CN101265425B - Method for reducing heat value of gaseous liquefied natural gas - Google Patents
Method for reducing heat value of gaseous liquefied natural gas Download PDFInfo
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Abstract
The invention relates to a method for reducing the heat value of the gaseous liquefied natural gas. The method comprises the following process steps: firstly, the liquefied natural gas is gasified; secondly, the gasified liquefied natural gas is decompressed; thirdly, the pre-reforming is performed to the gasified liquefied natural gas; fourthly, the pre-reformed gas is reacted in a convector to form reformed gas, and fifthly, the reformed gas treatment is performed. The components of the gasified liquefied natural gas comprises 88.2 to 99.4 percent of firedamp, 0.2 to 7.8 percent of ethane, 0.1 to 3.3 percent of propane and 0.1 to 1.7 percent of butane calculated by volume, and the heat value is 10440 to 10700 Kcal/Nm<3>; the components of the product gas comprises 75.1 to 53.8 percent of fire damp, 14 to 30.8 percent of hydrogen gas, 2.4 to 5.4 percent of carbon monoxide and 1.8 to 3.7 percent of carbon dioxide calculated by volume, the heat value is 7500 to 9000 Kcal/Nm<3>, and thepressure is 3.3 to 6.3 MPa. The method of the invention adopts the converted volume expansion energy of the liquefied natural gas after the heat exchange as the power, and therefore the mechanical equipment, such as a compressor, is saved to supply power to the gasified natural gas; the method adopts the linkage operation and the converging of two different process lines (pressure reduction and heat reduction), and the final product natural gas is obtained.
Description
Technical field
The present invention relates to control the calorific value of natural gas liquids (LNG), particularly relate to a kind of method that reduces heat value of gaseous liquefied natural gas.
Background technology
According to the national energy strategic planning, China will be before 2010 in the east several large-scale natural gas liquids receiving stations of coastal construction.Domestic first natural gas liquids receiving station-Guangdong receiving station with formally receive in June, 2006 from Australian natural gas liquids; The natural gas liquids receiving station in Fujian, Shanghai, Jiangsu, Zhejiang also among building, will begin to receive the natural gas liquids from country variant soon successively at present.Every component of the natural gas liquids of the oil-gas field of country variant and liquefaction process production, gas quality index have nothing in common with each other, calorific value and combustion quality also have nothing in common with each other, different sources of the gas mixes the interchangeability that must consider terminal user's gas-fired equipment at pipe network, therefore require the natural gas supply merchant that unified standard calorific value is provided, to guarantee terminal user's, safety stable with gas.Separate the natural gas liquids light hydrocarbon component and have in the prior art; Processing methodes such as nitrogen injection, air or waste gas in natural gas liquids, but the nitrogen injection cost is higher, dilution air can make the oxygen level in the Sweet natural gas improve, the operating safety that relates to pipeline, select to inject waste gas and need near receiving station, possess the waste gas gas source condition, and carbonic acid gas in the waste gas and moisture can cause corrosive pipeline, shorten pipeline work-ing life.Owing to be that high pressure injects all kinds of gases, then energy consumption increases in addition, and running cost improves; To enter the distance of looped network or Heavenly Stems and Earthly Branches net far because of two or more different natural air-air sources again, various source of the gas proportions change because of pressure and operational throughput change in the pipe-line transportation, are difficult to realize that blending accomplishes that accurate proportioning makes it keep stable burning index and calorific value.Still can't solve at present calorific value control, also can't formulate unified liquefied natural gas product calorific value standard range at the various natural gas liquids of usefulness.
The gaseous liquefied natural gas Trade Measures mode of existing national regulation is a volume metering; Among the standard GB 17820-1999 " Sweet natural gas " that carries out in the relevant technical indicator of two class gas the calorific value index much smaller than the calorific value of the various natural gas liquids of present import.
Summary of the invention
In view of the foregoing, the invention provides a kind of method that reduces heat value of gaseous liquefied natural gas.Present method adopts two different process routes (decompression, reduction of heat) to cooperate coordinated operation, obtains the finished product gaseous liquefied natural gas after converging, and the amount of the component of gaseous liquefied natural gas and the calorific value natural gas liquids by entering bypass reduction of heat device is adjusted control.The heat that is higher than the regulation of national standard can be converted into volume, reach the purpose of calorific value control, the energy consumption of this method self is below 2%, and solve oxygen level height in the prior art simultaneously, pipeline is perishable, energy consumption is high and calorific value, burning index are difficult to problems such as control.
