The evolution of the combined cycle power plant- I

Published on: 

This is the first of a two-part series

Today the world has available a large and very efficient green natural gas burning gas turbine and steam turbine combined cycle (CC) power plant to generate Tesla electric power. There have been many twists and  turns, starts and stops and ups and downs to get there.  Many dedicated engineers were involved.  It has been a rocky road to travel, but here we are.  General Electric seven months ago in France broke the World record in power plant efficiency when its latest 9FA gas turbine CC  power plant burning natural gas recorded the efficiency to be a whopping 62.22 % when generating 605 MW.   At the time of the announcement GE stated that an efficiency of 65 % and higher will be reached in three short years. There are significant gas turbine improvements coming such as the use of CMCs.

Lee S. Langston in the just out March 2017 issue of ASME Mechanical Engineering Magazine makes a bold statement in his series As the Turbine Turns “Electric Power and Natural Gas Synergism” when he writes “This proven performance makes CC plants the most efficient heat engines in mankind's history”.  He goes on to say that the gas turbines is most suitable for peaking, mid range and base load operation.  He talks about how clean burning they are using natural gas fuel.  He also says that these plants can be installed quickly at half the cost of coal plants and one fifth the cost of nuclear plants. The CC emits far less CO2 than the coal plants as Lee points out. He mentions that the US (and I say other parts of the World) now has an abundance of natural gas because of the development of recent shale fracking.  Also I might add that our sweet crude oil production is way up because of  fracking.  North America will become oil and gas independent soon with the promise of the XL pipeline from Canada, the cross over Dakota pipeline and the change in the Mexican laws allowing outside companies to drill there in partnership with Pemex.

I am now over 92 and have lived through the development of the efficient CC having graduated from the University of Arizona in 1950 and then joining General Electric testing the first El Paso Natural Gas Company's 5000 HP GT pumpers.  I then supervised the the installation of several of these units in Arizona before being assigned as a gas and steam turbine application engineer in Houston, Texas.  I became personally acquainted with many of the pioneering GE gas turbine slide rule engineers.  I was part of the evolution of the CCs as will be presented.  Because of my background my perspective is  founded on my experience with GE.  However Westinghouse also played an important part in the evolution of the CC as will be discuss.  I might also say that there is much information about the industrial gas turbine on the internet written by historians and professors. They give many useful facts and figures but do not know the nitty gritty of the matter as to why things happen and have not gotten their noses rubbed into the ups and downs of happenings.

First Real Gas Turbine

Let us start from the beginning with our CC story.  Brown Boveri Company (BBC) by 1930 had developed the velox boiler and there was a French engineer by the name of Eugene J. Houdry who was hired that year by Vacuum Oil company, later to become Sun Oil Company (Sunoco), to develop a new process of cracking crude oil to make high octane gasoline and other petroleum products.  He did so  with a new process named after him and knowing about BBC'c vortex boilers ask BBC to design and build Sunoco a new compressor – expander train for a pressurized cat cracker.  It cost a lot of money for an electric motor to drive the air compressor that potentially could be saved.

Using Sunoco data, BBC responded and said they could build a single shaft train consisting of an axial flow air compressor with a compression ratio of 4.2 and an axial flow flow expander.  Their analysis showed that extra power was available with the 1150 degree F entrance temperature to the expander.  Therefor they  added a 1000 KW  60 hertz generator to the train through a speed reducing gear.  Actually 900 KW was produced when the unit was placed in operation.  The successful Sunoco operation marked the first actual gas turbine by by definition.

First BBC Stand Alone Gas  Turbine

BBC having the experience and know how of the velox boilers and the Houdry units in toe, in 1937 decided to design and build a stand alone gas turbine.  They build such a unit and it ran for the first time in mid 1939 developing 4000 KW at a little over 17 % efficiency with a 1350 degree F TIT burning distillate.  This event marked  the beginning the the gas turbines as we know them today.  The unit was very large,  bulky and heavy.  It had a huge single combustor mounted over the compressor and turbine sections.  Engineers from all over the World came to Switzerland to see it run.  The US engineers said it was far to big and heavy to ever be made to power an airplane.

There were three engineers who were most favorably impressed with the new gas turbine.  The first was Sir Frank Whittle of England and the second was Hans von Ohain of Germany.  These two engineers independently, not knowing what the other was up to, shrunk the BBC unit and made a jet engine out of it to power the first jet fighter planes. The rest is history.

