In transfer block the mass fractions should go to the second stream as long as you can designate the name of the receiving stream.

There are other ways to do it. A pseudo stream can carry properties with virtually no flow into a multiplier box to set the flow in a physical output stream.

A Fortran or Excel subroutine can be written to transfer the compositions.

Dear Mr. Jerry Decker.

Thanks for your reply.

From the Aspen Plus Manual it follows that Mass Fraction variable can be accessed only as results and cannot be changed or set. So, it can be obtained from the stream, but can't be set to the stream.

As I understand, the stream composition can be recalculated through the mass flow rate of the stream and the mass flow rates of the stream components. Do you mean a Calculator Block when you said about Fortran or Excel subroutine ? Or maybe you could advice better way how to do it.

Thanks.

I don't know about Aspen Plus but in Hysis there are many easy ways to create a copy of a stream. ctrl C ctrl V is a simple way or a divider with a negative stream or a spreadsheet "define" a stream "from" any other stream and any copy of a stream will have the same composition on any basis (mole, vol, wt  ...).  I expect Aspen Plus also has similar functionality to easily copy streams.

Dear Mr. Rick Manner

You are right. Aspen Plus has the similar instruments. But I no need to copy all parameters of the stream, only mass fractions. Unfortunately, as I said before, the mass fraction can't be set to the stream (it is possible to set it manually, but not to copy to the stream). In my simulation two streams have same mass fractions, but other parameters (pressures, temperatures, flow rates) are different.

Dear Olekskil:

,  Once you copy the entire stream you can delete, change or ignore any (at least some)  of the properties you don't like..

Probably the easiest approach would be to just transfer mole fractions to mole fractions.  If you have transferred all the mole fractions you would also have transferred the mass fractions.  Otherwise, you should be able to use a calculator block, but transferring mole fractions is easier.

Dear Mr. Lloyd Chauncey Brown.

Could you explain the way how to transfer the mole fractions properly? Thanks.

I was wrong.  You can't transfer either mole fraction or mas fraction using a transfer block.  You can use a calculation block.  I have attached the BKP file for a simple flowsheet in which I transfer mass fractions from one stream to another.  I first define input variables for each mass flow for each component of the input stream and output for each component of the output stream.  I also define an input variable for the total mass flow of the output stream.  I could have included a variable for the total mass flow of the input stream but instead I calculated the mass flow of the input stream from the component flows in the Fortran section of the block.  I did this in case I wanted to leave out minor components.  I then calculated the mass flow of each component of the output stream equating it to the product of the mass flow of the component in the input stream and the ratio of the mass flow of the output stream to the mass flow of the input stream.  The net result is a stream with the mass fractions of the input stream and the mass flow initially in the output stream.

Dear Mr. Lloyd Chauncey Brown

Thanks for your help. Your way is convenient for my modelling.

Thanks all for help!