Scholarly article on topic 'Carbon Dioxide Separation Technology from Biogas by “Membrane/Absorption Hybrid Method”'

Carbon Dioxide Separation Technology from Biogas by “Membrane/Absorption Hybrid Method” Academic research paper on "Materials engineering"

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{"Biogas separation" / "carbon dioxide separation" / "membrane/absorption hybrid method ;CH4 " / "CO2 "}

Abstract of research paper on Materials engineering, author of scientific article — Takafumi Tomioka, Toru Sakai, Hiroshi Mano

Abstract “Membrane/absorption hybrid method” is a technology developed by Research Institute of Innovative Technology for the Earth (RITE) aiming to separate I collect carbon dioxide in exhaust combustion gas at low cost and in high purity. RITE and Taiyo Nippon Sanso Corporation (TNSC) had developed a biogas concentration unit that utilizes “membrane / absorption hybrid method” jointly. We had succeeded to improve the regeneration efficiency of carbon dioxide absorption solution for circulated use while maintaining high methane gas recovery rate, and improved the recovery rate of carbon dioxide. Moreover, it turned out that separation cost can be reduced by using the separation process using the source of surplus waste heat at a biogas generation site.

Academic research paper on topic "Carbon Dioxide Separation Technology from Biogas by “Membrane/Absorption Hybrid Method”"

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Energy Procedia 37 (2013) 1209 - 1217

GHGT-11

Carbon dioxide Separation Technology from Biogas by "Membrane/Absorption Hybrid Method"

Takafumi Tomioka^, Torn Sakaia, Hiroshi Manob

aTaiyo Nippon Sanso Corporation, 1-3-26 Koyama Shinagawa-ku,Tokyo 142-8558, Japan bResearch Institute of Innovative Technology for the Earth (RITE),9-2 Kizugawadai Kizugawa-s hi, Kyoto 619-0292, Japan

Abstract

"Membrane / absorption hybrid method" is a technology developed by Research Institute of Innovative Technology for the Earth (RITE) aiming to separate / collect carbon dioxide in exhaust combustion gas at low cost and in high purity. RITE and Taiyo Nippon Sanso Corporation (TNSC) had developed a biogas concentration unit that utilizes "membrane / absorption hybrid method" jointly. We had succeeded to improve the regeneration efficiency of carbon dioxide absorption solution for circulated use while maintaining high methane gas recovery rate, and improved the recovery rate of carbon dioxide. Moreover, it turned out that separation cost can be reduced by using the separation process using the source of surplus waste heat at a biogas generation site.

© 2013 The Authors. Published by Elsevier Ltd. Selection and/or peer-review under responsibility of GHGT

Keywords:biogas separation;carbon dioxide separation;membrane/absorption hybrid method; CH4; CO2

1.Introduction

Biogas is one of the carbon-neutral energy sources. Biogas is emitted by anaerobic fermentation of "stock raising waste, raw sludge, garbage (reclaimed land), and food waste".

The combustion calorie of biogas is low because of composition of about 60% (volume) of methane, and about 40% (volume) of carbon dioxide, Use of biogas requires an expensive special-purpose machine, and it is limited to the warm water supply by a boiler, an electric power supply, electricity sales to utilities with a cogeneration dynamo, etc.

In order to promote the further effective use of biogas, We think that biogas use can be promoted by increasing use ranges, such as fuel for natural gas vehicles, a diffused combustion appliance for city gas, and city gas lead pipe pouring. For that purpose, it is necessary to refine the methane concentration in biogas more than 98% (volume), and to obtain fuel gas with a combustion calorie equivalent to natural gas (city gas 12A). (Fig. 1)

1876-6102 © 2013 The Authors. Published by Elsevier Ltd. Selection and/or peer-review under responsibility of GHGT doi:10.1016/j.egypro.2013.05.219

Moreover, by removing carbon dioxide, since 40% reduction of gas capacity is possible, the voltage rise equipment and the storage tank for momentary storage of methane become miniaturizable. Furthermore, the economic effect in respect of equipment also increases.^

In recent years, a methane fermentation tub is installed in a sewage disposal plant, a dairy institution, a waste disposal plant, etc., In addition to the usage, such as warm water and power generation, methane refining is incorporated for effective use of biogas, and various use test and utilization test, such as gas utilization in a CNG vehicle, the fuel for fuel cells, and the external institution by container filling and transportation and pouring to a city gas pipeline, are carried out. Moreover, it is in the also globally same tendency.

