CN104058564A - Treatment system for preparing soilless culture medium by sintering sludge - Google Patents

Abstract

The invention provides a treatment system for preparing a soilless culture medium by sintering sludge and relates to the technical field of treatment of sludge by sintering technology and recycling the sludge to prepare the soilless culture medium. Aiming at the technical problem that the contents of heavy metal and organic pollutant in sludge are high, harm is big and nutritional ingredients are not fully utilized, the treatment system is characterized by comprising the following steps: adding waste lye to the sludge to squeeze and dehydrate the sludge, then adding excessive Mg salt into dehydrated filtrate to recover nitrogen and phosphor, thus obtaining struvite sediment; adding industrial solid waste to the primarily dehydrated sludge to fix residual phosphor in the sludge, stabilize residual heavy metal in a sintering process and reduce the moisture content of the sludge; and meanwhile drying the sludge by utilizing waste heat produced during sintering, thus obtaining deeply dehydrated sludge; extruding and moulding the deeply dehydrated sludge and then sintering in a sintering machine for 15-85 minutes at the temperature of 800-1300 DEG C, wherein the volatilization of heavy metal in the sludge can be prompted and the organic pollutants in the sludge can be thoroughly decomposed into harmless gases through sintering, and moreover smoke produced during sintering is cleaned and emitted after reaching the emission standard, and finally a sludge sintered body is obtained after the sintering is finished. The obtained struvite is taken as slow release fertilizer and mixed with the sludge sintered body to jointly serve as soilless culture medium used for potting or landscaping.

Description

A soilless cultivation substrate treatment system made by sludge sintering

technical field

The invention relates to a harmless treatment system for sludge, in particular to a system for treating sludge with sintering technology and making soilless cultivation substrate as resources.

Background technique

In 2012, the total treatment capacity of urban sewage treatment facilities put into operation across the country reached 149 million cubic meters, with an average daily water treatment volume of 116 million cubic meters and a national average daily sludge production of about 63,000 tons. The resulting large amount of sludge is urgently needed Treatment and disposal; pollutants from industry, mining, agriculture and surface runoff have polluted water body sediments to varying degrees. Contaminated sediment poses a threat to human health and the environment worldwide. After the external sources of water pollution are increasingly controlled, polluted water sediments have gradually become an important internal source of water pollution that cannot be ignored.

Heavy metals such as Zn, Cu, and Cr in sludge have high content and high activity, and some typical organic pollutants are highly toxic and have long residual effects. The utilization of sludge resources must solve the problem of removal and purification of heavy metals and organic pollutants in sludge. At present, the disposal methods of sludge mainly include throwing into the sea, landfill, composting, incineration and so on. Sludge throwing into the sea is prohibited by the international law of the sea due to serious pollution problems; the landfill method occupies a large amount of land, and the sludge is prone to leakage, which poses a hazard to the environmental safety of the site and its surroundings; although sludge composting can recycle sludge However, the sludge contains a large number of pathogens and heavy metals such as copper, lead, zinc, chromium, cadmium, and harmful substances that are difficult to degrade such as polychlorinated biphenyls and dioxins. Many problems; in the process of sludge incineration, the volume of sludge can be minimized to achieve reduction, and all organic matter can be carbonized to kill pathogens. At the same time, the potential organic energy of sludge can be fully utilized for the drying of sludge itself. It is considered to be an effective transitional disposal method.

According to statistics, the highest total N, total P and total K contents of municipal sludge are 51.6, 51.3 and 12.5g/kg, respectively, and the average contents are 27, 14.3 and 7g/kg, respectively, which has high resource utilization value. In the existing sludge incineration technology, during the incineration process, the ammonia nitrogen in the sludge is easily converted into nitrogen oxides and causes secondary damage with the volatilization of the flue gas. At the same time, most of the incineration ash produced is made into building materials. Nutrients have not been utilized, and resources have not been fully realized.

