Sludge and household garbage collaborative incineration treatment method

Abstract

The invention discloses a sludge and household garbage collaborative incineration treatment method. The method comprises the steps of sludge pretreatment, household garbage pretreatment, auxiliary material treatment, collaborative incineration, flue gas treatment and ash treatment. According to the method, the stability of collaborative incineration is guaranteed through low-temperature drying of the sludge, preparation of the refuse derived fuel and optimization of auxiliary materials. And a two-step combustion and quenching technology is adopted, so that the generation of NOx and dioxin is effectively inhibited. And preliminary incineration desalination and differential stabilization processes are innovatively introduced, so that the problems of high-salinity slagging and heavy metal leaching are solved. After the ash residues are separated and metal is recycled, accurate curing is carried out by combining a wide pH chelating agent and intelligent response microcapsules, and resource utilization and long-term environmental safety are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sludge treatment, in particular to a sludge and household garbage co-processing incineration method. BACKGROUND

[0002] With the continuous acceleration of urbanization, the amount of sludge generated in the municipal sewage treatment process increases year by year. Sludge is rich in organic matter, pathogens and heavy metals, and if not properly disposed of, it can easily cause serious secondary pollution and pose a threat to the environment and human health.

[0003] At the same time, the output of municipal household garbage is also rising. At present, incineration has become one of the mainstream ways of disposing of household garbage, as it can achieve reduction, harmlessness and energy recovery.

[0004] However, the existing treatment technologies all have significant limitations:

[0005] Sludge treatment problem: Current sludge is mostly treated by landfill, composting or incineration alone. These methods generally have problems such as occupying a large amount of land resources, producing odors and disturbing the public, high energy consumption, and difficulty in properly disposing of the ash after incineration.

[0006] Household garbage incineration problem: The calorific value of household garbage itself fluctuates greatly, and when a large amount of low-calorific-value garbage is mixed in, it will seriously affect the stability of the incineration process, making it difficult to maintain the furnace temperature.

[0007] Co-processing difficulty: If high-moisture, low-calorific-value sludge is directly mixed into the household garbage incinerator for processing, it will easily cause the furnace temperature to drop, resulting in incomplete combustion. This not only reduces energy efficiency, but also increases the risk of generating harmful substances such as dioxin, bringing new environmental hazards, for which we propose a sludge and household garbage co-processing incineration method. SUMMARY

[0008] The purpose of the present application is to provide a sludge and household garbage co-processing incineration method to solve the problems in the background art.

[0009] To achieve the above-mentioned purpose, the present application provides the following technical solution: A sludge and household garbage co-processing incineration method, the sludge and household garbage co-processing incineration method comprising the following steps:

[0010] Step 1: Sludge pretreatment: The sludge is dewatered to reduce its moisture content to below 60%, then low-temperature drying is used to reduce the moisture content of the sludge to below 30% to obtain dried sludge, and then the dried sludge is crushed and sieved to a particle size of less than 20mm to obtain sludge powder;

[0011] Step two: domestic waste pretreatment: domestic waste mechanical screening, removing non-combustible materials, crushing the combustible waste to a particle size of 50mm or less to form a waste-derived fuel, and measuring the derived waste heat value as a basis for proportioning;

[0012] Step three: auxiliary material treatment: selecting fly ash and steel slag as the synergistic auxiliary material, drying and crushing the synergistic auxiliary material, and screening the synergistic auxiliary material to reduce the particle size of the synergistic auxiliary material to 50mm or less;

[0013] Step four: synergistic incineration: the waste-derived fuel, sludge powder and synergistic auxiliary material are sequentially placed from top to bottom into the combustion furnace, the combustion furnace has an incineration temperature of 850-1100℃ and an incineration residence time of 2-5s, and then secondary air is used to accelerate combustion to form ash;

[0014] Step five: flue gas purification: when the flue gas is discharged, it passes through a dust cloth bag and an activated carbon layer to adsorb dust and heavy metals in the flue gas, and then lime slurry solution is sprayed into the discharged flue gas;

[0015] Step six: ash treatment: the iron in the ash after incineration is crushed and magnetically separated, and aluminum and copper non-ferrous metals are recovered by eddy current separation, and then a stabilizing agent is sprayed onto the remaining ash for solidification treatment.

