A simple mathematical predictive tool for estimation of a hydrate inhibitor injection rate

Abstract

Formiranje hidrata u proizvodnji, postrojenjima za obradu i cjevovodima je problem koji industriju prirodnoga plina stoji milijune dolara. Stoga je shvaćanje početka nastanka hidrata nužno za prevladavanje problema hidrata. Cilj prvog koraka ove studije je razvitak korelacije, jednostavne za korištenje, za predviđanje uvjeta za nastajanje hidrata "slatkih" prirodnih plinova.. Ta jednostavna korelacija predviđa tlak nastajanja hidrata "slatkih" prirodnih plinova za tlak do 400 bara (40 000 kPa) i temperature između 13,15 °C i 24,85 °C (260 K i 298 K), kao i molne mase u rasponu od 16 do 29. U slijedećem koraku razvijene su nove empirijske korelacije radi predviđanja potrebnog masenog postotka mono etilen glikola (MEG) u obogaćenim otopinama i količine protjecanja u jedinici vremena za željeno snižavanje temperature formiranja plinskog hidrata. Ove korelacije su napravljene za prirodni plin relativne gustoće 0.6 kod tlaka od 3, 5, 7 i 9 MPa (30, 50, 70 i 90 bara) koji su primjenjivi za masni prirodni plin temperature od 20, 30, 40 i 50 °C. Kako bi se proširila primjenjivost ovih korelacija na širi spektar mješavina prirodnoga plina relativne gustoće do 0,8, dana su dva poopćena korekcijska faktora. Točnost ove jednostavne metode uspoređena je s rezultatima simulacije dobivenim korištenjem komercijalnoga softwarea pri čemu se je pokazala izuzetna podudarnost. U svim slučajevima postotak pogreške iznosio je približno 2% i 5% za predviđanje pada temperature formiranja hidrata i obroka utiskivanja mono etilen glikola (MEG). Jednadžbe koje su razvijene u ovoj studiji mogu biti od značajne praktičke važnosti za inženjere i znanstvenike za brzu provjeru uvjeta formiranja hidrata prirodnih plinova s ili bez prisustva inhibitora bez potrebe za primjenom bilo kakvih eksperimentalnih mjerenja. Kemijski i procesni inženjeri će ustanoviti da su jednostavne jednadžbe prilagođene korisniku s jasnim izračunima bez složenih izraza.The formation of hydrates in production, processing facilities and pipelines has been a problem to the natural gas industry, that cost several millions of dollars.. Therefore, an understanding of the inception of hydrate formation is necessary to overcoming hydrate problems. The aim of the first step of this study is to develop a simple-to-use correlation for predicting hydrate-forming conditions of sweet natural gases. This simple correlation estimates hydrate formation pressure of sweet natural gases for pressures up to 40 000 kPa and temperatures between 260 K and 298 K as well as molecular weights in the range of 16 to 29. In the next step, novel empirical correlations are developed to predict the required MEG weight percent in the rich solution and the flow-rate for desired depression of the gas hydrate formation temperature. These correlations are generated for a natural gas with relative density of 0.6 at pressures of 3, 5, 7, and 9 MPa, which are applicable to wet gas temperatures of 20, 30, 40, and 50 °C. In order to extend the application of these correlations to wide ranges of natural gas mixtures with specific gravities of up to 0.8, two generalized correction factors are also provided. The accuracy of this simple method is compared with the simulation results obtained by commercial software which showed excellent agreement. In all cases the error percent was approximately 2% and 5% for predicting hydrate formation temperature depression and MEG injection rate, respectively. The fitted equations developed in this study can be of immense practical value for the engineers and scientists to have a quick check on hydrate formation condition of natural gases with or without presence of inhibitor without opting for any experimental measurements. In particular, chemical and process engineers would find the simple equations to be user-friendly with transparent calculations involving no complex expressions