Flake ice maker and flooded Ammonia system

[Nico]

Has anyone experiance with e.g. the F600 Geneglace icemaker or similar on a flooded Ammonia system using natural flow.
Geneglace wants me to put a 5x flow (with a pump) for this equipment, but that reduces the relyability and increases invest cost.

[cricri]

10095

Dear Nico
F600 ABF NH3 (Avec Bouteille Flood) is a standard from Généglace. So it works!
See attached piping diagram.

Regards

[Nico]

Good info Cricri, thanks.
Will offer this to y client than.

The system will look like this:
Three F600 but I will connect them to one separator.
Supply will be by gravity circulation and oil removal by a small (hot) gas powered pulse pump.
Will use an open screw compressor with open flash economizer.
In the economizer vessel I'll have a coil for cooling the supply water for the ice machines.
The pressure will be kept at 1C evaporating temperature. The advantage is that even in cold weather I still have a good mass flow on my economizer for pre-cooling the water.
Capacity control by varation of the crushing knife rotation speed based on evaporating temperature.
The latter is not a standard for these machines, but it is very effective to keep the same minimum flake thickness all the time and also very energy friendly because the thicker ice layer would resist heat transfer. The evaporating temperature will fluctuate from -18.5C in hottest summertime to -23 at minimum alowed condensing temperature.
For Dutch climate and air colled condenser (dT10K) I have an avarage COP of 4.24 (hour based calculation for 20 years).
To my opinion nice numbers. It is the limitation of the condensing pressure (by compressor manufacturer not alowed under 20C) that prevents better preformance.

[Magoo]

Closed flash econo., would give more stable conditions. Discuss your design with Geneglace before leaping into anything. Cricri is very knowledgable with this equipment

[Nico]

I don't get why open flash would be less stable, could you explain that Magoo?
The Economizer will be a shell and plate type vessel whereas not the refrigerant but the water goes through the plates as a basic load for the eco port. On top of that there is the flashing of the refrigerant from the condenser inside the shell.
To prevent freezing of the water there is a limitation for minimum pressure (pressure actuated valve) which also guarantees minimum pressure difference between eco and separator vessel. Expansion from condensor by float valve, expansion from eco to separator by float valve.

[cricri]

Hi Nico,
you are going into a hard chalenge,
- a F600 with gravity feed it's OK with the design of Généglace. trying this with one LP vessel supplying 3 F600 could be difficult. Généglace won't share their knowledge about gravity feed.
- at lower water temperatures than 10°C, depending of the ambiant temperature, flake ice can stay in the water tank and block the float valve.
- with a LP vessel feeded by a float valve there is a strong probability to drop the éco pressure lower than 0°C when the plant stop and then to freeze your PHE
- to remove oil from an icemaker operated with ammonia, you need to warm it. the oil stays like large spots stuck on the wall of the cylinder. during this time there is no ice produced.
- be carefull, if you are out of the Généglace spec, you are alone!

a few weeks ago we started 2 F900/ NH3 feeded by pump. 2 screw compressors with VLT and without eco.
it works fine as usual.

[Nico]

Thanks again Cricri.
Better safe than sorry; I'll keep that pump in the budget to be installed in the system.

The design and instructions from Geneglace haven't changed the last fifteen+ years as far as I know.
Very odd as the quality of the oil and the oil separators made a giant progress in that time.
My oil return from a <-35C freezer used to be troublesome but not anymore.
Oil carry over <10ppm from the oil separator used to be exclusively by the Grenco Oil Washer, now every 3-stage oil separator does that.
First I will see what the machine does without that pump running. If I can't succeed than I still have the option to switch on that pump.
At least that way I can get some knowledge that Geneglace seems not willing to share.

Good point about freezing the plate heat exchanger during stand-still when the gas equalization through the HP float valve continues.
Thanks, I missed that:confused:.
Fortunately at the same cost I can change that for a level transmitter and expansion valve so that won't be a problem:).

Did you use variable crusher speed before Cricri?
I haven't but I am planning to use that as part of the capacity control strategy. That strategy is in short: let the compressor always run 100% capacity and vary the load.

During summer / winter, day and night capacity of the compressor changes and thus the evaporating temperature and thus the ice thickness and the ice maker capacity. When I speed up the crusher at lower evaporating temperature and visa-versa than I can keep the ice thickness to a minimum e.g. 2mm and the ice maker capacity to a maximum. This way I will always have the same flake structure and I will be able to do without capacity control on the compressor and still keep good COP.
For example:
Using a Hall 3218 with ECO and three F600 ice makers I'll have 20C condensing temperature as lower limit and than the balance condition will be To -23C when ice crusher speed of 115.4rpm The compressor will do Qo 59.8kW with a COP of 4.63.
In hottest summer I'll expect a maximum condensing temperature of 46C. The new equilibrium will be To -19.1C at ice crusher speed of 90rpm and Qo 48.5kW and COP 2.12.

We considered to offer optional connection to the wheather forecast so that we can make use of the coldest hours of the day, but with a gain of <4.5hours maximum that won't pay off. Instead to avoid the hottest hours we will start the production cycle at 14:00h in the summer (expecting to finish between 12:00h and 14:00h) and shifting gradually to 16:00h afternoon in winter (expecting to finish at 11:30h). The cycle will stop when the silo is full. This way the system is self corrective and still makes some more use of the coldest hours.
Shame that most compressors won't take lower condensing temperatures as that makes a big difference here in the North.

Geneglace are not exclusive ice makers (Buus has a good NH3 alternative) and a arrogant, protective and conservative attitude won't help them in the end. Not happy about that for their machines are sound design!

We'll meet our client tomorrow, I'll keep you informed.

[Nico]

Made an error abouit the Hall compressor capacity her above: that should be 3 times the given value.
I quoted the capacity per ice maker.
Nico.

[cricri]

Hi Nico,

I've never tryed to vary the speed of the crusher. why not?
be carefull that you will loose some torque at motor start and some power at low speed. beter to start at 50Hz.
don't misunderstand what I said about Geneglace. I said that the design of the flooded system is especialy designed to provide a good flow rate in the générator. With a conventional surge drum you cannot garantie such a rate. about this topic you couldn't get any help.
for any other subject, no problem!
I had some very bad experiences whith other manufacturers, in my opinion Geneglace provide strong and simple generators.
cricri