1、 STD=API/PETRO PUBL 4b8O-ENGL 1998 0732290 ObL5b35 bBL E American Petroleum Institute Strdwu fir Tdqi AMINE UNIT AIR EMISSIONS MODEL EVALUATION HEALTH AND ENVIRONMENTAL SCIENCES DEPARTMENT PUBLICATION NUMBER 4680 DECEMBER 1998 SWEET GAS l-+ I- F R SOURGAS IE LEAN AMINE SOLVENT OoLER PUMP FLASH AMINE
2、 0 FLASH TANK LEAN / RICH HEAT EXCHANGER ACID GAS TO SULFUR - R E G E N E R A T O R Y RECOVERY COOLER 4 REBOILER U“ n PUMP American Petroleum Ihstitute American Petroleum Institute Environmental, Health, and Safety Mission and Guiding Principles MISSION The members of the American Petroleum Institut
3、e are dedicated to continuous efforts to improve the compatibility of our operations with the environment while economically developing energy resources and supplying high quality products and services to consumers. We recognize our responsibility to work with the public, the government, und others
4、to develop and to use natural resources in un environmentally sound manner while protecting the health and safety of our employees and the public. To meet these responsibilities, API members pledge to manage our businesses according to the following principles using sound science to prioritize risks
5、 and to implement cost-effective management practices: a To recognize and to respond to community concerns about our raw materials, products and operations. c PRINCIPLES o To operate our plants and facilities, and to handle our raw materials and products in a manner that protects the environment, an
6、d the safety and health of our employees and the public. o To make safety, health and environmental considerations a priority in our planning, and our development of new products and processes. o To advise promptly, appropriate officials, employees, customers and the public of information on signifi
7、cant industry-related safety, health and environmental hazards, and to recommend protective measures. o To counsel customers, transporters and others in the safe use, transportation and disposal of our raw materials, products and waste materials. o To economically develop and produce natural resourc
8、es and to conserve those resources by using energy efficiently. o To extend knowledge by conducting or supporting research on the safety, health and environmental effects of our raw materials, products, processes and waste materials. a To commit to reduce overall emission and waste generation. o To
9、work with others to resolve problems created by handling and disposal of hazardous substances from our operations. o To participate with government and others in creating responsible laws, regulations and standards to safeguard the community, workplace and environment. o To promote these principles
10、and practices by sharing experiences and offering assistance to others who produce, handle, use, transport or dispose of similar raw materials, petroleum products and wastes. STD=API/PETRO PUBL 4bBO-ENGL le198 m 0732290 Obl5b37 454 m Amine Unit Air Emissions Model Evaluation Health and Environmental
11、 Sciences Department API PUBLICATION NUMBER 4680 PREPARED UNDER CONTRACT BY: EDMONTON, ALBERTA CANADA D6 ROBINSON RESEARCH LTD. DECEMBER 1998 American Petroleum Institute STDIAPI/PETRO PUBL Llb0-ENGL $998 W 0732290 Ob15b38 390 m API PUBLICATIONS NECESSARILY ADDRESS PROBLEMS OF A GENERAL NATURE. WITH
12、 RESPECT TO PARTICULAR CIRCUMSTANCES, LOCAL, STATE, AND FEDERAL LAWS AND REGULATIONS SHOULD BE REVIEWED. API IS NOT UNDERTmG TO MEET THE DUTIES OF EMPLOYERS, MA“FAC- TURERS, OR SUPPLIERS TO WARN AND PROPERLY TRAIN AND EQUIP THEIR EMPLOYEES, AND OTHERS EXPOSED, CONCERNING HEALTH AND SAFETY RISKS AND
13、PRECAUTIONS, NOR UNDERTAKING THEIR OBLIGATIONS UNDER LOCAL, STATE, OR FEDERAL LAWS. NOTHING CONTAINED IN ANY API PUBLICATION IS TO BE CONSTRUED AS GRANTING ANY RIGHT, BY IMPLICATION OR OTHERWISE, FOR THE MANU- FACTURE, SALE, OR USE OF ANY METHOD, APPARATUS, OR PRODUCT COV- ERED BY LETTERS PATENT. NE
