A natural gas deep integration processing system and method

Abstract

The application discloses a natural gas deep integration processing system and method, and belongs to the field of chemical separation technology. Raw material natural gas enters a three-stage compression device in a raw gas separation and compression unit, after separation, compression and cooling, light components enter a demercuration unit for demercuration, a deacidification unit for deacidification and an alkali purification unit for removal of organic sulfur, then pass through a precooling unit and a dehydration unit and are sent into a low-temperature separation unit, the separated purified gas is partly sent out as a product, partly used as fuel gas, and the other part is used as regeneration gas to enter the dehydration unit for regeneration. Hydrocarbon condensate generated by each unit is treated by a process condensate stripping unit and then enters a deethanizer for separation, and heavy components are sent into a depropanizer after alkali washing and are cut into liquefied petroleum gas and C4 / C5 mixed fraction products. In the system, a heat conducting oil unit uses tail gas of the raw gas separation and compression unit to provide heat for the system, and a propane refrigeration unit provides cold energy for the system. The system has high product purity and low energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation technology, specifically relating to a deep integrated natural gas processing system and method. Background Technology

[0002] In the natural gas processing sector, with the large-scale development of large gas fields, the processing capacity demand for single natural gas processing units is gradually expanding. Raw natural gas typically contains hydrogen sulfide, carbon dioxide, organic sulfur, mercury, moisture, and heavy hydrocarbon components such as ethane and propane. To meet the requirements of commercial natural gas for calorific value, dew point, and impurity content, while simultaneously recovering high-value ethane and higher-value hydrocarbons, a processing technology integrating deep purification, condensate recovery, and product fractionation needs to be constructed.

[0003] However, as equipment scales up, the requirements for product yield, energy consumption, and environmental protection become increasingly stringent, revealing numerous shortcomings in existing, poorly integrated processing solutions. Regarding cold energy utilization, the cold energy configuration of the mercury removal and pre-cooling dehydration units is limited and fails to form a cascaded coupling with the propane refrigeration unit, resulting in high refrigeration compression power consumption. In terms of thermal integration, heat recovery in the mercury removal and acid removal units is insufficient, and the heat transfer oil unit suffers significant waste heat loss. In wastewater treatment, the treatment depth of sulfur-containing wastewater and waste alkali generated by the process condensate stripping and alkali purification units is inadequate. In tail gas treatment, the efficiency of the sulfur recovery and thermal oxidation units decreases when the composition of the feed gas fluctuates, making it difficult to consistently meet emission standards for pollutants such as sulfur dioxide. Furthermore, the fuel gas pipeline network lacks refined control methods, forcing some gas to be vented, resulting in energy waste. Overall, existing systems struggle to simultaneously achieve high natural gas recovery rates, deep impurity removal, and energy system optimization, especially at ultra-large-scale processing volumes, highlighting the challenges of utility consumption and environmental pressures.

[0004] Therefore, there is an urgent need to develop a large-scale, highly efficient, and deep natural gas treatment system and method that is highly integrated, utilizes energy in stages, removes impurities thoroughly, and meets stringent environmental protection requirements. This system should ensure the efficient recovery of high-purity natural gas and hydrocarbon products while significantly reducing the plant's overall energy consumption and emissions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to provide a deep integrated natural gas processing system and method.

[0006] The specific technical solution adopted in this invention is as follows:

[0007] In a first aspect, the present invention provides a natural gas deep integrated processing system, including a feed gas separation and compression unit, a mercury removal unit, an acid removal unit, a precooling unit, a dehydration unit, a low-temperature separation unit, an ethane removal unit, an alkali purification unit, a propane refrigeration unit, a propane removal tower, a fuel gas separator, a process condensate stripping unit, a thermal oxidizer, a heat transfer oil unit, and a sulfur recovery unit.

[0008] The three-stage compression unit in the feed gas separation and compression unit receives feed natural gas from upstream, and after three-stage separation, compression, and cooling, it is connected to the high-pressure buffer tank. The light component gas phase outlet at the top of the high-pressure buffer tank is connected to the hot-side inlet of the feed gas cooler in the mercury removal unit, and the hot-side outlet of the feed gas cooler is connected to the feed gas separator. The gas phase outlet at the top of the feed gas separator is connected to the cold-side inlet of the feed gas heater, and the cold-side outlet of the feed gas heater is connected to the mercury removal tower. The gas phase outlet at the top of the mercury removal tower is connected to the acid gas absorption tower in the acid removal unit.

[0009] The gas phase outlet at the top of the acid gas absorption tower is connected to the alkali washing tower in the alkali purification unit; the gas phase outlet at the top of the alkali washing tower is connected to the hot-side inlet of the raw material gas heater; the hot-side outlet of the raw material gas heater is connected to the hot-side inlet of the purified gas cooler in the pre-cooling unit; the hot-side outlet of the purified gas cooler is connected to the cold-side inlet of the raw material gas cooler; the cold-side outlet of the raw material gas cooler is connected to the dehydration tower in the dehydration unit; the gas phase outlet at the top of the dehydration tower is connected to the hot-side inlet of the dry gas cooler in the low-temperature separation unit; the hot-side outlet of the dry gas cooler is connected to the absorption tower after passing through the dry gas expander.

[0010] The gas phase outlet at the top of the absorption tower is divided into three branches. The first branch is piped out of the boundary area and connected to the downstream purified gas product recovery device. The second branch is connected to the inlet of the fuel gas separator. The third branch returns to the dehydration unit and passes through the regenerated gas heater, dehydration tower, and regenerated gas cooler in sequence before connecting to the regenerated gas separator. The gas phase outlet at the top of the regenerated gas separator and the gas phase outlet at the top of the flash tank are respectively connected to the first-stage separator of the three-stage compression equipment through pipelines for natural gas recovery.

[0011] The fuel gas outlet at the top of the fuel gas separator is divided into two branches. One branch is connected to the thermal oxidizer after pressure reduction, and the other branch is connected to the inlet of the gas turbine in the feed gas separation and compression unit. The outlet of the gas turbine is connected to the hot side inlet of the thermal oil heater. The combustion exhaust gas from the hot side outlet of the thermal oil heater is directly discharged at high altitude. The condensate outlet at the bottom of the fuel gas separator is connected to the first-stage separator in the three-stage compression equipment for condensate recovery.

