Non-condensable gas treatment method for thermal desorption of oil-based rock debris

Abstract

The invention relates to the field of environment-friendly treatment of oil gas, and particularly discloses a non-condensable gas treatment method for thermal desorption of oil-based rock debris, which comprises the following steps: feeding non-condensable gas into an alkali liquor tank to absorb acid gas, and then feeding the non-condensable gas into a water separation tank to separate water and impurities; the non-condensable gas discharged from the water separation tank is filtered and pressurized, then is fed into the incinerator for combustion, is firstly combusted and oxidized in a combustion chamber at the rear section of the incinerator, the hearth temperature is more than or equal to 850 DEG C, the flue gas retention time is more than or equal to 1.5 S, then enters a cooling chamber at the front section for water spraying quenching, and is discharged from a flue gas outlet at the front end after the flue gas temperature is reduced to 200 DEG C or below. The invention has the advantages of simple process, good safety and reliability, complete oxygenolysis after combustion, up-to-standard emission of flue gas, and long service life of equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas environmental protection, in particular to a non-condensable gas treatment method for oil-based drilling debris thermal desorption. BACKGROUND

[0002] In recent years, oil-based drilling debris thermal desorption treatment technology has been widely used in oil-based drilling debris environmental protection due to its advantages such as oil content in residue less than 0.3% and oil recovery rate higher than 75%. The thermal desorption process is mainly physical reaction. The oil-based drilling debris absorbs heat on the surface, the temperature rises rapidly, and water and oil hydrocarbons move violently to desorb from the surface of the oil-based drilling debris. The oil and water vapor is then liquefied and recovered by the condensing system. Part of the gas that cannot be condensed and liquefied is called non-condensable gas. The treatment of non-condensable gas has the following characteristics: 1) complex and unstable composition, containing combustible gas (methane, hydrogen), oxygen, acid gas (H2S, CO2), oil mist, dust, etc., and the gas volume fluctuates greatly, which can change between 5~90Nm 3 / h; 2. High heat value fluctuation, high treatment difficulty. 3. Contains oxygen, has the risk of flash explosion, contains oil mist, which is easy to adhere to the surface of the pipeline or nozzle, forming carbon deposition or blockage, affecting the service life and reliability of the equipment. The existing non-condensable gas of oil-based drilling debris thermal desorption is treated by direct venting and burning, which is not completely decomposed by burning, and there is a problem of environmental pollution.

[0003] CN115838602A discloses an oil-based drilling debris treatment system, which only discloses that the non-condensable gas is sent into a dehydration purification tower for treatment and then sent back to a thermal phase separation device. CN118699032A discloses an oil-based drilling debris resource treatment method and its application, which records that the non-condensable gas is used as fuel. The problem of direct burning as fuel is not solved. SUMMARY

[0004] The purpose of the present application is to solve the above technical problems, and to provide a non-condensable gas treatment method for oil-based drilling debris thermal desorption, which is simple in process, safe and reliable, completely oxidized after burning, flue gas can be discharged up to standard, and the service life of the equipment is long.

[0005] The technical solution is to first send the non-condensable gas into a water separation tank to separate water and impurities, and then send it into a lye tank to absorb acid gas. The non-condensable gas out of the lye tank is filtered and pressurized, then sent into a incinerator for burning, first burned and oxidized in the combustion chamber at the rear section of the incinerator, the furnace temperature is ≥850℃, and the flue gas residence time is ≥1.5S, then enters the cooling chamber at the front section for water injection quenching, and the flue gas temperature is reduced to below 200℃ and discharged from the front flue gas outlet.

[0006] When the non-condensable gas flow of the alkali liquor tank is less than or equal to the single-strand set value, single-strand feeding is adopted; when the non-condensable gas flow is greater than the single-strand set value, two-strand feeding is adopted, and the two strands of non-condensable gas are filtered, pressurized and then ignited and combusted through the same burner before entering the incinerator.

[0007] The filtering includes coarse filtering and fine filtering, and the non-condensable gas is first filtered through the coarse filter to remove large particles, and then filtered through the fine filter to remove small particles.

[0008] The coarse filter is a bag-type dust collector, and the fine filter is a ceramic fiber filter.

[0009] The non-condensable gas is further filtered through an oil mist filter after the fine filtering, and the oil mist filter is used to remove small oil droplets.

