CN101028579A

CN101028579A - Method for purifying marsh gas by membrane separating technology

Info

Publication number: CN101028579A
Application number: CNA2006101461570A
Authority: CN
Inventors: 张晓忠
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-11-12
Filing date: 2006-11-12
Publication date: 2007-09-05

Abstract

A process for cleaning the marsh gas in order to use it as non-toxic fuel features that a membrane separation technique is used for separating CH4, CO2, H2O and H2S from marsh gas.

Description

The method of purifying marsh gas by membrane separating technology

Technical field:

The present invention relates to a kind of method of marsh gas purifying, belong to biological downstream separation engineering, former biogas removes CO through the selective gas diffusion barrier ₂, H ₂O and small amount of H ₂S reaches the purification purpose, produces the needs of automobile-used biogas or civil methane for back operation compression.

Background technology:

Marsh gas purifying in China at present beyond example, also few people research.Because the biogas of China mainly is to make life fuel and generating two big purposes at present, there is no need to carry out deep purifying, only need preliminary desulfurization and dehydration, need not remove carbon dioxide.But biogas will just must reach country's " automobile compressed natural gas " standard as vehicle fuel, just needs deep purifying.

The marsh gas purifying technology mainly is to remove CO ₂And small amount of H ₂O, H ₂S.Method commonly used both at home and abroad at present has: molten Ji absorption process and solid absorption method (containing transformation absorption).As countries such as Sweden in Europe, Denmark, Belgium, mostly adopt pressure swing adsorption method and WATER-WASHING METHOD abroad.Pressure swing adsorption method (PSA) is to be adsorbent with the molecular sieve, pressurization absorption, decompression desorb.Its principle is: under different pressure, owing to molecular sieve there are differences methane and carbon dioxide adsorption, thereby reach the separation purpose.Methane is in the enrichment of the adsorption tower port of export, and carbon dioxide is then removed because of desorb.But the dynamic adsorbance of adsorbent is limited, and when handling than atm number, it is huge that device seems, cost also increases thereupon.WATER-WASHING METHOD is generally made absorbent with alkaline aqueous solution, removes CO as potash or ammoniacal liquor by chemical absorbing ₂And H ₂The S sour gas.But this method regeneration expense height, the energy consumption height, the technology complicated operation produces contaminated wastewater simultaneously.

The gas componant that originates in the biogas is as follows:

Gas	CH ₄	CO ₂	H ₂O	N ₂	O ₂	H ₂	H ₂S
Gas	CH ₄	CO ₂	H ₂O	N ₂	O ₂	H ₂	H ₂S	Content % (V/V)	55～65	30～38	2～3	≤1	≤0.5	≤0.4	500～ 1500ppm

CO wherein ₂, H ₂O and H ₂S is severe corrosion equipment and pipeline in compression process or when making the vehicle fuel combustion process, CO ₂Reduce the methane value (fuel value) of biogas again, in view of these two reasons, CO ₂, H ₂O and H ₂S must remove before compression.Pernicious gas CO in the biogas ₂Content the highest, so the subject matter of marsh gas purifying is to remove CO ₂, moreover, H ₂S, H ₂O also removes in the lump, and reaches the standard of China's " compressed natural gas used as vehicle fuel ": CH ₄〉=97%, CO ₂≤ 3%, H ₂S≤15mg/m ³

This piece-rate system is similar to the associated gas separation of C O in the gas industry very much ₂Technology.China and external most of existing process units are that solvent absorption removes CO simultaneously at present ₂, H ₂O and H ₂S.Commonly used have hydramine method (MEA, diethanol amine, diglycolamine etc.), alkaline solution method (as hot potash method) and a sulfone amine method (sulfolane, NHD are typical solvent).These methods have shown very big superiority really when handling the large-scale natural gas engineering, but for middle-size and small-size gas engineering marsh gas purifying engineering particularly, the investment that just seems is big, equipment is complicated, the technology trouble.