Method of the present invention realizes by following process steps:
Step 1. liquefied natural gas gasifying
The main component that is stored in the low-temperature liquefaction Sweet natural gas storage tank is the natural gas liquids of methane, ethane, propane and butane, in gasifier with the water indirect heat exchange, the liquid liquefied Sweet natural gas in heat absorption back in a disguised form is a gaseous liquefied natural gas, 600 times of volumetric expansions, gaseous liquefied natural gas directly enters gas pipe line, and the covert volumetric expansion after the natural gas liquids heat exchange can be as the power of next step.
The decompression of step 2. gaseous liquefied natural gas
With pressure is the unstripped gas of 4.0～7.0MPa, its component is that the gaseous liquefied natural gas of methane, ethane, propane and butane is divided into two strands of gaseous liquefied natural gas, wherein one gaseous liquefied natural gas is stand-by by pressure regulator valve decompression back, described pressure is that the component by volume of the gaseous liquefied natural gas of 4.0～7.0MPa is a methane 88.2～99.4%, ethane 0.2～7.8%, propane 0.1～3.3%, butane 0.1～1.7%, calorific value are 10440～10700Kcal/Nm
3
After another strand gaseous liquefied natural gas reduces pressure by variable valve, enter the reduction of heat device, be further divided into two strands of gaseous liquefied natural gas of A, B, wherein B thigh gaseous liquefied natural gas enters converter as heating fuel gas after the pressure regulator valve decompression, the gas fume after burning temperature is 850～1000 ℃, and flue gas enters flue; The hot flue gas that A-share gaseous liquefied natural gas and converter come out is by the preheating heat exchanger preheating, A-share gaseous liquefied natural gas temperature reaches 450～600 ℃, A-share gaseous liquefied natural gas after the preheating and temperature are that 450～550 ℃ superheated vapour mixes back composition gas mixture, the water of gas mixture and the mass ratio of carbon are 1.5～2.0: 1, gas mixture enters pre-converter, the aspect ratio of pre-converter is 3～5: 1, and the filling nickel content is the nickel catalyst of 50～70 weight % in the pre-converter, and carrier is Al
2O
3Under the effect of catalyzer, reaction obtains the prerotation gasification, the component by volume of prerotation gasification is the dry gas and the unreacted water vapour of methane 76～79%, hydrogen 16～18%, carbon monoxide 0.1～0.6% and carbonic acid gas 4.0～6.0%, and prerotation gasification dry gas calorific value is 7500～8100Kcal/Nm
3, temperature is 450～550 ℃, pressure is 3.8～6.9MPa.
Prerotation gasification and another part superheated vapour mix, and the water in the gas mixture and the mass ratio of carbon are 2.5～4.0: 1, and gas mixture enters converting furnace, and the filling nickel content is the nickel catalyst of 6.5～12 weight % in the boiler tube, and carrier is Al
2O
3Under the catalysis of catalyzer, methane in the prerotation gasification further reaction is cracked into carbon monoxide, carbonic acid gas and hydrogen, reduce calorific value, the component by volume of reaction back reforming gas dry gas is dry gas and the unreacted water vapour that methane 13.0～14.0%, hydrogen 66～67%, carbon monoxide 11.0～12.0% and carbonic acid gas 8.0～9.0% are formed, and reforming gas dry gas calorific value is 3600～3700Kcal/Nm
3, temperature is 750～850 ℃, pressure is 5.8～6.2MPa.
The cooling of step 5. reforming gas, processed
Reforming gas enters the waste heat boiler of being made up of waste heat exchanger and drum, temperature drops to 250～280 ℃, reforming gas cools off by cooling heat exchanger, first water trap and second water trap and dewaters, and the water of condensation that second water trap is discharged returns the water inlet system of waste heat boiler.Reforming gas temperature after the dehydration is reduced to 20～40 ℃, reforming gas is blended into product gas on demand mutually by gaseous liquefied natural gas stand-by in pressure regulator valve step-down and the step 2, the component by volume of product gas is a methane 75.1～53.8%, hydrogen 14～30.8%, carbon monoxide 2.4～5.4%, carbonic acid gas 1.8～3.7%, calorific value are 7500～9000Kcal/Nm
3, pressure is 3.3～6.3MPa, product gas enters the downstream gas distributing system from product gas outlet.
