Patent ID: 7281498

Claim:
A compact apparatus comprising: a) a water tank defining a closed chamber for holding a preselected quantity of water and heat exchanger means immersed in said water and spaced from the bottom of said water tank therein and having a boiling zone defined by the free upper surface of said water and said heat exchanger means for boiling and circulating said water therein, a steam separation zone defined by said free upper surface of said water and the top of said water tank for separating steam from said boiling water therein and a solids separation zone defined by said bottom of said water tank and said heat exchanger means for separating and accumulating solids from said boiling water therein, said steam separation zone having steam outlet means for discharging said steam, said solids separation zone having inlet opening means for incoming cold make up water and return condensate and outlet opening means for blowing down said solids and draining said water from said water tank and said water tank having a flanged opening means for installing said heat exchanger means and a separate flanged opening means for cleaning said water tank and said heat exchanger means, b) said heat exchanger means having inlet and exit opening means for passing combustion products through said heat exchanger means in an indirect heat exchange relationship with said water in said water tank thereby preheating said incoming cold make up water and heating circulating and boiling said water while cooling said combustion products, c) burner means being located inside said heat exchanger means for burning fuel with combustion air to produce said combustion products, d) means for delivering said fuel and combustion air to said burner means, e) means for controlling said combustion of said fuel with said air in said burner means, f) exhaust outlet conduit means communicating with said exit opening means of said heat exchanger means for discharging said cooled combustion products, g) means for feeding said cold make up water and return condensate into said solids separation zone, h) means for maintaining a level of said water in said water tank within preset water level limits, i) means for withdrawing said solids from said solids separation zone, j) means for draining said water from said water tank, k) means for protecting said water tank against an accidental increase in operating pressure, I) means for protecting said water tank against an accidental increase in operating temperature, m) means for controlling and maintaining production of said steam in response to a steam demand measured by steam demand sensor means, and n) a heat insulation surrounding said water tank and a casing for housing said compact apparatus.