The low-temperature sludge drying technology represented by sludge dehumidifiers and dryers represents the future direction of technological development. Low temperature sludge drying technology is a treatment technique that uses dry and hot air generated by a low-temperature drying system to circulate and dry sludge within the system. There are many types of sludge, mainly including sludge generated by industrial enterprises, such as electroplating sludge, printing and dyeing sludge, river sludge, water plant sludge, and sewage plant sludge. Among them, domestic sludge (also known as municipal sludge) is a large amount of sludge generated in a long-term and stable manner with the increase of urban sewage treatment capacity. If not treated in a timely manner, it poses a great threat to the environment. The main source of domestic sludge is the products of purification processes such as residential sewage and municipal sewage. Unlike soil sludge such as water plant sludge, it has a higher organic matter content and also contains a large amount of nutrients such as nitrogen and phosphorus. Due to the fact that the sewage treatment plant also accepts some industrial wastewater, its sludge still contains a certain proportion of heavy metal ions and chemicals, as well as a large number of pathogenic microorganisms. Another characteristic is the moisture content of sludge. Usually, sewage treatment plants will dehydrate the produced sludge, which is composed of liquid and solid parts. Separating the moisture in the sludge and reducing its volume is a very important part. The domestic sludge dryer is a new energy-saving and environmentally friendly product that uses a dehumidification heat pump to condense, dehumidify, and dry sludge through hot air circulation. Dehumidification heat pump is a device that uses a refrigeration system to cool and dehumidify humid air while recovering the latent heat of condensation of air moisture through the principle of heat pump to heat the air. In short, a dehumidification heat pump is a device that combines dehumidification (dehumidification and drying) with a heat pump (energy harvesting). It can fully achieve the reduction, stabilization, harmlessness, and resource utilization of municipal sludge. The final sludge particles can be used as fertilizers, fuels, incineration, building materials, biofuels, landfill cover, land use, etc. Sludge with a solid content of 20% can be dried into dried mud blocks with a solid content of 90% using plate and frame filter presses, belt filter presses, and centrifugal dewatering machines. This technology can reduce the volume of sludge by 1/4, only requiring electricity and no other auxiliary energy, and the energy consumption is one-third of that of conventional drying equipment. Sludge drying is a device that evaporates the moisture in the sludge through heating, and there is no need to evenly distribute the sludge during feeding. There is also no requirement for humidity, as long as the external temperature is between 10-35 degrees Celsius, the entire system can maintain efficient operation.
Technical characteristics of domestic sludge dryer:
1. It can fully achieve the "reduction, stabilization, harmlessness, and resource utilization" treatment of sludge, and the final sludge particles can be used as fertilizers, fuels, incineration, building materials, biofuels, landfill cover, land use, etc.
2. Adopting continuous mesh belt drying mode, suitable for various types of sludge drying systems (including sludge with high sand content), with a long service life.
3. The 80% moisture content sludge cake can be dried into 10% moisture content sludge particles; The sludge reduction capacity is 1/4-1/5, and the calorific value of urban sludge after drying can reach 3000 kcal/kg.
4. The patented technology of sludge extrusion molding and crushing molding adopts different paving modes according to the different solid content of sludge.
5. Low temperature (40-75 ℃) fully enclosed drying process, no exhaust emissions, no need for odor treatment system; The use of low-temperature drying can fully avoid the volatilization of different types of organic compounds in sludge and the volatilization of odorous gases (the volatilization temperature of chain hydrocarbons and aromatic hydrocarbons is between 100-300 ℃, the volatilization temperature of cycloalkanes is mainly between 250-300 ℃, the volatilization temperature of nitrogen-containing compounds, amines, oximes is mainly between 200-300 ℃, and the volatilization temperature of alcohols, ethers, fatty ketones, amides, nitriles, etc. are all above 300 ℃. Advanced layered air distribution and mixed air dust prevention technology is efficient and stable. In addition, the volatilization temperature of aldehydes and aniline is mainly between 150 ℃, and the volatilization temperature of lipids is between 150-250 ℃).
