CN1558143A - Method for treating papermaking, tanning, printing and dyeing industrial waste liquid by circulating fluidized combustion method - Google Patents

Abstract

The present invention belongs to the field of environment protecting technology, and is especially the comprehensive utilization of papermaking black liquor and black mud and tanning, printing and dyeing effluent. Waste liquid, waste water, black mud and coal powder are mixed and produced into waste liquid-coal mixture as boiler fuel, which is burnt in circulating fluidizing bed boiler. Middle section effluent is first adsorbed with coal powder and lime to absorb its short fiber, lignin and other inflammable matter, and the adsorbed coal mud is used in making the waste liquid-coal mixture. The waste treating process produces steam and hot water for use in production.

Description

Method for treating papermaking, tanning, printing and dyeing industrial waste liquid by circulating fluidized combustion method

technical field

It belongs to the environmental protection technology field of industrial production sludge, waste liquid, cooking liquid (black liquor, red liquor), tail liquid and wastewater treatment and comprehensive utilization, especially related to papermaking black liquor, sludge and tanning, printing and dyeing industry tail liquid, Sewage treatment and comprehensive utilization.

Background technique

At present, there are certain deficiencies in the treatment methods of cooking liquor (black liquor, red liquor), waste water, tail liquor, and sludge produced in the production process of papermaking, tanning, and printing and dyeing industries, especially the treatment of black liquor in paper mills has become an important issue. Worldwide problems, even some paper mills had to stop production due to the inability to control the pollution.

At present, my country's papermaking pollution control technologies are mainly divided into four categories:

(1) Alkali recovery technology, which has large investment, high operating costs, and limited production scale, cannot be adopted by paper mills with a scale of less than 20,000 tons/year, and about 55% of the completed alkali recovery production lines have not been put into use.

(2) Physicochemical plus biochemical technology, using various chemical agents for sedimentation, flocculation, air flotation and other physical and chemical methods plus activated sludge aeration or anaerobic fermentation for biochemical treatment. This type of technology requires a lot of investment and occupies an area Large, high operating costs, poor pollution control effect.

(3) Evaporation and concentration technology. This method evaporates, concentrates, and dries black liquor into products. However, due to the undeveloped market for the converted products, the technology cannot be used. The boiler burns out. Due to the complicated process and high processing cost, the technology cannot be promoted.

(4) At present, domestic enterprises that use recycled waste paper to make paper produce a large amount of black mud in the production process. At present, most paper-making enterprises cannot process and utilize the black mud, and can only dig pits and bury it. From a formal point of view, these black mud The mud has been processed, but this landfill method has actually caused long-term serious pollution to the surrounding environment, soil and groundwater.

To sum up, the current typical black liquor and wastewater pollution treatment process has the following problems:

1. Large investment and high processing costs, which small and medium paper mills cannot afford. my country's paper industry developed under the conditions of severe shortage of funds and difficult supply of wood raw materials. It mainly develops small grass pulp and paper mills. These enterprises are small in scale, low in product grade, poor in equipment level and personnel quality, and low in profit Low pollution production coefficient, pollution control is restricted by treatment cost.

2. The technical reliability of the completed environmental protection treatment facilities is poor, and normal operation cannot be guaranteed, and it is even more difficult to ensure compliance with emission standards, resulting in a waste of invested funds for enterprises.

3. The biochemical treatment process cannot operate normally, and it is generally maintained by adding flocculants.

4. Pollution control lacks comprehensive utilization value for enterprises and cannot bring direct benefits to enterprises. Enterprises are passively governed and lack initiative.

Contents of the invention

Aiming at the ubiquitous problems of existing environmental protection technologies for waste liquid and wastewater pollution treatment in papermaking, tanning, and printing and dyeing industries, the present invention provides an environmental protection technology for pollution control that is widely used and can generate direct economic benefits for enterprises.

