CN113731157A - Resource method for synchronously recycling ammonia nitrogen and carbon dioxide - Google Patents
Resource method for synchronously recycling ammonia nitrogen and carbon dioxide Download PDFInfo
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- B01D53/34—Chemical or biological purification of waste gases
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- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
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- B01D53/34—Chemical or biological purification of waste gases
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D53/34—Chemical or biological purification of waste gases
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- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
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- C01C1/24—Sulfates of ammonium
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- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/18—Carbonates
- C01F11/181—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by control of the carbonation conditions
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F3/005—Combined electrochemical biological processes
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
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Abstract
The invention discloses a resource method for synchronously recycling ammonia nitrogen and carbon dioxide, which comprises the following steps: 1) decomposing ammonia nitrogen and carbon dioxide synchronous absorption liquid into ammonia gas and carbon dioxide mixed gas under the action of waste heat by utilizing waste heat resources; 2) then introducing the mixed gas into the desulfurized gypsum suspension to obtain ammonium sulfate liquid and calcium carbonate solid; 3) a small amount of calcium ions and sulfate ions are ionized in water, and the calcium ions meet carbonate ions and are combined to generate calcium carbonate which is difficult to dissolve in water, so that the concentration of the calcium ions is reduced. The invention provides a sustainable coupling system which realizes the liquid-phase to gas-phase conversion of carbon and nitrogen resources of ammonia and carbon dioxide synchronous absorption liquid by utilizing waste heat resources, recovers carbon and nitrogen elements by utilizing a calcium sulfate waste residue turbid liquid, and establishes reduction, harmless and resource treatment, waste heat recycling and synchronous resource utilization of ammonia nitrogen and carbon dioxide for desulfurized gypsum.
Description
Technical Field
The invention belongs to the technical field of resource utilization of carbon dioxide fixation in waste gas and nitrogen source recovery in sewage, and particularly relates to a resource method for synchronously recovering ammonia nitrogen and carbon dioxide.
Background
The growing industry is also bringing huge industrial waste residues while increasing GDP, taking desulfurized gypsum as an example, the desulfurized gypsum is a byproduct associated with Flue Gas Desulfurization (FGD). The FGD process is a technology for removing sulfur dioxide in coal-fired or oil-fired flue gas by a limestone-gypsum wet method. The technology is mature, has high stability and good benefit, the desulfurization efficiency is as high as more than 95 percent, but a large amount of desulfurization gypsum is inevitably generated. In order to meet the increasingly strict pollutant emission standards, the requirements of flue gas treatment technology are higher and higher, and the improvement of flue gas desulfurization facilities is more and more perfect. FIG. 1 shows the variation of the yield of desulfurized gypsum in China in 2010-2018; FIG. 2 shows the main production industry and the yield of desulfurized gypsum in 2018. From the figure, it can be seen that the yield of the desulfurized gypsum is gradually reduced year by year as a whole, but the overall yield is still large. The desulfurized gypsum produced by the power, heat and power production and supply industries is the most from the industry, and accounts for 81.20% of the total national desulfurized gypsum production.
With the increase of the national environmental protection pressure and the maturity of the desulfurization technology, people pay attention to the treatment and disposal of the desulfurization gypsum. The effective component of the desulfurized gypsum is calcium sulfate dihydrate (CaSO)4·2H2O) content is more than or equal to 93 percent, the particles are fine, the grade is high, the residual water content is 5-15 percent, the viscosity is high, and the appearance of the particles containing impurities is generally gray, grey yellow, light yellow and the like. The desulfurized gypsum is used as an industrial byproduct, can be used for producing cement retarders with low additional value, building gypsum, gypsum plasterboards and the like in the building material industry, and can also be used as road building roadbed, cast-in-place wall materials and the like. Besides, because of the desulfurized gypsumHas unique physical and chemical properties, and can be used for agricultural production and soil improvement. However, there have been few studies on re-extraction and utilization of sulfur resources having high added values in desulfurized gypsum. The treatment standards and technical requirements of the desulfurized gypsum in China are not written, and related enterprises can not guarantee the safety performance and possibly have the problem of uneven product quality by processing according to experience. The desulfurized gypsum in China is not utilized in a large amount at present, and the desulfurized gypsum has relatively complex impurities, contains calcium carbonate, incompletely oxidized calcium sulfite and soluble salts of sulfates or chlorides of sodium, magnesium and potassium. Wherein, chloride ions have strong corrosivity to metals, and magnesium, sodium and potassium ions are easy to separate out crystals in a humid environment, so that the surface of a gypsum product has a frosting phenomenon. The addition of excessive desulfurized gypsum in the gypsum product easily causes expansion cracking and carbonization phenomena, and influences the durability. Therefore, the acceptance of the desulfurized gypsum by the masses is poor, and the industrial scale is difficult to form. Therefore, a method suitable for the characteristics of China, high in value and capable of effectively utilizing the desulfurized gypsum needs to be developed.
