CN106582277B - A kind of denitrating system and its method using catalyzing hydrogen peroxide - Google Patents

Abstract

The invention relates to the field of industrial process oxidation catalysis and environmental treatment of fossil fuel combustion, and discloses a denitrification system and method using catalytic hydrogen peroxide. After the hydrogen oxide vapor is fully mixed, it passes through the catalyst layer, and the catalytic oxidation reaction is completed under the action of the corrugated plate catalyst, and the generated acid gas is absorbed by the lye to realize the removal of nitrogen oxides; the present invention uses titanium dioxide in the form of anatase as the substrate , iron oxide is the co-catalyst; the oxidant and catalyst used in the present invention have the advantages of high denitrification efficiency, reasonable process design, environmental protection, non-toxicity, low cost, and stable product quality. , will not cause secondary pollution to the environment.

Description

A denitrification system and method using catalytic hydrogen peroxide

technical field

The invention relates to the technical field of nitrogen oxide treatment, in particular to a denitrification system using catalytic hydrogen peroxide and a method thereof.

Background technique

Fossil fuel combustion is an important source of man-made emissions of nitrogen oxides (NO _x ) in the atmosphere, and nitrogen oxides, such as acid rain, photochemical smog and ozone depletion, have caused great harm to the normal life and production of residents. With the increasingly serious problem of NO _X pollution, the governments of various countries have increased the control of NO _X emissions

The most commonly used NO _X treatment solution for fossil fuel combustion is selective catalytic reduction (Selective Catalytic Reduction, SCR), which has certain technical defects, such as high temperature window (320-400 ° C), high investment and operation costs, and ammonia escape, etc. The use of ozone oxidation denitrification overcomes the disadvantages of high SCR denitrification temperature, but there are still problems of incomplete oxidation of NO _X and the need for secondary treatment of the reaction product; and hydrogen peroxide (H ₂ O ₂ ) has the ability to oxidize, However, it needs to be activated by a catalyst to produce free radicals with stronger oxidizing ability. Chinese patent document CN103463978A discloses a method for simultaneous desulfurization and denitrification of flue gas by using H ₂ O ₂ catalytic oxidation, but does not consider the problem that the life of strong oxidizing free radicals is very short, so the utilization rate of H ₂ O ₂ is not high; US Patent US6793903 A H ₂ O ₂ catalyzed denitration process is also disclosed. The selected catalyst can achieve high denitration efficiency, but the deep oxidation of NO _X has not been realized, that is, there are more nitrite radicals after the reaction.

In summary, it is particularly necessary to develop a catalyst and its process with high denitrification efficiency, complete oxidation and high utilization of H ₂ O ₂ .

Contents of the invention

_In order to solve the problems of low utilization rate of H2O2 and incomplete oxidation in the denitrification process of the prior art, the present invention provides a denitrification system and method using catalytic _hydrogen peroxide, which can reduce NO in the flue gas after dedusting _X realizes deep oxidation, and the treated tail gas can be absorbed by alkali solution to achieve efficient removal of NO _X.

In order to achieve the above object, the technical scheme that the present invention takes is as follows:

_A denitrification system using catalytic _hydrogen peroxide, comprising H2O2 storage and delivery system, lye storage and delivery system, catalyst unit, reaction tower ₆ and waste liquid delivery unit _; the H2O2 storage and delivery system This system comprises the H2O2 solution storage tank ₂ that communicates with the upper part of the reaction tower ₆ , and the _{No. 1} flow meter 3, the No. 1 delivery pump 4 and the The heating device 5 is arranged in the reaction tower 6, communicates with the grid 7 at the end of the pipeline, and the low temperature control system ₁ connected with the H2O2 solution storage tank ₂ , and the lye storage and transportation system includes a reaction tower The lye storage tank 9 connected to the bottom of 6, No. two flow meter 10 and No. two pressurized delivery pump 11 arranged on the connecting pipeline between the lye storage tank 9 and the reaction tower 6, and the connecting pipeline arranged in the reaction tower 6 The spray device 12 at the end; the catalyst unit is a corrugated plate 8 that is arranged in the reaction tower 6 and is located between the grid 7 and the spray device 12; the waste liquid delivery unit is connected to the reaction tower 6 No. 3 transfer pump 13 at the bottom.

The catalyst covered on the corrugated plate 8 is a titanium-based catalyst coated with iron elements, wherein the molar ratio of iron to titanium is 1-5:100.

