HYDRAULIC ANALYSIS CALCULATION FOR ASH SLURRY PIPELINE

HYDRAULIC ANALYSIS CALCULATION FOR ASH SLURRY PIPELINE

The velocity of slurry in pipelines shall be in the range 1.8 m/s to 2.5m/s to avoid increasing the wear rate of the pipeline (if operating velocity above 2.5m/s) and risks of settling out and causing a blockage inside pipeline (if operating velocity below 1.8m/s). This slurry is non-Newtonian fluid so that the formula of Durand equation will be applied to calculate the friction loss of slurry.

The difference i - i_w represents an increase in pressure drop due to the presence of solids in the slurry. The effect of particle size on slurry pressure drop is accounted for by the inclusion of the drag coefficient C_D.

In most industrial applications, the particle size is not uniform, so the equation above can be written as follows:

Step 1: Calculation C_DRe_w² based on input data.

C_DRe_w² = ρ_l(4gd³(ρ_s - ρ_l)/(3µ²g_c²

Whereas:

C_D – Drag coefficient

d – Particle diameter (m)

g – Acceleration due to gravity (9.81 m/s²)

ρ_l – Density of liquid (kg/m³)

ρ_s – Density of solid particle (kg/m³)

Re_w = d ρ_l w₀/(gµ)

w₀ – settling velocity (m/s)

µ - viscosity of liquid (kg.s/m).

Step 2: Find the drag coefficient of particles of individual size fraction based on result of step 1

Source: Piping handbook, seventh edition.

Step 3: Calculation of friction loss of slurry

Calculation follows below equation:

i_w – friction loss for water (mH₂O/m) were calculated by software.

i – Friction loss for slurry

C_vi – volume fraction of solid having size d_i

C_Di – Drag coefficient of particle having size d_i

N – Total number of size fraction into which given particle size distribution is divided.

Calculation file: Download 

Calculating Physical Properties Of Slurries

 A slurry consists of solid particles suspended in a liquid. A slurry pipeline is used to transport slurries from the source such as a coal mine to its destination such as a coal power plant. In this case the coal slurry will be a mixture of coal and water, which is a transportation medium used to propel the combined solid-liquid mass through the pipeline using centrifugal pumps to provide the required pressure.

Slurries may be newtonian or non-newtonian in nature. When the particle concentration of solid within the liquid is less than 10 percent by volume, the slurry may be considered newtonian. When the slurry concentration is higher than 10 percent, it is generally regarded as non-newtonian.

Physical Properties of a Slurry:

Since the slurry consists of solid particles suspended in a liquid, the properties of a slurry mixture will depend upon those of the constituents. The density of slurry can be calculated from the following equation:

ρ_m = 100 / (C_w/ρ_s) + [(100 - C_w) / ρ_L] 

where:

ρ_m =density of slurry mixture, kg/m³
C_w = solids concentration by weight, %
ρ_s = density of solid in mixture, kg/m³
ρ_L = density of liquid in mixture, kg/m³

The variable C_w represents the amount of solid in the mixture by weight. The term C_v is a corresponding value in terms of volume. Thus C_w may be 50 percent solids by weight, whereas C_v may be 15 percent solids by volume. The term volume fraction represented by the symbol Φ is equal to C_v/100. The term volume ratio represents the ratio of the volume of solid to the volume of liquid. Thus we get the following equations for the volume fraction and volume ratio:

Φ = C_v / 100

Volume Ratio = Φ / 1 - Φ

where:
C_v = Concentration of solids by volume, %
Φ = Volume fraction

The concentration of solids by volume C_v and the concentration of solids by weight C_w are related to the solid density and the mixture density by the following equation:

C_v = C_w*(ρ_m / ρ_s)

where:
C_v = solid concentration by volume, %

The viscosity of a dilute suspension consisting of solids in a liquid can be calculated approximately from the volume fraction Φ and the viscosity of the liquid using the following equation:

µ_m = µ_L*(1 + 2.5Φ)

where:

µ_m = viscosity of slurry mixture, cP
µ_L = viscosity of liquid in slurry mixture, cP

The preceding equation of the mixture viscosity applies only to laminar flow and to spherical particles. Also the equation does not apply for solid concentrations exceeding 1 percent by volume.

