CN111455709B

CN111455709B - Production process of APMP

Info

Publication number: CN111455709B
Application number: CN202010426952.5A
Authority: CN
Inventors: 孙世杰; 刘泽华; 刘纪营; 钟洪霞; 张淑侠
Original assignee: Shandong Sun Household Paper Ltd; Shandong Taiyang Honghe Paper Industry Co ltd; Yanzhou Tianzhang Paper Industry Co ltd; SHANDONG TAIYANGZHIYE CO Ltd
Current assignee: Shandong Sun Household Paper Ltd; Shandong Taiyang Honghe Paper Industry Co ltd; Yanzhou Tianzhang Paper Industry Co ltd; SHANDONG TAIYANGZHIYE CO Ltd
Priority date: 2020-05-19
Filing date: 2020-05-19
Publication date: 2021-12-03
Anticipated expiration: 2040-05-19
Also published as: CN111455709A

Abstract

The invention discloses a production process of APMP, which applies sodium polyhydroxyacrylate to the production bleaching process of chemi-mechanical pulp APMP instead of sodium silicate. Because the sodium polyhydroxyacrylate does not contain silicon and other substances which are easy to scale, the scaling problem is obviously reduced under the condition that the dosage of the hydrogen peroxide is not obviously increased; the car brushing period can be prolonged to more than one month from about ten days, so that the production efficiency is greatly improved, and the production equipment is effectively protected.

Description

Production process of APMP

Technical Field

The invention relates to the technical field of fabric bleaching, in particular to an APMP production process.

Background

APMP is an Alkaline peroxide mechanical pulp, acronym, which means Alkaline hydrogen peroxide chemi-mechanical pulp. The APMP pulp is produced by preparing full-bleaching pulp without separate bleaching, and by using NaOH and H₂O₂The paper pulp with different quality characteristics can be made by changing and combining the dosage, and the paper pulp is suitable for the requirements of different paper making. Therefore, is atThe whole pulping process is accompanied by pulping and bleaching. In the production process of the chemi-mechanical pulp, a lot of metal ions greatly interfere with bleaching, and the bleaching effect of hydrogen peroxide is damaged. Sodium silicate is used as a bleaching auxiliary agent, and can provide certain alkalinity for the whole bleaching environment; secondly, the function of penetrating, buffering and stabilizing agent is achieved. However, when the sodium silicate is used for a long time, the silicic acid and ions in the sodium silicate are easily combined with calcium ions, iron ions and the like, so that the scaling phenomenon is frequent. The scaling phenomenon easily blocks equipment such as squeezing, pulping machines, pipelines, screws and the like, so that the negative effects of increased pressure of production equipment, increased power consumption and the like are caused. Manufacturers have to regularly scale production equipment in order to provide a consistent output. This has a negative impact on the efficiency of the plant and the overall pulp production.

At present, the waste paper deinking technology using sodium polyhydroxyacrylate instead of silicate is available, but the technology of applying sodium polyhydroxyacrylate in APMP production is not disclosed. With the increasing demand of white and common double-sided offset paper in the market, the pulp preparation advantage of APMP is more obvious: firstly, the hue of the paper can be adjusted, and the opacity of the paper can be increased; secondly, the production cost can be greatly reduced. As the paper machine capacity increases and the output of the double-sided offset paper increases, the demand for APMP also increases. Therefore, in order to increase the yield of the chemi-mechanical pulp in production, the invention aims to solve the technical problems of how to research and develop sodium polyhydroxyacrylate to replace sodium silicate for production and reduce the influence of frequent shutdown on the pulp amount.

Disclosure of Invention

The invention provides a production process of APMP aiming at the defects, and sodium polyhydroxyacrylate is used for replacing sodium silicate in the production and bleaching process of the chemi-mechanical pulp APMP. Because the sodium polyhydroxyacrylate does not contain silicon and other substances which are easy to scale, the scaling problem is obviously reduced under the condition that the dosage of the hydrogen peroxide is not obviously increased; the car brushing period can be prolonged to more than one month from about ten days, so that the production efficiency is greatly improved, and the production equipment is effectively protected.

