Cost, control stream

Environmental control is essential to meet EPA demands. It has been estimated that for a plant consuming 37 million Btu/ton of ammonia produced, environmental control will require 0.7 million Btu, and environmental costs will be 1.1 percent of the operating costs. Discharge streams that require processing to eliminate undesirable contaminants include (1) the regeneration acid and base for boiler feed-water treatment units, (2) the regeneration steam for natural gas desulfurization catalysts, (3) the low temperature shift condensate (ammonia, amines, and methanol), and (4) CO2 removal process regeneration effluents. 

In terms of an economic determination, gas temperature adjustment is often the most important cost factor in determining whether to use a biofilter or a more conventional system. If the process gas stream is at an extremely high temperature (-i-I00° C), the cost of cooling the inlet gas stream might favor more conventional methods for odor control such as thermal oxidation. 

At the central platform, water and hydrocarbon liquids are first removed in knockout drums. Then saturated natural gas, free of any liquid droplets, enters the twin expanders. The gas is cooled below its dewpoint, allowing heavy hydrocarbon components and water vapor to condense in the discharge stream. Turboexpanders were chosen for two main reasons They are more compact than competing methods of controlling the dewpoint and their operating costs are typically lower than those of many alternatives. 

Pollutants that require an unusually high level of control or that require the fabric filter bags or the unit itself to be constructed of special materials, such as Gore-Tex or stainless steel, will increase the costs of the system. The additional costs for controlling more complex waste streams are not reflected in the estimates given below. For these types of systems, the capital cost could increase by as much as 75 % and the operational and maintenance (O M cost could increase by as much as 20%. 

It is important to establish the volume of the process stream that is to be treated. There are companies that have not needed to buy pollution control equipment in the past. Their approach to eliminating pollution has been the more exhaust, the better. This is particularly true in the low margin industries. The more complex and high volume industries, e.g., the chemical industry, have normally been concerned about the air exhausted from their plant and have paid attention to the exhaust volume by process control. The industries that have not paid attention to exhaust volume are not sufficiently aware that when buying pollution control equipment the cost of that equipment is going to depend on two elements ... 

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