CN114380626A

CN114380626A - Preparation method for extracting medium-trace element fertilizer by using asbestos tailings

Info

Publication number: CN114380626A
Application number: CN202110648773.0A
Authority: CN
Inventors: 慕湧; 李秉勃; 田富才; 王力
Original assignee: Ruojiang Shengdi Asbestos Tailing Reutilization Technology Development Co ltd
Current assignee: Mu Yong
Priority date: 2021-06-10
Filing date: 2021-06-10
Publication date: 2022-04-22

Abstract

A preparation method for extracting medium and trace element fertilizer by using asbestos tailings comprises the following steps: the first step, a pretreatment procedure; step two, a magnetic separation process; step three, raw material proportioning; fourthly, preparing coal powder; fifthly, putting the raw materials into a kiln; sixthly, calcining; step seven, a semi-finished product grinding process; and eighth, a finished product preparation procedure. The invention provides a preparation method for extracting medium and trace element fertilizer by using asbestos tailings, which is used for extracting silicon, calcium and magnesium fertilizers in the tailings by a harmless method to prepare the medium and trace element fertilizer, effectively improving the economic effect in the tailing disposal process and solving the problem of difficult tailing disposal.

Description

Preparation method for extracting medium-trace element fertilizer by using asbestos tailings

Technical Field

The invention relates to a preparation method of a plant fertilizer, in particular to a preparation method of a trace element fertilizer extracted from asbestos tailings.

Background

At present, 15.3 thousands of mines exist in China, 80% of mineral resources are common and associated minerals, and most of the mineral resources are not comprehensively utilized. Due to the laggard economic condition, production technical level and management condition, laggard mine production process and old equipment in China, a large amount of valuable mineral resources in China are not fully explored, evaluated and reasonably developed and utilized, and the resources are damaged and wasted seriously. The comprehensive utilization rate of the co-associated mineral resources in China is less than 20%, the total recovery rate of the mineral resources is only 30%, the difference is large compared with the advanced countries in foreign countries, and the resource waste is quite remarkable.

Most of these undeveloped and unutilized valuable resources are discarded into the tailings of beneficiation and wet leaching. Most of the tailings contain various colored, black, rare and precious, rare earth, nonmetallic minerals and other valuable components, and are valuable secondary mineral resources.

Among them, the asbestos ore of the Aljinshan series is the largest asbestos deposit in China at present. The ore body is large in scale and high in grade (2-5%), and the reserves account for 64.3% of the whole country. Asbestos is exploited on the ore vein by local governments of Xinjiang Ruoqiang county, Xinjiang production and construction Bingqu and local governments of Qinghai province, and is the largest asbestos production base in China.

The fertilizer is one of the material bases for agricultural production and is used for providing one or more nutrient elements necessary for plants. According to the current fertilizer classification method in China, the fertilizer can be divided into macroelement fertilizers (such as nitrogen, phosphorus and potassium fertilizers), mineral medium and trace element fertilizers (such as silicon, calcium and magnesium fertilizers) and trace element fertilizers (such as iron, zinc, copper and chlorine fertilizers) according to different requirements of crops.

The absence of any element can affect the normal growth and development of crops.

Taking silicon fertilizer as an example, the silicon fertilizer belongs to mineral medium and trace element powder. In 1787, Lawa tin was first found to be present in rocks. The Chinese Chua Delong is introduced into China systematically, and the industrial production and the wide application in agriculture are realized. In 1996, the academy of sciences in Henan province was provided with the research center for silicon fertilizer engineering technology in Henan province, and the silicon fertilizer standard in China is established and promulgated by the center. The medium trace element fertilizer mainly comprises a citrate soluble medium trace element fertilizer and a water soluble medium trace element fertilizer, wherein the citrate soluble medium trace element fertilizer is the medium trace element fertilizer which is insoluble in water and can be absorbed by plants after being dissolved in acid, is usually processed by high-temperature calcination technology and the like of waste steel slag, fly ash and ore of a steel mill, has larger application amount (about 25-50 kg per mu) and is suitable for soil base application; the water-soluble medium-trace element fertilizer is a medium-trace element fertilizer which is dissolved in water and can be directly absorbed by plants, the absorption utilization rate of crops is higher, the fertilizer is synthesized by high-temperature chemistry, the production process is more complex, the cost is higher, but the application amount is smaller, the fertilizer is generally used for foliar spraying, flushing application and drip irrigation, and can also be used for basal application and topdressing, the specific dosage can be according to the silicon preference condition of the crop variety,

The silicon deficiency of the local soil and the specific content of the medium trace element fertilizer.

The citrate soluble medium and trace element fertilizer is absorbed too slowly, and the water soluble medium and trace element fertilizer is absorbed too fast. Silicon is a fourth major mineral element, an ideal soil conditioner, a medium trace element fertilizer is slow-released and long-acting, the absorption of the silicon element by crops is guaranteed to reach the optimal level, and products produced according to the raw materials are comprehensive in nutrients, high in content, strong in activity and high in absorption utilization rate. At present, more products are developed or being developed, and more medium and trace element fertilizer products appear on the market.