[0016] If high-moisture, low-calorific-value sludge is directly mixed into domestic waste incinerators for treatment, it is easy to cause the furnace temperature to drop, resulting in incomplete combustion. This not only reduces energy utilization efficiency, but also increases the risk of generating harmful substances such as dioxins, bringing new environmental hazards. The present application co-incinerates the pretreated sludge powder, waste-derived fuel and synergistic auxiliary material, which not only effectively utilizes the high calorific value of domestic waste to make up for the low calorific value of sludge, ensuring the stability and completeness of combustion, but also contains free calcium oxide and iron oxide in an amount of not less than 5% by mass in fly ash. The added free calcium oxide can react with hydrogen chloride in the flue gas to form calcium chloride and water, which can reduce the concentration of HCl in the gas phase, thereby inhibiting the synthesis of dioxins from the source. Moreover, iron oxide can act as a catalyst at high temperatures to promote the complete oxidation and decomposition of chlorine-containing organic matter, converting it into harmless carbon dioxide, water and hydrogen chloride, thereby reducing the content of dioxins in the final flue gas. In addition, steel slag usually contains high amounts of calcium, iron, magnesium and other metal oxides. The feeding method of sequentially placing the materials from top to bottom in step four, combined with the air distribution strategy of primary air and secondary air, forms good conditions for stratified combustion and turbulent mixing, which helps to prolong the residence time of flue gas in the high-temperature zone, improve combustion efficiency, and reduce the generation of incomplete combustion products.

[0017] Further description of the above technical solutions:

[0018] The step four cooperates with the incineration furnace, and the outlet of the furnace is provided with a quenching device, so that the high-temperature flue gas is cooled to below 200 DEG C.

[0019] As a further description of the above technical solution:

[0020] The fly ash in the auxiliary material in the step three auxiliary material processing step contains free calcium oxide and iron oxide with a mass fraction of not less than 5%.

[0021] As a further description of the above technical solution:

[0022] The step four cooperates with the incineration process and is divided into two-step combustion, the first step air supply content is 60-80%, the combustion temperature is 850-950 DEG C, and the second step combustion process is supplemented with air, and the combustion temperature is 950-1100 DEG C.

[0023] As a further description of the above technical solution:

[0024] The iron in the step six ash treatment is mixed with the auxiliary material in the step three.

[0025] As a further description of the above technical solution:

[0026] The step four cooperates with the incineration process and is divided into two-step combustion, the first step air supply content is 60-80%, the combustion temperature is 850-950 DEG C, and the second step combustion process is supplemented with air, and the combustion temperature is 950-1100 DEG C.

[0027] As a further description of the above technical solution:

[0028] In the step three auxiliary material processing, the auxiliary material further includes kaolin and montmorillonite, and the mass ratio of the kaolin and montmorillonite to the mass of the sludge powder is 5-10%.

[0029] As a further description of the above technical solution:

[0030] In the step six ash treatment, the ash is measured for acid neutralization capacity index before being sprayed with the stabilizer, and the differentiating stabilization treatment is implemented according to the acid neutralization capacity index value of the ash.

[0031] The differentiating stabilization process includes: for the high-ash acid neutralization capacity index value ash, a weak alkali responsive chelating agent and a carbonization promoter are used; for the low-ash acid neutralization capacity index value ash, a wide pH responsive chelating agent and an alkaline slow-release material are used; for the medium-ash acid neutralization capacity index value ash, a standard chelating agent and an adsorbent are used.

