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3.11.3.1 Calculation of energy requirements and efficiency

Drying is a commonly used method in many industrial sectors. In a dryer system, first of all the damp material is heated to the vaporisation temperature of water, then the water is evaporated at a constant temperature.
Figure 3.45 demonstrates the bandwidths for the specific secondary energy consumption per kilogram of evaporated water at maximum load and with maximum possible evaporation performance for various types of dryers. For the purposes of comparison, it has been assumed that the convection dryers use electrical resistance heating.

3.11.3.2 Direct heating

Direct heating is achieved primarily by convection. A warm or hot gas, usually air (which may be mixed with the combustion gases of the fuel) or steam ( see Section 3.11.3.4) is passed through, over or around the material(s) to be dried, which may be in e.g. a rotating drum, on racks or jigs.
Typical direct drying systems are:
●with a flowing gas:
○ e.g. rotating drum, drying oven or kiln, tunnel dryers, spiral belt dryers, tray dryers
●with aerated solids:
○ e.g. through circulator, batch dryers, stationary rack dryers
●with large scale agitation of solids:
○ e.g fluidised bed, spin flash drying.

3.11.3.3 Indirect heating

Direct heating is achieved by conduction. The heat is transferred to the material to be dried by a heated surface. The material may be stationary or continually transferred from one hot surface to another.
Typical indirect drying systems are:
●flat and strip materials, such a s textiles, paper or board use drum driers. The moist material is wrapped around rotating horizontal cylinders heated internally, usually with steam
●low viscosity materials such as solutions of organic or inorganic material, a roller drier is usually used. The material flows onto heated rollers as a thin layer, and the dried solid is removed with a scraper blade as a film, flakes or powder
●pasty materials are dried by:
○ grooved roller drier (which produces short segments for further drying),
○ hollow screw drier which use one or two hollow Archimedes screws turning in a trough. The screws are heated with hot water, saturated steam, or hot oils, etc.
○ all phase drier which is a contact drier with stirrer and kneader. The housing, lid, hollow main roller and its disc elements are heated with steam, hot water or hot oil
●Granular materials are dried by:
○ rotary driers, either with heated pipes within the drum or the material to be dried in within tubes i n t he heated drum. These have low air velocity, which is useful for dusty materials
○ screw conveyor driers with paddles which turn in a heated container
○ cone worm drier with a cone-shaped stirrer rotating in a heated funnel shaped jacket
○ tray driers, with heated trays
○ spiral tube driers, in which the material is only briefly in contact with the heated surface of the tube and is transported pneumatically. It can be sealed and may be used for organic solvent removal, with solvent recovery.

3.11.3.6 Mechanical vapour recompression or heat pumps with evaporation

Concentration by evaporation coupled with MVR (mechanical vapour recompression) or a heat pump, is a highly efficient technique f or waste water treatment. I n particular, this technique makes it possible to significantly reduce waste water volumes sent to treatment at a low cost, as well as allowing water recycling.
To evaporate one tonne of water, 700 to 800 kWh/t energy power is required. It is possible to reduce the energy needs by using heat recovery solutions, such as heat pumps, including mechanical vapour recompression ( MVR) ( see Section 3.3.2), or multiple effect evaporators with thermo-compression.

3.11.3.1 能源需求與效率計算

在工業部門中乾燥是常用的製程處理程序。在乾燥機系統中首先將加入的原料加熱到水的蒸發溫度，然後其中水分蒸發出來到常溫。
圖3.45說明了各種不同的乾燥機進行第二次加熱乾燥所需的能耗，其指標是以最大負荷及最大功效下蒸發每公斤水所需的能量。其中對流乾燥機是以電阻加熱的方式進行。

3.11.3.2 直接加熱處理

直接加熱處理基本上是應用熱對流原理。通常是以熱空氣或蒸汽通過或包圍原物料將之烘乾，熱空氣可能是和燃料的燃燒氣體混合的氣體，所使用的機具可能是迴轉筒、開架床或篩選機。
典型的烘乾機系統有下列幾種：
●利用流動氣體：如旋轉筒、烘乾窯爐、隧道式烘乾爐、迴旋帶式烘乾機、盤式烘乾機等
●利用充氣固體：如通過循環機、分批烘乾機、固定式開架烘乾機
●利用大型固體攪動機器：如流體床、旋轉閃蒸烘乾技術等

3.11.3.3 間接加熱

間接加熱是透過熱傳導來達成。(譯註:英文Direct應為Indirect之誤)。熱量透過一個熱表面體將熱傳導給原物料)，原物料可能是固定或連續性地在熱表面體間移動。
典型的間接烘乾系統：
●平面及條狀的原物料，像紡織品、紙張或紙板，使用滾筒狀的烘乾機。含水的材料捲在旋轉平放的圓筒上，自內部加熱，通常熱源是蒸汽。
●低粘度的原物料，如有機或無機物溶液，其烘乾通常是用滾筒式烘乾機。原物料流進熱滾筒中形成一層薄膜，烘乾後的固體物則用刮刀刮成薄片、脆片或粉狀而加以移除。
●膏狀的原物料：
○ 凹槽式滾筒烘乾機(切成一小段供下一階段烘乾)
○ 空心螺桿烘乾機：使用一或二套阿基米德空心螺桿在筒槽中轉動螺桿，靠熱水飽和蒸汽或熱油加熱
○ 全相烘乾機：是一種有攪拌器與捏揉器的接觸型乾燥機，外罩蓋子，主滾筒及其圓盤靠蒸汽、熱水及熱油加熱
●顆粒狀原物料：
○ 迴轉式烘乾機：筒內有加熱管或要被烘乾的原物料在加熱筒管內兩種。其通過空氣速度較慢，適合用來乾燥粉塵狀的原物料
○ 螺旋式輸送烘乾機：在加熱容器內有鰭片狀的轉子轉動烘乾
○ 錐形蝸管烘乾機：以一錐形攪拌器在加熱爐夾套中迴轉
○ 盤狀烘乾機：加熱盤
○ 迴轉管式烘乾機：原物料只是與管子的熱表面接觸，然後以氣動方式送出。此種烘乾機作業可密封，故可用在有機溶劑分離而將溶劑回收。

3.11.3.6 帶有蒸發功能的機械蒸氣再壓縮系統或熱泵

經由MVR或熱泵的蒸發濃縮方法是很高效率的廢水處理技術。可貴之處在於此技術可顯著地減少送到廢水處理廠的廢水量，而且成本低，水可以回收再利用。
蒸發一噸的水需要700~800度的能源(電力)，如使用熱回收方法可節省能源。這些方法包括熱泵、MVR或多效式熱能-壓縮系統。

3.11.3.1 Calculation of energy requirements and efficiency

No data submitted.

3.11.3.2 Direct heating

None identified.

3.11.3.3 Indirect heating

Likely to use more energy than direct heating, due to losses in the transfer of heat, as this process has two stages: heating the surface then heating the material.

3.11.3.6 Mechanical vapour recompression or heat pumps with evaporation

The concentration of waste water streams may require different management and treatment techniques (i.e. may no longer be suitable for waste water discharge).

3.11.3.1 能源需求與效率計算

無

3.11.3.2 直接加熱處理

無法確定

3.11.3.3 間接加熱

間接加熱烘乾技術要比直接加熱技術耗能，因為過程要將用具先加熱，然後再移轉熱量給原物料，造成熱傳送的損失。

3.11.3.6 帶有蒸發功能的機械蒸氣再壓縮系統或熱泵

不同廢水的濃度需要不同的管理與處理技術，不適合流入一般廢水排放水中。