A process for preparing rock wool by high-temperature melting of fly ash without water washing

Abstract

The present invention relates to the technical field of fly ash treatment, and discloses a process for preparing rock wool by high-temperature melting of fly ash without water washing, which comprises the following steps: fly ash unloading: the fly ash after entering the site is stored in a raw material silo (vertical), and the fly ash is directly transported from the waste-producing unit to the project site by a special closed tank truck. In the process for preparing rock wool by high-temperature melting of fly ash without water washing, fly ash, quartz stone and alumina are mixed and put into a high-temperature melting furnace for heating, and the melt is cooled and drawn into fibers under the combined action of the centrifugal force of the centrifuge and the high-speed airflow ejected by the wind ring, and the fibers fed into the fiber forming system are collected, and then the fibers are formed into rock wool through subsequent processing. While making rock wool, the fly ash is subjected to high-temperature heat treatment, which can make full use of the high chlorine and heavy metal content of the fly ash, and the heavy metals and chlorine are synergistically volatilized into the flue gas, and finally captured in the concentrated ash, so as to achieve the purpose of dechlorination and heavy metal removal of the fly ash.

Description

Technical Field

[0001] The invention relates to the technical field of fly ash treatment, and in particular to a process for preparing rock wool by high-temperature melting of fly ash without water washing. Background Art

[0002] The incineration of domestic waste in a grate furnace will produce 3-5% of domestic waste incineration fly ash (hereinafter referred to as fly ash). Since domestic waste contains 40%-75% kitchen waste and about 20% plastic, the chloride content in the fly ash is relatively high, and the chlorine content is mostly between 10% and 20%, and can reach up to 30%. At present, the methods for treating chloride in fly ash include water washing, acid washing, and heat treatment processes.

[0003] The fly ash water washing process can effectively remove soluble chlorine in fly ash, but it is difficult to remove insoluble chlorine. The fly ash acid washing pretreatment process is to add a certain proportion of acid on the basis of the water washing process to convert insoluble chlorine into soluble chlorine and then remove it. The dechlorination effect is better than simple water washing. However, both the water washing and acid washing pretreatment processes inevitably cause heavy metals and other pollutants to migrate from the solid phase to the liquid phase. The wastewater contains a large amount of heavy metal ions and chloride ions, etc., and water purification is required later. Therefore, a process for preparing rock wool by high-temperature melting of fly ash without water washing is proposed to solve the above problems. Summary of the invention

[0004] 1. Technical issues to be resolved In view of the shortcomings of the prior art, the present invention provides a process for preparing rock wool by high-temperature melting of fly ash without water washing, which has the advantages of high-temperature melting heat treatment and effective dechlorination of fly ash, thus solving the problem of inability to effectively treat chlorides in fly ash.

