GENERAL DESCRIPTION SECTION

CHEVRONTEXACO PETROLEUM COMPANY

GUATEMALA REFINERY

GENERAL DESCRIPTION OF THE CRUDE UNIT

Overview

This facility is located in Escuintla, Guatemala. The crude unit has been expanded from 9,235 to 15,200 barrels per day capacity, and miscellaneous facilities have been enlarged to support the crude unit expansion. Further modifications to the crude preheater exchangers expanded the capacity to 17,000 barrels per day.

This revamp features a new Lower Crude Tower with side strippers for diesel, light gas oil, and heavy gas oil; a new crude heater; six new heat exchangers and four fin-fan product coolers; a product blending manifold; two drums; and sixteen new pumps.

A new furnace will operate in series with the existing crude furnace. The existing furnace was revamped to two tube passes and coils added to superheat steam.

Finished products from the Crude Unit are now Av-jet, Diesel, and Turbine fuels; kerosene; and low-pour, medium-pour, and high-pour fuel oils.

B.Design Basis

The expanded Crude Unit will fractionate crude oil into gas, SR naphtha, light kerosene, heavy kerosene, diesel distillate, light gas oil, heavy gas oil, and residuum.

The blending manifold recombines these streams in various proportions to make sales products, namely Av-jet, kerosene, diesel fuel, turbine fuel, low-pour fuel oil, medium-pour fuel oil, and high-pour fuel oil. The blending manifold has been designed with flexibility to produce whatever products the market demands.

C.Description of Flow

The Crude Unit (Section 100) is designed to separate a charge of 17,000 BPSD of 36° crude into gas, SR Naphtha, light kerosene, heavy kerosene, diesel oil, light gas oil, heavy gas oil, and residuum. The SR Naphtha goes to the SR Naphtha Debutanizer (DA-404). The light kerosene and a major portion of the heavy kerosene are combined and the combined kerosene is split into feed to Kerosene Hydrotreater (2,600 barrels per day) and a stream to the blending manifold. The other streams are all used in blending products at the new manifold – including kerosene returned from the Hydrotreater.

1.Crude Oil Charge

From the storage tank FB-501, the crude oil is pumped by GA-501 or 501S, and metered by the flow recorder-controller FRC-101. The crude oil is then preheated in a series of exchangers. The crude flows through the tube-side of all exchangers except the E-103 Crude/Resid exchanger.

The first exchanger in the crude preheat train is EA-101, the upper crude tower overhead/crude exchanger. The second preheat service is EA-102A and B, where heat is picked up from the circulating reflux drawn from tray 15 of the upper crude tower DA-101. The third preheat service is EA-111, where heat is exchanged from the lower circulating reflux, drawn from tray 16 of the lower crude tower DA-105.

The charge flows at about 266°F. to the flashed crude drum FA-104, where the flashed vapors separate and are fed to the flash zone of the lower crude tower DA-105. The remaining crude from FA-104 is pumped by GA-109 or 109S and is further preheated in the following sequence of heat exchangers:

EA-112A and B, Lower Circulating Reflux/Flashed Crude Exchanger

EA-113, Diesel/Flashed Crude Exchanger

EA-114, Light Gas Oil/Flashed Crude Exchanger

EA-119, Heavy Gas Oil/Flashed Crude Exchanger

EA-120 A&B, Residuum/Flashed Crude Exchanger

2.Crude Heaters

The crude charge, at about 500°F., splits and is flow-controlled through each pass of No. 1 crude heater (BA-101), which has been converted to two-pass design. The passes remain separate flowing to and through crude heater BA-102. Then, at about 720°F. and controlled by TIC-150, the streams recombine and flow to the flash zone of the lower crude tower. In the convection section of BA-101, 50 psig steam is superheated and supplied to the strippers.

3.Lower Crude Tower DA-105 and its Strippers

The crude charge is about 83% vaporized at the 690°F. temperature of the flash zone in DA-105. The lower crude tower DA-105 has four stripping trays below the flash zone and fourteen trays about the flash zone. All are sieve trays except tray 5. The trays are numbered from the bottom of the tower.

The flashed resid liquid, draining from the flash zone of DA-105, is stripped with superheated steam in the bottom stripping trays to produce residuum.

Vapors from the flash zone feed, plus the stripped vapor from the resid, flow upward thru tray 5.

Tray 5 is a bubble cap tray. The total liquid to tray 5 is trapped and feeds the heavy gas oil stripper DA-107.

Feed to the light gas oil stripper DA-106B is withdrawn from tray 9, and the feed to the diesel stripper DA-106A is withdrawn from tray 13.

