1、 Technical Publication TP - 30 GPA RESEARCH PROJECT No. 006 FOAMING IN GLYCOL AND AMINE SYSTEMS PREPARED BY GAS TECHNOLOGY INSTITUTE 1700 S. MOUNT PROSPECT ROAD DES PLAINES, IL 60018 HOWARD S. MEYER GTI PROJECT 20208 July 2007 Gas Processors Association 6526 East 60th Street, Tulsa, Oklahoma 74145 P
2、hone: 918/493-3872, Fax: 918/493-3875, Website: iFOREWORD The numerous gas processing facilities owned or operated by the Gas Processors Association member companies represent a vast body of practical experience and knowledge. It was the objective of the project, the results of which are presented i
3、n this Technical Publication, to leverage this experience by extracting relevant information from the member facilities with a view towards providing practical guidance for operating and design personnel. The focus of this particular work was the seemingly ubiquitous phenomenon of foaming in gas tre
4、ating plants. In commissioning this work, the GPA Section F Research Steering Committee guiding the work had to depart from its traditional emphasis on fundamental property data research and enter the realm of questionnaires and statistical analysis. As such, this publication provides insight not on
5、ly in the problems of foaming and how they are dealt with in actual operating facilities, but also in the pitfalls and limitations associated with this type of project: The quality of the findings is only as good as the breadth and statistical relevance of the responses received. Foaming is a very c
6、omplex problem with a substantial number of potential causes and remedies, both of operational and process design nature. Commensurately, any statistically relevant message from a plant questionnaire requires a substantial number of responses, specifically, one that is sufficiently larger than the n
7、umber of investigated variables. One result of this work is certainly, that statistical relevance cannot confidently be claimed based on the number of responses received and, therefore, the pointers towards solving the problem of foaming are still not as clear as might have been hoped. Notwithstandi
8、ng this limitation, this publication provides detailed insight into the variables that affect foaming and how individual facilities have addressed foaming problems. It also shows the breadth of designs currently in use. This information can be quite useful to design and operations personnel when con
9、templating new or revamped facilities. Furthermore, the substantial literature reference provided in the appendix affords the interested reader ample opportunity for additional in-depth study and knowledge. Arild Wilson Karl Gerdes Steering Committee Chairman Section F Committee Chairman iiDISCLAIME
10、R AND COPYRIGHT NOTICE GPA publications necessarily address problems of a general nature and may be used by anyone desiring to do so. Every effort has been made by GPA to ensure accuracy and reliability of the information contained in its publications. With respect to particular circumstances, local
11、, state, and federal laws and regulations should be reviewed. It is not the intent of GPA to assume the duties of employers, manufacturers, or suppliers to warn and properly train employees, or others exposed, concerning health and safety risks or precautions. GPA makes no representation, warranty,
12、or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal regulation with which this publication may conflict, or any infringement of letters of pa
13、tent regarding apparatus, equipment, or method so covered. GPA does not endorse or recommend any commercial products or services. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorseme
14、nt, recommendation, or favoring by GPA or their members. Inclusion of a private company, author or contributors views or opinions does not mean they state or reflect those of GPA or their members, and private parties may not use them for advertising or product endorsement purposes. Copyright 2008 by
15、 Gas Processors Association. All rights reserved. No part of this Report may be reproduced without written consent of the Gas Processors Association. iiiTABLE OF CONTENTS FOREWORD . i DISCLAIMER AND COPYRIGHT NOTICE. ii TABLE OF CONTENTS.iii LIST OF TABLES. iv LIST OF FIGURES . iv 1.0 INTRODUCTION 1
16、-1 2.0 RESULTS AND CONCLUSIONS 2-2 3.0 DISCUSSION OF LITERATURE RESULTS. 3-3 4.0 DISCUSSION OF SURVEY RESULTS . 4-6 4.1 General Demographics.4-8 4.2 Post Treatment of the Data 4-8 4.3 Foaming and Antifoam Usage Criteria4-12 4.4 Effect of Process Solution on Foaming .4-13 4.5 Location of Foaming by S
17、everity 4-14 4.6 Feed Conditioning4-15 4.7 Solution Temperature Differences.4-16 4.8 Solution Color, Clarity, and Odor4-18 4.9 Trace Hydrocarbons.4-18 4.10 Filtration.4-19 4.11 Solids in Solution.4-21 4.12 Impact of Foaming.4-22 4.13 Solids Related Foaming .4-22 4.14 Antifoam Rates 4-23 4.15 Antifoa
