CN107399745B - Sodium cyanide powder production system and production method - Google Patents
Sodium cyanide powder production system and production method Download PDFInfo
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- CN107399745B CN107399745B CN201710724005.2A CN201710724005A CN107399745B CN 107399745 B CN107399745 B CN 107399745B CN 201710724005 A CN201710724005 A CN 201710724005A CN 107399745 B CN107399745 B CN 107399745B
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Abstract
The invention discloses a sodium cyanide powder production system and a production method, wherein the production system comprises a reactor, a reactor discharge pump, a reactor cooler, an evaporative crystallization system, a centrifugal separator, a flash evaporation dryer, a cyclone separator and a forming and packaging system, and is characterized in that: the evaporative crystallization system includes the evaporimeter, the evaporimeter condenser, the evaporimeter circulating pump, crystallizer and underflow pump, the reactor sets up hydrocyanic acid feed inlet and sodium hydroxide feed inlet, the reactor passes through the reactor discharge pump respectively with the reactor cooler, the top absorption section and the evaporimeter intercommunication of reactor, the upper end mother liquor circulation import intercommunication of reactor cooler and reactor, evaporimeter and crystallizer intercommunication, the crystallizer passes through underflow pump and centrifuge intercommunication, centrifuge and flash dryer intercommunication, flash dryer and cyclone intercommunication, cyclone and shaping packaging system intercommunication, the advantage is: simple and reasonable structure, and ensures the safe, continuous and efficient industrial production of the sodium cyanide powder.
Description
Technical Field
The invention relates to the field of sodium cyanide preparation, in particular to a sodium cyanide powder production system and a sodium cyanide powder production method.
Background
The sodium cyanide product has wide application, is mainly used in the fields of refining of precious metals and rare metals, chemical synthesis, pesticides, medicines, electroplating industry and the like, and has two types of solid and liquid. The prior process method for producing the sodium cyanide product mainly comprises the following steps: the sodium ammonia method, the cyanide melt method, the anderon method, the methanol ammonia oxidation method, the acrylonitrile byproduct method and the light oil cracking method, wherein the sodium ammonia method and the cyanide melt method are eliminated by the national regulation. The process for producing sodium cyanide by the acrylonitrile by-product method is approximately the same: the byproduct hydrocyanic acid of an acrylonitrile device is neutralized and reacted with sodium hydroxide to obtain liquid sodium cyanide solution, and then the sodium cyanide product is produced through the working procedures of evaporation, crystallization, separation, drying and the like.
However, under the conditions of heating, air contact or moisture, sodium cyanide produces highly toxic and flammable hydrogen cyanide gas, so that the sodium cyanide product is deteriorated, and the technological processes of synthesis, evaporative crystallization, separation, drying, molding and the like of the sodium cyanide product are difficult. The existing industrial sodium cyanide production system has less research, the equipment structure in most production systems is more complex, and the loss of sodium cyanide products is more.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides the sodium cyanide powder production system and the production method, which have simple and reasonable structure and process and can ensure safe, continuous and efficient industrial production of the sodium cyanide powder.
The technical scheme adopted by the invention for solving the technical problems is as follows: a sodium cyanide powder production system, which comprises a reactor, a reactor discharge pump, a reactor cooler, at least one evaporative crystallization system, a centrifugal separator, a flash evaporation dryer, a cyclone separator and a forming and packaging system, the evaporative crystallization system comprises an evaporator, an evaporator condenser, an evaporator circulating pump, a crystallizer and a thick slurry pump, the reactor is provided with a hydrocyanic acid feed inlet and a sodium hydroxide feed inlet, a material outlet of the reactor is respectively communicated with a material inlet of the reactor cooler, an upper absorption section of the reactor and a lower material inlet of the evaporator through the reactor discharge pump, the material outlet of the reactor cooler is communicated with the mother liquor circulating inlet at the upper end of the reactor, a material outlet at the bottom end of the evaporator is communicated with a material inlet at the upper end of the crystallizer, a gas outlet at the top end of the evaporator is communicated with a gas inlet of the evaporator condenser, the upper clear liquid outlet of the crystallizer is communicated with the adjusting groove, the middle layer liquid outlet of the crystallizer is communicated with the material inlet of the evaporator through the evaporator circulating pump, the lower layer thick slurry of the crystallizer is conveyed to a material inlet of the centrifugal separator through the thick slurry pump, the material outlet of the centrifugal separator is communicated with the material inlet of the flash dryer, the bottom of the flash dryer is provided with a communicated crusher, the top material outlet of the flash evaporation dryer is communicated with the material inlet of the cyclone separator, and a material outlet at the bottom end of the cyclone separator is communicated with a material inlet of the forming and packaging system through a screw conveyor.
