CA1058357A - Method of improving smelt properties and reducing dissolving tank explosions during pulping of wood with sodium based liquors - Google Patents
Method of improving smelt properties and reducing dissolving tank explosions during pulping of wood with sodium based liquorsInfo
- Publication number
- CA1058357A CA1058357A CA211,277A CA211277A CA1058357A CA 1058357 A CA1058357 A CA 1058357A CA 211277 A CA211277 A CA 211277A CA 1058357 A CA1058357 A CA 1058357A
- Authority
- CA
- Canada
- Prior art keywords
- smelt
- alkali metal
- added
- dissolving tank
- sodium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C11/00—Regeneration of pulp liquors or effluent waste waters
- D21C11/12—Combustion of pulp liquors
- D21C11/122—Treatment, e.g. dissolution, of the smelt
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0006—Controlling or regulating processes
- B01J19/002—Avoiding undesirable reactions or side-effects, e.g. avoiding explosions, or improving the yield by suppressing side-reactions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00049—Controlling or regulating processes
- B01J2219/00245—Avoiding undesirable reactions or side-effects
- B01J2219/00259—Preventing runaway of the chemical reaction
- B01J2219/00263—Preventing explosion of the chemical mixture
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Paper (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Certain additives such as lithium hydroxide, potassium hydroxide, lithium carbonate, potassium carbonate and alkali metal borates or mixtures thereof can be added to the smelt produced by pulping wood with a sodium based liquor containing such compounds as sodium carbonate and sodium hydroxide to lower the melting point and make the smelt softer and more fluid so that when it enters the dissolving tank violent explosions are substantially eliminated. These additives do not interfere with pulping and paper strength is not affected by their use.
Certain additives such as lithium hydroxide, potassium hydroxide, lithium carbonate, potassium carbonate and alkali metal borates or mixtures thereof can be added to the smelt produced by pulping wood with a sodium based liquor containing such compounds as sodium carbonate and sodium hydroxide to lower the melting point and make the smelt softer and more fluid so that when it enters the dissolving tank violent explosions are substantially eliminated. These additives do not interfere with pulping and paper strength is not affected by their use.
Description
BACKGROUND OF THE INVENTION
Molten smelt and water are a hazardous combination of compounds which are present in large quantities in a wood pulping mill. When such smelt mixes with water in a uncontrollable manner, violent explosions can occur. These explosions can take place in the recovery furnace when a boiler tube breaks and water comes into contact with molten smelt at the bottom of the furnace.
Dissolving tank explosions occur when molten smelt contacts the water or green liquor in the dissolving tank. Both of these explosions are extremely hazardous and have been a continuing concern to the paper industry for many years~ The dissolving tank explosions, while perhaps not posing as serious a threat to closing down a mill as a boiler explosion, nevertheless are an ever present threat to the safety of operating personnel and have forced cessation of mill operations in the past. It is the prevention and con .. . .
' 20 ,~, ' ,s :`~ , ' ' :'' ' .,. ' ' '' `;` ".
, .:,;
',:.~'; , ;
: 30 : ,.' -1-. . .
;"~ ,:
~ ~058357 trol of dissolving tank exploslons to which the present in-vention is primarily directed.
It is known in the art that the temperature and composition of the dissolving liquor in a straight soda pulp-ing operation influences the severity of the smelt-water re-action in that higher temperature result in less violence of quenching as does the use of pure water as compared to the pulping liquor containing dissolved salts. It was established that the addition of more than 5% NaCl or 10% NaOH to the smelt consistently produced explosions whereas pure Na2C03 was not explosive. Thus, the physical state of the smelt was found to be important and the prior art suggested shattering the molten smelt stream with steam ~ets prior to entering the dissolving tank.
