*1.6.2 Modeling of the desalting process with electrostatic desalter*

The exercise of modeling is a variant very often useful and used in the modeling of units and devices [7, 14, 19]. This task is interesting in case we do not have a simulator or simulation and modeling program like Hysys Aspen to solve this operation. In the framework of modeling the desalination unit, we use the ASTM D 341-2003 standard is based on Walter's equation and proposes the dependence of the kinematic viscosity of crude oil (hydrocarbon):

$$
\lg \times \lg(\nu + \mathbf{0}, \mathbf{8}) = a + b \times \lg T,\tag{6}
$$

$$a = \lg \times \lg(\nu\_1 + 0, 8) - b \times \lg T\_1 \tag{7}$$


#### **Table 2.**

*The material balance of electrostatic desalter.*

$$b = \frac{\lg \times \left[\frac{\lg(\nu\_1 + 0, \aleph)}{\lg(\nu\_2 + 0, \aleph)}\right]}{\lg \frac{T\_1}{T\_2}},\tag{8}$$

For to determine the *E-Critical* and *E-Real* for the desalter with the following data. Water content in oil – 1%; λ (interfacial surface tension) = 12 dyn/cm; d (the diameter of the droplets) = 1.5 � <sup>10</sup>–2.55 m or 4.228�10�<sup>1</sup> cm; <sup>φ</sup> (dielectric constant of the emulsion) = 2; l (distance between electrodes) = 20 cm; U (voltage of the

> ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi <sup>2</sup> � <sup>12</sup> <sup>2</sup> � <sup>4</sup>*:*<sup>228</sup> � <sup>10</sup>�<sup>1</sup>

*E-Real* < *E-Critical*, consequently, the dispersion of droplets will not. The elec-

water – 1.5�10–2.55 meter. The residence time of the emulsion in the apparatus –

eter – 3 m. The maximum surface deposition: *<sup>S</sup>* <sup>¼</sup> *<sup>D</sup>* � *<sup>L</sup>* <sup>¼</sup> <sup>10</sup>*:*<sup>19</sup> � <sup>3</sup> <sup>¼</sup> <sup>30</sup>*:*57 m<sup>2</sup>

The efficiency of the electric desalter depends on the values S/V, where S – the

residence time in the apparatus, h; *τ<sup>W</sup>* – time required for precipitation of water

*<sup>τ</sup>* <sup>¼</sup> *hEm UEm*

where *hEm* – the height of the emulsion layer in the apparatus, m; *UEm* – the

<sup>¼</sup> *hEm Uwater* � *Uwo*

*Uwater* � *Uwo* ≥ *UEm* or *UWater* ≥2 � *UEm:* (18)

� 9*:*81 � ð Þ 965*:*3 � 838*:*4

where *Uwater* – deposition rate of water droplets in a stationary medium, m/h;

The linear velocity of the oil in the electrostatic desalter must be at least 2 times

18 � *μcrudeoil* � *ρcrudeoil*

where *d* – diameter of water drops, m; *ρH2O*, *ρ crude oil* – the density of water and

<sup>18</sup> � <sup>7</sup>*:*<sup>055</sup> � <sup>10</sup>�<sup>4</sup> � <sup>838</sup>*:*<sup>4</sup>

less than the calculated rate of water droplet deposition. The deposition rate is

*UWater* <sup>¼</sup> *<sup>d</sup>*<sup>2</sup> � *<sup>g</sup>* � *<sup>ρ</sup><sup>H</sup>*2*<sup>O</sup>* � *<sup>ρ</sup>crudeoil* � �

*μcrude oil* – kinematic viscosity of oil at sludge temperature, m<sup>2</sup>

*UWater* <sup>¼</sup> <sup>1</sup>*:*5*:*10�2, <sup>552</sup> � �<sup>2</sup>

. For effective sludge must be met the condition *τ* ≥ *τW*, where *τ -* oil

<sup>20</sup> <sup>¼</sup> 1100 V*=*cm*:*

, *ρ90Н<sup>20</sup>* = 965.3 kg/m<sup>3</sup>

¼ 2035*:*1 V*=*cm*:*

/h with temperature

.

