Pulping process

Abstract

The application discloses a pulping method. The pulping method comprises the following steps: transferring wood chips to a pre-pumping tank for soaking, and adding a pulping defoaming agent into the pre-pumping tank; extruding, dewatering and conveying the soaked wood chips, and separating liquid and wood; screening the separated liquid, separating soaking black liquor and solid-liquid mixture, and inputting the soaking black liquor into a wastewater collection tank; inputting the solid-liquid mixture into a sand-water separator, adding a pulping defoaming agent, and separating solid and sand-water black liquor, and inputting the sand-water black liquor into the wastewater collection tank; adding a pulping defoaming agent into the wastewater collection tank; and evaporating and recycling the black liquor in the wastewater collection tank. Through the above method, the pulping method can improve the foaming phenomenon of the black liquor and improve the evaporation and recycling efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking, and particularly relates to a pulping method. BACKGROUND

[0002] The waste water produced by the alkali method (caustic soda method and sulfate method) pulping process of the papermaking industry contains a large amount of lignin, is black-brown, and is called black liquor. Because a large amount of organic lignin is dissolved in the cooking process, the black liquor is easy to foam. If the foaming black liquor is not properly treated, the evaporation recovery treatment efficiency of the black liquor will be affected. SUMMARY

[0003] Embodiments of the present application provide a pulping method, which can improve the foaming phenomenon of the black liquor and improve the evaporation recovery efficiency.

[0004] Embodiments of the present application provide a pulping method. The pulping method comprises:

[0005] Transferring wood chips into a pre-pump tank for soaking, and adding a pulping defoaming agent into the pre-pump tank;

[0006] Squeezing, dewatering and conveying the soaked wood chips, and separating liquid and wood material;

[0007] Screening the separated liquid, and separating soaking black liquor and solid-liquid mixture;

[0008] Inputting the soaking black liquor into a waste water collection tank;

[0009] Inputting the solid-liquid mixture into a sand-water separator, adding a pulping defoaming agent and separating solid and sand-water black liquor, and inputting the sand-water black liquor into the waste water collection tank;

[0010] Adding a pulping defoaming agent into the waste water collection tank;

[0011] Evaporating and recovering the dilute black liquor in the waste water collection tank.

[0012] Optionally, after the soaked wood chips are squeezed, dewatered and conveyed, and the liquid and the wood material are separated, the method further comprises:

[0013] After the wood material sequentially passes through a primary thickening section, a bleaching section, a washing section, a secondary thickening section, a pressure screening section and a multi-disc thickening section, separating wood pulp and clear filtrate, and adding a pulping defoaming agent into the clear filtrate;

[0014] Inputting the clear filtrate into the washing section, the bleaching section, the pre-pump tank or the waste water collection tank.

[0015] Optionally, the total amount of the pulping defoaming agent is 0.2-0.75 kg / adt.

[0016] Optionally, the total amount of pulp defoamer added in the first 40-60 days of a total cycle of 70-80 days of evaporation recovery treatment is 0.2-0.55 kg / adt, and the total amount of pulp defoamer added in the remaining cycle is 0.5-0.75 kg / adt.

[0017] Optionally, the amount of pulp defoamer used in the pre-pump tank is 30-50%;

[0018] The amount of pulp defoamer used in the sand-water separator is 5-10%;

[0019] The amount of pulp defoamer used in the wastewater collection tank is 40-60%;

[0020] The amount of pulp defoamer used in the clear filtrate is 5-20%.

[0021] Optionally, the evaporation recovery treatment of the dilute black liquor in the wastewater collection tank includes:

[0022] The dilute black liquor is added to a multi-stage evaporation effect tank for evaporation concentration;

[0023] The multi-stage evaporation effect tank includes a plurality of evaporation effect tanks arranged in series, wherein the heating steam enters from one end of the plurality of evaporation effect tanks arranged in series, passes through each evaporation effect tank in turn, and the dilute black liquor enters from the other end of the plurality of evaporation effect tanks arranged in series, passes through each evaporation effect tank in turn for concentration;

[0024] The concentrated black liquor after evaporation concentration is subjected to combustion and causticization recovery.

[0025] Optionally, the evaporation concentration of the dilute black liquor in the multi-stage evaporation effect tank includes:

[0026] In the plurality of evaporation effect tanks, an evaporation defoamer is added to the evaporation effect tank with a mass concentration of the dilute black liquor between 12-25%.