The characteristic of the energy consumption structure mainly comprising coal in China cannot be changed for a long time in the future, wherein the power industry is a large coal-fired household, and the annual emission of sulfur dioxide accounts for more than 40% of the total national emission. The amount of the desulfurized gypsum in the power plant is huge, and the desulfurized gypsum is mostly piled up in occupied areas, so that the desulfurized gypsum will erode land, occupy farmlands, destroy the environment, pollute air and water if the desulfurized gypsum is not treated in time. The extensive desulfurization gypsum management and utilization state violates the national control policy of 'reduction, harmlessness and reclamation' of solid wastes.
The waste heat refers to energy which is not utilized in energy utilization equipment under certain economic and technical conditions, and comprises seven types of waste heat of high-temperature waste gas, waste heat of cooling medium, waste heat of waste gas and waste water, waste heat of high-temperature products and slag, waste heat of chemical reaction, waste liquid of combustible waste gas and waste material, and waste heat of high-pressure fluid. According to investigation, the total waste heat resources of all industries account for 17% -67% of the total fuel consumption, and the recyclable waste heat resources account for 60% of the total waste heat resources. Such as coal-fired power plants, glass, metallurgy, petrifaction, building materials, light textile, ceramics and other industries, can generate a large amount of flue gas waste heat. Taking a coal-fired power plant as an example, in the actual coal-fired power generation process, due to the influence of various factors, the heat value of the coal is not fully utilized, and boiler tail gas, continuous sewage discharged by the boiler and residual heat in slag discharged from the bottom of the boiler have comprehensive utilization values. The heat energy lost by the discharged smoke accounts for 5-12% of the total heat energy generated by the coal, accounts for 80% or even higher of the total heat loss of the boiler, and is the important point of waste heat utilization of the thermal power plant. In heat-engine plants in China, the exhaust gas temperature of a boiler is generally 125-150 ℃. The heat energy loss caused by the higher temperature of the discharged smoke is one of the difficulties faced by the thermal power plant, and how to fully utilize the heat energy generated by the combustion of coal is one of the main measures for seeking benefit and development of the thermal power plant in the difficulties.
Carbon dioxide (CO)2) Is a typical greenhouse gas and has wide sources. The industrial revolution has caused the emission of greenhouse gases in large quantities, the global greenhouse effect is intensified, the complex influence is generated on the earth climate and the ecological system, a series of environmental problems are caused, and the threat to the survival of human beings is greatly increased. The reduction of greenhouse gases is a core means for solving the problems of global warming and extreme climate, and the control of CO2Emissions are the most direct and efficient method of greenhouse gas emission reduction. At present, CO2Separation and immobilization techniques generally include absorption separation (both physical and chemical), adsorption separation, membrane, cryogenic separation, catalytic combustion (catalytic oxidation), and CO2Trapping and sealing techniques, among which the chemical absorption separation method and the membrane method are more commonly used. The chemical absorption method is currently recognized as a relatively mature CO capture2The method of (1). Wherein ammonia water as a common alkaline absorbent can be used for absorbing CO2A gas. The pH of a Microbial Electrochemical System (MESs) is increased due to cathode reaction, and cations directionally migrate to a cathode region under the action of an electric field, so that the aim of synchronously recovering ammonia nitrogen in sewage and carbon dioxide in waste gas can be fulfilled based on the principle. The anode of MESs is oxidized to degrade organic pollutants and reduced at the cathode to generate hydroxyl ions, so that the alkali of the catholyteDegree of increase, NH in the wastewater4 +The ammonia solution is moved from the anode chamber to the cathode chamber under the action of an electric field and is enriched in the cathode chamber to form high-concentration high-pH ammonia solution for absorbing CO in the waste gas2Acid gas, to obtain NH-rich gas at the cathode4 +With CO3 2-、HCO3 -The ammonia nitrogen and the carbon dioxide are synchronously absorbed. The resource utilization of the ammonia nitrogen and carbon dioxide synchronous absorption liquid can be combined with the production of the fertilizer. The ammonium bicarbonate dissolved in the direct absorption solution is unstable in chemical property and needs to be recovered. However, the solubility of ammonium bicarbonate at ambient temperature (20 ℃) was 21.7g/100g water, while the solubility of 11.9g/100g water was still present at 0 ℃. The cooling crystallization method consumes a large amount of energy and can only recover<50% ammonium bicarbonate. Meanwhile, ammonium bicarbonate is often volatilized in a large amount in the processes of transportation, storage and application, and the utilization rate of the ammonium bicarbonate is only about 27%. Therefore, an environment-friendly, efficient and sustainable resource utilization mode needs to be established.