, the kinematic

/s, the diameter of the globules of

, (16)

, which length – 10.19 m, diam-

; V – the volume of the

, (17)

m*=*s, (19)

/s.

m*=*s

r

*EReal* <sup>¼</sup> <sup>22000</sup>

trostatic desalter receives crude oil, the amount of Q = 162 m<sup>3</sup>

*crude oil* = 838.4 kg/m<sup>3</sup>

electrodes) = 22000 v.

*Crude Distillation Unit (CDU)*

*DOI: http://dx.doi.org/10.5772/intechopen.90394*

С (preheat). *ρ<sup>90</sup>*

90<sup>0</sup>

device, m<sup>3</sup>

oil, kg/m<sup>3</sup>

**117**

.

droplets, an hour.

*ECritical* ¼ 382 �

viscosity of crude oil *<sup>μ</sup>oil crude* = 7.055 � <sup>10</sup>�<sup>4</sup> <sup>m</sup><sup>2</sup>

30 minutes is applied to the device volume 96 m<sup>3</sup>

average area of the horizontal section of the device, m<sup>2</sup>

velocity of the crude oil flow during its lower flow, m/h.

calculated using the Stokes formula [7, 25]:

*<sup>τ</sup><sup>W</sup>* <sup>¼</sup> *hEm UReal*

*Uwo* – real deposition rate of water droplets in the rising oil flow, m/h.

where ν – viscosity, cSt, T is the absolute temperature, K; a and b are the constants determined by two known values of viscosity ν<sup>1</sup> and ν<sup>2</sup> at temperatures, respectively, T1 and T2. The empirical formula of formula Filonov – Reynolds is more convenient for analytical solutions:

$$
\mu\_t = \frac{1}{\mathbb{C}} \times \left(\mathbb{C} \cdot \mu\_{t\_s}\right)^\chi \tag{9}
$$

where.

$$\chi = \frac{1}{1 + a(t - t\_o) \times \lg\left(C \cdot \mu\_{t\_o}\right)};\tag{10}$$

νt, ν<sup>o</sup> – Dynamic viscosity of the oil at temperatures t and to, respectively, mPa�s; *α* and *C* are empirical coefficients.

$$\text{If } \nu\_o \ge 1000 \text{ mPa} \cdot \text{s}, \text{then C} = 10, 1/\text{mPa} \cdot \text{s}; \text{a} = 2.52 \cdot 10^{-3} \text{ 1/} ^\circ \text{C}; \tag{11}$$

$$\text{If } 10 \le \nu\_o < 1000 \text{ mPa} \cdot \text{s}, \text{then } \text{C} = 100, \text{1/mPa} \cdot \text{s}; \text{a} = 1.44 \cdot 10^{-3} \text{ 1/} ^\circ \text{C}; \quad \text{(12)}$$

$$\text{If } \nu\_o < 10 \text{ mPa} \cdot \text{s, then } C = 1000, 1/\text{mPa} \cdot \text{s;} \text{a} = 0.76 \cdot 10^{-3} \text{ 1/°C}. \tag{13}$$

$$\infty = \frac{1}{[1 + 0.76 \times (90 - 100)] \times \log \left( 1000 \times 0.0014144 \right)}$$

ν= <sup>1</sup> <sup>1000</sup> � ð Þ <sup>1000</sup> � <sup>0</sup>*:*<sup>0014144</sup> *<sup>x</sup>* <sup>¼</sup> 7.055�10�<sup>4</sup>

In modeling of electrostatic desalter to determine his maximum performance and the required number of devices for desalting crude oil.

$$E\_{\rm critical} = \theta \times \sqrt{\frac{2 \times \lambda}{\phi \times d}}, \mathbf{v}/\text{cm},\tag{14}$$

The interaction between water droplets can be increased by increasing the electric field strength, Е.

