Exhaust gas cooler

1. An exhaust gas cooler comprising:

a steam drum containing first water;

an exhaust heat boiler for heating the first water in the steam drum to produce steam by heat exchange between the first water and exhaust gas;

an economizer for heat exchange between the exhaust gas, after the heat exchange between the first water and the exhaust gas, and the heated first water supplied from the steam drum;

a feedwater pipe for supplying the first water with second water having a lower temperature than the first water;

a temperature detection member that detects an inlet temperature, which is a temperature of the first water flowing into the economizer; and

an inlet-supply-amount control member that controls an inlet supply amount, which is a supply amount of the second water supplied to the first water flowing into the economizer,

wherein the exhaust gas cooler is configured such that the first water flowing out of the economizer is introduced into the steam drum,

wherein the second water is divided and supplied to the first water flowing out of the economizer and the first water flowing into the economizer, and

wherein the inlet-supply-amount control member controls the inlet supply amount such that the inlet temperature is in a predetermined setting temperature range.

2. The exhaust gas cooler according to claim 1 ,

wherein part of the second water is supplied to the first water flowing out of the economizer between the economizer and the steam drum.

3. The exhaust gas cooler according to claim 1 ,

wherein the exhaust gas is exhaust gas from a combustion furnace in an integrated coal gasification combined cycle power plant.