Maintaining a Biogas Purification System SARBS 1

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Arnold Dorsey
6 years ago
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1 Maintaining a Biogas Purification System SARBS 1

2 TIPS FOR MAINTENANCE SAVINGS SARBS 2

3 REVIEW OF BIOGAS TREATMENT PROCESSES SARBS 3

4 1. Inlet raw gas coalescer 2. H 2 S Removal Bioscrubber Iron Sponge SulfaTreat SARBS 4

5 SARBS 5

6 SARBS 6

7 SARBS 7

8 3. Particulate Filter 4. Blower(s) or Compressors 5. Moisture Removal System Compressor Recirculation Pump Condenser SARBS 8

9 SARBS 9

10 6. Water Droplet Coalescer 7. Siloxane Removal System 8. Final Particulate Filter SARBS 10

11 Where to look for ways to save on maintenance SARBS 11

12 Coalescers and Filters are only a small part of the O&M Budget, so not much can be gained by tweaking these SARBS 12

13 Two potential areas of savings: 1) Replace non-cleanable filter elements with cleanable mesh pad type elements; 2) Possibly eliminate coalescers ahead of iron sponge vessels SARBS 13

14 Implement a preventative maintenance program for blowers and moisture removal equipment. This is critical as the equipment ages. Budget key parts replacements SARBS 14

15 As an alternative to in-house programs, consider purchasing a service maintenance agreement from a 3 rd party. These are inexpensive and will free up labor resources for more critical plant matters SARBS 15

16 So far, we have discussed items that contribute to only 15% to 20% of the total maintenance budget SARBS 16

17 The two biggest cost items are: 1) H 2 S removal media and 2) Siloxane removal media replacement SARBS 17

18 H 2 S removal media replacement can be as much as 40% to 45% of the total maintenance cost on a digester gas purification system SARBS 18

19 As a rule, it costs about $1.00 to $2.50 per pound of H2S removed from a digester gas stream (the higher number is for SulfaTreat ). This includes the new media, labor, disposal and transportation costs SARBS 19

20 One pound of H 2 S is equivalent to 1 MMSCF of digester gas containing just 11.4 ppmv of H 2 S SARBS 20

21 The costs add up fast. A digester gas stream with a high siloxanes level can cost $100 s each day for purification SARBS 21

22 Ways to save on H 2 S removal: 1) Keep ph of iron sponge above ) Make sure there are 2 ppmv of oxygen for each ppmv of H 2 S in the biogas SARBS 22

23 3) Try an air scour to restore the iron sponge effectiveness. Oxygen will enhance the H 2 S removal and extend the media life SARBS 23

24 4) Review H 2 S Removal System design parameters to determine if the proper equipment is being used. Some rules of thumb: SARBS 24

25 Consider the use of a bioscrubber if H 2 S level is above 250 ppmv. Iron Sponge and SulfaTreat are best used if the H 2 S level is 100 to 400 ppmv SARBS 25

26 If a bioscrubber can be installed, it can reduce H 2 S removal O&M costs by 75% or more. This offers an attractive payback on the capital investment SARBS 26

27 Siloxane removal media replacement can be as much as 50% to 55% of the total maintenance cost on a digester gas purification system SARBS 27

28 As a rule, it costs about $4.00 to $4.50 per pound of siloxanes removed from a digester gas stream. This includes the new carbon media, labor, disposal and transportation costs SARBS 28

29 One pound of siloxanes is equivalent to 1 MMSCF of digester gas containing just 0.97 ppmv (970 ppbv) of total siloxanes SARBS 29

30 The costs add up fast. A digester gas stream with a high siloxanes level can cost $100 s each day for purification SARBS 30

31 Ways to save on siloxanes removal: 1) Consider a carbon exchange service (CXS) or a carbon recycle service (CRS). These can save as Much as 50% of the cost of new media and disposal of the spent media SARBS 31

32 2) Consider replacing the nonregenerable siloxane removal system with a regenerable one, such as the CompHeet Process. This can save as much as 75%, and has a good payback SARBS 32

33 Perform a review your Siloxane Removal System design parameters to determine if a regenerable system is a good fit. A rule of thumb: SARBS 33

34 Consider the use of a regenerable siloxane removal system if the total of the siloxanes and VOCs exceeds 25 ppmv SARBS 34

35 Another area for potential savings is in analytical tests. Consider the use of a multifunction in-line analyzer and use a laboratory only for tests it cannot perform SARBS 35

36 Wrap-up and Questions SARBS 36

37 You can reach me at: (Office) SARBS 37

Treatment of Digester Gas

Treatment of Digester Gas Tom Mossinger, PE SCAP Energy Management Committee Meeting February 28, 2013 Digester Gas Composition Approximately 60% CO 2 Approximately 40% CH 4 Water vapor saturated at 95-100