Stack sulfur dioxide concentration

Figure 4. Conversion vs. stack sulfur dioxide concentration for an IFP unit with 93% design conversion...

A trash incinerator has an effective stack height of 100 m. On a sunny day with a 2 m/s wind the concentration of sulfur dioxide 200 m directly downwind is measured at 5.0 X 10-5 g/m3. Estimate the mass release rate (in g/s) of sulfur dioxide from this stack. Also estimate the maximum sulfur dioxide concentration expected on the ground and its location downwind from the stack. 

Conventional sulfuric acid plants have traditionally been used to recover sulfur dioxide from smelter gases, but these are inadequate to meet the proposed sulfur dioxide emission standards. Double absorption, which removes sulfur tri-oxide from the partially converted sulfur dioxide gas stream, reduces the sulfur dioxide emission to less than 500 ppm in the undiluted stack gas. Two double absorption plants using Lurgi technology have been operating with copper converter gas since early 1973. In spite of the wide and frequent variations in gas volume and sulfur dioxide concentration, these plants have consistently maintained sulfur dioxide emission levels well below 500 ppm. This paper presents data on the design and operating conditions for these plants. 

Stack gas from smelters handling sulfur ores, on the other hand, can have very high sulfur dioxide concentrations. Therefore, the economics of recovering sulfur values fiom such gases can be much more favorable. Of course, the problems of discharging such gases without sulfur dioxide removal are also much more acute. 

Re OPe from Flue Gases. Recovery of sulfur dioxide from flue gases has been described (25,93,227). The stack gas from smelting often contains sufficient sulfur dioxide (ca 6 wt %) for economic conversion to sulfuric acid the lower concentration ki power plant stack gases generally requkes some method for concentrating the sulfur dioxide. 

Preferably, the HjS flare system should consist of a segregated header and separate line routed up the side of a conventional elevated flare stack, sharing the same structure, pilots and igniters. However, the HjS header may be tied into the regular flare seal drum if there are special mechanical design problems associated with the separate stack e.g., in the case of a flare which is to be dismantled for overhaul. Flare elevation must be sufficient to meet atmospheric pollution and ground level concentration requirements for the sulfur dioxide produced. 

The environmental problem of sulfur dioxide emission, as has been pointed out, is very much associated with sulfidic sources of metals, among which a peer example is copper production. In this context, it would be beneficial to describe the past and present approaches to copper smelting. In the past, copper metallurgy was dominated by reverberatory furnaces for smelting sulfidic copper concentrate to matte, followed by the use of Pierce-Smith converters to convert the matte into blister copper. The sulfur dioxide stream from the reverberatory furnaces is continuous but not rich in sulfur dioxide (about 1%) because it contains carbon dioxide and water vapor (products of fuel combustion), nitrogen from the air (used in the combustion of that fuel), and excess air. The gas is quite dilute and unworthy of economical conversion of its sulfur content into sulfuric acid. In the past, the course chosen was to construct stacks to disperse the gas into the atmosphere in order to minimize its adverse effects on the immediate surroundings. However, this is not an en-... 

Descriptions of field studies of power-plant stack plumes were given by Davis et al. The ozone concentration appears to be lower in regions of high sulfur dioxide content. At 32 km downwind from the stacks, it was claimed that the ozone concentration in the plume (now 11 km wide) is higher than the ambient concentration ( 0.08 ppm) by approximately 0.02 ppm. Simultaneous measurements of nitric oxide and nitrogen dioxide were integrated across the plume. Values of the ratio of nitric... 

The dilute acid was then concentrated at atmospheric pressure, producing a reusable acid but also a number of troublesome by-products. Sulfur trioxide vapor was produced as the acid became more concentrated. This produced an intolerable fog, so electrostatic precipitators were installed and the remaining vapor was decomposed by heat into sulfur dioxide which was discharged from a high stack. 

The effects of local air contaminants on forests have stabilized in the vicinity of existing point-sources of air pollutants. In numerous cases improvements have been achieved. In the case of sulfur dioxide, increasing stack heights and use of scrubbers have reduced ground level concentrations of sulfur dioxide. New industries and electrical plants in the U.S. can employ the best available air quality technology. 

The oxides of sulfur are measured both in ambient air, where their concentration is usually a small fraction of one ppm, and in stacks and other industrial emissions, where their concentrations are in hundreds of ppm. As already discussed in Section 3.2.11, sulfur dioxide absorbs radiation over a broad range of wavelengths, which includes both the IR (Table 3.20) and UV regions. 

Sulfur dioxide is being emitted from a stack at a rate of 50 sefs, and the prevailing wind velocity is 15 ft/s. The stack exit gas velocity is 60 fl/s. The stack diameter is 3,5 feet. Eslimtiie tlie physical stack height necessary to meet an air pollution standard of 5 ppmv maximum SO2 (30 rain average concentration) GLC. 

Tn 1970, 20 million tons of sulfur dioxide emitted from steam electric-power plants. Without control measures these emissions will increase to 40 million tons by 1980. With typical SO2 concentrations in stack gas currently in the range of 1000-2000 ppm, target levels for future control legislation correspond to 50-150 ppm SO2 in the stack, and there are not sufficient low sulfur fuels to meet these standards. To fill the gap between projected supplies of low sulfur fuels and our nation s energy requirements, an economical, high efficiency process to remove SO2 from the fiue gases of power plants is required. Such a process must also recover SO2 in a form which can be readily handled and sold, in recognition of the quantities involved. Furthermore such a process must be compatible with the many constraints public utilities face in its installation and operation. 

A smokestack with an effective height of 25 m emits sulfur dioxide (S02) at a rate of 10 kg/hr. What is the contribution of this stack to ground-level S02 concentrations at a school yard 8 km downwind, if wind speed is 4.5 m/sec on a sunny midwinter day Assume unlimited mixing height. 

Air quality monitoring near the incinerator and in district communities showed that measured stack emission concentrations were well within project limits and much lower than previously predicted. For example, mobile monitoring carried out downwind at distances of 100 m, 200 m, 500 m, 1 km, 2 km and 5 km showed that agent incineration had little impact on ambient air quality. Sulfur dioxide and nitrogen dioxide concentrations were usually below the minimum. 

Single-bed catalysts had been used to produce sulfur from dry sulfur dioxide gases. Ryason 1,2) used either Cu, Pd, Ag, Co, or Ni supported on alumina. Khalafalla and Haas (3) optimized the composition of iron-alumina catalysts to produce sulfur from dry gases containing sulfur dioxide and carbon monoxide. Querido and Short (4) demonstrated the feasibility of reducing sulfur dioxide by carbon monoxide on a copper-alumina catalyst at concentrations and temperatures typical of power plant stack gases. 

The first phase determined that the citrate system best met all of the critical requirements for an ideal sulfur dioxide absorption medium, including the system s capability for efficient removal of sulfur dioxide over a broad concentration range, e.g., the high levels in smelter waste gas, the sulfur dioxide-lean stack gas emitted by power plants, and the intermediate range represented by Claus plants. The results of the second phase of the program, dealing with the process chemistry, forms the basis for much of this paper. 

Once growth stops, desorption of the gas occurs until the equilibrium concentration is reached. However, if the gas can be complexed by a fast enough chemical reaction, then it would be possible to contain the gas. Additives which result in a chemical reaction are present in the Stack gases themselves. Several additives for sulfur dioxide are vanadium pentoxlde, manganese sulfate, and soot Ccarbon). Preliminary work in this area was done with manganese sulfate by Matteson et al. [10]. 

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