Scrubber slurry

Variables affecting this process have recently been reviewed [44]. With either reagent, however, a throwaway product is obtained. Land has to be allocated for lagoon disposal of the spent scrubber slurries, or other systems have to be set up to handle the waste solid. Recent variations of this approach are to employ a zeolite prepared from fly ash [45] or the alkalinity of fly ash itself in water slurry as means to capture sulfur dioxide. 

The current model is a step closer toward a reliable working description of the sulfite oxidation rate in scrubber slurries. By incorporating a boundary layer description of the film around each particle, this model predicts the conditions at the particle surface which drive the mass transfer. The interfacial area for mass transfer was discovered to be more closely represented by a sphere than by a plate-like shape. From the model, using highly catalyzed experiments, a mass transfer coefficient of 0.015 cm sec-1 was found - quite close to literature correlation predictions. 

The model developed in this paper is part of the growing body of knowledge describing the conditions in scrubber slurries. Even as an interim step, the current work has produced useful results. At the outset, the choice of a spherical... 

The scrubber slurry pH does not significantly effect adipic acid coprecipitation (at least over the pH range tests). 

HOOC(CH2)4COOH, that buffers the pH in the scrubber slurry. In theory, any acid which is intermediate in strength between carbonic acid and sulfurous acid, and whose calcium salt is reasonably soluble, may be employed. However, adipic acid was selected because it is one of the most cost-effective organic acid buffers on a molar basis and is commercially abundant. Its main use is as a raw material in the manufacturing of nylon. 

Easier forced oxidation in the scrubber slurry loop or bleed stream, and a smaller air (and compressor energy) requirement... 

Forced oxidation is achieved by air sparging of the slurry in an oxidation tank, either on the bleed stream to the solids dewatering system or on the recirculated slurry within the scrubber slurry loop. For a one-scrubber-loop forced oxidation system, the slurry effluent from all scrubbers in the system (e.g., the venturi scrubber and spray tower at Shawnee constitute a two-scrubber system, and the spray tower alone or TCA, a one-scrubber system) are sent to a single effluent hold tank, which is the oxidation tank. For a two-loop forced oxidation system, there are two scrubbers in series (e.g., venturi and spray tower at Shawnee) with effluent from each scrubber going to a separate tank the effluent hold tank for the upstream scrubber (with respect to gas flow) is the oxidation tank. For either one-loop or two-loop forced oxidation systems, the oxidation tank may be followed by a second tank, in series, to provide further limestone dissolution and gypsum desupersaturation time prior to recycle to the scrubber. 

After autoclaves the slurry is flashed in flash tanks. Vent gases from autoclaves and flash tanks are fed to a scrubber. Slurry from the flash tanks flows to a screw thickener. Nickel powder containing slurry from the screw thickener is fed to a nickel powder filter. After the filter the nickel powder is dried, cooled, briquetted and packed for the customer. 

Flue Gas — 150 66 - 8 B U wet flue gas (spool 5950) after H 0 spray, scrubber slurry (CaSOj) mainly, also Ca(OH) or CaC03 plus CaS0 pH 3-12 during upsets... 

Scrubbini Liquors Sulfur Dioxide - ISO 66 — 6 - - wet flue gas after HyO spray, scrubber slurry (CaSOy mainly. alsoCa 0H)y or CaCOy plus CaSO.. 3-12) during upsets. 

Saarberg-HoUer (S-H-V) Process. The S-H-U process is a limestone wet scrubbing process with formic acid enhancement The S-H-U absorber has both cocunent and counter-current sections. The flue gas enters the absorber at the top of the cocurrent flow section and flows downward past several levels of spray nozzles where the pH drops rapidly. The scrubber slurry collects in the sump. The flue gas then turns upward into the second scrubbing stage, the countercurrent flow section, where the final increment of SO2 removal occurs. The flue gas exits either through a combination of a vertical flow and a horizontal flow mist eliminator or vertical flow mist eliminators. 