[0027] Optionally, when the wood chips are full eucalyptus wood chips, the total amount of pulp defoamer is 0.5-0.75 kg / adt.

[0028] Optionally, the total cycle of evaporation recovery treatment is 70-80 days, the total amount of pulp defoamer added in the first 40-60 days is 0.5-0.55 kg / adt, and the total amount of pulp defoamer added in the remaining cycle is 0.7-0.75 kg / adt.

[0029] Optionally, the amount of pulp defoamer used in the pre-pump tank is 35-40%;

[0030] The amount of pulp defoamer used in the sand-water separator is 5-10%;

[0031] The dosage of the defoaming agent in the wastewater collection tank is 45-55%;

[0032] The dosage of the defoaming agent in the clear filtrate is 5-15%.

[0033] Optionally, when the wood chip ratio includes eucalyptus wood chips and acacia wood chips, the total dosage of the defoaming agent is 0.5-0.55 kg / adt.

[0034] Optionally, the total operation period of the evaporation recovery treatment is 70-80 days, the total dosage of the defoaming agent added in the period of 30 days before is 0.2-0.3 kg / adt, the total dosage of the defoaming agent added in the period of 30 days to 60 days is 0.3-0.35 kg / adt, and the total dosage of the defoaming agent added in the period of 60 days after is 0.5-0.55 kg / adt.

[0035] Optionally, the dosage of the defoaming agent in the pre-pump tank is 30-35%;

[0036] The dosage of the defoaming agent in the sand-water separator is 5-10%;

[0037] The dosage of the defoaming agent in the wastewater collection tank is 40-50%;

[0038] The dosage of the defoaming agent in the clear filtrate is 15-20%.

[0039] The beneficial effects of the present application are: different from the prior art, black liquor is generated in multiple different stages during the pulping process, by controlling each stage where black liquor is generated and adding a defoaming agent during the entire pulping process, the generated black liquor is treated, the foaming of the generated black liquor is reduced, thereby playing a role in protecting the pulping equipment on the one hand, and reducing the foaming of the black liquor during the evaporation treatment process, thereby improving the evaporation recovery efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0040] Fig. 1 is a schematic diagram of the pulping process in the pulping method of the present application;

[0041] Fig. 2 is a schematic diagram of the evaporation recovery treatment process in the pulping method of the present application;

[0042] Fig. 3 is a flowchart of the pulping method of the present application. DETAILED DESCRIPTION

[0043] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0044] The wastewater produced by the alkali method (caustic soda method and sulfate method) of the papermaking industry contains a large amount of lignin and is black-brown, which is called black liquor. The present inventors found in the research process that the black liquor is easy to foam, mainly because a large amount of organic lignin is dissolved in the cooking process. Among them, different wood chips are used for pulping, and the foaming degree of the black liquor is also different. Foaming will cause the air content in the pulp and black liquor to increase, and the pulp washing effect and the thickness of the pulp will be affected, resulting in reduced production efficiency.

[0045] In the related art, the black liquor is concentrated by evaporation treatment during recovery and treatment, and then sent to an alkali furnace for combustion, and then causticized to recover effective alkali, so as to achieve the purpose of chemical recovery and utilization. However, the composition of the black liquor is complex, and the composition of the black liquor under different wood chip ratios is different, which also causes differences in the treatment of the black liquor during evaporation recovery.

[0046] The present inventors found through previous research analysis and data accumulation that when the lignin and organic matter of 100% eucalyptus wood are dissolved more, under the action of high temperature and high pressure, this component is more prone to foaming when the black liquor is concentrated to a certain concentration, and the performance requirements of the defoaming agent are higher under high temperature and high pressure in the evaporation recovery. If not treated in time or the effect is not good, the foam will carry fine components including fibers to the outer wall of the evaporation tube, and the outer wall is in a closed state, which is difficult to clean. If this condition exists for a long time, it will cause poor steam flow on the outer wall, thereby reducing the evaporation efficiency. If it is blocked, the evaporation tank can only be replaced. When the foam is serious, there will be a phenomenon of black water running, causing the quality of the condensate water to be unqualified, and also causing waste of secondary treatment. In order to improve the above technical problems, the present application can provide the following embodiments.