[0005] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a process for preparing rock wool by high-temperature melting of fly ash without water washing, comprising the following steps: 1) Fly ash unloading: After entering the site, the fly ash is stored in the raw material silo (vertical). The fly ash is directly transported from the waste-producing unit to the project site by a special closed tank truck, and the fly ash in the tank is transported to the fly ash special raw material silo (vertical) on site by air transportation in a closed pipeline; 2) Fly ash batching: Due to the differences in the composition of fly ash in different batches, it is necessary to mix the fly ash according to its characteristics. The fly ash in the silo is pneumatically transported to the fly ash batching silo; 3) Raw material briquetting: fly ash is transported from the raw material silo to the closed mixer by means of spiral feeding through a closed pipeline. After uniform mixing, it is pressed into a cylindrical block with a diameter of about 10 mm by a raw material briquetting machine to form fly ash solidified material. The vibrating screen under the raw material briquetting machine screens the fine particles. The screened small particles are re-briquetted by the elevator back-pressing briquetting device. The pressed fly ash solidified material enters the feeding system (silo); 4) Feeding: Quartz stone and alumina are crushed and sieved into solid particles of 10-40mm, which enter the feeding system (silo) through a closed conveyor. After the proportion is adjusted by a metering device, they are transported into the high-temperature melting furnace in batches by a feeding elevator; 5) High temperature melting: Fly ash contains a large amount of oxides such as silicon dioxide, calcium oxide, aluminum oxide, magnesium oxide, potassium oxide, sodium oxide, etc. By adding quartz and aluminum oxide, the ratio of SiO2-Al2O3-(CaO+MgO+Na2O+K2O) is adjusted to increase the dynamic fluidity of fly ash in the melting furnace, and promote the slag to be in a solid-liquid coexistence state in a wider temperature range. The heat of oxygen-enriched combustion using natural gas and oxygen-enriched air is used to heat the materials in the melting furnace to 1350-1600℃, and the materials form liquid substances. The liquid substances drip to the lower layer of 1600-1650℃ due to gravity, and the liquid fluid is further stratified and in a In the solid-liquid coexistence state, the melt flows into the subsequent centrifuge from the liquid outlet tank at the bottom of the furnace body, and the materials enter the oxygen-enriched melting furnace in batches, about 10-15 batches / h, and the material stays in the furnace for about 1h. The molten flue gas generated in the melting furnace is sent to the subsequent flue gas purification system for treatment and then discharged; the chloride salts (sodium chloride, potassium chloride, calcium chloride, magnesium chloride) generated in the melting furnace gather in the temperature range of 1350-1600℃, and are discharged together with the slag liquid after high-temperature gasification, and discharged with the liquid outlet tank. The exhaust device is set above the liquid outlet tank to inhale the chloride salt vapor into the chloride salt recovery device for cooling and recovery. In this step, molten waste gas (including liquid waste gas) G4, alloy slag S1, and crystallized salt S2 are generated; 6) Fiber forming system: The high-temperature melt flows into the centrifuge through the liquid outlet tank. The melt flowing into the centrifuge is cooled and drawn into fibers under the combined action of the centrifugal force of the centrifugal roller and the high-speed airflow ejected by the wind ring. In the cotton collecting pendulum section, centrifugation is mainly carried out by wind force. The bottom of the centrifuge will produce some centrifugal waste slag S3 formed by excessive cooling. The main component is still the melt, which is recycled after returning to the feeding process; 7) Cotton collecting pendulum section: The fibers fed into the fiber forming system are collected by means of triangular mesh belt collection. Primary cotton felt is formed on the surface of the high-speed cotton collecting mesh plate under the combined action of the centrifuge, air ring blowing and cotton collector exhaust. The square meter weight of the primary cotton felt is adjusted by changing the speed of the cotton collecting drum to meet the product requirements. The primary cotton felt formed on the cotton collecting mesh plate is sent to the pendulum cotton spreading machine via a belt conveyor. The primary cotton felt is laid on the forming conveyor into a multi-layer folded secondary cotton felt layer under the reciprocating swing of the pendulum belt; 8) Molding and cutting: The rock wool after the cotton collecting pendulum is extruded and formed by the collecting and molding device, and then enters the cutting process. The cutting section is equipped with a longitudinal saw, and the spacing can be adjusted according to the product specifications. The length direction is controlled by a cross-cutting saw and an automatic length measuring controller. In order to adapt to the cutting of products with different bulk densities, this cutting section is equipped with a cross-cutting conveyor and a cross-cutting guillotine. The former is suitable for high bulk density products, and the latter is suitable for low bulk density products. 9) Packaging: Rock wool products are automatically packed by packaging machines and then put into storage; 10) Flue gas treatment: The flue gas generated in step 5) is treated at the same time, and the chloride salt in the flue gas is discharged through the exhaust port of the melting furnace. The temperature of the exhaust port will cause the chloride to form fine particles. After the flue gas enters the flue gas purification system for treatment, it is discharged into the waste salt collection bin for collection; 11) Discharge the chloride salt and fly ash in the waste salt collection bin into the dissolution tank, add fresh water to the dissolution tank, introduce the wastewater in the dissolution tank into the plate and frame filter press equipment, and use the plate and frame filter press to separate and remove the fly ash, impurities, heavy metals, etc. that are insoluble in water to produce sludge; 12) The wastewater is then introduced into a high-density sedimentation tank, and PAM and heavy metal scavengers are added to the high-density sedimentation tank. The (organic sulfur) heavy metal scavenger is added to directly react with most of the heavy metals in the wastewater to form precipitation and remove the heavy metals in the wastewater. Polyacrylamide (PAM) shortens the reaction and sedimentation time; 13) The treated wastewater is led to another sedimentation tank, and sodium carbonate is added to the sedimentation tank to make the Ca2+ in the ash washing wastewater react with it to form calcium carbonate precipitation. A large amount of HCO3-, OH- and CO32- are produced during the hydrolysis process, which increases the alkalinity in the system. The Ca2+ contained in the water washing liquid reacts with CO32- to form CaCO3 precipitation. The wastewater in the sedimentation tank is led to the filter, so that the filter removes the residual particles in the wastewater that cannot be settled; 14) Introduce the washing wastewater into the mechanical vapor recompression (MVR) evaporator, adopt the principle of "high temperature sodium precipitation, mother liquor circulation", and use MVR evaporation technology to extract NaCl and KCl. The material concentrated by the MVR evaporator produces sodium chloride crystals and potassium chloride crystals in the separator; 15) The precipitated crystal salt settles to the bottom of the separator and is discharged to the centrifuge. The obtained supernatant is sent to the washing section. Since the raw materials contain a certain amount of impurities, it is necessary to discharge a small amount of flash crystallization mother liquor to the impurity salt evaporator for separate evaporation to produce a small amount of impurity salt to ensure the purity of the final sodium chloride and potassium chloride crystal salt.

[0006] Preferably, the step 1) generates fly ash loading and unloading waste gas G1, which is discharged after being treated by bag dust removal, and the fly ash is collected by bags and returned to the fly ash silo. The batching process in the step 2) generates batching waste gas G2, which is discharged after being treated by bags, and the fly ash is collected by bags and returned to the fly ash silo. The step 3) generates briquetting waste gas G3, which is discharged after being treated by bags, and the fly ash is collected by bags and returned to the fly ash silo. The step 7) mainly generates fiber-type G5 dust pollutants during the cotton collection process, and the dust is discharged through a 35m high P5 exhaust chimney after being treated in a matching negative pressure filter chamber. In the step 8), dust is generated during the cutting process of rock wool, and a gas collection hood is installed above the cutting machine to collect waste gas G6 and the cotton collecting pendulum waste gas G5, which are treated by a bag dust collector and discharged through a 35m high P5 exhaust chimney. Uncollected waste gas is discharged in an unorganized form.

