Water Tube Boiler Jerk Load

I don't have a steam table close at hand, but I wonder how big a vessel it would take to "stockpile" 3-4 tons of steam at 150 psi.

Have you investigated your solid-fuel stoking system to see how much it can be "ramped up" to match the intermittent high demands?

What you have seems like nearly 15 TPH steam generation with 100C feed water temperature. Obviously you are not feeding feed water at that temperature + not carrying out proper water treatment and because, it is a water tube boiler(water inside tube - flame outside) the boiler has drastically dropped in efficiency and may be at 70% efficiency thus resulting in generating hardly 10 TPH. Your steam demand on startup from cold and during high peak load is resulting in this lock-out as a result of the boiler getting "under-capacity".

The advice for adding a pressure vessel of 3-4 tons (10.0 ton + 4 ton = 14 TPH) is actually a recommendation of a a "steam accumulator" to sustain this excessive pressure drop during peak load.

(1) Intial advice is to install a Back-pressure Reducing Valve to minimize this +

(2) Accumulators will further help in both process steam requirement and cost saving on an unnecessary purchase of a supporting small boiler.

Ducon is spot on.

Your instantaneous demand is greater than your average boiler output.

A backpressure valve between the source and load will sense when the boiler pressure is being pulled down. It will shut off to protect the boiler from being sucked dry. However, it won't provide enough steam to finish your jerk load.

An accumulator in the line is a horizontal tank half filled with water at the flash point of your system needs. When you have a jerk the entire surface of the water is available and will flash off steam when the downstream valve is opened and the pressure drops. The system refills at its liesure. There are formulas for sizing this for your process.