[0032] As a further description of the above technical solutions:

[0033] The wide pH response chelating agent takes porous diatomite as a carrier, contains dithiocarbamate or trithiol triazine, nano hydrotalcite or hydroxyl carbonate as a pH buffer component;

[0034] The double-shell microcapsule manufacturing raw material is calcium hydroxide, the inner shell is polyacrylic acid, and the outer shell is polylactic acid.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] 1. The present application uses pre-treated sludge powder, waste-derived fuel and specific synergistic adjuvants for synergistic incineration, uses high-calorific-value waste to make up for the low calorific value of sludge, ensures the stability and efficiency of the incineration process, and realizes the synergistic resource utilization of the two wastes;

[0037] 2. The two-stage combustion method of anoxic combustion and oxygen-rich combustion is adopted, the combustion temperature and atmosphere are effectively controlled, the generation of thermal-type nitrogen oxides is significantly reduced, the synthesis of dioxin precursors is inhibited, an emergency cooling device is arranged at the downstream position of the furnace outlet of the combustion furnace, the high-temperature flue gas can be rapidly cooled to below 200 DEG C in a short time, the temperature window for the secondary synthesis of dioxin is controlled, thereby effectively inhibiting the secondary synthesis of dioxin, and the fly ash containing not less than 5% free calcium oxide and iron oxide is selected as an adjuvant, which can act as a catalyst or a reactant at high temperature to promote the complete decomposition of chlorine-containing organic matter and further inhibit the generation of dioxin;

[0038] 3. In addition, a low-temperature preliminary incineration step with an incineration temperature of 500-650 DEG C is arranged before main incineration, the soluble salt in the sludge is migrated and enriched on the surface of the particles, and then is separated by air flow disturbance and falls into the salt collection area, thereby effectively avoiding the problems of slagging and corrosion of the incinerator caused by high salt content, and kaolin and montmorillonite are added in the adjuvant, which can react with alkali metal ions to generate stable silicate minerals at high temperature, thereby "fixing" the soluble salt into insoluble mineral phase and improving the stability of the ash.

[0039] 4. Finally, a differential stabilization treatment process is adopted, the most suitable chelating agent and stabilization material are selected according to the acid neutralization capacity index of the ash, precise and efficient heavy metal stabilization is realized, and double-shell microcapsules are added in the stabilization process, which can intelligently release alkaline substances when the pH decreases, thereby maintaining the stability of the ash for a long time and preventing the leaching of heavy metals. DETAILED DESCRIPTION

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1:

[0042] This invention provides a technical solution: a method for co-incinerating sludge and municipal solid waste, the method comprising the following steps:

[0043] Step 1: Sludge pretreatment: The sludge is dewatered to reduce its moisture content to below 60%, and then the moisture content is reduced to below 30% by low-temperature drying to obtain dried sludge. The dried sludge is then crushed and screened to a particle size of less than 20mm to obtain sludge powder.

[0044] Step 2: Pre-treatment of municipal solid waste: Mechanically screen municipal solid waste to remove non-combustible materials, crush combustible waste to a particle size of less than 50mm to form waste-derived fuel, and determine the calorific value of the derived waste as the basis for proportioning;

[0045] Step 3: Auxiliary material treatment: Fly ash and steel slag are selected as co-auxiliary materials. The co-auxiliary materials are dried and crushed, and then screened to reduce the particle size to below 50 mm. The fly ash in the co-auxiliary materials contains not less than 5% free calcium oxide and iron oxide by mass. The free calcium oxide and iron oxide can act as catalyst carriers or reactants during high-temperature incineration, promoting the complete decomposition of chlorinated organic compounds and inhibiting the synthesis of dioxin precursors.

[0046] Step 4: Co-incineration: Waste-derived fuel, sludge powder and co-processing materials are laid from top to bottom into the combustion furnace. The combustion temperature of the combustion furnace is 850-1100℃ and the combustion residence time is 2-5s. Then, secondary air is used to accelerate combustion and form ash. The primary combustion is used for drying and combustion, and the secondary air is used to enhance disturbance and complete combustion.

