©  Copyright 2013 Chemical Engineering & Gas Processing Multipurpose micro reactor and catalyst test setup Interlock description  In order to prevention of undesirable state in the system, the interlock logic has been accomplished to provide a  high level safety for the device and operator by stopping the system when tripped. The temperatures of all the  heaters and pre-heaters can be set at two level point of high and high-high temperature. If the operating conditions  exceed the high temperature set-point at any reason, the alarm system warns and if the problem doesn't resolve,  the emergency shut down is activated and electricity of the system except the PLC control panel and HMI shut off  automatic. All the pre-heater temperatures are adjustable at range of 0 to 500 °C. Also, the temperature interlock is  employed in each pump in order to safety of reactors and catalysts so that the pumps will not start as long as the  pre-heater temperature reaches the given set point.  This setup is also equipped with pressure transmitter and BPR ( figure 5) for control of system and the flash drum  pressures. The pressure set point for PTs is visible and definable at the levels of high pressure, high-high pressure  and low pressure which provides a high pressure security by a precise PID control loop. A high- high pressure  interlock turns off the pump and heaters and opens the related BPR when ESD alarm is activated. The BPRs of the  DME synthesis  section are operated at pressure range of 0-25 bar and those of the propylene synthesis section are programmed  for pressures of 0-10 bar. Since the BPRs show forward pressure, according to the intended BPRs as illustrated in  appendix A, BPR parallel reactor (I) from PT -111, BPR parallel reactor (II) from PT-121 and BPR parallel reactor  (III) from PT-131 receive the system commands. Also in the propylene synthesis section, BPR 170 from PT-170 and  BPR 250 from PT-230 accept the commands.  Figure 5. Pressure transmitter & BPR which are applied in this device In addition, all the flash tanks, feed and water storage tanks are provided with level sensors and motor valves. The  level interlocks are programmed to commit the motor valves at high or low level condition. Based on this design,  level sensors send the commands to open the motor valves at high level alarm and close them at a specified time or  low level condition.  Since the drums No.170 and 250 are equipped with level transmitter (LT), hence opening and closing of the motor  valves manage based on the set point. Furthermore, there are the low level interlocks between the feed and water  storages with the related pumps. Once the water or feed level reduces below the limit value, the PLC sends a shut  down command to the related pumps.  Start up and operating procedure In present work, in order to investigation of effective operating parameters in DME manufacture, a series  experiments were carried out in first section of the setup (DME synthesis section). At first, a calibration protocol for  sensors that require calibration was developed. A lubricant pump is provided with a mixture of 80 percent by volume  of HPLC grade water and 20 percent by volume of isopropyl alcohol. In order to start up of the pumps, they are  primed by a flooded suction, the suction valves are opened and the liquid is allowed to flow into the pump. Also an  air release valve is opened at the highest point in the pump casing to ensure that all the air/vapor is bled from the  pump as it fills with the pumpage. Also, the feed, water and lubricant storage tanks are filled.  The setup is connected to the power source and all the fuses are switched on from the heater and power control  station. The electricity power of the PLC control panel is provided by turning on the UPS. Then, HMI is switched by  the operator key on the control desk and user can be accessed to the system by entering the password. It should be  checked the valves and flow meters be at the desired status. For the present work, since the parallel reactor II and  its equipments are operated in the system, it is only required to close valve -120 in order to connection of effluent  line to the GC. Next, the refrigeration system is started after checking up the heat exchangers. All the temperature  and pressure and level set points are set via HMI and until the operating parameters reach the set points, the  amount of catalyst required is weighted and loaded into the parallel reactor II. The heat tracing temperatures are  also set at desired value by the heat tracing control panel. When the pre-heater temperature reaches the  set point, the pump turns on and is set at the required flow rate.  Gas chromatography A gas chromatograph is a chemical analysis instrument for separating chemicals in a complex sample. It provides  both qualitative and quantitative information for individual compounds present in a sample. The gas chromatograph  makes it possible to separate the volatile components of a very small sample and to determine the amount of each  component present. The essentials required for the method are an injection port through which samples are loaded,  a "column" on which the components are separated, a regulated flow of a carrier gas (often helium) which carries  the sample through the instrument, a detector, and a data processor. In gas chromatography, the temperature of the  injection port, column, and detector are controlled by thermostatted heaters. Different chemical constituents of a  sample pass in a gas stream (carrier gas, mobile phase) at different rates which depend on their various chemical  and physical properties and their interaction with a specific column filling (called the stationary phase). As the  chemicals exit the end of the column, they are detected and identified electronically. The function of the stationary  phase in the column separates different components, causing each one to exit the column at a different time  (retention time). Other parameters that can be used to alter the order or time of retention are the carrier gas flow  rate, and the temperature. A schematic diagram of the GC apparatus has been illustrated in figure 6.   Figure 6. The schematic diagram f gas chromatography Instrumental components   Gas supply and carrier gas  The carrier gas serves as the mobile phase that moves the sample through the column. It must be chemically inert.  The carrier gas system also contains a molecular sieve to remove water and other impurities. Commonly used  gases include nitrogen, helium, argon, and carbon dioxide. The choice of carrier gas is often dependent upon the  type of detector which is used.  In this study, with regard to type of the detector (FID), availability and safety, helium is applied as carrier gas in the  GC system.   Sample injection port  The column inlet (or injector) provides the means to introduce a sample into a continuous flow of carrier gas. The  inlet is a piece of hardware attached to the column head. The temperature of the injector is controlled so that all  components in the sample will be vaporized and for optimum column efficiency, the sample should be injected in so  small amount. The column inlets have different types. In this device two type of the "S/SL (Split/Splitless) injector"  for manual injection via a syringe and "gas sampling valve" in order to automate injection of very small amount of  gas products. The S/SL injector is a hollow, heated, glass-lined cylinder where the sample is injected through the  septum (figure 7). The injector can be used in one of two modes; split or splitless. For present investigation, it was  set at temperature of 240 .C and splitless method was used under split flow of 0.8 ml/min and split ratio of 1/30.  Figure 7. The split /splitless injector References:  Mohadese Nazari, Determining Optimum Operating Condition of DME Production via Dehydration of Methanol over Acidic Gamma  Alumina Catalyst., M. Sc. Thesis, Petroleum University of Technology .,January 2011.  Omid Rahmanpour, Enhancement of the stability of Gamma Alumina catalyst using Multi Wall Carbon Nano Tubes (MWCNTs) as a  support for methanol dehydration., M. Sc. Thesis, Petroleum University of Technology .,2012.  Gas chromatography, 2008:< http://www.chromatography-online.org/topics/gas/chromatography.html>  Gas chromatography, Sheffield Hallam University, online learning:< http://teaching.shu.ac.uk/hwb/chemistry/tutorials>