CN108823684B - Efficient and energy-saving nmmo solution concentration system and concentration method - Google Patents
Efficient and energy-saving nmmo solution concentration system and concentration method Download PDFInfo
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Abstract
The invention relates to a high-efficiency energy-saving nmmo solution concentration system and a concentration method, wherein the concentration system comprises at least two stages of concentration units which are sequentially arranged, each stage of concentration unit comprises a separator and a heater which are communicated through a connecting pipeline and mutually perform material circulation, each separator is provided with a secondary steam outlet, the steam outlet of the separator of the last stage of concentration unit is used for discharging redundant secondary steam, the steam outlets of the separators of other concentration units are communicated with the heater of the next stage of concentration unit through an air outlet pipeline, each heater is provided with a solution outlet, the solution outlet of the heater of the first stage of concentration unit is used for discharging concentrated high-concentration nmmo solution through an outlet pipeline, and the solution outlets of the heaters of other concentration units are communicated with the separator of the previous stage of concentration unit through an outlet pipeline. The invention adopts a countercurrent reduced pressure evaporation system and process to realize low-concentration low-temperature evaporation and high-concentration high-temperature evaporation, and effectively utilizes secondary steam as a heating heat source.
Description
Technical Field
The invention relates to a solution concentration system and a solution concentration method, in particular to a high-efficiency and energy-saving nmmo solution concentration system and a concentration method, and particularly relates to a nmmo solution concentration system and a concentration method in a lyocell fiber production process.
Background
In the production process of the lyocell fiber, the cleaning procedure of the tows needs to use clear water to clean nmmo carried by the tows, and a relatively thorough cleaning effect is achieved, so that a relatively large washing water amount needs to be ensured, the concentration of the obtained nmmo solution is too low, and the solution needs to be evaporated and concentrated and then recycled. Generally, the obtained nmmo concentration is about 15-25%, but the nmmo concentration needs to be evaporated and concentrated to 85% according to production requirements and then recycled.
Because nmmo is expensive, the recovery rate directly affects the future operation cost. The research on the efficient nmmo recovery device and the process is the economic guarantee for the final realization of industrialization.
The concentration of nmmo material has a high influence on the boiling point of its solution, and its decomposition occurs easily at temperatures above 110 ℃ and there is a risk of explosion, depending on the nature of the nmmo material. Therefore, a reduced pressure evaporation process is required, and the requirement on the vacuum degree is high.
The common multi-effect evaporation system mostly adopts a concurrent flow evaporation process, and the concentrated solution is discharged in a final effect. Because the boiling point of the end-effect solution is high and the conditions for secondary steam utilization are harsh, part of the primary fresh steam source must be supplemented, and part of the waste heat cannot be recycled finally.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provide a high-efficiency and energy-saving nmmo solution concentration system and a concentration method, a countercurrent reduced-pressure evaporation system and a countercurrent reduced-pressure evaporation process are adopted, low-concentration low-temperature evaporation and high-concentration high-temperature evaporation are realized, the evaporation intensity can be improved, and secondary steam is effectively used as a heating heat source.
The technical scheme for solving the technical problems is as follows: an efficient energy-saving nmmo solution concentration system comprises at least two stages of concentration units which are sequentially arranged, wherein each stage of concentration unit comprises a separator and a heater which are communicated through a connecting pipeline and mutually perform material circulation, each separator is provided with a secondary steam outlet, the separator of the last stage of concentration unit is also provided with a solution inlet for introducing low-concentration nmmo solution to be concentrated, and the steam outlet of the last stage of concentration unit is used for discharging redundant secondary steam, the steam outlets of the separators of other concentration units are communicated with the heaters of the next-stage concentration unit through an air outlet pipeline, each heater is provided with a solution outlet, the heater of the first-stage concentration unit is provided with a steam inlet for introducing fresh steam, the solution outlet of the first-stage concentration unit discharges concentrated high-concentration nmmo solution through an outlet pipeline, the solution outlets of the heaters of other concentration units are communicated with the separator of the previous concentration unit through a liquid outlet pipeline.
On the basis of the technical scheme, the invention can be further improved as follows.
Furthermore, a steam outlet of the separator of the last stage of concentration unit is communicated to a condenser through an air outlet pipeline, and a condensed water discharge pipe with a valve is arranged at the bottom of the condenser.
The further scheme has the advantages that the temperature of secondary steam generated by separation of the separator of the last-stage concentration unit is low and is not suitable for recycling, so that the secondary steam can be introduced into the condenser and condensed by normal-temperature cooling water, and the generated condensed water is periodically discharged from the condenser and directly discharged or further utilized.
Furthermore, heaters of all stages of concentration units are respectively communicated to condensers through non-condensable gas pipelines, valves are respectively arranged on the non-condensable gas pipelines, and the condensers are communicated with an air inlet of a vacuum pump.
