Organic waste rake dryeroverview

Organic waste, also known as wet waste, refers to the waste of organic components in urban household waste. A large part of it is kitchen food residue and hotel kitchen waste. So it is important to handle these things well for environmental protection. The process is as follows: first, remove the non degradable components in the kitchen waste, crush and sort it by water, and form an organic milk slurry. Then, it enters the fermentation tank, adds a certain proportion of auxiliary materials and fermentation bacteria, and undergoes aerobic fermentation to form a solid liquid mixture. Then it is sent to the dryer for drying, and through processes such as granulation, drying, and bagging, high-quality bio organic compound fertilizer is produced. Rake drying utilizes the characteristic of intermittent operation to carry out fermentation and drying in the same equipment. Fully mix the organic waste with bacterial strains and beds, and ferment them through enzymes at a suitable temperature to decompose carbohydrates, fats, proteins, etc. in the organic waste into carbon dioxide, ammonia, water vapor, etc. After deodorization with high-temperature catalysts, colorless and odorless gases are emitted, reducing the amount by more than 90%. The residue is non-toxic and is an excellent organic fertilizer. Our company has designed an energy-saving and environmentally friendly rake dryer based on the physical parameters provided by the customer. This article discusses its design and selection process.

Organic waste rake dryercharacteristic

(1) Simple structure, easy operation, long service life, stable and reliable performance.

(2) Strong applicability, wide application, fast drying speed: Due to the use of jacket heating and high vacuum exhaust, the rake dryer is suitable for almost all materials of different properties and states, especially for explosive, easily oxidized, and paste like materials.

(3) The product has high quality, and during the drying process, the rake teeth continuously rotate in both directions, causing the dried material to shake evenly and avoiding overheating of the material. Moisture is also easily released.

(4) Low steam consumption.

(5) Easy to operate, recyclable volatile gases, and minimal environmental pollution.

(6) The product has fine particle size and does not require a crushing operation procedure.

The main components of organic waste rake dryer

1. Shell;

2. Rake teeth;

3. Special discharge device;

4. Feeding device;

5. Crushing rod;

6. Seals can be divided into mechanical seals and packing seals;

7. Mixing shafts with multiple structures;

8. Transmission device

Organic waste rake dryerWorking principle

The dried material is added from the middle of the upper part of the shell, and under the stirring of the constantly rotating rake teeth, the axial direction of the material is moved back and forth, and the surface in contact with the inner wall of the shell is constantly updated, while being indirectly heated by steam; Under the uniform stirring of the rake teeth and the crushing effect of the crushing rod, the surface of the material continuously updates and increases, making it more conducive to the discharge of moisture; After the moisture and other tail gases from gasification are removed from dust and potentially condensable gases by dry or wet dust collectors and condensers, non condensable gases that meet emission standards are pumped out and released by vacuum pumps.

Organic waste rake dryerThermodynamic calculation

The material parameters provided by the customer: 2 tons of organic waste with a moisture content of 65% to 80%, 1 ton of rice bran or wheat bran with a moisture content of 10% to 15%, and a total of 3 tons of processed raw materials. The overall moisture content can reach 50% to 55% suitable for biological fermentation, and the moisture content of the material after fermentation and drying is 10%. The processing capacity is 3t/d, equivalent to 0.143t/h (calculated based on 24 hours of daily work, considering the feeding and discharging time). The drying heat source uses saturated water vapor at 0.1 MPa (gauge pressure).

(1) Original conditions:

Material Name: Organic Waste

Initial moisture content: θ 1=55%

Moisture content after drying: θ 2=10%

Wet material quantity: G1=143 kg/h

Dry material quantity: G2=71.5 kg/h

Absolute dry material quantity: Gc=64.35 kg/h

Initial temperature of material: t1=20 ℃

Material drying temperature: t2=70 ℃
(2) Evaporation water volume:

Ｗ=Ｇ1－Ｇ2＝143-71.5=71.5 kg/h

(3) Heat required for drying:

Ｑ=W·γw+Gc·Cs·（t２-t１）+Ｇ１·θ１·Cw·(t２-t１)

=71.5×2331.2+64.35×1.0×(70-20）+143×0.55×4.18×（70-20）

=186 336.15 kJ/h

In the formula: γ w=2331.2 kJ/kg (latent heat of evaporation of water)

Cs=1.0 kJ/kg ·℃ (heat capacity of material)

Cw=4.18 kJ/kg ·℃ (heat capacity of water)

(4) Arithmetic mean temperature difference: Δ tm=＝72.1 ℃

(5) Determination of the required heat transfer area of the dryer: Take the heat transfer coefficient K=90W/m2 ·℃

Then A=Q/K ·Δ tm=8m^２

Organic waste rake dryerUsage effect

The rake dryer we designed has been in use in a certain company for one year, with an annual processing capacity of 1000 tons per unit and a steam consumption savings of nearly 20% compared to other traditional forms such as convection drying. Due to the saving of fermentation equipment, labor and transportation equipment have been reduced, resulting in nearly half of the electricity saved. Achieved the expected energy-saving requirements.

Organic waste rake dryerapplication prospect

Rake dryers are mostly in the form of micro negative pressure or vacuum. During the drying process, the moisture can vaporize at low temperatures, which can achieve low-temperature drying. This is beneficial for the drying of heat sensitive materials in certain drugs, foods, and agricultural products. For example, when the temperature of liquid sugar exceeds 70 ℃, some components will turn brown, reducing the product's commercial value; Some catalysts will change their chemical properties if they exceed the operating temperature; Proteins undergo denaturation at high temperatures, altering the nutritional composition of the material. In addition, drying at low temperatures is reasonable for the utilization of thermal energy. This reduces production costs, improves product quality, lowers labor intensity for workers, and protects the environment. So since the successful development of the rake dryer, it has been widely used in industries such as pharmaceuticals, chemicals, dyes, pesticides, and food.