Boiler Feedwater

What a Tanzanian Sugar Mill Learned from Monitoring Steam Properties

By David G. Daniels

BOILERS CONDENSATE CONDUCTIVITY COOLING WATER FOOD AND BEVERAGE INDUSTRIAL WATER ION EXCHANGE MONITORING REGENERATION REVERSE OSMOSIS SILICA STEAM TURBINE SUGAR MILL

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Abstract

A sugar mill in Tanzania installed a new bagasse-fueled boiler that operated at 45-bar to supply super-heated steam to a small single shaft turbine/generator set. Adding a steam turbine for power generation required that the sugar mill monitor steam purity for the first time. Additional instrumentation and training were required for mill chemistry personnel. This article will discuss the approach that was taken to adapt steam chemistry monitoring at this site and the improvements that the mill saw.

The sugar mill near Moshi, Tanzania, has been in existence for more than 50 years. The mill is one of Tanzania's largest sugar estates with more than 16,000 hectares of land, over half of which is in sugarcane cultivation. Over the years, the mill owner (TCP) has made significant investments in the rehabilitation and upgrading of fields, infrastructure, and equipment.

In 2006, TPC added a 45-bar bagasse-fired boiler to their site. The boiler produces superheated steam at 485ºC for a nominal 20 megawatts (MW) turbine/generator set.

Prior to this time, the mill had relied on six 12-bar boilers to provide steam to four small turbines to drive the mill equipment, steam to multi-effect evaporators to concentrate the cane juice, and a small 3-MW turbine/generator to cover the factory needs during operation. The mill was relying on the grid for everything else, especially for irrigation pumps, which required for 3 MW at the time (now 5 MW).

The existing electrical grid at the time was unreliable. The new turbine generator allowed the mill to generate all of its own power (including for irrigation) and provided additional power to the grid, which increased the stability and reliability of electricity in the area. Included the in this expansion was a demineralizer system. Previously, the mill had relied on evaporators to produce high-purity water for the boilers.

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