The evaporative crystallization system also comprises a water ring vacuum pump which is connected with the evaporator and is used for maintaining the vacuum degree in the evaporator. The evaporation water quantity can be adjusted only by changing the pressure regulating valve of the water ring vacuum pump, so that the concentration of the sodium cyanide slurry is controlled, and the water ring vacuum pump is simple in structure, small in occupied area, easy to maintain, low in energy consumption and less in discharge capacity.
The shaping packaging system include charging means, make-up machine, shale shaker, cooling feed bin and measurement packagine machine, cyclone's bottom material export pass through screw conveyer with the material import intercommunication of charging means, the material export of charging means with the material import intercommunication of make-up machine, the material export of make-up machine with the material import intercommunication of shale shaker, the material export of shale shaker with the top material import intercommunication of cooling feed bin, first crushed aggregates export of shale shaker pass through hoist mechanism with the material import intercommunication of charging means, the bottom material export of cooling feed bin with measurement packagine machine intercommunication.
The device comprises a dissolving and recovering system, wherein a mother liquor outlet of the centrifugal separator is communicated with a material inlet of the dissolving and recovering system, and a second crushed material outlet of the vibrating screen is communicated with the material inlet of the dissolving and recovering system. Therefore, the recovery rate of the sodium cyanide can be improved, and the waste is reduced.
The centrifugal separator adopts a reciprocating type centrifugal separator. Thereby, continuous feeding and discharging can be realized, the feeding and discharging amount is completely controlled by the feeding valve, and the cleaning time and unnecessary product loss are reduced.
The reactor is externally provided with a cooling heat exchange device, and the flash dryer is internally provided with a plurality of layers of rotational flow sheets. Thereby further cooling the reactor and removing the reaction heat; and the multilayer vortex sheets can form a stable fluidized bed, and meanwhile, the vortex sheets also play a role in ensuring the retention time and classification necessary for drying.
A method for producing sodium cyanide powder comprises the following steps:
(1) liquid hydrocyanic acid is respectively and continuously fed into a reactor according to the flow rate of 1-1.8 m/s and the flow rate of 30-60 percent of sodium hydroxide solution according to the flow rate of 1.2-1.5 m/s, and the liquid hydrocyanic acid and the sodium hydroxide solution are mixed to complete neutralization reaction, so as to obtain sodium cyanide reaction liquid, wherein the operating pressure in the reactor is normal pressure, the filling gas is inert gas, the temperature in the reactor is kept at 30-60 ℃, the height of the reaction liquid level in the reactor is kept at 65-85 percent, and the concentration of the sodium hydroxide in the reaction liquid is 0.5-5 percent;
(2) extracting a part of sodium cyanide reaction liquid from a reactor by using a reactor discharge pump according to the flow of 35-75 t/h, keeping the flow velocity of 1-8 m/s in the reactor, and respectively and circularly conveying the part of sodium cyanide reaction liquid to an absorption section of the reactor, a cooler of the reactor and an evaporator, wherein the cooler of the reactor is used for cooling the sodium cyanide reaction liquid and then conveying the cooled sodium cyanide reaction liquid to the reactor again to serve as reaction mother liquid, the circulating flow of the absorption section of the reactor is 10-35 t/h, and the circulating flow of the reaction mother liquid is 10-45 t/h;
(3) feeding the sodium cyanide reaction solution conveyed in the step (2) from a material inlet at the lower end of an evaporator, introducing steam into a heating cylinder of the evaporator, carrying out vacuum evaporation on the sodium cyanide reaction solution to remove moisture, obtaining a gas phase and a sodium cyanide concentrated solution, allowing the sodium cyanide concentrated solution to fall into a crystallizer from a material outlet at the bottom end of the evaporator, allowing the gas phase to enter an evaporator condenser from a gas phase outlet at the top end of the evaporator, pumping noncondensable gas in the evaporator condenser to a waste gas treatment system by a vacuum pump, wherein the evaporation pressure in the evaporator is kept to be 25-40 mmHg by a water ring vacuum pump, the evaporation temperature is 30-50 ℃, and the amount of evaporated water is 2000-2800 kg/h;