[0012] The bottom liquid phase outlets of all separators in the three-stage compression unit of the raw gas separation and compression unit, the bottom heavy oil phase outlet of the three-phase separator in the deethane removal unit, and the bottom liquid phase outlet of the regenerated gas separator in the dehydration unit are all connected to the stripping separator in the process condensate stripping unit via pipelines; the oil phase outlet at the bottom of the stripping separator is connected to the deethane removal tower, and the liquid phase outlet at the bottom of the stripping separator is connected to the stripping tower; the gas phase outlet at the top of the stripping separator is connected to the thermal oxidizer; and the wastewater outlet at the bottom of the stripping tower is connected to the boundary area.

[0013] The three-phase separator receives natural gas condensate and condensate oil from upstream, as well as hydrocarbon condensate from the bottom of the feed gas separator and the purified gas separator. The gas phase outlet at the top and the light oil phase outlet at the bottom of the three-phase separator are connected to the gas phase and liquid phase inlets of the deethanizer, respectively. The light component outlet at the top of the deethanizer is connected to the first-stage separator of the three-stage compression unit, and the heavy component outlet at the bottom of the deethanizer is connected to the settling separator after passing through the alkali mixer in the alkali purification unit. The oil phase outlet of the settling separator and the liquid phase outlet at the bottom of the absorption tower are connected to the propane de-isolation tower via pipelines. The wastewater outlet at the bottom of the settling separator is connected to the boundary area. The gas phase outlet at the top of the settling separator is connected to the thermal oxidizer.

[0014] The heat transfer oil unit receives heat from the exhaust gas of the raw gas separation and compression unit, and provides heat to the system through the heat transfer oil as a high-temperature medium; the propane refrigeration unit provides cooling capacity to the precooling unit, the low-temperature separation unit and the propane removal tower, forming a propane refrigeration cycle; the sulfur recovery unit receives acid gas from the deacidification unit, and obtains elemental sulfur product through the desulfurization process.

[0015] Preferably, the heat transfer oil unit includes a heat transfer oil circulation pump and a high-level expansion tank; the outlet of the heat transfer oil circulation pump is connected to the cold side inlet of the heat transfer oil heater in the raw material gas separation and compression unit through a pipeline; the cold side outlet of the heat transfer oil heater is connected to the inlet of the high-level expansion tank; the outlet of the high-level expansion tank provides heat transfer oil to the location where the system requires a high-temperature heat source, and the heat transfer oil returns to the inlet of the heat transfer oil circulation pump after completing the heating.

[0016] Preferably, the propane refrigeration unit is equipped with a propane compressor and a propane condenser, and the propane refrigeration cycle is specifically configured as follows:

[0017] The hot-side outlet of the propane condenser is divided into two branches. One branch returns to the propane compressor after evaporating in the refrigerant channel of the purified gas cooler in the precooling unit. The other branch returns to the propane compressor after evaporating in the refrigerant channel of the dry gas cooler in the low-temperature separation unit. The outlet of the propane compressor is connected to the inlet of the propane condenser, forming a propane refrigeration cycle.

[0018] Preferably, the sulfur recovery unit employs a wet oxidation desulfurization process to recover elemental sulfur components from the acid gas; the sulfur recovery unit includes a desulfurization tower and a regeneration tank, with the specific connection method as follows:

[0019] The liquid phase outlet at the bottom of the acid gas absorption tower is connected to the flash tank; the liquid phase outlet at the bottom of the flash tank is connected to the amine regeneration tower; the acid gas outlet at the top of the amine regeneration tower is connected to the desulfurization tower via a pipeline; the liquid phase outlet at the bottom of the desulfurization tower is connected to the regeneration tank, and the gas phase outlet at the top of the desulfurization tower is connected to the thermal oxidizer; sulfur foam is obtained by flotation at the top of the regeneration tank, and elemental sulfur is sent out of the boundary area via a pipeline; the desulfurization lean liquid at the bottom of the regeneration tank is connected to the liquid phase inlet at the top of the desulfurization tower.

[0020] Preferably, the top outlet and bottom outlet of the propane stripper are connected to the boundary area via pipelines, and are respectively connected to the downstream liquefied petroleum gas recovery unit and the heavy component mixed fraction recovery unit.

[0021] Preferably, the mercury removal tower is filled with a solid adsorbent for adsorbing elemental mercury, wherein the solid adsorbent is one or more of activated carbon, alumina, or molecular sieve.

[0022] Preferably, the deacidification unit adopts a wet deacidification process using an alkanolamine solution, wherein the acid gas absorption tower is equipped with an alkanolamine solution circulation loop for absorbing acidic components in the raw material gas.

[0023] Preferably, the dehydration unit includes two dehydration towers connected in parallel, both of which are filled with molecular sieve adsorbent; the dehydration unit adopts a variable temperature adsorption process, and operates alternately in a manner where one tower adsorbs and dehydrates while the other tower is heated and regenerated.

[0024] Secondly, the present invention provides a method for utilizing the natural gas deep integrated processing system described in the first aspect, the specific steps of which are as follows:

[0025] S1: Raw material natural gas purification and treatment:

[0026] Raw natural gas from upstream enters the raw gas separation and compression unit. After three stages of separation, compression, and cooling, it enters the mercury removal unit to remove trace amounts of mercury. The mercury-removed natural gas then enters the acid removal unit to remove acidic components, followed by the alkali purification unit for deep removal of organic sulfur. The natural gas after organic sulfur removal first returns to the mercury removal unit to recover cooling energy, and then enters the pre-cooling unit for further cooling. The pre-cooled natural gas returns to the mercury removal unit again to provide pre-cooling energy, and after its own heating, it enters the dehydration unit for deep drying. The dehydrated natural gas enters the low-temperature separation unit, where it is cooled by a dry gas cooler and expanded by a dry gas expander before entering the absorption tower for low-temperature separation. The gas phase obtained at the top of the absorption tower is divided into three parts: one part is sent out of the boundary as qualified purified gas product, one part is returned to the dehydration unit as regeneration gas, and the remaining part enters the fuel gas separator as fuel gas. The flash vapor obtained from the flash tank in the acid removal unit and the gas regenerated by the dehydration tower in the dehydration unit are returned to the first-stage separator of the three-stage compression equipment in the raw gas separation and compression unit to achieve material recovery.