[0047] The present application provides a pulping method, which combines Figs. 1 to 3 The pulping method comprises the following steps.

[0048] S10: soaking the wood chips in the pre-pump tank, and adding a pulping defoaming agent in the pre-pump tank.

[0049] The raw material for pulp manufacturing is various types of wood chips, such as pine, eucalyptus or acacia. In the pulping process, the wood chips are first transferred from the storage to the pre-pump tank for soaking. The wood chips are soaked to remove impurities such as sand, wood chips or stones, and to soften the wood chips. The liquid in the pre-pump tank after soaking the wood chips contains organic matter lignin. By adding a pulp defoamer to the pre-pump tank, the foaming of the liquid in the pre-pump tank is improved, and the foaming of the liquid soaked into the wood chips is improved to reduce the foaming of the liquid after the wood chips are dehydrated.

[0050] S20: The soaked wood chips are pressed, dehydrated and transported, and the liquid and wood material are separated.

[0051] In order to remove excess water, air and resin from the wood chips, the wood chips need to be pressed and dehydrated to separate the black liquor. In the process of pressing and dehydrating, the wood chips can also be transported to the next step. Specifically, the soaked wood chips can be pressed and dehydrated by a dehydration screw and a screw press defibrator. By pressing and dehydrating, the liquid mixed with solid impurities can be separated, and the wood material after pressing and dehydrating can also be separated.

[0052] S30: The separated liquid is screened, and the soaking black liquor and the solid-liquid mixture are separated.

[0053] The separated liquid is the liquid mixed with solid impurities as described above. In order to fully recover the black liquor, the separated liquid needs to be further screened (for example, the separated liquid is passed through an inclined screen) to separate the soaking black liquor. The black liquor carried by the solid cannot be completely screened out, so after the soaking black liquor is separated, a solid-liquid mixture is formed.

[0054] S31: The soaking black liquor is input into the wastewater collection tank.

[0055] S32: The solid-liquid mixture is input into the sand-water separator, a pulp defoamer is added, and the solid and sand-water black liquor are separated, and the sand-water black liquor is input into the wastewater collection tank.

[0056] Since the solid-liquid mixture contains a lot of black liquor, in order to fully recover, the solid-liquid mixture needs to be sand-water separated. Further, in order to improve the foaming of the black liquor in the separation process and the subsequent process, a pulp defoamer needs to be added. After the solid-liquid mixture is separated into solid and sand-water black liquor, the sand-water black liquor is also input into the wastewater collection tank for recycling.

[0057] S40: A pulp defoamer is added to the wastewater collection tank.

[0058] The wastewater collection tank collects most of the black liquor generated in the pulping process. The black liquor collected in the wastewater collection tank can be evaporated and recovered in subsequent processes. In order to improve the foaming phenomenon of the black liquor during the evaporation and recovery process, a pulping defoaming agent needs to be further added to the wastewater collection tank.

[0059] S50: Evaporating and recovering the dilute black liquor in the wastewater collection tank.

[0060] Evaporating and recovering the dilute black liquor in the wastewater collection tank includes:

[0061] S51: Adding the dilute black liquor to the multi-stage evaporation tank for evaporation and concentration.

[0062] The multi-stage evaporation tank includes a plurality of evaporation tanks arranged in series. The heating steam enters from one end of the plurality of evaporation tanks arranged in series, passes through each evaporation tank in turn, and the dilute black liquor enters from the other end of the plurality of evaporation tanks arranged in series, passes through each evaporation tank in turn for concentration. The steam input from one end of the evaporation tank can heat the dilute black liquor therein, and the dilute black liquor can also generate steam, which can further re-enter the next stage of evaporation tank to heat the dilute black liquor therein. After the dilute black liquor enters from the other end of the plurality of evaporation tanks, the dilute black liquor is evaporated and concentrated for several times, and its mass concentration continuously rises.

[0063] The present inventors found in the research process that the amount of foaming during the evaporation and recovery process of black liquor is related to the mass concentration of black liquor. The foaming degree of black liquor is not serious when the mass concentration is low, and the foaming degree of black liquor is not serious when the mass concentration is high after continuous concentration. The foaming degree of black liquor is most serious when the mass concentration is between 12-25%. Therefore, in some embodiments, an evaporation defoaming agent is added to the evaporation tank in which the mass concentration of the dilute black liquor is between 12-25% among the plurality of evaporation tanks. Alternatively, the addition of the evaporation defoaming agent can be selectively added according to whether the foaming occurs, and the amount of addition is not specifically limited herein.

