CN107311478B

CN107311478B - Energy-saving environment-friendly recovery method for comprehensively recycling white mud

Info

Publication number: CN107311478B
Application number: CN201710703803.7A
Authority: CN
Inventors: 杨泽荣
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-08-16
Filing date: 2017-08-16
Publication date: 2020-03-20
Anticipated expiration: 2037-08-16
Also published as: CN107311478A

Abstract

The invention discloses an energy-saving and environment-friendly recovery method for comprehensively utilizing lime mud, wherein the discharge end of a dehydrator is communicated with the feed end of a calciner only through a calcining screw hoist, waste heat generated in the cooling process of a cooler flows back to the discharge end of the dehydrator through a heat pipe in one-way transmission to carry out primary preheating on dehydrated lime mud discharged by the dehydrator, and high-temperature gas for calcining in the calciner carries out secondary preheating on the dehydrated lime mud entering the calciner from the calcining screw hoist to form a preheating cavity with uniformly raised preheating temperature from the discharge end of the dehydrator to the feed end of the calciner, and the dehydrated lime mud directly enters the calciner for calcining after being preheated in the spiral lifting process of the calcining screw hoist; and the sulfur-containing flue gas generated in the calcining process is introduced into the desulfurizing tower from a high-temperature flue gas outlet positioned at the tail end of the calcining furnace body through a flue. The invention comprehensively utilizes the substances and energy in the white mud recovery, and is economical and environment-friendly.

Description

Energy-saving environment-friendly recovery method for comprehensively recycling white mud

Technical Field

The invention relates to the technical field of white mud recycling in a papermaking process, in particular to an energy-saving and environment-friendly recycling method for recycling white mud comprehensively.

Background

Alkaline pulping is a widely used process in most pulp and paper mills today. During the causticizing process of alkaline pulping and papermaking, a large amount of white mud with precipitated calcium carbonate as a main component is generated. Causticization is to remove Na in green liquor produced by alkaline pulping and papermaking₂CO₃And Ca (OH)₂Causticizing to generate white liquor containing NaOH and CaCO containing precipitate₃And (3) carrying out reaction process of the white mud. According to the detection, the white mud recovered by the paper mill contains CaCO₃、NaOH、Ca(OH)₂CaO, S, etc., wherein CaCO₃The content is 80-92%.

The white mud is a main byproduct generated in the alkali recovery process of pulping black liquor in the paper industry, and the main chemical component of the white mud is calcium carbonate, and in addition, the white mud also contains a part of impurities such as calcium oxide, silicon, metal salt and the like. At present, in the alkali recovery process, 1 ton of alkali can be recovered, and 2-2.2 tons of white mud can be separated, so the white mud is one of main solid wastes in the paper making industry.

The main common modes for harmlessly treating papermaking white mud comprise:

a1 calcining to lime and recycling in alkali recovery section;

a2 extracted and refined calcium carbonate is used as paper filler and used for producing building materials such as cement, paint and the like;

a3, using the white mud as a flue gas desulfurizer of the coal-fired boiler;

④ the waste white mud is buried directly.

However, the extraction efficiency of calcining the existing white mud into lime or extracting refined calcium carbonate is not high, and the economic value of byproducts is limited; the white mud used as a flue gas desulfurizer of the coal-fired boiler needs to have the precondition of 'having the coal-fired boiler', and the application range is limited; the waste white mud is directly buried, which can cause environmental pollution.

On the other hand, calcining the white mud into lime or extracting refined calcium carbonate can indeed recycle the white mud and increase the yield of byproducts, but the existing recovery process and recovery method only focus on the recovery of the white mud, and few technical solutions consider the treatment of other auxiliary materials, consumed energy and other emissions in the white mud recovery process.

Disclosure of Invention

The invention aims to provide an energy-saving and environment-friendly recovery method for comprehensively recycling white mud, which not only improves the recovery efficiency of white mud extraction products, but also fully utilizes heat energy and water energy required in the recovery process, and allows the gas generated in the recovery process to be discharged after being subjected to environment-friendly treatment.

The invention is realized by the following technical scheme: the energy-saving and environment-friendly recovery method for recycling and comprehensively utilizing the lime mud comprises the steps of sequentially carrying out dehydration by a dehydrator, calcination by a calciner, cooling by a cooler and grinding and sorting by a lime machine to obtain a finished product, wherein sulfur-containing flue gas generated in the calcination process of the calciner is introduced into a desulfurizing tower for desulfurization; the calcining furnace is an electric heating type rotary calcining furnace with an obliquely arranged calcining furnace body, and the calcining furnace body is provided with a dehydrated white mud inlet, a high-temperature ash powder outlet and a high-temperature flue gas outlet.

The discharge end of the dehydrator is communicated with the feed end of the calciner only through a calcining screw elevator, waste heat generated in the cooling process of the cooling machine flows back to the discharge end of the dehydrator through a heat pipe in one-way transmission to carry out primary preheating on dehydrated white mud discharged by the discharge end of the dehydrator, and meanwhile, high-temperature gas for calcining in the calciner carries out secondary preheating on the dehydrated white mud entering the calciner from the calcining screw elevator, so that a preheating cavity with uniformly raised preheating temperature is formed in the calcining screw elevator from the discharge end of the dehydrator to the feed end of the calciner, and the dehydrated white mud directly enters the calciner for calcining after being preheated in the screw lifting process of the calcining screw elevator.

The dehydrated white mud enters a rotary calcining furnace from a dehydrated white mud inlet at the higher tail end of the calcining furnace body at the flow rate of 5-6kg/m3 & min, slowly passes through the calcining furnace body which rotates at 1-5r/min, inclines for 3 +/-0.1 degrees and is provided with tiger teeth on the inner wall, is fully calcined in the calcining furnace body at the calcining temperature of 255-1210 ℃ for 15-30min, and the calcined ash powder is conveyed to a cooler from a high-temperature ash powder outlet at the lower head end of the calcining furnace body for cooling; and the sulfur-containing flue gas generated in the calcining process is introduced into the desulfurizing tower from a high-temperature flue gas outlet positioned at the tail end of the calcining furnace body through a flue.

The applicant submits a patent application of a utility model to the national intellectual property office in 2017, month 07 and 24, and the application number is as follows: 201720900026.0, respectively; the patent names are: an energy-saving and environment-friendly recovery system for comprehensively recycling white mud discloses a technical scheme of a set of recovery system. The energy-saving and environment-friendly recovery system for comprehensively recycling the white slime comprises a white slime raw material box, a centrifugal dehydrator, a rotary calcining furnace, a rotary cooling machine, an ash-calcium classifier and a finished product packaging machine which are sequentially connected, wherein the rotary calcining furnace is also connected with a flue and is connected with a desulfurizing tower through the flue.

The recovery method can recycle the white mud through the recovery system.

The dehydrator used in the dehydration step in the present invention is a centrifugal dehydrator. The calcining furnace used in the calcining procedure is an electrothermal rotary calcining furnace which can be regulated and controlled by temperature. The cooling machine used in the cooling process of the present invention is a water-cooled rotary cooling machine. The ash calcium machine used in the grinding and grading procedure is an ash calcium grader.

And a dehydrated white mud outlet of the centrifugal dehydrator is communicated with a dehydrated white mud inlet of the rotary calciner through a calcining spiral elevator. And a heat pipe for recovering and utilizing waste heat and conducting heat in one direction is communicated between the rotary cooler and the calcining spiral elevator.

The recovery system is based on a solid state circulation line of main components of the white mud, and comprises a white mud raw material box, a centrifugal dehydrator, a rotary calcining furnace, a rotary cooler, an ash calcium classifier and a finished product packaging machine which are sequentially connected.

