08 Evaporator

EVAPORATOR

TEKNOLOGI

PrinsipMengurangi cairan dari larutan, suspensi, atau emulsi dengan cara menguapkan cairannya

Evaporasi termasuk separasi termal atau proses konsentrasi termal

Evaporasi didefinisikan sebagai proses penguapan cairan dari larutan encer sehingga dihasilkan larutan pekat (pemekatan larutan) dan uap.

TEKNOLOGIKriteria Pemilihan Evaporator• Kapasitas yang diinginkan

– Jumlah, suhu jam operasi, perubahan produk, pengendalian, dll• Karakteristik produk

– Kepekaan terhadap panas, viskositas dan sifat-sifat aliran, kecenderungan berbusa, pengendapan dan pengerakan, perilaku pendidihan, dll

• Kebutuhan media– Seperti steam, air pendingin, energi listrik, bahan pembersih, suku cadang,

dll.• Modal dan biaya lain• Biaya operasi dan perawatan• Pemilihan bahan konstruksi• Kondisi lapangan

– Seperti ketersediaan ruang, iklim (untuk lapangan di luar), dll.• Peraturan atau hukum yang berlaku

– Meliputi keselamatan kerja, penmcegahan kecelakaan, emisi suara, kebutuhan lingkungan, dll

TEKNOLOGIPenerapan• Product concentration• Dryer feed pre-concentration• Volume reduction• Water / solvent recovery• Crystallization

Beberapa Jenis Evaporator• Falling Film Evaporators• Rising Film Evaporators• Forced Circulation Evaporators• Plate Evaporators

Falling Film Evaporator

A: ProductB: VaporC: ConcentrateD: Heating SteamE: Condensate1: Head2: Calandria3: Calandria, Lower part4: Mixing Channel5: Vapor Separator

Falling Film EvaporatorIn falling film evaporators the liquid product (A) usually enters the evaporator at the head (1) of the evaporator. In the head the product is evenly distributed into the heating tubes. A thin film enters the heating tube are it flows downwards at boiling temperature and is partially evaporated. In most cases steam (D) is used for heating the evaporator. The product and the vapor both flow downwards in a parallel flow. This gravity-induced downward movement is increasingly augmented by the co-current vapor flow. The separation of the concentrated product (C) form its vapor (B) is undergoing in the lower part of the heat exchanger (3) and the separator (5).

Falling Film EvaporatorFalling film evaporators can be operated with very low temperature differences between the heating media and the boiling liquid, and they also have very short product contact times, typically just a few seconds per pass. These characteristics make the falling film evaporator particularly suitable for heat-sensitive products, and it is today the most frequently used type of evaporator.

Falling Film Evaporator

Falling Film Evaporator

Rising Film Evaporator

A: ProductB: VaporC: ConcentrateD: Heating SteamE: Condensate

Rising Film Evaporator

Beroperasi dengan prinsip “termosifon”. Feed product (A) enters the bottom of the heating tubes and as it heats, steam begins to form. The ascending force of this steam produced during the boiling causes liquid and vapors to flow upwards in parallel flow. At the same time the production of vapor increases and the product is pressed as a thin film on the walls of the tubes, and the liquid rises upwards. This co-current upward movement against gravity has the beneficial effect of creating a high degree of turbulence in the liquid. This is advantageous during evaporation of highly viscous products and products that have a tendency to foul the heating surfaces.

Rising Film Evaporator

Forced Circulation Evaporator

A: ProductB: VaporC: ConcentrateD: Heating SystemE: Condensate

1) Heat Exchanger2) Flash Vessel (Separator)3) Circulation Pump4) Concentrate Pump

Forced Circulation Evaporator

Forced circulation evaporators are used if boiling of the product on the heating surfaces is to be avoided due to the fouling characteristics of the product, or to avoid crystallization. The flow velocity in the tubes must be high, and high-capacity pumps are required.

Forced Circulation Evaporator

Plate Evaporator

A) ProductB) VaporC) ConcentrateD) SteamE) CondensateF) Excess Vapor

1) Plate Evaporator2) Separator

Plate EvaporatorInstead of tube and shell heat exchangers, framed plates can be used as an heating surface. These plate assemblies are similar to plate heat exchangers, but are equipped with large passages for the vapor flow. In these units a product plate and a steam plate are connected alternately. The product passage is designed for even distribution of liquid on the plate surfaces and low pressure drop in the vapor phase.

Plate EvaporatorPlate evaporators are of compact design. Separators are flanged directly to the plate packages with short interconnecting pipe-work. Thus, space requirements are low and the building height normally does not exceed 10-13 ft (3-4m). This means that plate evaporators can be installed in most buildings. Very often GEA Niro delivers these units preassembled as skid-mounted systems, further simplifying installation.

Plate Evaporator

Plate Evaporator

Plate Evaporator

Single Effect Evaporator

Single Effect Evaporator

Multiple Effect Evaporator (Forward)

Multiple Effect Evaporator (Forward)

Multiple Effect Evaporator (Forward)

Number of effects

Steam consumption(kg steam/kg

water evaporated)

Total running cost (relative to a single- effect evaporator)

1 1.1 12 0.57 0.523 0.40 0.37

TABLE 8.1STEAM CONSUMPTION AND RUNNING COSTS OF EVAPORATORS

Multiple Effect Evaporator (Forward)

Multiple Effect Evaporator (Backward)

SOAL

Bahan baku berupa larutan pekat dan kemungkinan terjadi pengendapan atau pengerakan cukup besar. Bahan yang dipekatkan tidak peka terhadap panas. Atas dasar itu jenis evaporator apa yang Anda reklomendasikan?