Special-puipose machine (Cogeneration,Boiler,etc. )

Food factry Milk Farm Swage Plant

CNG Car

Berner (City gas12A type)

Fig. 1 Image of biogas use

2. Membrane / absorption hybrid method

"Membrane / absorption hybrid method" are the technology developed aiming at taking in the advantage of the chemistry absorbing method and a membrane separation method, and separating and collecting the carbon dioxide in flue gas with low cost and high purity by RITE.

In order to apply this technology to the biogas refining fields, in collaboration with RITE, research and development in carbon dioxide recovery rate improvement technology and separation performance improvement technology effective in refining of 98% (volume) of methane concentration was done from the 2003 fiscal year.

It is low cost, and since this technology can separate carbon dioxide with high selectivity, when it applies to refining of biogas, it maintains a high methane recovery rate and is technology in which methane refining (separation of the carbon dioxide of high purity) of high purity is possible.

Moreover, it is the technology of having a possibility that methane and carbon dioxide can use the biogas of the limited amount of emergence effectively.

2-1. A principle and the feature of Membrane / absorption hybrid method

"Membrane / absorption hybrid method" are separation technology which is made to diffuse carbon dioxide and is collected by making an absorbing solution absorb carbon dioxide, sending to one side of a porous membrane, decompressing another side of a porous membrane, and carrying out the flash of the absorbing solution to a reduced-pressure atmosphere from a membranous detailed hole. 2)

The key map (Fig. 2) and the feature at the case of applying a membrane / absorption hybrid method to biogas refining are shown below.

(1) By the dry type membrane separation method or the PSA method, high concentration refining of difficult methane and coexistence of a high recovery rate are possible for this technology.

(2) Compared with the heating reproduction method in the chemistry absorbing method, heat degradation of an absorbing solution can be controlled for this technology.

(3) Continuation extraction of high-concentration carbon dioxide is possible for this technology.

Separation CH4

Absorption column (C02 absorption)

Biogas-*

(CH4+C02)

C02 absorption solution

Hollow-fiber membrane module

Decompression (C02 release)

C02 absorption solution (Regeneration)

Tube-side Shell-side

® Membrane O

Mimute pore >1atm

^Decompression

Fig.2 Schematic flow diagram of biogas separation in "membrane / absorption hybrid method"

2-2. Separation performance of Membrane / absorption hybrid method

Generally the carbon dioxide levels of flue gas are 10-15% (volume). On the other hand, the carbon dioxide levels in biogas are about 40% (volume).

It is necessary to remove the carbon dioxide levels in biogas below to 2% (volume), and to make it the methane concentration more than 98% (volume) in biogas refining.

By this system, die absorbing solution which absorbed carbon dioxide is introduced into a membrane module, and decompression reproduction is carried out. Therefore, it becomes important for improvement in biogas separation performance to raise the diffusion efficiency of the carbon dioxide in a membrane module. Moreover, the long-term durability over an absorbing solution is also required.

RITE and TNSC evaluate separation performance by lab scale test equipment using imitation gas (CH4+CO2) about various membrane modules of the different film quality of the material, membrane structure, and membrane penetration fluid volume. From these results, we determined the specification of the membrane module excellent in the diffusion efficiency (separation performance) of carbon dioxide, and separation cost and durability.

The variation per hour of the biogas separation performance of a membrane module and absorbing solution penetration performance which showed the best diffusion efficiency in Fig. 3 is shown.

