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This
is going to be one of these work letters. We are in the process
of implementing many different environmental projects to comply with
the latest EPA regulations. This is one of those projects.
We are installing the ability to inject activated carbon into the duct
work of the units. The activated carbon adsorbs the mercury with
in the flue gas and then the activated carbon is collected in the
scrubber towers. This addition or carbon should allow the units
to be compliant with the new Mercury and Air Toxins Rule (or
MATS). It goes into affect for Apache Station in April of 2016. |
| The activated
carbon injection system requires a silo (the highlight of this letter)
to house the carbon which comes in as a powder and is then
pneumatically conveyed to injection lances located in the ducts.
This project happens to be one of mine. The silo came in on a
truck and was set down on the road horizontally. We employed the
use of some cranes to stand it up. |
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The cranes used were supplied from
Marco Crane and Rigging Company. We had a 95 ton tail crane with
a 275 ton head crane. The idea was to lift the silo up with the
head crane and use the tail crane to rotate it to vertical prior to
disconnecting. Once the tail crane let go, then the head crane
would simply swing the silo into place. |
| The silo
(although it is not obvious) has a slopped bottom of 60 degrees.
All of the injection equipment is located withing the bottom of the
silo structure (or skirt). The silo has the ability to hold a 10
day supply of carbon when we are operating both units at full load
around the clock. As we are planning to switch the fuel on one of the units from coal to gas, that will increase the silo to a 20 day supply as it is only required on the coal burning unit. |
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The lift was fairly smooth. The only glitch
was in the transition from the horizontal to vertical position, the two
slack slings got caught on a flange on the silo roof. We had to
lower the silo top and use a man lift to hold the cables out of the way
while the transition was made. On a side note, one of the crane operators is a guy that I graduated with from high school. His name is Ben Beamis. I hadn't seen him since high school, but his parents still live in San Manual. |  |
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This activated
carbon equipment will allow the mercury emissions to be reduced from
the current rate of 4~6 pounds of mercury per Trillion Btus (TBtu)
burned in the furnace to reduced to 1.2 pounds of mercury emitted per
TBtu. The heat rate of the unit is roughly 10,300 Btu per
kWh. The units are 195 MW (295,000 kW). So if my
calculations are correct, at full load each unit burns 1.76 x 10^13 Btu
per year. So reducing the mercury by 4.6 pounds per trillion Btu
will reduce the mercury emitted by 0.3 pounds per year. If you get bored, run the math and let me know if I did that correct. |  |
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After the silo
was erected we flew up the catwalk to access the top of the silo.
During the design phase, we opted to not have a ladder access to the
top of the silo, but rather use a catwalk from the unit. This
cost a little extra, but I didn't want to have to climb up 80 feet to
reach the top. So far it seems to be coming together pretty well. Below is a photo I took on the way into the plant on Monday. With it being winter time, the sand hill cranes are back for the winter and they were flying across the road as I was driving in. Pretty sight, but they are sure loud. |  |
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