Circulating reflux is withdrawn from tray 16 into the accumulator FA-105 at a rate controlled by LIC-154 on FA-105. This reflux is pumped by GA-110 or 110S on flow control (FRC-152), combines with the bottom liquid from the upper crude tower DA-101, flows through the shell side of EA-1111 and EA-112 to exchange heat to the crude, and returns to the top tray of DA-105.

4.Residuum

The bottom residuum product is pumped by GA-114 or 114S, flows through the tube side of EA-103 and the shell side of EA-120 A&B to transfer heat to the crude, then flows to the blending manifold and the fuel oil coolers at about 500°F. The flow rate is controlled by LIC-150 on the bottom of DA-105.

5.Heavy Gas Oil

The total liquid from tray 5 in DA-105 flows through a seal loop to tray 4 of the heavy gas oil stripper DA-107. Here it is stripped with superheated steam. The heavy gas oil product is pumped by GA-113 or 114S from the bottom of DA-107 through EA-119 and to the blending manifold at about 490°F.

The flow rate is controlled by the level in the bottom of DA-107. Vapor from the top of DA-107 feeds to DA-105 below tray 6 of that column.

6.Light Gas Oil

Light gas oil feeds by hand control to tray 4 of the light gas oil stripper DA-106B. Here it is stripped with superheated steam. The LGO product is pumped by GA-112 or 111S from the bottom of DA-106B, through EA-114 and air cooler EC-115, to the blending manifold at about 180°F. The LGO flow rate is controlled by the level in the bottom of DA-106B.

7.Diesel

Diesel oil feeds by hand control to tray 4 of the diesel stripper DA-106A. Here it is stripped with superheated steam. The diesel product is pumped by GA-111 or 111S from the bottom of DA-106A through EA-113 and coolers EA-108 & EA 109 to the blending manifold at about 140°F. The flow rate is controlled by the level in the bottom of DA-106A.

8.Upper Crude Tower DA-101

The overhead vapor from the lower crude tower DA-105 flows to the former flash zone of the upper crude tower DA-101. DA-101 has 23 trays above the flash zone and 4 bottom stripping trays. The trays are numbered from the top.

No stripping steam is used for the bottom stripping trays. The liquid bottoms from DA-101 are pumped by GA-106 or 106S to combine with the circulating reflux for the DA-105 tower. The flow rate is controlled by bottom level in DA-101.

Heavy Kerosene is withdrawn from Tray 18 and Light Kerosene is withdrawn from Tray 8 of DA-101.

Circulation Reflux is withdrawn from tray 15 of DA-101, pumped by GA-104 or 104S through the shells of EA-102A and B to transfer heat to the crude, and returned onto tray 14.

The overhead vapor from the DA-101 tower is partially condensed in EA-101, further condensed in EA-104 and EA 110 and sent to the accumulator FA-101. Reflux is pumped by GA-101 or 104S from FA-101 onto the top tray of DA-101 tower. The reflux flow is controlled by TIC-104 on the DA-101 overhead vapor line. The wild SR Naphtha Debutanizer DA-104. The flow rate is controlled by FRC-105.

The pressure at the top of DA.-101 is controlled by PIC-101 which will admit fuel gas to the overhead or vent off-gas from the accumulator FA-101 as required.

Off-gas from the accumulator FA-101 flows to the compressor GB-402 or it can be sent to flare.

Water condensed in the accumulator FA-101 is drawn from the water boot at a rate controlled by the interface level control LC-103, and is sent to the sour water stripper DA-104.

Ammonia is used to reduce corrosion in the atmospheric crude tower overhead system. The rate of ammonia injection will be set as required to keep the water withdrawn from FA-101 at a pH of 6.0 to 7.5. Petromen solution made of filming and neutralizing amines is also injected into the overhead system to control the corrosion rate.

9.Heavy Kerosene

Heavy kerosene is withdrawn from tray 18 of DA-101, by HCV-103, and feeds onto the top tray of the stripper DA-103. The heavy kerosene is stripped with superheated steam. The heavy kerosene product is pumped from DA-103 by GA-105 or 106S. A portion is taken through the EA-105 Cooler, by FRC-172, for blending at about 120°F. to the diesel fuel product. The remainder is taken by LIC-102 to combine with light kerosene.

~~10.~~Light Kerosene

Light kerosene is withdrawn from tray 18 of DA-101 by HIC-102, onto the top tray of stripper DA-102. Here it is stripped with superheated steam. Light kerosene product flows to the accumulator FA-203 and is pumped from FA-203 by GA-102 or 108.

