21 March 2016

An upgrade to the existing Alidex plant at Tongaat Hulett Starch’s Germiston mill, costing some R130 million, has resulted in an increase of its enzyme glucose output to 300 tonnes from 130 tonnes per day. The expansion was driven by increased customer demand in the spray drying sector.

Stewart Krook, Marketing director at Tongaat Hulett Starch explains the reasoning behind the expansion of the Alidex plant, ‘We identified that we were short of capacity to supply product to our customers on time and in full.

The spray drying market was growing substantially faster than our current GDP. In order to meet the increased demand for final products, our customers had themselves invested to increase their output. With this growth in the local and export markets, which resulted in the need for more glucose, we found ourselves well short of capacity to supply everyone in the market.’

As a result, glucose had to be imported, which had a detrimental effect on all participants in the local value chain. To pursue the glucose market more aggressively, the company implemented two strategies. ‘We decided to increase the capacity on our acid glucose plant and also invested in an additional enzyme glucose production plant. This was the biggest single undertaking by Tongaat Hulett Starch since the commissioning of the Kliprivier Mill,’ Krook states.

The project resulted in additional downstream benefits. ‘We are proud that we are touching the lives of maize farmers as we are procuring more maize. Much needed foreign exchange is now staying in the country and allowing South African producers to pursue export programmes for local products. As additional product is put through the plant, production costs are optimised. Benefits in the downstream value chain, for instance transport and logistics operations, are also impacting on sustaining jobs.’

Extra capacity on enzyme glucose was also driven through standardisation by customers in the spray drying sector. The company invested some R130 million in the upgrade, on the back of a long-term supply agreement. This has additional benefits as Tongaat Hulett Starch’s acid glucose is now being freed up. Tongaat Hulett Starch can now offer all its customers in the spray drying and confectionary sectors the grade of glucose they want, to optimise their product and plant efficiencies. Different spray towers use different products and the ability to meet the entire spectrum of market requirements has been very beneficial to the company.

According to project engineer Shahir Jayram, the team had a firm understanding of the operation, technology, engineering and project management requirements of the project. ‘We are very proud that during the construction phase, the mill continued to seamlessly supply Alidex to customers without any interruption to the Germiston operation.’

Tongaat Hulett Starch engaged the services of an engineering, procurement and construction management service provider to assist with project implementation. This was a fast-tracked initiative and final costing and commissioning were completed within one year. Jayram is particularly proud that not one loss-of-time injury occurred during the construction and commissioning phases of the project.

Processing systems that work

There are two methods to produce glucose syrup: the enzyme/enzyme or acid/enzyme process. Equipment at the mill is in the process of being ramped up to its intended design rate of 300 tonnes per day.

‘We are in the process of optimising specific unit operations to yield improved plant efficiencies. We are not only doing things smarter, but also simpler,’ Jayram states.

During the acid enzyme converting phase, maize is changed from a solid to a liquid state. The first phase takes place in the cooker, where steam is used to provide the heat required for conversion. This takes place in the presence of an acid catalyst. Product then goes through a reactor under the correct pressure and temperature to ensure complete conversion. Thereafter the product reacts with an enzyme to produce maltodextrin. ‘The amount of enzyme (liquefaction) added, determines the level of sweetness required. We produce two grades, a 20 DE and 30 DE syrup. On the full sweetness scale, our product offers a mild and moderate sweetness, which is perfect for use in products such as coffee creamers.’

After liquefaction the product then moves to the filtration plant. Filtration removes fats and proteins to render a clearer product. The standard is that the glucose product must be totally transparent or water white.

‘The filter medium we use is diatomaceous earth. A check filter ensures that no filter medium advances through the process. Ion exchange is the next step where the glucose syrup is demineralised in line with international standards,’ Jayram explains. ‘Carbon treatment is then implemented to remove colour forming bodies and to improve the appearance and shelf life of the glucose. A consumer will not buy a product if there is any colour deviation and the coffee creamer market is particularly unforgiving.’

A two-stage evaporation process concentrates the product to specification. The new evaporator station was designed and built by the Tongaat Hulett Starch’s Technology Group. This group renders process, engineering and project management support to all of the Tongaat Hulett Starch operations.

Quality control remains an important differentiator at Tongaat Hulett Starch. In the factory, the operator does initial process sampling and samples are also sent to the central laboratory. If any deviations are found, the necessary corrective action is immediately taken. In the final product phase, repeat samples are tested in the mixing tank and a final check is run to determine whether pH, sugar profiles and conductivity meet all specifications.

A sophisticated air filtration (ultra violet light) system was installed onto the new Alidex storage tank. Disinfection with UV light kills any microbes to offset contamination in the storage tank. Tongaat Hulett Starch is so impressed with the new system that further roll-outs in other parts of the factory are expected during the year.

All about control

The company uses the Foxboro Intelligent Distributed Control system, which allows the operating team to dial straight into the plant control system. This helps the engineers in trouble-shooting and assists the operator to eradicate and resolve issues. It also enables root causes analysis off-site.

Tongaat Hulett Starch’s Germiston mill is set for further improvement this year. ‘We are planning a replacement of the starch wash battery. This will ensure that the plant is able to increase its throughput and overall efficiency,’ Krook concludes.

Source: Food Review – March 2016