The beneficial effect of adopting above-mentioned further scheme is that in each heater, except can producing the secondary steam, still can produce some noncondensable gas, and these gases need be taken away to guarantee the vacuum in each concentration unit, so need the vacuum pump to take away. Specifically, the gas can be completely introduced into a condenser, condensed by water, and then pumped away by a vacuum pump, wherein the gas cannot be condensed.
Further, the separator and the heater of each stage of the concentration unit perform material circulation with each other by a forced circulation pump provided in the connection pipe.
Furthermore, each liquid outlet pipeline is respectively provided with a concentration online detector and a valve.
The concentration of the solution processed by each concentration unit is different, when the concentration of the solution in one concentration unit meets the requirement of entering the upper-stage concentration unit, the solution needs to be introduced, the concentration online detector can be designed to monitor the concentration of the solution in the concentration unit, and the flow of the solution is controlled by the valve on the liquid outlet pipeline after the index is reached.
Furthermore, valves are respectively arranged at a solution inlet of the separator of the last stage concentration unit and a steam inlet of the heater of the first stage concentration unit, and are used for respectively controlling the low-concentration nmmo solution to be treated and the fresh steam to enter the whole concentration system.
Further, the heaters of the concentration units at all levels are sequentially communicated through condensed water pipelines, the heat exchanger of the concentration unit at the last level discharges condensed water through the condensed water pipelines, and valves are respectively arranged on the condensed water pipelines.
Adopt above-mentioned further scheme's beneficial effect be when concentrated system shut down, pause use or overhaul of the equipments, need all discharge residual material and comdenstion water in the concentrated system, based on this requirement, can set up the condensate water pipeline in the bottom of each heater, communicate in proper order from the past backward to through the condensate water pipeline discharge residual material and the comdenstion water of last heater, corresponding each set up the valve on the condensate water pipeline respectively, through opening or closing of electronic control system control valve.
Further, the high-efficiency energy-saving nmmo solution concentration system comprises a four-stage concentration unit. In the preferred embodiment of the present invention, the concentration system is a four-stage concentration unit, i.e. a four-effect countercurrent reduced-pressure evaporation concentration system.
The invention also relates to a high-efficiency and energy-saving method for concentrating nmmo solution, which realizes the concentration of nmmo solution by utilizing the four-effect countercurrent reduced-pressure evaporation concentration system and comprises the following steps:
(1) preheating the low-concentration nmmo solution, feeding the low-concentration nmmo solution into a fourth-stage concentration unit from a solution inlet, continuously heating and evaporating the solution in a heater of the fourth-stage concentration unit through secondary steam fed by the third-stage concentration unit, performing gas-liquid separation on a separator of the fourth-stage concentration unit, discharging redundant secondary steam from a steam outlet, and introducing the obtained first-stage concentrated solution into the third-stage concentration unit;
(2) continuously heating and evaporating the primary concentrated solution in a heater of the third-stage concentration unit through secondary steam sent by the second-stage concentration unit, carrying out gas-liquid separation on a separator of the third-stage concentration unit, sending the obtained secondary steam into the fourth-stage concentration unit, and introducing the obtained secondary concentrated solution into the second-stage concentration unit;
(3) continuously heating and evaporating the secondary concentrated solution in a heater of the secondary concentration unit through secondary steam sent by the primary concentration unit, carrying out gas-liquid separation in a separator of the secondary concentration unit, sending the obtained secondary steam into a third concentration unit, and introducing the obtained third concentrated solution into the primary concentration unit;
(4) and continuously heating and evaporating the third-level concentrated solution in a heater of the first-level concentration unit through fresh steam fed from a steam inlet, carrying out gas-liquid separation on a separator of the first-level concentration unit, feeding obtained secondary steam into the second-level concentration unit, and discharging obtained fourth-level concentrated solution through a solution outlet to finish concentration.
Further, in the fourth-stage concentration unit, the temperature of secondary steam sent by the third-stage concentration unit is 55-60 ℃, the concentration of the entering low-concentration nmmo solution is 15-25 wt%, the evaporation temperature is 40-55 ℃, the vacuum degree is-88-95 kpa, and the concentration of the first-stage concentrated solution is 30-35 wt%; in the third-stage concentration unit, the temperature of secondary steam sent by the second-stage concentration unit is 70-85 ℃, the evaporation temperature is 65-75 ℃, the vacuum degree is-70-80 kpa, and the concentration of a second-stage concentrated solution is 40-50 wt%; in the second-stage concentration unit, the temperature of secondary steam sent by the first-stage concentration unit is 90-100 ℃, the evaporation temperature is 85-95 ℃, the vacuum degree is-35 to-60 kpa, and the concentration of the third-stage concentrated solution is 65-70 wt%; in the first-stage concentration unit, the temperature of fresh steam fed from a steam inlet is 105-100 ℃, the evaporation temperature is 100-105 ℃, the vacuum degree is-10 to-20 kpa, and the concentration of a discharged four-stage concentrated solution is 80-85 wt%.