The technical scheme of the production process of the APMP comprises the step of applying the sodium polyhydroxy acrylate to the production bleaching process of the chemi-mechanical pulp APMP instead of sodium silicate.

Raw materials sequentially pass through a wood chip bin, a belt conveyor, a wood chip washer, a wood chip mixing tank, a wood chip pump, an inclined dewatering screw, a pre-steaming bin, 1# MSD, 2# MSD, a vertical pre-soaking device, a reaction bin, a horizontal conveying screw, a feeding screw, a 1# main mill, a cyclone separator, a PSD, a cooling screw, a bleaching tower, a 1# medium concentration pump, SCP, a dilution screw, a latency tank, a 1# low concentration mill, a 2# middle slurry tank, a 1# F50 pressure screen, a multi-disc concentrator and a 3# medium concentration pump to reach a slurry tower, wherein waste liquid generated in the production process is dried by an evaporator, and the residual concentrated waste liquid is sent to an alkali recovery for treatment;

adding sodium polyhydroxyacrylate into 1# MSD, 2# MSD and bleaching tower respectively, wherein the mass ratio of sodium polyhydroxyacrylate to sodium polyhydroxyacrylate is 1.5:1.5:4, and the total amount of sodium polyhydroxyacrylate to sodium polyhydroxyacrylate is 7kg/t pulp.

Mixing sodium polyhydroxyacrylate with alkali and DTPA, then mixing with hydrogen peroxide in a mass ratio of 7:27:3:80, and pumping into an addition point to be bleached.

The raw material is at least one of poplar wood chips, acacia wood chips and eucalyptus wood chips, and the storage time is 3-6 months; the wood chip bin keeps a high material level not lower than 40% and sufficient steam, and the temperature of the wood chip bin is not lower than 60 ℃.

The temperature of the wood chip washing water in the wood chip washer is kept above 95 ℃; the concentration of the wood chips out of the wood chip washer is 5 percent, the inclined dewatering spiral is lined with the sieve plate, and a large amount of water is discharged from the sieve plate and enters the washing water tank through the inclined sieve.

The material level of the presteaming bin is not less than 50 percent, the temperature is controlled at 90-105 ℃, air entrained by wood chips is discharged, and the air enters MSD through a metering screw.

The screen drums of the 1# MSD and the 2# MSD are equal in diameter, the spiral shaft is reduced in diameter, the raw materials are continuously pushed forwards, the torque of the 1# MSD and the 2# MSD is not less than 80kNm, the raw materials are extruded and kneaded in the pushing process, water is removed, the dryness of wood chips reaches more than 60%, and when the extruded wood chips are discharged from an expansion discharge port and enter a vertical pre-soaking device, the added chemicals can enable the wood chips to rapidly expand and be fully absorbed by the wood chips. The temperature of the wood chips entering the reaction bin is not less than 60 ℃, and the material level of the reaction bin is not less than 30%.

The model of the No. 1 main mill is as follows: the diameter of a rotor is 64 inches, the maximum diameter of a grinding plate is 70 inches, the power is 14MW, and the rotating speed of the rotor is 1500 r/min; the disc mill is divided into a crushing area, a middle area, a coarse grinding area and a fine grinding area from inside to outside; the wood chips are dissociated into coarse fragments at the inlet of the grinding zone, the coarse fragments are dissociated into coarse fiber bundles in the middle of the grinding zone, the coarse fiber bundles are arranged in a non-directional mode, are separated into fibers parallel to the grinding teeth and are ground into fragments vertical to the grinding teeth; the fibers in the coarse grinding area are mainly subjected to the friction and the shearing force of the disc teeth, and the fibers in the fine grinding area flow forwards along the tooth grooves, so that the pulp strength is greatly improved; the energy generated by the disc mill is 10 percent used for grinding wood chips and 90 percent used for heating water, and steam is generated for recycling.

The refining energy consumption of the wood chips through the 1# main mill is controlled to be 400-800 kWh/admt, the pressure of a main milling chamber is less than 3bar, the gap of a main milling disc is controlled to be-5 mm, the refining concentration is controlled to be 31-40%, the D65 whiteness of a refiner is controlled to be 50-70, and the freeness of the discharged pulp is 650-750 mL.