There was no tendency for the penetration flow of an absorbing solution to fall with progress of time in this membrane module. Moreover, it turned out that biogas separation performance can also maintain 98% (volume) of more than refining methane concentration.

In the membrane module of different specification, there were some to which it swells with an absorbing solution and the membrane penetration flow of an absorbing solution falls.

100 98 96 94 ; 92 90 88 86 84 82 80

-♦— CH4 conc.

-©— Membrane flow rate

1.3 £

1.0 2 I

50 100 150 200 250 300 Time Dependence [hrs]

Fig.3 Time Dependence of "methane separation performance"and "membrane penetration flowing quantity of absorption liquid "

The membrane quality of the material excelled field of separation performance and durability in polyethylene most, as a result of evaluating polysulfone, polyether sulfone, polyethylene, etc.

The lab scale test estimated an absorbing solution, and operation pressure and temperature besides membrane module evaluation.

About the absorbing solution, biogas separation performance was compared for the lst-3rd class amine which is industrially flexible, such as monoethanolamine (MEA) and methyldiethanolamine (MDEA), by several kinds.

As a result, diethanolamine (DEA) showed the sufficient balance as absorption / diffusion characteristic of carbon dioxide.

The purity concentration of the carbon dioxide in biogas separation of a membrane and an absorption hybrid technique is obtained on 96-99% (volume) of a dry basis as a measurement example.

The purity concentration of the carbon dioxide is affected with the conditions of the separation operation conditions (temperature, pressure, etc.) in methane refining, or the composition of equipment absorption / diffusion part.

The carbon dioxide after separation by this method has high purity, and has suggested the simultaneous utilization on the possibility of future separation methane and carbon dioxide.

3. A field examination and improvement technology

The actual substantiation unit which has the biogas throughput (10m3 (normal) /h) of a practical use scale in the "Kyoto Protocol goal achievement industrial technique development promotion enterprise" (20062007 fiscal year) of RITE was manufactured, and real gas continuous running at a biogas generation site performed the check of equipment performance and practicality.

3-1. Actual substantiation unit

The specification outline of actual substantiation unit is shown in the Table. 1. Moreover, a schematic flow diagram is shown in Fig. 4 and substantiation unit appearance is shown in the Fig.5.

Gas/Liquid separator!. Gas pump Liquid pump Vacuum pump

Fig.4 Schematic flow diagram of each method substantiation unit

Table. 1 Overall summary of substantiation unit

Size of unit W3000 x D1700 x H2700 mm

Biogas processing flow rate 10 m3(normal)/h

Absorption liquid sending flow rate 9-18 m3/h Absorption liquid Diethanolamine solution

Operating pressure Gas: -0.09 ~ 0.05 MPa(gauge)

Liquid: 0.03 ~ 0.1 MPa(gauge) Operating temperature_30-40 °C_

This equipment always fills a membrane module with an absorbing solution, and is maintaining the airtightness of a decompression part and a pressure portion.

The airtightness (surface) is carrying out ganged control of the inverter and absorption tower surface sensor of a liquid pump, and holds stability.

Fig.5 External view of membrane / absorption hybrid substantiation unit

In this system, the diffusion performance of the carbon dioxide in a membrane module influences greatly methane refining performance (Gas/liquid-ratio and power cost).

We were compact and adopted the membrane module of the hollow fiber type which can take many membrane penetration fluid volume. Moreover, the filling density of the hollow fiber used what was converted into 50% of standard membrane modules.3) (Fig. 6)

Fig. 6 Hollow fiber membrane module

3-2. The real gas methane separation field test of actual substantiation unit

We installed actual field test substantiation unit in the biogas generation site in a dairy institution (Hokkaido). Then, we carried out continuous running by real gas for two months, and checked biogas separation performance and the durability of each apparatus, membrane module, and absorbing solution. The biogas separation performance of the actual substantiation unit in a field test is shown in Fig. 7.