[0007] Preferably, in the step 8), waste scraps are generated during the cutting process. Subsequently, the scraps cut off by the longitudinal saw are crushed by a scrap recovery system, and then sent to a cotton collector by wind power for reuse.

[0008] Preferably, in step 3), the fly ash is in granular form, containing 36% calcium oxide, and the fly ash:sodium silicate solution are mixed, stirred and briquette-pressed in a ratio of 20:3.

[0009] Preferably, in the step 5), the lower part of the oxygen-enriched melting furnace is a melting section, a melt tank is arranged at the bottom of the melting furnace, a plurality of natural gas nozzles distributed in a ring array are arranged on the outside of the melting section, the natural gas nozzles are inclined downward and arranged off-center, a flue gas pipe and a feed port are arranged at the upper part of the melting furnace, and fly ash solidification material, quartz stone and alumina enter from the upper part of the oxygen-enriched melting furnace through a feeding system, and enter the bottom of the final oxygen-enriched melting furnace downward by gravity, during which the raw materials can be preheated to remove moisture therein.

[0010] Preferably, the oxygen-enriched melting furnace uses natural gas and oxygen-enriched air to enter the oxygen-enriched melting furnace through a closed heat-resistant pipe at a temperature range of 1350-1600°C. The oxygen-enriched combustion is ensured by adjusting the natural gas and oxygen intake to ensure the temperature. In this temperature range, calcium carbonate and magnesium carbonate can form calcium oxide, magnesium oxide, etc.

[0011] Preferably, in the step 10), when the temperature of the garbage fly ash in the melting furnace reaches 450°C, the chlorine element in the fly ash begins to function, causing the melting furnace to continue to rise. When the temperature reaches above 830°C, the chloride will be gasified. When the combustion temperature of the melting furnace reaches above 1500°C, all the chloride salts are volatilized, the exhaust port temperature is 200-250°C, the flue gas temperature drops below 400°C, and the chloride forms fine particles.

[0012] (III) Beneficial effects Compared with the prior art, the present invention provides a process for preparing rock wool by high-temperature melting of fly ash without water washing, which has the following beneficial effects: The process for preparing rock wool by high-temperature melting of fly ash without water washing comprises the following steps: briquetting fly ash to form fly ash solidified material, mixing the fly ash with quartz stone and alumina, and putting the fly ash solidified material into a high-temperature melting furnace for heating; the melt is discharged into a centrifuge through a liquid outlet trough; the liquid melt is cooled and drawn into fibers under the combined action of the centrifugal force of the centrifuge and the high-speed airflow ejected by the air ring; the fibers fed into the fiber forming system are collected by a triangular mesh belt cotton collecting method; primary cotton felt is formed on the surface of a high-speed cotton collecting mesh plate under the combined action of the centrifuge, the air blowing of the air ring and the exhaust of the cotton collecting machine; the primary cotton felt formed on the cotton collecting mesh plate is sent to a pendulum cotton spreading machine via a belt conveyor; the primary cotton felt is spread on a forming conveyor under the reciprocating swing of the pendulum belt. The multi-layer folded secondary cotton felt layer plays the role of preparing rock wool, and during the high-temperature incineration process of fly ash, organic chlorine (generally insoluble chlorine) will be completely converted into hydrogen chloride gas, and inorganic chlorine (generally soluble chlorine) will be partially converted into hydrogen chloride and partially exist in the form of chloride due to its strong bond energy. Hydrogen chloride and chloride can promote the volatilization of heavy metals at high temperature. Therefore, high-temperature heat treatment of fly ash can make full use of the high chlorine and heavy metal content of fly ash, and the heavy metals and chlorine will be synergistically volatilized into the flue gas, and finally captured in the concentrated ash, which can not only achieve the purpose of dechlorination and heavy metal removal of fly ash, but also provide technical conditions for the enrichment and recovery of soluble salts and heavy metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is the process flow of fly ash comprehensive utilization and pollution generation link diagram in the present invention; Figure 2 It is the pseudo three-phase diagram of SiO2-Al2O3-(CaO+MgO+Na2O+K2O) of the flow temperature of ash samples under different (CaO+MgO) / (Na2O+K2O) ratios in the present invention (the red dots represent fly ash); Figure 3 Schematic diagram of raw material inlet and outlet and related temperature ranges in the present invention; Figure 4 It is a process flow chart of the chlorine salt water washing system in the present invention. DETAILED DESCRIPTION