The present invention is made up of following two major parts:

1. Preparation of waste liquid coal slurry

According to the different raw materials used, it can be divided into the following three schemes:

(1) Make waste liquid coal slurry by filtering, absorbing, and settling effective energy substances in the middle section of wastewater. The process flow is shown in Figure 1, mainly consisting of the following equipment:

1 Circulating fluidized bed coal slurry boiler; 2 Dust collector; 3 Filter tank; 4 Treatment pool; 5 Wastewater settling tank bottom flow storage tank; 6 Settling tank; 7 Slurry tank; Powder bin; 11 blower; 12 boiler slurry pump; 13 induced draft fan; 14-1 screw pump for conveying coal slurry in the lower part of the sedimentation tank; 14-2 screw pump; 14-3 shear pump; 15 waste liquid coal slurry storage tank ;16 rainproof environmental protection chimney cap; 17 black liquor storage tank;

Coal powder, coal-based activated carbon and quicklime are added to the filter tank 3, and a multi-stage filter tank 3 can be built as required. The coal powder, coal-based activated carbon and quicklime added in the filter tank 3, as filter materials, have strong adsorption and flocculation properties. Most of the fine fibers, lignin and other substances contained in the filter are filtered out and adsorbed in the filter materials such as coal powder in the filter tank 3. The remaining part and some fine coal powder exist in the filtered water in the form of colloid and flow into the sedimentation tank 6. , through flocculation to produce a sedimentation effect, so that the fine short fibers, lignin and other combustible substances in the middle waste water settle together with the coal powder, the water in the upper part of the sedimentation tank flows into the treatment water tank, and the coal slurry in the lower part of the sedimentation tank passes through the lower part of the sedimentation tank The screw pump 14-1 transports it to the bottom flow storage tank 5 of the waste water settling tank.

The coal powder and other filter materials in the filter tank are supersaturated into coal slime after a period of use, and the saturated coal slime in the filter tank 3 is transported to the bottom flow storage tank 5 of the wastewater sedimentation tank by the screw pump 14-1, and the bottom flow of the wastewater sedimentation tank The storage tank 5 is used as a secondary sedimentation tank, the water in the upper part of the bottom flow storage tank 5 of the waste water settling tank is discharged into the treatment pool 4, and the coal slime in the lower part of the bottom flow storage tank 5 of the waste water settling tank is transported to the pulping tank 7 by the screw pump 14-2 middle.

The filter material in the filter tank 3 contains a certain amount of coal-based activated carbon and calcium hydroxide, which can denitrify, dephosphorize, decolorize and deodorize the middle wastewater while filtering.

The coal slime sent into the slurry tank 7 should be assayed before each batch is added to check the moisture therein, etc., and then add a certain amount of coal powder or waste water in proportion, so that the ratio of coal and moisture is about 7:3 , add the dispersant to start the agitator on the top of the pulping tank, stir, then add the stabilizer to continue stirring, then after shearing and aging treatment by the shear delivery pump 14-3, then transport it to the waste liquid coal slurry storage tank 15 storage.

The water in the treatment pool 4 is pumped to the original wastewater treatment equipment of the enterprise for further treatment, and then returned to the production system for use.

Before each batch of waste liquid coal slurry is produced, a small test is required to determine the proportion or quantity of various components. The waste liquid coal slurry in the storage tank 15 is regularly stirred as required.

(2) Make waste liquid coal slurry with waste liquid (cooking liquid)

The process flow chart is shown in accompanying drawing 2, and the equipment of the combustion part of the waste liquid coal slurry is the same as that of accompanying drawing 1, except that the pulping part is composed of the following main parts.

7' slurry tank, 8' black mud storage tank, 9' additive tank, 10' coal particle storage tank, 12' boiler slurry pump, 14'-2 screw pump, 14'-3 shear delivery pump, 15' Waste liquid coal slurry storage tank, 17' black liquid storage tank, 18 waste liquid storage tank, 19 crusher, 20 ball mill.

According to the different coal used, it can be divided into two different production methods:

a. If coal washing particles are used to make waste liquid coal slurry, after the coal washing particles are crushed and weighed by the crusher 19, they are sent to the ball mill 20 through the conveying equipment, and the black liquor in the black liquor storage tank 8' is passed through the screw pump 14-2, Send it into the ball mill 20 in proportion, grind the coal particles to a coal slurry with a particle size of 50-100 μm, then transport it to the slurry tank 7 by the screw pump 14'-2, add a stabilizer for stirring, and then transport through shearing After the pump 14-3 shears and matures, it is transported to the black liquor storage tank 15 for storage.