First United States Industrial Gas Turbines

Who was the third engineer?  He was a famous General Electric steam turbine engineer whose name was Glenn Warren.  He headed up all of GE's steam turbine designs and business.  He thought the place to start was an industrial gas turbine for a railroad locomotive.  He, with the help of the American Locomotive Company (Alco), laid out an arrangement on paper for a gas turbine electric (GTE) locomotive.  The second world war came along and Glenn had to temporarily shelf his gas turbine plans.  He had to concentrate on developing and making turbo super chargers for piston plane engines and later to make the first US jet engine patterned after the first Whittle engine.

After  WW II, in 1947, Glenn dusted off his GTL study and asked Bruce Buckland,  Alan Howard and others  in GE Steam Turbine work to design and build a 4500 HP single shaft industrial gas turbine suitable for a railroad locomotive using steam turbine design practices.  This unit was called the heavy duty frame 3.  Bruce had previously designed the first axial flow compressor for the GE TG100 turbo prop engine in Schenectady.  This project was transferred to Lynn.  Bruce and Alan stayed in Schenectady to develop the first locomotive gas turbine.

GE built 2 prototype 4500 HP units. They had an efficiency of about 17 per cent.  The first unit was used to build an Alco gas turbine electric (GTE) locomotive.  This unit was sent to an Eastern railroad for a few months and then transferred to the Union Pacific Railroad Company (UP) for extensive testing (1948 to 1949).  UP asked GE/Alco to furnish them a batch of 25 of these GTE units burning bunker C oil which was very cheap at the time.  Bruce Buckland and his team solved the problem of treating the bunker C by washing the nasty stuff with water, centrifuging it and adding epson salt to neutralize the corrosive vanadium pent oxide so the turbines could run about 5000 hours before the combustion liners and turbine blading had to be replaced because of hot corrosion.  Then UP ordered another batch of  30 of the 8500 HP GE /Alco units which were called the “Big Blows” by UP.  They were rated at 6000 feet elevation and 100 degrees F inlet.  At 1000 feet and 80 degrees F the unit would produce about 12000 HP.  This was called the Frame 5 unit.  After about 16 years UP had to abandon all of their gas Turbine locomotives because the price of bunker C jumped sky high when the refineries found a was to crack the gummy stuff to make gasoline out of it. Westinghouse also built two 4000 HP gas turbines in 1949 for railroad use but did not get any more orders.  The first burned distillate and the second tried to burn residual fuel.

The second GE  prototype frame 3 was sold to an electric utility company that had a 40 MW steam turbine generator plant.  It was located at their Belle Isle pant in Oklahoma City, Oklahoma.  The frame 3 exhausted to a feed water heater to improve the plant efficiency and produce more power.  The unit ran astonishingly well burning natural gas and in a few years the company bought a second unit. The first unit marks the first time in the USA that a gas turbine was used to generate electric power.  Another giant step had thus been taken in the evolution of the combined cycle.  This unit has received world wide publicity over the years.


US Transcontinental Gas Pipeline Gas Turbines

After the single shaft frame 3 was designed GE re designed the unit and made it into a two shaft 5000 HP regenerative cycle unit with a 25 % cycle efficiency for the transcontinental pipelines.  The regenerator was a large vertically standing tube type heat exchanger.  At the time natural gas cost about 20 cents per thousand cubic feet and therefore efficiency was not overly important.  The reciprocating engine efficiency was about 38 %.  However the maintenance costs of the reciprocating engine was very high compared to the gas turbines.

GE in late 1949 sold 28 of these units to The El Paso Natural Gas Company to pump natural gas from west Texas to California.  GE also sold 4 units to Northern Natural Gas Company and one to United Gas Company.  Then the orders stopped as the reciprocating engine companies improved their engines and made them larger.

Something had to be done.  The GE business was on the chopping block by corporate GE but Glenn Warren was able to keep it going.  He had faith in the industrial gas turbine.   GE then formed a sales team in 1952 in Houston, Texas in an effort to sell  more units to the transcontinental pipeline companies located there.  The Houston team was headed by Aaron E. Holland and Bill Strong.  I was asked to be the third member of the team to make pipeline flow studies with HP requirements and station locations and assist in telling the pipeline company how easy and quickly the turbines could be installed.  Another salesman was located at Dallas to call on Texas Eastern Pipeline Company in Shreveport near Dallas and I was asked to assist him.  His name was Jim Rockwell.  GE still had the salesman in El Paso, the manager of the office Mr. Vankirk, to call on the gas company there.