Compared with the traditional asbestos tailing treatment, the scheme optimizes the extraction scheme, improves the economic benefit of tailing treatment by using the medium trace element fertilizer prepared from the silicon, calcium and magnesium fertilizer elements in the tailings, solves the problems that the peripheral environment is easily subjected to secondary pollution in the traditional tailing treatment process, the treatment of the secondary pollution needs higher cost and energy, and the recycling principle of tailing treatment waste is not met.

Disclosure of Invention

In order to solve the defects of the prior art, the invention provides a preparation method for extracting medium and trace element fertilizer by using asbestos tailings, which is used for extracting silicon, calcium and magnesium fertilizers in the tailings to prepare the medium and trace element fertilizer by a harmless method, so that the economic effect in the tailing disposal process is effectively improved, and the problem of difficult tailing disposal is solved.

A preparation method for extracting medium and trace element fertilizer by using asbestos tailings comprises the following steps:

the first step, a pretreatment procedure;

step two, a magnetic separation process;

step three, raw material proportioning;

fourthly, preparing coal powder;

fifthly, putting the raw materials into a kiln;

sixthly, calcining;

step seven, a semi-finished product grinding process;

and eighth, a finished product preparation procedure.

Preferably, the pretreatment process comprises:

conveying the asbestos tailings to a crusher for crushing;

and conveying the crushed asbestos tailings to a ball mill through a conveying device to be ground to 200 meshes.

Preferably, the magnetic separation process includes:

selecting iron, nickel, chromium and cobalt from the asbestos tailings ground to 200 meshes by a belt conveyor magnetic separation system;

collecting iron, nickel, chromium and cobalt metals selected by the magnetic separation system to obtain an iron alloy fine powder product;

and the residual tailing sand enters a batching station warehouse for storage and is used as the next raw material batching process.

Preferably, the raw meal batching process comprises:

a. conveying limestone to a crusher through a plate feeder, conveying the crushed limestone to a stocker through a belt, and uniformly conveying the limestone into a circular storage yard for storage;

b. taking the limestone in the circular storage yard by a bridge type scraper reclaimer, and conveying the limestone to a limestone warehouse by a belt;

c. the materials are prepared by a belt scale according to the mass ratio of 65 percent of asbestos tailings, 35 percent of limestone and 5 percent of activating agent, and are conveyed to a grid wheel by a belt to be put into a grinding machine;

d. the materials are dried and ground, then are brought to a cyclone cylinder by an air exhaust machine, and raw materials are collected by the cyclone cylinder and then enter a finished product chute through a dividing wheel;

e. part of materials are conveyed to a kiln tail bag by a circulating fan to be collected again, and large materials cannot be carried out by wind and are discharged out of the mill from a slag discharge port, and are lifted by a slag discharge hopper to enter the mill again for grinding;

f. the fine powder materials collected by the bag are converged with the dust-collected fine powder of the cyclone cylinder after passing through a zipper machine, a dividing wheel, a chute, and then are lifted to the top of the homogenizing warehouse by a bucket, and enter the homogenizing warehouse through a six-nozzle distributor via the chute.

h. Waste gas with a certain temperature passing through a pipeline of the high-temperature fan enters the mill from a nozzle under the suction action of the circulating fan, then enters a bag for dust collection along with materials through the cyclone cylinder and the circulating fan, and is exhausted into the atmosphere through the tail exhaust fan.

Preferably, the coal dust preparation comprises:

conveying the purchased raw coal to a crusher for primary crushing;

inputting the crushed raw coal into a raw coal bin through a conveyor, metering the crushed raw coal through a constant feeder, and inputting the raw coal into a grinder for grinding through a flap valve; the raw coal entering the grinder is dried, ground, screened and treated by waste gas to obtain coal powder;

after the coal powder is screened and classified, coarse powder is sent into a mill by a screw conveyor to be ground again, and fine powder enters a bag to be collected by dust and then is sent into a coal powder bin by the screw conveyor.

Preferably, the kiln entering raw material process includes:

after the raw material proportioning process, raw materials are metered and input into a rotary blanking device;

the rotary feeder can pre-heat the raw material to heat the raw material;

the heated raw material is fed into the rotary kiln through a rotary feeder.

Preferably, the calcination process includes:

before the raw materials enter a rotary kiln, heating the rotary kiln to 100 ℃;

inputting the raw material into the rotary kiln after heating, and then sealing and continuing heating;

raising the temperature in the rotary kiln to 900 ℃ for 30 minutes;

after high-temperature firing for 30 minutes, the SiO2, MgO and CaO in the raw material undergo crystal form transformation at high temperature to form a crystal structure material with a simple structure, and the crystal structure material comprises a mixed crystal material of 65% of asbestos tailings, 30% of limestone and 5% of an activating agent;

the waste gas generated in the firing process is divided into primary waste gas, secondary waste gas and direct exhaust gas through treatment.