In the above-mentioned structure, the white mud raw materials of the tape residual alkali that the papermaking process produced leaves in the white mud raw materials case, when carrying out white mud recovery operation:

A. the white mud raw material with residual alkali in the white mud raw material box enters a centrifugal dehydrator for dehydration, solid after solid-liquid separation is dehydrated white mud, and liquid is residual alkali aqueous solution (mixed solution mainly containing sodium hydroxide);

B. the dehydrated white mud enters a rotary calcining furnace, is dried and then is calcined into solid ash calcium powder (calcium carbonate powder or lime powder);

C. high-temperature ash calcium powder discharged from the rotary calcining furnace enters a rotary cooling machine for cooling;

D. feeding the cooled ash calcium powder discharged by the rotary cooler into an ash calcium classifier for grinding and classifying;

E. and (4) packaging the classified ash calcium powder in a finished product packaging machine.

Wherein, when the working temperature in the high-temperature calcining chamber of the rotary calcining furnace is controlled to be 255-310 ℃, the high-temperature ash calcium powder is mainly calcium carbonate powder; when the working temperature in the high-temperature calcining chamber of the rotary calcining furnace is controlled to be 800-1000 ℃, the high-temperature ash calcium powder is mainly the mixture of calcium oxide powder and calcium carbonate powder; when the working temperature in the high-temperature calcining chamber of the rotary calcining furnace is controlled to be 1100-1200 ℃, the high-temperature ash calcium powder is mainly calcium oxide powder, namely lime powder.

Main component of white mudIs CaCO₃、NaOH、Ca(OH)₂CaO, S and white mud can generate a plurality of reactions in the heating process, wherein the main reactions are as follows:

Ca(OH)₂+SO₂＝CaSO₃+H₂O 2CaSO₃+O₂＝O₂＝2CaSO₄

2NaOH+SO₂＝Na₂SO₃+H₂O 2Na₂SO₃+O₂＝2Na₂SO₄

(1) when the calcining temperature is below 350 ℃, sulfur is mainly combusted to generate sulfur dioxide gas, calcium hydroxide reacts with sulfur dioxide to generate calcium sulfate, and sodium hydroxide reacts with sulfur dioxide to generate sodium sulfate. Experiments show that SO is generated when white mud is heated to 230 DEG C₂Releasing SO at 260 DEG C₂The release reaches a peak; in one aspect, SO₂Discharging the high-temperature flue gas from the rotary calcining furnace to a desulfurizing tower; on the other hand, with CaCO₃、NaOH、Ca(OH)₂The "sulfur fixation" reaction occurs to form sulfate.

Experiments prove that the preparation rate of the calcium carbonate powder is highest when the calcining temperature is controlled at 260 ℃.

(2) When the calcining temperature is above 800 ℃, the calcium carbonate and the calcium sulfate begin to decompose to generate carbon dioxide gas and sulfur dioxide gas.

Experiments show that when the calcining temperature exceeds 1100 ℃, the preparation rate of the calcium oxide can reach more than 98 percent.

The proportion of calcium carbonate and the proportion of calcium oxide are uniform in mass percentage.

In addition, the residual alkali water solution discharged by the centrifugal dehydrator can be recycled in a papermaking process after being recycled, or is introduced into a desulfurizing tower for desulfurization treatment, so that the material cost is saved through recycling, the treatment cost of strong alkaline pollutants is reduced, and the method is economical and environment-friendly.

In the above structure, the rotary calciner can generate sulfur-containing flue gas, and the recovery system can also perform flue gas treatment:

m, an exhaust fan arranged in the flue works, and the high-temperature flue gas and the high-temperature ash calcium powder in a high-temperature calcining chamber of the rotary calcining furnace are subjected to solid-gas separation by wind power and are introduced into a desulfurizing tower for desulfurization through the flue;

and N, enabling the high-temperature flue gas subjected to solid-gas separation to enter a desulfurizing tower through a flue to be subjected to desulfurization treatment, and discharging the flue gas subjected to desulfurization reaching the standard.

Wherein, the desulfurizing tower sprays residual alkali aqueous solution or white mud turbid liquid from top to bottom, and the high temperature flue gas moves from bottom to top, and the desulfurizer fully contacts with the high temperature flue gas, and other nature discharge such as carbon dioxide after the desulfurization, and the solid-liquid mixture that produces in the desulfurization process subsides naturally, both cools down and the desulfurization. The flue gas desulfurization process can be used for carrying out desulfurization treatment on the flue gas according with the environmental protection requirement without adding extra purchased materials, and is economical and environment-friendly.

In conclusion, the recovery system can efficiently extract ash calcium powder (calcium carbonate powder or lime powder) from white mud generated by papermaking through dehydration, high-temperature calcination, cooling and grinding classification, can recycle the separated residual alkali aqueous solution into the papermaking process, and can also utilize the white mud to perform desulfurization treatment on sulfur-containing flue gas and generate certain gypsum. The whole recovery system comprehensively utilizes or treats solid (calcium carbonate powder, lime powder and gypsum), liquid (residual alkali aqueous solution) and gas (carbon dioxide after desulfurization) generated in the recovery process of the papermaking waste white mud, and is economical and environment-friendly.

It is worth to say that the invention makes full use of the heat energy in the whole system: firstly, a preheating drying chamber and a high-temperature calcining chamber in the rotary calcining furnace are both high and low ends of a cavity, the high end of the inner cavity of the heat-preserving furnace body is a preheating drying chamber, the bottom end of the inner cavity of the heat-preserving furnace body is a high-temperature calcining chamber provided with an electric heating device independently, and heat in the high-temperature calcining chamber is radiated to the preheating drying chamber in the inner cavity of the heat-preserving furnace body to further dry the dehydrated white mud which just enters the rotary calcining furnace; secondly, the whole system is also provided with a heat pipe which is connected with the rotary cooler and the inlet end of the rotary calciner for dewatering the white mud; the heat pipe transmits the waste heat generated by heat exchange in the rotary cooler back to the second lifting device, and the dewatered white mud discharged from the centrifugal dehydrator is preheated only by the waste heat so as to be further dewatered and dried. The lower the water content of the lime mud entering the high temperature calcination chamber, the less heat energy needs to be consumed. The invention carries out preheating treatment by utilizing the waste heat discharged by the high-temperature calcining chamber, can further effectively reduce the water content of the white mud entering the high-temperature calcining chamber without additionally providing heat energy, greatly shortens the high-temperature calcining time and saves energy.

The inner wall of the high-temperature calcining chamber is provided with a plurality of tiger teeth; the tiger teeth are flanges higher than the inner wall of the high-temperature calcining chamber. The flange in the invention can repeatedly impact the dehydrated white mud in the high-temperature calcining chamber, thereby scattering the white mud blocks and further improving the high-temperature calcining efficiency. Furthermore, one end of the flange close to the inner wall of the high-temperature calcining chamber is the lower end, and the cross section of the flange is of a structure with a small upper part and a large lower part. The flange is big end down, can utilize the better white mud piece of striking caking of pointed end structure, and the reinforcing is broken up the effect. Furthermore, the lower end of the flange is smoothly transited with the inner wall of the high-temperature calcining chamber. The flange and the inner wall of the high-temperature calcining chamber are in smooth transition, so that the white mud blocks are effectively prevented from being bartered on the flange or the inner wall of the high-temperature calcining chamber.

The rotary cooling machine comprises a cooling machine body provided with a waste heat backflow port, a rotary cylinder which is sleeved in the cooling machine body and forms a cooling cavity with the cooling machine body, and a cold water spraying device arranged in the cooling cavity.