The invention has the beneficial effects that: aiming at the characteristic that the concentration of the nmmo solution affects the boiling point, the invention adopts a countercurrent reduced pressure evaporation system and process to concentrate the nmmo solution with low concentration, thereby realizing low-concentration low-temperature evaporation and high-concentration high-temperature evaporation.
Drawings
FIG. 1 is a schematic structural diagram of a high-efficiency energy-saving nmmo solution concentration system of the invention.
In the drawings, the components represented by the respective reference numerals are listed below:
1. a liquid inlet pipeline, 11, a first effect separator, 12, a first effect forced circulation pump, 13, a first effect heater, 14, a first effect concentration online detector, 21, a second effect separator, 22, a second effect forced circulation pump, 23, a second effect heater, 24, a second effect concentration online detector, 31, a third effect separator, 32, a third effect forced circulation pump, 33, a third effect heater, 34, a third effect concentration online detector, 41, a fourth effect separator, 42, a fourth effect forced circulation pump, 43, a fourth effect heater, 44, a fourth effect concentration online detector, 51, a condenser, 52 and a vacuum pump.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
As shown in figure 1, the invention relates to a high-efficiency energy-saving nmmo solution concentration system, which comprises at least two stages of concentration units which are arranged in sequence, wherein each stage of concentration unit comprises a separator and a heater which are communicated through a connecting pipeline and perform material circulation mutually, each separator is provided with a secondary steam outlet, the separator of the last stage of concentration unit is also provided with a solution inlet for introducing low-concentration nmmo solution to be concentrated, and the steam outlet is used for discharging redundant secondary steam, the steam outlets of the separators of other concentration units are communicated with the heaters of the next-stage concentration unit through an air outlet pipeline, each heater is provided with a solution outlet, the heater of the first-stage concentration unit is provided with a steam inlet for introducing fresh steam, the solution outlet of the first-stage concentration unit discharges concentrated high-concentration nmmo solution through an outlet pipeline, the solution outlets of the heaters of other concentration units are communicated with the separator of the previous concentration unit through a liquid outlet pipeline.
Specifically, a solution inlet of a separator of the last stage of concentration unit is communicated with a liquid inlet pipeline 1, the liquid inlet pipeline 1 is communicated with a low-concentration nmmo solution obtained after flushing, a steam inlet of a heater of the first stage of concentration unit is communicated with an air inlet pipeline, the air inlet pipeline is communicated with a fresh steam system, fresh steam generated by the fresh steam system enters from the steam inlet through the air inlet pipeline, a solution outlet of the heater of the first stage of concentration unit is communicated with a storage tank through a liquid outlet pipeline, the concentrated high-concentration nmmo solution is collected in the storage tank for standby, and the storage tank is used when waiting for next fiber production.
On the basis of the technical scheme, a steam outlet of the separator of the last stage of concentration unit is communicated to a condenser 51 through an air outlet pipeline, and a condensed water discharge pipe with a valve is arranged at the bottom of the condenser 51. Heaters of all stages of concentration units are respectively communicated to a condenser 51 through non-condensable gas pipelines, valves are respectively arranged on the non-condensable gas pipelines, and the condenser 51 is communicated with an air inlet of a vacuum pump 52. The concentration system of the invention combines the vacuum pump 52 with the condenser 51, each heater and the separator of the last stage concentration unit are communicated to the condenser 51 through the non-condensable gas pipeline, the condenser condenses the condensable steam through the cooling water, and the non-condensable gas is pumped away through the vacuum pump 52, thus ensuring the vacuum degree in each concentration unit, and the invention has simple structure, simple steps and convenient operation.
The separator and the heater of each stage of concentration unit mutually circulate materials through a forced circulation pump arranged on a connecting pipeline. The solution in the separator and the heater needs to continuously and circularly flow between the two devices to realize better evaporation and concentration effects, so a forced power system needs to be added to promote the flow of the solution, and a forced circulating pump can be arranged on a connecting pipeline to solve the problem.
And a concentration online detector and a valve are respectively arranged on each liquid outlet pipeline. The concentration of the solution processed by each concentration unit is different, when the concentration of the solution in one concentration unit reaches the requirement of entering the previous concentration unit, the solution needs to be introduced, a concentration online detector can be designed to monitor the concentration of the solution in the concentration unit, and the flow of the solution is controlled by a valve on a liquid outlet pipeline after the index is reached. Specifically, the concentration information measured by the online concentration detector can be received through the electronic control system, the concentration information is compared with a preset threshold value, and when the concentration information reaches or exceeds the threshold value, the valve is controlled to be opened, and the solution is guided into the upper-stage concentration unit.
