Municipal sludge and household garbage co-fired dioxin inhibitor and preparation method thereof

Abstract

The invention discloses a dioxin inhibitor for co-combustion of municipal sludge and household garbage and a preparation method of the dioxin inhibitor, and belongs to the technical field of incineration flue gas purification. The dioxin inhibitor is prepared from the following components in parts by weight: 10 to 40 parts of urea, 20 to 50 parts of ammonium phosphate, 20 to 30 parts of alkali metal oxide, 40 to 60 parts of fly ash, 2 to 3 parts of bentonite, 20 to 40 parts of a pore forming agent and 10 to 30 parts of a modifier, and the modifier is selected from nitrate and N, N-dimethyl-4-nitrobenzylamine. According to the characteristics of pollutants in co-combustion of municipal sludge and household garbage, through component setting of the inhibitor, dioxin emission is effectively reduced, meanwhile, the burden of follow-up dioxin treatment is relieved, the dioxin treatment cost of garbage incineration is reduced, the garbage incineration heat value is increased, and the garbage incineration process is more environmentally friendly and more economical.

Description

Technical Field

[0001] The present application relates to a dioxin inhibitor for the mixed combustion of municipal sludge and domestic garbage, belonging to the technical field of incineration flue gas purification. Background Art

[0002] There are three main ways to deal with domestic waste: landfill, composting, anaerobic fermentation and incineration. Each of these methods has its own advantages and disadvantages and different scopes of application. Among them, incineration is currently a more recognized solid waste disposal technology, which can not only reduce the mass of solid waste by 70% and the volume by 90%, but also recover heat and electricity.

[0003] However, due to the complex composition of domestic waste, including plastics, heavy metals and other substances, SO will be generated during the incineration process. x 、NO x , HCl, dust, heavy metals and other toxic substances, especially persistent organic pollutants (POPs) dioxins (PCDD / F). Among them, 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD) is the most toxic, 1,000 times more toxic than potassium cyanide, and has cumulative toxicity, causing serious pollution to the production environment and the water and soil around the factory.

[0004] Existing dioxin inhibitors have been used in actual production as "special medicines" to inhibit the generation of dioxins during the incineration of domestic waste. However, since my country's current incineration plants mainly deal with domestic waste, and the treatment of industrial solid waste is also urgently needed, in order to effectively reduce the amount and toxicity of solid waste and achieve efficient energy recovery, domestic waste can be co-disposed with some industrial solid waste. The content of acid gas in mixed incineration materials is higher, which often causes corrosion to equipment and pipelines. At the same time, different types of garbage will also affect the effect of existing dioxin inhibitors. Therefore, there is an urgent need for a dioxin inhibitor suitable for the mixed treatment of solid waste and domestic waste. Summary of the invention

[0005] In order to solve the above problems, the present application proposes a dioxin inhibitor for the co-incineration of municipal sludge and domestic waste and a preparation method thereof. This scheme targets the characteristics of pollutants in the co-incineration of municipal sludge and domestic waste, and through the component setting of the inhibitor, effectively reduces dioxin emissions while reducing the burden of subsequent dioxin treatment.

[0006] According to one aspect of the present application, a dioxin inhibitor for co-burning of municipal sludge and domestic waste is provided, which is prepared from the following components: 10 to 40 parts of urea, 20 to 50 parts of ammonium phosphate, 20 to 30 parts of alkali metal oxides, 40 to 60 parts of fly ash, 2 to 3 parts of bentonite, 20 to 40 parts of pore formers and 10 to 30 parts of modifiers, wherein the modifier is selected from nitrates and N,N-dimethyl-4-nitrobenzylamine.

[0007] Urea can consume chlorine sources at low temperatures and react with dioxin precursors at high temperatures to prevent the formation of dioxins. 2+ , Fe 3+ Heavy metal catalysts combine to form complexes, which reduce the activity of metal catalysts.

[0008] Phosphorus in ammonium phosphate can react with Cu 2+ The reaction has a passivating effect on the metal catalyst; the ammonium ion can decompose NH3, consume the chlorine source in the incinerated garbage, and block the formation of dioxins; in addition, ammonium phosphate can induce heavy metals to adsorb on the surface of phosphate and chelate to precipitate, reducing the de novo formation of dioxins.