Disclosure of Invention
Aiming at the problems of fixation of carbon dioxide in waste gas and resource utilization of nitrogen source recovery in sewage at present. The invention provides a method for decomposing ammonia nitrogen and carbon dioxide synchronous absorption liquid into ammonia gas and carbon dioxide mixed gas under the action of waste heat by utilizing waste heat resources. And then introducing the mixed gas into the desulfurized gypsum suspension to obtain ammonium sulfate liquid and calcium carbonate solid. K of calcium carbonatespIs 8.7x10-9K of calcium sulfatespIs 9.1X 10-6The solubility product of calcium sulfate is greater than that of calcium carbonate, the calcium sulfate is slightly soluble in water, a small amount of calcium ions and sulfate ions are ionized in the water, and the calcium ions meet carbonate ions and are combined to generate calcium carbonate which is insoluble in water, so that the concentration of the calcium ions is reduced. The fixation of carbon dioxide in the mineral form of calcium carbonate is a reasonable route that is feasible with low cost technology. And calcium sulfate suspension is used as absorption liquid, calcium ions are continuously dissolved out of calcium sulfate solids due to the difference of solubility product constants when carbon dioxide is dissolved, so that the concentration of the calcium ions is ensured, and the reaction is promoted to be carried out in the direction of generating calcium carbonate precipitates. The concentrated solution of ammonium sulfate can be used as nitrogen fertilizer, and the concentrated solution of calcium carbonate can be used as nitrogen fertilizerIs a product of fixing carbon dioxide. The coupling system can finally realize the reduction, harmless and resource treatment of the desulfurized gypsum, the reutilization of waste heat resources, the synchronous recovery and resource utilization of the ammonia nitrogen in the wastewater and the carbon dioxide in the wastewater.
Advantageous effects
The invention designs a coupling system aiming at the problem of resource utilization of desulfurized gypsum, waste heat, ammonia nitrogen in waste water and carbon dioxide in waste gas. The ammonia nitrogen in the wastewater and the carbon dioxide in the waste gas are recovered at the cathode side by utilizing a microbial electrochemical system to generate NH-rich gas4 +With CO3 2-、HCO3 -The synchronous absorption liquid of (1). And transferring ammonia nitrogen and carbon dioxide generated by heating decomposition of ammonium bicarbonate in the synchronous absorption liquid to a gaseous state by utilizing waste heat resources. And introducing the mixed gas into the calcium sulfate suspension, and replacing sulfate ions in the calcium sulfate to generate ammonium sulfate by utilizing the fact that the solubility product of the calcium sulfate is larger than that of the calcium carbonate and the calcium ions are subjected to repeated decomposition reaction when meeting carbonate ions to generate calcium carbonate which is insoluble in water. Most of NH is removed by synchronous absorption liquid of microbial electrochemical system4 +With CO3 2-、HCO3 -And then the ammonia nitrogen and the carbon dioxide in the waste gas can be recycled and collected continuously. In the process, the waste heat utilization can provide enough heat for the thermal decomposition of ammonium bicarbonate, and the high-concentration ammonium sulfate liquid fertilizer and the regenerated calcium carbonate are in the form of final products for recovering nitrogen and carbon elements. On one hand, the successful construction of the system realizes the purposes of reduction, harmlessness and resource treatment of the desulfurized gypsum, and the sulfate ions in the calcium sulfate are replaced to generate ammonium sulfate, and meanwhile, the calcium carbonate can fix carbon dioxide gas; on the other hand, the system realizes the reutilization of waste heat, which is an important way for improving the economic development, saving resources and reducing the energy consumption, and is a sustainable coupling system capable of realizing the reduction, harmless and resource treatment of the desulfurized gypsum, the reutilization of the waste heat and the resource of the ammonia nitrogen and carbon dioxide synchronous absorption liquid.