The bleaching time of the bleaching tower is 70-80 minutes, the bleaching temperature is controlled at 80-90 ℃, the concentration is 25-30%, a scraper discharger is arranged at the bottom of the bleaching tower, and slurry at the bottom of the bleaching tower is diluted into 10% concentration by adding turbid filtrate.

After bleaching, the pulp extrudes a large amount of residual chemical agents and waste water through mechanical extrusion, the pulp enters a turbid filtrate pool, diluted spiral filtrate contains more available fibers, the filtrate firstly enters a multi-disc thickener for concentration, good pulp enters a digestion tank, and waste liquid enters an evaporator for evaporation.

The invention has the beneficial effects that:

the invention uses sodium polyhydroxyacrylate to replace sodium silicate for hydrogen peroxide bleaching of APMP, and effectively solves the problems of main mill and system scaling. The use and replacement periods of various wearing parts such as grinding sheets, squeezing screen frames, small multi-disc fan blades and the like are greatly prolonged, the production efficiency is greatly improved, the power consumption and the steam consumption are saved, the operating cost is reduced, and the loss of excessive energy consumption is avoided. The brushing cycle is prolonged from about 3 times per month to 1.5 months per time, and the labor intensity of workers is greatly reduced while the pulp yield is increased; the consumption of water is effectively reduced, because the cleaning process is mainly cleaning by high-pressure water. Therefore, after the vehicle brushing period is reduced, the consumption of clean water is also greatly reduced. The use of the bleaching auxiliary reduces the scaling phenomenon, the waste liquor evaporator runs stably, the evaporation efficiency is improved, and the treatment efficiency of black liquor is improved.

Drawings

FIG. 1 is a photograph showing the condition of a grinding chip when sodium silicate is used;

figure 2 shows the situation of the grinding sheet by the process of the invention.

The specific implementation mode is as follows:

for better understanding of the present invention, the technical solution of the present invention will be described in detail with specific examples, but the present invention is not limited thereto.

Example 1

A production process of APMP adopts sodium polyhydroxyacrylate to replace sodium silicate, raw materials sequentially pass through a wood chip bin, a belt conveyor, a wood chip washer, a wood chip mixing tank, a wood chip pump, an inclined dewatering screw, a pre-steaming bin, 1#, 2# MSD, a vertical pre-soaking device, a reaction bin, 1#, 2# horizontal conveying screws, 1#, 2# material plug feeding screws, 1# main mill, a cyclone separator, PSD, a cooling screw, a bleaching tower, 1# medium concentration pump, 1# SCP, 1# dilution screw, a submergence tank, 1#, 2# low concentration mill, a middle slurry tank, 1#, 2# F50 pressure sieves, a multi-disc concentrator, a 3# medium concentration pump and a slurry tower; wherein the waste liquid generated in the production process is dried by an evaporator, and the residual concentrated waste liquid is sent to alkali recovery for treatment.

Adding 1# MSD, 2# MSD and a bleaching tower into sodium polyacrylate respectively, wherein the dosage ratio is 1.5:1.5:4, the total dosage is 7kg/t pulp.

1. The wood chips are selected to be full poplar, the new condition proportion and the old condition proportion of the wood chips are about 9:1, and the material level of the wood chip bin is controlled to be not less than 40% in the production process. The temperature of the wood chip washer is controlled to be not less than 80 ℃ in production, and the temperature of the washing water is not less than 95 ℃.

2. The material level of the pre-steaming bin is controlled to be not less than 50 percent in the production process, the temperature is controlled to be 90-105 ℃, the torque of MSD is not less than 80kNm, the temperature of wood chips entering the reaction bin is not less than 60 ℃, and the material level of the reaction bin is not less than 30 percent.

3. The pulping energy consumption of the wood chips through the 1# main mill is controlled to be 400-800 kWh/admt, the pressure of a main grinding chamber is less than 3bar, the gap of a main grinding disc is controlled to be-5 mm, the concentration of the pulping is controlled to be 31-40%, the D65 whiteness of the pulping machine is controlled to be about 50-70, the freeness of the discharged pulp is 650 plus 750mL, and the vibration frequency of the pulping machine is controlled to be in a proper range.