[0009] In addition to absorbing chlorine sources and passivating heavy metals, alkali metal oxides can also block the conversion of precursors such as chlorophenols and anthracenes into dioxins, change the pH value of the fly ash surface, and reduce the formation of dioxins.

[0010] During the process of garbage combustion, urea, ammonium phosphate and alkali metal oxides cooperate with each other to inhibit the production of dioxins from three aspects: de novo formation of dioxins, formation of precursors and dioxin formation catalysts, which can effectively reduce the dioxins produced by garbage incineration.

[0011] Since the mixed combustion of municipal sludge and domestic waste has a higher calorific value, fly ash, bentonite, pore-forming agents and modifiers can form porous materials during the incineration process. They can not only physically adsorb the dioxins produced, but also chemically adsorb the dioxins and their precursors through modification, making the dioxins less likely to be released. At the same time, the porous structure can provide binding sites for other dioxin inhibitors, thereby fully exerting the inhibitory effect.

[0012] The mixture of municipal sludge and domestic waste has a low temperature and contains moisture in the early stage of incineration. Under this condition, N, N-dimethyl-4-nitrobenzylamine in the fly ash particles undergoes ion exchange with nitrate to modify the fly ash particles. The modified fly ash particles can form π-π bonds with dioxins and their precursors containing aromatic structures to achieve chemical adsorption.

[0013] Optionally, the pore-forming agent is activated carbon and calcium carbonate, and the ratio of the two is (10-20):1.

[0014] Activated carbon and calcium carbonate are oxidized or decomposed at temperatures above 850°C. On the one hand, they act as pore formers to form pores. On the other hand, calcium oxide, the decomposition product of calcium carbonate, can inhibit dioxins in porous materials, thereby improving the dioxin inhibition effect. At the same time, activated carbon and calcium carbonate produce pores at high temperatures, which can prevent municipal sludge or fluid domestic waste under low temperature conditions from clogging the micropores of porous materials, rendering their adsorption ineffective.

[0015] The pore-forming performance of calcium carbonate is poor. If the content ratio of calcium carbonate in the pore-forming agent is too high, the pore-forming effect will be poor.

[0016] Optionally, the porosity of the porous material formed by the fly ash, bentonite, pore former and modifier during the incineration process is 36-55%. Too large a porosity is accompanied by a problem of reduced mechanical strength of the porous material, which affects the adsorption effect.

[0017] Optionally, the modifier comprises nitrate and N,N-dimethyl-4-nitrobenzylamine in a mass ratio of (1:1-1.2); the nitrate is at least one of magnesium nitrate or calcium nitrate.

[0018] If the amount of N, N-dimethyl-4-nitrobenzylamine added is too little, it cannot form a sufficient combination with nitrate, reducing the efficiency of the product's coordinated chemical adsorption; if the amount of N, N-dimethyl-4-nitrobenzylamine added is too much, the excess N, N-dimethyl-4-nitrobenzylamine cannot be effectively combined and becomes a precursor of dioxins during the subsequent incineration process.

[0019] Optionally, the alkali metal oxide is at least one of calcium oxide or magnesium oxide.

[0020] The ammonium phosphate salt includes one or more of diammonium phosphate, diammonium hydrogen phosphate and ammonium polyphosphate, preferably diammonium phosphate.

[0021] Optionally, the mass ratio of the fly ash to bentonite is 20:1; the mass ratio of the fly ash to bentonite is 5:3.

[0022] The porous ceramics formed under this ratio have higher porosity, larger specific surface area and good adsorption activity.

[0023] Optionally, 1 to 2 portions of transition metal oxides are also included.

[0024] Transition metal oxides can promote the oxidation and decomposition of generated dioxins, further reducing dioxin emissions. Excessive transition metal oxides have little effect on the reaction catalysis process, but they will combine with acidic gases to reduce the inhibitory effect of S and N on dioxin generation.

[0025] Optionally, the oxide of the transition metal is one or more of vanadium-titanium blast furnace slag, titanium tailings, and tungsten smelting slag.

[0026] Selecting industrial waste residues such as vanadium-titanium blast furnace slag, titanium tailings, and tungsten smelting slag as catalysts for dioxin decomposition can, on the one hand, meet the needs of oxidative decomposition of a small amount of dioxins generated after inhibition, and on the other hand, it can also reduce treatment costs and promote the reuse of industrial waste residues.