Current designs for venturi scrubbers generally use the vertical downflow of gas through the venturi contactor and incorporate three features (I) a wet-approach or flooded-waU entry sec tion, to avoid dust buildup at a wet-dry pmction (2) an adjustable throat for the venturi (or orifice), to provide for adjustment of the pressure drop and (3) a flooded elbow located below the venturi and ahead of the entrainment separator, to reduce wear by abrasive particles. The venturi throat is sometimes fitted with a refractoiy fining to resist abrasion by dust particles. The entrainment separator is commonly, but not invariably, of the cyclone type. An example of the standard form of venturi scrubber is shown in Fig. 17-48. The wet-approach entiy section has made practical the recirculation of slurries. Various forms of adjustable throats, which may be under manual or automatic control. 

In Venturi scrubbers the gas is the motive fluid. This equipment is of simple design and is able to handle slurries and large volumes of gas, but the gas pressure drop may be high. When the reaction is slow, further holdup in a spray chamber is necessary. 

For PM applications, wet scrubbers generate waste in the form of a slurry or wet sludge. This creates the need for both wastewater treatment and solid waste disposal. Initially, the slurry is treated to separate the solid waste from the water. The treated water can then be reused or discharged. Once the water is removed, the remaining waste will be in the form of a solid or sludge. 

Semidry Scrubbers The advantage of semidry scrubbers is in that they remove contaminants by way of a solid waste that is easier to dispose of (less expensive). Initially, the scrubbing medium is wet (such as a lime or soda ash slurry). Then a spray dryer is used to atomize the slurry into the gas which evaporates the water in the droplets. As this takes place, the acid in the gas neutralizes the alkali material and forms a fine white solid. Most of the white solids are removed at the bottom of the scrubber while some are carried into the gas stream and have to be removed by a filter or electrostatic precipitator (discussed later). Although semidry systems cost 5-15% more than wet systems, when combined with a fabric filter, they can achieve 90-95% efficiencies. Dry scrubbers are sometimes used in a very similar fashion, but without the help of gas-liquid-solid mass transfer, these systems use much higher amounts of the solid alkali materials. 

In wet FGD systems, fine gas exiting from the particulate collector flows to an absorber. In the absorber, the flue gas comes into contact with the sorbent slurry. The innovative scrubbers in the CCT program featured a variety of technologies to maximize SO, absorption and to minimize the waste disposal problems (sludge). 

Nowadays economy and ecology render the reuse of the sulfite solution increasingly important. Normally the scrubber liquor is recovered as dilution water directly in the neutralization of sulfonation plant or in the slurry preparation unit of synthetic detergent plants. In some special cases, when the presence of sulfites is incompatible with the slurry composition, it is possible to install as optional a sulfite oxidation unit. This oxidation takes place with atmospheric air. 

In wet scrubbing the dust is removed by counter-current washing with a liquid, usually water, and the solids are removed as a slurry. The principal mechanism involved is the impact (impingement) of the dust particles and the water droplets. Particle sizes down to 0.5 /i.m can be removed in suitably designed scrubbers. In addition to removing solids, wet scrubbers can be used to simultaneously cool the gas and neutralise any corrosive constituents. 

Generally, water is used in this plant to cool, leach, filter wash, scrub, heat, and washdown. The unreacted ore is slurred and sent, along with chromium and other impurities originally present in the ore, to the treatment plant. The boiler blowdown, which is sometimes contaminated with chromium escaping from the process area, adds to the volume of wastewater coming from the plant. The non-contact cooling water from the plant contains dissolved sulfate, chloride, and chromate thus it is sent to a wastewater treatment plant. The scrubber water may be used to slurry the ore or discharged. 

For PM applications, wet scrubbers generate waste in the form of a slurry or wet sludge. This creates the need for both wastewater treatment and solid waste disposal. Initially,... 

The abatement of chlorine vents and the subsequent destruction of the resulting sodium hypochlorite has been the subject of many studies. There are a variety of approaches to the waste hypochlorite destruction including chemical dosing, homogeneous and slurry catalysis as well as fixed-bed catalysis. For the most part these processes treat the hypochlorite at its natural strength the stoichiometric equivalent strength of the caustic soda fed to the scrubber. 

---