$$ERad = \frac{U}{l}, \mathbf{v}/\mathbf{cm} \tag{15}$$

#### *Crude Distillation Unit (CDU) DOI: http://dx.doi.org/10.5772/intechopen.90394*

For to determine the *E-Critical* and *E-Real* for the desalter with the following data. Water content in oil – 1%; λ (interfacial surface tension) = 12 dyn/cm; d (the diameter of the droplets) = 1.5 � <sup>10</sup>–2.55 m or 4.228�10�<sup>1</sup> cm; <sup>φ</sup> (dielectric constant of the emulsion) = 2; l (distance between electrodes) = 20 cm; U (voltage of the electrodes) = 22000 v.

$$E\_{Critical} = 382 \times \sqrt{\frac{2 \times 12}{2 \times 4.228 \cdot 10^{-1}}} = 2035.1 \text{ V/cm.}$$

$$E\_{Real} = \frac{22000}{20} = 1100 \text{ V/cm.}$$

*E-Real* < *E-Critical*, consequently, the dispersion of droplets will not. The electrostatic desalter receives crude oil, the amount of Q = 162 m<sup>3</sup> /h with temperature 90<sup>0</sup> С (preheat). *ρ<sup>90</sup> crude oil* = 838.4 kg/m<sup>3</sup> , *ρ90Н<sup>20</sup>* = 965.3 kg/m<sup>3</sup> , the kinematic viscosity of crude oil *<sup>μ</sup>oil crude* = 7.055 � <sup>10</sup>�<sup>4</sup> <sup>m</sup><sup>2</sup> /s, the diameter of the globules of water – 1.5�10–2.55 meter. The residence time of the emulsion in the apparatus – 30 minutes is applied to the device volume 96 m<sup>3</sup> , which length – 10.19 m, diameter – 3 m. The maximum surface deposition: *<sup>S</sup>* <sup>¼</sup> *<sup>D</sup>* � *<sup>L</sup>* <sup>¼</sup> <sup>10</sup>*:*<sup>19</sup> � <sup>3</sup> <sup>¼</sup> <sup>30</sup>*:*57 m<sup>2</sup> . The efficiency of the electric desalter depends on the values S/V, where S – the average area of the horizontal section of the device, m<sup>2</sup> ; V – the volume of the device, m<sup>3</sup> . For effective sludge must be met the condition *τ* ≥ *τW*, where *τ -* oil residence time in the apparatus, h; *τ<sup>W</sup>* – time required for precipitation of water droplets, an hour.

$$
\pi = \frac{h\_{Em}}{U\_{Em}},
\tag{16}
$$

where *hEm* – the height of the emulsion layer in the apparatus, m; *UEm* – the velocity of the crude oil flow during its lower flow, m/h.

$$
\tau\_W = \frac{h\_{Em}}{U\_{Real}} = \frac{h\_{Em}}{U\_{water} - U\_{wo}},
\tag{17}
$$

where *Uwater* – deposition rate of water droplets in a stationary medium, m/h; *Uwo* – real deposition rate of water droplets in the rising oil flow, m/h.

$$U\_{water} - U\_{wo} \ge U\_{Em} \text{ or } U\_{Water} \ge 2 \times U\_{Em}.\tag{18}$$

The linear velocity of the oil in the electrostatic desalter must be at least 2 times less than the calculated rate of water droplet deposition. The deposition rate is calculated using the Stokes formula [7, 25]:

$$U\_{Water} = \frac{d^2 \times \text{g} \times (\rho\_{H\_2O} - \rho\_{crudeoil})}{\text{18} \times \mu\_{crudeoil} \cdot \rho\_{crudeoil}} \text{ m/s},\tag{19}$$

where *d* – diameter of water drops, m; *ρH2O*, *ρ crude oil* – the density of water and oil, kg/m<sup>3</sup> .

