Sterling 350-2100 CFM Closed Loop Drying System, What is Desiccant?, Process/Regeneration Cycle

2-5 The Closed Loop Drying System

ACS dryers force hot, dry air through the resin in the drying hopper, where the air picks up moisture from the material and is drawn back to the dryer.

In the dryer, moisture is stripped from the air by a desiccant bed. The dried process air is then re-heated and delivered back into the drying hopper to dry material again.

This system is a "closed loop", because ambient (outside) air is never introduced into the process air. The closed loop system is used by ACS because the process air is typically much drier than ambient air, even after carrying moisture out of the plastic resin. Recycling process air maintains drying efficiency at a consistently high level.

Figure 1: WD/SDA/CDA 350-2100 Dryer Specifications

Model	Amp		Dimensions			Hose	Shipping	Process	Regen	Desiccant
Number	Draw					Connection	Weight	Blower	Blower	Lbs./Bed
			(Inches)			(Inches)
	460-3-60	L		W	H	I.D.	Lbs.	Hp.	Hp.	Large	Small
350		56		56	73	4	1000	5	½	30	76
350-RT		56		56	73	4	1000	5	½	30	76
425		61		52	82	5	1100	7½	½	30	90
425-RT		61		52	82	5	1100	7½	½	30	90
500		63		66	94	5	1200	7½	¾	40	100
500-RT		63		66	94	5	1200	7½	¾	40	100
600		58		56	88	6	1450	10	¾	40	120
600-RT		58		56	88	6	1450	10	¾	40	120
700		59		66	93	6	1600	10	¾	40	135
700-RT		59		66	93	6	1600	10	¾	40	135
850	103	88		84	90	8		3	¾	120	120
850-RT	141	88		84	90	8		3	¾	120	120
1000	113	88		84	90	8		7½	¾	120	130
1000-RT	146	88		84	90	8		7½	¾	120	130
1250	138	88		84	90	8		7½	¾	120	180
1250-RT	194	88		84	90	8		7½	¾	120	180
1500	156	94		100	90	8		7½	¾	120	240
1500-RT	213	94		100	90	8		7½	¾	120	240
1800	179	94		100	90	8		10	¾	120	310
1800-RT	235	94		100	90	8		10	¾	120	310
2100	203	94		100	98	10		15	¾	120	360
2100-RT	278	94		100	98	10		15	¾	120	360

2-6 What is Desiccant?

Desiccant is a material which attracts and holds (absorbs) water from the air. The desiccant ACS dryers use is a synthetic crystalline metal aluminosilicate that is blended with a clay binder and formed into beads.

Absorbed water is driven from saturated desiccant by heating it to a high temperature (reducing the desiccant's capacity to hold water) and forcing air through it. This moisture removal process is called "regeneration".

2-7 The Process/Regeneration Cycle

ACS dryers have two desiccant beds. While one bed is on-line in the process air loop, the other is off-line being regenerated.

350-2100 cfm Dryers Chapter 2: Functional Description 13 of 58