The component by volume of the gaseous liquefied natural gas of 4.0～7.0MPa of the present invention is a methane 88.2～99.4%, ethane 0.2～7.8%, and propane 0.1～3.3%, butane 0.1～1.7%, calorific value are 10440～10700Kcal/Nm
3The component by volume of prerotation gasification dry gas is a methane 76～79%, hydrogen 16～18%, and carbon monoxide 0.1～0.6%, carbonic acid gas 4.0～6.0%, calorific value are 7500～8100Kcal/Nm
3, temperature is 450～550 ℃, pressure is 3.8～6.9MPa; The component by volume of reforming gas dry gas is a methane 13.0～14.0%, hydrogen 66～67%, and carbon monoxide 11.0～12.0%, carbonic acid gas 8.0～9.0%, calorific value are 3600～3700Kcal/Nm, and temperature is 750～850 ℃, and pressure is 5.8～6.2MPa; The component by volume of product gas is a methane 75.1～53.8%, hydrogen 14～30.8%, and carbon monoxide 2.4～5.4%, carbonic acid gas 1.8～3.7%, calorific value are 7500～9000Kcal/Nm
3, pressure is 3.3～6.3MPa.
Temperature of the present invention is the waste heat boiler that 750～850 ℃ reforming gas enters waste heat exchanger and drum composition, utilize the waste heat heating deionization soft water production high pressure steam of reforming gas, high-pressure steam pressure is 3.3～6.9MPa, temperature is 240～290 ℃, it is 450～550 ℃ that high pressure steam entered the superheat steam temperature that heat exchanger obtains after overheated, and high pressure steam is mainly pre-converter and converter provides reaction required steam.
B thigh gaseous liquefied natural gas of the present invention enters converter as heating fuel gas after the pressure regulator valve decompression, the flue-gas temperature of fuel gas after the converter internal combustion is 850～1000 ℃, flue gas enters flue, the hot flue gas that A-share gaseous liquefied natural gas and converter come out, by the afterheat heat exchanger preheating, flue-gas temperature after the heat exchange is reduced to 600～700 ℃, flue gas after the heat exchange entered heat exchanger heating high-pressure steam, obtain 450～550 ℃ superheated vapour, flue-gas temperature is reduced to 160～180 ℃, by the induced draft fan emptying.
Beneficial effect of the present invention
1. method of the present invention has utilized the covert volumetric expansion after the natural gas liquids heat exchange to provide power thereby saved mechanical means such as use compressor to gaseous natural gas as power.
2. present method adopts two different process routes (decompression, reduction of heat) to cooperate coordinated operation, obtains the finished product Sweet natural gas after converging, and the amount of the component of product gas and the calorific value natural gas liquids by entering bypass reduction of heat device is adjusted control.
3. present method heat provides by the combustion parts gaseous liquefied natural gas, and all steam and steam superheating provide by heat exchange by reforming gas, fume afterheat, and the gaseous liquefied natural gas that enters hydrocarbon steam conversion reaction pre-inversion section is provided by fume afterheat.
This method is to utilize the expansion energy of gas after liquid transferpump of natural gas liquids and the heat exchange in sum, reach thermal equilibrium through the part pre-inversion, process gas all returns original device, by process control, make liquefied natural gas product gas by volume contain hydrogen more than 5%, help to improve combustion quality; The heat that will be higher than Sweet natural gas national standard 15%～40% is converted into volume; This method can be regulated the calorific value and the burning index of control liquefied natural gas product gas, carries out modifiedly thereby reach natural gas liquids to quality parameter scopes such as various different calorific values, realizes the unified purpose of gaseous liquefied natural gas product application standard.This method and system can save mechanical supercharging equipment such as using compressor fully.
Description of drawings
Fig. 1 is a process flow sheet of the present invention.
Fig. 2 is the process flow sheet of reduction of heat device of the present invention.
Number in the figure is represented: 1-raw material gas inlet, 2-pressure regulator valve, 3～reliever, 4-pressure regulator valve, 5-reduction of heat device, 6-pressure regulator valve, 7-product gas outlet, 8-drum, the 9-waste heat exchanger, the 10-high pressure steam, 11-crosses heat exchanger, the 12-superheated vapour, the 13-pressure regulator valve, 14-preheating heat exchanger, 15-converter, 16-pre-converter, the 17-cooling heat exchanger, 18-first water trap, 18 '-the second water trap, the 19-gas blower, 20-induced draft fan, 21-reducing valve.
Embodiment
For better implement the present invention, specify below by embodiment, but protection scope of the present invention is not subjected to the qualification of embodiment content.
Embodiment 1: present embodiment is 1,118 ten thousand Nm to air demand
3The gaseous liquefied natural gas of/day adopts the present invention to carry out the calorific value adjustment, and adjusted calorific value is 9000Kcal/Nm
3The main component of gaseous liquefied natural gas is: methane 91.2%, ethane 4.4%, propane 2.9%, butane 1.3%, other 0.2%, calorific value is 10570Kcal/Nm
3Concrete technical process and processing condition:
1. liquefied natural gas gasifying
The main component that is stored in the low-temperature liquefaction Sweet natural gas storage tank is the natural gas liquids of methane, ethane, propane and butane, in gasifier with the water indirect heat exchange, the liquid liquefied Sweet natural gas in heat absorption back in a disguised form is a gaseous liquefied natural gas, 600 times of volumetric expansions, gaseous liquefied natural gas directly enters gas pipe line.Covert volumetric expansion after the natural gas liquids heat exchange can be as the power of next step.