(4) after the sodium cyanide concentrated solution stays in a crystallizer for 1-10 hours, the sodium cyanide concentrated solution is layered into supernatant liquid, middle-layer microparticle solution and lower-layer thick slurry, the supernatant liquid overflows to an adjusting tank, the middle-layer microparticle solution returns to an evaporator from a material inlet of the evaporator through an evaporator circulating pump to serve as a crystal nucleus, the crystal nucleus circulates by the way to keep the supersaturation of sodium cyanide reaction solution in the evaporator, and the lower-layer thick slurry is output through a thick slurry pump, wherein the crystallization temperature is 30-50 ℃, and the main components of the thick slurry comprise 8-18% of sodium cyanide crystals, 30-45% of sodium cyanide solution and 40-50% of water;
(5) thickening the thick slurry, sending the thickened slurry into a centrifugal separator, separating the thickened slurry into wet crystals and separated mother liquor, conveying the wet crystals to a flash evaporation dryer through a screw conveyor, wherein the centrifugal temperature is 30-45 ℃, and the moisture content of the wet crystals is 5-10 wt%;
(6) heating air to 185 ℃ or higher, introducing the air from the lower part of the flash dryer, forming high-speed rotating hot air flow from bottom to top, rapidly drying smaller wet crystals in the flash dryer to obtain dry powder, discharging the dry powder from the top end to a cyclone separator, enabling the larger wet crystals to fall into a crusher at the bottom of the flash dryer, crushing the dry powder, rotating and rising along with the hot air flow, drying the crushed dry powder, and discharging the dry powder from the top end to the cyclone separator, wherein the drying temperature is 45-70 ℃, and the moisture content of the dry powder is less than or equal to 0.9wt%;
(7) and separating the dried powder by a cyclone separator to obtain sodium cyanide powder.
And (3) conveying the sodium cyanide powder obtained in the step (7) to a feeder through a screw conveyor, then conveying the sodium cyanide powder to a forming machine for pressing to obtain a tablet mixture comprising formed tablets and crushed aggregates, conveying the tablet mixture to a vibrating screen, recycling the crushed aggregates to the feeder through a first crushed aggregate outlet of the vibrating screen by a lifting mechanism for pressing again, and allowing the formed tablets to fall into a cooling bin through a material outlet of the vibrating screen for cooling and then enter a metering packaging machine to obtain a sodium cyanide product.
And (3) conveying the tablet mixture to a vibrating screen, conveying the blocks to a dissolving and recycling system through a second crushed material outlet of the vibrating screen, and conveying the separated mother liquor obtained in the step (5) to the dissolving and recycling system through a gas-liquid separator.
Monitoring hydrocyanic acid flow, sodium hydroxide flow, circulating flow of an absorption section of a reactor, circulating flow of reaction mother liquor, circulating flow in the reactor and pressure in the reactor in real time, and closing a hydrocyanic acid feeding valve if monitoring that abnormality occurs; and monitoring the temperature and pressure in the flash dryer, the material level of the cyclone separator and the material level of the feeder in real time, monitoring the working states of the spiral conveyor, the feeder and the forming machine in real time, and stopping the feeding of the centrifugal separator if monitoring that the abnormality occurs.
Compared with the prior art, the invention has the advantages that: the whole production system has simple and compact structure, the production process is greatly simplified, and the energy is saved and the efficiency is high; in the reaction stage, the reaction is always carried out under the alkaline condition, so that the hydrocyanic acid can be effectively prevented from self-polymerization; a water ring vacuum pump is adopted in the evaporative crystallization system to maintain the vacuum degree required by evaporation, so that the whole structure is compact, the energy consumption is low, and the discharge capacity is small; the dissolving and recovering system is arranged to reduce material waste, and the reaction can be stopped or the centrifugal feeding can be stopped in time when the reaction system and the centrifugal feeding system are abnormal through the interlocking loop arranged, so that the production safety is ensured, the material waste is reduced, and the industrial production is facilitated.
