What is sludge dryer?
is an indirect heating and low speed agitation type dryer
. There are two or four hollow rotating shafts inside the equipment, and the hollow shafts are densely arranged in parallel with fan-shaped wedge-shaped hollow blades with special and clever structural design. The shafts rotate relative to each other, using the principle and structure of the same angular speed and different linear speed to cleverly achieve the self-cleaning effect of the sludge on the shafts, which maximally prevents the phenomenon of "holding the shaft" during the sludge drying process.
What is sludge?
Sludge is a solid precipitated material produced by water and sewage treatment processes. Its main characteristics are high water content (up to 99% or more), high organic content, easy decay and odor, and fine particles, small specific gravity, and gelatinous liquid state. Sludge is mainly classified by source: domestic sewage sludge, industrial wastewater sludge and feedwater sludge. The disposal and treatment of various kinds of sludge has become a persistent problem that restricts urban development and urban health.
Working principle of sludge dryer
The sludge drying machine can dry the materials with 90% water content to finished products at one time. In view of the characteristics of sludge drying process which is easy to form unity lumps, the material plate structure form of general single-channel dryer is changed and the combined self-cleaning device is adopted, which greatly extends the application range of single-channel dryer and can dry not only all kinds of sludge but also all kinds of high viscosity materials.
The drying sludge enters the guide plate inside the dryer from the feeder through the chute, and with the rotation of the barrel, the sludge is guided to the inclined lifting plate, which is lifted to the center of the barrel and gradually overflows, forming a material curtain through which the high temperature airflow passes to preheat the sludge and evaporate some water. When the sludge spills and moves to the movable grate type wing plate, the material is intermingled with the preheated grate type wing plate, and the heat is transferred to the material to make part of the water evaporate. At the same time, the wing plate entrainment material lift, spill, repeat many times, the material and hot airflow convection and contact heat exchange. At the same time, the sweeping device buried in the material also slips along the inner side of the circular lifting plate, sweeping down the material adhering to the inner wall of the lifting plate. When the sweeping device with the barrel after the vertical line, and in the back of the circular arc lifting plate dragging, will adhere to the lifting plate outside the wall of the material sweep down. With the continuous rotation of the cylinder, some water evaporates and the sludge is further dried. At the same time, the sweeping device also plays a role in breaking the sludge ball, which improves the drying speed, and finally the dried sludge becomes loose material with low moisture and is discharged from the discharge port.
Feature of sludge dryer
a. Because the heat required for drying relies on indirect heating by heat conduction, the drying process does not require or only requires a small amount of gas to take away the moisture. It greatly reduces the loss of this part of heat taken away by airflow and improves the heat utilization rate, which is an energy-saving drying equipment.
b. Stirring and mixing make the materials turn over violently, so as to obtain high heat transfer coefficient, so the floor space and space are small, which saves the plant infrastructure cost. The amount of gas used in the drying process is small, the flow rate is low, and the amount of dust taken away by the gas is small, so it is convenient to recover the gas dust after drying, and the volume of recovery equipment is small, which can save the investment in equipment. For the drying process that needs to recover solvent, the solvent concentration can be greatly improved. Due to the special structure of the paddle, the material alternately receives extrusion and relaxation in the drying process, which strengthens the drying. The filling rate of materials in the drying chamber is high, which can reach 80%-90%. The residence time of materials can be adjusted from a few minutes to a few hours by adjusting the parameters such as charging speed, stirring shaft speed and material filling degree.
c. The sludge machine can be used for sludge drying in many fields such as municipal sludge, printing and dyeing sludge, paper sludge, electroplating sludge, etc. It has high thermal efficiency, wide range of use, low operating cost, and can also realize continuous production.
Why should we use sludge dryer?
The sludge dryer allows the sludge to pass through the "gelling phase area" as quickly as possible during the drying process. At the same time, the ingenious structure allows the sludge to be dried in a bi-directional shear state. The dried sludge is continuously fed by the screw feeder into the dosing port of the rotary sludge dryer in a quantitative manner. After entering the body, the sludge is turned and stirred by the rotation of the paddles, which continuously updates the heating interface and is in contact with the body and the paddles, and is fully heated so that the surface water contained in the sludge evaporates. At the same time, the sludge is conveyed into the spiral track along the outlet direction with the rotation of the paddle shaft and continues to be agitated during the conveying process so that the water seeping out of the sludge continues to evaporate. Finally, the evenly dried qualified product is discharged from the discharge port. The jacketed shell structure is adopted, so that the sludge is evenly heated at each interface in the machine, and the shaft body is rotated, so that the sludge is constantly tossed in the equipment and the heated surface is constantly renovated. Thus, the cooking efficiency of the equipment is greatly improved, which not only achieves the purpose of sludge drying but also realizes the low-cost operation of the whole set of equipment.
Different materials choose different drying processes, and it is very important to choose the right drying process. The general single-stage drum dryer does not dry for the characteristics of the material to make the baked material color poor, sludge is a kind of material is not easy to dry, so that the baked material skin dries inside wet and dry wet unevenly, and the use of DC scrolling plus AC reciprocating fast dryer, so that the baked material color is good, saving resources to improve economic efficiency.
Sludge material can be treated in sludge dryer
a. Domestic sludge and sewage treatment plant sludge. Domestic sludge has high organic content and contains a large number of pathogens, bacteria and parasites. For this problem, sludge dryer machine can be used to kill bacteria and pathogens through high temperature drying process, which can realize the recycling of resources and produce high economic and social benefits.
b. Printing and dyeing sludge. Printing and dyeing sludge has low calorific value but high content of heavy metals, which is suitable for heavy metal recovery after drying using sludge drying system, which can bring considerable income to the enterprise.
c. Paper sludge. Paper sludge still has a high-water content after dewatering, a large paper sludge yield, and a large number of fibers in the sludge. After drying with sludge drying equipment, it is possible to achieve comprehensive recycling of paper sludge as a resource.
d. Electroplating sludge. The treatment of wastewater by electroplating is the main reason for the generation of electroplating sludge. Electroplating sludge has small organic content and small calorific value, but also contains a lot of heavy metals and recoverable resources, so it also has a high economic value for reuse.
e. Tannery sludge. In the process of leather processing, there are a lot of hides and chemical substances left behind, and the content of organic matter is very high, and there are more toxic substances, and improper treatment will have damage to the environment and secondary pollution.
f. Petrochemical sludge. In industrial production, the composition of petrochemical sludge is complicated, and it contains many different kinds of heavy metals. Generally petrochemical sludge contains oil, viscosity, and high-water content, small organic content, more volatile substances, ordinary sludge drying equipment cannot be effectively disposed of, easy to flash explosion or fire explosion and other situations.
Sludge drying process
The presence of water in sludge is different and it can be divided into free water, interstitial water, surface adsorbed water and internal water. The form of water is different and the degree of difficulty of wastewater sludge drying is also different. In the drying process of sewage sludge drying, it can be divided into: concentration - dehydration - drying.
|Concentration||The first step of drying is completed by gravity concentration, flotation concentrate or centrifugal concentration method.
|Dehydration||The common dewatering method is mechanical dewatering. Of course, there will also be vacuum dewatering, pressure dewatering, and dewatering with pressure.
|Drying||The choice of sludge dryer varies depending on the use. Just like the belt dryer to dry sludge.
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