D21C

PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS

REGENERATION OF PULPING LIQUORS

APPARATUS THEREFOR

In this subclass non-limiting references (in the sense of paragraph 39 of the Guide to the IPC) may still be displayed in the scheme.

D21C1/00

Pretreatment of the finely-divided materials before digesting of waste paper D21C5/02

D21C1/02

with water or steam

D21C1/04

with acid reacting compounds

D21C1/06

with alkaline reacting compounds

D21C1/08

with oxygen-generating compounds

D21C1/10

Physical methods for facilitating impregnation

D21C3/00

Pulping cellulose-containing materials digesters D21C7/00

D21C3/003

with organic compounds D21C3/20 and D21C3/222 take precedence

D21C3/006

with compounds not otherwise provided for

D21C3/02

with inorganic bases or alkaline reacting compounds, e.g. sulfate processes

D21C3/022

in presence of S-containing compounds

D21C3/024

with NH₃ or H₂O

D21C3/026

in presence of O₂, e.g. air

D21C3/028

in presence of O₃

D21C3/04

with acids, acid salts or acid anhydrides

D21C3/003 and D21C3/222 take precedence

D21C3/045

in presence of O₂ or O₃

D21C3/06

sulfur dioxide

sulfurous acid

bisulfites

sulfites

D21C3/08

calcium bisulfite

D21C3/10

magnesium bisulfite

D21C3/12

sodium bisulfite

D21C3/14

ammonium bisulfite

D21C3/16

nitrogen oxides

nitric acid

nitrates, nitrites

D21C3/18

with halogens or halogen-generating compounds bleaching cellulose pulp D21C9/12

D21C3/20

with organic solvents

or in solvent environment

D21C3/22

Other features of pulping processes

D21C3/222

Use of compounds accelerating the pulping processes

D21C3/224

Use of means other than pressure and temperature

D21C3/226

Use of compounds avoiding scale formation

D21C3/228

Automation of the pulping processes

D21C3/24

Continuous processes

D21C3/26

Multistage processes

D21C3/263

at least one stage being in presence of oxygen

D21C3/266

the same pulping agent being used in all stages D21C3/263 takes precedence

D21C3/28

Prevention of foam

D21C5/00

Other processes for obtaining cellulose, e.g. cooking cotton linters obtaining fibres for spinning D01C;

Processes characterised by the choice of cellulose-containing starting materials

D21C5/005

Treatment of cellulose-containing material with microorganisms or enzymes

D21C5/02

Working-up waste paper mechanical part D21B1/08, D21B1/32

D21C5/022

Chemicals therefor

D21C5/025

De-inking

D21C5/027

Chemicals therefor

D21C7/00

Digesters

D21C7/02

Rotary digesters

D21C7/04

Linings

D21C7/06

Feeding devices

D21C7/08

Discharge devices

D21C7/10

Heating devices

D21C7/12

Devices for regulating or controlling

D21C7/14

Means for circulating the lye

D21C7/16

Safety devices

D21C9/00

After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters

; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere polysaccharides, derivatives thereof C08B; paper-making D21B - D21H

D21C9/001

Modification of pulp properties purification D21C9/08

D21C9/002

by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives

D21C9/004

inorganic compounds

D21C9/005

organic compounds

D21C9/007

by mechanical or physical means

D21C9/008

Prevention of corrosion or formation of deposits on pulp-treating equipment D21C9/08, D21H21/02 take precedence

D21C9/02

Washing

; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents

D21C9/04

in diffusers

; Washing of pulp of fluid consistency without substantially thickening

D21C9/06

in filters

; Washing of concentrated pulp, e.g. pulp mats, on filtering surfaces

D21C9/08

Removal of fats, resins, pitch or waxes;

Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching fats, waxes C11B; natural resins C09F1/00; hemicellulose C08B37/14; purification by mechanical means D21D5/00