The cold water spray set comprises a spray pipe, a water inlet pipe, a water outlet pipe, a water tank and a water pump which are connected in a circulating manner, cooling water in the water tank is pumped into the water inlet pipe penetrating through the cooling machine body through a water pump pressurizing pump, cooling water in the water inlet pipe is sprayed to the outer wall of the rotary cylinder from the spray pipe positioned in the cooling cavity, and the sprayed cooling water is sprayed to the outer wall of the rotary cylinder and high-temperature ash powder in the rotary cylinder to perform heat exchange, then falls down and flows back to the water tank from the water outlet pipe.

The heat pipe conducts unidirectional heat transfer from the rotary cooler to the calcining spiral lifter, the evaporation end of the heat pipe is positioned in the cooling cavity and close to one end of the water outlet pipe, and the condensation end of the heat pipe is positioned in the calcining spiral lifter between the centrifugal dehydrator and the rotary calciner. The heat pipe is internally sealed and is not communicated with the external connection. The waste heat of heat exchange in the rotary cooler is transferred into the calcining spiral elevator through the heat pipe, and the dehydrated lime mud which is discharged from the centrifugal dehydrator and is not completely dehydrated is pre-dried.

And the spray pipe is provided with a plurality of spray heads for spraying cooling water to the outer wall of the rotary cylinder.

According to the invention, the outer wall of the rotary cylinder internally filled with high-temperature ash calcium powder is subjected to flowing water type cooling spraying by a cold water spraying device with cold water circulation. The high-temperature ash calcium powder and the cooling water only exchange heat on the outer wall of the rotary cylinder without direct contact, and the high-temperature ash calcium powder is kept in a dry state while being cooled. And the cooling water only circulates in the spray pipe, the water inlet pipe, the water outlet pipe, the water tank, the water pump and the cooling cavity.

In order to better realize the invention, in the calcining process of the calcining furnace, the main components of the calcined ash powder are controlled by controlling the calcining temperature, and the method specifically comprises the following steps:

controlling the calcining temperature to 255-310 ℃ to prepare ash powder with calcium carbonate as a main component;

controlling the calcining temperature to 800-1000 ℃ to prepare ash powder taking the mixture of calcium carbonate and calcium oxide as the main component;

controlling the calcining temperature to 1100-1200 ℃ to prepare the ash powder taking calcium oxide as the main component.

In order to better realize the invention, in the calcining process of the calcining furnace, the calcining temperature is controlled to 260 ℃ and calcined white mud is retained for more than 15min to prepare the ash powder with the calcium carbonate mass ratio not less than%.

In order to better realize the invention, in the calcining process of the calcining furnace, the calcining temperature is controlled to 800 ℃, and calcined white mud is retained for more than 15min to prepare the ash powder with the calcium oxide mass ratio not less than 50%.

In order to better realize the invention, in the calcining process of the calcining furnace, the calcining temperature is controlled to 1000 ℃ and calcined white mud is retained for more than 15min to prepare the ash powder with the calcium oxide mass ratio not less than 75%.

In order to better realize the invention, in the calcining process of the calcining furnace, the calcining temperature is controlled to 1100 ℃, and calcined white mud is retained for more than 15min to prepare the ash powder with the calcium oxide mass ratio not less than 98%.

In order to better realize the invention, the tiger teeth are convex parts which are arranged on the inner wall of the calcining furnace body and are smoothly protruded towards the center of the calcining furnace body, and the distribution rule and the size of a single tiger tooth of a plurality of tiger teeth distributed on the inner wall surface of the calcining furnace body meet the following conditions: from the tail end to the head end of the calcining furnace body, a plurality of tiger teeth are distributed from sparse to dense, and the size of each tiger tooth is gradually reduced.

In order to better realize the invention, the dewatering machine adopted in the dewatering process of the dewatering machine is a centrifugal dewatering machine internally provided with a centrifugal cylinder, a frequency converter, a centrifugal motor, a clutch and a rotating speed sensor, the centrifugal dewatering machine is also provided with a dewatering controller, the dewatering controller controls the positive and negative rotation change and the rotating speed adjustment of the centrifugal motor through the frequency converter, meanwhile, the dewatering controller controls the connection/disconnection of the clutch, and the centrifugal motor drives the centrifugal cylinder to act through the clutch; wherein, the clockwise rotation of the centrifugal cylinder is positive rotation, and the anticlockwise rotation of the centrifugal cylinder is negative rotation.

In the dehydration process of the dehydrator, the rotating speed of the centrifugal cylinder is periodically changed, and specifically means that: in a period, the centrifugal cylinder starts to rotate forwards from the rotation speed of 0 r/min, firstly the linear speed is increased to 600-.

In order to better realize the invention, raw water is intermittently fed into the first dehydration period and the second dehydration period when the dehydrator dehydrates, namely: and when the forward rotation speed or the reverse rotation speed of the centrifugal cylinder is lower than 100 revolutions per minute in the first period and the second period of the dehydration work, introducing high-temperature raw water which is led out from a cooling machine and is used for carrying out water cooling on the high-temperature calcined ash powder to generate heat exchange, and flushing and dealkalizing the residual alkali white mud by using the high-temperature raw water.

In order to better realize the invention, the residual alkali liquor separated from the white mud with residual alkali in the dehydration process of the dehydrator is directly recycled for the papermaking process.

In order to better realize the method, the residual alkali liquor separated from the white mud with residual alkali in the dehydration process of the dehydrator is firstly introduced into the temporary storage barrel for storage, the residual alkali liquor is mixed with the white mud with residual alkali precipitated and separated in the white mud raw material box to form a desulfurizer, and the desulfurizer is sprayed into the desulfurizing tower from the upper part of the desulfurizing tower through a desulfurizer supply pump to carry out desulfurization treatment on the sulfur-containing flue gas.

The white mud raw material with residual alkali to be recovered is firstly stored in a white mud raw material box for standing and precipitation for later use. Diluting the white mud raw material with residual alkali into suspension with the white mud concentration of 22% -24% by using diluent, using the suspension as a desulfurizer in a desulfurizing tower in the invention, and desulfurizing sulfur-containing gas discharged from a calcining furnace, thereby obtaining carbon dioxide gas meeting emission standards.

The invention relates to a method for recycling lime mud with residual alkali, which is subjected to causticization treatment in a papermaking process. The main line for recycling in the technical scheme is to take white mud with residual alkali as a raw material to obtain a finished product (calcium carbonate, calcium oxide, a mixture of calcium carbonate and calcium oxide) through dehydration, calcination, cooling, grinding and sorting, wherein one of the auxiliary lines is used for utilizing waste heat in the calcination process, the other auxiliary line is used for environmentally-friendly emission of sulfur-containing flue gas generated in the calcination process after desulfurization treatment, the third auxiliary line is used for utilizing residual alkali liquid removed from the white mud with residual alkali, and the fourth auxiliary line is used for mixing and diluting the residual alkali liquid and the white mud with residual alkali to form a desulfurizer for desulfurization treatment of the sulfur-containing flue gas in the calcination process.

In summary, the recovery method of the invention comprises the following main raw materials: white mud raw materials, water and electric energy are to be recovered; the process product is as follows: residual alkali liquor, sulfur-containing flue gas, high-temperature gas carrying heat energy generated from a calcining furnace, medium-temperature gas carrying heat energy generated from a cooling machine, hot water carrying heat energy through heat exchange in the cooling process, and staged products of white mud raw materials after various working procedures; the final product was: residual alkali liquid, desulfurized gas and ash calcium powder. The medium-temperature gas carrying heat energy generated from the cooler can be unidirectionally transmitted to the front end of the calcining spiral elevator through a heat pipe, and primary preheating is carried out on the dehydrated lime mud to be calcined; the high-temperature gas carrying heat energy generated from the calcining furnace directly radiates heat from the rotary furnace to the dehydrator and is used for secondary preheating of the dehydrated lime mud to be calcined.

