Focus on Motors,Drives & Gear Units: Drives up to challenge of chemical plant

At a Kemira Chemicals plant, the movement of raw materials for fertilizers relies on both gearmotors and frequency converters. Both have been selected for reliability and flexibility, a requirement for the continuous movement of widely different materials.

Those are the operating conditions facing Kemira Danmark A/S, a manufacturer of fertilizers and industrial acids, situated in Fredericia, Denmark, and part of the global Kemira Group. The company also has operations in Canada: Kemira Chemicals Canada in Maitland, Ont., and Kemira Paper Chemicals Canada in Dorion, Que.

The movement of tons of different materials is part of everyday life in an industry with rapidly changing customer needs. Sren Larsen, electronics engineer, explains:

“One day a recipe requires materials conveyed at 10 kg (22 lb) per hour, the day after the requirement is one metric ton (2,204 lb) per hour — on the same belt, with continuous flow”.

Such processes place tough demands on motor controls, which must be able to change motor speeds over a constantly expanding capacity range. At Kemira, these requirements are mainly met by equipping approximately 100 motors in the plant -many of them Bauer gearmotors — with VLT frequency converters from Danfoss.

“Our experience with the VLT frequency converters goes way back to the early 1970s, and the first devices are still running. Actually, I have only replaced one converter in my 15 years at Kemira,” Larsen states.

Bo Andersen, a mechanical engineer at one of the firm’s plants, particularly appreciates the ability of the converters to maintain stable and exact motor speed, even in the critical low-speed range. Other brands have been tested, especially for smaller drive units, but they have been isolated examples.

“This is also due to the fact that our technicians generally find VLT frequency converters easy to program and start working with. They also appreciate the manuals being in their mother tongue, and daily operation so simple that operators can easily adjust a frequency by themselves,” Andersen says.

Punctual and reliable delivery, and easy access to service and backup add to the satisfaction with Danfoss converters at Kemira. To illustrate the point, a recent incident took the electronics engineer by surprise when he saw the amount of torque produced by a VLT converter.

“We had a material — damp, cornflour-like and with a tendency to lump — that was extremely difficult to transport with a screw conveyor. To help us out, Danfoss invited us to visit its laboratory. The results of a simulation there gave food for thought,” Larsen says. Together with his staff he is presently converting the new knowledge gained into a viable solution to the problem.

Bauer gearmotors have also acquired a good reputation at Kemira. Situated in various critical applications like slat elevators and sluices throughout the plant, many of the motors have been running almost non-stop for about 20 years. And as Andersen notes after a quick glance at his computer screen (where all fault messages from the plant are statistically collected), 1999 and 2000 have shown no faults or breakdowns on those motors.

“As a matter of fact, there is nothing much to say about them. We just never hear of them. They are durable and robust — and just keep on running,” Andersen points out.

Kemira Danmark A/S has a total yearly output of about 1,250,000 tons, produced by some 400 employees. The main product is NPK, a widely used agricultural fertilizer containing nitrogen, phosphate and potash. It is produced in the following steps:

Solid, liquid and gaseous raw materials are mixed in a range of reactor tanks.

The solution is sprayed into a revolving granulation and drying kiln where it is distributed as a thin liquid layer on the granules.

Water is evaporated from the surface of the granules by means of hot-air blowers.

The dried granules are screened in order to obtain a granule size of 2-4 millimetres.

The finished product is cooled and finally treated with an anti-caking agent before being stored.

Kemira has two NPK plants at its disposal, and the yearly output totals some 750,000 tons. Many of the processes involved in the fertilizer production feature Danfoss VLT frequency converters and Bauer gearmotors.

Kemira is a global chemical industry group with headquarters in Finland and production facilities in 39 countries. The group employs 10,700 people around the world. Kemira’s core business includes water treatment chemicals, pulp and paper chemicals, decorative paints and industrial coatings.

Other important business areas for the company are specialized plant nutrients and industrial chemicals. The products are used in, for example, drinking water production, wastewater treatment as well as in the manufacture of food products, paints and paper.

Besides high-quality chemical products, Kemira also offers its customers application expertise, support services and the opportunity to take part in joint development.

Danfoss Canada’s motion controls division incorporates elements of motion control from Bauer geared motors and industrial drives to manage those motors. It has facilities in Mississauga, Calgary and Vancouver. (Bauer was acquired by Danfoss in 1999 and became the gearmotors division of the company.) The company’s industrial controls division builds UL/CSA approved motor control gear and panels at its Mississauga facility. It also offers a wide range of industrial control components such as control valves and pressure/temperature transmitters through facilities in Mississauga and Calgary.

Asbjrn Jonassen, a sales engineer for transmission technology with Danfoss, is based in Nordborg, Denmark. He can be reached by e-mail at asj@danfoss.com. Product data is available on the Internet at www.danfoss.ca. Information about Kemira can be found at www.kemira.com.