~~11.~~Combined Kerosene

The light kerosene stream and a portion of the heavy kerosene stream are combined. A portion of the combined kerosene is taken to the kerosene hydrotreater charge drum FA-102 by LIC-155 on FA-102. The remaining combined kerosene is taken by LRC-104 on FA-203, to the blending manifold after being cooled to 120°F in EA-106.

~~12.~~Blending Manifold

a.General

The blending manifold has been designed by the Texas Petroleum Company for flexibility in meeting the sales requirements for finished products. The streams to the blending manifold are as follows:

Hydrotreated Kerosene

Combined Light and Heavy Kerosene

Heavy Kerosene

Diesel Oil

Light Gas Oil

Heavy Gas Oil

Residuum

The product streams from the blending manifold are as follows:

Av-jet

Kerosene

Diesel Fuel

Turbine Fuel

Fuel Oil – Low Pour

Fuel Oil – Medium Pour

Fuel Oil – High Pour

The blending manifold is arranged so that each product is blended by flow control on one stream and the second stream added by level control on the bottom of a stripper or on an accumulator. The flow of the second stream is recorded. Each stream from the Crude Unit to the manifold is split, with a portion taken to a product blend by flow control, and the remainder flows to another product blend on level control on the bottom of the respective stripper or accumulator. Therefore, for each blend, the stream on flow control should be adjusted as required by product specifications, in proportion to the other blend stream on level control.

b.Av-jet and Kerosene

Av-jet and Kerosene will be produced from the hydrotreated kerosene. The flow of Kerosene is controlled by FRC-174. The remainder of the hydrotreated kerosene flows to the Av-jet storage, by LIC-302 and FR-175.

c.Diesel Fuel

Diesel fuel will be blended from heavy kerosene by FRC-171, combined kerosene by LRC-104 and FR-173, and diesel oil by LIC-153 and FR-172.

d.Turbine Fuel

Turbine fuel will be blended from diesel oil by FRC-162, and light gas oil, by LIC-152 and FR-163.

e.Fuel Oils

The blending manifold was designed by the Texas Petroleum Company to blend Low-Pour, Medium-Pour, and High-Pour Fuel Oils simultaneously.

Low-Pour Fuel Oil will be blended from Resid, by FRC-165, and either combined kerosene, heavy kerosene or diesel, by FRC-166.

Medium-Pour Fuel Oil may be blended from the following streams:

Resid (FIC-167 or LIC-150 and FR-167)

Light Gas Oil (FRC-168)

Either Combined Kerosene, Heavy Kerosene or Diesel (FIC-164 and FR-164)

Heavy Gas Oil (LIC-152 and FR-161)

High-Pour Fuel Oil may be blended from the following streams:

Resid (LIC-150 or FIC-167 and FR-169)

Heavy Gas Oil (LIC-152 and FR-161)

Light Gas Oil (FRC-170)

D.Description of Process Controls

The process flow described in the previous pages is controlled in these functional areas:

1.Crude Charge

2.Crude Heaters

3.Lower Crude Tower and its Strippers

4.Upper Crude Tower and its Strippers

5.Blending

6.Product Coolers

1.Crude Charge

Flow of crude to the Crude Unit is controlled by FRC-101 which includes a low flow alarm to indicate interruption of crude charge. The operator then handles this emergency. The pressure controller PRC-150 is provided to avoid vaporization Upstream of the Crude Flash Drum FA-104. Liquid level in this drum is recorded by LR-156 and low-level and high-level alarms are provided. The operator can adjust the level with FRC-101 (Crude Charge) or FRC-150 and 151 (flows to each pass in BA-101 Crude Heater).

GA-109 and GA-109S pump the liquid from FA-104 through the rest of the heat exchangers. GA-109S is driven by a stream turbine; when the pump discharge pressure falls below a set point, pressure switch PS-153 sounds an alarm (PAL-153) and trips a manual-reset solenoid valve (HOA-153) shutting down the steam to the turbine. The flow rate of flashed crude is controlled by PRCV-152, which is positioned by PRC-152 (pressure to Crude Heater inlet). Flow through the heaters is regulated by FRC-150 and FRC-151. These controllers are to be used to equalize the flow through the two-pass heaters.

2.Crude Heaters

The flashed crude splits into two parallel tube passes which are kept separate through the Crude Heaters BA-101 and BA-102 to rejoin the transfer line from BA-102. Each tube pass is provided with a flow/recorder – controller, a low-flow alarm, and a pressure gauge at the inlet of BA-101; temperature recorder, temperature point (TI), and pressure gauge on the transfer lines between the Crude Heaters; and a temperature recorder and pressure gauge on the outlet of BA-102 Heater.