B, when adopting pulverized coal to make waste liquid coal slurry, technological process is also as shown in accompanying drawing 2, but equipment such as crusher 19 ball mill 20 will be removed, coal pulverized warehouse (not shown in the figure), black liquor storage tank 17 and the additive tank 9 are directly connected to the pulping tank 7, and the coal powder and the black liquor in the black liquor storage tank 8' are sent to the pulping tank 7 through the conveying equipment in proportion to be stirred, and then added to the additive tank 9' The transported stabilizer is then sheared and matured by the shear transport pump 14'-3, and then transported to the waste liquid coal slurry storage tank 15' for storage.

Before each batch of waste liquid coal slurry is produced, coal or coal powder, waste liquid, and black liquor must be assayed, and a small test must be carried out to determine the proportion of coal, coal powder, waste liquid, black liquor and additives. The waste liquid coal slurry in the tank 15' must be stirred regularly as required.

(3) Use sludge and black mud to make waste liquid coal slurry

According to the different coal used, it can be divided into two different production methods:

A, technological process is also as shown in accompanying drawing 2, as adopting coal washing grain to make black mud (sludge) coal slurry, after coal washing grain is crushed and weighed through crusher 19, deliver to ball mill 20 by conveying equipment, black mud ( Sludge) is added to the ball mill 20 through the screw pump 14'-2, waste water and dispersant in proportion, and the coal particles are ground into a coal slurry with a particle size of 50-100 μm, and then sent to the slurry tank by the screw pump 14'-2 7', adding a stabilizer for stirring, then shearing and aging by the shear delivery pump 14'-3, and then sending it to the storage tank 15' for storage.

B, when adopting pulverized coal to make black mud (sludge) waste liquid coal slurry, technological process is also as shown in accompanying drawing 2, but equipment such as crusher 19 ball mill 20 will be removed. Connect the pulverized coal bin (not shown in the figure) black mud storage tank 8' and the additive tank 9' directly to the pulping tank 7', and pass the black mud (sludge) in the pulverized coal and black mud storage tank 8' through The dispersant delivered by the screw pump 14'-2, waste water and additive tank 9' is added to the pulping tank 7' according to the required proportion, stirred, and then stabilizer is added to continue stirring, and then the shear pump 14'- 3 After shearing and aging, transport to storage tank 15' for storage.

Before making each batch of black mud (sludge) coal slurry, coal or coal powder, black mud (sludge) must be tested, and a small test must be carried out to determine the coal or coal powder, black mud (sludge), waste water, additives proportion. The waste liquid coal slurry made of black mud in the storage tank 15' must be stirred regularly as required.

2. Waste liquid coal slurry combustion

In order to apply waste liquid coal slurry produced by waste water, waste liquid (black liquid), black mud, etc. as combustion, the present invention modifies the circulating fluidized bed boiler 1 .

At present, circulating fluidized bed boilers at home and abroad all use dry coal powder as fuel, and a screw conveyor is used in the lower part of the boiler to send coal into the furnace. The circulating fluidized bed boiler 1 burning waste liquid coal slurry is based on the original boiler design, and a waste liquid coal slurry supply port is installed on the top or middle of the boiler. If the circulating fluidized bed boiler 1 only uses waste liquid coal slurry as fuel, then The spiral coal feeding equipment is cancelled. If the boiler uses coal and waste liquid coal slurry as two fuels, the spiral coal feeding machine is retained.

Circulating fluidized bed boiler 1 that burns waste liquid coal slurry is ignited in a hot air flow state. After the diesel oil is atomized by the ignition gun, it is burned in the pre-combustion cylinder, and the high-temperature flue gas generated is sent to the isobaric air chamber to heat the air duct Air, the heated high-temperature air enters the fluidized bed material layer through the air distribution plate. When the bed material is heated to more than 450°C, a small amount of waste liquid coal slurry is added to the circulating fluidized bed boiler 1, and the furnace temperature rises at this time Sooner, when the temperature inside the circulating fluidized bed boiler 1 reaches 600°C, the slurry supply volume can be gradually increased, the furnace temperature rises quickly, and the waste liquid coal slurry has been combusted normally. At this time, the oil supply is stopped and the pre-combustion chamber is cut off. Complete the ignition, increase the supply of waste liquid coal slurry, and adjust the blower 11 and the induced draft fan 13 to the air volume required for normal load operation.

