CN108396580B - Method for improving passivation evaporation efficiency of black liquor - Google Patents
Method for improving passivation evaporation efficiency of black liquor Download PDFInfo
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- CN108396580B CN108396580B CN201810089520.2A CN201810089520A CN108396580B CN 108396580 B CN108396580 B CN 108396580B CN 201810089520 A CN201810089520 A CN 201810089520A CN 108396580 B CN108396580 B CN 108396580B
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- 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
- D21C11/10—Concentrating spent liquor by evaporation
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Abstract
The invention relates to the technical field of papermaking and pulping, in particular to a method for improving passivation evaporation efficiency of black liquor, which comprises the steps of pre-effect evaporation, circulating high-temperature passivation, flash evaporation, post-effect evaporation and pressurization treatment, wherein the pressure of medium-pressure steam used for high-temperature passivation is controlled to be 1-1.5 MPa, the temperature is controlled to be 130-150 ℃, and the time for high-temperature passivation is 40-80 min. The invention promotes the degradation of polysaccharide and lignin, reduces the viscosity of the black liquor and improves the fluidity of the black liquor through the integral optimization and the synergistic action of the process, thereby improving the heat transfer efficiency, being beneficial to the evaporation of water in the black liquor to obtain the high-concentration black liquor with the solid concentration of more than 68 percent, further improving the evaporation efficiency and the heat efficiency of a subsequent alkali recovery furnace and reducing the whole energy consumption.
Description
Technical Field
The invention relates to the technical field of papermaking pulping, in particular to a method for improving passivation evaporation efficiency of black liquor.
Background
In the process of pulping by a sulfate method, washing liquid waste water after washing and cooking is black brown, namely black liquor, and the black liquor contains inorganic matters in the cooking liquor, a large amount of degradation products of lignin, hemicellulose and cellulose, organic acids and other toxic substances dissolved out from plant fiber raw materials, so the black liquor needs to be treated. In the prior art, because the viscosity of black liquor is relatively high, especially the bamboo pulp black liquor, under the same conditions, the viscosity of the bamboo pulp black liquor is greater than that of wood pulp black liquor, the viscosity of the black liquor is continuously increased when the black liquor is increased to a certain concentration through evaporation concentration, and the viscosity is increased, so that the heat transfer efficiency, the conveying and the like of the black liquor are directly influenced, the evaporation concentration is not facilitated, the difficulty is brought to the production of the black liquor with higher concentration, and more steam is consumed; meanwhile, the concentration of the black liquor which enters the alkali recovery furnace after evaporation and concentration and is combusted is low, so that the black liquor is not beneficial to combustion, the heat efficiency of the alkali recovery furnace is influenced, the energy consumption in the whole system is high, and the energy conservation is not beneficial.
Disclosure of Invention
The invention aims to provide a method for improving the black liquor passivation evaporation efficiency aiming at the defects of the prior art, which can reduce the viscosity of the black liquor, improve the concentration of the black liquor after evaporation concentration to more than 68 percent, and further improve the evaporation efficiency and the thermal efficiency of a subsequent alkali recovery furnace.
In order to achieve the purpose, the invention adopts the following technical scheme:
the method for improving the efficiency of black liquor passivation evaporation comprises the following steps:
step one, front effect evaporation:
conveying the dilute black liquor obtained after bamboo pulp cooking and washing to a four-effect evaporator system, wherein the dilute black liquor sequentially enters a fourth-effect evaporator and a third-effect evaporator for evaporation treatment, the steam temperature of the fourth-effect evaporator is 62-70 ℃, and the steam temperature of the third-effect evaporator is 75-82 ℃;
step two, circulating high-temperature passivation:
(1) preheating treatment:
conveying the black liquor treated by the third effect evaporator to a black liquor preheater for preheating treatment;
(2) high-temperature passivation:
pumping the preheated black liquor into a high-temperature passivation pot, and performing high-temperature passivation by adopting medium-pressure steam, wherein the pressure of the medium-pressure steam is 1-1.5 MPa, the temperature is 130-150 ℃, and the high-temperature passivation time is 40-80 min;
(3) and (3) circulating treatment: the black liquor in the high-temperature passivation pot returns to the black liquor preheater through a circulating pump;
step three, flash evaporation cooling:
sending the black liquor after high-temperature passivation to a flash evaporation tank for flash evaporation treatment, and conveying steam generated by flash evaporation to a black liquor preheater for preheating the black liquor;
step four, after-effect evaporation:
sequentially sending the black liquor subjected to flash evaporation treatment to a second-effect evaporator and a first-effect evaporator for evaporation treatment, wherein the steam temperature of the second-effect evaporator is 105-115 ℃, and the steam temperature of the first-effect evaporator is 120-125 ℃, so as to obtain high-concentration black liquor;
step five, pressurization treatment:
and (4) sending the high-concentration black liquor treated by the first effect evaporator to a pressurizing tank for pressurizing treatment to obtain high-pressure high-concentration black liquor for later use.