For higher-concentration suspensions the viscosity of the mixture can be calculated using a modified form of the above equation attributed to D. G. Thomas.

µ_m = µ_L*[1 + 2.5*Φ + 10.05*Φ² + 0.00273*exp(16.6*Φ)]

where the terms are as defined above

Some example calculations:

Example 1:
A slurry mixture consisting of magnetite in water has a concentration of 65 percent solids by weight, and the specific gravity of the solids is 5.2. Calculate the specific gravity, volume fraction, and volume ratio of the slurry mixture.

Calculations:

Inputs:
C_w = 65%
ρ_s = 5.2

Results:

SG_m = 100 / (65/5.2) + (35/1.0) = 2.10
C_v = 65*(2.1 / 5.2) = 26.25%
Φ = 26.25 / 100 = 0.2625
Volume Ratio = 0.2625 / (1 - 0.2625) = 0.3559

Example 2:

A slurry consists of raw salt in a brine solution. Experiments indicate that this slurry weighs 1522 kg/m³). Calculate the concentration of solids by weight and by volume and the volume ratio. Use 2082 kg/m³ for the density of salt and 1281 kg/m³ for the density of brine.

Calculations:

Input:
Slurry Density, ρ_m = 1522 kg/m³
Liquid Density, ρ_L = 1281 kg/m³
Solid Density, ρ_s = 2082 kg/m³

Results:
1522 = 100 / (C_w / 2082) + [(100 - C_w) / 1281]

C_w / 2082 + 100 / 1281 - C_w / 1281 = 100 / 1522

C_w*((1/2082) - (1/1281)) = 100*((1/1522) - (1/1281))

C_w*(-0.0003) = -0.0124

C_w = 41.2%

C_v = 41.2*(1522 / 2082) = 30%

Volume Fraction Φ = 30 / 100 = 0.3
Volume Ratio = 0.3 / (1 - 0.3) = 0.4286

Example 3:

Calculate the viscosity of a slurry mixture consisting of salt (50 percent by weight) in saturated brine assuming a newtonian fluid. The viscosity of brine is 2.0 cP, and the density of brine is 1200 kg/m³ and that of salt is 2082 kg/m³.

Calculations:

Inputs:
Liquid Density, ρ_L = 1200 kg/m³
Solid Density, ρ_s = 2082 kg/m³
C_w = 50%

Results:
ρ_m = 100 / (50/2082) + (50/1200) = 1522 kg/m³
C_v  = 50*(1522 / 2082) = 36.55%
Φ = 36.55 / 100 = 0.3655
µ_m = 2.0*[1 + 2.5*0.3655 +10.05*(0.3655)² + 0.00273*exp(16.6*0.3655)] = 8.9 cP

To conclude, the above methods can be used to calculate the density, viscosity, volume fraction and volume ratio of slurries.

Hoping to have quite a few comments and from the members of Cheresources.

Reference: Chapter 10, Slurry & Sludge Systems Piping, "Piping Calculations Manual" by E. Shashi Menon

How To Write A Plant Operating Manual

 How To Write A Plant Operating Manual
Most Process Engineers, specially the senior process engineers are required to write a plant operating manual for a new greenfield project during their career. Mind you, this is quite different from updating an existing operating manual for a brownfield project where the scope of the project is modification and debottlenecking. Updation of an existing operating manual is a simpler exercise compared to writing a new operating manual where you follow the format of the existing operating manual and only provide an addendum to the existing operating manual related to the scope of the project.

The real challenge lies in writing a new operating manual and that is where the experience of the process engineer comes into fore.

In this blog entry I have tried to put across general guidelines on preparing a plant operating manual based on my experience of writing a few of them. These guidelines are generic in nature and do not subscribe to any company philosophy for writing an operating manual.

