Acid Gas Removal (Part 3: Amine Treating Unit)

Finishing post about Acid Gas Removal, here is an explanation about the most common process that is used to remove acid gas in LNG plant: Amine Treating Unit (ATU).

Amine Treating Unit uses chemical solvents to remove the acid gas. MEA (Monoethanol Amine) and DEA (Diethanol Amine) are solvents that commonly used in ATU. But currently, DEA is more commonly used as chemical solvents because of reasons below, compare with MEA:

- DEA is weaker base, it reduces the corrosion problem

- DEA has lower vapor loss due to low vapor pressure

- DEA requires less heat for regeneration

- DEA does not require reclaimer to remove contaminants

Below is typical gas sweetening by chemical reaction:

1. Amine Absorber/Contactor

Amine absorber has counter-current flow between sour gas and solvents. The tower can be designed as tray column or packed column. Tray column has larger diameter, usually has 20-24 actual tray. For preliminary design, a tray spacing 24 in and a minimum diameter capable of separating 150-200 micron droplets can be assumed. Packed column has smaller diameter and size of tower must be obtained from manufacturer's published literature.

Commonly, amine absorber include an integral gas scrubber section in the bottom of tower to remove entrained water and hydrocarbon liquids from the gas to protect the amine solution from contamination. This scrubber has same diameter as the tower. Alternatively, a separate scrubber vessel (inlet separator) can be provided so that the tower height can be decreased. This vessel is designed in accordance with two phase separator design.

Outlet separator is required while using MEA as solvents, to help reducing MEA losses in the overhead sweet gas. DEA does not require this outlet separator.

2. Flash Drum

The rich amine solution from the absorber is flashed to a separator to remove any hydrocarbons and small percentage of acid gas. Some liquid hydrocarbon may begin to collect in separator, hence need provision to remove liquid hydrocarbon. Typically flash tank is designed for 2-3 minutes retention time for the amine solution while operating half full.

3. Amine Reboiler

The reboiler provides the heat input to amine stripper, which reverses chemical reaction and drives off acid gas. Amine reboiler may be either a kettle reboiler or an indirect fired heater. The higher reboiler duty, the higher condenser duty, the higher reflux ration, and thus the lower number of trays required and vice versa. For design, reboiler temperature in stripper operating at 10 psig can be assumed 245 F for 20% MEA and 250 F for 35% DEA.

4. Amine Stripper

Amine stripper use heat and steam to reverse the chemical reactions with CO2 and H2S. The steam acts as a stripping gas to remove the CO2 and H2S from the liquid solution and to carry these gases to the overhad. The tower can be trayed or packed with packing normally used for small diameter columns.

The typical stripper consists of a tower operationg at 10-20 psig with 20 trays, a reboiler, and an overhead condenser. The rich amine feed is entering the third or fourth tray from the top. The lean amine is removed at the bottom of stripper and acid gas is removed from the top.

For most field gas units, it is not necessary to specify stripper size. Vendors have standard design amine circulation packages for a given amine circulation rate, acid-gas loading, and reboiler.

5. Overhead Condenser and Reflux Accumulator

Amine-stripper overhead condenser is typically air-cooled, fin-fan exchangers. Their duty can be determined as required to cool the overhead gases and condense the overhead steam to water. The inlet temperature can be found using the partial pressure of the overhead steam by using steam tables. The cooler outlet temperature is typically 130-145 F, depending on the ambient temperature.

The reflux accumulator is a separator used to separate the acid gases from the condensed water. The water is accumulated and pumped back to the top of stripper as reflux. With the vapor and liquid rates known, the accumulator can be sized for two phase separator.

6. Rich/Lean Amine Exchanger

Rich/lean amine exchanger is usually shell-and-tube exchanger with the corrosive rich amine flowing through the tubes. The purpose of these exchanger is to reduce the reboiler duty by recovering some of the sensible heat from the lean amine.

For design, an approach temperature of about 30 F provides economic design balancing the cost of the rich/lean exchanger and the reboiler. The reboiler duties recommended above assume a 30 F approach.

7. Amine Cooler

The amine cooler is typically air-cooled, fin-fan cooler, which lowers the lean amine temperature before it enters the absorber. The lean amine entering the absorber should be approximately 10 F warmer than the sour gas entering the absorber. Lower amine temperature may cause the gas to cool in the absorber and thus condense the hydrocarbon liquid. Higher temperature would increase the amine vapor pressure and thus increase amine losses to the gas. The duty for the cooler can be calculated from the lean-amine flow rate, the lean-amine temperature leaving the rich/lean exchanger and the sour-gas inlet temperature. Solvent tank is required to contain lean amine.

