CN114835142B - Method for recovering carbon dioxide from industrial kiln tail gas and producing lithium carbonate - Google Patents

Abstract

The invention relates to a method for recovering carbon dioxide from industrial kiln tail gas and producing lithium carbonate. After removing particulate matter from industrial kiln tail gas, denitrification and desulfurization treatment is carried out, and the treated tail gas is pressurized to 0.1-0.7 MPa. Dehydration, and then use the double-tower temperature swing adsorption device to remove NOx and SO ₂ to obtain purified tail gas, pass it into the four-tower pressure swing adsorption device for carbon dioxide separation, and finally pass the obtained carbon dioxide into the lithium hydroxide solution Preparation of lithium carbonate. The present invention utilizes the temperature swing adsorption method to remove trace sulfides and nitrogen oxides in the tail gas, so that the total concentration of _SO2 and NOx in the tail gas is less than 1ppm. The present invention also adopts the pressure swing adsorption method to recover carbon dioxide, and the obtained carbon dioxide gas has high purity and recovery With high efficiency and large processing capacity, the separated and refined high-purity carbon dioxide can be used as raw material in the carbonization process to produce battery-grade lithium carbonate, realizing the resource utilization of carbon dioxide in industrial kiln tail gas.

Description

A method for recovering carbon dioxide from industrial kiln tail gas and producing lithium carbonate

technical field

The invention relates to a method for recovering carbon dioxide from industrial kiln tail gas and producing lithium carbonate, which belongs to the technical field of environmental engineering.

Background technique

Over the past 10 years, the world's CO ₂ emissions have been increasing year by year, leading to excessively high CO ₂ concentrations in the air and an increasingly pronounced greenhouse effect, posing a serious threat to human survival and sustainable socio-economic development; Only by reducing 6 billion tons of CO ₂ emissions can we effectively prevent global climate change. How to control CO ₂ emissions has become a serious problem facing the world.

The fuel of industrial kilns (combustion) is mostly natural gas. The CO ₂ concentration of natural gas kiln flue gas is low (5-15%), the partial pressure is small (0.10-1 bar), the composition is complex, and the CO ₂ capture and recovery efficiency is relatively low. At the same time, CO ₂ needs a _lot of compression energy before transportation and storage, and the energy _consumption and cost of carbon capture are relatively high. CO ₂ emissions are of great significance.

In the prior art, _CO2 recovery and separation technologies mainly include absorption method, cryogenic condensation method, membrane separation method and adsorption method. The low-temperature condensation method is only suitable for working conditions where the _CO2 concentration is higher than 60%. This method requires more equipment, large investment, high energy consumption, and poor separation effect. Simple, easy to operate, low energy consumption, the disadvantage is that pretreatment, dehydration and filtration are often required, and it is difficult to obtain high-purity CO ₂ ; currently CO ₂ recovery and capture mostly use chemical absorption, which can be used in gas When the _CO2 content is low, the concentration of _CO2 after concentration can reach 99.99%, but the investment cost of this process is large, the loss of chemical absorbent is large, the equipment is corroded seriously, and the energy consumption is high, and the cost of separation and recovery is high.

The separation and purification of _CO2 by adsorption method has the advantages of low energy consumption, long service life of adsorbent, simple process flow, high degree of automation, good environmental benefits, and no pollution. The key to the adsorption method lies in the performance of the adsorbent. Low concentration, the performance of the adsorbent is easily affected by nitrogen oxides, sulfides and moisture, etc., resulting in low adsorption capacity of the adsorbent, high cycle treatment costs, and the selectivity of the existing industrially used adsorbents to carbon dioxide is low . Recently, it has been reported that the adsorbents that may be used for the purification and separation of CO ₂ from industrial furnace tail gas are zeolite material-13X molecular sieve and carbon-based material-activated carbon, and other materials have not yet entered the stage of adsorbent commercialization. 13X molecular sieve has strong hydrophilicity, and components such as water, sulfide, and nitride in flue gas have strong competitive adsorption with CO ₂ on its surface, which seriously affects the separation and purification of CO ₂ ; activated carbon is low in sensitivity to moisture, but At low pressure, activated carbon has a lower _CO2 adsorption capacity than zeolite. On the other hand, in the prior art, the research on PSA purification, separation and recovery of CO ₂ is limited to simulated flue gas with few components, while the actual industrial kiln tail gas has complex components and many impurities, so the CO ₂ in industrial kiln tail gas When recycling, we face more challenges and need to conduct research and improvement on the basis of existing technologies.