Preferably, the semi-finished product grinding process comprises:

cooling the calcined crystalline material, and then conveying, crushing and grinding the cooled crystalline material;

carrying out primary grinding and secondary grinding on the crystallized material;

grinding the mixture to 100-mesh particles in the first stage, grinding the mixture to 180-mesh powder in the second stage, collecting dust generated during grinding by a bag through an exhaust fan, and taking the collected dust as medium and trace element powder;

the medium-trace element powder is used as a semi-finished product to be prepared into a finished fertilizer, and the particles which are not subjected to fan racing selection are used as metallurgical raw materials for sale.

Preferably, the finished product manufacturing process comprises:

the medium trace element powder is made into plant fertilizer particles through a granulation production line, and the plant fertilizer particles with the plant activating effect are packaged and bagged for sale.

Preferably, the activator comprises 87% potassium sulfate, 7% copper sulfate, 5% sodium sulfide and 3% hydrochloric acid.

The activating agent potassium sulfate is used for improving the activity of medium trace element powder so as to be absorbed by plants, and the copper sulfate, the sodium sulfide and the hydrochloric acid are used for improving the activity of asbestos so as to be convenient for the asbestos calcining crystallization reaction.

Preferably, the preparation method includes a dust disposal step:

entering a bag through a circulating fan for dust collection, and separating the dust collection into waste dust collection at the front end and semi-finished product dust collection;

the waste material dust collection is that a circulating fan is arranged on a pulverizer at the front end, a dust collection bag is arranged on the circulating fan, the collected dust avoids secondary pollution to the surrounding environment, and the collected dust can be used as raw material ingredients to be mixed and then fired;

the finished product dust is collected by a bag through an exhaust fan in the crushing process and the grinding process after firing, and the collected dust is the medium and trace element powder.

Preferably, hot air generated in a high-temperature fan in the raw material proportioning process passes through the hot air of the grate cooler during normal production, and provides a heat source for drying the coal mill under the action of a kiln tail exhaust fan and a circulating fan.

Preferably, the waste gas generated in the calcination is cooled by a humidifying pipe and then is used as a drying heat source of a raw material system, and is discharged into the atmosphere after dust collection and removal by a kiln tail bag, and the waste gas discharged into the atmosphere solves the dust problem.

Compared with the prior art, the gain effect of the invention is as follows:

the invention can refine the alloy powder in the asbestos processing process and prepare the tailings after refining the alloy powder into potash fertilizer through proportioning and calcining processes by optimizing the asbestos processing process, thereby improving the economic benefit of asbestos processing, solving the influence on the surrounding environment in the asbestos processing and avoiding the occurrence of secondary pollution.

Drawings

FIG. 1 is a schematic view of the process of the present invention.

The specific implementation mode is as follows:

as shown in fig. 1, a preparation method for extracting medium trace element fertilizer by using asbestos tailings comprises the following steps:

the first step, a pretreatment procedure;

step two, a magnetic separation process;

step three, raw material proportioning;

fourthly, preparing coal powder;

fifthly, putting the raw materials into a kiln;

sixthly, calcining;

step seven, a semi-finished product grinding process;

and eighth, a finished product preparation procedure.

The technical principle of the invention is as follows:

through two parts of magnetization de-weighting and high-temperature activation, heavy metals can be effectively removed from asbestos tailings after magnetic separation, the asbestos tailings and iron elements are enriched to form byproduct iron complex fine powder, and the tailings after impurity removal are added with limestone and an activating agent and then are subjected to high-temperature calcination, so that Ca elements are added into the product, the crystal structure recombination of mineral substances such as SiO2, MgO, CaO and the like in the middle of the asbestos tailings is realized, and the asbestos tailings become fertilizer components capable of being absorbed by plants. Meanwhile, the activity of the mineral substances can be effectively increased through high-temperature calcination, so that the trace elements in the mineral substances in the product can be absorbed by plants more easily.

The process principle of the invention is

The reaction mechanism of the process technology is as follows

MgO [ Si4O10] (OH)8 → 3 MgO.2SiO 2+2H2O, mechanochemical reaction in a ball mill.

3 MgO.2SiO 2 → 3MgO +2SiO2, local reaction in the rotary kiln.

MgO & SiO2(s) → MgO & SiO2(l), and a stevensite liquefaction reaction.

MgO. SiO2(s) → MgO(s) + SiO2(s), decomposition reaction in the solid state.

Alpha SiO2(s) → beta SiO2(l), crystal transformation reaction of silicon dioxide at high temperature, and fertilizer effect reaction.

Preparing raw materials:

raw and auxiliary material finished product data (%)

Name (R)	Loss	SiO	Al O	Fe2o3	CaO	MgO	SO	R2O	∑
										Stevensite	15.59	31.50	1.30	5.05	3.20	38.83	0.56	0.09	96.12
Limestone	40.03	5.30	1.72	0.64	50.34	1.09	0	0.30	99.32

Raw material ratio (%)

Name (R)	Stevensite	Limestone	Activating agent
				Ratio of	65％	30％	5％

Material balance (ten thousand tons)

The process flow of the invention is as follows:

(1) a pretreatment procedure:

the waste asbestos tailings of asbestos enterprises are firstly crushed in a jaw crusher, and the crushed asbestos tailings are transported to a factory by an automobile and ground by a ball mill to about 200 meshes.

