METHOD FOR DETECTING OPERATIONAL FAILURES

Abstract

The present invention is related to the field of detection of operational failures, more specifically with the monitoring of head loss in equipment such as reactors, heat exchangers and adsorption vessels. The invention uses a method for continuous monitoring of equipment head loss, in order to assist in the early identification and action on this type of problem, avoiding or reducing losses resulting from its occurrence.

Claims

1- A METHOD FOR DETECTING OPERATIONAL FAILURES, characterized in that it comprises: 1. calculating the current (from the plant) and limit (from the equipment design) normalized equipment head loss values from equation (1): $\Delta \mathrm{Pnormalized}=\left(\Delta P\right)\times {\left(\frac{W_{\mathrm{ref}\mathrm{head}}}{W_{\mathrm{head}}}\right)}^{1.89}\times {\left(\frac{R_{\mathrm{gas}/\mathrm{ref}\mathrm{head}}}{R_{\mathrm{gas}/\mathrm{head}}}\right)}^{0.88}$ 2. calculating the evolution rate of the current normalized ΔP, from the angular coefficient of the line of historical values; 3. calculating the moving average of current and limit normalized ΔPs, using historical values; 4. designing the time for the equipment to reach the normalized ΔP limit value, using the moving average values calculated in item 3 and the rate calculated in item 2, based on equations (2) and (3): $\mathrm{Time}\Delta P\mathrm{limit}=\frac{\left(\Delta P_{\mathrm{normalized}\mathrm{limit}\left(\mathrm{moving}\mathrm{average}\right)}-\Delta P_{\mathrm{current}\mathrm{normalized}\left(\mathrm{moving}\mathrm{average}\right)}\right)}{\mathrm{rate}},$ $\mathrm{and}\mathrm{Date}\Delta P\mathrm{limit}=\left(\mathrm{Time}\Delta P\mathrm{limit}\right)+\left(\mathrm{current}\mathrm{date}\right);$ 5. calculating the remaining campaign time from Equation (4):
Remaining campaign time=(expected date of the end of the campaign)−(current date); 6. calculating R from Equation (5): $R=\frac{\mathrm{Time}\Delta P\mathrm{limit}}{\mathrm{Remaining}\mathrm{campaign}\mathrm{time}};$ 7. issuing the alert level.

2- THE METHOD according to claim 1, characterized in that it calculates the evolution rate of the current normalized ΔP from the angular coefficient of the line of historical values between 10 and 100 days.

3- THE METHOD according to claim 2, characterized in that it calculates the evolution rate of the current normalized ΔP from the angular coefficient of the line of historical values, preferably between 20 and 60 days.

4- THE METHOD according to claim 3, characterized in that it calculates the evolution rate of the current normalized ΔP from the angular coefficient of the straight line of historical values, preferably in the interval of the last 45 days.

5- THE METHOD according to claim 1, characterized in that it calculates the moving average of the current and limit normalized ΔPs between 10 and 100 days.

6- THE METHOD according to claim 5, characterized in that it calculates the moving average of the current and limit normalized ΔPs preferably between 20 and 60 days.

7- THE METHOD according to claim 6, characterized in that it calculates the moving average of the current and limit normalized ΔPs, more preferably in the interval of the last 45 days.

8- THE METHOD according to claim 1, characterized in that item 7 has the following alert levels: Level 0—indication of level 0; Level 1—Level 1 indication and 80% “different from zero” indication in the last 20 days; Level 2—Level 2 indication on the day and 80% “different from zero” indication in the last 14 days; Level 3—Level 3 indication on the day and 80% “different from zero” indication in the last 7 days.

9- THE METHOD according to claims 1 and 8, characterized in that the alert levels are available in the unit control system or in the unit monitoring system.

10- THE METHOD according to claim 1, characterized in that the equipment is selected from reactors, heat exchangers and adsorption vessels with porous beds.

11- THE METHOD according to claim 10, characterized in that the reactors are preferably selected from fluid catalytic bed reactors, dripping bed reactors, continuous flow reactors, continuous stirred tank reactors.

12- THE METHOD according to claim 11, characterized in that the fluid catalytic bed reactors are preferably selected from the fluid catalytic cracking reactors.

13- THE METHOD according to claim 11, characterized in that the dripping bed reactors are preferably selected from the hydrotreatment reactors.

14- THE METHOD according to claims 10, 11, 12, and 13, characterized in that the equipment is preferably selected from reactors, heat exchangers and adsorption systems in oil exploration and production areas, natural gas processing and petroleum refining units.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0034] There follows below a detailed description of a preferred embodiment of the present invention, by way of example and in no way limiting. Nevertheless, it will be clear to a technician skilled on the subject, from reading this description, possible additional embodiments of the present invention still comprised by the essential and optional features below.