Contents of the invention

The object of the invention is to solve the above-mentioned deficiencies in the prior art, and a kind of method of reclaiming carbon dioxide and producing Lithium Retard from industrial kiln tail gas is provided.

In order to achieve the above object, the present invention provides the following technical solutions:

A method for reclaiming carbon dioxide and producing lithium carbonate from industrial kiln tail gas, comprising the steps:

(1) Preprocessing:

After the industrial kiln exhaust gas is passed through the cyclone dust collector to remove particulate matter, it is then subjected to denitrification treatment and desulfurization treatment to obtain pretreated exhaust gas;

(2) Adsorption and purification of trace sulfides and nitrogen oxides:

The tail gas pretreated in step (1) is pressurized to 0.1-0.7MPa by a compressor, then enters a water-gas separation tank for dehydration, and then uses a double-tower temperature swing adsorption device to remove NOx and SO ₂ to obtain a purified tail gas ;

The double-tower temperature swing adsorption device includes two adsorption towers, both of which contain adsorbents;

(3) Separation and purification of carbon dioxide:

Pass the purified tail gas into a four-tower pressure swing adsorption device for separation of carbon dioxide. The four-tower pressure swing adsorption device includes four sequentially connected pressure swing adsorption towers, and the four pressure swing adsorption towers are all filled with adsorbents. It is used to absorb CO ₂ in flue gas purification tail gas, and the other components that are not easy to be adsorbed are directly emptied from the top of the tower; finally, the adsorbents in the four pressure swing adsorption towers are desorbed to obtain carbon dioxide gas;

(4) preparation of lithium carbonate:

Pass the carbon dioxide gas obtained in step (3) into the lithium hydroxide solution, stir and mix evenly, when a large amount of solids appear in the solution, stop feeding carbon dioxide gas, raise the temperature to 90-110° C., and keep it warm for 10-60 minutes, Centrifuge while hot to obtain crude lithium carbonate, and after purification, obtain battery-grade lithium carbonate.

Further, in step (1), the denitration treatment adopts a high-temperature SCR process, which is carried out in an SCR denitration catalytic reactor, using ammonia water as a reducing agent, and V ₂ O ₅ -WO ₃ -MoO ₃ /TiO ₂ as a denitration catalyst , The reaction temperature is 300-400°C.

Further, in step (2), the adsorbent is one or a combination of two or more of activated carbon with an iodine value>1000, modified silica gel, modified fly ash, active zeolite or mordenite in any proportion.

Further, in step (2), after the two adsorption towers of the double-tower temperature swing adsorption device are saturated, the temperature is raised to 80-150°C, and hot nitrogen is used to purge and regenerate for 1-20min. The adsorbent can be recycled and used. The gas enters step (1) for denitration treatment and desulfurization treatment.

Further, in step (3), the adsorbent is nitrogen-doped activated carbon, carbon fiber, carbon nanotube, graphene, highly hydrophobic 13X, high silicon ZSM-5, all-silicon ZSM molecular sieve or mesoporous silica Any one or a combination of two or more in any proportion.

Further, in step (4), the concentration of the lithium hydroxide solution is 50-90g/L.

Further, in step (4), the purification method is: add water to the crude lithium carbonate, control the solid-liquid ratio to 1:1-1:5, stir and heat up to 90-95°C, centrifuge while hot, repeat 1- After 3 times, vacuum dry.