[0027] S2: Process condensate stripping treatment:

[0028] The stripping separator in the process condensate stripping unit receives heavy condensate from the bottom of all separators in the three-stage compression unit, heavy oil condensate from the bottom of the three-phase separator, and heavy condensate from the bottom of the regenerated gas separator, and performs separation treatment. The hydrocarbon condensate obtained from the oil phase outlet at the bottom of the stripping separator enters the de-ethanizer in the de-ethanizer unit for recovery. The liquid phase generated at the bottom of the stripping separator is treated in the stripping tower to obtain wastewater, which is discharged into the boundary area. The acid gas generated at the top of the stripping separator enters the thermal oxidizer for harmless treatment.

[0029] S3: Ethane removal and gas fractionation treatment:

[0030] The three-phase separator in the deethane removal unit receives natural gas condensate and condensate oil from the boundary area, as well as hydrocarbon condensate from the bottom of the feed gas separator and the purified gas separator, and performs preliminary separation. The gas phase obtained from the top of the three-phase separator and the light oil phase obtained from the bottom are respectively fed into the deethane removal tower for processing. The light component obtained from the top of the deethane removal tower is returned to the first-stage separator of the three-stage compression equipment for recovery, and the heavy component obtained from the bottom of the deethane removal tower is fed into the alkali purification unit for deep removal of organic sulfur. The heavy component with removed organic sulfur is fed into the depropane removal tower for fractionation, and liquefied petroleum gas and C4 / C5 mixed fraction are respectively sent out of the boundary area as products.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) The system provided by this invention breaks down the energy barriers between units and constructs a tiered network for the utilization of cooling and heating, with the propane refrigeration unit and the heat transfer oil unit as the core. Specifically, the cooling requirements of the mercury removal unit and the dehydration unit are incorporated into the temperature design of the propane refrigeration unit to achieve tiered cooling supply. At the same time, the waste heat of the high-temperature exhaust gas discharged from the gas turbine is directly transferred to the heat transfer oil unit, so that the waste heat of the exhaust gas can be directly used for the needs of various high-temperature heat sources in the system, which greatly reduces the overall energy consumption of the system.

[0033] (2) This invention systematically solves the problem of incomplete treatment of sulfur-containing wastewater and waste alkali in traditional natural gas processing units by organically linking the process condensate stripping unit, alkali purification unit, sulfur recovery unit, and thermal oxidizer. The process condensate stripping unit adopts a high-efficiency stripping process to finely separate the light and heavy components in the hydrocarbon-containing condensate discharged from each unit, ensuring that the recovered hydrocarbons meet the requirements of subsequent deep processing, while significantly reducing the interfering components entering the sulfur recovery unit. Combined with the efficiency-enhancing design of the front-end mercury removal, acid removal, and dehydration units, the sulfur recovery unit and thermal oxidizer can maintain high conversion rates and thermal oxidation efficiency even when the feed gas fluctuates significantly, effectively stabilizing the emission levels of pollutants such as sulfur dioxide.

[0034] (3) The present invention includes a pre-cooling unit before the dehydration unit to pre-cool and reduce the temperature of the purified gas before it enters the molecular sieve dehydration tower, thereby pre-condensing and separating most of the heavy hydrocarbon components and reducing the saturation of heavy hydrocarbons in the gas phase. On the one hand, this avoids the problem of heavy hydrocarbons being released with water vapor in the dehydration unit, resulting in oil in the wastewater; on the other hand, it effectively protects the molecular sieve bed from heavy hydrocarbon contamination, ensuring long-term stability of the dehydration operation. At the same time, the deacidification unit condenses the heavy hydrocarbon components, thereby inhibiting the foaming contamination of the alkanolamine solution (such as MDEA) from the source, stabilizing the deacidification index, protecting the activity of the solvent and adsorbent, and reducing the load and freezing blockage risk of the downstream low-temperature separation unit, significantly extending the safe operation cycle of the entire unit.

[0035] (4) This invention achieves separation of C1 / C2 light components and C3 by sending the hydrocarbon condensate generated by each unit into the deethaner unit for distillation. + The efficient separation of heavy components is achieved. Simultaneously, utilizing the high-temperature distillation environment within the deethaner column, trace amounts of water carried in the condensate are distilled off from the top of the column along with the lighter components, resulting in a nearly anhydrous heavy hydrocarbon product in the bottom liquid. This effectively avoids the adverse effects of moisture on subsequent alkaline washing desulfurization and propane dedistillation processes, thus improving C3 efficiency. + The improved quality of the recombinant components also provides excellent feeding conditions for downstream deep processing.

[0036] (5) The system provided by this invention is adaptable to natural gas feedstocks of different sources and compositions, has high operational flexibility, and the device can maintain stable and efficient operation over a wide range of operating conditions. The mercury content in the purified natural gas obtained after processing by this invention is less than 0.01 μg / Nm³. 3 The CO2 impurity content is less than 50 ppmv, the water content is less than 1 ppmv, and the sulfur content is less than 0.1 ppmv. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the overall process of the natural gas deep integrated processing system provided by the present invention;

[0038] Figure 2 This is a schematic diagram showing the specific connections of the natural gas deep integrated processing system provided in this embodiment;

[0039] In the diagram: Raw material gas separation and compression unit 1, gas turbine 1-1, heat transfer oil heater 1-2, three-stage compression equipment 1-3, high-pressure buffer tank 1-4, mercury removal unit 2, raw material gas cooler 2-1, raw material gas separator 2-2, raw material gas heater 2-3, mercury removal tower 2-4, acid removal unit 3, acid gas absorption tower 3-1, amine liquid regeneration tower 3-2, flash tank 3-3, precooling unit 4, purified gas cooler 4-1, purified gas separator 4-2, dehydration unit 5, dehydration tower 5-1, regeneration gas heater 5-2, regeneration gas cooler 5-3, regeneration gas separator... Unit 5-4, Low-temperature separation unit 6, Dry gas cooler 6-1, Dry gas expander 6-2, Absorption tower 6-3, Ethane removal unit 7, Three-phase separator 7-1, Ethane removal tower 7-2, Alkali purification unit 8, Alkali washing tower 8-1, Alkali mixer 8-2, Settling separator 8-3, Propane refrigeration unit 9, Propane compressor 9-1, Propane condenser 9-2, Propane removal tower 10, Fuel gas separator 11, Process condensate stripping unit 12, Stripping separator 12-1, Stripping tower 12-2, Thermal oxidizer 13, Heat transfer oil unit 14, Sulfur recovery unit 15. Detailed Implementation

