Method for evaluating slag quantity of dry pulverized coal gasification furnace in real time

Abstract

The invention relates to the technical field of coal chemical industry, in particular to a method for evaluating the slag quantity of a dry pulverized coal gasifier in real time, which comprises the following steps: arranging a thermometer in a slag pool of the dry pulverized coal gasifier, arranging a thermometer and a flowmeter behind a quenching water heat exchanger, and arranging a regulating valve on a cooling water outlet pipeline of the quenching water heat exchanger; adjusting the outlet flow Q of the slag water circulating pump to be a constant value according to the reading of the flowmeter; the temperature t of the quenching water after the quenching water heat exchanger is controlled to be a constant value by using a regulating valve and a temperature controller of a cooling water outlet pipeline; based on the principle that the specific heat capacity of quenching water and molten slag and the temperature of the molten slag before quenching are constant, the real-time slag production amount of the gasifier is calculated through a preset formula, the method for evaluating the slag production amount of the dry pulverized coal gasifier in real time can evaluate the slag production amount of the dry pulverized coal gasifier in real time, guide personnel to carry out as-fired coal operation adjustment, and improve the slag production amount of the dry pulverized coal gasifier. Frequent fluctuation of the slag yield of the gasifier is avoided, and safe and stable operation of the burner cover and the slag conveyor is ensured.

Description

A method for real-time assessment of dry pulverized coal gasification slag quantity Technical Field

[0001] This invention relates to the field of coal chemical technology, and in particular to a method for real-time evaluation of the amount of dry pulverized coal gasification slag. Background Technology

[0002] The dry pulverized coal pressurized gasifier is designed with four coal burners arranged in a "corner-circle" configuration to form a combustion reaction zone inside the furnace (as shown in Figure 1). Pulverized coal and oxygen are fully contacted and combusted inside the furnace through the coal burners. After the pulverized coal is completely combusted in the combustion reaction zone of the gasifier, the lighter components become fly ash, which is mixed with syngas and transported to the subsequent systems; the heavier components become slag, which is thrown onto the water-cooled wall near the coal burners by centrifugal force.

[0003] Unlike conventional thermal power boilers, the water-cooled walls of the dry pulverized coal pressurized gasifier, both in the reaction zone and below, are equipped with pins and silicon carbide wear-resistant linings. The slag from the combustion of pulverized coal is thrown onto the water-cooled walls with pins and wear-resistant linings. Due to gravity, the liquid slag, after being thrown onto the water-cooled walls, begins to flow towards the gasifier's slag discharge port. As the slag flows downward, it undergoes localized heat transfer with the pins on the water-cooled walls, causing the slag temperature to gradually decrease. Finally, it flows through the gasifier's slag discharge port into the liquid slag pool for quenching, and is then intermittently discharged to the slag removal machine via slag collection tanks and slag discharge tanks (as shown in Figure 2).

[0004] The coal fed into the gasifier often needs to be mixed with several types of coal before use. In actual operation, the uniformity of the coal after mixing is of great concern to prevent the amount of slag produced by the gasifier from fluctuating. This can lead to slag overflow in the gasifier burner hood and increase the instantaneous operating load of the slag remover. In severe cases, it can cause accidents such as burner hood leakage and slag remover chain breakage, threatening the safe and stable operation of the gasifier.

[0005] Currently, the only way to assess the slag production level of a gasifier is by weighing the slag removed by the slag remover. This method can only statistically analyze the average level of slag production over a period of time and has a significant lag. Technicians cannot promptly assess the uniformity of the coal blending process to guide adjustments to the coal blending operation. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention is proposed.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for real-time evaluation of the amount of slag in a dry pulverized coal gasification furnace, comprising: installing a thermometer in the slag pool of the dry pulverized coal gasification furnace; installing a thermometer and a flow meter after the quenching water heat exchanger; installing a regulating valve on the cooling water outlet pipeline of the quenching water heat exchanger; adjusting the outlet flow rate Q of the slag-water circulation pump to a constant value according to the flow meter reading; controlling the quenching water temperature t_quenching water after the quenching water heat exchanger to a constant value using the regulating valve and temperature controller of the cooling water outlet pipeline; and calculating the real-time slag production of the gasification furnace using a preset formula based on the specific heat capacity of the quenching water and molten slag and the principle that the molten slag temperature is constant before quenching.

[0008] As a preferred embodiment of the method for real-time evaluation of dry pulverized coal gasification slag quantity described in this invention, the thermometers in the slag pool are arranged at 120° intervals around the slag pool, with a total of 3 thermometers. The water temperature tslag pool in the slag pool is the average value of the 3 thermometer measurements, i.e., tslag pool = (tslag pool 1 + tslag pool 2 + tslag pool 3) / 3.

