Apparatus and method for producing energy at a pulp mill
AssigneeAndritz Inc.
InventorsKari Saviharju, Jorma Simonen, Olli Arpalahti, Lasse Koivisto
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Abstract
A spent liquor recovery boiler in the pulp and paper industry including a water/steam circulation system having superheaters, the circulation system connected to a steam turbine comprising a high-pressure part, and a furnace for burning spent liquor to produce flue gases, and including an upper portion through which the flue gases flow, wherein the steam/water circulation system of the recovery boiler is provided with a reheater for reheating steam from the high-pressure part of the turbine.
Claims24
A spent liquor recovery boiler in the pulp and paper industry comprising:
- a water or steam circulation system having superheaters, said circulation system being connected to a steam turbine comprising a high-pressure stage, and
- a furnace for burning spent liquor to produce flue gases, and including an upper portion through which the flue gases flow,
- wherein the steam or water circulation system is provided with a reheater for reheating steam from the high-pressure stage of the turbine, and the reheater further comprises a first section in flue gas generated by and flowing through the furnace and connected to a steam outlet of the high-pressure stage of the turbine, and a second section receiving steam from the first section and heated by a combustor separate from the furnace burning the spent liquor.
A method of producing energy at a pulp mill having a recovery boiler and a turbine with a high-pressure part, said method comprising
- a) combusting spent liquor from a pulping process in a furnace of the recovery boiler to generate flue gases;
- b) recovering heat from the flue gases to produce steam in the recovery boiler;
- c) superheating the steam from step b),
- d) expanding the steam from step c) to a temperature in a range of 250° C. to 400° C. in the high-pressure part of the turbine, and
- e) wherein the recovery boiler is provided with a reheater, and the expanded steam from step d) is reheated to a temperature in a range of 450° C. to 600° C. in the reheater wherein the expanded steam is reheated in a first stage of the reheater by the flue gases from step a) and in a second stage of the reheater by heat generated by combusting a second fuel separately from the combustion of the spent liquor.
A system for combusting spent liquor and generating steam comprising:
- a recovery boiler comprising a furnace combusting the spent liquor and having a flue passage for a flow of flue gases generated in the furnace by the burning of the spent liquor;
- a combustion cavity associated with the recovery boiler and including a burner combusting a second fuel distinct from the spent liquor;
- a first reheater in the flue passage and receiving expanded steam discharged from a first steam turbine, wherein the flue gases heat the expanded steam passing through the first reheating stage, and
- a second reheater in the combustion cavity such that gases generated by the combustion the second fuel heat steam in the second reheating stage.
Dependencies are inferred from the claim text.