[0040] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0041] like Figure 1As shown, in a preferred embodiment of the present invention, this embodiment provides a deep integrated natural gas processing system. The system includes a feed gas separation and compression unit 1, a mercury removal unit 2, an acid removal unit 3, a precooling unit 4, a dehydration unit 5, a cryogenic separation unit 6, an ethane removal unit 7, an alkali purification unit 8, a propane refrigeration unit 9, a propane removal tower 10, a fuel gas separator 11, a process condensate stripping unit 12, a thermal oxidizer 13, a heat transfer oil unit 14, and a sulfur recovery unit 15. The feed gas separation and compression unit 1 includes a gas turbine 1-1, a heat transfer oil heater 1-2, a three-stage compression device 1-3, and a high-pressure buffer tank 1-4. The mercury removal unit 2 includes a feed gas cooler 2-1, a feed gas separator 2-2, a feed gas heater 2-3, and a mercury removal tower 2-4. The acid removal unit 3 includes an acid gas absorption tower 3-1, an amine regeneration tower 3-2, and a flash tank 3-3. The precooling unit 4 includes a purified gas cooler 4-1 and a purified gas separator 4-2. The dehydration unit 5 includes a dehydration tower 5-1, a regenerated gas heater 5-2, a regenerated gas cooler 5-3, and a regenerated gas separator 5-4. The low-temperature separation unit 6 includes a dry gas cooler 6-1, a dry gas expander 6-2, and an absorption tower 6-3. The ethane removal unit 7 includes a three-phase separator 7-1 and an ethane removal tower 7-2. The alkali purification unit 8 includes an alkali washing tower 8-1, an alkali mixer 8-2, and a settling separator 8-3. The propane refrigeration unit 9 includes a propane compressor 9-1 and a propane condenser 9-2. The process condensate stripping unit 12 includes a stripping separator 12-1 and a stripping tower 12-2.

[0042] In this embodiment, the three-stage compression equipment 1-3 in the raw gas separation and compression unit 1 includes a first-stage separator, a first-stage compressor, a first-stage aftercooler, a second-stage separator, a second-stage compressor, a second-stage aftercooler, a third-stage separator, a third-stage compressor, and a third-stage aftercooler connected in sequence.

[0043] Specifically, such as Figure 2 As shown, the three-stage compression unit 1-3 in the raw gas separation and compression unit 1 receives raw natural gas from upstream. After entering the three-stage compression unit 1-3, the raw natural gas sequentially passes through a first-stage separator for gas-liquid separation, a first-stage compressor for pressurization, and a first-stage aftercooler for cooling before entering a second-stage separator for gas-liquid separation. It then passes through a second-stage compressor for pressurization and a second-stage aftercooler for cooling before entering a third-stage separator for gas-liquid separation. Finally, it passes through a third-stage compressor for pressurization and a third-stage aftercooler for cooling before entering a high-pressure buffer tank 1-4.

[0044] The light component gas phase outlet at the top of the high-pressure buffer tank 1-4 is connected to the hot-side inlet of the raw material gas cooler 2-1 in the mercury removal unit 2. The hot-side outlet of the raw material gas cooler 2-1 is connected to the raw material gas separator 2-2. The raw material gas separator 2-2 has a gas phase outlet at the top and a hydrocarbon condensate outlet at the bottom, respectively. The gas phase outlet is connected to the cold-side inlet of the raw material gas heater 2-3, and the cold-side outlet of the raw material gas heater 2-3 is connected to the mercury removal tower 2-4. The raw material natural gas is first cooled in the raw material gas cooler 2-1, causing the heavy components to further condense and precipitate. It then enters the raw material gas separator 2-2 for gas-liquid separation. The separated gas phase enters the cold side of the raw material gas heater 2-3, is heated, and then sent to the mercury removal tower 2-4. In this embodiment, the mercury removal tower 2-4 is filled with a solid adsorbent for adsorbing elemental mercury. Those skilled in the art can choose one or more of activated carbon, alumina, or molecular sieves according to actual needs.

[0045] The gas phase outlet at the top of the mercury removal tower 2-4 is connected to the acid gas absorption tower 3-1 within the acid removal unit 3. In this embodiment, the acid gas absorption tower 3-1 is equipped with an alkanolamine solution circulation loop. After the mercury-removed raw natural gas enters the acid gas absorption tower 3-1, it comes into countercurrent contact with the alkanolamine solution flowing from top to bottom, and the acidic components in the raw natural gas are absorbed and removed by the alkanolamine solution. The acid gas absorption tower 3-1 has a gas phase outlet at the top and a liquid phase outlet at the bottom, respectively, with the gas phase outlet at the top connected to the alkaline scrubbing tower 8-1 within the alkaline purification unit 8. After the acid removal treatment, the raw natural gas enters the alkaline scrubbing tower 8-1 and is discharged countercurrently with the alkaline solution therein, further removing residual organic sulfur components.

[0046] The gas phase outlet at the top of the alkaline scrubbing tower 8-1 is connected to the hot-side inlet of the raw gas heater 2-3. The purified raw natural gas from the alkaline scrubbing tower 8-1 enters the raw gas heater 2-3 as a heat source, heating the cold raw gas before it enters the mercury removal tower 2-4, while simultaneously cooling itself, thus achieving heat recovery from the hot and cold streams within the system. The hot-side outlet of the raw gas heater 2-3 is connected to the hot-side inlet of the purified gas cooler 4-1 in the pre-cooling unit 4. The purified gas, after heat recovery, enters the purified gas cooler 4-1 for further cooling. The hot-side outlet of the purified gas cooler 4-1 is connected to the cold-side inlet of the raw gas cooler 2-1. After cooling in the purified gas cooler 4-1, the purified gas enters the cold side of the raw gas cooler 2-1, acting as a cold source to pre-cool the raw gas before it enters the raw gas separator 2-2. After heating itself, it exits from the cold-side outlet of the raw gas cooler 2-1.