*μcrude oil* – kinematic viscosity of oil at sludge temperature, m<sup>2</sup> /s.

$$U\_{Water} = \frac{\left(1.5.10^{-2.552}\right)^2 \times 9.81 \times (965.3 - 838.4)}{18 \times 7.055 \times 10^{-4} \times 838.4} \,\mathrm{m/s}$$

*Analytical Chemistry - Advancement, Perspectives and Applications*

$$\mathbf{U\_{water}} = \mathbf{0}.0021 \text{ m/s.}$$

It is necessary to check the Reynolds number (Re) by the formula:

$$
\Re U\_{Water} \times \frac{d}{\nu\_{crudeoil}}.\tag{20}
$$

*1.6.3 Mechanical modeling of electrostatic desalter (theory)*

Permissible internal overpressure.

*DOI: http://dx.doi.org/10.5772/intechopen.90394*

*Crude Distillation Unit (CDU)*

on the steel grade and operating temperature).

ment is resistant to corrosion.

estimated length of the shell.

**119**

external pressure:

This task is as interesting as the one already solved. In case we do not have a simulator or simulation and modeling program like Ansys to solve this vital operation [1, 18, 29, 30]. The calculation of the strength of a cylindrical shell under internal pressure. The wall thickness is determined by the formula (25).

*SR* <sup>¼</sup> *<sup>P</sup>* � *<sup>D</sup>*

½ � *<sup>p</sup> <sup>D</sup>* <sup>¼</sup> <sup>2</sup> � ½ �� *<sup>σ</sup> <sup>ϕ</sup>* � ð Þ *<sup>S</sup>* � *<sup>C</sup>*

P is the pressure in the device, mPa; SR – the calculated value of wall thickness, mm; D- intern diameter of the shell, mm; ½ � *σ* – permissible voltage, mPa (depends

The steel grade is chosen depending on the properties of the processed medium. For butt and t-shaped double-sided seams performed by automatic welding, the coefficient of the strength of the weld *ϕ* ¼ 1, for the same manual stitches, *φ = 0.9*.

V is the rate of corrosion (usually take 0.1–0.2 mm/year); T – the service life of

The choice of corrosion resistance of materials is made concerning this environ-

The wall thickness calculated using this formula is rounded up to the nearest standard sheet thickness (4, 6, 8, 10, 12, 14, 18, 20 mm). The calculation of shells loaded with external over-pressure consists in determining the permissible external pressure since the wall thickness of the shell was determined earlier. Permissible

½ � *<sup>p</sup> pp* <sup>¼</sup> ½ � *<sup>Р</sup> <sup>р</sup>* ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

½ � *P <sup>р</sup>* durability allowable pressure corresponding to the strength condition:

½ � *<sup>P</sup> <sup>D</sup>* <sup>¼</sup> <sup>2</sup> � ½ �� *<sup>σ</sup> <sup>ϕ</sup>* � ð Þ *<sup>S</sup>* � *<sup>C</sup>*

*i* – coefficient of stability (for the operating conditions of *i* = 2.4), *lR* – the

*lR* ¼ *l* � 2 � *h*<sup>0</sup> þ

<sup>1</sup> <sup>þ</sup> ½ � *<sup>Р</sup> <sup>р</sup>* ½ � *Р <sup>Е</sup>*

*HD*

the device (usually take 10–12 years). For materials resistant to the processed medium, in the absence of data on permeability, it is recommended to take C = 2 mm. Condition for reliable operation *Р* <½ � *P <sup>D</sup>* must be observed.

Increase taking into account corrosion C is determined by the formula:

<sup>2</sup> � ½ �� *<sup>σ</sup> <sup>ϕ</sup>* � *<sup>P</sup>* ; (27)

*<sup>D</sup>* <sup>þ</sup> ð Þ *<sup>S</sup>* � *<sup>C</sup>* (28)

*С* ¼ V � T, (29)

*S*≥*SR* þ *C* (30)

� �<sup>2</sup> <sup>r</sup> , (31)

*<sup>D</sup>* <sup>þ</sup> ð Þ *<sup>S</sup>* � *<sup>C</sup> :* (32)

<sup>3</sup> , (33)

The condition must be met:

$$10^{-4} \le \text{Re} \le 0.4 \tag{21}$$

$$2\Re 0.00208974 \times \frac{1.5 \cdot 10^{-2.85}}{7.055 \times 10^{-4}} = 0.0125, \text{Re} < 0.4$$

