There is provided a drain recovery system with which power for driving a feedwater pump can be reduced and the feedwater pump can be driven at low costs. The drain recovery system includes: a buffer tank; an assist tank disposed below the buffer tank; a first drain supply line that connects a load device and the buffer tank; a second drain supply line that connects the buffer tank and the assist tank; a drain supply valve; a communication line that establishes communication between the assist tank and the buffer tank; a communication valve; a steam supply line that supplies steam from a boiler to the assist tank; a steam supply valve; a feedwater line that supplies drain from the assist tank to the boiler; and a feedwater pump.

There is provided a drain recovery system with which power for driving a feedwater pump can be reduced and the feedwater pump can be driven at low costs. The drain recovery system includes: a buffer tank; an assist tank disposed below the buffer tank; a first drain supply line that connects a load device and the buffer tank; a second drain supply line that connects the buffer tank and the assist tank; a drain supply valve; a communication line that establishes communication between the assist tank and the buffer tank; a communication valve; a steam supply line that supplies steam from a boiler to the assist tank; a steam supply valve; a feedwater line that supplies drain from the assist tank to the boiler; and a feedwater pump.

A modular heat recovery steam generator (mHRSG) comprises a first boiler module comprising a plurality of pipes having at least one pipe with a flanged end; a first piping deck comprising a plurality of pipes having at least one pipe with a flanged end, wherein the pipe with the flanged end is secured to the pipe with the flanged end of the first boiler module using bolts; a second boiler module comprising a plurality of pipes having at least one pipe with a flanged end; a second piping deck comprising a plurality of pipes having at least one pipe with a flanged end, wherein the pipe with the flanged end is secured to the pipe with the flanged end of the second boiler module using bolts; and a main stack. The first boiler module is operatively coupled to the second boiler module and the second boiler module is operatively coupled to the main stack.

A modular heat recovery steam generator (mHRSG) comprises a first boiler module comprising a plurality of pipes having at least one pipe with a flanged end; a first piping deck comprising a plurality of pipes having at least one pipe with a flanged end, wherein the pipe with the flanged end is secured to the pipe with the flanged end of the first boiler module using bolts; a second boiler module comprising a plurality of pipes having at least one pipe with a flanged end; a second piping deck comprising a plurality of pipes having at least one pipe with a flanged end, wherein the pipe with the flanged end is secured to the pipe with the flanged end of the second boiler module using bolts; and a main stack. The first boiler module is operatively coupled to the second boiler module and the second boiler module is operatively coupled to the main stack.