The importance of the physical characterisitics of the smelt and especially the size of the molten smelt par-ticles under the surface of the liquor was recognized in the prior art. It was concluded that if the molten smelt is pre-sent in the form of small spheres~ it does not explode when quenched with water. ~owever, if the smelt is not flawing from the furnace in a steady stream the usual shattering device is inadequate to prevent the dissolving tank explosions which result when a molten globule falls from the furnace spout into the tank. The prevention of the freezing up of the smelt and the maintenance of a steady flow of' molten smelt by other than physical means is the principal ob~ect of this invention.
~ . " . ., SUMMARY OF THE INVENTION
_ In its broadest aspects, thR present invention in-volves the addition of an alkali metal compound preferably alkali metal hydroxides, carbonates and borates or mixtures thereof (other than sodium carbonate~ to a sodium based smelt produced from a wood pulping process in an amount sufficient to lower the melting point of the original smelt to improve molten smelt fluidity and prevent smelt spout plugging as well as dissolving tank explosions. In`addition, the smelt is softer and can be more readily removed from the spout if soldification does occur. More specifically, this invention is concerned with chemical means for improving the properties of sodium carbonate smelt produced from a non-sulfur wood pulping process such as one utilizing sodium carbonate and sodium hydroxide as the cooking liquor. Sodium carbonate smelts in particular require higher temperatures to prevent them from solidifying in the furnace compared to smelts containing sulfur produced by kraft or neutral sulfite semichemical processes.
Thus, in accordance with the present teachings, an improvement is provided in the cyclic pulping and chemical recovery process for producing paper pulp from ligno cellulosic materials which utilize an aqueous sodium based cooking liquor at elevated temperatures and pressures where-in the aqueous filtrate is separated from the pulp by washing, then concentrated and ignited in a recovery furnace to form a smelt which is dissolved in water and reconstituted for further use. The improvement in such a process comprises adding an alkali metal compound or mixtures thereof which are selected from the group consisting of LiOH, KOH, Li2CO3, K2CO3 and alkali metal borates to the pulping cycle in an amount sufficient to lower the melting point of .~
F~ 3 -0~83S7 the smelt to improve smelt fluidity and reduce dissolving tank explosions.
- 3a -.. .. .
1058357 F-l,003 GENER~L DESCRIPTION OF THE INVENTION
. . , ~
The depression of the melting point of a pure com-pound by adding a second component is a well known scienkific fact. However, more than ~ust lGwering the melting point is involved in adding chemicals to a smelt produced in a wood pulping process. For example, an~ chemical which is added must be non-explosive, non-corrosive, water soluble, economical, recoverable and above all, compatible with the other constituents ln the pulping liquor and no~ detrimental to the pulp pro-perties. It has now been found that only a llmited number of compounds meet the desired requirements. These compounds include lithium carbonate, lithium hydroxide, , potassium carbonate, potassium hydroxide~ potassiu~m borate, sodium borate and lithium borate. Of these, khe preferred compounds are potassium carbonate J potassium hydroxide and sodium borate.
The chemicals employed to decrease the melting point of the smelt are used in various concentrations. In general, any potassium containing compound can be used and preferably non-toxic compounds. Thus, the alkali metal hydroxides and carbonates are used in concentrations of from 1 to 80 mole percent based on Na20 but the maximum effect of K2C03 is achieved at about 40 mole percenk which lowers the melting point of NazCO3 smelt about 280F compared ko the melting point of 1593F for 100,~ Na2CO3 smelt. Sincè KOH is very similar to NaOH, it is converted to K2CO3 in the recovery pro- ¦
cess and is effective at the same concentrations~ Borax, on _ 1~ _ , .. . , ~
. ' ~ 1058357 P-1300~
l 1 the other hand, ca~ be used ln lower concentrations on the order o~ from 2.to lO mole percent based on Na20. Tnus, ¦ 10 mole percent of borax lowers the melting point of pure ¦ Na2C03 smelt about 500F to 1093F In these concentrations, ¦ smelt fluidity is optlmized whereas smelt spout plugging and ¦ dissolving tank explosions are minimlzed.