(2) Magnetic separation process

And in the discharging process of the ball mill, the materials are further separated into iron, nickel, chromium and cobalt through a belt conveyor magnetic separation system. And collecting the metals such as iron, nickel, chromium, cobalt and the like selected by the magnetic separation system to obtain the iron alloy fine powder product. And the residual tailing sand enters a batching station warehouse for storage and is used as a raw material for the next process.

(3) A raw material process:

the limestone is conveyed to the crusher by the plate feeder, and the crushed limestone is conveyed to the stacker by a belt to be uniformly sent into the circular storage yard for storage. Limestone in the circular storage yard is taken by a bridge type scraper reclaimer and is conveyed to a limestone warehouse by a belt. The asbestos tailings, limestone and activating agent are weighed by a belt scale according to a certain proportion and then conveyed to a dividing wheel by a belt to be ground. The materials are dried and ground and then are brought to a cyclone cylinder by an air exhaust machine, and raw materials are collected by the cyclone cylinder and then enter a finished product chute through a dividing wheel; part of the raw materials are conveyed to a kiln tail bag by a circulating fan to collect dust and are collected again. The large materials can not be carried by wind and are discharged out of the mill through the slag discharge port, and the large materials are lifted by the slag discharge hopper and enter the mill again for grinding. The fine powder materials collected by the bag are converged with the dust-collected fine powder of the cyclone cylinder after passing through a zipper machine, a dividing wheel, a chute, and then are lifted to the top of the homogenizing warehouse by a bucket, and enter the homogenizing warehouse through a six-nozzle distributor via the chute.

Waste gas with a certain temperature passing through a pipeline of the high-temperature fan enters the mill from a nozzle under the suction action of the circulating fan, then enters a bag for dust collection along with materials through the cyclone cylinder and the circulating fan, and is exhausted into the atmosphere through the tail exhaust fan.

Hot air source: hot air of the grate cooler provides a heat source for drying the coal mill under the action of a kiln tail exhaust fan and a circulating fan during normal production;

(4) preparing coal powder:

the raw coal source is as follows: raw coal is taken by a raw coal yard loader and is delivered to a grinding head raw coal bin by a belt conveyor. Raw coal in the raw coal bin is fed into the air swept mill by the flap valve after being metered by the constant feeder, hot gas of the grate cooler is pumped into the rotary mill cylinder under the suction action of the main exhaust fan of the coal mill, and when the raw coal enters the drying bin, because the drying chamber is provided with a special lifting plate to lift the raw coal, the raw coal containing moisture is dried by the strong heat exchange with hot air, the dried raw coal enters the grinding chamber through the compartment plate provided with the lifting plate, the grinding body in the grinding chamber is carried up and thrown down by the rotating cylinder, thereby crushing and grinding the raw coal into coal powder, sending the coal powder into the high-efficiency powder concentrator under the suction action of the exhaust fan, grading the coal powder by the powder concentrator, the coarse powder is sent into the mill by the screw conveyer to be ground again, the fine powder enters the bag to be collected and sent into the coal powder bin by the screw conveyer, and the gas filtered by the dust collector is exhausted into the atmosphere by the exhaust fan. The waste gas brought by the coal powder after entering the coal powder bin is discharged by an independent fan after being filtered by dust collected by a bag arranged at the top of the coal powder bin.

(5) Raw materials entering a kiln:

raw materials enter a feeding standard bin from a raw material bin through a pneumatic stop valve, an electric flow valve and a chute, the raw materials entering the kiln are discharged from the feeding standard bin, are metered by a Coriolis force scale to a feeding chute after passing through the pneumatic stop valve, the electric flow valve and the chute, are lifted to the top of a preheater through a bucket and enter a secondary uptake flue of the preheater through the chute and a rotary feeder. After the calcination reduction reaction of the rotary kiln, the fiber in the middle of the tailings becomes a recrystallized mineral structure, and the harm of asbestos fiber to the environment is eliminated. In the same calcination state, the crystal structures of SiO2, MgO, CaO and the like in the middle of the minerals are subjected to crystal transformation at high temperature to form crystal structures with simple structures.

(6) Calcination of

In the preheater, raw material and hot air flow are heat exchanged, and then fed into the furnace to make carbonate decomposition, then fed into the five-stage cyclone cylinder through vertical flue to make material-gas separation and fed into the kiln to make calcination. The decomposed materials are subjected to solid phase reaction and sintering reaction in the kiln to form clinker. And the high-temperature clinker discharged from the kiln enters a grate cooler for cooling and conveying. And dust collected by the kiln head bag is converged with clinker discharged from the grate cooler and is conveyed to a clinker storage through a diagonal chain. One part of the waste gas of the grate cooler for cooling the clinker is fed into the kiln to be used as secondary air of the kiln, one part of the waste gas is fed into the decomposing furnace to be used as tertiary air, the other part of the waste gas is used as a drying heat source of the coal mill system, and the rest gas is discharged into the atmosphere after dust collection and removal by the bag.