Drawings
FIG. 1 is a flow chart of an apparatus for producing NaCN powder according to the present invention.
The system comprises a reactor 1, a reactor discharge pump 2, a reactor cooler 3, an evaporator 4, an evaporator condenser 5, an evaporator circulating pump 6, a crystallizer 7, a thick slurry pump 8, a centrifugal separator 9, a flash dryer 10, a cyclone separator 11, a feeder 12, a forming machine 13, a vibrating screen 14, a cooling bin 15, a metering and packaging machine 16, a reactor absorption section 17, a cyclone 18, a first spiral conveyor 19, an air blower 20, a heater 21, a pulverizer 22, a second spiral conveyor 23, a lifting mechanism 24 and a dissolving and recycling system 25.
Detailed Description
The sodium cyanide powder production system and method of the present invention will be described in further detail with reference to the drawings, but the present invention is not limited thereto.
As shown in fig. 1, a sodium cyanide powder production system mainly comprises a reactor 1, a reactor discharge pump 2, a reactor cooler 3, an evaporator 4, an evaporator condenser 5, an evaporator circulating pump 6, a crystallizer 7, a thick slurry pump 8, a centrifugal separator 9, a flash dryer 10, a cyclone separator 11 and a forming and packaging system.
In the reaction process, the reactor 1 is provided with a hydrocyanic acid feed inlet and a sodium hydroxide feed inlet, a material outlet of the reactor is respectively communicated with a material inlet of the reactor cooler 3, a reactor absorption section 17 at the top of the reactor 1 and a lower material inlet of the evaporator 4 through a reactor discharge pump 2, and a material outlet of the reactor cooler 3 is communicated with an upper mother liquor circulating inlet of the reactor 1. The reactor discharge pump 2 forcibly circulates to maintain a flow rate of 1 to 8m/s in the reactor 1, thereby enabling the reaction raw materials to be sufficiently mixed. After the reaction, sodium cyanide reaction liquid is obtained and is extracted by a reactor discharge pump 2, and a part of the sodium cyanide reaction liquid directly enters a reactor absorption section 17 at the top of the reactor 1 and is used for absorbing unreacted hydrogen cyanide; one part of the reaction product enters from a mother liquor circulating inlet at the upper end of the reactor 1 after being cooled by the reactor cooler 3, and certain reaction heat can be taken away by circulating one part of the mother liquor; the other part of the sodium cyanide reaction solution is sent to the evaporation process. The reactor 1 is also provided with a cooling heat exchange device which can be a cooling coil or a heat exchanger and is used for further cooling and removing reaction heat.
In the evaporative crystallization process, the evaporative crystallization process is two parallel systems so as to adjust the production load more flexibly. The saturated sodium cyanide solution sent from the reaction process enters from the material inlet at the lower end of the two parallel evaporators 4, and the amount of the sodium cyanide entering the two evaporators 4 respectively can be adjusted by adjusting valves according to actual production requirements. The material outlet at the bottom end of the evaporator 4 is communicated with the material inlet at the upper end of the crystallizer 7, the sodium cyanide concentrated solution obtained after evaporation falls into the corresponding crystallizer 7 from the bottom, and the vacuum degree between the crystallizer 7 and the evaporator 4 keeps the potential difference. The top gas outlet of the evaporator 4 is communicated with the gas inlet of the evaporator condenser 5, and the non-condensable gas of the evaporator condenser 5 is pumped to a waste gas treatment system by a vacuum pump. The upper layer clear liquid outlet of the crystallizer 7 is communicated with the adjusting groove, the middle layer liquid outlet of the crystallizer 7 is communicated with the material inlet of the evaporator 4 through an evaporator circulating pump 6, and the lower layer thick slurry of the crystallizer 7 is conveyed to the separation and drying process through a thick slurry pump 8. The evaporative crystallization system further comprises a water ring vacuum pump which is connected with the evaporator 4 and used for keeping the vacuum degree in the evaporator 4, a suction inlet of the water ring vacuum pump is connected with the gas phase of the evaporator 4, and a discharge outlet of the water ring vacuum pump is connected to the waste gas treatment system, so that the evaporation water amount can be adjusted only by changing a pressure regulating valve of the water ring vacuum pump, the concentration of the sodium cyanide slurry is controlled, and the water ring vacuum pump is simple in structure, small in occupied area, easy to maintain, low in energy consumption and less in discharge capacity.
