I have operated in a plant that was built in 1904 and most plants from this era spin the turbine with steam power but also use river or lake water as a cooling source for the turbine as well, the same way modern plants use cooling towers or build lakes next to the plant. The plant I worked was just as large and neoclassical in the main turbine as this one .If you like to see it and would be able to travel to the midwest I could help you out .th e plant has been updated and is still operational. However only the equipment has been remodeled the plant looks the same as it did in 1904.
The pipe size depends on the volume of steam needed to spin the turbine. we rate it in pounds of steam per hour. the pipes are arched to allow for the pipe to expand as they warm up when the system is on line. as far as size goes our plant uses 60" diameter pipe I have seen 48" 36" and 72" diameter depending on need
I believe it is called a shaker screen use to size the coal pieces depending on what type of equipment was going to burn the coal. I'm not 100 percent sure but I have seen similar equipment in my career .
I guess since they had the coal and the power plant making steam why not use it . One other thought would be cheaper to operate and may have provided more torque than a electric motor of that time period
judging by the hoppers it looks like they could be chain grate boilers, the coal was placed on the chain grate and the grate moved from the front to the back of the boilers. just a guess would need more pics
I am a power plant operator and JT is right on target. the crushers are located inline with the boiler front and after the coal passes thru it is blown into the firebox on the boilers
could be a forced draft fan for putting more air into the boiler but hard to tell from this picture. could also be a fan for air movement in the coal storage bins