Waste gas treatment: the high-temperature gas of the preheater is cooled by a humidifying pipe and then is used as a drying heat source of a raw material system or is discharged into the atmosphere after dust collection and dust removal by a kiln tail bag.

(7) Semi-finished product grinding mill

And (3) crushing and ball-milling the cooled semi-finished product to 180-200 meshes to obtain trace element powder in mineral substances of the product, conveying the powder subjected to secondary ball milling into a packaging working section by using conveying equipment, weighing and packaging, and warehousing the finished product.

(8) Finished product

Collecting dust by an exhaust fan bag, grinding the powder to obtain medium trace element powder, preparing plant fertilizer by a granulator, and selling the plant fertilizer, wherein particles which are not collected by the exhaust fan bag are sold to a lead-zinc smelting plant as a lead-zinc smelting raw material.

The preparation equipment comprises the following components:

(1) crushing plant

As for the crushing of limestone and asbestos tailings, a single-stage crushing and a two-stage crushing can be selected, with the development of the equipment manufacturing industry in recent years, a single-stage crushing system replaces a two-stage crushing system due to the reliable manufacturing quality and the simple process flow, and according to the scale of a factory, the system recommends the PCF20.18 single-stage hammer crusher, the installed capacity of the single-stage hammer crusher is 710kW, the production capacity of the single-stage hammer crusher is 450t/h, and the annual utilization rate of the single-stage hammer crusher is 25.27%.

(2) Pre-homogenization

In order to fully utilize mineral resources, reduce stripping amount and stabilize raw material components, the design considers setting a pre-homogenization storage yard for asbestos tailings and limestone. At present, limestone and asbestos tailing pre-homogenization storage yards of 3200t/d production lines in China mainly have three schemes of a conventional phi 80m, a low-investment phi 60m circular pre-homogenization storage yard and a rectangular pre-homogenization storage yard. Under the condition of the same storage capacity and the same material taking machine, the occupied area of the circular storage yard is reduced by more than 30% compared with that of the rectangular storage yard, the investment is saved by about 30-40%, the circular storage yard without end material stacking can continuously stack and take materials, the automatic control is convenient to realize, the operation and maintenance cost is low, and the circular storage yard should be selected preferentially. 24000 tons of effective storage capacity of a phi 80m storage yard, 7.15 days of storage period and 8-10 homogenization effects can meet the requirements of storage and homogenization of asbestos tailings and limestone of two 3200t/d production lines, and in order to save investment, a phi 80m circular pre-homogenization storage yard scheme is recommended.

(3) Raw material powder mill

The grinding is usually carried out by a middle-discharge drying mill or a vertical mill, and the technical and economic comparison of the two schemes is shown in the table:

comparison of the schemes of the pulverizing system

Comparison of the schemes of the pulverizing system

From the comparison results, it can be seen that: the scheme I and the scheme III have the advantages of less system equipment, simple flow, low civil engineering cost, low power consumption, low noise, stronger drying capacity than medium discharge grinding, large granularity of the materials allowed to be ground and the like. Although the scheme II has the advantages of less total investment, strong abrasion resistance, strong adaptability to raw materials, small equipment maintenance amount and the like, the scheme II allows the granularity of the materials to be ground to be small, the water content to be ground to be low, the drying capacity to be weak, the unit power consumption to be high, the noise to be high, and the scheme II is unfavorable for energy conservation and environmental protection.

In recent years, with the continuous maturity of the manufacturing technology of the domestic vertical mill, the domestic vertical mill is used more and more, and compared with the imported vertical mill, the domestic vertical mill has the advantages of price, delivery date and the like, so the project recommends the scheme of the three-domestic vertical mill.

(4) Firing system

The clinker firing adopts a kiln external decomposition calcining system consisting of a set of five-stage preheating pre-decomposition system, a phi 4.3 multiplied by 64m rotary kiln, a novel air beam grate cooler and the like. 3000t of clinker is produced per day, and the decomposition rate of calcium carbonate in raw materials entering the kiln is more than 92 percent. The waste heat of the system waste gas is used for drying raw materials and raw coal, a bag dust collector is adopted for purifying the waste gas at the head of the kiln at the tail of the kiln, and the dust concentration of the discharged waste gas is below 50mg/Nm 3.

1. Adopt CNC type cyclone preheater, have following structural feature:

the novel cyclone cylinder adopts a three-center 270-degree wrap angle, so that air flow is smoothly introduced into the cyclone cylinder, and high efficiency and low resistance are both considered;

the C1 cone is provided with a reflecting cone and a guide plate, so that the external circulation volume of the system is reduced;

the cone body of the cyclone cylinder is designed into an inclined cone, so that secondary flying of materials at the bottom of the cone body caused by the deflection of airflow is reduced;

the air inlet is in a tangent angle pentagon shape with the same angle and variable height, conforms to the movement direction of fluid, reduces collision of inlet airflow and backflow, reduces fluid resistance loss and improves separation efficiency;

the air outlet is provided with the pulsating air pipe, so that the short circuit of the material at low wind speed is avoided, and the dispersion and heat exchange of the material are enhanced.