14、ITHER SHOULD ANYTHING CONTAINED IN THE PUBLICATION BE CONSTRUED AS INSURING ANYOM AGAINST LIABIL- ITY FOR INFRINGEMENT OF LETERS PA=. All rights reserved No part of this work may be repmduced, stored in a retrieval system, or transmitted by any means, electronic, mechanicai. photocopying, recording,
15、 or otherwise, without prior written permission from the publisher Contact the publisher, API Publishing Services, 1220 L Street, h?W, Washington, D.C. 20005. Copyright (P 1998 American Petroleum institute iii STD.API/PETRO PUBL 4b8O-ENGL 1998 O732290 Ob15b39 227 ACKNOWLEDGMENTS THE FOLLOWING PEOPLE
16、 ARE RECOGNEED FOR THEIR CONTRIBUTIONS OF TIME AND EXPERTISE DURING THIS STUDY AND IN THE PREPARATION OF THIS REPORT API STAFF CONT ACT Paul Martino, Health and Environmental Sciences Department WMBFS OF THE AMINE UNIT EMISSIONS PROJECT GROUP Vernon Schievelbein, Chairman, Texaco Inc. Tom Backhouse,
17、 Phillips Petroleum Company William Fishback, Mobil Exploration e EXECUTIVE SUMMARY 1 1 . 2 . 3 . 4 . INTRODUCTION 3 THE AMINECalc MODEL 5 2.1 The Amine Process . 5 2.2 Model Descriptions . 7 2.3 Model Input Requirements 10 MODEL RESULTS 11 3.1 Model Inputs 11 3.2 Result Comparisons 14 Statistical A
18、nalysis on Result Cornpanso ns . 30 DISCUSSION AND RECOMMENDATIONS 31 4.1 Discussion . 31 4.2 Recommendations . 32 3.3 REFERENCES . 33 APPENDIX A: TEST CASE SIMULATION RUNS . A-1 LIST OF FIGURES Fime 2-1 2-2 2-3 3-1 3 -2 3-3 3-4 3-5 3 -6 3-7 Typical Amine Sweetening Unit 6 Flow Diagram for Mass Bala
19、nce Calculation 8 Flow Diagram for Sour GadNGL Process Simulation 8 Result Comparisons for Toluene 24 Result Comparisons for Ethylbenzene . 25 Result Comparisons for n-Hexane . 27 Result Comparisons for Total BTEX 28 Result Comparisons for Benzene . 23 Result Comparisons for Xylenes . 26 Result Comp
20、arisons for Total WS . 29 STD.API/PETRO PUBL 4680-ENGL 1778 = 0732290 Ob15b42 811 m LIST OF TABLES Table 2- 1 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 Program Options and Input Requirements . 10 Input Data for Case Simulations 12 Feed Gas Compositions in Mole Percent 13 Result Comparisons for Case 1 Rege
21、nerator Vent 15 Result Comparisons for Case 1 Flash Vent . 15 Regenerator Vent Emissions for Case 2 16 BTEX Stripper Efficiency . 16 Result Comparisons for Case 2 Regenerator Vent 17 Result Comparisons for Case 3 Regenerator Vent 18 Result Comparisons for Case 3 Flash Vent . 18 3-10 Result Compariso
22、ns for Case 4 Regenerator Vent 19 3-11 Result Comparisons for Case 5 Regenerator Vent 20 3-12 Result Comparisons for Case 6 Regenerator Vent 20 3-13 Result Comparisons for Case 6 Flash Vent . 21 3-14 Legend for Bar Chart Abscissa . 22 3-15 Average Standard Deviation for Each Component . 30 STD-API/P
23、ETRO PUBL 4680-ENGL 1998 0732290 Ob15b43 758 D EXECUTIVE SUMMARY The implementation of the 1990 Clean Air Act Amendments (CU) in the United States has created the need for a reliable method to estimate and report hydrocarbon emissions from amine based sour gas and natural gas liquid (NGL) sweetening
24、 units. To address this need, a sohare simulation package, called Amine Unit Air Emission Model (AMINECalc Version 1.0) was developed for the American Petroleum Institute (NI) by DB Robinson Research Ltd. (DBRR). The output simulated by the AMTNECalc Model is designed to suit the needs of regulatory
25、 reporting requirements. Thus, the major objective of this project is to develop a reliable and user- Ciendly software package that will gain acceptance by the US Environmental Protection Agency (EPA) and amine unit operators. With the intention of validating the model, API requested DBRR to evaluat
