SU1414840A1 - Method of producing fertilizers from flue gases of thermal power plants - Google Patents

Abstract

The invention relates to the production of fertilizers for agriculture from the flue gases of thermal power plants. The aim of the invention is to increase the yield of the finished product and increase the content of microelements in it in easily digestible form. The method is carried out by absorbing flue gases with water in the presence of ozone in a circulating mode, introducing finely dispersed fly ash, ammonizing the mixture, and introducing the ash into the water or into the flue gas stream just before the absorption stage. The method allows to increase the yield of fertilizer by 12% and increase the concentration of trace elements in it by 2.5 times. (L

Description

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This invention relates to the production of agricultural fertilizers.

The purpose of the invention is to increase the yield of the finished product and increase the content of trace elements in it in an easily absorbable form.

The method of producing fertilizers from the flue gases of the TPP includes a stage of their absorption by water in the presence of an oxidizing agent - ozone, in the tdarculation mode, the introduction of fine fly ash from the last stages of the ash collector, followed by neutralization of the resulting mixture with ammonia, and the fly ash is introduced into the water or into the stream the flue gases immediately before the absorption stage, and the circulation of gases in the irrigation circuit is carried out until the required amount is obtained. the degree of extraction of trace elements from fly ash.

The proposed method differs from the known method of introducing fly ash into the water or into the gas stream. The introduction of ash by a known method into the mixture of acids formed after absorption of gases by water leads to the fact that at low pH solutions together with microelements, alkaline, alkaline earth metals, as well as compounds of iron and aluminum, are transferred from the ash to i more than 50% of the ash composition,: Dissolving these components leads to: neutralizing the mixture of acids and increasing the pH of the solution, which in turn inhibits (up to complete termination of) the dissolution of microsleems. The presence of a braking effect on the dissolution of ash does not allow a significant increase in the transition of microelements to a more liquid plant that is more digestible by plants.

In the proposed method, the ash is introduced directly into water or sprayed in a stream of dtsm gases before the absorption of sulfur and nitrogen oxides from dm gases, while the hall participates in the absorption process. Changing the sequence of technological operations for obtaining fertilizers leads to the elimination of the inhibitory effect of the pH of the solution on the leaching of trace elements and intensifies the process of producing fertilizers. With repeated circulation of water and ash through the absorption apparatus, a gradual decrease in the pH of the solution (due to the formation of acids) is observed, which in turn accelerates the dissolution process.

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ash. In addition, fly ash contains up to 20% of iron compounds, as well as impurities of manganese and copper, which are catalysts for the oxidation of SOj to PO3. The presence of ash in the absorption solution at the absorption stage significantly increases the rate of transition of sulfur dioxide to sulfuric acid, which contributes to the intensification of the process of obtaining fertilizer, increasing their yield and enrichment with dissolved microelements.

During the circulation of the coarse ash into the liquid phase, first of all, those microelements, which are part of easily soluble compounds of alkali and alkaline earth metals, and then trace elements from iron compounds, pass. The same trace elements, which are associated with the aluminosilicate carcass of the soils, leach out extremely slowly and their extraction is impractical due to a sharp decrease in the rate of fertilizer formation. Therefore, the circulation of fly ash in the gas cleaning circuit should be carried out until a sharp decrease in the rate of dissolution of trace elements, which is determined by the concentration and distribution of trace elements in a particular ash.

Fly ash can either be introduced into a liquid absorbent (water) tank before it is fed to the stage.

flue gas treatment, or sprayed in the flue gas stream before the absorption apparatus. In the latter case, the introduction of ash into the absorption solution proceeds in the process. its contact with smoke gaz. The same situation takes place in the processing of flue gases of a pie-coal boiler, which always contain flying ashes.

Example. Flue gases containing, 30,3 ± 0,5 :, N0 0,35t1; Oj 140t15, sent to an absorption apparatus irrigated with water. To intensify the processes of oxidation, ozone is introduced into the zone of gas contact with water. / calculation of 2 g O, per 1 nm of the processed / mo gas. In the process of such processing lower oxides of sulfur () and nitrogen (N0

The & and NO.) are oxidized to higher (ZOZ and NjO;, -), which are absorbed by water to form a mixture of sulfuric and nitric acids. In the water before it is supplied to the irrigation of the absorption apparatus,

fly ash in the amount of 30 kg per 1 ton of solution. Fly ash has the following composition, wt.%: SiO 45-50; 23-25; , Ge2.0з 18-21; CaO 5-7; MgO 1-2; + KjO 2-3. The ash can be introduced to the absorption stage by spraying it in the flue gas stream. After the absorption of sulfur and nitrogen oxides, the ash suspension is collected in the circulating capacity of the liquid absorbent and is pumped again to the irrigation of the absorption apparatus. During the circulation process, an increase in the concentration of the mixture of acids occurs, in suspension and leaching of soluble components from the ash, including trace elements. The circulation of the suspension is carried out until the concentration of the sulfate ion in the solution is 20 g / l. Then the suspension is neutralized with ammonia water to a pH of 7-8 to produce liquid complex fertilizers containing ammonium sulfate and nitrate, leached trace elements and an insoluble ash residue. The concentration of manganese ions in the solution is 2.1 g / t. Dry fertilizer yield (sulphate and

ammonium nitrate) 6.8 kg per 1000 nm flue gas.

The proposed method of obtaining fertilizers as compared with the known one allows increasing the yield of fertilizers by 12% and increasing the concentration of microelements in the easily absorbed dissolved form of plants by about 2.5 times. This ensures that the quality of fertilizers does not increase the cost of their production.

Claims (1)

Invention Formula The method of producing fertilizers from flue gases of thermal power plants, including the absorption of gases by water in the presence of ozone in the circulation mode, the introduction of fine fly ash, the ammoniation of the mixture, characterized in that, in order to increase the yield of the finished product and increase the content of trace elements in easily digestible form , the introduction of the ash is carried out in-water or into the flue gas stream immediately before the absorption stage.