Sludge is in the form of a colloidal liquid, with a moisture content of over 99%, but only when the moisture content falls below 50%, can resource utilization be possible, so sludge must be dehydrated before disposal. The dewatered filtrate obtained from sludge dehydration contains a certain concentration of nutrients such as ammonia nitrogen and phosphorus, which are directly or indirectly discharged into sewage treatment plants for conventional treatment along with wastewater, but have not been fully utilized.

Therefore, the development of a sludge sintering technology for the harmless and resource utilization of sludge and dewatered filtrate is an effective way for domestic sludge treatment and disposal.

Contents of the invention

Purpose of the present invention: In order to overcome the deficiencies in the above technologies, provide a kind of sludge sintering technology that can make full use of the nutrients and calorific value in the sludge, and can realize the harmlessness and reduction of sludge. The flue gas produced by sintering is purified, and the sludge sintered body obtained after sintering is used as a soilless culture substrate to realize the utilization of sludge resources.

The present invention is achieved through the following technical solutions:

(1) Add waste lye to sludge with a moisture content of 80-99%, adjust the pH of the sludge to 9-10, and perform physical dehydration after fully stirring to obtain preliminary dewatered sewage with a moisture content of 60-75%. mud. Alkaline environment can promote the denaturation of bacterial surface proteins, causing the dissolution of some cell wall cell membranes, and the release of intracellular nitrogen and phosphorus, which increases the nitrogen and phosphorus content in the sludge dewatering filtrate;

Described sludge is municipal sludge, water body sediment;

(2) Under alkaline conditions, add excess Mg salt to the sludge dehydration filtrate, adjust the magnesium/phosphorus molar ratio to 1.2-1.6, so that Mg ²⁺ can fully react with nitrogen and phosphorus in the dehydration filtrate to form struvite, the reaction is as follows , the filtrate obtained by filtering the struvite is subjected to conventional sewage treatment, and discharged to the sewage treatment plant after reaching the standard;

Mg ²⁺ +NH ⁴⁺ +PO ₄ ^3- +6H ₂ O→Mg NH ₄ PO ₄ 6H ₂ O↓

The Mg salt is salt industry waste brine;

(3) Adding the preliminary dewatered sludge to industrial solid waste can fix the remaining phosphorus in the sludge, stabilize the heavy metals remaining in the sintering process, and reduce the moisture content of the sludge. At the same time, the waste heat generated by sintering can be used to dry the sludge , to obtain deep dewatered sludge with a moisture content of 35-45%;

The industrial solid waste is calcium carbide slag, slag or red mud with a water content of 2-6%, and the addition ratio is 3-100% of the preliminary dewatered sludge;

(4) After the deep dewatered sludge is extruded, it is sent to the sintering machine for sintering. The sintering temperature is 800-1300°C, and the sintering time is 15-85min. Sludge sintered body, due to the high content of organic matter in the sludge, a large amount of gas is generated during the sintering process, resulting in more holes in the sintered body. The natural environment is conducive to the precipitation of the remaining P in the sintered body, and the water retention, fertilizer and air permeability are good. (2) The struvite obtained in (2) is used as a slow-release fertilizer and sludge sintered body mixed together as a soilless culture substrate for potted plants or landscaping;

The particle size of the sludge sintered body is 0.5-10mm, and the total porosity is 45%-55%;

(5) After utilizing the waste heat of the flue gas generated by the sintering machine, it is first cooled rapidly to prevent the regeneration of dioxin-like persistent organic pollutants. Alkali reaction to remove acidic substances such as HCl, HF, SO ₂ , NO _x ;

The waste lye is industrial waste lye containing 2% to 10% of _NaOH and _Na2CO3 ;

(6) The flue gas from the deacidification reaction tower is subjected to bag dust removal, and activated carbon powder is sprayed in front of the bag to absorb the residual volatile heavy metals and a small amount of desorbed dioxin in the flue gas, and the purified flue gas is emptied;

(7) Add stabilizer and curing agent to the fly ash collected by the deacidification reaction tower and bag filter, stabilize and solidify, and send it to the landfill for safe landfill after reaching the standard;

The curing agent is cement or lime, and the addition amount is 5%-15% of the total amount of fly ash;

The stabilizer is sulfide, soluble phosphate or mercapto collector, and the added amount is 0.5%-5% of the total amount of fly ash.