2. Rotary kiln

The rotary kiln of the invention adopts a rotary kiln with phi 4.3 multiplied by 60, three-gear supporting, the inclination is 3.5 percent, the power of a main motor is 4000kW, and direct current speed regulation is carried out. The kiln head cover adopts a large kiln head cover design, the air speed ratio in the kiln head cover is lower, and the kiln head cover also plays a role of a dust settling chamber. Two kiln doors are arranged, so that the maintenance work is convenient. The kiln hood is provided with a tertiary air suction opening, so that tertiary air with higher temperature can be pumped and supplied to the preheater decomposing furnace.

3. Air beam grate cooler

The clinker cooler adopts a novel third-generation air beam grate cooler DLX2500, and the effective area of a grate bed is 65.24m 2. The clinker leaving the cooler is at ambient temperature +65 ℃. The third generation grate cooler is greatly improved in the aspects of clinker cooling, uniform distribution of secondary and tertiary air temperature and red hot clinker on a grate bed, prevention of 'blow-through', 'red river' and 'snowman' phenomena and the like, further improves the stability and operability, improves the heat recovery performance and improves the heat efficiency. Compared with a Fuller second-generation grate cooler, the heat consumption of clinker per kilogram can be saved by 125-170 kJ, the cooling air quantity can be reduced by 20-40%, and the grate cooler has the advantages of high load per unit area of a grate bed, small area of the grate bed, light weight of equipment and the like; the defects that the prior grate cooler is not small enough in the area division of the cooler, and the resistance distribution of a middle material layer is uneven, so that the excessive heat of a local grate bed is damaged are overcome; the high resistance of the grid plate enhances the stability of the anti-material layer; the high penetrability of the grid plate is beneficial to gas-solid heat exchange in the charge bed, particularly the red river phenomenon of the red fine material can be effectively controlled, the temperature of the tertiary air is increased, and the heat energy recovery is improved.

(5) Pulverized coal preparation system

The coal powder preparation is realized by adopting a domestic vertical mill, when the water content of raw coal is less than or equal to 8 percent and the granularity of raw materials entering the mill is less than or equal to 40mm, the mill-out water content is less than or equal to 0.5 percent, the mill-out fineness is 0.08mm, the screen residue is 8-10 percent, the production capacity is 22t/h, and the annual utilization rate is 65.85 percent. And extracting the waste gas of the kiln head grate cooler as a drying heat source. The economic comparison of the vertical mill and the tube mill is shown in the following table:

coal milling protocol comparison

The comparison result shows that the vertical mill scheme has the advantages of simple system flow, low civil engineering cost, outdoor arrangement, low power consumption, low noise, strong drying capacity, large grinding granularity and the like. At present, the domestic vertical coal mill processing technology is mature and reliable, so the vertical mill scheme is recommended for coal powder preparation.

(6) Characteristics of production process design

The equipment selection is carried out to achieve reliable production, advanced technology, reasonable price, energy conservation, consumption reduction and environmental protection, and ensures the long-term stable, safe and efficient operation of the production line. The design scheme is elaborately optimized, the investment is reduced, and advanced and mature process technology and production method are adopted, so that the yield can be reached as soon as possible after the production of the invention, and good economic benefit is obtained.

Equipment level: the energy-saving equipment developed and introduced in China at the end of the nineties and manufactured by domestic conversion reaches the current domestic advanced level.

Arranging in the open air: in order to save capital construction investment, the equipment is arranged in the open air as much as possible under the condition of meeting the production requirement from the actual condition of local meteorological conditions, so that the civil engineering cost is saved, some maintenance equipment with low utilization rate is saved, and the maintenance of the equipment is convenient.

(7) The main characteristics of equipment type selection are as follows:

a. selecting a preheating pre-decomposition system;

b. the clinker cooling adopts a third generation of aerated beam grate cooler, and has the advantages of large cooling capacity per unit area, small cooling air quantity per unit clinker, low discharge temperature, high temperature of secondary air and tertiary air, light weight of equipment and the like;

c. the raw materials are conveyed mechanically in storage and in kiln tail, so that a large amount of power consumption can be saved;

d. the material weight metering level on the process production line is advanced. A constant feeder, a rotor scale, an electronic belt scale and the like are adopted;

e. each dust lifting point is provided with a dust remover with advanced performance according to the respective characteristics.