[0009] As a preferred embodiment of the method for real-time evaluation of dry coal gasification slag quantity described in this invention, the constant control of the outlet flow rate Q of the slag-water circulation pump is achieved by adjusting the outlet manual valve of the slag-water circulation pump, and the temperature controller is configured logically through the DCS screen to achieve constant temperature control of the quenching water temperature.

[0010] As a preferred embodiment of the method for real-time evaluation of the amount of dry pulverized coal gasification slag described in this invention, the specific heat capacity C of the slag is in the range of 1.2 to 1.3 kJ / kg·℃, preferably 1.25 kJ / kg·K.

[0011] As a preferred embodiment of the method for real-time evaluation of the amount of dry pulverized coal gasification slag described in this invention, the slag temperature t before quenching is related to the gasifier temperature and the ash melting point FT of the coal fed into the furnace. The gasifier temperature is controlled at about 200°C higher than the FT slag temperature, the FT slag temperature is about 1250°C, and the gasifier temperature is about 1450°C.

[0012] As a preferred embodiment of the method for real-time evaluation of the amount of dry pulverized coal gasification slag described in this invention, wherein: Where α is a coefficient related to the temperature of the molten slag.

[0013] As a preferred embodiment of the method for real-time evaluation of the amount of dry pulverized coal gasification slag described in this invention, the slag inlet radius r is approximately 1 m, and the slag pool liquid surface blackness is approximately 0.98.

[0014] As a preferred embodiment of the method for real-time evaluation of the amount of slag in a dry pulverized coal gasification furnace as described in this invention, the latent heat of vaporization generated by the contact between quenching water and molten slag is negligible relative to the radiative heat transfer of the gasifier.

[0015] As a preferred embodiment of the method for real-time evaluation of the amount of dry pulverized coal gasification slag described in this invention, wherein the radiative heat transfer of the gasifier is calculated according to Boltzmann's law, and the Boltzmann constant is taken as 5.67×10-8W / m2・K4.

[0016] As a preferred embodiment of the method for real-time evaluation of dry pulverized coal gasification slag quantity described in this invention, it further includes establishing a trend curve of real-time slag production Qslag of the gasifier on the DCS screen, with the interval between two adjacent time points of the curve being 1 second.

[0017] The beneficial effects of the present invention are as follows: The method for real-time evaluation of the amount of slag in a dry pulverized coal gasifier provided by the present invention can evaluate the amount of slag produced by the dry pulverized coal gasifier in real time, guide the personnel to adjust the coal feeding operation, avoid frequent fluctuations in the amount of slag produced by the gasifier, and ensure the safe and stable operation of the burner hood and slag remover. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Among them: Figure 1 is a schematic diagram of "four-corner tangential circle" combustion of coal burners in a gasifier.

[0019] Figure 2 is a schematic diagram of the liquid slag discharge process of the gasifier.

[0020] Figure 3 is a schematic diagram of the additional equipment required for calculating the slag discharge of the gasifier. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0024] Referring to Figures 1-3, specifically, a thermometer is installed in the slag pool of the dry pulverized coal gasifier, and a thermometer and flow meter are installed after the quenching water heat exchanger. A regulating valve is installed on the cooling water outlet pipeline of the quenching water heat exchanger. Based on the flow meter reading, the outlet flow rate Q of the slag-water circulation pump is adjusted to a constant value. The temperature t of the quenching water after the quenching water heat exchanger is controlled to a constant value using the regulating valve and temperature controller of the cooling water outlet pipeline. Based on the specific heat capacity of the quenching water and molten slag, and the principle that the molten slag temperature is constant before quenching, the real-time slag production of the gasifier is calculated using a preset formula.

[0025] Three thermometers are placed around the slag pool at 120° intervals. The water temperature tslag pool in the slag pool is the average value of the three thermometer measurements, i.e., tslag pool = (tslag pool 1 + tslag pool 2 + tslag pool 3) / 3. The constant flow rate Q of the slag water circulation pump is achieved by adjusting the outlet manual valve. The temperature controller is logically configured through the DCS screen to achieve constant temperature control of the quenching water. The specific heat capacity Cslag of the molten slag ranges from 1.2 to 1.3 kJ / kg·℃, preferably 1.25 kJ / kg·K.

[0026] The slag temperature (t) before quenching is related to the gasifier temperature and the ash melting point (FT) of the incoming coal. The gasifier temperature is controlled approximately 200°C higher than the FT of the slag temperature. The FT value for the slag is approximately 1250°C, and the gasifier temperature is approximately 1450°C. Where α is a coefficient related to the temperature of the molten slag.

[0027] The radius of the slag inlet of the gasifier, rslag inlet, is approximately 1 m. The emissivity of the liquid surface in the slag pool is approximately 0.98. The latent heat of vaporization generated by the contact between the quenching water and the molten slag is negligible compared to the radiative heat transfer of the gasifier. The radiative heat transfer of the gasifier is calculated according to Boltzmann's law, and the Boltzmann constant is taken as 5.67 × 10-8 W / m2・K4. The system also includes establishing a trend curve of the real-time slag production Qslag of the gasifier on the DCS screen, with the interval between two adjacent time points on the curve being 1 second.

