Primarily shop-assembled and shipped by rail, truck, or barge to their final destination, today's industrial-class watertube steam boilers often are called “package” units. The term “package,” however, can be misleading, creating the impression these boilers can be purchased “off the shelf,” installed, and used to produce steam in a matter of weeks. In reality, package-boiler projects often are years in the making, requiring coordination and great attention to detail. This article discusses all that goes into a successful package-boiler project.

Project Phases

A typical package-boiler project can be organized into six distinct phases of work. Depending on the application and business requirements, at least 18 to 24 months should be allowed for the process.

Phase 1: project requirements and business case

Often at least two years before steam is needed from a boiler, operating requirements are established and important decisions about how the boiler will be integrated into an application are made. Most new-boiler projects are driven by one or more of the following:

• The need to replace equipment nearing — or at — the end of its service life. Built and installed during the 1960s and ‘70s, thousands of today's industrial-class watertube package boilers are nearing or have reached the end of their practical service lives, as evidenced by chronic leaks and fouling and poor efficiency. While much can be done to “plug the dyke” through repair, cleaning, and replacement of components, sooner or later, these units will have to be replaced. Particularly in the petrochemical industry, millions of dollars can be lost for every day a boiler is not operating.

• A desire to reduce operating costs. Today's boilers can be configured to deliver an average efficiency of 83 percent when a feedwater economizer is used and over 90 percent when a condensing exchanger and air pre-heaters are used. With today's fluctuating energy costs, just a 1-percent improvement in efficiency can mean significant savings.

• The need to reduce emissions to meet new air-quality standards. Sometimes, an older boiler can be retrofitted with a selective-catalytic-reduction (SCR) solution or an ultralow-nitrogen-oxide (NOx) burner and flue-gas-recirculation (FGR) solution to meet emissions requirements. However, when reduced emissions is coupled with improved efficiency, such retrofits can have a less attractive payback than a new boiler.

• The need to support business growth. Operating costs, return on investment, and emissions requirements are no less important when the reason to consider a new boiler is to meet the growth demands of one's business.

In any case, core questions about a boiler solution must be answered before budgeting can begin:

• What is the required steam capacity? If operation across a wide range of capacities is needed, a single boiler will be limited on both the top and the low ends of capacity, with predictable performance often ranging from 25 to 100 percent of design capacity. If predictable performance across a wider range of capacities is required, modularization across several boilers, which provides flexibility to operate all boilers at 100-percent capacity or only one at less than 25-percent capacity, can be considered. Operating ranges vary based on the steam pressure a solution requires and whether the plan is to generate saturated steam or superheated steam, assuming both high pressure and high temperature are required.

• What fuels will be burned? Boilers can be configured to operate on multiple gas and liquid fuels. Many petrochemical operations have the luxury of burning waste gas or byproducts from their refining processes. Depending on the chemical content of waste gas, boilers often can serve as both steam generators and incinerators.

• What are the emissions limits? Often, the most important question regarding emissions limits concerns NOx. Some regions require 9 ppm of NOx, although many are moving to 5-ppm limits. The most stringent emissions standards often are met by coupling low- and ultralow-NOx burner technology with FGR and SCR solutions.

• Where will the boiler be placed, and how will it connect to the rest of the operation? Space in a plant can be at a premium, particularly when an existing boiler is being replaced. Boilers can be configured in a number of horizontal and vertical arrangements to optimize available space.

Phase 2: budget

A budget should consider all equipment used to meet business needs and operating requirements. Often, a boiler represents less than 25 percent of the overall cost of a solution. The cost of auxiliary equipment, control systems, instrumentation and monitoring equipment, civil construction and site work, installation, and start-up should be considered. If an engineering firm is enlisted, those costs should be considered as well.