[0027] Optionally, the ammonium phosphate salt includes one or more of diammonium phosphate, diammonium hydrogen phosphate and ammonium polyphosphate.

[0028] Preferably, diammonium phosphate is used, as diammonium phosphate has a higher blocking activity.

[0029] Fly ash is combined with bentonite and activated carbon to form porous materials during the waste incineration process. In this solution, it is porous ceramics, which have higher porosity and stronger adsorption than fly ash alone.

[0030] In a second aspect, the present invention provides a method for preparing a dioxin inhibitor for co-incineration of municipal sludge and domestic waste, which is used to prepare the aforementioned dioxin inhibitor for co-incineration of municipal sludge and domestic waste, comprising the following steps:

[0031] S1. Mix urea, ammonium phosphate, alkali metal oxide and transition metal oxide uniformly and crush them;

[0032] S2, fully grinding, sieving and mixing fly ash, bentonite, pore former and modifier, adding deionized water, stirring thoroughly, compacting and granulating, and drying to obtain fly ash particles;

[0033] S3. Evenly mix the products obtained in S1 and S2 to obtain the finished dioxin inhibitor.

[0034] Optionally, the drying temperature is 120-160° C.; and the sieving mesh size is 400 meshes.

[0035] Optionally, the mass ratio of the total mass of the fly ash, bentonite and activated carbon to deionized water is 1:0.8-1.5.

[0036] The beneficial effects of this application include but are not limited to:

[0037] 1. The dioxin inhibitor provided in the present application uses urea, ammonium phosphate, calcium oxide and fly ash as the components of the inhibitor, inhibits the generation of dioxins through multiple pathways such as passivating catalysts, combining dioxin precursors and chlorine sources, and greatly reduces the generation of dioxins; at the same time, the generated dioxins are decomposed to further reduce the emission of dioxins; the modified porous material is used as the skeleton material of the inhibitor to achieve physical adsorption and chemical adsorption of dioxins and their precursors, and provide reaction sites for the inhibitor component and the decomposition catalyst, so that the inhibition and decomposition catalytic process reactions are more sufficient.

[0038] 2. The dioxin inhibitor provided in the present application forms porous ceramics during the waste incineration process by adding fly ash and combining it with bentonite and activated carbon, thereby providing a stronger adsorption effect and avoiding failure caused by the fluid in municipal sludge and domestic waste blocking the pores. At the same time, there is no need to directly add expensive porous ceramics, thereby reducing the cost of waste treatment. In addition, the subsequent activated carbon adsorption process can be omitted or simplified to improve the treatment efficiency.

[0039] 3. The dioxin inhibitor provided in the present application uses vanadium-titanium blast furnace slag, titanium tailings, and tungsten smelting slag as dioxin oxidation and decomposition catalysts, which meets the catalytic requirements while reducing the cost of treatment; in addition, the present application mixes the dioxin oxidation and decomposition catalyst with the inhibitory component to act together in the incineration equipment, avoiding the dioxins being adsorbed by fly ash or subsequent activated carbon before oxidation and decomposition, thereby improving the treatment efficiency and preventing the pollution risks that may be caused by the intermediate steps.

[0040] 4. The dioxin inhibitor provided in the present application uses calcium oxide as one of the inhibitor components and limits its composition. In addition to inhibiting the generation of dioxins, it can also bind excessive acidic substances such as S and N in the mixed incineration of municipal sludge and domestic garbage, thereby reducing acid-base corrosion of incineration equipment. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0042] A dioxin inhibitor is prepared by the following method:

[0043] S1. Mix urea, ammonium phosphate, alkali metal oxide and transition metal oxide uniformly and crush them;

[0044] S2, fully grinding fly ash, bentonite, pore former and modifier, passing through a 400-mesh sieve and mixing evenly, then adding deionized water 1.2 to 1.5 times the mass of the solid matter, fully stirring and compacting and granulating, and drying at 120 to 160° C. to obtain fly ash particles;

[0045] S3. Evenly mix the products obtained in S1 and S2 to obtain the finished dioxin inhibitor.

