Author: anderthalbAdmin

Sampling Points and Parameters for Low-Pressure Industrial Steam Generators

Brad Buecker and Ken Kuruc

Although thousands of low-pressure steam generators exist at industrial plants around the globe, the chemistry of such units has not received the same attention as that of high-pressure units. The conditions in these steam generators are typically not as harsh as in utility units, yet water/steam chemistry control is still very important for the plants’ steam/condensate systems. This article discusses many of the most important sampling points and parameters for industrial steam generators, and it illustrates the benefits of proper chemistry control to maintaining equipment reliability and availability.

PPCHEM^® 2020, 22(4), 142–150

Modelling of Mechanical Oxygen Removal in a Power Plant Deaerator

Daniel Zinemanas

Oxygen removal is an integral part of the water/steam cycle chemical treatment in power plants and is generally performed in the deaerator. Understanding of this process, particularly during transient conditions, is important to analyze the plant data, and for this goal modelling of this process can be helpful. It is thus the main motivation of this paper to develop a simple workable theoretical model of the mechanical oxygen removal process in a power plant deaerator. Results of the model are compared to power plant operational data and show a very good match between the calculated and the measured data. Thus, the model can be useful in understanding the deaerator’s behavior and performance as well as for design or training.

PPCHEM^® 2020, 22(4), 152–157

A Practical View on the Dissolution of Air in Demineralized Water

Robert Svoboda

The equilibrium of the components of air with water can be calculated by means of Henry’s law and the ionization equilibria. This article gives guidance for such calculations and covers conditions up to 100 °C. At 25 °C and 1013mbar atmospheric pressure, the equilibrium for oxygen in water is 8.4 mg · kg^–1. With 410 ppm CO₂ in air, its mass fraction in water is 694 μg · kg^–1 CO₂, where 595 μg · kg^–1 are present as dissolved gas and 99 μg · kg^–1 are ionized to HCO^3-. The result is a slightly acidic water with pH = 5.65 and 0.89 μS · cm^–1 conductivity. In generator cooling water systems with neutral water treatment, this will cause an increase in copper release. With alkaline water treatment, the contact with untreated air can lead to the deterioration of alkaline conditions.

PPCHEM^® 2020, 22(4), 160–169

Treating Make-up Water and Condensate by Reverse Osmosis in an LP Vinyl Records Pressing Plant

Pavel Hübner

At the Czech company GZ Media a.s., which produces vinyl records, the vinyl presses are heated by steam and after pressing, the steam is rinsed from the press by cooling water. The condensate therefore contains a high proportion of cooling water.

In the original system, the losses of steam and cooling water were replaced by filtrated and softened raw water. The polluted condensate was also treated by filtration and softening. The water used as make-up, which was originally considered drinking water, has been replaced for economic reasons by surface water with high salinity and alkalinity. Due to high operational costs and other considerations the original design was replaced with a new one in 2019.

The new system treats the mixture of raw water and cooled condensate by on-line coagulation followed by reverse osmosis. The hot condensate is cooled by heat exchange, which transfers the heat to the permeate as feedwater. The new system exhibits very low boiler blow-down, minimal consumption of chemicals and low operator attendance.

PPCHEM^® 2020, 22(3), 104–109

Calculations to Manage Phosphate and Caustic Treatment

Randy C. Turner

Phosphate and/or caustic (NaOH) treatment boiler water treatment is often employed to reduce the risk of corrosion.

This paper describes empirical calculations for proper control of phosphate and caustic treatment which could be incorporated into an Excel spreadsheet which includes several calculations, of which the most important are:

1. Boiler water ammonia corrected pH
2. Sodium to phosphate molar ratio
3. Free sodium hydroxide concentration
4. Amount of phosphate and/or caustic to dose for a specific concentration at the current operating pressure

This can also be used to calculate how much caustic must be added to an AVT treated boiler to achieve a desired pH-value.

PPCHEM^® 2020, 22(3), 112–117

The Impact of Low-Load Operation on Power Plant Chemistry

Frank Udo Leidich

Nowadays conventional power plants are more challenged in regard to load flexibility and especially frequent(very) low-load operation. While the so-called “dark doldrums” must be managed without de-stabilizing the grid,a bright sunny and windy day requires almost no conventional power generation. This kind of operation not onlystresses the plant components mechanically and thermally, leading to accelerated aging of the plant, but the physico-chemical operation also becomes more challenging. This paper highlights the most important aspects of theimpact of low-load operation on the chemical operation of a power plant. It is shown that it pays to operate the unitwith water and steam that is as clean as possible.

PPCHEM^® 2020, 22(3), 118–129