7 Dec, 2015
Improvements in the Steels Used in Oil and Gas Processing Equipment over the Last Half Century
In the post-World war II period, the steels used in the oil and gas industry were quite different from what we use today. This tip of the month (TOTM) presents a brief overview of improvements in the steels used in oil and gas processing equipment for safer and more reliable operations.
Read More >9 Nov, 2015
Adsorption Dehydration: Two-Tower vs. Three-Tower System
There are different process configurations for adsorption dehydration systems. The most common arrangements are two-tower and three-tower configurations. In past articles, we have discussed the efficient operation of molecular sieve dehydration units. Specifically, the benefits of standby time in the adsorption dehydration processes and impact of feed gas conditions. This month’s Tip of the Month compares the required size of major equipment for the two-tower system with the three-tower system, considering a number of key parameters.
Read More >5 Oct, 2015
What is the Impact of Feed Gas Conditions on the Adsorption Dehydration System?
Adsorption dehydration units can reduce the water content of a gas stream to less than 0.1 ppmv. The gas industry normally uses adsorption dehydration units upstream of a liquefied natural gas (LNG) plant or a deep natural gas liquid (NGL) extraction plant where the gas temperature reduces to less than -160 °C (-256 °F) and -100 °C (-148 °F), respectively. Removal of water content to this very low level is essential to prevent freezing. This month’s article discusses feed gas flow rate, pressure, and temperature effect(s).
Read More >3 Sep, 2015
Gas-Liquid Separators Sizing Parameter
In this Tip of the Month (TOTM), we will focus on the application of Souders-Brown approach in gas-liquid separators and present diagram, simple correlations and tables to estimate the Souders-Brown equation constant, KS (the so called sizing parameter). We will consider both vertical and horizontal gas-liquid separators. Knowing the actual gas flow rate through the vessel, one can use KS parameter to determine the maximum allowable gas velocity through the vessel and determine the required separator diameter. One can also use the appropriate value of KS to size the mist extractor in the vessel. The performance of a gas-liquid separator is highly dependent on the value of KS; therefore, the choice of appropriate KS –values is important.
Read More >3 Aug, 2015
Effect of Relative Density (Specific Gravity) on the Saturated Water Content of Sweet Natural Gases
In this Tip of the Month (TOTM), we will study the effect of relative density (Specific Gravity, SG) on the saturated water content of sweet natural gases. The results of this study include the water content of sweet natural gases as a function of relative density in the range of 0.60 to 0.80. Four temperatures of 4.4, 23.9, 37.8 and 149 °C (40, 75, 100, and 300 °F) were considered. For each temperature, the saturated water content was calculated for pressures of 1724, 3448, 6897, and 13 793 kPaa (250, 400, 100 and 2000 psia).
Read More >6 Jul, 2015
How to Estimate Compressor Efficiency
In this article, we will demonstrate how to determine the efficiency of a compressor from measured flow rate, composition, suction and discharge temperatures and pressures. A rigorous calculation based on an equation of state and a shortcut method are considered and the results are compared. From a calculation viewpoint alone, the compressor power calculation is particularly sensitive to the specification of mass flow rate, suction temperature and pressure, and discharge temperature and pressure. A compressor is going to operate under varying values of the variables affecting its performance. Thus the most difficult part of a compressor calculation is specification of a reasonable range for each variable and not the calculation itself.
Read More >2 Jun, 2015
Effect of Chemical Additive on Crude Oil Pipeline Pressure Drop
For transportation of crude oil, the pumping power requirement varies as the crude oil viscosity changes. Increasing °API or line average temperature reduces the crude oil viscosity. The reduction of viscosity results in higher Reynolds number, lower friction factor and in effect, lower pumping power requirements. To reduce pressure drop and increase pipeline capacity, oil industry has utilized drag reducing agents. Drag-reducing agents, or drag-reducing polymers, are additives in pipelines that reduce turbulence in a pipe. Usually used in petroleum pipelines, they increase the pipeline capacity by reducing turbulence and therefore allowing the oil to flow more efficiently. In addition to drag reducing agents, another group of chemicals called “Incorporative Additives”, which reduces crude oil viscosity, may be used. In this Tip of the Month, we will demonstrate the effect of an incorporative additive on crude oil viscosity and consequently on pressure drop for crude oil pipeline transportation.
Read More >4 May, 2015
Benefits of Standby Time in Adsorption Dehydration Process
Molecular sieves are used upstream of turboexpander units and LNG facilities to dehydrate natural gas to <0.1 ppmv. In the natural gas industry, the molecular sieves employ heat to drive off the adsorbed water. The cyclical heating/cooling of the adsorbent results in a capacity decline due to a gradual loss of crystalline structure and/or pore closure. A more troublesome cause of capacity decline is contamination of the molecular sieves due to liquid carryover from the upstream separation equipment. Because of the capacity decline curves flatten out, available standby time may be able to extend the life of a molecular sieve unit when your unit is operating on fixed cycle times. Other operating options include: running each cycle to water breakthrough; and, reducing the cycle times in discreet steps throughout the life of the adsorbent. To illustrate the benefits of standby time, a case study was evaluated and the results are presented.
Read More >10 Apr, 2015
Estimating Sour Gas Water Content by New Correlations and Simplified Charts
In April's "Tip of the Month," we will present a set of correlations and simplified charts for estimating sour gas water content directly without having to look up the water content of sweet gas. These correlations are based on the Wichert and Wichert chart (Figure 20-9 of the GPSA data book) and Wagner and Pruss water vapor equation and Bukacek correlation for estimating sweet gas water content. The proposed correlations are valid for pressures up to 24 MPa (3500 psia), temperatures up to 175°C (350°F) and H2S equivalent concentrations of up to 50 mole %. The accuracy of the proposed correlations was compared against limited experimental data and a rigorous method using an equation of state.
Read More >3 Mar, 2015
Process Safety and Low Oil Prices
In this edition of our Tip of the Month series, we reflect back to December 2008, and get a reminder from the United States Chemical Safety Board (CSB) to remain focused on process safety and accident prevention during this time of lower oil prices. During the economic downturn of 2008, oil prices dropped significantly. The latest drop in crude oil prices is similar. At that time, the CSB produced a video message asking companies to stay focused on process safety. That message is still very relevant today.
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