Beneficial effects of the present invention:

The invention provides a method for recovering carbon dioxide from the tail gas of industrial kilns and producing lithium carbonate. The method can recover carbon dioxide in the tail gas of industrial kilns to the greatest extent without producing three wastes. The invention uses the temperature swing adsorption method to remove industrial Trace sulfides and nitrogen oxides in the kiln tail gas, _SO2 and NOx total concentration in the tail gas after purification treatment<1ppm; the present invention adopts the pressure swing adsorption method to reclaim carbon dioxide, and the obtained carbon dioxide gas has high purity (carbon dioxide volume concentration>99 %) with high recovery rate and large processing capacity; the separated and refined high-purity carbon dioxide is used as raw material in the carbonization process to produce battery-grade lithium carbonate, which realizes the resource utilization of carbon dioxide in industrial kiln tail gas, and contributes to the reduction of "carbon emission reduction", "Carbon neutrality" is of great significance.

Description of drawings:

Fig. 1 is the process flow chart of the method for reclaiming carbon dioxide and producing lithium carbonate from industrial kiln tail gas in embodiment 1;

Fig. 2 is the process flow chart of the adsorption purification of trace sulfides, nitrogen oxides and the separation and purification of carbon dioxide in embodiment 1;

Among them, 1-compressor; 2-water-gas separation tank; 3-two-tower temperature swing adsorption device; 4-four-tower pressure swing adsorption device.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Apparently, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention belong to the protection scope of the present invention.

Example 1

In this embodiment, the kiln tail gas used is natural gas oxygen-enriched combustion kiln tail gas. After analysis, its water vapor content is 4.70-6.78v%, the _O2 concentration is 13.90-15.10v%, and the _CO2 concentration is 2.51-4.39v% %, NOx concentration is 0.037~0.060v% (500~800ppm), _SO2 concentration is 0.014v% (~400ppm), CO concentration is 0.02~0.6v%, _H2 concentration is 0.01~0.06%, and the rest is _N2 . The carbon dioxide in the tail gas of the industrial kiln is recovered, and the recovered carbon dioxide gas is used in the ore lithium extraction enterprise to prepare high-purity battery-grade lithium carbonate. The method is as follows:

As shown in Figure 1-2, a method for recovering carbon dioxide from industrial kiln tail gas and producing lithium carbonate comprises the following steps:

(1) Preprocessing:

After the industrial kiln tail gas is passed through the cyclone dust collector to remove particulate matter, the denitrification and desulfurization system is used for denitrification and desulfurization treatment to obtain pretreated tail gas;

The denitrification and desulfurization system includes an SCR denitrification catalytic reactor, a waste heat boiler and a spray absorption tower connected in sequence. The denitrification treatment adopts a high-temperature SCR process, which is carried out in the SCR denitrification catalytic reactor, using ammonia water as a reducing agent, V ₂ O ₅ -WO ₃ -MoO ₃ /TiO ₂ is a denitrification catalyst, the reaction temperature is 300-400°C, the nitrogen oxides NOx in the tail gas react with ammonia water to produce nitrogen and water, and the concentration of nitrogen oxides in the tail gas is controlled at 1-10ppm. After entering the waste heat boiler for heat exchange and cooling, after the temperature drops below 300°C, it enters the spray absorption tower for desulfurization treatment. The acidic oxide SO ₂ and other pollutants in the tail gas are absorbed and the tail gas is fully purified; the slurry after absorbing SO ₂ reacts to form CaSO ₃ , and CaSO ₄ 2H ₂ O is formed by in situ forced oxidation and crystallization .

The components of the pretreated tail gas were analyzed, and the results are shown in Table 1:

Table 1

It can be seen that after denitration treatment and desulfurization treatment, the NOx in the tail gas is 1-10mg/m ³ , SO ₂ <50mg/m ³ , and the gauge pressure is only 0.02-0.1KPa.