[0064] In some embodiments, the evaporation tank near the steam input end includes a plurality of alternately usable evaporators, so that the evaporation efficiency is improved by alternating use during the evaporation and recovery process. In some embodiments, after the plurality of evaporation tanks concentrate the dilute black liquor, the dilute black liquor can be mixed in the lime mud mixing tank and then input to the efficient evaporation tank for further evaporation treatment to obtain concentrated black liquor.

[0065] S52: Burning and causticizing recovery of the concentrated black liquor after evaporation and concentration.

[0066] The concentrated black liquor after evaporation and concentration in the evaporation tank can be sent to the lime kiln for burning and then causticizing recovery of available alkali, so as to achieve the purpose of chemical recovery and utilization.

[0067] In some embodiments, after the wood chips are soaked, pressed, dewatered, and transported, and the liquid and wood substance are separated, the method further comprises:

[0068] S60: After the wood substance is sequentially subjected to a primary thickening section, a bleaching section, a washing section, a secondary thickening section, a pressure screening section, and a multi-disc thickening section, the wood pulp and the clear filtrate are separated, and a pulp defoaming agent is added to the clear filtrate.

[0069] The dewatered wood substance can be sequentially subjected to further pulping processes, such as high consistency grinding, washing, low consistency grinding, pressure screening, and multi-disc thickening, so as to form the final wood pulp. In the foregoing processes, the clear filtrate is separated after the multi-disc thickening filtration, and the mass concentration of the clear filtrate is lower than that of the black liquor generated in the previous processes.

[0070] S70: The clear filtrate is input to a washing section, a bleaching section, a pre-pump tank, or a waste water collection tank.

[0071] Since the mass concentration of the clear filtrate is low, it can be used for washing in the washing section, bleaching in the bleaching section, or soaking in the pre-pump tank, or directly input to the waste water collection tank. Since the clear filtrate is added to other processes, a pulp defoaming agent needs to be added to reduce foaming during the other processes, so as to improve production efficiency. Further, a large amount of water is also needed for bleaching and washing. The mass concentration of the black liquor output from the washing section is lower than that of the black liquor output from the bleaching section. Therefore, in order to save water resources, the black liquor output from the washing section can be used to input to the bleaching section for bleaching, or directly input to the waste water collection tank. Further, the mass concentration of the black liquor output from the bleaching section is also lower than that of the black liquor generated in the previous processes, so it can be used for soaking of wood chips in the pre-pump tank or directly input to the waste water collection tank.

[0072] It should be noted that the soaking black liquor, sand water black liquor, clear filtrate, dilute black liquor, and concentrated black liquor are all black liquor in a broad sense, and all dissolve lignin. In the foregoing steps, the black liquor generated in different stages is distinguished by name, and the main difference is that the concentrations of the black liquors are different. Different names should not be understood as specific limitations on the specific steps of the pulping method. The wood chips, wood substance, and wood pulp in the foregoing pulping process are mainly used to distinguish the products of different processes in the pulping section, and the different names are used to indicate the products in different steps through the possible forms of the products. The different names should not be understood as specific limitations on the specific steps of the pulping method.

[0073] In combination with the foregoing pulping method, the amount of the defoaming agent used in the pulping process is specifically described as follows.

[0074] In some embodiments, the pulp defoaming agent is a modified silicon polyether defoaming agent, and the evaporation defoaming agent is a polyether surfactant.

[0075] In some embodiments, the total amount of pulp defoaming agent is 0.2-0.75 kg / adt, for example 0.3 kg / adt, 0.35 kg / adt, 0.5 kg / adt, 0.55 kg / adt or 0.7 kg / adt.