¦ The chemicals employed in the present method of ¦ improving smelt properties and reducing dissolving tank ex-¦ plosions can be added at any point in the liquor cycle but ¦ preferably whe~e good control is available such as in the ¦ white liquor make up tank or. in the black liquor tank. It I i8 only necessary that the smelt contain an amount of such ¦ chemicals sufficient to lo~1er the melting point of the smelt ¦ 80 that stoppage does not occur due to a build-up of solid ¦ smelt prior to entering the dissolving tank.
By employing the chemicals described hereinbe~ore in the concentrations noted, several benefits result such ¦ as (l) fluidity of the smelt increases thus preventing major ¦ plugging of the spout from the~furnace and the resulting dissolving tank explosions when the plug is knocked off and ¦ a surge of smelt discharges from the furnace (2) there are no adverse effects on the pulp properties or paper produced therefrom (~) the chemical compounds used do not sensitize the sodium carbonate smelt (4) alkali metal salts existing in the pulping liquor after the digesting operation are so efficiently removed that very little ;na~ce-up chemical is required (5) chemical costs are substantially the same as .. -. , .
' . ',' ' ', :
1058357 F-1~003 l when only sodium compounds are used in the cooking liquor and (6) fuel savings a1~e appreciable. .
Although,the examples which follow are based upon the substitution or addition of various amounts of K2~03, KOH or borax in a cooking liquor containing a mixture of NaOH
and Na2CO3 which othe~ise would produce a 100% Na2CO3 smelt lt is to be understood that the conditions and amounts of chemicals are not to be limited thereto but that substantially the same desirable results are obtained when one employs the specified conditions or other chemicals hereinbefore enumerated to lcwer the melting point of a sodium based smelt.
THE PREFERRED E.~BODIMENTS
, . EXAMPLES 1 ~
Hardwoods containing 35% aspen were pulped using a 15, cooking liquor containing 85% by weight of sodium carbonate ând 15% by weight of sodium hydroxide both based on Na20.
Each cook consisted of 2000 grams of hardwood chips on an oven dried basis. Various amounts of K2C03 and KOH were substituted for the NazCO3 and NaOH of the standard cook and various amounts of borax were added thereto for comparison w~th the standard cook which used 5% by weight of total chemi~al expressed as Na20. A iiquor to wood ratio of 6 to l was used and each cook was heated to 340F. within 50 minutes and held there for another 45 minut,es. The cooked chips after each treatment were then defibered and the resulting pulp re-fined to 450 Canadian Standard Freeness. The refined pulp was converted into handsheets and the properties Or the paper deterrnined at 26 pounds per thousand square feet by standard . F-13003 lOS8357 1 procedure. The conditions employed, pulp yield obtained and the strength properties of the sheets are shown in the table ~elow wherein ring crush ls expressed in pounds per 6" o~ .
. sample length, tear in grams per 16 sheets, tensile in pounds p~. 1" wldth, corrugating medium test (CMT) in pounds per 10 flutes and additive as percent of total chemical expressed as Na2C.
Additive & % Pulp Ring .
Total~Chemical Yield % Crush Tear Tensile CMT
Standard 74.1 59 70 31.849.6 Standard . 76.9 63 72 ~1.555.7 Standard 79 7 60 70 33.056.0 Borax 2.7 76.2 67 72 30.3. 45.3 Borax 5.2 77.0 61 72 33,058.4 K2C03 10 75.2 57 . 73 31.151.6 K2CO3 25 77.1 59 69 30.~52.9 . KOH+Is'2CO3 20 77,0 59 7030.7 48.8 KOH+K2CO3 35 74.8 67 66 29.647.6 . KO~+K2CO3 50 76-5 64 69 30.151.2 From the foregoing data, it is apparent that the yield and physical properties Or the corrugating medium are not signi~icantly a~fected when various amounts of borax, K2CO3 and KOH are used in the cooking liquor compared to the . s-tandard cooking liquor containing.only NaOH and Na2CO3. In each instance where an additive was employed, the smelttem-. perature was drastically reduced and dissolving tank explosions . were diminished or eliminated.