2. gaseous liquefied natural gas decompression
Gaseous liquefied natural gas 1 pressure is 6.5MPa, and flow is 46.58 ten thousand Nm
3/ h, major ingredient with volume percent count methane 91.2%, ethane 4.4%, propane 2.9%, butane 1.3%, other 0.2%, calorific value is 10570Kcal/Nm
3This portion gas is divided into two strands of materials, and a part is stand-by by pressure regulator valve 2 decompression backs.
3. gaseous liquefied natural gas pre-inversion
Gaseous liquefied natural gas enters reduction of heat device 5, be further divided into two strands of gaseous liquefied natural gas of A, B, wherein B thigh gaseous liquefied natural gas enters converter 15 as heating fuel gas through pressure regulator valve 13 decompressions, and the gas fume after burning temperature is 850～1000 ℃, and flue gas enters flue; The hot flue gas that A-share gaseous liquefied natural gas and converter 15 come out is by preheating heat exchanger 14 preheatings, A-share gaseous liquefied natural gas temperature is 500～550 ℃, A-share gaseous liquefied natural gas after the preheating and superheated vapour 12 mix, and superheated vapour 12 temperature are 450～550 ℃, and flow is 55T/h.Mix the gas mixture of forming the back and enter pre-converter 16 reactions, pre-transform teactor is cylindrical tube shape, fixed-bed reactor, aspect ratio: 3～5: 1, filling nickel content is the nickel catalyst of 50～70 weight % in the reactor, steam and methane are with 450～550 ℃ temperature, 1.5～2: go out under 1 water carbon mass ratio is enterprising, obtain the prerotation gasification.The dry gas major ingredient of prerotation gasification is counted methane 77.7%, hydrogen 17.2%, carbon monoxide 0.3%, carbonic acid gas 4.8%, calorific value 7900Kcal/Nm with volume percent
3, 450～500 ℃ of temperature, pressure 6.3～6.4MPa, flow 4.81 ten thousand Nm
3/ h.The prerotation gasification also contains unreacted water vapour 52T/h in addition.
4. converter transforms
Prerotation gasification and unreacted water vapour and another part superheated vapour 12 are mixed into converter 15 chargings, and the water of gas mixture and the mass ratio of carbon are 2.5～4.0: 1.The amount of superheated vapour 12 is 16T/h, pre-inversion G﹠W steam enters converter 15 boiler tubes after mixing, effect at 6.5～12 weight % nickel catalysts issues biochemical reaction, and methane wherein further reaction is cracked into carbon monoxide and carbonic acid gas, reduces calorific value.Reacted reforming gas dry gas part major ingredient is counted methane 13.4% with volume percent, hydrogen 66.9%, and carbon monoxide 11.6%, carbonic acid gas 8.1%, calorific value are 3660Kcal/Nm
3, 750～850 ℃ of temperature, pressure 5.8～6.2MPa, flow 12.29 ten thousand Nm
3/ h.Also has unreacted water vapour 49T/h in addition.
The heat of converter 15 is provided in converter 15 internal combustion by fuel natural gas, and combustion air is sent in the converter 15 combustion-supporting by gas blower 19, and fuel gas is in the burner hearth internal combustion, and the gas fume after burning temperature is 850～1000 ℃, and flue gas enters flue.
5. waste heat recovery
Reforming gas enters waste heat exchanger 9, and waste heat exchanger 9 and drum 8 are formed waste heat and crossed stove, utilizes the waste heat heating deionization soft water production high pressure steam 10 of reforming gas, and high pressure steam 10 pressure are 6.5MPa, and temperature is 285 ℃, and flow is 130T/h.High pressure steam 10 is sent a part and is low-pressure steam by reducing valve 21 decompressions from drum 8, use to do him.Another part flow is 71T/h, and it is overheated to enter heat exchanger 11.450～550 ℃ of vapor temperatures after overheated, superheated vapour 12 are mainly pre-converter 16 and converter 15 provides reaction required steam.