4. The pulp inlet concentration of the bleaching tower is controlled to be about 25.0-40.0%, the pH value of the pulp is controlled to be 9.00-10.50, the corresponding pulp outlet concentration is 9.0-13.0%, and the pH value of the pulp is controlled to be 7.50-8.50.

5. The No. 1 and No. 2F 50 pressure screen. 6mm between the rotor and the screen cylinder. The periphery of the rotor of the F50 pressure screen is in a rack shape, and the slit width is 0.15 mm. The multi-disc thickener has most tailing pulp to be ground in the front pulp tank and few slag removers when the pulp is relatively clean, and most slag removers are preferably used for removing slag when the pulp is relatively dirty.

6. Production control of the evaporator: the evaporator had a design evaporation capacity of 150T/H. Power consumption amount: 19.4 degrees per ton of wastewater, which mainly comprises the following components: a fan, a condenser, a light pollution flash tank, a heat exchanger and a circulating pipe. The upper part of the evaporation is a nozzle for distributing the waste liquid, and the top part is a dripping separator. The waste liquid enters the evaporator, is pumped to the upper part of the plate by the circulating pump and is uniformly distributed on the surface of the plate by the distribution nozzle, and the waste liquid freely flows to the bottom like a layer of film on the surface of the plate. Steam enters from the inner part of the plate and is condensed at the inner side, the heat of the steam enables the waste liquid to boil, secondary steam is released from the waste liquid, water vapor is discharged through the dripping water separator and is led to the suction side of the compression fan through a steam pipeline, and the steam enters the inner part of the plate after being compressed by the fan and is used as a heat source for continuous use. The blower increased the pressure of the steam by about 0.24Bar and the temperature by about 7 ℃ (from 94 ℃ to 101 ℃). The fan is equipped with guide vanes to control the output. The water vapor is condensed into two parts at the inner side of the evaporation plate, 85-90% of the water vapor is condensed into light pollution in the main condensation area, 10-15% of the water vapor is condensed at the upper part, the water vapor carries away easily-evaporated compounds in the condensate in the main condensation area, and the condensate in the post-condensation area is more dirty and called heavy pollution.

Example 2

1. Wood powder development:

old poplar wood is taken from a chemical mechanical pulp farm, is put into a wood flour grinder to be ground into wood flour, and the dryness of the wood flour is measured.

2. Application experiments

1) Taking 40g of absolutely dry wood powder, putting the absolutely dry wood powder into a firm thick plastic bag, adding the absolutely dry wood powder for the first time, adding 40% of the total dosage, preparing dilution water, sequentially adding caustic soda, a chelating agent and a penetrating agent, adding sodium silicate into No. 1, adding sodium polyhydroxyacrylate into No. 2 and No. 3, respectively adding 4kg/t and 6kg/t pulp of sodium polyhydroxyacrylate, uniformly mixing, and adding into the plastic bag. Adjusting the concentration of the slurry to 28%, repeatedly kneading uniformly, adding hydrogen peroxide, and repeatedly kneading uniformly.

2) Placing the kneaded slurry in a water bath kettle prepared in advance, setting the temperature at 92 deg.C, and ensuring that the slurry in the bag is completely immersed in water, wherein the reaction time after the first stage of adding the medicine is about 60 min.

3) And after 60min, starting to prepare a second section of medicine adding, wherein the medicine adding amount of each slurry is 60% of the total medicine adding amount, the medicine adding sequence is consistent with that of the first section of medicine adding, and repeatedly kneading the slurry uniformly. The second stage heat preservation time is 50 min.

4) After the heat preservation is finished, the slurry is washed for a plurality of times, a slurry sample is filtered by a filter flask, and the whiteness of the slurry sample is measured after the slurry sample is dried.

5) The amount of chemicals used per ton of pulp (dry in absolute terms) is shown in table 1:

TABLE 1

Note: 1. DTPA, penetrant and sodium polyhydroxyacrylate are all diluted to 1/50, and the rest are all added in stock solution. The osmotic agent is added in its entirety during the first stage.