[0047] The cold-side outlet of the raw gas cooler 2-1 is connected to the dehydration tower 5-1 in the dehydration unit 5. In this embodiment, the dehydration unit 5 includes two dehydration towers 5-1 connected in parallel, both filled with molecular sieve adsorbent. The dehydration unit 5 employs a temperature-switching adsorption process, alternating between adsorption and dehydration in one tower and heating and regeneration in the other. The purified gas from the raw gas cooler 2-1, after being heated, enters the dehydration tower 5-1 and comes into contact with the molecular sieve adsorbent inside the tower. Water vapor in the gas is adsorbed by the molecular sieve, achieving deep drying. The gas phase outlet at the top of the dehydration tower 5-1 is connected to the hot-side inlet of the dry gas cooler 6-1 in the low-temperature separation unit 6. The hot-side outlet of the dry gas cooler 6-1 is connected to the absorption tower 6-3 after passing through the dry gas expander 6-2. The dry gas obtained after deep drying is pre-cooled by dry gas cooler 6-1 and then enters dry gas expander 6-2 for adiabatic expansion. The temperature is further reduced to a low temperature, causing the heavy components in the dry gas to condense into liquid. Then it enters absorption tower 6-3 for low temperature distillation separation.

[0048] The gas phase outlet at the top of the absorption tower 6-3 is divided into three branches. The first branch is piped out of the boundary area and connected to the downstream purified gas product recovery unit. The second branch is connected to the inlet of the fuel gas separator 11. The third branch returns to the dehydration unit 5, and then passes through the regeneration gas heater 5-2, dehydration tower 5-1, and regeneration gas cooler 5-3 before connecting to the regeneration gas separator 5-4. The gas in the third branch serves as regeneration gas. After being heated to the regeneration temperature by the regeneration gas heater 5-2, it is sent to the dehydration tower 5-1 to regenerate the molecular sieve that has completed adsorption saturation. The regenerated gas, carrying the desorbed water vapor, enters the regeneration gas cooler 5-3 for cooling and then enters the regeneration gas separator 5-4 for gas-liquid separation. The gas phase outlet at the top of the regeneration gas separator 5-4 and the gas phase outlet at the top of the flash tank 3-3 are respectively connected to the first-stage separator of the three-stage compression equipment 1-3 through pipelines for natural gas recovery.

[0049] In this embodiment, the fuel gas separator 11 also receives natural gas from the boundary area. The fuel gas outlet at the top of the fuel gas separator 11 is divided into two branches. One branch, after depressurization, connects to the thermal oxidizer 13, sending a portion of the fuel gas into the thermal oxidizer 13 for use as auxiliary fuel. The other branch connects to the inlet of the gas turbine 1-1 in the feed gas separation and compression unit 1, sending a portion of the fuel gas into the gas turbine 1-1 as driving fuel. The outlet of the gas turbine 1-1 is connected to the hot-side inlet of the thermal oil heater 1-2. While the gas turbine 1-1 is burning fuel gas to do work, the high-temperature exhaust gas discharged from its outlet enters the hot side of the thermal oil heater 1-2, where it exchanges heat with the thermal oil flowing through the cold side, transferring heat to the thermal oil and thus achieving efficient recovery and utilization of waste heat from the exhaust gas. The combustion exhaust gas obtained from the hot-side outlet of the thermal oil heater 1-2 is directly discharged at high altitude. The condensate outlet at the bottom of the fuel gas separator 11 is connected to the first-stage separator in the three-stage compression equipment 1-3 for condensate recovery.

[0050] In this embodiment, the heat transfer oil unit 14 receives heat from the exhaust gas of the gas turbine 1-1 in the feed gas separation and compression unit 1, and provides heat to the system using heat transfer oil as a high-temperature medium. Specifically, the heat transfer oil unit 14 is equipped with a heat transfer oil circulation pump and a high-level expansion tank. The outlet of the heat transfer oil circulation pump is connected to the cold side inlet of the heat transfer oil heater 1-2 in the feed gas separation and compression unit 1 via a pipeline. Driven by the circulation pump, the heat transfer oil enters the cold side of the heat transfer oil heater 1-2 and exchanges heat with the high-temperature exhaust gas on the hot side to raise its temperature. The cold side outlet of the heat transfer oil heater 1-2 is connected to the inlet of the high-level expansion tank, and the heated high-temperature heat transfer oil enters the high-level expansion tank. The high-level expansion tank provides thermal expansion space for the heat transfer oil system, and its outlet is connected to each heat-using device in the system that requires a high-temperature heat source via pipelines, delivering the high-temperature heat transfer oil to each heat-using device. After the heat transfer oil completes its heating, it returns to the inlet of the heat transfer oil circulation pump.

[0051] The bottom liquid phase outlets of all separators (including primary, secondary, and tertiary separators) in the three-stage compression equipment 1-3 of the feed gas separation and compression unit 1, the bottom heavy oil phase outlet of the three-phase separator 7-1 in the deethane removal unit 7, and the bottom liquid phase outlet of the regenerated gas separator 5-4 in the dehydration unit 5 are connected to the stripping separator 12-1 in the process condensate stripping unit 12 via pipelines. After the three streams converge, they enter the stripping separator 12-1 for three-phase separation. The oil phase outlet at the bottom of the stripping separator 12-1 is connected to the deethane removal tower 7-2, and the liquid phase outlet at the bottom of the stripping separator 12-1 is connected to the stripping tower 12-2. The gas phase outlet at the top of the stripping separator 12-1 is connected to the thermal oxidizer 13. The wastewater outlet at the bottom of the stripping tower 12-2 is discharged out of the boundary area and, after passing inspection, is discharged into the subsequent wastewater treatment system.

[0052] The three-phase separator 7-1 receives natural gas condensate and condensate oil from upstream, as well as hydrocarbon condensate from the bottom of the feed gas separator 2-2 and the purified gas separator 4-2, and performs thorough separation within the separator. The gas phase outlet at the top of the three-phase separator 7-1 is connected to the gas phase inlet of the deethanizer 7-2 via a pipeline, and the light oil phase outlet at the bottom of the separator 7-1 is connected to the liquid phase inlet of the deethanizer 7-2 via a pipeline. The gas phase and light oil phase separated by the three-phase separator 7-1 are fed into the deethanizer 7-2 from different feed locations for rectification and separation.