(2) Adsorption and purification of trace sulfides and nitrogen oxides:

The tail gas pretreated in step (1) is pressurized to 0.7MPa by the compressor, and then enters the water-gas separation tank for dehydration, and the water concentration in the tail gas is controlled to be <50mg/m ³ , and the dehydrated tail gas enters the double-tower temperature swing adsorption device. The double-tower temperature-swing adsorption device comprises an adsorption tower A and an adsorption tower B which are connected, and both the adsorption tower A and the adsorption tower B contain an adsorbent (the organic amine impregnated activated carbon with an iodine value>1400mg/g, which is prepared by Sinopharm Group Chemical Reagent Co., Ltd. Co., Ltd.), both ends are encapsulated with quartz sand. The tail gas after dehydration enters the adsorption tower A from the upper end at room temperature to remove a small amount of NOx and SO ₂ , and the purified tail gas is obtained at the lower end of the adsorption tower A, which is used as the raw material for subsequent CO ₂ separation and purification; the adsorption tower A is heated up after the adsorption is saturated to 150°C (switch the tail gas to adsorption tower B for adsorption), use 150°C hot nitrogen and atmospheric pressure to purge and regenerate for 5 minutes, and purge the tail gas directly into the denitration and desulfurization system in step (1); after the adsorption tower A is completely regenerated, it is cooled to room temperature Then enter the next cycle for adsorption; when the adsorption tower A is adsorbing, the temperature of the adsorption tower B is raised, nitrogen is purged, and the adsorption-regeneration process of the two towers is carried out alternately.

(3) Separation and purification of carbon dioxide:

Pass the purified tail gas into a four-tower pressure swing adsorption device for separation of carbon dioxide. The four-tower pressure swing adsorption device includes four sequentially connected pressure swing adsorption towers C, D, E, F, and four pressure swing adsorption towers Both of them are filled with adsorbent 13X molecular sieve (synthesized by the method of Example 1 in CN200910183869.3), which is used to absorb and purify _CO2 in the tail gas. Both ends of the adsorber are packed with inert alumina; After the four-tower pressure swing adsorption device, the CF four-tower adsorption process is: one tower is in the adsorption stage, and the other three are in the depressurization, flushing and boosting stages respectively. Taking tower C as an example, ① tail gas enters tower C to absorb high-purity CO ₂ (volume concentration>99.9%), and the purified tail gas is discharged directly; ② average pressure drop: tower C is put forward into tower D; Pressure-The gas in the C tower is put forward into the E tower; ④ Reverse depressurization: The gas is reduced to the lowest pressure (atmospheric pressure), so that the adsorbed substances can be desorbed and discharged; Pure gas flushes Tower C in reverse to achieve final regeneration; ⑥Equalizing pressure rise: Use the equalizing gas from Tower D to pressurize Tower C ⑦Charging: Use the product gas from Tower E (which is in the process of adsorption) to fill Tower C to the required level. the required adsorption pressure.

After the _CO2 absorption in the tail gas is completed, the adsorbents in the four PSA towers are desorbed to obtain carbon dioxide gas;

(4) preparation of lithium carbonate:

Dissolve 600 kg of battery-grade lithium hydroxide monohydrate in distilled water, prepare a lithium hydroxide solution with a concentration of 80 g/L, place it in a reaction kettle, stir for 100 minutes, and filter out insoluble impurities by pressure filtration to obtain lithium hydroxide filtrate; Pass the carbon dioxide gas obtained in step (3) into the lithium hydroxide filtrate, preferably CO ₂ The flow rate is 3L/s, and the stirring speed is 70 rpm. When a large amount of solids appear in the solution, stop passing CO ₂ and heat up to 100°C, keep warm for 30 minutes and centrifuge to obtain crude lithium carbonate; add water to the crude lithium carbonate according to the solid-to-liquid ratio of 1:3, stir and heat up to 95°C, then centrifuge while it is hot to obtain wet lithium carbonate, repeat the above conditions for 1 The second time, the lithium carbonate wet product is placed in a vacuum oven to dry to obtain lithium carbonate. The purity of lithium carbonate measured by the method in YS/T 546-2021 "High Purity Lithium Carbonate" is 99.99%.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (5)

