bahan absorben

8/10/2019 BAHAN Absorben

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Absorben

Absorben adalah cairan yang dapat melarutkan bahan yang akan diabsorpsi pada

permukaannya, baik secara fisik maupun secara reaksi kimia.Absorben sering juga disebut

sebagai cairan pencuci.

Persyaratan absorben :

1.

Memiliki daya melarutkan bahan yang akan diabsorpsi yang sebesar mungkin (kebutuhan

akan cairan lebih sedikit, volume alat lebih kecil).

2. Selektif

3. Memiliki tekanan uap yang rendah

4.

Tidak korosif.

5.

Mempunyai viskositas yang rendah

6. Stabil secara termis.

7. Murah

http://id.wikipedia.org/wiki/Absorben

Absorben adalah cairan yang dapat melarutkan bahan yang akan diabsorpsi pada

permukaannya,baik secara fisik atau dengan reaksi kimia. Absorben (juga disebut cairan

pencuci) harus memenuhi persyaratan yang sangat beragam. Misalnya bahan itu harus :

Memiliki daya melarutkan bahan yang akan diabsorpsi yang sebesar mungkin (kebuthan

akan cairan lebih sedikit,volume alat lebih kecil)

Sedapat mungkin sangat reaktif

Memiliki tekanan uap yang tinggi

Mempunyai viskositas yang rendah

Stabil secara termis dan murah

Absorben yang sering digunakan adalah air (untuk gas-gas yang dapat larut, atau untuk

pemisahan partikel debu dan tetesan cairan), natrium hidroksida (untuk gas-gas yang dapat

bereaksi seperti asam) dan asam sulfat (untuk gas-gas yang dapat bereaksi seperti basa)

https://fatysahinknowledge.wordpress.com/2011/11/15/absorber/

LAPORAN OPERASI TEKNIK KIMIA ABSORBSI

Dasar Teori



http://alexschemistry.blogspot.com/2013/03/laporan-operasi-teknik-kimia-absorbsi.html







Absorbsi merupakan salah satu proses pemisahan dengan mengontakkan campuran gas

dengan cairan sebagai penyerapnya. Penyerap tertentu akan menyerap setiap satu atau lebih

komponen gas. Pada absorbsi sendiri ada dua macam proses yaitu :

a. Absorbsi fisik

Absorbsi fisik merupakan absorbsi dimana gas terlarut dalam cairan penyerap tidak disertai dengan

reaksi kimia. Contoh absorbsi ini adalah absorbsi gas H2S dengan air, metanol, propilen, dan

karbonat. Penyerapan terjadi karena adanya interaksi fisik, difusi gas ke dalam air, atau pelarutan

gas ke fase cair. Dari asborbsi fisik ini ada beberapa teori untuk menyatakan model mekanismenya,

yaitu :

1. teori model film

2. teori penetrasi

3. teori permukaan yang diperbaharui

b. Absorbsi kimia

Absorbsi kimia merupakan absorbsi dimana gas terlarut didalam larutan penyerap disertai dengan

adanya reaksi kimia. Contoh absorbsi ini adalah absorbsi dengan adanya larutan MEA, NaOH, K2CO3,

dan sebagainya. Aplikasi dari absorbsi kimia dapat dijumpai pada proses penyerapan gas CO2 pada

pabrik amoniak. Penggunaan absorbsi kimia pada fase kering sering digunakan untuk mengeluarkan

zat terlarut secara lebih sempurna dari campuran gasnya. Keuntungan absorbsi kimia adalah

meningkatnya koefisien perpindahan massa gas, sebagian dari perubahan ini disebabkan makin

besarnya luas efektif permukaan. Absorbsi kimia dapat juga berlangsung di daerah yang hampir

stagnan disamping penangkapan dinamik.

Hal-hal yang mempengaruhi dalam prsoses adsorbsi :

Zat yang diadsorbsi

Luas permukaan yang diadsorbsi

Temperatur

Tekanan


The aims of this project is to present a comprehensive review of different processes available

and suitable for removal of CO2 from natural gas to meet LNG production specifications and

explore the capability of HYSYS process simulator to predict the CO2 removal process






operating conditions range at which hydrocarbon and chemical loss (amine solvent) can be

minimized.

The simulation results shows that increasing amine CO2 capturing capacity at low

temperature and lowering the amine residence time in the stripper, reduces the tendency for

CO2 emission and chemical (solvent) loss.

The chemical solvents and physical solvents or combination of these two have been used

extensively in existing base load LNG facilities (David Coyle et. al 2003).

Simulation of a typical amine solvent based CO2 removal plant using HYSYS process

simulator to establish optimum operating conditions that will improve process environmental

performance will be considered in detail.

This project therefore summarizes the various processes available and suitable for removal of

CO2 from natural gas to meet the LNG stringent specification of about 50-100 ppmv or 2-3%

CO2 concentration in the product stream. Different processes scalability, advantages and

disadvantages will be highlighted. Simulation of a typical amine solvent based CO2 removal

plant using HYSYS process simulator to establish optimum operating conditions that will

improve process environmental performance will be considered in detail.

High CO2 partial pressure in the feed gas (345 kpa) enhances the possibilities of employing

physical solvent, while the presence of significant amount of heavy hydrocarbon discourages

the use of physical solvent. Low CO2 partial pressures and low outlet pressure of the product

stream may favour application of chemical solvents (Tennyson et al 1977).

Removal of CO2 by physical absorption processes are based on the solubility of CO2 within

the solvents. Higher CO2 partial pressure and lower temperature favors the solubility of CO2

in the solvents (Absorbent), at these conditions complete removal of acid gas from natural

gas is possible.

Salako2005

As overall selection criteria, the characteristics of a good solvent for absorption process

fulfils the following main features: high gas solubility, high solvent selectivity, high

volatility, low effects on product and environment, high chemical stability, low cost and more

availability, non corrosive, low viscosity, non flammable and low freezing point.



At equilibrium conditions, solubility of gases is referred as the quantity of gas dissolved in a

given quantity of solvent. Further at equilibrium, the partial pressure (fugacity) of a

component in the gas is equal to the fugacity of the same component in the liquid.This

defines the equilibrium thermodynamic criterion for the relation of the concentration of a

component in the gas and its corresponding concentration in the liquid (Meyers 2001).

In the process of absorption, the selective solvent (absorbent) in a plate of packed column is

contracted countercurrently with the gas to be processed (ascorbate). In physical absorption,

the desired gas component being absorbed (ascorbate) is more soluble in the liquid solvent

(absorbent) than other components in the gas phase but does not react chemically with the

absorbent.

Physical absorption processes are the type of absorption processes where the solvent interacts

only physically with the dissolved gas. In this process, the solvent is used as an absorbent

with thermodynamic properties such that the relative absorption of CO2 is more favored over

the other components of the gas mixture.

Mostly, physical solvent systems are used when the feed gas is characterized by high CO2

partial pressure and low temperatures. Although heavy hydrocarbon restricts the wide use of

physical solvent, its absorption capacity can be higher than chemical solvents. In addition,low CO2 partial pressures as well as low outlet pressure of the product stream may also

discourage the application of physical solvents (Ebenezer and Gudmundsson 2006).

Removal of CO2 from the feed gas by physical solvent absorption is based on the solubility

of CO2 within the solvents. The partial pressure and the temperature of the feed gas are the

two major factors that determine the solubility of CO2. Although there are too many physical

solvent processes for the removal of CO2 from natural gas, not all the processes available are

capable of removing CO2 to meet LNG specification of 50-100 ppmv of <2.5% of CO2 in

the product stream (Ebenezer and Gudmundsson 2006).

InTech-

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