We are pleased to report that an article authored by our Hydrogen Sales team has been published inPowerWatch India, May 2012 issue. We reproduce the article below for easy reference.
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With the advent of modern and technologically advanced equipment in the power sector, specifically higher capacity Turbine Generators, Hydrogen gas is increasingly being used for cooling purposes due to benefits such as lower drag coefficient and excellent heat removal capability.
Availability of Hydrogen is critical, to the extent, that few hours non-availability will lead to several crores lost in costly shut down. Increasingly Power companies are setting up their own Hydrogen Generation plants within their premises to avoid issues with supply of Hydrogen through outside vendors such as quality and supply interruptions. Also, as one can expect, with the power market preferring to go for larger capacity generators, the stakes attached to “good quality hydrogen” are also higher.
In the past, it was almost certain that the Hydrogen Gas Generation plant would be kept a significant distance away from any critical power plant equipment due to the concerns with the safety of Hydrogen gas and also concerns with storing large quantities of Hydrogen gas either in large storage tanks or in several cylinders. In power plants, Water Electrolysis method of Hydrogen Generation is the most preferred technology, scoring high due to a fine balance in the size of the Hydrogen Gas plant required and the capital expenditure thereof. Other technologies are far more expensive.
In this article, we wish to assess how Hydrogen is ultimately delivered to the point of use, i.e., the Turbine Generator where Hydrogen is required. We must consider that there are two distinct needs of Hydrogen in a power plant, in respect to volume of Hydrogen required. First, let us consider the lower volume. On a daily basis there are leakages of Hydrogen from the TG that must be made-up and there is a drop in purity due to ambient ingress. This must be made up with dry and pure Hydrogen. However, make-up requirement on a daily basis is fairly small. For the second application, bulk volume of Hydrogen is required during the initial fill of the TG or a refill after maintenance has been done on a TG.
This is by far the most widely adopted method in Indian Power plants for the last few decades, and it continues to be adopted by “un-informed” modern power plants, UMPPs and Supercritical Power stations for their Hydrogen delivery.
In this method (see image 1), Hydrogen Generation plant is built at a remote site and an operator fills Hydrogen Gas cylinder at 150 kg/cm2 pressure for around 8 to 12 hours in a day (as only daylight working is permitted by Controller of Explosives). Trolley full of cylinders is delivered to the individual TG buildings where empty cylinders are exchanged with the filled ones. Another operator at the TG building then has the job of changing cylinders on almost a daily basis as per the requirement of the TG.
A more practical and safer method is delivery of Hydrogen through a fixed pipeline. In this particular scenario, while the Hydrogen Generation plant is still built in a remote area, the Hydrogen is stored in bulk either in large storage tanks or in a fixed cylinder cascade. This practice is in use at a few Power plants across India with very good success. This method was introduced by the Russian power equipment suppliers and continue to be in satisfactory use past 30 years .
The Hydrogen Generation plant is installed near to or even on the zero level of the TG building and is directly hooked up to the cylinder manifold to allow for direct supply of Hydrogen to the TG (see image 2). In order to cater to the bulk Hydrogen requirement, the Hydrogen gas is also taken to compressors for cylinder filling. However, the compressors are sited some distance away due to the safety requirements of clearances etc. Furthermore, cylinders are required to be filled on rare occasions, when the stock is to be replenished.
Now we will consider these delivery methods and rate them along various parameters to help understand why increasingly the world is moving to online hydrogen generation and delivery at TG unit.
Safety of a Hydrogen Generation plant is foremost due to the explosive nature of Hydrogen gas. We need to take into account several factors when evaluating safety such as inventory of Hydrogen in the Generation plant, possibility of Oxygen and Hydrogen gases mixing thereby resulting in explosion. We also need to take into account the hazardous nature of the technology used for producing Hydrogen and locate the Hydrogen plant accordingly on the power plant site.
Quality is a measurable parameter and one can measure quality of the Hydrogen Generation plant along the following key characteristics:
– Life of critical parts
– Probability of failure
– Demands for maintenance
It is also desirable for the Hydrogen plant to conform to leading quality standards such as CE certified, UL listed and where possible conform to ISO specifications for Water Electrolysis (ISO-22734).
Hydrogen is critical to the operation of the Hydrogen-cooled Turbine Generator and hence the reliability of the Hydrogen plant is very important. It is desirable for the power company to get a product that has low maintenance requirement as well as very low possibility of failure. In built redundancy shall be a bonus.
The cost of hydrogen is simply cost of power used. For a power plant with a 600 MW TG this daily cost is just Rs. 210/-. Now if much manpower and trained operators are used their daily usage impact can be up to Rs. 1000/- per day. Best is that Hydrogen unit must be capable to run un-manned.
While the Hydrogen Plant will be a small factor of the total cost of the Power plant, it is possible to optimize the capital expenditure. This is possible by “right sizing” the equipment in line with the actual Hydrogen required by the power plant on an annual basis and also to reduce the costs associated with the building and also storage requirements of Hydrogen.
If the Hydrogen plant is planned to be operated 8-12 hours a day in order to abide by Indian rules for cylinder filling during daylight hours only, obviously the size of the Hydrogen plant will be double than what is actually required. However, if modern technologies and piped delivery is adopted, the Hydrogen plant can be operated hassle-free round the clock and the size considered can be closer to the actual requirement.
It is obvious that the power company will want their Hydrogen plant to be easy to operate. However, many of the current technologies are far from “easy-to-operate” due to requirement of hazardous chemicals and also constant monitoring to prevent unsafe operation.
Daily filling of cylinders and transporting the gas is not what can be considered easy and hence, alternative methods such as piped delivery of Hydrogen gas is definitely an “easier” way to deliver Hydrogen.
Scheduled maintenance requirements should be as low as possible to allow for uninterrupted operation of the Hydrogen plant.
Now for filtering the essence of the article the following table is developed for comparative study which makes the picture clearer. We have rated these various considerations across the different methods of delivery and this is given in the table below.
The above modern methods of delivering Hydrogen directly to the TG and increasingly by means of robust pipes is a way that has become possible with modern Hydrogen Generation technologies such as solid polymer electrolyte (membrane type Water Electrolysis) which is not only inherently safe, but also eliminates concerns with older technologies such as possible mixing of Oxygen and Hydrogen gases.
World’s leading Membrane type Water Electrolysis Hydrogen Generator is Proton OnSite, USA and it’s partner in India – MVS Engineering Ltd. Proton equipment is operating at over 200 power plants across the world and in various power plants in India including NTPC. Several more power plants in India are now adopting this safe technology and many projects are now underway.
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Proton Onsite designs and manufactures Proton Exchange Membrane (PEM) electrochemical systems to make hydrogen from water in a zero pollution process producing safe, pure, reliable onsite hydrogen to meet today’s global hydrogen requirements. Proton has been developing and manufacturing world-class electrolysis systems since 1996, with thousands of units deployed world-wide, on every continent. With a reputation for building robust, reliable, and safe systems, federal, state, and commercial partners repeatedly seek the creative solutions that Proton OnSite has proven it is capable of delivering. For more information, visitwww.ProtonOnsite.com.
MVS Engineering is a turnkey supplier of Gas generation equipment, Air and liquid drying equipment. MVS was founded in 1977 and has supplied nearly 7000 Skid mounted units worldwide. Read more about the company in the About Us section of our website.
Specifically for Proton OnSite’s products, MVS is Proton’s engineering partner in India for sales, service and turnkey supply of engineered solutions. Whether you require a single Hydrogen Generator or a complete Hydrogen solution including compression, bottle filling etc., MVS is your one stop provider.