Wednesday, December 2, 2015

Generating Electricity with Natural Gas

Oil and gas embedded in shale rock formations had been locked in the rock. But the development of horizontal drilling and fracing techniques has made it economical to produce from these formations. That, coupled with more and more environmental impact restrictions, has made gas cheaper than coal. So more electricity is now being generated using gas. In addition to converting boilers from coal to gas and using gas turbines, I learned of a third way of creating rotating energy from gas from a bill insert from Midwest Energy --- big internal combustion engines.

Big Internal Combustion Engines

Midwest Energy October 2015 Bill Insert
Internal combustion engines have been used a long time to provide emergency power. Where I worked, there were a couple of semi-trailer sized buildings with an exhaust stack and the word CAT on the side. These were the emergency power generators for our computer servers. But engines are being scaled up to take advantage of cheaper natural gas to be the regular (non-emergency) power source for entire communities.

The following is from a bill insert.

Midwest Energy expanded their plant from 75 MW to 103 MW by adding three more gensets. Each unit weights more than 150 tons and costs nearly $5 million each. They were shipped from Wartsila's (both "a"s should have two dots over them) plant in Finland to a Houston port where they were transferred to flat cars to go to Hays, KS where trucks transported them the final 6.5 miles.

From Wartsila's genset page, I conclude the engine was a medium speed (720 rpm) with 20 cylinders in a V configuration, each with a 34 cm. bore. Browsing their web site indicates they started as a company that made large diesel engines for ships and have expanded into ship, hydro, bearings&seals and oil&gas products. Some info on the largest Wartsila (This would be marine use, not power plant, because it is low RPM --- 22-102.)

GE's Jenbacher 920 Engine
I found that GE also makes internal combustion solutions for power generation. This makes sense since they have been manufacturing internal combustion engines for their diesel locomotives for decades.

A video of a Honda engine being transported down a road (skip to about 1:00). Is this going to another natural gas generation plant? Six more Wartsila gensets being imported, this time through Duluth's Port Terminal.

MWM Diesel also makes diesel engines for gensets (specs). (Navistar seems to have bought the South American operations.) I assume the video was made in a plant in Europe. Even though some employees are wearing clothes consistent with being bought by Caterpillar in 2013, I didn't see a single employee wearing a hard hat. In an environment where there were a lot of cranes moving things around for assembly.

Screenshot 70,000 hp 2-stroke MAN B&W from 10 Biggest Engines
These engines are diesel, but it does show that the really big internal combustion engines are used for power plants as well as marine service.

Video of installing engines and generators into a building.
"A new Cat G3516H natural gas-fired generator set for 2 MW of power. The G3516H can simultaneously provide electricity for electrical loads and heat energy for thermal requirements. The system also uses waste heat to produce steam to create cool water for air conditioning. These byproducts of a CHP system make it more efficient than traditional energy systems" Article also has a video.
Cat Products posted via Cat Electric Power
Mexico's largest integrated steelmaking company produces 5 million metric tons of liquid steel annually for hot- and cold-rolled coil. Their challenge was met through Cat CG260-16 gas powered engines.
40 Cat® CG260-16 generator sets produce 160 MW of power for four separate plants at AHMSA.
Internal combustion engines running on natural gas were developed a long time ago to compress natural gas for transmission in pipelines.

Gas Turbines

Bird's Eye View
Gas turbines started in the power generation application as peaking plants. The graphs I have seen (e.g. KCET) indicate that we use 50% more power during the daytime than we do during the night. Equivalently, nighttime usage is two-thirds of our daytime usage. To quickly ramp up to generate the extra power needed during the day, peaking plants were developed. Basically, they hooked a jet engine to an alternator and stuck a 90-degree elbow and stack on the exhaust end of the turbine to shoot the gasses up into the air. Every time I drive south on I-57, I see the row of stacks of the pictured peaking plant north of Monee, IL. If you have ever set in an airplane at the end of a runway for takeoff, you know that they can spin up fast. Notice the peaking plant is really a bunch of smaller plants so that they can start up just the number needed to meet current demand. The down side of using gas turbines is that their operating expense is more than steam turbine plants. And I learned from Jason Munster's post that they should not run continuously month in and month out. I'm guessing bearing wear and metal fatigue due to prolong exposure to very high temperatures. I found some more details in a New Jersey posting --- in the summer when they had a week of 90+ degree days, they not only fired up their old, (small, dirty, expensive to run) coal plants, they had 48 of their 53 gas turbine generators running.

20150913,16 4796c
While I was trying to find Nelson, IL,  I noticed an interesting looking plant on the other side of a farm field. So when I was done with Nelson, I headed back to I-88 on a road that would take me east of this plant. The evening sun was not my friend, especially for the first picture.

Sauk Valley cropped from GE
But the sign was my friend. This Invenergy plant is a 600 MW combined-cycle plant using two GE 7F gas turbines and two GE A10 steam turbines. Obviously, gas turbines have been scaled up and made more reliable so that they can be part of a base power plant now. The initial plans were for twice the capacity, but one (or more, I lost track) bankruptcies interfered with those plans. From another GE press release, I learned "The plant will be connected to ComEd's 345kV Bus at TSS 155 Nelson via the interconnect customer's one-mile-long 345kV generator lead."

John W. Coke -> Rail & Highway Heavy Loads
280-tonne gas turbine
Update: Examples of how big gas turbines can get.
From J.E. Oswalt & Sons

John W Coke -> Rail & Highway Heavy Loads
Siemens gas turbine weighing 310 mtons

Video of transporting the "World's most powerful gas turbine". It weights 400 tons and can provide electricity for 400,000 homes. The posting from which I got this link has some photos of the rail transport.

Reginald McDowell posted
It's been a while since I caught one of these, but CSX brought down 2 GE 9-F Gas Turbines on CSX W999-21 today. Here's a few shots from the chase.
[There are more pictures in the posting.]
David Makar The earlier one (from the other article): "We understand that they’re heading for Moxie Energy’s new Freedom Generation Plant, a natural gas power plant that will generate about 325 megawatts of power for each of two turbines, and then use a heat recovery process to generate an additional 200 megawatts of power from the hot exhaust gases that would otherwise be waste heat."
Screenshot @ -2:50
Screenshot @ -2:04, soon before the overhead crane breaks and drops onto the rotor
John W. Coke posted three photos with the comment:
The largest and most efficient gas turbine in the world.
Dimension: L11.40 m x W5.10 m x H5.20 m
Weight: 435.70 ton


(new window)  When I finally saw the turbine, it looks like it may be steam instead of gas. But I added this while it played, so I'm going to leave this since it does show how they transport big turbines.

Mitsubishi has achieved 63% thermal efficiency.

A turbine on an 8-axle flatcar where only the inlet is wrapped in plastic (source)

Gas Fired Boilers and Steam Turbines

This is the standard coal-burning plant design where the boiler is converted to burn gas instead of coal.

Update: more gas-fired plants, no more coal-fired plants.

A turbine on an 8-axle flatcar where only the inlet is wrapped in plastic

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