Method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment

Abstract

Disclosed is a method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment. The method solves the issues in the existing techniques that includes narrow predicting range, high workload in installation and maintenance, and time lag in predicting corrosion and spontaneous combustion inside equipment. The method comprises a step of a dual index system prediction, which includes a step of monitoring a temperature and a step of detecting SO.sub.2 gas generated by spontaneous combustion. The time when spontaneous combustion occurs can be accurately calculated by using a fitted quantitative relationship formula generated by the spontaneous combustion of corrosion products. The method has a low Labor cost. The method has a low labor cost and, does not require on-site gas detection to be carried out by means of manual detection, which both reduces the cost and ensures the detection accuracy.

Claims

1. A method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment, comprising the steps of using a dual index prediction system that further comprises: monitoring a temperature, further comprising: performing real-time temperature measurement using a thermocouple (2) connected on an outer wall of a sulfur-related petrochemical equipment (1), displaying the temperature measurement value on a temperature measuring instrument (3), and transmitting temperature rise data to a temperature parameter data processing device (4); comparing the temperature rise data with a critical temperature rise threshold using the temperature parameter data processing device (4) to determine whether to turn on alarm, and sending a signal to a DCS central control system (5) when turning on alarm is needed; and turning on alarm by the DCS central control system (5) after receiving the signal; and monitoring SO.sub.2 gas generated from spontaneous combustion, further comprising: measuring the SO.sub.2 gas concentration in the sulfur-related petrochemical equipment (1) by a wireless SO.sub.2 gas detector (7) connected to the sulfur-related petrochemical equipment (1), determining a degree of sulfidation in the sulfur-related petrochemical equipment (1) based on the SO.sub.2 gas concentration, and transmitting the degree of sulfidation data to a gas concentration parameter data processing device (6); selecting a critical SO.sub.2 gas concentration value from a fitted formula corresponding to the degree of sulfidation; using the gas concentration parameter data processing device (6), comparing degree of sulfidation data to the critical SO.sub.2 gas concentration value from the fitted formula corresponding to the degree of sulfidation to determine whether to turn on alarm, and sending another signal to the DCS central control system (5) when turning on alarm is needed; and turning on alarm by the DCS central control system (5) after receiving the signal or the another signal; wherein the critical temperature rise threshold Δ T.sub.s, is calculated from the formula
ΔT.sub.s=C.sub.sΔT.sub.max wherein Δ T.sub.s is the critical temperature rise threshold that predicts the spontaneous combustion fire in the sulfur-related petrochemical equipment (1) and is measured in Celsius; wherein C.sub.s is a safety control coefficient; more preferably, C.sub.s=0.5 is used by default; C.sub.s=0.2 to 0.8 is adopted in large space buildings; and wherein Δ T.sub.max is the maximum temperature rise that is reached in the initial stage of oxidation when a spontaneous combustion fire occurs in the petrochemical equipment (1), T.sub.max is measured in Celsius.

2. The method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment according to claim 1, wherein Δ T.sub.s is capped at 30° C., wherein when an internal temperature of the sulfur-related petrochemical equipment (1) is above 30° C., a cooling procedure is activated to lower the temperature of the sulfur-related petrochemical equipment (1).

3. The method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment according to claim 1, wherein the critical SO.sub.2 gas concentration value γ.sub.s from the fitted formula corresponding to the degree of sulfidation is calculated as:
γ.sub.s=C.sub.sγ.sub.max wherein γ.sub.s is critical SO.sub.2 gas concentration value that predicts the spontaneous combustion fire in the sulfur-related petrochemical equipment (1) and is measured in mg/ul; wherein C.sub.s is a safety control coefficient, with a range of 0.2 to 0.8; and wherein γ.sub.max is the maximum concentration of SO.sub.2 gas.

4. The method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment according to claim 3, wherein corrosion status in the sulfur-related petrochemical equipment (1) includes mild sulfidation and advanced sulfidation.

5. The method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment according to claim 4, further comprising: providing the following fitted formula that describe the relationship between SO.sub.2 gas concentration γ and reaction time t;
γ=−3×10.sup.−9t.sup.5+2×10.sup.−7t.sup.4−3×10.sup.−6t.sup.3−0.0002t.sup.2+0.0055t−0.0101  for mild sulfidation;
γ=−5×10.sup.−7t.sup.4+4×10.sup.−5t.sup.3−0.0012t.sup.2+0.0129t−0.0125  for advanced sulfidation; wherein γ is SO.sub.2 gas concentration in the sulfur-related petrochemical equipment (1), t is reaction time and measured by minutes; calculating the corresponding time t.sub.max when γ reaches a maximum value γ.sub.max, by finding the first derivative on both sides of the above formula and assuming $\frac{\mathrm{dy}}{\mathrm{dt}}=0;$ obtaining γ.sub.max by substituting ta into the formula; wherein the critical SO.sub.2 gas concentration value γ.sub.s that predicts the spontaneous combustion fire is set at 0.017 mg/ul in mild sulfidation; and wherein the critical SO.sub.2 gas concentration value γ.sub.s that predicts the spontaneous combustion fire is set at 0.012 mg/ul in advanced sulfidation.

6. The method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment according to claim 1, wherein corrosion status in the sulfur-related petrochemical equipment (1) includes mild sulfidation and advanced sulfidation.