It is the new and high technology that grew up in recent years that application of membrane separation technology is separated in gas.It is to utilize each material in the system different and have the dissolving-diffusion of selection to the compatibility of film, reaches the separation purpose.With regard to methane and carbon dioxide system, to separate in the material of selecting at film, seepage velocity differs 10～150 times nearly, has very high industrial application value.Especially at CO ₂In the high bionethanation system of content, no matter being investment, operating cost or maintenance cost all has more economy than above separation method, is the new and high technology that cost performance is best, investment economizes most.

Membrane separation device can be formed modular form, and according to the difference of handling gas flow, module is the amount doesn't matter, and is flexible, and little per hour treating capacity is tens cubes, big reaches several all places.Its outstanding feature is: 1. need not additional materials and reagent and add; 2. pollution-free, environmental friendliness; 3. process compatibility is strong; 4. technology is simple, the floor space minimum; 5. investment economizes most, and treating capacity is changeable; 6. can remove several pernicious gases simultaneously; 7. product makings amount is stable.

This new and high technology removes CO in numerous natural gas such as the U.S., Canada, associated gas ₂Be widely used, 500 covering devices of surpassing industry operation is arranged.Domestic device just at sea in the gas engineering, removes CO as " day nation " Filmtec Corp. ₂Carry out industrial test.So bionethanation system will remove CO ₂With remove CO in the casing-head gas ₂Very similar, be CO in the biogas ₂Content is than the CO in the casing-head gas ₂Big many of content.So the process operation parameter of design is different with the processing casing-head gas.

Summary of the invention:

The object of the present invention is to provide a kind of key technology--economically viable original biogas purification method in " industrial methane " (automobile-used and civilian) production process.Adopt emerging high-tech membrane separation technique purified gases.

Technological process and operating parameter that described film separates purifying biogas are summarized as follows:

Originate in biogas cabinet (1) (preferably dry gas-holder) pressure and remain on 4～12KPa, 4～35 ℃ of temperature.Through one-level drain sump (2) and digester (3), be depressed into outlet pressure 0.8～1.2MPa by oil-free gas compressor (4), transfer to 40～45 ℃ of temperature.Enter pans (6) through secondary drain sump (5), through three grades of accurate filters (7), the micronic dust of filtering d 〉=0.01 μ m enters membrane separator (8) by the middle pressure biogas of pans (6) outlets.This device is the membrane module with the hollow-fibre membrane combination, two-stage series connection.After gas separates through membrane separator, CO ₂Preferential by film, dense CO is so incensed that in infiltration ₂With a small amount of CH ₄, it is preceding to be partly refluxed to compressor (4), partially draining (or again after desulfurization, be compressed into " industrial carbon dioxide " and sell).The port of export obtains the methane rich dry gas of purifying, enters clean biogas storage tank (9), and pressure is 0.7～0.10MPa.The same with natural gas then, be compressed to 20～25MPa by skid-mounted type CNG gas station (10), adorn the gas bomb group or add gas column (11), sell automobile-used.

The invention has the beneficial effects as follows:

1, purifying marsh gas by membrane separating technology of the present invention can remove the CO that originates in biogas simultaneously ₂And small amount of H ₂O, H ₂S.Needn't resemble transformation absorption (PSA) method, select different absorption systems for use, remove CO respectively ₂, H ₂S and H ₂O with simplified apparatus, reduces investment.

2, the present invention is a manufacture biogas, can buy car in installments with the key technology of biogas and civil methane, for utilizing organic waste exploitation biomass energy, replaces natural gas that immeasurable meaning is arranged.

