The spent liquor (SL) of a thermomechanical pulping (TMP) process introduces a high load to the wastewater system of this process. To reduce this load, fly ash from a biomass boiler is used and the application of fly ash improves the performance of biological process. Three different alternatives are introduced to apply fly ash to treat spent liquor.

A system and process is disclosed for treating foul condensate such as foul condensate produced in a Kraft pulp mill. Foul condensate is directed through a steam stripper to produce a clean condensate that is partially evaporated by a volatile rich vapor stream produced by the steam stripper in the course of treating the foul condensate. Vapor produced by the evaporation of the clean condensate is directed to one or more electrically driven mechanical vapor re-compressors that produce the steam that is used in the steam stripper.

A system and process is disclosed for treating foul condensate such as foul condensate produced in a Kraft pulp mill. Foul condensate is directed through a steam stripper to produce a clean condensate that is partially evaporated by a volatile rich vapor stream produced by the steam stripper in the course of treating the foul condensate. Vapor produced by the evaporation of the clean condensate is directed to one or more electrically driven mechanical vapor re-compressors that produce the steam that is used in the steam stripper.

Embodiments herein relate to a system (200; 300; 400; 500) for obtaining methanol from foul condensate (101) of a pulping process. The system (200; 300; 400; 500) comprises a primary stripper (102) arranged to strip the foul condensate (101) from pollutants, whereby a first methanol-containing condensate is obtained from the polluted stripper off gases (SOGs). The system (200; 300; 400; 500) also comprises a first acidification unit (202) arranged to acidify the first methanol-containing condensate. Further, the system (200; 300; 400; 500) comprises a secondary stripper (204) arranged to strip the acidified first methanol-containing condensate from pollutants to obtain a second methanol-containing condensate, and a distillation column (107) arranged to distil the second methanol-containing condensate from the secondary stripper (204) so as to obtain methanol. Embodiments herein also relate to a method performed in a system (200; 300; 400; 500) for obtaining methanol from foul condensate (101) of a pulping process.

Embodiments herein relate to a system (200; 300; 400; 500) for obtaining methanol from foul condensate (101) of a pulping process. The system (200; 300; 400; 500) comprises a primary stripper (102) arranged to strip the foul condensate (101) from pollutants, whereby a first methanol-containing condensate is obtained from the polluted stripper off gases (SOGs). The system (200; 300; 400; 500) also comprises a first acidification unit (202) arranged to acidify the first methanol-containing condensate. Further, the system (200; 300; 400; 500) comprises a secondary stripper (204) arranged to strip the acidified first methanol-containing condensate from pollutants to obtain a second methanol-containing condensate, and a distillation column (107) arranged to distil the second methanol-containing condensate from the secondary stripper (204) so as to obtain methanol. Embodiments herein also relate to a method performed in a system (200; 300; 400; 500) for obtaining methanol from foul condensate (101) of a pulping process.

An arrangement in a recovery boiler having a furnace for combusting waste liquor and a flue gas duct including vertical flue gas channels, at least some of which are provided with heat recovery units for recovering heat from flue gases. The first flue gas channel downstream of the furnace is provided with a reheater and one of the following heat recovery units: an economizer or a boiler bank. The reheater and the second heat recovery unit are located one after the other in the horizontal incoming direction of the flue gas, so that in a flue gas channel the flue gas flows in a vertical direction from above downwards and heats the reheater and the second heat recovery unit simultaneously. The heat recovery elements of the reheater and the second heat recovery unit may be positioned side by side in a direction that is crosswise with respect to the horizontal incoming direction of the flue gas.

An arrangement in a recovery boiler having a furnace for combusting waste liquor and a flue gas duct including vertical flue gas channels, at least some of which are provided with heat recovery units for recovering heat from flue gases. The first flue gas channel downstream of the furnace is provided with a reheater and one of the following heat recovery units: an economizer or a boiler bank. The reheater and the second heat recovery unit are located one after the other in the horizontal incoming direction of the flue gas, so that in a flue gas channel the flue gas flows in a vertical direction from above downwards and heats the reheater and the second heat recovery unit simultaneously. The heat recovery elements of the reheater and the second heat recovery unit may be positioned side by side in a direction that is crosswise with respect to the horizontal incoming direction of the flue gas.

A system for producing aqueous sulphuric acid is provided, the system including a first heat exchanger configured to cool aqueous sulphuric for producing cooled aqueous sulphuric acid; a pre-cooling unit comprising an inlet or inlets for receiving the gas containing sulphur trioxide and the cooled aqueous sulphuric acid, an outlet for letting out aqueous sulphuric acid and the gas containing sulphur trioxide, and a first nozzle for spraying the cooled aqueous sulphuric acid onto the gas containing sulphur trioxide. The system further includes a condensation tower comprising a first inlet for receiving the cooled gas containing sulphur trioxide and aqueous sulphuric acid from the pre-cooling unit and means for circulating the aqueous sulphuric acid within the condensation tower by spraying. An associated method and pre-cooling unit suitable for cooling gas comprising sulphur trioxide from at least 400 C. to at most 150 C. are also provided.

A system for producing aqueous sulphuric acid is provided, the system including a first heat exchanger configured to cool aqueous sulphuric for producing cooled aqueous sulphuric acid; a pre-cooling unit comprising an inlet or inlets for receiving the gas containing sulphur trioxide and the cooled aqueous sulphuric acid, an outlet for letting out aqueous sulphuric acid and the gas containing sulphur trioxide, and a first nozzle for spraying the cooled aqueous sulphuric acid onto the gas containing sulphur trioxide. The system further includes a condensation tower comprising a first inlet for receiving the cooled gas containing sulphur trioxide and aqueous sulphuric acid from the pre-cooling unit and means for circulating the aqueous sulphuric acid within the condensation tower by spraying. An associated method and pre-cooling unit suitable for cooling gas comprising sulphur trioxide from at least 400 C. to at most 150 C. are also provided.

The invention relates to the use of biomethanol from the pulp industry in the production of biohydrogen. The preferred biomethanol comprises purified biomethanol derived from black liquor. The invention also relates to a process for the production of biohydrogen from crude biomethanol recovered from black liquor and to a process for producing hydrocarbon biofuel using such biohydrogen as a hydrogen source. The invention further relates to a biofuel production facility for producing fuel from biohydrogen and biohydrocarbon, and to biofuel so produced. The invention makes it possible to produce a biofuel, wherein 100% of the raw material stems from non-fossil sources.