[0053] The light component outlet at the top of the deethaner 7-2 is connected to the first-stage separator of the three-stage compression unit 1-3. The C1 / C2 light components separated at the top of the tower return to the first-stage separator and re-enter the system with the feed gas for recycling. The heavy component outlet at the bottom of the deethaner 7-2 passes through the alkali mixer 8-2 in the alkali purification unit 8 and is then connected to the settling separator 8-3. The C3 collected at the bottom of the tower... + The heavy components are thoroughly mixed with the alkali solution in the alkali mixer 8-2, where the organic sulfur components react with the alkali solution and are removed. The resulting mixture enters the settling separator 8-3 for sedimentation and stratification. The oil phase outlet of the settling separator 8-3 and the liquid phase outlet at the bottom of the absorption tower 6-3 are connected to the propane removal tower 10 via pipelines. The purified oil phase separated by the settling separator 8-3 is mixed with the C3 discharged from the bottom of the absorption tower 6-3 in the low-temperature separation unit 6. + After the hydrocarbon condensates are combined, they are sent together to propane stripper 10 for further rectification and fractionation. Propane stripper 10 will separate C3... + The components are separated into liquefied petroleum gas (LPG) and a C4 / C5 mixed fraction, PHF, which are then discharged as products from the boundary area. The wastewater outlet at the bottom of the settling separator 8-3 is connected to the boundary area, allowing the alkaline wastewater generated during the alkaline washing process to be discharged from the system after settling separation. The gas phase outlet at the top of the settling separator 8-3 is connected to the thermal oxidizer 13, and the small amount of hydrocarbon gases flashed during the alkaline washing and settling processes are sent to the thermal oxidizer 13 for incineration.

[0054] In the system provided in this embodiment, the propane refrigeration unit 9 provides cooling capacity to the precooling unit 4, the cryogenic separation unit 6, and the propane removal tower 10, forming a propane refrigeration cycle. The specific configuration is as follows: the outlet of the propane compressor 9-1 is connected to the inlet of the propane condenser 9-2. The high-temperature, high-pressure propane vapor compressed by the propane compressor 9-1 enters the propane condenser 9-2, where it is condensed into liquid propane by the cooling medium. The hot-side outlet of the propane condenser 9-2 is divided into two branches. One branch returns to the propane compressor 9-1 via the refrigerant channel inside the purified gas cooler 4-1 in the precooling unit 4, and the other branch returns to the propane compressor 9-1 via the refrigerant channel inside the dry gas cooler 6-1 in the cryogenic separation unit 6, thus forming the propane refrigeration cycle.

[0055] In the system provided in this embodiment, the sulfur recovery unit 15 adopts a wet oxidation desulfurization process, receiving acid gas from the deacidification unit 3 and obtaining elemental sulfur product through the desulfurization process. In this embodiment, the sulfur recovery unit 15 is equipped with a desulfurization tower and a regeneration tank. The specific connection method is as follows: the liquid phase outlet at the bottom of the acid gas absorption tower 3-1 is connected to the flash tank 3-3; the liquid phase outlet at the bottom of the flash tank 3-3 is connected to the amine regeneration tower 3-2. The rich amine liquid, rich in acidic components, discharged from the bottom of the acid gas absorption tower 3-1, is first sent to the flash tank 3-3 to flash-evaporate the absorbed raw material gas, and then sent to the amine regeneration tower 3-2 for heating and regeneration, releasing the acidic gas. The acid gas outlet at the top of the amine regeneration tower 3-2 is connected to the desulfurization tower through a pipeline. Inside the desulfurization tower, the acidic gas comes into countercurrent contact with the desulfurization lean liquid, is absorbed by the desulfurization liquid, and undergoes an oxidation reaction to convert into elemental sulfur. The liquid phase outlet at the bottom of the desulfurization tower is connected to the regeneration tank, and the liquid that has absorbed sulfur enters the regeneration tank for oxidation regeneration. The gas phase outlet at the top of the desulfurization tower is connected to the thermal oxidizer 13. Unreacted tail gas discharged from the top of the desulfurization tower is sent to the thermal oxidizer 13 for incineration. Elemental sulfur foam is obtained by flotation at the top of the regeneration tank. This foam is then piped out of the boundary area and undergoes subsequent filtration and sulfur melting processes to obtain elemental sulfur products. The desulfurization lean liquor at the bottom of the regeneration tank is connected to the liquid phase inlet at the top of the desulfurization tower via a pipe, circulating back to the desulfurization tower to continue participating in the desulfurization reaction, thus achieving the recycling of the desulfurization liquor.

[0056] This embodiment also provides a method for deep integrated processing of natural gas using the above-mentioned system, the specific steps of which are as follows:

[0057] S1: Raw material natural gas purification and treatment:

[0058] The raw natural gas from upstream enters the raw gas separation and compression unit 1. After three-stage separation, compression, and cooling, it enters the mercury removal unit 2 to remove trace amounts of mercury. The mercury-removed natural gas then enters the acid removal unit 3 to remove acidic components, and then enters the alkali purification unit 8 for deep removal of organic sulfur. The natural gas after organic sulfur removal first returns to the mercury removal unit 2 to recover cooling energy, and then enters the pre-cooling unit 4 for further cooling. The pre-cooled natural gas returns to the mercury removal unit 2 again to provide pre-cooling energy, and after its own heating, it enters the dehydration unit 5 for deep drying. The dehydrated natural gas then enters the low-temperature separation unit 6. After being cooled by the dry gas cooler 6-1 and expanded by the dry gas expander 6-2, the gas enters the absorption tower 6-3 for low-temperature separation. The gas phase obtained at the top of the absorption tower 6-3 is divided into three parts: one part is sent out of the boundary area as qualified purified gas product, one part is returned to the dehydration unit 5 as regeneration gas, and the remaining part is entered into the fuel gas separator 11 as fuel gas. The flash vapor obtained from the flash tank 3-3 in the deacidification unit 3 and the gas regenerated by the dehydration tower 5-1 in the dehydration unit 5 are returned to the first-stage separator of the three-stage compression equipment 1-3 in the raw material gas separation and compression unit 1 to realize material recovery.