` 10583S7 EXAMPLE 11 -~
In actual mill operations using a cooking liquor com-prising only sodium hydroxide and sodium carbonate with no add-itive to lower the melting point of the smelt resulting there-from, the smelt solidified in the recovery furnace spout, formed icicle-like projections 4 to 5 feet long which hung from the spout into the dissolving tank, plugged the spout hole and caused the molten smelt to solidify to a dangerous level in the furnace. Frequent plugging of the spout oeeur-ed requiring acetylen~ torches and a jack hammer to melt and chisel the solid-ified smelt off the spout and to ppen the spout hole. During thechiseling operation, large chunks of smelt fell into the dis-solving tank and upon contact with the water exploded violently which was extremely hazardous to the mill personael. Over a period of 30 days, about ~0~, spout pluggings occured.
When potassium carbonate, borax potassium hydroxide or mixtures thereof were added to the cooking liquor in the amounts specified in the preceding examples, only 14 spout pluggings oc~red during the same period of time. The additives kept the smelt soft and any accumulation usually fell off the spout unassisted in small chunks before any significant build-up took place. Whenever one of the infrequent pluggings did occur, the spout was readily clear~d by piercing the smelt with a metal lance.
If desired, other compounds such as lithium carbonate or potassium borate may be substituted for the compounds used in the examples with equally good results. All the compounds previously enumerated will lower the melting point of the ^ ~~ ' F-13003 ~
10S835~
1 smelt to keep it flowing smoothly into the dissolvlng tank :
and thus prevent smelt solidification and the devastating e~- .
plosions whlch have occurred in t~le past when huge particles of smelt contacted the water ln the dissolving tank. Concentra-tions of the compounds used to i~prove smelt properties can vary widely up to 80% based on Na,-,0 but for economic reasons a range of from 10 to 50% is preferred.
It will be apparent to those skilled in the art of wood pulping and chemical recovery that the same techniques herein described can be used advantageously in other types o~ chemical recovery processes and particularly those employ-ing a fluidized bed.
. ' , " .
.
.
, ' . .
' 20 ~ ~
. .
.
Molten smelt and water are a hazardous combination of compounds which are present in large quantities in a wood pulping mill. When such smelt mixes with water in a uncontrollable manner, violent explosions can occur. These explosions can take place in the recovery furnace when a boiler tube breaks and water comes into contact with molten smelt at the bottom of the furnace.
Dissolving tank explosions occur when molten smelt contacts the water or green liquor in the dissolving tank. Both of these explosions are extremely hazardous and have been a continuing concern to the paper industry for many years~ The dissolving tank explosions, while perhaps not posing as serious a threat to closing down a mill as a boiler explosion, nevertheless are an ever present threat to the safety of operating personnel and have forced cessation of mill operations in the past. It is the prevention and con .. . .
' 20 ,~, ' ,s :`~ , ' ' :'' ' .,. ' ' '' `;` ".
, .:,;
',:.~'; , ;
: 30 : ,.' -1-. . .
;"~ ,:
~ ~058357 trol of dissolving tank exploslons to which the present in-vention is primarily directed.
It is known in the art that the temperature and composition of the dissolving liquor in a straight soda pulp-ing operation influences the severity of the smelt-water re-action in that higher temperature result in less violence of quenching as does the use of pure water as compared to the pulping liquor containing dissolved salts. It was established that the addition of more than 5% NaCl or 10% NaOH to the smelt consistently produced explosions whereas pure Na2C03 was not explosive. Thus, the physical state of the smelt was found to be important and the prior art suggested shattering the molten smelt stream with steam ~ets prior to entering the dissolving tank.