Flue gas enters the gaseous liquefied natural gas of pre-converter 16 by preheating heat exchanger 14 preheatings in flue.Flue-gas temperature is reduced to 600～700 ℃ after the heat exchange.Flue gas after the heat exchange entered heat exchanger 11 heating high-pressure steam 10.After this flue gas also can further carry out heat exchange with combustion air, makes temperature be reduced to 160～180 ℃ by induced draft fan 20 emptyings.
6. reforming gas is handled
Reforming gas is through behind the waste heat exchanger 9, temperature drops to 250～280 ℃, separate out water of condensation by first water trap 18, the reforming gas of preliminary hydro-extraction is by cooling heat exchanger 17 and second water trap, 18 ' further cooled dehydrated, and the water of condensation that first water trap 18, second water trap 18 ' are discharged turns back to the waste heat boiler water inlet system.Synthetic gas temperature after the dehydration is reduced to 20～40 ℃, is depressurized to 5.5MPa by pressure regulator valve 6 again, and the composition of synthetic gas is counted methane 13.4%, hydrogen 66.9%, carbon monoxide 11.6%, carbonic acid gas 8.1%, calorific value 3660Kcal/Nm with volume percent
3Synthetic gas and another part gaseous liquefied natural gas material 3 mix, and obtaining adjusted product gas 7 flows of calorific value is 54.04 ten thousand Nm
3/ h.Air demand is 1,297 ten thousand Nm after the calorific value adjustment
3/ day, gas composition is: methane 73.5%, ethane 3.4%, propane 2.2%, butane 1.0%, hydrogen 15.5%, carbon monoxide 2.7%, carbonic acid gas 1.9%, calorific value 9000Kcal/Nm
3The stand-by decompression gas of voltage stabilizing is blended into product gas on demand in synthetic gas and the above-mentioned steps 2, and the product airshed is 54.04Nm
3/ h, calorific value are 9000Kcal/Nm
3Product gas is sent into the downstream gas distributing system from product gas outlet 7.
Result of implementation sees Table 1.
Table 1
| Component | Unit | Unstripped gas | Decompression gas | A, B gas | Synthetic gas | Product gas | The prerotation gasification | Reforming gas |
| Methane | ％ | 91.2 | 13.4 | 73.5 | 77.7 | 13.4 | ||
| Ethane | ％ | 4.4 | 3.4 | |||||
| Propane | ％ | 2.9 | 2.2 | |||||
| Butane | ％ | 1.3 | 1 | |||||
| Hydrogen | ％ | 66.9 | 15.5 | 17.2 | 66.9 | |||
| Carbon monoxide | ％ | 11.6 | 2.7 | 0.3 | 11.6 | |||
| Carbonic acid gas | ％ | 8.1 | 1.9 | 4.8 | 8.1 | |||
| Other | ％ | 0.2 | ||||||
| Calorific value | Kcal/Nm 3 | 10570 | 3660 | 9000 | 7900 | 3660 |
| Flow | Ten thousand Nm 3/h | 46.58 | 41.75 | 4.83 | 12.29 | 54.04 | 4.81 | 12.29 |
| Pressure | MPa | 6.8 | 5.5 | 6.5 | 5.7-6.1 | 5.5 | 6.3-6.4 | 5.8-6.2 |
| Temperature | ℃ | 20-40 | 450-550 | 750-850 | ||||
| Water vapour | T/h | 52 | 49 |
Embodiment 2:
Present embodiment is 1,118 ten thousand Nm to air demand
3The LNG gas of/day adopts the present invention to carry out the calorific value adjustment, and adjusted calorific value is 7500Kcal/Nm
3The main component of LNG gas with volume percent count methane 91.2%, ethane 4.4%, propane 2.9%, butane 1.3%, other 0.2%, calorific value is 10570Kcal/Nm
3
Concrete technical process and processing condition:
1. liquefied natural gas gasifying technology is with embodiment 1
2. gaseous liquefied natural gas decompression
Unstripped gas enters reduction of heat device 5 components with embodiment 1, and flow is 110,000 Nm
3/ h, pressure are 6.5MPa.This portion gas is divided into two strands of materials, and a part is stand-by by pressure regulator valve 2 decompression backs.