6. The entire drying process can be carried out under closed environmental conditions, without any gas being discharged into the external environment, and without causing secondary environmental pollution; There are no pollutant emissions during the drying process, and the hygiene conditions in the drying workshop are good; Adopting centralized water cooling mode, the cooling effect is excellent, and the working temperature in the workshop is excellent.
7. The system runs safely, without any safety hazards, and does not require nitrogen flushing operation; The oxygen content during the sludge drying process is less than 12%, the dust concentration is less than 60g/m3, the particle temperature is less than 70 ℃, and there is no dust during the entire drying process (air flow rate is less than 2 m/s).
8. The speed of the conveyor belt is controlled by frequency conversion, and the moisture content of the sludge discharge can be adjusted (10-30%) to meet the requirements of various types of processes.
9. By adopting Ling's advanced heat pump dehumidification technology, energy savings of over 40% can be achieved, with a power consumption of approximately 0.3% per 20 days; Traditional sludge drying equipment requires energy consumption, as well as electricity, cooling water, chemicals, etc; Adopting the off peak and off peak electricity consumption mode can save energy by more than 60%.
10. The equipment occupies a small area and is easy to install; The equipment occupies an area of approximately 3.5m2 for every 1000kg of water evaporated.
11. The daily processing capacity of a single drying line can reach 45 tons (80% moisture content sludge cake), and the daily processing capacity of sludge cake with a moisture content of 55% can reach 140 tons. It can be suitable for sludge dispersion or centralized treatment mode. By treating the sludge cake, capacity reduction can be achieved, saving sludge transportation costs (more than 100 yuan per ton of sludge transportation cost depending on the route) and reducing environmental pollution during transportation.
12. Adopting PLC+touch screen control system, fully automatic operation, convenient operation and management; Dry wet bulb temperature and humidity control, variable frequency control of feed rate, molding control, solid content control of discharge, material laying control, manual control, etc.
Sludge is a solid sediment produced during water and wastewater treatment processes. Due to the significant changes in the properties of various types of sludge, classification is necessary, and their treatment and disposal processes are also different. Based on their sources, they can be roughly divided into categories such as municipal sludge, pipeline sludge, river and lake sludge, industrial sludge, etc. There are significant differences in the volatilization temperature of different types of organic matter in sludge. In the process of wastewater purification, pollutants in the wastewater are removed through biochemical degradation. Biological treatment can degrade most organic pollutants into water and gas (aerobic treatment produces oxygen and carbon dioxide, anaerobic treatment produces CH4 as the main gas), while metal pollution (including heavy metals) cannot be treated and is concentrated in sludge. The sludge produced by sewage treatment has a high moisture content. Due to the characteristic of water binding with sludge particles, mechanical removal has certain limitations. The organic matter content, ash content, and especially the amount of coagulant added in the sludge have a significant impact on the solid content of the sludge. Generally speaking, mechanical dewatering can achieve a solid content of 20% -50%, and the resulting sludge is called sludge cake. The moisture content of the mud cake is still high, and its disposal difficulty and cost are still high, so it is necessary to further reduce it. At this point, in addition to natural air drying, only by inputting heat to form evaporation can large-scale reduction be achieved. The use of heat for drying is called thermal drying. The domestic sludge dryer discussed in this article is a thermal drying technology.
Air source heat pump - is a device that uses a refrigeration system to cool and dehumidify humid air while recovering the latent heat of condensation of air moisture through the principle of heat pump to heat the air. Dehumidification heat pump=a combination of dehumidification (dehumidification and drying) and heat pump (energy recovery). The high cost of sludge drying is the main bottleneck restricting the application scale of drying technology. The domestic sludge dryer uses a dehumidification heat pump to use hot air circulation condensation dehumidification drying for sludge; 90% of the heating capacity of traditional sludge thermal drying systems is converted into exhaust heat loss (latent heat of water vapor and sensible heat of hot air); Dehumidification and drying is the process of recovering latent heat of water vapor and sensible heat of air in exhaust, without any waste heat emissions during the dehumidification and drying process;
The COP of heat pump heating is generally between 3-5, which means that the traditional drying heating power of 4kw only requires 1kw of electrical power input in heat pump drying. Heat source=2424KJ/kg of condensation heat released by phase change of water vapor in air at atmospheric pressure of -30 ℃; 2355KJ/kg at 60 ℃ and 2258KJ/kg at 100 ℃ (coal calorific value 18000KJ/kg).