That is, other additional chemical agents are not needed to be added in the whole recovery method, the main raw material is white mud with residual alkali generated by papermaking, except necessary production equipment, water and electric energy are provided in the white mud recovery process, and the full recovery and utilization of materials and energy in the whole process can be realized.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the recovery method mainly comprises five procedures of dehydration, calcination, cooling, grinding and sorting and desulfurization, other additional chemical agents are not required to be introduced, except necessary production equipment, the input raw materials are white mud with residual alkali, water, electric energy and the like to be recycled, ash calcium powder finished products are produced, gas discharged after desulfurization reaches the discharge standard, and residual alkali liquor capable of being recycled to a papermaking process; that is, the recovery method of the invention can not generate secondary pollution and discharge no toxic and harmful substances in the whole process of recovering the ash calcium powder from the causticized white mud raw material generated by papermaking, and all products can be reused;

(2) the recovery method of the invention also recycles the energy generated in the white mud recovery process, specifically, the waste heat generated in the calcining process and the cooling process is introduced into the calcining spiral elevator which is connected with the dehydrator and the rotary furnace, the dehydrated white mud which is dehydrated and prepared to enter the calcining process is preheated, no additional preheating chamber is needed, the spiral elevator for lifting and transporting is fully utilized to form a preheating chamber, thereby not only saving the energy of heat energy, but also saving the space and reducing the transition process between the processes;

(3) the invention can respectively treat the waste white mud generated in the paper making process, the residual alkali aqueous solution separated in the white mud recovering process and the sulfur-containing carbon dioxide gas generated in the ash calcium powder extracting process, only the gas after dust removal and desulfurization is discharged, the calcium carbonate powder, the lime powder or the gypsum powder solid can be recycled after extraction or used as the raw material for producing and processing other products, the residual alkali aqueous solution obtained by centrifugal dehydration can be used for desulfurization or recycled in the paper making process, and the substances or energy in the whole recovering system can be comprehensively utilized, thereby being economic and environment-friendly;

(4) the finished product of the calcium carbonate powder prepared by the invention can be directly used as a filler of a light partition wall board or other wall board materials;

(5) according to the invention, the rotary calcining furnace is provided with the tiger teeth, agglomerated white mud blocks are scattered by using a mechanical structure, and the tiger teeth repeatedly impact and break the white mud blocks in the calcining furnace body, so that the calcining efficiency is improved, and the energy consumption is reduced;

(6) in the invention, the high-temperature ash calcium powder and the cooling water in the rotary cooling machine have effective heat exchange and are separated from each other in a dry-wet manner;

(7) in the invention, the cooled ash calcium powder is directly ground and classified by using the ash calcium classifier, so that a finished product with the particle size meeting the requirement is directly obtained, and the recycling rate of the whole white mud is improved.

Drawings

FIG. 1 is a schematic view of the main steps of the present invention.

FIG. 2 is a schematic diagram of the system of the present invention.

FIG. 3 is a timing chart showing one operation cycle of the centrifugal dehydrator according to the present invention.

FIG. 4 is a schematic view of a trapezoid-like structure of the cross section of a tiger tooth in the present invention.

FIG. 5 is a schematic structural view of the cross section of a tiger tooth in the invention being triangle-like.

FIG. 6 is a graph showing the relationship between the calcination time and the calcium carbonate content in the calcined soot in test two of example 2.

Wherein: 1. a white mud raw material tank; 2. a first screw elevator; 3. a centrifugal dehydrator; 4. calcining the spiral elevator; 5. a rotary calciner; 53. tiger teeth; 6. a desulfurizing tower; 7. a rotary cooler; 8. a lime-calcium classifier; 9. a finished product packaging machine; 10. a desulfurizer preparation box; 11. a heat pipe.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto. It will be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the invention and to simplify the description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be considered limiting of the invention.

Example 1:

as shown in fig. 1 and 2, the energy-saving and environment-friendly recovery method for comprehensively recycling white slime comprises a white slime raw material box 1, a centrifugal dehydrator 3, a rotary calciner 5, a rotary cooler 7, an ash-calcium classifier 8 and a finished product packaging machine 9 which are sequentially connected, wherein the rotary calciner 5 is also connected with a flue and is connected with a desulfurizing tower 6 through the flue.

The rotary calcining furnace 5 comprises a heat preservation furnace body provided with a dehydrated white mud inlet, a high-temperature ash powder outlet and a high-temperature flue gas outlet, and the rotary calcining furnace 5 is obliquely arranged; the discharge end of a centrifugal dehydrator 3 for outputting the dehydrated white mud is connected with a dehydrated white mud inlet of a rotary calciner 5 through a calcination rotary hoisting machine, a high-temperature ash powder outlet for outputting dry ash powder is connected with an ash powder inlet of a rotary cooler 7, and a high-temperature flue gas outlet for outputting flue gas in the calcination process is connected with a desulfurizing tower 6 through a flue. And a heat pipe 11 for recovering and utilizing waste heat and conducting heat in one direction is communicated between the rotary cooler 7 and the calcining spiral elevator. The white mud raw material box 1 is connected with the centrifugal dehydrator 3 through a first screw elevator 2.

The recovery system mainly extracts the ash calcium powder from the white mud by the following path: white mud raw material → white mud raw material tank 1 → centrifugal dehydrator 3 → rotary calciner 5 → rotary cooler 7 → ash calcium classifier 8 → finished product packaging machine 9 → calcium carbonate powder finished product or lime powder finished product.

The main gas circulation path generated in the white mud recovery process of the recovery system is as follows: the carbon dioxide gas containing sulfur produced in the rotary calciner 5 → the flue → the desulfurizing tower 6 → is discharged to the atmosphere.

The main path of liquid circulation separated in the white mud recovery process of the recovery system is as follows: the residual alkali water solution separated from the centrifugal dehydrator 3 → in the paper making process or is introduced into a desulfurizing tower 6 for desulfurization.

In addition, the white mud raw material can be diluted to be used as a desulfurizer for desulfurization and dust removal of sulfur-containing carbon dioxide gas in the desulfurizing tower 6.

The heat pipe 11 conducts heat unidirectionally from the rotary cooler 7 to the calcining spiral elevator 4, the evaporation end of the heat pipe 11 is positioned in the cooling cavity and near one end of the water outlet pipe, and the condensation end of the heat pipe is positioned in the calcining spiral elevator 4 between the centrifugal dehydrator 3 and the rotary calciner 5. The heat pipe 11 is internally sealed and is not communicated with the outside. The residual heat of the heat exchange in the rotary cooler 7 is transferred to the calcining screw lifter 4 through the heat pipe 11, and the dehydrated lime mud discharged from the centrifugal dehydrator 3 and not completely dehydrated is pre-dried.

The inner wall of the calcining furnace body is provided with a plurality of tiger teeth 53; the tiger teeth 53 are flanges higher than the inner wall of the calcining furnace body. The end of the flange close to the inner wall of the calcining furnace body is the lower end, and the cross section of the flange is of a structure with a small upper part and a big lower part.

The lower end of the flange is connected with the inner wall of the calcining furnace body into a whole: when the calcining furnace body is a cylindrical cavity, the lower outline of the cross section of the flange is actually an arc; when the calciner body is a square column type cavity, the lower profile of the flange cross section is a straight line. When the calcining furnace body is a cylindrical cavity: as shown in fig. 4, the cross section of the flange is in a trapezoid-like shape with a small upper end and a large lower end; alternatively, as shown in fig. 5, the cross-section of the flange is triangular-like with a small upper end and a large lower end. And the lower end of the flange is in smooth transition with the inner wall of the calcining furnace body.