[0010] The alkali liquor tank includes three-stage alkali liquor tanks, and the non-condensable gas flows through the three-stage alkali liquor tanks in sequence, wherein the alkali liquor concentration in the first-stage alkali liquor tank is 5-8 wt%, the alkali liquor concentration in the second-stage alkali liquor tank is 2-4 wt%, and the alkali liquor concentration in the third-stage alkali liquor tank is 0.5-1 wt% or clean water.

[0011] The incinerator is a horizontal type, and the combustion chamber is divided into a main combustion zone, a reburning zone and a burnout zone from back to front, and the combustion chamber is combusted by using staged air supply, including providing the main combustion zone of the combustion chamber with first-stage air of 50%~60% of the total air volume, providing the reburning zone with second-stage air of 30%~40% of the total air volume, and providing the burnout zone with third-stage air of 10%~20% of the total air volume.

[0012] The main combustion zone accounts for 60%~70% of the volume of the combustion chamber, the reburning zone accounts for 20%~30% of the volume of the combustion chamber, and the burnout zone accounts for 10%~20% of the volume of the combustion chamber.

[0013] The O2 concentration of the first-stage air is 15%~18%, the O2 concentration of the second-stage air is 10%~12%, and the O2 concentration of the third-stage air is 5%~8%.

[0014] The cooling chamber is provided with a plurality of cooling water guns for water spray quenching.

[0015] Beneficial effects: 1) According to the characteristics of the non-condensable gas for oil-based drilling debris thermal desorption, the non-condensable gas is pretreated before entering the incinerator, the water and impurities such as mud and sand are separated in the water distribution tank, then the non-condensable gas enters the alkali liquor tank to absorb acidic gases, remove H2S, CO2 and other acidic gases, reduce corrosiveness, further remove dust, increase pressure to adapt to gas fluctuation, maintain constant pressure at the incinerator inlet, ensure uniform combustion power field, avoid backfire or insufficient combustion caused by pressure fluctuation, and meet the requirements of entering the furnace; 2) Preferably, three-stage alkali liquid tanks are arranged, the first-stage alkali liquid tank is a main absorption section, the alkali liquid concentration is 5-8 wt%, 80% of hydrogen sulfide and most of organic acids can be removed; the second-stage alkali liquid tank is a deep purification section, the alkali liquid concentration is 2-4 wt%, residual acid gas is removed and ph is stabilized; the third-stage alkali liquid tank is an emergency standby section, 0.5-1 wt% alkali liquid or clean water is used to prevent trace penetration, and effective removal of acid gas is ensured by using three-stage alkali liquid gradient absorption.

[0016] 3) A combustion chamber and a cooling chamber are arranged in the incinerator, the furnace temperature is strictly controlled to be greater than or equal to 850 DEG C, and the flue gas residence time is greater than or equal to 1.5 S to ensure that the organic matter is completely decomposed, the temperature of the discharged flue gas is controlled in combination with quenching to inhibit the generation of dioxin, and the damage of high-temperature flue gas to the pipeline is reduced.

[0017] 4) In view of the problem that the amount of non-condensable gas fluctuates in a large range, two pipelines are arranged after the water separation tank, and corresponding filtering and boosting equipment are matched, when the gas amount is small, one standby is used, when the gas amount is large, two pipelines are started at the same time, which is good in flexibility and adaptability, compared with only one pipeline, smaller power and volume of equipment can be selected, equipment investment and operation energy consumption are effectively saved, and emergency situations when one pipeline or equipment fails can also be coped with.

[0018] 5) Three-stage processes of coarse filtration, fine filtration and oil mist filtration are adopted, coarse filtration (such as a bag dust collector) removes particles greater than 50 μm, fine filtration (such as a ceramic fiber filter element) intercepts dust of 1-5 μm to reduce the plugging of the incineration nozzle by oil sludge, and an oil mist filter (such as an electrostatic trap) intercepts gaseous oil droplets to prevent them from adhering to form tar or plugging the nozzle in the high-temperature zone. The three work together to reduce the interference of particulate matter on the combustion process, improve the decomposition rate of organic matter, reduce the content of volatile organic compounds (VOCs) in flue gas, further reduce the generation of NOx precursors, reduce the maintenance frequency of the incineration system, and improve the operation continuity.

[0019] 6) A staged air supply design is adopted, the oxygen content of each stage of air is gradually reduced, the main combustion zone is rich in oxygen for combustion to inhibit thermal NOx, and the reduction atmosphere (low O2) in the reburning zone reduces the generated NOx to N2, achieving low nitrogen emission; the staged air supply optimizes the power field to ensure that the organic matter is fully oxidized at 850 DEG C, and the decomposition rate is greater than or equal to 99.9%; a small amount of air is supplemented in the burnout zone to reduce the carbon content of fly ash; and zoned oxygen control can avoid local oxygen enrichment or oxygen deficiency to prevent the risk of flash explosion.