*hEm* is the height of the emulsion level in the devices, m = meter

$$h\_{\rm Em} = 0.75 \times D - h\_1,\tag{22}$$

where h1 the distance from the bottom of the electric Hydrator to the oil-water interface. We choose *h1* = 0.75 m � *UEm* – the velocity of the oil flow during its lower flow, m/h, *hEm* ¼ 0*:*75 � 3 � 0*:*75 ¼ 1*:*69 m

$$U\_{Em} = \frac{h\_{Em}}{\tau} \tag{23}$$

$$U\_{Em} = \frac{1,69}{0.75} = 2.25 \text{m/h} = 6.259 \cdot 10^{-4} \text{ m/s}.$$

Knowing the Uw, determine the Uwo and the required cross-section of the electric dehydrator (S). The actual deposition rate of water droplets in the rising oil stream will be:

$$UReal = U\_{water} - U\_{Em} \tag{24}$$

$$UReal = 2.08 \times 10^{-3} - 6.259 \times 10^{-4} = 1.464 \cdot 10^{-3} \text{m/s}.$$

The performance of the desalter:

$$J = \text{UReal} \times \text{S}, \text{m}^3/\text{s} \tag{25}$$

$$J = \mathbf{1.464 \cdot 10^{-3} \times 30.57 = 0.045 \text{ m}^3/\text{s} = 161.3 \text{ m}^3/\text{h} \dots$$

The number of devices (N):

$$N = \frac{Q}{J},\tag{26}$$

where *Q* – the quantity of emulsion supplied to the unit, m<sup>3</sup> /h; *J* – The performance of the desalter, m<sup>3</sup> /h.

The required number of parallel running for the electrostatic desalter:

$$N = \frac{162}{161.3} = 1.005$$

#### *1.6.3 Mechanical modeling of electrostatic desalter (theory)*

This task is as interesting as the one already solved. In case we do not have a simulator or simulation and modeling program like Ansys to solve this vital operation [1, 18, 29, 30]. The calculation of the strength of a cylindrical shell under internal pressure. The wall thickness is determined by the formula (25).

$$S\_R = \frac{P \times D}{2 \times [\sigma] \times \phi - P};\tag{27}$$

Permissible internal overpressure.

$$[p]\_D = \frac{2 \times [\sigma] \times \phi \times (\mathbf{S} - \mathbf{C})}{D + (\mathbf{S} - \mathbf{C})} \tag{28}$$

P is the pressure in the device, mPa; SR – the calculated value of wall thickness, mm; D- intern diameter of the shell, mm; ½ � *σ* – permissible voltage, mPa (depends on the steel grade and operating temperature).

The steel grade is chosen depending on the properties of the processed medium. For butt and t-shaped double-sided seams performed by automatic welding, the coefficient of the strength of the weld *ϕ* ¼ 1, for the same manual stitches, *φ = 0.9*. Increase taking into account corrosion C is determined by the formula:

$$\mathbf{C} = \mathbf{V} \times \mathbf{T},\tag{29}$$

V is the rate of corrosion (usually take 0.1–0.2 mm/year); T – the service life of the device (usually take 10–12 years). For materials resistant to the processed medium, in the absence of data on permeability, it is recommended to take C = 2 mm. Condition for reliable operation *Р* <½ � *P <sup>D</sup>* must be observed.

The choice of corrosion resistance of materials is made concerning this environment is resistant to corrosion.

$$S \ge S\_{\mathcal{R}} + C \tag{30}$$

The wall thickness calculated using this formula is rounded up to the nearest standard sheet thickness (4, 6, 8, 10, 12, 14, 18, 20 mm). The calculation of shells loaded with external over-pressure consists in determining the permissible external pressure since the wall thickness of the shell was determined earlier. Permissible external pressure:

$$[p]\_{pp} = \frac{[P]\_p}{\sqrt{\mathbf{1} + \left(\frac{[P]\_p}{[P]\_\mathcal{E}}\right)^2}},\tag{31}$$