The temperature of the crude stream in the transfer lines from the Crude Heater BA-101 is controlled by TIC-103 which averages the temperatures. TIC-103 adjusts the flow of fuel oil (on instrument air pressure of 9 – 15 psig) or flow of fuel gas (on instrument air pressure of 3 – 9 psig). Assuming that both fuel gas and fuel oil are used to fire the furnace, the demand for fuel will first open the fuel gas control valve, then as more heat is required, will open the fuel oil control valve. It is, however, possible to operate with either fuel gas or fuel oil separately on temperature control, TIC-103. If or any reason it is desired to shut off the fuel gas flow or to manually control the flow from the control board, HCV-101, in normal position, can be used to make these adjustments. In the manual position HCV-.101 can also be used to close the fuel gas firing valve and PC-712 will vent low-pressure fuel.

The No. Crude Heater BA-102 is fired also with fuel oil and fuel gas. The fuel oil rate to the burners is controlled by TIC-150 in the outlet combined transfer line. This instrumentation is shown on Lummus Dwg. No. I-STD-521-101-1. Thermocouple TE-150 measures the transfer line temperature, and its leads are connected to an E/P Transducer (TT-150) behind the panel which converts the electronic signal from the thermocouple to a pneumatic signal which goes to the controller TIC-150. The controller output goes through a trip relay to the control valve on the fuel oil line. The relay (TY-150) is set to trip at 3.25 psig and requires a manual reset. A minimum-flow restrictive orifice bypasses the control valve, allowing maintenance of a very low fire in the burner for refractory-curing and miscellaneous reasons. This orifice is supplied at 1/16”.

Atomizing steam to the burners is maintained a little above fuel oil line pressure with a differential-pressure control valve, PDCV-150. A pressure regulator (PCV-150) controls the pilot gas flow.

3.Control of Tower Pressure

The overhead pressure of the Upper Crude Tower DA-101 is controlled by PIC-101 as follows:

Instrument Air Signal PSIG	Operation
3 – 6	Opens valve “A” to admit fuel gas
6 – 12	Controls valve “B” on gas recycle of Compressor GB-402\|
12 – 15	Opens valve “C” to vent off gas from the FA-101 Accumulator to the flare

4.Flash Zone

The temperature of the flash zone in the Lower Crude Tower DA-105 is controlled by TIC-150 on the transfer line from the Crude Heater BA-102.

5.Control of Products

The final boiling point of the overhead naphtha stream is controlled by the tower vapor line temperature, held constant by TIC-104, which regulates the flow of reflux to the top of the tower. An increase in reflux will lower the final boiling point of the naphtha. The final boiling point of each of the side draw-off streams is governed by the quantity withdrawn and increases with increased withdrawal rate.

The initial boiling point of the material from each side-stream stripper is controlled by the rate of withdrawal of the next lighter cut and by the quantity of stripping steam. Increasing the draw rate of the lighter cut will increase the initial boiling point of the next heavier cut. Increasing the stripping steam tends to increase the initial boiling point of a product.

Product	Feed Rate to Stripper	Stripping Steam Meter	Product Flow Meter
Light Kerosene	HIC-102		FR-176
Heavy Kerosene	HIC-103		FR-110
Diesel Oil	HIC-152	FI-155	FR-160
Light Gas Oil	HIC-151	FI-154	FR-159
Heavy Gas Oil		FI-153	FR-161

The production of Light Kerosene is controlled by the draw rate (HIC-103) to the Heavy Kerosene Stripper DA-103 and by the level (LIC-102) in the bottom of the stripper.

A portion of the Heavy Kerosene may be blended to Diesel Fuel with the control FRC-171.

The remainder of the Heavy Kerosene and all of the Light Kerosene flow together to combined Kerosene. This Combined Kerosene stream is split into feed to the Kerosene Hydrotreater and a stream for blending to Diesel Fuel. The feed rate to the Kerosene Hydrotreater is controlled by FRC-104 which recycles the excess from the charge pump back to the Hydrotreater Charge Drum, FA-102 and sounds an alarm for low Hydrotreater feed rate. The remainder of the Combined Kerosene to Diesel Fuel is controlled by LRC-104 on the Light Kerosene Accumulator FA-203.