[0047] Step 5: Flue gas purification: When the flue gas is discharged, it passes through the dust collector bag and activated carbon layer to adsorb dust and heavy metals in the flue gas. Then, lime slurry solution is sprayed onto the discharged flue gas.

[0048] Step Six: Ash and Slag Treatment: After incineration, the ash and slag are crushed and magnetically separated to remove iron. Eddy current separation is used to recover aluminum and copper non-ferrous metals. Then, a stabilizer is sprayed onto the remaining ash and slag for solidification treatment.

[0049] By co-incinerating pretreated sludge powder, waste-derived fuel, and co-excipients, the high calorific value of municipal solid waste is effectively utilized to compensate for the low calorific value of sludge, ensuring the stability and completeness of combustion. Furthermore, the fly ash contains at least 5% free calcium oxide and iron oxide by mass. The added free calcium oxide can react with hydrogen chloride in the flue gas to produce calcium chloride and water. This setup reduces the concentration of HCl in the gas phase, thereby inhibiting dioxin synthesis at its source. At high temperatures, iron oxide acts as a catalyst, promoting the complete oxidation and decomposition of chlorinated organic matter, converting it into harmless carbon dioxide, water, and hydrogen chloride, thus reducing the dioxin content in the final flue gas. Steel slag typically contains high levels of calcium, iron, magnesium, and other metal oxides. The top-to-bottom feeding method in step four, combined with the primary and secondary air distribution strategy, creates favorable stratified combustion and turbulent mixing conditions. This helps extend the residence time of flue gas in the high-temperature zone, improves combustion efficiency, and reduces the generation of incomplete combustion products.

[0050] Example 2:

[0051] In step four, the co-incineration step, a rapid cooling device is installed downstream of the furnace outlet of the combustion furnace to cool the discharged high-temperature flue gas to below 200°C.

[0052] Among these methods, rapidly reducing the temperature of the discharged high-temperature flue gas to below 200°C allows the flue gas to quickly pass through the temperature window for dioxin resynthesis, thereby effectively inhibiting the formation of dioxins.

[0053] The fourth step of the co-combustion process is divided into two combustion steps. In the first step, the air supply content is 60-80% and the combustion temperature is 850-950℃. In the second step, the air is supplemented and the combustion temperature is 950-1100℃.

[0054] The first step, oxygen-deficient combustion, can be performed with an air supply of only 60-80%, creating a reducing environment. In this atmosphere, nitrogen in the fuel and nitrogen in the air are difficult to fully oxidize to form thermal NOx. At the same time, the small amount of NOx already generated may be reduced to nitrogen by incompletely burned hydrocarbons or carbon monoxide and other reducing gases. The combustion temperature is controlled at 850-950℃, which also helps to suppress the formation of high-temperature thermal NOx. The second step, oxygen-enriched combustion, builds on the first stage by supplementing the remaining air to form an oxygen-enriched environment. This combustion process can raise the temperature to 950-1100℃, which ensures that the combustible gases and soot that were not fully burned in the first stage are fully burned, achieving complete combustion. At the same time, it raises the combustion temperature to the high-temperature range required for the complete decomposition of dioxins.

[0055] The iron extracted by magnetic separation in step six is ​​mixed with the synergistic additives from step three.

[0056] The method involves recycling the iron metal recovered from the incineration ash as part of the co-processing feedstock, thus achieving a closed-loop circulation of materials within the system and preventing the loss of valuable metal resources. Moreover, the recovered iron is mainly metallic iron, which may play a certain catalytic role in the subsequent incineration process, improve the melting characteristics of the slag, and help stabilize the combustion process.

[0057] The fourth step involves adding a preliminary incineration step at the front end of the co-incineration process. The temperature of the preliminary incineration furnace is 500-650℃, and the incineration time is 10-20 minutes. The preliminary incineration causes the soluble salts in the sludge to migrate and accumulate on the particle surface at low temperature. The salt-enriched ash slag is detached by airflow disturbance during the movement of the grate and falls into the salt collection area at the bottom of the incinerator.