The H ₂ O ₂ solution storage tank 2, the H ₂ O ₂ solution storage tank 2 and the reaction tower 6 are connected to the pipeline, that is, the H ₂ O ₂ delivery pipeline, the inner surface of the grid 7, and the H ₂ O ₂ steam in the reaction tower 6 _The mixing zone with the flue gas is coated with an inert material that does not promote the decomposition of _H2O2 and the digestion of hydroxyl radicals.

The inert material is silicon dioxide or plastic or fluoroplastic.

_A denitrification method using catalytic _hydrogen peroxide, the temperature of the H2O2 solution in the H2O2 solution storage tank ₂ is controlled by the low temperature control system ₁ , the H2O2 solution is measured by the _{No. 1} flow meter 3, and the No. 1 The delivery pump ₄ transports the flow through the heating device ₅ and turns it into H2O2 steam. _The H2O2 steam passes through the grid ₇ and mixes with the dedusted flue gas entering from the flue gas inlet A of the reaction tower 6 to form a mixed gas. The mixed gas passes through the _The corrugated plate ₈ coated with catalyst reacts, and the H2O2 steam in the mixed gas reacts with the _NOx in the flue gas to generate acid gas containing nitrous acid and nitric acid; the lye in the lye storage tank 9 passes through the No. The flow meter 10 measures, and is transported by the second delivery pump 11 to the spray device 12 to form alkaline atomized droplets, which wash the acid gas to generate nitrite and nitrate solutions, nitrite and nitrate The nitrate solution is drawn out of the reaction tower through the liquid outlet B through the No. 3 delivery pump 13, and then converted into a solid product through evaporation and crystallization.

The temperature controlled by the low temperature control system 1 is 5-10°C.

The mass concentration of the H ₂ O ₂ solution is 3-6%, and the molar ratio of H ₂ O ₂ to NO _X in the flue gas is (10-15):1.

The heating temperature of the heating device 5 is 140-160°C.

The flue gas temperature is 160-240°C.

The reaction principle of the present invention is as follows:

(1) H ₂ O ₂ molecules generate hydroxyl radicals on the surface of titanium dioxide. Part of the titanium atoms in the titanium dioxide structure are replaced by iron atoms, which can further promote the generation of hydroxyl radicals. The reaction principle is as follows:

(≡Ti(IV)-OH) _surf +H ₂ O ₂ →(≡Ti(IV)-OOH) _surf +H ₂ O

H ₂ O ₂ +Fe→Fe-<OH>+·OH

(2) Hydroxyl radicals react with nitric oxide to generate high _- priced NO _X , which dissolves

In water, nitrous acid and nitric acid are generated, and the reaction principle is as follows:

Ti-<O>+2NO→Ti+N ₂ O ₃

Ti-<O>+NO→Ti+NO ₂

3Ti-<O>+2NO→Ti+N ₂ O ₅

N ₂ O ₃ +H ₂ O→2HNO ₂

N ₂ O ₅ +H ₂ O→2HNO ₃

(3) Nitrite and nitric acid vapors are absorbed by lye to generate nitrite and nitrate

(lye is example with NaOH), and reaction principle is as follows:

NaOH+HNO ₂ →NaNO ₂ +H ₂ O

NaOH+HNO ₃ →NaNO ₃ +H ₂ O

Compared with the prior art, the present invention has the following beneficial effects:

1. Taking full account of the short life of strong oxidizing substances, the arrangement of H ₂ O ₂ vaporization and flue gas mixing and corrugated plate structure is adopted. Once H ₂ O ₂ is activated, active substances will react with NO _X in time, ensuring While the denitrification efficiency is as high as 90%, the utilization rate of H ₂ O ₂ is greatly improved.

2. The physical properties of H ₂ O ₂ have been fully considered, and protective measures have been added during the storage and transportation of H ₂ O ₂ , such as coating inert materials on low-temperature storage and transportation pipeline structures, which can avoid H ₂ before the reaction to the greatest extent. Self-decomposition of _O2 .

3. The use of cheap transition metal oxide catalysts (iron titanide materials) can realize the deep oxidation of NO _X , and most of the products are converted into nitrates, which reduces the cumbersome process of secondary treatment of wastewater solutions, and the denitrification temperature range (180-220°C) is far lower than the conventional denitrification temperature, the process operation is simple, easy to implement, it has wide applicability to various fossil fuel combustion industrial processes, and the investment and operation costs are low.

In the present invention, titanium dioxide in the form of anatase is used as a substrate, and iron oxide is used as a cocatalyst; the oxidizing agent and catalyst used in the present invention have the advantages of high denitrification efficiency, reasonable process design, environmental protection, non-toxicity, low cost, and stable product quality. The denitration products in the process can be used as agricultural fertilizers or industrial raw materials without causing secondary pollution to the environment.