In the separation and drying process, the thick slurry conveyed by the thick slurry pump 8 is thickened by the cyclone 18 and enters the centrifugal separator 9 through the material inlet of the centrifugal separator 9, and the material outlet of the centrifugal separator 9 is communicated with the material inlet of the flash dryer 10 through the first screw conveyor 19. The centrifugal separator 9 employs a reciprocating centrifugal separator, thereby enabling continuous feeding and discharging, the feeding and discharging amounts of which are completely controlled by a feed valve, reducing the washing time and unnecessary product loss. Air sucked by the blower 20 is heated by the heater 21 and then enters from an air inlet below the flash dryer 10, high-speed rotating airflow similar to tornado is formed in the main tower, and the size of the annular gap at the bottom is adjusted according to different natures of sodium cyanide materials, so that the air speed is in a proper state. The heater 21 can be a steam heater or an electric heater according to the actual conditions of the plant and the consideration of the maintenance cost in the early investment and the later period, and the heated air temperature is not lower than 185 ℃. The bottom of the flash dryer 10 is provided with a pulverizer 22 communicated with the flash dryer, and some large wet crystals fall into the pulverizer 22 under the action of gravity to be forcibly pulverized and micronized because the high-speed airflow is insufficient to crush the large wet crystals and rotate at high speed, and then rotate and rise along with the high-speed airflow to finish the drying process. In order to ensure that the final moisture of the material at the drying outlet is extremely low and the product quality is not influenced by the fluctuation of the initial moisture, a plurality of layers of spinning disks are arranged in the flash dryer 10, so that a stable fluidized bed is formed, and meanwhile, the spinning disks also play a role in ensuring the retention time and classification necessary for drying. The top material outlet of the flash dryer 10 is communicated with the material inlet of the cyclone separator 11, the cyclone separator 11 is a II-level cyclone separator 11, the material rotates in a spiral state in the cyclone separator 11, and the finished material flows out of a star-shaped discharge valve at the bottom end and is communicated with the material inlet of the forming and packaging system through a second screw conveyor 23. And a small amount of residual residues enter the waste gas treatment system along with the airflow flowing out from the top end through the induced draft fan. The flash evaporation drying system has the advantages of small system resistance, low energy consumption, low labor intensity and good operating environment.
In the forming and metering packaging process, the forming and packaging system specifically comprises a feeder 12, a forming machine 13, a vibrating screen 14, a cooling bin 15 and a metering packaging machine 16. The material outlet at the bottom end of the cyclone separator 11 is communicated with the material inlet of the feeder 12 through a second screw conveyor 23, the material outlet of the feeder 12 is communicated with the material inlet of the forming machine 13, the material outlet of the forming machine 13 is communicated with the material inlet of the vibrating screen 14, the material outlet of the vibrating screen 14 is communicated with the material inlet at the top end of the cooling bin 15, the first crushed material outlet of the vibrating screen 14 is communicated with the material inlet of the feeder 12 through a lifting mechanism 24, and the material outlet at the bottom end of the cooling bin 15 is communicated with the metering and packaging machine 16.
The embodiment also comprises a dissolving and recovering system 25, the mother liquor outlet of the centrifugal separator 9 is communicated with the material inlet of the dissolving and recovering system 25, and the second crushed material outlet of the vibrating screen 14 is communicated with the material inlet of the dissolving and recovering system 25.