In the technical scheme, the flash evaporation gas generated in the second step is connected with the second effect evaporator and the first effect evaporator through a steam pipeline.
In the technical scheme, in the fifth step, the pressure of the high-pressure high-concentration black liquor is 1.2-1.3 MPa.
In the technical scheme, in the fifth step, the viscosity of the high-pressure high-concentration black liquor is 102-116 mPa.s.
The invention has the beneficial effects that:
the method for improving the passivation evaporation efficiency of the black liquor comprises the steps of conveying the dilute black liquor obtained after bamboo pulp is steamed and washed to a four-effect evaporator system, carrying out front-effect evaporation on the dilute black liquor sequentially through a fourth-effect evaporator and a third-effect evaporator, controlling the steam temperature of the fourth-effect evaporator to be 62-70 ℃, and controlling the steam temperature of the third-effect evaporator to be 75-82 ℃; then, circulating high-temperature passivation is carried out, wherein the pressure of medium-pressure steam used for high-temperature passivation is controlled to be 1-1.5 MPa, the temperature is controlled to be 130-150 ℃, and the time of high-temperature passivation is 40-80 min; and (3) carrying out flash evaporation cooling on the black liquor subjected to high-temperature cyclic passivation, then carrying out after-effect evaporation treatment, controlling the steam temperature of a second-effect evaporator to be 105-115 ℃, controlling the steam temperature of a first-effect evaporator to be 120-125 ℃, and finally carrying out pressurization treatment to obtain the high-pressure high-concentration black liquor. Through the overall optimization and the synergistic effect of the processes, the residual alkali in the black liquor in the step of circulating high-temperature passivation reacts with the polysaccharide and the macromolecular lignin dissolved in the black liquor, the polysaccharide and the lignin are promoted to be degraded, the fluidity of the black liquor is improved, and the viscosity of the finally obtained high-concentration black liquor is reduced to 102-116 mPa.s, so that the heat transfer efficiency is improved, the evaporation of water in the black liquor is facilitated to obtain the high-concentration black liquor with the solid concentration of more than 68%, the evaporation efficiency and the thermal efficiency of a subsequent alkali recovery furnace are improved, the thermal efficiency of a boiler is improved, meanwhile, steam generated in the high-temperature passivation process is used as secondary steam for a back-effect evaporator and a black liquor preheater, and the whole energy consumption is.
Detailed Description
The invention is further illustrated by the following examples.
Example 1.
The invention relates to a method for improving passivation evaporation efficiency of black liquor, which comprises the following steps:
step one, front effect evaporation:
conveying the dilute black liquor obtained after the bamboo pulp is steamed and washed to a four-effect evaporator system, wherein the dilute black liquor sequentially enters a fourth-effect evaporator and a third-effect evaporator for evaporation treatment, the steam temperature of the fourth-effect evaporator is 67 ℃, and the steam temperature of the third-effect evaporator is 80 ℃;
step two, circulating high-temperature passivation:
(1) preheating treatment:
conveying the black liquor treated by the third effect evaporator to a black liquor preheater for preheating treatment;
(2) high-temperature passivation:
pumping the preheated black liquor into a high-temperature passivation pot, and performing high-temperature passivation by adopting medium-pressure steam, wherein the pressure of the medium-pressure steam is 1.2MPa, the temperature is 140 ℃, and the high-temperature passivation time is 60 min;
(3) and (3) circulating treatment: the black liquor in the high-temperature passivation pot returns to the black liquor preheater through a circulating pump;
step three, flash evaporation cooling:
sending the black liquor after high-temperature passivation to a flash evaporation tank for flash evaporation treatment, and conveying steam generated by flash evaporation to a black liquor preheater for preheating the black liquor;
step four, after-effect evaporation:
the black liquor after flash evaporation treatment is sequentially sent to a second-effect evaporator and a first-effect evaporator for evaporation treatment, the steam temperature of the second-effect evaporator is 110 ℃, the steam temperature of the first-effect evaporator is 123 ℃, and high-concentration black liquor is obtained;
step five, pressurization treatment:
sending the high-concentration black liquor treated by the first effect evaporator to a pressurizing tank for pressurizing treatment to obtain high-pressure high-concentration black liquor for later use; the pressure of the high-pressure high-concentration black liquor is 1.25MPa, and the viscosity is 109mPa.