26、e the model prediction by comparing the simulation results with field data collected from operating plants. This report evaluates the model prediction as well as recommends improvements and modifications to the model to refine the predictions. SECTION 1 INTRODUCTION The implementation of the 1990 Cl
27、ean Air Act Amendments (CU) in the United States has caused the need for a reliable method to estimate and report hydrocarbon emissions from amine based sour gas and natural gas liquid (NGL) sweetening units. To address this need, a software simulation package, called Amine Unit Air Emission Model (
28、AMINECalc Version 1.0) was developed for the American Petroleum Institute (MI) by DB Robinson Research Ltd. (DBRR). Many of the amine units in the field are fitted with sulfur recovery units (SRUs) to control hydrogen sulfide (H2S) andor carbon dioxide (C02) and do not release volatile organic compo
29、unds (VOCs) and hazardous air pollutants (HAPS) to the atmosphere. However, some amine units do not have SRUs because they are used primarily to remove only CO2 fi-om natural gas without H2S; consequently some amine regenerators have the potential to release HAPs and VOCs to the atmosphere. The AMIN
30、ECalc model was developed primarily for those units having the potential to emit VOCs and HAPs to the atmosphere. The calculation algorithm of this package is based on AMSIM, a commercial software package developed by DBRR. Equipped with a rigorous non-equilibrium stage model and the Peng- Robinson
31、equation of state, AMSIM was designed to provide accurate and reliable solutions for sow gas and liquefied petroleum gas processes. The emphasis of this commercial software package was on acid gas (H2S and C02) removal, and its predictions have been constantly verified by actual plant data. The obje
32、ctive of the current project is to develop a PC-based emission model to predict HAPS and VOCs fi-om flash tanks and solvent regenerators of a natural gas sweetening unit. The AMINECalc model was re-engineered from AMSIM and enhanced to accommodate three types of calculations: mass balance calculatio
33、n, gas process simulation, and NGL process simulation. The emphasis is on HAPs which include benzene, toluene, ethylbenzene and xylenes (BTEX), as well as VOCs emitted from amine units. STD.API/PETRO PUBL 4bO-ENGL L998 I 0732290 ObL5b45 520 Amine unit operators may be required to report the emission
34、s to the appropriate regulatory agencies. In order to gain wide acceptance by end users, special attention has been paid to the program intm+ace design. Extensive computer iiteracy or simulation emperience is not a requirement to operate the AMINECalc simulator. Users with a basic knowledge of Windo
35、wsm should be at ease when using the program. 4 STD=API/PETRO PUBL 4b80-ENGL 1998 W 0732290 ObLSb4b 467 SECTION 2 THE AMINECalc MODEL Among many treatment processes for sour gas, uie absorption technology using aqueous solutions of alkanolamines is popular for economic reasons. The use of simulation
36、 software for sweetening processes has steadily increased over the years. This section will provide a general background of the amine process. 2.1 THE AMINE PROCESS Figure 2-1 presents a process flow diagram of a typical amine-sweetening unit. The system consists of two major unit operations: absorp
37、tion and regeneration. A feed stream, which is either natural gas or natural gas liquid (NGL) containing acid gases (H2S andor COz), is introduced into an absorption column where it is counter-currently contacted with an amine solution. The acid gas contents are removed through chemical reactions wi