[0058] Pretreatment at a low temperature of 500-650℃ avoids salt melting, fundamentally preventing slagging and corrosion problems. During low-temperature incineration, soluble salts migrate and accumulate on the surface of sludge particles. When the material moves on the grate, the surface particles or salt crystals are blown off by airflow disturbance, actively separating and falling into the salt collection area at the bottom. The separated salts are collected in the salt collection area and can be disposed of as hazardous waste in a specialized and safe manner, avoiding the problem of heavy metal leaching and toxicity exceeding the standard in the overall ash slag due to its dispersion in a large amount of ash slag.

[0059] In step three, the auxiliary materials processing also includes kaolin and montmorillonite, with the mass ratio of kaolin and montmorillonite being 5-10% of the mass of the sludge powder.

[0060] During high-temperature incineration, these minerals react with alkali metal ions to form stable silicate minerals, converting soluble salts into insoluble mineral phases.

[0061] In step six, ash and slag treatment, before the stabilizer is sprayed, the acid neutralization capacity index of the ash and slag is measured, and differentiated stabilization treatment is implemented based on the acid neutralization capacity index value of the ash and slag.

[0062] The differentiated stabilization process includes: using a weakly alkaline responsive chelating agent and a carbonization promoter for ash with a high acid neutralization index; using a wide pH responsive chelating agent and an alkaline slow-release material for ash with a low acid neutralization index; and using a combination of a standard chelating agent and an adsorbent for ash with a medium acid neutralization index.

[0063] Among them, by pre-measuring the acid neutralization capacity index of ash residue, treatment on demand and precise drug administration were achieved, avoiding waste of drugs or insufficient stability.

[0064] For ash with high acid neutralization capacity: Weak base responsive chelating agent is used to avoid the chelating agent from failing due to the excessive alkalinity of the ash itself. Combined with carbonation promoter, it can accelerate the conversion of calcium hydroxide to calcium carbonate in the ash, forming a denser carbonate coating layer that locks in heavy metals for a long time.

[0065] For ash with low acid neutralization capacity: a wide pH-responsive chelating agent is used to ensure effective chelation of heavy metals under various environments, and the use of alkaline slow-release materials can prevent the leaching of heavy metals due to acid corrosion. For medium ash: a combination of standard chelating agent and adsorbent is used for treatment.

[0066] The wide pH-responsive chelating agent uses porous diatomaceous earth as a carrier and contains dithiocarbamate or trithiotriazine, nano-hydrotalcite or hydroxycarbonate as pH buffer components.

[0067] The stabilization treatment involves adding double-shell microcapsules, which are manufactured from calcium hydroxide, with an inner shell of polyacrylic acid and an outer shell of polylactic acid.

[0068] The above-mentioned design releases hydroxide ions to neutralize hydrogen ions under acidic conditions and absorbs hydroxide ions under alkaline conditions, thereby stabilizing the pH value of the ash microenvironment and ensuring that the chelating agent can maintain optimal activity and stability over a wide pH range. In addition, the chelating agent can actively capture and fix existing heavy metal ions, and the microcapsules can passively monitor the environment. Once there is a risk of acidification, alkaline substances are immediately released to maintain environmental stability, prevent new heavy metal leaching, and create a favorable reaction environment for the chelating agent.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for co-incinerating sludge and municipal solid waste, characterized in that: The method for co-incinerating sludge and municipal solid waste includes the following steps: Step 1: Sludge pretreatment: The sludge is dewatered to reduce its moisture content to below 60%, and then the moisture content is reduced to below 30% by low-temperature drying to obtain dried sludge. The dried sludge is then crushed and screened to a particle size of less than 20mm to obtain sludge powder. Step 2: Pre-treatment of municipal solid waste: Mechanically screen municipal solid waste to remove non-combustible materials, crush combustible waste to a particle size of less than 50mm to form waste-derived fuel, and determine the calorific value of the derived waste as the basis for proportioning; Step 3: Auxiliary material processing: Select fly ash and steel slag as co-auxiliary materials. The co-auxiliary materials are dried and crushed, and then screened to reduce the particle size of the co-auxiliary materials to below 50mm. Step 4: Co-incineration: Waste-derived fuel, sludge powder and co-processing materials are laid from top to bottom into the combustion furnace. The combustion temperature of the combustion furnace is 850-1100℃ and the combustion residence time is 2-5s. Then, secondary air is used to accelerate combustion and form ash. Step 5: Flue gas purification: When the flue gas is discharged, it passes through the dust collector bag and activated carbon layer to adsorb dust and heavy metals in the flue gas. Then, lime slurry solution is sprayed onto the discharged flue gas. Step Six: Ash and Slag Treatment: After incineration, the ash and slag are crushed and magnetically separated to remove iron. Eddy current separation is used to recover aluminum and copper non-ferrous metals. Then, a stabilizer is sprayed onto the remaining ash and slag for solidification treatment.