[0046] The dioxin inhibitors of the following examples and comparative examples are obtained by the above preparation method:

[0047] Example 1

[0048] The components of the dioxin inhibitor are: 40 parts of urea, 20 parts of diammonium hydrogen phosphate, 30 parts of calcium oxide, 40 parts of fly ash, 2 parts of bentonite, 24 parts of pore formers (activated carbon: calcium carbonate = 10:1), 15 parts of magnesium nitrate and 15 parts of N, N-dimethyl-4-nitrobenzylamine. 65 parts of water are added to the fly ash particles during the preparation process, and the particles are dried at 120°C to finally prepare dioxin inhibitor 1#.

[0049] Example 2

[0050] The components of the dioxin inhibitor are: 10 parts of urea, 50 parts of ammonium polyphosphate, 20 parts of magnesium oxide, 60 parts of fly ash, 3 parts of bentonite, 36 parts of pore formers (activated carbon: calcium carbonate = 20:1), 5 parts of calcium nitrate and 5 parts of N, N-dimethyl-4-nitrobenzylamine. 69 parts of water are added during the preparation of fly ash particles, and the particles are dried at 160°C to finally prepare dioxin inhibitor 2#.

[0051] Example 3

[0052] The components of the dioxin inhibitor are: 15 parts of urea, 40 parts of diammonium dihydrogen phosphate, 30 parts of calcium oxide, 60 parts of fly ash, 3 parts of bentonite, 36 parts of pore formers (activated carbon: calcium carbonate = 20:1), 15 parts of magnesium nitrate and 15 parts of N, N-dimethyl-4-nitrobenzylamine. 86 parts of water are added during the preparation of fly ash particles, and the particles are dried at 160°C to finally prepare dioxin inhibitor 3#.

[0053] Example 4

[0054] The difference from Example 3 is that it further comprises 1 part of vanadium-titanium blast furnace slag and 1 part of titanium tailings to prepare dioxin inhibitor 4#.

[0055] Example 5

[0056] The difference from Example 3 is that it further includes 1 portion of tungsten smelting slag to prepare dioxin inhibitor 5#.

[0057] Example 6

[0058] The difference from Example 4 is that the ratio of activated carbon to calcium carbonate is 1:10, and dioxin inhibition 6# is prepared.

[0059] Example 7

[0060] The difference from Example 4 is that the ratio of activated carbon to calcium carbonate is 15:1, and dioxin inhibition 7# is prepared.

[0061] Example 8

[0062] The difference from Example 4 is that the sieve mesh number of fly ash, bentonite, pore former and modifier is 200 mesh, and dioxin inhibitor 8# is prepared.

[0063] Example 9

[0064] The difference from Example 4 is that 3 parts of bentonite are replaced by 2 parts of bentonite.

[0065] Example 10

[0066] The difference from Example 4 is that 36 parts of the pore former are replaced by 40 parts of the pore former.

[0067] Embodiment 11

[0068] The difference from Example 3 is that 5 portions of tungsten smelting slag are further included to prepare dioxin inhibitor 5#.

[0069] Comparative Example 1

[0070] The difference from Example 4 is that 15 parts of urea, 40 parts of ammonium phosphate, and 30 parts of calcium oxide are replaced with 85 parts of ammonium phosphate to obtain dioxin inhibition D1#.

[0071] Comparative Example 2

[0072] The difference from Example 4 is that fly ash is replaced with red mud to prepare dioxin inhibition D2#.

[0073] Comparative Example 3

[0074] The difference from Example 4 is that N,N-dimethyl-4-nitrobenzylamine is replaced with ammonium nitrate to prepare dioxin inhibition D3#.

[0075] Comparative Example 4

[0076] The difference from Example 4 is that 60 parts of fly ash and 3 parts of bentonite are replaced by 30 parts of fly ash and 30 parts of bentonite to prepare dioxin inhibitor D4#.

[0077] Experimental Example 1

[0078] Mixed garbage was burned in a 25t / h circulating fluidized bed boiler, of which municipal sludge accounted for 15%, and the amount of dioxin inhibitor added was 0.25t / h. The inhibitor was added before entering the boiler, and the addition of the inhibitor was accompanied by the tumbling and stirring of the garbage. The incineration temperature in the boiler was not less than 850℃. The flue gas was sampled and tested, and the sampling and analysis methods of dioxins were referred to the "Determination of Dioxins in Ambient Air and Waste Gas by Isotope Dilution High Resolution Gas Chromatography-High Resolution Mass Spectrometry" (HJ 77.2-2008).

