5 replies to this topic

[chemical eng.]

Hi my friends,
I am working on amine solvent volume calculation; I want to calculate the amine losses in daily basis.
I prepared excel sheet for this calculation, but I faced a problem for losses calculation,
Can any one help me how I can monitor the losses, I observed that the volume is decreasing but I think it is manly water.
Is there any professional way to calculate the losses?
many thanks in advance.

[Zauberberg]

It would be good to upload your spreadsheet so we can all see the approach you have selected for this task.

Actual amine losses depend on several things:

- Absorber configuration (wash water trays Y/N)
- Make-up point(s)
- Separation devices for treated gas and handling of liquid that is knocked-out
- The route of flash gas from solvent flash gas drum
- Conditions of the regenerator overhead receiver

Normally, one usually monitors amine make-up quantity on a weekly/monthly basis, assuming that you normally operate with a fairly constant solvent concentration.

[chemical eng.]

Zauberberg
you mean that the make up can be considered as losses.
many thanks for your help.
really my sheet is just volume calcualtion by using volume equation of cylinders and elliptical ends no more no less.
regards

[Zauberberg]

If there is no change in the system inventory (volume) and solvent concentration, the quantity of amine added to the system is actually the quantity you have lost between the make-up cycles.

In a properly designed gas plants, there should be an overhead KO drum downstream of absorber in the gas path and all the liquid phase captured in this drum is recycled to the rich solvent flash vessel: that way you prevent amine losses with the treated gas. Another two sources of amine losses are:

- vapor phase from the rich solvent flash drum (usually fuel gas or flared/vented)
- acid gas from the regenerator overhead receiver

There will always be amine losses due to definite volatility of amine (very low but definite), and these cannot be avoided but should always be minimized - as much as practically feasible.

[Art Montemayor]

chemical eng.:

Through the years I have been involved in the design, fabrication, installation, and operation of Acid gas removal plants – primarily the so-called “Amine Plants”.

I started my engineering career 50 years ago, primarily in charge of supervising the daily operation of continuous, 24-hr/day operation of CO₂ amine plants. I am very proud of the experience and results we gained during this phase in my career because I saw plain and humble operators and supervisors achieve results and goals that are considered by many engineers today to be “non-achievable”. This was done in the 1960’s in countries considered as “under-developed” and using a maximum of locally fabricated equipments and carbon steel construction.

The major unit manufacturing cost was, at that time, imported amines – principally monoethanolamine (MEA). One of my plant supervisors in Peru, Mr. German Huanuco, succeeded in achieving and maintaining a monthly MEA consumption of less than one kilo per metric tonne of CO₂ produced. I have yet to see an acid gas unit produce that low a consumption. German achieved his results by applying daily dedication to gas analysis, amine strength maintenance, amine redistillation operation, recovery of all CO₂ Stripper overheads condensate, efficient condensate wash of absorber overheads outlet, and the elimination of all solution leaks. He religiously maintained a close control of his MEA weighed inventory and monitored all MEA make up rates and took his unit consumption calculations at the end of each month. I have seen and witnessed USA engineers who also supervised acid gas units and couldn’t come close to the confirmed results achieved by German. This personal experience – as well as others – has proved to me (and others) that the efficient operation of a production unit doesn’t necessarily depend on an educated and prepared university engineer. I have personally witnessed plant operators without an engineering degree out-perform top university-degreed engineers in the field. The main difference in results is always good engineering common sense and hard, dedicated work to the assignment.

I make a specific note in this thread to your complete lack of attention and importance to the excellent advice and counsel that Zauberberg offers: “upload your spreadsheet so we can all see the approach you have selected for this task”. This is not only good advice; it is essential to understand what you are (or have) been doing. For example, I hope you don’t believe that you can actually “calculate” amine losses using a computer program, equation, or a simulator. The “professional way to calculate” amine losses has always been – and continues to be – the common sense, empirical way: you monitor and report the weighed amine existing before the production run and the weighed amine inventory at the end of the production run. The difference is what you are officially charged with as a production cost – and that is the bottom line.

You also state: “really my sheet is just volume calcualtion by using volume equation of cylinders and elliptical ends no more no less”, this doesn’t make for a proper engineering explanatiion – in any language. Do you mean to communicate that you are measuring the amine consumed from a storage tank inventory? Then please state so, because what you are doing is not a “calculation”. It is a measurement, not a calculation. As I stated above, the usual and normal way of amine control is to weigh the actual amount of amine added to the system as make up to the solution. If you are a good supervisor you will confirm the amount of Amine inventory existing on a weekly basis to ensure that the weighed amounts you are adding conform to the actual existing inventory in stock.

One significant item that was omitted from Zauberberg’s posts was the normal amine loss expected from every amine unit that has ever operated: the amount of amine lost due to degradation. The way that MEA is kept clean and in proper operational use is by judicious employment of a redistillation unit as well as activated carbon adsorbers in the main recirculation line. MEA is normally redistilled to remove the heavier, corrosive amine by-products of the unit.

You further add: “I observed that the volume is decreasing but I think it is manly water”. You – or your staff – should be constantly monitoring the strength of the amine solution. To fail to do this, you are adding to your own demise. An acid removal unit is a Unit Operation that depends on a continuous, steady state operation. If you fail to maintain a specific, constant amine solution strength 100% of the time, you are upsetting the design heat and mass balance and can’t achieve design conditions. This should be fairly obvious and not require excessive ingenuity.

I hope that this experience – combined with that which Zauberberg has capably contributed - answers your basic question on how you can monitor amine losses.

[Zauberberg]

Excellent remark, Art - regarding amine losses due to degradation. I have completely forgotten about this item. Thank you for completing the answer.
I would gladly give you a star for this post but it looks like this function is disabled when it is related to administrators.