Pumping system losses can be reduced by lowering system pressures, reducing friction losses, and stopping leaks. For example, high pressure steam can first be expanded through a noncondensing turbine to do useful work, and then the turbine exhaust steam used for process or building heating. Instead of using pressure-reducing valves, look for opportunities to cascade steam use, within acceptable limits on steam pressure, temperatures, and quality. Sometimes steam must be provided at high pressure. Electricity might even be better for heating in a particular case, if line losses and the effect of more precise temperature control are included. This would be true in cases where the steam loads are small, or are distant from the steam plant. In some cases, electric motors or some alternative drive system will be more efficient than steam turbines. Instead, a substitute energy source could be found for the high-pressure load. If most of the loads are at lower pressures, steam should not be supplied at high pressure. For heating purposes, pressures are more typically in the range 0.1 to 0.3 MN/m 2. Steam is also used to transfer fluids by means of steam jets. In industrial operations, this may be 1 to 3 MN/m 2 if steam turbine driven equipment is used. Steam usually will be supplied at the pressure of the highest load. Īpply the cascade principal to steam uses.Review steam uses to see if more efficient alternatives exist Supply steam at the lowest pressure possible Steam is used for heating purposes, for operating steam driven equipment, or for heating buildings. A simple schematic of the oxy-combustion system is shown in Fig. The next step is to condense the water and purify the CO 2 until it is 99% pure so that it can be transported in the supercritical state. The content of CO 2 in these exhaust gases is about 75% (wet basis). The latter originates from the ASU (air separation unit) and parasite air entries due to the lack of a seal of the PC cycle (combustion chamber, deduster, gas-gas heater, etc.). The flow of uncycled CO 2 still contains water vapor, impurities (particularly some NO x and SO x amounts that remain in the exhaust gas of scrubbing systems), and incondensable gases such as oxygen, nitrogen, and argon. This avoids full resizing of the boiler and its associated exchangers. A big part of the exhaust gases is recycled in the boiler to maintain the usual temperature levels of pulverized coal (PC) without capture. In precombustion technologies, combustion is made using pure oxygen (up to 97% purity) however, a small amount of nitrogen and argon remains. Separation of water vapor from the gas stream is simple condensation can provide the suitable separation. ![]() Read moreĬomplete combustion of hydrocarbons (without impurities) in the presence of enough oxygen produces water vapor and carbon dioxide. Some of these toxic combustion gases produce immediate asphyxiant symptoms, while others (e.g., HCl, HBr, NO 2) fall into an irritant category and produce symptoms following the exposures. One also needs to consider that in fire situations, oxygen levels drop and exposure to low oxygen atmospheres will have additional adverse physiological effects. Other commonly found fire gases include nitrogen oxides, ammonia, hydrogen sulfide, sulfur dioxide, and fluorine compounds. ![]() Halogenated or flame-retardant materials generally produce HCl or HBr. If the materials contain nitrogen, HCN and NO 2, the two principal thermo-oxidative products of toxicological concern, are also likely to be generated. When oxygen is limited, the primary gases formed during the combustion of most organic materials are CO, CO 2, and water. It is during incomplete combustion under various atmospheric conditions in either flaming or nonflaming modes that compounds of greater toxicological concern are generated. Gad, in Reference Module in Biomedical Sciences, 2023 Primary toxic combustion gasesĬomplete combustion of a polymer containing carbon, hydrogen, and oxygen in an atmosphere with sufficient O 2 yields CO 2 and water.
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