Refineries, a Cement Plant, and a Wine Region: Flue Gas Desulfurization, pH Control, and Lime Softening Around San Francisco Bay
Sulfur off the crackers in the north bay, acidic waste through crush season, and recycled water arriving harder than the supply it replaced. RDP Technologies builds the equipment that prepares lime for each of those.
Bring Us a Duty Browse What We BuildNot the Market People Assume It Is
The Bay Area gets described as a post industrial economy, which is true of the city and misleading about the region. The north bay shoreline carries one of the largest refining clusters on the West Coast, a major cement operation runs in the hills above the peninsula, and the wine country immediately north processes fruit at industrial scale for several months of every year. All three consume lime, and they do it under an air district and a regional water board that are among the most demanding in the country. For utility owned plants around the bay, see instead our San Francisco water and wastewater treatment page.
Flue Gas Desulfurization at North Bay Refineries and the Peninsula Cement Works
Sulfur handling along the Carquinez Strait is a long standing business. The refineries at Richmond, Martinez, Benicia and Rodeo run catalytic cracking, sulfur recovery and tail gas treating, and several have added wet gas scrubbing over the years under some of the tightest refinery specific air rules written anywhere in the United States. The cement plant above Cupertino releases sulfur from fuel and from the rock it calcines, and industrial boilers around the bay contribute the balance. The regional air district here does not resemble a state agency in a lighter touch jurisdiction, and equipment gets specified accordingly.
Two arrangements handle the work. In a wet tower the gas stream meets circulating lime or limestone, and captured sulfur leaves bound into a calcium compound with the blowdown. Injection and semi dry designs run without circulation, dosing dry reagent into the duct before particulate removal. Both are only as consistent as the reagent, and where a continuous monitor is reporting to a district this active, drift is not a private problem.
Reagent preparation is what we manufacture. A charge that is weighed rather than measured out by volume holds the slurry at its design concentration, and since one vessel serves both forms of the material, changing supplier never means changing equipment.
Sorbent and Slurry Preparation
pH Adjustment for Refinery Effluent and Winery Waste Through Crush Season
Two very different industries drive neutralization demand around this bay. Refining produces spent caustic, acidic process water and unit upsets that arrive nowhere near a permitted range, discharged under a regional water board with a long institutional memory about what has gone into these waters before. North of the bridge, winemaking generates a stream that surprises people who have not treated it, strongly acidic, extremely high in organic load, and concentrated into a few intense months around harvest rather than spread across the year.
Lime suits both because a single addition covers more than one parameter. The pH adjustment satisfies the discharge condition while dissolved metals convert to hydroxides and settle for removal, which matters more on the refinery side. On winery effluent the value is different, since the reagent handles a severe acid load cheaply at a facility that has no interest in becoming a chemical plant.
What both need is feed that responds rather than sits at a setting. Dosing follows the plant's chosen measurement, and effluent stays inside its window as the load moves underneath. Several points of application draw from a single circulating loop with individual metering, and slurry kept moving does not lay down the deposit that closes a line over a season.
See the Dosing Loop
Lime Softening Where Industry Runs on Recycled Water and High Pressure Steam
Sierra snowmelt reaches this region remarkably soft, which is why hardness has historically been somebody else's problem here. That is changing for a specific reason. Bay Area industry is now a substantial consumer of municipally supplied recycled water, particularly for cooling, and recycled water carries a considerably higher dissolved mineral load than the potable supply it replaces. A cooling tower that never needed softening on Hetch Hetchy water frequently does once it switches, and the change arrives as a policy decision rather than as a gradual drift.
Refinery steam generation adds the second driver. Cracking and reforming demand steam at pressures where silica carryover stops being an academic concern, and the feedwater train ahead of those boilers has real work to do regardless of how soft the raw supply looks.
Lime softening remains the economical answer at those volumes. Lime raises pH so calcium precipitates in carbonate form and magnesium separates as hydroxide, with soda ash entering wherever the noncarbonate share must also fall, and heat brings silica out alongside it. On Tekkem equipment the two ingredients are weighed out ahead of the reaction, the batch is held until slaking has run its course, and dilution happens last, which is what lets a basin behave the same way through a change of supply.
The Weighing Approach
What Happens to a Reagent System When the Plant Changes What It Processes
This region has done something unusual over the past few years. Two of its refineries stopped processing crude and began processing renewable feedstocks instead, a conversion that changes almost everything about the sulfur balance, the wastewater character and the treatment load on a site. Those are large examples of a question every industrial plant eventually faces, which is what happens to the utility equipment when the thing being made changes.
Reagent systems are more exposed to this than most. Sulfur content in a feedstock drives scrubbing demand directly, and a plant that halves its sulfur load finds its lime system running far below the range it was specified for, where accuracy is usually worst. The opposite case is equally awkward, with a system asked to deliver more than it was built to.
How gracefully a system survives that comes down to turndown. Preparing in batches is an advantage, since the quality of an individual batch does not depend on how busy the day is, and the concentration it gets diluted to can be set anywhere across a broad span. Anyone weighing a conversion should be asking harder questions about the bottom of the operating range than the top.
Papers on the Technology
Where the Economics Flip on Small and Intermittent Lime Applications
Nearly everything written about this equipment assumes a large continuous duty, and that assumption does not fit a good share of the sites in this region. A winery treating effluent for a few months a year, a specialty manufacturer neutralizing a modest stream, or a small industrial site with an occasional batch to correct is working with a completely different set of economics, and it deserves a straight answer rather than a scaled down version of a large plant pitch.
At low and intermittent consumption, hydrated lime usually makes more sense than quicklime. It costs meaningfully more per ton, but it needs no slaking equipment, it handles simply, and at small volumes the price premium never grows into the figure that would justify the capital. The handling advantage also matters more where nobody on site is a water treatment professional.
We would rather tell a small site that plainly than sell it a slaker it will not use hard enough to justify. Where volumes are genuinely large, or where a facility already stores quicklime for another purpose, the calculation flips and the preparation equipment pays. The useful question is never which is better in the abstract, only which is better at the tonnage a given site actually consumes.
Range of Installed SizesSmall Jobs and Large Ones Both Welcome
Tell us the stream, the volume, and how often it runs. If the honest answer is that you do not need our equipment, you will get that answer.
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