38、th the amine. After the absorbing treatment, the natural gas or the NGL is ready for consumer use or for further chemical processing. This process is often referred to as a gas sweetening process. The treated gas or liquid is cailed sweetened gas or liquid while the amine solution entering and leavi
39、ng the column is commoniy known as the lean and rich amine solution respectively. After selectively absorbing the acid gases Com the stream, the rich amine solution requires regeneration before it can be reused. The function of the regeneration column is to strip absorbed acid gases from the rich am
40、ine solution. A flash tank is commonly installed downstream fiom the absorber to recover dissolved and entrained hydrocarbons and to reduce the hydrocarbon contents of the acid gas product. Together with other gaseous hydrocarbon species, hazardous air pollutants (HAPS) are potentially emitted Com f
41、lash tanks and regenerators. Using the comprehensive AMINECalc model, one can estimate hydrocarbon emissions Corn amine sweetening units. STD*API/PETRO PUBL 4680-ENGL 3798 0732290 Ob35647 333 A B S O R B E SWEETGAS SOLVENT PUMP T LEAN 0 FLASH TANK kid HEAT EXCHANGER 9- ACID GAS TO SULFUR RECOVERY SG
42、 LN VE Figure 2-1: Typical Amine Sweetening Unit STD*API/PETRO PUBL 4b8O-ENGL 3998 m 0732290 ObLSb48 23T m 2.2 MODEL DESCRIPTIONS The AMINECalc package offers three options: mass balance calculation gas process (gas feed) simulation NGL (liquid feed) simulation. The mass balance calculation option i
43、s a descriptive calculation that has the flexibility to allow users to specie their cases according to the availability of their plant data. The two simulation options allow users to perform rigorous process modeling that predicts hydrocarbon emissions from amine units based on operating conditions.
44、 Option 1: Mass Balance Calculation The mass balance calculation option requires input of the flow rates of lean amine stream exiting a regenerator and flow rates and compositions of the rich amine stream exiting an absorption column. As shown in Figure 2-2, a rich amine stream enters a flash tank a
45、t a pressure lower than the absorber pressure. By executing a flash calculation on the flash tank, the program calculates the flow rate and compositions of the vent gas. Simulated information of the flashed liquid and the input data of the lean amine stream are used in a mass balance calculation to
46、give an estimate of the contents of the stripped acid gas at the top of the regenerator. Option 2: Gas Process Simulation The gas process simulation requires the input of sour gas feed data and lean amine circulation rate as well as the number of trays of the absorber. Figure 2-3 is the flow diagram
47、 for the sour gas treating process. The program will rigorously simulate the operation of the absorber column and calculate the hydrocarbon contents in the rich amine stream. The calculated information of the rich amine stream will then be used to predict the flows of the flash gas and the stripped
48、acid gas of the solvent regenerator. STD.API/PETRO PUBL 4680-ENGL 1998 0732290 ObL5649 L7b W Lean Amine Flash Gas A Rich FLASH TANK Figure 2-2 Flow Diagram for Mass Balance Calculation Sweet Gas t Flash Gas Acid Gas Flow FLASH TANK Figure 2-3 Flow Diagram for Sour Gas/NGL Process Simulation 8 STD*AP
49、I/PETRO PUBL 4bBO-ENGL 3998 - 0732290 ObL5b50 978 Option 3: NGL Process Simulation The NGL process simulation has the same flow diagram as shown in Figure 2-3 and requires the same input information. The difference between the NGL Process Simulation and the Gas Process Simulation is that the feed in the NGL Process Simulation is in liquid form and the absorber is a liquid-liquid contactor instead of a vapor-liquid absorption column. Through a liquid-liquid extraction simulation, the contents of the sweetened NGL from the top of the absorber, along with the flash vent and