The importance of the physical characterisitics of the smelt and especially the size of the molten smelt par-ticles under the surface of the liquor was recognized in the prior art. It was concluded that if the molten smelt is pre-sent in the form of small spheres~ it does not explode when quenched with water. ~owever, if the smelt is not flawing from the furnace in a steady stream the usual shattering device is inadequate to prevent the dissolving tank explosions which result when a molten globule falls from the furnace spout into the tank. The prevention of the freezing up of the smelt and the maintenance of a steady flow of' molten smelt by other than physical means is the principal ob~ect of this invention.
~ . " . ., SUMMARY OF THE INVENTION
_ In its broadest aspects, thR present invention in-volves the addition of an alkali metal compound preferably alkali metal hydroxides, carbonates and borates or mixtures thereof (other than sodium carbonate~ to a sodium based smelt produced from a wood pulping process in an amount sufficient to lower the melting point of the original smelt to improve molten smelt fluidity and prevent smelt spout plugging as well as dissolving tank explosions. In`addition, the smelt is softer and can be more readily removed from the spout if soldification does occur. More specifically, this invention is concerned with chemical means for improving the properties of sodium carbonate smelt produced from a non-sulfur wood pulping process such as one utilizing sodium carbonate and sodium hydroxide as the cooking liquor. Sodium carbonate smelts in particular require higher temperatures to prevent them from solidifying in the furnace compared to smelts containing sulfur produced by kraft or neutral sulfite semichemical processes.
Thus, in accordance with the present teachings, an improvement is provided in the cyclic pulping and chemical recovery process for producing paper pulp from ligno cellulosic materials which utilize an aqueous sodium based cooking liquor at elevated temperatures and pressures where-in the aqueous filtrate is separated from the pulp by washing, then concentrated and ignited in a recovery furnace to form a smelt which is dissolved in water and reconstituted for further use. The improvement in such a process comprises adding an alkali metal compound or mixtures thereof which are selected from the group consisting of LiOH, KOH, Li2CO3, K2CO3 and alkali metal borates to the pulping cycle in an amount sufficient to lower the melting point of .~
F~ 3 -0~83S7 the smelt to improve smelt fluidity and reduce dissolving tank explosions.
- 3a -.. .. .
1058357 F-l,003 GENER~L DESCRIPTION OF THE INVENTION
. . , ~
The depression of the melting point of a pure com-pound by adding a second component is a well known scienkific fact. However, more than ~ust lGwering the melting point is involved in adding chemicals to a smelt produced in a wood pulping process. For example, an~ chemical which is added must be non-explosive, non-corrosive, water soluble, economical, recoverable and above all, compatible with the other constituents ln the pulping liquor and no~ detrimental to the pulp pro-perties. It has now been found that only a llmited number of compounds meet the desired requirements. These compounds include lithium carbonate, lithium hydroxide, , potassium carbonate, potassium hydroxide~ potassiu~m borate, sodium borate and lithium borate. Of these, khe preferred compounds are potassium carbonate J potassium hydroxide and sodium borate.
The chemicals employed to decrease the melting point of the smelt are used in various concentrations. In general, any potassium containing compound can be used and preferably non-toxic compounds. Thus, the alkali metal hydroxides and carbonates are used in concentrations of from 1 to 80 mole percent based on Na20 but the maximum effect of K2C03 is achieved at about 40 mole percenk which lowers the melting point of NazCO3 smelt about 280F compared ko the melting point of 1593F for 100,~ Na2CO3 smelt. Sincè KOH is very similar to NaOH, it is converted to K2CO3 in the recovery pro- ¦
cess and is effective at the same concentrations~ Borax, on _ 1~ _ , .. . , ~
. ' ~ 1058357 P-1300~
l 1 the other hand, ca~ be used ln lower concentrations on the order o~ from 2.to lO mole percent based on Na20. Tnus, ¦ 10 mole percent of borax lowers the melting point of pure ¦ Na2C03 smelt about 500F to 1093F In these concentrations, ¦ smelt fluidity is optlmized whereas smelt spout plugging and ¦ dissolving tank explosions are minimlzed.