[0059] S2: Process condensate stripping treatment:

[0060] The stripping separator 12-1 in the process condensate stripping unit 12 receives heavy phase condensate from the bottom of all separators in the three-stage compression unit 1-3, heavy oil phase condensate from the bottom of the three-phase separator 7-1, and heavy phase condensate from the bottom of the regenerated gas separator 5-4, and performs separation treatment. The hydrocarbon condensate obtained from the oil phase outlet at the bottom of the stripping separator 12-1 enters the de-ethanizer 7-2 in the de-ethanizer unit 7 for recovery. The liquid phase generated at the bottom of the stripping separator 12-1 enters the stripping tower 12-2 for treatment to obtain wastewater, which is discharged into the boundary area. The acid gas generated at the top of the stripping separator 12-1 enters the thermal oxidizer 13 for harmless treatment.

[0061] S3: Ethane removal and gas fractionation treatment:

[0062] In the deethane removal unit 7, the three-phase separator 7-1 receives natural gas condensate and condensate oil from the boundary area, as well as hydrocarbon condensate from the bottom of the feed gas separator 2-2 and the purified gas separator 4-2, and performs preliminary separation. The gas phase obtained from the top of the three-phase separator 7-1 and the light oil phase obtained from the bottom enter the deethane removal tower 7-2 for processing. The light component obtained from the top of the deethane removal tower 7-2 is returned to the first-stage separator of the three-stage compression equipment 1-3 for recovery. The heavy component obtained from the bottom of the deethane removal tower 7-2 enters the alkali purification unit 8 for deep removal of organic sulfur. The heavy component after removal of organic sulfur enters the depropane removal tower 10 for fractionation, and liquefied petroleum gas and C4 / C5 mixed fraction are sent out of the boundary area as products.

[0063] The purified natural gas obtained after this embodiment has a mercury content of less than 0.01 μg / Nm³. 3 The CO2 impurity content is less than 50 ppmv, the water content is less than 1 ppmv, and the sulfur content is less than 0.1 ppmv.

[0064] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A natural gas deep integrated processing system, characterized in that, It includes a raw gas separation and compression unit, a mercury removal unit, an acid removal unit, a precooling unit, a dehydration unit, a low-temperature separation unit, an ethane removal unit, an alkali purification unit, a propane refrigeration unit, a propane removal tower, a fuel gas separator, a process condensate stripping unit, a thermal oxidizer, a heat transfer oil unit, and a sulfur recovery unit. The three-stage compression unit in the feed gas separation and compression unit receives feed natural gas from upstream, and after three-stage separation, compression, and cooling, it is connected to the high-pressure buffer tank. The light component gas phase outlet at the top of the high-pressure buffer tank is connected to the hot-side inlet of the feed gas cooler in the mercury removal unit, and the hot-side outlet of the feed gas cooler is connected to the feed gas separator. The gas phase outlet at the top of the feed gas separator is connected to the cold-side inlet of the feed gas heater, and the cold-side outlet of the feed gas heater is connected to the mercury removal tower. The gas phase outlet at the top of the mercury removal tower is connected to the acid gas absorption tower in the acid removal unit. The gas phase outlet at the top of the acid gas absorption tower is connected to the alkali washing tower in the alkali purification unit; the gas phase outlet at the top of the alkali washing tower is connected to the hot-side inlet of the raw material gas heater; the hot-side outlet of the raw material gas heater is connected to the hot-side inlet of the purified gas cooler in the pre-cooling unit; the hot-side outlet of the purified gas cooler is connected to the cold-side inlet of the raw material gas cooler; the cold-side outlet of the raw material gas cooler is connected to the dehydration tower in the dehydration unit; the gas phase outlet at the top of the dehydration tower is connected to the hot-side inlet of the dry gas cooler in the low-temperature separation unit; the hot-side outlet of the dry gas cooler is connected to the absorption tower after passing through the dry gas expander. The gas phase outlet at the top of the absorption tower is divided into three branches. The first branch is piped out of the boundary area and connected to the downstream purified gas product recovery device. The second branch is connected to the inlet of the fuel gas separator. The third branch returns to the dehydration unit and passes through the regenerated gas heater, dehydration tower, and regenerated gas cooler in sequence before connecting to the regenerated gas separator. The gas phase outlet at the top of the regenerated gas separator and the gas phase outlet at the top of the flash tank are respectively connected to the first-stage separator of the three-stage compression equipment through pipelines for natural gas recovery. The fuel gas outlet at the top of the fuel gas separator is divided into two branches. One branch is connected to the thermal oxidizer after depressurization, and the other branch is connected to the inlet of the gas turbine in the feed gas separation and compression unit. The outlet of the gas turbine is connected to the hot side inlet of the thermal oil heater. The condensate outlet at the bottom of the fuel gas separator is connected to the first-stage separator in the three-stage compression equipment to realize condensate recovery. The bottom liquid phase outlets of all separators in the three-stage compression unit of the raw gas separation and compression unit, the bottom heavy oil phase outlet of the three-phase separator in the deethane removal unit, and the bottom liquid phase outlet of the regenerated gas separator in the dehydration unit are all connected to the stripping separator in the process condensate stripping unit via pipelines; the oil phase outlet at the bottom of the stripping separator is connected to the deethane removal tower, and the liquid phase outlet at the bottom of the stripping separator is connected to the stripping tower; the gas phase outlet at the top of the stripping separator is connected to the thermal oxidizer; and the wastewater outlet at the bottom of the stripping tower is connected to the boundary area. The three-phase separator receives natural gas condensate and condensate oil from upstream, as well as hydrocarbon condensate from the bottom of the feed gas separator and the purified gas separator. The gas phase outlet at the top and the light oil phase outlet at the bottom of the three-phase separator are connected to the gas phase and liquid phase inlets of the deethanizer, respectively. The light component outlet at the top of the deethanizer is connected to the first-stage separator of the three-stage compression unit, and the heavy component outlet at the bottom of the deethanizer is connected to the settling separator after passing through the alkali mixer in the alkali purification unit. The oil phase outlet of the settling separator and the liquid phase outlet at the bottom of the absorption tower are connected to the propane de-isolation tower via pipelines. The wastewater outlet at the bottom of the settling separator is connected to the boundary area. The gas phase outlet at the top of the settling separator is connected to the thermal oxidizer. The heat transfer oil unit receives heat from the exhaust gas of the raw gas separation and compression unit, and provides heat to the system through the heat transfer oil as a high-temperature medium; the propane refrigeration unit provides cooling capacity to the precooling unit, the low-temperature separation unit and the propane removal tower, forming a propane refrigeration cycle; the sulfur recovery unit receives acid gas from the deacidification unit, and obtains elemental sulfur product through the desulfurization process.

