CN102773246B - Method for solidifying/stabilizing treatment of fly ashes in incineration of medical wastes - Google Patents

Abstract

The invention relates to a method for the solidifying/stabilizing treatment of fly ashes in the incineration of medical wastes, which aims at the characteristics of high chlorine content, high sulphur content, high basic oxide content and high calcium-silicon ratio of fly ashes in the incineration of medical wastes so as to provide an economic innocent treatment method with low pollution for fly ashes in the incineration of medical wastes. The invention uses humic acid to fix the heavy metal in the medical wastes at a time, uses limited cement to fix and stabilize the fly ashes in the medical wastes and humic acid reaction product, thereby realizing secondary stabilization to the heavy metal, and the cement solidified body capacity-increase is limited or substantially scarce. According to the method, the components of fly ashes in the incineration of medical wastes are firstly measured, humic acid accounting for 10 percent or 20 percent or 30 percent of the fly ashes in the incineration of the wastes is added, and the mixture is kept for 24h or 72h or 240h at room temperature. Then, the cement with the mass less than 30% of the mass of the fly ashes in the incineration and the humic acid reaction product is added, and a right amount of deionized water is also added for stirring, and the mixture is placed in a mould for solidifying for 24h. The operation of demoulding is carried out after 24h, and an obtained solidified body is continuously solidified for 3 days or 7 days or 14 days under the same condition. Compared with a method of constructing independent treatment equipment for the fly ashes in the incineration of the medical wastes, the expense is lower. The method for the solidifying/stabilizing treatment of the fly ashes in the incineration of the medical wastes has better popularization prospect.

Description

A method for solidification/stabilization treatment of medical waste incineration fly ash

technical field

The invention relates to a method for harmless treatment of fly ash from incineration of medical waste, in particular to a method for solidification/stabilization treatment of fly ash from incineration of medical waste containing heavy metals, and belongs to the technical field of hazardous waste treatment.

Background technique

Medical waste is a special pollutant. In 2002, the total amount of medical waste produced nationwide was about 650,000 tons, with an average daily production of 1,780 tons. In 2010, the number of beds in medical institutions increased by 5% compared with 2002, and the amount of medical waste generated reached 680,000 tons. Although its output accounts for only 3% of municipal solid waste, it may contain a variety of infectious bacteria, viral chemical pollutants, needles, sharps, and radioactive substances, which are extremely dangerous.

Incineration technology is the mainstream medical waste treatment and disposal technology in my country, and it is one of the most effective methods to destroy infectious and toxic substances and reduce volume and weight. After medical waste is incinerated, the pathogens in the waste are completely eliminated; after incineration, the combustible components in the waste are decomposed by pyrolysis, which can generally reduce the weight by 80% and reduce the capacity by more than 90%, and the reduction effect is good.

Medical waste incineration will produce a certain amount of incineration fly ash. The characteristics of medical waste incineration fly ash are:

(1) High chlorine characteristics: the chlorine content of medical waste incineration fly ash is higher than that of domestic waste incineration fly ash, and chlorine salts in domestic waste incineration fly ash mostly exist in the form of NaCl, KCl, CaCl ₂ and other forms, with the lowest content The highest value and the highest value are 0.88% and 30% respectively, most of them are distributed between 10-20%, and the average value is 15.41%, which is mainly related to the nature of domestic waste, the working conditions of incineration and the differences in flue gas purification equipment. For medical waste, the content of plastics is much higher than that of domestic waste. Therefore, the content of chlorine in fly ash of medical waste incineration is significantly higher than that of domestic waste incineration fly ash.

(2) High sulfur characteristics: The sulfur content in the fly ash of medical waste incineration is relatively high, close to 10%.

(3) High alkalinity characteristics: The K ₂ O and Na ₂ O contents in the fly ash of domestic waste incineration are similar, with an average content of 6.06% and 5.33%, while the content of alkaline oxides in fly ash of medical waste incineration is much higher than that of domestic waste Incineration fly ash, K ₂ O and Na ₂ O content were 23% and 3.5%.

(4) High-calcium-silicon characteristics: The calcium-silicon ratio of fly ash from medical waste incineration is as high as 13.8. The methods applied to the harmless and stabilized treatment of incineration fly ash mainly include solidification stabilization, wet chemical treatment and high temperature treatment. Solidification stabilization mainly includes cement solidification, chelating agent stabilization, compression solidification and other types; wet chemical treatment mainly includes two types of acid extraction and waste gas neutralization carbonation; high temperature treatment technology mainly includes two types of sintering solidification and melting vitrification .

The high-temperature melting and solidification method is also called vitrification method. It uses a temperature higher than the melting point of the material to make the incineration fly ash reach a molten state. The stable slag formed after the molten liquid is cooled can be used as a roadbed material or realize resource utilization. Its disadvantage is that the processing cost is high.

Cement is solidified by adding Portland cement to fly ash to form high-strength lumps similar to rocks. The high alkalinity hydroxides in cement can convert heavy metals into low-soluble substances such as hydroxides, thereby retaining heavy metals. Hydrate colloids such as calcium silicate and calcium aluminate formed by the reaction gradually harden over time and finally form a crystalline state, covering heavy metal ions to form a stable structure and achieve the final strength of the solidified body. Cement solidification technology has low processing costs, and the system is mature and easy to operate. However, the high compatibilization ratio of the solidified/stabilized product also reduces the relative advantage of low cost of the cement solidification method.

