also provides essential insight that can increase the overall thermal-cycle efficiency of the steam-generation system.

Ideally, every plant should strive to achieve the highest possible thermal-cycle efficiency; the steam balance provides the information needed to achieve this objective. An optimal steam balance ensures that the end users — that is, the steam-consuming processes — can consume the correct amount of energy at the correct steam pressure and temperature, with the required steam quality. A system that has achieved an optimal steam balance has no energy losses that might otherwise occur from steam leakage, excessive low-pressure steam venting, flash steam venting and condensate loss.

Establishing the correct steam balance can be very challenging because so many different dynamics are at work in any given steam system. These include modulating steam loads, variable production times, un-accountable losses, insulation inefficiencies, turbine operation and more.

Steam venting to the atmosphere is one the largest waste of energy in any steam and condensate system. Inveno Engineering,LLC engineering team members have the experience with modern technologies to eliminate the need to vent steam in any plant operation. Inveno Engineering LLC has enabled more than 1,000 plants to use today’s flash steam recovery, pressurized condensate systems, thermocompressors, and vent condensers to improve their steam venting and substantially reduce energy use.

Inveno Engineering LLC can help you integrate these technologies into your plants. With today’s competitive international market, all plants need to reduce operating costs, and lowering energy consumption can have a positive impact on the bottom line. A plant’s steam and condensate systems cannot afford to vent any utility steam, blow through steam, or flash steam to the atmosphere. An additional benefit of not venting steam is a significant reduction in emissions in the boiler operation.

Any steam venting from the steam and condensate system is the top reason for lost energy in today’s steam systems. Can this objective be accomplished? Yes. Many plants have accomplished the goal of not venting steam, and they were rewarded with a high steam system thermal-cycle efficiency.

Of course, lowering energy costs also makes the plant more profitable and better able to compete in today’s international market.

The steam balance is always the first necessary part in any steam system optimization and management program. The valuable knowledge gained from a steam balance can help plant engineers use the steam system in the most efficient way, and this knowledge also provides essential insight that can support efforts to increase the steam system’s thermal-cycle efficiency. The perfect steam balance has no energy losses from steam venting, excessive low-pressure steam venting, flash steam venting, condensate loss, and so on.

However, a high percentage of plants do not have a steam balance program, which typically leads to the following results:

• flash steam being vented;
• utility steam being vented to meet the process steam demands;

 

blowthrough steam vented from the following:

• process blowthrough,
• bypass valves opened, and
• steam trap station failures; and
• low-pressure nonutilized steam.

 

Ideally, every plant should strive to achieve the highest steam thermal-cycle efficiency possible. The steam balance provides the information needed to achieve this goal.

With today’s energy pricing and the need to reduce emissions, a plant’s steam/condensate systems cannot afford to vent flash steam to the atmosphere. The modulating steam system’s operational design requires the condensate to be recovered by a gravity (0 psig) condensate system.

A typical system will incorporate a condensate receiver that allows the flash steam to vent to the atmosphere. The venting of the flash steam ensures the condensate receiver is never pressurized. To prevent the flash steam loss to the atmosphere, plants install devices such as “flash steam vent condensers” in the flash steam vent line.

Depending on the installation costs, plants will typically recover the cost of a flash steam vent condenser within ten operational months. The cost-saving benefits a flash steam vent condenser offers include allowing a plant to recover the flash steam energy and to use that energy to heat a fluid for a process. The other benefit is reducing emissions: by recovering the flash steam energy, the boilers will have to produce less steam, reducing emissions from the boiler operation.

Flash Steam Recovery Systems (Modulating Steam Conditions)

If the condensate/flash steam (two-phase flow) is being discharged from a modulating steam/condensate process, it means the process application has a steam control valve modulating the steam to the process and the control valve can operate from zero (closed) to 100 percent (full open) and anywhere in between. (See Figure 1.) The steam pressure after the steam control and before the process heat exchanger can vary (P2 reading) depending the process conditions. The pressure at P2 can range from full line pressure that is being delivered to the steam control valve (P1) all the way down to zero (0) pressure.

Pressurized condensate systems can provide plants with a minimum of between 15% and 35% savings in fuel costs when compared to a conventional atmospherically vented condensate system. That is a tremendous opportunity for facilities, since fuel prices have gone up and are expected to increase even further. The pressurized condensate system is not a luxury; rather, it is a necessary component to maximize and increase the steam system’s efficiency. Unfortunately, not all steam plants or steam applications can implement a high-pressure condensate return system. Therefore, proper preliminary engineering assessment, design review, and knowledge of the application are necessary to ensure a successful condensate system. In the examples that are included in the technical paper, we achieved an energy savings of $ 226,700.00 by implementing a 50 psig pressurized condensate system. The project was implemented at a cost of $305,400.00, yielding a 1.3-year payback.

WHAT IS A PRESSURIZED CONDENSATE SYSTEM?

Pressurized condensate recovery systems operate continuously at a pressure above 15 psig, and the condensate recovery system is not vented to the atmosphere. The pressure in the condensate system is sustained by the dynamics of the system or a systematic control process loop. Typical condensate systems operate with backpressure because their condensate line is improperly sized for two-phase flow and because plants neglect steam trap stations blowing steam into the condensate line. These items alone can cause unwanted and uncontrollable pressure in the condensate recovery system. A pressurized condensate recovery system differs in that the condensate return line pressure is systematically controlled and managed to a predetermined set point that matches the peak performance level of the steam system process and integrates into the dynamics of the steam balance.