½ � *P <sup>р</sup>* durability allowable pressure corresponding to the strength condition:

$$[P]\_D = \frac{2 \times [\sigma] \times \phi \times (\mathbf{S} - \mathbf{C})}{D + (\mathbf{S} - \mathbf{C})}. \tag{32}$$

*i* – coefficient of stability (for the operating conditions of *i* = 2.4), *lR* – the estimated length of the shell.

$$l\_R = l - 2 \times h\_0 + \frac{H\_D}{3},\tag{33}$$

*E* is the modulus of elasticity*. l* = length of the cylindrical part of the corpus; *h0* – the height of the bottom flanging, *HD* – the height of bottom edge. Allowable pressure of conditions of stability within the limits of elastic deformation:

$$[\mathbf{P}]\_E = \frac{\mathbf{18} \cdot \mathbf{10}^{-6} \times \mathbf{E}}{i} \times \frac{D}{l\_R} \left[\frac{\mathbf{100} \times (\mathbf{S} - \mathbf{C})}{D}\right]^2 \times \sqrt{\frac{\mathbf{100} \times (\mathbf{S} - \mathbf{C})}{D}}\tag{34}$$

½ � *<sup>Р</sup> <sup>Е</sup>* <sup>¼</sup> <sup>18</sup>�10�6��1*:*86�10�<sup>5</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.90394*

*Crude Distillation Unit (CDU)*

Permissible external pressure:

**1.7 Summary**

oil implies:

acterized by:

reservoir;

**121**

<sup>2</sup>*:*<sup>4</sup> � <sup>3000</sup>

• degassing – removal of gases from crude oil;

• dewatering – removal of water from crude oil.

washing with water from salts;

<sup>10640</sup> � <sup>100</sup>�ð Þ <sup>14</sup>�<sup>4</sup> <sup>3000</sup> h i<sup>2</sup>

<sup>1</sup><sup>þ</sup> <sup>1</sup>*:*<sup>12</sup> ð Þ <sup>0</sup>*:*<sup>0252319</sup>

The desalting and dewatering of crude oil take begins on the oil fields. This operation is part of the processing of crude oil, and a good pre-treatment of crude

If the desalting of crude oil is carried out qualitatively, the oil has almost no harmful effect on the equipment. Most of the impurities that cause corrosion of the metal are in the remains of formation water. Therefore, the fundamental task of desalting is to remove water drops from the oil. This is a fairly complex process, because the water in crude oil is in the form of droplets with a size quantity often. The improvement and appreciation of the oil pretreatment process level are char-

• providing effective sludge at high viscosity and density of oil through the use

• increasing the degree of dehydration and desalination of oil due to effective

prepared oil due to more complete and qualitative removal of the intermediate layer from it, as well as due to a more uniform distribution of fluid flow rates

• improving the efficiency of the sump and improving the quality of the

• ensuring uniform receipt of production of wells for the installation of oil treatment and prevention of failures of its work through the use of the

• improving the performance of the electrostatic desalter, that is, expanding the range of workloads, improving the efficiency of desalination and dehydration,

The poor pre-treatment (desalting process) of crude oil can lead to considerable extra costs. We are talking about the high cost of transportation if the product is not cleared of unnecessary substances that give it extra volume and weight as well as financial investments in equipment. After all, oil, which is not derived from salt, can very quickly damage the pipeline. The requirements for the oil content of the

of a sump with intermediate partitions of variable height;

when entering the sump and its cross-section;

as well as reducing the cost of oil pre-treatment.

Condition for reliable operation ½ � *Р <sup>E</sup>* ≤½ � *p pp* (0.0252 mPa ≤ 0.0252 mPa) observed.

2 <sup>q</sup> =0.0252 mPa.

½ � *<sup>p</sup> pp* <sup>¼</sup> <sup>1</sup>*:*<sup>12</sup> ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

�

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 100�ð Þ 14�4 <sup>3000</sup> <sup>q</sup>

= 0.0252 mPa

Condition for reliable operation ½ � *Р <sup>Е</sup>* ≤ ½ � *p pp* must be observed.