The rotary cooling machine 7 comprises a cooling machine body provided with a waste heat backflow port, a rotary cylinder which is sleeved in the cooling machine body and forms a cooling cavity with the cooling machine body, and a cold water spraying device arranged in the cooling cavity.

The rotary cylinder forms a cylindrical cavity which is only provided with a high-temperature ash calcium powder inlet and a low-temperature ash calcium powder outlet. Furthermore, the rotary drum can be rotated along its axis by the driving means. The driving device can adopt a structure that the output end of the driving motor is provided with a driving tooth meshed with the outer wall of the rotary drum.

In the embodiment, the high-temperature ash calcium powder and the low-temperature cooling water only exchange heat at the rotary cylinder wall without directly contacting, and the ash calcium powder is separated from the water and is convenient to keep a dry state after being cooled, and then enters the ash calcium classifier 8 for powder grinding and classification.

A desulfurizer preparation box 10 is also arranged between the white mud raw material box 1 and the desulfurizing tower 6; the desulfurizer preparation box 10 is provided with a white mud raw material inlet communicated with the white mud raw material box 1 through a raw material supply pump, a diluent inlet externally connected with a liquid for diluting the white mud raw material, and a desulfurizer incidence channel for downwards spraying diluted white mud slurry into the desulfurizing tower 6 from the upper part of the desulfurizing tower 6; and a desulfurizer supply pump is arranged on the desulfurizer incidence channel.

The desulfurizing tower 6 is directly purchased in the market. In this example, the white mud material was introduced into the desulfurizing tower 6 as a desulfurizing agent.

According to inspection, paper millsThe main component of the recovered white mud is CaCO₃、NaOH，CaCO₃The content is 80-92%. Wherein, CaCO₃The particle size is less than 45 mu m and accounts for more than 90 percent of the total amount, the desulfurization activity is better, and simultaneously, the desulfurization promoting components Na2O, MgO and the like are contained, so that the desulfurization rate of the flue gas can completely reach more than 90 percent, and the white mud is converted into gypsum in the desulfurization process of the flue gas, so that the white mud has certain economic utilization value. Therefore, the method can simultaneously solve the treatment problem of solid and gas wastes in a paper mill, and achieve the purposes of treating wastes with processes of wastes against one another, reducing cost and improving efficiency.

The process flow for desulfurizing by utilizing the white mud raw material comprises the following steps: the white mud raw material and the diluent are prepared into suspension with the calcium carbonate concentration of 20-25% in a desulfurizer preparation box 10 at normal temperature, then the suspension is used as a desulfurizer to be sprayed into a desulfurizing tower 6 from the middle upper part of the desulfurizing tower 6, and a descending desulfurizer and an ascending flue gas are mixed in a counter-current mode and react for desulfurization.

The diluent can be external water supply or residual alkali water solution separated by the centrifugal dehydrator 3.

On one hand, if the desulfurizing tower 6 is only sprayed with the aqueous solution from top to bottom, the dust fall effect can be achieved, but the desulfurizing effect is general; if the separated residual alkali aqueous solution is used as a desulfurizer to spray from top to bottom in the desulfurizing tower 6, the dust fall effect and the desulfurizing effect are both moderate; and turbid liquid diluted by white mud raw materials is used as a desulfurizer to spray from top to bottom, so that the dust settling effect and the desulfurization effect are good.

On the other hand, the upper part and the top of the desulfurizing tower 6 are provided with a plurality of layers of high-temperature dustproof cloth, so that the gas exhausted to the atmosphere from the top of the desulfurizing tower 6 is blocked by particles in the flue gas, and the dust removal effect is improved.

Example 2:

this example focuses on the recovery process.

As shown in figure 1, the energy-saving and environment-friendly recovery method for comprehensively utilizing lime mud comprises the steps of sequentially dehydrating the causticized lime mud with residual alkali generated in papermaking by a dehydrator, calcining by a calciner, cooling by a cooler and grinding and sorting by a lime machine to obtain a finished product. Introducing sulfur-containing flue gas generated in the calcining process of the calcining furnace into a desulfurizing tower for desulfurization; the calcining furnace is an electric heating type rotary calcining furnace with an obliquely arranged calcining furnace body, and the calcining furnace body is provided with a dehydrated white mud inlet, a high-temperature ash powder outlet and a high-temperature flue gas outlet.

The dehydrated white mud enters a rotary calcining furnace from a dehydrated white mud inlet at the higher tail end of the calcining furnace body at the flow rate of 5-6kg/m3 & min, slowly passes through the calcining furnace body which rotates at 1-5r/min, inclines for 3 +/-0.1 degrees and is provided with tiger teeth on the inner wall, is fully calcined in the calcining furnace body at the calcining temperature of 260-1200 ℃ for 15-30min, and the calcined ash powder is conveyed to a cooler from a high-temperature ash powder outlet at the lower head end of the calcining furnace body for cooling; and the sulfur-containing flue gas generated in the calcining process is introduced into the desulfurizing tower from a high-temperature flue gas outlet positioned at the tail end of the calcining furnace body through a flue.

First, the calcination temperature of 260 ℃ to 1200 ℃ is selected according to the product to be produced. The final products produced in different calcination temperature stages are different.

In the calcining process of the calcining furnace, the main components of the calcined ash powder are controlled by controlling the calcining temperature, and the method specifically comprises the following steps:

Secondly, the dehydrated white mud is 5-6kg/m³The min flow enters the calcining furnace body, the calcining furnace body is inclined at 3 degrees +/-0.1 degree, rotates at 1-5r/min, and the calcining time is 15-30min, and the parameters supplement the calcining effect.

The calcining furnace body rotates at an excessively high speed, needs to be driven by high-power equipment and has no other obvious benefits; the calcining furnace body has too low rotation speed and the white mud has too low flowing speed, so that the particles are not easy to collide to break up lumps; more importantly, the residence time (calcining time) of the lime mud in the calcining chamber can be adjusted by the rotating speed of the calcining furnace body.

The inclined angle of the calcining furnace body is also used for facilitating the free transmission of the white mud in the calcining chamber and ensuring the detention time of the white mud in the calcining chamber.

The calcination time has the greatest influence on the quality of the calcined ash, the calcination time is long, the calcination is sufficient, the main component content in the ash is high, and the consumed energy is more; the calcination time is short, the calcination is not sufficient, the consumed energy is less, but the main component content in the ash powder is slightly low.

The applicant researches the technological parameters during calcination through several groups of experiments, and detects the cooled ash powder after calcination through detection means such as XRD, SEM and the like.

Test one: the method is characterized in that an electric heating type rotary calcining furnace (the model of the rotary calcining furnace is phi 2.5-19m) with the diameter of the calcining furnace body of 2.5m and the length of the calcining furnace body of 19m is adopted for calcining at 260 ℃, the flow rate of only dehydrated white mud entering the calcining furnace body is different, other conditions are the same, and the calcining condition is shown in table 1:

TABLE 1

And (3) sampling and detecting the calcined ash powder under the condition of the three groups of parameters, wherein each group of parameters takes 10 data to obtain the content condition of the main components of the calcined ash powder.

