“Boiler Feed and Cooling Water Treatment issues were discussed in” Hot Topic Hour on Thursday, December 6, 2012
With a number of new combined cycle power plants under construction, and regulatory pressure to recycle cooling water and to use treated municipal wastewater, there is a great deal of interest in technologies to purify the water used to make steam and to clean the recirculated cooling water to maximize the number of cycles and minimize maintenance problems. Five speakers in the Hot Topic Hour (actually 2.5 hours) yesterday provided lots of valuable information.
Brad Buecker, Process Specialist with Kiewit Power Engineers, provided an overview of the most common and modern makeup water production methods, including reverse osmosis, portable mixed-bed polishing and electrodeionization (EDI). He also reviewed some wastewater treatment technologies. He identified High Efficiency Reverse Osmosis (HERO) as an emerging technology licensed by Aquatech and GE. Veolia also offers OPUS®.
Tom Muilenberg, Senior Manager for Industrial Sales at MIOX Corporation, discussed a novel approach using on-site generated chlorine-based biocide that uses only salt, water and electricity to provide the control. With increasing use of treated municipal wastewater for cooling it is important to use a powerful biocide. Another consideration is the potential transmission of bacteria which is aerosolized from the cooling tower heat transfer. A number of power plants have found cost savings by using on-site generation.
Stephen Dominick, Regional Sales Manager for Ovivo Water USA, provided a good overview of the water decisions relative to various power plants. He pointed out that nuclear powerplants use 500 to 1100 gallons per MWh, whereas coal-fired power plants use about half as much and combined cycle gas turbines use less than 230 gallons/MWh. He addressed a number of treatment technologies including the membrane bioreactor. There is lots of experience now with the Kubota flat plate membrane technology. Because electrodeionization does not use chemicals, it is attractive.
Bernhard Doll, Dipl.-Ing., Vice President of Marketing for Industrial Water at Pall GmbH, discussed the “Significant Cost Savings Obtained Using Advanced Membrane Systems for Cooling Tower Water Treatment.” Power plants around the world are striving to upgrade conventional water treatment systems. One way they are achieving this is by employing reliable membrane technologies such as microfiltration. Pall has worked with power plants to increase the amount of water being purified and minimizing the reject. At Indiantown, where there is a zero liquid discharge system, Pall replaced the brine concentrators with an MF and RO system. This reduced energy costs and increased water recovery. The salts are injected into a spray drier and solid power is the end product. McIlvaine posed the question to Bernhard as to whether the membrane reject could be injected back into the hot gas system. It could be injected before the air pre-heater to reduce SO3 or ahead of the scrubber to reduce the quench water requirement. In an upcoming Alert we will pursue this further.
Bob Bartholomew, Associate at Sheppard T. Powell Associates, LLC, discussed the causes and present methods of controlling sources of dissolved oxygen in condensate systems and in feedwater systems for heat recovery steam generator (HRSG) units. Low dissolved oxygen concentration limits in condensate and in many feedwater systems for HRSGs or conventional boilers can be difficult to maintain. He explained how this can be accomplished. One simple suggestion is to observe any leaking water during shut downs. As this is where the air would enter during operation. In answers to audience questions, Bob agreed that many power plants are not addressing this problem to the extent which they should.
BIOS, ABSTRACTS AND PHOTOS can be seen at:
BIOS, ABSTRACTS, PHOTOS - DECEMBER 6, 2012.htm
The individual presentations are as follows: