An alternative fuel project is a complicated endeavour. Among the numerous issues that must be considered, some will inevitably take a lower priority. Selecting which airlock valve to use on the system should not be one of them.

The consequences of the valve choices will directly affect the success of the project in several areas including:

  • Cost effectiveness;
  • Production output;
  • Safety and fail safe back-up systems.

The purpose of this article is to highlight some of the most important things to consider when selecting valves for your project, as well as open the door to alternative ways of using fuels to create heat for various processes.

The quality of the seal

The first consideration when selecting an airlock valve for your project should always be what quality of seal your project requires. It should also include what the implications of excessive air entry into the system are.

There are of course many valve options and each option has its advantages. Not all are created equal when it comes to sealing under difficult operating conditions.

Over the years, as Plattco has worked on alternative fuel projects, it has seen that the negative consequences of a seal that is undependable or hard to maintain are frequently underestimated. As a result, systems suffer increasingly diminished output and significantly inflated operating and maintenance costs. When Plattco has been consulted to solve these problems, the payback on a reliable seal has often been virtually instantaneous.

Double Flap Airlock Valves®

Plattco designs and manufactures Double Flap Airlock Valves and believes that they are the best at providing a seal that will last and can be easily renewed in difficult applications. Throughout the years it has conducted numerous tests and found that the leakage rate of rotary valves and other airlock options can be as much as three times greater than that of a Plattco Double Flap Airlock Valve.

Process and material details

In every system there are important details about the materials being processed that are crucial to determining what valves to choose. Although the incredible diversity of systems and materials makes it impossible to list all considerations, here are the three that Plattco feels are the most important:

  • Temperature – Valves in these systems can see very high temperatures. This can affect sealing capability and can cause warping of the valve over time. It is imperative that the valve be constructed of an alloy that will withstand the maximum design temperatures including those that might occur during upset conditions.
  • Particle size – Variable sizes of the feed material in these projects provide a challenge when specifying the valve. Jams and blockages can be very disruptive and costly. A good rule of thumb is to ensure that the valve inlet and outlet size be at least three times the size of the largest single particle that will be passing through the system.
  • Material properties – Often the materials being conveyed can be sticky or stringy and may have a high moisture content or a tendency to bridge. In such cases the valves need to have a full throat opening and minimal ledges where material can build up in the conveying system.

The role of valves in protecting the system

Another crucial consideration when selecting valves is what role they can play in protecting the system in case of major upset. The diagrams below are examples of systems where the valves play an important function in minimising potential damage.

In Figure 1 temperature sensors are typically installed in the chute below the lower slide gate and will automatically close both slide gates and the Double Flap Airlock Valves when they detect high temperatures. In this example, properly installed temperature switches combined with the unique qualities of the valves and slide gates, provide protection against damage that could be caused by a fire below the feed valve.

In Figure 2 if there is a loss of airline pressure which control the actuation of the valves and slide gates, the system will make sure the valves close by utilising a reserve air tank that contains enough air to close all the valves. The reserve tank will supply air only when there is a drop in airline pressure below whatever pressure the switches are set at - in this case 60 psi.

Experience and flexibility

Another crucial consideration is the experience of the valve supplier and the flexibility they have to fine-tune their product to meet your system requirements. Because Plattco designs and manufactures double flap valves, it is naturally prejudiced in their favour, but it knows that all types of valves will work in certain applications. The question is, 'what will work for you?'

Plattco has designed and continues to design valves for some of the most difficult applications imaginable. As a result of its experience and knowledge it has been able to develop a very powerful product line.

Plattco has found that to maximise the performance of its customers' alternative fuel systems, it needs to customise its equipment more often than not.

The interaction of the system design, with highly variable material, requires a sophisticated understanding of valve capabilities, along with the ability to adjust the valve design accordingly, so your system will operate at its peak performance.

Other alternative fuels processes

Another thing to consider when looking at using alternative fuels in lieu of fossil fuels to create heat is a gasification process. Alternative fuels can easily be converted into bio-fuels or electricity through a simple stand-alone gasification process which requires much less capital cost than, for example, a pet-coke processing system. The valves used on gasification processes are also very critical, because the process must not allow oxygen to enter into the system. There are many types of gasification processes available and there is a large push to move these projects forward because they are proving to be more efficient than conventional combustion methods for alternative fuels. They also often require fewer pollution controls.

Summary

Plattco Corporation has been manufacturing high quality double flap airlock valves and slide gates for over fifty years. Its products are used for feed and discharge in dozens of industries throughout the world. It has created many innovations and is the holder of a number of patents in dry material handling valves. Plattco has provided solutions to valve needs in many alternative fuel projects.

The choice of valves is not the most exciting subject when planning an alternative fuels project. Envisioning lower costs and increased efficiencies is far more compelling. However, the valve choice will be one of the most important decisions you will make in realising your vision. Every project is unique and no prescription can cover every choice. When designing your next alternative fuels project, take the time to carefully take into account several considerations such as these:

  • How important is the seal in your process and how will you maintain it? Standard off-the-shelf valves may be woefully inadequate to achieve the system performance you want.
  • Your process and the materials you use will dramatically affect the performance of the valve. When you are making your choice, consider the details carefully. It will be worth it.
  • The valves you choose can be an important element in your safety failsafe systems.
  • Your system is unique. Choosing a supplier that has the experience, reliability and sophistication to match your needs perfectly is the intelligent choice.
  • Gasification should be considered for replacing fossil fuels with alternative fuels. The valves in these processes are also critical.