The effort payed off and GE soon received orders from Tennessee Gas Company, Trunkline Gas Company, Transcontinental Gas Company (Transco) and Texas Eastern Gas Company.  By this time the frame 3 gas turbine was up rated to 6700 HP and then shortly thereafter to 7600 HP.  GE also the Frame 5 to sell and Jim Rockwell was successful in selling Texas Eastern several of these lager 12000 HP single shaft units.  GE also sold 4 more derated 5000 HP units to El Paso Gas company.

Transco Gas Turbine Installation

Transco had 3 steam turbine stations each with three 5000 HP De Laval steam turbines and centrifugal compressor units located in Louisiana having been installed by Stone and Webster.  The efficiency of the stations was rather poor being about 22 %.  Transco needed to add horsepower to the center station and decided to install a gas turbine there.  I came up with the idea of exhausting the frame 3 gas turbine to a 600 psig – 750 degree F steam (station's system) waste heat boiler followed by an over sized feed water heater to heat feed water for all 3 steam turbines thus being able to get more power from the steam turbines and improve the station's overall efficiency.  Transco made GE furnish the boiler/heater with the gas turbine package.  GE was hungry for an order so accepted doing so.

The boiler selected was from Struther Wells.  It had horizontal extended surface boiler tubes. Thermodynamic wise the boiler and feed water heater worked very well,  but after operating a few months the boiler horizontal tubes started to leak badly.  GE had a problem so GE helped Struther Wells re designed the boiler, put in new tubes and added a circulating water pump.  This work was supervised by GE's field engineer John Uhr.  Thereafter the boiler worked just fine.

GE In and Out of the Boiler Business

This re design effort led GE to start making and selling boilers to go along with their gas turbines.  This seemed to be a good idea at first and in a couple of years they sold a supplementary fired boiler that developed severe problems.  Paul Lahay was placed in charge of the boiler effort.  In short order corporate GE closed down the GE boiler business.  Recently GE got back into the boiler business when it acquired Alstom from France and the boiler business came with the take over package.

All was not lost when GE dropped the boilers because GE learned a lot about boilers and the special designs need for gas turbine.  GE was also starting to learn more about how to design gas turbines for heat recovery.  Also a young salesman for the boilers was Douglas (Doug) M. Todd.  He was a go getter for the GE boilers.  He and I had many meeting together as he was eager to learn all he could about gas turbines and their application.  After the boiler close down he went to the GE gas turbine department as a salesman.  He rose quickly in the organization to become the sales general manager of all the GE gas turbines.  He became an expert on coal gasification and wrote many papers on this subject.  There was another spin off.  The name of the waste heat boiler was changed by GE  to “Heat Recovery Steam Generator” (HRSG).  This name stuck with the industry and is used to this day.  Another learning step had been taken by GE in the quest for the Combined Cycle only to go backwards a bit when it went in and then out of the boiler business.

Texas Eastern Combined Cycle Study

In 1955 Texas Eastern Gas Company wanted to look at the possibility of a combined cycle for their frame 5 gas turbines.  I was asked to make a study as to how to go about making CCs out of the frame 5.  I, at the time, came up with the idea of the two drum boiler, the second one of a lower pressure and temperature so that the boiler stack temperature could be lowered for better cycle efficiency.  An admission steam turbine was applied to accept the extra steam at the lower pressure and temperature and expand this extra steam to produce more power.

I presented the report containing steam charts and drawings to Texas Eastern and sent a copy to GE Schenectady.  Very soon thereafter I got a phone call from Jack Mangan of the GE gas turbine department.  He thought I had a  new and good idea with the multi drum concept and thought I should apply for a patent.  He sent me all the GE information an patents but I was not interested and only wanted to apply and sell gas turbines.  I must say though that this concept of using multi drums at two  steam temperatures and pressures was a big leap forward for the Combined Cycle.   However nothing came of the  study as Texas Eastern did not develop the CC.

This idea proved  to be another important step in the evolution of the the combined cycle but not many people know how the multi drum HRSG came to be.  GE grabbed the idea and ran with it. Westinghouse only sold a few gas turbines to the pipeline companies and was not a very big factor.