Let us begin the exercise with what are the basic minimum requirements to start writing an operating manual

Following input documents are required during preparation of Operating Manual:

a. Basis of Design – Process Description
b. Process & Utility Flow Diagrams (PFDs and UFDs)
c. Piping & Instrument Diagrams (P&ID’s)
d. Deatiled process description from "Technology Licensor" for proprietary processes if applicable
e. Operating and Miantenance manuals of vendor equipment and packages (e.g. Instrument Air Package, Compressor Systems, Pumps, Water Treatment Plants, Fired Heaters etc.)
f. Function logic narrative provided by Instrumentation

Procedure:

Operating Manual is generally a Microsoft Word document.

Structure:
 The Operating Manual is a structured document with a particular narrative style. The following is the sequence of the document:

- Coversheet with project title and document name i.e. Operating Manual
- 1^st sheet with project title, document name i.e. Operating Manual
- List of Contents which includes:
   . Abbreviations and Definitions
   . Introduction which provides an overview of the project
   . Process & Utility System Description
   . Process Control and Automation
   . Equipment Description
   . Start-Up Procedure
   . Normal Operating Procedure
   . Shutdown Procedure
   . Health, Safety & Environment (HSE)
   . Appendices

Abbreviations & Definitiions:
The abbreviations and definitions of terms used in the entire document are summarized here.

Introduction:
This section provides the brief overview of the project which includes the purpose of the facility and what it contains.

Process & Utility System Description:
This section describes in detail the overall facility. The narrative should be in such a manner that the description is in the correct sequence of the process for easy understanding. Utility systems which supplement the main process should be described as a separate sub-section. Wherever possible, process description should be supplemented by simple sketches showing the major equipment and process control for a particular unit operation. This enhances the understanding of the process.

Process Control & Automation:
This section provides the description of the overall controls required for the safe, reliable and uninterrupted operation of the plant / unit. This could include flow, pressure, temperature and level control of the plant / unit for the smooth operation of the plant / unit. Controls required for start-up, planned shutdown and to change plant / unit capacity should be mentioned. High and Low alarms for process operating parameters are also described in this section.

Plant section-wise or unit-wise control systems should be addressed in a sequential manner in order to explain the process control in continuity.

All process safety and shutdown interlocks, automation provided for emergency shutdown of entire plant or unit of the plant should be described in this section. An example of an emergency shutdown could be the description of the Fire and Gas Monitoring system which initiates the plant or unit shutdown.

Tag numbers of instruments used for process control and automation should be mentioned for sake of clarity.

Equipment Description:
This section provides the functional description of the individual equipment or group of equipment which form a unit operation in the overall context of the entire facility. Description could include operating and design conditions for the individual equipment.

Providing tag nos. for the equipment is recommended.

Wherever possible, sketches are recommended for the sake of clarity.

Start-up Procedure:
This section provides the description of the start-up procedure for the plant / unit under consideration:

The first sub-section of this section should address the readiness of the plant to be started-up. By readiness it is meant that the plant / unit is ready to accept the process or utility fluid, raw materials or reactants. This requires that the commissioning check-lists prepared for the plant / unit are ticked off and signed off by the start-up team.  A list of the check-lists may be provided in this section which have been signed-off to indicate readiness.

The second sub-section should address the start-up of the utility systems prior to the start-up of the main process. Utility systems could include charging up headers for instrument air, cooling water, inert gas for blanketing / purging etc.

The third sub-section should address the start-up of the main process. This section should describe the valves (manual or automated) and instruments to be lined up for introducing the process fluid (e.g. hydrocarbons, chemicals) into the equipment or equipments (e.g. piping, vessels, tanks, reactors) of the plant / unit being started up.

Wherever applicable, reference of vendor documents for any equipment / package unit should be provided in this section.

Normal Operating Procedure:
This section provides the description of the normal operation of the plant / unit and indicates the parameters to be monitored for maintaining the product quality and operational reliability of the plant / unit.

Operating parameters should be mentioned for a particular equipment or unit or the entire plant in this section. Sketches describing the normal operation are recommended for the sake of clarity. Field logging and maintaining history records of critical process parameters from the DCS or SCADA need to be mentioned in this section. Requirements of manning a particular plant section or unit should be mentioned in this section including field monitoring intervals by operating personnel for a particular equipment or unit.

While describing any operation it is recommended that equipment, instrument and line tag nos. be mentioned for the sake of clarity.