Description of drawings

Figure 1 is a schematic diagram of the denitrification system of the present invention.

Fig. 2 is a structural schematic diagram of the corrugated plate of the present invention.

In the figure: 1-low temperature control system; 2-H ₂ O ₂ solution storage tank; 3-No. 1 flow meter; 4-No. 1 delivery pump; 5-heating device; 6-reaction tower; 7-grid; 8- Corrugated plate; 9-alkali storage tank; 10-No. 2 flow meter; 11-No. 2 delivery pump; 12-spray device; 13-No. 3 delivery pump; A-flue gas inlet; B-liquid outlet; C - Net flue gas outlet.

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will describe in detail with reference to the drawings and specific embodiments.

As shown in Figure 1, a kind of denitrification method that adopts catalytic hydrogen peroxide of the present invention is as follows:

The temperature of the H ₂ O ₂ solution in the H ₂ O ₂ solution storage tank 2 is controlled by the low temperature control system 1, and the H ₂ O ₂ solution is measured by the No. 1 flow meter 3, and is transferred by the No. 1 delivery pump 4 and flows through the heating device 5 into H ₂ O ₂ steam, H ₂ O ₂ steam passes through the grid 7 and mixes with the dust-removing flue gas entering from the flue gas inlet A of the reaction tower 6 to form a mixed gas, and the mixed gas passes through the corrugated plate 8 coated with iron titanium oxide catalyst To react, the H2O2 steam in the mixed gas reacts with the _NOx in the flue gas to generate _acid gas containing nitrous _acid and nitric acid; the lye in the lye storage tank 9 is metered by the No. The delivery pump 11 is delivered to the spraying device 12 to form alkaline atomized droplets, which wash the acid gas to generate nitrite and nitrate solutions, and the nitrite and nitrate solutions pass through the No. 3 delivery pump 13 is withdrawn from the reaction tower through the liquid outlet B, and then transformed into a solid product through evaporation and crystallization.

As shown in FIG. 2 , it is a schematic diagram of the corrugated plate 8 .

The percentages in the following examples are mole percentages unless otherwise specified

Example 1:

H ₂ O ₂ mass fraction in the solution storage tank (2) is 3% H ₂ O _The solution is measured by the No. 1 flowmeter (3), and is transferred by the No. 1 delivery pump (4) and flows through the heating device (5) into H ₂ O ₂ steam, H ₂ O ₂ steam is mixed with the dedusted flue gas entering from the flue gas inlet A of the reaction tower (6) through the grid (7), the NO content in the flue gas is 600ppm, and the inlet flue temperature is 180 °C, the mixed gas passes through the corrugated plate (8) coated with 1% Fe-TiO ₂ catalyst to generate acid gas containing nitrous acid and nitric acid, and the space velocity ratio is 60000h ^-1 . The lye in the lye storage tank 9 is metered by the No. 2 flow meter (10), and is transported to the spraying device (12) by the No. 2 delivery pump (11) to form alkaline atomized droplets, and the alkaline atomized droplets The acid gas is washed to generate nitrite and nitrate solutions, which are pumped out of the reaction tower through the No. 3 delivery pump (13), and then evaporated and crystallized. The denitrification efficiency is as high as 90%. The waste liquid at the bottom of the reaction tower is detected by ion chromatography, and the molar ratio of nitrate and nitrite is 7.2:1.

Example 2:

When using the method of Example 1 for denitrification, wherein the concentration of nitrogen monoxide in the treated flue gas is 750ppm, the catalyst is 2% Fe-TiO ₂ , the space velocity ratio is 60000h ^-1 , the mass fraction of hydrogen peroxide is 4%, and the over The molar ratio of hydrogen oxide to nitrogen monoxide is 12:1, the inlet smoke temperature is 200°C, the oxidized acid gas is sprayed and absorbed by alkali solution, and the denitrification efficiency reaches 92%, and the waste liquid at the bottom of the reaction tower is detected by ion chromatography for nitric acid The molar ratio of root and nitrite is 7.4:1.

Example 3:

When using the method of Example 1 for denitrification, wherein the concentration of nitric oxide in the treated flue gas is 550ppm, the catalyst is 3% Fe-TiO ₂ , the space velocity ratio is 60000h ^-1 , the mass fraction of hydrogen peroxide is 4%, and the over The molar ratio of hydrogen oxide to nitrogen monoxide is 16:1, and the inlet smoke temperature is 220°C. The oxidized acid gas is sprayed and absorbed by alkali solution, and the denitrification efficiency reaches 91%. The waste liquid at the bottom of the reaction tower is detected by ion chromatography for nitric acid The molar ratio of root to nitrite is 6.9:1.