[0076] In some embodiments, one complete running cycle of evaporation recovery treatment is 70-80 days, wherein the complete running cycle of the plurality of evaporation tanks refers to the cleaning treatment after the complete running cycle. During the evaporation treatment of the plurality of evaporation tanks, the evaporation tanks are gradually contaminated, which will affect the foaming of the black liquor in the evaporation treatment stage to different degrees. Therefore, during the pulping process of wood chips, the amount of pulp defoaming agent can be adjusted according to the different running cycles of the evaporation treatment at the same period. Specifically, in the early and middle stages of evaporation recovery treatment, the foaming phenomenon is relatively not serious, and a smaller amount of pulp defoaming agent can be used. Specifically, in the period before 40-60 days, the total amount of pulp defoaming agent added is 0.2-0.55 kg / adt, for example 0.3 kg / adt, 0.35 kg / adt or 0.5 kg / adt. In the remaining period, that is, in the later stage of evaporation recovery treatment, the foaming phenomenon is relatively serious, and the total amount of pulp defoaming agent added is 0.5-0.75 kg / adt, for example 0.55 kg / adt or 0.7 kg / adt.

[0077] In some embodiments, the concentration of black liquor in the pre-pump tank, sand-water separator, wastewater collection tank and clean filtrate is different, so the amount of defoaming agent added therein is also different. The present inventors have determined the following addition ratio after continuous research. Specifically, the amount of pulp defoaming agent used in the pre-pump tank is 30-50%, for example 32%, 38%, 45% or 48%. The amount of pulp defoaming agent used in the sand-water separator is 5-10%, for example 7%, 8% or 9%. The amount of pulp defoaming agent used in the wastewater collection tank is 40-60%, for example 41%, 45%, 52%, 58%. The amount of pulp defoaming agent used in the clean filtrate is 5-20%, for example 10%, 15% or 18%.

[0078] In actual production, the present inventors have also found that different wood chip ratios will result in different foaming phenomena of black liquor in the pulping process. Based on this, the present inventors have also proposed a control method for the total amount and mass ratio of pulp defoaming agent under different wood chip ratios. Based on the foregoing reasons, the foaming phenomenon of black liquor in the running cycle of evaporation recovery treatment will be different, and the concentration of black liquor in different stages will be different, which will not be described here. The amount and ratio will be introduced directly as follows.

[0079] In some embodiments, where the wood chips are all eucalyptus chips, the total amount of pulping defoamer used is 0.5-0.75 kg / adt, for example, 0.55 kg / adt or 0.7 kg / adt.

[0080] In some embodiments, the total operating cycle of the evaporation recovery treatment is 70-80 days. During the first 40-60 days of the cycle, the total amount of pulping defoamer added is 0.5-0.55 kg / adt, for example, 0.52 kg / adt or 0.54 kg / adt. During the remaining cycle, the total amount of pulping defoamer added is 0.7-0.75 kg / adt, for example, 0.72 kg / adt or 0.74 kg / adt.

[0081] Based on the previous embodiment, the dosage of defoamer in the pre-pump tank is 35-40%, for example, 36%, 38%, or 39%. The dosage of defoamer in the sand-water separator is 5-10%, for example, 7%, 8%, or 9%. The dosage of defoamer in the wastewater collection tank is 45-55%, for example, 46%, 51%, or 54%. The dosage of defoamer in the filtrate is 5-15%, for example, 9%, 10%, or 13%.

[0082] In some embodiments, where the wood chip ratio includes eucalyptus chips and acacia chips, the total amount of pulping defoamer is 0.5-0.55 kg / adt, for example, 0.52 kg / adt, 0.53 kg / adt, or 0.54 kg / adt.

[0083] In some embodiments, the total operating cycle of the evaporation recovery treatment is 70-80 days. During the first 30 days, the total amount of pulping defoamer added is 0.2-0.3 kg / adt, for example, 0.23 kg / adt, 0.25 kg / adt, or 0.28 kg / adt. During the 30-60 day cycle, the total amount of pulping defoamer added is 0.3-0.35 kg / adt, for example, 0.32 kg / adt, 0.33 kg / adt, or 0.34 kg / adt. During the cycle after 60 days, the total amount of pulping defoamer added is 0.5-0.55 kg / adt, for example, 0.52 kg / adt, 0.53 kg / adt, or 0.54 kg / adt.

[0084] Based on the previous embodiment, the dosage of defoamer in the pre-pump tank is 30-35%, for example, 32%, 33%, or 34%. The dosage of defoamer in the sand-water separator is 5-10%, for example, 7%, 8%, or 9%. The dosage of defoamer in the wastewater collection tank is 40-50%, for example, 43%, 45%, or 48%. The dosage of defoamer in the filtrate is 15-20%, for example, 16%, 17%, or 18%.