[0035] The method for evaluating the head loss of equipment is described as follows: [0036] 1. calculating the current (from the plant) and limit (from the equipment design) normalized ΔP values from equation (1):

[00001]$\Delta \mathrm{Pnormalized}=\left(\Delta P\right)\times {\left(\frac{W_{\mathrm{ref}\mathrm{head}}}{W_{\mathrm{head}}}\right)}^{1.89}\times {\left(\frac{R_{\mathrm{gas}/\mathrm{ref}\mathrm{head}}}{R_{\mathrm{gas}/\mathrm{head}}}\right)}^{0.88}$ [0037] 2. calculating the evolution rate of the current normalized ΔP, from the angular coefficient of the line of historical values; [0038] 3. calculating the moving average of current and limit normalized ΔPs, using historical values; [0039] 4. designing the time for the unit to reach the normalized ΔP limit value, using the moving average values calculated in item 3 and the rate calculated in item 2, based on equations (2) and (3):

[00002]$\mathrm{Time}\Delta P\mathrm{limit}=\frac{\left(\Delta P_{\mathrm{normalized}\mathrm{limit}\left(\mathrm{moving}\mathrm{average}\right)}-\Delta P_{\mathrm{current}\mathrm{normalized}\left(\mathrm{moving}\mathrm{average}\right)}\right)}{\mathrm{rate}},$$\mathrm{and}\mathrm{Date}\Delta P\mathrm{limit}=\left(\mathrm{Time}\Delta P\mathrm{limit}\right)+\left(\mathrm{current}\mathrm{date}\right);$ [0040] 5. calculating the remaining campaign time from Equation (4):

Remaining campaign time=(expected date of the end of the campaign)−(current date); [0041] 6. calculating R from Equation (5):

[00003]$R=\frac{\mathrm{Time}\Delta P\mathrm{limit}}{\mathrm{Remaining}\mathrm{campaign}\mathrm{time}};$ [0042] 7. issuing the alert level in the unit monitoring system.

[0043] The issuance of the alert level is given according to the following criteria: [0044] a) Level 0—indication of level 0 on the day (Table 1)—no alert; [0045] b) Level 1—Indication level 1 on the day (Table 1) and 80% indication “different from zero” in the last 20 days; [0046] c) Level 2—Level 2 indication on the day (Table 1) and 80% “different from zero” indication in the last 14 days [0047] d) Level 3—Indication level 3 on the day (Table 1) and 80% indication “different from zero” in the last 7 days.

[0048] Historical values show the range of 10 to 100 days of operation, preferably 20 to 60 days of operation and more preferably in the last 45 days of operation.

[0049] Table 1 presents the alert levels, shown below.

TABLE-US-00001 TABLE 1 Remaining campaign time × R Campaign Time R Remaining 0.25- 0.33- 0.4- 0.5- 0.7- 1- (days) <0.25 0.33 0.4 0.5 0.7 1 1.5 >1.5 <180 3 3 3 3 3 3 1 0 180-270 3 3 3 3 3 3 0 0 270-360 3 3 3 3 3 2 0 0 360-450 3 3 3 3 2 1 0 0 450-540 3 3 3 2 1 0 0 0 540-720 3 3 2 1 1 0 0 0 >729 3 2 2 1 1 0 0 0 Key: 0—Normal situation; 1—minor problem; 2—medium problem; 3—severe problem.

EXAMPLES

[0050] The following examples are presented in order to more fully illustrate the nature of the present invention and the way to practice the same, without, however, being considered as limiting its content.

[0051] In the following examples, the methodology used to monitor head loss performed the daily monitoring of the evolution rate of this variable using historical data for the last 45 days. Next, the remaining time for safe operation of the unit was designed. The identification of the head loss problem occurs when the designed operating time is lower than the scheduled operating time. The method allows issuing an alert where it is most convenient, such as in the unit control system or if it exists in a unit monitoring system, so that the refinery engineering and operation can act on the unit in order to identify the cause(s) of the problem and seek to avoid losses resulting from the event. For cases where it is not possible to identify the cause(s) or the identified problem has no solution, the early detection promoted by the method allows the refinery to reduce the losses resulting from this event and prepare for a scheduled shutdown, which has a lower cost than an emergency shutdown.

Example 1

[0052] The diesel HDT (hydrotreatment) unit of refinery A, which has 5 reactors, operated with head loss values between 1.5 and 3.5 kgf/cm.sup.2 (147.1 and 343.2 KPa) in each reactor and a total scheduled operating time of 2,200 days. After day 1,800, the first two reactors had head loss values above the historical average and a constant upward trend, reaching critical values for the unit operation after 1,950 days of operation. The methodology detected and signaled the problem from day 1790 of operation.

Example 2

[0053] The diesel HDT unit of refinery B, which has 3 reactors, operated with head loss values between 1.0 and 3.0 kgf/cm.sup.2 (98.07 and 294.2 KPa) in each reactor and a total scheduled operating time of 1.110 days. After day 750, one of the reactors showed head loss values above the historical average and a constant upward trend, reaching critical values for the unit operation after 866 days of operation. The methodology detected and signaled the problem for the first time after 667 days of operation, returning to indicate a situation of normality a few days later. The second detection, definitively, occurred from day 735 of operation.

Example 3

[0054] The diesel HDT unit of refinery C, which has 4 reactors, operated with head loss values between 1.0 and 3.0 kgf/cm.sup.2 (98.07 and 294.2 KPa) in each reactor and a total scheduled operating time of 2,169 days. After day 356, one of the reactors showed head loss values above the historical average and a constant upward trend, reaching critical values for the unit operation after 576 days of operation. The methodology detected and signaled the problem after 341 days of operation. In this case, the refinery team was unable to identify the causes of the problem, but using the developed method allowed the refinery to prepare for a scheduled shutdown. Without using the method, the refinery would identify the problem when it was already in a serious situation and the unit would be shut down on an emergency basis, resulting in greater disbursement by the refinery.