Valves are respectively arranged at the solution inlet of the separator of the last stage concentration unit and the steam inlet of the heater of the first stage concentration unit. The solution inlet of the separator of the last stage concentration unit is used for entering low-concentration nmmo solution to be treated, the steam inlet of the heater of the first stage concentration unit is used for entering fresh steam, valves can be arranged on two pipelines communicated with the first stage concentration unit and the second stage concentration unit, and the valves are controlled to be opened or closed through an electronic control system, so that the low-concentration nmmo solution to be treated and the fresh steam are respectively controlled to enter the whole concentration system.
The heaters of all the stages of concentration units are sequentially communicated through condensed water pipelines, the heat exchanger of the last stage of concentration unit discharges condensed water through the condensed water pipelines, and valves are respectively arranged on the condensed water pipelines. When concentrated system shut down, pause use or overhaul of the equipments, need all discharge with remaining material and comdenstion water in the concentrated system, based on this requirement, can set up the condensate water pipeline in the bottom of each heater, communicate in proper order backward in the past to through the condensate water pipeline discharge residual material and the comdenstion water of last heater, corresponding each set up the valve on the condensate water pipeline respectively, through opening or closing of electronic control system control valve.
The valves can adopt electromagnetic valves which can be used in conventional pipelines, and are respectively communicated to an electronic control system for unified control.
The high-efficiency energy-saving nmmo solution concentration system comprises a four-stage concentration unit. In the preferred embodiment of the present invention, the concentration system is a four-stage concentration unit, i.e. a four-effect countercurrent reduced-pressure evaporation concentration system. It should be noted that the following concentration system including a four-stage concentration unit is only a preferred example of the present invention, and is not intended to limit the present invention, and it should not be understood that it is necessary to have a four-stage concentration unit, and other reasonably different numbers of concentration units should be understood to be within the scope of the present invention, such as two-stage, three-stage, five-stage, six-stage, etc.
The concentration process of the concentration system of the present invention is described below by taking a four-effect countercurrent reduced-pressure evaporation concentration system comprising a four-stage concentration unit as an example.
The invention also relates to a high-efficiency and energy-saving method for concentrating nmmo solution, which realizes the concentration of nmmo solution by utilizing the four-effect countercurrent reduced-pressure evaporation concentration system and comprises the following steps:
(1) preheating the low-concentration nmmo solution, feeding the low-concentration nmmo solution into a fourth-stage concentration unit from a solution inlet, continuously heating and evaporating the solution in a heater of the fourth-stage concentration unit through secondary steam fed by the third-stage concentration unit, performing gas-liquid separation on a separator of the fourth-stage concentration unit, discharging redundant secondary steam from a steam outlet, and introducing the obtained first-stage concentrated solution into the third-stage concentration unit;
(2) continuously heating and evaporating the primary concentrated solution in a heater of the third-stage concentration unit through secondary steam sent by the second-stage concentration unit, carrying out gas-liquid separation on a separator of the third-stage concentration unit, sending the obtained secondary steam into the fourth-stage concentration unit, and introducing the obtained secondary concentrated solution into the second-stage concentration unit;
(3) continuously heating and evaporating the secondary concentrated solution in a heater of the secondary concentration unit through secondary steam sent by the primary concentration unit, carrying out gas-liquid separation in a separator of the secondary concentration unit, sending the obtained secondary steam into a third concentration unit, and introducing the obtained third concentrated solution into the primary concentration unit;
(4) and continuously heating and evaporating the third-level concentrated solution in a heater of the first-level concentration unit through fresh steam fed from a steam inlet, carrying out gas-liquid separation on a separator of the first-level concentration unit, feeding obtained secondary steam into the second-level concentration unit, and discharging obtained fourth-level concentrated solution through a solution outlet to finish concentration.
In the fourth-stage concentration unit, the temperature of secondary steam sent by the third-stage concentration unit is 55-60 ℃, the concentration of the entering low-concentration nmmo solution is 15-25 wt%, the evaporation temperature is 40-55 ℃, the vacuum degree is-88-95 kpa, and the concentration of the first-stage concentrated solution is 30-35 wt%; in the third-stage concentration unit, the temperature of secondary steam sent by the second-stage concentration unit is 70-85 ℃, the evaporation temperature is 65-75 ℃, the vacuum degree is-70-80 kpa, and the concentration of a second-stage concentrated solution is 40-50 wt%; in the second-stage concentration unit, the temperature of secondary steam sent by the first-stage concentration unit is 90-100 ℃, the evaporation temperature is 85-95 ℃, the vacuum degree is-35 to-60 kpa, and the concentration of the third-stage concentrated solution is 65-70 wt%; in the first-stage concentration unit, the temperature of fresh steam fed from a steam inlet is 105-100 ℃, the evaporation temperature is 100-105 ℃, the vacuum degree is-10 to-20 kpa, and the concentration of a discharged four-stage concentrated solution is 80-85 wt%.
