Loss of reboiler heat

Check valve failure Blocked discharge Control valve failure Thermal expansion of liquid Heat exchanger tube rupture Reflux failure and overhead system Loss of reboiler heat Venting of storage tank Failure of individual motor Accidental closure of valve... 

Loss of reboiler heat means loss of heat input to the column, and in most cases, this will not result in any relief. However, dming frachonahon, failme of reboiler duty will increase tiie light ends fed into the bottom product, and if the bottom product is further processed to a second frachonahon coliunn, the feed to the second column will be lighter. The impact of lighter feed to the second column needs to be analyzed properly. 

Emergency Conditions in Integrated Plants - In integrated plants, a process upset in one unit may have an effect on other units (e.g., loss of flow of a pumparound which is used as a source of heat for reboiling other towers). All possibilities such as these must be carefiiUy considered and the potential for resulting overpressure evaluated. 

A noteworthy point is, however, that the heat for the reboiler is supplied at 377 K, which is often available as waste heat in a chemical plant. Waste heat is usually rejected (hence the term "waste"), so heat integration could improve the process efficiency and reduce total exergy losses for the entire chemical plant (see Figure 10.14). Now, what Figure 10.14 shows is that heat integration can sometimes reduce the exergy losses of a chemical plant as well as reduce... 

A loss of heat along the column causes increased condensation and reduced evaporation. Thus, the amount of vapor diminishes in the upward part of the column, where the flow of liquid is also less than at the bottom. Where heat loss occurs, more vapor has to be produced in the reboiler or steam generator, resulting in a loss in energy efficiency. 

Olefins Demethanizer Condensate seal was lost on a vertical thermoeiphon reboiler causing loss of heat transfer. Losing reboiler condensate seal can lower reboiler heat transfer rate. 

Figure 13.12 Simultaneous loss of condenser cooling and reboiler heating, (a) Base model loss of Qc and Qr. (b) Rigorous model loss of CW and steam.

Stripper. Absorber bottoms at 322 K is preheated to 380 K in a heat exchanger using the hot stripper bottoms at 400 K and fed to the top of a stripping column with 10 stages and operating at 2 atm in the column and 1.5 atm in the reflux drum. Reboiler heat input is 54.12 MW to maintain a reflux-drum temperature of 363 K, as suggested by Desideri and Paolucci as a balance between stripper reboiler energy and water losses in the vapor from the reflux dmm. 

Fig-5 refers the BAHE-2 Gas/Liquid exchanger streams temperature trends. Most important point here hot stream (i.e. feed gas) outiet temperamre is almost constant —65degC even when hot inlet stream temperature is varying. This is mainly because 1. Cold stream-2 (i.e. side reboiler) is driven by thermosiphon hence self-adjusts the flow thorough exchanger as heat load varies. 2. Cold stream-1 (i.e. expander feed separator liquid) flow impacted due to loss of level in drum when feed gas C3+ content reduces. 

The potassium carbonate system operates mainly isothermal-COg absorption at high pressure and COg release at low pressure. In the absorptim step the pressure is typically about 3.0 MPa (reformer pressure minus pressure losses), and the temperature may be 100°C. The COg is absorbed chemically by the conversion of potassium carbonate to bicarbonate. When the solution pressure is reduced to about atmospheric pressure, part of the COg and water vapor escape. COg release is assisted by steam stripping. The steam is raised in the regenerator reboiler heated by the gas from the LTS shift converter thus, some or most of the heat required by the COg removal process is derived from the heat in the incoming gas. The regenerated solution is returned to the absorber. 

Boiling point Ease of retrofit Vent losses Possibility ofNCls accumulation Reboiler temperature Reboiler heat load... 

These results show that there is no control penalty for going to the partial heat-integrated systems when auxiliary reboilers or condensers are added. This result is to be expected because there is no loss of control degrees of freedom. 

In the treatment of a natural gas stream with lean oil, the less volatile components (lower Rvalues) primarily are absorbed in the lower part of the column, while the more volatile components (higher Rvalues) primarily are absorbed in the upper part of the column [27], Thus, in a column treating a 470 psia natural gas stream to remove all of the C-5 and heavier components, one-sixth of the ethane also will be absorbed. While the rich oil could be deethanized in a separate column, there is an advantage to the use of a single column called a reboiled absorber. This compound column really consists of an upper section, which acts as an absorber, and a lower section, which acts as a stripper. By incorporating a reboiler at the bottom of the column, the ethane can be liberated from the heated rich oil and caused to leave the system at the top of the absorption section. In this case, the absorption section acts as a rectifier for the stripped vapor to prevent the loss of less volatile components in the overhead gas stream. 

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