Is it possible to "pump" a powder the same way liquids can be pumped?
If so, what are the challenges? If not, what are some alternatives?
I believe it's termed "injecting" not "pumping" but yes, it's certainly possible.
Coal fired electric power plants grind the coal to a very fine dust and then blow the dust into the central burner.
This particular article is a summary of some DOE research for a Blast Furnace Granulated Coal Injection System Demonstration Project.
And this article discusses some of the hazards from a National Fire Protection Association perspective. Coal dust having the particular dangerous property of being explosive and all that...
As far as specifics regarding danger, I suspect it will vary depending upon the material(s) involved in the powder.
While pumping powders as a mix with swiftly moving gas is viable, one of frequently used alternatives for both powders and granular materials is Archimedes' Screw.
Essentially, a helix in a diagonal pipe making the material "pour/roll" upwards the curve, allowing lifting it a long distance. This solution is frequently used in farming equipment for transporting grain or granulates. While it doesn't provide "pressure" for moving it through inert pipes, a "pipeline" of such screws can go a long way, and while it restricts transport angle, it provides a viable alternative especially for heavier materials where extreme air flows would be required to move them.
There is a key difference between liquids and powders:
In practice, this means that to pump a powder, you inject air or another gas as fluidizing agent. The pumped or blown air carries the powder, like a dust-storm within the pipe.
In food process you can "pump" powder with vacuum, sugar works very well, and some other products need sometimes some technical adjustment (pression or open/close cycles valves) . But water in the pipes is ban and last point it's only for small quantities and short distance 20meters max i think.
You can pump both liquids and powders into a "mold" using injection molding.
It works more easily with liquids, but it can also be done with small particles such as powders that are injected into heated molds with sufficient force.
We have dry cement bulkers truck running on local roads, feeding dry cement to mixer factory where it is turned into wet mixed cement. Pump air into the truck to 'blow' cement out.
This video shows cement and sand are 'blow' by air. Powder (cement/sand) are placed in closed container. Air blow in and powder come out on, says, 2 to 3 inch diameter, tubing. Powder can be transferred in construction site, at horizontal and vertical distance of tens of meters. You can see the blue air-compressor in the video. Here is a similar video.