Combustion system and combustion method

1. A combustion system comprising a boiler and a flue gas treatment system downstream of the boiler, the flue gas treatment system comprising:

a desulphurization unit; and

a carbonator and a calciner defining a carbonator/calciner loop, the flue gas from the desulphurization unit being fed into the carbonator;

wherein no air pre-heaters, for pre-heating combustion oxidizer to be supplied into the boiler using heat of flue gas, are provided at the boiler and between the boiler and the carbonator;

wherein the flue gas discharged from the boiler has a temperature above 350° C.; and

wherein the gas treatment system includes a dust removal unit upstream of the desulphurization unit.

2. The combustion system of claim 1 , wherein the desulphurization unit includes at least a sorbent injector and at least a filter, the at least a sorbent injector for supplying sorbent into the flue gas for reaction with at least gaseous sulphur components contained in the flue gas to form at least solid sulphur components, and the least a filter for catching the at least solid sulphur components.

3. The combustion system of claim 1 , further comprising a heat exchanger is provided between the desulphurization unit and the carbonator, to heat the flue gas supplied into the carbonator.

4. A method for operating a combustion system having a boiler and a flue gas treatment system downstream of the boiler, the method comprising:

combusting a fuel with an oxidizer generating flue gas;

removing sulphur components from the flue gas; and

supplying the flue gas deprived of the sulphur components into a carbonator of a carbonator/calciner loop,

wherein no pre-heating of the oxidizer to be supplied into the boiler, using heat of the flue gas, at the boiler and between the boiler and the carbonator is carried out,

wherein the flue gas discharged from the boiler has a temperature above 350° C.; and

further comprising removing dust from the flue gas before removing the sulphur components.

5. The method of claim 4 , wherein removing sulphur components comprises:

injecting a sorbent into the flue gas, for the sorbent to react with gaseous sulphur components contained in the flue gas to form at least solid sulphur components; and

catching the solid sulphur components.

6. The method of claim 5 , wherein the solid sulphur components are removed by passing the flue gas through at least a filter.

7. The method of claim 4 , wherein the flue gas is heated after removing sulphur components therefrom and before supplying the flue gas into the carbonator.

8. The method of claim 4 , wherein the flue gas discharged from the boiler has a temperature above 380° C.

9. The method of claim 4 , wherein the temperature of the flue gas into which the sorbent is injected and that is passed through at least a filter is above 350° C.

10. The method of claim 9 , wherein the temperature of the flue gas into which the sorbent is injected and that is passed through at least a filter is above 380° C.

11. The method of claim 4 , further comprising removing acidic components from the flue gas together with the sulphur components.