¦ The chemicals employed in the present method of ¦ improving smelt properties and reducing dissolving tank ex-¦ plosions can be added at any point in the liquor cycle but ¦ preferably whe~e good control is available such as in the ¦ white liquor make up tank or. in the black liquor tank. It I i8 only necessary that the smelt contain an amount of such ¦ chemicals sufficient to lo~1er the melting point of the smelt ¦ 80 that stoppage does not occur due to a build-up of solid ¦ smelt prior to entering the dissolving tank.
By employing the chemicals described hereinbe~ore in the concentrations noted, several benefits result such ¦ as (l) fluidity of the smelt increases thus preventing major ¦ plugging of the spout from the~furnace and the resulting dissolving tank explosions when the plug is knocked off and ¦ a surge of smelt discharges from the furnace (2) there are no adverse effects on the pulp properties or paper produced therefrom (~) the chemical compounds used do not sensitize the sodium carbonate smelt (4) alkali metal salts existing in the pulping liquor after the digesting operation are so efficiently removed that very little ;na~ce-up chemical is required (5) chemical costs are substantially the same as .. -. , .
' . ',' ' ', :
1058357 F-1~003 l when only sodium compounds are used in the cooking liquor and (6) fuel savings a1~e appreciable. .
Although,the examples which follow are based upon the substitution or addition of various amounts of K2~03, KOH or borax in a cooking liquor containing a mixture of NaOH
and Na2CO3 which othe~ise would produce a 100% Na2CO3 smelt lt is to be understood that the conditions and amounts of chemicals are not to be limited thereto but that substantially the same desirable results are obtained when one employs the specified conditions or other chemicals hereinbefore enumerated to lcwer the melting point of a sodium based smelt.
THE PREFERRED E.~BODIMENTS
, . EXAMPLES 1 ~
Hardwoods containing 35% aspen were pulped using a 15, cooking liquor containing 85% by weight of sodium carbonate ând 15% by weight of sodium hydroxide both based on Na20.
Each cook consisted of 2000 grams of hardwood chips on an oven dried basis. Various amounts of K2C03 and KOH were substituted for the NazCO3 and NaOH of the standard cook and various amounts of borax were added thereto for comparison w~th the standard cook which used 5% by weight of total chemi~al expressed as Na20. A iiquor to wood ratio of 6 to l was used and each cook was heated to 340F. within 50 minutes and held there for another 45 minut,es. The cooked chips after each treatment were then defibered and the resulting pulp re-fined to 450 Canadian Standard Freeness. The refined pulp was converted into handsheets and the properties Or the paper deterrnined at 26 pounds per thousand square feet by standard . F-13003 lOS8357 1 procedure. The conditions employed, pulp yield obtained and the strength properties of the sheets are shown in the table ~elow wherein ring crush ls expressed in pounds per 6" o~ .
. sample length, tear in grams per 16 sheets, tensile in pounds p~. 1" wldth, corrugating medium test (CMT) in pounds per 10 flutes and additive as percent of total chemical expressed as Na2C.
Additive & % Pulp Ring .
Total~Chemical Yield % Crush Tear Tensile CMT
Standard 74.1 59 70 31.849.6 Standard . 76.9 63 72 ~1.555.7 Standard 79 7 60 70 33.056.0 Borax 2.7 76.2 67 72 30.3. 45.3 Borax 5.2 77.0 61 72 33,058.4 K2C03 10 75.2 57 . 73 31.151.6 K2CO3 25 77.1 59 69 30.~52.9 . KOH+Is'2CO3 20 77,0 59 7030.7 48.8 KOH+K2CO3 35 74.8 67 66 29.647.6 . KO~+K2CO3 50 76-5 64 69 30.151.2 From the foregoing data, it is apparent that the yield and physical properties Or the corrugating medium are not signi~icantly a~fected when various amounts of borax, K2CO3 and KOH are used in the cooking liquor compared to the . s-tandard cooking liquor containing.only NaOH and Na2CO3. In each instance where an additive was employed, the smelttem-. perature was drastically reduced and dissolving tank explosions . were diminished or eliminated.