Beneficial effects of the present invention:

Adding waste lye to sludge can promote the dissolution of ammonia nitrogen and phosphorus during sludge dehydration, and reduce the amount of ammonia nitrogen converted into nitrogen oxides during sludge sintering. Adding Mg salt to sludge dehydration filtrate can effectively recover nitrogen and phosphorus, and obtain Struvite precipitation; adding industrial solid waste to the preliminary dewatered sludge can fix the remaining phosphorus in the sludge, stabilize the residual heavy metals in the sintering process, and reduce the moisture content of the sludge; the moisture content of the deep dewatered sludge is lower than 50% , the external high temperature can cause the sludge to achieve self-sustained combustion, which saves a lot of energy; sintering can promote the volatilization of heavy metals in the sludge and completely decompose organic pollutants into harmless gases such as CO ₂ and H ₂ O, resulting in relatively high heavy metal content and leaching amount. The low sludge sintered body can purify the flue gas generated by sintering to prevent secondary pollution. The obtained struvite is used as a slow-release fertilizer mixed with the sludge sintered body and used as a soilless culture substrate for potted plants or landscaping. Due to the high content of organic matter in the sludge, a large amount of gas is generated during the sintering process, which makes the sintered body produce more Porous and porous, the natural environment is conducive to the precipitation of the remaining P in the sintered body, which can effectively use the nutrients in the sludge, and has good water and fertilizer retention and air permeability. The invention realizes harmless and resourceful sludge from the perspective of using waste to produce waste.

Description of drawings

Figure 1 is a flow chart of the soilless culture substrate system made from sludge sintering

specific embodiment

Example 1

Add 50kg of sludge with a water content of 95% to industrial waste lye containing NaOH and Na ₂ CO ₃ 10%, fully stir to adjust the pH of the sludge to 10, and dewater by physical pressing to obtain a preliminary dewatered sludge with a water content of 75% , in the dehydration filtrate, add the waste bittern of salt making industry, make the magnesium/phosphorus mol ratio be 1.6, after fully reacting, filter, obtain 12.4g struvite coarse precipitation.

Add calcium carbide slag with a water content of 2% to the preliminary dewatered sludge, and the added amount is 3% of the preliminary dewatered sludge. After drying, a deep dewatered sludge with a water content of about 40% is obtained, which is sent to the sintering machine for sintering, and the sintering temperature is 1100 ℃, sintering time 60min, sintering is completed, unloading, natural cooling to obtain sludge sintered body.

The flue gas produced by sintering is used for indirect drying of the preliminary dewatered sludge, and then sprayed with water for rapid cooling and cooling, and then enters the deacidification reaction tower to react with the waste lye, and then carries out bag dust removal. After the treatment reaches the standard, the clean flue gas is discharged into the atmosphere; Collect the fly ash produced by the deacidification reaction tower and bag filter, add 5% lime and 5% sodium sulfide, and the solidified/stabilized fly ash will enter the landfill site for safe landfill after reaching the standard.

The average particle size of the sludge sintered body is 3mm, the total porosity is 53.2%, the P content is 7.45g/kg, the heavy metal leaching amount: Cu0.03mg/kg, Zn4.12mg/kg, Cr1.53mg/kg, Pb0mg/kg, Cd0 mg/kg.

In this example, the analysis method and limits of sintered heavy metal content refer to HJ/T350-2007 "Evaluation Standards for Soil Environmental Quality of Exhibition Land (Provisional)"; the limits of smoke emission standards refer to GB16297-1996 "Comprehensive Emission Standards for Air Pollutants" 》; The limit value of heavy metal leachate after fly ash solidification/stabilization refers to GB16889-2008 "Standards for Pollution Control of Domestic Waste Landfill Sites".

