Test run parameters

4.1.1 Test run parameters

The test run parameters are presented in Table 9. For the test runs, two basic parameter sets were used. A shorter, 150 min (2.5 h) test run, was performed with 4 mm/s of fluid flow velocity over heater rod. The longer, 1080 min (18 h) test run was performed with 1 mm/s of fluid flow velocity over heating rod. Both fluid velocities were in all cases laminar flows.

Table 9 – Test run parameter

Parameter Test run time 150 min Test run time 1080 min

Heater rod temp [ °C] 330 330

The main test run parameter was the heater rod target temperature and fluid flow velocity.

Secondary parameters, that mainly affect how hot the tested sample will enter the actual heating rod, were feed reservoir target temperature, pipelines heat tracing target temperature and pump casing heat tracing target temperature.

The last parameters that can be set are the overall pressure level during test and receiving reservoir target temperature. These last parameters have least effect on overall test results.

The receiving reservoir target temperature was set high enough to prevent compounds from collected liquid to form precipitates. The overall pressure was set higher than vapour pres-sure of possible low boiling CTO components to prevent them from vaporizing and causing

pressure spikes. The test equipment had an over pressure safety interlock that would cause equipment to abort the test if pressure would increase during test.

Table 10 – Test plan with key parameters

Run Run

Test plan is seen on Table 10. Test’s done with higher flow velocities (R446 – R448), it was observed that oil inlet temperature to heater rod assembly was creeping during the test and overshot the target oil inlet temperature (90 °C) being 95… 96 °C after the test was ran for 1.5 h.

For this reason, in the following test run (R449) the inlet pipeline heat tracing was lowered to 85 °C to see if this inlet temperature overshot was caused by the inlet line heat tracing

temperature control loop or was the heat actually conducting from the heater rod assembly to the inlet temperature probe. After lowering the inlet line tracing temperature to 85 °C for following tests, it was noted that the oil inlet temperature had also stabilized to 90…91 °C.

This indicates that the prior overshot was caused by the pipelines heat tracing control loop issues.

When the first longer 18 h test run (R450) with lower flow velocity was ran, it was observed that with inlet line heat tracing setting to 85 °C, the inlet temperature lagged from target 90

°C being max 80 °C. For this reason, the inlet line heat tracing target temperature was raised to 95 °C for the following 18 h test run and it was observed that when the test was in stable state, oil inlet temperature had stabilized to around 85… 86 °C. Therefore, the following tests were decided to be done with inlet line heat tracing target temperature set to 95 °C.

The reason for the target oil temperature lagging with lower pump rate was concluded to be caused by heat loss of untraced and uninsulated parts of the system seen on Figure 15; the inlet pipe heat tracing and insulation is terminated before line ends, the couplings between elements do not have insulation neither does the heater rod assembly. Due to this reason the oil temperature decreases between the traced and insulated parts and the heater tube inlet branch, where the inlet temperature measurement is located. With lower flow velocities the oil temperature will decrease 10 °C before reaching the heater rod assembly.

Figure 17 – Heater rod assembly and thermocouples insulated.

As both tested fluids CTO and TOP generally have components that could possibly cause clogging and solidify on colder non-insulated outer surfaces of the heater rod assembly, it was of interest to see how a properly insulated setup will behave. One test run with proper insulation around the bare metal parts of the heater rod assembly was conducted. The insu-lated heater rod assembly is presented in Figure 17. For this test, TOP 2135 sample was decided to be used, as it had most fluctuation on outlet temperature during the previous test runs (R460 and R450), however R450 had slightly lower initial line tracing temperature used and therefore R460 was used as reference to compare the data between un-insulated (R460) and insulated (R465) test runs. Effect of insulation is seen in Figure 18 below.

Figure 18 – Effect of insulation, rod 330 °C

Logically, improving the insulation, both inlet and outlet temperature did rise during test run except the very first minutes when test had not yet stabilized properly. When ignoring the lowest and the highest temperature differences at 2 min and 840 min run times, the average temperature increase in inlet was +17.4% and in outlet +11.6% when the heater rod assem-bly was well insulated. Also, it can be seen that when the test run was well stabilized after 60 minutes, the insulated heater rod assembly and connecting lines were actually conducting heat so well that it started to heat the feed already upsteam from the inlet temperature meas-urement point. When the inlet line heater was set to maximum of 95 °C and other upstream line heaters to 90 °C, the feed was already at 101 … 104 °C when reaching the inlet temper-ature measurement point.

TOP 2135 Insulated / Non-insulated Flow speed 1mm/s

Insulated Outlet Non-Insulated Outlet Insulated inlet Non-Insulated inlet