(8) The optimization characteristics are as follows:

a. arranging equipment in the open air: in order to save capital construction investment, the equipment is arranged in the open air as much as possible under the condition of meeting the production requirement from the actual condition of local meteorological conditions, so that the civil engineering cost is saved, some overhauling equipment with low utilization rate is saved, and the overhauling and maintenance of the equipment are facilitated;

b. the raw material mill adopts a vertical mill: the vertical mill has the characteristics of less system equipment, simple flow, low civil engineering cost, low power consumption, low noise, strong drying capacity, large granularity of materials to be milled and the like;

c. the general map layout makes the best use of the terrain;

d. raw material feeding into a kiln metering bin: the inverted cone structure form of the homogenizing silo bottom is fully utilized, and the raw material metering silo is arranged at the bottom of the raw material homogenizing silo, so that the investment can be saved, and the power consumption can be reduced;

e. the arrangement among the kiln tail, the raw material homogenizing warehouse and the raw material mill waste gas treatment is compact, the hot air pipeline is short, the heat loss is reduced, and the capital investment is saved.

(8) Host device

Host device performance is shown in the following table:

the invention also comprises an associated control system:

the production line is supposed to adopt the principle of combining a central monitoring computer, a PLC control system and a conventional instrument to monitor the production process by stabilizing process parameters, ensuring product quality and improving production efficiency and considering the principles of economy, applicability and investment saving. The control, display and accident alarm of main technological parameters are introduced into the operator station for monitoring. The operator can operate, control and maintain the system through a conventional instrument, a PLC control system and a central monitoring computer, so as to achieve the purposes of stabilizing process parameters, ensuring the product quality, reducing the labor intensity and ensuring the safe production. Meanwhile, a part of local display instruments are arranged on the site for facilitating field operation.

The system consists of a central monitoring management control computer and a PLC field control substation to form an IPC + PLC distributed control system. The network switches of the industrial Ethernet are connected to realize data information sharing and exchange. A set of monitoring management computer-operating station (an engineer station) is arranged in the existing office building to monitor the device in a centralized manner, so that the defects of centralized control system such as centralized danger degree, poor reliability, difficult expansion, large use amount of control cables and the like are overcome, and the centralized control of information, scheduling and management and the dispersion of functions and control dangers are realized. When the operator station in the office building breaks down, each field substation can work independently and stably, and the system reliability is improved fundamentally.

The disposal method for avoiding secondary pollution comprises the following steps:

waste water

The invention has no production sewage discharge and can be completely recycled.

The discharge conditions of the domestic sewage of the invention are listed, including the discharge source, discharge amount, pollutant name, production amount, treatment method, discharge amount and the like of the wastewater.

Exhaust gas

The emission conditions of the exhaust pollutants of each device and facility comprise an exhaust emission source, an organized emission source and an unorganized emission source, emission quantity, pollutant names, concentration, emission rate, emission characteristics, treatment method and emission destination.

Solid waste

And the discharge conditions of the solid wastes of each workshop comprise solid waste discharge sources, discharge amount, composition, solid waste types, discharge characteristics, treatment methods and discharge destination.

Noise(s)

Noise emission of moving machines such as fans and pumps, including name, number and space of noise sources

Position, noise reduction (prevention) measure, and noise value before/after noise reduction.

Treatment of waste water

(1) The device area of the invention is used for sorting and treating the process wastewater, equipment, ground washing water and domestic sewage generated by the production devices of the invention.

(2) In order to implement the principle of one water with multiple purposes and recycling and reduce the discharge amount of wastewater, the invention recycles multiple kinds of wastewater.

Exhaust gas treatment

The dust removing system is divided according to the production process flow, a relatively centralized dust removing system is adopted, a closed exhaust hood is arranged at all dust raising points, the air is sent to a bag type dust remover through an air pipe, and the air filtered by the dust remover is exhausted into the atmosphere. The indoor environment can reach the national sanitary standard, and the discharged gas can reach the limit value of the emission of the atmospheric pollutants. The dust collected by the dust removal system meets the process requirements and returns to the process system. The method does not meet the process requirements, and adopts a centralized treatment mode to avoid the generation of secondary dust as much as possible.

Solid waste (waste liquid) treatment

The solid waste of the invention is mainly domestic garbage and waste metal granular materials.

The daily life garbage is collected with daily life garbage of other workshops and then transported out by a park sanitation department for harmless treatment.

The waste metal particles produced in the production process can be uniformly collected and then sent to a waste steel recovery enterprise for recycling treatment.

Noise abatement

The main exhaust fan, the Roots fan, the ball mill, the granulator, the air compressor, the pump and the like generate large mechanical noise, and the sound value can reach 90-100 dB (A). Set up the fan room to main exhaust fan, reduce the influence to the environment outside the workshop through the house separation effect. The Roots blower adopts an elastic joint and is additionally provided with a silencer. For the air blower and the pump, a vibration reduction foundation is adopted and a sound insulation device is arranged; the ball mill and the granulator adopt an isolated closed room to reduce noise. Through the measures of noise prevention and noise reduction, the predicted value and the superposed value of the predicted value and the background value when the noise reaches the factory boundary reach the standard, and the quality level of the sound environment cannot be reduced.

The invention adopts domestic advanced technology and equipment, has low production energy consumption and material consumption and less three-waste pollutant discharge, is matched with feasible environmental protection measures, and realizes organized standard discharge of each pollution source.