As shown in fig. 1, more specifically, when the concentration system includes a four-stage concentration unit, that is, the concentration system is a four-effect countercurrent evaporation concentration system, which includes a liquid inlet pipe 1, a first effect separator 11, a first effect forced circulation pump 12, a first effect heater 13, a first effect concentration online detector 14, a second effect separator 21, a second effect forced circulation pump 22, a second effect heater 23, a second effect concentration online detector 24, a third effect separator 31, a third effect forced circulation pump 32, a third effect heater 33, a third effect concentration online detector 34, a fourth effect separator 41, a fourth effect forced circulation pump 42, a fourth effect heater 43, a fourth effect concentration online detector 44, a condenser 51, and a vacuum pump 52, the concentration system is connected as described above.
As shown in figure 1, when in use, the concentration method comprises the following steps:
(1) the recycled low-concentration nmmo solution enters a fourth-effect separator 41 through a liquid inlet pipeline 1, a fourth-effect forced circulation pump 42 is used for material circulation, secondary saturated steam generated by a third-effect separator 31 is used for heating a fourth-effect heater 43, the fourth-effect separator 41 is used for separating the generated secondary steam, the secondary steam is guided into a condenser 51 and is condensed by normal-temperature cooling water, meanwhile, non-condensable gas is pumped away by a vacuum pump 52, and the vacuum degree of the fourth-effect heater 43 is guaranteed to be-88 to-95 kpa. The concentration of the solution is detected by a fourth effect concentration online detector 44, and the solution enters the third effect separator 31 after reaching the set concentration.
(2) The nmmo solution from the fourth-effect heater 43 enters the third-effect separator 31, the third-effect forced circulation pump 32 is used for material circulation, the second-effect separator 21 generates secondary saturated steam for heating the third-effect heater 33, the third-effect separator 31 separates the generated secondary steam for heat exchange and condensation of the fourth-effect heater 43, non-condensable gas is pumped away by the vacuum pump 52, and the vacuum degree of the third-effect heater 33 is guaranteed to be-65-75 kpa. The concentration of the solution is detected by a third-effect concentration online detector 34, and the solution enters a second-effect separator 21 after reaching the set concentration.
The primary operating parameters of the third effect heater 33: triple effect heating steam temperature: 70-85 ℃, triple effect feed concentration: 30-35%, triple effect evaporation temperature: 65-75 ℃, triple effect vacuum degree: -70-80 kpa, triple effect output set concentration: 40-50 percent.
(3) The nmmo solution from the third-effect heater 33 enters the second-effect separator 21, the second-effect forced circulation pump 22 is used for material circulation, the first-effect separator 11 generates secondary saturated steam for heating the second-effect heater 23, the second-effect separator 21 separates the generated secondary steam for heat exchange and condensation of the third-effect heater 33, non-condensable gas is pumped away by the vacuum pump 52, and the vacuum degree of the second-effect heater 23 is guaranteed to be-30 to-50 kpa. The concentration of the solution is detected by a second-effect concentration online detector 24, and the solution enters the first-effect separator 11 after reaching the set concentration.
The secondary effect heater 23 has the main operating parameters: temperature of double-effect heating steam: 90-100 ℃, double-effect feed concentration: 40-50%, double-effect evaporation temperature: 85-95 ℃, double-effect vacuum degree: 35-60 kpa, the set concentration of the secondary effect discharge: 65-70 percent.
(4) The nmmo solution from the second effect heater 23 enters the first effect separator 11, the first effect forced circulation pump 12 is used for material circulation, fresh saturated steam is introduced for heating the first effect heater 13, the first effect separation chamber 11 is separated to generate secondary steam for heat exchange and condensation of the second effect heater 23, non-condensable gas is pumped away by the vacuum pump 52, and the vacuum degree of the first effect heater 13 is guaranteed to be-10 to-15 kpa. The concentration of the solution is detected by a first effective concentration online detector 14, and the solution is discharged to a storage tank for recycling after reaching the set concentration.
Primary operation parameters of the first effect heater 13: first effective heating steam temperature: 105 ℃ and 110 ℃, the first effect feed concentration: 65-70%, primary evaporation temperature: 100-: -20-10 kpa, one effect output set concentration: 80-85 percent.