Circulating fluidized bed boiler 1 adopts high-level negative pressure slurry supply, medium and large boilers (35 tons of power above 29MW) are equipped with two to three slurry supply ports in the middle of the front wall, and waste liquid coal slurry is input into the furnace, medium and small boilers Furnace top slurry supply is adopted. This slurry supply method makes full use of the height of the boiler, speeds up the precipitation of water and volatile components in the waste liquid coal slurry, and is beneficial to combustion and ignition.

The waste liquid coal slurry is directly sent to the circulating fluidized bed boiler 1 by the storage tank 15' through the screw slurry pump 12 at a pressure of about 0.3Mpa. There are no filters, nozzles and atomization devices in the middle. After the slurry mouth enters the circulating fluidized bed boiler 1, it becomes drop-shaped, and the drop-shaped waste liquid coal slurry in the furnace becomes finer particles due to the disturbance of the fluidized hot air flow in the furnace. During the falling process, the slurry droplets are heated, decomposed and start to burn, and then enter the fluidized bed composed of quartz sand and limestone. During the continuous heating process of the hot fluidized bed material, the slurry drops rapidly The precipitation of water and volatile matter is completed, and the combustion and coke combustion are carried out, and the fine particles of the granular waste liquid coal slurry group in the fluidized state are further disintegrated, and the fine particles are taken out of the dense phase area by the hot flue gas and enter the suspension chamber to continue burning , a fly ash separation and return device is installed at the outlet or rear of the combustion chamber. The media materials and larger unburned particles carried out by the hot flue gas are separated and captured by the separator, and the return device installed at the lower part of the separator, Send it back to the dense-phase area of the combustion chamber for cyclic combustion, with a combustion efficiency of 98%.

The waste liquid coal slurry is burned at a low temperature of 850-950°C in the furnace, which effectively suppresses the generation of thermal NOx during the combustion process of the fuel. Since quartz sand and limestone are used as media materials in the furnace, the limestone decomposes at high temperature to generate CaO and waste The SO ₂ generated by the combustion of sulfur in the coal powder in the coal liquid slurry reacts to generate CaSO ₄ . The response is:

The emission of _SO2 in the flue gas is suppressed, and the direct desulfurization in the circulating fluidized bed boiler 1 is realized. The particle size of the limestone (desulfurizer) added to the circulating fluidized bed boiler 1 is selected to be about 1-2mm, and the calcium/sulfur molar ratio is 1.5-2.5 when the desulfurization efficiency reaches 85%-95%. Combustible substances such as lignin and hemicellulose contained in the waste liquid are converted into heat energy after being burned in the furnace, and other substances such as alkalis generate sodium salts, sodium calcium and other substances during the combustion process, which are mixed in the fly ash and discharged.

The flue gas of circulating fluidized bed boiler 1 contains burnt fly ash, which is collected by electrostatic precipitator or bag filter 2, and the dust removal rate can reach 99.9%, so that the concentration of soot in the flue gas is less than 80mg/m ³ . The emission concentration of SO ₂ in flue gas is less than 100mg/m ³ , the emission concentration of NO _x is less than 150mg/m ³ , and the Ringelmann blackness of flue gas is less than 1, meeting the national standard for atmospheric environmental protection.

Circulating fluidized bed boiler 1 can be a hot water boiler, low-pressure steam boiler or medium-temperature medium-pressure steam boiler. The steam produced can be used for steam production by enterprises, and can also be used for heating or power generation, forming an integration of waste water treatment, steam consumption and power generation , save a lot of energy costs and waste water treatment costs for enterprises, and increase income. Every ton of black liquor burned in the paper industry (the calorific value in papermaking black liquor is 8.37-10.04MJ/kg) is equivalent to saving 0.28-0.34 for the enterprise tons of standard coal.

