Mesh Belt Dryer

Working Principle

The mesh belt dryer is a continuous production drying equipment. The main heating methods are electric heating, steam heating and hot air heating. The main principle is to spread the material evenly on the mesh belt. The mesh belt is made of 12-60 steel mesh belt, which is dragged by the transmission device to move back and forth in the dryer. The drying machine is discharged from the moisture exhaust hole to achieve the purpose of drying. The length of the box is composed of standard sections. In order to save space, the dryer can be made into a multi-layer type. 6-40m, effective width 0.6-3.0m.

The whole equipment consists of feeding system, hot air system, discharge system, and moisture discharge system.

The charging system makes the materials evenly dispersed on the screen plate and conveyed to the drying section at a uniform speed. The hot air system is to provide the heat source required for drying, providing 80~120℃ hot air to the drying chamber. When the conveyor belt passes through, the hot air passes through the materials on the conveyor belt from top to bottom or from bottom to top so that the materials can be dried evenly and finally discharged by the discharge system.

Applications

Conveyor mesh belt dryer is a commonly used continuous drying equipment, which can be widely used in chemical, food, medicine, building materials, electronics and other industries, especially suitable for drying sheet, strip and granular materials with good ventilation. Paste-like materials such as filter cakes can also be dried after being formed by a granulator or an extruder.

Technical Parameters

Model	DW-1.2-8A	DE-1.2-10A	DW-2.0-8A	DW-2.0-10A
Quantity of unit	4	5	4	5
Length of the drying section	8M	10M	8M	10M
Operation temperature	50-140℃
Steam pressure	0.2-0.8Mpa
Steam consumption	120-300kg/h	150-375kg/h	180-500kg/h	225-600kg/h
Drying time	0.2-1.2h	0.25-1.5h	0.2-1.2h	0.25-1.5h
Drying strength	6-30kg.h2o/㎡.h
Power	11.4kw	13.6kw	12.5kw	14.7kw

Model	DW3-1.2-8B	DW3-1.2-10B	DW3-2.0-8B	DW3-2.0-10B
Quantity of unit	8	10	8	10
Length of the drying section	24M	30M	24M	30M
Operation temperature	50-140℃
Steam pressure	0.2-0.8Mpa
Steam consumption	240-550kg/h	300-750kg/h	350-1000kg/h	400-1200kg/h
Drying time	0.2-1.2h	0.25-1.5h	0.2-1.2h	0.25-1.5h
Drying strength	6-30kg.h2o/㎡.h
Power	21.7kw	26.1kw	29.2kw	35.2kw

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Our Mesh Belt Dryer Projects (Vegetable & Seaweed)

I: Drying Solutions for Vegetable Dehydration

1. Mesh Belt Dryer Model Selection for Vegetable Dehydration

Heat balance calculation: Take the average local temperature as t0=20℃, air moisture content as d0=0.01Kg/Kg dry air.

1. Required dry moisture: W=600×(80-3)/(100-80)=2310kg/h.
2. Heat required for moisture evaporation: Q1=W (595+0.45t2- t0)=1392000Kcal/h.
3. Heat required for material warming: Q2= W2 [0.5(1- w2) + w2](t2- t0) = 47600Kcal/h.
4. Heat required for system loss: Q3= (0.15 ~ 0.2) × (Q1+ Q2) = 220,000Kcal/h.
5. Mass flow rate of drying hot air: M=( Q1+ Q2+ Q3) ÷ [(0.24+0.45 d0)( t1- t2)-0.1×0.24(t2- t0)] ≈ 121,000Kg/h.
6. Provide total heat: Q0=M(0.24+0.45 d0)(t1- t0)=2958450K cal/h.
7. Check the reasonableness of the set exhaust air temperature: Exhaust air moisture content: d2 = d1 + W water / G = 0.01 + 2310/121000 = 0.03kg water / kg dry gas, check the air enthalpy wet diagram can be found in the corresponding dew point temperature t dew = 31.64 ℃, then t2 – t dew = 28 ℃ > 20 ℃, to ensure that the exhaust air does not condense.

Due to the nature of the material, we decided to choose a set of DW5-2.25X20 five-layer mesh belt dryer (each layer is 20m long and 2.25m wide).

2. Fan Selection

• Circulating fan: 4-72-6c-11kw Air volume: 18000m3/h Air pressure: 1200pa.
• Dehumidification fan: 4-72-8C-30kw Air volume: 30000m3/h Wind pressure: 900pa.

3. Equipment Introduction

• Equipment material: The whole equipment adopts steel frame structure, the outer wall is made of stainless steel plate and the inner wall is stainless steel. The 1, 2, 3, 4 and 5 layers of mesh belts are made of stainless steel. The spreader bar and protective cover of the mesh belt are all stainless steel. The chain, sprocket, track, circulating fan and moisture exhaust fan of the mesh belt are made of carbon steel.
• Feeding method: The screw conveyor is used to lift the material to the first layer.
• Heating method: steam heating, heat exchange by carbon steel column fin radiator, the temperature of each unit can be set and controlled independently.
• Transmission device: The transmission device has a large reduction ratio, so that the drying time can be controlled in 2~3 hours to improve the applicable range of the equipment.

4. Parameters of DW5-2.25X20 Mesh Belt Dryer for Vegetables Dehydration

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II: Drying Solutions for Seaweed (carrageenan)

1. Mesh Belt Dryer Model Selection for Seaweed Drying

Heat balance calculation: Take the average local temperature as t0=20℃, air moisture content as d0=0.01Kg/Kg dry air.

• Required dry moisture: W=200×(90%-12%)/(1-12%)=178kg/h.
• Heat required for evaporation of moisture: Q1=178×(595+0.45×75-20)≈10.8×104Kcal/h.
• Heat required for material warming: Q2=200×(0.4×(1-15%)+15%)×(60-20)≈0.4×104Kcal/h.
• Heat required for system loss: Q3=0.15×(10.8+0.4)×104≈1.68×104Kcal/h.
• Required air volume of the system: LG=(Q1+Q2+Q3)/[(0.24+0.45×0.011)(115-75)-0.1×0.24(75-20)]=11162kg/h.
• Total heat provided by heat source: Q0=11162×(0.24+0.45×0.011)(115-20)≈26×104Kcal/h.

Exhaust emission verification: With the machine exhaust moisture tail gas moisture content Hs: Hs = 0.011 + 178/11162 ≈ 0.026Kg/Kg dry air. According to the above parameters to check the air enthalpy and humidity diagram: air moisture content of 0.026Kg/kg dry air; dry bulb temperature of 75 ℃; air relative humidity of 3.53%; wet bulb temperature of 42 ℃; dew point of 27 ℃; dry, wet bulb temperature difference Δt = 75-42 = 33 ℃ > 20 ℃, regarded as a reasonable temperature setting for moisture discharge.

According to our company’s experience in using equipment in similar industries, the average drying intensity of mesh belt dryer is 10-15Kg water/m2.h. The design is taken as 12Kg water/m2-h, then the effective area of drying required A: A=178/12≈15m2. Combined with the above calculation, DW1.5×10 belt dryer is selected for production.

2. Parameters of DW1.5×10 Mesh Belt Dryer for Seaweed Drying