[0014] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] See also Figure 1-4A process for preparing rock wool by high-temperature melting of fly ash without water washing, comprising the following steps: 1) Fly ash unloading: After entering the site, the fly ash is stored in the raw material silo (vertical). The fly ash is directly transported from the waste-producing unit to the project site by a special closed tank truck. The fly ash in the tank is transported to the fly ash special raw material silo (vertical) on site by air transportation in a closed pipeline. The entire unloading and transportation process is fully closed. This process generates fly ash loading and unloading waste gas G1, which is discharged after being treated by bag dust removal. The bag collects the fly ash and returns it to the fly ash silo; 2) Fly ash batching: Due to the differences in the composition of fly ash in different batches, it is necessary to mix according to the characteristics of fly ash. The fly ash in the silo is pneumatically transported to the fly ash batching silo. There are two fly ash batching silos, which are operated under full negative pressure. The batching process generates batching waste gas G2, which is discharged after being treated by bag dust removal. The fly ash collected by the bag is returned to the fly ash silo; 3) Raw material briquetting: Since fly ash is granular and contains 36% calcium oxide, it is easy to stick together into blocks after adding water glass (sodium silicate solution). At the same time, the blocks entering the oxygen-enriched melting furnace can ensure air permeability and prevent fire extinguishing. Therefore, the fly ash and sodium silicate solution need to be mixed, stirred and briquette in a ratio of 20:3. The fly ash is transported from the raw material silo to the closed mixer through a closed pipeline by means of spiral feeding. After uniform stirring, it is pressed into a cylindrical block with a diameter of about 10 mm by a raw material briquetting machine to form a fly ash solidified material. The vibrating screen under the raw material briquetting machine screens the fine particles. The screened small particles are re-briquetted by the elevator back-pressing briquetting device. The pressed fly ash solidified material enters the feeding system (silo). This process produces briquetting waste gas G3, which is discharged after bag dust removal treatment. The bag collects the fly ash and returns it to the fly ash silo; 4) Feeding: Quartz stone and alumina are crushed and sieved into solid particles of 10-40mm, which enter the feeding system (silo) through a closed conveyor. After the proportion is adjusted by a metering device, they are transported into the high-temperature melting furnace in batches by a feeding elevator. This process is closed, and the fly ash solidification material, quartz stone, and alumina particles are all larger than 10mm, so there is basically no dust generated during the operation; 5) High-temperature melting: Fly ash contains a large amount of oxides such as silicon dioxide, calcium oxide, aluminum oxide, magnesium oxide, potassium oxide, and sodium oxide. By adding quartz and alumina, the ratio of SiO2-Al2O3-(CaO+MgO+Na2O+K2O) is adjusted, the dynamic fluidity of fly ash in the melting furnace is increased, and the slag is promoted to be in a solid-liquid coexistence state in a wider temperature range.

[0016] The lower part of the oxygen-enriched melting furnace is the melting section. A melt tank is arranged at the bottom of the melting furnace. A plurality of natural gas nozzles distributed in a circular array are arranged on the outside of the melting section. The natural gas nozzles are inclined downward and eccentrically arranged. A flue gas pipe and a feed port are arranged at the upper part of the melting furnace.

[0017] Among them, fly ash solidification material, quartz stone, and alumina enter from the upper part of the oxygen-enriched melting furnace through the feeding system, and enter the bottom of the final oxygen-enriched melting furnace downward by gravity. During this period, the raw materials can be preheated to remove moisture. Natural gas and oxygen-enriched air enter from the oxygen-enriched melting furnace at a temperature range of 1350-1600℃ through a closed heat-resistant pipeline. By adjusting the intake of natural gas and oxygen, it is ensured that oxygen-enriched combustion is carried out and the temperature is guaranteed. In this temperature range, calcium carbonate and magnesium carbonate can form calcium oxide, magnesium oxide, etc.

[0018] CaCO3 CaO+CO2↑ MgCO3 MgO+CO2↑ The heat of oxygen-enriched combustion using natural gas and oxygen-enriched air is used to heat the material in the melting furnace to 1350-1600°C, and the material forms a liquid substance. The liquid substance drips to the lower layer of 1600-1650°C due to gravity, and the liquid fluid is further stratified and is in a solid-liquid coexistence state. The melt flows into the subsequent centrifuge from the liquid outlet trough at the bottom of the furnace body, and the material enters the oxygen-enriched melting furnace in batches, about 10-15 batches / h, and the material stays in the furnace for about 1h. The molten flue gas generated in the melting furnace is sent to the subsequent flue gas purification system for treatment and then discharged; the chloride salts (sodium chloride, potassium chloride, calcium chloride, magnesium chloride) generated in the melting furnace are gathered in the temperature range of 1350-1600°C, and are discharged together with the slag liquid after high-temperature gasification, and are discharged with the liquid outlet trough. An exhaust device is set above the liquid outlet trough to inhale the chloride salt vapor into the chloride salt recovery device for cooling and recovery. In this step, molten waste gas (including liquid waste gas) G4, alloy slag S1, and crystallized salt S2 are generated.

[0019] Among them, silicon dioxide is the most important component of glass. It plays the role of a glass network structure former in the glass structure and is the main former of the [SiO4] tetrahedral structure. Al2O3 and MgO act as network intermediates in the glass structure and sometimes also play a role in strengthening the network skeleton strength. CaO is generally used as a network modifier of the glass structure to make the glass network skeleton loose. The melting and boiling points of the main components in fly ash (since fly ash is a mixture, the actual melting and boiling points will be lower than the values ​​in the following table) further determine the whereabouts of the main components in fly ash, see Table 1 for details.