18、m Types .4-24 4.16 Antifoam Application Location .4-24 4.17 Operating Changes to Control Foaming 4-25 4.18 Is / Is Not Analysis.4-25 5.0 FURTHER RESEARCH NEEDS 5-27 6.0 ACCURACY AND PRECISION.6-28 7.0 APPENDIX A SURVEY DATA RAW STATISTICS7-29 8.0 APPENDIX B LITERATURE SEARCH .8-76 ivLIST OF TABLES T
19、able 1 Mapping of Responses (Part 1):.4-9 Table 2 Mapping of Responses (Part 2):.4-10 Table 3 Mapping of Responses (Part 3):.4-11 Table 4 Occurrence of Foaming by Solvent .4-13 Table 5 Frequency of Foaming and Antifoam Usage for All Process Solutions4-14 Table 6 Foaming and Antifoaming Usage by Proc
20、ess Solution Type4-14 Table 7 Location of Foaming by Process Solution Type4-15 Table 8 Feed Conditioning Equipment by Process Solution Type.4-16 Table 9 Solution Color, Clarity, and Odor4-18 Table 10 Trace Hydrocarbon Composition, mole percent4-19 Table 11 Usage of Particle and Carbon Filters .4-20
21、Table 12 Particle and Carbon Filter Combinations and the Reported Foaming/Antifoam Usage.4-21 Table 13 Presence of Solids in the Solution .4-21 Table 14 Impacts of Foaming . 4-22 Table 15 Solids Related Foaming.4-23 Table 16 Antifoam Usage .4-23 Table 17 Specific Antifoam Usage.4-23 Table 18 Antifoa
22、m Chemical Type.4-24 Table 19 Antifoam Injection Locations 4-24 Table 20 Operating Changes to Control Foaming 4-25 Table 21 DEA Gas Treating Comparison.4-26 LIST OF FIGURES Figure 1 GPA Survey4-7 Figure 2 Delta T for Glycol Systems 4-17 Figure 3 Delta T for Amine Systems 4-17 1-11.0 INTRODUCTION Foa
23、ming in glycol and amine systems results in significant capital and operating costs to the industry. Von Phul states that solvent foaming has been described as the number one operational problem encountered in natural gas processing plants and refinery sweetening processes today, with millions of do
24、llars lost every year in capacity reduction, lost solvent, downstream process damage and environmental discharges that can be directly attributed to solvent foaming. The added capital investment can include a series of inlet separators, water wash columns, filter separators, coalescing filters, and
25、sand/particle/carbon filters. GPA initiated Research Project 006 to gather pertinent information on the nature and conditions for foaming. This resulted in a questionnaire that was sent to the GPA membership and returned by the industry representatives. The data represent some 100 amine and glycol t
26、reating units, located within facilities worldwide. This project was directed at using the data, along with literature information, to provide engineers and operators with specific practices to help reduce the incidences of foaming. GPA and GTI acknowledge the effort of the companies that responded
27、to the survey. 2-22.0 RESULTS AND CONCLUSIONS Foaming is very common within the gas processing community. 69 out of the 75 amine treating units and 18 of the 29 glycol units responded that they had some degree of foaming with their solvent. While the sample size of the survey was too small to identi
28、fy the overriding set of factors that helps control foaming, no common conventional wisdom, common practice, equipment, nor chemical were identified that prevented the reported foaming. The survey provided data on two glycol solutions (90% TEG), and ten amine solutions. With the exception of ethylen
29、e glycol dehydration, between 33% and 100% (depending on the solvent) of the respondents reported foaming. While the use of antifoam was the most commonly reported operational change performed to control foaming, it is neither universally performed nor successful. Silicon and then polyglycols were t
30、he most commonly reported antifoam types used. Antifoam addition rates varied by over four orders of magnitude without any indication of it resolving the problem. The antifoam was predominantly applied to the lean solution, the regenerator, and then to the absorber for the amine systems and equally
31、applied in the glycol system. There was slightly more foaming reported in the absorber for the glycol system than in the flash or regenerator. Foaming occurred more in the amine absorber and regenerator than in the flash vessels. The units had a wide range of feed conditioning and filtration systems
32、 to clean the inlet gas and recirculating solvent. No specific combination of these systems was found to prevent foaming. Neither color, clarity, or odor provided a clear indication of whether the solvent would foam or not. Maintaining temperature differentials between the inlet gas feed and the lea
33、n solvent of greater than 10F was not sufficient to ensure the prevention of foaming: Foaming was observed in some instances when the temperature differential was at or greater than the guideline and in other instances did not occur when the solvent was colder than the gas. Also, the presence or con
34、centration of higher molecular weight hydrocarbons in the gas did not necessarily result in foaming. The presence of solids was a very strong indicator of foaming. Only two units that reported total dissolved solids and/or iron sulfide did not have foaming, while 16 units with some total dissolved s
