Temperature reboiler

Reboiler temperature increases with a limit often set by thermal decomposition of the material being vaporized, causing excessive fouling. 

A widening of the temperature differences across columns, since light nonkey components cause a decrease in condenser temperature and heavy nonkey components cause an increase in the reboiler temperature. 

Formex pro-cess, Snam-progetti /V-formyl-morph o-line (FM) water is added to the FM to increase its se-lectivity and also to avoid high reboiler temperatures during solvent recovery by distillation 40 perforated-tray ex-tractor, FM density at 1.15 aids phase separation low corrosion allows use of carbon steel equipment... 

Fixed Tube Sheet Both tube sheets fixed to shell Condensers liquid-liquid gas-gas gas-liquid cooling and heating, horizontal or vertical, reboiling Temperature difference at extremes of about 200°F. Due to differential expansion 1.0... 

Verify the reboiler temperature with a test thermometer and be sure the temperature is in the recommended range of 350°F to 400°F for triethylene glycol. The temperature can be raised closer to 400°F, if needed, to remove more water from the glycol. 

TheiTnal decomposition, caused by an excessive reboiler temperature (over 404°F), deposits on the firetube, or a poor reboiler design. 

Calculate approximate reboiler duty with 250°F reboiler temperature. 

An excessive circulation rate may overload the reboiler and prevent good glycol regeneration. The heat required by the reboiler is directly proportional to the circulation rate. Thus, an increase in circulation rate may decrease reboiler temperature, decreasing lean glycol concentration, and actually decrease the amount of water that is removed by the glycol from the gas. Only if the reboiler temperature remains constant will an inc.rea,se in circulation rate lower the dew point of the gas. 

Tower operating pressure is determined most often by the temperature of the available condensing medium, 100-120 F if cooling water or by the maximum allowable reboiler temperature, 150 psig steam, 366 F. 

To estimate the stage, and the condenser and reboiler temperatures, procedures are required for calculating dew and bubble points. By definition, a saturated liquid is at its bubble point (any rise in temperature will cause a bubble of vapour to form), and a saturated vapour is at its dew point (any drop in temperature will cause a drop of liquid to form). 

Vacuum operation should be avoided and the reboiler temperature kept as low as possible to minimize fouling,... 

By approaching the refinery design from a crude oil perspective, the advantage of preseparation by stepwise condensation after HTFT synthesis was reduced. The refinery design included primary separation steps typically found in crude oil refineries, namely, an atmospheric distillation unit (ADU) that is followed by a vacuum distillation unit (VDU). Despite the design intent, the operation of these units, out of necessity, had to be different. The reboiler temperature of the ADU was... 

In case 2, the shell-side reboiler temperature rises from 240 to 280°F (one reason for such a rise in temperature could be an increase in tower pressure). Now AT = (320°F - 280°F) = 40°F. Looking at the equation above, it looks as if Q will drop in half to 5000 lb/h (which is about the same as 5,000,000 Btu/h). Thus, the flow of steam to the reboiler has been cut in half, even though the control valve position has not moved. 

In such a process an additive or solvent of low volatility is introduced in the separation of mixtures of low relative volatilities or for concentrating a mixture beyond the azeotropic point. From an extractive distillation tower, the overhead is a finished product and the bottoms is an extract which is separated down the line into a product and the additive for recycle. The key property of the additive is that it enhance the relative volatilities of the substances to be separated. From a practical point of view, the additive should be stable, of low cost, require moderate reboiler temperatures particularly for mixtures subject to polymerization or thermal degradation, effective in low to moderate concentrations, and easily recoverable from the extract. Some common additives have boiling points 50-100°C higher than those of the products. 

If the normal boiling point of the overhead composition is below the coldest cold utility, then the minimum condenser temperature in a column will be equal to the temperature of the coldest cold utility plus ATroi . They take the values of 341.92,343.01,353.54 and 341.92 for tasks 1,2,3 and 4 respectively. The maximum reboiler temperature, if critical conditions are not approached by the hottest hot utility, will be the temperature of the hottest hot utility minus ATm n- Based on the data, the maximum reboiler temperature is 411 K. 

Coking in reboilers and rerun columns is caused in many cases by operating at excessive temperatures. In these cases, the difficulty can be reduced and sometimes be eliminated by reducing the temperature of the reboiler. Temperatures of 400°F. and above should be avoided. The breakdown of esters and other sulfur compounds in the rerun reboiler usually results in the production of corrosive alkylate and corrosion in the rerun column. A reduction in the reboiler temperature is sometimes sufficient to clear up this situation, but in some cases, an injection of mono- or triethanolamine into the feed is required. 

Use intermediate condensers and reboilers (if possible). This pushes the operating lines closer to the equilibrium line (Figure 10.17), thus reducing inherent column inefficiencies. The use of waste heat may also be possible now without upgrading to the reboiler temperature. A potential disadvantage may be that extra trays are needed. 

---