After the waste liquid coal slurry is burned, the fly ash collected by the dust collector 2 can be used. After the waste liquid coal slurry is suspended and cleanly burned by the circulating fluidized bed boiler 1, the fly ash produced is collected by the dust collector 2 and transported by the sealed The device is transported to the sealed ash bin 5, and after reaching a certain amount, it is transported away by a pulverized coal ash truck, completely avoiding the pollution of the fly ash to the environment, and the fly ash has a high comprehensive utilization value. There are two main types of uses:

a. Fly ash has gelling properties and contains CaSO ₄ . It is a substitute for slag and gypsum required for the manufacture of cement. It supplements the lack of slag resources and is a raw material for making cement. It can be made into 325% with 50% of cement clinker. #Cement, fly ash with high CaSO ₄ content can be used to make special cement and expansion agent.

b. Since the waste liquid coal slurry contains a large amount of alkali, lignin, polysaccharide, calcium salt and other substances, when burning in the furnace at 850-950°C, the above substances will be converted into sodium salt, calcium salt, nitrogen, calcium phosphate, etc. Highly active substances are discharged together with fly ash. Fly ash containing high active substances such as sodium salt, calcium salt, nitrogen, and calcium phosphate is not only a good base material for making organic fertilizers, but also can be used as an acidic soil improver.

Description of drawings

Accompanying drawing 1: Process flow chart of preparing waste liquid coal slurry and burning waste liquid coal slurry by treating middle-stage wastewater of papermaking, tanning, and printing and dyeing industries by circulating fluidized combustion method.

Accompanying drawing 2: Process flow chart of preparing waste liquid coal slurry and burning waste liquid coal slurry by treating papermaking, leather, printing and dyeing industrial waste liquid (cooking liquid), sludge and black mud by circulating fluidized combustion method.

Detailed ways

Taking a paper mill with an annual output of 15,000 tons of straw pulp as an example, 100 tons of black liquor is discharged every day, and the black liquor produced in the production process is treated and comprehensively utilized by the circulating fluidized suspension clean combustion method.

Install a 75t/h circulating fluidized bed waste liquid coal slurry steam boiler, choose Datong coal powder with calorific value 29.3MJ/kg, ash content ≤ 6%, particle size 50-100μm, according to coal powder: black liquor = 6 : The ratio of 4 is input to the pulping tank 7 after passing through the metering device. An agitator is installed on the pulping tank 7, which is a double-screw rod-type structure. Then add a dispersant, after stirring, add an appropriate amount of stabilizer, stir again, and then shear and mature to make a waste liquid coal slurry with a solid content of 65-70% and a water content of 35-30%. The waste liquid coal slurry is sent to the circulating fluidized bed steam boiler with a screw pump, and the boiler burns 10.5 tons of waste liquid coal slurry per hour, producing 75 tons per hour (pressure 1.6Mpa ~ 3.82Mpa, temperature 240 ~ 450 ℃) steam supply Used in paper mills. The flue gas after combustion is dusted by the electrostatic precipitator and then discharged.

The circulating fluidized combustion method is used to treat the black liquor project of the paper mill. The investment cost is about 10.2 million yuan, and the annual processing of black liquor is more than 30,000 tons. It can save 30,000 tons of fuel coal for the enterprise every year, which is equivalent to 8.4 million yuan in fuel costs. Yuan. The ex-factory price of pulverized coal is about 240-280 yuan/ton. According to data calculation, when the calorific value of pulverized coal is 33.47MJ/kg and the price is 260 yuan/ton, the cost of coal-water slurry made is 260 yuan/ton, and its calorific value is 23.9MJ/kg. According to the price of coal powder with calorific value of 33.47MJ/kg at 260 yuan/ton, plus the calorific value of wastewater coal slurry generated from papermaking black liquor is 24.38MJ/kg, the cost is only 228 yuan/ton. If the above-mentioned coal powder with the same price is used and the papermaking black mud is used to produce wastewater coal slurry with the same calorific value, the cost is only 186 yuan/ton. The cost of the waste liquid coal slurry produced by the invention is at least 15-28% lower than that of the coal water slurry. The investment in the black liquor treatment project is 10.2 million yuan, and only 8.4 million yuan in fuel costs can be saved every year. All the capital can be recovered in 1.21 years after the project is put into operation.

Claims (4)

1. A method for treating the waste liquid from paper-making, leather-making and printing-dyeing industries features that the waste liquid and sludge are used to prepare the fuel of boiler, i.e. waste liquid coal slurry, which is used to produce steam or hot water by circulating fluidized-bed boiler combustion.