3. gaseous liquefied natural gas pre-inversion
Gaseous liquefied natural gas enters the technology of part of reduction of heat device 5 with embodiment 1, it is gaseous liquefied natural to be divided into two strands of A, B, wherein B thigh gaseous liquefied natural gas enters converter 15 as heating fuel gas through pressure regulator valve 13 decompressions, the gas fume after burning temperature is 850～1000 ℃, and flue gas enters flue; The hot flue gas that A-share gaseous liquefied natural gas and converter 15 come out is by preheating heat exchanger 14 preheatings, and the temperature after the preheating of A-share gaseous liquefied natural gas is 500～550 ℃.A-share gaseous liquefied natural gas after the preheating and superheated vapour 12 mix, and superheated vapour 12 temperature are 450～550 ℃, and flow is 126T/h.Mix the gas mixture of forming the back and enter pre-converter 16 reactions, pre-transform teactor is cylindrical tube shape, fixed-bed reactor, aspect ratio: 3～5: 1, filling nickel content is the nickel catalyst of 50～70 weight % in the reactor, steam and methane are with 450～550 ℃ temperature, 1.5～2: go out under 1 water carbon mass ratio is enterprising, obtain the prerotation gasification.The dry gas major ingredient of prerotation gasification is counted methane 77.7% with volume percent, hydrogen 17.2%, and carbon monoxide 0.3%, carbonic acid gas 4.8%, calorific value are 7900Kcal/Nm
3, temperature is 450～500 ℃, pressure is 6.3～6.4MPa, flow 10.95 ten thousand Nm
3/ h.The prerotation gasification also contains unreacted water vapour 119T/h in addition.
4. converter transforms
Prerotation gasification and unreacted water vapour and another part superheated vapour 12 are mixed into converter 15 chargings, and the water of gas mixture and the mass ratio of carbon are 2.5～4.0: 1.The amount of superheated vapour 12 is 16T/h, pre-inversion G﹠W steam enters converter 15 boiler tubes after mixing, effect at 6.5～12 weight % nickel catalysts issues biochemical reaction, and methane wherein further reaction is cracked into carbon monoxide and carbonic acid gas, reduces calorific value.Reacted reforming gas dry gas part major ingredient is: methane 13.4%, and hydrogen 66.9%, carbon monoxide 11.6%, carbonic acid gas 8.1%, calorific value are 3660Kcal/Nm
3, 750～850 ℃ of temperature, pressure 5.8～6.2MPa, flow 27.67 ten thousand Nm
3/ h.Also has unreacted water vapour 110T/h in addition.
The heat of converter 15 is provided in converter 15 internal combustion by fuel natural gas, and combustion air is sent in the converter 15 combustion-supporting by gas blower 19, and fuel gas is in the burner hearth internal combustion, and the gas fume after burning temperature is 850～1000 ℃, and flue gas enters flue.
5. waste heat recovery
Reforming gas enters waste heat exchanger 9, and waste heat exchanger 9 and drum 8 are formed waste heat and crossed stove, utilizes the waste heat heating deionization soft water production high pressure steam 10 of reforming gas, and high pressure steam 10 pressure are 6.5MPa, and temperature is 285 ℃, and flow is 295T/h.High pressure steam 10 is sent a part and is low-pressure steam by reducing valve 21 decompressions from drum 8, use to do him.Another part flow is 162T/h, and it is overheated to enter heat exchanger 11.450～550 ℃ of vapor temperatures after overheated, superheated vapour 12 are mainly pre-converter 16 and converter 15 provides reaction required steam.
Flue gas enters the gaseous liquefied natural gas of pre-converter 16 by preheating heat exchanger 14 preheatings in flue.Flue-gas temperature is reduced to 600～700 ℃ after the heat exchange.Flue gas after the heat exchange entered heat exchanger 11 heating high-pressure steam 10.After this flue gas also can further carry out heat exchange with combustion air, makes temperature be reduced to 160～180 ℃ by induced draft fan 20 emptyings.
6. reforming gas is handled
Reforming gas is through behind the waste heat exchanger 9, temperature drops to 250～280 ℃, separate out water of condensation by first water trap 18, the reforming gas of preliminary hydro-extraction is by cooling heat exchanger 17 and second water trap, 18 ' further cooled dehydrated, and the water of condensation that first water trap 18, second water trap 18 ' are discharged turns back to the waste heat boiler water inlet system.Synthetic gas temperature after the dehydration is reduced to 20～40 ℃, be depressurized to 5.5MPa by pressure regulator valve 6 again, it is 3660Kcal/Nm that the composition of synthetic gas is counted methane 13.4%, hydrogen 66.9%, carbon monoxide 11.6%, carbonic acid gas 8.1%, calorific value with volume percent
3Synthetic gas and another part gaseous liquefied natural gas decompression gas 3 mix, and obtaining adjusted product gas 7 flows of calorific value is 63.25 ten thousand Nm
3/ h.Air demand is 1,518 ten thousand Nm after the calorific value adjustment
3/ day, gas composition is: methane 57.2%, ethane 2.5%, propane 1.6%, butane 0.7%, hydrogen 29.3%, carbon monoxide 5.2%, carbonic acid gas 3.5%, calorific value 7500Kcal/Nm
3The stand-by decompression gas of voltage stabilizing is blended into product gas on demand in synthetic gas and the above-mentioned steps 2, and the product airshed is 63.25Nm
3/ h, calorific value are 7500Kcal/Nm
3Product gas is sent into the downstream gas distributing system from product gas outlet 7.