` 10583S7 EXAMPLE 11 -~
In actual mill operations using a cooking liquor com-prising only sodium hydroxide and sodium carbonate with no add-itive to lower the melting point of the smelt resulting there-from, the smelt solidified in the recovery furnace spout, formed icicle-like projections 4 to 5 feet long which hung from the spout into the dissolving tank, plugged the spout hole and caused the molten smelt to solidify to a dangerous level in the furnace. Frequent plugging of the spout oeeur-ed requiring acetylen~ torches and a jack hammer to melt and chisel the solid-ified smelt off the spout and to ppen the spout hole. During thechiseling operation, large chunks of smelt fell into the dis-solving tank and upon contact with the water exploded violently which was extremely hazardous to the mill personael. Over a period of 30 days, about ~0~, spout pluggings occured.
When potassium carbonate, borax potassium hydroxide or mixtures thereof were added to the cooking liquor in the amounts specified in the preceding examples, only 14 spout pluggings oc~red during the same period of time. The additives kept the smelt soft and any accumulation usually fell off the spout unassisted in small chunks before any significant build-up took place. Whenever one of the infrequent pluggings did occur, the spout was readily clear~d by piercing the smelt with a metal lance.
If desired, other compounds such as lithium carbonate or potassium borate may be substituted for the compounds used in the examples with equally good results. All the compounds previously enumerated will lower the melting point of the ^ ~~ ' F-13003 ~
10S835~
1 smelt to keep it flowing smoothly into the dissolvlng tank :
and thus prevent smelt solidification and the devastating e~- .
plosions whlch have occurred in t~le past when huge particles of smelt contacted the water ln the dissolving tank. Concentra-tions of the compounds used to i~prove smelt properties can vary widely up to 80% based on Na,-,0 but for economic reasons a range of from 10 to 50% is preferred.
It will be apparent to those skilled in the art of wood pulping and chemical recovery that the same techniques herein described can be used advantageously in other types o~ chemical recovery processes and particularly those employ-ing a fluidized bed.
. ' , " .
.
.
, ' . .
' 20 ~ ~
. .
.
Claims (9)
1. In a cyclic pulping and chemical recovery pro-cess for producing paper pulp from ligno cellulosic materials utilizing an aqueous sodium based cooking liquor at elevated temperatures and pressures wherein the aqueous filtrate is separated from the pulp by washing, then concentrated and ignited in a recovery furnace to form a smelt which is dis-solved in water and reconstituted for further use, the improve-ment which comprises adding an alkali metal compound or mixtures thereof selected from the group consisting of LiOH, KOH, Li2CO3, K2CO3 and alkali metal borates to the pulping cycle in an amount sufficient to lower the melting point of the smelt to improve smelt fluidity and reduce dissolving tank explosions.
2. A process as in Claim 1 in which the alkali metal compound is potassium carbonate.
3. A process as in Claim 1 in which the compound added is lithium carbonate.
4. A process as in Claim 1 in which the alkali metal compound added is potassium hydroxide.
5. A process as in Claim 1 in which the alkali metal borate is borax.
6. A process as in Claim 1 in which the alkali metal borate is potassium borate.
7. A process as in Claim 1 in which the alkali metal borate is added in a concentration of from 2 to 10 mole percent based on sodium oxide.
8. A process as in Claim 1 in which the alkali metal hydroxides and carbonates are added in a concentration of from 1 to 80 mole percent based on sodium oxide.
