Heat economy enhancements for the recovery and use of energy obtained from spent cooking liquors
AssigneeAndritz-Ahlstrom Inc.
InventorsElla Sun Yu, C. Bertil Stromberg, Rolf C. Ryham, R. Fred Chasse
Life of this patent
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Abstract
Useable steam, e.g. substantially clean useable steam, is produced from a chemical cellulose pulping system hot spent treatment liquor (e.g. black liquor) with optimum energy efficiency by passing the spent liquor to a reboiler, and then pressurizing (e.g. with an eductor, fan, or compressor) the clean steam discharged from the reboiler. The clean steam can be used to steam incoming chips (e.g. in a chip bin) without significantly increasing the TRS load on the pulp mill NCG system.
Claims20
A method of producing chemical cellulose pulp in an energy efficient manner using a treatment vessel in a digester system, comprising:
- (a) introducing a slurry of comminuted cellulosic fibrous material and liquid to a treatment vessel to produce cellulose pulp;
- (b) treating the material in the vessel with treatment chemical at a temperature greater than 140° C. and a pressure greater than 5 bar gage to produce a treated material and a spent treatment liquor, including sulphur compounds;
- (c) removing the spent treatment liquid from the vessel at a first temperature;
- (d) passing the spent liquor in indirect heat exchange relationship with a cooler liquor having a second temperature lower than the first temperature to produce steam at a first pressure, and at a third temperature higher than the second temperature;
- (e) increasing the pressure of the steam to a second pressure by at least about 0.2 bar more than the first pressure;
- and
- (f) using the steam at the second pressure in the digester system.
A method of producing steam having less noncondensible gases than steam produced by flashing black liquor, including sulphur compounds, directly into steam, in a digester system, comprising:
- (a) passing hot black liquor, including sulphur compounds, at a temperature of about 120-165° C. from a digester through a heat exchanger;
- (b) passing an evaporable liquid to be evaporated through the heat exchanger into heat exchange contact with the hot black liquor so that the evaporable liquid is heated so that it is ultimately evaporated to produce steam having less noncondensible gases than steam produced by flashing black liquor, including sulphur compounds, directly into steam;
- (c) increasing the pressure of steam from (b) by at least 0.2 bar gage;
- and
- (d) using the steam from (c) in the digester system.
A digester system comprising:
- a digester having a hot spent treatment liquor outlet;
- a feed system for feeding comminuted cellulose material to said digester;
- a steam generator operatively connected to said spent treatment liquor outlet to use the heat of the spent treatment liquor to produce steam from another liquid, said steam generator having a steam outlet and a spent treatment liquor outlet;
- a pressure increasing device, connected to said steam generator steaming outlet, which increases the pressure of the steam from said steam generator;
- and
- a utilization device operatively connected to said pressure increasing device to utilize the steam therefrom.
Dependencies are inferred from the claim text.