The strippers for Diesel, Light Gas Oil, and Heavy Gas Oil are provided with pressure gauges, level gauges, level transmitters and board-mounted level indicators, and flow-indicators for the stripping steam. Also the Diesel Stripper has low and high-level alarms; the Light Gas Oil Stripper has a low-level alarm.

Color inspection glasses are provided on the Diesel product line downstream of FR-160 and on the Light Gas Oil product line downstream of FR-159.

The tray above the flash zone in the DA-105 Lower Crude Tower is a total trap-out bubble cap tray. Thus all the liquid down-flow to this tray feeds to the Heavy Gas Oil Stripper DA-107 through a liquid seal loop.

6.Heat Removal by Circulating Reflux

Removal of heat from the Upper and Lower Crude Towers is controlled by the following:

a.Top reflux, TIC-102 and meter FI-103

b.Circulating reflux to Upper Crude Tower, FIC-102

c.Circulating reflux to Lower Crude Tower, FRC-152 on the draw from Tray 16 in the Lower Crude Tower, and LIC-101 and FR-158 on the bottoms from the Upper Crude Tower.

For constant feed rates and temperatures to DA-101 and DA-105, the heat balance requires that when one of these streams is increased, another must be reduced. Heat is removed from the circulating reflux streams by exchange with the crude oil charge. Increasing the upper circulating reflux by FIC-102 removes more heat from the Upper Crude Tower, causes TIC-102 to reduce the top reflux, makes the separation poorer between the Naphtha and Light Kerosene streams provided the top trays of the Upper Crude Tower are not overloaded, and makes the separation poorer between the Light Kerosene and Heavy Kerosene streams. Increasing the lower circulating reflux decreases the final boiling point of the Heavy Kerosene.

7.Controls at Blending Manifold

a.Fuel Oils

Residuum will be blended simultaneously to Low Pour, Medium Pour, and High Pour Fuel Oils. The flow rate of Residuum to the Low Pour Fuel Oil is controlled by FRC-165. The air switch HSP-150 operates a two-position, four-way instrument valve so that the control valve LICV-150 (Residuum to High Pour Fuel Oil) and the control valve FICV-151 (Residuum to Med. Pour Fuel Oil) may be switched to be controlled by either FIC-167 or LIC-150 (level in the bottom of the DA-105, Lower Crude Tower).

For the Medium-Pour Fuel Oil the air signal from the flow transmitter FT-167 on the Residuum stream will set the ratio switch FRS-168 to ration the Light Gas Oil (FRC-168) or the Kerosene-Diesel (FRC-166).

Heavy Gas Oil will be controlled by the level (LIC-151) in the DA-107 Stripper and metered by FR-161. This stream may be blended to either Med.-Pour or High-Pour Fuel Oil.

A manifold is provided with block valves to blend either Combined Kerosene, Heavy Kerosene, or Diesel to Low-Pour Fuel Oil by FRC-164 and Medium-Pour Fuel Oil by FRC-166 with the ratio control set from FT-167 on the Residuum stream.

Light Gas Oil is blended to High-our Fuel Oil by FRC-170.

b.Turbine Fuel

Turbine fuel is blended from Light Gas Oil by LIC-152 on DA-106B Stripper and FR-163 and from Diesel by FRC-162. The meters FR-163 and FRC-162 record on a tow-pen recorder-controller.

c.Diesel Fuel

Diesel fuel is blended from Diesel (level control LIC-153 on DA-106A Stripper and meter FR-172), Heavy Kerosene (control FRC-171), and Combined Kerosene (level control LRC-104 on the FA-203 Light Kerosene Stripper Accumulator and meter FR-173). The meters FRC-171 and FR-172 record on a two-pen recorder-controller.

d.Av-jet and Kerosene

Hydrotreated Kerosene is split to the Kerosene product by FRC-174 and to Av-jet by LC-302 on the bottom of the DA-301 Kerosene Stripper and by FR-175. The meters FRC-174 and FR-175 record on a two-pen recorder-controller.

8.Air Fan Coolers

Air Fan Coolers are provided as follows:

Item	Service	Temperature Control
EC-115	Light Gas Oil	TIC-151
EC-116	Low-Pour Fuel Oil	TIC-152
EC-117	Medium-Pour Fuel Oil	TIC-153
EC-118	High-Pour Fuel Oil	TIC-154

The temperature of the products from each cooler should not exceed 210°F to avoid violent vaporization of any water in the respective field storage tanks. The temperature-controllers will position the adjustable louvers above the coolers to regulate the cooling air flow.

Each cooler is provided with a steam coil below the process coil to melt out the solid residual which may form at low temperatures.