Agent stabilization refers to the addition of agents to incineration fly ash, chemical additives used to stabilize heavy metals in incineration fly ash, mainly including inorganic heavy metal stabilizers and organic liquid chelating agents. Heavy metals and chemicals form insoluble substances to prevent the leaching of heavy metals. The disadvantage of drug stabilization is that it is expensive.

The properties of fly ash from medical waste incineration and domestic waste incineration are somewhat different. Therefore, the treatment technology for fly ash from domestic waste incineration is not completely suitable for fly ash from medical waste incineration. Due to the relatively small amount of fly ash produced by medical waste incineration, it has not yet Sufficient attention, targeted processing technology is also very scarce. How to properly dispose of fly ash from medical waste incineration and achieve the goal of pollution control is a technical problem that needs to be solved urgently.

Contents of the invention

The present invention is aimed at solving the above problems, aiming at the characteristics of high chlorine, high sulfur, high alkaline oxide content and high calcium-silicon ratio in the fly ash of medical waste incineration, and provides an economical and low-pollution medical waste incineration fly ash without Hazardous treatment methods.

The present invention combines the chemical agent method with the cement fixation method, uses humic acid as the chemical agent, uses the strong combination of humic acid and heavy metals to stabilize heavy metals, reduces the solubility and mobility of heavy metals, and makes up for the fact that cement alone cannot guarantee Shortcomings of long-term stability, while using cement to enhance the hardness of the humic acid solidified body. The purpose of the present invention is achieved through the following technical solutions:

(1) The composition of fly ash from medical waste incineration is determined first. The pH value of fly ash from medical waste incineration is usually above 12. Heavy metals are easy to dissolve when encountering leachate at this pH value or under landfill conditions. Mix the fly ash of medical waste incineration with humic acid evenly according to a certain ratio, keep it at room temperature for a certain period of time, and use humic acid and heavy metals in the fly ash of medical waste incineration to form heavy metal complexes;

(2) Mix the reaction product of medical waste incineration fly ash and humic acid with ordinary Portland cement in a certain proportion, add an appropriate amount of deionized water for stirring, and place it in a mold at a relative humidity greater than 90% and room temperature After 24 hours of curing, demoulding after 24 hours, the obtained cured body continued to cure for the required time under the same conditions, that is, the selected curing time was 3 days, 7 days and 14 days.

The present invention has the following advantages:

(1) Use humic acid to fix heavy metals, and then use cement to strengthen and fix heavy metals, making the solidified body very stable;

(2) The use of humic acid to first fix heavy metals can significantly reduce the amount of cement used for subsequent cement curing, so that the volume increase of the solidified body is not obvious;

(3) The use of cement solidification can well reduce the leaching concentration of heavy metals in the cement solidification body of fly ash incineration of medical waste, and realize safe landfill;

(4) Using humic acid to fix the heavy metals in the fly ash of medical waste incineration once, and cement to fix the heavy metals in the fly ash of medical waste incineration for the second time, compared with the construction of separate medical waste incineration fly ash treatment equipment, the cost is lower;

(5) Dioxin can be encapsulated in the cement solidified body by cement solidification.

Detailed ways

The method for harmless disposal of fly ash from incineration of medical waste described in the present invention is to firstly measure the composition of fly ash from incineration of medical waste, and evenly mix the fly ash from incineration of medical waste with humic acid according to a certain ratio, and the addition ratio of humic acid is Respectively 10%, 20%, 30% (mass percentage content), kept at room temperature for 24h, 72h, 240h.

The reaction product of medical waste incineration fly ash and humic acid is uniformly mixed with ordinary Portland cement in a certain proportion. Ordinary Portland cement is 10%, 20%, 30% of the mass of the reaction product of medical waste incineration fly ash and humic acid. %, add an appropriate amount of deionized water to stir, put it in the mold and cure it at room temperature for 24 hours at a relative humidity greater than 90%, demould after 24 hours, and the obtained cured body continues to cure for the required time under the same conditions, that is, select The curing times are 3 days, 7 days and 14 days.

The method of the present invention will be described below through specific examples, but the present invention is not limited thereto. The test method described in the following examples, if no special instructions, is a conventional method; said equipment and materials, if no special instructions, can be obtained from industrial production or commercial channels;

Example 1

Dry the fly ash of medical waste incineration at 105°C for 24 hours, and evenly add 10% (mass percentage) humic acid (commercial humic acid, humic acid content > 90%) to the dried medical waste incineration fly ash. Residue <5%, water content <8%), keep at room temperature for 72h. The reaction product and ordinary portland cement are mixed according to a certain ratio. The proportion of cement in the mixture is 10% (mass percentage). The cement used in the test is ordinary portland cement with a specification of 425 (Ordinary Portland Cement), after mixing evenly, add an appropriate amount of deionized water for stirring, then pour it into a mold of Φ20mm×30mm, cure it at room temperature for 24 hours at a relative humidity greater than 90%, and demould after 24 hours to obtain a cured body Continue curing to the required time under the same conditions, that is, the selected curing time is 3 days, 7 days and 14 days.