8. Amine Solution Purification

For MEA, reclaimer is required to removed contaminants due to reaction of MEA with COS and CO2, to form heat-stable salt. Reclaimer is a kettle-type reboiler operating on a small side stream of lean solution. The temperature in the reclaimer is maintained such that the water and MEA boil to the overhead and are piped back to the stripper. The heat-stable salt remain in reclaimer until the reclaimer is full. Then the reclaimer is shut-in and dumped to waste disposal. The impurities are removed but the MEA bonded to the salt is also lost.

DEA system is not requiring reclaimer because the reaction with COS and CS2 are reversed in the stripper. The small amount of degradation products from CO2 can be removed by a carbon filter on a side stream of lean solution.

9. Material of Construction

For DEA: stress-relieved carbon steel
For MEA: corrosion-resistant metals (304 SS)

Reference:
1. DMAN-TPE-ENGPRO-008 Acid Gas Treating Design Manual 

2. GPSA Section 21: Hydrocarbon Treating

Bogor City Travelling

Last Saturday my family and my brother in law's family had a vacation at Bogor. Bogor is kinda like Bandung, city that many Jakarta people go to there while holiday. First, we went to buy roti unyil at Venus and brownies talas at Rumah Talas. After that, we went to Bogor Botanical Garden. At there, we just take walk around, see "Jembatan Gantung", take photo near rare trees and went to Bhineka Park. At that park, there is a eagle bird relief from plants and flowers. Below are the photos:

Bhinneka Park at Bogor Botanical Garden (taken from travel.detik.com.)

 

 

My family at the park

From Bogor Botanical Garden, we went to SKI Tajur, where there is a bag & shoes sale center, playground for children, and food court. My daughter and her cousins are very happy playing there. They ride mini becak, battery train, and with the parents ride combo bicycle :)

At Bogor Botanical Garden and SKI Tajur

For the closing of vacation, we choose Pizza Kayu Bakar Kedai Kita for dinner. This restaurant is so full of the traveler, especially from Jakarta. We must wait first before we can eat there. Fortunately, before the big rain, we get seat in there and we get the "lesehan" seat style. Yeayyy! We ordered Pizza BBQ Smoked Beef, Spaghetti Carbonara, I Fu Mie, Cap Cay, and Special Fried Rice. Overall the food is delicious and the portion is so big! It can be eaten by two people I think :)

Hmmm.. so many places at Bogor that we have not been visited, like Pia Apple and so on. Hopefully next time, me and my family can be back to more explore the Bogor city!

Long Weekend in Bandung (Mar '14)

Long weekend last month, my hubby, my baby, and I went to Bandung again :) Not so many place we visited that week because on the first day we went to there, Cipularang toll road was in traffic jam. We just visited Bebek Dower on Rest Area to have a lunch and after we arrived at home, it was rainy. So we couldn't go anywhere.

In the second day, my hubby, my baby, my mother, and I went out to Paris Van Java (PVJ). Actually, the traffic is not good too and there was still rainy, even the water above the road was flooding. But fortunately, we still arrived there. We had lunch at Richeese Factory, where the portion of food couldn't make we full so we ordered two times hahaha.. The food was yummy and the cheese sauce is the thing that make this place is different with other restaurant. The hot spicy chicken is the best food in there I think :9 After that, we visited the Lactasari Farm at PVJ Sky Level, where children can give milk and food to goat, sheep, and rabbit. But we didn't enter this place, just take the photo outside because I think my daughter had not understand the activity :) 

In front of Lactasari Farm PVJ

On the evening, my hubby, my baby, and I went to Batagor Ibenk's located in front of Polres Cimahi. But the batagor is sold out, so we ordered mie yamin. And it's delicious! Hahahaha.. Every long weekend all we do is just eating and eating.

On the third day, we just went back to Jakarta. See you again Bandung, on this month's long weekend! :)

One Year Kid's Activity

Inspired by Pinterest, I would like to post about one year kid's activity that is taken from my daughter's activity of course :)

Here are the list:

1. Eat by herself

Even though her appetite is decreasing after she reach one year old, but her ability to take the food into her mouth by herself is increasing. It is better to serve her a finger food such as fruits like watermelon or papaya than serve her rice and soup, because in the end the food will be messy on the floor, on her face and her clothes. She also likes to eat biscuits like picture below:

2. Sleeping or get relaxed

All baby and kid relatively like this activity. While sleeping, baby's and kid's brain is developed. My daughter still have a nap 1-3 times day and a night sleep like an adult ;p She also likes to get relaxed at the top of many pillows and/or blanket like this photo:

3. Take a bath in water bucket and of course playing with water

My daughter love to playing with water, like any other child. She takes a bath two times a day, in the morning and in the afternoon. After she can stand up by herself, she takes a bath like adult, not in the baby bucket anymore. But she still likes get into water bucket (the bucket that usually used for soaking clothes) and playing with the ball in that bucket.