[0085] The following will be illustrated by a specific production example of using full eucalyptus wood and eucalyptus wood combined with acacia in actual production process.

[0086]

[0087] The above table can at least obtain the following information:

[0088] (1) Organic salt and lignin (dissolved): The black liquor component of 100% full new eucalyptus is higher than that containing 55% acacia.

[0089] (2) Sodium chloride: The black liquor component of 100% full eucalyptus is slightly more than that containing 55% acacia.

[0090] In summary, the COD value of the black liquor of 100% full new eucalyptus is higher than that of 55% acacia, in addition, the dissolved lignin (salt) has a higher active surface energy, plus organic salts such as sodium acetate have a certain buffer stability, which is one of the sources of abundant foam. (Lignin is a biological macromolecule with three-dimensional network structure formed by three phenylpropane units connected by ether bonds and carbon-carbon bonds, containing rich aromatic ring structure, aliphatic and aromatic hydroxyl groups, and active groups such as quinone groups).

[0091] Based on the above analysis, the inventors added the following proportion of pulping defoaming agent, and the foaming phenomenon was obviously improved.

[0092]

[0093] Specifically, in the related art, 35% of the pulping defoaming agent is added to the pre-pump tank, 9% of the pulping defoaming agent is added to the sand-water separator, 38% of the pulping defoaming agent is added to the wastewater collection tank, and 18% of the pulping defoaming agent is added to the clear filtrate.

[0094] In the case of full wood chips, 38% of the pulping defoaming agent is added to the pre-pump tank, 7% of the pulping defoaming agent is added to the sand-water separator, 45% of the pulping defoaming agent is added to the wastewater collection tank, and 10% of the pulping defoaming agent is added to the clear filtrate. The above proportion is used under full eucalyptus, compared with the proportion in the related art, the evaporation ratio can be increased by 0.8T (water) / T (steam).

[0095] In the case of mixing acacia chips and eucalyptus chips, 32% of the pulping defoaming agent is added to the pre-pump tank, 8% of the pulping defoaming agent is added to the sand-water separator, 41% of the pulping defoaming agent is added to the wastewater collection tank, and 18% of the pulping defoaming agent is added to the clear filtrate. The above proportion is used under the proportion containing acacia chips, compared with the proportion in the related art, the evaporation ratio in the evaporation recovery stage can be increased by 0.2T (water) / T (steam).

[0096] In summary, in the pulp-making process, there are multiple different stages that produce black liquor. By controlling each stage that produces black liquor throughout the entire process of pulp-making and adding a defoaming agent, and adaptively managing and jointly controlling the amount of defoaming agent added according to different wood chip types, the generated black liquor is treated, and the foaming of the black liquor is reduced, thereby playing a role in protecting the pulp-making equipment on the one hand, and reducing the foaming of the black liquor during the evaporation treatment process, thereby improving the evaporation recovery efficiency. The present application also combines wood chip raw material pulp-making and evaporation recovery operation cycles, which can effectively control the generation of foam in the evaporation recovery stage, improve the evaporation recovery operation efficiency and evaporation ratio, reduce the risk of scaling and damage to the equipment. The steam resource is effectively saved, and waste is reduced. After joint control, the defoaming agent is effectively utilized. Compared with before optimization, the comprehensive defoaming agent consumption is reduced by 0.2-0.4 kg / t of pulp, the chemical cost is effectively reduced, and waste is avoided.

