Around Bismarck and Mandan, Flue Gas Desulfurization Is the Main Event, With Lime Softening and pH Adjustment Close Behind
The lignite units northwest of here, the refinery across the river, and the produced water coming east out of the Bakken all depend on carefully prepared lime. That preparation equipment is what RDP Technologies has built for more than forty years.
Reach Us Directly The Equipment We BuildA Small Metro Sitting Next to a Very Large Amount of Coal
Bismarck is not a big city, but the industrial capacity within an hour of it is out of all proportion to its size. Several of the largest lignite fired generating stations in the United States sit along the Missouri to the northwest, a commercial coal gasification plant operates among them, and a refinery runs directly across the river at Mandan. That combination makes central North Dakota a heavier consumer of this reagent than metros ten times its population. Our Tekkem lime feed systems are the equipment behind that consumption.
Flue Gas Desulfurization Across the North Dakota Lignite Fleet
Lignite is a demanding fuel and the stations burning it here are among the largest of their kind anywhere. The generating complex spread across Mercer, Oliver and McLean counties, at Underwood, Beulah, Stanton and Center, was built directly on the coal seam and has operated sulfur control equipment for decades. The gasification plant at Beulah adds a category of its own, since converting lignite to synthetic gas requires removing sulfur compounds from the raw product stream as a process requirement rather than only as an emissions one. All of it answers to the state environmental quality department under EPA Region 8.
Control equipment divides the usual way. A wet absorber keeps lime or limestone moving past the gas stream, and captured sulfur exits as a calcium compound in the blowdown. Injection and semi dry arrangements use no circulation, delivering dry reagent into the duct ahead of particulate removal. Lignite makes both harder than they would be on another fuel, because its ash and sulfur chemistry vary more from seam to seam than a specification sheet suggests.
That variability is the argument for preparing reagent by weight. A charge measured on load cells arrives at the design concentration whether or not the fuel behaved this week, and one vessel handles quicklime and hydrated lime alike, so a plant experimenting with a different reagent is not rebuilding a feed house to do it.
Feed Systems for Absorbers
pH Adjustment for Refinery Effluent, Scrubber Blowdown, and Bakken Produced Water
Three quite different streams create neutralization demand in this part of the state. The refinery at Mandan produces spent caustic and process water outside any permitted range. The generating stations produce scrubber blowdown, a stream that is a direct consequence of the sulfur removal happening upstream and one that carries dissolved metals and high dissolved solids with it. Further west, the Bakken generates produced water in volumes that have made treatment for reuse a serious business rather than an afterthought, and that brine is among the most concentrated encountered anywhere in North American oil production.
Lime does several jobs in those settings at once. The pH adjustment returns a stream to its permitted band, dissolved metals turn into hydroxides and settle, and on produced water the calcium chemistry works against scale forming constituents that would otherwise foul everything downstream. One reagent, several outcomes, which is why it persists where simpler alternatives exist on paper.
The operational difficulty is that none of these streams behaves predictably. A refinery has upsets, scrubber blowdown tracks whatever the boiler is doing, and produced water arrives as trucks and pipelines deliver it. Feed driven by live measurement instead of a static setpoint is what keeps a result steady under that, with each dosing location drawing independently from a circulating loop that never stops moving.
Dose Control in Practice
Lime Softening on Missouri River and High Sulfate Groundwater Supply
Water in this state is hard by any standard. The Missouri carries a substantial mineral load past Bismarck, and the groundwater across much of North Dakota is harder still, frequently with sulfate concentrations that create problems of their own well before hardness becomes the limiting issue. Industry here draws on both. Generating stations take enormous volumes from the river for cooling, the refinery runs cooling and steam, and the ethanol plants scattered through the region need soft water for fermentation and boilers alike.
Lime softening handles that mineral load at the volumes involved. The reagent lifts pH, calcium precipitates out in carbonate form while magnesium leaves as a hydroxide, and soda ash gets introduced wherever the noncarbonate share needs cutting too. Run at temperature the reaction captures silica as well, and that is the reason hot process equipment stays in service ahead of higher pressure steam generation.
Everything specified downstream rests on the softener doing the same thing every day. Tekkem equipment weighs the lime and the water on separate cells at the outset, keeps the batch running until the reaction has genuinely finished, and establishes working strength only at the end. Winter here also moves intake temperature further than almost anywhere in the country, and a system that corrects for that by measurement rather than assumption is the one still producing the right slurry in January.
Batch Preparation Detail
Why Carbon Capture Raises the Bar on Upstream Sulfur Removal
North Dakota has been working on carbon capture longer and more seriously than most places, with a commercial capture operation already running at the gasification plant and further projects proposed at the generating stations. That matters to anyone responsible for a scrubber, because capture changes what the equipment upstream of it has to deliver.
The reason is chemical. Amine based capture solvents react with sulfur dioxide, and the products of that reaction are heat stable salts that do not regenerate. Every molecule of sulfur reaching the absorber permanently consumes solvent, and solvent is expensive. A gas stream that satisfied an emissions limit comfortably can still carry far more sulfur than a capture system can tolerate economically, which means desulfurization has to go deeper than the permit alone would require.
Deeper removal means more reagent and tighter control over it, and it makes reagent consistency a solvent cost question rather than only a compliance question. Anyone evaluating capture at an existing station should be looking hard at the sulfur polishing stage and at whether the feed equipment serving it can hold the concentration that the deeper duty demands.
Engineering References
Equipment That Has to Work Where Help Is Hours Away
A plant in Mercer County is a long way from a specialty contractor. The nearest vendor technician may be in another state, the parts counter that stocks an unusual component is not nearby, and a January breakdown is a different kind of problem when the site is forty miles from the nearest town of any size. Equipment that assumes a service call is a short drive away was designed for somewhere else.
Simplicity is worth more here than anywhere. The reaction vessel contains a single moving component, with bearings and seals located entirely outside it, clear of the abrasive conditions that shorten equipment life, which means fewer occasions on which anybody has to come at all. Roughly 65 plants have reported lower maintenance labor and spend after converting, and that figure means more at a remote site than at one with a machine shop across the yard.
Support has to work at a distance too. Controls that can be examined remotely, documentation thorough enough that a local millwright can act on it, and parts availability from a manufacturer that has supported this equipment for over four decades are what make a remote installation practical rather than a standing risk. We would rather solve a problem over the phone than schedule a flight, and the equipment is designed with that in mind.
Where the Systems AreDistance Is Not a Problem We Are New To
Tell us the duty, the fuel or the stream, and where the site sits. We have equipment running in places considerably harder to reach than this.
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