Heat recovery boiler and hot banking releasing method thereof

A heat recovery boiler having an inlet side operatively connected to a combustion system and an outlet side operatively connected to an exhaust system, comprising:

• a casing;
• a superheater constituted by a pipe line in form of a heat transfer pipe;
• an evaporator provided with a steam drum;
• an economizer, said superheater, said evaporator and said economizer being operatively arranged in the casing along a flow of an exhaust gas from the combustion system;
• a lead pipe connecting an inlet side of the pipe line constituting the superheater to said steam drum;
• a superheated steam pipe line connecting an outlet side of the pipe line constituting the superheater to the steam drum of the evaporator;
• a drain pipe operatively connected to the pipe line through a bottom connection pipe;
• a superheater bypass pipe incorporated with a superheater bypass valve,
• said pipe line constituting the superheater being composed of one straight pipe line, said straight pipe line having an outlet side being connected to the superheated steam pipe through a connection portion which is arranged at a portion downstream side of a connection portion between the drain pipe and the bottom connection pipe, said connection portion between the superheated steam pipe and said pipe line being formed with a rising portion;
• and
• said superheater bypass pipe having one end operatively connected to said steam drum and another one end operatively connected to a portion downstream side of said rising portion.

A heat recovery boiler having an inlet side operatively connected to a combustion system and an outlet side operatively connected to an exhaust system, comprising:

• a casing;
• a superheater constituted by a pipe line in form of a heat transfer pipe;
• an evaporator provided with a steam drum;
• an economizer, said superheater, said evaporator and said economizer being operatively arranged in the casing along a flow of an exhaust gas from the combustion system;
• a lead pipe connecting an inlet side of the pipe line constituting the superheater to the steam drum;
• a superheated steam pipe line connecting an outlet side of the pipe line constituting the superheater to the steam drum of the evaporator;
• a drain pipe operatively connected to the pipe line constituting the superheater;
• and
• a superheater bypass pipe incorporated with a superheater bypass valve and having one end operatively connected to the steam drum and another one end operatively connected to the superheated steam pipe,
• said pipe line being composed of at least four pipe line sections which are connected by means of head connection pipes and bottom connection pipes respectively at head side portions and bottom side portions of the pipe line sections totally in a meandering fashion;
• and
• said pipe line being incorporated with a superheater intermediate bypass pipe through which at least one of saturated steam and non-condensable gas is supplied.

A hot banking releasing method of a heat recovery boiler, which has an inlet side operatively connected to a combustion system and an outlet side operatively connected to an exhaust system and which comprises:

• a casing;
• a superheater constituted by a pipe line in form of a heat transfer pipe;
• an evaporator provided with a steam drum;
• an economizer, said superheater, said evaporator and said economizer being operatively arranged in the casing along a flow of an exhaust gas from the combustion system;
• a lead pipe connecting an inlet side of the pipe line constituting the superheater to the steam drum;
• a superheated steam pipe line connecting an outlet side of the pipe line constituting the superheater to the steam drum of the evaporator;
• a drain pipe operatively connected to the pipe line constituting the superheater;
• and a superheater bypass pipe incorporated with a superheater bypass valve and having one end operatively connected to the steam drum and another one end operatively connected to the superheated steam pipe,
• the hot banking releasing method being for enclosing exhaust gas from the combustion system in the casing and releasing the hot banking while maintaining feed water in the casing at a high temperature, and
• said hot banking releasing method comprising the steps of:
• opening the superheater bypass valve incorporated to the superheater bypass pipe;
• opening a drain valve provided for the drain pipe;
• applying a pressing force to water collected in the bottom of said superheater by passing saturated steam generated from the steam drum through the lead pipe and the superheater bypass pipe;
• and
• blowing drain water out of a plant through the drain valve.

A hot banking releasing method of a heat recovery boiler, which has an inlet side operatively connected to a combustion system and an outlet side operatively connected to an exhaust system and which comprises:

• a casing;
• superheater constituted by a pipe line in form of a heat transfer pipe;
• an evaporator provided with a steam drum;
• an economizer, said superheater, said evaporator and said economizer being operatively arranged in the casing along a flow of an exhaust gas from the combustion system;
• a lead pipe connecting an inlet side of the pipe line constituting the superheater to the steam drum;
• a superheated steam pipe line connecting an outlet side of the pipe line constituting the superheater to the steam drum of the evaporator;
• a drain pipe operatively connected to the pipe line constituting the superheater;
• and a superheater bypass pipe incorporated with a superheater bypass valve and having one end operatively connected to the steam drum by way of a non-condensable gas system and another one end operatively connected to the superheated steam pipe,
• said hot banking releasing method being for enclosing exhaust gas from the combustion system in the casing and releasing the hot banking while maintaining feed water in the casing at a high temperature, and
• said hot banking releasing method comprising the steps of, at a time when a saturated steam pressure of a steam drum is less than a predetermined set pressure:
• opening a valve provided for the non-condensable gas system;
• branching the inlet side of the superheater from the communication pipe connected to the steam drum;
• opening the superheater bypass valve incorporated to the superheater bypass pipe;
• opening a drain valve provided for the drain pipe provided in the bottom of the superheater;
• applying a pressing force to drain water collected in the bottom of said superheater by passing a non-condensable gas from the non-condensable gas system through the lead pipe and the superheater bypass pipe;
• blowing drain water out of a plant through the drain valve;
• closing the valve of the non-condensable gas system;
• closing again the drain valve temporarily;
• and
• blowing the non-condensable gas out of the system through the drain valve.