3. Test data

The whiteness of the pulp samples tested is shown in table 2:

TABLE 2

Numbering	1#	2#	3#
				Ton pulp dosage kg	28	4	6
D65 whiteness%	73.5	70.8	72.6

From the laboratory data, the effect of the sodium polyhydroxyacrylate on improving the bleaching slurry of the hydrogen peroxide is basically equivalent under the condition of using 6kg/t of slurry, which shows that the bleaching effect of the hydrogen peroxide can be effectively improved by using the sodium polyhydroxyacrylate.

Example 3

In the production process, the yield is controlled to be about 115-120 admt/class, the raw material is 100 percent of new poplar, and the whiteness standard of the pulp is 75.0-77.0 percent. The original process uses sodium silicate (prepreg section 5kg/admt + bleaching section 18kg/admt), and the addition amount is 23 kg/admt. The amount of sodium polyhydroxyacrylate added was 7kg/admt (3 kg/admt in the presoaking stage + 4kg/admt in the bleaching stage).

1. Hydrogen peroxide consumption is shown in Table 3 (workshop application random data detection)

TABLE 3

From the above table, it can be seen that, after the sodium polyhydroxyacrylate is used, the amount of the hydrogen peroxide is increased to a certain extent, but the whiteness of the pulp is not reduced, which shows that the sodium polyhydroxyacrylate has a good promotion effect on bleaching by hydrogen peroxide.

2. System cycle of vehicle cleaning

In 1-4 months when the sodium silicate is used, the system brushing time is respectively 1 month 15 days, 1 month 26 days, 2 months 8 days, 2 months 23 days, 3 months 12 days, 3 months 26 days and 4 months 25, the system brushes the vehicle about 2 times per month, and the chemical dosing system is cleaned once per week. After the bleaching control agent is used, the system is stopped when the vehicle is brushed for 5 months and 16 days and when the vehicle is fully brushed for 7 months and 12 days; 7, month and 29 days; 9 months and 6 days. The system brushing interval is more than 1 month in each month, and the chemical dosing system does not need to be specially shut down for cleaning.

3. The main grinding scaling condition is shown in attached figures 1 and 2 of the specification

FIG. 2 shows the lapping conditions when sodium polyhydroxyacrylate is used.

It is evident from the figure that when sodium silicate is used, scaling is evident, and when sodium polyhydroxyacrylate is used, the scaling is obviously reduced after the grinding plate.

4. Wearing part replacement is shown in Table 4

TABLE 4

Time of use	Small multi-disc fan blade	Main grinding sheet of squeezing screen frame	Main grinding sheet
				Using sodium silicate	3 months old	3 months old	1300 hours
Using sodium polyhydroxyacrylate	For 5 months	8 months old	1800 hours

5. Energy consumption and yield are shown in Table 5

TABLE 5

。

From the above it is evident that:

1. the brushing cycle is prolonged from about 3 times per month to more than 1 time per month, and the labor intensity of workers is greatly reduced while the pulp yield is increased; the consumption of water is effectively reduced, because the cleaning process is mainly cleaning by high-pressure water. Therefore, after the vehicle brushing period is reduced, the consumption of clean water is greatly reduced.

2. The main mill and the system do not scale any more, the use and replacement periods of various wearing parts such as grinding plates, squeezing screen frames and small multi-disc fan blades are greatly prolonged, the production effective work is greatly improved, the power consumption and the steam consumption are saved, the operation cost is reduced, and the loss of excessive energy consumption is avoided.

3. Because the scale deposition phenomenon is reduced compared with sodium silicate, the waste liquid evaporator runs stably, the evaporation efficiency is improved, and the treatment efficiency of black liquor is improved.