2. The method for treating the waste liquid in the industries of papermaking, tanning and printing and dyeing by the circulating fluidized combustion method according to claim 1, wherein the waste liquid and sludge in the production process are prepared into boiler fuel-waste liquid coal slurry, and the method is divided into 3 preparation schemes according to different used raw materials:

(1) adsorbing, precipitating and filtering the wastewater in the middle production section, and preparing the substances containing effective energy into waste liquid coal slurry; adding coal powder with the particle size of 20-50 mu m into a filter tank, building a plurality of filter tanks according to the requirement of water treatment amount, adding a certain amount of coal activated carbon and quicklime into the coal powder in the filter tanks to serve as adsorption and filtration materials, performing the functions of dephosphorization, denitrification, deodorization and decoloration, and adsorbing combustible substances such as short fibers, lignin and the like in the wastewater in the middle section; sending the filtered coal filter mud absorbing combustible substances in the wastewater into a manufacturing tank, and adding coal dust, wastewater and additives according to the moisture content in the coal mud to prepare waste liquid coal slurry;

(2) the waste liquid coal slurry is prepared from waste liquid, cooking liquid (black liquid and red liquid) and coal, if the waste liquid is papermaking black liquid, a large amount of combustible substances such as lignin, hemicellulose and the like are contained, the calorific value of each kilogram of the black liquid is 8.37-10.04 MJ/kg, the black liquid is prepared into boiler fuel-waste liquid coal slurry, and the waste liquid coal slurry can be prepared by the following two preparation methods according to different coal conditions:

a. if the coal is pulverized coal, adding pulverized coal and waste liquor or cooking liquor (black liquor and red liquor) according to the proportion of 6: 4 and stabilizing agent into a pulping tank to prepare waste liquor coal slurry, if the solid content of the waste liquor or cooking liquor is less than 6%, making the waste liquor coal slurry into the first scheme of the claim, adsorbing, settling and filtering the waste liquor coal slurry into coal powder slurry, and then sending the coal powder slurry into the pulping tank to prepare waste liquor coal slurry;

b. if the coal particles are washed, preparing waste liquid coal slurry from the washed coal particles and waste liquid or cooking liquor, feeding the washed coal particles and the waste liquid or cooking liquor into a ball mill according to a proportion for wet grinding, grinding the washed coal particles into mixed slurry with the particle size of 50-100 mu m, feeding the mixed slurry into a slurry preparation tank, and adding a proper amount of additives to prepare waste liquid coal slurry;

(3) the waste liquid coal slurry is prepared by utilizing the sludge or the black mud, and the waste liquid coal slurry can be prepared by the following two preparation methods according to different coal conditions:

a. if the coal powder is coal powder, adding the coal powder (with the particle size of 50-100 mu m), the papermaking black mud and the wastewater into a pulping tank according to the proportion of 6: 2, and adding an additive to prepare waste liquid coal slurry;

b. if the coal washing particles are coal washing particles, the coal washing particles, papermaking black mud, wastewater and a dispersing agent are added into a ball mill according to the proportion of 6: 2 for wet grinding, the coal washing particles are ground into mixed slurry with the particle size of 50-100 mu m, and then the mixed slurry is sent into a slurry making tank to be added with a stabilizing agent to prepare waste liquid coal slurry.

3. A method of treating waste liquid from the paper, leather and printing industries according to claim 2, wherein the calorific value of coal is 29.3MJ/kg, the ash content is less than 6%, and the raw material is tested and subjected to a pilot plant before each batch of pulp is made.

4. The method for treating the waste liquid in the paper-making, leather-making and printing and dyeing industry by the circulating fluidized combustion method according to claim 1, wherein the waste liquid coal slurry is cleanly combusted in the circulating fluidized bed boiler, the waste liquid coal slurry is fed into the circulating fluidized bed boiler from the middle part or the top part of the circulating fluidized bed boiler for combustion by a screw pump under the pressure of about 0.3Mpa, the temperature of a boiler hearth is controlled to be 850-950 ℃, and coking and NO are prevented_xAdding limestone and quartz sand as medium material into boiler furnace to make SO produced in combustion₂Formation of CaSO₄Inhibit SO in flue gas₂And in the combustion process of the hearth, unburnt coal dust particles are separated and captured by a boiler separator and then are sent back to the hearth through a returning device to be continuously combusted, so that efficient circulating combustion is realized.

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