[0020] 7) The method can adapt to a large range of gas fluctuations, the removal rate of organic matter is greater than or equal to 99.9%, the energy consumption is reduced by 20%-30%, and NOx is less than 150 mg / Nm 3 , which is better than the 200 mg / Nm 3 limit value of GB 18484-2020. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Flow chart of the present application.

[0022] Figure 2 Schematic diagram of the incinerator in the method of the present application.

[0023] Wherein, 1-combustion chamber, 1.1-main combustion zone, 1.2-reburning zone, 1.3-combustion completion zone, 2-cooling chamber, 3-cooling water gun, 4-burner, 5-incondensable gas interface. DETAILED DESCRIPTION

[0024] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0025] In the following examples, the single-strand set value of the incondensable gas (composition see Table 1) flow is 90 Nm 3 / h, each incondensable gas pipeline corresponds to a matching filter and a booster device, wherein the coarse filter uses a bag-type dust collector, the fine filter uses a ceramic fiber filter, the oil mist filter uses an oil mist filter, and the booster step uses a variable frequency booster fan matched with a backflow regulating valve to maintain stable inlet pressure.

[0026] Table 1: Incondensable gas composition Referring to Figure 2 , the incinerator in the method of the present application is horizontal, two incondensable gas interfaces 5 are connected to the rear burner 5, the rear section is the combustion chamber 1, which is sequentially divided into the main combustion zone 1.1, the reburning zone 1.2 and the combustion completion zone 1.3 from back to front, and the front section is the cooling chamber 2, which is provided with multiple cooling water guns 3 for water quenching. Figure 2 It is only a schematic diagram, the air inlets of the main combustion zone 1.1, the reburning zone 1.2 and the combustion completion zone 1.3 are not shown in the figure, but the present application indicates that the primary air, the secondary air and the tertiary air correspond to the main combustion zone 1.1, the reburning zone 1.2 and the combustion completion zone 1.3, so it does not affect the understanding of the person skilled in the art.

[0027] Example 1: When the incondensable gas flow is ≤90 Nm 3When the flow rate of the non-condensable gas is 120 Nm3 / h, the non-condensable gas is first separated from water in a water separation tank, and then the acidic gas is removed in a three-stage alkali tank, wherein the alkali concentration in the first-stage alkali tank is controlled to be 5-8 wt%, the alkali concentration in the second-stage alkali tank is controlled to be 2-4 wt%, and the alkali concentration in the third-stage alkali tank is controlled to be 0.5-1 wt% alkali or clean water. An online alkali density meter can be arranged at the outlet of each alkali tank to analyze and calculate the alkali concentration in the alkali tank in real time or at a fixed time. If the alkali concentration is lower than the corresponding range, concentrated alkali is automatically added. If the alkali concentration is higher than the corresponding range, the addition of concentrated alkali is stopped. The non-condensable gas discharged from the third-stage alkali tank is intercepted by a bag filter to remove particles larger than 50 μm, filtered by a ceramic fiber filter to remove dust of 1-5 μm, and then removed from small oil droplets by an electrostatic oil mist filter. After being pressurized to meet the operating pressure requirement of the furnace, the non-condensable gas enters a horizontal incinerator. The combustion chamber 1 is supplied with air in three stages, i.e., primary combustion zone (first-stage air: 60% of the total air volume, O2 15%-18% by volume), re-combustion zone (second-stage air: 30% of the total air volume, O2 10%-12% by volume), and burnout zone (third-stage air: 10% of the total air volume, O2 5%-8% by volume). The furnace chamber temperature is maintained at 850-1000℃, and the flue gas residence time is ≥1.5 seconds. After combustion, the flue gas enters the cooling chamber 2 and is rapidly cooled to below 200℃ by a plurality of atomizing water guns. The discharged flue gas (see Table 2 for sampling results) has an organic matter decomposition rate of ≥99.9% and NOx<150 mg / Nm 3 , and the energy consumption of single-line processing is reduced by 25%.