The cured body is tested using the national standard HJ/T299-2007 toxic leaching procedure. The test uses 3 parallel samples, and the test results take the average value of the 3 parallel samples.

Table 1 shows the chemical composition of fly ash from medical waste incineration, Table 2 shows the chemical composition of ordinary Portland cement, Table 3 shows the heavy metal content in fly ash from medical waste incineration, and Table 4 shows the leaching characteristics of heavy metals in fly ash from medical waste incineration. 5 is the leaching characteristics of heavy metals after the fly ash of medical waste incineration is fixed and stabilized by humic acid, and then fixed/stabilized by cement for the second time.

Table 1 Chemical composition of fly ash from medical waste incineration (wt.%)

Table 2 Chemical composition of ordinary portland cement (wt%)

Table 3 Heavy metal content in fly ash of medical waste incineration (wt.%)

Table 4 Leaching characteristics of heavy metals in fly ash of medical waste incineration (μg/L)

Table 5 The leaching characteristics of heavy metals after secondary fixation/stabilization of fly ash from medical waste incineration (μg/L)

Example 2

The chemical composition, heavy metal content and heavy metal leaching characteristics of the fly ash from medical waste incineration are the same as in Example 1, and the chemical composition of ordinary Portland cement is the same as in Example 1. The fly ash from medical waste incineration was dried at 105°C for 24 hours, and the dried 20% (mass percentage) of humic acid (commercial humic acid) was evenly added to the fly ash of medical waste incineration, and kept at room temperature for 240 hours. Mix the reaction product and ordinary Portland cement according to a certain ratio, and the proportion of cement in the mixture is 20% (mass percentage). After the mixture is evenly mixed, add an appropriate amount of deionized water for stirring, and then pour it into In a mold of Φ20mm×30mm, cure for 24 hours at a relative humidity greater than 90% and room temperature, demould after 24 hours, and the cured body obtained continues to cure to the required time under the same conditions, that is, the selected curing time is 3 days, days and 14 days.

The cured body is tested using the national standard HJ/T299-2007 toxic leaching procedure. The test uses 3 parallel samples, and the test results take the average value of the 3 parallel samples. The test results are shown in Table 6.

Table 6 The leaching characteristics of heavy metals after secondary fixation/stabilization of medical waste incineration fly ash (μg/L)

Example 3

The chemical composition, heavy metal content and heavy metal leaching characteristics of the fly ash from medical waste incineration are the same as in Example 1, and the chemical composition of ordinary Portland cement is the same as in Example 1. The fly ash from medical waste incineration was dried at 105°C for 24 hours, and the dried Add 30% (mass percentage) of humic acid (commercial humic acid) evenly to the fly ash of medical waste incineration, and keep it at room temperature for 240 hours. Mix the reaction product and ordinary Portland cement according to a certain ratio, and the proportion of cement in the mixture is 30% (mass percentage). After the mixture is evenly mixed, add an appropriate amount of deionized water for stirring, and then pour it into In a mold of Φ20mm×30mm, cure for 24 hours at a relative humidity greater than 90% and room temperature, demould after 24 hours, and the cured body obtained continues to cure to the required time under the same conditions, that is, the selected curing time is 3 days, days and 14 days.

The cured body is tested using the national standard HJ/T299-2007 toxic leaching procedure. The test uses 3 parallel samples, and the test results take the average value of the 3 parallel samples. The test results are shown in Table 7.

Table 7 The leaching characteristics of heavy metals after secondary fixation/stabilization of medical waste incineration fly ash (μg/L)

Claims (3)

1. a method for medical refuse burning flyash curing/stabilizing process, the method comprises 2 key steps, and the 1st step is the heavy metal that use humic acid fixes in medical refuse burning flyash, 2nd step is the fixing product using Portland cement to fix the 1st step, make heavy metal obtain sufficient secondary by these 2 steps to fix, specifically first the composition of medical refuse burning flyash is measured, medical refuse burning flyash and humic acid are prepared according to mass percent, wherein the adding proportion of humic acid is 10% or 20% or 30%, 24h or 72h or 240h is kept under room temperature, then cement is added, cement quality accounts for 10% or 20% or 30% of medical refuse burning flyash and humic acid reaction product quality, add appropriate deionized water to stir, be placed in mould and be greater than 90% and cured at room temperature 24h in relative humidity, the demoulding after 24h, the firming body obtained continues solidification 3 days or 7 days or 14 days under the same conditions, national standard HJ/T299-2007 toxicity is adopted to leach program test to firming body, test employing 3 Duplicate Samples, test result gets the mean value of 3 Duplicate Samples.

2. the method for medical refuse burning flyash curing/stabilizing process as claimed in claim 1, the normal portland cement of the cement adopted in the method to be specification be 425 labels.

3. the method for medical refuse burning flyash curing/stabilizing process as claimed in claim 1, the die size adopted in the method is Φ 20mm × 30mm.