Table 1 Heavy metal content in sintered body (unit: mg/kg)

Table 2 Content of harmful substances in flue gas after purification

Test items Purified flue gas limit value Pb(mg/m ³ ) ND 0.7 Cd(mg/m ³ ) 0.09 0.85 HCl (mg/m ³ ) ND 1.9 Dioxins (ng I-TEQ/Nm ³ ) 0.004 0.1

Table 3 Leach amount of heavy metals after solidification/stabilization of fly ash (unit: mg/kg)

Example 2

Add 50kg of sludge with a water content of 90% to industrial waste lye containing 6% NaOH and Na ₂ CO ₃ , fully stir and adjust the pH of the sludge to 9.5, and after dehydration by physical pressing, a preliminary dewatered sewage with a water content of 65% is obtained Mud, in the dehydration filtrate, add waste bittern from the salt industry to make the magnesium/phosphorus molar ratio 1.4. After fully reacting, filter to obtain 9.1g struvite coarse precipitate.

Add slag with a water content of 4% to the preliminary dewatered sludge, and the amount added is 50% of the preliminary dewatered sludge. After drying, a deep dewatered sludge with a water content of about 45% is obtained, which is sent to the sintering machine for sintering, and the sintering temperature is 1200°C , sintering time 15min, sintering is completed, unloading, natural cooling to obtain sludge sintered body.

The flue gas treatment steps are the same as those in Example 1, except that 10% lime and 3% soluble phosphate are added to the fly ash.

The average particle size of the sludge sintered body is 5mm, the total porosity is 47.2%, the P content is 8.36g/kg, and the heavy metal leaching amount: Cu0.17mg/kg, Zn4.99mg/kg, Cr1.86mg/kg, Pb0.08mg/kg kg, Cd0.04mg/kg.

The limits of the sintered body refer to Example 1.

Table 4 Heavy metal content in sintered body (unit: mg/kg)

Table 5 Content of harmful substances in flue gas after purification

Test items Purified flue gas limit value Pb(mg/m ³ ) 0.05 0.7 Cd(mg/m ³ ) ND 0.85 HCl (mg/m ³ ) ND 1.9 Dioxins (ng I-TEQ/Nm ³ ) 0.012 0.1

Table 6 Leach amount of heavy metals after solidification/stabilization of fly ash (unit: mg/kg)

Example 3

Add 50kg of sludge with a water content of 80% to industrial waste lye containing 3% NaOH and Na ₂ CO ₃ , fully stir to adjust the pH of the sludge to 9, and dewater by physical pressing to obtain a preliminary dewatered sewage with a water content of 60%. Mud, in the dehydration filtrate, add waste bittern from the salt industry to make the magnesium/phosphorus molar ratio 1.2. After fully reacting, filter to obtain 4.9g struvite coarse precipitate.

Add red mud with a moisture content of 6% to the primary dewatered sludge, the amount added is 26% of the primary dewatered sludge, and after drying, a deep dewatered sludge with a moisture content of about 35% is obtained, which is sent to the sintering machine for sintering, and the sintering temperature is 900 ℃, sintering time 45min, sintering is completed, unloading, natural cooling to obtain sludge sintered body.

The flue gas treatment steps are the same as in Example 1, except that 15% lime and 0.5% mercapto collector are added to the fly ash.

The average particle size of the sludge sintered body is 8mm, the total porosity is 43.4%, the P content is 10.36g/kg, and the heavy metal leaching amount: Cu0.19mg/kg, Zn3.53mg/kg, Cr1.14mg/kg, Pb0.06mg/kg kg, Cd0.13mg/kg.

The limits of the sintered body refer to Example 1.