7. The method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment according to claim 6, further comprising: providing the following fitted formula that describes the relationship between SO.sub.2 gas concentration γ and reaction time t;
γ=−3×10.sup.−9t.sup.5+2×10.sup.−7t.sup.4−3×10.sup.−6t.sup.3−0.0002t.sup.2+0.0055t−0.0101  for mild sulfidation;
γ=−5×10.sup.−7t.sup.4+4×10.sup.−5t.sup.3−0.0012t.sup.2+0.0129t−0.0125  for advanced sulfidation; wherein γ is SO.sub.2 gas concentration in the sulfur-related petrochemical equipment (1), t is reaction time and measured by minutes; calculating the corresponding time t.sub.max when γ reaches a maximum value γ.sub.max by finding the first derivative on both sides of the above formula and assuming $\frac{\mathrm{dy}}{\mathrm{dt}}=0;$ obtaining γ.sub.max by substituting t.sub.max into the formula; wherein the critical SO.sub.2 gas concentration value γ.sub.s that predicts the spontaneous combustion fire is set at 0.017 mg/ul in mild sulfidation; and wherein the critical SO.sub.2 gas concentration value γ.sub.s that predicts the spontaneous combustion fire is set at 0.012 mg/ul in advanced sulfidation.

8. The method for predicting corrosion and spontaneous combustion of sulfur-related petrochemical equipment according to claim 6, wherein the corrosion status in the sulfur-related petrochemical equipment (1) is mild sulfidation when SO.sub.2 gas is generated 150 seconds after initial oxidation of the spontaneously combustion; and wherein the corrosion status in the sulfur-related petrochemical equipment (1) is advanced sulfidation when SO.sub.2 gas is generated within 150 seconds of initial oxidation of the spontaneously combustion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a structural diagram showing a system for predicting corrosion and spontaneous combustion of a sulfur-related petrochemical equipment, wherein 1 refers to sulfur-related petrochemical equipment, 2 refers to thermocouple, 3 refers to temperature measuring instrument, 4 refers to temperature parameter data processing device, 5 refers to DCS central control system, 6 refers to gas concentration parameter data processing device, and 7 refers to wireless SO.sub.2 gas detector.

(2) FIG. 2 shows a flow chart of a method for predicting corrosion and spontaneous combustion of a sulfur-related petrochemical equipment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) The technical solutions of the present invention will be further described below with reference to the drawings and specific examples.

Embodiment I

(4) As shown in FIG. 1 and FIG. 2, the steps of the embodiment are:

(5) 1. Based on the size of the floating roof tank, weld a porcelain sleeve with sheathed thermocouple to the bottom of a sulfur-related petrochemical equipment (1) and to the outer wall of the sulfur-related petrochemical equipment (1) corresponding to the corrosion-prone part inside the wall and to the top of the gas phase space. The thermocouple time constant is 15 seconds. The cold terminus of the thermocouple is connected to one end of a compensation wire, and the other end of the compensation wire is connected to a temperature measuring instrument (3). The temperature measuring instrument (3) is connected with a temperature parameter data processing device.

(6) Set the critical temperature rise threshold ΔT.sub.s=30° C. at the temperature parameter data processing equipment, and obtain real-time temperatures through the thermocouple at parts of the equipment prone to corrosion and spontaneous combustion. When the temperature measured by any thermocouples exceeds the critical temperature rise threshold ΔT.sub.s=30° C., transmit the time required for the temperature to rise to the critical temperature rise threshold, i.e., the critical time (t ΔT.sub.s), to the DCS system for further processing.

(7) After the corrosion spontaneous combustion occurs, the temperature measuring instrument (3) provides a feedback of the reaction start time, by combining with the time of occurrence of the SO.sub.2 gas detected by the wireless SO.sub.2 gas detector (7), analysis is performed to determine the degree of sulfidation of the corrosives in the floating roof tank. Choose, according to the degree of sulfidation, a fitted formula describing quantitative relationship between the SO.sub.2 gas concentration and time; obtain γ.sub.max, i.e., the maximum concentration of SO.sub.2 gas under research conditions, and γ.sub.s, i.e., critical SO.sub.2 gas concentration value. Meanwhile, measure the SO.sub.2 gas concentration in the sulfur-related petrochemical equipment (1) in real time using the wireless SO.sub.2 gas detector (7), and feedback the SO.sub.2 concentration value every 10 seconds through the wireless SO.sub.2 gas detector (7). If the measured SO.sub.2 gas concentration reaches the critical SO.sub.2 gas concentration value, another warning signal is needed, the time required for the storage tank SO.sub.2 gas concentration to reach the critical SO.sub.2 gas concentration value (tγ.sub.s) is fed back to the DCS system (5).

(8) When the time required for the temperature to rise to the critical temperature rise threshold, i.e., the critical time (t Δ T.sub.s), is transmitted or fed to the DCS system (5), or when the time required for the storage tank SO.sub.2 gas concentration to reach the critical SO.sub.2 gas concentration value (tγ.sub.s) is fed back to the DCS system (5), or when both times are fed back to the DCS system (5), the DNS control phase will turning on an alarm for an early warning that corrosion spontaneous combustion occurs in the floating roof, to provide operators with early warning.