Due to the nature of nmmo material, the concentration has higher influence on the boiling point of the solution, so the process of low-concentration low-temperature evaporation and high-concentration high-temperature evaporation can overcome the problems and realize better evaporation effect and energy-saving effect.
The technical effects of the four-effect countercurrent reduced-pressure evaporation concentration system and method according to the present invention will be described in detail below with reference to the following examples and comparative examples.
Example 1:
the four-effect countercurrent reduced-pressure evaporation concentration system has the technical parameters as follows: the nmmo concentration of the four-effect feeding is 15%, the temperature of the four-effect heating steam is 56 ℃, the temperature of the four-effect evaporation is 42 ℃, the four-effect vacuum is-94 kpa, and the concentration of the four-effect discharging is 25%. The temperature of triple-effect heating steam is 75 ℃, the temperature of triple-effect evaporation is 66 ℃, the triple-effect vacuum is-82 kpa, and the concentration of triple-effect discharge is 45%. The temperature of double-effect heating steam is 93 ℃, the temperature of double-effect evaporation is 85 ℃, the double-effect vacuum is-55 kpa, and the concentration of double-effect discharge is 65%. The temperature of the first-effect heating steam is 105 ℃, the first-effect evaporation temperature is 100 ℃, the first-effect vacuum is-20 kpa, and the concentration of the first-effect discharge material is 83%.
Example 2:
the four-effect countercurrent reduced-pressure evaporation concentration system has the technical parameters as follows: the nmmo concentration of the four-effect feeding is 18 percent, the temperature of the four-effect heating steam is 57 ℃, the temperature of the four-effect evaporation is 44 ℃, the four-effect vacuum is-90 kpa, and the concentration of the four-effect discharging is 31 percent. The temperature of triple-effect heating steam is 78 ℃, the temperature of triple-effect evaporation is 67 ℃, the triple-effect vacuum is-83 kpa, and the concentration of triple-effect discharge is 44%. The temperature of the double-effect heating steam is 91 ℃, the temperature of the double-effect evaporation is 86 ℃, the double-effect vacuum is-57 kpa, and the concentration of the double-effect discharge is 63%. The temperature of the first-effect heating steam is 105 ℃, the first-effect evaporation temperature is 98 ℃, the first-effect vacuum is-17 kpa, and the concentration of the first-effect discharge is 82%.
Example 3:
the four-effect countercurrent reduced-pressure evaporation concentration system has the technical parameters as follows: the nmmo concentration of the four-effect feeding is 21 percent, the temperature of the four-effect heating steam is 55 ℃, the four-effect evaporation temperature is 40 ℃, the four-effect vacuum is-95 kpa, and the concentration of the four-effect discharging is 30 percent. The temperature of triple-effect heating steam is 79 ℃, the temperature of triple-effect evaporation is 67 ℃, the triple-effect vacuum is-83 kpa, and the concentration of triple-effect discharge is 45%. The temperature of double-effect heating steam is 93 ℃, the temperature of double-effect evaporation is 89 ℃, the double-effect vacuum is-55 kpa, and the concentration of double-effect discharge is 64%. The temperature of the first-effect heating steam is 107 ℃, the temperature of the first-effect evaporation is 101 ℃, the first-effect vacuum is-15 kpa, and the concentration of the first-effect discharge is 80%.
Example 4:
the four-effect countercurrent reduced-pressure evaporation concentration system has the technical parameters as follows: the nmmo concentration of the four-effect feeding is 25 percent, the temperature of the four-effect heating steam is 60 ℃, the four-effect evaporation temperature is 46 ℃, the four-effect vacuum is-88 kpa, and the concentration of the four-effect discharging is 32 percent. The temperature of triple-effect heating steam is 84 ℃, the temperature of triple-effect evaporation is 73 ℃, the triple-effect vacuum is-80 kpa, and the concentration of triple-effect discharge is 50%. The temperature of the double-effect heating steam is 96 ℃, the temperature of the double-effect evaporation is 92 ℃, the double-effect vacuum is-50 kpa, and the concentration of the double-effect discharge is 67%. The temperature of the first-effect heating steam is 110 ℃, the first-effect evaporation temperature is 108 ℃, the first-effect vacuum is-10 kpa, and the concentration of the first-effect discharge is 85%.
Comparative example 1
The method is similar to the steps of the method, but adopts a four-effect concurrent flow evaporation system for concentration, and the technical parameters are as follows: the concentration of the one-effect feed nmmo is 15%, the temperature of the one-effect heating steam is 115 ℃, the one-effect evaporation temperature is 106 ℃, the one-effect gauge pressure is 15kpa, and the concentration of the one-effect discharge is 35%. The temperature of the double-effect heating steam is 103 ℃, the temperature of the double-effect evaporation is 99 ℃, the double-effect vacuum is-1 kpa, and the concentration of the double-effect discharge is 45%. The temperature of triple-effect heating steam is 95 ℃, the triple-effect evaporation temperature is 86 ℃, the triple-effect vacuum is-93 kpa, and the concentration of triple-effect discharge is 69%. The four-effect heating steam temperature is 105 ℃, the four-effect evaporation temperature is 96 ℃, the four-effect vacuum is-93 kpa, and the four-effect discharge concentration is 83%.