Drawings
FIG. 1 is a graph of the yield of desulfurized gypsum in China in 2010-2018.
FIG. 2 shows the main production industry and the yield of desulfurized gypsum in 2018.
FIG. 3 shows a system for recycling calcium sulfate waste residue carbon and nitrogen.
FIG. 4 is a schematic diagram, a front view and a plan view of a calcium sulfate waste residue carbon and nitrogen resource utilization device:
(a) the method comprises the following steps Schematic diagram of reactor dimension chart device
(b) The method comprises the following steps Front view
(c) The method comprises the following steps And (4) a top view.
FIG. 5 shows the recovery rates of ammonia nitrogen and inorganic carbon in the calcium sulfate waste residue carbon and nitrogen resource utilization system.
FIG. 6 shows the water loss rate during heating of the ammonia nitrogen and carbon dioxide synchronous absorption liquid.
FIG. 7 shows the sulfate ion concentration in the calcium sulfate suspension.
Detailed Description
The present invention is further illustrated by the following examples.
Example 1:
ammonia nitrogen and carbon dioxide synchronous absorption liquid (absorption liquid for short): the carbon dioxide is absorbed by an ammonium radical-containing solution in a high pH environment, and the carbon dioxide is characterized by containing high-concentration ammonia nitrogen elements (ammonium radicals and free ammonia) and inorganic carbon elements (carbonate, bicarbonate and soluble CO 2).
Recovering the liquid: a recovery liquid mainly comprising a calcium sulfate suspension. The absorption liquid is heated to generate decomposition reaction to generate ammonia gas and carbon dioxide gas, and calcium carbonate precipitation and liquid-phase high-concentration ammonium sulfate solution are generated after the reaction of the recovery liquid.
The calcium sulfate waste residue carbon and nitrogen resource utilization system mainly comprises a waste heat recovery device (a first part), a hydrothermal solution evaporation device (a second part) and a carbon and nitrogen absorption device (a third part), as shown in fig. 3.
1. Waste heat recovery device (first part)
The waste heat resources have wide sources, wide temperature range and various existing forms, and the proper types and utilization modes can be selected according to the transmission or conversion characteristics of the energy of the waste heat resources in the utilization process. The heat exchange technology is the most direct economic method with higher efficiency for recovering waste heat resources, and the utilization of the waste heat by the technical equipment does not change the form of waste heat energy, and only directly transmits the waste heat energy to the energy consumption flow of the self process through the heat exchange equipment, thereby reducing the primary energy consumption. The corresponding devices are various heat exchangers, including traditional heat exchangers with various structures, heat pipe heat exchangers, waste heat steam generators (waste heat boilers) and the like.
The heat exchanger is a heat exchange device which is mature in development and wide in application, and is an important means for fully recovering various waste heat resources and improving the energy utilization rate. And (3) performing heat transfer on the heat sources such as the high-temperature flue gas waste heat, the chemical reaction waste heat, the combustible gas waste heat and the high-temperature product waste heat and the normal-temperature ammonia nitrogen and carbon dioxide synchronous absorption liquid to obtain the high-temperature absorption liquid. Ammonium bicarbonate in the absorption liquid is easily decomposed by heating to generate mixed gas of ammonia gas and carbon dioxide, and the high-temperature absorption liquid and the mixed gas are conveyed to a subsequent device through a corrosion-resistant heat-insulating pipeline. The waste heat smoke has large dust content and contains more corrosive substances, and the problems of dust deposition, corrosion, abrasion and the like of equipment are easily caused. Therefore, the waste heat is required to be subjected to necessary primary precipitation before entering the heat exchanger, and the heat exchanger is required to have the characteristics of good heat transfer effect, high heat utilization rate, easy cleaning of deposited dust, wear resistance, corrosion resistance and the like.