9. A process as in Claim 1 in which the alkali metal hydroxides and carbonates are added in a concentration of from 5 to 50 mole percent based on sodium oxide.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US406498A US3873413A (en) | 1973-10-15 | 1973-10-15 | Method of improving smelt properties and reducing dissolving tank explosions during pulping of wood with sodium based liquors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1058357A true CA1058357A (en) | 1979-07-17 |
Family
ID=23608241
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA211,277A Expired CA1058357A (en) | 1973-10-15 | 1974-10-11 | Method of improving smelt properties and reducing dissolving tank explosions during pulping of wood with sodium based liquors |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US3873413A (en) |
| JP (1) | JPS524642B2 (en) |
| BR (1) | BR7408536D0 (en) |
| CA (1) | CA1058357A (en) |
| DE (1) | DE2448891C3 (en) |
| ES (1) | ES430977A1 (en) |
| FR (1) | FR2247576B1 (en) |
| GB (1) | GB1489349A (en) |
| SE (1) | SE412424B (en) |
| ZA (1) | ZA746077B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4106978A (en) * | 1977-01-31 | 1978-08-15 | Combustion Engineering, Inc. | Method of preventing explosions using a smelt water explosion inhibitor |
| US6348128B1 (en) * | 1998-06-01 | 2002-02-19 | U.S. Borax Inc. | Method of increasing the causticizing efficiency of alkaline pulping liquor by borate addition |
| US6294048B1 (en) * | 1998-06-01 | 2001-09-25 | U.S. Borax Inc. | Method for regenerating sodium hydroxide by partial autocausticizing sodium carbonate containing smelt by reaction with a borate |
| US20050037226A1 (en) * | 2003-08-12 | 2005-02-17 | Peascoe Meisner Roberta A. | Alkali resistant refractories |
| US7735435B2 (en) * | 2006-05-24 | 2010-06-15 | Diamond Power International, Inc. | Apparatus for cleaning a smelt spout of a combustion device |
| US7854847B2 (en) * | 2006-11-09 | 2010-12-21 | Rayonier Trs Holdings Inc. | Process of purifying wood pulp with caustic-borate solution and recovering the purifying chemical |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3447895A (en) * | 1966-12-01 | 1969-06-03 | Combustion Eng | Method of preventing smelt-water explosions |
| US3615175A (en) * | 1969-03-24 | 1971-10-26 | Combustion Eng | Preventing physical explosion due to the interaction of liquid water and molten chemical compounds |
| US3650889A (en) * | 1970-08-03 | 1972-03-21 | Combustion Eng | Pollution controlled polysulfide recovery process |
-
1973
- 1973-10-15 US US406498A patent/US3873413A/en not_active Expired - Lifetime
-
1974
- 1974-09-25 ZA ZA00746077A patent/ZA746077B/en unknown
- 1974-10-11 GB GB44140/74A patent/GB1489349A/en not_active Expired
- 1974-10-11 CA CA211,277A patent/CA1058357A/en not_active Expired
- 1974-10-14 FR FR7434424A patent/FR2247576B1/fr not_active Expired
- 1974-10-14 ES ES430977A patent/ES430977A1/en not_active Expired
- 1974-10-14 BR BR8536/74A patent/BR7408536D0/en unknown
- 1974-10-14 SE SE7412884A patent/SE412424B/en not_active IP Right Cessation
- 1974-10-14 DE DE2448891A patent/DE2448891C3/en not_active Expired
- 1974-10-15 JP JP49118608A patent/JPS524642B2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| SE7412884L (en) | 1975-04-16 |
| FR2247576A1 (en) | 1975-05-09 |
| BR7408536D0 (en) | 1975-08-05 |
| ZA746077B (en) | 1976-04-28 |
| JPS5064502A (en) | 1975-05-31 |
| ES430977A1 (en) | 1976-10-16 |
| DE2448891C3 (en) | 1978-04-27 |
| FR2247576B1 (en) | 1977-11-10 |
| SE412424B (en) | 1980-03-03 |
| GB1489349A (en) | 1977-10-19 |
| DE2448891A1 (en) | 1975-04-17 |
| US3873413A (en) | 1975-03-25 |
| DE2448891B2 (en) | 1977-09-01 |
| JPS524642B2 (en) | 1977-02-05 |
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