[0097] The above is only an embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation using the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A pulping process characterized by, The method comprises the following steps: transferring wood chips to a pre-pumping tank for soaking, and adding a pulping defoaming agent into the pre-pumping tank; extruding, dewatering and conveying the soaked wood chips, and separating liquid and wood materials; screening the separated liquid, and separating soaking black liquor and solid-liquid mixture; inputting the soaking black liquor into a wastewater collection tank; inputting the solid-liquid mixture into a sand-water separator, adding a pulping defoaming agent, and separating solid and sand-water black liquor, and inputting the sand-water black liquor into the wastewater collection tank; adding a pulping defoaming agent into the wastewater collection tank; evaporating and recovering the dilute black liquor in the wastewater collection tank; the step of evaporating and recovering the dilute black liquor in the wastewater collection tank comprises the following steps: adding the dilute black liquor into a plurality of evaporating effect tanks for evaporation and concentration; in the plurality of evaporating effect tanks, adding an evaporation defoaming agent into the evaporating effect tank with a mass concentration of the dilute black liquor between 12% and 25%; the plurality of evaporating effect tanks comprise a plurality of evaporating effect tanks arranged in series, wherein heating steam enters one end of the plurality of evaporating effect tanks arranged in series, and sequentially passes through each evaporating effect tank, and the dilute black liquor enters the other end of the plurality of evaporating effect tanks arranged in series, and sequentially passes through each evaporating effect tank for concentration; combusting and causticizing the concentrated black liquor after evaporation and concentration; wherein, the total amount of the pulping defoaming agent is 0.2-0.75 kg / adt; the amount of the pulping defoaming agent in the pre-pumping tank is 30-50%; the amount of the pulping defoaming agent in the sand-water separator is 5-10%; the amount of the pulping defoaming agent in the wastewater collection tank is 40-60%.

2. The pulping method according to claim 1, wherein after the step of extruding, dewatering and conveying the soaked wood chips, and separating liquid and wood materials, the method further comprises the following steps: after the wood materials sequentially pass through a primary thickening section, a bleaching section, a washing section, a secondary thickening section, a pressure screening section and a multi-disc thickening section, separating wood pulp and clear filtrate, and adding a pulping defoaming agent into the clear filtrate, and the amount of the pulping defoaming agent in the clear filtrate is 5-20%; inputting the clear filtrate into the washing section, the bleaching section, the pre-pumping tank or the wastewater collection tank.

3. The pulping method according to claim 2, wherein during the process of pulping the wood chips, the amount of the pulping defoaming agent is adjusted according to different running periods of the simultaneous evaporation treatment, wherein one complete running period of the evaporation recovery treatment is 70-80 days, and during the period of 40-60 days, the total amount of the pulping defoaming agent is 0.2-0.55 kg / adt, and during the remaining period, the total amount of the pulping defoaming agent is 0.5-0.75 kg / adt.

4. The pulping method according to claim 2, wherein when the wood chips are whole eucalyptus wood chips, the total amount of the pulping defoaming agent is 0.5-0.75 kg / adt.

5. The pulping method according to claim 4, wherein ​ ​ ​ In the process of wood chip pulping, the dosage of the pulping defoaming agent is adjusted according to the different operation periods of the contemporaneous evaporation treatment, wherein the total operation period of the evaporation recovery treatment is 70-80 days, the total dosage of the pulping defoaming agent added in the first 40-60 days is 0.5-0.55 kg / adt, and the total dosage of the pulping defoaming agent added in the remaining period is 0.7-0.75 kg / adt.

6. The pulping method according to claim 5, characterized in that: the dosage of the pulping defoaming agent in the pre-pump tank is 35-40%; the dosage of the pulping defoaming agent in the sand-water separator is 5-10%; the dosage of the pulping defoaming agent in the wastewater collection tank is 45-55%; the dosage of the pulping defoaming agent in the clear filtrate is 5-15%.

7. The pulping method according to claim 2, characterized in that: when the wood chip ratio comprises eucalyptus wood chips and acacia wood chips, the total dosage of the pulping defoaming agent is 0.5-0.55 kg / adt.

8. The pulping method according to claim 7, characterized in that: in the process of wood chip pulping, the dosage of the pulping defoaming agent is adjusted according to the different operation periods of the contemporaneous evaporation treatment, wherein the total operation period of the evaporation recovery treatment is 70-80 days, the total dosage of the pulping defoaming agent added in the first 30 days is 0.2-0.3 kg / adt, the total dosage of the pulping defoaming agent added in the period of 30-60 days is 0.3-0.35 kg / adt, and the total dosage of the pulping defoaming agent added in the period after 60 days is 0.5-0.55 kg / adt.

9. The pulping method according to claim 8, characterized in that: the dosage of the pulping defoaming agent in the pre-pump tank is 30-35%; the dosage of the pulping defoaming agent in the sand-water separator is 5-10%; the dosage of the pulping defoaming agent in the wastewater collection tank is 40-50%; the dosage of the pulping defoaming agent in the clear filtrate is 15-20%.

Images