[0020] Table 1 - Melting and boiling points and destinations of main components in fly ash 6) Fiber forming system: The high-temperature melt flows into the centrifuge through the liquid outlet tank. The melt flowing into the centrifuge is cooled and drawn into fibers under the combined action of the centrifugal force of the centrifugal roller and the high-speed airflow ejected by the wind ring. In the cotton collecting pendulum section, centrifugation is mainly carried out by wind force. The bottom of the centrifuge will produce some centrifugal waste slag S3 formed by excessive cooling. The main component is still the melt, which is recycled after returning to the feeding process; 7) Cotton collection pendulum section: The fibers sent into the fiber forming system are collected by the triangular mesh belt cotton collection method. The initial cotton felt is formed on the surface of the high-speed cotton collection mesh plate under the combined action of the centrifuge, wind ring blowing and cotton collector exhaust. The square meter weight of the initial cotton felt is adjusted by changing the speed of the cotton collection drum to meet the product requirements. The initial cotton felt formed on the cotton collection mesh plate is sent to the pendulum cotton spreading machine via a belt conveyor. The initial cotton felt is laid on the forming conveyor into a multi-layer folded secondary cotton felt layer under the reciprocating swing of the pendulum belt. The pendulum felt laying makes the cotton felt of the product more uniform and ensures the uniformity of the density of the product in the horizontal and vertical directions. The cotton collection process of the project mainly produces fiber-type G5 dust pollutants, which are discharged through a 35m high P5 exhaust pipe after being treated in the matching negative pressure filter chamber.

[0021] 8) Molding and cutting: The rock wool after the cotton collecting pendulum is extruded and molded by the collecting and molding device and enters the cutting process. The cutting section is equipped with a longitudinal saw, and the spacing can be adjusted according to the product specifications. The control in the length direction is completed by a cross-cutting saw and an automatic length measurement controller. In order to adapt to the cutting of products with different bulk densities, this cutting section is equipped with a cross-cutting conveyor and a cross-cutting guillotine. The former is suitable for high bulk density products, and the latter is suitable for low bulk density products. This project generates dust during the cutting process of rock wool. A gas collection hood is installed above the cutting machine to collect the exhaust gas G6 and the cotton collecting pendulum exhaust gas G5. It is treated by a bag dust collector and discharged through a 35m high P5 exhaust pipe. Uncollected exhaust gas is discharged in an unorganized form.

[0022] Waste scraps will be generated during the cutting process. Subsequently, the scraps cut off by the longitudinal saw will be crushed through the scrap recovery system and sent to the cotton collector for reuse using wind power.

[0023] 9) Packaging: Rock wool products are automatically packed by packaging machines and then put into storage; 10) Flue gas treatment: The flue gas generated in step 5) is treated at the same time, and the chloride salt in the flue gas is discharged through the exhaust port of the melting furnace. The temperature of the exhaust port will cause the chloride to form fine particles. After the flue gas enters the flue gas purification system for treatment, it is discharged into the waste salt collection bin for collection; When the temperature of the garbage fly ash in the melting furnace reaches 450°C, the chlorine element in the fly ash begins to play a role, causing the melting furnace to continue to rise. When the temperature reaches above 830°C, the chloride will be gasified. When the combustion temperature of the melting furnace reaches above 1500°C, all the chloride salts are volatilized, the exhaust port temperature is 200-250°C, and the flue gas temperature drops below 400°C. The chloride forms fine particles, which are discharged into the waste salt collection bin for collection after entering the cyclone dust collector and ceramic filter high-temperature dust collector for treatment along with the flue gas; 11) Discharge the chlorine salt and fly ash in the waste salt collection bin into the dissolution tank, and add fresh water to the dissolution tank. The dissolution tank is used to store washing wastewater and has a homogenizing function. The wastewater in the dissolution tank is introduced into the plate and frame filter press equipment, and the plate and frame filter press is used to separate and remove the fly ash, impurities, heavy metals, etc. that are insoluble in water, to produce sludge; 12) The wastewater is then introduced into a high-density sedimentation tank, and PAM and heavy metal scavengers are added to the high-density sedimentation tank. The (organic sulfur) heavy metal scavenger is added to directly react with most of the heavy metals in the wastewater to form precipitation and remove the heavy metals in the wastewater. Polyacrylamide (PAM) shortens the reaction and sedimentation time; 13) The treated wastewater is led to another sedimentation tank, and sodium carbonate is added to the sedimentation tank to make the Ca2+ in the ash washing wastewater react with it to form calcium carbonate precipitation. A large amount of HCO3-, OH- and CO32- are produced during the hydrolysis process, which increases the alkalinity in the system. The Ca2+ contained in the water washing liquid reacts with CO32- to form CaCO3 precipitation. The wastewater in the sedimentation tank is led to the filter, so that the filter removes the residual particles in the wastewater that cannot be settled; 14) Introduce the washing wastewater into the mechanical vapor recompression (MVR) evaporator, adopt the principle of "high temperature sodium precipitation, mother liquor circulation", and use MVR evaporation technology to extract NaCl and KCl. The material concentrated by the MVR evaporator produces sodium chloride crystals and potassium chloride crystals in the separator; 15) The precipitated crystal salt settles to the bottom of the separator and is discharged to the centrifuge. The obtained supernatant is sent to the washing section. Since the raw materials contain a certain amount of impurities, it is necessary to discharge a small amount of flash crystallization mother liquor to the impurity salt evaporator for separate evaporation to produce a small amount of impurity salt to ensure the purity of the final sodium chloride and potassium chloride crystal salt.