In biogas separation with real gas continuous running, 98% (volume) of refining methane concentration and the methane recovery rate of 96-98% were obtained, and it has checked that it was satisfactory with practicality including the durability of each apparatus. Moreover, the absorbing solution penetration flow of a membrane module, the absorbing solution state, and the control system were stabilized, and have been maintained.

Run time [day]

Fig.7 Biogas separation performance (Field-Test)

• CH4 conc.(%(volume)) = 100 - CO2 conc.(%(volume))

• CH4 recovery rate(%) = separation CH4 flow-rate(m3(normal)/h) / source CH4 flow-rate(m3(normal)/h) 3-3. Improvement technology

In the research (N2-C02 separation) by RITE, there was a report that the separation energy of carbon dioxide can be sharply reduction by applying the process of using decompression and a heat source together to reproduction of an absorbing solution.45

At a biogas generation site, a boiler, cogeneration apparatus, etc. which were set by the amount of biogas generations are used. The warm water from these apparatus is mainly used for warming, freeze proofing, etc. of a fermenter and an institution. However, it can use as a surplus heat source in many cases.

We examined the cost cut effect of this equipment by the case of applying this process to biogas refining. The equipment flow of a surplus heat source use process is shown in Fig. 8.

In a new process, the absorbing solution cooling of an absorption part, the absorbing solution of a diffusion part,and each heat exchanger required for the heat recollection of warming and an absorbing

Fig. 8 Biogas separation new process of menbrane and absorption method

The difference in temperature of absorption / diffusion part and the relation of the rate of gas/liquid-ratio (at refining methane 98% (volume) ) by this process are shown in Fig. 9.

As compared with the case where there is no utilization of waste heat, the rate of mind liquior ratio has been improved greatly. As compared with the case where it has no absorption / diffusion part difference in temperature, on the conditions whose differences in temperature are 15 °C, the liquid flow rate was reduction to about 1/4, and the low degree of vacuum was improvement to -85kPa (gauge) from -90kPa (gauge). The miniaturization of a membrane module, gas / liquid separating unit, piping, etc. became possible from reduction of this separation energy, and reduction of the liquid flow rate. (Table.2)

M § ¡1)

5 10 15 20

Diffusion-absorption part difference in temp, (t)

Fig.9 Biogas separation performance of new process

Table.2 The equipment improvement effect by a new process

Item Membrane/Absorptio Hybrid (10m3(normal) /h)

New process (calc.) substantiation unit

CH4 concentration %(volume) ^98

CH4 recovery rate % 96~98

Source-of-power unit ratio - 0.75 1

4. Conclusion

We furthered technical development focusing on 98% (volume) of refining methane concentration in biogas refining.

This membrane and an absorption hybrid technique are the technology in which the selectivity of carbon dioxide is high. Therefore, there is a possibility to carbon dioxide separation / recovery uses other than biogas of being applicable. As an example of application, they are selective removal, recovery and storage, use of both separation gas, etc.

From now on, we will advance examination of the applicability of this technology also to the use which removes only carbon dioxide from the mixed gas of a hydrogen atmosphere and nitrogen atmosphere. Moreover, examination of applicability is similarly advanced about the use which can harness the feature that high purity is obtained with both methane and carbon dioxide.

A part of this work was supported by Ministry of Economy, Trade and Industry (METI), Japan.

References

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2) M.Teramoto, H.Mano et al..Separation and Purification Technology.30,215-227(2003)

3) T.Tomioka,M.Mizuno,T.Sakai,Y.Akai. The collection of the Kyoto Protocol goal achievement technical development promotion business result debrief session summaries. Edited by RITE.Kyoto.2007-ll,RITE.Kyoto,RITE,2007,13-14

4) Y.Fujioka,K.Yamada,H.Mano,K.Okabe,M.Nakamura,H.Araki,Y.Takahara,H.Saisho,Y.Mitsushita. The collection of program research-and-development result debrief session summaries. Edited by RITE.Kyoto.2007-11 ,RITE.Kyoto,RITE.2007,28-30.