Result of implementation sees Table 2.
Table 2
| Component | Unit | Unstripped gas | Decompression gas | A, B gas | Synthetic gas | Product gas | The prerotation gasification | Reforming gas |
| Methane | ％ | 91.2 | 13.4 | 57.2 | 77.7 | 13.4 | ||
| Ethane | ％ | 4.4 | 2.5 | |||||
| Propane | ％ | 2.9 | 1.6 | |||||
| Butane | ％ | 1.3 | 0.7 | |||||
| Hydrogen | ％ | 66.9 | 29.3 | 17.2 | 66.9 | |||
| Carbon monoxide | ％ | 11.6 | 5.2 | 0.3 | 11.6 | |||
| Carbonic acid gas | ％ | 8.1 | 3.5 | 4.8 | 8.1 | |||
| Other | ％ | 0.2 |
| Calorific value | Kcal/Nm 3 | 10570 | 3660 | 7500 | 7900 | 3660 | ||
| Flow | Ten thousand Nm 3/h | 46.58 | 35.58 | 11 | 27.67 | 63.25 | 10.95 | 27.67 |
| Pressure | MPa | 6.8 | 5.5 | 6.5 | 5.7-6.1 | 5.5 | 6.3-6.4 | 5.8-6.2 |
| Temperature | ℃ | 20-40 | 450-550 | 750-850 | ||||
| Water vapour | T/h | 119 | 110 |
Claims (4)
1. method that reduces heat value of gaseous liquefied natural gas is characterized in that this method comprises following processing step:
(1) liquefied natural gas gasifying
The main component that is stored in the low-temperature liquefaction Sweet natural gas storage tank is the natural gas liquids of methane, ethane, propane and butane, in gasifier with the water indirect heat exchange, the liquid liquefied Sweet natural gas in heat absorption back in a disguised form is a gaseous liquefied natural gas, 600 times of volumetric expansions, gaseous liquefied natural gas directly enters gas pipe line, and the covert volumetric expansion after the natural gas liquids heat exchange can be as the power of next step;
(2) gaseous liquefied natural gas decompression
With pressure is that the main component of 4.0～7.0MPa is that the gaseous liquefied natural gas of methane, ethane, propane and butane is divided into two strands of gaseous state materials, wherein one gaseous liquefied natural gas material is stand-by by pressure regulator valve [2] decompression back, described pressure is that the component by volume of the gaseous liquefied natural gas of 4.0～7.0MPa is a methane 88.2～99.4%, ethane 0.2～7.8%, propane 0.1～3.3%, butane 0.1～1.7%, calorific value are 10440～10700Kcal/Nm
3
(3) gaseous liquefied natural gas pre-inversion
Another strand gaseous liquefied natural gas material is after pressure regulator valve [4] decompression, enter reduction of heat device [5], be divided into two strands of gaseous state materials of A, B, wherein B thigh gaseous liquefied natural gas enters converter [15] as heating fuel gas after pressure regulator valve [13] decompression, the gas fume after burning temperature is 850～1000 ℃, and flue gas enters flue; The hot flue gas that A-share gaseous liquefied natural gas and converter come out is by preheating heat exchanger [14] preheating, A-share gaseous liquefied natural gas temperature reaches 450～600 ℃, A-share gaseous liquefied natural gas after the preheating and temperature are that 450～550 ℃ of superheated vapours [12] mix, the water in the gas mixture and the mass ratio of carbon are 1.5～2.0: 1, gas mixture enters pre-converter [16], the aspect ratio of pre-converter [16] is 3～5: 1, the filling nickel content is the nickel catalyst of 50～70 weight % in the pre-converter, and carrier is Al
2O
3Under the effect of catalyzer, reaction obtains the prerotation gasification, the component by volume of prerotation gasification is the dry gas and the unreacted water vapour of methane 76～79%, hydrogen 16～18%, carbon monoxide 0.1～0.6% and carbonic acid gas 4.0～6.0%, and prerotation gasification dry gas calorific value is 7500～8100Kcal/Nm
3, temperature is 450～550 ℃, pressure is 3.8～6.9MPa.