Four classifications of condensate systems are used in plants today:

1. gravity or atmospheric (condensate line pressure maintained at or close to 0 psig),
2. low pressure (1 to 15 psig),
3. medium pressure (16 to 99 psig), and
4. high pressure (100 psig or higher).

  Pressurized condensate system technology is not new in the steam world; these systems can be documented back to 1941. Though the technology may be considered old, it has been overlooked over the years due to relatively inexpensive fuel prices. As fuel prices have risen and, with them, the need for optimization to reduce overall operational costs, industrial plants are paying more attention to these systems, because they have proven to be a significant way to decrease expenses. Pressurized condensate systems are considered one of the top three items to optimize a steam system with a very attractive payback for the investment.

WHY STEAM PLANT OPERATIONS NEED TO IMPROVE THE STEAM SYSTEM THERMAL CYLCE EFFICIENCY

The traditionally, business people see steam simply as a source of heat and power for producing the final product. Today’s cost-conscious industrial professionals are also seeing it as a source of potential to increase the corporation profits. Achieving a high steam system thermal cycle efficiency will increase profits by an average of 15 to 21%.

A high percentage of the steam systems at use in industrial applications today are operating far below world-class standards in steam system thermal cycle efficiency. Industry professionals are finding that even small improvements made to their often-ignored steam systems can yield big benefits in operating reliability, efficiency, and can contribute generously to an organization’s bottom line.

In today’s competitive market, we cannot ignore the achievable savings in improving a neglected steam system and reducing wasted steam energy. An average industrial plant will have fuel budget of $ 3,500,000.00 and just improving the steam thermal cycle efficiency by only 10% will net a savings of $ 350,000.00 for the plant bottom line.

Using less fuel in the boiler operation to produce steam will lower the emissions that are emitted from the boiler operation. Therefore, not only energy is reduced, but emissions are reduced, thus improving the plant environmental impression.

WHAT IS STEAM SYSTEM THERMAL CYCLE EFFICIENCY?

What is steam thermal cycle efficiency, and what affects the efficiency? These are questions that all steam system managers must be able to answer.

The average steam system thermal cycle efficiency is 56.3%, which means that 43.7% of the energy consumed in boilers is wasted or lost. It is impossible to use all the energy input into the boilers. Therefore, the operation will have a few acceptable losses, but a high percentage of losses can be prevented or eliminated. Some plants may be more efficient, and some plants may be less efficient. But not until the steam system is benchmarked will plant management know how much energy is being lost in the steam system.

Insulating steam lines, condensate lines and process equipment can dramatically reduce energy consumption and emissions. Inveno’s Insulation Assessment program evaluates the condition of your existing insulation and helps you determine which type of insulation you should select, how to install the insulation, and how to service the insulation to optimize energy efficiency.

Steam thermocompressing is one of many ways a plant can improve its steam venting and thereby increase plant efficiency. With more than 30 years of experience with thermo compressing steam, we can help you determine what steam must be thermocompressed, which intermediate pressure to deliver the steam to, and how to balance the steam.

Vent condensers capture the energy from flash steam and deliver it to another heat source. Because they reduce fuel consumption, flash steam vent condensers have a payback period of less than a one year on most systems. We engineer the vent condenser to achieve the proper flash steam flow rates, heat sink flow rates, and pressures—and meet the appropriate codes—to ensure proper operation and efficiency.

With today’s high fuel costs, any boiler that produces more than 12,000 pounds of steam per hour will benefit from an economizer. Economizers take energy from boiler operations, combustion flames, and gasses and, rather than discharging that energy into the atmosphere, capture it for productive use. Two types of economizers are available, non-condensing and condensing. Non-condensing economizers are relatively low cost and deliver efficiency gains of roughly 82 percent. Condensing systems are more expensive but can bring boiler efficiency above 94 percent. We can explain the pluses and minuses of each option for your operation to allow you to capture energy and improve efficiency in the most cost effective manner.

Water chemistry often causes boilers to develop sediments. Continuous and bottom blow down systems remove these sediments. All boilers need continuous blow down heat recovery to extract the energy from the boiler water before discharging it into the waste system. Larger boilers also require bottom blow down heat recovery. Many systems are available and making the selection can be confusing. Inveno’s engineers have installed hundreds of these systems. Let us help you determine the most effective system for reducing energy loss for your boiler system.

All heat transfer systems require 100 percent steam quality unless the plant specifies otherwise. Lower steam ratings reduce heat transfer performance—and negatively impact your final product. Inveno’s engineers can measure your existing steam quality, determine the cause of any deficits (e.g. insulation, condensate, or piping) and develop a road map for correction to meet your steam and product quality goals.

Steam flow measurement provides a critical gauge of steam system performance. Maximum and minimum flow rates, piping configuration, and pressure tell you the efficiency of your plant and how much energy is being consumed. Inveno can work with any measurement solution manufacturer to give you your choice of options. The result? You achieve the most precise measurements so you can make better decisions about how to manage your system efficiently.