Wow, that's a long ways from what I experienced. My high school chemistry instructor actually flipped through the Anarchist's Cookbook looking for things that we could safely experiment with in the lab. It's sad that my experience is much more the exception than the rule.

While you are right that conventional coal plants can be made just as clean as gasification, it's just much more expensive to scrub a conventional coal plant than a gasification plant. The difference is quite significant.

Most of the savings is due to more beneficial thermodynamics. Syngas (the product of gasification) has a much higher concentration of CO2 than exhaust gas (the product of a conventional plant). This higher concentration (also higher pressure and temperature than at the exhaust stack) provide a larger driving force for the removal of CO2 from the gas stream. This larger driving force means that there is less need for capital investment in scrubbing equipment. It also means that less energy is utilized in scrubbing the gas. Finally, since gasification results in more complete oxidation of the carbon, the plant is overall more efficient. The result is cheaper energy from the same coal.

http://pubs.acs.org/isubscribe/journals/cen/85/i44/html/8544gov1.html

Adding scrubbing and sequestering equipment onto existing plants is estimated to add 75% to the cost of energy from coal. Coal gasification (with carbon sequestration) would only add around 33% to the cost of energy from coal.