[0024] Among them, the cyclone dust collector, also known as the cyclone separator, is composed of an air inlet pipe, an exhaust pipe, a cylinder, a cone and an ash discharge valve. Among mechanical dust collectors, the cyclone dust collector is the most efficient one. It is suitable for the removal of non-sticky and non-fibrous dust, mostly used to remove particles larger than 20μm. It is a medium-efficiency dust collector and can be used for the purification of high-temperature flue gas. It is a widely used dust collector that can be used for boiler flue gas dust removal, multi-stage dust removal and pre-dust removal. The dust removal efficiency for dust particles with a diameter of >20μm can reach more than 80%; the filtration accuracy of the ceramic filter high-temperature dust collector is 0.3um, which can achieve 5mg / Nm 3 To meet the needs of ultra-clean emissions, the dust removal efficiency is as high as 99.9%, achieving near-zero emission requirements. It is widely used in high-temperature dust removal in cement kilns, glass kilns, ceramic kilns, chemical plants and other industries.

[0025] The principle of the mechanical vapor recompression (MVR) evaporator is to use a high-efficiency steam compressor to compress the secondary steam generated by evaporation, convert electrical energy into thermal energy, increase the enthalpy of the secondary steam, and pump the secondary steam with increased thermal energy into the evaporation chamber for heating to achieve the recycling of the existing thermal energy of the secondary steam, so that the purpose of evaporation and concentration can be achieved through the self-circulation of the evaporator without the need for external fresh steam. The system temperature, pressure, motor speed, and system evaporation balance are controlled through PLC, industrial computer (FA), configuration, etc.

[0026] The beneficial effects of the present invention are as follows: fly ash can be briquette to form fly ash solidified material, which is mixed with quartz stone and alumina and put into a high-temperature melting furnace for heating. The melt is discharged into a centrifuge through a liquid outlet trough. Under the combined action of the centrifugal force of the centrifuge and the high-speed airflow ejected by the wind ring, the liquid melt is cooled and stretched into fibers. The fibers fed into the fiber forming system are collected by a triangular mesh belt cotton collection method. Under the combined action of the centrifuge, the wind ring blowing and the cotton collector exhaust, primary cotton felt is formed on the surface of the high-speed cotton collecting mesh plate. The primary cotton felt formed on the cotton collecting mesh plate is sent to the pendulum cotton spreading machine via a belt conveyor. Under the reciprocating swing of the pendulum belt, the primary cotton felt is laid on the shaping conveyor into a multi-layer folded secondary cotton felt layer. The rock wool after the cotton collecting pendulum is extruded and formed by a collecting and forming device and enters the cutting process. The cut rock wool products are then automatically packaged by a packaging machine and put into storage.

[0027] During the high-temperature incineration process of fly ash, organic chlorine (generally insoluble chlorine) will be completely converted into hydrogen chloride gas. Inorganic chlorine (generally soluble chlorine) will be partially converted into hydrogen chloride and partially exist in the form of chloride due to its strong bond energy. Hydrogen chloride and chloride can promote the volatilization of heavy metals at high temperatures. Therefore, high-temperature heat treatment of fly ash can make full use of the high chlorine and heavy metal content of fly ash, and volatilize heavy metals and chlorine synergistically into the flue gas, and finally be captured in the concentrated ash. This can not only achieve the purpose of dechlorination and heavy metal removal of fly ash, but also provide technical conditions for the enrichment and recovery of soluble salts and heavy metals.

[0028] Therefore, high-temperature heat treatment of fly ash can make full use of the high chlorine and heavy metal content of fly ash, and volatilize heavy metals and chlorine into flue gas, and finally capture them in concentrated ash. Then, "water washing + water washing liquid pretreatment (heavy metal capture + decalcification + filtration) + evaporation crystallization" is used to remove the chloride salts and some heavy metals in the water washing liquid. Dioxins are stable in nature, slightly soluble in most organic solvents, and extremely difficult to dissolve in water. They are also resistant to acids, alkalis, oxidants and reductants. Adding heavy metal capture agents and PAM in the water washing process will have little effect on the polarity of water and will not affect the solubility of dioxins in water. Therefore, this process will not have a significant elution effect on dioxins in fly ash, and the amount of dioxins entering the water washing liquid is also very small. Dioxins in the water washing liquid are mainly attached to suspended matter in the water. In the water washing wastewater treatment process, filters are used to remove suspended matter in the water. After treatment, the wastewater enters the MVR evaporation treatment to effectively control the content of dioxins in the crystallized salt. After the water washing liquid is treated, it is evaporated and crystallized to obtain sodium chloride crystal salt, potassium chloride crystal salt and waste salt residue.