A method for producing sodium cyanide powder comprises the following steps: (1) liquid hydrocyanic acid is respectively and continuously fed into a reactor 1 according to the flow velocity of 1-1.8 m/s and the flow velocity of 1.2-1.5 m/s for the sodium hydroxide solution with the concentration of 30-60 percent, and the liquid hydrocyanic acid is mixed to complete neutralization reaction, so as to obtain sodium cyanide reaction liquid. Wherein the operation pressure in the reactor 1 is normal pressure, the filling gas is inert gas, in this embodiment, nitrogen is used, the temperature in the reactor 1 is maintained at 30-60 ℃, the height of the reaction liquid surface in the reactor 1 is maintained at 65-85%, the concentration of sodium hydroxide in the reaction liquid is 0.5-5%, and the flow rate of the reaction liquid in the reactor 1 is about 2m/s, thereby preventing the danger of self-polymerization caused by hydrocyanic acid feeding amount fluctuation or local over-concentration.
(2) Extracting a part of sodium cyanide reaction liquid from a reactor 1 by using a reactor discharge pump 2 according to the flow of 35-75 t/h, keeping the flow rate of 1-8 m/s in the reactor 1, and respectively circularly conveying the part of sodium cyanide reaction liquid to a reactor absorption section 17, a reactor cooler 3 and an evaporator 4, wherein the reactor cooler 3 cools the sodium cyanide reaction liquid and then conveys the cooled sodium cyanide reaction liquid to the reactor 1 again as reaction mother liquid, the circulating flow of the reactor absorption section 17 is 10-35 t/h, and the circulating flow of the reaction mother liquid is 10-45 t/h.
(3) And (3) allowing the sodium cyanide reaction solution conveyed in the step (2) to enter from a material inlet at the lower end of the evaporator 4, introducing steam into a heating cylinder of the evaporator 4, performing vacuum evaporation on the sodium cyanide reaction solution to remove moisture, obtaining a gas phase and a sodium cyanide concentrated solution, allowing the sodium cyanide concentrated solution to fall into a crystallizer 7 from a material outlet at the bottom end of the evaporator 4, allowing the gas phase to enter an evaporator condenser 5 from a gas phase outlet at the top end of the evaporator 4, and pumping non-condensable gas of the evaporator condenser 5 to a waste gas treatment system by using a vacuum pump. Wherein the evaporation pressure in the evaporator is kept to be 25-40 mmHg by a water ring vacuum pump, the evaporation temperature is 30-50 ℃, and the evaporation water amount is 2000-2800 kg/h.
(4) After the sodium cyanide concentrated solution stays in the crystallizer 7 for 1-10 hours, the sodium cyanide concentrated solution is layered into supernatant liquor, middle-layer micro-particle liquor and lower-layer concentrated slurry, the supernatant liquor overflows to the adjusting tank, the middle-layer micro-particle liquor returns to the evaporator 4 from a material inlet of the evaporator 4 through an evaporator circulating pump 6 to be used as a crystal nucleus, the circulation is carried out, the supersaturation of sodium cyanide reaction solution in the evaporator 4 is kept, and the lower-layer concentrated slurry is output through a slurry pump 8. Wherein the crystallization temperature is 30-50 ℃, the main components of the thick slurry comprise 8-18% of sodium cyanide crystals, 30-45% of sodium cyanide solution and 40-50% of water, the approximate proportion of the materials in the crystallizer is as follows, and the ratio of supernatant liquid to recycled middle microparticle liquid to centrifugal lower thick slurry is = 6: 44: 10.
(5) The thickened slurry is sent into a centrifugal separator 9 after being thickened, the thickened slurry is separated into wet crystals and separated mother liquor, the wet crystals are conveyed to a flash evaporation dryer 10 through a first spiral conveyer 19, and the separated mother liquor is conveyed to a dissolving and recovering system 25 through a gas-liquid separator. Wherein the centrifugal temperature is 30-45 ℃, and the moisture content of the wet crystal is 5-10 wt%.
(6) Heating air to 185 ℃ or higher, introducing the heated air from the lower part of the flash dryer 10, forming high-speed rotating hot air flow from bottom to top, drying the smaller wet crystals in the flash dryer 10 quickly to obtain dry powder, discharging the dry powder from the top end to the cyclone separator 11, allowing the larger wet crystals to fall into the crusher 22 at the bottom of the flash dryer 10, crushing the wet crystals, lifting the crushed crystals along with the hot air flow in a rotating manner, drying the crushed crystals to obtain dry powder, and discharging the dry powder from the top end to the cyclone separator 11. Wherein the drying temperature is 45-70 ℃, and the moisture content of the dried powder is less than or equal to 0.9wt%.