Shutdown Procedure:
This section provides the description of the shutdown procedures to stop the operation of the plant.

The first sub-section of this section deals with normal shutdown due to either scheduled maintenance and / or inspection or modification / de-bottlenecking of the plant. In this sub-section, description should be provided for planned reduction / removal of inventory of the process fluids from the equipment or unit to be shutdown. This would include stoppage of fresh feed, gradual reduction of plant / unit throughput to minimise off-specification product and final draining and purging of the equipment / unit for the purpose of complete emptying prior to handing over for maintenance / inspection or modifications / de-bottlenecking.

The second sub-section deals with emergency shutdown procedures due to any emergency such as an external fire, water flooding, earth quake, loss of containment of process fluid (gas or liquid leak) etc. In this section description should be provided for the methods for isolation of equipment or unit due to either manual initiation or automatic initiation of an emergency. Manual initiation is emergency initiated by the operator of the plant / unit whereas automatic initiation is emergency initiated by automatic detection of an emergency such as detection of fire or gas leak by an automated Fire & Gas detection system.

Usage of tag nos. for equipment, valves and instruments while providing the shutdown procedure description is recommended.

Health, Safety & Environment:
This section describes the HSE aspects of the facility that need to be considered.

Health:
This sub-section relates to the health of the people and working in the plant or living in the vicinity of the plant whose health should be a concern for the management of the plant. This should also address the health and well being of animals and other living organisms present in the vicinity of the plant, for e.g. marine life in any water body which would be effected by the operations of the plant.

In this sub-section a brief description of toxicity of the chemicals used in the plant / unit, acceptable noise levels for humans and other animals, magnitude of injuries due to fire and explosion, first aid measures for treating injuries etc. should be provided.

Safety:
This sub-section relates to the safe start-up, operation and shutdown of the plant during its entire lifetime. This section should address the normal hazards those are encountered in day-to-day operations of the plant. This section should also address the safety measures available to prevent any accident.

Some of the normal hazards could be loss of containment of any hazardous fluid due to overflow, leak or rupture, static electricity build-up, accidental fall from heights, burns due to exposure to hot surfaces, exposure to toxic fluids while collecting samples and piling up of flammable solid waste (wood, paper, cloth etc.).

Description of safety measures should include:
- Special operating procedures for activities like sample collection and regular maintenance of rotating machinery
- Issuance of work permits for hot work and vessel entry
- Usage of personal protective equipment (hard hats, safety shoes, eye goggles, ear muffs, breathing apparatus etc.)
- Provision of field sign boards indicating the type of hazard
- Regular house-keeping
- Emergency evacuation procedures

Environment:
This sub-section describes the limits for discharge of hazardous solid, liquid and gaseous effluents to the environment based on local laws and regulations and procedures for compliance to them.

Appendices:
The appendices should preferably include the list of Process & Utility Flow Diagrams (PFDs / UFDs), Piping & Instrument Diagrams (P&IDs), Cause and Effect Diagrams (CEDs) and reference vendor documents, table for Alarm / Trip setpoints and lubrication schedule.

The above mentioned guidelines should help a process engineer to get started on a plant operating manual.
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Process Engineering

1.     Introduction of Process Engineering

1.1 Function of Process Engineering

- Transfer the laboratory and pilot plant process information

to fulfill the requirement of process plant mechanical design and instrument and control design

- Major activities include the material and energy balance, sizing of piping and equipment, setting up the requirement of instrument and equipment operation condition such as temperature and pressure.

- Guideline for the plant operation.

1.2 Basic Requirement of a Process Plant

Now, process engineers are always required to proceed the

design in the consideration of the following requirement:

-Safety

-Operability

-Maintenance requirement

-Minimum environmental impact

-Energy efficiency

-Economy

1.3 Process engineers’ role

- Collect process information including licensor list, rule of thumb plant investment cost, pros and cons of each process to assist the project and sales groups in the pursuit of business.

- Provide technical consultancy to the client or project for plant operation trouble shooting.

- Assist or be in charge of the plant start-up and performance test.