2. The natural gas deep integrated processing system according to claim 1, characterized in that, The heat transfer oil unit includes a heat transfer oil circulation pump and a high-level expansion tank; the outlet of the heat transfer oil circulation pump is connected to the cold side inlet of the heat transfer oil heater in the raw material gas separation and compression unit through a pipeline; the cold side outlet of the heat transfer oil heater is connected to the inlet of the high-level expansion tank; the outlet of the high-level expansion tank provides heat transfer oil to the location where the system requires a high-temperature heat source, and the heat transfer oil returns to the inlet of the heat transfer oil circulation pump after completing the heating.

3. The natural gas deep integrated processing system according to claim 1, characterized in that, The propane refrigeration unit is equipped with a propane compressor and a propane condenser. The specific configuration of the propane refrigeration cycle is as follows: The hot-side outlet of the propane condenser is divided into two branches. One branch returns to the propane compressor after evaporating in the refrigerant channel of the purified gas cooler in the precooling unit. The other branch returns to the propane compressor after evaporating in the refrigerant channel of the dry gas cooler in the low-temperature separation unit. The outlet of the propane compressor is connected to the inlet of the propane condenser, forming a propane refrigeration cycle.

4. The natural gas deep integrated processing system according to claim 1, characterized in that, The sulfur recovery unit employs a wet oxidation desulfurization process to recover elemental sulfur components from acid gas. The sulfur recovery unit includes a desulfurization tower and a regeneration tank, with the specific connection method as follows: The liquid phase outlet at the bottom of the acid gas absorption tower is connected to the flash tank; the liquid phase outlet at the bottom of the flash tank is connected to the amine regeneration tower; the acid gas outlet at the top of the amine regeneration tower is connected to the desulfurization tower via a pipeline; the liquid phase outlet at the bottom of the desulfurization tower is connected to the regeneration tank, and the gas phase outlet at the top of the desulfurization tower is connected to the thermal oxidizer; sulfur foam is obtained by flotation at the top of the regeneration tank, and elemental sulfur is sent out of the boundary area via a pipeline; the desulfurization lean liquid at the bottom of the regeneration tank is connected to the liquid phase inlet at the top of the desulfurization tower.

5. The natural gas deep integrated processing system according to claim 1, characterized in that, The top and bottom outlets of the propane removal tower are connected to the boundary area via pipelines, respectively, and are connected to the downstream liquefied petroleum gas recovery unit and the heavy component mixed fraction recovery unit.

6. The natural gas deep integrated processing system according to claim 1, characterized in that, The mercury removal tower is filled with a solid adsorbent for adsorbing elemental mercury, and the solid adsorbent is one or more of activated carbon, alumina, or molecular sieve.

7. The natural gas deep integrated processing system according to claim 1, characterized in that, The deacidification unit adopts a wet deacidification process using an alkanolamine solution, wherein the acid gas absorption tower is equipped with an alkanolamine solution circulation loop for absorbing acidic components in the raw material gas.

8. The natural gas deep integrated processing system according to claim 1, characterized in that, The dehydration unit includes two dehydration towers connected in parallel, both of which are filled with molecular sieve adsorbent. The dehydration unit adopts a variable temperature adsorption process, alternating between one tower for adsorption and dehydration and the other tower for heating and regeneration.

9. A method using the natural gas deep integrated processing system according to any one of claims 1 to 8, characterized in that, The specific steps are as follows: S1: Raw material natural gas purification and treatment: Raw natural gas from upstream enters the raw gas separation and compression unit. After three stages of separation, compression, and cooling, it enters the mercury removal unit to remove trace amounts of mercury. The mercury-removed natural gas then enters the acid removal unit to remove acidic components, followed by the alkali purification unit for deep removal of organic sulfur. The natural gas after organic sulfur removal first returns to the mercury removal unit to recover cooling energy, and then enters the pre-cooling unit for further cooling. The pre-cooled natural gas returns to the mercury removal unit again to provide pre-cooling energy, and after its own heating, it enters the dehydration unit for deep drying. The dehydrated natural gas enters the low-temperature separation unit, where it is cooled by a dry gas cooler and expanded by a dry gas expander before entering the absorption tower for low-temperature separation. The gas phase obtained at the top of the absorption tower is divided into three parts: one part is sent out of the boundary as qualified purified gas product, one part is returned to the dehydration unit as regeneration gas, and the remaining part enters the fuel gas separator as fuel gas. The flash vapor obtained from the flash tank in the acid removal unit and the gas regenerated by the dehydration tower in the dehydration unit are returned to the first-stage separator of the three-stage compression equipment in the raw gas separation and compression unit to achieve material recovery. S2: Process condensate stripping treatment: The stripping separator in the process condensate stripping unit receives heavy condensate from the bottom of all separators in the three-stage compression unit, heavy oil condensate from the bottom of the three-phase separator, and heavy condensate from the bottom of the regenerated gas separator, and performs separation treatment. The hydrocarbon condensate obtained from the oil phase outlet at the bottom of the stripping separator enters the de-ethanizer in the de-ethanizer unit for recovery. The liquid phase generated at the bottom of the stripping separator is treated in the stripping tower to obtain wastewater, which is discharged into the boundary area. The acid gas generated at the top of the stripping separator enters the thermal oxidizer for harmless treatment. S3: Ethane removal and gas fractionation treatment: The three-phase separator in the deethane removal unit receives natural gas condensate and condensate oil from the boundary area, as well as hydrocarbon condensate from the bottom of the feed gas separator and the purified gas separator, and performs preliminary separation. The gas phase obtained from the top of the three-phase separator and the light oil phase obtained from the bottom are respectively fed into the deethane removal tower for processing. The light component obtained from the top of the deethane removal tower is returned to the first-stage separator of the three-stage compression equipment for recovery, and the heavy component obtained from the bottom of the deethane removal tower is fed into the alkali purification unit for deep removal of organic sulfur. The heavy component with removed organic sulfur is fed into the depropane removal tower for fractionation, and liquefied petroleum gas and C4 / C5 mixed fraction are respectively sent out of the boundary area as products.

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