It can be seen from table 1 that, in group a1, when the flow of the dehydrated lime mud entering the rotary calcining furnace is too large, the dehydrated lime mud still containing a small amount of moisture and other impurities will agglomerate and form balls due to the influence of oxygen consumption speed, heat dispersion condition and the like in the calcining environment, and the dehydrated lime mud still containing a small amount of moisture and other impurities will adhere to the inner wall of the calcining furnace body after agglomeration and form balls when the condition is serious, so that the subsequent calcining effect is influenced, and the quality of the calcined product is reduced. If a large amount of lumps are adhered to the inner wall of the calciner body, a worker is required to carry out shoveling operation from a manhole, or a scraper is arranged on the inner wall of the calciner body to carry out regular scraping treatment. Of course, the scrapers can also be used for pushing the input and the output of the material (the dehydrated lime mud) in the calcining chamber so as to control the residence time of the material (the dehydrated lime mud) in the calcining chamber. On the other hand, in the group A3, when the flow rate of the dewatered lime mud entering the rotary kiln for calcination is low, the oxygen in the calcination chamber is sufficient and the heat is rapidly dispersed, the dewatered lime mud does not generally agglomerate, the impurity reaction is more sufficient and the lime powder is separated in a gas form, and the content of calcium carbonate in the calcined lime powder is higher than that in the calcined lime powder in the group a 2. However, the calcium carbonate content in the calcined ashes of group A3 was only slightly higher than that of group A2, and the yield was far from the same. In the group A2, the white mud can generate a small amount of agglomeration during the calcination process, but because the technical scheme provided by the invention is also provided with tiger teeth for crushing and agglomerating the white mud on the inner wall of the calcination furnace body, and the white mud is driven to mutually impact and impact the white mud and the tiger teeth by matching with the rotation of the calcination furnace body, on one hand, the agglomerated white mud is rarely adhered to the inner wall of the calcination furnace body to form rings, and on the other hand, the white mud agglomerates are easily broken up.

In conclusion, an electric heating type rotary calcining furnace (the model of the rotary calcining furnace is phi 2.5-19m) with the diameter of the calcining furnace body of 2.5m and the length of the calcining furnace body of 19m is adopted to calcine at 260 ℃, the inclination angle of the calcining furnace body is 3 degrees, the rotating speed of the calcining furnace body is 3r/min, the calcining time is 15min, and the dehydrated white mud enters the rotary calcining furnace according to the parameters of 500kg/min (approximately equal to 5.36 kg/m)³Min), the agglomeration condition in the calcining process is controllable, and the quality of the calcined ash powder meets the basic requirements.

Further, according to the production process parameters of group A2, the daily output of a rotary calcining furnace is 240 tons.

(II) test II: an electric heating type rotary calcining furnace (the model of the rotary calcining furnace is phi 2.5-19m) with the diameter of the calcining furnace body of 2.5m and the length of the calcining furnace body of 19m is adopted for calcining at 260 ℃, only the calcining time of the dehydrated white mud is different, other conditions are the same, and the calcining condition is shown in a table 2 and a figure 6:

TABLE 2

And (3) sampling and detecting the calcined ash powder under the condition of the eight groups of parameters, and taking 10 data of each group of parameters and calculating the average number of the data to obtain the content condition of the main components of the calcined ash powder.

From the data in table 2 of the second test and fig. 6 (the relationship between the calcination time in the second test and the calcium carbonate content in the calcined ash), it is seen that the increase of the calcination time is beneficial to increase the calcium carbonate content in the ash, but in the scheme of preparing the by-product mainly comprising calcium carbonate at 260 ℃, the calcination time is controlled to be more than 12min, so that more than 80% of the calcium carbonate in the ash can be ensured, but the increase of the calcium carbonate content is gradual along with the continuous increase of the calcination time. Therefore, the factors such as the quality of the ash powder, the energy consumption and the like are comprehensively considered, and the calcination time in the process is controlled to be about 15min (14-16min), so that more than 80% of calcium carbonate in the ash powder can be effectively ensured.

In combination with the above, when the product with calcium carbonate as the main component is extracted from the white mud in the papermaking process, the calcination process adopts the calcination temperature of 260 ℃, the inclination angle of the calcination furnace body of 3 degrees, the rotation speed of the calcination furnace body of 3r/min, the calcination time of 15min and the entering flow of the dehydrated white mud of 5-6kg/m³Min, the mass fraction of calcium carbonate in the ash powder obtained by calcination is guaranteed to be more than 80%, calcium oxide with high activity generated in the causticization process is reserved, the energy consumption can be effectively controlled, and the comprehensive economic benefit is highest.

(III) test III: the method adopts an electric heating type rotary calcining furnace (the model of the rotary calcining furnace is phi 2.5-19m) with the diameter of the calcining furnace body of 2.5m and the length of the calcining furnace body of 19m, and calcines at 800 ℃, 900 ℃, 1000 ℃, 1100 ℃ and 1200 ℃ respectively, and the calcining conditions are the same under the same other conditions, and are shown in the table 3:

TABLE 3

And (3) sampling and detecting the calcined ash powder under the condition of the 5 groups of parameters, and averaging 10 data of each group of parameters to obtain the content condition of the main components of the calcined ash powder. The calcium oxide activity is reduced due to the fact that the temperature is too high and the calcination time is too long.

Therefore, when a finished product with the calcium oxide content of more than 98% needs to be prepared, the calcining process comprises the following steps: the calcining temperature is 1100 ℃, the calcining furnace body inclination angle is 3 degrees, the calcining furnace body rotating speed is 3r/min, the calcining time is 15min, and the dehydrated white mud inlet flow is 5-6kg/m³·min。

The calcining process comprises the following steps: the calcining temperature is 800 ℃, the calcining furnace body inclination angle is 3 degrees, the calcining furnace body rotating speed is 3r/min, the calcining time is 15min, and the dehydrated white mud inlet flow is 5-6kg/m³Min, the finished product of sierozem powder with the calcium oxide content of more than 50 percent can be prepared.

The calcining process comprises the following steps: the calcining temperature is 1000 ℃, the calcining furnace body inclination angle is 3 degrees, the calcining furnace body rotating speed is 3r/min, the calcining time is 15min, and the dehydrated white mud inlet flow is 5-6kg/m³And min, preparing the finished product of the sierozem powder with the calcium oxide content of more than 75 percent.

Other parts of this embodiment are the same as embodiment 1, and thus are not described again.

Example 3:

in this embodiment, the present invention is further optimized on the basis of embodiment 1 or 2, the tiger teeth are protrusions that are arranged on the inner wall of the calciner body and protrude smoothly toward the center of the calciner body, and the distribution rule and the size of a single tiger tooth of a plurality of tiger teeth distributed on the inner wall of the calciner body satisfy the following conditions: from the tail end to the head end of the calcining furnace body, a plurality of tiger teeth are distributed from sparse to dense, and the size of each tiger tooth is gradually reduced.

In this example, the design of the tiger teeth is in accordance with the calcination process of the dehydrated lime mud in the calcination chamber. Although the white mud raw material with residual alkali is dehydrated and preheated, the white mud still contains less than 10% of moisture when entering the calcining chamber for calcining, the dehydrated white mud still has the conditions of agglomeration and caking, the agglomeration and caking at the feeding end are large, the moisture is slowly evaporated, partial substances are decomposed, the lumps are separated, or the lumps and the wall surface of the calcining furnace body are impacted with each other along with the increase of the calcining time, and the volumes of the agglomeration and the caking are reduced. Therefore, in the embodiment, the tiger tooth structure is reasonably designed according to the change of materials in the calcining process of the dehydrated lime mud, physical impact is fully utilized, lumps are scattered, and the calcining efficiency is improved.

The rest of this embodiment is the same as embodiment 1 or 2, and therefore, the description thereof is omitted.

Example 4:

the embodiment is further optimized on the basis of any one of the embodiments 1 to 3, the dewatering machine adopted in the dewatering process of the dewatering machine is a centrifugal dewatering machine with a built-in centrifugal cylinder, a frequency converter and a centrifugal motor, the centrifugal cylinder is driven by the centrifugal motor controlled by the frequency converter capable of rotating forward and backward, and the centrifugal cylinder rotates clockwise to be forward rotation and rotates anticlockwise to be backward rotation.