(4) the prerotation gasification reacts in converter [15] and generates reforming gas
Prerotation gasification and another part superheated vapour [12] mix, and the water in the gas mixture and the mass ratio of carbon are 2.5～4.0: 1, and gas mixture enters converter [15], and the filling nickel content is the nickel catalyst of 6.5～12 weight % in the boiler tube, and carrier is Al
2O
3Under the catalysis of nickel catalyst, methane in the prerotation gasification further is cracked into carbon monoxide, carbonic acid gas and hydrogen, reduce calorific value, the component by volume of reacted reforming gas dry gas is a methane 13.0～14.0%, hydrogen 66～67%, carbon monoxide 11.0～12.0%, carbonic acid gas 8.0～9.0%, calorific value are 3600～3700Kcal/Nm
3, temperature is 750～850 ℃, pressure is that 5.8～6.2MPa and unreacted water vapour are formed;
(5) reforming gas is handled
Reforming gas enters the waste heat boiler of being made up of waste heat exchanger [9] and drum [8], temperature drops to 250～280 ℃, reforming gas is by cooling heat exchanger [17], first water trap [18] and second water trap [18 '] cool off, dehydration, the water of condensation that second water trap [18 '] is discharged returns the water inlet system of waste heat boiler, reforming gas temperature after the dehydration is reduced to 20～40 ℃, reforming gas by pressure regulator valve [13] step-down after with step (2) in stand-by gaseous liquefied natural gas be blended into product gas on demand mutually, the component by volume of product gas is a methane 75.1～53.8%, hydrogen 14～30.8%, carbon monoxide 2.4～5.4%, carbonic acid gas 1.8～3.7%, calorific value are 7500～9000Kcal/Nm
3, pressure is 3.3～6.3MPa, product gas enters the downstream gas distributing system from product gas outlet [7].
2. method according to claim 1 is characterized in that: the nickel catalyst in the step (3) in the pre-converter [16] be nickel content be 50～70 weight % be the catalyzer of carrier with the aluminium sesquioxide; Nickel catalyst in the step (4) in the converter [15] be nickel content be 6.5～12 weight % be the catalyzer of carrier with the aluminium sesquioxide.
3. method according to claim 1, it is characterized in that: 750～850 ℃ reforming gas enters the waste heat boiler of being made up of waste heat exchanger [9] and drum [8] and carries out heat exchange in the step (4), utilize waste heat to add hot deionized water production high pressure steam [10], the pressure of high pressure steam [10] is 3.3～6.9MPa, temperature is 240～290 ℃, high pressure steam [10] entered further heating of heat exchanger [11], obtained 450～550 ℃ superheated vapour [12].
4. method according to claim 1, it is characterized in that: B thigh gaseous liquefied natural gas material enters converter [15] as heating fuel gas in the step (3) after pressure regulator valve [13] decompression, the flue-gas temperature of fuel gas after converter [15] internal combustion is 850～1000 ℃, flue gas enters flue, the hot flue gas that A-share gaseous liquefied natural gas and converter [15] come out is by preheating heat exchanger [14] preheating, flue-gas temperature after the heat exchange is reduced to 600～700 ℃, flue gas after the heat exchange entered heat exchanger [11] heating high-pressure steam [10], obtain 450～550 ℃ superheated vapour [12], flue-gas temperature is further reduced to 160～180 ℃ again, by induced draft fan [20] emptying.
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|---|---|---|---|---|
| WO2000079179A1 (en) * | 1999-06-23 | 2000-12-28 | Chicago Bridge & Iron Company | System and apparatus for condensing boil-off vapor from a liquified natural gas container |
| US6564579B1 (en) * | 2002-05-13 | 2003-05-20 | Black & Veatch Pritchard Inc. | Method for vaporizing and recovery of natural gas liquids from liquefied natural gas |
| CN1648219A (en) * | 2004-01-20 | 2005-08-03 | 上海浦东新区海科(集团)公司 | City natural gas of mixed air and light hydrocarbon gas and its producing method |
| CN1894537A (en) * | 2003-12-15 | 2007-01-10 | Bp北美公司 | Systems and methods for vaporization of liquefied natural gas |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000079179A1 (en) * | 1999-06-23 | 2000-12-28 | Chicago Bridge & Iron Company | System and apparatus for condensing boil-off vapor from a liquified natural gas container |
| US6564579B1 (en) * | 2002-05-13 | 2003-05-20 | Black & Veatch Pritchard Inc. | Method for vaporizing and recovery of natural gas liquids from liquefied natural gas |
| CN1894537A (en) * | 2003-12-15 | 2007-01-10 | Bp北美公司 | Systems and methods for vaporization of liquefied natural gas |
| CN1648219A (en) * | 2004-01-20 | 2005-08-03 | 上海浦东新区海科(集团)公司 | City natural gas of mixed air and light hydrocarbon gas and its producing method |
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