Scrubbers operating data

Scrub. Medium, Table I. Ldq. Recycle Scrubber Operating Data Pres, Resid, Resid, LosSy Salty Ashy ... 

The collection efficiency of wet scrubbers is dependent on parameters such as the size and quantity of liquid droplets, the liquid/gas ratio, high wa-ter-to-particle relative velocity, wettability of dust, particle density, gas viscosity, etc. For any specific application, the design procedure is to review operating data available from the technical literature or from manufacturers for similar applications. If data are not available, it may be necessary to per form pilot scale tests, which can be used for scale-up purposes. 

The scrubbing liquor is recirculated at the scrubber. A bleed of the scrubbing liquor is required to control the build-up of sulfuric acid, selenium, mercury and other species. This is the so-called weak acid bleed. The volume of this bleed is relatively small. However, it is concentrated since it results from a recirculation loop at the scrubber. Historical data from the Valleyfield operation show that the average concentration of selenium in the weak acid bleed is in the order of 50 mg/1 with peaks up to 180 mg/1 the average mercury concentration is 30 mg/1 (SNC-Lavalin (3)). The concentration of selenium in such a bleed first depends on the specific selenium content of the zinc concentrate being proeessed. It is known that some zinc ore deposits are characterized by high contents of selenium. Unless adequate treatment technologies are available for the removal of selenium fi-om the acid plant effluent, future development of such deposits may encounter environmental obstacles. 

The total releases to air from the facility must be entered m Part III, Section 5 of Form R in pounds per year. The stack test results provide the concentration of metallic lead in each exhaust stream in grains per cubic toot and the exhaust rate in cubic feet per minute. Using the appropriate conversion factors, knowing the scrubber efficiency (from the manufacturer s data), and assuming yourfacility operates 24 hours per day, 300 days per year, you can calculate the total lead releases from the stack test data. Because point (stack) releases of lead are 2,400 pounds per year,-which is greater than the 999 pounds per year ranges in column A. 1, you must enter the actual calculated amount in column A.2 of Section 5.2. 

Although there are numerous scrubber designs, typical characteristics of four of the more common types are listed in Table 13.8. Table 13.9 presents data on the features, operating principles and problem areas with these common scrubbers. A brief description of each scrubber type follows. 

Figure 17-46 shows such a performance curve for the collection of coal fly ash by a pilot-plant venturi scrubber (Raben "Use of Scrubbers for Control of Emissions from Power Boilers, United States-U.S.S.R. Symposium on Control of Fine-Particulate Emissions from Industrial Sources, San Francisco, 1974). The scatter in the data reflects not merely experimental errors but actual variations in the particle-size characteristics of the dust. Because the characteristics of an industrial dust vary with time, the scrubber performance curve necessarily must represent an average material, and the scatter in the data is frequently greater than is shown in Fig. 17-46. For best definition, the curve should cover as wide a range of contacting power as possible. Obtaining the data thus requires pilot-plant equipment with the flexibility to operate over a wide range of conditions. Because scrubber performance is not greatly affected by the size of the unit, it is feasible to conduct the tests with a unit handling no more than 170 m3/h (100 ftVmin) of gas.

Anthropogenic sources of fluoride include fossil fuel combustion and industrial waste. Hydrogen fluoride is water soluble and emissions are readily controlled by acid gas scrubbers. HF emission from coal combustion, that is considered to be the main anthropogenic source of HF, was estimated to be 0.18 Tg annually emission of HF from the combustion of petroleum and natural gas is almost certainly negligible [24]. Apparently only limited data are available concerning total annual emissions of HF from industrial operations however, there is evidence that emissions of fluorides have been declining [24,25]. 

The design of a 4 x 4 Latin square has been used in researching effects of water pressure, air flow and number of nozzles in operation on scrubber efficiency. Research outcomes are shown in Table 2.65. Do the analysis of variance for the given data. 

Preliminary tests with the pilot-scale unit confirmed laboratory results and showed that essentially complete removal of SO2 from the gas phase could be achieved in the larger equipment by injecting ammonia and steam. Many other tests were conducted to isolate the eflFects of some operating variables, including minimal development of the water scrubber. Results of these tests, however, are not described the data are outside the scope of this paper. 

A venturi scrubber is employed to reduce the discharge of fly ash to the atmosphere. The unit is presently treating 215,000 acfm of gas, with a concentration of 4.25 gr/ft, and operating at a pressure drop of 32 in. H2O. Experimental studies have yielded the following particle size collection efficiency data ... 

Three identical venturi scrubbers are connected in series. If each operates at the same efficiency and liquid-to-gas ratio, qilqg, calculate the liquid-to-gas ratio, assuming the Johnstone equation to apply. Data are provided below. 

Pollution Unlimited, an Aldo Leone Corporation, has submitted design plans to Theodore Consultants for a packed ammonia scrubber on an airstream containing NH3. The operating and design data provided by Pollution Unlimited, Inc. are given below. Theodore Consultants remember reviewing plans for a nearly identical scrubber for Pollution Unlimited, Inc. in 1988. After consulting old files, the consultants find all the conditions were identieal except for the gas flowrate. What recommendation should be made ... 

The power required to move flue gas through the scrubber, from the absorber inlet to the mist eliminator outlet, was calculated from pressure drop and gas flow-rate data reported in the literature for a range of superficial velocities, liquid/gas ratios, and internal scrubber packings. A fan of the wet induced-draft type was assumed for each case, operating on saturated flue gas at 125°F. The gas-side power input was added to the power delivered through the slurry recirculation pumps which was calculated from the volumetric flow rates and the minimum discharge pressures required for the given scrubbers. The total power input for SO2 absorption was thus determined as ... 

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