[0029] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for preparing rock wool by high-temperature melting of fly ash without water washing, characterized in that: The following steps are involved: 1) Fly ash unloading: After entering the site, the fly ash is stored in the raw material silo (vertical). The fly ash is directly transported from the waste-producing unit to the project site by a special closed tank truck, and the fly ash in the tank is transported to the fly ash special raw material silo (vertical) on site by air transportation in a closed pipeline; 2) Fly ash batching: Due to the differences in the composition of fly ash in different batches, it is necessary to mix the fly ash according to its characteristics. The fly ash in the silo is pneumatically transported to the fly ash batching silo; 3) Raw material briquetting: fly ash is transported from the raw material silo to the closed mixer by means of spiral feeding through a closed pipeline. After uniform mixing, it is pressed into a cylindrical block with a diameter of about 10 mm by a raw material briquetting machine to form fly ash solidified material. The vibrating screen under the raw material briquetting machine screens the fine particles. The screened small particles are re-briquetted by the elevator back-pressing briquetting device. The pressed fly ash solidified material enters the feeding system (silo); 4) Feeding: Quartz stone and alumina are crushed and sieved into solid particles of 10-40mm, which enter the feeding system (silo) through a closed conveyor. After the proportion is adjusted by a metering device, they are transported into the high-temperature melting furnace in batches by a feeding elevator; 5) High temperature melting: Fly ash contains a large amount of oxides such as silicon dioxide, calcium oxide, aluminum oxide, magnesium oxide, potassium oxide, sodium oxide, etc. By adding quartz and aluminum oxide, the ratio of SiO2-Al2O3-(CaO+MgO+Na2O+K2O) is adjusted to increase the dynamic fluidity of fly ash in the melting furnace, and promote the slag to be in a solid-liquid coexistence state in a wider temperature range. The heat of oxygen-enriched combustion using natural gas and oxygen-enriched air is used to heat the materials in the melting furnace to 1350-1600℃, and the materials form liquid substances. The liquid substances drip to the lower layer of 1600-1650℃ due to gravity, and the liquid fluid is further stratified and in a In the solid-liquid coexistence state, the melt flows into the subsequent centrifuge from the liquid outlet tank at the bottom of the furnace body, and the materials enter the oxygen-enriched melting furnace in batches, about 10-15 batches / h, and the material stays in the furnace for about 1h. The molten flue gas generated in the melting furnace is sent to the subsequent flue gas purification system for treatment and then discharged; the chloride salts (sodium chloride, potassium chloride, calcium chloride, magnesium chloride) generated in the melting furnace gather in the temperature range of 1350-1600℃, and are discharged together with the slag liquid after high-temperature gasification, and discharged with the liquid outlet tank. The exhaust device is set above the liquid outlet tank to inhale the chloride salt vapor into the chloride salt recovery device for cooling and recovery. In this step, molten waste gas (including liquid waste gas) G4, alloy slag S1, and crystallized salt S2 are generated; 6) Fiber forming system: The high-temperature melt flows into the centrifuge through the liquid outlet tank. The melt flowing into the centrifuge is cooled and drawn into fibers under the combined action of the centrifugal force of the centrifugal roller and the high-speed airflow ejected by the wind ring. In the cotton collecting pendulum section, centrifugation is mainly carried out by wind force. The bottom of the centrifuge will produce some centrifugal waste slag S3 formed by excessive cooling. The main component is still the melt, which is recycled after returning to the feeding process; 7) Cotton collecting pendulum section: The fibers fed into the fiber forming system are collected by means of triangular mesh belt collection. Primary cotton felt is formed on the surface of the high-speed cotton collecting mesh plate under the combined action of the centrifuge, air ring blowing and cotton collector exhaust. The square meter weight of the primary cotton felt is adjusted by changing the speed of the cotton collecting drum to meet the product requirements. The primary cotton felt formed on the cotton collecting mesh plate is sent to the pendulum cotton spreading machine via a belt conveyor. The primary cotton felt is laid on the forming conveyor into a multi-layer folded secondary cotton felt layer under the reciprocating swing of the pendulum belt; 8) Molding and cutting: The rock wool after the cotton collecting pendulum is extruded and formed by the collecting and molding device, and then enters the cutting process. The cutting section is equipped with a longitudinal saw, and the spacing can be adjusted according to the product specifications. The length direction is controlled by a cross-cutting saw and an automatic length measuring controller. In order to adapt to the cutting of products with different bulk densities, this cutting section is equipped with a cross-cutting conveyor and a cross-cutting guillotine. The former is suitable for high bulk density products, and the latter is suitable for low bulk density products. 9) Packaging: Rock wool products are automatically packed by packaging machines and then put into storage; 10) Flue gas treatment: The flue gas generated in step 5) is treated at the same time, and the chloride salt in the flue gas is discharged through the exhaust port of the melting furnace. The temperature of the exhaust port will cause the chloride to form fine particles. After the flue gas enters the flue gas purification system for treatment, it is discharged into the waste salt collection bin for collection; 11) Discharge the chloride salt and fly ash in the waste salt collection bin into the dissolution tank, add fresh water to the dissolution tank, introduce the wastewater in the dissolution tank into the plate and frame filter press equipment, and use the plate and frame filter press to separate and remove the fly ash, impurities, heavy metals, etc. that are insoluble in water to produce sludge; 12) The wastewater is then introduced into a high-density sedimentation tank, and PAM and heavy metal scavengers are added to the high-density sedimentation tank. The (organic sulfur) heavy metal scavenger is added to directly react with most of the heavy metals in the wastewater to form precipitation and remove the heavy metals in the wastewater. Polyacrylamide (PAM) shortens the reaction and sedimentation time; 13) The treated wastewater is led to another sedimentation tank, and sodium carbonate is added to the sedimentation tank to make the Ca2+ in the ash washing wastewater react with it to form calcium carbonate precipitation. A large amount of HCO3-, OH- and CO32- are produced during the hydrolysis process, which increases the alkalinity in the system. The Ca2+ contained in the water washing liquid reacts with CO32- to form CaCO3 precipitation. The wastewater in the sedimentation tank is led to the filter, so that the filter removes the residual particles in the wastewater that cannot be settled; 14) Introduce the washing wastewater into the mechanical vapor recompression (MVR) evaporator, adopt the principle of "high temperature sodium precipitation, mother liquor circulation", and use MVR evaporation technology to extract NaCl and KCl. The material concentrated by the MVR evaporator produces sodium chloride crystals and potassium chloride crystals in the separator; 15) The precipitated crystal salt settles to the bottom of the separator and is discharged to the centrifuge. The obtained supernatant is sent to the washing section. Since the raw materials contain a certain amount of impurities, it is necessary to discharge a small amount of flash crystallization mother liquor to the impurity salt evaporator for separate evaporation to produce a small amount of impurity salt to ensure the purity of the final sodium chloride and potassium chloride crystal salt.