(7) And separating the dried powder by a cyclone separator 11 to obtain sodium cyanide powder.
And (3) conveying the sodium cyanide powder obtained in the step (7) to a feeder 12 through a second screw conveyor 23, then conveying the sodium cyanide powder to a forming machine 13 for pressing to obtain a tablet mixture including formed tablets, blocks and crushed aggregates, conveying the tablet mixture to a vibrating screen 14, recovering the crushed aggregates to the feeder 12 through a first crushed aggregate outlet of the vibrating screen 14 by a lifting mechanism 24 for pressing again, conveying the blocks to a dissolving and recovering system 25 through a second crushed aggregate outlet of the vibrating screen 14, cooling the formed tablets through a material outlet of the vibrating screen 14 into a cooling bin 15, and then conveying the cooled formed tablets to a metering and packaging machine 16 to finally obtain a sodium cyanide product.
In addition, the flow of hydrocyanic acid, the flow of sodium hydroxide, the circulating flow of the absorption section 17 of the reactor, the circulating flow of reaction mother liquor, the circulating flow in the reactor 1 and the pressure in the reactor 1 are monitored in real time in the reaction process, and if the monitoring shows that the abnormality occurs, a hydrocyanic acid feed valve is closed, so that the safe production of sodium cyanide is ensured. In the separation, drying and forming processes, the temperature and pressure in the flash dryer 10, the material level of the cyclone separator 11 and the material level of the feeder 12 are monitored in real time, meanwhile, the working states of the heater 21, the second screw conveyor 23, the feeder 12 and the forming machine 13 are monitored in real time, if the abnormal conditions are monitored, the centrifugal separator 9 is stopped to feed materials, so that material waste is reduced, and after the faults are relieved, the centrifugal separator 9 is recovered to feed materials.
It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and the scope of the present invention is not limited thereby, and the present invention may be modified in materials and structures, or replaced with technical equivalents, in the constructions of the above-mentioned various components. Therefore, all structural equivalents to which the disclosure and drawings pertain, whether direct or indirect, are intended to be covered by the present invention.
Claims (4)
1. A production method of sodium cyanide powder is characterized by comprising the following steps:
(1) liquid hydrocyanic acid is respectively and continuously fed into a reactor according to the flow rate of 1-1.8 m/s and the flow rate of 30-60 percent of sodium hydroxide solution according to the flow rate of 1.2-1.5 m/s, and the liquid hydrocyanic acid and the sodium hydroxide solution are mixed to complete neutralization reaction, so as to obtain sodium cyanide reaction liquid, wherein the operating pressure in the reactor is normal pressure, the filling gas is inert gas, the temperature in the reactor is kept at 30-60 ℃, the height of the reaction liquid level in the reactor is kept at 65-85 percent, and the concentration of the sodium hydroxide in the reaction liquid is 0.5-5 percent;
(2) extracting a part of sodium cyanide reaction liquid from a reactor by using a reactor discharge pump according to the flow of 35-75 t/h, keeping the flow velocity of 1-8 m/s in the reactor, and respectively and circularly conveying the part of sodium cyanide reaction liquid to an absorption section of the reactor, a cooler of the reactor and an evaporator, wherein the cooler of the reactor is used for cooling the sodium cyanide reaction liquid and then conveying the cooled sodium cyanide reaction liquid to the reactor again to serve as reaction mother liquid, the circulating flow of the absorption section of the reactor is 10-35 t/h, and the circulating flow of the reaction mother liquid is 10-45 t/h;
(3) feeding the sodium cyanide reaction solution conveyed in the step (2) from a material inlet at the lower end of an evaporator, introducing steam into a heating cylinder of the evaporator, carrying out vacuum evaporation on the sodium cyanide reaction solution to remove moisture, obtaining a gas phase and a sodium cyanide concentrated solution, allowing the sodium cyanide concentrated solution to fall into a crystallizer from a material outlet at the bottom end of the evaporator, allowing the gas phase to enter an evaporator condenser from a gas phase outlet at the top end of the evaporator, pumping noncondensable gas in the evaporator condenser to a waste gas treatment system by a vacuum pump, wherein the evaporation pressure in the evaporator is kept to be 25-40 mmHg by a water ring vacuum pump, the evaporation temperature is 30-50 ℃, and the amount of evaporated water is 2000-2800 kg/h;