Table 7 Heavy metal content in sintered body (unit: mg/kg)

Table 8 Contents of harmful substances in flue gas after purification

Test items Purified flue gas limit value Pb(mg/m ³ ) 0.03 0.7 Cd(mg/m ³ ) 0.06 0.85 HCl (mg/m ³ ) ND 1.9 Dioxins (ng I-TEQ/Nm ³ ) 0.008 0.1

Table 9 Leach amount of heavy metals after solidification/stabilization of fly ash (unit: mg/kg)

Claims (8)

1. A sludge sintering system soilless culture substrate treatment system, the steps are: (1) Add waste lye to sludge with a moisture content of 80-99%, adjust the pH of the sludge to 9-10, and perform physical dehydration after fully stirring to obtain preliminary dewatered sewage with a moisture content of 60-75%. mud; (2) Under alkaline conditions, add excess Mg salt to the sludge dewatering filtrate, adjust the magnesium/phosphorus molar ratio to 1.2-1.6, so that Mg ²⁺ can fully react with the nitrogen and phosphorus in the dehydrating filtrate to form struvite, after filtration The filtrate is subjected to conventional sewage treatment and discharged to the sewage treatment plant after reaching the standard; (3) The initial dewatered sludge is added to industrial solid waste to fix the remaining phosphorus in the sludge, stabilize the heavy metals remaining in the sintering process, and reduce the moisture content of the sludge. At the same time, use the waste heat generated by sintering to dry the sludge to obtain a moisture content of 35-45% deep dewatered sludge; (4) After the deep dewatered sludge is extruded, it is sent to the sintering machine for sintering. The sintering temperature is 800-1300°C, and the sintering time is 15-85min. Sludge sintered body, the content of organic matter in the sludge is high, a large amount of gas is generated during the sintering process, resulting in more holes in the sintered body, the natural environment is conducive to the precipitation of the remaining P in the sintered body, and the water retention and fertilizer permeability are good. 2) The struvite obtained in 2) is used as a slow-release fertilizer and mixed with sludge sintered body as a soilless culture substrate for potted plants or landscaping; (5) After utilizing the waste heat of the flue gas generated by the sintering machine, it is first cooled rapidly to prevent the regeneration of dioxin-like persistent organic pollutants. Alkali reaction to remove acidic substances such as HCl, HF, SO ₂ , NO _x ; (6) The flue gas from the deacidification reaction tower is subjected to bag dust removal, and activated carbon powder is sprayed in front of the bag to absorb the residual volatile heavy metals and a small amount of desorbed dioxin in the flue gas, and the purified flue gas is emptied; (7) Add stabilizer and curing agent to the fly ash collected by the deacidification reaction tower and bag filter for stabilization and curing, and send it to the landfill site for safe landfill after reaching the standard. 2. A soilless culture substrate treatment system made of sludge sintering according to claim 1, characterized in that: the sludge is municipal sludge or water body sediment. 3. A kind of sludge sintering system for soilless culture substrate treatment system according to claim 1, characterized in that: the Mg salt is waste brine from the salt making industry. 4. A soilless culture substrate treatment system made of sludge sintering according to claim 1, characterized in that: industrial solid waste is calcium carbide slag, slag or red mud with a moisture content of 2-6%, and the addition ratio is preliminary dehydration 3-100% of sludge. 5. A substrate treatment system for soilless culture by sludge sintering according to claim 1, characterized in that: the particle size of the sludge sintered body is 0.5-10mm, and the total porosity is 45%-55%. 6 . The substrate treatment system for soilless culture by sludge sintering according to claim 1 , wherein the waste lye is industrial waste lye containing 2-10% of NaOH and Na ₂ CO ₃ . 7. A substrate treatment system for soilless culture by sludge sintering according to claim 1, characterized in that: the curing agent is cement or lime, and the amount added is 5%-15% of the total amount of fly ash. 8. A kind of sludge sintering soilless culture substrate treatment system according to claim 1, characterized in that: the stabilizer is a sulfide, soluble phosphate or mercapto collector, and the addition amount is 0.5% of the total amount of fly ash %-5%.