4. Watching and listening kids song from VCD

My hubby is bought some VCD containing kids songs for my daughter. She likes it very much. Even if she want to watch it, she tries plug the cables by herself, to tell anyone that she wants to watch it. While watching it, she can extremely serious or dancing by herself :D

5. Playing

All kids love playing. My daughter likes to play ball and any other toys, push little trolley, make scribbled on the magnetic board, or just making mess at home hehehe.. She also likes playing with her cousin or stay under the bed. What a kid :)

6. Riding bicycle

She loves to be pushed while she is riding her bicycle :)

7. Have a walk in the afternoon and have a vacation with me and my hubby on the weekend

My daughter is a kid that can not be at home for whole day. She likes when we get her out of the house, even only go to near neighborhood. She even like to wear shoes and raise one's hand to her jacket after afternoon bath, try to tell that she want to have a walk in the afternoon with her grandpa.

8. Have a cuddles at the bed

Me and my hubby likes to have a cuddle with my daughter at the bed. Make her laugh by tempting, tickling, or kissing her and she also likes to riding me as a horse ;)


9. Learning to kiss and talk

She now can kisses hand when meet a people and gives a kiss bye when someone is leaving house. She can say "daaah" for bye bye, "muah" for a kiss, "jatuh" while drop something, "ga mau" when she don't wants something, "iya" when she agrees something, "nek" and "kek" for calling her grandma and grandpa, while calling my hubby "a" and calling me "ka" because I call my hubby "Aa" and my hubby call me "Ika" hahaha.. She also likes talking by herself while holding a phone, just like adult talking with their phone ;)


10. Reading books

I give her pillows book that colorful and has a short story in there. I also have already bought a books that contains 365 stories to be read before bed time. Hopefully I can habituate reading story before she gets asleep (before I myself get asleep hehehe..).

Cooking Demo with Chef Kong's and Lock & Lock

On Saturday (22/4/2014), I joined an event that I knew from KEB (Kumpulan Emak Blogger): Cooking Demo with Chef Kong's and Lock & Lock, which held at Foodmart Gourmet Cilandak Town Square. Chef Kong's is a chef that usually seen at Metro TV on 8-11 Show. I motivated to join it because I want to see a chef's cooking demo and want to get Lock&Lock products free. Hihihi..

 The Cooking Demo

There were 3 recipes that was cooked by Chef, which are Chili Grilled Chicken, Ginger Fish, and Purple Sweet Potato Dorayaki. Here are the recipes:

1. Chili Grilled Chicken

Ingredients:
- Chicken (3)
- Green chili (200 gr)
- Garlic (20 gr)
- Onion (40 gr)
- Lemongrass (1 pcs)
- Lime leaves (5 pcs)
- Salt, pepper, and sugar

Put all the ingredients in a glassware, and then cook it in oven at temperature 200 C, for 15 minutes.

Ingredients for the condiment:
- Onion (5 pcs)
- Red cayenne pepper (10 pcs)
- Lemongrass (2 pcs)
- "Terasi"
- Orange limo
- Salt, pepper, and sugar

Puree all condiment ingredients and then cook in frying pan with a little cooking oil.

2. Ginger Fish

Ingredients:
- Fillet fish (1)
- Ginger (3 phalange)
- Garlic (3 pcs)
- Onion (3 pcs)
- Tomato (1 pcs)
- Sesame oil (1 teaspoon)
- Fish sauce (1 teaspoon)
- Salt, pepper, and sugar

Put all the ingredients in a glassware, and then cook it in oven at temperature 200 C, for 15 minutes.

3.  Purple Sweet Potato Dorayaki

Ingredients:
- Purple sweet potato flour (200 gr)
- Fluor (400 gr)
- Egg (4 pcs)
- Coconut milk (150 mL)
- Salt (1/2 teaspoon)
- Baking powder (1 teaspoon)
- Grated coconut (1/2 pcs)
- Sugar

Put all ingredients in a bowl, stir well. Take 1 tablespoon dough and cook it in frying pan with a little cooking oil or margarine.

Nyaaam! I taste it all hahaha.. And I got Lock&Lock plasticware too, 2 pieces and a big one! :)