D21C9/083

with inorganic compounds D21C9/086 takes precedence

D21C9/086

with organic compounds or compositions comprising organic compounds

D21C9/10

Bleaching

; Apparatus therefor

D21C9/1005

Pretreatment of the pulp, e.g. degassing the pulp

D21C9/101

in solvent medium

D21C9/1015

with use of means other than pressure, temperature

D21C9/1021

Electrochemical processes

D21C9/1026

Other features in bleaching processes

D21C9/1031

Pulse, dynamic, displacement processes

D21C9/1036

Use of compounds accelerating or improving the efficiency of the processes

D21C9/1042

Use of chelating agents

D21C9/1047

Conserving the bleached pulp

D21C9/1052

Controlling the process

D21C9/1057

Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16

D21C9/1063

with compounds not otherwise provided for, e.g. activated gases

D21C9/1068

with O₂ closed, see

D21C9/147

D21C9/1073

with O₃ closed, see

D21C9/153

D21C9/1078

with Mn-containing compounds

D21C9/1084

with reducing compounds

D21C9/1089

with dithionites

D21C9/1094

with H₂

D21C9/12

with halogens or halogen-containing compounds D21C9/16 takes precedence

D21C9/123

with Cl₂O

D21C9/126

with perhalogeno compounds

D21C9/14

with ClO₂ or chlorites

D21C9/142

with ClO₂/Cl₂ in a multistage process involving ClO₂/Cl₂ exclusively

D21C9/144

with ClO₂/Cl₂ and other bleaching agents in a multistage process

D21C9/147

with oxygen or its allotropic modifications D21C9/16 takes precedence

D21C9/153

with ozone

D21C9/16

with per compounds

D21C9/163

with peroxides

D21C9/166

with peracids

D21C9/18

De-watering de-watering in general F26B

Elimination of cooking or pulp-treating liquors from the pulp

D21C9/002, D21C9/02 take precedence; paper-making machines D21F; strainers in digesters D21C7/00; presses in general B30B

D21C9/185

comprising at least one step where the pulp is suspended in a gaseous medium, e.g. flash drying

D21C11/00

Regeneration of pulp liquors

or effluent waste waters

D21C11/0007

Recovery of by-products, i.e. compounds other than those necessary for pulping, for multiple uses or not otherwise provided for volatile compounds obtained by decomposition of spent liquors in order to regenerate them D21C11/125; compounds obtained by fractionating the liquors in order to regenerate them D21C11/0042

D21C11/0014

Combination of various pulping processes with one or several recovery systems (cross-recovery)

D21C11/0021

Introduction of various effluents, e.g. waste waters, into the pulping, recovery and regeneration cycle (closed-cycle)

D21C11/0028

Effluents derived from the washing or bleaching plants

D21C11/0035

Introduction of compounds, e.g. sodium sulfate, into the cycle in order to compensate for the losses of pulping agents

D21C11/0042

Fractionating or concentration of spent liquors by special methods concentration by evaporation D21C11/10

D21C11/005

Treatment of liquors with ion-exchangers

D21C11/0057

Oxidation of liquors, e.g. in order to reduce the losses of sulfur compounds, followed by evaporation or combustion if the liquor in question is a black liquor deodorisation of gases D21C11/08; combustion D21C11/12, D21C11/14

D21C11/0064

Aspects concerning the production and the treatment of green and white liquors, e.g. causticizing green liquor

D21C11/0071

Treatment of green or white liquors with gases, e.g. with carbon dioxide for carbonation; Expulsion of gaseous compounds, e.g. hydrogen sulfide, from these liquors by this treatment (stripping); Optional separation of solid compounds formed in the liquors by this treatment oxidation of liquors (black, green or white) D21C11/0057; treatment of pulp gases D21C11/06

D21C11/0078

Treatment of green or white liquors with other means or other compounds than gases, e.g. in order to separate solid compounds such as sodium chloride and carbonate from these liquors; Further treatment of these compounds fractionating of spent liquors D21C11/0042

D21C11/0085

Introduction of auxiliary substances into the regenerating system in order to improve the performance of certain steps of the latter, the presence of these substances being confined to the regeneration cycle introduction of compounds in order to make up for the losses of pulping agents D21C11/0035; conventional causticizing of green liquors D21C11/0064; fractionating of spent liquors D21C11/0042

D21C11/0092

Substances modifying the evaporation, combustion, or thermal decomposition processes of black liquor treatment of solid substances (ash) separated from combustion gases D21C11/066; avoiding scale-forming during evaporation D21C11/106

D21C11/02

acid, neutral or alkaline

sulfite lye

D21C11/04

of alkali lye

D21C11/06

Treatment of pulp gases

Recovery of the heat content of the gases;

Treatment of gases arising from various sources in pulp and paper mills; Regeneration of gaseous SO₂, e.g. arising from liquors containing sulfur compounds

D21C11/063

Treatment of gas streams comprising solid matter, e.g. the ashes resulting from the combustion of black liquor evaporation of pulp liquors by direct contact with gases D21C11/103; post-combustion of gases D21C11/127

D21C11/066

Separation of solid compounds from these gases; further treatment of recovered products

D21C11/08

Deodorisation

Elimination of malodorous compounds, e.g. sulfur compounds such as hydrogen sulfide and mercaptans, from gas streams oxidation of liquors D21C11/0057; post-combustion of gases D21C11/127

D21C11/10

Concentrating spent liquor by evaporation evaporators B01D

D21C11/103

Evaporation by direct contact with gases, e.g. hot flue gases

D21C11/106

Prevention of incrustations on heating surfaces during the concentration, e.g. by elimination of the scale-forming substances contained in the liquors

D21C11/12

Combustion of pulp liquors

D21C11/122

Treatment, e.g. dissolution, of the smelt

D21C11/125

Decomposition of the pulp liquors in reducing atmosphere or in the absence of oxidants, i.e. gasification or pyrolysis

D21C11/127

with post-combustion of the gases

D21C11/14

Wet combustion

; Treatment of pulp liquors without previous evaporation, by oxidation of the liquors remaining at least partially in the liquid phase, e.g. by application or pressure oxidation of black, green or white liquors D21C11/0057