2. The method for co-incinerating sludge and municipal solid waste according to claim 1, characterized in that: In step four, the co-incineration step, a rapid cooling device is installed downstream of the furnace outlet of the combustion furnace to cool the discharged high-temperature flue gas to below 200°C.

3. The method for co-incinerating sludge and municipal solid waste according to claim 1, characterized in that: In step three, the auxiliary material processing step, the fly ash in the synergistic auxiliary material contains not less than 5% by mass of free calcium oxide and iron oxide.

4. The method for co-incinerating sludge and municipal solid waste according to claim 1, characterized in that: The fourth step of the co-combustion process is divided into two combustion steps. In the first step, the air supply content is 60-80% and the combustion temperature is 850-950℃. In the second step, the air is supplemented and the combustion temperature is 950-1100℃.

5. The method for co-incinerating sludge and municipal solid waste according to claim 4, characterized in that: The iron extracted by magnetic separation in step six is ​​mixed with the synergistic additives from step three.

6. The method for co-incinerating sludge and municipal solid waste according to claim 5, characterized in that: The fourth step involves adding a preliminary incineration step at the front end of the co-incineration process. The temperature of the preliminary incineration furnace is 500-650℃, and the incineration time is 10-20 minutes. The preliminary incineration causes soluble salts in the sludge to migrate and accumulate on the surface of the particles. The salt-enriched ash is separated from the sludge by airflow disturbance during the movement of the grate and falls into the salt collection area at the bottom of the incinerator.

7. The method for co-incinerating sludge and municipal solid waste according to claim 6, characterized in that: In step three, the auxiliary materials processing also includes kaolin and montmorillonite, with the mass ratio of kaolin and montmorillonite being 5-10% of the mass of the sludge powder.

8. The method for co-incinerating sludge and municipal solid waste according to claim 7, characterized in that: In step six, ash and slag treatment, before the stabilizer is sprayed, the acid neutralization capacity index of the ash and slag is measured, and differentiated stabilization treatment is implemented based on the acid neutralization capacity index value of the ash and slag. The differentiated stabilization process includes: using a weak alkali-responsive chelating agent and a carbonization promoter for ash with a high acid neutralization capacity index value; For ash residue with a low acid neutralization capacity index, a wide pH-responsive chelating agent and an alkaline slow-release material are used; for ash residue with a medium acid neutralization capacity index, a combination of a standard chelating agent and an adsorbent is used for treatment.

9. A method for co-incinerating sludge and municipal solid waste according to claim 8, characterized in that: The wide pH-responsive chelating agent uses porous diatomaceous earth as a carrier and contains dithiocarbamate or trithiotriazine, nano-hydrotalcite or hydroxycarbonate as pH buffer components. The stabilization treatment involves adding double-shell microcapsules, which are manufactured from calcium hydroxide, with an inner shell of polyacrylic acid and an outer shell of polylactic acid.