#### *1.6.4 Resolution example based on our electrostatic desalter*

P – pressure in the device, mPa = 1.1; D-inner diameter of the shell, mm = 3000. The increase in corrosion C is determined by the formula (27).

$$C = 0.2 \times 20 = 4 \text{ mm}$$

V is the rate of corrosion (usually take 0.1–0.2 mm/year); T – the service life of the device (usually take 10–12 years), but we take 20 years. For materials resistant to the processed medium, in the absence of data on permeability, it is recommended to take C = 2 mm. According to the table of corrosion resistance of materials, we choose the steel grade 316Ti, S31635-USA (ASTM/AISI), or 1.4571, X6CrNiMoTi17-12-2-Germany (DIN/WNr). ½ � *σ* = 168.6 mPa. The coefficient of the strength of the weld is assumed *ϕ* ¼ 1. The service life is 20 years. The corrosion rate is 0.2 mm/year. Increase taking into account corrosion C = 4 mm.

$$\begin{array}{l} \mathbf{S}\_{\mathrm{R}} = \frac{1.1 \times 3000}{2 \times 168.6 \times 1 - 1.1} = \mathbf{9.819} \text{ mm.} \\\\ \mathbf{S} = \mathbf{9.819} + \mathbf{4} = \mathbf{13.819} \text{ mm.} \end{array}$$

The wall thickness calculated using this formula is rounded up to the nearest standard sheet thickness (4, 6, 8, 10, 12, 14, 18, 20 mm). We assume S = 14 mm.

$$[p]\_D = \frac{2 \times 345 \times 1 \times (14 - 4)}{3000 + (14 - 4)} = 1.12 \text{ mPa}.$$

Condition for reliable operation *Р* <½ � *P* (1.1 mPa < 1.12 mPa) observed.

The calculation of shells loaded with external over-pressure consists in determining the permissible external pressure since the wall thickness of the shell was determined earlier.

½ � *P <sup>р</sup>* the allowable pressure corresponding to the strong condition.

$$\left[P\right]\_{\mathfrak{p}} = \frac{2 \times 168.6 \times 1 \times (14 - 4)}{3000 + (14 - 4)} = 1.12$$

*E* is the modulus of elasticity, *i* – coefficient of stability (for the operating conditions of *<sup>i</sup>* = 2.4), *lR* – the estimated length of the Desalter. *<sup>Е</sup>* = 1.86�10<sup>5</sup> mPа; *l* = 10,190 mm; *HD* = 1500 mm; *h0* = 25 mm.

$$l\_R = 10190 - 2 \times 25 + \frac{1500}{3} = 10640 mm$$

Allowable pressure of conditions of stability within the limits of elastic deformation:

*Crude Distillation Unit (CDU) DOI: http://dx.doi.org/10.5772/intechopen.90394*

$$\left[P\right]\_E = \frac{18 \cdot 10^{-6} \times 1.86 \cdot 10^{-5}}{2.4} \times \frac{3000}{10640} \times \left[\frac{100 \times (14 - 4)}{3000}\right]^2 \times \sqrt{\frac{100 \times (14 - 4)}{3000}} = 0.0252 \text{ mPa}$$

Permissible external pressure:

$$\left[p\right]\_{pp} = \frac{1.12}{\sqrt{1 + \left(\frac{112}{0.025239}\right)^2}} = 0.0252 \text{ mPa.}$$

Condition for reliable operation ½ � *Р <sup>E</sup>* ≤½ � *p pp* (0.0252 mPa ≤ 0.0252 mPa) observed.