As a preferred embodiment, the flash gas generated in step two is connected to the second effect evaporator and the first effect evaporator through a steam line.
Example 2.
The invention relates to a method for improving passivation evaporation efficiency of black liquor, which comprises the following steps:
step one, front effect evaporation:
conveying the dilute black liquor obtained after the bamboo pulp is steamed and washed to a four-effect evaporator system, wherein the dilute black liquor sequentially enters a fourth-effect evaporator and a third-effect evaporator for evaporation treatment, the steam temperature of the fourth-effect evaporator is 62 ℃, and the steam temperature of the third-effect evaporator is 75 ℃;
step two, circulating high-temperature passivation:
(1) preheating treatment:
conveying the black liquor treated by the third effect evaporator to a black liquor preheater for preheating treatment;
(2) high-temperature passivation:
pumping the preheated black liquor into a high-temperature passivation pot, and performing high-temperature passivation by adopting medium-pressure steam, wherein the pressure of the medium-pressure steam is 1MPa, the temperature is 130 ℃, and the high-temperature passivation time is 80 min;
(3) and (3) circulating treatment: the black liquor in the high-temperature passivation pot returns to the black liquor preheater through a circulating pump;
step three, flash evaporation cooling:
sending the black liquor after high-temperature passivation to a flash evaporation tank for flash evaporation treatment, and conveying steam generated by flash evaporation to a black liquor preheater for preheating the black liquor;
step four, after-effect evaporation:
the black liquor after flash evaporation treatment is sequentially sent to a second-effect evaporator and a first-effect evaporator for evaporation treatment, the steam temperature of the second-effect evaporator is 105 ℃, the steam temperature of the first-effect evaporator is 120 ℃, and high-concentration black liquor is obtained;
step five, pressurization treatment:
sending the high-concentration black liquor treated by the first effect evaporator to a pressurizing tank for pressurizing treatment to obtain high-pressure high-concentration black liquor for later use; the pressure of the high-pressure high-concentration black liquor is 1.2MPa, and the viscosity is 102mPa.
As a preferred embodiment, the flash gas generated in step two is connected to the second effect evaporator and the first effect evaporator through a steam line.
Example 3.
The invention relates to a method for improving passivation evaporation efficiency of black liquor, which comprises the following steps:
step one, front effect evaporation:
conveying the dilute black liquor obtained after the bamboo pulp is steamed and washed to a four-effect evaporator system, wherein the dilute black liquor sequentially enters a fourth-effect evaporator and a third-effect evaporator for evaporation treatment, the steam temperature of the fourth-effect evaporator is 70 ℃, and the steam temperature of the third-effect evaporator is 82 ℃;
step two, circulating high-temperature passivation:
(1) preheating treatment:
conveying the black liquor treated by the third effect evaporator to a black liquor preheater for preheating treatment;
(2) high-temperature passivation:
pumping the preheated black liquor into a high-temperature passivation pot, and performing high-temperature passivation by adopting medium-pressure steam, wherein the pressure of the medium-pressure steam is 1.5MPa, the temperature is 150 ℃, and the high-temperature passivation time is 40 min;
(3) and (3) circulating treatment: the black liquor in the high-temperature passivation pot returns to the black liquor preheater through a circulating pump;
step three, flash evaporation cooling:
sending the black liquor after high-temperature passivation to a flash evaporation tank for flash evaporation treatment, and conveying steam generated by flash evaporation to a black liquor preheater for preheating the black liquor;
step four, after-effect evaporation:
the black liquor after flash evaporation treatment is sequentially sent to a second-effect evaporator and a first-effect evaporator for evaporation treatment, the steam temperature of the second-effect evaporator is 115 ℃, the steam temperature of the first-effect evaporator is 125 ℃, and high-concentration black liquor is obtained;
step five, pressurization treatment:
sending the high-concentration black liquor treated by the first effect evaporator to a pressurizing tank for pressurizing treatment to obtain high-pressure high-concentration black liquor for later use; the pressure of the high-pressure high-concentration black liquor is 1.3MPa, and the viscosity is 116mPa.
