September 5, 2018

Venting Steam is the No. 1 Largest Energy Loss In the Steam System




My name is Kelly Paffel. I’m technical manager for Inveno Engineering, LLC, located in Tampa, Florida. We’re a domestic and international engineering firm focused on steam system.

I’m here today with Graham, our senior field engineer, and we want to discuss venting steam is the number one largest energy loss in the steam system.

Steam venting to atmosphere. With today’s competitive international market, all plants need to reduce operating costs and reduction in energy consumption. One of the major areas that can help increase your bottom line is steam venting.

Steam and condensate systems today cannot afford to vent any steam to atmosphere. No utility steam, no blow through steam, no flash steam can be vented to atmosphere today. It’s a substantial energy loss and a cost to the plant operation.

It is the major energy loss in a steam system. Venting is the number one major loss of energy in today’s steam system. You want to optimize the steam system, stop venting steam to atmosphere. There’s no reason to vent steam to atmosphere today.

Not only energy, but elimination of steam venting will help reduce emissions. Here’s an example here of a vent to atmosphere. And we always say venting steam, all it does is heat up the ducts. As you can see, the duct is flying [low 00:01:47].

Can steam venting be eliminated? Yes. In the part two of this segment, we’ll talk about the different ways to eliminate steam venting.

Can this objective be accomplished? Yes, there are many plants that have accomplished the goal of not venting steam, and the plant was rewarded with a high steam system thermal cycle efficiency. Of course lowering your energy costs, which makes a plant more profitable, are able to compete in today’s international market.

But to stop venting, change must occur. Steam venting is abnormal and not normal for the steam system.

Changes need to occur. Several reasons apply in vent steam atmosphere, but with changes in the steam system and the condensate system, a steam and condensate system today does not need to vent steam.

As shown here in this picture here, this plant here has no steam vents to atmosphere.

One of the things preventing steam venting is having a steam balance. Steam balance always the first necessary part in any steam system optimization and management program. A perfect steam balance has no energy losses from steam venting or excessive low pressure steam venting, flash steam venting, or condensate losses.

However, a high percentage of plants do not have a steam balance program, which has a typical end result of the following items. No steam balance? The end results are flash team being vented to atmosphere, utility steam being vented to meet process steam demands. Blow through steam vented from the following: processed blow through, bypass valves open, steam trap station failures, and low pressure non-utilized steam being vented to atmosphere.

Steam balance. The optimal steam balance ensures that all unit and users can achieve the correct volume of energy at the correct steam pressure/temperature with the required steam quality.

One of the things in the steam system the end user needs is 100% steam quality. The steam balance ensures that we have 100% steam quality.

An unbalanced steam system, the energy losses can be tremendous. As shown here in this picture here, this one vent from a unbalanced steam system has a steam loss of 12,784 pounds per hour, which a total energy cost per year of $402,726 and emissions down below here for CO2 and NOX.

Flash steam will occur in the steam system. The typical steam system will incorporate atmospheric condensate receiver. Flash steam is then vented to atmosphere. Where does the flash comes from? Steam traps in operation. As you can see, the condensate and the flash, depending on the pressure. Higher the pressure, the more flash will occur. If this flash steam is not recovered, then it’s vented to atmosphere.

There are systems such as modulating process steam, where the condensate system needs to operate at zero pressure to allow proper drainage from the heat transfer. Therefore, flash is required to be consumed or vented, and we want to consume it in a number of different ways, which will be in part two of this discussion.

Unfortunately, a large number of plants just vent to flash steam, which is a substantial energy loss in the system.

Here is a condensate tank being vented to atmosphere.

Now this has one vent, one vent has a cost of $76,584 a year, just one vent venting to atmosphere. So as you can see, stop venting steam has a pretty fast payback to it and a substantial reward in energy reduction.

Blow through steam is generated by several issues: processes that require a small percentage of blow through steam to operate the process correctly. A rotating dryer needs a percentage of blow through steam to help evacuate the dryer, but there are bypass valves around components like steam trap stations that allow steam from the steam headers to blow into the condensate system.

And of course we have steam trap system failures, which allow steam to blow into the condensate system.

A process blow through steam is required for a limited number of processes, mostly for rotating dryers. Bypass valves around components that allow steam to freely flow into the condensate totally unacceptable for the steam system operation.

And you can see here, the vent from the condensate tank system.

Blow through steam, example of energy losses from blow through steam is this here, this condensate receiver tank here.

This one small vent has an energy loss of $45,045 per year. Besides, it spews condensate up into the atmosphere, which falls back onto the roof and causes roof damage, and truth is presents a safety issue for the plant personnel.

Example of steam trap station failures venting the steam from steam trap failures. This one vent has an energy loss of $98,204 a year. Besides the CO2 emissions and the NOX. This is at a cost of $8.45 per a thousand pounds of steam, and this is a 2,125 pound per hour loss.

Another venting goes on is unbalanced steam header pressures. Steam header balancing can be a struggle with the different changes in the process steam demands changing to meet the production and requirements.

Processes are up and down, headers become unstable, and pressure control. Unfortunate, an easy way to stabilize a steam header pressure is to vent steam to atmosphere and reduce or eliminate the over-pressurized operation, which is seen here in this picture is a unstable header, the steam being vented to atmosphere, which causes a significant energy loss.

This one vent here, from the unbalance steam header has an energy loss of $87,050 a year based on a $4.90 per thousand pounds of steam, which has a steam loss of $2,101 pounds per hour.

Another venting that goes on is from the steam deaerator. The steam serves as a scrubbing agent to reduce the partial pressures of the gasses being removed. Gasses to be removed, so a percentage of steam is required to be vented with the gasses to ensure gas removal. This is a tray-type deaerator, and this is the venting that’s going on to remove the non-condensable gasses.

But this one vent here has energy loss of $14,494 per year. This vent should be set up on non-condensable testing for oxygen levels in the deaerator. Deaerator should be running at seven parts per billion oxygen without sulfite being added.

So to achieve the proper amount of venting, can have a significant energy reduction.

We definitely don’t want to be aggressive like this vent here off of the deaerator, which will set up a substantial amount of energy losses due to this aggressive venting, which does not have to be or does not require to be that aggressive. We just want a very small percentage of steam to travel with the non-condensable gasses to be removed out of the deaerator operation.

Safety concerns. When we vent steam, we can get high velocities and if the condensate tank has a lack of a Devon’s Loop from the condensate tank, then there’ll be a burping action occur as shown in this video. Condensate coming pouring down, which is going to be at 212 degrees or 100 degrees C and will set up a safety issue for anyone walking within the vicinity of this vent.

So not only venting has an energy loss but also presents a safety issue for plant personnel.

Tomorrow’s goal: stop venting steam, improve the operation, improve reliability, save energy, reduce emissions, and stop heating up the ducts as they fly over all these vents up here.

It’s a tremendous waste of energy, so tomorrow’s goal: stop venting steam, improve operation, improve reliability, save energy, and reduce emissions.

And that concludes our presentation on venting steam. The next presentation that we will present is the different ways or changes that can be implemented to stop venting steam to atmosphere. Our approach is we are your team members. We can do steam system assessment, steam balancing, steam system performance training, long-term impacts, upgrades, processing, improve reliability and safety for your plant operation. So if you have any questions, please email me or Graham. Our email addresses are located down below here, and we’d be more than happy to help you. Have a great day.