2. The process for preparing rock wool by high-temperature melting of fly ash without water washing according to claim 1, characterized in that: The step 1) generates fly ash loading and unloading waste gas G1, which is discharged after being treated by bag dust removal, and the fly ash is collected by bags and returned to the fly ash silo. The batching process in the step 2) generates batching waste gas G2, which is discharged after being treated by bags, and the fly ash is collected by bags and returned to the fly ash silo. The step 3) generates briquetting waste gas G3, which is discharged after being treated by bags, and the fly ash is collected by bags and returned to the fly ash silo. The step 7) mainly generates fiber-type G5 dust pollutants during the cotton collection process, and the dust is discharged through a 35m high P5 exhaust pipe after being treated in a matching negative pressure filter chamber. In the step 8), dust is generated during the cutting process of rock wool, and a gas collection hood is installed above the cutting machine to collect waste gas G6 and the cotton collecting pendulum waste gas G5, which are treated by bag dust collectors and discharged through a 35m high P5 exhaust pipe. Uncollected waste gas is discharged in an unorganized form.

3. The process for preparing rock wool by high-temperature melting of fly ash without water washing according to claim 1, characterized in that: In the step 8), waste scraps will be generated during the cutting process. Subsequently, the scraps cut by the longitudinal saw will be crushed by the scrap recovery system and sent to the cotton collector by wind power for reuse.

4. The process for preparing rock wool by high-temperature melting of fly ash without water washing according to claim 1, characterized in that: In step 3), the fly ash is in granular form and contains 36% calcium oxide. The fly ash and sodium silicate solution are mixed, stirred and briquette-pressed in a ratio of 20:

3.

5. The process for preparing rock wool by high-temperature melting of fly ash without water washing according to claim 1, characterized in that: In the step 5), the lower part of the oxygen-enriched melting furnace is the melting section, a melt tank is arranged at the bottom of the melting furnace, a plurality of natural gas nozzles distributed in a circular array are arranged on the outside of the melting section, the natural gas nozzles are inclined downward and arranged off-center, a flue gas pipe and a feed port are arranged at the upper part of the melting furnace, and fly ash solidification material, quartz stone and alumina enter from the upper part of the oxygen-enriched melting furnace through the feeding system, and enter the bottom of the final oxygen-enriched melting furnace downward by gravity, during which the raw materials can be preheated to remove moisture therein.

6. The process for preparing rock wool by high-temperature melting of fly ash without water washing according to claim 5, characterized in that: The oxygen-enriched melting furnace uses natural gas and oxygen-enriched air to enter the oxygen-enriched melting furnace through a closed heat-resistant pipe at a temperature range of 1350-1600°C. The oxygen-enriched combustion is ensured by adjusting the natural gas and oxygen intake to ensure the temperature. In this temperature range, calcium carbonate and magnesium carbonate can form calcium oxide, magnesium oxide, etc.

7. The process for preparing rock wool by high-temperature melting of fly ash without water washing according to claim 1, characterized in that: In the step 10), when the temperature of the garbage fly ash in the melting furnace reaches 450°C, the chlorine element in the fly ash begins to function, causing the melting furnace to continue to rise. When the temperature reaches above 830°C, the chloride will be gasified. When the combustion temperature of the melting furnace reaches above 1500°C, all the chloride salts are volatilized, the exhaust port temperature is 200-250°C, the flue gas temperature drops below 400°C, and the chloride forms fine particles.

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