In the dehydration process of the dehydrator, the rotating speed of the centrifugal cylinder is periodically changed. As shown in fig. 3, one cycle of dehydration refers to: the centrifugal cylinder starts to rotate forwards from 0 r/min (point O is the starting point of a period), the centrifugal cylinder is firstly linearly accelerated to 650 r/min (point A) within 5-15 seconds and continuously rotates forwards for 1 min (point B), then naturally decelerated to 0 r/min (point C), the centrifugal cylinder starts to rotate backwards after stopping rotating for 0-10 seconds (point D), is linearly accelerated to 650 r/min (point E) within 5-15 seconds and continuously rotates backwards for 1 min (point F), then naturally decelerated to 0 r/min (point G), the centrifugal cylinder stops rotating for 10-30 seconds (point H), and a dewatering period is finished. The same batch of lime mud with residual alkali is circulated for 4-6 times according to the period.

In the embodiment, the dehydration efficiency is improved by adopting a mode of periodically positive and negative rotation of the centrifugal cylinder for dehydration, and the dehydration rate is at least seven times according to the dehydration mode. On the other hand, the fastest rotation speed is designed to be 600-. The rotating speed is increased, the dewatering effect is better under the same condition, but the energy consumption is also obviously increased. Through a large number of experiments, in the invention, the effect of carrying out centrifugal dehydration on the white mud with residual alkali at the highest rotating speed of 600-.

Further, when the dehydrator dehydrates, raw water is intermittently introduced into the first dehydration period and the second dehydration period, namely: and when the forward rotation speed or the reverse rotation speed of the centrifugal cylinder is lower than 100 revolutions per minute in the first period and the second period of the dehydration work, introducing high-temperature raw water which is led out from a cooling machine and is used for carrying out water cooling on the high-temperature calcined ash powder to generate heat exchange, and flushing and dealkalizing the residual alkali white mud by using the high-temperature raw water.

In this embodiment, the dehydration is performed by repeating 4 to 6 cycles, and in the first cycle and the second cycle, raw water is introduced to wash the white sludge to be subjected to residual alkali, so as to further remove soluble substances, especially alkaline substances (NaOH, etc.), thereby preparing for subsequent processes. In addition, in this embodiment, the high-temperature water after heat exchange in the cooling process is directly introduced into the centrifuge cylinder for washing, on one hand, the solubility is higher when the temperature is higher; on the other hand, an external water source is not needed, cooling water is recycled, and energy conservation and emission reduction are realized. The raw water cooled by the high-temperature raw water can also be directly used for washing the white mud with residual alkali in the dehydration process, but the effect is slightly worse than that of the high-temperature raw water, but the raw water can be accepted.

In the dehydration process, high-temperature raw water or raw water is washed to obtain white mud with residual alkali, and the white mud is separated by a centrifugal cylinder to form residual alkali liquor. The residual alkali liquor can be directly recycled to the papermaking process. The residual alkali liquor can also be used as a diluent for preparing the desulfurizer.

Tests prove that the desulfurizer with the white mud concentration of 22-24% has the best desulfurization effect.

Other parts of this embodiment are the same as any of embodiments 1 to 3, and thus are not described again.

Example 5:

the energy-saving and environment-friendly recovery method for comprehensively recycling the white mud further optimizes any one of embodiments 1 to 4 and comprises a white mud raw material box 1, a first spiral elevator 2, a centrifugal dehydrator 3, a calcining spiral elevator 4, a rotary calciner 5, a rotary cooler 7, an ash calcium classifier 8 and a finished product packaging machine 9 which are sequentially connected, wherein the rotary calciner 5 is also connected with a flue and is connected with a desulfurizing tower 6 through the flue.

The inner wall of the calcining furnace body is provided with a plurality of tiger teeth 53; the tiger teeth 53 are flanges higher than the inner wall of the calcining furnace body. The end of the flange close to the inner wall of the calcining furnace body is the lower end, the cross section of the flange is of a structure with a small upper part and a big lower part, and the lower end of the flange is in smooth transition with the inner wall of the calcining furnace body.

And a heat pipe 11 for recovering and utilizing waste heat and conducting heat in one direction is communicated between the rotary cooler 7 and the calcining spiral elevator 4. One end of the heat pipe 11 is communicated with a cooling cavity of the rotary cooler 7, and the other end of the heat pipe 11 is communicated with the front half of the calcining spiral elevator 4. The heat pipe 11 transfers the waste heat of the heat exchange between the cooling water and the high-temperature ash calcium powder to the inner cavity of the calcining spiral elevator 4 and dries and preheats the entering dehydrated white mud.

The rotary cooling machine 7 comprises a cooling machine body provided with a waste heat backflow port, a rotary cylinder which is sleeved in the cooling machine body and forms a cooling cavity with the cooling machine body, and a cold water spraying device arranged in the cooling cavity;

The recovery system also comprises an electric control chamber, the work of the whole recovery system is uniformly and automatically controlled by a central controller in the electric control chamber, and the central controller in the electric control chamber is respectively connected with control elements in a first spiral elevator 2, a centrifugal dehydrator 3, a calcining spiral elevator 4, a rotary calcining furnace 5, a desulfurizing tower 6, a rotary cooling machine 7, an ash-calcium classifier 8 and a finished product packaging machine 9 for automatic control. The control system in this embodiment is a very mature prior art, and the improvement point of the present invention is not described here, so that it is not described again.

Other parts of this embodiment are the same as any of embodiments 1 to 4, and thus are not described again.

Example 6:

in this example, the centrifugal dehydrator in example 1 was replaced with a strong extrusion dehydrator. The centrifugal dehydrator and the strong extrusion dehydrator are both the existing products sold in the market, the invention only adopts the centrifugal dehydrator or the strong extrusion dehydrator to carry out dehydration treatment on the white mud raw material, and the improvement point of the invention is not in the centrifugal dehydrator or the strong extrusion dehydrator, so the internal structure, the working principle and the like of the invention are not described in detail. Other parts of this embodiment are the same as embodiment 1, and thus are not described again.

Example 7:

according to example 6, the recycling process in this example includes the following steps performed in order:

step S1: storing white mud generated in papermaking production into a white mud raw material box for precipitation, standing and layering;

step S2: taking the lower layer of white mud with residual alkali, and carrying out strong extrusion dehydration to realize solid-liquid separation of the dehydrated white mud and the residual alkali aqueous solution;

step S3: the dehydrated white mud enters a rotary calcining furnace to be calcined and crushed at high temperature, and high-temperature ash calcium powder and sulfur-containing flue gas are output;

step S4: the sulfur-containing flue gas enters a desulfurizing tower through a flue to be desulfurized and then is discharged to the atmosphere, and meanwhile, the high-temperature ash calcium powder enters a rotary cooler to be cooled;

step S5: the cooled ash calcium powder enters an ash calcium classifier for further dry powder grinding and classification;

step S6: and (4) the classified ash calcium powder enters a finished product packaging machine for classified packaging.

In the step S4, the residual alkali white slime in the white slime raw material box in the step S1 and the residual alkali aqueous solution in the step S2 are simultaneously introduced into the desulfurizer configuration box, and mixed to form a suspension with a white slime concentration of 22-24%, and the suspension is used as a desulfurizer to desulfurize the sulfur-containing high-temperature flue gas which ascends and moves at the bottom of the desulfurization tower.