Comparative example 2
The method is similar to the steps of the method, but adopts a four-effect concurrent flow evaporation system for concentration, and the technical parameters are as follows: the nmmo concentration of the first-effect feed is 25 percent, the temperature of the first-effect heating steam is 114 ℃, the evaporation temperature of the first-effect is 106 ℃, the surface pressure of the first-effect is 15kpa, and the concentration of the first-effect discharge is 33 percent. The temperature of the double-effect heating steam is 104 ℃, the temperature of the double-effect evaporation is 98 ℃, the double-effect vacuum is-2 kpa, and the concentration of the double-effect discharge is 42%. The temperature of triple-effect heating steam is 94 ℃, the triple-effect evaporation temperature is 87 ℃, the triple-effect vacuum is-94 kpa, and the concentration of triple-effect discharge is 68%. The four-effect heating steam temperature is 105 ℃, the four-effect evaporation temperature is 95 ℃, the four-effect vacuum is-93 kpa, and the four-effect discharge concentration is 85%.
And (4) analyzing results:
through the comparison of the two modes, the heat sources of the four-effect countercurrent reduced-pressure evaporation process all adopt the previous secondary steam as a heating heat source, the heat transfer temperature difference is stable, and the temperature of the fresh steam heat source for one-effect heating is low. In the four-effect concurrent evaporation process, the trend of the first-effect secondary steam, the second-effect secondary steam and the third-effect secondary steam is the same as that of the four-effect countercurrent process, but the temperature of a heating heat source of the fourth-effect evaporation solution is higher due to the rising of the boiling temperature of the fourth-effect evaporation solution, so that the first-effect high-temperature secondary steam or the second-effect high-temperature fresh steam is required for heating, and the steam consumption is increased. The temperature of secondary steam generated by the third effect evaporation and the fourth effect evaporation of the four-effect cocurrent evaporation process is 40-43 ℃, the secondary steam cannot be reused and needs to be condensed by a condenser, and only the secondary steam generated by the fourth effect evaporation and evaporation of the four-effect countercurrent reduced-pressure evaporation process enters the condenser for condensation.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. The high-efficiency energy-saving nmmo solution concentration system is characterized by comprising at least two stages of concentration units which are sequentially arranged, wherein each stage of concentration unit comprises a separator and a heater which are communicated through a connecting pipeline and mutually perform material circulation, each separator is provided with a secondary steam outlet, the separator of the last stage of concentration unit is also provided with a solution inlet for introducing low-concentration nmmo solution to be concentrated, and the steam outlet of the last stage of concentration unit is used for discharging redundant secondary steam, the steam outlets of the separators of other concentration units are communicated with the heaters of the next-stage concentration unit through an air outlet pipeline, each heater is provided with a solution outlet, the heater of the first-stage concentration unit is provided with a steam inlet for introducing fresh steam, the solution outlet of the first-stage concentration unit discharges concentrated high-concentration nmmo solution through an outlet pipeline, the solution outlets of the heaters of other concentration units are communicated with the separator of the previous concentration unit through a liquid outlet pipeline.
2. The system for concentrating nmmo solution with high efficiency and energy saving as claimed in claim 1, wherein the steam outlet of the separator of the last stage of concentration unit is communicated to the condenser through an air outlet pipeline, and the bottom of the condenser is provided with a condensed water discharge pipe with a valve.
3. The system for concentrating nmmo solution with high efficiency and energy saving as claimed in claim 2, wherein the heaters of the concentrating units at each stage are respectively communicated to the condenser through non-condensable gas pipelines, each non-condensable gas pipeline is respectively provided with a valve, and the condenser is communicated with the air inlet of the vacuum pump.
4. The system for concentrating nmmo solution with high efficiency and energy saving as claimed in claim 1, wherein the separator and the heater of each stage of the concentrating unit are mutually circulated by a forced circulation pump disposed at the connecting pipeline.
5. The system for concentrating nmmo solution as claimed in claim 1, wherein each outlet pipe is provided with an on-line concentration detector and a valve.
6. The system for concentrating nmmo solution with high efficiency and energy saving as claimed in claim 1, wherein valves are respectively provided at the solution inlet of the separator of the last stage concentration unit and the steam inlet of the heater of the first stage concentration unit.
