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October 7, 2019

Pressurized Condensate System for Industrial Plants Part 1

Part 1 — Pressurized Condensate Systems for industrial steam and condensate systems that have a tremendous benefit to increase the plant’s steam system thermal cycle efficiency.  The videos are in three parts; and this is part one.  Also, technical papers and articles are on our web site to help plant engineers understand all the benefits to the pressurized condensate system.

Pressurized condensate systems can provide plants with a minimum of between 5% 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.

My name is Kelly Paffel, Technical Manager for Inveno Engineering, LLC. Today I would love to talk about pressurized condensate recovery systems, the solution to increasing the steam thermal cycle efficiency. One of the things that I’ll be talking about in these presentations is steam system thermal cycle efficiency. A benchmark that all plants must know is what is their steam system thermal cycle efficiency. This will be a series of pressurized condensate recovery discussions.

Pressurized condensate systems. What will be covered is why recover condensate? Simple. Standard condensate systems, which are utilized in most plants. And what is a pressurized condensate system? When we talk about pressurized condensate systems, what really are we talking about? Of course, the cost benefits and how to implement it and what type of process applications can adapt to a pressurized condensate system, and what components are needed to accomplish this opportunity.

Steam and condensate energy. Steam is comprised of two types of energies, simple, latent and sensible energy. The liquid, better known as the condensate, contains the sensible energy from condensing of the steam vapor or latent energy has been released to the process. So latent energy is released, then we give the latent energy up to the process and condenses down into the condensate. We don’t recover the sensible energy in the process because it’s a low amount of energy and it would take too much heat transfer area to recover that. So we anticipate the plant will recover the condensate back to the boiler plant with as much BTU as possible.

Condensate contains as much as 16% of the energy. So in here, this condensate sitting in this tank, here, contains roughly about 16% of the energy. Therefore, we can’t afford to waste this energy today.

And what causes condensate losses? We talk to plants all the time. You know, your benchmark should be 90% return, which we’ll talk about. And the problems with not returning condensate, pumps, piping, production issues all contribute to the loss of the condensate. As you can see, condensate, the flash coming out if a pump’s cavitating, causing us not to return to condensate back to the boiler operation.

Condensate system optimization, one of the top five optimization items for the steam system, is recover the condensate. You know, today the benchmark’s about 90% or higher. Now, if there’s direct injection applications out there in the process, of course we’re not going to get 90% return. No. We have plants that are getting 96% return and they want to do better. So your benchmark is 90% or higher if you do not do direct injection. The other thing is elimination of atmospheric system, if possible, and going into the pressurized return system.

A general note, condensate recovery. Condensate, therefore, needs to return to the boiler plant operation in order to improve the steam system thermal cycle efficiency. Reduce the following: not energy efficiency, but reduce energy. Chemical costs, make up water costs, sewer system disposal costs, and meet environmental regulations.

Today, the thing is, is that what we did in condensate systems five years ago, it’s not what we do today. You know, the market’s changed, technology has changed, and we have to change also. So the change is to go to the pressurized return system if possible. So today industrial plants are changing to the pressurized condensate system to improve the steam system thermal cycle efficiency, reduce the utility cost, and increase the profitability of the company. Plants cannot afford to just return condensate by atmospheric pump systems. So just returning by standard atmospheric pump systems isn’t increasing our steam system thermal cycle efficiency. It’s still doing what we did 20 years ago. Pressurized condensate system improves the steam system thermal cycle efficiency by reducing the wasted energy. And I’ll talk about the different components and what a standard system, the inefficiencies of a standard condensate system, and what the pressurized system does to recover that energy.

The pressurized condensate system, the system can provide 5% to 35% savings in fuel costs. And that’s very substantial. You know, 35%, can it be obtained? Yes. If the system can adapt to it, we have accomplished that. Compared to the conventional atmospheric vented condensate systems. And we’ll go through the calculations in the next series. The savings can be substantial. So we’re really looking, today, at pressurized condensate systems, if possible. And the other thing, the nice thing about pressurized condensate systems, they’re typically low cost for implementation. And most of the time less than a one year payback, which is very attractive to the plant operation.

And the condensate system classifications, there’s four classifications of a condensate system. Standard condensate systems, which are gravity or atmospheric. Condensate line pressure maintained at or close to zero PSI. Low pressure, 1 to 15 PSI. A pressurized condensate system is the medium pressure, 16 to 99 PSI. And the high pressure’s 100 PSI or higher. People say they have a high pressure condensate return system and they’re operating at 65 PSI. That’s not a high pressure. That’s a medium pressure. Medium pressure, 16 to 99 PSI.

Understanding a pressurized condensate system. The typical condensate system operates with back pressure due to the following: condensate line undersize, neglect the steam traps blowing steam into the condensate line. Of course, it’s going to cause pressure. So most condensate systems are running under some uncontrolled pressure. These items alone can cause pressure in the condensate system.

A pressurized condensate system difference. The difference is that the condensate return pressure is systematically controlled to a predetermined set point that is matched to the process peak performance level. So we maintain a pressure in the condensate system to a predetermined … We control the pressure in the condensate system and control it a number of different ways.

Condensate pressure in the system is controlled by dynamics of the system design. Essentially, if we do a cascade flash system, we’re controlling the pressure in that condensate system by the dynamics of the system. Controlled by a control system. Flash tank control system. This happens to be shown here in this picture, a tank system that has controlled pressure into the flash steam system, which gives us a controlled pressure in the condensate return system because a return system’s going back to a pressurized vessel that we do control.

The other thing is, is that process condensate systems will have different designs depending on the application. So down here, these are some high pressure process heating coils. Of course, we’re maintaining our pressures above [inaudible 00:09:11] point on the steam so we can return under pressure in the condensate system. Down here, these are some reboilers. Again, we can go into a pressurized system with a thermal compressor added into it. However, these are modulating loads and they have to come down here to a atmospheric system.

So in the next series, we’ll talk a little bit more about the dynamics of the systems and what has to be looked at to make the system work together with a pressurized system. Just don’t go out and implement the pressurized system without looking at the dynamics of it. So in the next series, you’ll see what we talk about in the systems and how to implement.