Claims

1. A production process of APMP is characterized in that raw materials sequentially pass through a wood chip bin, a belt conveyor, a wood chip washer, a wood chip mixing tank, a wood chip pump, an inclined dewatering screw, a presteaming bin, 1# MSD, 2# MSD, a vertical pre-soaking device, a reaction bin, a horizontal conveying screw, a feeding screw, a 1# main mill, a cyclone separator, a PSD, a cooling screw, a bleaching tower, a 1# medium-concentration pump, an SCP, a dilution screw, a latency tank, a 1# low-concentration mill, a 2# low-concentration mill, an intermediate pulp tank, a 1# F50 pressure sieve, a multi-disc concentrator and a 3# medium-concentration pump to reach a pulp tower, wherein waste liquid generated in the production process is dried by an evaporator, and the residual concentrated waste liquid is sent to an alkali recovery for treatment; adding sodium polyhydroxyacrylate into 1# MSD, 2# MSD and a bleaching tower respectively, wherein the mass consumption ratio is 1.5:1.5:4, and the total consumption is 7kg/t pulp;

the screen drums of the 1# MSD and the 2# MSD have the same diameter, the spiral shaft is reduced in diameter, the raw materials are continuously pushed forwards, the torque of the 1# MSD and the 2# MSD is not less than 80kNm, the raw materials are extruded and kneaded in the pushing process, the moisture is removed, the dryness of wood chips reaches more than 60%, and when the extruded wood chips are discharged from an expansion discharge port and enter a vertical pre-steeping device, the added chemicals can rapidly expand the wood chips and are fully absorbed by the wood chips; the temperature of the wood chips entering the reaction bin is not less than 60 ℃, and the material level of the reaction bin is not less than 30%.

2. The APMP production process according to claim 1, wherein the sodium polyhydroxyacrylate is mixed with the alkali and the DTPA, and then mixed with the hydrogen peroxide in a mass ratio of 7:27:3:80, and pumped into the addition point to be bleached.

3. The APMP production process according to claim 1, wherein the raw material is at least one of poplar wood chips, acacia wood chips and eucalyptus wood chips, and the storage time is 3-6 months; the wood chip bin keeps a high material level not lower than 40% and sufficient steam, and the temperature of the wood chip bin is not lower than 60 ℃.

4. The APMP production process of claim 1, wherein the temperature of the chip washing water in the chip washer is maintained above 95 ℃; the concentration of the wood chips out of the wood chip washer is 5 percent, the inclined dewatering spiral is lined with the sieve plate, and a large amount of water is discharged from the sieve plate and enters the washing water tank through the inclined sieve.

5. The APMP production process according to claim 1, wherein the presteaming bin level is not less than 50%, the temperature is controlled at 90-105 ℃, air entrained with wood chips is discharged and enters MSD through a metering screw.

6. The APMP production process according to claim 1, wherein the model number 1# main mill is: the diameter of a rotor is 64 inches, the maximum diameter of a grinding plate is 70 inches, the power is 14MW, and the rotating speed of the rotor is 1500 r/min; the disc mill is divided into a crushing area, a middle area, a coarse grinding area and a fine grinding area from inside to outside; the wood chips are dissociated into coarse fragments at the inlet of the grinding zone, the coarse fragments are dissociated into coarse fiber bundles in the middle of the grinding zone, the coarse fiber bundles are arranged in a non-directional mode, are separated into fibers parallel to the grinding teeth and are ground into fragments vertical to the grinding teeth; the fibers in the coarse grinding area are mainly subjected to the friction and the shearing force of the disc teeth, and the fibers in the fine grinding area flow forwards along the tooth grooves, so that the pulp strength is greatly improved; the energy generated by the disc mill is 10 percent used for grinding wood chips and 90 percent used for heating water, and steam is generated for recycling.

7. The APMP production process according to claim 1, wherein the refining energy consumption of the wood chips through the No. 1 main mill is controlled to be 400-800 kWh/admt, the pressure of a main milling chamber is less than 3bar, the gap between the main milling disks is controlled to be-5 mm, the refining concentration is controlled to be 31-40%, the D65 whiteness of the refiner is controlled to be 50-70, and the freeness of the discharged pulp is 650-750 mL.

8. The APMP production process according to claim 1, wherein the bleaching time of the bleaching tower is 70-80 minutes, the bleaching temperature is controlled at 80-90 ℃, the concentration is 25-30%, a scraper discharger is arranged at the bottom of the bleaching tower, and slurry at the bottom of the bleaching tower is diluted to 10% concentration by adding turbid filtrate.