Sludge has high moisture content, large volume, high organic content, embryonic structure, difficult dewatering, high dewatering cost, and excessive heavy metal and bacterial content. Easy to generate secondary pollution, the production continues to grow at a rate of 10-15% per year, with a sharp increase. Not only that, our sludge dryer also has many advantages: it occupies a small area, does not require an external platform, and saves infrastructure costs; Adopting a fully intelligent automatic control system, with low operating costs and central monitoring, there is no need to set up special positions, only a daily routine check is required; Low maintenance cost, its maintenance cost is only equivalent to maintaining one air conditioner; High operational flexibility, able to meet different requirements for sludge dryness (30% to 90%) on site by adjusting PLC parameters; The evaporation temperature is low, and the distilled water is equivalent to ordinary water; Due to the fact that the temperature of the dried air after heating is only 40 ℃, it avoids the generation of explosions and suppresses the generation of odors. When using a domestic sludge dryer to reduce the moisture content to 30% -40%, the appearance of the sludge becomes loose, granular, with better carrying capacity, less odor, good hydrophobicity, and can be effectively incinerated, buried, etc., making it more convenient to handle.
Structure of domestic sludge dryer:
Sludge dehumidification and drying=hot air circulation+condensation dehumidification and drying (dehumidification heat pump). There are two core processes involved. One: Heat absorption (hot air) vaporization of sludge moisture=moist air+dry material (vaporization); Secondly: ★ Wet air passes through a dehumidification heat pump=condensed water+dry hot air (condensation)1) Adopting heat pump heat recovery technology, the closed drying mode has no waste heat emissions; 2) Low temperature drying process below 80 ℃; 3) Static placement, without mechanical static friction with the contact surface; 4) There is no "adhesive phase" stage in the drying process of urban sludge (about 60%); 5) The dry material is in granular form and poses no dust hazard; 6) Low discharge temperature (<50 ℃), no need for cooling, direct storage;
Innovative technology of air source heat pump sludge dryer:
1) Three effect dehumidification and reheating technology can be used, with lower outlet humidity and high drying efficiency; Simultaneously adopting triple effect technology can save a significant amount of energy consumption for fans.
2) Adopting a layered air distribution system to meet the requirements of rapid dehydration of wet mud and short low-temperature drying cycle; 1. Sent to the cement plant and mixed with clinker to produce cement; 2. Directly mixing and burning with raw coal for utilization reduces boiler coal consumption and improves economic benefits; 3. Replace clay and coal powder by sending them to brick factories for the production of lightweight bricks; 4. Used as a slow-release fertilizer to increase crop yields; 5. Used as a chemical raw material for production; 6. Used as a soil amendment to improve soil erosion resistance and water retention performance
3) Modular structure design, strong load regulation capability, easy installation, and convenient relocation.
4) Both the conveying and feeding motors adopt variable frequency stepless speed regulation, which is suitable for adjusting dry materials with different moisture contents (10% -50%) and has stronger adaptability.
Scope of application of domestic sludge dryer:
It can also be used for drying various types of sludge such as electroplating sludge, leather sludge, papermaking sludge, alumina sludge, municipal life sludge, leather sludge, chemical sludge, steam sludge, printing and dyeing sludge, etc. It is suitable for dehumidification and drying of sludge in electroplating, hardware products, paper mills, electrolytic aluminum, alumina, soy sauce residue, sewage treatment, wastewater treatment, dyeing plants, printing plants, fruit residue, biological agents, biotechnology, fertilizers, pharmaceutical plants, hazardous waste solid recovery and disposal companies, chemical plants, feed mills, water companies, industrial park sludge and sewage treatment plants, municipal sewage treatment departments and other units.