The invention improves the profit after the treatment of the asbestos tailings by treating the asbestos tailings, so that the treatment of the asbestos tailings can be virtuous and cyclic, and effectively solves the problems of complicated treatment process of the asbestos tailings, high energy consumption of each device, poor economic benefit of asbestos tailings treatment and easy secondary pollution to the surrounding environment in the tailings treatment process.

Claims

1. A preparation method for extracting medium trace element fertilizer by using asbestos tailings is characterized by comprising the following steps:

the first step, a pretreatment procedure;

step two, a magnetic separation process;

step three, raw material proportioning;

fourthly, preparing coal powder;

fifthly, putting the raw materials into a kiln;

sixthly, calcining;

step seven, a semi-finished product grinding process;

eighthly, a finished product preparation procedure;

the pretreatment process comprises the following steps:

conveying the asbestos tailings to a crusher for crushing;

conveying the crushed asbestos tailings to a ball mill through a conveying device to grind the crushed asbestos tailings to 200 meshes;

the magnetic separation process comprises the following steps:

the residual tailing sand enters a batching station warehouse for storage and is used as the next raw material batching process;

the raw material batching procedure comprises the following steps:

1. conveying limestone to a crusher through a plate feeder, conveying the crushed limestone to a stocker through a belt, and uniformly conveying the limestone into a circular storage yard for storage;

2. taking the limestone in the circular storage yard by a bridge type scraper reclaimer, and conveying the limestone to a limestone warehouse by a belt;

3. the materials are prepared by a belt scale according to the mass ratio of 65 percent of asbestos tailings, 35 percent of limestone and 5 percent of activating agent, and are conveyed to a grid wheel by a belt to be put into a grinding machine;

4. the materials are dried and ground, then are brought to a cyclone cylinder by an air exhaust machine, and raw materials are collected by the cyclone cylinder and then enter a finished product chute through a dividing wheel;

5. part of materials are conveyed to a kiln tail bag by a circulating fan to be collected again, and large materials cannot be carried out by wind and are discharged out of the mill from a slag discharge port, and are lifted by a slag discharge hopper to enter the mill again for grinding;

6. fine powder materials collected by the bag dust collection are converged with dust-collected fine powder of the cyclone cylinder after passing through a zipper machine, a dividing wheel, a chute, and then are lifted to the top of the homogenization warehouse by a bucket, and enter the homogenization warehouse through a six-nozzle distributor via the chute;

7. waste gas with a certain temperature passing through a pipeline of a high-temperature fan enters a mill from a nozzle ring under the suction action of a circulating fan, then enters a bag for dust collection along with materials through a cyclone cylinder and the circulating fan, and is exhausted into the atmosphere through a tail exhaust fan;

the preparation of the coal dust comprises the following steps:

conveying the purchased raw coal to a crusher for primary crushing;

inputting the crushed raw coal into a raw coal bin through a conveyor, metering the crushed raw coal through a constant feeder, and inputting the raw coal into a grinder for grinding through a flap valve;

the raw coal entering the grinder is dried, ground, screened and treated by waste gas to obtain coal powder;

after the coal powder is screened and classified, coarse powder is sent into a mill by a screw conveyor to be ground again, and fine powder enters a bag to be collected by dust and then is sent into a coal powder bin by the screw conveyor;

the kiln raw material feeding process comprises the following steps:

the rotary feeder can pre-heat the raw material to heat the raw material;

inputting the heated raw material into a rotary kiln through a rotary feeder;

the calcination process includes:

raising the temperature in the rotary kiln to 900 ℃ for 30 minutes;

waste gas generated in the firing process is divided into primary waste gas, secondary waste gas and direct exhaust gas through treatment;

the semi-finished product grinding process comprises the following steps:

the medium trace element powder is used as a semi-finished product to be prepared into a finished fertilizer, and the particles which are not subjected to fan racing selection are used as metallurgical raw materials for sale;

the finished product manufacturing procedure comprises:

2. The method for preparing the fertilizer for extracting the medium and trace elements from the asbestos tailings as claimed in claim 1, wherein the activating agent comprises 87% of potassium sulfate, 7% of copper sulfate, 5% of sodium sulfide and 3% of hydrochloric acid.

3. The method for preparing the fertilizer for extracting the medium and trace elements from the asbestos tailings according to claim 1, which is characterized by comprising the following dust treatment process:

4. The method for preparing fertilizer for extracting trace elements from asbestos tailings as claimed in claim 1, wherein the hot air generated by the high temperature fan in the raw material proportioning process is used as a heat source for drying the coal mill under the action of the kiln tail exhaust fan and the circulating fan.

5. The method for preparing the fertilizer for extracting the medium and trace elements from the asbestos tailings according to claim 1, wherein the waste gas generated in the calcining process is cooled by a humidifying pipe and then is used as a drying heat source of a raw material system, and is discharged into the atmosphere after dust collection and removal are carried out by a kiln tail bag, and the problem of dust is solved by the waste gas discharged into the atmosphere.