7. The system for concentrating nmmo solution with high efficiency and energy saving as claimed in claim 1, wherein the heaters of the concentrating units at each stage are sequentially communicated through condensed water pipes, the heat exchanger of the concentrating unit at the last stage discharges condensed water through the condensed water pipes, and valves are respectively arranged on the condensed water pipes.
8. The system for concentrating energy-efficient nmmo solution as claimed in any one of claims 1 to 7, wherein the system for concentrating energy-efficient nmmo solution comprises a four-stage concentration unit.
9. A method for concentrating nmmo solution with high efficiency and energy saving, which is characterized in that the concentration system of claim 8 is used for concentrating nmmo solution, and the method comprises the following steps:
(1) preheating the low-concentration nmmo solution, feeding the low-concentration nmmo solution into a fourth-stage concentration unit from a solution inlet, continuously heating and evaporating the solution in a heater of the fourth-stage concentration unit through secondary steam fed by the third-stage concentration unit, performing gas-liquid separation on a separator of the fourth-stage concentration unit, discharging redundant secondary steam from a steam outlet, and introducing the obtained first-stage concentrated solution into the third-stage concentration unit;
(2) continuously heating and evaporating the primary concentrated solution in a heater of the third-stage concentration unit through secondary steam sent by the second-stage concentration unit, carrying out gas-liquid separation on a separator of the third-stage concentration unit, sending the obtained secondary steam into the fourth-stage concentration unit, and introducing the obtained secondary concentrated solution into the second-stage concentration unit;
(3) continuously heating and evaporating the secondary concentrated solution in a heater of the secondary concentration unit through secondary steam sent by the primary concentration unit, carrying out gas-liquid separation in a separator of the secondary concentration unit, sending the obtained secondary steam into a third concentration unit, and introducing the obtained third concentrated solution into the primary concentration unit;
(4) and continuously heating and evaporating the third-level concentrated solution in a heater of the first-level concentration unit through fresh steam fed from a steam inlet, carrying out gas-liquid separation on a separator of the first-level concentration unit, feeding obtained secondary steam into the second-level concentration unit, and discharging obtained fourth-level concentrated solution through a solution outlet to finish concentration.
10. The method for concentrating the nmmo solution in the high-efficiency and energy-saving manner as claimed in claim 9, wherein in the fourth-stage concentration unit, the temperature of secondary steam sent by the third-stage concentration unit is 55-60 ℃, the concentration of the low-concentration nmmo solution is 15-25 wt%, the evaporation temperature is 40-55 ℃, the vacuum degree is-88-95 kpa, and the concentration of the primary concentrated solution is 30-35 wt%; in the third-stage concentration unit, the temperature of secondary steam sent by the second-stage concentration unit is 70-85 ℃, the evaporation temperature is 65-75 ℃, the vacuum degree is-70-80 kpa, and the concentration of a second-stage concentrated solution is 40-50 wt%; in the second-stage concentration unit, the temperature of secondary steam sent by the first-stage concentration unit is 90-100 ℃, the evaporation temperature is 85-95 ℃, the vacuum degree is-35 to-60 kpa, and the concentration of the third-stage concentrated solution is 65-70 wt%; in the first-stage concentration unit, the temperature of fresh steam fed from a steam inlet is 105-100 ℃, the evaporation temperature is 100-105 ℃, the vacuum degree is-10 to-20 kpa, and the concentration of a discharged four-stage concentrated solution is 80-85 wt%.
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| CN101089262A (en) * | 2006-06-13 | 2007-12-19 | 上海里奥纤维企业发展有限公司 | Recovery and purification method for solvent preparing cellulose fibre by solvent method |
| CN101088993A (en) * | 2006-06-13 | 2007-12-19 | 上海里奥纤维企业发展有限公司 | NMMO evaporating process |
| CN102167465A (en) * | 2011-03-17 | 2011-08-31 | 天津工业大学 | Recovery method of spinning waste liquor by means of concentrating |
| CN105854319A (en) * | 2016-06-06 | 2016-08-17 | 北京浦仁美华节能环保科技有限公司 | MVR evaporation and concentration process of NMMO solvent |
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| CN101089262A (en) * | 2006-06-13 | 2007-12-19 | 上海里奥纤维企业发展有限公司 | Recovery and purification method for solvent preparing cellulose fibre by solvent method |
| CN101088993A (en) * | 2006-06-13 | 2007-12-19 | 上海里奥纤维企业发展有限公司 | NMMO evaporating process |
| CN102167465A (en) * | 2011-03-17 | 2011-08-31 | 天津工业大学 | Recovery method of spinning waste liquor by means of concentrating |
| CN105854319A (en) * | 2016-06-06 | 2016-08-17 | 北京浦仁美华节能环保科技有限公司 | MVR evaporation and concentration process of NMMO solvent |
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