Introduction: Plant Utility

CHAPTER 1
TOPICS FOR INTRODUCTORY LECTURE

1. What are public utilities?
2. What are plant utilities of chemical industry?
3. Difference between basic utilities and derived utilities.
4. Inferences from utility values.
5. Reasons for generous sizing of utility facilities.
6. Contribution of plant utility cost to product cost

1.1 Public Utilities:
They comprise fuel gas, water, electricity, transport services, drainage services, and means of communication and are regarded as essential to the life of all community members, irrespective of their lifestyle. The supplier may be different for each city/town/village. With reference to Mumbai city, following utility suppliers are there:

• Gas (fuel)- Mahanagar Gas Limited
• Water-Brihanmumbai Municipal Corporation
• Electricity-Bombay Electricity Supply & Transport Company, Adani Power, Tata Power, etc.
• Transport Services—One could commute and/or transport goods through rail, road, water & air routes.
• Rail route-Indian Railways
• Road route- Brihanmumbai Municipal Corporation
• Water route- Various shipping companies
• Air route-Various Airlines
• Drainage Services- Brihanmumbai Municipal Corporation
• Means of Communication: (postal, telegram, telephone, telex, fax, email, etc.)
• Postal ,Telegram & Telex-Government of India
• Telephone (landline)-MTNL, Tata Communications, etc.
• Telephone (mobile)-Various organizations like Vodafone, Airtel, Jio, etc.
• Fax & Email: Various organizations.

1.2. Plant Utilities of Chemical Industry:

By analogy, we call some facilities as plant utilities as they are essential & common to practically all chemical plants.

 - However, their specifications, i.e., quality & quantity vary from plant to plant. System specifications vary from chemical to chemical & for a given chemical, it varies with differing plant capacity.

 - Examples of plant utilities are:

• Heating Systems, viz., hot water, steam, thermic fluids, Dowtherm heaters/vaporizers, etc.-each has varying operating temperature levels.
• Cooling Systems, viz., cooling water, refrigeration system, etc.—varying operating temperature levels.
• Water Systems, viz., Water can be used for cooling water, boiler feed water, process water, firefighting with water, special purposes, general purposes like plant cleaning, human usage, etc.
• Air Systems, viz., Instrument Air, Plant Air, vacuum system, etc.
• Flare Systems-for converting obnoxious chemicals into harmless chemicals by combustion process.
• Environment Protection Systems ---gaseous, liquid & solid waste handling, treatment systems & disposal systems

Summary of raw materials & Utility Requirement:

Utility Values For different Plant Capacity:

1.3. Difference between basic utilities and derived utilities.

Certain items are imported to plant from outside, e.g., raw water, electricity, fuel, utility system treatment chemicals. They are known as basic utilities. They are used for generating derived utilities.

Chemical plant generates certain utilities from basic utilities. They are known as derived utilities, e.g.

1. Cooling Tower Make up water from raw water, water treatment chemicals & electricity
2. Cooling water from recirculating water, make-up water, treatment chemicals & electricity.
3. Boiler Feed Make up water from raw water, water treatment chemicals & electricity
4. Steam from fuel, electricity, and boiler feed water & treatment chemicals.
5. Plant air from air, electricity & cooling water.
6. Instrument air from plant air & drying substances

1.4. Inferences from Utility Values:

 - For a given chemical & its production capacity, we can infer for each utility required equipment capacity either on hourly or daily basis.
 - Illustration: For Urea plant having production rate of 100T/D, we can specify following:

 = Electricity : 604 kW
 = Steam : 10 T/Hr
 = Cooling water : 458 T/Hr

• This information is essential for procuring utility package which gets reflected in capital cost.
• As a rule of thumb, capital cost of utilities package is 15% of battery limit plant capital cost.
• We can also compute operating cost of utilities per ton of product-it gets reflected in direct production cost.
• In reality, as plant capacity increases, consumption of specific utility per ton of production decreases marginally. This reduction in unit value is due to higher efficiency of equipment & systems at higher production rate.

1.5. Reasons for generous sizing of utility facilities.

As each utility caters to needs of various plant equipment, we provide more margin (say 15-20%), while ordering utility systems to avoid future bottlenecks. For example, calculations give steam generator capacity of 10TPH, then we will order steam generator of 12TPH capacity. This allows marginal variations/alterations in requirement by specific equipment and/or trying to have marginally higher production than rated capacity of plant.

Additional capital cost of higher capacity utility is relatively small as it is governed by 6/10th rule, i.e., 20% higher steam generator will cost only 11.5% more.

1.6 Contribution of plant utility cost to product cost:

As a rule of thumb, we can state that utilities contribute 20- 25% to product cost, i.e., product costing Rs. 100/kg will have contribution of utilities of Rs. 20-25 per kg. Thus it plays significant role in cost of product.
Exact value will vary from product to product & efficiency of process design. More energy integrated plant will have lesser consumption & contribution but more of capital cost.

Summary: Plant utilities are integral part of chemical product manufacturing facilities. Their specifications depend upon chemical chosen for manufacturing & its production capacity. Also, capital cost & operating cost of plant utilities contribute significantly to economics of chemical plants.

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Author
Dr. Anant Jhaveri
Trainer – Polymerupdate Academy