3, the present invention is that investment economizes most in the biogas purification method, effect the best way.Compare with the pressure swing adsorption (PSA) that at present external (Germany) is advanced, with former biogas treating capacity 760M ³/ h (18000Nm ³/ day former biogas is amounted to automobile-used biogas 10000NM ³/ day), equipment investment is compared as follows:

	Germany	China	Remarks
	Germany	China	Remarks	Transformation absorption	1,000,000 Euros	4,000,000 yuan
Film separates		2,000,000 yuan	2-9 in the flow chart	Transformation absorption	1,000,000 Euros	4,000,000 yuan

And the absorption of membrane separation technique and transformation compares, and mist is had stronger selectivity, so total recovery and separation are all high than transformation absorption, thereby running cost is also much lower.

Description of drawings

The process chart of film isolation of purified biogas

The specific embodiment:

1, supporting biogas engineering

The supporting biogas engineering of the present invention should be the large-sized biogas engineering (China stipulate total pond molten 〉=1000m ³), daily output biogas is at 2000Nm ³More than, purify just meaningful.The raw material of producing biogas can be excrement dirt, straw, house refuse; Also can be high concentrated organic wastewater and waste residue, as the discarded object of discharges such as Alcohol Plant, starch factory, slaughterhouse and fermentation industry; It also can be the municipal refuse landfill gas.But the fresh excrement dirt that preferably large-scale professional plant discharges every day.The method of producing biogas can be that wet method (TS≤20%) also can be dry method (TS＞20%).

2, embodiment 1:

With daily output 10000Nm ³Automobile-used biogas is example, needs former biogas 18000Nm ³It is 760Nm that the biogas amount is handled in design ³/ h, 2,000,000 yuan of equipment investments comprise purchasing and installing of all devices in " 2-9 " in the process chart, instrument, pipeline, do not comprise factory building, soil, Equipment Foundations.The membrane separator of key equipment (8) selects for use the U.S. to produce doughnut pattern membrane module, and other are homemade or home-built equipment.Former gas holder (1) Central Plains biogas ingredient stability is at CH ₄55-60%, CO ₂30-38%, H ₂O (g) 2-3%, H ₂S 500-1500PPm.After the purification, the pure qi (oxygen) jar reaches CH in (9) ₄〉=97%, CO ₂≤ 3%, H ₂S≤15mg/Nm ³, dew points at normal pressure is-13 ℃.Equipment reaches more than 80% the total recovery of methane.Can be for filling 600 bottles of automobile-used biogas, bottle volume 70L, pressure 200MPa, folding 14Nm ³Natural gas is equivalent to 16 L90 ^#Gasoline.

3, embodiment 2

To produce civilian bottled biogas 2000Nm daily ³Be example, need to originate in biogas 3600Nm ³, it is 160Nm that the biogas amount is handled in design ³/ h, 500,000 yuan of equipment investments are only used the one-level membrane separator, and other equipment are identical with example 1 with operating condition, and just size is littler.Purify back biogas CH ₄Content 〉=90%, CO ₂≤ 10%, yield can be increased to more than 90%, can be for filling 300 bottles of civil methanes.Bottle volume 70L pressure 10Mpa, folding 7Nm ³Natural gas is equivalent to 12L oil liquefaction vapour.

Claims

1, a kind of economical and effective method of marsh gas purifying is characterized in that: the CO in the purifying marsh gas by membrane separating technology ₂And H ₂S.

2, according to claim 1 described purifying marsh gas by membrane separating technology, it is characterized in that: membrane material comprises polyimides (PI), dimethyl silicone polymer (PDMS), acetate fiber (CA).

3, according to claim 1 described purifying marsh gas by membrane separating technology, it is characterized in that: the membranous type formula comprises hollow-fibre membrane, rolled film and board-like film.

4, according to claim 1 described purifying marsh gas by membrane separating technology, it is characterized in that: technological parameter is raw material biogas pressure: 4～12KPa, pressure: 0.8～1.2MPa before the film.

5, according to claim 1 described purifying marsh gas by membrane separating technology, it is characterized in that: former biogas pre-treatment must remove through accurate tertiary filter 〉=particulate of 0.01 μ m, with the diaphragm separator.