International Sugar Journal

Sugar syrup treatment with CCIX – continuous countercurrent ion exchange

Abstract

The paper describes and discusses Puritech’s CCIX – continuous countercurrent ion exchange purification technology for sugar syrups.

Introduction

White sugar, most people prefer clean white sugar for their coffee or tea. Energy and sweet drinks producers use sweet clean glucose, fructose or dextrose to flavour these beverages. The fact is that these sweeteners need to be processed to exacting standards for use under these conditions.

In the production of sugars and sweeteners, several purification steps are required to get impurities removed. The use of ion exchangers is common during the purification process, to remove these impurities or ash from the sugar juice.

Before entering the ion exchanger, clarification decreases the level of suspended solids, organic non-sugar impurities or colour from the sugar syrup.

Fixed bed systems are commonly used in the sugar industry but have a very poor process performance. See figure 1.

Figure 1 – Fixed bed systems

More complex multi-bed or merry-go-around systems have been designed to improve the process performance of the ion exchanger. Incorporation of complex process designs and process flexibility requires additional valves at the top and bottom of each ion exchange column. For each extra process phase, 2 valves are required per column.

This process flexibility is done by creating valve trees at the top and bottom of each ion exchange column. See figure 2

Figure 2 – Fixed bed with valves trees

In a traditional fixed bed, each process step is in sequence and only the resin volume in the exchange zone (MTZ = Mass Transfer Zone) is used. The resin above and below this MTZ doesn’t contribute to the performance of the ion exchanger. The total resin inventory is much larger than needed.

In the mid 80’s, a new carousel type system was developed by AST – Advanced Separation Technologies in the USA which uses a multiport valve at the center of the multiple column ion exchanger. Typically, a 20 or 30 vessel configuration was used. These ion exchange columns had to turn around on a turntable and the multiport valve indexes to keep track with the table.

One multiport valve replaced the complete valve tree configuration at the top and bottom of each ion exchange column (see figure 2) and created a huge process flexibility and process performance advantage.

The first generation of CCIX –technologies (Continuous Countercurrent Ion eXchange) was informed by:

Continuous because all process phases are online and simultaneously active on the ion exchange beds. Adsorption of impurities is mostly done in a parallel ion exchange bed configuration to increase the surface area of the Mass Transfer Zone (= MTZ) as maximum as possible.

The rinse and regeneration columns are in series configuration to extend the MTZ and make use of the water and chemicals as efficient as possible. Smaller ion exchange beds are used to improve the efficiency of flow distribution through the resin.

Countercurrent is an ion exchange term which means that the process flow direction and the resin flow direction are opposite from each other. This countercurrent processflow has been proven to have the highest exchange rate possible with ion exchangers.

In the industry often misused as counterflow, which is change of flow direction over the resin beds from downflow to upflow (backwash) or vice-versa.

This type of continuous countercurrent ion exchangers are now used worldwide by all major sugar- and sweetener producers.

The reason for its success lays in the fact that significant process improvements are realized with CCIX compared to conventional fixed or multiple bed ion exchangers.

Some of the applications where CCIX technology is used in the sugar syrup treatment process are:

Color removal from cane sugar or sugar syrups. Figure 3 shows typical process configuration for color removal in a single adsorption pass.

Figure 3. Single pass Sugar colour removal process

A sweeten-off process zone where the sugar from the ion exchange column is recovered and partially used in the sweeten-on zone. This to avoid dilution of the main sugar syrup product. This sweeten-off zone which usually consist out of 3 columns in series can also be used as the cross regeneration zone. Cross regeneration is used to strip dirt and proteins from the resin beads. This is done on a regular basis to keep the performance of the resin intact.

Deashing of glucose / fructose or dextrose

See typical process configuration with a cation and anion ion exchanger (figure 4).

Figure 4 – Deashing glucose process schematic

The following process improvements are achieved by producers who switched over from fixed bed to continuous countercurrent ion exchange technology:

(1)        50% to 70% less resin inventory

(2)        +/- 30% savings in chemical usage

(3)        50 – 70% less rinse water consumption

(4)        the above mentioned advantages creates a 50 – 70% less waste production

The first generation Ionic Separator – ISEPTM

One of the first CCIX technologies available was the ISEPTM from Advanced Separation Technologies, later purchased by Calgon Carbon. This “Ionic Separator” also called ISEPTM, was patented in 1984 and numerous systems have been installed worldwide (figure 5). This ISEPTM uses a multiport valve which consist out of an upper and lower disk with nozzles. At the upper disk the process connections and process configuration is established. At the bottom disk, which indexes after a specific process time, the ion exchange vessels are connected with flexible hoses. These ion exchange vessels are mounted on a turntable which is continuously turning. This ion exchange resin inventory must be turned around to be able to do the process.

Figure 5 – ISEPTM – Ionic separator

Several new process applications have been developed by the ISEPTM technology such as deashing or demineralization of sugars; chromatographic applications; potassium nitrate and sulphate process schematic, hydrometallurgy applications etc.

The 2nd generation continuous ion exchanger–Septor

In the mid nineties, Septor Technologies in The Netherlands developed their Septor system (figure 6) which has been sold later on towards Outotec and eventually to a Chinese manufacturer. The Septor system also uses a multiport valve and a turntable to move all ion exchange vessels around. The multiport valve was imbedded in the turntable to avoid the use of flexible hoses.

Figure 6 – Septor – Principle schematic

The 3rd generation continuous ion exchanger – ION-IXTM

To overcome the movement of all ion exchange vessels, which in some industrial applications can be 9 meters (27 ft) in height, 8 meters (24 ft) in diameter, weighing more than 200.000 kg ( 441.000 lb), PuriTech developed their patented process valve ION-IXTM in which all ion exchange vessels are standing still (figure 7). Inside the ION-IXTM process valve a process disk indexes from one port to the next to switch the process towards the next process step.

Figure 7 – ION-IXTM Deashing System

PuriTech’s ION-IXTM system overcomes the downfalls of the ISEPTM and Septor systems. All vessels are standing still and the system can be configured in whatever configuration suitable to be installed at the space available from the customer.

Conclusion

CCIX – Continuous countercurrent ion exchange provides huge process advantages over conventional fixed bed or multibed ion exchange systems. PuriTech’s ION-IXTM is the most advanced system available on the market and provides the process benefits of CCIX-technology combined with the mechanical simplicity in one very compact and effective ion exchange system.

The ION-IXTM system has been developed beginning of 2000 and nowadays more than 120 units worldwide have been installed and are operational.

PuriTech – Company profile

PuriTech is an international separation technology company. Our technology is based on its patented continuous countercurrent ion exchanger – ION-IXTM.

Our main office and manufacturing plant is based in Olen – Belgium.

PuriTech started pilot trials in 2001 to develop the ION-IXTM technology and received after years of extensive test work worldwide patents for its multiport process valve.

This innovative process valve design allows PuriTech to dramatically improve the liquid – resin contact efficiency applied in liquid adsorption separation technology. It reduces the plant operating costs and capital expenditure.

Our company can undertake feasibility studies using specially designed pilot plants and we can simulate process designs with our own developed process software.

ION-IXTM systems are applied in a wide variety of ion exchange applications where very low waste or the recovery of high value components is required. Most applications are in water treatment; hydrometallurgy; sugar treatment and recovery of high value elements.