Air injection system

In most cases, FBCs employ some type of air injection system in the floor of the furnace both to impart turbulence into the burning fuel bed and supply combustion air. Secondary and tertiary air ports may be located above the burning fuel bed. 

Humidified Compressed Air Injeetion System are about the same. This is due to the faet that though the initial eost to install the Compressed Air System, for a turbine of about 100 MW, is about 3.7 million as compared to about 1.7 million for a steam injection system, the power generated by the Heated and Humidified Compressed Air Injection System is much higher. 

The rate of return on the steam injection system is higher than the Compressed Air Injection System. This is due to the fact that though the efficiency of the steam injection system and the compressed air injection system is about the same, however, the initial cost of the steam injected system being over 50% lower than the compressed air injection system accounts for the difference. 

BIOHOCH An aerobic wastewater treatment process. Optimimum reactor design and a proprietary air injection system achieve 50 percent of the energy consumption of similar systems. Fifty systems had been installed worldwide by 1994. Licensed by Brown-Minneapolis Tank and Hoechst-Uhde Corporation. 

Air injection systems, by their very nature, start with no initial hydraulic control because flow is away from the injection point. Contaminants are sometimes spread laterally by water displacement until control is established. 

The installation cost of a hot-air injection system including stainless steel wells is about 15,000 to 22,000 for a 50-kW system. The electricity would cost about 3600 per month. These costs do not include the vapor extraction portion of the system. 

The installation cost for a humid air injection system varies from about 15,000 for a 50-kW plastic pipe system to about 45,000 for a 200-kW high-temperature system. The operating costs would be about 3600 and 8000 per month, respectively. 

The waters in question are pumped to a membrane bioreactor equipped with an air injection system, where part of the feed is recycled, making it move across a membrane ultrafiltration system, to prevent the presence of suspended microelements in the later phase of reverse osmosis. From the ultrafiltration process, two streams are obtained a concentrated stream of salts and microbial mass, which is recycled to the bioreactor, and a permeate stream that passes to the reverse osmosis plant. 

Add air permeation Air permeation may be added to the system actively via an air injection system or passively through a vent. In particular, adding judicious (often very small) amounts of air at the location in the press feed system where the interstitial gas pressure is lowest can often be beneficial in reducing the likelihood of a feed rate limitation. 

Air injection systems offer a finer atomization which make combustion and mixing phenomena a little easier to solve. 

One approach was to operate the engine sufficiently reducing (rich) so that a catalyst to reduce NO could be positioned upstream both of an air injection system in the exhaust and of the oxidation catalyst. This was the dual bed catalyst, system and in this arrangement, the H2, CO, and HC could first reduce the NO and the remaining HC and CO would be oxidized in the second bed. Rh proved to be the best catalyst for the selective removal of NO in the reducing atmosphere (21). It had less NH3 formation than Pt or Pd. 

A major advantage of air sparging is that it requires only simple materials to constmct a field system. No special equipment needs to be designed and all equipment used is easily obtained. Equipment required for the air injection system and soil vapor extraction system is summarized in this section. 

For optimum combustion, the fuel should vaporize rapidly and mix intimately with the air. Even though the design of the injection system and combustion chamber play a very important role, properties such as volatility, surface tension, and fuel viscosity also affect the quality of atomization and penetration of the fuel. These considerations justify setting specifications for the density (between 0.775 and 0.840 kg/1), the distillation curve (greater than 10% distilled at 204°C, end point less than 288°C) and the kinematic viscosity (less than 8 mm /s at -20°C). 

The performance of the catalytic converter is affected by the conditions of air/fuel control provided by the fuel metering system. A slowly responding fuel metering system can dramatically decrease the conversion efficiency of the converter compared to a fast response multipoint fuel injection system. 

Injection Pre.s.sure. The injeetion pressure must be between 75-100 psia (5-7 Bar) above the Compressor Diseharge Pressure. In the ease of the Heated and Humidified Compressed Air injeeted system, the air must be saturated. 

Main fuel injector. This unit is designed to deliver a fuel-air mixture to the catalyst that is uniform in composition, temperature, and velocity. A multi-venturi tube (MVT) fuel injection system was developed by GE specifically for this purpose. It consists of 93 individual venturi tubes arrayed across the flow path, with four fuel injection orifices at the throat of each venturi. 

The most common application of carbon adsorption in municipal water treatment is in the removal of taste and odor compounds. Figure 12 provides an example of a process flow diagram for a municipal water treatment plant. In this example water is pumped from the river into a flotation unit, which is used for the removal of suspended solids such as algae and particulate matter. Dissolved air is the injected under pressure into the basin. This action creates microbubbles which become attached to the suspended solids, causing them to float. This results in a layer of suspended solids on the surface of the water, which is removed using a mechanical skimming technique. Go back to Chapter 8 if you need to refresh your memory on air flotation systems. 

Water pump seals, hoses for air-conditioning systems, seals in cooling systems and covers in diesel injection systems... 

Probably the most significant control technology breakthrough came m 1977, when Volvo released a computer-controlled, fuel-mjected vehicle equipped with a three-way catalyst. The new catalytic converters employed platinum, palladium, and rhodium to simultaneously reduce NO and oxidize CO and HC emissions under carefully controlled oxygen conditions. The new Bosch fuel injection system on the vehicle provided the precise air/fuel control necessary for the new catalyst to perform effectively. The combined fuel control and three-way catalyst system served as the foundation for emissions control on the next generation of vehicles. 

Such tight mixture control is beyond the capability of the traditional carburetor. Consequently, after sorting through a number of alternatives, industry has settled on closed-loop-controlled port-fuel injection. Typically, an electronically controlled fuel injector is mounted in the intake port to each cylinder. A sensor in the air intake system tells an onboard computer what the airdow rate is, and the computer tells the fuel injectors how much fuel to inject for a stoichiometric ratio. An oxygen sensor checks the oxygen content in the exliaust stream and tells the computer to make a correction if the air/fuel ratio has drifted outside the desired range. This closed-loop control avoids unnecessary use ot an inefficient rich mixture during vehicle cruise. 

This chapter provided several cost recommendations that, once implemented, would provide cost-effective added value to the operation of the FCC. Examples of such items include tips on debottlenecking the air blower, wet gas compressor, and catalyst circulation. This chapter also discussed the latest technologies regarding the riser termination devices, as well as feed injection systems. Prior to implementing any new technologies, it is critical that the objectives and the limitations of the unit are clearly defined to ensure the expected benefits of the new technology are realized. 

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