2. Hot liquid evaporator (second part)
After passing through a waste heat recovery device, the waste heat recovery device contains high-concentration ammonia nitrogen elements (ammonium ions and free ammonia) and inorganic carbon elements (carbonate ions, bicarbonate ions and soluble CO)2) The absorption liquid of (2) changes from a normal temperature to a high temperature state. The external heat preservation device prevents the temperature of the high-temperature absorption liquid from dissipating outwards. The heat-insulating device is a scientific and efficient energy-saving technical measure, can slow down the heat dissipation and conduction speed, and mainly comprises an anticorrosive layer, a heat-insulating layer and a protective layer.
The high-temperature absorption liquid is subjected to thermal decomposition reaction to generate mixed gas mainly containing ammonia gas and carbon dioxide. NH is rich in ammonia nitrogen and carbon dioxide synchronous absorption liquid4 +With CO3 2-、HCO3 -Under the action of high temperature, ammonium bicarbonate is decomposed to produce ammonia gas and carbon dioxide gas. The high-temperature absorption liquid and the mixed gas obtained by the waste heat recovery device are separated in the heat preservation device, the mixed gas can be directly conveyed to a subsequent carbon and nitrogen absorption device through a corrosion-resistant pipeline, and the rest high-temperature absorption liquid can be continuously subjected to decomposition reaction in the device to generate the mixed gas.
Therefore, the hydrothermal evaporation device is required to have the characteristics of good sealing performance, good heat preservation effect, long heat preservation time, good stability and the like. In order to improve the decomposition rate of the ammonium bicarbonate, functions of stirring, shaking and the like can be added in the device to accelerate mass transfer, so that the absorption liquid is heated uniformly, and the gas-liquid separation is accelerated.
3. Carbon and nitrogen absorber (third part)
The carbon and nitrogen absorption device is a place for generating ammonium sulfate and calcium carbonate by double decomposition reaction of calcium sulfate suspension and mixed gas. The main component of the desulfurized gypsum is calcium sulfate dihydrate, the solubility product of the calcium sulfate is larger than that of the calcium carbonate, the calcium sulfate is slightly soluble in water, and a small amount of calcium ions and sulfate ions are ionized in the water environment. The calcium sulfate suspension is used as a recovery liquid, the mixed gas is dissolved when contacting with the liquid, and calcium ions are continuously dissolved from calcium sulfate solids due to the difference of solubility product constant when carbon dioxide is dissolved, so that the concentration of the calcium ions is ensured, and the reaction is promoted to be carried out in the direction of generating calcium carbonate precipitates.
Because the impurities in the desulfurized gypsum are complex, the absorption device needs to have enough mechanical strength and corrosion resistance, and has the characteristics of simple structure, convenient manufacture and maintenance, wide operation range, stable operation and low energy consumption. In order to improve the reaction rate of the double decomposition reaction of the contact of the desulfurized gypsum and the mixed gas, the optimal gas-liquid contact mode and reaction conditions need to be selected, the gas and the liquid have enough contact area and contact time, the gas and the liquid have strong disturbance correspondingly, the mass transfer resistance is reduced, and the reaction efficiency is improved. The gas-liquid two-phase flow can be in countercurrent or in cocurrent. The gas-liquid two-phase contact may include: directly introducing mixed gas into liquid to react, such as direct aeration; dispersing the mixed gas in the liquid in a bubble form to react, such as bubbling; contacting the gas with the liquid drops, and capturing the gas and the liquid drops through liquid film collision to generate reactions, such as spraying, filling and the like.
4. Regulation and control mode of calcium sulfate waste residue carbon nitrogen resource utilization system
In the operation process of the calcium sulfate waste residue carbon nitrogen resource utilization system, the optimal treatment effect can be realized by regulating and controlling various parameters. Regulating and controlling the thermal decomposition rate by regulating and controlling the heating temperature of the heat exchanger, the heating time of the absorption liquid, the pH value of the absorption liquid, the concentration of the absorption liquid, the stirring speed, the flowing rate of the absorption liquid, the reaction time and the like; the mass transfer rate of gas and liquid and the replacement rate of sulfate ions can be regulated and controlled by regulating and controlling the quality of the calcium sulfate waste residues, the granularity of the calcium sulfate waste residues, the pH value of the calcium sulfate suspension, the recovery time, the gas-liquid contact mode, the recovery temperature, the flow velocity of mixed gas and the like.