1. a method for reclaiming carbon dioxide and producing lithium carbonate from industrial kiln tail gas, is characterized in that, comprises the steps: (1) Preprocessing: After the industrial kiln exhaust gas is passed through the cyclone dust collector to remove particulate matter, it is then subjected to denitrification treatment and desulfurization treatment to obtain pretreated exhaust gas; (2) Adsorption and purification of trace sulfides and nitrogen oxides: The tail gas pretreated in step (1) is pressurized to 0.1~0.7MPa through a compressor, then enters a water-gas separation tank for dehydration, and then uses a double-tower temperature swing adsorption device to remove NO x and SO ₂ to obtain purified exhaust; The double-tower temperature swing adsorption device includes two adsorption towers, both of which contain adsorbents; (3) Separation and purification of carbon dioxide: Pass the purified tail gas into a four-tower pressure swing adsorption device for separation of carbon dioxide. The four-tower pressure swing adsorption device includes four sequentially connected pressure swing adsorption towers, and the four pressure swing adsorption towers are all filled with adsorbents. It is used to absorb CO ₂ in flue gas purification tail gas, and the other components that are not easy to be adsorbed are directly emptied from the top of the tower; finally, the adsorbents in the four pressure swing adsorption towers are desorbed to obtain carbon dioxide gas; (4) Preparation of lithium carbonate: Put the carbon dioxide gas obtained in step (3) into the lithium hydroxide solution, stir and mix evenly, when a large amount of solids appear in the solution, stop feeding the carbon dioxide gas, raise the temperature to 90-110°C, and keep it warm for 10-60 minutes, Centrifugal separation while hot to obtain lithium carbonate crude product, after purification, obtain lithium carbonate; In step (2), the adsorbent is one of activated carbon with an iodine value > 1000, modified silica gel, modified fly ash, active zeolite or mordenite, or a combination of two or more in any proportion; In step (3), the adsorbent is any one of nitrogen-doped activated carbon, carbon fiber, carbon nanotube, graphene, 13X molecular sieve, high-silicon ZSM-5, all-silicon ZSM molecular sieve or mesoporous silica Or a combination of two or more in any proportion. 2. The method for recovering carbon dioxide from industrial kiln tail gas and producing lithium carbonate as claimed in claim 1, characterized in that, in step (1), the denitrification treatment adopts a high-temperature SCR process, and in the SCR denitrification catalytic reactor It is carried out in-house, with ammonia water as the reducing agent, V ₂ O ₅ -WO ₃ -MoO ₃ /TiO ₂ as the denitration catalyst, and the reaction temperature is 300~400°C. 3. The method for recovering carbon dioxide from industrial kiln tail gas and producing lithium carbonate as claimed in claim 1, characterized in that, in step (2), after the two adsorption towers of the double-tower temperature swing adsorption device are saturated, the temperature rises To 80-150°C, hot nitrogen is used to purge and regenerate for 1-20min, the adsorbent is used after recycling and regeneration, and the purge tail gas enters step (1) for denitrification and desulfurization treatment. 4. The method for recovering carbon dioxide from industrial kiln tail gas and producing lithium carbonate as claimed in claim 1, characterized in that, in step (4), the concentration of the lithium hydroxide solution is 50-90g/L. 5. the method for reclaiming carbon dioxide and producing lithium carbonate from industrial kiln tail gas as described in any one of claims 1 to 4, it is characterized in that, in step (4), described purification method is: add water in lithium carbonate crude product , control the solid-liquid ratio to 1:1~1:5, stir and heat up to 90-95°C, centrifuge while hot, repeat 1-3 times, and then vacuum dry.

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