When the working temperature in the high-temperature calcining chamber is adjusted to 255-310 ℃ by the rotary calcining furnace through the electric heating device in the step S3, the calcium carbonate powder in the step S5 is mainly calcium carbonate, and the prepared calcium carbonate powder can be directly used as a light partition board filler or other wallboard materials.

When the calcination temperature is controlled at 260 ℃, the mass percent of the calcium carbonate powder in the ash calcium powder is more than 80 percent.

When the working temperature in the high-temperature calcining chamber is adjusted to 800-1000 ℃ by the rotary calcining furnace in the step S3 through the electric heating device, the calcined sierozem powder in the step S5 is a mixed powder material taking calcium carbonate powder and calcium oxide powder as main materials. The mass percentage of the calcium carbonate powder or the calcium oxide powder can be adjusted by controlling the calcination temperature.

In the step S3, when the working temperature in the high-temperature calcining chamber is adjusted to 1100-1200 ℃ by the rotary calcining furnace through the electric heating device, the calcium powder in the step S5 is mainly lime.

When the calcining temperature is controlled at 1100 ℃, the mass percent of the calcium oxide powder in the ash calcium powder is more than 98 percent.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.

Claims

1. The energy-saving and environment-friendly recovery method for recycling and comprehensively utilizing the lime mud comprises the steps of sequentially carrying out dehydration by a dehydrator, calcination by a calciner, cooling by a cooler and grinding and sorting by a lime machine to obtain a finished product, wherein sulfur-containing flue gas generated in the calcination process of the calciner is introduced into a desulfurizing tower for desulfurization; the calcining furnace is an electrothermal rotary calcining furnace with an obliquely arranged calcining furnace body, and the calcining furnace body is provided with a dehydrated white mud inlet, a high-temperature ash powder outlet and a high-temperature flue gas outlet; the method is characterized in that:

the discharge end of the dehydrator is communicated with the feed end of the calciner only through a calcining screw elevator, waste heat generated in the cooling process of the cooler flows back to the discharge end of the dehydrator through a heat pipe which is transmitted in a single direction to carry out primary preheating on dehydrated white mud discharged by the dehydrator, and meanwhile, high-temperature gas for calcining in the calciner carries out secondary preheating on the dehydrated white mud entering the calciner from the calcining screw elevator, so that a preheating cavity with uniformly raised preheating temperature is formed in the calcining screw elevator from the discharge end of the dehydrator to the feed end of the calciner, and the dehydrated white mud directly enters the calciner for calcining after being preheated in the screw lifting process of the calcining screw elevator;

the dehydrated white mud accounts for 5-6kg/m³The min flow enters a rotary calcining furnace from a dehydrated white mud inlet positioned at the higher tail end of the calcining furnace body, slowly passes through the calcining furnace body which rotates at 1-5r/min, inclines for 3 +/-0.1 degrees and is provided with tiger teeth on the inner wall, fully calcines for 15-30min at the calcining temperature of 255-1210 ℃ in the calcining furnace body, and the calcined ash powder is conveyed to a cooler from a high-temperature ash powder outlet positioned at the lower head end of the calcining furnace body for cooling; and the sulfur-containing flue gas generated in the calcining process is introduced into the desulfurizing tower from a high-temperature flue gas outlet positioned at the tail end of the calcining furnace body through a flue.

2. The energy-saving and environment-friendly recovery method for comprehensively recycling lime mud according to claim 1, which is characterized in that: in the calcining process of the calcining furnace, the main components of the calcined ash powder are controlled by controlling the calcining temperature, and the method specifically comprises the following steps:

3. The energy-saving and environment-friendly recovery method for comprehensively recycling lime mud according to claim 2, which is characterized in that: in the calcining process of the calcining furnace, the calcining temperature is controlled to 260 ℃, and calcined white mud is retained for more than 15min to prepare ash powder with the calcium carbonate mass ratio not less than 80%.

4. The energy-saving and environment-friendly recovery method for comprehensively recycling lime mud according to claim 2, which is characterized in that: in the calcining process of the calcining furnace, the calcining temperature is controlled to 800 ℃, and calcined white mud is retained for more than 15min to prepare ash powder with the mass ratio of calcium oxide not less than 50%.

5. The energy-saving and environment-friendly recovery method for comprehensively recycling lime mud according to claim 2, which is characterized in that: in the calcining process of the calcining furnace, the calcining temperature is controlled to 1000 ℃, and calcined white mud is made to stay for more than 15min, so that ash powder with the mass ratio of calcium oxide not less than 75% is prepared.

6. The energy-saving and environment-friendly recovery method for comprehensively recycling lime mud according to claim 2, which is characterized in that: in the calcining process of the calcining furnace, the calcining temperature is controlled to 1100 ℃, and calcined white mud is retained for more than 15min to prepare the ash powder with the calcium oxide mass ratio not less than 98%.

7. The energy-saving and environment-friendly recovery method for recovering and comprehensively utilizing white mud according to any one of claims 1 to 6, characterized in that: the tiger teeth are convex parts which are arranged on the inner wall of the calcining furnace body and are smoothly protruded towards the center of the calcining furnace body, and the distribution rule and the size of a single tiger tooth of a plurality of tiger teeth distributed on the inner wall surface of the calcining furnace body meet the following conditions: from the tail end to the head end of the calcining furnace body, a plurality of tiger teeth are distributed from sparse to dense, and the size of each tiger tooth is gradually reduced.

8. The energy-saving and environment-friendly recovery method for recovering and comprehensively utilizing white mud according to any one of claims 1 to 6, characterized in that: the centrifugal dehydrator is also provided with a dehydration controller, the dehydration controller controls the forward and reverse rotation change and the rotation speed regulation of the centrifugal motor through the frequency converter, the dehydration controller controls the connection/disconnection of the clutch, and the centrifugal motor drives the centrifugal cylinder to act through the clutch; wherein, the clockwise rotation of the centrifugal cylinder is positive rotation, and the anticlockwise rotation of the centrifugal cylinder is negative rotation;

in the dehydration process of the dehydrator, the rotating speed of the centrifugal cylinder is periodically changed, and specifically means that: in a period, the centrifugal cylinder starts to rotate forwards from the rotation speed of 0 r/min, firstly linearly increases the speed to 600-; the same batch of lime mud with residual alkali is circularly reciprocated for 4-6 times according to the period, namely the same batch is dewatered through 4-6 dewatering periods.

9. The energy-saving and environment-friendly recovery method for recovering and comprehensively utilizing white mud according to claim 8, is characterized in that: when the dehydrator dehydrates, raw water is intermittently introduced into the first dehydration period and the second dehydration period, and the method specifically comprises the following steps: and when the forward rotation speed or the reverse rotation speed of the centrifugal cylinder is lower than 100 revolutions per minute in the first period and the second period of the dehydration work, introducing high-temperature raw water which is led out from a cooling machine and is used for carrying out water cooling on the high-temperature calcined ash powder to generate heat exchange, and flushing and dealkalizing the residual alkali white mud by using the high-temperature raw water.

10. The energy-saving and environment-friendly recovery method for recovering and comprehensively utilizing white mud according to any one of claims 1 to 6, characterized in that: residual alkali liquor separated from the white mud with residual alkali in the dehydration process of the dehydrator is directly recovered for recycling in a papermaking process; or residual alkali liquor separated from the white mud with residual alkali in the dehydration process of the dehydrator is firstly introduced into the temporary storage barrel for storage, the residual alkali liquor and the raw material of the white mud with residual alkali are mixed to form a desulfurizer with the white mud concentration of 22-24%, and the desulfurizer is sprayed into the desulfurizing tower from the upper part of the desulfurizing tower through a desulfurizer supply pump to perform desulfurization treatment on sulfur-containing flue gas.