RSST

Reactive System Screening Tool (RSST) The RSST is a calorimeter that quickly and safely determines reactive chemical hazards. It approaches the ease of use of the DSC with the accuracy of the VSP. The apparatus measures sample temperature and pressure within a sample containment vessel. Tne RSST determines the potential for runaway reactions and measures the rate of temperature and pressure rise (for gassy reactions) to allow determinations of the energy and gas release rates. This information can be combined with simplified methods to assess reac tor safety system relief vent reqiiire-ments. It is especially useful when there is a need to screen a large number of different chemicals and processes. 

Reactive Systems Screening Tool (RSST ) Temperature history of runaway reaction, rates of temperature and pressure rise (for gas producing reactions)... 

What is the potential temperature rise by undesired reactions or thermal decomposi- tion, such as from contaminants, impurities, etc. What are the consequences What is the maximum pressure Enthalpy of undesired reaction Specific heat Rate of undesired reaction as a function of temperature DTA/DSC Dewar flask experiments APTAC /ARC /RSST/VSP... 

The RSST charts also point out another important difference between resoles and novolacs. Fig. 2 shows that resole reactions take place in two distinct stages with initiation temperatures at about 40-50°C and 100-140°C, respectively. 

Fig. 2. RSST results on various resoles. The three bulk-charged resoles are at approximately 58% solids, 50% solids, and 40% solids. The programmed formaldehyde has no water charged except that contained in the 50% formaldehyde. The 50 and 58% solids resins reach self-heat rates of nearly 600°C/min. The 40% solids resin does not exceed 10 C/min. (Chart courtesy of Borden Chemical and Bill Burleigh.)...

Fig. 3. RSST results on some typical production novolacs. The solids on these materials are 74, 70, and 62%, respectively. Note that the reaction does not become initiated significantly below 70 C and that the high solids system is capable of self-heating rates as high as 5500°C/min under these conditions. (Chart courtesy of Borden Chemical and Bill Burleigh.)...

Anonymous, RSST. The Reactive System Screening Tool, Eauske and Assoc, Buit Ridge, IL. 

Fauskes Assoeiates Ine. developed the RSST as an inexpensive sereening tool [15,16]. The RSST (Figures 12-14 and 12-15) eonsists of a spherieal glass reaetion vessel and immersion heater (optional). 

Figure 12-14. Reactive system screening tool (RSST) apparatus. (Source Fauskes Associates Inc.)...

The possible installation of the RSST on site when the samples cannot be transported. 

Only open cell tests are possible using the RSST. 

Eauske, El. K., The Reaetive System Sereen Tool (RSST) An Easy, Inexpensive Approaeh to the DIERS Proeedure, Int. Symp. on Runaway Reaetion, Pressure Relief Design, and Effluent Handling, AIChE, pp. 51-63, Mareh 11-13, 1998. 

The Fauske and Associates Reactive System. Screening Tool (RSST) w as developed as a result of the DIERS studies and allow s rapid evaluadon of the potential for runaway reactions. It measures the rate of energy and gas release during the runaway and is valuable for screening various process s)stems before commercial designs are completed (see Figure 7-61). 

Several commercial calorimeters are available to characterize runaway reactions. These include the accelerating rate calorimeter (ARC), the reactive system screening tool (RSST), the automatic pressure-tracking adiabatic calorimeter (APTAC), and the vent sizing package (VSP). Each calorimeter has a different sample size, container design, data acquisition hardware, and data sensitivity. 

The RSST (reactive system screening tool) is a laboratory device used to characterize the reactive nature of liquid materials. It is essentially an adiabatic calorimeter, with the test sample heated at a constant temperature rate until an exothermic reaction is encountered. 

Assume that a sample is being heated in the RSST. During an exothermic reaction, the energy of reaction heats the sample and increases its temperature. If the reaction is first order in concentration, then, if the heat of reaction is approximately constant, the increase in temperature will also be first order, a. Show that for a first-order system, a plot of... 

Consequence of runaway reaction Temperature rise rates Gas evolution rates Adiabatic Dewar Adiabatic calorimetry Pressure ARC VSP/RSST RC1 pressure vessel... 

ARC = Accelerating Rate Calorimeter (Columbia Scientific Instrument Corp.) DSC = Differential Scanning Calorimeter DTA = Differential Thermal Analysis RC1 = Reactor Calorimeter (Mettler-Toledo Inc.) RSST = Reactive System Screening Tool (Fauske and Associates) VSP = Vent Size Package (Fauske and Associates) ... 

The tests available relative to the first two questions are discussed in Sections 2.3.1 and 2.3.2, while those for the third question are reviewed in Chapter 3 (e.g., RSST and VSP). 

To investigate the gas evolution during decomposition and/or a runaway, both the ARC and RSST simultaneously record the temperature rise and the pressure rise, which is usually proportional to the gas evolution during decomposition. 

Experimental data can be obtained from the DSC and from reaction calorimeters for the conditions of the desired reactions, and from the DSC, the ARC, the Reactive System Screening Test (RSST—Fauske and Associates) and from the Vent Size Package (VSP) for conditions allowing undesired reactions. The pressure effect can be studied using the ARC or DIERS methods. From the results of these tests, the rate of temperature rise and the maximum acceptable conditions for specific equipment can be calculated. The same holds for the pressure rise rate. 

The maximum pressure increase due to desired and undesired reactions is, in practice, often investigated in laboratory equipment such as the ARC, RSST, and VSP (see Chapter 2, and Section 3.3 below) to verify the results from the mass balance. These test show the pressure history for a set of extreme conditions and, therefore, provide an estimate for gas production which can be used in scale-up calculations. Limitations in the applications of such tests may occur because of the test size relative to the plant scale. These aspects are discussed in Section 3.3.4. Such tests must be carried out for the complete range of temperatures which may occur on the plant scale. 

The Reactive System Screening Tool (RSST), marketed by Fauske and Associates, is a relatively new type of apparatus for process hazard calorimetry [192, 196-198]. The equipment is designed to determine the potential for runaway reactions and to determine the (quasi) adiabatic rates of temperature and pressure rise during a runaway as a function of the process, vessel, and other parameters. 

The basic features of the RSST are illustrated in Figure 3.16. The RSST... 

The RSST apparatus can be operated with its own controller or with a computer interface. Heating rates depend on the Cp of the reactive sample, and can be varied from 0.25°C/min to approximately 2°C/min. Isothermal experiments can also be run. The contents of the test cell can be mixed with a... 

FIGURE 3.16. Schematic of the RSST Showing the Glass Test Cell and the Containment Vessel. 

A typical temperature-time curve from a run in the RSST is shown in Figure 3.17. 

Data acquired from an RSST experiment show the potential of a runaway reaction (reactive or nonreactive), the temperature history of the runaway, and the rates of temperature and pressure rise (the latter in the case of gas-produc-... 

---