[0079] Experimental Example 2

[0080] The porosity of the porous material after incineration in Experimental Example 1 was measured.

[0081] Experimental Example 3

[0082] The contents of nitrogen oxides and sulfur dioxide in the flue gas sampled in Experimental Example 1 were measured. The sulfur dioxide was measured using the "Constant Potential Electrolysis Method for the Determination of Sulfur Dioxide in Waste Gas from Stationary Pollution Sources" (HJ57-2017), and the nitrogen oxide was measured using the "Constant Potential Electrolysis Method for the Determination of Nitrogen Oxides in Waste Gas from Stationary Pollution Sources" (HJ693-2014).

[0083] Characterization example

[0084] The measured data of the substances in Experimental Examples 1 to 3 are as follows:

[0085]

[0086]

[0087] It can be seen from the data in the table that after adding the inhibitor described in this scheme, the content of dioxins, nitrogen oxides and sulfur dioxide is greatly reduced, which improves production efficiency and safety, reduces pollutant emissions, and makes waste incineration more economical and environmentally friendly.

[0088] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0089] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A dioxin inhibitor for the co-incineration of municipal sludge and domestic garbage, characterized in that: The invention is prepared from the following components by weight: 10 to 40 parts of urea, 20 to 50 parts of ammonium phosphate, 20 to 30 parts of alkali metal oxide, 40 to 60 parts of fly ash, 2 to 3 parts of bentonite, 20 to 40 parts of pore former and 10 to 30 parts of modifier, wherein the modifier is selected from nitrate and N,N-dimethyl-4-nitrobenzylamine.

2. The dioxin inhibitor for mixed combustion of municipal sludge and domestic waste according to claim 1, characterized in that: The pore-forming agent is activated carbon and calcium carbonate, and the ratio of the two is (10-20):

1.

3. The dioxin inhibitor for mixed combustion of municipal sludge and domestic waste according to claim 1, characterized in that: The modifier is a nitrate and N,N-dimethyl-4-nitrobenzylamine in a mass ratio of (1:1-1.2); the nitrate is at least one of magnesium nitrate and calcium nitrate.

4. The dioxin inhibitor for mixed combustion of municipal sludge and domestic waste according to claim 1, characterized in that: The alkali metal oxide is at least one of calcium oxide and magnesium oxide; the ammonium phosphate salt includes one or more of diammonium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium polyphosphate.

5. The dioxin inhibitor for mixed combustion of municipal sludge and domestic waste according to claim 1, characterized in that: The mass ratio of the fly ash to bentonite is 20:1; the mass ratio of the fly ash to the pore-forming agent is 5:

3.

6. The dioxin inhibitor for co-incineration of municipal sludge and domestic waste according to claim 1, characterized in that: It also includes 1 to 2 parts of transition metal oxides.

7. The dioxin inhibitor for co-incineration of municipal sludge and domestic waste according to claim 6, characterized in that: The oxide of the transition metal is one or more of vanadium-titanium blast furnace slag, titanium tailings, and tungsten smelting slag.

8. A method for preparing a dioxin inhibitor for co-burning of municipal sludge and domestic garbage, characterized in that: The method for preparing the dioxin inhibitor for mixed combustion of municipal sludge and domestic garbage as claimed in claims 1 to 7 comprises the following steps: S1. Mix urea, ammonium phosphate, alkali metal oxide and transition metal oxide uniformly and crush them; S2, fully grinding, sieving and mixing fly ash, bentonite, pore former and modifier, adding deionized water, stirring thoroughly, compacting and granulating, and drying to obtain fly ash particles; S3. Evenly mix the products obtained in S1 and S2 to obtain the finished dioxin inhibitor.

9. The method for preparing a dioxin inhibitor for co-incineration of municipal sludge and domestic waste according to claim 8, characterized in that: The drying temperature is 120-160° C.; the sieving mesh number is 400 meshes.

10. The method for preparing a dioxin inhibitor for co-incineration of municipal sludge and domestic waste according to claim 8, wherein the mass ratio of the total mass of the fly ash, bentonite, pore former and modifier to the mass ratio of deionized water is 1:1.2-1.5.

Images