1. Calcium sulfate waste residue carbon nitrogen resource utilization system
Calcium sulfate waste residue carbon nitrogen utilization system includes two parts: heating heat preservation device and calcium sulfate waste residue carbon nitrogen utilization device, heating heat preservation device mainly comprises 250 mL's ground tapered bottle and curved plug air extraction joint, adopts the water bath heating mode that can regulate and control heating temperature and magnetic stirring speed simultaneously. The calcium sulfate waste residue carbon and nitrogen resource utilization device is made of transparent organic plastics, and the basic requirements are as follows: the novel glass fiber reinforced plastic composite material is required to be transparent and has smooth inner walls; the reactor is a cylindrical cavity, the outer diameter is 9cm, the inner diameter is 8cm, the total height is 11cm, and the material thickness is 0.5 cm. And thirdly, the reactor is provided with a flange-type opening, the upper cover plate is connected with the cylindrical cavity through screws, the sealing position is required to be good in sealing performance, and the upper cover plate and the cavity can be connected through a rubber gasket. The reactor is stirred magnetically, and is provided with 3 tubes, namely a left upper gas absorption tube (taking a front view as an example, 5cm away from the bottom surface of the reactor, 60-degree included angle with a cavity, 8cm in length and 1cm in outer diameter), a left lower precipitation outlet (1.5 cm in length and 1cm in outer diameter), and a right lower supernatant outlet (2.3 cm away from the bottom surface of the reactor, 1.5cm in length and 1cm in outer diameter). The heating and heat-preserving device is connected with the calcium sulfate waste residue carbon and nitrogen resource utilization device by a rubber pipe for conveying mixed gas. The schematic diagram, the front view and the plan view of the calcium sulfate waste residue carbon nitrogen resource utilization device are shown in FIG. 4.
2. Implementation mode of calcium sulfate waste residue carbon nitrogen resource utilization system
The heating and heat preservation device adopts a water bath heating mode capable of simultaneously regulating and controlling the heating temperature and the magnetic stirring speed, adopts different heating temperatures with single stirring speed to carry out experiments, and sets the temperatures to be 70 ℃, 80 ℃, 90 ℃ and 100 ℃. Ammonia nitrogen and carbon dioxide synchronous absorption liquid component (/ L): NH (NH)4HCO3,5.06g；NaHCO30.84 g; the pH of the solution is 7.5-8.5, and 200mL of the absorption solution is heated for 24h each time. The ground conical bottle and the joint, the joint and the rubber pipe, and the rubber pipe and the gas absorption pipe are sealed to prevent gas leakage. The calcium sulfate waste residue carbon nitrogen resource utilization device adopts magnetic stirring, the rotating speed is 200r/min, the contact area is increased, the reaction speed is improved, and the absorption time is 24 hours. Calcium sulfate suspension components: CaSO42g, 140mL of deionized water. And at the optimal heating temperature, the ammonia nitrogen and carbon dioxide synchronous absorption liquid is replaced every cycle, and the calcium sulfate suspension continuously absorbs for 4 cycles. Experiments research the recovery rate of ammonia nitrogen and inorganic carbon, the change of pH, the water loss rate of the ammonia nitrogen and carbon dioxide synchronous absorption liquid in the heating process and the sulfate ion concentration in the calcium sulfate suspension liquid in the calcium sulfate waste residue carbon and nitrogen resource utilization system.
3. Operation result of calcium sulfate waste residue carbon nitrogen resource utilization system
Taking 24h as a period, heating 200mL of ammonia nitrogen and carbon dioxide synchronous absorption liquid at different temperatures in each experiment, and recording the pH, conductivity, ammonia nitrogen concentration and inorganic carbon concentration changes of the absorption liquid at the beginning and the end of the heating temperature; and the pH, the conductivity, the ammonia nitrogen concentration, the inorganic carbon concentration and the sulfate ion concentration of the calcium sulfate suspension at the temperature are changed, and the specific data are shown in the following table.