### **1.7 Summary**

The desalting and dewatering of crude oil take begins on the oil fields. This operation is part of the processing of crude oil, and a good pre-treatment of crude oil implies:


If the desalting of crude oil is carried out qualitatively, the oil has almost no harmful effect on the equipment. Most of the impurities that cause corrosion of the metal are in the remains of formation water. Therefore, the fundamental task of desalting is to remove water drops from the oil. This is a fairly complex process, because the water in crude oil is in the form of droplets with a size quantity often. The improvement and appreciation of the oil pretreatment process level are characterized by:


The poor pre-treatment (desalting process) of crude oil can lead to considerable extra costs. We are talking about the high cost of transportation if the product is not cleared of unnecessary substances that give it extra volume and weight as well as financial investments in equipment. After all, oil, which is not derived from salt, can very quickly damage the pipeline. The requirements for the oil content of the

water and especially for chlorides more stringent on the refineries. The oil content of water before processing must be no more than 0.1% of the mass and for salts-no more than 5 mg/l [3, 31]. These related requirements using much more expensive equipment (columns, heat exchangers, reboilers, etc.). Also, these the requirements induce to reduce the energy consumption, to reduce the corrosion of the equipment, to increase the life of the catalysts, improves the quality of the petroleum products. If these requirements not performed, the oil is necessarily subjected to desalting and dehydration at the electric desalting plant (electrostatic desalter). The surfactants are added if the crude oil contains a lot of suspended solids. The crude oil is heated usually to a temperature of 50 to 90°C to reduce viscosity and surface tension for easier mixing and separation of water.

between the initial boiling point of the components. As a result, the oil is divided into fractions up to fuel oil and tar and even base oil. The distillation of oil can be

The single evaporation of oil is a one-step separation technique. The single evaporation process involves heating the oil to increase the temperature and enthalpy to the true boiling point (TBP) of the vapor-liquid mixture. The process of multiple evaporations is a sequence of single evaporation with a gradual increase in the heating temperature. Distillation by gradual evaporation is a slight change in the oil's state with every single evaporation. The main devices in which the distillation

The difficulty of separating crude oils is mainly determined by the volatility of the key components or by the difference in the boiling point of the key components [34]. The closer the relative volatility is to one per mole, the more plates or plates are needed and more irrigation is needed to achieve the same purity of distillate and residue. For key components, two adjacent components are taken for key components, one belonging to the distillate, the other to the residual product. The relative volatility of these adjacent components and their proportion in crude oil are the main criterion determining the difficulty of sufficiently clear separation from crude oil [34]. More the tangent of the angle of inclination of the TBP increase, the easier the separation conditions are. The wider the crude oil TBP intervals, more the distillate and the residue obtained during the process are clean. As we all know, crude oil from the bowels of the Earth contains salt as dissolved salt in a tiny drop of water that forms water into an emulsion [1, 9]. This water cannot be completely separated by gravity or mechanical means. The deep separation of water from the emulsion occurs with electrostatic at the plant, before the

After desalting process, the crude oil is heated in heat exchangers or reboilers (preheating of crude oil). Of course, preheating is not sufficient, since the oil must be partially evaporated to the extent that all products except atmospheric residues must be in the vapor phase when the oil enters the atmospheric column. Thus, the furnace is required to raise the temperature between 330 and 385°C depending on the components of oil [35]. The partially evaporated crude oil is transferred to the flash zone column located at a point below the distillation column and above what is called the stripping section. The main distillation column is generally up to 50 m with a 30–50 valve [34]. The size of the column is determined by the number of plates and the amount of steam. Besides, the amount of steam is determined by the content of crude oil in volatile elements or compounds. As a result, the rising steam in huge amounts and at top flow rates, requires a large diameter column above the flash zone [1, 34]. At the bottom of the section, water vapor is injected into the column to remove the atmospheric residue of any light hydrocarbon and reduce the partial pressure of hydrocarbon vapors in the flash zone [20]. This causes the true boiling point of hydrocarbons to decrease and causing more hydrocarbons to boil and raise the column to eventually thicken and removed as lateral flows. As hot vapors grow from the flash zone, they ascend into the column through the plates to the upper zone of the column [36]. A portion part of the light fraction of naphtha or gasoline returns to the column in the form of reflux. This reflux allows controlling

carried out [34]:

• Multiple evaporations

*Crude Distillation Unit (CDU)*

• Gradual evaporation

distillation process [20].

**123**

• Single evaporation or flash vaporization

*DOI: http://dx.doi.org/10.5772/intechopen.90394*

of oil are distillation columns, reboilers, furnaces, etc. [1].