- Be capable to do the most of refinery and some petrochemical process plants Front End Engineering Design (FEED)

2. Major Activities of Process Engineering

Basically the process engineering activities are classified into

different areas as listed:

- Feasibility study

- Process design

- System design

- Utility system design

- Plant start up assistance

3. Design Procedure

3.1 Design Work Flow

If the client has already purchased a commercial process license, in most case, the licensor will perform the process design and supplies a PDP (Process design package). In the PDP, at least the PFD, material and energy balance, critical equipment data sheet, and operation procedure should be provided. The process engineers will follow the client specification to complete the process design including the issue or modification of P&ID and other design such as the preparation of equipment data sheets, hydraulic checks, line sizing/list, instrument process data sheets, operation manual, and others.

3.2 Content of Process Design Package

Typical process design package(PDP) will include the following data:

- Introduction

- Design basis

- Process description

- Material and energy balance

- Chemical and utility consumption

- Piping and material specification

- PFD

- P&ID

- Equipment list

- Equipment process data sheet/specification

- Instrument process data sheet/specification

- Reference plot plant

- Effluent data

- Operation procedure

- Key control philosophy in some PDP

4. Feasibility Study

4.1 Major Scope of Feasibility Study

Feasibility study is the first step in the evaluation of the plant investment. It will provide the technical and economical information to assist in the decision making of the investment including some or all of license selection, plant scale, plant site selection, and others. For some of the activities such as market survey and others, process engineers may need

assistance from outside source or other discipline to complete the study.

- Market survey

- Process survey

- Plant site selection

- Capital investment cost estimation

- Operation cost estimation

- Economic analysis

- Sensitivity analysis

4.2 Data Required for Feasibility Study

- Market information such as raw material, product, catalyst, and chemical availability, cost, growth rate…

- Process data such as equipment list and data sheet

- Plant site data such as climate, transportation, and other

infrastructure availability and cost

- Utility including fuel, electricity, water, and other utility

availability and cost

- Labor cost

- Local code and regulation

- Tax information

5. Design Basis

The design basis should include at least the following information:

a. Site conditions (site elevation, temperature, humidity and etc.)

b. Battery limit condition (Temperature /pressure of the process and utility fluid.)

c. Code and regulation in:

- Safety

- Environmental protection

- Specific equipment codes and standard such as boiler, pressure vessel, heat exchanger, pumps and etc.

d. Project specific requirement such as

- Spare philosophy

- Over design and turn down requirement

- Equipment, piping and instrument specific requirement such as type, design conditions, and etc.

6. Process Engineering Design

6.1 Process Design

a. Process simulation

b. Material and energizing balance

c. PFD

d. Equipment sizing

- Static equipment: Fired heater, heat exchanger, tower, drum, silo, tank, filter….

- Rotary machine: pump, compressor, steam turbine, fan/blower,

conveyor, and agitator….

- Package equipment: Desalter, chilling water system…

e. Equipment list

6.2 System Design

a. P&ID

b. Utility flow diagram(UFD)

c. Instrument and control process data

d. Line sizing

f. System hydraulic calculation /check

g. Safety relief system

h. HAZOP study

i. Operation manual

6.3 Offsite/Utility System Requirement

6.3.1 Tankage

a. Raw material

b. Final product

c. Intermediate product

d. Off spec. product

e. Utilities

f. Wastewater or other effluent

6.3.2 Utility System

a. Steam/condensate: HP, MP, LP…

b. Water System: raw water, potable water, cooling water, BFW, Demineralized water, process water, fire water

c. Air: Plant air, instrument air

d. Fuel: Fuel oil, fuel gas

e. Gas: N2

f. Electricity

7. Assistance in plant starting

7.1 Typical process plant start up procedures

a. Precommissioning activities

- Piping cleaning: water flushing, air blowing, steam

blowing, or chemical cleaning

- Tightness test and/or vacuum test

- Refractory and system dry out

- Air removal

- Instrument calibration

- Instrument function test

- Electrical facilities test such as motor no load running test

- Catalyst/packing loading

b. Equipment test run

c. System test run

d. Other procedure prior to feed-in such as catalyst conditioning or oil circulation

e. Feed-in

f. Performance test