TABLE 1 absorption experiment data record table at different heating temperatures
As shown in fig. 5, the recovery rates of ammonia nitrogen and inorganic carbon both show an increasing trend with the increase of the heating temperature; under the same heating temperature, the recovery rate of the inorganic carbon is higher than that of ammonia nitrogen, and the recovery rate is the highest at 100 ℃, namely 32.2% and 78.5% respectively; as shown in fig. 6, the water loss rate increases with the increase of the heating temperature, and the water loss rate is 3.5% at maximum at 100 ℃. As shown in FIG. 7, the concentration of sulfate ions increased with the increase of the heating temperature, and the concentration of sulfate ions in the suspension was 6.56g/L at 100 ℃ at the maximum, and the purity of calcium carbonate was 64%.
The absorption liquid is repeatedly absorbed for 4 periods, the sulfate ions in the suspension can reach 9.40g/L, and the purity of the calcium carbonate is 91%.
Claims (7)
1. A resource method for synchronously recycling ammonia nitrogen and carbon dioxide is characterized by comprising the following steps:
1) decomposing ammonia nitrogen and carbon dioxide synchronous absorption liquid into ammonia gas and carbon dioxide mixed gas under the action of waste heat by utilizing waste heat resources;
2) then introducing the mixed gas into the desulfurized gypsum suspension to obtain ammonium sulfate liquid and calcium carbonate solid;
3) a small amount of calcium ions and sulfate ions are ionized in water, and the calcium ions meet carbonate ions and are combined to generate calcium carbonate which is difficult to dissolve in water, so that the concentration of the calcium ions is reduced.
2. The resource method for synchronously recycling ammonia nitrogen and carbon dioxide as claimed in claim 1, wherein the absorption liquid containing high concentration ammonia nitrogen and inorganic carbon is changed from normal temperature to high temperature after passing through the waste heat recycling device.
3. The resource method for synchronously recycling ammonia nitrogen and carbon dioxide as claimed in claim 1, wherein the high-temperature absorption solution is subjected to thermal decomposition reaction to generate ammonia gas and dioxideThe mixed gas with carbon as the main body, the ammonia nitrogen and the carbon dioxide synchronous absorption liquid are rich in NH4 +With CO3 2-、HCO3 -And the ammonium bicarbonate is decomposed at high temperature to generate ammonia gas and carbon dioxide gas.
4. The resource method for synchronously recycling ammonia nitrogen and carbon dioxide as claimed in claim 1, wherein the high-temperature absorption liquid and the mixed gas obtained by the waste heat recycling device are separated in the heat preservation device, the mixed gas is directly conveyed to a subsequent carbon and nitrogen absorption device through a corrosion-resistant pipeline, and the rest high-temperature absorption liquid can be continuously subjected to decomposition reaction in the device to generate the mixed gas.
5. The resource method for synchronously recycling ammonia nitrogen and carbon dioxide as claimed in claim 1, wherein the calcium sulfate suspension and the mixed gas are subjected to a double decomposition reaction to generate ammonium sulfate and calcium carbonate.
6. The resource method for synchronously recycling ammonia nitrogen and carbon dioxide as claimed in claim 1, wherein the gas-liquid two-phase flow mode comprises counter-flow and parallel flow;
the gas-liquid two-phase contact method comprises the following steps: directly introducing mixed gas into liquid to react, such as direct aeration; dispersing the mixed gas in the liquid in a bubble form to react; contacting the gas with the liquid drop, and capturing the liquid drop by liquid film collision to generate reaction.
7. The resource method for synchronously recycling ammonia nitrogen and carbon dioxide as claimed in claim 1, wherein the calcium sulfate waste residue carbon nitrogen resource utilization system realizes the optimal treatment effect by regulating and controlling various parameters in the operation process:
the thermal decomposition rate is regulated and controlled by regulating and controlling the heating temperature of the heat exchanger, the heating time of the absorption liquid, the pH value of the absorption liquid, the concentration of the absorption liquid, the stirring speed, the flowing speed of the absorption liquid and the reaction time.
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| CN110790360A (en) * | 2019-10-21 | 2020-02-14 | 天津大学 | Resource, ammonia recovery and synchronous carbon dioxide absorption system for high ammonia nitrogen organic wastewater and regulation and control method thereof |
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| CN101497455A (en) * | 2009-03-13 | 2009-08-05 | 李睿德 | Method for producing limestone powder and aluminium ammonium sulfate using heat-engine plant desulfurized gypsum and fly ash |
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