Each embodiment in the above scheme is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. In each embodiment The technical features involved can be combined with each other on the premise that they do not constitute conflicts with each other.

In the description of the present invention, the terms "No. 1", "No. 2" and so on are used for descriptive purposes only, and should not be understood as indicating or implying relative importance.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, these improvements and Retouching should also be regarded as the protection scope of the present invention.

Claims (6)

1. A kind of 1. denitrification apparatus using catalyzing hydrogen peroxide, it is characterised in that：Including H₂O₂Storage is deposited with induction system, alkali lye Storage and induction system, catalyst elements, reaction tower (6) and waste liquid supply unit composition；The H₂O₂Storage includes with transport system The H connected with reaction tower (6) top₂O₂Solution storage tanks (2), are successively set on H₂O₂Solution storage tanks (2) and reaction tower (6) No.1 flowmeter (3), No.1 delivery pump (4) and heater (5) on connecting pipeline, it is arranged in reaction tower (6), communicating pipe The grid (7) of road end, and and H₂O₂The low-temperature control system (1) of solution storage tanks (2) connection；Alkali lye storage with it is defeated Fortune system includes the alkali lye accumulator tank (9) connected with reaction tower (6) bottom, is arranged on alkali lye accumulator tank (9) and connects with reaction tower (6) No. two flowmeters (10) and No. two pressurized delivered pumps (11) on siphunculus road, and be arranged in reaction tower (6), connecting pipeline end The spray equipment (12) at end；The catalyst elements are to be arranged in reaction tower (6) and be located at grid (7) and spray equipment (12) Between the corrugated plating (8) for being covered with catalyst；The waste liquid supply unit is No. 3 delivery pumps for being connected to reaction tower (6) bottom (13)；

   The catalyst that is covered with the corrugated plating (8) is the Ti-base catalyst coated with load ferro element, and wherein iron and titanium rubs Your ratio is (1~5):100.
2. A kind of 2. denitrification apparatus using catalyzing hydrogen peroxide according to claim 1, it is characterised in that：The H₂O₂It is molten Liquid holding vessel (2), H₂O₂Solution storage tanks (2) and reaction tower (6) connecting pipeline are H₂O₂The inner surface of conveyance conduit, grid (7) And reaction tower (6) interior H₂O₂The Mixed Zone coated inert material coating of steam and flue gas, will not promote decomposing H₂O₂And resolution Hydroxyl radical free radical.
3. A kind of 3. denitrification apparatus using catalyzing hydrogen peroxide according to claim 2, it is characterised in that：The inertia material Expect for silica or plastics or fluoroplastics.
4. 4. the method for denitration of the denitrification apparatus using catalyzing hydrogen peroxide described in claim any one of 1-3, it is characterised in that： H is controlled by low-temperature control system (1)₂O₂H in solution storage tanks (2)₂O₂The temperature of solution, H₂O₂Solution passes through No.1 flowmeter (3) measure, H is changed into by the heated device of No.1 delivery pump (4) transport Stream (5)₂O₂Steam, H₂O₂Steam by grid (7) with The dedusting flue gas entered from the smoke inlets (A) of reaction tower (6) be mixed into mixed gas, and mixed gas is by coated with urging The corrugated plating (8) of agent is reacted, the H in mixed gas₂O₂Steam and the NO in flue gas_XReaction generation comprising nitrous acid and The sour gas of nitric acid；Alkali lye in alkali lye storage tank (9) measures through No. two flowmeters (10), is conveyed by No. two delivery pumps (11) To forming alkaline atomized drop in spray equipment (12), alkaline atomized drop sour gas is carried out washing generation nitrite and Nitrate solution, nitrite and nitrate solution detach reaction tower, Ran Houzai by No. three delivery pumps (13) through liquid outlet (B) Solid product is converted into by evaporative crystallization；

   The H₂O₂The mass concentration of solution is 3~6%, H₂O₂With NO in the flue gas_XMol ratio be (10~15):1；

   The heating-up temperature of the heater (5) is 140~160 DEG C.
5. 5. method of denitration according to claim 4, it is characterised in that the temperature that the low-temperature control system (1) controls is 5 ~10 DEG C.
6. 6. method of denitration according to claim 5, it is characterised in that：Described flue-gas temperature is 160-240 DEG C.