[0028] Table 2 Example 2 When the flow rate of the non-condensable gas is 120 Nm 3When h, the non-condensable gas first separates moisture through a water trap, and then removes acidic gas through a three-stage lye tank, wherein the lye concentration in the first-stage lye tank is controlled at 5-8 wt%, the lye concentration in the second-stage lye tank is controlled at 2-4 wt%, and the lye concentration in the third-stage lye tank is controlled at 0.5-1 wt% lye or clean water; the non-condensable gas from the third-stage lye tank is divided into two streams, which are respectively intercepted by corresponding bag filters to remove particles above 50 μm, ceramic fiber filters to remove dust of 1-5 μm, and electrostatic oil mist filters to remove small oil droplets, and then are respectively introduced into the combustor 5 of the horizontal incinerator 5 through corresponding two non-condensable gas interfaces 5 after being pressurized to 10 kPa±10%. The combustion chamber 1 of the incinerator has a main combustion zone (primary air: 65% of the total air volume, O2 concentration 16% by volume), a reburning zone (secondary air: 25% of the total air volume, O2 concentration 11% by volume), and a burnout zone (tertiary air: 10% of the total air volume, O2 concentration 56% by volume), and is supplied with air in stages to maintain the furnace temperature at 850-1000℃ and the flue gas residence time to be ≥1.5 seconds. The flue gas after combustion is rapidly cooled to below 200℃ by a plurality of groups of atomizing water guns in the cooling chamber 2 and is discharged. The flue gas after combustion is rapidly cooled to below 200℃ by a plurality of groups of atomizing water guns in the cooling chamber 2 and is discharged. The discharged flue gas (see Table 3 for sampling results) has an organic matter decomposition rate of ≥99.9% and NOx<150 mg / Nm 3 , and the comprehensive energy consumption is reduced by 15% compared with the single-line mode.

[0029] Table 3

Claims

1. A method for treating non-condensable gas from thermal desorption of oil-based rock cuttings, characterized in that, The non-condensable gas is first sent to a water separator to separate moisture and impurities, and then sent to an alkali tank to absorb acidic gases. The non-condensable gas exiting the alkali tank is filtered, pressurized, and then sent to the incinerator for combustion. It first undergoes combustion and oxidation in the combustion chamber at the rear of the incinerator, with a furnace temperature ≥850℃ and a flue gas residence time ≥1.5S. Then it enters the cooling chamber at the front for rapid cooling by water spraying, reducing the flue gas temperature to below 200℃ before being discharged from the flue gas outlet at the front.

2. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 1, characterized in that, When the non-condensable gas flow rate from the alkali tank is less than or equal to the single-stream set value, single-stream feeding is adopted. When the non-condensable gas flow rate is greater than the single-stream set value, it is divided into two streams. The two streams of non-condensable gas are filtered and pressurized separately, and then ignited and burned by the same burner before entering the incinerator.

3. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 1 or 2, characterized in that, The filtration includes coarse filtration and fine filtration. Non-condensable gas is first filtered by coarse filtration to remove large particles, and then filtered by fine filtration to remove small particles.

4. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 3, characterized in that, The coarse filter uses a bag filter, and the fine filter uses a ceramic fiber filter.

5. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 3, characterized in that, The fine filter is then subjected to oil mist filtration, where tiny oil droplets are removed.

6. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 1 or 2, characterized in that, The alkali solution tank includes a three-stage alkali solution tank, through which non-condensable gas flows sequentially. The concentration of alkali solution in the first-stage alkali solution tank is controlled at 5-8 wt%, the concentration in the second-stage alkali solution tank is controlled at 2-4 wt%, and the concentration in the third-stage alkali solution tank is 0.5-1 wt% alkali solution or water.

7. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 1 or 2, characterized in that, The incinerator is horizontal, and its combustion chamber is divided into a main combustion zone, a re-combustion zone, and a burnout zone from back to front. The combustion chamber adopts staged air supply for combustion: including providing 50% to 60% of the total air volume to the main combustion zone, providing 30% to 40% of the total air volume to the re-combustion zone, and providing 10% to 20% of the total air volume to the burnout zone.

8. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 7, characterized in that, The main combustion zone occupies 60% to 70% of the combustion chamber volume, the re-combustion zone occupies 20% to 30% of the combustion chamber volume, and the burnout zone occupies 10% to 20% of the combustion chamber volume.

9. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 7, characterized in that, The O2 concentration for Level 1 wind is 15%~18% by volume, for Level 2 wind it is 10%~12% by volume, and for Level 3 wind it is 5%~8% by volume.

10. The method for treating non-condensable gas from thermal desorption of oil-based rock cuttings as described in claim 1 or 2, characterized in that, The cooling chamber is equipped with multiple cooling water guns for rapid cooling.

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