[0028] A thermometer is installed in the slag pool, and a thermometer and flow meter are installed after the quenching water heat exchanger. A regulating valve is installed on the cooling water outlet pipeline of the quenching water heat exchanger (as shown in Figure 3). Based on the flow meter reading, the outlet flow rate Q of the slag-water circulation pump is adjusted to a constant value. The temperature t of the quenching water after the quenching water heat exchanger is controlled to a constant value using the regulating valve and temperature controller on the cooling water outlet pipeline. The formula is introduced as follows: Wherein, tslag pool is the average water temperature at various points within the slag pool; tmolten slag is the temperature of the molten slag before quenching, which is related to the gasifier temperature and the ash melting point of the incoming coal. Generally, the gasifier temperature is controlled at approximately 200°C higher than the ash melting point of the incoming coal (FTmolten slag). After heat exchange through the water-cooled wall, the slag flowing through the slag inlet... According to empirical formulas, the latent heat of vaporization of quenching water when it comes into contact with molten slag is... According to Boltzmann's law, the radiative heat transfer from the gasifier furnace to the slag pool via the slag inlet can be calculated. .

[0029] By transforming the above formula, the real-time slag production of the gasifier can be obtained: Given that the carbon content (Cslag) is between 1.2 and 1.3 kJ / kg·℃, the specific value of Cslag is influenced by the proportion of various oxides in the slag. In this calculation formula, let Cslag = ... 1.25 kJ / kg·K As a correction factor for C (slag); known C (quenching water) = 4.184 kJ / kg·K; Q (evaporation water volume) is extremely small, and the latent heat of vaporization generated by the contact between quenching water and slag is negligible compared to the radiative heat transfer in the gasifier; Boltzmann constant. =5.67×10⁻⁸ W / m²·K⁴; Blackness of the liquid surface in the gasification furnace slag pool ≈0.98; FT molten slag ≈1250℃; T gasifier ≈1450℃; T slag pool temperature is generally controlled below 50℃; slag opening radius r is generally around 1m. Based on the above information, calculate... The value is approximately equal to 0. Therefore, the calculation formula can be simplified to obtain the real-time slag production of the gasifier: .

[0030] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A method for real-time assessment of the amount of dry pulverized coal gasification slag, characterized in that: This includes installing a thermometer in the slag pool of the dry pulverized coal gasifier, installing a thermometer and a flow meter after the quenching water heat exchanger, and installing a regulating valve on the cooling water outlet pipeline of the quenching water heat exchanger; adjusting the outlet flow rate Q of the slag-water circulation pump to a constant value based on the flow meter reading; controlling the quenching water temperature t of the quenching water after the quenching water heat exchanger to a constant value using the regulating valve and temperature controller of the cooling water outlet pipeline; and calculating the real-time slag production of the gasifier using a preset formula based on the specific heat capacity of the quenching water and molten slag, and the principle that the molten slag temperature is constant before quenching.

2. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 1, characterized in that: The thermometers in the slag pool are arranged at 120° intervals around the slag pool, with a total of 3 thermometers. The water temperature tslag pool in the slag pool is the average value of the 3 thermometer measurements, i.e., tslag pool = (tslag pool 1 + tslag pool 2 + tslag pool 3 3. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 2, characterized in that: By adjusting the outlet manual valve of the slag-water circulation pump, the constant control of the outlet flow rate Q of the slag-water circulation pump can be achieved. The temperature controller is logically configured through the DCS screen to achieve constant temperature control of the quenching water temperature.

4. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 3, characterized in that: The specific heat capacity C of the slag is in the range of 1.2 to 1.3 kJ / kg·℃, preferably 1.25 kJ / kg·K.

5. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 4, characterized in that: The slag temperature t before quenching is related to the gasifier temperature and the ash melting point FT of the coal fed into the furnace. The gasifier temperature is controlled at about 200°C higher than the FT slag temperature. The FT slag temperature is about 1250°C and the gasifier temperature is about 1450°C.

6. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 5, characterized in that: Where α is a coefficient related to the temperature of the molten slag.

7. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 6, characterized in that: The radius r of the gasifier slag inlet is approximately 1m, and the blackness of the slag pool surface is approximately 0.

98.

8. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 7, characterized in that: The latent heat of vaporization generated by the contact between quenching water and molten slag is negligible compared to the radiative heat transfer of the gasifier.

9. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 8, characterized in that: The radiative heat transfer of the gasifier is calculated according to Boltzmann's law, and the Boltzmann constant is taken as 5.67×10-8W / m2・K4.

10. The method for real-time evaluation of the amount of dry pulverized coal gasification slag as described in claim 9, characterized in that: It also includes establishing a trend curve of the real-time slag production Q_slag of the gasifier on the DCS screen, with the interval between two adjacent time points on the curve being 1 second.

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