(4) after the sodium cyanide concentrated solution stays in a crystallizer for 1-10 hours, the sodium cyanide concentrated solution is layered into supernatant liquid, middle-layer microparticle solution and lower-layer thick slurry, the supernatant liquid overflows to an adjusting tank, the middle-layer microparticle solution returns to an evaporator from a material inlet of the evaporator through an evaporator circulating pump to serve as a crystal nucleus, the crystal nucleus circulates by the way to keep the supersaturation of sodium cyanide reaction solution in the evaporator, and the lower-layer thick slurry is output through a thick slurry pump, wherein the crystallization temperature is 30-50 ℃, and the main components of the thick slurry comprise 8-18% of sodium cyanide crystals, 30-45% of sodium cyanide solution and 40-50% of water;
(5) thickening the thick slurry, sending the thickened slurry into a centrifugal separator, separating the thickened slurry into wet crystals and separated mother liquor, conveying the wet crystals to a flash evaporation dryer through a screw conveyor, wherein the centrifugal temperature is 30-45 ℃, and the moisture content of the wet crystals is 5-10 wt%;
(6) heating air to 185 ℃ or higher, introducing the air from the lower part of the flash dryer, forming high-speed rotating hot air flow from bottom to top, rapidly drying smaller wet crystals in the flash dryer to obtain dry powder, discharging the dry powder from the top end to a cyclone separator, enabling the larger wet crystals to fall into a crusher at the bottom of the flash dryer, crushing the dry powder, rotating and rising along with the hot air flow, drying the crushed dry powder, and discharging the dry powder from the top end to the cyclone separator, wherein the drying temperature is 45-70 ℃, and the moisture content of the dry powder is less than or equal to 0.9wt%;
(7) and separating the dried powder by a cyclone separator to obtain sodium cyanide powder.
2. The method for producing NaCN powder according to claim 1, wherein the NaCN powder obtained in step (7) is conveyed to a feeder by a screw conveyor and then conveyed to a forming machine for pressing, a tablet mixture comprising formed tablets and crushed aggregates is obtained after pressing, the tablet mixture is conveyed to a vibrating screen, the crushed aggregates are recycled to the feeder by a lifting mechanism through a first crushed aggregate outlet of the vibrating screen for pressing again, the formed tablets fall into a cooling bin through a material outlet of the vibrating screen for cooling and then enter a metering and packaging machine, and a NaCN product is obtained.
3. The method for producing NaCN powder as claimed in claim 2, wherein the tablet mixture comprises lumps, the lumps are transported to a dissolution recovery system through a second crushed material outlet of the vibrating screen after the tablet mixture is transported to the vibrating screen, and the separated mother liquor obtained in step (5) is transported to the dissolution recovery system through a gas-liquid separator.
4. The method for producing sodium cyanide powder according to claim 3, wherein the hydrocyanic acid flow rate, the sodium hydroxide flow rate, the circulation flow rate of the absorption section of the reactor, the circulation flow rate of the reaction mother liquor, the circulation flow rate in the reactor, and the pressure in the reactor are monitored in real time, and if an abnormality is detected, the hydrocyanic acid feed valve is closed; and monitoring the temperature and pressure in the flash dryer, the material level of the cyclone separator and the material level of the feeder in real time, monitoring the working states of the spiral conveyor, the feeder and the forming machine in real time, and stopping the feeding of the centrifugal separator if monitoring that the abnormality occurs.
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| CN111994920B (en) * | 2020-08-31 | 2021-07-23 | 营创三征(营口)精细化工有限公司 | Production method and system of solid sodium cyanide |
| CN114588871A (en) * | 2022-03-16 | 2022-06-07 | 安徽省安庆市曙光化工股份有限公司 | Potassium cyanide production system and production method |
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