Modular maize mills

by Bryan McGee
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Maize, although originally introduced from the Americas by early Portuguese settlers, has become a staple food for a large proportion of the indigenous sub-Saharan African population. The white varieties are preferred for most of the traditional food types, while yellow varieties are favored for some specialist requirements and for animal feed.

South Africa is the region’s top maize producer and generally grows a surplus to domestic requirements. In the last crop year, 1.73 million hectares were planted with white maize, yielding 4.31 tonnes per hectare, while 1.06 million hectares of yellow maize were planted, yielding 4.92 tonnes per hectare, some of which were transgenic.

The climate favors harder varieties which process particularly successfully on the new processing systems. The immense social changes that have resulted from the economic developments in this region have created a demand, even in the rural areas, for improved and more refined food quality, which impacts the milling processes for both wheat and maize.

RAPID INSTALLATION

In the last few years, the South African milling industry, in response to its deregulation and the development of new equipment both overseas and locally, has been in the forefront of exploiting new technologies for the degerming, milling and onward processing of maize for human consumption. The objective has been to raise the quality and optimize the economics of production of these foods.

In the past, large-capacity plants in traditional-type building structures have proved cost-effective for the supply of these maize products to their mainly urban markets. However, it was recognized that the high capital cost and longer time periods for implementation of this type of plant do not suit all applications and that a more flexible concept, which could be more rapidly installed and commissioned, would bring great benefits to smaller-scale operators and their customers.

A local engineering company, Techmach Technology of Krugersdorp, South Africa, in collaboration with its associate, Satake in the United Kingdom (U.K.), have pioneered a new modular maize mill, called 4M, of 6-tph capacity for the sub-Saharan market. This ground-breaking concept was developed in response to the opening up of opportunities for independent entrepreneurial as well as the larger, well-established companies.

The design comprises modules which are units of function as well as of construction, and which can be combined for the flexible production of high-quality maize products comparable with those from the best industrial milling systems. For a new plant, conventional mill buildings can represent a large proportion of the overall investment and are inevitably slow to construct. In contrast, a modular plant is self-supporting and requires only a simple slab for mounting, basic services and, in view of the moderate climate of the region, a light shed-like structure to provide protection for the equipment. The four functional modules for cleaning, deeming, polishing and milling can be supplied as a full set for a new plant or individually for upgrading an existing system.

The 4M system is built up from major modules in which machines and associated equipment are preassembled within their welded and bolted steel framework in the Techmach workshop and are ready for delivery to the customer in 3-foot by 40-foot containers.

PREASSEMBLED MODULES

After receipt on site, the modules are lifted into position and quickly bolted together to form a rigid assembly. The preassembly is completed to a remarkable degree, as it includes not only many principal machines but also pneumatic conveying cyclones and airlock assemblies, mechanical handling equipment, ducting, cable trays, piping and electrical systems comprising PLC control through touch screen, MCC panels, and all electrical hardware.

The only major items of machinery which require individual handling are the three roller mills and the plansifter. The roller mills are simply moved into their final position on the base slab on which the modules are mounted, and the sifter is suspended from its predetermined supports.

Deon Cronje, the director responsible for this product, said the benefits of this modular approach are many and include very easy and rapid site installation so that it is not unusual to commence production within six to eight weeks from delivery of the plant to site. He also reiterated how, in addition to these low and predictable installation costs, the building costs are exceptionally low since all that is required is a concrete base to support the free-standing modules and a simple enclosure, such as a warehouse structure, for weather protection.

In the event that market conditions change in the future, the modules can be readily separated and reassembled at an alternative location. Services required from the customer are limited to supplies of electrical power, compressed air and water.

Of course, external facilities for receipt and storage of the raw maize and for packing and distribution of products will differ as has been demonstrated at the various sites in southern, central and western Africa, where 4M mills have been installed and are operating.

The core technology of the 4M modular mill is centered on a maize degerming system comprised of a preconditioner followed by a vertical degermer and polisher.

This degerming system was originally conceived and pioneered with the help of Allem Brothers at Viljoenskroon in the Free State Province and the support of engineers from Satake headquarters in Hiroshima, Japan and its division in the U.K. There are nearly 100 such units in operation in southern Africa.

The effectiveness of this process in decorticating and degerming maize enables the subsequent milling system to be simple in terms of equipment and process flow and is therefore easy to operate and control. In the case of a 6-tonne-per-hour mill, only one four section-sifter and three roller mills are required.

A modular wheat flour mill of similar concept has been developed to provide equivalent benefits for customers wishing to make a rapid strategic investment in flour milling without compromising quality or yield.

Bryan McGee can be contacted at bryan@bcmcgee.co.uk. Deon Cronje of Techmach Technology can be contacted at deon@techmach.co.za.

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