35、olids and 23 with iron sulfide solids did have foaming. 3-33.0 DISCUSSION OF LITERATURE RESULTS GTI performed a comprehensive literature search related to foaming, especially in amine and glycol systems. The listing of references is given in Appendix B. It includes approximately 125 references from
36、the Laurance Reid Gas Conditioning Conference, Gas Processors Association Annual Meetings, Oil and Gas Journal, and others. Besides the title, authors, source, date, the references include a subjective interest rating of high, medium or low, based on the material contained within. For many reference
37、s, a short comment is also included. The following are some of the industrys rules of thumb for controlling foaming in amine and glycol systems. Add antifoam before or as soon as foaming occurs Clean solvents do not foam1 Solids including iron sulfides will cause foaming. Foaming does not occur if t
38、he solids concentration of the recirculation amine is kept to 1 mg/liter (ppm).2 Hydrocarbon liquids from the upstream processes or from the gas will also promote foaming Surfactants added to defoam or as antifoaming agents can promote foaming.3 Maintaining a temperature differential of 10-15F betwe
39、en solvent and gas will prevent hydrocarbons from condensing from the gas into the solvent4 Controlling the gas and liquid flow rates can control foaming Foam is generally defined as gas dispersed in liquid in such a ratio that its bulk density approaches that of a gas rather than a liquid. It is si
40、mply a structure of expanded liquid surface area containing the gas that was agitated or entrained in the liquid. The energy from agitation generates the surface area. The low surface tension of the liquid makes the energy more efficient in the generation of the surface area, and the liquid surface
41、stays stable because it cannot drain effectively from the structure. The properties of the soap or detergent normally employed to generate stable foam are those of lowering surface tension and increasing the liquid viscosity in the bubble film. Antifoam is a chemical added to the solution to prevent
42、 the formation of foam, while a defoamer is added to breakup existing foam. Neither of these types of products remove the source of foaming. Details of foaming mechanisms have been described elsewhere.5, 6, 71Pauley, C.R., Hashemi, R., Coathien, S., “Ways to Control Amine Unit Foaming Offered,” Oil
43、and Gas Journal, December 11, 1989. 2Brown, R.L., Hashemi, R., “Predicting Contamination Levels of Upset Conditions in Amine Sweetening Systems,” Pall Industrial Process, Scientific solvent degradation, corrosion, and the devices used to remove the contaminants cannot be 100% efficient. Solvent degr
44、adation products that attack protective corrosion layers in system piping generate solid particles. Erosion corrosion also adds to entrained solid particles that act as contaminants. Being a recirculating system, even small levels of inefficient contaminant removal result in increasing concentration
45、s and process upsets. Foaming under plant conditions is most often attributed to solvent contamination by solids, liquid hydrocarbon, well treating chemicals, corrosion inhibitors, lubricants, acidic amine degradation products, and antifoam additives. Most of these compounds are known to be, or to c
46、ontain surfactants. Solvent foaming under plant conditions can be difficult to recognize. This is especially true if it is localized at one high turbulence point in the system. For example, if liquid hydrocarbon is being carried into the contactor with the inlet gas it will most likely flow into the
47、 flash drum with the rich solvent, not up the tower with the gas. Foam created in the flash drum might show up as variation in liquid level, booster pump cavitation, unusual vapor space in the rich side particle filters, higher differential pressure across the carbon bed, or possibly even a change i
48、n heat transfer efficiency at the lean/rich exchanger. Hydrocarbon mists might be carried further into the contactor with the gas. They would eventually be scrubbed from the gas by the solvent. Once in the solvent, surfactants in the liquid hydrocarbon could cause solvent foaming. The large number o
49、f symptoms makes identifying the problem quickly difficult at best. Coastal Chemical8provides the following antifoam selection criteria: Fresh alkanolamine and glycol solutions do not foam. However, when the solution is put into service and contaminated with hydrocarbons or other impurities, the solution may have a tendency to foam. In these cases, antifoam may be used to treat the symptom. While it is recognized that some plants have operated successfully with continuous injection of antifoam, long term, it is best to treat the cause of the sympto