As a preferred embodiment, the flash gas generated in step two is connected to the second effect evaporator and the first effect evaporator through a steam line.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (4)
1. A method for improving the efficiency of passivation evaporation of black liquor is characterized in that: the method comprises the following steps:
step one, front effect evaporation:
conveying the dilute black liquor obtained after bamboo pulp cooking and washing to a four-effect evaporator system, wherein the dilute black liquor sequentially enters a fourth-effect evaporator and a third-effect evaporator for evaporation treatment, the steam temperature of the fourth-effect evaporator is 62-70 ℃, and the steam temperature of the third-effect evaporator is 75-82 ℃;
step two, circulating high-temperature passivation:
(1) preheating treatment:
conveying the black liquor treated by the third effect evaporator to a black liquor preheater for preheating treatment;
(2) high-temperature passivation:
pumping the preheated black liquor into a high-temperature passivation pot, and performing high-temperature passivation by adopting medium-pressure steam, wherein the pressure of the medium-pressure steam is 1-1.5 MPa, the temperature is 130-150 ℃, and the high-temperature passivation time is 40-80 min;
(3) and (3) circulating treatment: the black liquor in the high-temperature passivation pot returns to the black liquor preheater through a circulating pump;
step three, flash evaporation cooling:
sending the black liquor after high-temperature passivation to a flash evaporation tank for flash evaporation treatment, and conveying steam generated by flash evaporation to a black liquor preheater for preheating the black liquor;
step four, after-effect evaporation:
sequentially sending the black liquor subjected to flash evaporation treatment to a second-effect evaporator and a first-effect evaporator for evaporation treatment, wherein the steam temperature of the second-effect evaporator is 105-115 ℃, and the steam temperature of the first-effect evaporator is 120-125 ℃, so as to obtain high-concentration black liquor;
step five, pressurization treatment:
and (4) sending the high-concentration black liquor treated by the first effect evaporator to a pressurizing tank for pressurizing treatment to obtain high-pressure high-concentration black liquor for later use.
2. A method of increasing the efficiency of black liquor passivation evaporation according to claim 1, characterized by: and the flash evaporation gas generated in the second step is connected with the second effect evaporator and the first effect evaporator through a steam pipeline.
3. A method of increasing the efficiency of black liquor passivation evaporation according to claim 1, characterized by: in the fifth step, the pressure of the high-pressure high-concentration black liquor is 1.2-1.3 MPa.
4. A method of increasing the efficiency of black liquor passivation evaporation according to claim 1, characterized by: in the fifth step, the viscosity of the high-pressure high-concentration black liquor is 102-116 mPa · s.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101736639A (en) * | 2008-11-21 | 2010-06-16 | 天津晟成环境技术发展有限公司 | Process and equipment for improving concentration of straw pulping black liquor by alkali method |
| CN203866629U (en) * | 2014-03-18 | 2014-10-08 | 天津市恒脉机电科技有限公司 | Straw pulp black liquor passivation system |
| CN204919198U (en) * | 2015-07-15 | 2015-12-30 | 重庆理文造纸有限公司 | Recovery system of high enriched bamboo pulp black liquor |
| CN205077315U (en) * | 2015-07-15 | 2016-03-09 | 重庆理文造纸有限公司 | Evaporation passivation flash steam recycling system |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101736639A (en) * | 2008-11-21 | 2010-06-16 | 天津晟成环境技术发展有限公司 | Process and equipment for improving concentration of straw pulping black liquor by alkali method |
| CN203866629U (en) * | 2014-03-18 | 2014-10-08 | 天津市恒脉机电科技有限公司 | Straw pulp black liquor passivation system |
| CN204919198U (en) * | 2015-07-15 | 2015-12-30 | 重庆理文造纸有限公司 | Recovery system of high enriched bamboo pulp black liquor |
| CN205077315U (en) * | 2015-07-15 | 2016-03-09 | 重庆理文造纸有限公司 | Evaporation passivation flash steam recycling system |
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